WorldWideScience

Sample records for catalytic transfer hydrogenation

  1. Microscale Synthesis of Chiral Alcohols via Asymmetric Catalytic Transfer Hydrogenation

    Science.gov (United States)

    Peeters, Christine M.; Deliever, Rik; De Vos, Dirk

    2009-01-01

    Synthesis of pure enantiomers is a key issue in industry, especially in areas connected to life sciences. Catalytic asymmetric synthesis has emerged as a powerful and practical tool. Here we describe an experiment on racemic reduction and asymmetric reduction via a catalytic hydrogen transfer process. Acetophenone and substituted acetophenones are…

  2. Transfer Hydrogenation: Employing a Simple, In Situ Prepared Catalytic System

    KAUST Repository

    Ang, Eleanor Pei Ling

    2017-04-01

    Transfer hydrogenation has been recognized to be an important synthetic method in both academic and industrial research to obtain valuable products including alcohols. Transition metal catalysts based on precious metals, such as Ru, Rh and Ir, are typically employed for this process. In recent years, iron-based catalysts have attracted considerable attention as a greener and more sustainable alternative since iron is earth abundant, inexpensive and non-toxic. In this work, a combination of iron disulfide with chelating bipyridine ligand was found to be effective for the transfer hydrogenation of a variety of ketones to the corresponding alcohols in the presence of a simple base. It provided a convenient and economical way to conduct transfer hydrogenation. A plausible role of sulfide next to the metal center in facilitating the catalytic reaction is demonstrated.

  3. Iron Phthalocyanine as New Efficient Catalyst for Catalytic Transfer Hydrogenation of Simple Aldehydes and Ketones

    Czech Academy of Sciences Publication Activity Database

    Bata, P.; Notheisz, F.; Klusoň, Petr; Zsigmond, A.

    2015-01-01

    Roč. 29, JAN 2015 (2015), s. 45-49 ISSN 0268-2605 Institutional support: RVO:67985858 Keywords : heterogenized complexes * catalytic transfer hydrogenation * reusable catalyst Subject RIV: CC - Organic Chemistry Impact factor: 2.452, year: 2015

  4. Synthesis and Catalytic Hydrogen Transfer Reaction of Ruthenium(II) Complex

    International Nuclear Information System (INIS)

    Son, Jung Ik; Kim, Aram; Noh, Hui Bog; Lee, Hyun Ju; Shim, Yoon Bo; Park, Kang Hyun

    2012-01-01

    The ruthenium(II) complex [Ru(bpy) 2 -(PhenTPy)] was synthesized, and used for the transfer hydrogenation of ketones and the desired products were obtained in good yield. Based on the presented results, transition-metal complexes can be used as catalysts for a wide range of organic transformations. The relationship between the electro-reduction current density and temperature are being examined in this laboratory. Attempts to improve the catalytic activity and determine the transfer hydrogenation mechanism are currently in progress. The catalytic hydrogenation of a ketone is a basic and critical process for making many types of alcohols used as the final products and precursors in the pharmaceutical, agrochemical, flavor, fragrance, materials, and fine chemicals industries. The catalytic hydrogenation process developed by Noyori is a very attractive process. Formic acid and 2-propanol have been used extensively as hydrogenation sources. The advantage of using 2-propanol as a hydrogen source is that the only side product will be acetone, which can be removed easily during the workup process. Hydrogen transfer (HT) catalysis, which generates alcohols through the reduction of ketones, is an attractive protocol that is used widely. Ruthenium(II) complexes are the most useful catalysts for the hydrogen transfer (HT) of ketones. In this method, a highly active catalytic system employs a transition metal as a catalyst to synthesize alcohols, and is a replacement for the hydrogen-using hydrogenation process. The most active system is based on Ru, Rh and Ir, which includes a nitrogen ligand that facilitates the formation of a catalytically active hydride and phosphorus

  5. Synthesis and Catalytic Hydrogen Transfer Reaction of Ruthenium(II) Complex

    Energy Technology Data Exchange (ETDEWEB)

    Son, Jung Ik; Kim, Aram; Noh, Hui Bog; Lee, Hyun Ju; Shim, Yoon Bo; Park, Kang Hyun [Pusan National University, Busan (Korea, Republic of)

    2012-01-15

    The ruthenium(II) complex [Ru(bpy){sub 2}-(PhenTPy)] was synthesized, and used for the transfer hydrogenation of ketones and the desired products were obtained in good yield. Based on the presented results, transition-metal complexes can be used as catalysts for a wide range of organic transformations. The relationship between the electro-reduction current density and temperature are being examined in this laboratory. Attempts to improve the catalytic activity and determine the transfer hydrogenation mechanism are currently in progress. The catalytic hydrogenation of a ketone is a basic and critical process for making many types of alcohols used as the final products and precursors in the pharmaceutical, agrochemical, flavor, fragrance, materials, and fine chemicals industries. The catalytic hydrogenation process developed by Noyori is a very attractive process. Formic acid and 2-propanol have been used extensively as hydrogenation sources. The advantage of using 2-propanol as a hydrogen source is that the only side product will be acetone, which can be removed easily during the workup process. Hydrogen transfer (HT) catalysis, which generates alcohols through the reduction of ketones, is an attractive protocol that is used widely. Ruthenium(II) complexes are the most useful catalysts for the hydrogen transfer (HT) of ketones. In this method, a highly active catalytic system employs a transition metal as a catalyst to synthesize alcohols, and is a replacement for the hydrogen-using hydrogenation process. The most active system is based on Ru, Rh and Ir, which includes a nitrogen ligand that facilitates the formation of a catalytically active hydride and phosphorus.

  6. Green Synthesis of (R)-Terbutaline for Recyclable Catalytic Asymmetric Transfer Hydrogenation in Ionic Liquids.

    Science.gov (United States)

    Uchimoto, Hitomi; Ikeda, Miki; Tanida, Saori; Ohhashi, Kayo; Chihara, Yoshiko; Shigeta, Takashi; Arimitsu, Kenji; Yamashita, Masayuki; Nishide, Kiyoharu; Kawasaki, Ikuo

    2017-01-01

    We synthesize optically active (R)-terbutaline 2, which is an anti-asthmatic drug, through recyclable catalytic asymmetric transfer hydrogenation (RCATH). Various chloroketones 4 were prepared and RCATH was performed on them. The products exhibit moderate to high enantioselectivity. In particular, the hydrogenation of acyl substituted substrates 4c yields chiral secondary alcohols 5c in good yield and enantioselectivity. Furthermore, (R)-terbutaline 2 can be synthesized in one step from the resulting secondary alcohol 5 without racemization.

  7. Liquid-Phase Catalytic Transfer Hydrogenation of Furfural over Homogeneous Lewis Acid-Ru/C Catalysts.

    Science.gov (United States)

    Panagiotopoulou, Paraskevi; Martin, Nickolas; Vlachos, Dionisios G

    2015-06-22

    The catalytic performance of homogeneous Lewis acid catalysts and their interaction with Ru/C catalyst are studied in the catalytic transfer hydrogenation of furfural by using 2-propanol as a solvent and hydrogen donor. We find that Lewis acid catalysts hydrogenate the furfural to furfuryl alcohol, which is then etherified with 2-propanol. The catalytic activity is correlated with an empirical scale of Lewis acid strength and exhibits a volcano behavior. Lanthanides are the most active, with DyCl3 giving complete furfural conversion and a 97 % yield of furfuryl alcohol at 180 °C after 3 h. The combination of Lewis acid and Ru/C catalysts results in synergy for the stronger Lewis acid catalysts, with a significant increase in the furfural conversion and methyl furan yield. Optimum results are obtained by using Ru/C combined with VCl3 , AlCl3 , SnCl4 , YbCl3 , and RuCl3 . Our results indicate that the combination of Lewis acid/metal catalysts is a general strategy for performing tandem reactions in the upgrade of furans. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Production of dimethylfuran from hydroxymethylfurfural through catalytic transfer hydrogenation with ruthenium supported on carbon.

    Science.gov (United States)

    Jae, Jungho; Zheng, Weiqing; Lobo, Raul F; Vlachos, Dionisios G

    2013-07-01

    RuC ees' transfer: Transfer hydrogenation using alcohols as hydrogen donors and supported ruthenium catalysts results in the selective conversion of hydroxymethylfurfural to dimethylfuran (>80% yield). During transfer hydrogenation, the hydrogen produced from alcohols is utilized in the hydrogenation of hydroxymethylfurfural. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Catalytic Transfer Hydrogenation of Biomass-Derived Carbonyls over Hafnium-Based Metal-Organic Frameworks.

    Science.gov (United States)

    Rojas-Buzo, Sergio; García-García, Pilar; Corma, Avelino

    2018-01-23

    A series of highly crystalline, porous, hafnium-based metal-organic frameworks (Hf-MOFs) have been shown to catalyze the transfer hydrogenation reaction of levulinic ester to produce γ-valerolactone by using isopropanol as a hydrogen donor. The results are compared with their zirconium-based counterparts. The role of the metal center in Hf-MOFs has been identified and reaction parameters optimized. NMR studies using isotopically labeled isopropanol provide evidence that the transfer hydrogenation occurs through a direct intermolecular hydrogen transfer route. The catalyst, Hf-MOF-808, can be recycled several times with only a minor decrease in catalytic activity. The generality of the procedure has been demonstrated by accomplishing the transformation with aldehydes, ketones, and α,β-unsaturated carbonyl compounds. The combination of Hf-MOF-808 with the Brønsted-acidic Al-Beta zeolite gives the four-step one-pot transformation of furfural to γ-valerolactone in good yield of 75 %. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. The contrasting catalytic efficiency and cancer cell antiproliferative activity of stereoselective organoruthenium transfer hydrogenation catalysts.

    Science.gov (United States)

    Fu, Ying; Sanchez-Cano, Carlos; Soni, Rina; Romero-Canelon, Isolda; Hearn, Jessica M; Liu, Zhe; Wills, Martin; Sadler, Peter J

    2016-05-28

    The rapidly growing area of catalytic ruthenium chemistry has provided new complexes with potential as organometallic anticancer agents with novel mechanisms of action. Here we report the anticancer activity of four neutral organometallic Ru(II) arene N-tosyl-1,2-diphenylethane-1,2-diamine (TsDPEN) tethered transfer hydrogenation catalysts. The enantiomers (R,R)-[Ru(η(6)-C6H5(CH2)3-TsDPEN-N-Me)Cl] (8) and (S,S)-[Ru(η(6)-C6H5(CH2)3-TsDPEN-N-Me)Cl] (8a) exhibited higher potency than cisplatin against A2780 human ovarian cancer cells. When the N-methyl was replaced by N-H, i.e. to give (R,R)-[Ru(η(6)-Ph(CH2)3-TsDPEN-NH)Cl] (7) and (S,S)-[Ru(η(6)-Ph(CH2)3-TsDPEN-NH)Cl] (7a), respectively, anticancer activity decreased >5-fold. Their antiproliferative activity appears to be linked to their ability to accumulate in cells, and their mechanism of action might involve inhibition of tubulin polymerisation. This appears to be the first report of the potent anticancer activity of tethered Ru(II) arene complexes, and the structure-activity relationship suggests that the N-methyl substituents are important for potency. In the National Cancer Institute 60-cancer-cell-line screen, complexes 8 and 8a exhibited higher activity than cisplatin towards a broad range of cancer cell lines. Intriguingly, in contrast to their potent anticancer properties, complexes 8/8a are poor catalysts for asymmetric transfer hydrogenation, whereas complexes 7/7a are effective asymmetric hydrogenation catalysts.

  11. Catalytic Transfer Hydrogenation of Furfural to 2-Methylfuran and 2-Methyltetrahydrofuran over Bimetallic Copper-Palladium Catalysts.

    Science.gov (United States)

    Chang, Xin; Liu, An-Feng; Cai, Bo; Luo, Jin-Yue; Pan, Hui; Huang, Yao-Bing

    2016-12-08

    The catalytic transfer hydrogenation of furfural to the fuel additives 2-methylfuran (2-MF) and 2-methyltetrahydrofuran (2-MTHF) was investigated over various bimetallic catalysts in the presence of the hydrogen donor 2-propanol. Of all the as-prepared catalysts, bimetallic Cu-Pd catalysts showed the highest catalytic activities towards the formation of 2-MF and 2-MTHF with a total yield of up to 83.9 % yield at 220 °C in 4 h. By modifying the Pd ratios in the Cu-Pd catalyst, 2-MF or 2-MTHF could be obtained selectively as the prevailing product. The other reaction conditions also had a great influence on the product distribution. Mechanistic studies by reaction monitoring and intermediate conversion revealed that the reaction proceeded mainly through the hydrogenation of furfural to furfuryl alcohol, which was followed by deoxygenation to 2-MF in parallel to deoxygenation/ring hydrogenation to 2-MTHF. Finally, the catalyst showed a high reactivity and stability in five catalyst recycling runs, which represents a significant step forward toward the catalytic transfer hydrogenation of furfural. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Catalytic transfer hydrogenation/hydrogenolysis for reductive upgrading of furfural and 5-(hydroxymethyl)furfural.

    Science.gov (United States)

    Scholz, David; Aellig, Christof; Hermans, Ive

    2014-01-01

    The sequential transfer hydrogenation/hydrogenolysis of furfural and 5-hydroxymethylfurfural to 2-methylfuran and 2,5-dimethylfuran was studied over in situ reduced, Fe2 O3 -supported Cu, Ni, and Pd catalysts, with 2-propanol as hydrogen donor. The remarkable activity of Pd/Fe2 O3 in both transfer hydrogenation/hydrogenolysis is attributed to a strong metal-support interaction. Selectivity towards hydrogenation, hydrogenolysis, decarbonylation, and ring-hydrogenation products is shown to strongly depend on the Pd loading. A significant enhancement in yield to 62%, of 2-methylfuran and 2-methyltetrahydrofuran was observed under continuous flow conditions. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Hydrodehalogenation of alkyl iodides with base-mediated hydrogenation and catalytic transfer hydrogenation: application to the asymmetric synthesis of N-protected α-methylamines.

    Science.gov (United States)

    Mandal, Pijus K; Birtwistle, J Sanderson; McMurray, John S

    2014-09-05

    We report a very mild synthesis of N-protected α-methylamines from the corresponding amino acids. Carboxyl groups of amino acids are reduced to iodomethyl groups via hydroxymethyl intermediates. Reductive deiodination to methyl groups is achieved by hydrogenation or catalytic transfer hydrogenation under alkaline conditions. Basic hydrodehalogenation is selective for the iodomethyl group over hydrogenolysis-labile protecting groups, such as benzyloxycarbonyl, benzyl ester, benzyl ether, and 9-fluorenyloxymethyl, thus allowing the conversion of virtually any protected amino acid into the corresponding N-protected α-methylamine.

  14. Catalytic Transfer Hydrogenation of Furfural to Furfuryl Alcohol over Nitrogen-Doped Carbon-Supported Iron Catalysts.

    Science.gov (United States)

    Li, Jiang; Liu, Jun-Ling; Zhou, Hong-Jun; Fu, Yao

    2016-06-08

    Iron-based heterogeneous catalysts, which were generally prepared by pyrolysis of iron complexes on supports at elevated temperature, were found to be capable of catalyzing the transfer hydrogenation of furfural (FF) to furfuryl alcohol (FFA). The effects of metal precursor, nitrogen precursor, pyrolysis temperature, and support on catalytic performance were examined thoroughly, and a comprehensive study of the reaction parameters was also performed. The highest selectivity of FFA reached 83.0 % with a FF conversion of 91.6 % under the optimal reaction condition. Catalyst characterization suggested that iron cations coordinated by pyridinic nitrogen functionalities were responsible for the enhanced catalytic activity. The iron catalyst could be recycled without significant loss of catalytic activity for five runs, and the destruction of the nitrogen-iron species, the presence of crystallized Fe2 O3 phase, and the pore structure change were the main reasons for catalyst deactivation. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Catalytic solar thermochemical processing for enhance heat transfer and emission-free production of hydrogen

    OpenAIRE

    Ibrik, Karim; Al-Meer, Mariam; Ozalp, Nesrin

    2012-01-01

    Solar thermochemical processing offers production of many commodities via reduced or completely eliminated emission footprint. Although solar reactor design and flow configuration play key role in process efficiency, use of right catalyst further enhances the overall efficiency. Our research efforts to explain the physical phenomenon behind the increase of the overall efficiency via catalyst addition showed that there is a direct effect on the heat transfer which in turn effects methane decom...

  16. Field-controlled electron transfer and reaction kinetics of the biological catalytic system of microperoxidase-11 and hydrogen peroxide

    Directory of Open Access Journals (Sweden)

    Yongki Choi

    2011-12-01

    Full Text Available Controlled reaction kinetics of the bio-catalytic system of microperoxidase-11 and hydrogen peroxide has been achieved using an electrostatic technique. The technique allowed independent control of 1 the thermodynamics of the system using electrochemical setup and 2 the quantum mechanical tunneling at the interface between microperoxidase-11 and the working electrode by applying a gating voltage to the electrode. The cathodic currents of electrodes immobilized with microperoxidase-11 showed a dependence on the gating voltage in the presence of hydrogen peroxide, indicating a controllable reduction reaction. The measured kinetic parameters of the bio-catalytic reduction showed nonlinear dependences on the gating voltage as the result of modified interfacial electron tunnel due to the field induced at the microperoxidase-11-electrode interface. Our results indicate that the kinetics of the reduction of hydrogen peroxide can be controlled by a gating voltage and illustrate the operation of a field-effect bio-catalytic transistor, whose current-generating mechanism is the conversion of hydrogen peroxide to water with the current being controlled by the gating voltage.

  17. Hydrogen peroxide catalytic decomposition

    Science.gov (United States)

    Parrish, Clyde F. (Inventor)

    2010-01-01

    Nitric oxide in a gaseous stream is converted to nitrogen dioxide using oxidizing species generated through the use of concentrated hydrogen peroxide fed as a monopropellant into a catalyzed thruster assembly. The hydrogen peroxide is preferably stored at stable concentration levels, i.e., approximately 50%-70% by volume, and may be increased in concentration in a continuous process preceding decomposition in the thruster assembly. The exhaust of the thruster assembly, rich in hydroxyl and/or hydroperoxy radicals, may be fed into a stream containing oxidizable components, such as nitric oxide, to facilitate their oxidation.

  18. Activation of the C-H bond: catalytic hydroxylation of hydrocarbons by new cobaltic alkylperoxydic complexes; selective and catalytic cycloalkane dehydrogenation in presence of uranium for hydrogen transfer

    International Nuclear Information System (INIS)

    Brazi, E.

    1987-01-01

    The aim of the thesis is to improve efficiency and selectivity of chemical reactions for alkane transformations. In the first part decomposition of hydroperoxides and hydrocarbon hydroxylation by cobalt complexes is studied. In the second part cycloalkanes are dehydrogenated into aromatics with a Pt catalyst, trapping hydrogen by uranium. Uranium hydride UH 3 can yield very pure hydrogen at reasonable temperature [fr

  19. Iron piano-stool complexes containing NHC ligands outfitted with pendent arms: synthesis, characterization, and screening for catalytic transfer hydrogenation

    Science.gov (United States)

    Parthapratim Das; Thomas Elder; William W. Brennessel; Stephen C. Chmely

    2016-01-01

    Catalysis is a fundamental technology that is widely used in the food, petrochemical, pharmaceutical, and agricultural sectors to produce chemical products on an industrial scale. Well-defined molecular organometallic species are a cornerstone of catalytic methodology, and the activity and selectivity of these complexes can be modulated by judicious choice of metal and...

  20. Catalytic transfer hydrogenation for stabilization of bio-oil oxygenates: reduction of p-cresol and furfural over bimetallic Ni-Cu catalysts using isopropanol

    Science.gov (United States)

    Transfer hydrogenation and hydrodeoxygenation of model bio-oil compounds (p-cresol and furfural) and bio-oils derived from biomass via traditional pyrolysis and tail-gas reactive pyrolysis (TGRP) were conducted. Mild batch reaction conditions were employed, using isopropanol as a hydrogen donor over...

  1. Hydrogen transfer reaction of cyclohexanone with 2-propanol ...

    Indian Academy of Sciences (India)

    Unknown

    Addition of ceria into zinc oxide was found to increase the catalytic activity for hydrogen transfer reaction. The catalytic activity also depended on the method of preparation. Citrate process results in uniformly dispersed mixed oxide with higher catalytic activity. Keywords. Cyclohexanone; ceria; ZnO; diffuse reflectance; EPR.

  2. THEORETICAL STUDY OF CATALYTIC HYDROGENATION OF ...

    African Journals Online (AJOL)

    Preferred Customer

    Catalytic hydrotreating process is a technique of purification of the crude oil with the aim of the improvement of the quality and the stability of fuels and lubricants. This is performed by the destruction of heterocyclic compounds and by the saturation of unsaturated hydrocarbons under the effect of the hydrogen pressure in ...

  3. Self-Ignition Behavior of Propane-Air Mixtures with Hydrogen Addition in Catalytic Micro-Channels Coupling Reduced-Order Kinetic Model and Heat Transfer

    OpenAIRE

    Junjie Chen

    2016-01-01

    Hydrogen-assisted self-ignition of propane-air mixtures under ambient condition were carried out in platinum-coated micro-channels, using a two-dimensional model with reduced-order reaction schemes, heat conduction in the solid walls, convection and surface radiation heat transfer. The self-ignition behavior of the hydrogen-propane mixed fuel is compared for the case of heated feed is analyzed. Simulations indicate that hydrogen can successfully cause self-ignition of propane-air mixtures in ...

  4. Single step synthesis of gold-amino acid composite, with the evidence of the catalytic hydrogen atom transfer (HAT) reaction, for the electrochemical recognition of Serotonin

    Science.gov (United States)

    Choudhary, Meenakshi; Siwal, Samarjeet; Nandi, Debkumar; Mallick, Kaushik

    2016-03-01

    A composite architecture of amino acid and gold nanoparticles has been synthesized using a generic route of 'in-situ polymerization and composite formation (IPCF)' [1,2]. The formation mechanism of the composite has been supported by a model hydrogen atom (H•≡H++e-) transfer (HAT) type of reaction which belongs to the proton coupled electron transfer (PCET) mechanism. The 'gold-amino acid composite' was used as a catalyst for the electrochemical recognition of Serotonin.

  5. Intramolecular Energy Transfer, Charge Transfer & Hydrogen Bond

    Indian Academy of Sciences (India)

    Ultrafast Dynamics of Chemical Reactions in Condensed Phase: Intramolecular Energy Transfer, Charge Transfer & Hydrogen Bond. Dipak K. Palit Radaition & Photochemistry Division Bhabha Atomic Research Centre Mumbai 400 085, India.

  6. Advanced Catalytic Hydrogenation Retrofit Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Reinaldo M. Machado

    2002-08-15

    Industrial hydrogenation is often performed using a slurry catalyst in large stirred-tank reactors. These systems are inherently problematic in a number of areas, including industrial hygiene, process safety, environmental contamination, waste production, process operability and productivity. This program proposed the development of a practical replacement for the slurry catalysts using a novel fixed-bed monolith catalyst reactor, which could be retrofitted onto an existing stirred-tank reactor and would mitigate many of the minitations and problems associated with slurry catalysts. The full retrofit monolith system, consisting of a recirculation pump, gas/liquid ejector and monolith catalyst, is described as a monolith loop reactor or MLR. The MLR technology can reduce waste and increase raw material efficiency, which reduces the overall energy required to produce specialty and fine chemicals.

  7. Make the most of catalytic hydrogenations

    Energy Technology Data Exchange (ETDEWEB)

    Landert, J.P.; Scubla, T. [Biazzi S.A., Chailly-Montreux (Switzerland)

    1995-03-01

    Liquid-phase catalytic hydrogenation is one of the most useful and versatile reactions available for organic synthesis. Because it is environmentally clean, it has replaced other reduction processes, such as the Bechamp reaction, and zinc and sulfide reductions. Moreover, the economics are favorable, provided that raw materials free of catalyst poisons are used. The hydrogenation reaction is very selective with appropriate catalysts and can often be carried out without a solvent. Applications include reduction of unsaturated carbon compounds to saturated derivatives (for example, in vegetable-oil processing), carbonyl compounds to alcohols (such as sorbitol), and nitrocompounds to amines. the reactions are usually run in batch reactors to rapidly reach complete conversion and allow quick change-over of products. The paper describes the basics of hydrogenation; steering clear of process hazards; scale-up and optimization; and system design in practice.

  8. Catalytic hydrogen recombination for nuclear containments

    International Nuclear Information System (INIS)

    Koroll, G.W.; Lau, D.W.P.; Dewit, W.A.; Graham, W.R.C.

    1994-01-01

    Catalytic recombiners appear to be a credible option for hydrogen mitigation in nuclear containments. The passive operation, versatility and ease of back fitting are appealing for existing stations and new designs. Recently, a generation of wet-proofed catalyst materials have been developed at AECL which are highly specific to H 2 -O 2 , are active at ambient temperatures and are being evaluated for containment applications. Two types of catalytic recombiners were evaluated for hydrogen removal in containments based on the AECL catalyst. The first is a catalytic combustor for application in existing air streams such as provided by fans or ventilation systems. The second is an autocatalytic recombiner which uses the enthalpy of reaction to produce natural convective flow over the catalyst elements. Intermediate-scale results obtained in 6 m 3 and 10 m 3 spherical and cylindrical vessels are given to demonstrate self-starting limits, operating limits, removal capacity, scaling parameters, flow resistance, mixing behaviour in the vicinity of an operating recombiner and sensitivity to poisoning, fouling and radiation. (author). 13 refs., 10 figs

  9. Catalytic glycerol steam reforming for hydrogen production

    International Nuclear Information System (INIS)

    Dan, Monica; Mihet, Maria; Lazar, Mihaela D.

    2015-01-01

    Hydrogen production from glycerol by steam reforming combine two major advantages: (i) using glycerol as raw material add value to this by product of bio-diesel production which is obtained in large quantities around the world and have a very limited utilization now, and (ii) by implication of water molecules in the reaction the efficiency of hydrogen generation is increased as each mol of glycerol produces 7 mol of H 2 . In this work we present the results obtained in the process of steam reforming of glycerol on Ni/Al 2 O 3 . The catalyst was prepared by wet impregnation method and characterized through different methods: N 2 adsorption-desorption, XRD, TPR. The catalytic study was performed in a stainless steel tubular reactor at atmospheric pressure by varying the reaction conditions: steam/carbon ratio (1-9), gas flow (35 ml/min -133 ml/min), temperature (450-650°C). The gaseous fraction of the reaction products contain: H 2 , CH 4 , CO, CO 2 . The optimum reaction conditions as resulted from this study are: temperature 550°C, Gly:H 2 O ratio 9:1 and Ar flow 133 ml/min. In these conditions the glycerol conversion to gaseous products was 43% and the hydrogen yield was 30%

  10. Microchannel Reactor System for Catalytic Hydrogenation

    Energy Technology Data Exchange (ETDEWEB)

    Adeniyi Lawal; Woo Lee; Ron Besser; Donald Kientzler; Luke Achenie

    2010-12-22

    We successfully demonstrated a novel process intensification concept enabled by the development of microchannel reactors, for energy efficient catalytic hydrogenation reactions at moderate temperature, and pressure, and low solvent levels. We designed, fabricated, evaluated, and optimized a laboratory-scale microchannel reactor system for hydrogenation of onitroanisole and a proprietary BMS molecule. In the second phase of the program, as a prelude to full-scale commercialization, we designed and developed a fully-automated skid-mounted multichannel microreactor pilot plant system for multiphase reactions. The system is capable of processing 1 – 10 kg/h of liquid substrate, and an industrially relevant immiscible liquid-liquid was successfully demonstrated on the system. Our microreactor-based pilot plant is one-of-akind. We anticipate that this process intensification concept, if successfully demonstrated, will provide a paradigm-changing basis for replacing existing energy inefficient, cost ineffective, environmentally detrimental slurry semi-batch reactor-based manufacturing practiced in the pharmaceutical and fine chemicals industries.

  11. Intramolecular Energy Transfer, Charge Transfer & Hydrogen Bond

    Indian Academy of Sciences (India)

    Ultrafast Dynamics of Chemical Reactions in Condensed Phase: Intramolecular Energy Transfer, Charge Transfer & Hydrogen Bond · PowerPoint Presentation · Slide 3 · Slide 4 · Slide 5 · Slide 6 · Slide 7 · Slide 8 · Slide 9 · Slide 10 · Slide 11 · Slide 12 · Slide 13 · Slide 14 · Slide 15 · Slide 16 · Slide 17 · Slide 18 · Slide 19.

  12. Catalytic activity of noble metals promoting hydrogen uptake

    NARCIS (Netherlands)

    Borgschulte, A.; Westerwaal, R.J.; Rector, J.H.; Schreuders, H.; Dam, B.; Griessen, R.P.

    2006-01-01

    The engineering of pure and metal alloy catalysts for hydrogen absorption is needed to improve the kinetics of hydrogen-related devices. We introduce a new route to search for alloys that can yield superior catalytic behavior for hydrogen absorption, using an optical technique to measure the

  13. Cobaloxime-based photo-catalytic devices for hydrogen production

    Energy Technology Data Exchange (ETDEWEB)

    Fihri, A.; Artero, V.; Razavet, M.; Baffert, C.; Fontecave, M. [CEA Grenoble, DSV, iRTSV, Lab Chim et Biol Metaux, CNRS, UMR 5249, Univ Grenoble 1, F-38054 Grenoble 9 (France); Leibl, W. [CEA, DSV, iBiTecS, Lab Photocatalyse et Biohydrogene, CNRS, URA 2096, Gif Sur Yvette (France)

    2008-07-01

    In this paper is described the synthesis and activity of a series of novel hetero-dinuclear ruthenium-cobaloxime photo-catalysts able to achieve the photochemical production of hydrogen with the highest turnover numbers so far reported for such devices. First of all, substituting cobalt for rare and expensive platinum, palladium, or rhodium metals in photo-catalysts is a first step toward economically viable hydrogen production. Cobaloximes appear to be good candidates for H{sub 2}-evolving catalysts, and they may provide a good basis for the design of photo-catalysts that function in pure water as both the solvent and the sustainable proton source. Secondly, a molecular connection between the sensitizer and the H{sub 2}-evolving catalyst seems to provide advantages regarding the photo-catalytic activity. Structural modifications of this connection should allow a better tuning of the electron transfer between the light-harvesting unit and the catalytic center and thus an increase of the efficiency of the system. (O.M.)

  14. Catalytic partial oxidation of methanol and ethanol for hydrogen generation.

    Science.gov (United States)

    Hohn, Keith L; Lin, Yu-Chuan

    2009-01-01

    Hydrogen-powered fuel cell vehicles feature high energy efficiency and minor environmental impact. Liquid fuels are ideal hydrogen carriers, which can catalytically be converted into syngas or hydrogen to power vehicles. Among the potential liquid fuels, alcohols have several advantages. The hydrogen/carbon ratio is higher than that of other liquid hydrocarbons or oxygenates, especially in the case of methanol. In addition, alcohols can be derived from renewable biomass resources. Catalytic partial oxidation of methanol or ethanol offers immense potential for onboard hydrogen generation due to its rapid reaction rate and exothermic nature. These benefits stimulate a burgeoning research community in catalyst design, reaction engineering, and mechanistic investigation. The purpose of this Minireview is to provide insight into syngas and hydrogen production from methanol and ethanol partial oxidation, particularly highlighting catalytic chemistry.

  15. Hydrogen transfer reaction on rare earth oxides

    International Nuclear Information System (INIS)

    Minachev, Kh.M.; Atal'yan, O.K.; Markov, M.A.

    1978-01-01

    The ketone reduction by alcohols is studied on a large group of rare earth oxides. The reactions of octanol-2 with cyclohexan one, n. butanol with dipropyl ketone and acetone have been chosen for a model. It has been shown that La,Nd,Sm,Gd,Dy,Er and Y oxides are active in the reactions of hydrogen transfer from n. butanol to dipropyl ketone and acetone and from octanol-2 to cyclohexanone the last reaction being the most selective. The comparative reactivity of ketones-acceptors of hydrogen at their interaction with n. butanol is in conformity with the values of their normal oxidative potentials. By addition of ketone to n. butanol the general degree of catalytic transformation of the latter increases and the selectivity in ketonization ratio decreases. It has been established that catalyst activity increases with the temperature rise

  16. Method for low temperature catalytic production of hydrogen

    Science.gov (United States)

    Mahajan, Devinder

    2003-07-22

    The invention provides a process for the catalytic production of a hydrogen feed by exposing a hydrogen feed to a catalyst which promotes a base-catalyzed water-gas-shift reaction in a liquid phase. The hydrogen feed can be provided by any process known in the art of making hydrogen gas. It is preferably provided by a process that can produce a hydrogen feed for use in proton exchange membrane fuel cells. The step of exposing the hydrogen feed takes place preferably from about 80.degree. C. to about 150.degree. C.

  17. Formation of C–C Bonds via Iridium-Catalyzed Hydrogenation and Transfer Hydrogenation

    Science.gov (United States)

    Bower, John F.; Krische, Michael J.

    2011-01-01

    The formation of C–C bonds via catalytic hydrogenation and transfer hydrogenation enables carbonyl and imine addition in the absence of stoichiometric organometallic reagents. In this review, iridium-catalyzed C–C bond-forming hydrogenations and transfer hydrogenations are surveyed. These processes encompass selective, atom-economic methods for the vinylation and allylation of carbonyl compounds and imines. Notably, under transfer hydrogenation conditions, alcohol dehydrogenation drives reductive generation of organoiridium nucleophiles, enabling carbonyl addition from the aldehyde or alcohol oxidation level. In the latter case, hydrogen exchange between alcohols and π-unsaturated reactants generates electrophile–nucleophile pairs en route to products of hydro-hydroxyalkylation, representing a direct method for the functionalization of carbinol C–H bonds. PMID:21822399

  18. How absorbed hydrogen affects the catalytic activity of transition metals.

    Science.gov (United States)

    Aleksandrov, Hristiyan A; Kozlov, Sergey M; Schauermann, Swetlana; Vayssilov, Georgi N; Neyman, Konstantin M

    2014-12-01

    Heterogeneous catalysis is commonly governed by surface active sites. Yet, areas just below the surface can also influence catalytic activity, for instance, when fragmentation products of catalytic feeds penetrate into catalysts. In particular, H absorbed below the surface is required for certain hydrogenation reactions on metals. Herein, we show that a sufficient concentration of subsurface hydrogen, H(sub) , may either significantly increase or decrease the bond energy and the reactivity of the adsorbed hydrogen, H(ad) , depending on the metal. We predict a representative reaction, ethyl hydrogenation, to speed up on Pd and Pt, but to slow down on Ni and Rh in the presence of H(sub) , especially on metal nanoparticles. The identified effects of subsurface H on surface reactivity are indispensable for an atomistic understanding of hydrogenation processes on transition metals and interactions of hydrogen with metals in general. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Short hydrogen bonds in the catalytic mechanism of serine proteases

    Directory of Open Access Journals (Sweden)

    VLADIMIR LESKOVAC

    2008-04-01

    Full Text Available The survey of crystallographic data from the Protein Data Bank for 37 structures of trypsin and other serine proteases at a resolution of 0.78–1.28 Å revealed the presence of hydrogen bonds in the active site of the enzymes, which are formed between the catalytic histidine and aspartate residues and are on average 2.7 Å long. This is the typical bond length for normal hydrogen bonds. The geometric properties of the hydrogen bonds in the active site indicate that the H atom is not centered between the heteroatoms of the catalytic histidine and aspartate residues in the active site. Taken together, these findings exclude the possibility that short “low-barrier” hydrogen bonds are formed in the ground state structure of the active sites examined in this work. Some time ago, it was suggested by Cleland that the “low-barrier hydrogen bond” hypothesis is operative in the catalytic mechanism of serine proteases, and requires the presence of short hydrogen bonds around 2.4 Å long in the active site, with the H atom centered between the catalytic heteroatoms. The conclusions drawn from this work do not exclude the validity of the “low-barrier hydrogen bond” hypothesis at all, but they merely do not support it in this particular case, with this particular class of enzymes.

  20. Hydrogen production via catalytic processing of renewable feedstocks

    International Nuclear Information System (INIS)

    Nazim Muradov; Franklyn Smith; Ali T-Raissi

    2006-01-01

    Landfill gas (LFG) and biogas can potentially become important feedstocks for renewable hydrogen production. The objectives of this work were: (1) to develop a catalytic process for direct reforming of CH 4 -CO 2 gaseous mixture mimicking LFG, (2) perform thermodynamic analysis of the reforming process using AspenPlus chemical process simulator, (3) determine operational conditions for auto-thermal (or thermo-neutral) reforming of a model CH 4 -CO 2 feedstock, and (4) fabricate and test a bench-scale hydrogen production unit. Experimental data obtained from catalytic reformation of the CH 4 -CO 2 and CH 4 -CO 2 -O 2 gaseous mixtures using Ni-catalyst were in a good agreement with the simulation results. It was demonstrated that catalytic reforming of LFG-mimicking gas produced hydrogen with the purity of 99.9 vol.%. (authors)

  1. Hydrogen assisted catalytic biomass pyrolysis for green fuels

    DEFF Research Database (Denmark)

    Stummann, Magnus Zingler; Høj, Martin; Gabrielsen, Jostein

    2017-01-01

    due to coking of the catalyst is an inhibitive problem for this technology. The objective of the present work is to produce oxygen free gasoline and diesel from biomass by hydrogen assisted catalytic fast pyrolysis. Fast pyrolysis of beech wood has been performed in high-pressure hydrogen atmosphere......Fast pyrolysis of biomass is a well-known technology for producing bio-oil, however in order to use the oil as transportation fuel the oxygen content must be decreased from approximately 30 wt.% to below 1 wt.%. This can be achieved by catalytic hydrodeoxygenation (HDO). Unfortunately, deactivation...

  2. Hydrogen assisted catalytic biomass pyrolysis for green fuels

    DEFF Research Database (Denmark)

    Stummann, Magnus Zingler; Høj, Martin; Schandel, Christian Bækhøj

    Fast pyrolysis of biomass is a well-known technology for producing bio-oil, however in order to use the oil as transportation fuel the oxygen content must be decreased from approximately 30 wt.% to below 1 wt.%. This can be achieved by catalytic hydrodeoxygenation (HDO). Unfortunately, deactivation...... due to coking of the catalyst is an inhibitive problem for this technology. The objective of the present work is to produce oxygen free gasoline and diesel from biomass by hydrogen assisted catalytic fast pyrolysis. Fast pyrolysis of beech wood has been performed in high-pressure hydrogen atmosphere...

  3. Catalytic gasification of automotive shredder residues with hydrogen generation

    Science.gov (United States)

    Lin, Kuen-Song; Chowdhury, Sujan; Wang, Ze-Ping

    Hydrogen is a clean and new energy carrier to generate power through the Proton exchange membrane fuel cell (PEMFC) system. Hydrogen can be effectively turned out through the catalytic gasification of organic material such as automotive shredder residues (ASR). The main objective of this manuscript is to present an analysis of the catalytic gasification of ASR for the generation of high-purity hydrogen in a lab-scale fixed-bed downdraft gasifier using 15 wt.% NiO/Al 2O 3 catalysts at 760-900 K. In the catalytic gasification process, reduction of Ni(II) catalyst into Ni(0) has been confirmed through XANES spectra and consequently EXAFS data shows that the central Ni atoms have Ni-O and Ni-Ni bonds with bond distances of 2.03 ± 0.05 and 2.46 ± 0.05 Å, respectively. ASR is partially oxidized and ultimately converts into hydrogen rich syngas (CO and H 2) and increases of the reaction temperature are favored the generation of hydrogen with decomposition of the CO. As well, approximately 220 kg h -1 of ASR would be catalytically gasified at 760-900 K and 46.2 atm with the reactor volume 0.27 m 3 to obtain approximately 3.42 × 10 5 kcal h -1 of thermal energy during over 87% syngas generation with the generation of 100 kW electric powers.

  4. Converting sugars to sugar alcohols by aqueous phase catalytic hydrogenation

    Science.gov (United States)

    Elliott, Douglas C [Richland, WA; Werpy, Todd A [West Richland, WA; Wang, Yong [Richland, WA; Frye, Jr., John G.

    2003-05-27

    The present invention provides a method of converting sugars to their corresponding sugar alcohols by catalytic hydrogenation in the aqueous phase. It has been found that surprisingly superior results can be obtained by utilizing a relatively low temperature (less than 120.degree. C.), selected hydrogenation conditions, and a hydrothermally stable catalyst. These results include excellent sugar conversion to the desired sugar alcohol, in combination with long life under hydrothermal conditions.

  5. High rates of catalytic hydrogen combustion with air over coated ...

    Indian Academy of Sciences (India)

    BHASKAR DEVU MUKRI

    2017-08-02

    Aug 2, 2017 ... High rates of catalytic hydrogen combustion with air over. Ti0.97Pd0.03O2−δ coated cordierite monolith. BHASKAR DEVU MUKRI. ∗ and M S HEGDE. Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012, India. E-mail: bhaskardm@gmail.com. MS received 9 May 2017; ...

  6. Theoretical study of catalytic hydrogenation of oxirane and its methyl ...

    African Journals Online (AJOL)

    C3H6O) is its methyl derivative. Theoretical studies on catalytic hydrogenation of both compounds, in presence of aluminium chloride (AlCl3) catalyst, are carried out. The products of reactions are ethanol and propan-1-ol from oxirane and ...

  7. Review of literature on catalytic recombination of hydrogen--oxygen

    International Nuclear Information System (INIS)

    Homsy, R.V.; Glatron, C.A.

    1968-01-01

    The results are reported of a literature search for information concerning the heterogeneous, gas phase, catalytic hydrogen-oxygen recombination. Laboratory scale experiments to test the performance of specific metal oxide catalysts under conditions simulating the atmosphere within a nuclear reactor containment vessel following a loss-of-coolant blowdown accident are suggested

  8. THEORETICAL STUDY OF CATALYTIC HYDROGENATION OF ...

    African Journals Online (AJOL)

    Preferred Customer

    136.427 kJ) and reaction energy (-0.107 Hartree or -270.34 kJ). This negative value of reaction energy indicates that the reaction is exoenergetic. Figures 4 and 5 show respectively the variations of some interatomic distances, calculated by HF method, and those of Mulliken atomic charges during the hydrogenation process ...

  9. Catalytic Hydrogenation of Acetone to Isopropanol: An Environmentally Benign Approach

    Directory of Open Access Journals (Sweden)

    Ateeq Rahman

    2011-01-01

    Full Text Available The catalytic hydrogenation of acetone is an important area of catalytic process to produce fine chemicals. Hydrogenation of acetone has important applications for heat pumps, fuel cells or in fulfilling the sizeable demand for the production of 2-propanol. Catalytic vapour phase hydrogenation of acetone has gained attention over the decades with variety of homogeneous catalysts notably Iridium, Rh, Ru complexes and heterogeneous catalysts comprising of Raney Nickel, Raney Sponge, Ni/Al2O3, Ni/SiO2, or Co-Al2O3, Pd, Rh, Ru, Re, or Fe/Al2O3 supported on SiO2 or MgO and even CoMgAl, NiMg Al layered double hydroxide, Cu metal, CuO, Cu2O. Nano catalysts are developed for actone reduction Ni maleate, cobalt oxide prepared in organic solvents. Author present a review on acetone hydrogenation under different conditions with various homogeneous and heterogeneous catalysts studied so far in literature and new strategies to develop economic and environmentally benign approach. ©2010 BCREC UNDIP. All rights reserved(Received: 16th June 2010, Revised: 18th October 2010; Accepted: 25th October 2010[How to Cite:Ateeq Rahman. (2010. Catalytic Hydrogenation of Acetone to Isopropanol: An Environmentally Benign Approach. Bulletin of Chemical Reaction Engineering and Catalysis, 5(2: 113-126. doi:10.9767/bcrec.5.2.798.113-126][DOI: http://dx.doi.org/10.9767/bcrec.5.2.798.113-126 || or local:  http://ejournal.undip.ac.id/index.php/bcrec/article/view/798

  10. CATALYTIC HYDROGENATION AND OXIDATION OF BIOMASS-DERIVED LEVULINIC ACID

    OpenAIRE

    Yan Gong; Lu Lin; Zhipei Yan

    2011-01-01

    Levulinic acid (LA), 4-oxo-pentanoic acid, is a new platform chemical with various potential uses. In this paper, catalytic hydrogenation and oxidation of levulinic acid were studied. It was shown from experiments that levulinic acid can be hydrogenated to γ-valerolactone (GVL) over transition metal catalysts and oxidative-decarboxylated to 2-butanone (methyl-ethyl-ketone, MEK) and methyl-vinyl-ketone (MVK) by cupric oxide (CuO), cupric oxide/cerium oxide (CuO/CeO2), cupric oxide/ alumina (Cu...

  11. Hydrogen mitigation by catalytic recombiners and ignition during severe accidents

    International Nuclear Information System (INIS)

    Rohde, J.; Chakraborty, A.K.; Heitsch, M.; Klein-Hebling, W.

    1994-01-01

    A large amount of hydrogen is expected to be released within a large dry containment of a PWR shortly after the onset of a severe accident, leading to core melting. According to local gas concentrations, turbulence and structural configurations within the containment, the released hydrogen can reach the boundary of deflagration or under certain conditions cause local detonations threatening the containment integrity. During the last few years, several concepts of mitigation have been developed to limit the hydrogen concentrations and extensive efforts have been given to investigate the use of catalytic recombiners as well as the use of deliberate ignition within the contemplated framework of a 'Dual-concept'. Although the recent recommendation of the German Reactor Safety Commission (RSK) foresees the sole application of catalytic recombiners to remove hydrogen during severe accident, a review is planned within two years for the partial and directed additional application of early ignitions or post dilution of the atmosphere of the compartments in conjunction with the recombiners installed. This presentation will review the results of large number of experiments performed both in small scale and large scale to qualify the recombiners. It is also the subject of the presentation to address the requirements for proper and secure functioning of the catalyzers under the existing boundary conditions during the severe accidents. These requirements ask for measures, starting from the proper selection of catalysts, multi purposed catalytic devices and their protection against contamination during the standby condition as well as against aerosol deposition and surface poisoning during the propagation of an accident. A short review of the results to large scale experiments with the combined application of catalytic devices and igniters form also a part of this presentation. (author). 8 refs., 2 tabs., 7 figs

  12. Investigation of simultaneous tritium and deuterium transfer in a catalytic isotope exchange column for water detritiation

    International Nuclear Information System (INIS)

    Cristescu, I.; Tamm, U.; Cristescu, Ioana-R.; Glugla, M.; Caldwell-Nichols, C.J.

    2002-01-01

    A catalytic isotope exchange facility for water detritiation is operated at the Tritium Laboratory Karlsruhe (TLK) in order to investigate the simultaneous transfer of tritium and deuterium between various molecular hydrogen isotopes and deuteriated/tritiated water. Four catalyst-packing combinations from different manufacturers (SCK-CEN Belgium, Mendeleev University Russia, Institute of Cryogenics and Isotopic Technologies (ICIT) Romania-TLK, Showa Eng. Japan) are currently being tested. Experiments have been performed to determine the height equivalent of theoretical plate (HETP) and the mass transfer coefficients during deuterium, tritium or simultaneous deuterium and tritium exchange between deuteriated and tritiated water and gaseous hydrogen isotopes. In the simultaneously tritium and deuterium transfer experiments, both the transfer of tritium and deuterium from liquid to gas and the transfer of tritium from liquid to gas and deuterium in the opposite direction from gas to liquid was investigated

  13. Coal hydrogenation and deashing in ebullated bed catalytic reactor

    Science.gov (United States)

    Huibers, Derk T. A.; Johanson, Edwin S.

    1983-01-01

    An improved process for hydrogenation of coal containing ash with agglomeration and removal of ash from an ebullated bed catalytic reactor to produce deashed hydrocarbon liquid and gas products. In the process, a flowable coal-oil slurry is reacted with hydrogen in an ebullated catalyst bed reaction zone at elevated temperature and pressure conditions. The upward velocity and viscosity of the reactor liquid are controlled so that a substantial portion of the ash released from the coal is agglomerated to form larger particles in the upper portion of the reactor above the catalyst bed, from which the agglomerated ash is separately withdrawn along with adhering reaction zone liquid. The resulting hydrogenated hydrocarbon effluent material product is phase separated to remove vapor fractions, after which any ash remaining in the liquid fraction can be removed to produce substantially ash-free coal-derived liquid products.

  14. DWPF CATALYTIC HYDROGEN GENERATION PROGRAM - REVIEW OF CURRENT STATUS

    Energy Technology Data Exchange (ETDEWEB)

    Koopman, D.

    2009-07-10

    Significant progress has been made in the past two years in improving the understanding of acid consumption and catalytic hydrogen generation during the Defense Waste Processing Facility (DWPF) processing of waste sludges in the Sludge Receipt and Adjustment Tank (SRAT) and Slurry Mix Evaporator (SME). This report reviews issues listed in prior internal reviews, describes progress with respect to the recommendations made by the December 2006 external review panel, and presents a summary of the current understanding of catalytic hydrogen generation in the DWPF Chemical Process Cell (CPC). Noble metals, such as Pd, Rh, and Ru, are historically known catalysts for the conversion of formic acid into hydrogen and carbon dioxide. Rh, Ru, and Pd are present in the DWPF SRAT feed as by-products of thermal neutron fission of {sup 235}U in the original waste. Rhodium appears to become most active for hydrogen as the nitrite ion concentration becomes low (within a factor of ten of the Rh concentration). Prior to hydrogen generation, Rh is definitely active for nitrite destruction to N{sub 2}O and potentially active for nitrite to NO formation. These reactions are all consistent with the presence of a nitro-Rh complex catalyst, although definite proof for the existence of this complex during Savannah River Site (SRS) waste processing does not exist. Ruthenium does not appear to become active for hydrogen generation until nitrite destruction is nearly complete (perhaps less nitrite than Ru in the system). Catalytic activity of Ru during nitrite destruction is significantly lower than that of either Rh or Pd. Ru appears to start activating as Rh is deactivating from its maximum catalytic activity for hydrogen generation. The slow activation of the Ru, as inferred from the slow rate of increase in hydrogen generation that occurs after initiation, may imply that some species (perhaps Ru itself) has some bound nitrite on it. Ru, rather than Rh, is primarily responsible for the

  15. Reactivity and Catalytic Activity of Hydrogen Atom Chemisorbed Silver Clusters.

    Science.gov (United States)

    Manzoor, Dar; Pal, Sourav

    2015-06-18

    Metal clusters of silver have attracted recent interest of researchers as a result of their potential in different catalytic applications and low cost. However, due to the completely filled d orbital and very high first ionization potential of the silver atom, the silver-based catalysts interact very weakly with the reacting molecules. In the current work, density functional theory calculations were carried out to investigate the effect of hydrogen atom chemisorption on the reactivity and catalytic properties of inert silver clusters. Our results affirm that the hydrogen atom chemisorption leads to enhancement in the binding energy of the adsorbed O2 molecule on the inert silver clusters. The increase in the binding energy is also characterized by the decrease in the Ag-O and increase in the O-O bond lengths in the case of the AgnH silver clusters. Pertinent to the increase in the O-O bond length, a significant red shift in the O-O stretching frequency is also noted in the case of the AgnH silver clusters. Moreover, the hydrogen atom chemisorbed silver clusters show low reaction barriers and high heat of formation of the final products for the environmentally important CO oxidation reaction as compared to the parent catalytically inactive clusters. The obtained results were compared with those of the corresponding gold and hydrogen atom chemisorbed gold clusters obtained at the same level of theory. It is expected the current computational study will provide key insights for future advances in the design of efficient nanosilver-based catalysts through the adsorption of a small atom or a ligand.

  16. Heat-transfer data for hydrogen

    Science.gov (United States)

    Mc Carthy, J. R.; Miller, W. S.; Okuda, A. S.; Seader, J. D.

    1970-01-01

    Information is given regarding experimental heat-transfer data compiled for the turbulent flow of hydrogen within straight, electrically heated, round cross section tubes. Tube materials, test conditions, parameters studied, and generalized conclusions are presented.

  17. Simple and rapid hydrogenation of p-nitrophenol with aqueous formic acid in catalytic flow reactors

    Science.gov (United States)

    Kawasaki, Shin-ichiro; Suzuki, Akira

    2013-01-01

    Summary The inner surface of a metallic tube (i.d. 0.5 mm) was coated with a palladium (Pd)-based thin metallic layer by flow electroless plating. Simultaneous plating of Pd and silver (Ag) from their electroless-plating solution produced a mixed distributed bimetallic layer. Preferential acid leaching of Ag from the Pd–Ag layer produced a porous Pd surface. Hydrogenation of p-nitrophenol was examined in the presence of formic acid simply by passing the reaction solution through the catalytic tubular reactors. p-Aminophenol was the sole product of hydrogenation. No side reaction occurred. Reaction conversion with respect to p-nitrophenol was dependent on the catalyst layer type, the temperature, pH, amount of formic acid, and the residence time. A porous and oxidized Pd (PdO) surface gave the best reaction conversion among the catalytic reactors examined. p-Nitrophenol was converted quantitatively to p-aminophenol within 15 s of residence time in the porous PdO reactor at 40 °C. Evolution of carbon dioxide (CO2) was observed during the reaction, although hydrogen (H2) was not found in the gas phase. Dehydrogenation of formic acid did not occur to any practical degree in the absence of p-nitrophenol. Consequently, the nitro group was reduced via hydrogen transfer from formic acid to p-nitrophenol and not by hydrogen generated by dehydrogenation of formic acid. PMID:23843908

  18. Simple and rapid hydrogenation of p-nitrophenol with aqueous formic acid in catalytic flow reactors

    Directory of Open Access Journals (Sweden)

    Rahat Javaid

    2013-06-01

    Full Text Available The inner surface of a metallic tube (i.d. 0.5 mm was coated with a palladium (Pd-based thin metallic layer by flow electroless plating. Simultaneous plating of Pd and silver (Ag from their electroless-plating solution produced a mixed distributed bimetallic layer. Preferential acid leaching of Ag from the Pd–Ag layer produced a porous Pd surface. Hydrogenation of p-nitrophenol was examined in the presence of formic acid simply by passing the reaction solution through the catalytic tubular reactors. p-Aminophenol was the sole product of hydrogenation. No side reaction occurred. Reaction conversion with respect to p-nitrophenol was dependent on the catalyst layer type, the temperature, pH, amount of formic acid, and the residence time. A porous and oxidized Pd (PdO surface gave the best reaction conversion among the catalytic reactors examined. p-Nitrophenol was converted quantitatively to p-aminophenol within 15 s of residence time in the porous PdO reactor at 40 °C. Evolution of carbon dioxide (CO2 was observed during the reaction, although hydrogen (H2 was not found in the gas phase. Dehydrogenation of formic acid did not occur to any practical degree in the absence of p-nitrophenol. Consequently, the nitro group was reduced via hydrogen transfer from formic acid to p-nitrophenol and not by hydrogen generated by dehydrogenation of formic acid.

  19. Catalytic hydrogen peroxide decomposition La1-xSrxCoO3-δ perovskite oxides

    NARCIS (Netherlands)

    Dam, T.V.A.; Olthuis, Wouter; Bergveld, Piet; van den Berg, Albert

    2005-01-01

    Lanthanide perovskite oxides are mentioned as material for hydrogen peroxide sensor because they can catalytically decompose hydrogen peroxide in an aqueous medium. The catalytic properties of these perovskite oxides to hydrogen peroxide are suggested due to their oxygen vacancies influenced by the

  20. Catalytic Dehydrogenation of Ethane in Hydrogen Membrane Reactor

    Science.gov (United States)

    Galuszka, Jan; Giddings, Terry; Clelland, Ian

    The effect of a hydrogen permselective membrane (H-membrane) reactor on catalytic dehydrogenation of ethane was assessed using a fixed bed conventional reactor and a double tubular H-membrane reactor. A 5.0wt.% Cr2O3/γ-Al2O3 catalyst prepared by incipient wetness impregnation of a γ-Al2O3 (BET surface area = 50 m2/g) support was used at 555°C and 600°C. Although about 40% of H2 produced during dehydrogenation of ethane in the membrane reactor passed through the membrane, only moderate enhancement in ethane conversion was observed. The slow processes on the catalyst surface are thought to counterbalance the positive effect of membrane assisted hydrogen removal. Also, decreased selectivity to ethylene due to enhanced carbon formation in the membrane reactor led to faster deactivation of the catalyst. A strategy for commercialization of catalytic dehydrogenation of ethane through the development of a better hydrogen membrane might require a reevaluation.

  1. Catalytic steam reforming of ethanol for hydrogen production: Brief status

    Directory of Open Access Journals (Sweden)

    Bineli Aulus R.R.

    2016-01-01

    Full Text Available Hydrogen represents a promising fuel since it is considered as a cleanest energy carrier and also because during its combustion only water is emitted. It can be produced from different kinds of renewable feedstocks, such as ethanol, in this sense hydrogen could be treated as biofuel. Three chemical reactions can be used to achieve this purpose: the steam reforming (SR, the partial oxidation (POX and the autothermal reforming (ATR. In this study, the catalysts implemented in steam reforming of ethanol were reviewed. A wide variety of elements can be used as catalysts for this reaction, such as base metals (Ni, Cu and Co or noble metals (Rh, Pt and Ru usually deposited on a support material that increases surface area and improves catalytic function. The use of Rh, Ni and Pt supported or promoted with CeO2, and/or La2O3 shows excellent performance in ethanol SR catalytic process. The ratio of water to ethanol, reaction temperatures, catalysts loadings, selectivity and activity are also discussed as they are extremely important for high hydrogen yields.

  2. Benzothiazoline: versatile hydrogen donor for organocatalytic transfer hydrogenation.

    Science.gov (United States)

    Zhu, Chen; Saito, Kodai; Yamanaka, Masahiro; Akiyama, Takahiko

    2015-02-17

    CONSPECTUS: The asymmetric reduction of ketimines is an important method for the preparation of amines in optically pure form. Inspired by the biological system using NAD(P)H, Hantzsch ester has been extensively employed as a hydrogen donor in combination with chiral phosphoric acid for the transfer hydrogenation of ketimines to furnish amines with high to excellent enantioselectivities. We focused on 2-substituted benzothiazoline as a hydrogen donor in the phosphoric acid catalyzed transfer hydrogenation reaction of ketimines for the following reasons: (1) benzothiazoline is readily prepared just by mixing 2-aminobenzenethiol and aldehyde, (2) both reactivity (hydrogen donating ability) and enantioselectivity would be controlled by tuning the 2-substituent of benzothiazoline, and (3) benzothiazoline can be stored in a refrigerator under inert atmosphere without conceivable decomposition. Both the 2-position of benzothiazoline and the 3,3'-position of phosphoric acid are tunable in order to achieve excellent enantioselectivity. Benzothiazoline proved to be useful hydrogen donor in combination with chiral phosphoric acid for the transfer hydrogenation reaction of ketimine derivatives to afford the corresponding amines with high to excellent enantioselectivities by tuning the 2-substituent of benzothiazoline. Ketimines derived from acetophenone, propiophenone, α-keto ester, trifluoromethyl ketone, and difluoromethyl ketone derivatives proved to be suitable substrates. Benzothiazoline could be generated in situ starting from 2-aminobenzenethiol and aromatic aldehyde in the presence of ketimine and chiral phosphoric acid and successfully worked in the sequential transfer hydrogenation reaction. The reductive amination of dialkyl ketones also proceeded with high enantioselectivities. Use of 2-deuterated benzothiazoline led to the formation of α-deuterated amines with excellent enantioselectivities. The kinetic isotope effect (kH/kC = 3.8) was observed in the

  3. Recent advances in catalytic hydrogenation of carbon dioxide.

    Science.gov (United States)

    Wang, Wei; Wang, Shengping; Ma, Xinbin; Gong, Jinlong

    2011-07-01

    Owing to the increasing emissions of carbon dioxide (CO(2)), human life and the ecological environment have been affected by global warming and climate changes. To mitigate the concentration of CO(2) in the atmosphere various strategies have been implemented such as separation, storage, and utilization of CO(2). Although it has been explored for many years, hydrogenation reaction, an important representative among chemical conversions of CO(2), offers challenging opportunities for sustainable development in energy and the environment. Indeed, the hydrogenation of CO(2) not only reduces the increasing CO(2) buildup but also produces fuels and chemicals. In this critical review we discuss recent developments in this area, with emphases on catalytic reactivity, reactor innovation, and reaction mechanism. We also provide an overview regarding the challenges and opportunities for future research in the field (319 references).

  4. Catalytic Hydrogenation Reaction of Naringin-Chalcone. Study of the Electrochemical Reaction

    Directory of Open Access Journals (Sweden)

    B. A. López de Mishima

    2000-03-01

    Full Text Available The electrocatalytic hydrogenation reaction of naringin derivated chalcone is studied. The reaction is carried out with different catalysts in order to compare with the classic catalytic hydrogenation.

  5. Air-water transfer of hydrogen sulfide

    DEFF Research Database (Denmark)

    Yongsiri, C.; Vollertsen, J.; Rasmussen, M. R.

    2004-01-01

    The emissions process of hydrogen sulfide was studied to quantify air–water transfer of hydrogen sulfide in sewer networks. Hydrogen sulfide transfer across the air–water interface was investigated at different turbulence levels (expressed in terms of the Froude number) and pH using batch...... experiments. By means of the overall mass–transfer coefficient (KLa), the transfer coefficient of hydrogen sulfide (KLaH2S), referring to total sulfide, was correlated to that of oxygen (KLaO2) (i.e., the reaeration coefficient). Results demonstrate that both turbulence and pH in the water phase play...... a significant role for KLaH2S. An exponential expression is a suitable representation for the relationship between KLaH2S and the Froude number at all pH values studied (4.5 to 8.0). Because of the dissociation of hydrogen sulfide, KLaH2S increased with decreasing pH at a constant turbulence level. Relative...

  6. Sulfonamides as new hydrogen atom transfer (HAT) catalysts for photoredox allylic and benzylic C-H arylations.

    Science.gov (United States)

    Tanaka, Hirotaka; Sakai, Kentaro; Kawamura, Atsushi; Oisaki, Kounosuke; Kanai, Motomu

    2018-02-02

    A catalytic amount of a sterically and electronically tuned diarylsulfonamide promoted allylic and benzylic C-H arylations in cooperation with a visible light photoredox catalyst. This is the first example of the catalytic use of a sulfonamidyl radical to promote the hydrogen atom transfer process.

  7. Dynamic\tmodelling of catalytic three-phase reactors for hydrogenation and oxidation processes

    Directory of Open Access Journals (Sweden)

    Salmi T.

    2000-01-01

    Full Text Available The dynamic modelling principles for typical catalytic three-phase reactors, batch autoclaves and fixed (trickle beds were described. The models consist of balance equations for the catalyst particles as well as for the bulk phases of gas and liquid. Rate equations, transport models and mass balances were coupled to generalized heterogeneous models which were solved with respect to time and space with algorithms suitable for stiff differential equations. The aspects of numerical solution strategies were discussed and the procedure was illustrated with three case studies: hydrogenation of aromatics, hydrogenation of aldehydes and oxidation of ferrosulphate. The case studies revealed the importance of mass transfer resistance inside the catalyst pallets as well as the dynamics of the different phases being present in the reactor. Reliable three-phase reactor simulation and scale-up should be based on dynamic heterogeneous models.

  8. Electrocatalytic hydrogenation of organic molecules on conductive new catalytic material

    Energy Technology Data Exchange (ETDEWEB)

    Tountian, D. [Louis Pasteur Univ., Strasbourg (France). Laboratoire d' Electrochimie et de Chimie Physique du Corps Solide; Sherbrooke Univ., Sherbrooke, PQ (Canada). Dept. de Chimie, Centre de Recherche en Electrochimie et Electrocatalyse; Brisach-Wittmeyer, A.; Menard, H. [Sherbrooke Univ., Sherbrooke, PQ (Canada). Dept. de Chimie, Centre de Recherche en Electrochimie et Electrocatalyse; Nkeng, P.; Poillerat, G. [Louis Pasteur Univ., Strasbourg (France). Laboratoire d' Electrochimie et de Chimie Physique du Corps Solide

    2008-07-01

    Electrocatalytic hydrogenation (ECH) of organic molecules is a process where chemisorbed hydrogen is produced by electroreduction of water which reacts with the species in bulk. Greater emphasis is being placed on improving the nature of the building material of the electrodes in order to increase ECH efficiency. The effectiveness of the ECH is known to be linked to the nature of electrode materials used and their adsorption properties. This work presented the effect of conductive support material on ECH. The conductive catalysts were obtained from tin dioxide which is chemically stable. Palladium was the catalytic metal used in this study. The production of chemisorbed hydrogen was shown to depend on the quantity of metallic nanoaggregates in electrical contact with the reticulated vitreous carbon use as electrode. The conductive support, F-doped tin dioxide, was obtained by the sol-gel method. The electrocatalysts were characterized by different methods as resistivity measurements, linear sweep voltammetry, XRD, SEM, TGA/DSC, and FTIR analysis. The effects of temperature and time of calcination were also investigated. The study showed that the F-doped SnO2 electrocatalyst appeared to increase the rate of phenol electrohydrogenation. It was concluded that the improved electrocatalytic activity of Pd/F-doped SnO2 can be attributed to the simultaneous polarization of all the metallic Pd nanoaggregates present on the surface as well as in the pores of the matrix by contact with RVC. This results in a better production of chemisorbed atomic hydrogen with a large number of adlienation points. 9 refs., 3 figs.

  9. Noble metal ionic sites for catalytic hydrogen combustion: spectroscopic insights.

    Science.gov (United States)

    Deshpande, Parag A; Madras, Giridhar

    2011-01-14

    A catalytic hydrogen combustion reaction was carried out over noble metal catalysts substituted in ZrO(2) and TiO(2) in ionic form. The catalysts were synthesized by the solution combustion technique. The compounds showed high activity and CO tolerance for the reaction. The activity of Pd and Pt ion substituted TiO(2) was comparable and was higher than Pd and Pt ion substituted ZrO(2). The mechanisms of the reaction over the two supports were proposed by making use of the X-ray photoelectron spectroscopy and FT infrared spectroscopic observations. The reaction over ZrO(2) supported catalysts was proposed to take place by the utilization of the surface hydroxyl groups while the reaction over TiO(2) supported catalysts was hypothesized to be a hybrid mechanism utilizing surface hydroxyl groups and the lattice oxygen.

  10. Hydrogen production from biomass tar by catalytic steam reforming

    International Nuclear Information System (INIS)

    Yoon, Sang Jun; Choi, Young-Chan; Lee, Jae-Goo

    2010-01-01

    The catalytic steam reforming of model biomass tar, toluene being a major component, was performed at various conditions of temperature, steam injection rate, catalyst size, and space time. Two kinds of nickel-based commercial catalyst, the Katalco 46-3Q and the Katalco 46-6Q, were evaluated and compared with dolomite catalyst. Production of hydrogen generally increased with reaction temperature, steam injection rate and space time and decreased with catalyst size. In particular, zirconia-promoted nickel-based catalyst, Katalco 46-6Q, showed a higher tar conversion efficiency and shows 100% conversion even relatively lower temperature conditions of 600 deg. C. Apparent activation energy was estimated to 94 and 57 kJ/mol for dolomite and nickel-based catalyst respectively.

  11. Modelling of the aerosol deposition in a hydrogen catalytic recombiner

    International Nuclear Information System (INIS)

    Vendel, J.; Studer, E.; Zavaleta, P.; Hadida, Ph.

    1997-01-01

    Catalytic recombiners are used to remove the hydrogen released in case of a severe accident in a nuclear power plant, so as to reduce the risk of deflagration or detonation. H 2 PAR experiments are carried out to precise the behaviour of recombiners in term of poisoning by aerosols. Firstly, some calculations have been done with the Trio-EF code to assess the structure of convection loops in the experimental tent. We note that when the recombiner is active, it may have a strong influence on the flow inside the tent and may even interact with an other heat source such as a furnace. In the second part, we study the deposition of aerosols on catalytic plates for a given recombiner, when it is active or passive. We list the different mechanisms and quantify them by introducing the deposition velocity. In fact, thermophoresis appears to be the main mechanism, compared to brownian diffusion or difrusiophoresis, which governs aerosols deposition. It favours deposition on > plates and acts against it for > plates. (author)

  12. Organocatalytic asymmetric transfer hydrogenation of imines

    NARCIS (Netherlands)

    de Vries, Johannes G.; Mrsic, Natasa; Mršić, Nataša

    2011-01-01

    The asymmetric organocatalytic transfer hydrogenation of imines can be accomplished in good yields with high enantioselectivities through the use of BINOL-derived phosphoric acids as catalysts and Hantzsch esters or benzothiazoles as the hydride source. The same method can also be applied to the

  13. Hydrogen/deuterium transfer in coal liquefaction

    International Nuclear Information System (INIS)

    Cronauer, D.C.; McNeil, R.I.; Young, D.C.; Ruberto, R.G.

    1982-01-01

    Reactions have been made with deuterium-labelled solvent (d 4 - and d 12 -tetralin) and both Powhatan bituminous (Pittsburgh Seam) coal and model compounds under coal liquefaction conditions to study hydrogen transfer mechanisms. Powhatan coal liquefies quickly. Hydrogen transfer from the solvent to the reaction products continues throughout the heating period (up to 60 min). Significant hydrogen/deuterium exchange occurs and this strongly affects the distribution of deuterium in the products and also affects the extent of conversion as measured by the amount of THF-insoluble material. Increased deuteration of the solvent leads to decreased conversion. This exchange is enhanced by heavy aromatic species and by the presence of mineral matter and unconverted coal solids. (author)

  14. Experimental studies on catalytic hydrogen recombiners for light water reactors

    International Nuclear Information System (INIS)

    Drinovac, P.

    2006-01-01

    In the course of core melt accidents in nuclear power plants a large amount of hydrogen can be produced and form an explosive or even detonative gas mixture with aerial oxygen in the reactor building. In the containment atmosphere of pressurized water reactors hydrogen combines a phlogistically with the oxygen present to form water vapor even at room temperature. In the past, experimental work conducted at various facilities has contributed little or nothing to an understanding of the operating principles of catalytic recombiners. Hence, the purpose of the present study was to conduct detailed investigations on a section of a recombiner essentially in order to deepen the understanding of reaction kinetics and heat transport processes. The results of the experiments presented in this dissertation form a large data base of measurements which provides an insight into the processes taking place in recombiners. The reaction-kinetic interpretation of the measured data confirms and deepens the diffusion theory - proposed in an earlier study. Thus it is now possible to validate detailed numeric models representing the processes in recombiners. Consequently the present study serves to broaden and corroborate competence in this significant area of reactor technology. In addition, the empirical knowledge thus gained may be used for a critical reassessment of previous numeric model calculations. (orig.)

  15. Catalytic hydrogenation of CO2 over Pt- and Ni-doped graphene: A comparative DFT study.

    Science.gov (United States)

    Esrafili, Mehdi D; Sharifi, Fahimeh; Dinparast, Leila

    2017-10-01

    Today, the global greenhouse effect of carbon dioxide (CO 2 ) is a serious environmental problem. Therefore, developing efficient methods for CO 2 capturing and conversion to valuable chemicals is a great challenge. The aim of the present study is to investigate the catalytic activity of Pt- or Ni-doped graphene for the hydrogenation of CO 2 by a hydrogen molecule. To gain a deeper insight into the catalytic mechanism of this reaction, the reliable density functional theory calculations are performed. The adsorption energies, geometric parameters, reaction barriers, and thermodynamic properties are calculated using the M06-2X density functional. Two reaction mechanisms are proposed for the hydrogenation of CO 2 . In the bimolecular mechanism, the reaction proceeds in two steps, initiating by the co-adsorption of CO 2 and H 2 molecules over the surface, followed by the formation of a OCOH intermediate by the transfer of H atom of H 2 toward O atom of CO 2 . In the next step, formic acid is produced as a favorable product with the formation of CH bond. In our proposed termolecular mechanism, however, H 2 molecule is directly activated by the two pre-adsorbed CO 2 molecules. The predicted activation energy for the formation of the OCOH intermediate in the bimolecular mechanism is 20.8 and 47.9kcalmol -1 over Pt- and Ni-doped graphene, respectively. On the contrary, the formation of the first formic acid in the termolecular mechanism is found as the rate-determining step over these surfaces, with an activation energy of 28.8 and 45.5kcal/mol. Our findings demonstrate that compared to the Ni-doped graphene, the Pt-doped surface has a relatively higher catalytic activity towards the CO 2 reduction. These theoretical results could be useful in practical applications for removal and transformation of CO 2 to value-added chemical products. Copyright © 2017 Elsevier Inc. All rights reserved.

  16. Bimetallic promotion of cooperative hydrogen transfer and heteroatom removal in coal liquefaction

    Energy Technology Data Exchange (ETDEWEB)

    Eisch, J.J.

    1991-10-01

    The ultimate objective of this research is to uncover new catalytic processes for the liquefaction of coal and for upgrading coal-derived fuels by removing undesirable organosulfur, organonitrogen and organooxygen constituents. Basic to both the liquefaction of coal and the purification of coal liquids is the transfer of hydrogen from such sources as dihydrogen, metal hydrides or partially reduced aromatic hydrocarbons to the extensive aromatic rings in coal itself or to aromatic sulfides, amines or ethers. Accordingly, this study is exploring how such crucial hydrogen-transfer processes might be catalyzed by soluble, low-valent transition metal complexes and/or Lewis acids under moderate conditions of temperature and pressure. By learning the mechanism whereby H{sub 2}, metal hydrides or partially hydrogenated aromatics do transfer hydrogen to model aromatic compounds, with the aid of homogeneous, bimetallic catalysts, we hope to identify new methods for producing superior fuels from coal.

  17. Surface spintronics enhanced photo-catalytic hydrogen evolution: Mechanisms, strategies, challenges and future

    Science.gov (United States)

    Zhang, Wenyan; Gao, Wei; Zhang, Xuqiang; Li, Zhen; Lu, Gongxuan

    2018-03-01

    Hydrogen is a green energy carrier with high enthalpy and zero environmental pollution emission characteristics. Photocatalytic hydrogen evolution (HER) is a sustainable and promising way to generate hydrogen. Despite of great achievements in photocatalytic HER research, its efficiency is still limited due to undesirable electron transfer loss, high HER over-potential and low stability of some photocatalysts, which lead to their unsatisfied performance in HER and anti-photocorrosion properties. In recent years, many spintronics works have shown their enhancing effects on photo-catalytic HER. For example, it was reported that spin polarized photo-electrons could result in higher photocurrents and HER turn-over frequency (up to 200%) in photocatalytic system. Two strategies have been developed for electron spin polarizing, which resort to heavy atom effect and magnetic induction respectively. Both theoretical and experimental studies show that controlling spin state of OHrad radicals in photocatalytic reaction can not only decrease OER over-potential (even to 0 eV) of water splitting, but improve stability and charge lifetime of photocatalysts. A convenient strategy have been developed for aligning spin state of OHrad by utilizing chiral molecules to spin filter photo-electrons. By chiral-induced spin filtering, electron polarization can approach to 74%, which is significantly larger than some traditional transition metal devices. Those achievements demonstrate bright future of spintronics in enhancing photocatalytic HER, nevertheless, there is little work systematically reviewing and analysis this topic. This review focuses on recent achievements of spintronics in photocatalytic HER study, and systematically summarizes the related mechanisms and important strategies proposed. Besides, the challenges and developing trends of spintronics enhanced photo-catalytic HER research are discussed, expecting to comprehend and explore such interdisciplinary research in

  18. Direct catalytic hydrothermal liquefaction of spirulina to biofuels with hydrogen

    Science.gov (United States)

    Zeng, Qin; Liao, Hansheng; Zhou, Shiqin; Li, Qiuping; Wang, Lu; Yu, Zhihao; Jing, Li

    2018-01-01

    We report herein on acquiring biofuels from direct catalytic hydrothermal liquefaction of spirulina. The component of bio-oil from direct catalytic hydrothermal liquefaction was similar to that from two independent processes (including liquefaction and upgrading of biocrude). However, one step process has higher carbon recovery, due to the less loss of carbons. It was demonstrated that the yield and HHV of bio-oil from direct catalytic algae with hydrothermal condition is higher than that from two independent processes.

  19. Asymmetric transfer hydrogenation by synthetic catalysts in cancer cells

    Science.gov (United States)

    Coverdale, James P. C.; Romero-Canelón, Isolda; Sanchez-Cano, Carlos; Clarkson, Guy J.; Habtemariam, Abraha; Wills, Martin; Sadler, Peter J.

    2018-03-01

    Catalytic anticancer metallodrugs active at low doses could minimize side-effects, introduce novel mechanisms of action that combat resistance and widen the spectrum of anticancer-drug activity. Here we use highly stable chiral half-sandwich organometallic Os(II) arene sulfonyl diamine complexes, [Os(arene)(TsDPEN)] (TsDPEN, N-(p-toluenesulfonyl)-1,2-diphenylethylenediamine), to achieve a highly enantioselective reduction of pyruvate, a key intermediate in metabolic pathways. Reduction is shown both in aqueous model systems and in human cancer cells, with non-toxic concentrations of sodium formate used as a hydride source. The catalytic mechanism generates selectivity towards ovarian cancer cells versus non-cancerous fibroblasts (both ovarian and lung), which are commonly used as models of healthy proliferating cells. The formate precursor N-formylmethionine was explored as an alternative to formate in PC3 prostate cancer cells, which are known to overexpress a deformylase enzyme. Transfer-hydrogenation catalysts that generate reductive stress in cancer cells offer a new approach to cancer therapy.

  20. Catalytic alkylation of remote C-H bonds enabled by proton-coupled electron transfer.

    Science.gov (United States)

    Choi, Gilbert J; Zhu, Qilei; Miller, David C; Gu, Carol J; Knowles, Robert R

    2016-11-10

    Despite advances in hydrogen atom transfer (HAT) catalysis, there are currently no molecular HAT catalysts that are capable of homolysing the strong nitrogen-hydrogen (N-H) bonds of N-alkyl amides. The motivation to develop amide homolysis protocols stems from the utility of the resultant amidyl radicals, which are involved in various synthetically useful transformations, including olefin amination and directed carbon-hydrogen (C-H) bond functionalization. In the latter process-a subset of the classical Hofmann-Löffler-Freytag reaction-amidyl radicals remove hydrogen atoms from unactivated aliphatic C-H bonds. Although powerful, these transformations typically require oxidative N-prefunctionalization of the amide starting materials to achieve efficient amidyl generation. Moreover, because these N-activating groups are often incorporated into the final products, these methods are generally not amenable to the direct construction of carbon-carbon (C-C) bonds. Here we report an approach that overcomes these limitations by homolysing the N-H bonds of N-alkyl amides via proton-coupled electron transfer. In this protocol, an excited-state iridium photocatalyst and a weak phosphate base cooperatively serve to remove both a proton and an electron from an amide substrate in a concerted elementary step. The resultant amidyl radical intermediates are shown to promote subsequent C-H abstraction and radical alkylation steps. This C-H alkylation represents a catalytic variant of the Hofmann-Löffler-Freytag reaction, using simple, unfunctionalized amides to direct the formation of new C-C bonds. Given the prevalence of amides in pharmaceuticals and natural products, we anticipate that this method will simplify the synthesis and structural elaboration of amine-containing targets. Moreover, this study demonstrates that concerted proton-coupled electron transfer can enable homolytic activation of common organic functional groups that are energetically inaccessible using

  1. A study on the effect of heat transfer boundary condition within the catalytic recombiner and its implication on nuclear safety

    International Nuclear Information System (INIS)

    Agrawal, Nilesh; Ali, Seik Mansoor; Balasubramaniyan, V.

    2015-01-01

    A Passive Auto-catalytic recombiners (PAR) consists of an array of vertical catalyst coated plates. Hydrogen rich gas mixture flows between the plates and reacts exothermically leading to high plate temperature. This can lead to PAR induced deflagration which is a major safety concern. PAR induced deflagration can be avoided if heat transfer from the plates of a PAR is enhanced. Thus, numerical studies are carried out for reactive flow of gas mixture within one vertical channel with heat transfer controlled boundaries. Four different heat transfer boundary conditions, namely, adiabatic, natural convection, forced convection and pool boiling heat transfer boundary conditions are considered. The results show that the catalyst surface temperature can be controlled using enhanced heat transfer from the surface. Pool boiling heat transfer is especially very effective in controlling the temperature and ensuring high rate of reactions. The results may be useful in designing better PARs in the future. (author)

  2. Ruthenium(II) pincer complexes with oxazoline arms for efficient transfer hydrogenation reactions

    KAUST Repository

    Chen, Tao

    2012-08-01

    Well-defined P NN CN pincer ruthenium complexes bearing both strong phosphine and weak oxazoline donors were developed. These easily accessible complexes exhibit significantly better catalytic activity in transfer hydrogenation of ketones compared to their PN 3P analogs. These reactions proceed under mild and base-free conditions via protonation- deprotonation of the \\'NH\\' group in the aromatization-dearomatization process. © 2012 Elsevier Ltd. All rights reserved.

  3. Model for the simulation of catalytic isotope exchange between tritiated water and hydrogen/deuterium gas

    International Nuclear Information System (INIS)

    Cristescu, Ioana R.; Cristescu, I.; Bornea, Anisia; Penzhorn, R.-D.; Tamm, U.

    2001-01-01

    The objectives of the models presented in this paper are to simulate the deuterium enrichment performances of several catalytic exchange columns under test at the Tritium Laboratory in Karlsruhe (TLK). The models and the corresponding software are presently being verified by experiments aimed to provide the data required for the design of large isotopic exchange columns such as needed for the recovery of tritium from waste water generated during the operation of the tritium facilities of fusion machines. In the ongoing TLK experiments the transfer of deuterium takes place in a counter current isotopic exchange column. Pre-heated water is fed into the column from the top and deuterated hydrogen from the bottom. Condensed water vapor and deuterium-depleted hydrogen are removed from the top and deuterium enriched water from the bottom and analyzed by standard procedures. To describe the performance of the separation process two approaches were considered: a graphical approach (classical) that uses the operating line and equilibrium curve for the process and an analytical approach that solves the transport equations characterizing the isotopic exchange process. (authors)

  4. Effect of urea deproteinization on catalytic hydrogenation of natural rubber latex

    Science.gov (United States)

    Cifriadi, A.; Chalid, M.; Puspitasari, S.

    2017-07-01

    Natural rubber is unsaturated biopolymer which has low resistance to heat, oxygen, and ozone. Chemical modification of natural rubber by catalytic hydrogenation can improve its oxidative property. In this study, the catalytic hydrogenation of natural rubber was investigated in latex phase after reduction of protein content with urea. Hydrogenation of deproteinized natural rubber latex was performed by using diimide which generated insitu from hydrazine hydrate/hydrogen peroxide and catalyst (boric acid, cupric sulfate and cupric acetate) at 70°C for 5 h. The hydrogenation system was stabilized with sodium dodecyl sulphate. The hydrogenation of deproteinized natural rubber (HDPNR) was confirmed by FTIR analysis. The result indicated that cupric sulphate was extremely active catalyst which was showed by the elimination of C=C transmittance bands at 1660 cm-1 on HDPNR spectra and highest degree of hydrogenation. Furthermore, urea deproteinization increased possibility of side reactions during catalytic hydrogenation as seen on the reduction of gel content compared to undeproteinized natural rubber.

  5. The mechanism of the catalytic oxidation of hydrogen sulfide: II. Kinetics and mechanism of hydrogen sulfide oxidation catalyzed by sulfur

    NARCIS (Netherlands)

    Steijns, M.; Derks, F.; Verloop, A.; Mars, P.

    1976-01-01

    The kinetics of the catalytic oxidation of hydrogen sulfide by molecular oxygen have been studied in the temperature range 20–250 °C. The primary reaction product is sulfur which may undergo further oxidation to SO2 at temperatures above 200 °C. From the kinetics of this autocatalytic reaction we

  6. Thermal and catalytic ASVAHL processes under hydrogen pressure for converting heavy crudes and conventional residues

    Energy Technology Data Exchange (ETDEWEB)

    Peries, J.P.; Quignard, A.; Farjon, C.; Laborde, M.

    This article describes the comparative performances of thermal ASVAHL processes (TERVAHL T, TERVAHL H, TERVAHL HC) and catalytic ASVAHL processes (HYVAHL F, HYVAHL C) for two types of processing: (1) degasolined Boscan crude (basis of studies for transportation feasibility), and (2) Safaniya vacuum residue (basis of studies for residue refining). The results reveal the importance of the amount of fixed hydrogen, which affects the conversion obtained and the quality of the residues. The introduction of a TERVAHL HC soluble catalyst or one in catalytic suspension (catalytic hydrovisbreaking) or the use of a supported catalyst (HYVAHL hydrotreatment) enhances the activation of hydrogen. The combination of cracking, polycondensation and hydrogen reactions together with the operating conditions (temperatures, residence time and pressure) are what will define the conversion limits for a given stability of residues.

  7. The ab initio study of the catalytic hydrogenation of the oxirene

    Directory of Open Access Journals (Sweden)

    J.B. Mensah

    2008-04-01

    Full Text Available The oxirene is an unsaturated heterocyclic molecule with one oxygen atom and two carbon atoms. Its hydrogenation has been performed on two catalytic site based on molybdenum disulfide (MoS2 and tungsten disulfide (WS2 of MoS3H3+ and WS3H3+ type, respectively. The calculations were carried out using the SCF and MP2 methods and B3LYP functional calculations. The results obtained showed that the hydrogenation of the oxirene is possible on these two kinds of catalytic sites on the one hand, and the reaction product is the acetaldehyde molecule, on the other hand. The reaction process study that led to the results showed that the catalytic hydrogenation of the oxirene is a dissociative process. On the basis of the variation of some parameters during the process, a mechanism of the reaction has been proposed.

  8. Continuous-flow processes for the catalytic partial hydrogenation reaction of alkynes

    Directory of Open Access Journals (Sweden)

    Carmen Moreno-Marrodan

    2017-04-01

    Full Text Available The catalytic partial hydrogenation of substituted alkynes to alkenes is a process of high importance in the manufacture of several market chemicals. The present paper shortly reviews the heterogeneous catalytic systems engineered for this reaction under continuous flow and in the liquid phase. The main contributions appeared in the literature from 1997 up to August 2016 are discussed in terms of reactor design. A comparison with batch and industrial processes is provided whenever possible.

  9. Continuous-flow processes for the catalytic partial hydrogenation reaction of alkynes

    Science.gov (United States)

    Moreno-Marrodan, Carmen; Liguori, Francesca

    2017-01-01

    The catalytic partial hydrogenation of substituted alkynes to alkenes is a process of high importance in the manufacture of several market chemicals. The present paper shortly reviews the heterogeneous catalytic systems engineered for this reaction under continuous flow and in the liquid phase. The main contributions appeared in the literature from 1997 up to August 2016 are discussed in terms of reactor design. A comparison with batch and industrial processes is provided whenever possible. PMID:28503209

  10. Capture and transfer of pions in hydrogenous materials

    International Nuclear Information System (INIS)

    Armstrong, D.S.

    1990-05-01

    Pionic hydrogen is a short-lived exotic hydrogen isotope in which a negative pion replaces the atomic electron. The formation and subsequent interactions of pionic hydrogen are discussed, with emphasis on the process of pion transfer. Recent results using the pion charge-exchange reaction (π - , π 0 ) obtained at TRIUMF are reviewed. (Author) (35 refs., 3 tabs., 9 figs.)

  11. Catalytic hydrogenation using complexes of base metals with tridentate ligands

    Energy Technology Data Exchange (ETDEWEB)

    Hanson, Susan K.; Zhang, Guoqi; Vasudevan, Kalyan V.

    2017-02-14

    Complexes of cobalt and nickel with tridentate ligand PNHP.sup.R are effective for hydrogenation of unsaturated compounds. Cobalt complex [(PNHP.sup.Cy)Co(CH.sub.2SiMe.sub.3)]BAr.sup.F.sub.4 (PNHP.sup.Cy=bis[2-(dicyclohexylphosphino)ethyl]amine, BAr.sup.F.sub.4=B(3,5-(CF.sub.3).sub.2C.sub.6H.sub.3).sub.4)) was prepared and used with hydrogen for hydrogenation of alkenes, aldehydes, ketones, and imines under mild conditions (25-60.degree. C., 1-4 atm H.sub.2). Nickel complex [(PNHP.sup.Cy)Ni(H)]BPh.sub.4 was used for hydrogenation of styrene and 1-octene under mild conditions. (PNP.sup.Cy)Ni(H) was used for hydrogenating alkenes.

  12. Catalytic hydrogenation using complexes of base metals with tridentate ligands

    Energy Technology Data Exchange (ETDEWEB)

    Vasudevan, Kalyan V.; Zhang, Guoqi; Hanson, Susan K.

    2016-09-06

    Complexes of cobalt and nickel with tridentate ligand PNHP.sup.R are effective for hydrogenation of unsaturated compounds. Cobalt complex [(PNHP.sup.Cy)Co(CH.sub.2SiMe.sub.3)]BAr.sup.F.sub.4 (PNHP.sup.Cy=bis[2-(dicyclohexylphosphino)ethyl]amine, BAr.sup.F.sub.4=B(3,5-(CF.sub.3).sub.2C.sub.6H.sub.3).sub.4)) was prepared and used with hydrogen for hydrogenation of alkenes, aldehydes, ketones, and imines under mild conditions (25-60.degree. C., 1-4 atm H.sub.2). Nickel complex [(PNHP.sup.Cy)Ni(H)]BPh.sub.4 was used for hydrogenation of styrene and 1-octene under mild conditions. (PNP.sup.Cy)Ni(H) was used for hydrogenating alkenes.

  13. Palladium-catalysed transfer hydrogenation of alkenes in the presence of zinc powder and various organic acids

    Directory of Open Access Journals (Sweden)

    I.B. Masesane

    2005-06-01

    Full Text Available Catalytic transfer hydrogenation using palladium(II chloride, zinc powder and various organic acids proved effective for the reduction of a variety of alkenes at ambient temperature and atmospheric pressure. The method was found to be convenient, economical and uses a stable nonpyrophoric catalyst.

  14. Catalytic dehydrogenation of isobutane in the presence of hydrogen over Cs-modified Ni2P supported on active carbon

    Science.gov (United States)

    Xu, Yanli; Sang, Huanxin; Wang, Kang; Wang, Xitao

    2014-10-01

    In this article, an environmentally friendly non-noble-metal class of Cs-Ni2P/active carbon (AC) catalyst was prepared and demonstrated to exhibit enhanced catalytic performance in isobutane dehydrogenation. The results of activity tests reveal that Ni/AC catalyst was highly active for isobutane cracking, which led to the formation of abundant methane and coke. After the introduction of phosphorus through impregnation with ammonium di-hydrogen phosphate and H2-temperature programmed reduction, undesired cracking reactions were effectively inhibited, and the selectivity to isobutene and stability of catalyst increased remarkably. The characterization results indicate that, after the addition of phosphorous, the improvement of dehydrogenation selectivity is ascribed to the partial positive charges carried on Ni surface in Ni2P particles, which decreases the strength of Nisbnd C bond between Ni and carbonium-ion intermediates and the possibility of excessive dehydrogenation. In addition, Cs-modified Ni2P/AC catalysts display much higher catalytic performance as compared to Ni2P/AC catalyst. Cs-Ni2P-6.5 catalyst has the highest catalytic performance, and the selectivity to isobutene higher than 93% can be obtained even after 4 h reaction. The enhancement in catalytic performance of the Cs-modified catalysts is mainly attributed to the function of Cs to improve the dispersion of Ni2P particles, transfer electron from Cs to Ni, and decrease acid site number and strength.

  15. Hydrogen production by aqueous phase catalytic reforming of glycerine

    International Nuclear Information System (INIS)

    Ozguer, Derya Oncel; Uysal, Bekir Zuehtue

    2011-01-01

    Hydrogen is believed to be the one of the main energy carriers in the near future. In this research glycerine, which is produced in large quantities as a by-product of biodiesel process, was converted to hydrogen aiming to contribute to clean energy initiative. Conversion of glycerol to hydrogen was achieved via aqueous-phase reforming (APR) with Pt/Al 2 O 3 catalyst. The experiments were carried out in an autoclave reactor and a continuous fixed-bed reactor. The effects of reaction temperature (160-280 o C), feed flow rate (0.05-0.5 mL/dak) and feed concentration (5-85 wt-% glycerine) on product distribution were investigated. Optimum temperature for hydrogen production with APR was determined as 230 o C. Maximum gas production rate was found at the feed flow rates around 0.1 mL/min. It was also found that hydrogen concentration in the gas product increased with decreasing glycerol concentration in the feed.

  16. Low temperature catalytic reforming of heptane to hydrogen and syngas

    Directory of Open Access Journals (Sweden)

    M.E.E. Abashar

    2016-09-01

    Full Text Available The production of hydrogen and syngas from heptane at a low temperature is studied in a circulating fast fluidized bed membrane reactor (CFFBMR. A thin film of palladium-based membrane is employed to the displacement of the thermodynamic equilibrium for high conversion and yield. A mathematical model is developed to simulate the reformer. A substantial improvement of the CFFBMR is achieved by implementing the thin hydrogen membrane. The results showed that almost complete conversion of heptane and 46.25% increase of exit hydrogen yield over the value without membrane are achieved. Also a wide range of the H2/CO ratio within the recommended industrial range is obtained. The phenomena of high spikes of maximum nature at the beginning of the CFFBMR are observed and explanation offered. The sensitivity analysis results have shown that the increase of the steam to carbon feed ratio can increase the exit hydrogen yield up to 108.29%. It was found that the increase of reaction side pressure at a high steam to carbon feed ratio can increase further the exit hydrogen yield by 49.36% at a shorter reactor length. Moreover, the increase of reaction side pressure has an important impact in a significant decrease of the carbon dioxide and this is a positive sign for clean environment.

  17. A simple iridicycle catalyst for efficient transfer hydrogenation of N-heterocycles in water.

    Science.gov (United States)

    Talwar, Dinesh; Li, Ho Yin; Durham, Emma; Xiao, Jianliang

    2015-03-27

    A cyclometalated iridium complex is shown to catalyse the transfer hydrogenation of various nitrogen heterocycles, including but not limited to quinolines, isoquinolines, indoles and pyridinium salts, in an aqueous solution of HCO2H/HCO2Na under mild conditions. The catalyst shows excellent functional-group compatibility and high turnover number (up to 7500), with catalyst loadings as low as 0.01 mol % being feasible. Mechanistic investigation of the quinoline reduction suggests that the transfer hydrogenation proceeds via both 1,2- and 1,4-addition pathways, with the catalytic turnover being limited by the step of hydride transfer. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Catalytic hydrogenation of carbon dioxide using Ir(III)-pincer complexes.

    Science.gov (United States)

    Tanaka, Ryo; Yamashita, Makoto; Nozaki, Kyoko

    2009-10-14

    Catalytic hydrogenation of carbon dioxide in aqueous potassium hydroxide was performed using a newly synthesized isopropyl-substituted PNP-pincer iridium trihydride complex as a catalyst. Potassium formate was obtained with turnover numbers up to 3,500,000 and a turnover frequency of 150,000 h(-1), both of which are the highest values reported to date.

  19. Hydrogen from catalytic reforming of biomass-derived hydrocarbons in liquid water.

    Science.gov (United States)

    Cortright, R D; Davda, R R; Dumesic, J A

    2002-08-29

    Concerns about the depletion of fossil fuel reserves and the pollution caused by continuously increasing energy demands make hydrogen an attractive alternative energy source. Hydrogen is currently derived from nonrenewable natural gas and petroleum, but could in principle be generated from renewable resources such as biomass or water. However, efficient hydrogen production from water remains difficult and technologies for generating hydrogen from biomass, such as enzymatic decomposition of sugars, steam-reforming of bio-oils and gasification, suffer from low hydrogen production rates and/or complex processing requirements. Here we demonstrate that hydrogen can be produced from sugars and alcohols at temperatures near 500 K in a single-reactor aqueous-phase reforming process using a platinum-based catalyst. We are able to convert glucose -- which makes up the major energy reserves in plants and animals -- to hydrogen and gaseous alkanes, with hydrogen constituting 50% of the products. We find that the selectivity for hydrogen production increases when we use molecules that are more reduced than sugars, with ethylene glycol and methanol being almost completely converted into hydrogen and carbon dioxide. These findings suggest that catalytic aqueous-phase reforming might prove useful for the generation of hydrogen-rich fuel gas from carbohydrates extracted from renewable biomass and biomass waste streams.

  20. Hydrogen from catalytic reforming of biomass-derived hydrocarbons in liquid water

    Science.gov (United States)

    Cortright, R. D.; Davda, R. R.; Dumesic, J. A.

    2002-08-01

    Concerns about the depletion of fossil fuel reserves and the pollution caused by continuously increasing energy demands make hydrogen an attractive alternative energy source. Hydrogen is currently derived from nonrenewable natural gas and petroleum, but could in principle be generated from renewable resources such as biomass or water. However, efficient hydrogen production from water remains difficult and technologies for generating hydrogen from biomass, such as enzymatic decomposition of sugars, steam-reforming of bio-oils and gasification, suffer from low hydrogen production rates and/or complex processing requirements. Here we demonstrate that hydrogen can be produced from sugars and alcohols at temperatures near 500K in a single-reactor aqueous-phase reforming process using a platinum-based catalyst. We are able to convert glucose-which makes up the major energy reserves in plants and animals-to hydrogen and gaseous alkanes, with hydrogen constituting 50% of the products. We find that the selectivity for hydrogen production increases when we use molecules that are more reduced than sugars, with ethylene glycol and methanol being almost completely converted into hydrogen and carbon dioxide. These findings suggest that catalytic aqueous-phase reforming might prove useful for the generation of hydrogen-rich fuel gas from carbohydrates extracted from renewable biomass and biomass waste streams.

  1. Tandem ring-closing metathesis/transfer hydrogenation: practical chemoselective hydrogenation of alkenes.

    Science.gov (United States)

    Connolly, Timothy; Wang, Zhongyu; Walker, Michael A; McDonald, Ivar M; Peese, Kevin M

    2014-09-05

    An operationally simple chemoselective transfer hydrogenation of alkenes using ruthenium metathesis catalysts is presented. Of great practicality, the transfer hydrogenation reagents can be added directly to a metathesis reaction and effect hydrogenation of the product alkene in a single pot at ambient temperature without the need to seal the vessel to prevent hydrogen gas escape. The reduction is applicable to a range of alkenes and can be performed in the presence of aryl halides and benzyl groups, a notable weakness of Pd-catalyzed hydrogenations. Scope and mechanistic considerations are presented.

  2. Mixed diphosphine/diamine ruthenium (II) isomers: Synthesis, structural characterization and catalytic hydrogenation of ketones

    Science.gov (United States)

    Nascimento, Rebecca D.; Silva, Andressa K.; Lião, Luciano M.; Deflon, Victor M.; Ueno, Leonardo T.; Dinelli, Luis R.; Bogado, André L.

    2018-01-01

    The complexes trans-[RuCl2(dppb)(cydn)] (1), trans-[RuCl2(dppb)(opda)] (2) and cis-[RuCl2(dppb)(cydn)] (3) were synthesized from [{RuCl2(dppb)}2-μ-(dppb)] {where: dppb = 1,4-bis(diphenylphosphino)butane; cydn = cis and trans (±) 1,2-diaminocyclohexane, and opda = o-phenylenediamine}. The complexes were characterized by nuclear magnetic resonance of phosphorus (31P{1H} NMR), cyclic voltammetry (CV), infrared and ultraviolet/visible spectra (IR and UV/vis) as well as elemental analyses (CHN). The X-ray structures of (1) and (3) were determined and they are presented here. DFT calculations and experimental data showed that the trans isomers are obtained as thermodynamic products while the cis isomers are kinetic products. This behavior is different than described in the literature for similar complexes, where the cis isomer is obtained from the trans isomer. Additionally, the catalytic activity of the complexes (1), (2) and (3) was investigated, as pre-catalysts, in the reduction of the acetophenone and 4-methylacetophenone by transfer-hydrogenation.

  3. Method of generating hydrogen by catalytic decomposition of water

    Science.gov (United States)

    Balachandran, Uthamalingam; Dorris, Stephen E.; Bose, Arun C.; Stiegel, Gary J.; Lee, Tae-Hyun

    2002-01-01

    A method for producing hydrogen includes providing a feed stream comprising water; contacting at least one proton conducting membrane adapted to interact with the feed stream; splitting the water into hydrogen and oxygen at a predetermined temperature; and separating the hydrogen from the oxygen. Preferably the proton conducting membrane comprises a proton conductor and a second phase material. Preferable proton conductors suitable for use in a proton conducting membrane include a lanthanide element, a Group VIA element and a Group IA or Group IIA element such as barium, strontium, or combinations of these elements. More preferred proton conductors include yttrium. Preferable second phase materials include platinum, palladium, nickel, cobalt, chromium, manganese, vanadium, silver, gold, copper, rhodium, ruthenium, niobium, zirconium, tantalum, and combinations of these. More preferably second phase materials suitable for use in a proton conducting membrane include nickel, palladium, and combinations of these. The method for generating hydrogen is preferably preformed in the range between about 600.degree. C. and 1,700.degree. C.

  4. Hydrogen Production From catalytic reforming of greenhouse gases ...

    African Journals Online (AJOL)

    Hydrogen production from CO2 reforming of methane over 20wt%.Co/Nd2O3 has been investigated in a fixed bed stainless steel reactor. The 20wt%.Co/Nd2O3 catalyst was synthesized using wet impregnation method and characterized for thermal stability, textural property, crystallinity, morphology and nature of chemical ...

  5. Catalytic Metal Free Production of Large Cage Structure Carbon Particles: A Candidate for Hydrogen Storage

    Science.gov (United States)

    Kimura, Yuki; Nuth, Joseph A., III; Ferguson, Frank T.

    2005-01-01

    We will demonstrate that carbon particles consisting of large cages can be produced without catalytic metal. The carbon particles were produced in CO gas as well as by introduction of 5% methane gas into the CO gas. The gas-produced carbon particles were able to absorb approximately 16.2 wt% of hydrogen. This value is 2.5 times higher than the 6.5 wt% goal for the vehicular hydrogen storage proposed by the Department of Energy in the USA. Therefore, we believe that this carbon particle is an excellent candidate for hydrogen storage for fuel cells.

  6. Low temperature catalytic combustion of natural gas - hydrogen - air mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Newson, E.; Roth, F. von; Hottinger, P.; Truong, T.B. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    The low temperature catalytic combustion of natural gas - air mixtures would allow the development of no-NO{sub x} burners for heating and power applications. Using commercially available catalysts, the room temperature ignition of methane-propane-air mixtures has been shown in laboratory reactors with combustion efficiencies over 95% and maximum temperatures less than 700{sup o}C. After a 500 hour stability test, severe deactivation of both methane and propane oxidation functions was observed. In cooperation with industrial partners, scaleup to 3 kW is being investigated together with startup dynamics and catalyst stability. (author) 3 figs., 3 refs.

  7. Molecular catalytic hydrogenation of aromatic hydrocarbons and hydrotreating of coal liquids.

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Shiyong; Stock, L.M.

    1996-05-01

    This report presents the results of research on the development of new catalytic pathways for the hydrogenation of multiring aromatic hydrocarbons and the hydrotreating of coal liquids at The University of Chicago under DOE Contract No. DE-AC22-91PC91056. The work, which is described in three parts, is primarily concerned with the research on the development of new catalytic systems for the hydrogenation of aromatic hydrocarbons and for the improvement of the quality of coal liquids by the addition of dihydrogen. Part A discusses the activation of dihydrogen by very basic molecular reagents to form adducts that can facilitate the reduction of multiring aromatic hydrocarbons. Part B examines the hydrotreating of coal liquids catalyzed by the same base-activated dihydrogen complexes. Part C concerns studies of molecular organometallic catalysts for the hydrogenation of monocyclic aromatic hydrocarbons under mild conditions.

  8. Hydrogen production via catalytic steam reforming of fast pyrolysis oil fractions

    International Nuclear Information System (INIS)

    Wang, D.; Czernik, S.; Montane, D.; Mann, M.; Chornet, E.

    1997-01-01

    Hydrogen is the prototype of the environmentally cleanest fuel of interest for power generation using fuel cells, and as a co-adjuvant or autonomous transportation fuel in internal combustion engines. The conversion of biomass to hydrogen can be carried out through two distinct thermochemical strategies: (a) gasification followed by shift conversion; (b) catalytic steam reforming and shift conversion of specific fractions derived from fast pyrolysis and aqueous/steam processes of biomass. This paper shows that fast pyrolysis of biomass results in a bio-oil that can be adequately fractionated into valuable co-products leaving as by-product an aqueous fraction containing soluble organics (a mixture of alcohols, aldehydes and acids). This fraction can be converted to hydrogen by catalytic steam reforming followed by a shift conversion step. The methods used, the yields obtained and their economic significance will be discussed. (author)

  9. Selective catalytic reduction of nitrogen oxides from industrial gases by hydrogen or methane

    International Nuclear Information System (INIS)

    Engelmann Pirez, M.

    2004-12-01

    This work deals with the selective catalytic reduction of nitrogen oxides (NO x ), contained in the effluents of industrial plants, by hydrogen or methane. The aim is to replace ammonia, used as reducing agent, in the conventional process. The use of others reducing agents such as hydrogen or methane is interesting for different reasons: practical, economical and ecological. The catalyst has to convert selectively NO into N 2 , in presence of an excess of oxygen, steam and sulfur dioxide. The developed catalyst is constituted by a support such as perovskites, particularly LaCoO 3 , on which are dispersed noble metals (palladium, platinum). The interaction between the noble metal and the support, generated during the activation of the catalyst, allows to minimize the water and sulfur dioxide inhibitor phenomena on the catalytic performances, particularly in the reduction of NO by hydrogen. (O.M.)

  10. CATALYTICALLY ENHANCED SYSTEMS FOR HYDROGEN STORAGE. Final report

    International Nuclear Information System (INIS)

    Craig M. Jensen

    2007-01-01

    Previous U.S. DOE sponsored research at the University of Hawaii resulted in the development of methods of doping of sodium aluminum hydride, NaAlH4 with titanium, zirconium and other catalysts such that: dehydriding occurs at temperatures as low as 100 C; rehydriding requires less than 1 h; and >4 weight percent hydrogen can be repeatedly cycled through dehydriding/rehydriding. These materials appeared to be on the threshold of practical viability as hydrogen carriers for onboard fuel cells. However, it was apparent that further kinetic enhancement was required to achieve commercial viability. Thus, one of the primary goals of this project was to develop the requisite improved catalysts. Over the course of this project, a variety of titanium and zirconium dopant precursors were investigated. Moreover, the approach was to conduct guided search for improved catalysts by obtaining a fundamental understanding of the chemical nature of the titanium dopants and their mechanism of action. Therefore, the projected also aimed to determined the chemical nature of the titanium species that are formed upon mechanical milling of NaAlH4 with the dopant precursors through synchrotron X-ray and neutron diffraction as well as transmission electron microscopy, scanning electron microscopy, and electron paramagnetic resonance (EPR) spectroscopy. In addition to kinetic studies, insight into the mechanism of action of the dopants was gained through studies of the destabilization of hydrogen in NaAlH4 by the dopants through infrared, NMR, and anelastic spectroscopy

  11. Catalytic Hydrogenation of Bio-Oil for Chemicals and Fuels

    Energy Technology Data Exchange (ETDEWEB)

    Elliott, Douglas C.

    2006-02-14

    The scope of work includes optimizing processing conditions and demonstrating catalyst lifetime for catalyst formulations that are readily scaleable to commercial operations. We use a bench-scale, continuous-flow, packed-bed, catalytic, tubular reactor, which can be operated in the range of 100-400 mL/hr., from 50-400 C and up to 20MPa (see Figure 1). With this unit we produce upgraded bio-oil from whole bio-oil or useful bio-oil fractions, specifically pyrolytic lignin. The product oils are fractionated, for example by distillation, for recovery of chemical product streams. Other products from our tests have been used in further testing in petroleum refining technology at UOP and fractionation for product recovery in our own lab. Further scale-up of the technology is envisioned and we will carry out or support process design efforts with industrial partners, such as UOP.

  12. Bimetallic promotion of cooperative hydrogen transfer and heteroatom removal in coal liquefaction. Quarterly summary, June 1, 1991--August 31, 1991

    Energy Technology Data Exchange (ETDEWEB)

    Eisch, J.J.

    1991-10-01

    The ultimate objective of this research is to uncover new catalytic processes for the liquefaction of coal and for upgrading coal-derived fuels by removing undesirable organosulfur, organonitrogen and organooxygen constituents. Basic to both the liquefaction of coal and the purification of coal liquids is the transfer of hydrogen from such sources as dihydrogen, metal hydrides or partially reduced aromatic hydrocarbons to the extensive aromatic rings in coal itself or to aromatic sulfides, amines or ethers. Accordingly, this study is exploring how such crucial hydrogen-transfer processes might be catalyzed by soluble, low-valent transition metal complexes and/or Lewis acids under moderate conditions of temperature and pressure. By learning the mechanism whereby H{sub 2}, metal hydrides or partially hydrogenated aromatics do transfer hydrogen to model aromatic compounds, with the aid of homogeneous, bimetallic catalysts, we hope to identify new methods for producing superior fuels from coal.

  13. Liquid hydrogen transfer pipes and level regulation systems

    International Nuclear Information System (INIS)

    Marquet, M.; Prugne, P.; Roubeau, P.

    1961-01-01

    Describes: 1) Transfer pipes - Plunging rods in liquid hydrogen Dewars; transfer pipes: knee-joint system for quick and accurate positioning of plunging Dewar rods; system's rods: combined valve and rod; valves are activated either by a bulb pressure or by a solenoid automatically or hand controlled. The latter allows intermittent filling. 2) Level regulating systems: Level bulbs: accurate to 1 or 4 m; maximum and minimum level bulbs: automatic control of the liquid hydrogen valve. (author) [fr

  14. Production of hydrogen from bio-ethanol in catalytic membrane reactor

    International Nuclear Information System (INIS)

    Gernot, E.; Aupretre, F.; Deschamps, A.; Etievant, C.; Epron, F.; Marecot, P.; Duprez, D.

    2006-01-01

    Production of hydrogen from renewable energy sources offers a great potential for CO 2 emission reduction, responsible for global warming. Among renewable energies, liquid biofuels are very convenient hydrogen carriers for decentralized applications such as micro-cogeneration and transports. Ethanol, produced from sugar plants and cereals, allows a reduction of more than 60% of CO 2 emissions in comparison to gasoline. BIOSTAR is an R and D project, co-funded by the French Agency for Environment and Energy Management (ADEME) which aims at developing an efficient source of hydrogen from bio-ethanol, suitable for proton exchange membrane fuel cell systems. The objectives are to obtain, through catalytic process at medium temperature range, an efficient conversion of bio-ethanol into pure hydrogen directly usable for PEMFC. CETH has developed a catalytic membrane reformer (CMR), based on a patented technology, integrating a steam reforming catalyst as well as a combustion catalyst. Both catalysts have been developed and optimized for membrane reactor in partnership with the University of Poitiers. The composite metallic membrane developed by CETH allows hydrogen extraction near the hydrogen production sites, which enhances both efficiency and compactness. (authors)

  15. Hydrogenation of o-cresol on platinum catalyst: Catalytic experiments and first-principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yaping [Department of Physics and Engineering Physics, The University of Tulsa, Tulsa, OK 74104 (United States); Liu, Zhimin [School of Chemical, Biological and Materials Engineering, University of Oklahoma, Norman, OK 73019 (United States); Xue, Wenhua [Department of Physics and Engineering Physics, The University of Tulsa, Tulsa, OK 74104 (United States); Crossley, Steven P.; Jentoft, Friederike C. [School of Chemical, Biological and Materials Engineering, University of Oklahoma, Norman, OK 73019 (United States); Wang, Sanwu, E-mail: sanwu-wang@utulsa.edu [Department of Physics and Engineering Physics, The University of Tulsa, Tulsa, OK 74104 (United States)

    2017-01-30

    Highlights: • Hydrogenation of o-cresol over Pt results in formation of two products. • Dissociation of hydrogen from the −OH group involves a low activation energy. • Following hydrogenation of the aromatic ring forms 2-methyl-cyclohexanone. • Further hydrogenation produces the final product, 2-methyl-cyclohexanol. - Abstract: Catalytic experiments were performed for the hydrogenation of o-cresol in n-dodecane over a platinum catalyst. Batch reactions analyzed with an in-situ ATR IR probe suggest that the hydrogenation results in the formation of the final product, 2-methyl-cyclohexanol, with 2-methyl-cyclohexanone as the intermediate product. Ab initio density-functional theory was employed to investigate the atomic-scale mechanism of o-cresol hydrogenation on the Pt(111) surface. The formation of 2-methyl-cyclohexanone was found to involve two steps. The first step is a hydrogen abstraction, that is, the H atom in the hydroxyl group migrates to the Pt surface. The second step is hydrogenation, that is, the pre-existing H atoms on Pt react with the carbon atoms in the aromatic ring. On the other hand, 2-methyl-cyclohexanonol may be produced through two paths, with activation energies slightly greater than that for the formation of 2-methyl-cyclohexanone. One path involves direct hydrogenation of the aromatic ring. Another path involves three steps, with the partial hydrogenation of the ring as the first step, hydrogen abstraction of the −OH group as the second, and hydrogenation of remaining C atoms and the O atom the last.

  16. Hydrogenation of o-cresol on platinum catalyst: Catalytic experiments and first-principles calculations

    International Nuclear Information System (INIS)

    Li, Yaping; Liu, Zhimin; Xue, Wenhua; Crossley, Steven P.; Jentoft, Friederike C.; Wang, Sanwu

    2017-01-01

    Highlights: • Hydrogenation of o-cresol over Pt results in formation of two products. • Dissociation of hydrogen from the −OH group involves a low activation energy. • Following hydrogenation of the aromatic ring forms 2-methyl-cyclohexanone. • Further hydrogenation produces the final product, 2-methyl-cyclohexanol. - Abstract: Catalytic experiments were performed for the hydrogenation of o-cresol in n-dodecane over a platinum catalyst. Batch reactions analyzed with an in-situ ATR IR probe suggest that the hydrogenation results in the formation of the final product, 2-methyl-cyclohexanol, with 2-methyl-cyclohexanone as the intermediate product. Ab initio density-functional theory was employed to investigate the atomic-scale mechanism of o-cresol hydrogenation on the Pt(111) surface. The formation of 2-methyl-cyclohexanone was found to involve two steps. The first step is a hydrogen abstraction, that is, the H atom in the hydroxyl group migrates to the Pt surface. The second step is hydrogenation, that is, the pre-existing H atoms on Pt react with the carbon atoms in the aromatic ring. On the other hand, 2-methyl-cyclohexanonol may be produced through two paths, with activation energies slightly greater than that for the formation of 2-methyl-cyclohexanone. One path involves direct hydrogenation of the aromatic ring. Another path involves three steps, with the partial hydrogenation of the ring as the first step, hydrogen abstraction of the −OH group as the second, and hydrogenation of remaining C atoms and the O atom the last.

  17. Metal dependent catalytic hydrogenation of nitroarenes over water-soluble glutathione capped metal nanoparticles.

    Science.gov (United States)

    Sharma, Sachil

    2015-03-01

    The water soluble glutathione capped metal nanoparticles (M-GS, where M=Pd, Pt, Au and Ag; GS=glutathione) with size 2.4±0.2 nm were synthesized by borohydride reduction of metal ions in the presence of glutathione as capping ligand and used as catalyst for the hydrogenation of nitroaniline in aqueous phase. The rate of catalytic hydrogenation was dependent on metal type and the trend of catalytic activity over these M-GS nanoparticles was found to be Pd-GS (k(app)=0.0227 (±3×10(-4)))s(-1)≫Pt-GS (k(app)=0.0043 (±1×10(-4)))s(-1)>Au-GS (k(app)=0.0015 (±0.2×10(-4)))s(-1)>Ag-GS (k(app)=0.0008 (±0.2×10(-4)))s(-1). The similar trend of catalytic activity was found for the hydrogenation of nitrobenzene. Our experimental results, along taking into account the theoretical calculations done by other research groups, suggest that the observed catalytic activity trend is attributed to the "different rates of H2 molecule adsorption and dissociation" on the M-GS nanoparticles. The "high rate of H2 molecule adsorption" and "highly oxidized surface" make Pd-GS nanoparticles an ideal candidate for the rapid hydrogenation. On the basis of our experimental results, we proposed that small gaps between less densely packed branched thiol "glutathione molecules" provide the access to metal nanoparticle surface for the hydrogenation reaction. Copyright © 2014 Elsevier Inc. All rights reserved.

  18. Enhanced catalytic hydrogenation activity of Ni/reduced graphene oxide nanocomposite prepared by a solid-state method

    Science.gov (United States)

    Li, Yizhao; Cao, Yali; Jia, Dianzeng

    2018-01-01

    A simple solid-state method has been applied to synthesize Ni/reduced graphene oxide (Ni/rGO) nanocomposite under ambient condition. Ni nanoparticles with size of 10-30 nm supported on reduced graphene oxide (rGO) nanosheets are obtained through one-pot solid-state co-reduction among nickel chloride, graphene oxide, and sodium borohydride. The Ni/rGO nanohybrid shows enhanced catalytic activity toward the reduction of p-nitrophenol (PNP) into p-aminophenol compared with Ni nanoparticles. The results of kinetic research display that the pseudo-first-order rate constant for hydrogenation reaction of PNP with Ni/rGO nanocomposite is 7.66 × 10-3 s-1, which is higher than that of Ni nanoparticles (4.48 × 10-3 s-1). It also presents superior turnover frequency (TOF, 5.36 h-1) and lower activation energy ( E a, 29.65 kJ mol-1) in the hydrogenation of PNP with Ni/rGO nanocomposite. Furthermore, composite catalyst can be magnetically separated and reused for five cycles. The large surface area and high electron transfer property of rGO support are beneficial for good catalytic performance of Ni/rGO nanocomposite. Our study demonstrates a simple approach to fabricate metal-rGO heterogeneous nanostructures with advanced functions.

  19. Hydrogen assisted catalytic biomass pyrolysis. Effect of temperature and pressure

    DEFF Research Database (Denmark)

    Stummann, M.Z.; Høj, M.; Schandel, C. B.

    2018-01-01

    . The effect of varying the temperature (365–511 °C) and hydrogen pressure (1.6–3.6 MPa) on the product yield and organic composition was studied. The mass balance closed by a mass fraction between 90 and 101% dry ash free basis (daf). The yield of the combined condensed organics and C4+ varied between a mass...... fraction of 17 and 22% daf, corresponding to an energy recovery of between 40 and 53% in the organic product. The yield of the non-condensable gases varied between a mass fraction of 24 and 32% daf and the char yield varied between 9.6 and 18% daf. The condensed organics contained a mass fraction of 42...

  20. Formic Acid Free Flowsheet Development To Eliminate Catalytic Hydrogen Generation In The Defense Waste Processing

    Energy Technology Data Exchange (ETDEWEB)

    Lambert, Dan P.; Stone, Michael E.; Newell, J. David; Fellinger, Terri L.; Bricker, Jonathan M.

    2012-09-14

    The Defense Waste Processing Facility (DWPF) processes legacy nuclear waste generated at the Savannah River Site (SRS) during production of plutonium and tritium demanded by the Cold War. The nuclear waste is first treated via a complex sequence of controlled chemical reactions and then vitrified into a borosilicate glass form and poured into stainless steel canisters. Converting the nuclear waste into borosilicate glass canisters is a safe, effective way to reduce the volume of the waste and stabilize the radionuclides. Testing was initiated to determine whether the elimination of formic acid from the DWPF's chemical processing flowsheet would eliminate catalytic hydrogen generation. Historically, hydrogen is generated in chemical processing of alkaline High Level Waste sludge in DWPF. In current processing, sludge is combined with nitric and formic acid to neutralize the waste, reduce mercury and manganese, destroy nitrite, and modify (thin) the slurry rheology. The noble metal catalyzed formic acid decomposition produces hydrogen and carbon dioxide. Elimination of formic acid by replacement with glycolic acid has the potential to eliminate the production of catalytic hydrogen. Flowsheet testing was performed to develop the nitric-glycolic acid flowsheet as an alternative to the nitric-formic flowsheet currently being processed at the DWPF. This new flowsheet has shown that mercury can be reduced and removed by steam stripping in DWPF with no catalytic hydrogen generation. All processing objectives were also met, including greatly reducing the Slurry Mix Evaporator (SME) product yield stress as compared to the baseline nitric/formic flowsheet. Ten DWPF tests were performed with nonradioactive simulants designed to cover a broad compositional range. No hydrogen was generated in testing without formic acid.

  1. Volatility of the catalytic hydrogenation products of 1,4 bis(phenylethynyl)benzene

    Science.gov (United States)

    Sharma, Hom N.; Sangalang, Elizabeth A.; Saw, Cheng K.; Cairns, Gareth A.; McLean, William; Maxwell, Robert S.; Dinh, Long N.

    2017-11-01

    Measurements of equilibrium vapor pressures by effusion thermogravimetry and melting points by differential scanning calorimetry reveal that the melting temperature and equilibrium vapor pressures of 1,4-bis(phenylethynyl)benzene (DEB) do not vary monotonically with the hydrogenation extent. Contrary to intuition which suggests increasing volatility with hydrogenation, results indicate decreasing volatility for the first two hydrogenation steps before a non-monotonic upward trend, in which trans-isomers are less volatile. Insights on structural packing and functional groups were obtained from x-ray diffraction and infrared studies to shed light on the observed variation in the volatility of DEB with hydrogenation. Density functional theory calculations were performed to obtain molecular level information and to establish the thermodynamics of DEB hydrogenation reactions. A major factor influencing the observed melting points and volatility of the hydrogenated intermediate species is identified as the local attractive or repulsive carbon-hydrogen (CH) dipole interactions among the getter molecules in their respective crystal structures. Such collective CH dipole interactions can be used to predict the trends in the volatilities of catalytic hydrogenation processes.

  2. Heat transfer analysis of liquid piston compressor for hydrogen applications

    DEFF Research Database (Denmark)

    Kermani, Nasrin Arjomand; Rokni, Masoud

    2015-01-01

    A hydrogen compression technology using liquid as the compression piston is investigated from heat transfer point of view. A thermodynamic model, simulating a single compression stroke, is developed to investigate the heat transfer phenomena inside the compression chamber. The model is developed...

  3. A low-barrier hydrogen bond mediates antibiotic resistance in a noncanonical catalytic triad

    Science.gov (United States)

    2018-01-01

    One group of enzymes that confer resistance to aminoglycoside antibiotics through covalent modification belongs to the GCN5-related N-acetyltransferase (GNAT) superfamily. We show how a unique GNAT subfamily member uses a previously unidentified noncanonical catalytic triad, consisting of a glutamic acid, a histidine, and the antibiotic substrate itself, which acts as a nucleophile and attacks the acetyl donor molecule. Neutron diffraction studies allow for unambiguous identification of a low-barrier hydrogen bond, predicted in canonical catalytic triads to increase basicity of the histidine. This work highlights the role of this unique catalytic triad in mediating antibiotic resistance while providing new insights into the design of the next generation of aminoglycosides. PMID:29632894

  4. Research of Hydrogen Preparation with Catalytic Steam-Carbon Reaction Driven by Photo-Thermochemistry Process

    Directory of Open Access Journals (Sweden)

    Xiaoqing Zhang

    2013-01-01

    Full Text Available An experiment of hydrogen preparation from steam-carbon reaction catalyzed by K2CO3 was carried out at 700°C, which was driven by the solar reaction system simulated with Xenon lamp. It can be found that the rate of reaction with catalyst is 10 times more than that without catalyst. However, for the catalytic reaction, there is no obvious change for the rate of hydrogen generation with catalyst content range from 10% to 20%. Besides, the conversion efficiency of solar energy to chemical energy is more than 13.1% over that by photovoltaic-electrolysis route. An analysis to the mechanism of catalytic steam-carbon reaction with K2CO3 is given, and an explanation to the nonbalanced [H2]/[CO + 2CO2] is presented, which is a phenomenon usually observed in experiment.

  5. [Noncompetitive immunochemical determination of ribonuclease using transition metal ions and the effect of catalytic hydrogen release].

    Science.gov (United States)

    Dykhal, Iu I; Mediantseva, E P; Murtazina, N R; Safina, G R; Budnikov, G K; Kalacheva, N V

    2003-01-01

    A noncompetitive variant of immunochemical ribonuclease (RNase) determination has been developed, involving the use of Co(II) as a label. A variety of approaches to labeling the immunological reagent with the metal have been assessed. In the variant proposed, catalytic hydrogen release was used as a means of detecting the label, the amount of which was proportional to RNase concentration. Conditions making it possible to record catalytic hydrogen release fluxes were determined. In the presence of RNase, the electrocatalytic effect was maximum at a concentration of Co(II) in the ammoniac buffer, equal to 2 x 10(-4) M (pH 10.0). The dependence was linear in the range 4-2000 ng/ml RNase concentrations (threshold concentration, 2 ng/ml).

  6. A new type separation column for the water-hydrogen isotope catalytic exchange process

    International Nuclear Information System (INIS)

    Fedorchenko, O.A.; Alekseev, I.A.; Trenin, V.D.

    2001-01-01

    The catalytic water/hydrogen isotope exchange process is by right considered the most attractive for the solution a number of urgent problems of hydrogen isotope separation. A new type exchange reaction column is described and studied in details by computer simulation and with the help of McCabe-Thiele diagrams. It is shown that the new column in comparison with a traditional one needs less catalyst quantity and a smaller diameter for the solving of the same separation tasks. Generalized calculation data are presented in graphical form

  7. State of the art on hydrogen passive auto-catalytic recombiner (european union Parsoar project)

    International Nuclear Information System (INIS)

    Arnould, F.; Bachellerie, E.; Auglaire, M.; Boeck, B. de; Braillard, O.; Eckardt, B.; Ferroni, F.; Moffett, R.; Van Goethem, G.

    2001-01-01

    This paper presents an overview of the European Union PARSOAR project, which consists in carrying out a state of the art on hydrogen passive auto-catalytic recombiner (PAR) and a handbook guide for implementing these devices in nuclear power plants. This work is performed in the area ''Operational Safety of Existing Installations'' of the key action ''Nuclear Fission'' of the fifth Euratom Framework Programme (1998-2002). (author)

  8. State of the art on hydrogen passive auto-catalytic recombiner (european union Parsoar project)

    Energy Technology Data Exchange (ETDEWEB)

    Arnould, F.; Bachellerie, E. [Technicatome, 13 - Aix en Provence (France); Auglaire, M. [Tractebel Energy Engineering, Brussels (Belgium); Boeck, B. de [Association Vincotte Nuclear, Brussels (Belgium); Braillard, O. [CEA Cadarache, 13 - Saint Paul lez Durance (France); Eckardt, B. [Siemens AG, Offenbach am Main (Germany); Ferroni, F. [Electrowatt Engineering Limited, Zurich (Switzerland); Moffett, R. [Atomic Energy Canada Limited, Pinawa (Canada); Van Goethem, G. [European Commission, Brussels (Belgium)

    2001-07-01

    This paper presents an overview of the European Union PARSOAR project, which consists in carrying out a state of the art on hydrogen passive auto-catalytic recombiner (PAR) and a handbook guide for implementing these devices in nuclear power plants. This work is performed in the area ''Operational Safety of Existing Installations'' of the key action ''Nuclear Fission'' of the fifth Euratom Framework Programme (1998-2002). (author)

  9. Mesoporous Silica-Supported Sulfonyldiamine Ligand for Microwave-Assisted Transfer Hydrogenation

    Directory of Open Access Journals (Sweden)

    Shaheen M. Sarkar

    2015-01-01

    Full Text Available N-Sulfonyl-1,2-diamine ligands, derived from 1,2-diaminocyclohexane and 1,2-diaminopropane, were immobilized onto mesoporous SBA-15 silica. The SBA-15-supported sulfonyldiamine-Ru complex was prepared in situ under microwave heating at 60 W for 3 min. The prepared sulfonyldiamine-Ru complex was used as an efficient catalyst for the transfer hydrogenation of ketones to the corresponding secondary alcohols. The heterogeneous complex showed extremely high catalytic activity with 99% conversion rate under microwave heating condition. The complexes were regenerated by simple filtration and reused two times without significant loss of activity.

  10. Muon transfer from muonic hydrogen to heavier atoms

    International Nuclear Information System (INIS)

    Dupays, A.

    2004-06-01

    This work concerns muon transfer from muonic hydrogen to heavier atoms. Recently, a method of measurement of the hyperfine structure of ground-state muonic hydrogen based on the collision energy dependence of the muon transfer rate to oxygen has been proposed. This proposal is based on measurements which where performed at the Paul Scherrer Institute in the early nineties which indicate that the muon transfer from muonic hydrogen to oxygen increases by a factor of 4 going from thermal to 0.12 eV energies. The motivation of our calculations was to confirm this behaviour. To study the collision energy dependence of the muon transfer rate, we have used a time-independent close-coupling method. We have set up an hyperspherical elliptic formalism valid for nonzero total angular momentum which allows accurate computations of state-to-state reactive and charge exchange processes. We have applied this formalism to muon-transfer process to oxygen and neon. The comparison with experimental results is in both cases excellent. Finally, the neon transfer rate dependence with energy suggests to use neon instead of oxygen to perform a measurement of the hyperfine structure of muonic hydrogen. The results of accurate calculations of the muon transfer rates from muonic protium and deuterium atoms to nitrogen, oxygen and neon are also reported. Very good agreement with measured rates is obtained and for the three systems, the isotopic effect is perfectly reproduced. (author)

  11. Magnetically Recoverable Supported Ruthenium Catalyst for Hydrogenation of Alkynes and Transfer Hydrogenation of Carbonyl Compounds

    Science.gov (United States)

    A ruthenium (Ru) catalyst supported on magnetic nanoparticles (NiFe2O4) has been successfully synthesized and used for hydrogenation of alkynes at room temperature as well as transfer hydrogenation of a number of carbonyl compounds under microwave irradiation conditions. The cata...

  12. Gas Requirements in Pressurized Transfer of Liquid Hydrogen

    Science.gov (United States)

    Gluck, D. F.; Kline, J. F.

    1961-01-01

    Of late, liquid hydrogen has become a very popular fuel for space missions. It is being used in such programs as Centaur and Saturn. Furthermore, hydrogen is the ideal working fluid for nuclear powered space vehicles currently under development. In these applications, liquid hydrogen fuel is generally transferred to the combustion chamber by a combination of pumping and pressurization. The pump forces the liquid propellant from the fuel tank to the combustion chamber; gaseous pressurant holds tank pressure sufficiently high to prevent cavitation at the pump inlet and to maintain the structural rigidity of the tank. The pressurizing system, composed of pressurant, tankage, and associated hardware can be a large portion of the total vehicle weight. Pressurant weight can be reduced by introducing the pressurizing gas at temperatures substantially greater than those of liquid hydrogen. Heat and mass transfer processes thereby induced complicate gas requirements during discharge. These requirements must be known to insure proper design of the pressurizing system. The aim of this paper is to develop from basic mass and energy transfer processes a general method to predict helium and hydrogen gas usage for the pressurized transfer of liquid hydrogen. This required an analytical and experimental investigation, the results of which are described in this paper.

  13. A hydrogen-bonding network plays a catalytic role in photosynthetic oxygen evolution

    Science.gov (United States)

    Polander, Brandon C.; Barry, Bridgette A.

    2012-01-01

    In photosystem II, oxygen evolution occurs by the accumulation of photo-induced oxidizing equivalents at the oxygen-evolving complex (OEC). The sequentially oxidized states are called the S0-S4 states, and the dark stable state is S1. Hydrogen bonds to water form a network around the OEC; this network is predicted to involve multiple peptide carbonyl groups. In this work, we tested the idea that a network of hydrogen bonded water molecules plays a catalytic role in water oxidation. As probes, we used OEC peptide carbonyl frequencies, the substrate-based inhibitor, ammonia, and the sugar, trehalose. Reaction-induced FT-IR spectroscopy was used to describe the protein dynamics associated with the S1 to S2 transition. A shift in an amide CO vibrational frequency (1664 (S1) to 1653 (S2) cm-1) was observed, consistent with an increase in hydrogen bond strength when the OEC is oxidized. Treatment with ammonia/ammonium altered these CO vibrational frequencies. The ammonia-induced spectral changes are attributed to alterations in hydrogen bonding, when ammonia/ammonium is incorporated into the OEC hydrogen bond network. The ammonia-induced changes in CO frequency were reversed or blocked when trehalose was substituted for sucrose. This trehalose effect is attributed to a displacement of ammonia molecules from the hydrogen bond network. These results imply that ammonia, and by extension water, participate in a catalytically essential hydrogen bond network, which involves OEC peptide CO groups. Comparison to the ammonia transporter, AmtB, reveals structural similarities with the bound water network in the OEC. PMID:22474345

  14. Catalytic heat exchangers for small-scale production of hydrogen - feasibility study

    Energy Technology Data Exchange (ETDEWEB)

    Silversand, F. [Catator AB, Lund (Sweden)

    2002-02-01

    A feasibility study concerning heat-exchanger reactors in small-scale production of hydrogen has been performed on the request of Svenskt Gastekniskt Center AB and SWEP International AB. The basic idea is to implement different catalysts into brazed plate-type heat exchangers. This can be achieved by installing catalytic cylinders in the inlet-and outlet ports of the heat exchangers or through treatment of the plates to render them catalytically active. It is also possible to sandwich catalytically active wire meshes between the plates. Experiments concerning steam reforming of methanol and methane have been performed in a micro-reactor to gather kinetic data for modelling purposes. Performance calculations concerning heat exchanger reactors have then been conducted with Catator's generic simulation code for catalytic reactors (CatalystExplorer). The simulations clearly demonstrate the technical performance of these reactors. Indeed, the production rate of hydrogen is expected to be about 10 nm{sup 3}/h per litre of heat exchanger. The corresponding value for a conventional steam-reforming unit is about 1 nm{sup 3}/h or less per litre of reactor volume. Also, the compactness and the high degree of integration together with the possibilities of mass production will give an attractive cost for such units. Depending on the demands concerning the purity of the hydrogen it is possible to add secondary catalytic steps like water-gas shifters, methanation and selective oxidation, into a one-train unit, i.e. to design an all-inclusive design. Such reactors can be used for the supply of hydrogen to fuel cells. The production cost for hydrogen can be cut by 60 - 70% through the utilisation of heat exchanger reactors instead of conventional electrolysis. This result is primarily a result of the high price for electricity compared to the feed stock prices in steam reforming. It is important to verify the performance calculations and the simulation results through

  15. Oxygen transport membrane system and method for transferring heat to catalytic/process reactors

    Science.gov (United States)

    Kelly, Sean M; Kromer, Brian R; Litwin, Michael M; Rosen, Lee J; Christie, Gervase Maxwell; Wilson, Jamie R; Kosowski, Lawrence W; Robinson, Charles

    2014-01-07

    A method and apparatus for producing heat used in a synthesis gas production is provided. The disclosed method and apparatus include a plurality of tubular oxygen transport membrane elements adapted to separate oxygen from an oxygen containing stream contacting the retentate side of the membrane elements. The permeated oxygen is combusted with a hydrogen containing synthesis gas stream contacting the permeate side of the tubular oxygen transport membrane elements thereby generating a reaction product stream and radiant heat. The present method and apparatus also includes at least one catalytic reactor containing a catalyst to promote the stream reforming reaction wherein the catalytic reactor is surrounded by the plurality of tubular oxygen transport membrane elements. The view factor between the catalytic reactor and the plurality of tubular oxygen transport membrane elements radiating heat to the catalytic reactor is greater than or equal to 0.5.

  16. Substrate-mediated enhanced activity of Ru nanoparticles in catalytic hydrogenation of benzene

    KAUST Repository

    Liu, Xin

    2012-01-01

    The impact of carbon substrate-Ru nanoparticle interactions on benzene and hydrogen adsorption that is directly related to the performance in catalytic hydrogenation of benzene has been investigated by first-principles based calculations. The stability of Ru 13 nanoparticles is enhanced by the defective graphene substrate due to the hybridization between the dsp states of the Ru 13 particle with the sp 2 dangling bonds at the defect sites. The local curvature formed at the interface will also raise the Ru atomic diffusion barrier, and prohibit the particle sintering. The strong interfacial interaction results in the shift of averaged d-band center of the deposited Ru nanoparticle, from -1.41 eV for a freestanding Ru 13 particle, to -1.17 eV for the Ru/Graphene composites, and to -1.54 eV on mesocellular foam carbon. Accordingly, the adsorption energies of benzene are increased from -2.53 eV for the Ru/mesocellular foam carbon composites, to -2.62 eV on freestanding Ru 13 particles, to -2.74 eV on Ru/graphene composites. A similar change in hydrogen adsorption is also observed, and all these can be correlated to the shift of the d-band center of the nanoparticle. Thus, Ru nanoparticles graphene composites are expected to exhibit both high stability and superior catalytic performance in hydrogenation of arenes. © 2012 The Royal Society of Chemistry.

  17. Catalytic process for control of NO.sub.x emissions using hydrogen

    Science.gov (United States)

    Sobolevskiy, Anatoly; Rossin, Joseph A.; Knapke, Michael J.

    2010-05-18

    A selective catalytic reduction process with a palladium catalyst for reducing NOx in a gas, using hydrogen as a reducing agent. A zirconium sulfate (ZrO.sub.2)SO.sub.4 catalyst support material with about 0.01-2.0 wt. % Pd is applied to a catalytic bed positioned in a flow of exhaust gas at about 70-200.degree. C. The support material may be (ZrO.sub.2--SiO.sub.2)SO.sub.4. H.sub.2O and hydrogen may be injected into the exhaust gas upstream of the catalyst to a concentration of about 15-23 vol. % H.sub.2O and a molar ratio for H.sub.2/NO.sub.x in the range of 10-100. A hydrogen-containing fuel may be synthesized in an Integrated Gasification Combined Cycle power plant for combustion in a gas turbine to produce the exhaust gas flow. A portion of the fuel may be diverted for the hydrogen injection.

  18. Review of Catalytic Hydrogen Generation in the DWPF Chemical Processing Cell, Part II

    Energy Technology Data Exchange (ETDEWEB)

    Koopman, David C.; Lambert, Daniel P.; Baich, Mark A.

    2005-08-01

    The Savannah River National Laboratory is in the process of investigating factors suspected of impacting catalytic hydrogen generation in the Defense Waste Processing Facility, DWPF, Chemical Process Cell, CPC. Noble metal catalyzed hydrogen generation in simulation work constrains the allowable acid addition operating window in DWPF. This constraint potentially impacts washing strategies during sludge batch preparation. It can also influence decisions related to the addition of secondary waste streams to a sludge batch. Catalytic hydrogen generation data from 2002-2005 were reviewed. The data came from process simulations of the DWPF Sludge Receipt and Adjustment Tank, SRAT, and Slurry Mix Evaporator, SME. Most of the data was from the development work for the Sludge Batch 3 process flowsheet. This included simulant and radioactive waste testing. Preliminary Sludge Batch 4 data were also reviewed. A statistical analysis of SB3 simulant hydrogen generation data was performed. One factor considered in the statistical analysis was excess acid. Excess acid was determined experimentally as the acid added beyond that required to achieve satisfactory nitrite destruction.

  19. Transfer hydrogenation in open-shell nucleotides - a theoretical survey.

    Science.gov (United States)

    Achrainer, Florian; Zipse, Hendrik

    2014-12-22

    The potential of a larger number of sugar models to act as dihydrogen donors in transfer hydrogenation reactions has been quantified through the calculation of hydrogenation energies of the respective oxidized products. Comparison of the calculated energies to hydrogenation energies of nucleobases shows that many sugar fragment radicals can reduce pyrimidine bases such as uracil in a strongly exothermic fashion. The most potent reducing agent is the C3' ribosyl radical. The energetics of intramolecular transfer hydrogenation processes has also been calculated for a number of uridinyl radicals. The largest driving force for such a process is found for the uridin-C3'-yl radical, whose rearrangement to the C2'-oxidized derivative carrying a dihydrouracil is predicted to be exothermic by 61.1 kJ/mol in the gas phase.

  20. Decoupled catalytic hydrogen evolution from a molecular metal oxide redox mediator in water splitting.

    Science.gov (United States)

    Rausch, Benjamin; Symes, Mark D; Chisholm, Greig; Cronin, Leroy

    2014-09-12

    The electrolysis of water using renewable energy inputs is being actively pursued as a route to sustainable hydrogen production. Here we introduce a recyclable redox mediator (silicotungstic acid) that enables the coupling of low-pressure production of oxygen via water oxidation to a separate, catalytic hydrogen production step outside the electrolyzer that requires no post-electrolysis energy input. This approach sidesteps the production of high-pressure gases inside the electrolytic cell (a major cause of membrane degradation) and essentially eliminates the hazardous issue of product gas crossover at the low current densities that characterize renewables-driven water-splitting devices. We demonstrated that a platinum-catalyzed system can produce pure hydrogen over 30 times faster than state-of-the-art proton exchange membrane electrolyzers at equivalent platinum loading. Copyright © 2014, American Association for the Advancement of Science.

  1. Intermolecular Hydrogen Transfer in Isobutane Hydrate

    Directory of Open Access Journals (Sweden)

    Takeshi Sugahara

    2012-05-01

    Full Text Available Electron spin resonance (ESR spectra of butyl radicals induced with γ-ray irradiation in the simple isobutane (2-methylpropane hydrate (prepared with deuterated water were investigated. Isothermal annealing results of the γ-ray-irradiated isobutane hydrate reveal that the isobutyl radical in a large cage withdraws a hydrogen atom from the isobutane molecule through shared hexagonal-faces of adjacent large cages. During this “hydrogen picking” process, the isobutyl radical is apparently transformed into a tert-butyl radical, while the sum of isobutyl and tert-butyl radicals remains constant. The apparent transformation from isobutyl to tert-butyl radicals is an irreversible first-order reaction and the activation energy was estimated to be 35 ± 3 kJ/mol, which was in agreement with the activation energy (39 ± 5 kJ/mol of hydrogen picking in the γ-ray-irradiated propane hydrate with deuterated water.

  2. Triplet-Triplet Energy Transfer Study in Hydrogen Bonding Systems.

    Science.gov (United States)

    Wang, Zhijia; Zhao, Jianzhang; Guo, Song

    2015-01-01

    The 2,6-diiodoBodipy-styrylBodipy hydrogen bonding system was prepared to study the effect of hydrogen bonding on the triplet-triplet-energy-transfer (TTET) process. 2,6-DiiodoBodipy linked with N-acetyl-2,6-diaminopyridine (D-2) was used as the triplet energy donor, and the styrylBodipy connected with thymine (A-1) was used as triplet energy acceptor, thus the TTET process was established upon photoexcitation. The photophysical processes of the hydrogen bonding system were studied with steady-state UV-vis absorption spectroscopy, fluorescence spectroscopy, fluorescence lifetime measurement and nanosecond time-resolved transient absorption spectroscopies. The TTET of the intramolecular/hydrogen bonding/intermolecular systems were compared through nanosecond transient absorption spectroscopy. The TTET process of the hydrogen bonding system is faster and more efficient (kTTET = 6.9 × 10(4) s(-1), ΦTTET = 94.0%) than intermolecular triplet energy transfer (kTTET = 6.0 × 10(4) s(-1), ΦTTET = 90.9%), but slower and less efficient than intramolecular triplet energy transfer (kTTET > 10(8) s(-1)). These results are valuable for designing self-assembly triplet photosensitizers and for the study of the TTET process of hydrogen bonding systems.

  3. Mechanism of Pd(NHC)-catalyzed transfer hydrogenation of alkynes.

    Science.gov (United States)

    Hauwert, Peter; Boerleider, Romilda; Warsink, Stefan; Weigand, Jan J; Elsevier, Cornelis J

    2010-12-01

    The transfer semihydrogenation of alkynes to (Z)-alkenes shows excellent chemo- and stereoselectivity when using a zerovalent palladium(NHC)(maleic anhydride)-complex as precatalyst and triethylammonium formate as hydrogen donor. Studies on the kinetics under reaction conditions showed a broken positive order in substrate and first order in catalyst and hydrogen donor. Deuterium-labeling studies on the hydrogen donor showed that both hydrogens of formic acid display a primary kinetic isotope effect, indicating that proton and hydride transfers are separate rate-determining steps. By monitoring the reaction with NMR, we observed the presence of a coordinated formate anion and found that part of the maleic anhydride remains coordinated during the reaction. From these observations, we propose a mechanism in which hydrogen transfer from coordinated formate anion to zerovalent palladium(NHC)(MA)(alkyne)-complex is followed by migratory insertion of hydride, after which the product alkene is liberated by proton transfer from the triethylammonium cation. The explanation for the high selectivity observed lies in the competition between strongly coordinating solvent and alkyne for a Pd(alkene)-intermediate.

  4. Contribution to the study of catalytic hydrogen-deuterium exchange between hydrogen and hydrocarbons

    International Nuclear Information System (INIS)

    Ravoire, J.

    1958-01-01

    The hydrogen-deuterium exchange between molecular hydrogen and hydrocarbons over a platinum and charcoal catalyst was studied in a static system. The change in isotopic composition of molecular hydrogen was followed by a thermal conductivity method. Cyclo-pentane and cyclohexane were chosen because of their stability. A reversible inactivation of the catalyst was observed with both hydrocarbons. The reasons for this inactivation are unknown but it was shown that reactivation led to satisfactory reproducibility. A kinetic study was done with cyclohexane in the range 30 to 160 deg. C, and 40 to 360 mm for the pressure of hydrogen, and 10 to 70 mm for the pressure of cyclohexane. The order of the reaction with respect to cyclohexane pressure is always close to zero; the order with respect to that of hydrogen is 0.5 above 100 deg. C. It decreases with increasing temperature and becomes negative (-0.5 at 30 deg. C), characterizing an inhibition by hydrogen. At the same time, the apparent activation energy goes from 6 to 13 kcal/mole. (author) [fr

  5. Role of Hydrogen and Oxygen Activation over Pt and Pd-Doped Composites for Catalytic Hydrogen Combustion.

    Science.gov (United States)

    Singh, Satyapaul A; Vishwanath, Karan; Madras, Giridhar

    2017-06-14

    Removal of excess amount of hydrogen in a catalytic route is a safety measure to be implemented in fuel cell technologies and in nuclear power plants. Hydrogen and oxygen activation are crucial steps for hydrogen combustion that can be achieved by modifying supports with suitable noble metals. In the present study, Pt- and Pd-substituted Co 3 O 4 -ZrO 2 (CZ) were synthesized using PEG-assisted sonochemical synthesis. Ionic states of Pt and Pd in CZ supports were analyzed by X-ray photoelectron spectroscopy. Pd and Pt improved H 2 and O 2 activation extensively, which reduced the temperature of 50% conversion (T 50% ) to 33 °C compared with the support (CZ). The activation energy of PdCZ catalyst was decreased by more than 2 folds (13.4 ± 1.2 kJ mol -1 ) compared with CZ (34.3 ± 2.3 kJ mol -1 ). The effect of oxygen vacancies in the reaction mechanism is found to be insignificant with Pt- and Pd-substituted CZ supports. However, oxygen vacancies play an important role when CZ alone was used as catalyst. The importance of hydrogen and oxygen activation as well as the oxygen vacancies in mechanism was studied by H 2 -TPD, H 2 -TPR, and in situ FTIR spectroscopy.

  6. Hypergolic ignition of a catalytically promoted fuel with rocket grade hydrogen peroxide

    Science.gov (United States)

    Pourpoint, Timothee Louis

    The ignition delay for the incipient sustained reaction of hypergolic propellants is of crucial importance. Too short of a delay can lead to injector damage while too long of a delay can lead to very large pressure spikes and engine failure. The coupling of the physical and chemical processes controlling the ignition delays of hypergolic propellants renders the direct analysis of the transient ignition process very difficult. Well defined test conditions must, therefore, be specified to properly study the factors influencing the ignition delays of hypergolic propellants. Theories regarding the thermal ignition of conventional hypergolic propellants, such as nitrogen tetroxide and hydrazine-based fuels, have been established. The goals of the present research are to investigate the applicability of thermal ignition theories to the ignition processes occurring between a catalytically promoted fuel and hydrogen peroxide and to develop a model of the incipient reactions. The hypergolic fuel considered in the study is a methanol-based mixture containing a soluble metal catalyst. First, physical and chemical factors influencing an ignition event between liquid hypergolic propellants are discussed. Whenever possible, emphasis is placed on data obtained with fuels that are hypergolic with rocket grade hydrogen peroxide. Following this review, the applicability of traditional vaporization and ignition theories to the ignition of a catalytically promoted fuel with rocket grade hydrogen peroxide are discussed. An experimental program aimed at determining the effects of initial ambient pressure, initial ambient gas properties, and hydrogen peroxide concentration on ignition delay is presented. Results show that ignition delay can be reduced by increasing the hydrogen peroxide concentration or the initial ambient pressure. The combined effects of large thermal conductivity and large mass diffusion coefficient of helium rich environments are postulated to be responsible for the

  7. A novel carbohydrate labeling method utilizing transfer hydrogenation-mediated reductive amination.

    Science.gov (United States)

    Kovács, Zsuzsanna; Papp, Gábor; Horváth, Henrietta; Joó, Ferenc; Guttman, András

    2017-08-05

    One of the most frequently used high-resolution glycan analysis methods in the biopharmaceutical and biomedical fields is capillary electrophoresis with laser-induced fluorescence (CE-LIF) detection. Glycans are usually labeled by reductive amination with a charged fluorophore containing a primary amine, which reacts with the aldehyde group at the reducing end of the glycan structures. In this reaction, first a Schiff base is formed that is reduced to form a stable conjugate by a hydrogenation reagent, such as sodium cyanoborohydride. In large scale biopharmaceutical applications, such as clone selection for glycoprotein therapeutics, hundreds of reactions are accomplished simultaneously, so the HCN generated in the process poses a safety concern. To alleviate this issue, here we propose catalytic hydrogen transfer from formic acid catalyzed by water-soluble iridium(III)- and ruthenium(II)-phosphine complexes as a novel alternative to hydrogenation. The easily synthesized water-soluble iridium(III) and the ruthenium(II) hydrido complexes showed high catalytic activity in carbohydrate labeling. This procedure is environmentally friendly and reduces the health risks for the industry. Using carbohydrate standards, oligosaccharides released from glycoproteins with highly sialylated (fetuin), high mannose (ribonuclease B) and mixed sialo and neutral (human plasma) N-glycans, we demonstrated similar labeling efficiencies for iridium(III) dihydride to that of the conventionally used sodium cyanoborohydride based reaction. The derivatization reaction time was less than 20min with no bias towards the above mentioned specific glycan structures. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. PA-Tb-Cu MOF as luminescent nanoenzyme for catalytic assay of hydrogen peroxide.

    Science.gov (United States)

    Qi, Zewan; Wang, Li; You, Qi; Chen, Yang

    2017-10-15

    Metal organic frameworks (MOFs) with flexible structures and components have aroused great interest in designing functional materials. In this work, we designed and made a kind of PA-Tb-Cu MOF nanoenzyme capable of emitting fluorescence for the catalytic reaction of hydrogen peroxide (H 2 O 2 ). Luminescent Tb 3+ , catalytic Cu 2+ and bridging ligand were assembled and integrated into a single material nanoenzyme. This PA-Tb-Cu MOF nanoenzyme not only possessed excellent catalytic activity comparable to horseradish peroxidase but also can real-time fluorescently indicate the concentration of H 2 O 2 as low as 0.2µM during catalysis. Luminescent PA-Tb-Cu MOF nanoenzyme did not need a common combined use of natural/artificial enzymes and chromogenic reactions for the quantification of H 2 O 2 in widely-used enzyme-catalytic reactions. The present strategy assembled directly from functional ions/molecules provides a new way for the design and development of smart, multifunctional artificial enzymes for wide applications in biocatalysis, bioassays and nano-biomedicine. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Core-shell nanospheres Pt@SiO2 for catalytic hydrogen production

    Science.gov (United States)

    Hu, Yujuan; Wang, Yuqing; Lu, Zhang-Hui; Chen, Xiangshu; Xiong, Lihua

    2015-06-01

    Ultrafine platinum nanoparticles (NPs) embedded in silica nanospheres (Pt@SiO2) have been synthesized in a NP-5/cyclohexane reversed-micelle system followed by NaBH4 reduction. The as-synthesized core-shell nanocatalysts Pt@SiO2 were characterized by scanning electron microscopy, transmission electron microscopes, X-ray powder diffraction analysis, energy dispersive X-ray spectrometer and nitrogen adsorption-desorption investigations. Interestingly, the as-synthesized core-shell nanocatalysts Pt@SiO2 showed an excellent catalytic performance in hydrogen generation from the hydrolysis of ammonia borane (BH3NH3, AB) at room temperature. Especially, the catalytic performance of the Pt@SiO2 remained almost unchanged after the five recycles and even after the heat treatment (673 K), because the silica shells inhibit aggregation or deformation of the metal cores. Besides, the kinetic studies showed that the catalytic hydrolysis of AB was first order with respect to the catalyst concentration and zero order with respect to the substrate concentration, respectively. The excellent catalytic activity and stability of Pt@SiO2 can make it have a bright future in the practical application.

  10. Continuous catalytic hydrogenation of polyaromatic hydrocarbon compounds in hydrogen-supercritical carbon dioxide.

    Science.gov (United States)

    Yuan, Tao; Fournier, Anick R; Proudlock, Raymond; Marshall, William D

    2007-03-15

    A continuous hydrogenation device was evaluated for the detoxification of selected tri-, tetra-, or pentacyclic polyaromatic hydrocarbon (PAH) compounds {anthracene, phenanthrene, chrysene, and benzo[a]pyrene (B[a]P)} by hydrogenation. A substrate stream in hexane, 0.05-1.0% (w/v), was mixed with hydrogen-carbon dioxide (H2-CO2, 5-30% v/v) and delivered to a heated reactor column (25 cm x 1 cm) containing palladium supported on gamma alumina (Pd0/gamma-Al2O3) that was terminated with a capillary restrictor. The flow rate from the reactor, approximately 800 mL min(-1) decompressed gas, corresponded to 4 mL min(-1) fluid under the operating conditions of the trials. Reaction products were recovered by passing the reactor effluent through hexane. At 90 degrees C, the anthracene or phenanthrene substrate was hydrogenated only partially to octahydro and dodecahydro species and contained only a minor quantity of totally hydrogenated products. For substrates with increasing numbers of fused aromatic rings, the hydrogenation efficiency was decreased further. However, at an increasing temperature (90-150 degrees C) and increasing mobile phase flow rate (20.68 MPa corresponding to 2100 mL min(-1) decompressed gas), B[a]P and chrysene were hydrogenated, virtuallytotally, to their corresponding perhydro analogues (eicosahydrobenzo[a]pyrenes and octadecahydrochrysenes), respectively. That this approach might be useful for decontaminating soil extracts was supported by companion in vitro trials in which the substrate and products were assayed for mutagenic activity with five bacterial strains that are auxotrophic for histidine (Salmonella typhimurium TA98, TA100, TA1535, and TA1537) or tryptophan (Escherichia coliWP2 uvrA), using the bacterial reverse mutation assay (modified Ames test). Generally, substantial increases in revertant colony counts were not observed with any of the strains following exposure to the hydrogenation products in the absence or presence of the 10 or 30

  11. Probing hydrogen bonding interactions and proton transfer in proteins

    Science.gov (United States)

    Nie, Beining

    Scope and method of study. Hydrogen bonding is a fundamental element in protein structure and function. Breaking a single hydrogen bond may impair the stability of a protein. It is therefore important to probe dynamic changes in hydrogen bonding interactions during protein folding and function. Time-resolved Fourier transform infrared spectroscopy is highly sensitive to hydrogen bonding interactions. However, it lacks quantitative correlation between the vibrational frequencies and the number, type, and strength of hydrogen bonding interactions of ionizable and polar residues. We employ quantum physics theory based ab initio calculations to study the effects of hydrogen bonding interactions on vibrational frequencies of Asp, Glu, and Tyr residues and to develop vibrational spectral markers for probing hydrogen bonding interactions using infrared spectroscopy. In addition, proton transfer process plays a crucial role in a wide range of energy transduction, signal transduction, and enzymatic reactions. We study the structural basis for proton transfer using photoactive yellow protein as an excellent model system. Molecular dynamics simulation is employed to investigate the structures of early intermediate states. Quantum theory based ab initio calculations are used to study the impact of hydrogen bond interactions on proton affinity and proton transfer. Findings and conclusions. Our extensive density function theory based calculations provide rich structural, spectral, and energetic information on hydrogen bonding properties of protonated side chain groups of Asp/Glu and Tyr. We developed vibrational spectral markers and 2D FTIR spectroscopy for structural characterization on the number and the type of hydrogen bonding interactions of the COOH group of Asp/Glu and neutral phenolic group of Tyr. These developments greatly enhance the power of time-resolved FTIR spectroscopy as a major experimental tool for structural characterization of functionally important

  12. Detailed modelling of processes inside a catalytic recombiner for hydrogen removal

    International Nuclear Information System (INIS)

    Heitsch, M.

    1999-01-01

    Under accidental conditions, considerable amounts of hydrogen may be released into the containment. Catalytic reacting surfaces in recombiners are a reliable method to recombine this hydrogen and other burnable gases like carbon monoxide from the atmosphere in a passive way. Many experiments have been carried out to study the main phenomena occurring inside recombiners, like the efficiency of hydrogen removal, the start-up conditions, poisoning, oxygen starvation, steam and water impact, and others. In addition, the global behavior of a given recombiner device in a larger environment has been investigated in order to demonstrate the effectiveness and to facilitate the derivation of simplified models for long term, severe accident analyses. These long-term severe accident models are complemented by detailed investigations to understand the interaction of chemistry and flow inside a recombiner box. This helps to provide the dependencies of non-measurable variables (e.g. the reaction rate distribution), of local surface temperatures etc. to make long-term or system models more reliable. It also offers possibilities for increasing the chemical efficiency by optimising the geometric design properly. Computational Fluid Dynamics (CFD) codes are available for use as development tools to include the specifics of catalytic surface reactors. The present paper describes the use of the code system CFX [1] for creating a recombiner model. Some model predictions are compared to existing test data. (author)

  13. Induced Superaerophobicity onto a Non-superaerophobic Catalytic Surface for Enhanced Hydrogen Evolution Reaction.

    Science.gov (United States)

    Akbar, Kamran; Hussain, Sajjad; Truong, Linh; Roy, Sanjib Baran; Jeon, Jae Ho; Jerng, Sahng-Kyoon; Kim, Minsoo; Yi, Yeonjin; Jung, Jongwan; Chun, Seung-Hyun

    2017-12-20

    Despite tremendous progress in the development of novel electrocatalysts for hydrogen evolution reaction (HER), the accumulation of hydrogen gas bubbles produced on the catalyst surface has been rather poorly addressed. The bubbles block the surface of the electrode, thus resulting in poor performance even when excellent electrocatalysts are used. In this study, we show that vertically grown graphene nanohills (VGNHs) possess an excellent capability to quickly disengage the produced hydrogen gas bubbles from the electrode surface, and thus exhibit superaerophobic properties. To compensate for the poor electrolytic properties of graphene toward HER, the graphene surface was modified with WS 2 nanoparticles to accelerate the water-splitting process by using this hybrid catalyst (VGNHs-WS 2 ). For comparison purposes, WS 2 nanoparticles were also deposited on the flat graphene (FG) surface. Because of its superior superaerophobic properties, VGNHs-WS 2 outperformed FG-WS 2 in terms of both catalytic activity toward the HER and superaerophobicity. Furthermore, VGNHs-WS 2 exhibited a low onset potential (36 mV compared to 288 mV for FG-WS 2 ) and long-term stability in the HER over an extended period of 20 h. This study provides an efficient way to utilize highly conductive and superaerophobic VGNHs as support materials for intrinsic semiconductors, such as WS 2 , to simultaneously achieve superaerophobicity and high catalytic activity.

  14. Enantioselective organocatalytic partial transfer hydrogenation of lactone-fused quinolines.

    Science.gov (United States)

    Aillerie, Alexandre; de Talancé, Vincent Lemau; Moncomble, Aurélien; Bousquet, Till; Pélinski, Lydie

    2014-06-06

    The first enantioselective synthesis of 4-aza-podophyllotoxin derivatives by partial transfer hydrogenation of lactone-fused quinolines was achieved using a chiral Brønsted acid catalyst. This reaction was extended to a large scope of substrates with good yields and enantioselectivities.

  15. The Immobilization of a Transfer Hydrogenation Catalyst on Colloidal Particles

    NARCIS (Netherlands)

    van Ravensteijn, Bas G P|info:eu-repo/dai/nl/338806008; Schild, Dirk Jan; Kegel, Willem K.|info:eu-repo/dai/nl/113729464; Klein Gebbink, Robertus J M|info:eu-repo/dai/nl/166032646

    2017-01-01

    In this paper, we report a new synthetic procedure to immobilize a transfer hydrogenation catalyst on the surface of colloidal polystyrene particles. Using supports of colloidal dimensions allows for combining a relatively high surface area for catalyst binding, mobility of the catalyst, and facile

  16. Current Topics in the Asymmetric Transfer Hydrogenation of Imines

    Czech Academy of Sciences Publication Activity Database

    Januščák, J.; Václavík, Jiří; Šot, P.; Pecháček, J.; Vilhanová, B.; Kuzma, Marek; Kačer, P.

    2015-01-01

    Roč. 109, č. 7 (2015), s. 492-498 ISSN 0009-2770 R&D Projects: GA ČR GAP106/12/1276; GA MŠk(CZ) LO1509 Institutional support: RVO:61388971 Keywords : asymmetric transfer hydrogenation * ruthenium * isoquinoline Subject RIV: EE - Microbiology, Virology Impact factor: 0.279, year: 2015

  17. Marrying gas power and hydrogen energy: A catalytic system for combining methane conversion and hydrogen generation

    NARCIS (Netherlands)

    Beckers, J.; Gaudillère, C.; Farrusseng, D.; Rothenberg, G.

    2009-01-01

    Ceria-based catalysts are good candidates for integrating methane combustion and hydrogen generation. These new, tuneable catalysts are easily prepared. They are robust inorganic crystalline materials, and perform well at the 400 °C-550 °C range, in some cases even without precious metals. This

  18. An investigation of turbulent catalytically stabilized channel flow combustion of lean hydrogen - air mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Mantzaras, I.; Benz, P.; Schaeren, R.; Bombach, R. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    The catalytically stabilised thermal combustion (CST) of lean hydrogen-air mixtures was investigated numerically in a turbulent channel flow configuration using a two-dimensional elliptic model with detailed heterogeneous and homogeneous chemical reactions. Comparison between turbulent and laminar cases having the same incoming mean properties shows that turbulence inhibits homogeneous ignition due to increased heat transport away from the near-wall layer. The peak root-mean-square temperature and species fluctuations are always located outside the extent of the homogeneous reaction zone indicating that thermochemical fluctuations have no significant influence on gaseous combustion. (author) 4 figs., 6 refs.

  19. Theoretical study of catalytic hydrogenation of oxirane and its methyl derivative

    Directory of Open Access Journals (Sweden)

    U.A. Kuevi

    2012-12-01

    Full Text Available Oxirane (C2H4O is an unsaturated heterocyclic compound and methyloxirane (C3H6O is its methyl derivative. Theoretical studies on catalytic hydrogenation of both compounds, in presence of aluminium chloride (AlCl3 catalyst, are carried out. The products of reactions are ethanol and propan-1-ol from oxirane and methyloxirane, respectively. According to the variations of chemical parameters throughout the processes, the mechanisms of both reactions have been proposed.DOI: http://dx.doi.org/10.4314/bcse.v26i3.13

  20. Application of solid state catalytic hydrogen isotope exchange to the tritium labeling of lyoszyme

    International Nuclear Information System (INIS)

    Filikov, A.V.; Jones, J.R.

    1995-01-01

    Solid state catalytic hydrogen isotope exchange has been employed to label hen egg lysozyme with tritium. Optimization of reaction conditions so that amino acids and peptide bonds remained intact led to a tritiated products with 97% of the original enzymatic activity and 94% radiochemical purity. The specific activity when using a T 2 :H 2 mixture of 1:1000, was 16 mCi·mmol -1 . It is suggested that the currently adopted approach may have wide applications for other proteins able to tolerate lyophilization conditions without loss of activity. (Author)

  1. Revised Theoretical Model on Enantiocontrol in Phosphoric Acid Catalyzed H-Transfer Hydrogenation of Quinoline.

    Science.gov (United States)

    Pastor, Julien; Rezabal, Elixabete; Voituriez, Arnaud; Betzer, Jean-François; Marinetti, Angela; Frison, Gilles

    2018-03-02

    The enantioselective H-transfer hydrogenation of quinoline by Hantzsch ester is a relevant example of Brønsted acid catalyzed cascade reactions, with phosphoric acid being a privileged catalyst. The generally accepted mechanism points out the hydride transfer step as the rate- and stereodetermining step, however computations based on these models do not totally fit with experimental observations. We hereby present a computational study that enlightens the stereochemical outcome and quantitatively reproduces the experimental enantiomeric excesses in a series of H-transfer hydrogenations. Our calculations suggest that the high stereocontrol usually attained with BINOL-derived phosphoric acids results mostly from the steric constraints generated by an aryl substituent of the catalyst, which hinders the access of the Hantzsch ester to the catalytic site and enforces approach through a specific way. It relies on a new model involving the preferential assembly of one of the stereomeric complexes formed by the chiral phosphoric acid and the two reaction partners. The stereodetermining step thus occurs prior to the H-transfer step.

  2. Review of Catalytic Hydrogen Generation in the Defense Waste Processing Facility (DWPF) Chemical Processing Cell

    Energy Technology Data Exchange (ETDEWEB)

    Koopman, D. C.

    2004-12-31

    This report was prepared to fulfill the Phase I deliverable for HLW/DWPF/TTR-98-0018, Rev. 2, ''Hydrogen Generation in the DWPF Chemical Processing Cell'', 6/4/2001. The primary objective for the preliminary phase of the hydrogen generation study was to complete a review of past data on hydrogen generation and to prepare a summary of the findings. The understanding was that the focus should be on catalytic hydrogen generation, not on hydrogen generation by radiolysis. The secondary objective was to develop scope for follow-up experimental and analytical work. The majority of this report provides a summary of past hydrogen generation work with radioactive and simulated Savannah River Site (SRS) waste sludges. The report also includes some work done with Hanford waste sludges and simulants. The review extends to idealized systems containing no sludge, such as solutions of sodium formate and formic acid doped with a noble metal catalyst. This includes general information from the literature, as well as the focused study done by the University of Georgia for the SRS. The various studies had a number of points of universal agreement. For example, noble metals, such as Pd, Rh, and Ru, catalyze hydrogen generation from formic acid and formate ions, and more acid leads to more hydrogen generation. There were also some points of disagreement between different sources on a few topics such as the impact of mercury on the noble metal catalysts and the identity of the most active catalyst species. Finally, there were some issues of potential interest to SRS that apparently have not been systematically studied, e.g. the role of nitrite ion in catalyst activation and reactivity. The review includes studies covering the period from about 1924-2002, or from before the discovery of hydrogen generation during simulant sludge processing in 1988 through the Shielded Cells qualification testing for Sludge Batch 2. The review of prior studies is followed by a

  3. Hydrogen Production From Crude Bio-oil and Biomass Char by Electrochemical Catalytic Reforming

    Science.gov (United States)

    Li, Xing-long; Ning, Shen; Yuan, Li-xia; Li, Quan-xin

    2011-08-01

    We reports an efficient approach for production of hydrogen from crude bio-oil and biomass char in the dual fixed-bed system by using the electrochemical catalytic reforming method. The maximal absolute hydrogen yield reached 110.9 g H2/kg dry biomass. The product gas was a mixed gas containing 72%H2, 26%CO2, 1.9%CO, and a trace amount of CH4. It was observed that adding biomass char (a by-product of pyrolysis of biomass) could remarkably increase the absolute H2 yield (about 20%-50%). The higher reforming temperature could enhance the steam reforming reaction of organic compounds in crude bio-oil and the reaction of CO and H2O. In addition, the CuZn-Al2O3 catalyst in the water-gas shift bed could also increase the absolute H2 yield via shifting CO to CO2.

  4. Effects of current upon hydrogen production from electrochemical catalytic reforming of acetic acid

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yaqiong; Yuan, Lixia; Ye, Tongqi; Qiu, Songbai; Zhu, Xifeng; Li, Quanxin [Department of Chemical Physics, Lab of Biomass Clean Energy, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026 (China); Torimoto, Youshifumi [Oxy Japan Corporation, 7 Floor, Miya Building, 4-3-4, Kojimachi, Chiyoda-ku, Tokyo 102-0083 (Japan); Yamamoto, Mitsuo [College of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902 (Japan)

    2009-02-15

    Production of hydrogen from acetic acid (HAc) was performed by using a novel electrochemical catalytic reforming (ECR) approach over the 18%NiO/Al{sub 2}O{sub 3} catalyst. ECR was carried out in a fixed-bed continuous flow reactor, where an ac electric current was passed through the catalyst. A high yield of hydrogen (>90%) and carbon conversion (>90%) were obtained as the reforming temperature over 400 C via the ECR approach. The influences of the current on the HAc decomposition, its reforming, and the catalyst reduction in the ECR process have been investigated, which were compared with those in the common steam reforming (CSR) route. The mechanism of the HAc reforming in ECR was also discussed based on the present investigation. (author)

  5. Lewis Acid-Lewis Base Mediated Metal-Free Hydrogen Activation and Catalytic Hydrogenation

    OpenAIRE

    Sumerin, Victor

    2011-01-01

    Organocatalysis, the use of organic molecules as catalysts, is attracting increasing attention as one of the most modern and rapidly growing areas of organic chemistry, with countless research groups in both academia and the pharmaceutical industry around the world working on this subject. The literature review of this thesis mainly focuses on metal-free systems for hydrogen activation and organocatalytic reduction. Since these research topics are relatively new, the literature review al...

  6. Combining Ru, Ni and Ni(OH){sub 2} active sites for improving catalytic performance in benzene hydrogenation

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Lihua, E-mail: lihuazhu@stu.xmu.edu.cn [School of Metallurgy and Chemical Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, Jiang Xi (China); Department of Chemical and Biochemical Engineering, National Engineering Laboratory for Green Productions of Alcohols-Ethers-Esters, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005 (China); Sun, Hanlei; Zheng, Jinbao [Department of Chemical and Biochemical Engineering, National Engineering Laboratory for Green Productions of Alcohols-Ethers-Esters, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005 (China); Yu, Changlin, E-mail: yuchanglinjx@163.com [School of Metallurgy and Chemical Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, Jiang Xi (China); Zhang, Nuowei [Department of Chemical and Biochemical Engineering, National Engineering Laboratory for Green Productions of Alcohols-Ethers-Esters, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005 (China); Shu, Qing [School of Metallurgy and Chemical Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, Jiang Xi (China); Chen, Bing H., E-mail: chenbh@xmu.edu.cn [Department of Chemical and Biochemical Engineering, National Engineering Laboratory for Green Productions of Alcohols-Ethers-Esters, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005 (China)

    2017-05-01

    In this study, the Ru{sub 0.04}Ni{sub 0.96}/C(T) catalysts were successfully prepared by the simple methods of hydrazine-reduction and galvanic replacement, where 0.04/0.96 and T represented the Ru/Ni atomic ratio and reducing temperature of the catalyst in N{sub 2}+10%H{sub 2}, respectively. The nanostructures of the Ru{sub 0.04}Ni{sub 0.96} nanoparticles in the Ru{sub 0.04}Ni{sub 0.96}/C(T) catalysts were controlled by modulating their annealing temperature in N{sub 2}+10%H{sub 2} and characterized by an array of techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy energy dispersive X-ray spectroscopy (STEM-EDS) mapping and high-sensitivity low-energy ion scattering (HS-LEIS). The Ru{sub 0.04}Ni{sub 0.96}/C(30) catalyst, which was composed of Ru clusters or single atoms supported on Ni/Ni(OH){sub 2} nanoparticles, exhibited much better catalytic performance for benzene hydrogenation than the Ru{sub 0.04}Ni{sub 0.96}/C(T) catalysts reduced at above 30 °C, such as Ru{sub 0.04}Ni{sub 0.96}/C(160) with the nanostructure of partial Ru{sub 0.04}Ni{sub 0.9} alloy and Ru{sub 0.04}Ni{sub 0.96}/C(280) with the nanostructure of complete Ru{sub 0.04}Ni{sub 0.9} alloy. The reason was that the synergistic effect of multiple active sites – Ru, Ni and Ni(OH){sub 2} sites was present in the Ru{sub 0.04}Ni{sub 0.96}/C(30) catalyst, where hydrogen was preferentially activated at Ru sites, benzene was probably activated at Ni(OH){sub 2} surface and Ni acted as a “bridge” for transferring activated H{sup ∗} species to activated benzene by hydrogen spillover effect, hydrogenating and forming product – cyclohexane. This study also provided a typical example to illustrate that the synergy effect of multiple active sites can largely improve the catalytic hydrogenation performance. - Highlights: • The Ru

  7. A self-catalytic mixed-conducting membrane reactor for effective production of hydrogen from methane

    Science.gov (United States)

    Dong, Xueliang; Liu, Zhengkun; Jin, Wanqin; Xu, Nanping

    A supported mixed-conducting LNCO membrane with a pore-gradient structure LNO support was successfully prepared via a dry pressing and co-sintering route. The match of sintering behaviors between membrane and support was realized by the preparation of an ABB‧B‧‧B‧BA-type membrane. A scanning electron microscopy (SEM) test demonstrated that the surface of the supported membrane was dense and crack-free and the pore-gradient structure of the support can be observed clearly. The oxygen flux of the supported membrane was about 5.6 times that of the symmetric LNCO membrane. A self-catalytic mixed-conducting membrane reactor was constructed using the prepared membrane for hydrogen production from methane. It was found that this membrane reactor exhibited high performance and good stability for hydrogen production. At 1123 K, the CH 4 conversion, hydrogen selectivity and hydrogen production remained at about 60%, 89% and 8.0 ml(STP) cm -2 min -1, respectively, for more than 120 h.

  8. Effective modeling of hydrogen mixing and catalytic recombination in containment atmosphere with an Eulerian Containment Code

    International Nuclear Information System (INIS)

    Bott, E.; Frepoli, C.; Monti, R.; Notini, V.; Carcassi, M.; Fineschi, F.; Heitsch, M.

    1999-01-01

    Large amounts of hydrogen can be generated in the containment of a nuclear power plant following a postulated accident with significant fuel damage. Different strategies have been proposed and implemented to prevent violent hydrogen combustion. An attractive one aims to eliminate hydrogen without burning processes; it is based on the use of catalytic hydrogen recombiners. This paper describes a simulation methodology which is being developed by Ansaldo, to support the application of the above strategy, in the frame of two projects sponsored by the Commission of the European Communities within the IV Framework Program on Reactor Safety. Involved organizations also include the DCMN of Pisa University (Italy), Battelle Institute and GRS (Germany), Politechnical University of Madrid (Spain). The aims to make available a simulation approach, suitable for use for containment design at industrial level (i.e. with reasonable computer running time) and capable to correctly capture the relevant phenomenologies (e.g. multiflow convective flow patterns, hydrogen, air and steam distribution in the containment atmosphere as determined by containment structures and geometries as well as by heat and mass sources and sinks). Eulerian algorithms provide the capability of three dimensional modelling with a fairly accurate prediction, however lower than CFD codes with a full Navier Stokes formulation. Open linking of an Eulerian code as GOTHIC to a full Navier Stokes CFD code as CFX 4.1 allows to dynamically tune the solving strategies of the Eulerian code itself. The effort in progress is an application of this innovative methodology to detailed hydrogen recombination simulation and a validation of the approach itself by reproducing experimental data. (author)

  9. Catalytic Response and Stability of Nickel/Alumina for the Hydrogenation of 5-Hydroxymethylfurfural in Water.

    Science.gov (United States)

    Perret, Noémie; Grigoropoulos, Alexios; Zanella, Marco; Manning, Troy D; Claridge, John B; Rosseinsky, Matthew J

    2016-03-08

    The catalytic response of Ni on Al2O3 obtained from Ni-Al layered double hydroxides was studied for the liquid-phase hydrogenation of hydroxymethyl furfural to tetrahydrofuran-2,5-diyldimethanol (THFDM) in water. The successive calcination and reduction of the precursors caused the removal of interlayer hydroxyl and carbonate groups and the reduction of Ni(2+) to Ni(0). Four reduced mixed oxide catalysts were obtained, consisting of different amount of Ni metal contents (47-68 wt%) on an Al-rich amorphous component. The catalytic activity was linked to Ni content whereas selectivity was mainly affected by reaction temperature. THFDM was formed in a stepwise manner at low temperature (353 K) whereas 3-hydroxymethyl cyclopentanone was generated at higher temperature. Coke formation caused deactivation; however, the catalytic activity can be regenerated using heat treatment. The results establish Ni on Al2O3 as a promising catalyst for the production of THFDM in water. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Biomass to hydrogen-rich syngas via catalytic steam gasification of bio-oil/biochar slurry.

    Science.gov (United States)

    Chen, Guanyi; Yao, Jingang; Liu, Jing; Yan, Beibei; Shan, Rui

    2015-12-01

    The catalytic steam gasification of bio-oil/biochar slurry (bioslurry) for hydrogen-rich syngas production was investigated in a fixed-bed reactor using LaXFeO3 (X=Ce, Mg, K) perovskite-type catalysts. The effects of elemental substitution in LaFeO3, temperature, water to carbon molar ratio (WCMR) and bioslurry weight hourly space velocity (WbHSV) were examined. The results showed that La0.8Ce0.2FeO3 gave the best performance among the prepared catalysts and had better catalytic activity and stability than the commercial 14 wt.% Ni/Al2O3. The deactivation caused by carbon deposition and sintering was significantly depressed in the case of La0.8Ce0.2FeO3 catalyst. Both higher temperature and lower WbHSV contributed to more H2 yield. The optimal WCMR was found to be 2, and excessive introducing of steam reduced hydrogen yield. The La0.8Ce0.2FeO3 catalyst gave a maximum H2 yield of 82.01% with carbon conversion of 65.57% under the optimum operating conditions (temperature=800°C, WCMR=2 and WbHSV=15.36h(-1)). Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Pd(II-dissolved in ionic liquids: a recyclable catalytic system for the selective biphasic hydrogenation of dienes to monoenes

    Directory of Open Access Journals (Sweden)

    Dupont Jairton

    2000-01-01

    Full Text Available Palladium acetylacetonate dissolved in 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid catalyses the selective two-phase hydrogenation of conjugated and non-conjugated (functionalized and non-functionalized dienes into the respective monoenes. The system does not require the use of organic solvents, the products are removed by simple decantation or distillation and the recovered ionic catalytic solution can be reused several times without any significant changes in its catalytic activity and selectivity.

  12. Numerical study of methanol–steam reforming and methanol–air catalytic combustion in annulus reactors for hydrogen production

    International Nuclear Information System (INIS)

    Chein, Reiyu; Chen, Yen-Cho; Chung, J.N.

    2013-01-01

    Highlights: ► Performance of mini-scale integrated annulus reactors for hydrogen production. ► Flow rates fed to combustor and reformer control the reactor performance. ► Optimum performance is found from balance of flow rates to combustor and reformer. ► Better performance can be found when shell side is designed as combustor. -- Abstract: This study presents the numerical simulation on the performance of mini-scale reactors for hydrogen production coupled with liquid methanol/water vaporizer, methanol/steam reformer, and methanol/air catalytic combustor. These reactors are designed similar to tube-and-shell heat exchangers. The combustor for heat supply is arranged as the tube or shell side. Based on the obtained results, the methanol/air flow rate through the combustor (in terms of gas hourly space velocity of combustor, GHSV-C) and the methanol/water feed rate to the reformer (in terms of gas hourly space velocity of reformer, GHSV-R) control the reactor performance. With higher GHSV-C and lower GHSV-R, higher methanol conversion can be achieved because of higher reaction temperature. However, hydrogen yield is reduced and the carbon monoxide concentration is increased due to the reversed water gas shift reaction. Optimum reactor performance is found using the balance between GHSV-C and GHSV-R. Because of more effective heat transfer characteristics in the vaporizer, it is found that the reactor with combustor arranged as the shell side has better performance compared with the reactor design having the combustor as the tube side under the same operating conditions.

  13. CATALYTIC INTERACTIONS OF RHODIUM, RUTHENIUM, AND MERCURY DURING SIMULATED DWPF CPC PROCESSING WITH HYDROGEN GENERATION

    Energy Technology Data Exchange (ETDEWEB)

    Koopman, D

    2008-10-09

    Simulations of the Defense Waste Processing Facility (DWPF) Chemical Processing Cell (CPC) vessels were performed as part of the ongoing investigation into catalytic hydrogen generation. Rhodium, ruthenium, and mercury have been identified as the principal elemental factors affecting the peak hydrogen generation rate in the DWPF Sludge Receipt and Adjustment Tank (SRAT) for a given acid addition. The primary goal of this study is to identify any significant interactions between the three factors. Noble metal concentrations were similar to recent sludge batches. Rh ranged from 0.0026-0.013% and Ru ranged from 0.010-0.050% in the dried sludge solids, while initial Hg ranged from 0.5-2.5 wt%. An experimental matrix was developed to ensure that the existence of statistically significant two-way interactions could be determined without confounding of the main effects with the two-way interaction effects. The nominal matrix design consisted of twelve SRAT cycles. Testing included: a three factor (Rh, Ru, and Hg) study at two levels per factor (eight runs), two duplicate midpoint runs, and two additional replicate runs to assess reproducibility away from the midpoint. Midpoint testing can identify potential quadratic effects from the three factors. A single sludge simulant was used for all tests. Acid addition was kept effectively constant except to compensate for variations in the starting mercury concentration. Six Slurry Mix Evaporator (SME) cycles were performed to supplement the SME hydrogen generation database. Some of the preliminary findings from this study include: (1) Rh was linked to the maximum SRAT hydrogen generation rate in the first two hours after acid addition in preliminary statistical modeling. (2) Ru was linked conclusively to the maximum SRAT hydrogen generation rate in the last four hours of reflux in preliminary statistical modeling. (3) Increasing the ratio of Hg/Rh shifted the noble metal controlling the maximum SRAT hydrogen generation rate from

  14. Life cycle assessment of hydrogenated biodiesel production from waste cooking oil using the catalytic cracking and hydrogenation method.

    Science.gov (United States)

    Yano, Junya; Aoki, Tatsuki; Nakamura, Kazuo; Yamada, Kazuo; Sakai, Shin-ichi

    2015-04-01

    There is a worldwide trend towards stricter control of diesel exhaust emissions, however presently, there are technical impediments to the use of FAME (fatty acid methyl esters)-type biodiesel fuel (BDF). Although hydrogenated biodiesel (HBD) is anticipated as a new diesel fuel, the environmental performance of HBD and its utilization system have not been adequately clarified. Especially when waste cooking oil is used as feedstock, not only biofuel production but also the treatment of waste cooking oil is an important function for society. A life cycle assessment (LCA), including uncertainty analysis, was conducted to determine the environmental benefits (global warming, fossil fuel consumption, urban air pollution, and acidification) of HBD produced from waste cooking oil via catalytic cracking and hydrogenation, compared with fossil-derived diesel fuel or FAME-type BDF. Combined functional unit including "treatment of waste cooking oil" and "running diesel vehicle for household waste collection" was established in the context of Kyoto city, Japan. The calculation utilized characterization, damage, and integration factors identified by LIME2, which was based on an endpoint modeling method. The results show that if diesel vehicles that comply with the new Japanese long-term emissions gas standard are commonly used in the future, the benefit of FAME-type BDF will be relatively limited. Furthermore, the scenario that introduced HBD was most effective in reducing total environmental impact, meaning that a shift from FAME-type BDF to HBD would be more beneficial. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. Catalytic

    Directory of Open Access Journals (Sweden)

    S.A. Hanafi

    2014-03-01

    Full Text Available A series of dealuminated Y-zeolites impregnated by 0.5 wt% Pt catalysts promoted by different amounts of Ni, Pd or Cr (0.3 and 0.6 wt% were prepared and characterized as hydrocracking catalysts. The physicochemical and structural characterization of the solid catalysts were investigated and reported through N2 physisorption, XRD, TGA-DSC, FT-IR and TEM techniques. Solid catalysts surface acidities were investigated through FT-IR spectroscopy aided by pyridine adsorption. The solid catalytic activities were evaluated through hydroconversion of n-hexane and n-heptane employing micro-catalytic pulse technique directly connected to a gas chromatograph analyzer. The thermal stability of the solids was also investigated up to 800 °C. Crystallinity studies using the XRD technique of all modified samples proved analogous to the parent Y-zeolite, exhibiting nearly an amorphous and microcrystalline character of the second metal oxides. Disclosure of bimetallic catalysts crystalline characterization, through XRD, was not viable. The nitrogen adsorption–desorption isotherms for all samples concluded type I adsorption isotherms, without any hysteresis loop, indicating that the entire pore system is composed of micropores. TEM micrographs of the solid catalysts demonstrate well-dispersed Pt, Ni and Cr nanoparticles having sizes of 2–4 nm and 7–8 nm, respectively. The catalytic activity results indicate that the bimetallic (0.5Pt–0.3Cr/D18H–Y catalyst is the most active towards n-hexane and n-heptane isomerization while (0.5Pt–0.6Ni/D18H–Y catalyst can be designed as most suitable as a cracking catalyst.

  16. Efficient, crosswise catalytic promiscuity among enzymes that catalyze phosphoryl transfer.

    Science.gov (United States)

    Mohamed, Mark F; Hollfelder, Florian

    2013-01-01

    The observation that one enzyme can accelerate several chemically distinct reactions was at one time surprising because the enormous efficiency of catalysis was often seen as inextricably linked to specialization for one reaction. Originally underreported, and considered a quirk rather than a fundamental property, enzyme promiscuity is now understood to be important as a springboard for adaptive evolution. Owing to the large number of promiscuous enzymes that have been identified over the last decade, and the increased appreciation for promiscuity's evolutionary importance, the focus of research has shifted to developing a better understanding of the mechanistic basis for promiscuity and the origins of tolerant or restrictive specificity. We review the evidence for widespread crosswise promiscuity amongst enzymes that catalyze phosphoryl transfer, including several members of the alkaline phosphatase superfamily, where large rate accelerations between 10(6) and 10(17) are observed for both native and multiple promiscuous reactions. This article is part of a Special Issue entitled: Chemistry and mechanism of phosphatases, diesterases and triesterases. Copyright © 2012 Elsevier B.V. All rights reserved.

  17. Catalytic on-board hydrogen production from methanol and ammonia for mobile application

    Energy Technology Data Exchange (ETDEWEB)

    Soerijanto, H.

    2008-08-15

    This PhD thesis deals with the catalytic hydrogen production for mobile application, for example for the use in fuel cells for electric cars. Electric powered buses with fuel cells as driving system are well known, but the secure hydrogen storage in adequate amounts for long distance drive is still a topic of discussion. Methanol is an excellent hydrogen carrier. First of all it has a high H:C ratio and therefore a high energy density. Secondly the operating temperature of steam reforming of methanol is comparatively low (250 C) and there is no risk of coking since methanol has no C-C bond. Thirdly methanol is a liquid, which means that the present gasoline infrastructure can be used. For the further development of catalysts and for the construction of a reformer it is very important to characterize the catalysts very well. For the dimensioning and the control of an on-board production of hydrogen it is essential to draw accurately on the thermodynamic, chemical and kinetic data of the reaction. At the first part of this work the mesoporous Cu/ZrO{sub 2}/CeO{sub 2}-catalysts with various copper contents were characterized and their long-term stability and selectivity were investigated, and the kinetic data were determined. Carbon monoxide is generated by reforming of carbon containing material. This process is undesired since CO poisons the Pt electrode of the fuel cell. The separation of hydrogen by metal membranes is technically feasible and a high purity of hydrogen can be obtained. However, due to their high density this procedure is not favourable because of its energy loss. In this study a concept is presented, which enables an autothermal mode by application of ceramic membrane and simultaneously could help to deal with the CO problem. The search for an absolutely selective catalyst is uncertain. The production of CO can be neither chemically nor thermodynamically excluded, if carbon is present in the hydrogen carrier. Since enrichment or separation are

  18. Basic promoters effect over nickel/alumina catalyst on hydrogen production via methane catalytic partial oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Requies, J.; Cabrero, M. A.; Barrio, V. I.; Cambra, J. F.; Arias, P. L.; Guemez, B.; La Oarola, V.; Pena, M. A.; Fierro, J. L. G.

    2005-07-01

    The European Directives concerning the environment protection and the sustainable development include the green fuels production and utilization. Thus, one of their major objectives is related to the research on processes to obtain green fuels and their direct application or their transformation in clean energy carriers and final fuels as hydrogen. Hydrogen is an energy vector that is being considered by most countries and many energy companies as a possible long-term solution in the electricity, heating and transport energy markets, where it will offer greenhouse gas abatement and other local air quality benefits. Before the generalization of hydrogen production from renewable resources, other production processes can fulfil the objective of generating an energy infrastructure based on hydrogen. By the methane catalytic partial oxidation (CPO) process or by an analogous one, like Wet CPO, a synthesis gas can be produced. This gas can be further treated to maximize the hydrogen production or it can also be used to generate clean liquid fuels precursors via Fischer-Tropsch synthesis. In the present work, the hydrogen and/or synthesis gas production via CPO or Wet-CPO is studied using nickel catalyst supported on -Al2O3 promoted by basic metals (Ca and Mg). The conventional nickel supported catalysts are highly effective for these processes. Nevertheless, they are unsatisfactory with respect to coke formation. Deactivation of these catalysts by a coke formation is sometimes a serious limitation. The addition of calcium and magnesium onto Ni/ -Al2O3 aims to eliminate the coke formation, via a reduction on support acidity, and as a result to improve these catalysts performance. The catalysts were prepared by consecutive wet impregnation method, and -Al2O3 was employed as acid support. The nominal contents of nickel were 15 and 25 wt%. The nominal contents of promoters were 5 and 10 wt% of Mg or Ca. The catalyst textural characterization was studied using different

  19. Transition-Metal-Catalyzed Asymmetric Hydrogenation and Transfer Hydrogenation: Sustainable Chemistry to Access Bioactive Molecules.

    Science.gov (United States)

    Ayad, Tahar; Phansavath, Phannarath; Ratovelomanana-Vidal, Virginie

    2016-12-01

    Over the last few decades, the development of new and highly efficient synthetic methods to obtain chiral compounds has become an increasingly important and challenging research area in modern synthetic organic chemistry. In this account, we review recent work from our laboratory toward the synthesis of valuable chiral building blocks through transition-metal-catalyzed asymmetric hydrogenation and transfer hydrogenation of C=O, C=N and C=C bonds. Application to the synthesis of biologically relevant products is also described. © 2016 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Catalytic hydrogenation rate of polycyclic aromatic hydrocarbons in supercritical carbon dioxide containing polymer-stabilized palladium nanoparticles.

    Science.gov (United States)

    Liao, Weisheng; Liu, Hsin-Wang; Chen, Hsing-Jung; Chang, Wen-Yen; Chiu, Kong-Hwa; Wai, Chien M

    2011-01-01

    Catalytic hydrogenation of polycyclic aromatic hydrocarbons (PAHs) with up to four fused benzene rings over high-density-polyethylene-stabilized palladium nanoparticles in supercritical carbon dioxide via in situ UV/Vis spectroscopy is presented. PAHs can be efficiently converted to saturated polycyclic hydrocarbons using this green technique under mild conditions at 20 MPa of CO₂ containing 1 MPa of H₂ at 40-50°C. Kinetic studies based on in situ UV/Vis spectra of the CO₂ phase reveal that the initial hydrogenation of a given PAH and the subsequent hydrogenations of its intermediates are pseudo-first-order. The hydrogenation rate of the latter is always much smaller than that of the former probably due to increasing steric hindrance introduced by the hydrogenated benzene rings of PAHs which impedes the adsorption process and hydrogen access to PAHs on catalyst surfaces. Copyright © 2010 Elsevier Ltd. All rights reserved.

  1. Transfer hydrogenation catalysis in cells as a new approach to anticancer drug design

    Science.gov (United States)

    Soldevila-Barreda, Joan J.; Romero-Canelón, Isolda; Habtemariam, Abraha; Sadler, Peter J.

    2015-01-01

    Organometallic complexes are effective hydrogenation catalysts for organic reactions. For example, Noyori-type ruthenium complexes catalyse reduction of ketones by transfer of hydride from formate. Here we show that such catalytic reactions can be achieved in cancer cells, offering a new strategy for the design of safe metal-based anticancer drugs. The activity of ruthenium(II) sulfonamido ethyleneamine complexes towards human ovarian cancer cells is enhanced by up to 50 × in the presence of low non-toxic doses of formate. The extent of conversion of coenzyme NAD+ to NADH in cells is dependent on formate concentration. This novel reductive stress mechanism of cell death does not involve apoptosis or perturbation of mitochondrial membrane potentials. In contrast, iridium cyclopentadienyl catalysts cause cancer cell death by oxidative stress. Organometallic complexes therefore have an extraordinary ability to modulate the redox status of cancer cells. PMID:25791197

  2. Effect of catalytic cylinders on autothermal reforming of methane for hydrogen production in a microchamber reactor.

    Science.gov (United States)

    Yan, Yunfei; Guo, Hongliang; Zhang, Li; Zhu, Junchen; Yang, Zhongqing; Tang, Qiang; Ji, Xin

    2014-01-01

    A new multicylinder microchamber reactor is designed on autothermal reforming of methane for hydrogen production, and its performance and thermal behavior, that is, based on the reaction mechanism, is numerically investigated by varying the cylinder radius, cylinder spacing, and cylinder layout. The results show that larger cylinder radius can promote reforming reaction; the mass fraction of methane decreased from 26% to 21% with cylinder radius from 0.25 mm to 0.75 mm; compact cylinder spacing corresponds to more catalytic surface and the time to steady state is decreased from 40 s to 20 s; alteration of staggered and aligned cylinder layout at constant inlet flow rates does not result in significant difference in reactor performance and it can be neglected. The results provide an indication and optimize performance of reactor; it achieves higher conversion compared with other reforming reactors.

  3. Effect of Catalytic Cylinders on Autothermal Reforming of Methane for Hydrogen Production in a Microchamber Reactor

    Directory of Open Access Journals (Sweden)

    Yunfei Yan

    2014-01-01

    Full Text Available A new multicylinder microchamber reactor is designed on autothermal reforming of methane for hydrogen production, and its performance and thermal behavior, that is, based on the reaction mechanism, is numerically investigated by varying the cylinder radius, cylinder spacing, and cylinder layout. The results show that larger cylinder radius can promote reforming reaction; the mass fraction of methane decreased from 26% to 21% with cylinder radius from 0.25 mm to 0.75 mm; compact cylinder spacing corresponds to more catalytic surface and the time to steady state is decreased from 40 s to 20 s; alteration of staggered and aligned cylinder layout at constant inlet flow rates does not result in significant difference in reactor performance and it can be neglected. The results provide an indication and optimize performance of reactor; it achieves higher conversion compared with other reforming reactors.

  4. A Highly Efficient Heterogenized Iridium Complex for the Catalytic Hydrogenation of Carbon Dioxide to Formate.

    Science.gov (United States)

    Park, Kwangho; Gunasekar, Gunniya Hariyanandam; Prakash, Natarajan; Jung, Kwang-Deog; Yoon, Sungho

    2015-10-26

    A heterogenized catalyst on a highly porous covalent triazine framework was synthesized and characterized to have a coordination environment similar to that of its homogeneous counterpart. The catalyst efficiently converted CO2 into formate through hydrogenation with a turnover number of 5000 after 2 h and an initial turnover frequency of up to 5300 h(-1) ; both of these values are the highest reported to date for a heterogeneous catalyst, which makes it attractive toward industrial application. Furthermore, the synthesized catalyst was found to be stable in air and was recycled by simple filtration without significant loss of catalytic activity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. H2CAP - Hydrogen assisted catalytic biomass pyrolysis for green fuels

    DEFF Research Database (Denmark)

    Stummann, Magnus Zingler; Høj, Martin; Gabrielsen, Jostein

    Fast pyrolysis of biomass produces a high yield of bio-oil through well-established technologies [1]. To utilizethis oil as liquid fuel the oxygen content must be reduced from 15-30 wt.% down to <1 wt.%, which increases heating value and stability and decreases acidity [1]. Upgrading bio-oil by c......Fast pyrolysis of biomass produces a high yield of bio-oil through well-established technologies [1]. To utilizethis oil as liquid fuel the oxygen content must be reduced from 15-30 wt.% down to ...-oil by catalytic hydrodeoxygenation (HDO) is challenged by severe polymerization and coking upon heating the oil. Alternatively, performing fast pyrolysis in high-pressure hydrogen atmosphere in a fluid bed reactor with a HDO catalyst as bed medium, could immediately stabilize reactive pyrolysis vapors [2...

  6. β-Molybdenum nitride: synthesis mechanism and catalytic response in the gas phase hydrogenation of p-chloronitrobenzene

    NARCIS (Netherlands)

    Cárdenas-Lizana, F.; Gómez-Quero, S.; Perret, N.; Kiwi-Minsker, L.; Keane, M.A.

    2011-01-01

    A temperature programmed treatment of MoO3 in flowing N2 + H2 has been employed to prepare β-phase molybdenum nitride (β-Mo2N) which has been used to promote, for the first time, the catalytic hydrogenation of p-chloronitrobenzene. The reduction/nitridation synthesis steps have been monitored in

  7. In situ catalytic hydrogenation of model compounds and biomass-derived phenolic compounds for bio-oil upgrading

    Science.gov (United States)

    Junfeng Feng; Zhongzhi Yang; Chung-yun Hse; Qiuli Su; Kui Wang; Jianchun Jiang; Junming Xu

    2017-01-01

    The renewable phenolic compounds produced by directional liquefaction of biomass are a mixture of complete fragments decomposed from native lignin. These compounds are unstable and difficult to use directly as biofuel. Here, we report an efficient in situ catalytic hydrogenation method that can convert phenolic compounds into saturated cyclohexanes. The process has...

  8. Catalytic hydrogenation of cyclic carbonates: a practical approach from CO2 and epoxides to methanol and diols.

    Science.gov (United States)

    Han, Zhaobin; Rong, Liangce; Wu, Jiang; Zhang, Lei; Wang, Zheng; Ding, Kuiling

    2012-12-21

    Two birds with one stone: the simultaneous production of two important bulk chemicals, methanol and ethylene glycol, from CO(2) and ethylene oxide has been achieved under mild conditions by the highly efficient homogeneous catalytic hydrogenation of ethylene carbonate in the presence of a (PNP)Ru(II) catalyst. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Rh nanoparticles supported on ultrathin carbon nanosheets for high-performance oxygen reduction reaction and catalytic hydrogenation.

    Science.gov (United States)

    Lin, Chong; Wu, Guanghao; Li, Huiqin; Geng, Yanmin; Xie, Gang; Yang, Jianhui; Liu, Bin; Jin, Jian

    2017-02-02

    We reported a facile and scalable salt-templated approach to produce monodisperse Rh nanoparticles (NPs) on ultrathin carbon nanosheets with the assistance of calcination under inert gas. More importantly, in spite of the essentially poor ORR activity of Rh/C, the acquired Rh/C hybrid nanosheets display a comparable ORR activity to the optimal commercial Pt/C catalyst, which may be due to the extra-small size of Rh NPs and the 2D defect-rich amorphous carbon nanosheets that can facilitate the charge transfer and reactive surface exposure. Moreover, Rh/C nanosheets present the optimal current density and best durability with the minimum decline during the entire test, so that ∼93% activity after 20 000 s is achieved, indicating a good lifetime for ORR. In contrast, commercial Pt/C and commercial Rh/C exhibited worse durability, so that ∼74% and ∼85% activities after 20 000 s are maintained. What's more, in the model system of reduction of 4-nitrophenol (4-NP), the kinetic constant k for Rh/C nanosheets is 3.1 × 10 -3 , which is 4.5 times than that of the commercial Rh/C catalyst, revealing that our Rh/C hybrid nanosheets can be potentially applied in industrial catalytic hydrogenation. This work opens a novel and facile way for the rest of the precious metal NPs to be supported on ultrathin carbon nanosheets for heterogeneous catalysis.

  10. Experimental and Numerical Evaluation of the By-Pass Flow in a Catalytic Plate Reactor for Hydrogen Production

    DEFF Research Database (Denmark)

    Sigurdsson, Haftor Örn; Kær, Søren Knudsen

    2011-01-01

    Numerical and experimental study is performed to evaluate the reactant by-pass flow in a catalytic plate reactor with a coated wire mesh catalyst for steam reforming of methane for hydrogen generation. By-pass of unconverted methane is evaluated under different wire mesh catalyst width to reactor...... duct width ratios, the results show that altering this ratio from 0.98 to 0.96 results in an increase in by-pass mass flow of 22%. Effect of catalytic wire mesh flow resistance on by-pass flow has also been investigated and results show increased by-pass flow as catalytic wire mesh flow resistance...... increases. The numerical results are in good agreement with experimental data. The study improves the understanding of the underlying transport phenomena in these reactors and shows that the flow maldistribution in a catalytic plate reactor using a coated wire mesh has to be considered....

  11. Coupling of protein motions and hydrogen transfer during catalysis by Escherichia coli dihydrofolate reductase.

    Science.gov (United States)

    Swanwick, Richard S; Maglia, Giovanni; Tey, Lai-hock; Allemann, Rudolf K

    2006-02-15

    The enzyme DHFR (dihydrofolate reductase) catalyses hydride transfer from NADPH to, and protonation of, dihydrofolate. The physical basis of the hydride transfer step catalysed by DHFR from Escherichia coli has been studied through the measurement of the temperature dependence of the reaction rates and the kinetic isotope effects. Single turnover experiments at pH 7.0 revealed a strong dependence of the reaction rates on temperature. The observed relatively large difference in the activation energies for hydrogen and deuterium transfer led to a temperature dependence of the primary kinetic isotope effects from 3.0+/-0.2 at 5 degrees C to 2.2+/-0.2 at 40 degrees C and an inverse ratio of the pre-exponential factors of 0.108+/-0.04. These results are consistent with theoretical models for hydrogen transfer that include contributions from quantum mechanical tunnelling coupled with protein motions that actively modulate the tunnelling distance. Previous work had suggested a coupling of a remote residue,Gly121, with the kinetic events at the active site. However, pre-steady-state experiments at pH 7.0 with the mutant G121V-DHFR, in which Gly121 was replaced with valine, revealed that the chemical mechanism of DHFR catalysis was robust to this replacement. The reduced catalytic efficiency of G121V-DHFR was mainly a consequence of the significantly reduced pre-exponential factors, indicating the requirement for significant molecular reorganization during G121V-DHFR catalysis. In contrast, steady-state measurements at pH 9.5, where hydride transfer is rate limiting, revealed temperature-independent kinetic isotope effects between 15 and 35 degrees C and a ratio of the pre-exponential factors above the semi-classical limit, suggesting a rigid active site configuration from which hydrogen tunnelling occurs. The mechanism by which hydrogen tunnelling in DHFR is coupled with the environment appears therefore to be sensitive to pH.

  12. Charge transfer in proton-hydrogen collisions under Debye plasma

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharya, Arka [Department of Mathematics, Burdwan University, Golapbag, Burdwan 713 104, West Bengal (India); Kamali, M. Z. M. [Centre for Foundation Studies in Science, University of Malaya, 50603 Kuala Lumpur (Malaysia); Ghoshal, Arijit, E-mail: arijit98@yahoo.com [Department of Mathematics, Burdwan University, Golapbag, Burdwan 713 104, West Bengal (India); Department of Mathematics, Kazi Nazrul University, B.C.W. Campus, Asansol 713 304, West Bengal (India); Institute of Mathematical Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia); Ratnavelu, K. [Department of Mathematics, Kazi Nazrul University, B.C.W. Campus, Asansol 713 304, West Bengal (India)

    2015-02-15

    The effect of plasma environment on the 1s → nlm charge transfer, for arbitrary n, l, and m, in proton-hydrogen collisions has been investigated within the framework of a distorted wave approximation. The effect of external plasma has been incorporated using Debye screening model of the interacting charge particles. Making use of a simple variationally determined hydrogenic wave function, it has been possible to obtain the scattering amplitude in closed form. A detailed study has been made to investigate the effect of external plasma environment on the differential and total cross sections for electron capture into different angular momentum states for the incident energy in the range of 20–1000 keV. For the unscreened case, our results are in close agreement with some of the most accurate results available in the literature.

  13. Application of microscopy technology in thermo-catalytic methane decomposition to hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Mei, Irene Lock Sow, E-mail: irene.sowmei@gmail.com; Lock, S. S. M., E-mail: serenelock168@gmail.com; Abdullah, Bawadi, E-mail: bawadi-abdullah@petronas.com.my [Chemical Engineering Department, Universiti Teknologi PETRONAS, Bandar Sri Iskandar, 31750, Perak (Malaysia)

    2015-07-22

    Hydrogen production from the direct thermo-catalytic decomposition of methane is a promising alternative for clean fuel production because it produces pure hydrogen without any CO{sub x} emissions. However, thermal decomposition of methane can hardly be of any practical and empirical interest in the industry unless highly efficient and effective catalysts, in terms of both specific activity and operational lifetime have been developed. In this work, bimetallic Ni-Pd on gamma alumina support have been developed for methane cracking process by using co-precipitation and incipient wetness impregnation method. The calcined catalysts were characterized to determine their morphologies and physico-chemical properties by using Brunauer-Emmett-Teller method, Field Emission Scanning Electron Microscopy, Energy-dispersive X-ray spectroscopy and Thermogravimetric Analysis. The results suggested that that the catalyst which is prepared by the co-precipitation method exhibits homogeneous morphology, higher surface area, have uniform nickel and palladium dispersion and higher thermal stability as compared to the catalyst which is prepared by wet impregnation method. This characteristics are significant to avoid deactivation of the catalysts due to sintering and carbon deposition during methane cracking process.

  14. Recent Developments in the Area of Asymmetric Transfer Hydrogenation

    Directory of Open Access Journals (Sweden)

    Tim Walsgrove

    2001-01-01

    Full Text Available The use of an enantiomerically pure amino alcohol, coupled to a transfer hydrogenation process, in the asymmetric catalysis of the reduction of ketones to alcohols, is described. The process works well for unfunctionalised ketones, affording e.e.s of up to 98%, and excellent conversions. We have recently extended, for the first time in this application, the scope of the methodology to the reductions of a-heteroatom substituted substrates, through the use of the appropriate protecting groups on each atom.

  15. Catalytic hydrogenation of polyaromatic hydrocarbon (PAH) compounds in supercritical carbon dioxide over supported palladium.

    Science.gov (United States)

    Yuan, Tao; Marshall, William D

    2007-12-01

    A series of supported palladium catalysts were evaluated for their ability to mediate the complete hydrogenation of polycyclic aromatic hydrocarbon (PAH) compounds. Benzo[a]pyrene (B[a]P) or phenanthrene (Phe) in hexane was merged with a hydrogen-carbon dioxide [5% (w/w) H(2)/CO(2)] stream and transferred to a flow through mini-reactor (capacity ca. 1 g) that was maintained at 90 degrees C under a back-pressure of 20.68 MPa. Effluent from the reactor trapped in hexane was monitored/quantified by gas chromatography-mass spectrometry. Catalyst formulations supported on iron powder, high density polyethylene (HDPE) or gamma-alumina were prepared and compared in terms of hydrogenation activity as measured by the quantity of substrate per unit time that could be perhydrogenated to toxicologically innocuous products. Both of the Pd preparations supported on gamma-alumina were more efficient than a commercial Pd(0) (5% w/w) on gamma-Al(2)O(3) formulation or preparations supported on HDPE or the iron powder. Bimetallic mixtures with Pd increased the hydrogenation activity when co-deposited with Cu or Ni but not with Ag or Co. However, increases in hydrogenation activity by increasing the loading of Pd (or bimetallic mixture) on this surface were limited. Despite using supercritical carbon dioxide (scCO(2)) to swell the surfaces of the polymer, the deposition of nanoparticles within the polyethylene formulation was appreciably less active than either the oxidic or the Fe(0) formulations.

  16. Catalytic dehydrogenation of isobutane in the presence of hydrogen over Cs-modified Ni{sub 2}P supported on active carbon

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Yanli [Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin Key Laboratory of Applied Catalysis Science and Technology, College of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Sang, Huanxin [Tianjin Academy of Environmental Sciences, Tianjin 300191 (China); Wang, Kang [Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin Key Laboratory of Applied Catalysis Science and Technology, College of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Wang, Xitao, E-mail: wangxt@tju.edu.cn [Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin Key Laboratory of Applied Catalysis Science and Technology, College of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China)

    2014-10-15

    Graphical abstract: - Highlights: • Ni{sub 2}P catalyst is tested in dehydrogenation of isobutane for the first time. • The effects of Cs promoter on catalytic performance of Ni2P/AC were investigated. • Cs-Ni2P/AC exhibits high activity and selectivity for isobutane dehydrogenation. - Abstract: In this article, an environmentally friendly non-noble-metal class of Cs-Ni{sub 2}P/active carbon (AC) catalyst was prepared and demonstrated to exhibit enhanced catalytic performance in isobutane dehydrogenation. The results of activity tests reveal that Ni/AC catalyst was highly active for isobutane cracking, which led to the formation of abundant methane and coke. After the introduction of phosphorus through impregnation with ammonium di-hydrogen phosphate and H{sub 2}-temperature programmed reduction, undesired cracking reactions were effectively inhibited, and the selectivity to isobutene and stability of catalyst increased remarkably. The characterization results indicate that, after the addition of phosphorous, the improvement of dehydrogenation selectivity is ascribed to the partial positive charges carried on Ni surface in Ni{sub 2}P particles, which decreases the strength of Ni-C bond between Ni and carbonium-ion intermediates and the possibility of excessive dehydrogenation. In addition, Cs-modified Ni{sub 2}P/AC catalysts display much higher catalytic performance as compared to Ni{sub 2}P/AC catalyst. Cs-Ni{sub 2}P-6.5 catalyst has the highest catalytic performance, and the selectivity to isobutene higher than 93% can be obtained even after 4 h reaction. The enhancement in catalytic performance of the Cs-modified catalysts is mainly attributed to the function of Cs to improve the dispersion of Ni{sub 2}P particles, transfer electron from Cs to Ni, and decrease acid site number and strength.

  17. Highly enantioselective hydrogenation of N-aryl imines derived from acetophenones by using Ru-pybox complexes under hydrogenation or transfer hydrogenation conditions in isopropanol.

    Science.gov (United States)

    Menéndez-Pedregal, Estefanía; Vaquero, Mónica; Lastra, Elena; Gamasa, Pilar; Pizzano, Antonio

    2015-01-07

    The asymmetric reduction of N-aryl imines derived from acetophenones by using Ru complexes bearing both a pybox (2,6-bis(oxazoline)pyridine) and a monodentate phosphite ligand has been described. The catalysts show good activity with a diverse range of substrates, and deliver the amine products in very high levels of enantioselectivity (up to 99 %) under both hydrogenation and transfer hydrogenation conditions in isopropanol. From deuteration studies, a very different labeling is observed under hydrogenation and transfer hydrogenation conditions, which demonstrates the different nature of the hydrogen source in both reactions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Catalytic activity of mono and bimetallic Zn/Cu/MWCNTs catalysts for the thermocatalyzed conversion of methane to hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Erdelyi, B. [Department of Physical Chemistry, Faculty of Science, P.J. Šafárik University, Moyzesova 11, 041 54 Košice (Slovakia); Institute of Physics, Faculty of Science, P.J. Šafárik University, Park Angelium 9, 040 01 Košice (Slovakia); Oriňak, A., E-mail: andrej.orinak@upjs.sk [Department of Physical Chemistry, Faculty of Science, P.J. Šafárik University, Moyzesova 11, 041 54 Košice (Slovakia); Oriňaková, R. [Department of Physical Chemistry, Faculty of Science, P.J. Šafárik University, Moyzesova 11, 041 54 Košice (Slovakia); Lorinčík, J. [Research Center Rez, Hlavní 130, 250 68 Husinec-Řež (Czech Republic); Jerigová, M. [Department of Physical Chemistry, Comenius University, Mlynská dolina 842 15 Bratislava 4 (Slovakia); Velič, D. [Department of Physical Chemistry, Comenius University, Mlynská dolina 842 15 Bratislava 4 (Slovakia); International Laser Centre, Ilkovičová 3, 841 01 Bratislava (Slovakia); Mičušík, M. [Polymer institute, Slovak Academy of Sciences, Dubravská cesta 9, 84541 Bratislava (Slovakia); and others

    2017-02-28

    Highlights: • Zn/Cu/MWCNTs catalyst with good activity. • Methane conversion to hydrogen with high effectivity. • ZnO/Cu responsible for catalytic activity. - Abstract: Mono and bimetallic multiwalled carbon nanotubes (MWCNTs) fortified with Cu and Zn metal particles were studied to improve the efficiency of the thermocatalytic conversion of methane to hydrogen. The surface of the catalyst and the dispersion of the metal particles were studied by scanning electron microscopy (SEM), secondary ion mass spectrometry (SIMS) and with energy-dispersive X-ray spectroscopy (EDS). It was confirmed that the metal particles were successfully dispersed on the MWCNT surface and XPS analysis showed that the Zn was oxidised to ZnO at high temperatures. The conversion of methane to hydrogen during the catalytic pyrolysis was studied by pyrolysis gas chromatography using different amounts of catalyst. The best yields of hydrogen were obtained using pyrolysis conditions of 900 °C and 1.2 mg of Zn/Cu/MWCNT catalyst for 1.5 mL of methane.The initial conversion of methane to hydrogen obtained with Zn/Cu/MWCNTs was 49%, which represent a good conversion rate of methane to hydrogen for a non-noble metal catalyst.

  19. Hydrogenation-controlled phase transition on two-dimensional transition metal dichalcogenides and their unique physical and catalytic properties

    Science.gov (United States)

    Qu, Yuanju; Pan, Hui; Kwok, Chi Tat

    2016-01-01

    Two-dimensional (2D) transition metal dichalcogenides (TMDs) have been widely used from nanodevices to energy harvesting/storage because of their tunable physical and chemical properties. In this work, we systematically investigate the effects of hydrogenation on the structural, electronic, magnetic, and catalytic properties of 33 TMDs based on first-principles calculations. We find that the stable phases of TMD monolayers can transit from 1T to 2H phase or vice versa upon the hydrogenation. We show that the hydrogenation can switch their magnetic and electronic states accompanying with the phase transition. The hydrogenation can tune the magnetic states of TMDs among non-, ferro, para-, and antiferro-magnetism and their electronic states among semiconductor, metal, and half-metal. We further show that, out of 33 TMD monolayers, 2H-TiS2 has impressive catalytic ability comparable to Pt in hydrogen evolution reaction in a wide range of hydrogen coverages. Our findings would shed the light on the multi-functional applications of TMDs. PMID:27686869

  20. Selective Catalytic Hydrogenation of Arenols by a Well-Defined Complex of Ruthenium and Phosphorus–Nitrogen PN3–Pincer Ligand Containing a Phenanthroline Backbone

    KAUST Repository

    Li, Huaifeng

    2017-05-30

    Selective catalytic hydrogenation of aromatic compounds is extremely challenging using transition-metal catalysts. Hydrogenation of arenols to substituted tetrahydronaphthols or cyclohexanols has been reported only with heterogeneous catalysts. Herein, we demonstrate the selective hydrogenation of arenols to the corresponding tetrahydronaphthols or cyclohexanols catalyzed by a phenanthroline-based PN3-ruthenium pincer catalyst.

  1. Long-Range Electrostatics-Induced Two-Proton Transfer Captured by Neutron Crystallography in an Enzyme Catalytic Site.

    Science.gov (United States)

    Gerlits, Oksana; Wymore, Troy; Das, Amit; Shen, Chen-Hsiang; Parks, Jerry M; Smith, Jeremy C; Weiss, Kevin L; Keen, David A; Blakeley, Matthew P; Louis, John M; Langan, Paul; Weber, Irene T; Kovalevsky, Andrey

    2016-04-11

    Neutron crystallography was used to directly locate two protons before and after a pH-induced two-proton transfer between catalytic aspartic acid residues and the hydroxy group of the bound clinical drug darunavir, located in the catalytic site of enzyme HIV-1 protease. The two-proton transfer is triggered by electrostatic effects arising from protonation state changes of surface residues far from the active site. The mechanism and pH effect are supported by quantum mechanics/molecular mechanics (QM/MM) calculations. The low-pH proton configuration in the catalytic site is deemed critical for the catalytic action of this enzyme and may apply more generally to other aspartic proteases. Neutrons therefore represent a superb probe to obtain structural details for proton transfer reactions in biological systems at a truly atomic level. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Metal-free catalytic oxidation of sulfides to sulfoxides with ammonium nitrate, ammonium hydrogen sulfate and ammonium bromide as catalyst

    OpenAIRE

    Ghorbani-Choghamarani, Arash; Zolfigol, Mohammad Ali; Ayazi-Nasrabadi, Roia

    2010-01-01

    A general and metal-free catalytic oxidation of aliphatic and aromatic sulfides to their corresponding sulfoxides via combination of ammonium nitrate (NH4NO3), supported ammonium hydrogen sulfate on silica gel (NH4HSO4-SiO2) and a catalytic amount of ammonium bromide (NH4Br) in the presence of wet SiO2 (50%, w/w) has been investigated. The reactions were carried out heterogeneously and selectively in short reaction times in CH2Cl2 at room temperature. This protocol is mild and efficient compa...

  3. A study on the hydrogen recombination rates of catalytic recombiners and deliberate ignition

    International Nuclear Information System (INIS)

    Fineschi, F.; Bazzichi, M.; Carcassi, M.

    1994-01-01

    A study is being carried out by the Department of Nuclear and Mechanical Constructions (DCMN) at the University of Pisa on catalytic recombiners and on deliberately induced weak deflagration. The recombination rates of different types of catalytic devices were obtained from a thorough analysis of published experimental data. The main parameter that affects the effectiveness of these devices seems to be the molar density of the deficiency reactant rather than its volumetric concentration. The recombination rate of weak deflagrations in vented compartments has been assessed with experimental tests carried out in a small scale glass vessel. Through a computerized system of analysis of video recordings of the deflagrations, the flame surface and the burned gas volume were obtained as functions of time. Although approximations are inevitable, the method adopted to identify the position of the flame during propagation is more reliable than other non-visual methods (thermocouples and ion-probes). It can only easily be applied to vented weak deflagrations, i.e. when the hydrogen concentration is far from stoichiometric conditions and near to flammability limits, because the pressurization has to be limited due to the low mechanical resistance of the glass. The values of flame surface and burned gas volume were used as inputs for a computer code to calculate the recombining rate, the burning velocity and the pressure transient in the experimental test. The code is being validated with a methodology principally based on a comparison of the measurements of pressure with the calculated values. The research gave some very interesting results on a small scale which should in the future be compared with large scale data

  4. Low-Energy Catalytic Electrolysis for Simultaneous Hydrogen Evolution and Lignin Depolymerization.

    Science.gov (United States)

    Du, Xu; Liu, Wei; Zhang, Zhe; Mulyadi, Arie; Brittain, Alex; Gong, Jian; Deng, Yulin

    2017-03-09

    Here, a new proton-exchange-membrane electrolysis is presented, in which lignin was used as the hydrogen source at the anode for hydrogen production. Either polyoxometalate (POM) or FeCl 3 was used as the catalyst and charge-transfer agent at the anode. Over 90 % Faraday efficiency was achieved. In a thermal-insulation reactor, the heat energy could be maintained at a very low level for continuous operation. Compared to the best alkaline-water electrolysis reported in literature, the electrical-energy consumption could be 40 % lower with lignin electrolysis. At the anode, the Kraft lignin (KL) was oxidized to aromatic chemicals by POM or FeCl 3 , and reduced POM or Fe ions were regenerated during the electrolysis. Structure analysis of the residual KL indicated a reduction of the amount of hydroxyl groups and the cleavage of ether bonds. The results suggest that POM- or FeCl 3 -mediated electrolysis can significantly reduce the electrolysis energy consumption in hydrogen production and, simultaneously, depolymerize lignin to low-molecular-weight value-added aromatic chemicals. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Evaluation of industrially applied heat-transfer fluids as liquid organic hydrogen carrier systems.

    Science.gov (United States)

    Brückner, Nicole; Obesser, Katharina; Bösmann, Andreas; Teichmann, Daniel; Arlt, Wolfgang; Dungs, Jennifer; Wasserscheid, Peter

    2014-01-01

    Liquid organic hydrogen carrier (LOHC) systems offer a very attractive method for the decentralized storage of renewable excess energy. In this contribution, industrially well-established heat-transfer oils (typically sold under trade names, e.g., Marlotherm) are proposed as a new class of LOHC systems. It is demonstrated that the liquid mixture of isomeric dibenzyltoluenes (m.p. -39 to -34 °C, b.p. 390 °C) can be readily hydrogenated to the corresponding mixture of perhydrogenated analogues by binding 6.2 wt% of H2. The liquid H2 -rich form can be stored and transported similarly to diesel fuel. It readily undergoes catalytic dehydrogenation at temperatures above 260 °C, which proves its applicability as a reversible H2 carrier. The presented LOHC systems are further characterized by their excellent technical availability at comparably low prices, full registration of the H2 -lean forms, and excellent thermal stabilities. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. CNN pincer ruthenium catalysts for hydrogenation and transfer hydrogenation of ketones: experimental and computational studies.

    Science.gov (United States)

    Baratta, Walter; Baldino, Salvatore; Calhorda, Maria José; Costa, Paulo J; Esposito, Gennaro; Herdtweck, Eberhardt; Magnolia, Santo; Mealli, Carlo; Messaoudi, Abdelatif; Mason, Sax A; Veiros, Luis F

    2014-10-13

    Reaction of [RuCl(CNN)(dppb)] (1-Cl) (HCNN=2-aminomethyl-6-(4-methylphenyl)pyridine; dppb=Ph2 P(CH2 )4 PPh2 ) with NaOCH2 CF3 leads to the amine-alkoxide [Ru(CNN)(OCH2 CF3 )(dppb)] (1-OCH2 CF3 ), whose neutron diffraction study reveals a short RuO⋅⋅⋅HN bond length. Treatment of 1-Cl with NaOEt and EtOH affords the alkoxide [Ru(CNN)(OEt)(dppb)]⋅(EtOH)n (1-OEt⋅n EtOH), which equilibrates with the hydride [RuH(CNN)(dppb)] (1-H) and acetaldehyde. Compound 1-OEt⋅n EtOH reacts reversibly with H2 leading to 1-H and EtOH through dihydrogen splitting. NMR spectroscopic studies on 1-OEt⋅n EtOH and 1-H reveal hydrogen bond interactions and exchange processes. The chloride 1-Cl catalyzes the hydrogenation (5 atm of H2 ) of ketones to alcohols (turnover frequency (TOF) up to 6.5×10(4) h(-1) , 40 °C). DFT calculations were performed on the reaction of [RuH(CNN')(dmpb)] (2-H) (HCNN'=2-aminomethyl-6-(phenyl)pyridine; dmpb=Me2 P(CH2 )4 PMe2 ) with acetone and with one molecule of 2-propanol, in alcohol, with the alkoxide complex being the most stable species. In the first step, the Ru-hydride transfers one hydrogen atom to the carbon of the ketone, whereas the second hydrogen transfer from NH2 is mediated by the alcohol and leads to the key "amide" intermediate. Regeneration of the hydride complex may occur by reaction with 2-propanol or with H2 ; both pathways have low barriers and are alcohol assisted. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Catalytic partial oxidation and membrane separation to optimize the conversion of natural gas to syngas and hydrogen.

    Science.gov (United States)

    Capoferri, Daniela; Cucchiella, Barbara; Iaquaniello, Gaetano; Mangiapane, Alessia; Abate, Salvatore; Centi, Gabriele

    2011-12-16

    The multistep integration of hydrogen-selective membranes into catalytic partial oxidation (CPO) technology to convert natural gas into syngas and hydrogen is reported. An open architecture for the membrane reactor is presented, in which coupling of the reaction and hydrogen separation is achieved independently and the required feed conversion is reached through a set of three CPO reactors working at 750, 750 and 920 °C, compared to 1030 °C for conventional CPO technology. Obtaining the same feed conversion at milder operating conditions translates into less natural gas consumption (and CO(2) emissions) and a reduction of variable operative costs of around 10 %. It is also discussed how this energy-efficient process architecture, which is suited particularly to small-to-medium applications, may improve the sustainability of other endothermic, reversible reactions to form hydrogen. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Coumarin or benzoxazinone bearing benzimidazolium and bis(benzimidazolium) salts; involvement in transfer hydrogenation of acetophenone derivatives and hCA inhibition

    OpenAIRE

    Mert Olgun Karataş; Serkan Dayan; Nilgün Kayacı; Çiğdem Bilen; Emre Yavuz; Nahit Gencer; Bülent Alıcı; Nilgün Ozpozan Kalaycıoğlu; Oktay Arslan

    2015-01-01

    Four new salts of benzimidazolium and bis(benzimidazolium) which include coumarin or benzoxazinone moieties were synthesized and the structures of the newly synthesized compounds were elucidated on the basis of spectral analyses such as 1H-NMR, 13C-NMR, HSQC, IR, LC-MS and elemental analysis. Benzimidazolium salts were used intensively as N-heterocyclic carbene (NHC) precursors in the various catalytic reactions such as transfer hydrogenation (TH), C-H bond activation, Heck, Suzuki reaction e...

  9. Catalytic dry reforming of natural gas for the production of chemicals and hydrogen

    Directory of Open Access Journals (Sweden)

    Verykios Xenophon E.

    2002-01-01

    Full Text Available Carbon dioxide reforming of methane to synthesis gas was studied over Ni-based catalysts. It is shown that, in contrast to other Ni-based catalysts which exhibit continuous deactivation with time-on-stream, the rate over the Ni/La2O3 catalyst increases during the initial 2-3 h of reaction and then tends to be essentially invariable, displaying very good stability. X-ray diffraction, hydrogen and CO uptake studies, as well as high resolution TEM indicate that, under reaction conditions, the Ni particles are partially covered by La2O2CO3 species which are formed by interaction of La2O2 with CO2. Catalytic activity occurs at the Ni- La2O2CO3 interface, while the oxycarbonate species participate directly by reacting with deposited carbon, thus restoring the activity of the Ni sites at the interface. XPS and FTIR studies provide evidence in support of this mechanistic scheme. It was also found that methane cracking on Ni sites and surface reaction between deposited carbon and oxycarbonate species are the rate determining steps in the reaction sequence. A kinetic model is developed based on this mechanistic scheme, which is found to predict satisfactorily the kinetic measurements.

  10. Preparation of Modified Red Mud-Supported Fe Catalysts for Hydrogen Production by Catalytic Methane Decomposition

    Directory of Open Access Journals (Sweden)

    Quanrun Liu

    2017-01-01

    Full Text Available A modified red mud- (MRM- supported Fe catalyst (xFe/MRM was prepared using the homogeneous precipitation method and applied to methane decomposition to produce hydrogen. The TEM and SEM-EDX results suggested that the particle sizes of the xFe/MRM catalysts were much smaller than that of raw red mud (RM, and the active metal Fe was evenly distributed over the catalyst structure. Moreover, BET results indicated that the surface areas and pore volumes of the catalysts were significantly improved, and the pore sizes of xFe/MRM were distributed from 5 to 12 nm, which is typical for a mesoporous material. The activities of those catalysts for the catalytic decomposition of methane were studied at atmospheric pressure at a moderate temperature of 650°C; the results showed that the xFe/MRM catalysts were more active than RM and MRM. The methane conversion curves of xFe/MRM catalysts exhibited similar variation tendencies (three-step during the reaction despite different Fe contents, and the loading amount of Fe clearly affected the activity of the catalysts.

  11. Applications of the water--gas shift reaction. II. Catalytic exchange of deuterium for hydrogen at saturated carbon

    International Nuclear Information System (INIS)

    Laine, R.M.; Thomas, D.W.; Cary, L.W.; Buttrill, S.E.

    1978-01-01

    Previous studies on the homogeneous catalysis of the water-gas shift reaction by metal complexes of groups 6 and 8 had been carried out using aqueous alcoholic solutions of group 8 metal carbonyl complexes made basic with KOH. Substitution of triethylamine (Et 3 N) for KOH as base and alcohol for solvent led to the discovery that Et 3 N in the presence of D 2 O, CO, and Rh 6 (CO) 16 at 150 0 C undergoes an unusual catalytic exchange of deuterium for hydrogen. A suggested mechanism for this reaction is given and includes activation of hydrogen at a saturated carbon

  12. Hydrogen-bonding catalysis of sulfonium salts

    OpenAIRE

    Kaneko, Shiho; Kumatabara, Yusuke; Shimizu, Shoichi; Maruoka, Keiji; Shirakawa, Seiji

    2017-01-01

    Although quaternary ammonium and phosphonium salts are known as important catalysts in phase-transfer catalysis, the catalytic ability of tertiary sulfonium salts has not yet been well demonstrated. Herein, we demonstrate the catalytic ability of trialkylsulfonium salts as hydrogen-bonding catalysts on the basis of the characteristic properties of the acidic α hydrogen atoms on alkylsulfonium salts.

  13. Catalytic Ammonia Decomposition over High-Performance Ru/Graphene Nanocomposites for Efficient COx-Free Hydrogen Production

    Directory of Open Access Journals (Sweden)

    Gang Li

    2017-01-01

    Full Text Available Highly-dispersed Ru nanoparticles were grown on graphene nanosheets by simultaneously reducing graphene oxide and Ru ions using ethylene glycol (EG, and the resultant Ru/graphene nanocomposites were applied as a catalyst to ammonia decomposition for COx-free hydrogen production. Tuning the microstructures of Ru/graphene nanocomposites was easily accomplished in terms of Ru particle size, morphology, and loading by adjusting the preparation conditions. This was the key to excellent catalytic activity, because ammonia decomposition over Ru catalysts is structure-sensitive. Our results demonstrated that Ru/graphene prepared using water as a co-solvent greatly enhanced the catalytic performance for ammonia decomposition, due to the significantly improved nano architectures of the composites. The long-term stability of Ru/graphene catalysts was evaluated for COx-free hydrogen production from ammonia at high temperatures, and the structural evolution of the catalysts was investigated during the catalytic reactions. Although there were no obvious changes in the catalytic activities at 450 °C over a duration of 80 h, an aggregation of the Ru nanoparticles was still observed in the nanocomposites, which was ascribed mainly to a sintering effect. However, the performance of the Ru/graphene catalyst was decreased gradually at 500 °C within 20 h, which was ascribed mainly to both the effect of the methanation of the graphene nanosheet under a H2 atmosphere and to enhanced sintering under high temperatures.

  14. Catalytic effect of additional metallic phases on the hydrogen absorption behavior of a Zr-Based alloy

    International Nuclear Information System (INIS)

    Ruiz, F; Peretti, H; Castro, E; Real, S; Visitin, A; Triaca, W

    2005-01-01

    The electrochemical hydrogen absorption of electrodes containing Zr 0 .9Ti 0 .1(Ni 0 .5Mn 0 .25Cr 0 .20V 0 .05) 2 is studied in alkaline media by monitoring the activation and discharge capacity along charge-discharge cycling.The considered alloy is tested in both as melted and annealed condition in order to investigate the catalytic effect of small amounts of micro segregated secondary phases of the Zr-Ni system. Since these catalytic phases are only present in the as melted alloys, tests are also carried out using a composite material elaborated from powders of the annealed alloy with the addition of 18 wt.% of the suspected catalytic phases, melted separately.The hydrogen absorption-desorption behavior for the different cases is discussed and correlated with the metallurgical characterization of the materials.The catalytic effects are studied employing cyclic voltammetry and electrochemical impedance techniques. The results are analyzed in terms of a developed physicochemical model

  15. Analysis of phosphoinositide 3-kinase inhibitors by bottom-up electron-transfer dissociation hydrogen/deuterium exchange mass spectrometry.

    Science.gov (United States)

    Masson, Glenn R; Maslen, Sarah L; Williams, Roger L

    2017-05-16

    Until recently, one of the major limitations of hydrogen/deuterium exchange mass spectrometry (HDX-MS) was the peptide-level resolution afforded by proteolytic digestion. This limitation can be selectively overcome through the use of electron-transfer dissociation to fragment peptides in a manner that allows the retention of the deuterium signal to produce hydrogen/deuterium exchange tandem mass spectrometry (HDX-MS/MS). Here, we describe the application of HDX-MS/MS to structurally screen inhibitors of the oncogene phosphoinositide 3-kinase catalytic p110α subunit. HDX-MS/MS analysis is able to discern a conserved mechanism of inhibition common to a range of inhibitors. Owing to the relatively minor amounts of protein required, this technique may be utilised in pharmaceutical development for screening potential therapeutics. © 2017 The Author(s).

  16. Ruthenium supported on magnetic nanoparticles: An efficient and recoverable catalyst for hydrogenation of alkynes and transfer hydrogenation of carbonyl compounds

    Science.gov (United States)

    Ruthenium supported on surface modified magnetic nanoparticles (NiFe2O4) has been successfully synthesized and applied for hydrogenation of alkynes at room temperature as well as transfer hydrogenation of a number of carbonyl compounds under microwave irradiation conditions. The ...

  17. A conserved hydrogen-bond network in the catalytic centre of animal glutaminyl cyclases is critical for catalysis.

    Science.gov (United States)

    Huang, Kai-Fa; Wang, Yu-Ruei; Chang, En-Cheng; Chou, Tsung-Lin; Wang, Andrew H-J

    2008-04-01

    QCs (glutaminyl cyclases; glutaminyl-peptide cyclotransferases, EC 2.3.2.5) catalyse N-terminal pyroglutamate formation in numerous bioactive peptides and proteins. The enzymes were reported to be involved in several pathological conditions such as amyloidotic disease, osteoporosis, rheumatoid arthritis and melanoma. The crystal structure of human QC revealed an unusual H-bond (hydrogen-bond) network in the active site, formed by several highly conserved residues (Ser(160), Glu(201), Asp(248), Asp(305) and His(319)), within which Glu(201) and Asp(248) were found to bind to substrate. In the present study we combined steady-state enzyme kinetic and X-ray structural analyses of 11 single-mutation human QCs to investigate the roles of the H-bond network in catalysis. Our results showed that disrupting one or both of the central H-bonds, i.e., Glu(201)...Asp(305) and Asp(248)...Asp(305), reduced the steady-state catalysis dramatically. The roles of these two COOH...COOH bonds on catalysis could be partly replaced by COOH...water bonds, but not by COOH...CONH(2) bonds, reminiscent of the low-barrier Asp...Asp H-bond in the active site of pepsin-like aspartic peptidases. Mutations on Asp(305), a residue located at the centre of the H-bond network, raised the K(m) value of the enzyme by 4.4-19-fold, but decreased the k(cat) value by 79-2842-fold, indicating that Asp(305) primarily plays a catalytic role. In addition, results from mutational studies on Ser(160) and His(319) suggest that these two residues might help to stabilize the conformations of Asp(248) and Asp(305) respectively. These data allow us to propose an essential proton transfer between Glu(201), Asp(305) and Asp(248) during the catalysis by animal QCs.

  18. Incorporating nitrogen atoms into cobalt nanosheets as a strategy to boost catalytic activity toward CO2 hydrogenation

    Science.gov (United States)

    Wang, Liangbing; Zhang, Wenbo; Zheng, Xusheng; Chen, Yizhen; Wu, Wenlong; Qiu, Jianxiang; Zhao, Xiangchen; Zhao, Xiao; Dai, Yizhou; Zeng, Jie

    2017-11-01

    Hydrogenation of CO2 into fuels and useful chemicals could help to reduce reliance on fossil fuels. Although great progress has been made over the past decades to improve the activity of catalysts for CO2 hydrogenation, more efficient catalysts, especially those based on non-noble metals, are desired. Here we incorporate N atoms into Co nanosheets to boost the catalytic activity toward CO2 hydrogenation. For the hydrogenation of CO2, Co4N nanosheets exhibited a turnover frequency of 25.6 h-1 in a slurry reactor under 32 bar pressure at 150 °C, which was 64 times that of Co nanosheets. The activation energy for Co4N nanosheets was 43.3 kJ mol-1, less than half of that for Co nanosheets. Mechanistic studies revealed that Co4N nanosheets were reconstructed into Co4NHx, wherein the amido-hydrogen atoms directly interacted with the CO2 to form HCOO* intermediates. In addition, the adsorbed H2O* activated amido-hydrogen atoms via the interaction of hydrogen bonds.

  19. Transfer Hydrogenation of Alkenes Using Ethanol Catalyzed by a NCP Pincer Iridium Complex: Scope and Mechanism.

    Science.gov (United States)

    Wang, Yulei; Huang, Zhidao; Leng, Xuebing; Zhu, Huping; Liu, Guixia; Huang, Zheng

    2018-03-28

    The first general catalytic approach to effecting transfer hydrogenation (TH) of unactivated alkenes using ethanol as the hydrogen source is described. A new NCP-type pincer iridium complex ( BQ -NC O P)IrHCl containing a rigid benzoquinoline backbone has been developed for efficient, mild TH of unactivated C-C multiple bonds with ethanol, forming ethyl acetate as the sole byproduct. A wide variety of alkenes, including multisubstituted alkyl alkenes, aryl alkenes, and heteroatom-substituted alkenes, as well as O- or N-containing heteroarenes and internal alkynes, are suitable substrates. Importantly, the ( BQ -NC O P)Ir/EtOH system exhibits high chemoselectivity for alkene hydrogenation in the presence of reactive functional groups, such as ketones and carboxylic acids. Furthermore, the reaction with C 2 D 5 OD provides a convenient route to deuterium-labeled compounds. Detailed kinetic and mechanistic studies have revealed that monosubstituted alkenes (e.g., 1-octene, styrene) and multisubstituted alkenes (e.g., cyclooctene (COE)) exhibit fundamental mechanistic difference. The OH group of ethanol displays a normal kinetic isotope effect (KIE) in the reaction of styrene, but a substantial inverse KIE in the case of COE. The catalysis of styrene or 1-octene with relatively strong binding affinity to the Ir(I) center has ( BQ -NC O P)Ir I (alkene) adduct as an off-cycle catalyst resting state, and the rate law shows a positive order in EtOH, inverse first-order in styrene, and first-order in the catalyst. In contrast, the catalysis of COE has an off-cycle catalyst resting state of ( BQ -NC O P)Ir III (H)[O(Et)···HO(Et)···HOEt] that features a six-membered iridacycle consisting of two hydrogen-bonds between one EtO ligand and two EtOH molecules, one of which is coordinated to the Ir(III) center. The rate law shows a negative order in EtOH, zeroth-order in COE, and first-order in the catalyst. The observed inverse KIE corresponds to an inverse equilibrium

  20. Manganese-Oxygen Intermediates in O-O Bond Activation and Hydrogen-Atom Transfer Reactions.

    Science.gov (United States)

    Rice, Derek B; Massie, Allyssa A; Jackson, Timothy A

    2017-11-21

    Biological systems capitalize on the redox versatility of manganese to perform reactions involving dioxygen and its derivatives superoxide, hydrogen peroxide, and water. The reactions of manganese enzymes influence both human health and the global energy cycle. Important examples include the detoxification of reactive oxygen species by manganese superoxide dismutase, biosynthesis by manganese ribonucleotide reductase and manganese lipoxygenase, and water splitting by the oxygen-evolving complex of photosystem II. Although these enzymes perform very different reactions and employ structurally distinct active sites, manganese intermediates with peroxo, hydroxo, and oxo ligation are commonly proposed in catalytic mechanisms. These intermediates are also postulated in mechanisms of synthetic manganese oxidation catalysts, which are of interest due to the earth abundance of manganese. In this Account, we describe our recent efforts toward understanding O-O bond activation pathways of Mn III -peroxo adducts and hydrogen-atom transfer reactivity of Mn IV -oxo and Mn III -hydroxo complexes. In biological and synthetic catalysts, peroxomanganese intermediates are commonly proposed to decay by either Mn-O or O-O cleavage pathways, although it is often unclear how the local coordination environment influences the decay mechanism. To address this matter, we generated a variety of Mn III -peroxo adducts with varied ligand environments. Using parallel-mode EPR and Mn K-edge X-ray absorption techniques, the decay pathway of one Mn III -peroxo complex bearing a bulky macrocylic ligand was investigated. Unlike many Mn III -peroxo model complexes that decay to oxo-bridged-Mn III Mn IV dimers, decay of this Mn III -peroxo adduct yielded mononuclear Mn III -hydroxo and Mn IV -oxo products, potentially resulting from O-O bond activation of the Mn III -peroxo unit. These results highlight the role of ligand sterics in promoting the formation of mononuclear products and mark an important

  1. Pt nanoparticles modified by rare earth oxides: Electronic effect and influence to catalytic hydrogenation of 3-phenoxybenzaldehyde

    International Nuclear Information System (INIS)

    Mou, Zhigang; Han, Ming; Li, Gang; Du, Yukou; Yang, Ping; Zhang, Hailu; Deng, Zongwu

    2013-01-01

    Graphical abstract: - Highlights: • The rare earths modified Pt/Al 2 O 3 were prepared by colloidal deposition method. • Modification of Pt by the rare earth enhanced catalytic hydrogenation activity. • The activity improvement is due to electron interaction between Pt and rare earth. • The hydrogenation mechanism of rare earth modified Pt catalyst was proposed. - Abstract: The rare earth elements (La, Ce, Nd, Sm, Pr, and Gd) modified Pt/Al 2 O 3 catalysts were prepared by the colloidal deposition and chemical reduction methods, respectively. Pt nanoparticles with average size 3 ± 0.5 nm were uniformly dispersed on the surface of Al 2 O 3 for the samples prepared by the colloidal deposition method, which exhibited higher activities in the hydrogenation of 3-phenoxybenzadehyde than the corresponding samples prepared by chemical reduction method. Moreover, except Gd, the catalysts modified by rare earth elements showed better catalytic performance than unmodified Pt/Al 2 O 3 . For Pt–Ce/Al 2 O 3 catalyst, when the weight percent of Pt and Ce was 0.5 and 0.25, respectively, the hydrogenation conversion of 3-phenoxybenzaldehyde was 97.3% after 6 h reaction. This activity improvement is due to the electronic interaction between Pt and rare earth elements, which was investigated by X-ray photoelectron spectroscopy

  2. Pt nanoparticles modified by rare earth oxides: Electronic effect and influence to catalytic hydrogenation of 3-phenoxybenzaldehyde

    Energy Technology Data Exchange (ETDEWEB)

    Mou, Zhigang; Han, Ming; Li, Gang; Du, Yukou [College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123 (China); Yang, Ping, E-mail: pyang@suda.edu.cn [College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123 (China); Zhang, Hailu [Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215123 (China); Deng, Zongwu, E-mail: zwdeng2007@sinano.ac.cn [Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215123 (China)

    2013-11-15

    Graphical abstract: - Highlights: • The rare earths modified Pt/Al{sub 2}O{sub 3} were prepared by colloidal deposition method. • Modification of Pt by the rare earth enhanced catalytic hydrogenation activity. • The activity improvement is due to electron interaction between Pt and rare earth. • The hydrogenation mechanism of rare earth modified Pt catalyst was proposed. - Abstract: The rare earth elements (La, Ce, Nd, Sm, Pr, and Gd) modified Pt/Al{sub 2}O{sub 3} catalysts were prepared by the colloidal deposition and chemical reduction methods, respectively. Pt nanoparticles with average size 3 ± 0.5 nm were uniformly dispersed on the surface of Al{sub 2}O{sub 3} for the samples prepared by the colloidal deposition method, which exhibited higher activities in the hydrogenation of 3-phenoxybenzadehyde than the corresponding samples prepared by chemical reduction method. Moreover, except Gd, the catalysts modified by rare earth elements showed better catalytic performance than unmodified Pt/Al{sub 2}O{sub 3}. For Pt–Ce/Al{sub 2}O{sub 3} catalyst, when the weight percent of Pt and Ce was 0.5 and 0.25, respectively, the hydrogenation conversion of 3-phenoxybenzaldehyde was 97.3% after 6 h reaction. This activity improvement is due to the electronic interaction between Pt and rare earth elements, which was investigated by X-ray photoelectron spectroscopy.

  3. Energy Efficient Catalytic Activation of Hydrogen peroxide for Green Chemical Processes: Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Collins, Terrence J.; Horwitz, Colin

    2004-11-12

    A new, highly energy efficient approach for using catalytic oxidation chemistry in multiple fields of technology has been pursued. The new catalysts, called TAML® activators, catalyze the reactions of hydrogen peroxide and other oxidants for the exceptionally rapid decontamination of noninfectious simulants (B. atrophaeus) of anthrax spores, for the energy efficient decontamination of thiophosphate pesticides, for the facile, low temperature removal of color and organochlorines from pulp and paper mill effluent, for the bleaching of dyes from textile mill effluents, and for the removal of recalcitrant dibenzothiophene compounds from diesel and gasoline fuels. Highlights include the following: 1) A 7-log kill of Bacillus atrophaeus spores has been achieved unambiguously in water under ambient conditions within 15 minutes. 2) The rapid total degradation under ambient conditions of four thiophosphate pesticides and phosphonate degradation intermediates has been achieved on treatment with TAML/peroxide, opening up potential applications of the decontamination system for phosphonate structured chemical warfare agents, for inexpensive, easy to perform degradation of stored and aged pesticide stocks (especially in Africa and Asia), for remediation of polluted sites and water bodies, and for the destruction of chemical warfare agent stockpiles. 3) A mill trial conducted in a Pennsylvanian bleached kraft pulp mill has established that TAML catalyst injected into an alkaline peroxide bleach tower can significantly lower color from the effluent stream promising a new, more cost effective, energy-saving approach for color remediation adding further evidence of the value and diverse engineering capacity of the approach to other field trials conducted on effluent streams as they exit the bleach plant. 4) Dibenzothiophenes (DBTs), including 4,6-dimethyldibenzothiophene, the most recalcitrant sulfur compounds in diesel and gasoline, can be completely removed from model gasoline

  4. Catalytic autothermal reforming of diesel fuel for hydrogen generation in fuel cells. I. Activity tests and sulfur poisoning

    Science.gov (United States)

    Cheekatamarla, Praveen K.; Lane, Alan M.

    Polymer electrolyte membrane (PEM) fuel cells require hydrogen as the fuel source for generating power. Hydrogen can be produced in a fuel processor by the catalytic reforming of hydrocarbons. The objective of this paper is to present an analysis of the autothermal reforming (ATR) of synthetic diesel fuel in an adiabatic reactor using a Pt/ceria catalyst. ATR combines endothermic steam reforming and exothermic partial oxidation reactions in a single unit. This simple system provides higher efficiency and higher energy density than other conventional processes. The product composition as a function of the operating variables and the temperature and concentration profile inside the reactor were studied. Hydrogen was generated under adiabatic conditions by heating the feed mixture and ATR reactor to only 400 °C in contrast to higher temperatures reported in the literature. The stability of the catalyst and its response to the presence of S poison was also investigated.

  5. A review of recent advances on the effects of microstructural refinement and nano-catalytic additives on the hydrogen storage properties of metal and complex hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Varin, R. A.; Zbroniec, L. [University of Waterloo, Department of Mechanical and Mechatronics Engineering, Waterloo, Ontario (Canada); Polanski, M.; Bystrzycki, J. [Faculty of Advanced Technology and Chemistry, Military University of Technology, Warsaw (Poland)

    2011-07-01

    The recent advances on the effects of microstructural refinement and various nano-catalytic additives on the hydrogen storage properties of metal and complex hydrides obtained in the last few years in the allied laboratories at the University of Waterloo (Canada) and Military University of Technology (Warsaw, Poland) are critically reviewed in this paper. The research results indicate that microstructural refinement (particle and grain size) induced by ball milling influences quite modestly the hydrogen storage properties of simple metal and complex metal hydrides. On the other hand, the addition of nanometric elemental metals acting as potent catalysts and/or metal halide catalytic precursors brings about profound improvements in the hydrogen absorption/desorption kinetics for simple metal and complex metal hydrides alike. In general, catalytic precursors react with the hydride matrix forming a metal salt and free nanometric or amorphous elemental metals/intermetallics which, in turn, act catalytically. However, these catalysts change only kinetic properties i.e. the hydrogen absorption/desorption rate but they do not change thermodynamics (e.g., enthalpy change of hydrogen sorption reactions). It is shown that a complex metal hydride, LiAlH{sub 4}, after high energy ball milling with a nanometric Ni metal catalyst and/or MnCl{sub 2} catalytic precursor, is able to desorb relatively large quantities of hydrogen at room temperature, 40 and 80 {sup o}C. This kind of behavior is very encouraging for the future development of solid state hydrogen systems. (authors)

  6. Theoretical exploration of the mechanism of riboflavin formation from 6,7-dimethyl-8-ribityllumazine: nucleophilic catalysis, hydride transfer, hydrogen atom transfer, or nucleophilic addition?

    Science.gov (United States)

    Breugst, Martin; Eschenmoser, Albert; Houk, K N

    2013-05-01

    The cofactor riboflavin is biochemically synthesized by a constitutionally intricate process in which two molecules of 6,7-dimethyl-8-ribityllumazine react with each other to form one molecule of the cofactor and one molecule of 5-amino-6-(ribitylamino)uracil. Remarkably, this complex molecular transformation also proceeds non-enzymatically in boiling aqueous solution at pH 7.3. Four different mechanistic pathways for this transformation (nucleophilic catalysis, hydride transfer, hydrogen atom transfer, and a nucleophilic addition mechanism) have now been analyzed by density functional theory [M06-2X/def2-TZVPP/CPCM//M06-2X/6-31+G(d,p)/IEFPCM]. On the basis of these computational results, a so far unpublished nucleophilic addition mechanism is the lowest energy pathway yielding riboflavin. The previously proposed mechanism involving nucleophilic catalysis is higher in energy but is still a viable alternative for an enzyme-catalyzed process assisted by suitably positioned catalytic groups. Pathways involving the transfer of a hydride ion or of a hydrogen atom are predicted to proceed through higher energy transition states and intermediates.

  7. Catalytic hydrolysis of ammonia borane for hydrogen generation using cobalt nanocluster catalyst supported on polydopamine functionalized multiwalled carbon nanotube

    International Nuclear Information System (INIS)

    Arthur, Ernest Evans; Li, Fang; Momade, Francis W.Y.; Kim, Hern

    2014-01-01

    Hydrogen was generated from ammonia borane complex by hydrolysis using cobalt nanocluster catalyst supported on polydopamine functionalized MWCNTs (multi-walled carbon nanotubes). The impregnation-chemical reduction method was used for the preparation of the supported catalyst. The nanocluster catalyst support was formed by in-situ oxidative polymerization of dopamine on the MWCNTs in alkaline solution at room temperature. The structural and physical–chemical properties of the nanocluster catalyst were characterized by FT-IR (Fourier transform infrared spectroscopy), EDX (energy-dispersive X-ray spectroscopy), SEM (scanning electron microscope), XRD (X-ray diffraction) and TEM (transmission electron microscopy). The nanocluster catalyst showed good catalytic activity for the hydrogen generation from aqueous ammonia borane complex. A reusability test to determine the practical usage of the catalyst was also investigated. The result revealed that the catalyst maintained an appreciable catalytic performance and stability in terms of its reusability after three cycle of reuse for the hydrolysis reaction. Also, the activation energy for the hydrolysis of ammonia borane complex was estimated to be 50.41 kJmol −1 , which is lower than the values of some of the reported catalyst. The catalyst can be considered as a promising candidate in developing highly efficient portable hydrogen generation systems such as PEMFC (proton exchange membrane fuel cells). - Highlights: • Co/Pdop-o-MWCNT (Pdop functionalized MWCNT supported cobalt nanocluster) catalyst was synthesized for hydrogen generation. • It is an active catalyst for hydrogen generation via hydrolysis of ammonia borane. • It showed good stability in terms of reusability for the hydrogen generation

  8. Effect of Co crystallinity on Co/CNT catalytic activity in CO/CO{sub 2} hydrogenation and CO disproportionation

    Energy Technology Data Exchange (ETDEWEB)

    Chernyak, Sergei A., E-mail: chernyak.msu@gmail.com [Lomonosov Moscow State University, Department of Chemistry, Leninskiye Gory 1-3, Moscow 119991 (Russian Federation); Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences, Department of Physical Chemistry, Leninsky Avenue 31, Moscow 119991 (Russian Federation); Suslova, Evgeniya V.; Egorov, Alexander V.; Maslakov, Konstantin I. [Lomonosov Moscow State University, Department of Chemistry, Leninskiye Gory 1-3, Moscow 119991 (Russian Federation); Savilov, Serguei V.; Lunin, Valery V. [Lomonosov Moscow State University, Department of Chemistry, Leninskiye Gory 1-3, Moscow 119991 (Russian Federation); Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences, Department of Physical Chemistry, Leninsky Avenue 31, Moscow 119991 (Russian Federation)

    2016-05-30

    Highlights: • Amorphous and crystalline Co supported on CNTs were obtained by tuning of CNT surface. • CO and CO{sub 2} hydrogenation does not occur on amorphous Co particles. • Thermal activation of amorphous Co led to crystallization of metal. • Amorphous Co promotes CO disproportionation. • Carbon shells around the amorphous metal particles after the CO hydrogenation. - Abstract: Carbon nanotubes (CNTs) with different degree of surface oxidation were used as supports for 5 wt.% Co catalysts. CNTs and Co/CNT catalysts were analyzed by XPS, nitrogen adsorption, TEM and electron diffraction to reveal their structure. High oxidation degree of CNT surface (8.6 at.% of O) and low Co loading led to predominantly amorphous Co species. This resulted in the absence of catalytic activity in both CO and CO{sub 2} hydrogenation in opposite to the catalyst supported on less oxidized CNTs (5.4 at.% of O) where Co species were found to be crystalline. Thermal treatment of inactive catalyst in H{sub 2} and He led to the formation of Co crystal phase which was active in catalysis. Co particle size in catalyst supported on strongly oxidized CNTs was unchanged during CO hydrogenation in opposite to Co supported on less oxidized CNTs. Carbon shell formation on the surface of amorphous Co particles during CO hydrogenation was revealed, which testified CO disproportionation. Qualitative mechanism of CO hydrogenation on small Co particles was proposed.

  9. Production of hydrogen, liquid fuels, and chemicals from catalytic processing of bio-oils

    Science.gov (United States)

    Huber, George W; Vispute, Tushar P; Routray, Kamalakanta

    2014-06-03

    Disclosed herein is a method of generating hydrogen from a bio-oil, comprising hydrogenating a water-soluble fraction of the bio-oil with hydrogen in the presence of a hydrogenation catalyst, and reforming the water-soluble fraction by aqueous-phase reforming in the presence of a reforming catalyst, wherein hydrogen is generated by the reforming, and the amount of hydrogen generated is greater than that consumed by the hydrogenating. The method can further comprise hydrocracking or hydrotreating a lignin fraction of the bio-oil with hydrogen in the presence of a hydrocracking catalyst wherein the lignin fraction of bio-oil is obtained as a water-insoluble fraction from aqueous extraction of bio-oil. The hydrogen used in the hydrogenating and in the hydrocracking or hydrotreating can be generated by reforming the water-soluble fraction of bio-oil.

  10. Experimental and Mechanistic Understanding of Aldehyde Hydrogenation Using Au25 Nanoclusters with Lewis Acids: Unique Sites for Catalytic Reactions.

    Science.gov (United States)

    Li, Gao; Abroshan, Hadi; Chen, Yuxiang; Jin, Rongchao; Kim, Hyung J

    2015-11-18

    The catalytic activity of Au25(SR)18 nanoclusters (R = C2H4Ph) for the aldehyde hydrogenation reaction in the presence of a base, e.g., ammonia or pyridine, and transition-metal ions M(z+), such as Cu(+), Cu(2+), Ni(2+) and Co(2+), as a Lewis acid is studied. The addition of a Lewis acid is found to significantly promote the catalytic activity of Au25(SR)18/CeO2 in the hydrogenation of benzaldehyde and a number of its derivatives. Matrix-assisted laser desorption ionization (MALDI) and electrospray ionization (ESI) mass spectrometry in conjunction with UV-vis spectroscopy confirm the generation of new species, Au25-n(SR)18-n (n = 1-4), in the presence of a Lewis acid. The pathways for the speciation of Au24(SR)17 from its parent Au25(SR)18 nanocluster as well as its structure are investigated via the density functional theory (DFT) method. The adsorption of M(z+) onto a thiolate ligand "-SR-" of Au25(SR)18, followed by a stepwise detachment of "-SR-" and a gold atom bonded to "-SR-" (thus an "Au-SR" unit) is found to be the most likely mechanism for the Au24(SR)17 generation. This in turn exposes the Au13-core of Au24(SR)17 to reactants, providing an active site for the catalytic hydrogenation. DFT calculations indicate that M(z+) is also capable of adsorbing onto the Au13-core surface, producing a possible active metal site of a different kind to catalyze the aldehyde hydrogenation reaction. This study suggests, for the first time, that species with an open metal site like adducts [nanoparticle-M]((z-1)+) or fragments Au25-n(SR)18-n function as the catalysts rather than the intact Au25(SR)18.

  11. Microscale Enhancement of Heat and Mass Transfer for Hydrogen Energy Storage

    Energy Technology Data Exchange (ETDEWEB)

    Drost, Kevin [Oregon State Univ., Corvallis, OR (United States); Jovanovic, Goran [Oregon State Univ., Corvallis, OR (United States); Paul, Brian [Oregon State Univ., Corvallis, OR (United States)

    2015-09-30

    The document summarized the technical progress associated with OSU’s involvement in the Hydrogen Storage Engineering Center of Excellence. OSU focused on the development of microscale enhancement technologies for improving heat and mass transfer in automotive hydrogen storage systems. OSU’s key contributions included the development of an extremely compact microchannel combustion system for discharging hydrogen storage systems and a thermal management system for adsorption based hydrogen storage using microchannel cooling (the Modular Adsorption Tank Insert or MATI).

  12. A conceptual design of catalytic gasification fuel cell hybrid power plant with oxygen transfer membrane

    Science.gov (United States)

    Shi, Wangying; Han, Minfang

    2017-09-01

    A hybrid power generation system integrating catalytic gasification, solid oxide fuel cell (SOFC), oxygen transfer membrane (OTM) and gas turbine (GT) is established and system energy analysis is performed. In this work, the catalytic gasifier uses steam, recycled anode off-gas and pure oxygen from OTM system to gasify coal, and heated by hot cathode off-gas at the same time. A zero-dimension SOFC model is applied and verified by fitting experimental data. Thermodynamic analysis is performed to investigate the integrated system performance, and system sensitivities on anode off-gas back flow ratio, SOFC fuel utilization, temperature and pressure are discussed. Main conclusions are as follows: (1) System overall electricity efficiency reaches 60.7%(HHV) while the gasifier operates at 700 °C and SOFC at 850 °C with system pressure at 3.04 bar; (2) oxygen enriched combustion simplify the carbon-dioxide capture process, which derives CO2 of 99.2% purity, but results in a penalty of 6.7% on system electricity efficiency; (3) with SOFC fuel utilization or temperature increasing, the power output of SOFC increases while GT power output decreases, and increasing system pressure can improve both the performance of SOFC and GT.

  13. Symmetry in Cascade Chirality-Transfer Processes: A Catalytic Atroposelective Direct Arylation Approach to BINOL Derivatives.

    Science.gov (United States)

    Wang, Jin-Zheng; Zhou, Jin; Xu, Chang; Sun, Hongbin; Kürti, László; Xu, Qing-Long

    2016-04-27

    Herein we disclose a scalable organocatalytic direct arylation approach for the regio- and atroposelective synthesis of non-C2-symmetric 2,2'-dihydroxy-1,1'-binaphthalenes (BINOLs). In the presence of catalytic amounts of axially chiral phosphoric acids, phenols and naphthols are coupled with iminoquinones via a cascade process that involves sequential aminal formation, sigmatropic rearrangement, and rearomatization to afford enantiomerically enriched BINOL derivatives in good to excellent yields. Our studies suggest that the (local) symmetry of the initially formed aminal intermediate has a dramatic impact on the level of enantioinduction in the final product. Aminals with a plane of symmetry give rise to BINOL derivatives with significantly lower enantiomeric excess than unsymmetrical ones featuring a stereogenic center. Presumably asymmetric induction in the sigmatropic rearrangement step is significantly more challenging than during aminal formation. Sigmatropic rearrangement of the enantiomerically enriched aminal and subsequent rearomatization transfers the central chirality into axial chirality with high fidelity.

  14. Catalytic Hydrolysis of Ammonia Borane by Cobalt Nickel Nanoparticles Supported on Reduced Graphene Oxide for Hydrogen Generation

    Directory of Open Access Journals (Sweden)

    Yuwen Yang

    2014-01-01

    Full Text Available Well dispersed magnetically recyclable bimetallic CoNi nanoparticles (NPs supported on the reduced graphene oxide (RGO were synthesized by one-step in situ coreduction of aqueous solution of cobalt(II chloride, nickel (II chloride, and graphite oxide (GO with ammonia borane (AB as the reducing agent under ambient condition. The CoNi/RGO NPs exhibits excellent catalytic activity with a total turnover frequency (TOF value of 19.54 mol H2 mol catalyst−1 min−1 and a low activation energy value of 39.89 kJ mol−1 at room temperature. Additionally, the RGO supported CoNi NPs exhibit much higher catalytic activity than the monometallic and RGO-free CoNi counterparts. Moreover, the as-prepared catalysts exert satisfying durable stability and magnetically recyclability for the hydrolytic dehydrogenation of AB, which make the practical reusing application of the catalysts more convenient. The usage of the low-cost, easy-getting catalyst to realize the production of hydrogen under mild condition gives more confidence for the application of ammonia borane as a hydrogen storage material. Hence, this general method indicates that AB can be used as both a potential hydrogen storage material and an efficient reducing agent, and can be easily extended to facile preparation of other RGO-based metallic systems.

  15. Preparation of Cu-Fe-Al-O nanosheets and their catalytic application in methanol steam reforming for hydrogen production

    Science.gov (United States)

    Wang, Leilei; Zhang, Fan; Miao, Dinghao; Zhang, Lei; Ren, Tiezhen; Hui, Xidong; He, Zhanbing

    2017-03-01

    Candidates of precious metal catalysts, prepared in a facile and environmental way and showing high catalytic performances at low temperatures, are always highly desired by industry. In this work, large-scale Cu-Fe-Al-O nanosheets were synthesized by facile dealloying of Al-Cu-Fe alloys in NaOH solution. The composition, microscopic morphology, and crystal structure were respectively investigated using wavelength-dispersive x-ray spectroscopy with an electron probe microanalyzer, scanning electron microscopy, x-ray diffraction, and transmission electron microscopy. Furthermore, we found that the 2D Cu-Fe-Al-O nanosheets gave excellent catalytic performances in hydrogen production by methanol steam reforming at relatively low temperatures, e.g. 513 K.

  16. Effects of delocalization on intrinsic barriers for H-atom transfer: Implications for the radical hydrogen transfer reaction

    Energy Technology Data Exchange (ETDEWEB)

    Camaioni, D.M.; Autrey, S.T.; Ferris, K.F.; Franz, J.A.

    1992-08-01

    PM3 calculations of transition states (TS) for both normal H-atom transfer and radical hydrogen transfer (RHT) reactions of a a wide-variety of hydrocarbon structures have enabled development of quantitative structure-reactivity relationships. Results indicate that activation barriers for RHT reactions are large enough that thermoneutral and endothermic reactions should not compete with alternative multistep pathways.

  17. Thermo-Catalytic Methane Decomposition for Hydrogen Production: Effect of Palladium Promoter on Ni-based Catalysts

    Directory of Open Access Journals (Sweden)

    Irene Lock Sow Mei

    2016-08-01

    Full Text Available Hydrogen production from the direct thermo-catalytic decomposition of methane is a promising alternative for clean fuel production. However, thermal decomposition of methane can hardly be of any practical and empirical interest in the industry unless highly efficient and effective catalysts, in terms of both catalytic activity and operational lifetime have been developed. In this study, the effect of palladium (Pd as a promoter onto Ni supported on alumina catalyst has been investigated by using co-precipitation technique. The introduction of Pd promotes better catalytic activity, operational lifetime and thermal stability of the catalyst. As expected, highest methane conversion was achieved at reaction temperature of 800 °C while the bimetallic catalyst (1 wt.% Ni -1wt.% Pd/Al2O3 gave the highest methane conversion of 70% over 15 min of time-on-stream (TOS. Interestingly, the introduction of Pd as promoter onto Ni-based catalyst also has a positive effect on the operational lifetime and thermal stability of the catalyst as the methane conversion has improved significantly over 240 min of TOS. Copyright © 2016 BCREC GROUP. All rights reserved Received: 21st January 2016; Revised: 6th February 2016; Accepted: 6th March 2016 How to Cite: Mei, I.L.S., Lock, S.S.M., Vo, D.V.N., Abdullah, B. (2016. Thermo-Catalytic Methane Decomposition for Hydrogen Production: Effect of Palladium Promoter on Ni-based Catalysts. Bulletin of Chemical Reaction Engineering & Catalysis, 11 (2: 191-199 (doi:10.9767/bcrec.11.2.550.191-199 Permalink/DOI: http://dx.doi.org/10.9767/bcrec.11.2.550.191-199

  18. New nanosized catalytic membrane reactors for hydrogenation with stored hydrogen: Prerequisites and the experimental basis for their creation

    Science.gov (United States)

    Soldatov, A. P.; Tsodikov, M. V.; Parenago, O. P.; Teplyakov, V. V.

    2010-12-01

    The prerequisites and prospects for creating a new generation of nanosized membrane reactors are considered. For the first time, hydrogenation reactions take place in ceramic membrane pores with hydrogen adsorbed beforehand in mono- and multilayered oriented carbon nanotubes with graphene walls (OCNTGs) formed on the internal pore surface. It is shown for Trumem microfiltration membranes with D avg ˜130 nm that oxidation reactions of CO on a Cu0.03Ti0.97O2 ± δ catalyst and the oxidative conversion of methane into synthesis gas and light hydrocarbons on La + Ce/MgO are considerably enhanced when they occur in membranes. Regularities of hydrogen adsorption, storage, and desorption in nanosized membrane reactors are investigated through OCNTG formation in Trumem ultrafiltration membrane pores with D avg = 50 and 90 nm and their saturation with hydrogen at a pressure of 10-13 MPa. It is shown that the amount of adsorbed hydrogen reaches 14.0% of OCNTG mass. Using thermogravimetric analysis in combination with mass-spectrometric analysis, hydrogen adsorption in OCNTG is first determined and its desorption is found to proceed at atmospheric pressure at a temperature of ˜175°C. It is shown that adsorbed hydrogen affects the transport properties of the membranes, reducing their efficiency with respect to liquids by 4-26 times. This is indirect confirmation of its high activity, due apparently the dissociative mechanism of adsorption.

  19. Studies on catalysis by molten metals. X. Hydrogen transfer reactions between alcohols and ketones on liquid indium catalyst

    International Nuclear Information System (INIS)

    Miyamoto, A.; Ogino, Y.

    1976-01-01

    Hydrogen transfer reactions between alcohols and ketones were studied on liquid indium catalyst by using a pulse reaction technique, and a plausible reaction model is proposed to explain the experimental results including deuterium isotope effects. Further, the stereoselectivity observed in the transfer hydrogenation of methylcyclohexanones and the selectivities observed in the transfer hydrogenation of unsaturated ketones are discussed in terms of the proposed model

  20. Mechanistic studies of catalytic hydrogenation: gas tritiation and deuteration of 2-acetamidoacrylic acid and alpha-acetamidocinnamic acid

    International Nuclear Information System (INIS)

    Tang, Y.S.; Morimoto, H.; Un, S.; Rapoport, H.

    1986-01-01

    The difference of labeling in heterogeneous catalytic gas tritiations of 2-acetamidocinnamic acid and 2-acetamidoacrylic acid is demonstrated by 3 H NMR spectroscopy. The nonequivalent addition of tritium to the double bond of 2-acetamidoacrylic acid is due to simultaneous hydrogen-tritium exchange during adsorption on the catalyst surface. A new mechanistic interpretation has been proposed to explain the behavior of this substrate. These conclusions were substantiated by mass spectrometry results obtained using D 2 and deuterated solvents. Steric effects on vinylic exchange studied by GLRC were also reported. 2 refs.; 6 figs.; 3 tabs

  1. One-step preparation of biological aviation kerosene by catalytic hydrogenation of waste lard over Pt/SAPO-11

    Science.gov (United States)

    Zhang, X.; Chen, Y. B.; Li, X. Y.; Souliyathai, D.; Zhang, S. P.; Wang, Q.; Liu, Q.; Du, J. C.; Zhang, A. M.

    2017-11-01

    Biological aviation kerosene was produced by one-step catalytic hydrotreatment of waste lard oil over Pt/SAPO-11 in a high-pressure fixed bed micro reactor. The influence of reaction conditions such as temperature, pressure, hydrogen oil ratio, and space velocity on the deoxygenation rate, the selectivity of C8-C16 hydrocarbons and the isomerization rate of C8-C16 hydrocarbons have been investigated. The experimental results showed that the temperature of 400°C, pressure of 5 MPa, hydrogen oil ratio of 1000 and space velocity of 1.2 h-1 were the best experimental reaction conditions. Under these conditions, the conversion rate is 96.62%, the selectivity of C8-C16 hydrocarbons is 50.25%, and the isomerization rate of C8-C16 hydrocarbons is 35.68%.

  2. Session 4: Combinatorial research of methane catalytic decomposition on supported nitride catalysts for CO-free hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Jianghan, Shen; Hua, Wang; Zhongmin, Liu; Hongchao, Liu [Natural Gas Utilization and Applied Catalysis Lab., Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian P. R. (China)

    2004-07-01

    CO-free Hydrogen production is needed for proton exchange membrane fuel cells (PEMs) because CO strongly poisons the anode-electrocatalysts. Methane directly catalytic decomposition is an attractive way to produce CO-free hydrogen for the large abundance of methane and its high H/C ratio. It is more effective to employ high-throughput screening (HTS) technology in heterogeneous catalysis. In this paper, a combinatorial multi-stream reaction system with online multi-stream mass spectrometer screening (MSMSS) detection technique was applied to study the decomposition of methane over supported MoN{sub x}O{sub y} catalysts (supports = Al{sub 2}O{sub 3}, SiO{sub 2}, SBA-15, ZSM-5,13X, and NaY), which is a catalyst system seldom reported recently. (authors)

  3. Half-sandwich rhodium(III) transfer hydrogenation catalysts: Reduction of NAD(+) and pyruvate, and antiproliferative activity.

    Science.gov (United States)

    Soldevila-Barreda, Joan J; Habtemariam, Abraha; Romero-Canelón, Isolda; Sadler, Peter J

    2015-12-01

    Organometallic complexes have the potential to behave as catalytic drugs. We investigate here Rh(III) complexes of general formula [(Cp(x))Rh(N,N')(Cl)], where N,N' is ethylenediamine (en), 2,2'-bipyridine (bpy), 1,10-phenanthroline (phen) or N-(2-aminoethyl)-4-(trifluoromethyl)benzenesulfonamide (TfEn), and Cp(x) is pentamethylcyclopentadienyl (Cp*), 1-phenyl-2,3,4,5-tetramethylcyclopentadienyl (Cp(xPh)) or 1-biphenyl-2,3,4,5-tetramethyl cyclopentadienyl (Cp(xPhPh)). These complexes can reduce NAD(+) to NADH using formate as a hydride source under biologically-relevant conditions. The catalytic activity decreased in the order of N,N-chelated ligand bpy > phen > en with Cp* as the η(5)-donor. The en complexes (1-3) became more active with extension to the Cp(X) ring, whereas the activity of the phen (7-9) and bpy (4-6) compounds decreased. [Cp*Rh(bpy)Cl](+) (4) showed the highest catalytic activity, with a TOF of 37.4±2h(-1). Fast hydrolysis of the chlorido complexes 1-10 was observed by (1)H NMR (hydrogenation reactions was highly dependent on the nature of the chelating ligand and the Cp(x) ring. Competition reactions between NAD(+) and pyruvate for reduction by formate catalysed by 4 showed a preference for reduction of NAD(+). The antiproliferative activity of complex 3 towards A2780 human ovarian cancer cells increased by up to 50% when administered in combination with non-toxic doses of formate, suggesting that transfer hydrogenation can induce reductive stress in cancer cells. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  4. Comparison methods between methane and hydrogen combustion for useful transfer in furnaces

    International Nuclear Information System (INIS)

    Ghiea, V.V.

    2009-01-01

    The advantages and disadvantages of hydrogen use by industrial combustion are critically presented. Greenhouse effect due natural water vapors from atmosphere and these produced by hydrogen industrial combustion is critically analyzed, together with problems of gas fuels containing hydrogen as the relative largest component. A comparison method between methane and hydrogen combustion for pressure loss in burner feeding pipe, is conceived. It is deduced the ratio of radiation useful heat transfer characteristics and convection heat transfer coefficients from combustion gases at industrial furnaces and heat recuperators for hydrogen and methane combustion, establishing specific comparison methods. Using criterial equations special processed for convection heat transfer determination, a calculation generalizing formula is established. The proposed comparison methods are general valid for different gaseous fuels. (author)

  5. Catalytic Hydrogenation Activity and Electronic Structure Determination of Bis(arylimidazol-2-ylidene)pyridine Cobalt Alkyl and Hydride Complexes

    Science.gov (United States)

    Yu, Renyuan Pony; Darmon, Jonathan M.; Milsmann, Carsten; Margulieux, Grant W.; E. Stieber, S. Chantal; DeBeer, Serena

    2013-01-01

    The bis(arylimidazol-2-ylidene)pyridine cobalt methyl complex, (iPrCNC)CoCH3, was evaluated for the catalytic hydrogenation of alkenes. At 22 °C and 4 atm of H2 pressure, (iPrCNC)CoCH3 is an effective pre-catalyst for the hydrogenation of sterically hindered, unactivated alkenes such as trans-methylstilbene, 1-methyl-1-cyclohexene and 2,3-dimethyl-2-butene, representing one of the most active cobalt hydrogenation catalysts reported to date. Preparation of the cobalt hydride complex, (iPrCNC)CoH was accomplished by hydrogenation of (iPrCNC)CoCH3. Over the course of 3 hours at 22 °C, migration of the metal-hydride to the 4-position of the pyridine ring yielded (4-H2-iPrCNC)CoN2. Similar alkyl migration was observed upon treatment of (iPrCNC)CoH with 1,1-diphenylethylene. This reactivity raised the question as to whether this class of chelate is redoxactive, engaging in radical chemistry with the cobalt center. A combination of structural, spectroscopic and computational studies was conducted and provided definitive evidence for bis(arylimidazol-2-ylidene)pyridine radicals in reduced cobalt chemistry. Spin density calculations established that the radicals were localized on the pyridine ring, accounting for the observed reactivity and suggest a wide family of pyridine-based pincers may also be redox active. PMID:23968297

  6. A compact process for the treatment of olive mill wastewater by combining wet hydrogen peroxide catalytic oxidation and biological techniques

    International Nuclear Information System (INIS)

    Azabou, Samia; Najjar, Wahiba; Bouaziz, Mohamed; Ghorbel, Abdelhamid; Sayadi, Sami

    2010-01-01

    A system based on combined actions of catalytic wet oxidation and microbial technologies for the treatment of highly polluted OMW containing polyphenols was studied. The wet hydrogen peroxide catalytic oxidation (WHPCO) process has been investigated in the semi-batch mode at atmospheric pressure, using aluminium-iron-pillared inter layer clay ((Al-Fe)PILC), under two different catalytic processes: ((Al-Fe)PILC/H 2 O 2 /ultraviolet radiations) at 25 deg. C and ((Al-Fe)PILC/H 2 O 2 ) at 50 deg. C. The results show that raw OMW was resistant to the photocatalytic process. However ((Al-Fe)PILC/H 2 O 2 ), system operating at 50 deg. C reduced considerably the COD, colour and total phenolic contents, and thus decreased the inhibition of the marine photobacteria Vibrio fischeri luminescence by 70%. This study also examined the feasibility of coupling WHPCO and anaerobic digestion treatment. Biomethanisation experiments performed with raw OMW or pre-treated OMW proved that pre-treatments with ((Al-Fe)PILC/H 2 O 2 ) system, for more than 2 h, resulted in higher methane production. Both untreated OMW as well as 2-h pre-treated OMW revealed as toxic to anaerobic bacteria.

  7. A compact process for the treatment of olive mill wastewater by combining wet hydrogen peroxide catalytic oxidation and biological techniques

    Energy Technology Data Exchange (ETDEWEB)

    Azabou, Samia [Laboratoire des BioProcedes, Centre de Biotechnologie de Sfax, BP 1177, 3018 Sfax (Tunisia); Najjar, Wahiba [Laboratoire de Chimie des Materiaux et Catalyse, Faculte des Sciences de Tunis, Campus Universitaire, 2092 Tunis (Tunisia); Bouaziz, Mohamed [Laboratoire des BioProcedes, Centre de Biotechnologie de Sfax, BP 1177, 3018 Sfax (Tunisia); Ghorbel, Abdelhamid [Laboratoire de Chimie des Materiaux et Catalyse, Faculte des Sciences de Tunis, Campus Universitaire, 2092 Tunis (Tunisia); Sayadi, Sami, E-mail: sami.sayadi@cbs.rnrt.tn [Laboratoire des BioProcedes, Centre de Biotechnologie de Sfax, BP 1177, 3018 Sfax (Tunisia)

    2010-11-15

    A system based on combined actions of catalytic wet oxidation and microbial technologies for the treatment of highly polluted OMW containing polyphenols was studied. The wet hydrogen peroxide catalytic oxidation (WHPCO) process has been investigated in the semi-batch mode at atmospheric pressure, using aluminium-iron-pillared inter layer clay ((Al-Fe)PILC), under two different catalytic processes: ((Al-Fe)PILC/H{sub 2}O{sub 2}/ultraviolet radiations) at 25 deg. C and ((Al-Fe)PILC/H{sub 2}O{sub 2}) at 50 deg. C. The results show that raw OMW was resistant to the photocatalytic process. However ((Al-Fe)PILC/H{sub 2}O{sub 2}), system operating at 50 deg. C reduced considerably the COD, colour and total phenolic contents, and thus decreased the inhibition of the marine photobacteria Vibrio fischeri luminescence by 70%. This study also examined the feasibility of coupling WHPCO and anaerobic digestion treatment. Biomethanisation experiments performed with raw OMW or pre-treated OMW proved that pre-treatments with ((Al-Fe)PILC/H{sub 2}O{sub 2}) system, for more than 2 h, resulted in higher methane production. Both untreated OMW as well as 2-h pre-treated OMW revealed as toxic to anaerobic bacteria.

  8. Efficient transfer hydrogenation reaction Catalyzed by a dearomatized PN 3P ruthenium pincer complex under base-free Conditions

    KAUST Repository

    He, Lipeng

    2012-03-01

    A dearomatized complex [RuH(PN 3P)(CO)] (PN 3PN, N′-bis(di-tert-butylphosphino)-2,6-diaminopyridine) (3) was prepared by reaction of the aromatic complex [RuH(Cl)(PN 3P)(CO)] (2) with t-BuOK in THF. Further treatment of 3 with formic acid led to the formation of a rearomatized complex (4). These new complexes were fully characterized and the molecular structure of complex 4 was further confirmed by X-ray crystallography. In complex 4, a distorted square-pyramidal geometry around the ruthenium center was observed, with the CO ligand trans to the pyridinic nitrogen atom and the hydride located in the apical position. The dearomatized complex 3 displays efficient catalytic activity for hydrogen transfer of ketones in isopropanol. © 2011 Elsevier B.V. All rights reserved.

  9. Conformational dynamics of free and catalytically active thermolysin are indistinguishable by hydrogen/deuterium exchange mass spectrometry.

    Science.gov (United States)

    Liu, Yu-Hong; Konermann, Lars

    2008-06-17

    Conformational dynamics are thought to be a prerequisite for the catalytic activity of enzymes. However, the exact relationship between structural fluctuations and function is not well understood. In this work hydrogen/deuterium exchange (HDX) and electrospray ionization mass spectrometry (ESI-MS) are used for exploring the conformational dynamics of thermolysin. Amide HDX reflects the internal mobility of proteins; regions that undergo frequent unfolding-refolding show faster exchange than segments that are highly stable. Thermolysin is a zinc protease with an active site that is located between two lobes. Substrate turnover is associated with hinge bending that leads to a closed conformation. Product release regenerates the open form, such that steady-state catalysis involves a continuous closing/opening cycle. HDX/ESI-MS with proteolytic peptide mapping in the absence of substrate shows that elements in the periphery of the two lobes are most mobile. A comparison with previous X-ray data suggests that these peripheral regions undergo quite pronounced structural changes during the catalytic cycle. In contrast, active site residues exhibit only a moderate degree of backbone flexibility, and the central zinc appears to be in a fairly rigid environment. The presence of both rigid and moderately flexible elements in the active site may reflect a carefully tuned balance that is required for function. Interestingly, the HDX behavior of catalytically active thermolysin is indistinguishable from that of the free enzyme. This result is consistent with the view that catalytically relevant motions preexist in the resting state and that enzyme function can only be performed within the limitations given by the intrinsic dynamics of the protein. The data presented in this work indicate the prevalence of stochastic elements in the function of thermolysin, rather than supporting a deterministic mechanism.

  10. Ultrathin Alumina Mask-Assisted Nanopore Patterning on Monolayer MoS2 for Highly Catalytic Efficiency in Hydrogen Evolution Reaction.

    Science.gov (United States)

    Su, Shaoqiang; Zhou, Qingwei; Zeng, Zhiqiang; Hu, Die; Wang, Xin; Jin, Mingliang; Gao, Xingsen; Nötzel, Richard; Zhou, Guofu; Zhang, Zhang; Liu, Junming

    2018-03-07

    Nanostructured molybdenum disulfide (MoS 2 ) has been considered as one of the most promising catalysts in the hydrogen evolution reaction (HER), for its approximately intermediate hydrogen binding free energy to noble metals and much lower cost. The catalytically active sites of MoS 2 are along the edges, whereas thermodynamically MoS 2 favors the presence of a two-dimensional (2-D) basal plane and the catalytically active atoms only constitute a small portion of the material. The lack of catalytically active sites and low catalytic efficiency impede its massive application. To address the issue, we have activated the basal plane of monolayer 2H MoS 2 through an ultrathin alumina mask (UTAM)-assisted nanopore arrays patterning, creating a high edge density. The introduced catalytically active sites are identified by Cu electrochemical deposition, and the hydrogen generation properties are assessed in detail. We demonstrate a remarkably improved HER performance as well as the identical catalysis of the artificial edges and the pristine metallic edges of monolayer MoS 2 . Such a porous monolayer nanostructure can achieve a much higher edge atom ratio than the pristine monolayer MoS 2 flakes, which can lead to a much improved catalytic efficiency. This controllable edge engineering can also be extended to the basal plane modifications of other 2-D materials, for improving their edge-related properties.

  11. Hydrogen-bond dynamics and proton transfer in nanoconfinement

    NARCIS (Netherlands)

    van der Loop, T.H.

    2015-01-01

    Proton transfer is of fundamental importance to both biology and chemistry. Much is known about proton transfer in large water volumes but often proton transfer reactions take place in very small nanometer sized volumes for example between lipid layers and in proton channels in mitochondria and

  12. Base-free hydrogen generation from methanol using a bi-catalytic system.

    Science.gov (United States)

    Monney, Angèle; Barsch, Enrico; Sponholz, Peter; Junge, Henrik; Ludwig, Ralf; Beller, Matthias

    2014-01-21

    A bi-catalytic system, in which Ru-MACHO-BH and Ru(H)2(dppe)2 interact in a synergistic manner, was developed for the base-free dehydrogenation of methanol. A total TON > 4200 was obtained with only trace amounts of CO contamination (<8 ppm) in the produced gas.

  13. Prediction of Improved Performance of Catalytic Hydrogenation Reactor by Periodic Modulation of the Feed Rate

    Czech Academy of Sciences Publication Activity Database

    Staněk, Vladimír; Hanika, Jiří; Jiřičný, Vladimír; Stavárek, Petr; Tukač, V.; Lederer, J.

    2009-01-01

    Roč. 23, č. 3 (2009), s. 251-257 ISSN 1451-9372 R&D Projects: GA MPO FT-TA/039 Institutional research plan: CEZ:AV0Z40720504 Keywords : trickle bed * feed modulation * catalytic reactor Subject RIV: CI - Industrial Chemistry, Chemical Engineering

  14. Transition-metal-catalyzed hydrogen-transfer annulations: access to heterocyclic scaffolds.

    Science.gov (United States)

    Nandakumar, Avanashiappan; Midya, Siba Prasad; Landge, Vinod Gokulkrishna; Balaraman, Ekambaram

    2015-09-14

    The ability of hydrogen-transfer transition-metal catalysts, which enable increasingly rapid access to important structural scaffolds from simple starting materials, has led to a plethora of research efforts on the construction of heterocyclic scaffolds. Transition-metal-catalyzed hydrogen-transfer annulations are environmentally benign and highly atom-economical as they release of water and hydrogen as by-product and utilize renewable feedstock alcohols as starting materials. Recent advances in this field with respect to the annulations of alcohols with various nucleophilic partners, thus leading to the formation of heterocyclic scaffolds, are highlighted herein. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Osmium pyme complexes for fast hydrogenation and asymmetric transfer hydrogenation of ketones.

    Science.gov (United States)

    Baratta, Walter; Ballico, Maurizio; Del Zotto, Alessandro; Siega, Katia; Magnolia, Santo; Rigo, Pierluigi

    2008-01-01

    The osmium compound trans,cis-[OsCl2(PPh3)2(Pyme)] (1) (Pyme=1-(pyridin-2-yl)methanamine), obtained from [OsCl2(PPh3)3] and Pyme, thermally isomerizes to cis,cis-[OsCl2(PPh3)(2)(Pyme)] (2) in mesitylene at 150 degrees C. Reaction of [OsCl2(PPh3)3] with Ph2P(CH2)(4)PPh2 (dppb) and Pyme in mesitylene (150 degrees C, 4 h) leads to a mixture of trans-[OsCl2(dppb)(Pyme)] (3) and cis-[OsCl2(dppb)(Pyme)] (4) in about an 1:3 molar ratio. The complex trans-[OsCl2(dppb)(Pyet)] (5) (Pyet=2-(pyridin-2-yl)ethanamine) is formed by reaction of [OsCl2(PPh3)3] with dppb and Pyet in toluene at reflux. Compounds 1, 2, 5 and the mixture of isomers 3/4 efficiently catalyze the transfer hydrogenation (TH) of different ketones in refluxing 2-propanol and in the presence of NaOiPr (2.0 mol %). Interestingly, 3/4 has been proven to reduce different ketones (even bulky) by means of TH with a remarkably high turnover frequency (TOF up to 5.7 x 10(5) h(-1)) and at very low loading (0.05-0.001 mol %). The system 3/4 also efficiently catalyzes the hydrogenation of many ketones (H2, 5.0 atm) in ethanol with KOtBu (2.0 mol %) at 70 degrees C (TOF up to 1.5 x 10(4) h(-1)). The in-situ-generated catalysts prepared by the reaction of [OsCl2(PPh3)3] with Josiphos diphosphanes and (+/-)-1-alkyl-substituted Pyme ligands, promote the enantioselective TH of different ketones with 91-96 % ee (ee=enantiomeric excess) and with a TOF of up to 1.9 x 10(4) h(-1) at 60 degrees C.

  16. Catalytic Fast Pyrolysis of Biomass Impregnated with Potassium Phosphate in a Hydrogen Atmosphere for the Production of Phenol and Activated Carbon

    Science.gov (United States)

    Lu, Qiang; Zhang, Zhen-xi; Wang, Xin; Guo, Hao-qiang; Cui, Min-shu; Yang, Yong-ping

    2018-01-01

    A new technique was proposed to co-produce phenol and activated carbon (AC) from catalytic fast pyrolysis of biomass impregnated with K3PO4 in a hydrogen atmosphere, followed by activation of the pyrolytic solid residues. Lab-scale catalytic fast pyrolysis experiments were performed to quantitatively determine the pyrolytic product distribution, as well as to investigate the effects of several factors on the phenol production, including pyrolysis atmosphere, catalyst type, biomass type, catalytic pyrolysis temperature, and catalyst impregnation content. In addition, the pyrolytic solid residues were activated to prepare ACs with high specific surface areas. The results indicated that phenol could be obtained due to the synergistic effects of K3PO4 and hydrogen atmosphere, with the yield and selectivity reaching 5.3 wt% and 17.8% from catalytic fast pyrolysis of poplar wood with 8 wt% K3PO4 at 550°C in a hydrogen atmosphere. This technique was adaptable to different woody materials for phenol production. Moreover, gas product generated from the pyrolysis process was feasible to be recycled to provide the hydrogen atmosphere, instead of extra hydrogen supply. In addition, the pyrolytic solid residue was suitable for AC preparation, using CO2 activation method, the specific surface area was as high as 1,605 m2/g. PMID:29515994

  17. Catalytic Fast Pyrolysis of Biomass Impregnated with Potassium Phosphate in a Hydrogen Atmosphere for the Production of Phenol and Activated Carbon

    Directory of Open Access Journals (Sweden)

    Qiang Lu

    2018-02-01

    Full Text Available A new technique was proposed to co-produce phenol and activated carbon (AC from catalytic fast pyrolysis of biomass impregnated with K3PO4 in a hydrogen atmosphere, followed by activation of the pyrolytic solid residues. Lab-scale catalytic fast pyrolysis experiments were performed to quantitatively determine the pyrolytic product distribution, as well as to investigate the effects of several factors on the phenol production, including pyrolysis atmosphere, catalyst type, biomass type, catalytic pyrolysis temperature, and catalyst impregnation content. In addition, the pyrolytic solid residues were activated to prepare ACs with high specific surface areas. The results indicated that phenol could be obtained due to the synergistic effects of K3PO4 and hydrogen atmosphere, with the yield and selectivity reaching 5.3 wt% and 17.8% from catalytic fast pyrolysis of poplar wood with 8 wt% K3PO4 at 550°C in a hydrogen atmosphere. This technique was adaptable to different woody materials for phenol production. Moreover, gas product generated from the pyrolysis process was feasible to be recycled to provide the hydrogen atmosphere, instead of extra hydrogen supply. In addition, the pyrolytic solid residue was suitable for AC preparation, using CO2 activation method, the specific surface area was as high as 1,605 m2/g.

  18. Catalytic Fast Pyrolysis of Biomass Impregnated with Potassium Phosphate in a Hydrogen Atmosphere for the Production of Phenol and Activated Carbon.

    Science.gov (United States)

    Lu, Qiang; Zhang, Zhen-Xi; Wang, Xin; Guo, Hao-Qiang; Cui, Min-Shu; Yang, Yong-Ping

    2018-01-01

    A new technique was proposed to co-produce phenol and activated carbon (AC) from catalytic fast pyrolysis of biomass impregnated with K 3 PO 4 in a hydrogen atmosphere, followed by activation of the pyrolytic solid residues. Lab-scale catalytic fast pyrolysis experiments were performed to quantitatively determine the pyrolytic product distribution, as well as to investigate the effects of several factors on the phenol production, including pyrolysis atmosphere, catalyst type, biomass type, catalytic pyrolysis temperature, and catalyst impregnation content. In addition, the pyrolytic solid residues were activated to prepare ACs with high specific surface areas. The results indicated that phenol could be obtained due to the synergistic effects of K 3 PO 4 and hydrogen atmosphere, with the yield and selectivity reaching 5.3 wt% and 17.8% from catalytic fast pyrolysis of poplar wood with 8 wt% K 3 PO 4 at 550°C in a hydrogen atmosphere. This technique was adaptable to different woody materials for phenol production. Moreover, gas product generated from the pyrolysis process was feasible to be recycled to provide the hydrogen atmosphere, instead of extra hydrogen supply. In addition, the pyrolytic solid residue was suitable for AC preparation, using CO 2 activation method, the specific surface area was as high as 1,605 m 2 /g.

  19. Life cycle assessment of hydrogenated biodiesel production from waste cooking oil using the catalytic cracking and hydrogenation method.

    OpenAIRE

    Yano, Junya; Aoki, Tatsuki; Nakamura, Kazuo; Yamada, Kazuo; Sakai, Shin-ichi

    2015-01-01

    There is a worldwide trend towards stricter control of diesel exhaust emissions, however presently, there are technical impediments to the use of FAME (fatty acid methyl esters)-type biodiesel fuel (BDF). Although hydrogenated biodiesel (HBD) is anticipated as a new diesel fuel, the environmental performance of HBD and its utilization system have not been adequately clarified. Especially when waste cooking oil is used as feedstock, not only biofuel production but also the treatment of waste c...

  20. Heat transfer comparison between methane and hydrogen in a spark ignited engine

    Energy Technology Data Exchange (ETDEWEB)

    Sierens, Roger; Demuynck, Joachim; Paepe, Michel de; Verhelst, Sebastian [Ghent Univ. (Belgium)

    2010-07-01

    Hydrogen is one of the alternative fuels which are being investigated at Ghent University. NO{sub x} emissions will occur at high engine loads and they are a constraint for power and efficiency optimization. The formation of NO{sub x} emissions is temperature dependent. Consequently, the heat transfer from the burning gases to the cylinder walls has to be accurately modelled if precise computer calculations of the emissions are wanted. Several engine heat transfer models exist but they have been cited to be inaccurate for hydrogen. We have measured the heat flux in a spark ignited engine with a commercially available heat flux sensor. This paper investigates the difference between the heat transfer of hydrogen and a fossil fuel, in this case methane. Measurements with the same indicated power output are compared and the effect of the heat loss on the indicated efficiency is investigated. The power output of hydrogen combustion is lowered by burning lean in contrast to using a throttle in the case of methane. Although the peak in the heat flux of hydrogen is 3 times higher compared to methane for a high engine power output, the indicated efficiency is only 3% lower. The heat loss for hydrogen at a low engine load is smaller than that of methane which results in a higher indicated efficiency. The richness of the hydrogen-air mixture has a great influence on the heat transfer process in contrast to the in-cylinder mass in the case of methane. (orig.)

  1. Hydrazine as efficient fuel for low-temperature SOFC through ex-situ catalytic decomposition with high selectivity toward hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Song, Jia; Ran, Ran; Shao, Zongping [State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing University of Technology, No. 5 Xin Mofan Road, Nanjing 210009 (China)

    2010-08-15

    Hydrazine is a promising fuel for portable fuel cells because it is a liquid, it is carbon free and it has a high energy density. In this work, hydrazine was investigated as an efficient fuel for low temperature solid-oxide fuel cells (SOFCs) with a traditional nickel anode. A catalytic system with high selectivity toward hydrogen was developed using Ba{sub 0.5}Sr{sub 0.5}Co{sub 0.8}Fe{sub 0.2}O{sub 3-{delta}} (BSCF) as the main catalyst and potassium hydroxide as the promoter. The result of compositional analysis of the products showed that the hydrazine can be decomposed into hydrogen and nitrogen with 100% selectivity when an appropriate amount of KOH promoter is used. Acceptable power densities were achieved for a thin-film samaria-doped ceria (SDC) electrolyte cell operating on hydrazine decomposition products and hydrogen over a complete operation temperature range of 650-450 C. In addition, a similar cell with ammonia as the fuel displayed a much lower performance. (author)

  2. Activating basal-plane catalytic activity of two-dimensional MoS2 monolayer with remote hydrogen plasma

    KAUST Repository

    Cheng, Chia-Chin

    2016-09-10

    Two-dimensional layered transition metal dichalcogenide (TMD) materials such as Molybdenum disufide (MoS2) have been recognized as one of the low-cost and efficient electrocatalysts for hydrogen evolution reaction (HER). The crystal edges that account for a small percentage of the surface area, rather than the basal planes, of MoS2 monolayer have been confirmed as their active catalytic sites. As a result, extensive efforts have been developing in activating the basal planes of MoS2 for enhancing their HER activity. Here, we report a simple and efficient approach-using a remote hydrogen-plasma process-to creating S-vacancies on the basal plane of monolayer crystalline MoS2; this process can generate high density of S-vacancies while mainly maintaining the morphology and structure of MoS2 monolayer. The density of S-vacancies (defects) on MoS2 monolayers resulted from the remote hydrogen-plasma process can be tuned and play a critical role in HER, as evidenced in the results of our spectroscopic and electrical measurements. The H2-plasma treated MoS2 also provides an excellent platform for systematic and fundamental study of defect-property relationships in TMDs, which provides insights for future applications including electrical, optical and magnetic devices. © 2016 Elsevier Ltd.

  3. Effects of acido-basic support properties on the catalytic hydrogenation of acetylene on gold nano-particles

    Science.gov (United States)

    Manda, Abdullah Ahmed

    Metallic gold nanoparticles supported on gamma-Al2O 3 and magnesia-alumina mixed oxide, with different magnesia content have been prepared by sol-gel method and characterized by different techniques (inductive coupled plasma-mass spectroscopy (ICP-MS), XRD, BET surface area analysis, transmission electron microscopy (TEM), CO2 and NH 3 temperature programmed desorption (TPD), H2 temperature programmed reduction (TPR) and FTIR of adsorbed CO2). Such systems were found to produce catalysts with controllable acidity, varying from catalyst possessing large density of acidic and low density of basic sites, others with acidic and basic sites of equal strength and density, and others with large basic and low acid sites densities, respectively. The catalytic assessment of the generated acidity was carried out using 2-propanol decomposition as a test reaction. The results obtained indicate that the presence of magnesia and reduced gold nanopartilces has imparted the catalysts, 1%Au/4%Mg-Al 2O3 and 1%Au/8%Mg-Al2O3, with significant base-catalytic properties. Acetylene hydrogenation and formation of coke deposits were investigated on a gold catalyst supported on gamma-Al2O3 and gold supported on alumina-magnisia mixed oxide with different gold content; 1%Au/gamma-Al 2O3, 1%Au/15%Mg-Al2O3, 2%Au/15%Mg-Al 2O3 and 4%Au/15%Mg-Al2O3. The effect of the H2/C2H2 ratio was studied over a range of values. The catalytic activity and selectivity towards ethylene and other products were investigated at different reaction temperatures. Acetylene hydrogenation was investigated in the presence and absence of ethylene in stream. It is investigated that the adsorption of the triple bond is preferred over the double bond and during selective catalytic (SCR) of C2H2 the two hydrocarbons do not compete for the same adsorption sites. The deactivation of catalysts was studied by temperature programmed oxidation (TPO). Higher content of coke over 1%Au/Al2O3 catalyst was investigated in contrast to

  4. Enzyme catalytic resonance scattering spectral detection of trace hydrogen peroxide using guaiacol as substrate

    Directory of Open Access Journals (Sweden)

    Shiwen Huang

    2011-08-01

    Full Text Available Hydrogen peroxide oxidized guaiacol to form tetramer particles that exhibited a strong resonance scattering (RS peak at 530 nm in the presence of horseradish peroxidase (HRP in citric acid-Na2HPO4 buffer solution of pH 4.4. The RS peak increased when the concentration of hydrogen peroxide increased. The increased RS intensity (ΔI530 nm was linear to the hydrogen peroxide concentration in the range of 0.55-27.6 μM, with a linear regression equation of ΔI530 nm = 17.1C + 1.6, a relative coefficient of 0.9996 and a detection limit of 0.03 μM H2O2. This proposed method was applied to detect hydrogen peroxide in rain water, with sensitivity, selectivity, rapidity, and recovery of 98.0-104 %.

  5. Hybrid fiber gratings coated with a catalytic sensitive layer for hydrogen sensing in air.

    Science.gov (United States)

    Caucheteur, Christophe; Debliquy, Marc; Lahem, Driss; Megret, Patrice

    2008-10-13

    Using hydrogen as fuel presents a potential risk of explosion and requires low cost and efficient leak sensors. We present here a hybrid sensor configuration consisting of a long period fiber grating (LPFG) and a superimposed uniform fiber Bragg grating (FBG). Both gratings are covered with a sensitive layer made of WO(3) doped with Pt on which H(2) undergoes an exothermic reaction. The released heat increases the temperature around the gratings. In this configuration, the LPFG favors the exothermic reaction thanks to a light coupling to the sensitive layer while the FBG reflects the temperature change linked to the hydrogen concentration. Our sensor is very fast and suitable to detect low hydrogen concentrations in air whatever the relative humidity level and for temperatures down to -50 degrees C, which is without equivalent for other hydrogen optical sensors reported so far.

  6. Investigation of tritium removal by means of organic compounds. Catalytic hydrogenation (tritiation) of linoleic acid

    International Nuclear Information System (INIS)

    El-Sharnouby, A.; Weichselgartner, H.

    1984-11-01

    In the presence of noble-metal catalysts unsaturated fatty acids such as eruic acid and linoleic acid capture hydrogen (and tritium) quantitatively. The hydrogenation reaction of eruic acid has already been reported. The experimental results of the reaction of hydrogen (and tritium) with linoleic acid are now discussed in this paper. Obviously, the use of linoleic acid shows some advantages compared with eruic acid: - the hydrogenation reaction is faster, - linoleic acid is liquid, so that the choice of additional solvents is easier, and - linoleic acid is a more or less cheap natural product, which is available from a series of seeds, so that the cost of a technical tritium removal plant is not increased by the basic chemical material. (orig.)

  7. Maximizing renewable hydrogen production from biomass in a bio/catalytic refinery

    DEFF Research Database (Denmark)

    Westermann, Peter; Jørgensen, Betina; Lange, L.

    2007-01-01

    Biological production of hydrogen from biomass by fermentative or photofermentative microorganisms has been described in numerous research articles and reviews. The major challenge of these techniques is the low yield from fermentative production, and the large reactor volumes necessary...

  8. Identification of intrinsic catalytic activity for electrochemical reduction of water molecules to generate hydrogen

    KAUST Repository

    Shinagawa, Tatsuya

    2015-01-01

    Insufficient hydronium ion activities at near-neutral pH and under unbuffered conditions induce diffusion-limited currents for hydrogen evolution, followed by a reaction with water molecules to generate hydrogen at elevated potentials. The observed constant current behaviors at near neutral pH reflect the intrinsic electrocatalytic reactivity of the metal electrodes for water reduction. This journal is © the Owner Societies.

  9. Regio-Selective Intramolecular Hydrogen/Deuterium Exchange in Gas-Phase Electron Transfer Dissociation

    Science.gov (United States)

    Hamuro, Yoshitomo

    2017-05-01

    Protein backbone amide hydrogen/deuterium exchange mass spectrometry (HDX-MS) typically utilizes enzymatic digestion after the exchange reaction and before MS analysis to improve data resolution. Gas-phase fragmentation of a peptic fragment prior to MS analysis is a promising technique to further increase the resolution. The biggest technical challenge for this method is elimination of intramolecular hydrogen/deuterium exchange (scrambling) in the gas phase. The scrambling obscures the location of deuterium. Jørgensen's group pioneered a method to minimize the scrambling in gas-phase electron capture/transfer dissociation. Despite active investigation, the mechanism of hydrogen scrambling is not well-understood. The difficulty stems from the fact that the degree of hydrogen scrambling depends on instruments, various parameters of mass analysis, and peptide analyzed. In most hydrogen scrambling investigations, the hydrogen scrambling is measured by the percentage of scrambling in a whole molecule. This paper demonstrates that the degree of intramolecular hydrogen/deuterium exchange depends on the nature of exchangeable hydrogen sites. The deuterium on Tyr amide of neurotensin (9-13), Arg-Pro-Tyr-Ile-Leu, migrated significantly faster than that on Ile or Leu amides, indicating the loss of deuterium from the original sites is not mere randomization of hydrogen and deuterium but more site-specific phenomena. This more precise approach may help understand the mechanism of intramolecular hydrogen exchange and provide higher confidence for the parameter optimization to eliminate intramolecular hydrogen/deuterium exchange during gas-phase fragmentation.

  10. Catalytic activity of superconducting ceramics of Y-Ba-Cu-O type in reaction of H-D exchange of molecular hydrogen

    International Nuclear Information System (INIS)

    Parbuzin, V.S.; Gul'yants, V.V.

    1989-01-01

    Catalytic activity of high-temperature superconducting oxide ceramics of Y-Ba-Cu-O type in reaction of deuterium-hydrogen exchange was investigated under chromatographic conditions. Rate constants of the reaction and activation energy of the process, equal to 58 ± 2 kJ/mol, were determined in 350 - 450 K range and at 18250Pa hydrogen pressure. Assumption about applicability of Bonhoeffer-Farkas mechanism with adsorption on copper atoms, adjoinig oxygen vacancies, was made

  11. Thermal Balance Analysis of a Micro-Thermoelectric Gas Sensor Using Catalytic Combustion of Hydrogen

    Directory of Open Access Journals (Sweden)

    Daisuke Nagai

    2014-01-01

    Full Text Available A thermoelectric gas sensor (TGS with a combustion catalyst is a calorimetric sensor that changes the small heat of catalytic combustion into a signal voltage. We analyzed the thermal balance of a TGS to quantitatively estimate the sensor parameters. The voltage signal of a TGS was simulated, and the heat balance was calculated at two sections across the thermoelectric film of a TGS. The thermal resistances in the two sections were estimated from the thermal time constants of the experimental signal curves of the TGS. The catalytic combustion heat Qcatalyst required for 1 mV of ∆Vgas was calculated to be 46.1 μW. Using these parameters, we find from simulations for the device performance that the expected Qcatalyst for 200 and 1,000 ppm H2 was 3.69 μW and 11.7 μW, respectively.

  12. Thermal balance analysis of a micro-thermoelectric gas sensor using catalytic combustion of hydrogen.

    Science.gov (United States)

    Nagai, Daisuke; Akamatsu, Takafumi; Itoh, Toshio; Izu, Noriya; Shin, Woosuck

    2014-01-21

    A thermoelectric gas sensor (TGS) with a combustion catalyst is a calorimetric sensor that changes the small heat of catalytic combustion into a signal voltage. We analyzed the thermal balance of a TGS to quantitatively estimate the sensor parameters. The voltage signal of a TGS was simulated, and the heat balance was calculated at two sections across the thermoelectric film of a TGS. The thermal resistances in the two sections were estimated from the thermal time constants of the experimental signal curves of the TGS. The catalytic combustion heat Q(catalyst) required for 1 mV of ∆V(gas) was calculated to be 46.1 μW. Using these parameters, we find from simulations for the device performance that the expected Q(catalyst) for 200 and 1,000 ppm H₂ was 3.69 μW and 11.7 μW, respectively.

  13. H2CAP - Hydrogen assisted catalytic biomass pyrolysis for green fuels

    DEFF Research Database (Denmark)

    Arndal, Trine Marie Hartmann; Høj, Martin; Jensen, Peter Arendt

    2014-01-01

    Pyrolysis of biomass produces a high yield of condensable oil at moderate temperature and low pressure.This bio-oil has adverse properties such as high oxygen and water contents, high acidity and immiscibility with fossil hydrocarbons. Catalytic hydrodeoxygenation (HDO) is a promising technology...... that can be used to upgrade the crude bio-oil to fuel-grade oil. The development of the HDO process is challenged by rapid catalyst deactivation, instability of the pyrolysis oil, poorly investigated reaction conditions and a high complexity and variability of the input oil composition. However, continuous...... catalytic hydropyrolysis coupled with downstream HDO of the pyrolysis vapors before condensation shows promise (Figure 1). A bench scale experimental setup will be constructed for the continuous conversion of solid biomass (100g /h) to low oxygen, fuel-grade bio-oil. The aim is to provide a proof...

  14. Preparation and characterization of LTA-type zeolite framework dispersed ruthenium nanoparticles and their catalytic application in the hydrolytic dehydrogenation of ammonia–borane for efficient hydrogen generation

    International Nuclear Information System (INIS)

    Zahmakiran, Mehmet

    2012-01-01

    Highlights: ► Ru(0)NPs-ZK-4 were prepared and characterized by advanced analytical techniques. ► They achieve the hydrolysis of ammonia-borane with TOF = 5410 h −1 and TTO = 36700. ► They maintain 85% of their activity even at the fifth catalytic run. - Abstract: The safe and efficient hydrogen storage and production are major obstacles to use hydrogen as an energy carrier. Therefore, significant efforts have been focused on the development of new materials for the chemical hydrogen storage and production. Of particular importance, ammonia–borane (NH 3 BH 3 ) is emerging as one of the most promising solid hydrogen carrier due to its high gravimetric hydrogen storage capacity (19.6 wt.%) and low molecular weight (30.8 g/mol). ammonia–borane can release hydrogen gas upon catalytic hydrolysis under mild conditions. Herein, the discovery of a new catalytic material, ruthenium nanoparticles stabilized by ZK-4 zeolite framework, for this important reaction has been reported. This new catalyst system was prepared by borohydride reduction of ruthenium(III)-exchanged ZK-4 zeolite in water at room temperature. The characterization of the resulting material by advanced analytical tools shows the formation of ZK-4 zeolite dispersed ruthenium nanoparticles (2.9 ± 0.9 nm). The catalytic performance of the resulting supported ruthenium nanoparticles depending on activity, lifetime and reusability was demonstrated in the hydrolytic dehydrogenation of ammonia–borane. They were found to be highly active (initial TOF = 5410 h −1 ), long-lived (TTO = 36,700) and reusable catalyst (retaining of >85% of initial activity in the 5th reuse) in this important catalytic reaction at room temperature under air.

  15. Transfer of π- from hydrogen to deuterium in H2O + D2O mixtures

    International Nuclear Information System (INIS)

    Stanislaus, S.; Measday, D.F.; Vetterli, D.; Weber, P.; Aniol, K.A.; Harston, M.R.; Armstrong, D.S.

    1989-07-01

    The transfer of stopping π - mesons from hydrogen to deuterium has been investigated in mixtures of H 2 O+D 2 O as a function of D 2 O concentration. The concentration dependence of the transfer probability is similar to that observed for the gas mixtures of H 2 and D 2 but slightly more transfer is found for H 2 O+D 2 O. (Author) 17 refs., 2 tabs., 4 figs

  16. Muon transfer from muonic hydrogen to heavier atoms; Transfert de charge muonique

    Energy Technology Data Exchange (ETDEWEB)

    Dupays, A

    2004-06-01

    This work concerns muon transfer from muonic hydrogen to heavier atoms. Recently, a method of measurement of the hyperfine structure of ground-state muonic hydrogen based on the collision energy dependence of the muon transfer rate to oxygen has been proposed. This proposal is based on measurements which where performed at the Paul Scherrer Institute in the early nineties which indicate that the muon transfer from muonic hydrogen to oxygen increases by a factor of 4 going from thermal to 0.12 eV energies. The motivation of our calculations was to confirm this behaviour. To study the collision energy dependence of the muon transfer rate, we have used a time-independent close-coupling method. We have set up an hyperspherical elliptic formalism valid for nonzero total angular momentum which allows accurate computations of state-to-state reactive and charge exchange processes. We have applied this formalism to muon-transfer process to oxygen and neon. The comparison with experimental results is in both cases excellent. Finally, the neon transfer rate dependence with energy suggests to use neon instead of oxygen to perform a measurement of the hyperfine structure of muonic hydrogen. The results of accurate calculations of the muon transfer rates from muonic protium and deuterium atoms to nitrogen, oxygen and neon are also reported. Very good agreement with measured rates is obtained and for the three systems, the isotopic effect is perfectly reproduced. (author)

  17. Catalytic hydrogen production from fossil fuels via the water gas shift reaction

    International Nuclear Information System (INIS)

    Gradisher, Logan; Dutcher, Bryce; Fan, Maohong

    2015-01-01

    Highlights: • Hydrogen is a clean alternative to hydrocarbon fuels. • Hydrogen is primarily produced with the water gas shift reaction. • Development of water gas shift catalysts is essential to the energy industry. • This work summarizes recent progress in water gas shift catalyst research. - Abstract: The production of hydrogen is a highly researched topic for many reasons. First of all, it is a clean fuel that can be used instead of hydrocarbons, which produce CO 2 , a greenhouse gas emission that is thought to be the reason for climate change in the world. The largest source of hydrogen is the water gas shift (WGS) reaction, where CO and water are mixed over a catalyst to produce the desired hydrogen. Many researchers have focused on development of WGS catalysts with different metals. The most notable of these metals are precious and rare earth metals which, when combined, have unique properties for the WGS reaction. Research in this area is very important to the energy industry and the future of energy around the world. However, the progress made recently has not been reviewed, and this review was designed to fill the gap

  18. Synergic catalytic effect of Ti hydride and Nb nanoparticles for improving hydrogenation and dehydrogenation kinetics of Mg-based nanocomposite

    Directory of Open Access Journals (Sweden)

    Xiujuan Ma

    2017-02-01

    Full Text Available The Mg-9.3 wt% (TiH1.971-TiH−0.7 wt% Nb nanocomposite has been synthesized by hydrogen plasma-metal reaction (HPMR approach to enhance the hydrogen sorption kinetics of Mg at moderate temperatures by providing nanosizing effect of increasing H “diffusion channels” and adding transition metallic catalysts. The Mg nanoparticles (NPs were in hexagonal shape range from 50 to 350 nm and the average size of the NPs was 177 nm. The small spherical TiH1.971, TiH and Nb NPs of about 25 nm uniformly decorated on the surface of the big Mg NPs. The Mg-TiH1.971-TiH-Nb nanocomposite could quickly absorb 5.6 wt% H2 within 5 min at 573 K and 4.5 wt% H2 within 5 min at 523 K, whereas the pure Mg prepared by HPMR could only absorb 4 and 1.5 wt% H2 at the same temperatures. TiH1.971, TiH and Nb NPs transformed into TiH2 and NbH during hydrogenation and recovered after dehydrogenation process. The apparent activation energies of the nanocomposite for hydrogenation and dehydrogenation were 45.0 and 50.7 kJ mol−1, which are much smaller than those of pure Mg NPs, 123.8 and 127.7 kJ mol−1. The improved sorption kinetics of the Mg-based nanocomposite at moderate temperatures and the small activation energy can be interpreted by the nanostructure of Mg and the synergic catalytic effects of Ti hydrides and Nb NPs.

  19. Size Control of Iron Oxide Nanoparticles Using Reverse Microemulsion Method: Morphology, Reduction, and Catalytic Activity in CO Hydrogenation

    Directory of Open Access Journals (Sweden)

    Mohammad Reza Housaindokht

    2013-01-01

    Full Text Available Iron oxide nanoparticles were prepared by microemulsion method and evaluated in Fischer-Tropsch synthesis. The precipitation process was performed in a single-phase microemulsion operating region. Different HLB values of surfactant were prepared by mixing of sodium dodecyl sulfate (SDS and Triton X-100. Transmission electron microscopy (TEM, surface area, pore volume, average pore diameter, pore size distribution, and XRD patterns were used to analyze size distribution, shape, and structure of precipitated hematite nanoparticles. Furthermore, temperature programmed reduction (TPR and catalytic activity in CO hydrogenation were implemented to assess the performance of the samples. It was found that methane and CO2 selectivity and also the syngas conversion increased as the HLB value of surfactant decreased. In addition, the selectivity to heavy hydrocarbons and chain growth probability (α decreased by decreasing the catalyst crystal size.

  20. Catalytic activity of Pd-doped Cu nanoparticles for hydrogenation as a single-atom-alloy catalyst.

    Science.gov (United States)

    Cao, Xinrui; Fu, Qiang; Luo, Yi

    2014-05-14

    The single atom alloy of extended surfaces is known to provide remarkably enhanced catalytic performance toward heterogeneous hydrogenation. Here we demonstrate from first principles calculations that this approach can be extended to nanostructures, such as bimetallic nanoparticles. The catalytic properties of the single-Pd-doped Cu55 nanoparticles have been systemically examined for H2 dissociation as well as H atom adsorption and diffusion, following the concept of single atom alloy. It is found that doping a single Pd atom at the edge site of the Cu55 shell can considerably reduce the activation energy of H2 dissociation, while the single Pd atom doped at the top site or in the inner layers is much less effective. The H atom adsorption on Cu55 is slightly stronger than that on the Cu(111) surface; however, a larger nanoparticle that contains 147 atoms could effectively recover the weak binding of the H atoms. We have also investigated the H atom diffusion on the 55-atom nanoparticle and found that spillover of the produced H atoms could be a feasible process due to the low diffusion barriers. Our results have demonstrated that facile H2 dissociation and weak H atom adsorption could be combined at the nanoscale. Moreover, the effects of doping one more Pd atom on the H2 dissociation and H atom adsorption have also been investigated. We have found that both the doping Pd atoms in the most stable configuration could independently exhibit their catalytic activity, behaving as two single-atom-alloy catalysts.

  1. The role of hydrogen bonding in excited state intramolecular charge transfer.

    Science.gov (United States)

    Chipem, Francis A S; Mishra, Anasuya; Krishnamoorthy, G

    2012-07-07

    Intramolecular charge transfer (ICT) that occurs upon photoexcitation of molecules is a vital process in nature and it has ample applications in chemistry and biology. The ICT process of the excited molecules is affected by several environmental factors including polarity, viscosity and hydrogen bonding. The effect of polarity and viscosity on the ICT processes is well understood. But, despite the fact that hydrogen bonding significantly influences the ICT process, the specific role of hydrogen bonding in the formation and stabilization of the ICT state is not unambiguously established. Some literature reports predicted that the hydrogen bonding of the solvent with a donor promotes the formation of a twisted intramolecular charge transfer (TICT) state. Some other reports stated that it inhibits the formation of the TICT state. Alternatively, it was proposed that the hydrogen bonding of the solvent with an acceptor favors the TICT state. It is also observed that a dynamic equilibrium is established between the free and the hydrogen bonded ICT states. This perspective focuses on the specific role played by hydrogen bonding of the solvent with the donor and the acceptor, and by proton transfer in the ICT process. The utility of such influence in molecular recognition and anion sensing is discussed with a few recent literature examples in the end.

  2. Modeling and Simulation of the Hydrogenation of α-Methylstyrene on Catalytically Active Metal Foams as Tubular Reactor Packing

    Directory of Open Access Journals (Sweden)

    Farzad Lali

    2016-01-01

    Full Text Available This work presents a one-dimensional reactor model for a tubular reactor packed with a catalytically active foam packing with a pore density of 30 PPI in cocurrent upward flow in the example of hydrogenation reaction of α-methylstyrene to cumene. This model includes material, enthalpy, and momentum balances as well as continuity equations. The model was solved within the parameter space applied for experimental studies under assumption of a bubbly flow. The method of orthogonal collocation on finite elements was applied. For isothermal and polytropic processes and steady state conditions, axial profiles for concentration, temperature, fluid velocities, pressure, and liquid holdup were computed and the conversions for various gas and liquid flow rates were validated with experimental results. The obtained results were also compared in terms of space time yield and catalytic activity with experimental results and stirred tank and also with random packed bed reactor. The comparison shows that the application of solid foams as reactor packing is advantageous compared to the monolithic honeycombs and random packed beds.

  3. High performing and stable supported nano-alloys for the catalytic hydrogenation of levulinic acid to γ-valerolactone

    Science.gov (United States)

    Luo, Wenhao; Sankar, Meenakshisundaram; Beale, Andrew M.; He, Qian; Kiely, Christopher J.; Bruijnincx, Pieter C. A.; Weckhuysen, Bert M.

    2015-03-01

    The catalytic hydrogenation of levulinic acid, a key platform molecule in many biorefinery schemes, into γ-valerolactone is considered as one of the pivotal reactions to convert lignocellulose-based biomass into renewable fuels and chemicals. Here we report on the development of highly active, selective and stable supported metal catalysts for this reaction and on the beneficial effects of metal nano-alloying. Bimetallic random alloys of gold-palladium and ruthenium-palladium supported on titanium dioxide are prepared with a modified metal impregnation method. Gold-palladium/titanium dioxide shows a marked,~27-fold increase in activity (that is, turnover frequency of 0.1 s-1) compared with its monometallic counterparts. Although ruthenium-palladium/titanium dioxide is not only exceptionally active (that is, turnover frequency of 0.6 s-1), it shows excellent, sustained selectivity to γ-valerolactone (99%). The dilution and isolation of ruthenium by palladium is thought to be responsible for this superior catalytic performance. Alloying, furthermore, greatly improves the stability of both supported nano-alloy catalysts.

  4. Solar photo-catalytic hydrogen: systems considerations, economics, and potential markets. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Steele, R V; Witwer, J G

    1981-05-01

    A three part analysis was done consisting of (1) an examination of the physical principles of solar photocatalytic energy conversion and the status of research in this area, (2) an economic analysis of the potential costs of producing hydrogen from such a system, and (3) an analysis of the markets for hydrogen and the possible penetration of these markets by solar photocatalytic hydrogen. The cost range of flat plate thermal collectors, heliostats, and a photovoltaic system are compared. The cost range of flat plate thermal collectors was used to represent the cost of photocatalytic systems. On the basis of the photovoltaics cost outlook, it is found that photocatalytic systems would not cost less than $180 to $330 per m/sup 2/ range. On the basis of the heliostat cost outlook, a cost lower than $180 to $330 per m could be projected only for very large production volumes and very large installations. (LEW)

  5. Hydrogen and Carbon Nanotubes Production by Catalytic of Ethanol Over the Co-Mo Catalysts.

    Science.gov (United States)

    Diao, Jinxiang; Wang, Gang; Liu, Xiaojie; Wang, Hui

    2018-06-01

    A series of Cobalt-Carbon, Cobalt-Molybdenum-Carbon catalysts were prepared by impregnation. The molar ratios of Co:Mo were 9:1, 8:2 and 7:3 and the total metal weights of them in the supported catalysts were 5 wt%. Moreover, the effects of reaction temperature and the Co:Mo molar ratios on the produce hydrogen and carbon nanotubes were investigated systematically. Of all the catalysts, Co-Mo (5 wt%, Co:Mo = 9:1)/C was the most effective one on the basis of hydrogen yield (84%), ethanol conversion (95%) and the quality of carbon nanotubes at 600 °C. A small amount of Mo added into the Co/C catalysts resulted in increasing in the yield of hydrogen and improving on quality of carbon nanotubes from ethanol decomposition over the Co-Mo catalysts.

  6. Transfer hydrogenation reactions catalyzed by chiral half-sandwich ...

    Indian Academy of Sciences (India)

    Chiral ruthenium half-sandwich complexes were prepared using a chelating diamine made from proline with a phenyl, ethyl, or benzyl group, instead of hydrogen on one of the coordinating arms. Three of these complexes were obtained as single diastereoisomers and their configuration identified by X-ray crystallography.

  7. Catalytic reduction of nitrate and nitrite ions by hydrogen : investigation of the reaction mechanism over Pd and Pd-Cu catalysts

    NARCIS (Netherlands)

    Ilinitch, OM; Nosova, LV; Gorodetskii, VV; Ivanov, VP; Trukhan, SN; Gribov, EN; Bogdanov, SV; Cuperus, FP

    2000-01-01

    The catalytic behavior of mono- and bimetallic catalysts with Pd and/or Cu supported over gamma-Al2O3 in the reduction of aqueous nitrate and nitrite ions by hydrogen was investigated. The composition of the supported metal catalysts was analysed using secondary ion mass spectroscopy (SIMS) and

  8. Negative Effect of Calcination to Catalytic Performance of Coal Char-loaded TiO2 Catalyst in Styrene Oxidation with Hydrogen Peroxide as Oxidant

    Directory of Open Access Journals (Sweden)

    Mukhamad Nurhadi

    2018-01-01

    How to Cite: Nurhadi, M., Kusumawardani, R., Nur, H. (2018. Negative Effect of Calcination to Catalytic Performance of Coal Char-loaded TiO2 Catalyst in Styrene Oxidation with Hydrogen Peroxide as Oxidant. Bulletin of Chemical Reaction Engineering & Catalysis, 13 (1: 113-118 (doi:10.9767/bcrec.13.1.1171.113-118

  9. Biphasic catalytic conversion of fructose by continuous hydrogenation of HMF over a hydrophobic ruthenium catalyst.

    Science.gov (United States)

    Yang, Yanliang; Du, Zhongtian; Ma, Jiping; Lu, Fang; Zhang, Junjie; Xu, Jie

    2014-05-01

    The production of chemicals directly from sugars is an important step in biomass conversion. Herein, tetrahydro-2,5-furandimethanol (THFDM), obtained from fructose, is formed by using a combination of acid and hydrophobic Ru/SiO2 in a water/cyclohexane biphasic system. Two key factors enable the high selectivity towards THFDM: modifying the hydrogenation catalyst so that it has hydrophobic properties, and the continuous hydrogenation of generated 5-(hydroxymethyl)furfural in the cyclohexane phase. Moreover, the selectivity towards THFDM is found to depend strongly on the acid catalyst used. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Active Site Dynamical Effects in the Hydrogen Transfer Rate-limiting Step in the Catalysis of Linoleic Acid by Soybean Lipoxygenase-1 (SLO-1): Primary and Secondary Isotope Contributions.

    Science.gov (United States)

    Phatak, Prasad; Venderley, Jordan; Debrota, John; Li, Junjie; Iyengar, Srinivasan S

    2015-07-30

    Using ab initio molecular dynamics (AIMD) simulations that facilitate the treatment of rare events, we probe the active site participation in the rate-determining hydrogen transfer step in the catalytic oxidation of linoleic acid by soybean lipoxygenase-1 (SLO-1). The role of two different active site components is probed. (a) On the hydrogen atom acceptor side of the active site, the hydrogen bonding propensity between the acceptor side hydroxyl group, which is bound to the iron cofactor, and the backbone carboxyl group of isoleucine (residue number 839) is studied toward its role in promoting the hydrogen transfer event. Primary and secondary (H/D) isotope effects are also probed and a definite correlation with subtle secondary H/D isotope effects is found. With increasing average nuclear kinetic energy, the increase in transfer probability is enhanced due to the presence of the hydrogen bond between the backbone carbonyl of I839 and the acceptor oxygen. Further increase in average nuclear kinetic energy reduces the strength of this secondary hydrogen bond which leads to a deterioration in hydrogen transfer rates and finally embrances an Arrhenius-like behavior. (b) On the hydrogen atom donor side, the coupling between vibrational modes predominantly localized on the donor-side linoleic acid group and the reactive mode is probed. There appears to be a qualitative difference in the coupling between modes that belong to linoleic acid and the hydrogen transfer mode, for hydrogen and deuterium transfer. For example, the donor side secondary hydrogen atom is much more labile (by nearly a factor of 5) during deuterium transfer as compared to the case for hydrogen transfer. This appears to indicate a greater coupling between the modes belonging to the linoleic acid scaffold and the deuterium transfer mode and also provides a new rationalization for the abnormal (nonclassical) secondary isotope effect results obtained by Knapp, Rickert, and Klinman in J. Am. Chem. Soc

  11. Sustainable hydrogen from bio-oil - Catalytic steam reforming of acetic acid as a model oxygenate

    NARCIS (Netherlands)

    Takanabe, Kazuhiro; Seshan, K.; Lefferts, Leon; Aika, Ken-ichi

    2004-01-01

    Steam reforming of acetic acid as a model oxygenate present in bio-oil over Pt/ZrO2 catalysts has been studied. Pt/ZrO2 catalysts are very active, completely converting acetic acid and give hydrogen yield close to thermodynamic equilibrium. The catalyst deactivated by formation of oligomers, which

  12. Continuous-flow catalytic asymmetric hydrogenations: Reaction optimization using FTIR inline analysis

    Directory of Open Access Journals (Sweden)

    Magnus Rueping

    2012-02-01

    Full Text Available The asymmetric organocatalytic hydrogenation of benzoxazines, quinolines, quinoxalines and 3H-indoles in continuous-flow microreactors has been developed. Reaction monitoring was achieved by using an inline ReactIR flow cell, which allows fast and convenient optimization of reaction parameters. The reductions proceeded well, and the desired products were isolated in high yields and with excellent enantioselectivities.

  13. Catalytic Ring Hydrogenation of Benzoic Acid with Supported Transition Metal Catalysts in scCO2

    Directory of Open Access Journals (Sweden)

    Fengyu Zhao

    2007-07-01

    Full Text Available The ring hydrogenation of benzoic acid to cyclohexanecarboxylic acid overcharcoal-supported transition metal catalysts in supercritical CO2 medium has been studiedin the present work. The cyclohexanecarboxylic acid can be produced efficiently insupercritical CO2 at the low reaction temperature of 323 K. The presence of CO2 increasesthe reaction rate and several parameters have been discussed.

  14. In situ diffraction study of catalytic hydrogenation of VO₂: stable phases and origins of metallicity.

    Science.gov (United States)

    Filinchuk, Yaroslav; Tumanov, Nikolay A; Ban, Voraksmy; Ji, Heng; Wei, Jiang; Swift, Michael W; Nevidomskyy, Andriy H; Natelson, Douglas

    2014-06-04

    Controlling electronic population through chemical doping is one way to tip the balance between competing phases in materials with strong electronic correlations. Vanadium dioxide exhibits a first-order phase transition at around 338 K between a high-temperature, tetragonal, metallic state (T) and a low-temperature, monoclinic, insulating state (M1), driven by electron-electron and electron-lattice interactions. Intercalation of VO2 with atomic hydrogen has been demonstrated, with evidence that this doping suppresses the transition. However, the detailed effects of intercalated H on the crystal and electronic structure of the resulting hydride have not been previously reported. Here we present synchrotron and neutron diffraction studies of this material system, mapping out the structural phase diagram as a function of temperature and hydrogen content. In addition to the original T and M1 phases, we find two orthorhombic phases, O1 and O2, which are stabilized at higher hydrogen content. We present density functional calculations that confirm the metallicity of these states and discuss the physical basis by which hydrogen stabilizes conducting phases, in the context of the metal-insulator transition.

  15. H2CAP – Hydrogen assisted catalytic biomass pyrolysis for green fuels

    DEFF Research Database (Denmark)

    Stummann, Magnus Zingler; Høj, Martin; Gabrielsen, Jostein

    . The objective of thepresent work is to convert biomass into gasoline and diesel. Fast pyrolysis of beech wood have beenconducted at high hydrogen pressure in a fluid bed reactor with a hydrodeoxygenation (HDO) catalyst asbed medium followed by a fixed bed HDO reactor for complete oxygen removal before oil...

  16. Thermal Stress Analysis for a Transfer Line of Hydrogen Moderator in J-Parc

    Science.gov (United States)

    Tatsumoto, H.; Teshigawara, M.; Aso, T.; Ohtsu, K.; Maekawa, F.; Kato, T.

    2008-03-01

    An intense spallation neutron source (JSNS) driven by a 1-MW proton beam was constructed, as one of the main experimental facilities in J-PARC. In JSNS, supercritical hydrogen (1.5 MPa, 20 K) was selected as a moderator material. Three kinds of hydrogen moderator are installed (coupled, decoupled, and poisoned) to provide pulsed neutron beam with higher neutronic performance. The moderators contain cryogenic hydrogen transfer lines located in a radioactive area. Therefore, the transfer lines should be designed to have minimum pipe size and elbow-type bend sections to reduce the potential for radiation dose by radiation streaming. The design should also consider mechanical stress concentrations, deformation, and touching between the pipes due to the thermal shrinkage at the cryogenic hydrogen temperature. A FEM code analysis determined the appropriate locations of piping supporting spacers to keep the thermal stress below the allowable stress and to also avoid touching between the pipes.

  17. Transfer Hydrogenation in Open-Shell Nucleotides — A Theoretical Survey

    Directory of Open Access Journals (Sweden)

    Florian Achrainer

    2014-12-01

    Full Text Available The potential of a larger number of sugar models to act as dihydrogen donors in transfer hydrogenation reactions has been quantified through the calculation of hydrogenation energies of the respective oxidized products. Comparison of the calculated energies to hydrogenation energies of nucleobases shows that many sugar fragment radicals can reduce pyrimidine bases such as uracil in a strongly exothermic fashion. The most potent reducing agent is the C3' ribosyl radical. The energetics of intramolecular transfer hydrogenation processes has also been calculated for a number of uridinyl radicals. The largest driving force for such a process is found for the uridin-C3'-yl radical, whose rearrangement to the C2'-oxidized derivative carrying a dihydrouracil is predicted to be exothermic by 61.1 kJ/mol in the gas phase.

  18. Sub-10 nm Platinum Nanocrystals with Size and Shape Control: Catalytic Study for Ethylene and Pyrrole Hydrogenation

    Energy Technology Data Exchange (ETDEWEB)

    Tsung, Chia-Kuang; Kuhn, John N.; Huang, Wenyu; Aliaga, Cesar; Hung, Ling-I; Somorjai, Gabor A.; Yang, Peidong

    2009-03-02

    Platinum nanocubes and nanopolyhedra with tunable size from 5 to 9 nm were synthesized by controlling the reducing rate of metal precursor ions in a one-pot polyol synthesis. A two-stage process is proposed for the simultaneous control of size and shape. In the first stage, the oxidation state of the metal ion precursors determined the nucleation rate and consequently the number of nuclei. The reaction temperature controlled the shape in the second stage by regulation of the growth kinetics. These well-defined nanocrystals were loaded into MCF-17 mesoporous silica for examination of catalytic properties. Pt loadings and dispersions of the supported catalysts were determined by elemental analysis (ICP-MS) and H2 chemisorption isotherms, respectively. Ethylene hydrogenation rates over the Pt nanocrystals were independent of both size and shape and comparable to Pt single crystals. For pyrrole hydrogenation, the nanocubes enhanced ring-opening ability and thus showed a higher selectivity to n-butylamine as compared to nanopolyhedra.

  19. Tuning the catalytic CO hydrogenation to straight- and long-chain aldehydes/alcohols and olefins/paraffins

    Science.gov (United States)

    Xiang, Yizhi; Kruse, Norbert

    2016-10-01

    The catalytic CO hydrogenation is one of the most versatile large-scale chemical syntheses leading to variable chemical feedstock. While traditionally mainly methanol and long-chain hydrocarbons are produced by CO hydrogenation, here we show that the same reaction can be tuned to produce long-chain n-aldehydes, 1-alcohols and olefins, as well as n-paraffins over potassium-promoted CoMn catalysts. The sum selectivity of aldehydes and alcohols is usually >50 wt% whereof up to ~97% can be n-aldehydes. While the product slate contains ~60% n-aldehydes at /pCO=0.5, a 65/35% slate of paraffins/alcohols is obtained at a ratio of 9. A linear Anderson-Schulz-Flory behaviour, independent of the /pCO ratio, is found for the sum of C4+ products. We advocate a synergistic interaction between a Mn5O8 oxide and a bulk Co2C phase, promoted by the presence of potassium, to be responsible for the unique product spectra in our studies.

  20. Interdisciplinary study of the influence on effectiveness of catalytic hydrogen recombiners of operating conditions in the reactor containment

    International Nuclear Information System (INIS)

    Kelm, S.; Reinecke, E.A.; Schoppe, L.; Dornseiffer, J.; Leistner, F.; Juehe, S.

    2008-01-01

    At the Emsland nuclear power station, a total of 58 autocatalytic hydrogen recombiners were backfitted in 1999 as an additional measure of risk reduction in connection with major hydrogen releases after events going beyond the design basis. Annual in-service inspections after 2002 revealed that some of the catalyst sheets developed startup delays and marked evolutions of smoke and smell. Recombiners not meeting the inspection criterion were completely regenerated as a measure of precaution. A preventive study was conducted jointly with institutes of the Juelich Research Center and the Aachen Technical University to analyze the composition of the deposits, which was then compared with the chemical characteristics of potential sources in the reactor containment. At the same time, the influence on effectiveness of the catalyst sheets was examined. On the basis of a random evaluation of the in-service inspection logs of the past few years, representative samples were taken whose startup behavior and operating characteristics were studied in a test rig alongside chemical analyses so as to allow a correlation to be established between the analytical findings and the catalytic activity of the samples. The findings made allowed internal sources of the catalyst deposits to be excluded. The impurities are introduced with the outside air. As a consequence, the air ducts in the vicinity of the respective recombiners were inspected and optimization steps were taken in connection with in-service inspections and regeneration procedures. (orig.)

  1. Experimental studies on catalytic hydrogen recombiners for light water reactors; Experimentelle Untersuchungen zu katalytischen Wasserstoffkombinatoren fuer Leichtwasserreaktoren

    Energy Technology Data Exchange (ETDEWEB)

    Drinovac, P.

    2006-06-19

    In the course of core melt accidents in nuclear power plants a large amount of hydrogen can be produced and form an explosive or even detonative gas mixture with aerial oxygen in the reactor building. In the containment atmosphere of pressurized water reactors hydrogen combines a phlogistically with the oxygen present to form water vapor even at room temperature. In the past, experimental work conducted at various facilities has contributed little or nothing to an understanding of the operating principles of catalytic recombiners. Hence, the purpose of the present study was to conduct detailed investigations on a section of a recombiner essentially in order to deepen the understanding of reaction kinetics and heat transport processes. The results of the experiments presented in this dissertation form a large data base of measurements which provides an insight into the processes taking place in recombiners. The reaction-kinetic interpretation of the measured data confirms and deepens the diffusion theory - proposed in an earlier study. Thus it is now possible to validate detailed numeric models representing the processes in recombiners. Consequently the present study serves to broaden and corroborate competence in this significant area of reactor technology. In addition, the empirical knowledge thus gained may be used for a critical reassessment of previous numeric model calculations. (orig.)

  2. Dendrimer Templated Synthesis of One Nanometer Rh and Pt Particles Supported on Mesoporous Silica: Catalytic Activity for Ethylene and Pyrrole Hydrogenation.

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Wenyu; Kuhn, John N.; Tsung, Chia-Kuang; Zhang, Yawen; Habas, Susan E.; Yang, Peidong; Somorjai, Gabor A.

    2008-05-09

    Monodisperse rhodium (Rh) and platinum (Pt) nanoparticles as small as {approx}1 nm were synthesized within a fourth generation polyaminoamide (PAMAM) dendrimer, a hyperbranched polymer, in aqueous solution and immobilized by depositing onto a high-surface-area SBA-15 mesoporous support. X-ray photoelectron spectroscopy indicated that the as-synthesized Rh and Pt nanoparticles were mostly oxidized. Catalytic activity of the SBA-15 supported Rh and Pt nanoparticles was studied with ethylene hydrogenation at 273 and 293 K in 10 torr of ethylene and 100 torr of H{sub 2} after reduction (76 torr of H{sub 2} mixed with 690 torr of He) at different temperatures. Catalysts were active without removing the dendrimer capping but reached their highest activity after hydrogen reduction at a moderate temperature (423 K). When treated at a higher temperature (473, 573, and 673 K) in hydrogen, catalytic activity decreased. By using the same treatment that led to maximum ethylene hydrogenation activity, catalytic activity was also evaluated for pyrrole hydrogenation.

  3. Molecularly Defined Manganese Pincer Complexes for Selective Transfer Hydrogenation of Ketones.

    Science.gov (United States)

    Perez, Marc; Elangovan, Saravanakumar; Spannenberg, Anke; Junge, Kathrin; Beller, Matthias

    2017-01-10

    For the first time an easily accessible and well-defined manganese N,N,N-pincer complex catalyzes the transfer hydrogenation of a broad range of ketones with good to excellent yields. This cheap earth abundant-metal based catalyst provides access to useful secondary alcohols without the need of hydrogen gas. Preliminary investigations to explore the mechanism of this transformation are also reported. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Insights into the Hydrogen-Atom Transfer of the Blue Aroxyl.

    Science.gov (United States)

    Bächle, Josua; Marković, Marijana; Kelterer, Anne-Marie; Grampp, Günter

    2017-10-19

    An experimental and theoretical study on hydrogen-atom transfer dynamics in the hydrogen-bonded substituted phenol/phenoxyl complex of the blue aroxyl (2,4,6-tri-tert-butylphenoxyl) is presented. The experimental exchange dynamics is determined in different organic solvents from the temperature-dependent alternating line-width effect in the continuous-wave ESR spectrum. From bent Arrhenius plots, effective tunnelling contributions with parallel heavy-atom motion are concluded. To clarify the transfer mechanism, reaction paths for different conformers of the substituted phenol/phenoxyl complex are modelled theoretically. Various DFT and post-Hartree-Fock methods including multireference methods are applied. From the comparison of experimental and theoretical data it is concluded that the system favours concerted hydrogen-atom transfer along a parabolic reaction path caused by heavy-atom motion. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. A study of the effect of gamma radiation and doping on the catalytic activity of some oxides in the decomposition of hydrogen per-oxide

    International Nuclear Information System (INIS)

    Mousa, M.A.

    1987-01-01

    The rates of hydrogen peroxide decomposition on pure, doped and gamma-irradiated oxides Chromium oxide, Cobalt oxide, Magnesium oxide Nickel oxide, Ferric oxide, Magnesium ferri oxide were measured in a temperature range of 25-40 degree centigrade. It was found that lattice defect induced by doping and gamma-irradiation affect the catalytic properties of the oxides, either by activation or deactivation. The correlation between the catalytic activity for the hydrogen peroxide decomposition and the electronic defects produced by doping and by gamma-irradiation in the oxides is dicussed. Generally, it was found that the p-type semiconductor oxides are more active towards hydrogen peroxide decomposition than the n-type semiconductor oxides. (orig./A.B.)

  6. Influence of Intramolecular Charge Transfer and Nuclear Quantum Effects on Intramolecular Hydrogen Bonds in Azopyrimidines.

    Science.gov (United States)

    Bártová, Kateřina; Čechová, Lucie; Procházková, Eliška; Socha, Ondřej; Janeba, Zlatko; Dračínský, Martin

    2017-10-06

    Intramolecular hydrogen bonds (IMHBs) in 5-azopyrimidines are investigated by NMR spectroscopy and DFT computations that involve nuclear quantum effects. A series of substituted 5-phenylazopyrimidines with one or two hydrogen bond donors able to form IMHBs with the azo group is prepared by azo coupling. The barrier of interconversion between two rotamers of the compounds with two possible IMHBs is determined by variable temperature NMR spectroscopy and it is demonstrated that the barrier is significantly affected by intramolecular charge transfer. Through-hydrogen-bond scalar coupling is investigated in 15 N labeled compounds and the stability of the IMHBs is correlated with experimental NMR parameters and rationalized by path integral molecular dynamics simulations that involve nuclear quantum effects. Detailed information on the hydrogen bond geometry upon hydrogen-to-deuterium isotope exchange is obtained from a comparison of experimental and calculated NMR data.

  7. An Improved Strategy for the Synthesis of Ethylene Glycol by Oxamate-Mediated Catalytic Hydrogenation.

    Science.gov (United States)

    Satapathy, Anilkumar; Gadge, Sandip T; Bhanage, Bhalchandra M

    2017-04-10

    The present study reports an improved approach for the preparation of ethylene glycol (EG) by using carbon monoxide as C1 chemical by a two-step oxidative carbonylation and hydrogenation sequence. In the first step, oxamates are synthesized through oxidative cross double carbonylation of piperidine and ethanol by using Pd/C catalyst under phosphine ligand-free conditions and subsequently hydrogenated by Milstein's catalyst (carbonylhydrido[6-(di-t-butylphosphinomethylene)-2-(N,N-diethylaminomethyl)-1,6-dihydropyridine]ruthenium(II)). The presented stepwise oxamate-mediated coupling provides the basis for a new strategy for the synthesis of EG by selective upgrading of C1 chemicals. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. The reduction of carbon dioxide in iron biocatalyst catalytic hydrogenation reaction: a theoretical study.

    Science.gov (United States)

    Yang, Longhua; Wang, Hongming; Zhang, Ning; Hong, Sanguo

    2013-08-21

    The reaction mechanism of CO₂ hydrogenation catalyzed by [FeH(PP₃)]BF₄ (PP₃ = P(CH₂CH₂PPh₂)₃) had been investigated by DFT calculations. Our calculations indicated that the reduction of carbon dioxide could be carried out via two spin states, the high-spin (HS) triplet state and the low-spin (LS) singlet state. The minimum energy crossing points (MECPs) on the seam of two intersecting PESs (potential energy surfaces) were searched out. Some interesting phenomena, such as the open-loop phenomenon, and the O-rebound process, were demonstrated to be the important causes of the spin crossover. All these calculations gave us insight into the essence of the related experiment from the macro point of view, and helped to verify which spin states the related complexes pertinent were in. All of these researches would help advance the development of efficient and structurally tailorable CO₂ hydrogenation catalysts.

  9. Study on the synthesis of dimethyl 1,4-cyclohexanedicarboxylate by catalytic hydrogenation of dimethyl terephthalate

    Directory of Open Access Journals (Sweden)

    LI Yuanhua

    2016-12-01

    Full Text Available In the field of polymer industry,1,4-cyclohexanedimethanol (CHDM occupies an important position especially for the synthesis of highly valued polyester products.In industry,CHDM is prepared from dimethyl terephthalate (DMT through a two-step hydrogenation process Palladium supported on magnesium oxide (Pd/MgO was prepared by animpregnation method and was characterized by x-ray diffraction (XRD,transmission electron microscope (TEM and scan electron microscope (SEM.During the hydrogenation of DMT to synthesize dimethyl 1,4-cyclohexanedicarboxylate (DMCD,the as-prepared Pd/MgO was used as the catalyst with methyl acetate as the solvent.Under optimized reaction conditions (reaction temperature:180 ℃,reaction pressure:4.5 MPa,the conversion of DMT was 100% and the selectivity of DMCD was 99%.Such a catalyst shows a good potential in industrial applications.

  10. COx Free Hydrogen Production by Catalytic Decomposition of Methane Over Porous Ni/Al2O3 Catalysts

    International Nuclear Information System (INIS)

    Makvandi, S.; Alavi, S. M.

    2011-01-01

    The prepared meso porous spherical alumina with high-surface area was employed as a support for nickel catalysts in methane decomposition reaction. It was observed that, the catalytic activity of Ni/Al 2 O 3 catalysts was high at the initial times of reaction and decreased with time on stream, and finally reached a constant value. The deactivation rate of catalysts is dependent on the catalyst characteristics and the operating conditions. The activity results indicate that, the yield of hydrogen and the structure of deposited carbon are strongly dependent on the loading amount of Ni. The Scanning Electron Microscopy results showed that carbon formed on the catalysts in the form of filamentous carbon. Concerning hydrogen production, the 10% Ni/ Al 2 O 3 catalyst leads to a higher yield, due to the higher amount of active phases which can catalyze further the number of methane molecules, while lesser amounts of filamentous carbon were observed on this catalyst than for 5 and 7.5% Ni/ Al 2 O 3 catalysts at the same operating condition. The yield of hydrogen and structure of filamentous carbon also significantly depend on the reaction temperatures and residence time of gas in the reactor, as the 10% Ni/ Al 2 O 3 catalyst showed a remarkable stability with a decrease of about 14% at 800 d egree C and 25 ml/min after 240 min of reaction. The obtained results showed that the prepared Ni/ Al 2 O 3 catalysts had a good activity in methane decomposition reaction, which is one of the highest activities among those for low nickel loaded catalysts reported up until now.

  11. Influence of Adsorption Geometry in the Heterogeneous Enantioselective Catalytic Hydrogenation of a Prototypical Enone

    OpenAIRE

    Beaumont, SK; Kyriakou, G; Watson, DJ; Vaughan, OPH; Papageorgiou, AC; Lambert, RM

    2010-01-01

    Asymmetric catalysis is of paramount importance in organic synthesis and, in current practice, is achieved by means of homogeneous catalysts. The ability to catalyze such reactions heterogeneously would have a major impact both in the research laboratory and in the production of fine chemicals and pharmaceuticals, yet heterogeneous asymmetric hydrogenation of C═C bonds remains hardly explored. Very recently, we demonstrated how chiral ligands that anchor robustly to the surface of Pd nanopart...

  12. Relating catalytic activity and electrochemical properties: The case of arene-ruthenium phenanthroline complexes catalytically active in transfer hydrogenation

    Czech Academy of Sciences Publication Activity Database

    Štěpnička, P.; Ludvík, Jiří; Canivet, J.; Süss-Fink, G.

    2006-01-01

    Roč. 359, č. 8 (2006), s. 2369-2374 ISSN 0020-1693 R&D Projects: GA AV ČR IAA4040304 Institutional research plan: CEZ:AV0Z40400503 Keywords : arene complexes * chloro complexes * aqua complexes Subject RIV: CG - Electrochemistry Impact factor: 1.674, year: 2006

  13. Electro-catalytic conversion of ethanol in solid electrolyte cells for distributed hydrogen generation

    International Nuclear Information System (INIS)

    Ju, HyungKuk; Giddey, Sarbjit; Badwal, Sukhvinder P.S.; Mulder, Roger J.

    2016-01-01

    Highlights: • Ethanol assisted water electrolysis reduces electric energy input by more than 50%. • Partial oxidation of ethanol leads to formation of undesired chemicals. • Degradation occurs due to formation of by-products and poisoning of catalyst. • Better catalyst has the potential to increase ethanol to H 2 conversion efficiency. • A plausible ethanol electro-oxidation mechanism has been proposed - Abstract: The global interest in hydrogen/fuel cell systems for distributed power generation and transport applications is rapidly increasing. Many automotive companies are now bringing their pre-commercial fuel cell vehicles in the market, which will need extensive hydrogen generation, distribution and storage infrastructure for fueling of these vehicles. Electrolytic water splitting coupled to renewable sources offers clean on-site hydrogen generation option. However, the process is energy intensive requiring electric energy >4.2 kWh for the electrolysis stack and >6 kWh for the complete system per m 3 of hydrogen produced. This paper investigates using ethanol as a renewable fuel to assist with water electrolysis process to substantially reduce the energy input. A zero-gap cell consisting of polymer electrolyte membrane electrolytic cells with Pt/C and PtSn/C as anode catalysts were employed. Current densities up to 200 mA cm −2 at 70 °C were achieved at less than 0.75 V corresponding to an energy consumption of about 1.62 kWh m −3 compared with >4.2 kWh m −3 required for conventional water electrolysis. Thus, this approach for hydrogen generation has the potential to substantially reduce the electric energy input to less than 40% with the remaining energy provided by ethanol. However, due to performance degradation over time, the energy consumption increased and partial oxidation of ethanol led to lower conversion efficiency. A plausible ethanol electro-oxidation mechanism has been proposed based on the Faradaic conversion of ethanol and mass

  14. CFD simulation of hydrogen mixing and mitigation by means of passive auto-catalytic recombiners

    International Nuclear Information System (INIS)

    Kelm, S.; Reinecke, E-A.; Jahn, W.; Allelein, H-J.

    2011-01-01

    Modeling of passive auto-catalytic recombiners (PARs) operation in containment geometries involves a large variety of scales; thus, a CFD calculation resolving all these scales would be much too expensive. Therefore, the mechanistic PAR model REKO-DIREKT, developed at Forschungszentrum Juelich, has been coupled with the commercial CFD code ANSYS CFX in order to simulate PAR operation as well as the induced flow and transport phenomena. Based on a short introduction of REKO-DIREKT, its interface to CFX and the explicit coupling scheme is discussed. The paper is finalized by a first demonstration of simulation capabilities on the basis of the ThAI PAR-4 experiment (Becker Technologies GmbH, Eschborn, Germany). (author)

  15. Catalytic performance and characterization of cobalt-nickel nano catalysts for CO hydrogenation

    Energy Technology Data Exchange (ETDEWEB)

    Feyzi, Mostafa; Gholivand, Mohammad Bagher [Razi University, Kermanshah (Iran, Islamic Republic of); Babakhanian, Arash [Islamic Azad University, Kermanshah (Iran, Islamic Republic of)

    2014-01-15

    A series of Co-Ni nano catalysts were prepared by co-precipitation method. We investigated the effect of Co/Ni molar ratios precipitate and calcination conditions on the catalytic performance of cobalt nickel catalysts for Fisher-Tropsch synthesis (FTS). The catalyst containing 90%Co/10%Ni was found to be optimal for the conversion of synthesis gas to light olefins. The activity and selectivity of the optimal catalyst were studied in different operational conditions. The results show that the best operational conditions are the H{sub 2}/CO=2/1 molar feed ratio at 310 .deg. C and GHSV=1,200 h{sup -}1 under 5 bar of pressure. The prepared catalysts were characterized by powder X-ray diffraction (XRD), N{sub 2} adsorption-desorption measurements such as BET and BJH methods, transmission electron microscopy (TEM) and thermal gravimetric analysis (TGA)

  16. Biomedical and Forensic Applications of Combined Catalytic Hydrogenation-Stable Isotope Ratio Analysis

    Science.gov (United States)

    Sephton, Mark A.; Meredith, Will; Sun, Cheng-Gong; Snape, Colin E.

    2007-01-01

    Studies of biological molecules such as fatty acids and the steroid hormones have the potential to benefit enormously from stable carbon isotope ratio measurements of individual molecules. In their natural form, however, the body’s molecules interact too readily with laboratory equipment designed to separate them for accurate measurements to be made. Some methods overcome this problem by adding carbon to the target molecule, but this can irreversibly overprint the carbon source ‘signal’. Hydropyrolysis is a newly-applied catalytic technique that delicately strips molecules of their functional groups but retains their carbon skeletons and stereochemistries intact, allowing precise determination of the carbon source. By solving analytical problems, the new technique is increasing the ability of scientists to pinpoint molecular indicators of disease, elucidate metabolic pathways and recognise administered substances in forensic investigations. PMID:19662175

  17. Biomedical and Forensic Applications of Combined Catalytic Hydrogenation-Stable Isotope Ratio Analysis

    Directory of Open Access Journals (Sweden)

    Mark A. Sephton

    2007-01-01

    Full Text Available Studies of biological molecules such as fatty acids and the steroid hormones have the potential to benefit enormously from stable carbon isotope ratio measurements of individual molecules. In their natural form, however, the body’s molecules interact too readily with laboratory equipment designed to separate them for accurate measurements to be made.Some methods overcome this problem by adding carbon to the target molecule, but this can irreversibly overprint the carbon source ‘signal’. Hydropyrolysis is a newly-applied catalytic technique that delicately strips molecules of their functional groups but retains their carbon skeletons and stereochemistries intact, allowing precise determination of the carbon source. By solving analytical problems, the new technique is increasing the ability of scientists to pinpoint molecular indicators of disease, elucidate metabolic pathways and recognise administered substances in forensic investigations.

  18. Unusual non-bifunctional mechanism for Co-PNP complex catalyzed transfer hydrogenation governed by the electronic configuration of metal center.

    Science.gov (United States)

    Hou, Cheng; Jiang, Jingxing; Li, Yinwu; Zhang, Zhihan; Zhao, Cunyuan; Ke, Zhuofeng

    2015-10-07

    The mimic of hydrogenases has unleashed a myriad of bifunctional catalysts, which are widely used in the catalytic hydrogenation of polar multiple bonds. With respect to ancillary ligands, the bifunctional mechanism is generally considered to proceed via the metal-ligand cooperation transition state. Inspired by the interesting study conducted by Hanson et al. (Chem Commun., 2013, 49, 10151), we present a computational study of a distinctive example, where a Co(II)-PNP catalyst with an ancillary ligand exhibits efficient transfer hydrogenation through a non-bifunctional mechanism. Both the bifunctional and non-bifunctional mechanisms are discussed. The calculated results, which are based on a full model of the catalyst, suggest that the inner-sphere non-bifunctional mechanism is more favorable (by ∼11 kcal mol(-1)) than the outer-sphere bifunctional mechanism, which is in agreement with the experimental observations. The origin of this mechanistic preference of the Co(II)-PNP catalyst can be attributed to its preference for the square planar geometry. A traditional bifunctional mechanism is less plausible for Co(II)-PNP due to the high distortion energy caused by the change in electronic configuration with the varied ligand field. Considering previous studies that focus on the development of ligands more often, this computational study indicates that the catalytic hydrogenation mechanism is controlled not only by the structure of the ligand but also by the electronic configuration of the metal center.

  19. Mass and heat transfer on B7 ordered packing in hydrogen isotope separation by distillation

    International Nuclear Information System (INIS)

    Croitoru, Cornelia; Pop, Floarea; Titescu, Gheorghe; Stefanescu, Ioan; Trancota, Dan; Peculea, Marius

    2002-01-01

    This work presents theoretical and experimental data referring to mass and heat transfer on B7 ordered packing in deuterium isotope separation by distillation. The first part is devoted to the study of mass transfer in hydrogen isotopic distillation while the second one treats the mass and heat transfer in water isotopic distillation. A stationary mathematical model for the mass and heat transfer was developed based on multitubular column model with wet wall. This model allowed the calculation starting from theoretical data of the ordered packing efficiency, expressed by the transfer unit height, TUH. Also, from theoretical data the mass and heat transfer coefficients were determined. A test of the mathematical model was performed with the experimental data obtained from two laboratory installations for hydrogen isotope separation by distillation. From the first installation, experimental data concerning the B7 ordered packing efficiency were obtained for the deuterium separation by cryogenic distillation at the - 250 deg C level. With the second one data referring to the mass and heat transfer on the same packing were obtained for the deuterium separation by water distillation under vacuum at the 60 deg C level. The values of TUH, mass and heat transfer coefficients as theoretically evaluate and experimentally checked are in agreement with the respective values obtained in separation processes in chemical industry. This is the fact which endorses utilization of the model of multitubular column with wet wall for describing the transfer processes in distillation columns equipped with B7 ordered packing

  20. One-pot reduction of 5-hydroxymethylfurfural via hydrogen transfer from supercritical methanol

    DEFF Research Database (Denmark)

    Hansen, Thomas Søndergaard; Barta, Katalin; Anastas, Paul T.

    2012-01-01

    Catalytic conversion of HMF to valuable chemicals was achieved over a Cu-doped porous metal oxide in supercritical methanol. The hydrotalcite catalyst precursor is prepared following simple synthetic procedures, using inexpensive and earth-abundant starting materials in aqueous solutions. The hyd......Catalytic conversion of HMF to valuable chemicals was achieved over a Cu-doped porous metal oxide in supercritical methanol. The hydrotalcite catalyst precursor is prepared following simple synthetic procedures, using inexpensive and earth-abundant starting materials in aqueous solutions....... The hydrogen equivalents needed for the reductive deoxygenation of HMF originate from the solvent itself upon its reforming. Dimethylfuran, dimethyltetrahydrofuran and 2-hexanol were obtained in good yields. At milder reaction temperatures, a combined yield (DMF + DMTHF) of 58% was achieved. Notably...

  1. Altering intra- to inter-molecular hydrogen bonding by dimethylsulfoxide: A TDDFT study of charge transfer for coumarin 343

    Science.gov (United States)

    Liu, Xiaochun; Yin, Hang; Li, Hui; Shi, Ying

    2017-04-01

    DFT and TDDFT methods were carried out to investigate the influences of intramolecular and intermolecular hydrogen bonding on excited state charge transfer for coumarin 343 (C343). Intramolecular hydrogen bonding is formed between carboxylic acid group and carbonyl group in C343 monomer. However, in dimethylsulfoxide (DMSO) solution, DMSO 'opens up' the intramolecular hydrogen bonding and forms solute-solvent intermolecular hydrogen bonded C343-DMSO complex. Analysis of frontier molecular orbitals reveals that intramolecular charge transfer (ICT) occurs in the first excited state both for C343 monomer and complex. The results of optimized geometric structures indicate that the intramolecular hydrogen bonding interaction is strengthened while the intermolecular hydrogen bonding is weakened in excited state, which is confirmed again by monitoring the shifts of characteristic peaks of infrared spectra. We demonstrated that DMSO solvent can not only break the intramolecular hydrogen bonding to form intermolecular hydrogen bonding with C343 but also alter the mechanism of excited state hydrogen bonding strengthening.

  2. Isotope effects in hydrogen atom transfers. 9. Neighboring group participation

    International Nuclear Information System (INIS)

    Lewis, E.S.; Shen, C.C.

    1977-01-01

    The tritium isotope effects in hydrogen abstraction by bromine atoms from HC(Me) 2 CH 2 X have been measured in the photobromination reaction by a technique which measures the specific activity of the HBr product. At 1 0 C and with the reverse reaction suppressed or irrelevant the values for k/sub H//k/sub T/ are 3.9, 8.2, and 11.6 for X = CH 3 , Cl, and Br, respectively. An isotope effect of 3.5 for X = H was also measured, but the contribution of the reverse reaction was not established. The relatively large isotope effect for X = Br is interpreted in terms of a weakening of the CH bond by neighboring bromine participation. The smaller effect of chlorine may correspond to a minor participation, but the unfavorable inductive effect of the chlorine is also a factor. The case of X = Br is the microscopic reverse of the addition of HBr to 2-methylpropene, and the results are compared with isotope effects in the addition to HBr to olefins. The measurement of isotope effect is, within some described limitations, a convenient and general method for detecting neighboring group participation in hydrogen atom abstractions

  3. Heterogeneous catalytic hydrogenation of biobased levulinic and succinic acids in aqueous solutions.

    Science.gov (United States)

    Corbel-Demailly, Louis; Ly, Bao-Khanh; Minh, Doan-Pham; Tapin, Benoit; Especel, Catherine; Epron, Florence; Cabiac, Amandine; Guillon, Emmanuelle; Besson, Michèle; Pinel, Catherine

    2013-12-01

    Supported noble-metal catalysts (Ru, Pd or Pt) and the corresponding Re-promoted catalysts exhibit a high activity for the hydrogenation of biobased carboxylic acids. Levulinic acid and succinic acid are converted into the lactones or the diols depending on the nature of the catalyst and the reaction conditions. The highest selectivity to 1,4-pentanediol of 82 % is achieved at 140 °C in the presence of the 1.9 % Ru-3.6 % Re/C catalyst. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Determination of the level of DNA modification with cisplatin by catalytic hydrogen evolution at mercury-based electrodes.

    Science.gov (United States)

    Horáková, Petra; Tesnohlídková, Lucie; Havran, Ludek; Vidláková, Pavlína; Pivonková, Hana; Fojta, Miroslav

    2010-04-01

    Electrochemical methods proved useful as simple and inexpensive tools for the analysis of natural as well as chemically modified nucleic acids. In particular, covalently attached metal-containing groups usually render the DNA well-pronounced electrochemical activity related to redox processes of the metal moieties, which can in some cases be coupled to catalytic hydrogen evolution at mercury or some types of amalgam electrodes. In this paper we used voltammetry at the mercury-based electrodes for the monitoring of DNA modification with cis-diamminedichloroplatinum (cisplatin), a representative of metallodrugs used in the treatment of various types of cancer or being developed for such purpose. In cyclic voltammetry at the mercury electrode, the cisplatin-modified DNA yielded catalytic currents the intensity of which reflected DNA modification extent. In square-wave voltammetry, during anodic polarization after prereduction of the cisplatinated DNA, a well-developed, symmetrical signal (peak P) was obtained. Intensity of the peak P linearly responded to the extent of DNA modification at levels relevant for biochemical studies (rb = 0.01-0.10, where rb is the number of platinum atoms bound per DNA nucleotide). We demonstrate a correlation between the peak P intensity and a loss of sequence-specific DNA binding by tumor suppressor protein p53, as well as blockage of DNA digestion by a restriction endonuclease Msp I (both caused by the DNA cisplatination). Application of the electrochemical technique in studies of DNA reactivity with various anticancer platinum compounds, as well as for an easy determination of the extent of DNA platination in studies of its biochemical effects, is discussed.

  5. Vibrational energy transfer in hydrogen liquid and its isotopes

    International Nuclear Information System (INIS)

    Gale, G.M.; Delalande, C.

    1978-01-01

    The transfer of vibrational energy (V-V) from H 2 to isotopic impurities (HD or D 2 ) has been studied in the liquid state, between 15 and 30 K. The subsequent ralaxation (V-T) of the excited impurity by the H 2 liquid host has also been measured and contrasted with the vibrational relaxation behaviour of pure H 2 and D 2 liquids. The isothermal density dependence of both V-V and V-T transfer has been investigated in the fluid state at 30 K. High density relaxation rates are also compared to the data in the pure gases and to other available gas phase results. Measurements in the solid, near the triple-point temperature, are equally reported for each process studied. (Auth.)

  6. CFD Flow and Heat Transfer Simulation for Empty and Packed Fixed Bed Reactor in Catalytic Cracking of Naphtha

    OpenAIRE

    D. Salari; A. Niaei; P. Chitsaz Yazdi; M. Derakhshani; S. R. Nabavi

    2007-01-01

    This work aims to test the application of computational fluid dynamics (CFD) modeling to fixed bed catalytic cracking reactors. Studies of CFD with a fixed bed design commonly use a regular packing with N=2 to define bed geometry. CFD allows us to obtain a more accurate view of the fluid flow and heat transfer mechanisms present in fixed bed equipment. Naphtha was used as feedstock and the reactor length was 80cm. It is divided in three sections that catalyst bed packed in the middle section ...

  7. Tuning of catalytic CO2 hydrogenation by changing composition of CuO–ZnO–ZrO2 catalysts

    International Nuclear Information System (INIS)

    Witoon, Thongthai; Kachaban, Nantana; Donphai, Waleeporn; Kidkhunthod, Pinit; Faungnawakij, Kajornsak; Chareonpanich, Metta

    2016-01-01

    Graphical abstract: The catalyst with an optimum composition of Cu:Zn:Zr (38.2:28.6:33.2) exhibited a homogeneous dispersion of metal components, and achieved the highest methanol yield. - Highlights: • A series of CuO–ZnO–ZrO 2 catalysts with different metal compositions were prepared. • Binary CuO–ZrO 2 catalyst exhibited higher methanol selectivity. • Increasing Zn/Cu ratios provided a better inter-dispersion of metal components. • The optimum catalyst composition of Cu–Zn–Zr (CZZ-4) was 38.2:28.6:33.2. • The CZZ-4 achieved the highest methanol yield (219.7 g CH3OH kg cat −1 h −1 ) at 240 °C. - Abstract: CO 2 hydrogenation was carried out over a series of CuO–ZnO–ZrO 2 catalysts prepared via a reverse co-precipitation method. The influence of catalyst compositions on the physicochemical properties of the catalysts as well as their catalytic performance was investigated. The catalysts were characterized by means of N 2 -sorption, X-ray diffraction (XRD), inductively coupled plasma optical emission spectrometry (ICP-OES), scanning electron microscopy (SEM), H 2 -temperature programmed reduction (H 2 -TPR), H 2 and CO 2 temperature-programmed desorption (H 2 - and CO 2 -TPD). The binary CuO–ZrO 2 (67:33) catalyst exhibits the highest methanol selectivity at all reaction temperature and its maximum yield of methanol (144.5 g methanol kg cat −1 h −1 ) is achieved at 280 °C, owing to the strong basic sites and the largest CuO crystallite size. The addition of Zn to the binary CuO–ZrO 2 catalyst causes a higher Cu dispersion and an increased number of active sites for CO 2 and H 2 adsorption. However, the basic strength of the ternary CuO–ZnO–ZrO 2 catalysts is lower than the binary CuO–ZrO 2 catalyst which provides the maximum yield of methanol at lower reaction tempertures (240 and 250 °C), depending on the catalyst compositions. The optimum catalyst composition of Cu–Zn–Zr (38.2:28.6:33.2) gives a superior methanol

  8. Catalytic Activity of Urchin-like Ni nanoparticles Prepared by Solvothermal Method for Hydrogen Evolution Reaction in Alkaline Solution

    International Nuclear Information System (INIS)

    Abbas, Syed Asad; Iqbal, Muhammad Ibrahim; Kim, Seong-Hoon; Jung, Kwang-Deog

    2017-01-01

    Highlights: • Urchin-like Ni is prepared in solvothermal reaction. • Urchin-like Ni is formed via Ni(OH) 2 aggregates in ethanol and oleylamine. • Exchange current density of urchin-like Ni is 0.191 mA cm −2 . • Urchin-like Ni exceeds the catalytic performance of commercial Pt/C in HER. - Abstract: Ni nanoparticles with different morphologies were synthesized for hydrogen evolution reaction (HER) in alkaline solution. Here, Ni(acac) 2 was converted into Ni metal nanoparticles in solvothermal reactions with simple alcohols and oleylamine (OAm). The morphology of the resulting Ni nanoparticles was dependent mainly on the OAm/Ni molar ratio in alcohol solvent. Aggregates of spherical Ni nanoparticles (NiEt-OAm1) were observed at the OAm/Ni molar ratio of 1.0, whereas two echinoid Ni nanoparticles (NiEt-OAm4 and NiEt-OAm6) could be prepared in ethanol at the OAm/Ni molar ratios of 4.0 and 6.0. Ni(OH) 2 formed in ethanol during a reaction time of 5 h was then reduced into echinoid Ni nanoparticles after 8 h. Echinoid Ni nanoparticles were formed by atomic addition on the tops of the multipod Ni particles formed via Ni(OH) 2 /NiO aggregates. Webbed feet-like particles (NiIPA-OAm4) with plate edges were also observed in isopropanol under the same reaction conditions. The catalytic activities of the prepared Ni nanoparticles for the hydrogen evolution reaction were evaluated in alkaline solution. The NiEt-OAm4 with urchin-like morphology was much more active than the NiIPA-OAm4 with webbed feet-like morphology. The exchange current density of Ni catalysts was increased with increasing the OAm/Ni molar ratio. The NiEt-OAm6 exhibited an exchange current of 0.191 mA cm −2 and the NiEt-OAm4 exceeded electrocatalytic performance of a commercial Pt catalysts (40% Pt on Vulcan XC 72) in a stability test for 100 kiloseconds at −1.5 V (vs. Hg/HgO) in 1.0 M NaOH due to its high stability.

  9. Catalytic Performance of Fe-Mn/SiO2 Nanocatalysts for CO Hydrogenation

    Directory of Open Access Journals (Sweden)

    Mostafa Feyzi

    2013-01-01

    Full Text Available A series of x(Fe, Mn/SiO2 nanocatalysts (x=5, 10, 15, 20, 25, and 30 wt.% were prepared by sol-gel method and studied for the light olefins production from synthesis gas. It was found that the catalyst containing 20 wt.% (Fe, Mn/SiO2 is an optimal nano catalyst for production of C2–C4 olefins. Effects of sulfur treatment on the catalyst performance of optimal catalyst have been studied by espousing different volume fractions of H2S in a fixed bed stainless steel reactor. The results show that the catalyst treated with 6 v% of H2S had high catalytic performance for C2–C4 light olefins production. The best operational conditions were H2/CO = 3/2 molar feed ratio at 260°C and GHSV = 1100 h−1 under 1 bar total pressure. Characterization of catalysts was carried out using X-ray diffraction (XRD, scanning electron microscopy (SEM, transmission electron microscopy (TEM, and surface area measurements.

  10. In tandem or alone: a remarkably selective transfer hydrogenation of alkenes catalyzed by ruthenium olefin metathesis catalysts.

    Science.gov (United States)

    Zieliński, Grzegorz Krzysztof; Samojłowicz, Cezary; Wdowik, Tomasz; Grela, Karol

    2015-03-07

    A system for transfer hydrogenation of alkenes, composed of a ruthenium metathesis catalyst and HCOOH, is presented. This operationally simple system can be formed directly after a metathesis reaction to effect hydrogenation of the metathesis product in a single-pot. These hydrogenation conditions are applicable to a wide range of alkenes and offer remarkable selectivity.

  11. Hydrogen Transfer during Liquefaction of Elbistan Lignite to Biomass; Total Reaction Transformation Approach

    Science.gov (United States)

    Koyunoglu, Cemil; Karaca, Hüseyin

    2017-12-01

    Given the high cost of the tetraline solvent commonly used in liquefaction, the use of manure with EL is an important factor when considering the high cost of using tetraline as a hydrogen transfer source. In addition, due to the another cost factor which is the catalyst prices, red mud (commonly used, produced as a byproduct in the production of aluminium) is reduced cost in the work of liquefaction of coal, biomass, even coal combined biomass, corresponding that making the EL liquefaction an agenda for our country is another important factor. Conditions for liquefaction experiments conducted for hydrogen transfer from manure to coal; Catalyst concentration of 9%, liquid/solid ratio of 3/1, reaction time of 60 min, fertilizer/lignite ratio of 1/3, and the reaction temperature of 400 °C, the stirred speed of 400 rpm and the initial nitrogen pressure of 20 bar was fixed. In order to demonstrate the hydrogen, transfer from manure to coal, coal is used solely, by using tetraline (also known as a hydrogen carrier) and distilled water which is not hydrogen donor as a solvent in the co-liquefaction of experiments, and also the liquefaction conditions are carried out under an inert (N2) gas atmosphere. According to the results of the obtained liquefaction test; using tetraline solvent the total liquid product conversion percentage of the oil + gas conversion was 38.3 %, however, the results of oil+gas conversion obtained using distilled water and EL combined with manure the total liquid product conversion percentage was 7.4 %. According to the results of calorific value and elemental analysis, only the ratio of (H/C)atomic of coal obtained by using tetraline increased with the liquefaction of manure and distilled water. The reason of the increase in the amount of hydrogen due to hydrogen transfer from the manure on the solid surface of the coal, and also on the surface of the inner pore of the coal during the liquefaction, brings about the evaluation of the coal as a

  12. Understanding the role of water in aqueous ruthenium-catalyzed transfer hydrogenation of ketones

    NARCIS (Netherlands)

    Pavlova, A.; Meijer, E.J.

    2012-01-01

    We report an accurate computational study of the role of water in transfer hydrogenation of formaldehyde with a ruthenium-based catalyst using a water-specific model. Our results suggest that the reaction mechanism in aqueous solution is significantly different from that in the gas phase or in

  13. Magnetic Silica-Supported Ruthenium Nanoparticles: An Efficient Catalyst for Transfer Hydrogenation of Carbonyl Compounds

    Science.gov (United States)

    One-pot synthesis of ruthenium nanoparticles on magnetic silica is described which involve the in situ generation of magnetic silica (Fe3O4@ SiO2) and ruthenium nano particles immobilization; the hydration of nitriles and transfer hydrogenation of carbonyl compounds occurs in hi...

  14. Laboratory Measurements of Charge Transfer on Atomic Hydrogen at Thermal Energies

    Science.gov (United States)

    Havener, C. C.; Vane, C. R.; Krause, H. F.; Stancil, P. C.; Mroczkowski, T.; Savin, D. W.

    2002-01-01

    We describe our ongoing program to measure velocity dependent charge transfer (CT) cross sections for selected ions on atomic hydrogen using the ion-aloin merged-beams apparatus at Oak Ridge Natioiial Laboralory. Our focus is on those ions for which CT plays an important role in determining the ionization structure, line emis sion, and thermal structure of observed cosmic photoionized plasmas.

  15. Efficient Energy Transfer in Supramolecular, Hydrogen-Bonded Polypyridylruthenium-Osmium Complexes

    NARCIS (Netherlands)

    Rau, Sven; Schäfer, Bernhard; Schebesta, Sebastian; Grüßing, André; Poppitz, Wolfgang; Walther, Dirk; Duati, Marco; Browne, Wesley R.; Vos, Johannes G.

    Hydrogen bond association between ruthenium bibenzimidazole and carboxylated polypyridylosmium complexes results in stable supramolecular aggregates. The determined stability constant of logK approximate to 6 +/- 0.3 allows efficient energy transfer from the ruthenium to the osmium moiety. (C)

  16. Asymmetric transfer hydrogenation of 1-phenyl dihydroisoquinolines using Ru(II) diamine catalysts

    Czech Academy of Sciences Publication Activity Database

    Přech, J.; Václavík, J.; Šot, P.; Pecháček, J.; Vilhanová, B.; Januščák, J.; Syslová, K.; Pažout, R.; Maixner, J.; Zápal, Jakub; Kuzma, Marek; Kačer, P.

    2013-01-01

    Roč. 36, JUN 2013 (2013), s. 67-70 ISSN 1566-7367 R&D Projects: GA ČR GA104/09/1497; GA ČR GAP106/12/1276 Institutional support: RVO:61388971 Keywords : Asymmetric transfer hydrogen ation * N-alkylsulfonyl * Dihydroisoquinoline Subject RIV: CA - Inorganic Chemistry Impact factor: 3.320, year: 2013

  17. Energy Transfer to the Hydrogen Bond in the (H2O)2+ H2O Collision.

    Science.gov (United States)

    Shin, H K

    2017-12-08

    Trajectory procedures are used to study the collision between the vibrationally excited H 2 O and the ground-state (H 2 O) 2 with particular reference to energy transfer to the hydrogen bond through the inter- and intramolecular pathways. In nearly 98% of the trajectories, energy transfer processes occur on a subpicosecond scale (≤0.7 ps). The H 2 O transfers approximately three-quarters of its excitation energy to the OH stretches of the dimer. The first step of the intramolecular pathway in the dimer involves a near-resonant first overtone transition from the OH stretch to the bending mode. The energy transfer probability in the presence of the 1:2 resonance is 0.61 at 300 K. The bending mode then redistributes its energy to low-frequency intermolecular vibrations in a series of small excitation steps, with the pathway which results in the hydrogen-bonding modes gaining most of the available energy. The hydrogen bonding in ∼50% of the trajectories ruptures on vibrational excitation, leaving one quantum in the bend of the monomer fragment. In a small fraction of trajectories, the duration of collision is longer than 1 ps, during which the dimer and H 2 O form a short-lived complex through a secondary hydrogen bond, which undergoes large amplitude oscillations.

  18. General Tritium Labelling of Gentamicin C by catalytic hydrogen exchange Reaction with Tritiated Water

    International Nuclear Information System (INIS)

    Suarez, C.; Diaz, D.; Paz, D.

    1991-01-01

    Gentamicin C was labelled with tritium by means of a PtO2 catalyzed hydrogen exchange reaction. Under the conditions of the exchange (100 mg of gentamicin, basic form, 0,3 ml H2O-3H, and 50 mg of prereduced PtO2) the radiochemical yield was 0,24, 0,38 and 0,48 % at 120 degree celsius, for 8, 16 and 24 hours respectively. Chemical yield for purified gentamicin was about 60 %. Purification was accomplished with a cellulose column eluted with the lower phase of chloroform-methanol 17 % ammonium hydroxide (2:1:1, v/v) . Chemical purity, determined by HPLC, was 96,5 % and radiochemical one was 95. Main exchange degradation products show biological activity. (Author) 12 refs

  19. Controllable pneumatic generator based on the catalytic decomposition of hydrogen peroxide

    Science.gov (United States)

    Kim, Kyung-Rok; Kim, Kyung-Soo; Kim, Soohyun

    2014-07-01

    This paper presents a novel compact and controllable pneumatic generator that uses hydrogen peroxide decomposition. A fuel micro-injector using a piston-pump mechanism is devised and tested to control the chemical decomposition rate. By controlling the injection rate, the feedback controller maintains the pressure of the gas reservoir at a desired pressure level. Thermodynamic analysis and experiments are performed to demonstrate the feasibility of the proposed pneumatic generator. Using a prototype of the pneumatic generator, it takes 6 s to reach 3.5 bars with a reservoir volume of 200 ml at the room temperature, which is sufficiently rapid and effective to maintain the repetitive lifting of a 1 kg mass.

  20. Catalytic Glycerol Hydrodeoxygenation under Inert Atmosphere: Ethanol as a Hydrogen Donor

    Directory of Open Access Journals (Sweden)

    Efterpi S. Vasiliadou

    2014-12-01

    Full Text Available Glycerol hydrodeoxygenation to 1,2-propanediol (1,2-PDO is a reaction of high interest. However, the need for hydrogen supply is a main drawback of the process. According to the concept investigated here, 1,2-propanediol is efficiently formed using bio-glycerol feedstock with H2 formed in situ via ethanol aqueous phase reforming. Ethanol is thought to be a promising H2 source, as it is alcohol that can be used instead of methanol for transesterification of oils and fats. The H2 generated is consumed in the tandem reaction of glycerol hydrodeoxygenation. The reaction cycle proceeds in liquid phase at 220–250 °C and 1.5–3.5 MPa initial N2 pressure for a 2 and 4-h reaction time. Pt-, Ni- and Cu-based catalysts have been synthesized, characterized and evaluated in the reaction. Among the materials tested, Pt/Fe2O3-Al2O3 exhibited the most promising performance in terms of 1,2-propanediol productivity, while reusability tests showed a stable behavior. Structural integrity and no formation of carbonaceous deposits were verified via Temperature Programmed Desorption of hydrogen (TPD-H2 and thermogravimetric analysis of the fresh and used Pt/FeAl catalyst. A study on the effect of various operating conditions (reaction time, temperature and pressure indicated that in order to maximize 1,2-propanediol productivity and yield, milder reaction conditions should be applied. The highest 1,2-propanediol yield, 53% (1.1 g1,2-PDO gcat−1·h−1, was achieved at a lower reaction temperature of 220 °C.

  1. Fabrication of porous boron-doped diamond electrodes by catalytic etching under hydrogen-argon plasma

    Science.gov (United States)

    Shi, Chao; Li, Cuiping; Li, Mingji; Li, Hongji; Dai, Wei; Wu, Yongheng; Yang, Baohe

    2016-01-01

    Porous boron-doped diamond (BDD) was prepared by hydrogen-argon plasma etching using electrodeposited Ni nanoparticles as a catalyst. The etching process and formation mechanism of porous BDD were investigated by changing the etching time from 30 s to 300 s. Pores were produced due to the C atoms around Ni nanoparticles are easy to react with hydrogen plasma and form methane. With the increase of etching time, the pore size increased, the pore density decreased, and the pore depth first increased and then maintained unchanged. The sp2-bonded graphitic carbons existing on the surface of BDD increase with increasing etching time due to the increase of surface area. No preferential etching was observed due to the high energy of argon plasma. The electrochemical behaviors of the pristine and porous BDD electrodes were characterized by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS). The results showed that the porous BDD electrode exhibited high specific capacitance, which is attributed to its high electrical conductivity and large specific surface area. The highest specific capacitance of porous BDD electrode is 9.55 mF cm-2, which is 22 times higher than that of pristine BDD electrode. The specific capacitance retention of the porous BDD electrode reduced to 98.2% of the initial capacitance after 500 cycles and then increased to 120.0% after 10,000 cycles. For the first 500 cycles, the reduction of capacitance can be attributed to the dissolution of Ni nanoparticles that attached on the porous BDD surface or buried in the shallow layer. The capacitance increase after 10,000 cycles is due to the better contact of the electrolytic solution with the residual Ni with the increase of cycle number.

  2. Single cobalt sites in mesoporous N-doped carbon matrix for selective catalytic hydrogenation of nitroarenes

    KAUST Repository

    Sun, Xiaohui

    2017-11-20

    A supported cobalt catalyst with atomically dispersed Co-Nx sites (3.5 wt% Co) in a mesoporous N-doped carbon matrix (named Co@mesoNC) is synthesized by hydrolysis of tetramethyl orthosilicate (TMOS) in a Zn/Co bimetallic zeolitic imidazolate framework (BIMZIF(Co,Zn)), followed by high-temperature pyrolysis and SiO2 leaching. A combination of TEM, XRD XPS and X-ray absorption spectroscopy studies confirm the absence of cobalt nanoparticles and indicate that these highly dispersed cobalt species are present in the form of Co-Nx. The exclusive formation of Co-Nx sites in the carbon matrix is attributed to the presence of a large amount of Zn and N in the BIMZIF precursor together with the presence of SiO2 in the pore space of this framework, extending the initial spatial distance between cobalt atoms and thereby impeding their agglomeration. The presence of SiO2 during high-temperature pyrolysis is proven crucial to create mesoporosity and a high BET area and pore volume in the N-doped carbon support (1780 m2 g−1, 1.54 cm3 g−1). This heterogeneous Co@mesoNC catalyst displays high activity and selectivity (>99%) for the selective hydrogenation of nitrobenzene to aniline at mild conditions (0.5–3 MPa, 343–383 K). When more challenging substrates (functionalized nitroarenes) are hydrogenated, the catalyst Co@mesoNC displays an excellent chemoselectivity to the corresponding substituted anilines.The presence of mesoporosity improves mass transport of reactants and/or products and the accessibility of the active Co-Nx sites, and greatly reduces deactivation due to fouling.

  3. Magnetic porous PtNi/SiO2 nanofibers for catalytic hydrogenation of p-nitrophenol

    Science.gov (United States)

    Guan, Huijuan; Chao, Cong; Kong, Weixiao; Hu, Zonggao; Zhao, Yafei; Yuan, Siguo; Zhang, Bing

    2017-06-01

    In this work, the mesoporous SiO2 nanofibers from pyrolyzing precursor of electrospun nanofibers were employed as support to immobilize PtNi nanocatalyst (PtNi/SiO2 nanofibers). AFM, XRD, SEM, TEM, XPS, ICP-AES and N2 adsorption/desorption analysis were applied to systematically investigate the morphology and microstructure of as-prepared products. Results showed that PtNi alloy nanoparticles with average diameter of 18.7 nm were formed and could be homogeneously supported on the surface of porous SiO2 nanofiber, which further indicated that the SiO2 nanofibers with well-developed porous structure, large specific surface area, and roughened surface was a benefit for the support of PtNi alloy nanoparticles. The PtNi/SiO2 nanofibers catalyst exhibited an excellent catalytic activity towards the reduction of p-nitrophenol, and the catalyst's kinetic parameter ( k n = 434 × 10-3 mmol s-1 g-1) was much higher than those of Ni/SiO2 nanofibers (18 × 10-3 mmol s-1 g-1), Pt/SiO2 nanofibers (55 × 10-3 mmol s-1 g-1) and previous reported PtNi catalysts. The catalyst could be easily recycled from heterogeneous reaction system based on its good magnetic properties (the Ms value of 11.48 emu g-1). In addition, PtNi/SiO2 nanofibers also showed an excellent stability and the conversion rate of p-nitrophenol still could maintain 94.2% after the eighth using cycle.

  4. Formation of polyhedral ceria nanoparticles with enhanced catalytic CO oxidation activity in thermal plasma via a hydrogen mediated shape control mechanism

    International Nuclear Information System (INIS)

    Zheng Jie; Zhang Yaohua; Song Xubo; Li Xingguo

    2011-01-01

    Ceria nanoparticles with well defined facets are prepared in argon–hydrogen thermal plasma followed by controlled oxidation. With increasing hydrogen fraction in the plasma, a clear sphere-to-polyhedron shape transition is observed. The heat released during the hydrogenation of cerium, which significantly enhances the species mobility on the surface, favors the growth of well defined facets. The polyhedron ceria nanoparticles, though lower in specific surface area, exhibit superior catalytic performance for CO oxidation over the round particles, which is attributed to the higher density of the reactive {200} and {220} facets on the surface. The hydrogen mediated shape control mechanism provides new insights into the shape control of nanoparticles during thermal plasma processing.

  5. Surface kinetics for catalytic combustion of hydrogen-air mixtures on platinum at atmospheric pressure in stagnation flows

    Science.gov (United States)

    Ikeda, H.; Sato, J.; Williams, F. A.

    1995-03-01

    Experimental studies of the combustion of premixed hydrogen-air mixtures impinging on the surface of a heated platinum plate at normal atmospheric pressure were performed and employed to draw inferences concerning surface reaction mechanisms and rate parameters applicable under practical conditions of catalytic combustion. Plate and gas temperatures were measured by thermocouples, and concentration profiles of major stable species in the gas were measured by gas-chromatographic analyses of samples withdrawn by quartz probes. In addition, ignition and extinction phenomena were recorded and interpreted with the aid of a heat balance at the surface and a previous flow-field analysis of the stagnation-point boundary layer. From the experimental and theoretical results, conclusions were drawn concerning the surface chemical-kinetic mechanisms and values of the elementary rate parameters that are consistent with the observations. In particular, the activation energy for the surface oxidation step H + OH → H 2O is found to be appreciably less at these high surface coverages than in the low-coverage limit.

  6. Kinetic spectrophotometric determination of Bi(III based on its catalytic effect on the oxidation of phenylfluorone by hydrogen peroxide

    Directory of Open Access Journals (Sweden)

    SOFIJA M. RANČIĆ

    2009-08-01

    Full Text Available A new reaction was suggested and a new kinetic method was elaborated for determination of Bi(III in solution, based on its catalytic effect on the oxidation of phenyl-fluorone (PF by hydrogen peroxide in ammonia buffer. By application of spectrophotometric technique, a limit of quantification (LQ of 128 ng cm-3 was reached, and the limit of detection (LD of 37 ng cm-3 was obtained, where LQ was defined as the ratio signal:noise = 10:1 and LD was defined as signal 3:1 against the blank. The RSD value was found to be in the range 2.8–4.8 % for the investigated concentration range of Bi(III. The influence of some ions upon the reaction rate was tested. The method was confirmed by determining Bi(III in a stomach ulcer drug (“Bicit HP”, Hemofarm A.D.. The obtained results were compared to those obtained by AAS and good agreement of results was obtained.

  7. Pyrolysis of de-oiled seed cake of Jatropha Curcas and catalytic steam reforming of pyrolytic bio-oil to hydrogen.

    Science.gov (United States)

    Renny, Andrew; Santhosh, Viswanathan; Somkuwar, Nitin; Gokak, D T; Sharma, Pankaj; Bhargava, Sanjay

    2016-11-01

    The aim of this work was to study the pyrolysis of de-oiled seed cake of Jatropha Curcas and catalytic steam reforming of pyrolytic bio-oil to hydrogen. As per literature, presence of heavy nitrogenous and oxygenated compounds leads to catalyst deactivation. Here, an attempt has been made to tune pyrolytic reactions to optimize the N and O content of the pyrolytic bio-oil. Bio-oil conversion and hydrogen yield decreased as reaction progressed, which attributes to temporary loss of catalytic activity by blockage of catalyst pores by carbon deposition. Further, retention of steam reforming activity after repetitive steam activation suggests long-term catalyst usage. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. Functionalized cyclopentadienyl rhodium(III) bipyridine complexes: synthesis, characterization, and catalytic application in hydrogenation of ketones.

    Science.gov (United States)

    Wang, Wan-Hui; Suna, Yuki; Himeda, Yuichiro; Muckerman, James T; Fujita, Etsuko

    2013-07-14

    A series of highly functionalized cyclopentadienyl rhodium(III) complexes, [Cp'Rh(bpy)Br](ClO4) (Cp' = substituted cyclopentadienyl), was synthesized from various multi-substituted cyclopentadienes (Cp'H). [Rh(cod)Cl]2 and Cp'H were firstly converted to [Cp'Rh(cod)] complexes, which were then treated with Br2 to give the rhodium(III) dibromides [Cp'RhBr2]2. The novel complexes [Cp'Rh(bpy)Br](ClO4) were obtained readily by the reaction of 2,2'-bipyridine with [Cp'RhBr2]2. These rhodium complexes [Cp'Rh(bpy)Br](ClO4) were fully characterized and utilized in the hydrogenation of cyclohexanone and acetophenone with generally high yields, but they did not exhibit the same reactivity trends for the two substrate ketones. The different activity of these complexes for the different substrates may be due to the influence of the substituents on the Cp' rings.

  9. Model Catalytic Studies of Novel Liquid Organic Hydrogen Carriers: Indole, Indoline and Octahydroindole on Pt(111).

    Science.gov (United States)

    Schwarz, Matthias; Bachmann, Philipp; Silva, Thais Nascimento; Mohr, Susanne; Scheuermeyer, Marlene; Späth, Florian; Bauer, Udo; Düll, Fabian; Steinhauer, Johann; Hohner, Chantal; Döpper, Tibor; Noei, Heshmat; Stierle, Andreas; Papp, Christian; Steinrück, H-P; Wasserscheid, Peter; Görling, Andreas; Libuda, Jörg

    2017-10-20

    Indole derivatives were recently proposed as potential liquid organic hydrogen carriers (LOHC) for storage of renewable energies. In this work, we have investigated the adsorption, dehydrogenation and degradation mechanisms in the indole/indoline/octahydroindole system on Pt(111). We have combined infrared reflection absorption spectroscopy (IRAS), X-ray photoelectron spectroscopy (XPS) and DFT calculations. Indole multilayers show a crystallization transition at 200 K, in which the molecules adopt a strongly tilted orientation, before the multilayer desorbs at 220 K. For indoline, a less pronounced restructuring transition occurs at 150 K and multilayer desorption is observed at 200 K. Octahydroindole multilayers desorb already at 185 K, without any indication for restructuring. Adsorbed monolayers of all three compounds are stable up to room temperature and undergo deprotonation at the NH bond above 300 K. For indoline, the reaction is followed by partial dehydrogenation at the 5-membered ring, leading to the formation of a flat-lying di-σ-indolide in the temperature range from 330-390 K. Noteworthy, the same surface intermediate is formed from indole. In contrast, the reaction of octahydroindole with Pt(111) leads to the formation of a different intermediate, which originates from partial dehydrogenation of the 6-membered ring. Above 390 K, all three compounds again form the same strongly dehydrogenated and partially decomposed surface species. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Improving the catalytic activity of amorphous molybdenum sulfide for hydrogen evolution reaction using polydihydroxyphenylalanine modified MWCNTs

    Science.gov (United States)

    Li, Maoguo; Yu, Muping; Li, Xiang

    2018-05-01

    Molybdenum sulfides are promising electrocatalysts for hydrogen evolution reaction (HER) in acid medium due to their unique properties. In order to improve their HER activity, different strategies have been developed. In this study, amorphous molybdenum sulfide was prepared by a simple wet chemical method and its HER activity was further improved by using polydihydroxyphenylalanine (PDOPA) modified MWCNTs as supports. It was found that the PDOPA can effectively improve the hydrophilic properties of multiwalled carbon nanotubes (MWCNTs) and amorphous MoSx can uniformly grow on the surface of PDOPA@MWCNTs. Compared with MoSx and MoSx/MWCNTs, MoSx/PDOPA@MWCNTs show obviously enhanced HER activities due to the superior electrical conductivity and more exposed active sites. In addition, the effect of the ratio of MoSx and PDOPA@MWCNTs and the loading amount of catalysts on the electrodes are also investigated in detail. At the optimum conditions, MoSx/PDOPA@MWCNTs display an overpotential of 198 mV at 10 mA/cm2, a Tafel slope of 53 mV/dec and a good long-term stability in 0.5 M H2SO4, which make them promising candidates for HER application.

  11. Modification of Coal Char-loaded TiO2 by Sulfonation and Alkylsilylation to Enhance Catalytic Activity in Styrene Oxidation with Hydrogen Peroxide as Oxidant

    Directory of Open Access Journals (Sweden)

    Mukhamad Nurhadi

    2017-04-01

    Full Text Available The modified coal char from low-rank coal by sulfonation, titanium impregnation and followed by alkyl silylation possesses high catalytic activity in styrene oxidation. The surface of coal char was undergone several steps as such: modification using concentrated sulfuric acid in the sulfonation process, impregnation of 500 mmol titanium(IV isopropoxide and followed by alkyl silylation of n-octadecyltriclorosilane (OTS. The catalysts were characterized by X-ray diffraction (XRD, IR spectroscopy, nitrogen adsorption, and hydrophobicity. The catalytic activity of the catalysts has been examined in the liquid phase styrene oxidation by using aqueous hydrogen peroxide as oxidant. The catalytic study showed the alkyl silylation could enhance the catalytic activity of Ti-SO3H/CC-600(2.0. High catalytic activity and reusability of the o-Ti-SO3H/CC-600(2.0 were related to the modification of local environment of titanium active sites and the enhancement the hydrophobicity of catalyst particle by alkyl silylation. Copyright © 2017 BCREC GROUP. All rights reserved Received: 24th May 2016; Revised: 11st October 2016; Accepted: 18th October 2016 How to Cite: Nurhadi, M. (2017. Modification of Coal Char-loaded TiO2 by Sulfonation and Alkylsilylation to Enhance Catalytic Activity in Styrene Oxidation with Hydrogen Peroxide as Oxidant. Bulletin of Chemical Reaction Engineering & Catalysis, 12 (1: 55-61 (doi:10.9767/bcrec.12.1.501.55-61 Permalink/DOI: http://dx.doi.org/10.9767/bcrec.12.1.501.55-61

  12. Catalytic Transfer Hydrogenation of Furfural to Furfuryl Alcohol with Recyclable Al-Zr@Fe Mixed Oxides

    DEFF Research Database (Denmark)

    He, Jian; Li, Hu; Riisager, Anders

    2017-01-01

    and morphologies of the as-prepared catalysts were characterized by various techniques, including XRD analysis, N2 physisorption, vibrating sample magnetometry, thermal gravimetry analysis, X-ray fluorescence spectroscopy, NH3/CO2 temperature-programmed desorption, SEM, and TEM. The Al7Zr3@Fe3O4(1/1) catalyst...

  13. Solar Photo Catalytic Hydrogen Production from water using a dual bed photosystem

    Energy Technology Data Exchange (ETDEWEB)

    Florida Solar Energy Center

    2003-03-30

    A body of work was performed in which the feasibility of photocatalytically decomposing water into its constituent elements using a dual bed, or modular photosystem, under solar radiation was investigated. The system envisioned consists of two modules, each consisting of a shallow, flat, sealed container, in which microscopic photocatalytic particles are immobilized. The photocatalysts absorb light, generating free electrons and lattice vacancy holes, which are capable of performing reductive and oxidative chemistry, respectively. The photocatalysts would be chosen as to whether they specifically promote H{sub 2} or O{sub 2} evolution in their respective containers. An aqueous solution containing a redox mediator is pumped between the two chambers in order to transfer electron equivalents from one reaction to the other.

  14. Green diesel production via catalytic hydrogenation/decarboxylation of triglycerides and fatty acids of vegetable oil and brown grease

    Science.gov (United States)

    Sari, Elvan

    than activated carbon itself for both decarboxylation of oleic acid and hydrogenation of alkenes. In an additional effort to reduce Pd amount in the catalyst, Pd2Co/C catalysts with various Pd content were prepared and the catalytic activity study showed that 0.5 wt% Pd2Co/C catalyst performs even better than a 5 wt% Pd/C catalyst. Pd and Co alloys were very well dispersed and formed fine clusters, which led to a higher active metal surface area and hence favored the decarboxylation of oleic acid. This study showed that an alloy of Pd on carbon with a significantly low Pd content is much more active and selective to diesel hydrocarbons production from an unsaturated fatty acid in super-critical water and may be regarded as a prospective feasible decarboxylation catalyst for the removal of oxygen from vegetable oil/animal fat without the need of additional hydrogen.

  15. Cyanogel-derived N-doped C nanosheets immobilizing Pd-P nanoparticles: One-pot synthesis and enhanced hydrogenation catalytic performance

    Science.gov (United States)

    Zhang, Hao; Yan, Xiaohong; Huang, Yundi; Zhang, Mengru; Tang, Yawen; Sun, Dongmei; Xu, Lin; Wei, Shaohua

    2017-02-01

    For Pd-based nanocatalysts, stabilization of Pd nanoparticles on carbon support could not only effectively avoid particle aggregation and maintain catalytic stability during catalytic processes, but also facilitate enhancing the catalytic activity due to the synergy between Pd nanoparticles and carbon support. Furthermore, the incorporation of non-metal of phosphorus (P) into Pd could effectively modulate the electronic structure of Pd and thus help to boost the catalytic properties. However, one-pot synthesis of such nanohybrids remains a great challenge due to the distinct physiochemical properties of Pd, P and C components. Herein, we demonstrate a one-pot and scalable synthesis of highly dispersed PdP alloy nanoparticle-immobilized on N-doped graphitic carbon nanosheets (abbreviated as Pd-P@N-C nanosheets) by using inorganic-organic hybrid cyanogel as a reaction precursor. In virtue of both compositional and structural advantages, the as-synthesized Pd-P@N-C nanosheets manifest a superior catalytic activity and stability toward the hydrogenation of 4-nitrophenol (4-NP). We believe that the present work will provide a feasible and versatile strategy for the development of efficient catalysts for environmental remediation and can also be extendable to other carbon-based nanohybrids with desirable functionalities.

  16. Hydrogen-transfer and charge-transfer in photochemical and radiation induced reactions. Progress report, November 1, 1975--October 31, 1976

    International Nuclear Information System (INIS)

    Cohen, S.G.

    1976-10-01

    The relative importance of light absorption, quenching of triplet, and hydrogen transfer repair has been examined in retardation by mercaptans of photoreduction of aromatic ketones by alcohols. In the reduction of benzophenone by 2-propanol, retardation is efficient and, after correction for the first two effects, is due entirely to hydrogen-transfer repair, as indicated by deuterium labeling. In reduction of acetophenone by α-methylbenzyl alcohol, repair by hydrogen transfer is also operative. In reduction of benzophenone by benzhydrol, retardation is less efficient and is due to quenching, as the ketyl radical does not abstract hydrogen from mercaptan rapidly in competition with coupling. Deuterium isotope effects are discussed in terms of competitive reactions. Photoreduction of benzophenone by 2-butylamine and by triethylamine is retarded by aromatic mercaptans and disulfides. Of the retardation not due to light absorption and triplet quenching by the sulfur compounds, half is due to hydrogen-transfer repair, as indicated by racemization and deuterium labeling. The remainder is attributed to quenching by the sulfur compound of the charge-transfer-complex intermediate. Photoreduction by primary and secondary amines, but not by tertiary amines, is accelerated by aliphatic mercaptans. The acceleration is attributed to catalysis of hydrogen transfer by the mercaptan in the charge-transfer complex. The effect is large in hydrocarbon solvent, less in polar organic solvents and absent in water

  17. A Selective and Functional Group-Tolerant Ruthenium-Catalyzed Olefin Metathesis/Transfer Hydrogenation Tandem Sequence Using Formic Acid as Hydrogen Source.

    Science.gov (United States)

    Zieliński, Grzegorz K; Majtczak, Jarosława; Gutowski, Maciej; Grela, Karol

    2018-03-02

    A ruthenium-catalyzed transfer hydrogenation of olefins utilizing formic acid as a hydrogen donor is described. The application of commercially available alkylidene ruthenium complexes opens access to attractive C(sp3)-C(sp3) bond formation in an olefin metathesis/transfer hydrogenation sequence under tandem catalysis conditions. High chemoselectivity of the developed methodology provides a remarkable synthetic tool for the reduction of various functionalized alkenes under mild reaction conditions. The developed methodology is applied for the formal synthesis of the drugs pentoxyverine and bencyclane.

  18. Enhancement of atom transfer in different surface chemistry of hydrogenated vs. fluorinated tribromobenzene on Ag(111) and Cu(111)

    Science.gov (United States)

    Cecily mary glory, D.; Sambathkumar, K.; Madivanane, R.; Rajkamal, N.; Venkatachalapathy, M.

    2017-12-01

    Systematic interactions of hydrogenated & fluorinated tribromobenzene on Ag and Cu surfaces. First bromine dehalogenation takes place right upon adsorption due to catalytic properties of Ag. Different adsorption geometries of monomers and dimmers of 1,3,5-tribromo-2,4,6-trifluoro-benzene(TBFB) and 1,3,5-tribromobenzene(TBB). DFT calculations of the Csbnd Br binding energy dependent on the amount of remaining bromine atoms for both TBFB and TBB were performed. The experiments were performed at low temperature of 80 K.STM measurements where performed for of TBFB and TBB. STM show adsorbed molecules in a loose arrangement of molecules. NBO analysis the stability of the molecule arising within hyper-conjugative interactions. The HOMO and LUMO energies and electronic charge transfer (ECT) confirms that electronic transition. High field indicates that this molecule exhibit considerable electrical conductivity in atomic charges. The ESP map is found to be positive within the molecule. The negative charges have a tendency to drift from left to right. The computed thermodynamic parameters like heat capacities (Cºp,m), entropies (Sºm) and enthalpies changes (Hºm) are used for various electrical field.

  19. Purge gas recovery of ammonia synthesis plant by integrated configuration of catalytic hydrogen-permselective membrane reactor and solid oxide fuel cell as a novel technology

    Science.gov (United States)

    Siavashi, Fakhteh; Saidi, Majid; Rahimpour, Mohammad Reza

    2014-12-01

    The purge gas emission of ammonia synthesis plant which contains hazardous components is one of the major sources of environmental pollution. Using integrated configuration of catalytic hydrogen-permselective membrane reactor and solid oxide fuel cell (SOFC) system is a new approach which has a great impact to reduce the pollutant emission. By application of this method, not only emission of ammonia and methane in the atmosphere is prevented, hydrogen is produced through the methane steam reforming and ammonia decomposition reactions that take place simultaneously in a catalytic membrane reactor. The pure generated hydrogen by recovery of the purge gas in the Pd-Ag membrane reactor is used as a feed of SOFC. Since water is the only byproduct of the electrochemical reaction in the SOFC, it is recycled to the reactor for providing the required water of the reforming reaction. Performance investigation of the reactor represents that the rate of hydrogen permeation increases with enhancing the reactor temperature and pressure. Also modeling results indicate that the SOFC performance improves with increasing the temperature and fuel utilization ratio. The generated power by recovery of the purging gas stream of ammonia synthesis plant in the Razi petrochemical complex is about 8 MW.

  20. Hydrogen production by steam reforming of bio-alcohols. The use of conventional and membrane-assisted catalytic reactors

    Energy Technology Data Exchange (ETDEWEB)

    Seelam, P. K.

    2013-11-01

    The energy consumption around the globe is on the rise due to the exponential population growth and urbanization. There is a need for alternative and non-conventional energy sources, which are CO{sub 2}-neutral, and a need to produce less or no environmental pollutants and to have high energy efficiency. One of the alternative approaches is hydrogen economy with the fuel cell (FC) technology which is forecasted to lead to a sustainable society. Hydrogen (H{sub 2}) is recognized as a potential fuel and clean energy carrier being at the same time a carbon-free element. Moreover, H{sub 2} is utilized in many processes in chemical, food, metallurgical, and pharmaceutical industry and it is also a valuable chemical in many reactions (e.g. refineries). Non-renewable resources have been the major feedstock for H{sub 2} production for many years. At present, {approx}50% of H{sub 2} is produced via catalytic steam reforming of natural gas followed by various down-stream purification steps to produce {approx}99.99% H{sub 2}, the process being highly energy intensive. Henceforth, bio-fuels like biomass derived alcohols (e.g. bio-ethanol and bio-glycerol), can be viable raw materials for the H{sub 2} production. In a membrane based reactor, the reaction and selective separation of H{sub 2} occur simultaneously in one unit, thus improving the overall reactor efficiency. The main motivation of this work is to produce H{sub 2} more efficiently and in an environmentally friendly way from bio-alcohols with a high H{sub 2} selectivity, purity and yield. In this thesis, the work was divided into two research areas, the first being the catalytic studies using metal decorated carbon nanotube (CNT) based catalysts in steam reforming of ethanol (SRE) at low temperatures (<450 deg C). The second part was the study of steam reforming (SR) and the water-gas-shift (WGS) reactions in a membrane reactor (MR) using dense and composite Pd-based membranes to produce high purity H{sub 2}. CNTs

  1. UV-light-induced hydrogen transfer in guanosine-guanosine aggregates.

    Science.gov (United States)

    Hunger, Katharina; Buschhaus, Laura; Biemann, Lars; Braun, Michaela; Kovalenko, Sergey; Improta, Roberto; Kleinermanns, Karl

    2013-04-22

    Aggregates of a lipophilic guanine (G) derivative have been studied in n-hexane by femtosecond-to-microsecond UV-visible broadband transient absorption, stationary infrared and UV-visible spectroscopy and by quantum chemical calculations. We report the first time-resolved spectroscopic detection of hydrogen transfer in GG aggregates, which leads to (G-H)(·) radicals by means of G(+)G(-) charge transfer followed by proton transfer. These radicals show a characteristic electronic spectrum in the range 300-550 nm. The calculated superimposed spectrum of the species that result from NH⋅⋅⋅N proton transfer agrees best with the experimental spectrum. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Molecular hydrogen and catalytic combustion in the production of hyperpolarized 83Kr and 129Xe MRI contrast agents.

    Science.gov (United States)

    Rogers, Nicola J; Hill-Casey, Fraser; Stupic, Karl F; Six, Joseph S; Lesbats, Clémentine; Rigby, Sean P; Fraissard, Jacques; Pavlovskaya, Galina E; Meersmann, Thomas

    2016-03-22

    Hyperpolarized (hp) (83)Kr is a promising MRI contrast agent for the diagnosis of pulmonary diseases affecting the surface of the respiratory zone. However, the distinct physical properties of (83)Kr that enable unique MRI contrast also complicate the production of hp (83)Kr. This work presents a previously unexplored approach in the generation of hp (83)Kr that can likewise be used for the production of hp (129)Xe. Molecular nitrogen, typically used as buffer gas in spin-exchange optical pumping (SEOP), was replaced by molecular hydrogen without penalty for the achievable hyperpolarization. In this particular study, the highest obtained nuclear spin polarizations were P =29% for(83)Kr and P= 63% for (129)Xe. The results were reproduced over many SEOP cycles despite the laser-induced on-resonance formation of rubidium hydride (RbH). Following SEOP, the H2 was reactively removed via catalytic combustion without measurable losses in hyperpolarized spin state of either (83)Kr or (129)Xe. Highly spin-polarized (83)Kr can now be purified for the first time, to our knowledge, to provide high signal intensity for the advancement of in vivo hp (83)Kr MRI. More generally, a chemical reaction appears as a viable alternative to the cryogenic separation process, the primary purification method of hp(129)Xe for the past 2 1/2 decades. The inherent simplicity of the combustion process will facilitate hp (129)Xe production and should allow for on-demand continuous flow of purified and highly spin-polarized (129)Xe.

  3. Evaluation of heat transfer in a catalytic fixed bed reactor at high temperatures

    Directory of Open Access Journals (Sweden)

    JORGE L. M. M.

    1999-01-01

    Full Text Available Experimental results of fixed-bed heat-transfer experiments with no chemical reaction are presented and discussed. The runs were carried out in a tubular integral reactor heated by an electrical furnace at temperatures in the range of 100 to 500°C. Experimental temperature profiles were determined for the electrical furnace, for the reactor wall, and for the fixed bed center. Industrial catalyst for the prereforming of hydrocarbons was employed as the packing material. The effects of process conditions (furnace temperature, gas flow rate on the heat-transfer coefficients were evaluated. The experimental results were analyzed in terms of the external, wall, and internal thermal resistances, associated in series, and compared with model predictions. Under the conditions studied, the overall coefficient was mostly a function of the external effective heat-transfer coefficient. An alternative data treatment was proposed to determine the internal heat-transfer coefficient in fixed beds when wall temperature is not constant.

  4. Effect of hydrogen on the growth and morphology of single wall carbon nanotubes synthesized on a Fe-Mo/MgO catalytic system

    Energy Technology Data Exchange (ETDEWEB)

    Biris, Alexandru R. [National Institute for Research and Development of Isotopic and Molecular Technologies, Cluj Napoca, RO-3400 (Romania)], E-mail: biris@oc1.itim-cj.ro; Li Zhongrui; Dervishi, Enkeleda [Applied Science Department, University of Arkansas at Little Rock, 2801 S. University Ave, Little Rock, AR 72204 (United States); Nanotechnology Center, University of Arkansas at Little Rock, 2801 S. University Ave, Little Rock, AR 72204 (United States); Lupu, Dan [National Institute for Research and Development of Isotopic and Molecular Technologies, Cluj Napoca, RO-3400 (Romania); Xu Yang; Saini, Viney [Applied Science Department, University of Arkansas at Little Rock, 2801 S. University Ave, Little Rock, AR 72204 (United States); Nanotechnology Center, University of Arkansas at Little Rock, 2801 S. University Ave, Little Rock, AR 72204 (United States); Watanabe, Fumiya [Nanotechnology Center, University of Arkansas at Little Rock, 2801 S. University Ave, Little Rock, AR 72204 (United States); Biris, Alexandru S. [Applied Science Department, University of Arkansas at Little Rock, 2801 S. University Ave, Little Rock, AR 72204 (United States); Nanotechnology Center, University of Arkansas at Little Rock, 2801 S. University Ave, Little Rock, AR 72204 (United States)], E-mail: asbiris@ualr.edu

    2008-04-21

    Single wall carbon nanotubes were synthesized from thermal pyrolysis of methane on a Fe-Mo/MgO catalyst by radio frequency catalytic chemical vapor deposition (RF-CVD) using argon as a carrier gas. Controlled amounts of hydrogen (H{sub 2}/CH{sub 4}=0-1 v/v) were introduced in separate experiments along with the carbon source. The properties and morphology of the synthesized single wall carbon nanotubes were monitored by transmission electron microscopy, Raman scattering, and thermogravimetric analysis. The nanotubes with the highest crystallinity were obtained with H{sub 2}/CH{sub 4}=0.6. By monitoring the Radial Breathing Modes present in the Raman spectra of the single-wall carbon nanotube samples, the variation of the structural and morphological properties of the carbon nanotubes with the flow level of hydrogen, reflect changes of the catalyst systems induced by the presence of hydrogen.

  5. Hydrogen transfer in Pb–Li forced convection flow with permeable wall

    Energy Technology Data Exchange (ETDEWEB)

    Fukada, Satoshi, E-mail: sfukada@nucl.kyushu-u.ac.jp; Muneoka, Taiki; Kinjyo, Mao; Yoshimura, Rhosuke; Katayama, Kazunari

    2015-10-15

    Highlights: • The paper presents experimental and analytical results of Pb–Li eutectic alloy forced convection flow. • Analytical results are in good agreement with ones of hydrogen permeation in Pb–Li forced convection flow. • The results are useful for the design of liquid blanket of fusion reactors. - Abstract: Transient- or steady-state hydrogen permeation from a primary fluid of Li{sub 17}Pb{sub 83} (Pb–Li) through a permeable tube of Inconel-625 alloy to a secondary Ar purge is investigated experimentally under a forced convection flow in a dual cylindrical tube system. Results of the overall hydrogen permeation flux are correlated in terms of diffusivity, solubility and an average axial velocity of Pb–Li and diffusivity and solubility of the solid wall. Analytical solutions under proper assumptions are derived to simulate the transient- and steady-state rates of the overall hydrogen permeation, and close agreement is obtained between experiment and analysis. Two things are clarified from the comparison: (i) how the steady-state permeation rate is affected by the mass-transfer properties and the average velocity of Pb–Li and the properties of Inconel-625, and (ii) how its transient behavior is done by the diffusivity of the two materials. The results obtained here will give important information to estimate or to analyze the tritium transfer rate in fluidized Pb–Li blankets of DEMO or the future commercial fusion reactors.

  6. Diastereo- and Enantioselective Iridium Catalyzed Carbonyl (α-Cyclopropyl)allylation via Transfer Hydrogenation.

    Science.gov (United States)

    Tsutsumi, Ryosuke; Hong, Suckchang; Krische, Michael J

    2015-09-07

    The first examples of diastereo- and enantioselective carbonyl α-(cyclopropyl)allylation are reported. Under the conditions of iridium catalyzed transfer hydrogenation using the chiral precatalyst (R)-Ir-I modified by SEGPHOS, carbonyl α-(cyclopropyl)allylation may be achieved with equal facility from alcohol or aldehyde oxidation levels. This methodology provides a conduit to hitherto inaccessible inaccessible enantiomerically enriched cyclopropane-containing architectures. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Hydrogen-deuterium exchange of weak carbon acids under phase-transfer catalysis conditions

    International Nuclear Information System (INIS)

    Feldman, D.; Halpern, M.; Rabinovitz, M.

    1985-01-01

    A practical method for hydrogen-deuterium exchange is obtained via extractive hydroxide ion initiated phase-transfer catalysis. The reaction of NaOD/D 2 O system allows the easy production of compounds that otherwise would require very strong bases and aprotic solvents. The strong basicity of OD - anion is attributable to its relative freedom from water molecules when OD - is extracted into the depth of the organic layer. 22 references, 1 table

  8. Oxygen transfer materials with catalytic properties for biomass gasification[Dissertation 17302

    Energy Technology Data Exchange (ETDEWEB)

    Pecho, J.

    2007-06-15

    By application of olivine as bed material in a biomass gasifier such as the FICFB type (Fast Internal Circulating Fluidized Bed) in Guessing, Austria, an improvement of the gasification process was observed. Reduction of tars was measured and oxygen increase in the process was calculated. However, it took a while before these properties became clear. Aim of the project was to elucidate the mechanism with which olivine influences the system and to find a new material with improved properties for the gasification process. There were some factors which had be taken into account, e.g., amount of free lattice oxygen, reaction enthalpy, selectivity, mechanical and chemical stability, costs, desulphurization and decarbonisation. Several studies have shown that natural olivine ((Fe{sub x}Mg{sub 1-x}){sub 2}SiO{sub 4}) lowers tar formation in fluidized bed gasification of biomass. According to most authors, the phenomenon is related to the presence of iron oxide (Fe{sub 2}O{sub 3}) which is, e.g., formed during the calcination of olivine in air. To elucidate the role of the iron oxide, synthetic olivine with a molar ratio of Fe:Mg equal to unity has been exposed to gases that contained either wet methane or wet toluene as the only carbon source in a thermobalance interfaced to on-line gas analysis. The results provide strong evidence that the conversion of the carbon species is dominated by the stoichiometric reaction of binary iron oxide with hydrocarbons in the beginning of the reaction while catalytic reactions such as steam reforming contribute little to the observed tar reduction. This reaction path straightforwardly explains the influence of the olivine's origin or the pre-treatment on its chemical reactivity as it was reported by the various authors. To improve the catalytic properties and oxygen capacity of bed materials, we put our focus on perovskite type oxides La{sub x}Sr{sub 1-x}Cr{sub y}Mn{sub 1-y}O{sub 3} and Ba{sub 0.3}Sr{sub 0.7}Fe{sub 0.9}Mn{sub 0.1}O

  9. Cyanogel-derived N-doped C nanosheets immobilizing Pd-P nanoparticles: One-pot synthesis and enhanced hydrogenation catalytic performance

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hao; Yan, Xiaohong; Huang, Yundi; Zhang, Mengru; Tang, Yawen; Sun, Dongmei; Xu, Lin, E-mail: njuxulin@gmail.com; Wei, Shaohua, E-mail: weishaohua@njnu.edu.cn

    2017-02-28

    Highlights: • Cyanogel-bridged approach was developed for the synthesis of Pd-P@N-Cnanosheets. • Pd-P@N-C nanosheets exhibit high activity and stability for reduction of 4-NP. • Compositional and structural advantages account for the high catalytic activity. • The feasible synthesis could be extendable to other carbon-based nanohybrids. - Abstract: For Pd-based nanocatalysts, stabilization of Pd nanoparticles on carbon support could not only effectively avoid particle aggregation and maintain catalytic stability during catalytic processes, but also facilitate enhancing the catalytic activity due to the synergy between Pd nanoparticles and carbon support. Furthermore, the incorporation of non-metal of phosphorus (P) into Pd could effectively modulate the electronic structure of Pd and thus help to boost the catalytic properties. However, one-pot synthesis of such nanohybrids remains a great challenge due to the distinct physiochemical properties of Pd, P and C components. Herein, we demonstrate a one-pot and scalable synthesis of highly dispersed PdP alloy nanoparticle-immobilized on N-doped graphitic carbon nanosheets (abbreviated as Pd-P@N-C nanosheets) by using inorganic-organic hybrid cyanogel as a reaction precursor. In virtue of both compositional and structural advantages, the as-synthesized Pd-P@N-C nanosheets manifest a superior catalytic activity and stability toward the hydrogenation of 4-nitrophenol (4-NP). We believe that the present work will provide a feasible and versatile strategy for the development of efficient catalysts for environmental remediation and can also be extendable to other carbon-based nanohybrids with desirable functionalities.

  10. Characterization of Porphyrin-Co(III)-‘Nitrene Radical’ Species Relevant in Catalytic Nitrene Transfer Reactions

    OpenAIRE

    Goswami, Monalisa; Lyaskovskyy, Volodymyr; Domingos, Sérgio R.; Buma, Wybren Jan; Woutersen, Sander; Troeppner, Oliver; Ivanović-Burmazović, Ivana; Lu, Hongjian; Cui, Xin; Zhang, X. Peter; Reijerse, Edward J.; DeBeer, Serena; van Schooneveld, Matti M.; Pfaff, Florian Felix; Ray, Kallol

    2015-01-01

    To fully characterize the CoIII–‘nitrene radical’ species that are proposed as intermediates in nitrene transfer reactions mediated by cobalt(II) porphyrins, different combinations of cobalt(II) complexes of porphyrins and nitrene transfer reagents were combined, and the generated species were studied using EPR, UV–vis, IR, VCD, UHR-ESIMS, and XANES/XAFS measurements. Reactions of cobalt-(II) porphyrins 1P1 (P1 = meso-tetraphenylporphyrin (TPP)) and 1P2 (P2 = 3,5-DitBu-ChenPhyrin) with organi...

  11. Study of reactive transfer of hydrogen within intact clay-rock

    International Nuclear Information System (INIS)

    Didier, M.

    2012-01-01

    Hydrogen gas will be produced by anaerobic corrosion of radioactive waste containers in the geological repository. This gas could affect the geological layer (Callovo-Oxfordian) stability, first due to its reductive capacity and then also due to its continuous production for about 100,000 years. The local pressure increase could affect the properties of hydro-gaseous dynamic of hydrogen transfers. The reductive capacity of H 2 could change the redox properties of the Callovo-Oxfordian and the barrier hydraulic properties, and therefore (1) its mineralogy, (2) the speciation of outgoing radionuclides and (3) their transfer. Moreover, if the hydrogen gas transport is difficult within the geological layer, the pressure increase could cause cracking and create preferential pathways for radionuclides migration. An experimental device was developed to measure the entry pressure of H 2 (g) and transport parameters as permeability and diffusion coefficient through the CO x . The entry pressure is estimated to be between 49 and 63 bar. Knowing that the maximum expected pressure is about 80 bar, there may therefore be a displacement of hydrogen gas into the water saturated clay-rock. Moreover, for a saturation greater than 0.90 and at T = 23 C, permeability is measured to be close to 10 -23 m 2 and the diffusion coefficient to be as low as 10 -12 m 2 .s -1 . Therefore hydrogen gas will move slowly in the geological layer, for example it will take about 31,710 years to go through one meter of clay-rock by diffusion. These transport parameters are found to depend mainly on the sample water saturation and not much on temperature. Regarding hydrogen reactivity, under conditions close to those in the storage, H 2 will reduce up to 9 wt% of structural Fe (III) at 90 C and PH 2 = 5 bar. This reaction is not complete and hydrogen gas will mainly sorb on the material, with a sorption up to 0.05 wt% at 90 C and PH 2 = 0.45 bar. This process depends strongly on the water saturation of

  12. Reactivity of hydropersulfides toward the hydroxyl radical unraveled: disulfide bond cleavage, hydrogen atom transfer, and proton-coupled electron transfer.

    Science.gov (United States)

    Anglada, Josep M; Crehuet, Ramon; Adhikari, Sarju; Francisco, Joseph S; Xia, Yu

    2018-02-14

    Hydropersulfides (RSSH) are highly reactive as nucleophiles and hydrogen atom transfer reagents. These chemical properties are believed to be key for them to act as antioxidants in cells. The reaction involving the radical species and the disulfide bond (S-S) in RSSH, a known redox-active group, however, has been scarcely studied, resulting in an incomplete understanding of the chemical nature of RSSH. We have performed a high-level theoretical investigation on the reactions of the hydroxyl radical (˙OH) toward a set of RSSH (R = -H, -CH 3 , -NH 2 , -C(O)OH, -CN, and -NO 2 ). The results show that S-S cleavage and H-atom abstraction are the two competing channels. The electron inductive effect of R induces selective ˙OH substitution at one sulfur atom upon S-S cleavage, forming RSOH and ˙SH for the electron donating groups (EDGs), whereas producing HSOH and ˙SR for the electron withdrawing groups (EWGs). The H-Atom abstraction by ˙OH follows a classical hydrogen atom transfer (hat) mechanism, producing RSS˙ and H 2 O. Surprisingly, a proton-coupled electron transfer (pcet) process also occurs for R being an EDG. Although for RSSH having EWGs hat is the leading channel, S-S cleavage can be competitive or even dominant for the EDGs. The overall reactivity of RSSH toward ˙OH attack is greatly enhanced with the presence of an EDG, with CH 3 SSH being the most reactive species found in this study (overall rate constant: 4.55 × 10 12 M -1 s -1 ). Our results highlight the complexity in RSSH reaction chemistry, the extent of which is closely modulated by the inductive effect of the substituents in the case of the oxidation by hydroxyl radicals.

  13. Influence of different preparation conditions on catalytic activity of ag /gama-al/sub 2/o/sub 3/ for hydrogenation of coal slime pyrolysis

    International Nuclear Information System (INIS)

    Lei, Z.; Rong, C.

    2014-01-01

    This paper, introducing variable conditional factors with Ag/AL/sub 2/O/sub 3/ as catalyst, selects five variables to investigate the influences of experimental conditions on Ag/Al2O/sub 3/ catalytic activity and define the optimal process conditions. These variables include Ag loading amount, calcinations temperature, calcinations time, reduction temperature, reduction time. X ray diffraction (XRD), hydrogen temperature-programmed reduction (TPR), X ray photoelectron spectrum (XPS) and scanning electron microscopy (SEM) were utilized to characterize the catalytic activity of Ag/-Al/sub 2/O/sub 3/, active center structure and state and those of carrier were emphatically studied, In the meantime the effects of active center and carrier on catalytic activity are studied. The results showed that: (1) In the range of 600 degree C-900 degree C, the catalytic activity of Ag/-Al/sub 2/O/sub 3/ with different loading showed little difference when changing loading amount, in the range of 900 degree C-1100 degree C, when the loading was 5%, the catalytic activity was very high; From the XRD and SEM characterizations, when the loading was 5%, it showed strong intensity diffraction peak of Ag crystal, crystal Ag is the most important activity center to promote hydrogen yield. (2) the catalytic activity of Ag/-Al/sub 2/O/sub 3/ at 450 degree C was considerably higher than that at 400 degree C and 500 degree C. By BET, XRD and SEM characterization, it can be seen, the diffraction peaks intensity of Ag crystal at 450 degree C is higher and sharper than that at 400 degree C and 500 degree C and with the increase of calcinations temperature, the specific surface area of catalysts also increased. (3) In the range of 600 degree C - 1000 degree C, the effects of calcinations time can be negligible, while, with temperature higher than 1000 degree C, 4-hour-calcinations-time catalyst exhibits a more noticeable catalytic activity than 3-hour and 5-hour catalyst do; From the XRD

  14. Kinetics and the mass transfer mechanism of hydrogen sulfide removal by biochar derived from rice hull.

    Science.gov (United States)

    Shang, Guofeng; Liu, Liang; Chen, Ping; Shen, Guoqing; Li, Qiwu

    2016-05-01

    The biochar derived from rice hull was evaluated for its abilities to remove hydrogen sulfide (H2S) from gas phase. The surface area and pH of the biochar were compared. The biochar derived from rice hull was evaluated for its abilities to remove hydrogen sulfide (H2S) from gas phase. The surface area and pH of the biochar were compared. The different pyrolysis temperature has great influence on the adsorption of H2S. At the different pyrolysis temperature, the H2S removal efficiency of rice hull-derived biochar was different. The adsorption capacities of biochar were 2.09 mg·g(-1), 2.65 mg·g(-1), 16.30 mg·g(-1), 20.80 mg·g(-1), and 382.70 mg·g(-1), which their pyrolysis temperatures were 100 °C, 200 °C, 300 °C, 400 °C and 500 °C respectively. Based on the Yoon-Nelson model, it analyzed the mass transfer mechanism of hydrogen sulfide adsorption by biochar. The paper focuses on the biochar derived from rice hull-removed hydrogen sulfide (H2S) from gas phase. The surface area and pH of the biochar were compared. The different pyrolysis temperatures have great influence on the adsorption of H2S. At the different pyrolysis temperatures, the H2S removal efficiency of rice hull-derived biohar was different. The adsorption capacities of biochar were 2.09, 2.65, 16.30, 20.80, and 382.70 mg·g(-1), and their pyrolysis temperatures were 100, 200, 300, 400, and 500 °C, respectively. Based on the Yoon-Nelson model, the mass transfer mechanism of hydrogen sulfide adsorption by biochar was analyzed.

  15. A 2-(2’-pyridylquinoline ruthenium(II complex as an active catalyst for the transfer hydrogenation of ketones

    Directory of Open Access Journals (Sweden)

    Zacharopoulos Nikolaos

    2016-01-01

    Full Text Available The ruthenium(II complex cis-[RuCl2(PPh32(L1] (1 where L1 = 2-(2’-pyridylquinoline was obtained in high yield from the reaction of [RuCl2(PPh33] with L1. The new compound was characterized by different spectroscopic methods including FT-IR, UV-Vis, NMR (1H, 31P spectroscopy along with a mass spectrometric analysis (ESI-MS and conductivity measurements. 31P NMR spectroscopy provided evidence that the two PPh3 ligands are orientated trans to each other in an octahedral environment. Complex (1 was tested in the transfer hydrogenation of various ketones in 2-propanol at 82 oC. The catalytic activity of (1 displayed quantitative conversions for benzophenone and 4-chloroacetophenone.

  16. Liquid oxygen/liquid hydrogen boost/vane pump for the advanced orbit transfer vehicles auxiliary propulsion system

    Science.gov (United States)

    Gluzek, F.; Mokadam, R. G.; To, I. H.; Stanitz, J. D.; Wollschlager, J.

    1979-01-01

    A rotating, positive displacement vane pump with an integral boost stage was designed to pump saturated liquid oxygen and liquid hydrogen for auxiliary propulsion system of orbit transfer vehicle. This unit is designed to ingest 10% vapor by volume, contamination free liquid oxygen and liquid hydrogen. The final pump configuration and the predicted performance are included.

  17. A comparative parametric study of a catalytic plate methane reformer coated with segmented and continuous layers of combustion catalyst for hydrogen production

    Science.gov (United States)

    Mundhwa, Mayur; Parmar, Rajesh D.; Thurgood, Christopher P.

    2017-03-01

    A parametric comparison study is carried out between segmented and conventional continuous layer configurations of the coated combustion-catalyst to investigate their influence on the performance of methane steam reforming (MSR) for hydrogen production in a catalytic plate reactor (CPR). MSR is simulated on one side of a thin plate over a continuous layer of nickel-alumina catalyst by implementing an experimentally validated surface microkinetic model. Required thermal energy for the MSR reaction is supplied by simulating catalytic methane combustion (CMC) on the opposite side of the plate over segmented and continuous layer of a platinum-alumina catalyst by implementing power law rate model. The simulation results of both coating configurations of the combustion-catalyst are compared using the following parameters: (1) co-flow and counter-flow modes between CMC and MSR, (2) gas hourly space velocity and (3) reforming-catalyst thickness. The study explains why CPR designed with the segmented combustion-catalyst and co-flow mode shows superior performance not only in terms of high hydrogen production but also in terms of minimizing the maximum reactor plate temperature and thermal hot-spots. The study shows that the segmented coating requires 7% to 8% less combustion-side feed flow and 70% less combustion-catalyst to produce the required flow of hydrogen (29.80 mol/h) on the reforming-side to feed a 1 kW fuel-cell compared to the conventional continuous coating of the combustion-catalyst.

  18. Effect of carrier nature and Pt concentration on catalytic properties of deposited catalysts with respect to reaction of homomolecular isotopic exchange of hydrogen

    International Nuclear Information System (INIS)

    Korabel'nikova, L.M.; Vasilevich, A.A.

    1987-01-01

    Effect of carrier (Al 2 O 3 and SiO 2 ) nature and Pt concentration in deposited catalysts with respect to reaction of homomolecular isotopic exchange (HMIE) of hydrogen at -196 deg C and 66,6 Pa (0.5 mm of mercury) is studied. Dependence of specific catalytic activity of Pt/Al 2 O 3 and Pt/SiO 2 on platinum concentration is shown. It is found that large platinum crystallites in Pt/SiO 2 system have higher activity than small ones. The carrier effect on catalytic and surface properties of deposited platinum is detected. The most noticeably the carrier effect is manifested in the ranges of small degrees of carrier surface filling with metal. Optimum platinum concentrations in Pt/Al 2 O 3 and Pt/SiO 2 catalysts for hyrogen HMIE reaction are determined

  19. Synthesis and use of an asymmetric transfer hydrogenation catalyst based on iron(II) for the synthesis of enantioenriched alcohols and amines.

    Science.gov (United States)

    Zuo, Weiwei; Morris, Robert H

    2015-02-01

    The catalytic hydrogenation of prochiral ketones and imines is an advantageous approach to the synthesis of enantioenriched alcohols and amines, respectively, which are two classes of compounds that are highly prized in pharmaceutical, fragrance and flavoring chemistry. This hydrogenation reaction is generally carried out using ruthenium-based catalysts. Our group has developed an alternative synthetic route that is based on the environmentally friendlier iron-based catalysis. This protocol describes the three-part synthesis of trans-[amine(imine)diphosphine]chlorocarbonyliron(II) tetrafluoroborate templated by iron salts and starting from commercially available chemicals, which provides the precatalyst for the efficient asymmetric transfer hydrogenation of ketones and imines. The use of the enantiopure (S,S) catalyst to reduce prochiral ketones to the (R)-alcohol in good to excellent yields and enantioenrichment is also detailed, as well as the reduction to the amine in very high yield and enantiopurity of imines substituted at the nitrogen with the N-(diphenylphosphinoyl) group (-P(O)Ph2). Although the best ruthenium catalysts provide alcohols in higher enantiomeric excess (ee) than the iron complex catalyst used in this protocol, they do so on much longer time scales or at higher catalyst loadings. This protocol can be completed in 2 weeks.

  20. Theoretical Investigation of the Enzymatic Phosphoryl Transfer of β-phosphoglucomutase: Revisiting Both Steps of the Catalytic Cycle

    Energy Technology Data Exchange (ETDEWEB)

    Elsasser, Brigitta M.; Dohmeier-Fischer, Silvia; Fels, Gregor

    2012-07-12

    Enzyme catalyzed phosphate transfer is a part of almost all metabolic processes. Such reactions are of central importance for the energy balance in all organisms and play important roles in cellular control at all levels. Mutases transfer a phosphoryl group while nucleases cleave the phosphodiester linkages between two nucleotides. The subject of our present study is the Lactococcus lactis β-phosphoglucomutase (β-PGM), which effectively catalyzes the interconversion of β-D-glucose-1-phosphate (β-G1P) to β- D-glucose-6-phosphate (β-G6P) and vice versa via stabile intermediate β-D-glucose-1,6-(bis)phosphate (β-G1,6diP) in the presence of Mg2+. In this paper we revisited the reaction mechanism of the phosphoryl transfer starting from the bisphosphate β-G1,6diP in both directions (toward β-G1P and β-G6P) combining docking techniques and QM/MM theoretical method at the DFT/PBE0 level of theory. In addition we performed NEB (nudged elastic band) and free energy calculations to optimize the path and to identify the transition states and the energies involved in the catalytic cycle. Our calculations reveal that both steps proceed via dissociative pentacoordinated phosphorane, which is not a stabile intermediate but rather a transition state. In addition to the Mg2+ ion, Ser114 and Lys145 also play important roles in stabilizing the large negative charge on the phosphate through strong coordination with the phosphate oxygens and guiding the phosphate group throughout the catalytic process. The calculated energy barrier of the reaction for the β-G1P to β-G1,6diP step is only slightly higher than for the β-G1,6diP to β-G6P step (16.10 kcal mol-1 versus 15.10 kcal mol-1) and is in excellent agreement with experimental findings (14.65 kcal mol-1).

  1. Solvent dependent asymmetric hydrogenation with self-assembled catalysts: a combined catalytic, NMR- and IR-study.

    Science.gov (United States)

    Shuklov, Ivan A; Dubrovina, Natalia V; Barsch, Enrico; Ludwig, Ralf; Michalik, Dirk; Börner, Armin

    2009-03-28

    For the first time the hydrogen bond based structure of self-aggregated Rh-phosphine complexes in fluorinated alcohols was directly determined, which gives a rationale for the high enantioselectivity observed in the asymmetric hydrogenation.

  2. Evaluation of heat transfer in a catalytic fixed bed reactor at high temperatures

    OpenAIRE

    JORGE,L. M. M.; JORGE,R. M. M.; FUJII,F.; GIUDICI,R.

    1999-01-01

    Experimental results of fixed-bed heat-transfer experiments with no chemical reaction are presented and discussed. The runs were carried out in a tubular integral reactor heated by an electrical furnace at temperatures in the range of 100 to 500°C. Experimental temperature profiles were determined for the electrical furnace, for the reactor wall, and for the fixed bed center. Industrial catalyst for the prereforming of hydrocarbons was employed as the packing material. The effects of process ...

  3. Numerical simulation of coupled heat and mass transfer in metal hydride-based hydrogen storage reactor

    International Nuclear Information System (INIS)

    Muthukumar, P.; Ramana, S. Venkata

    2009-01-01

    In this paper, a numerical investigation of two-dimensional heat and mass transfer during absorption of hydrogen in a cylindrical metal hydride bed containing MmNi 6.4 Al 0.4 is presented. By considering the variation in cooling fluid temperature along the axial direction (variable wall temperature), the changes in hydrogen concentration, hydride equilibrium pressure, and average hydride bed temperature at different axial locations are presented. The average bed temperature profiles and hydrogen storage capacities at different supply pressures showed good agreement with the experimental data reported in the literature. As the absorption progresses, the change in cooling fluid temperature along the axial direction is found to decrease and becomes unchanged at the end of the absorption process. The effect of variable wall temperature on hydrogen absorption rate for different supply pressures and hydride bed thicknesses are presented. The effect of variable wall temperature on absorption time is found to be significant for the hydride beds of thickness of above 7.5 mm. For a supply pressure of 20 bar, the maximum difference in absorption time between variable wall temperature and constant wall temperature boundary conditions is about 300 s for 17.5 mm bed thickness

  4. Comparative investigation of surface transfer doping of hydrogen terminated diamond by high electron affinity insulators

    Energy Technology Data Exchange (ETDEWEB)

    Verona, C.; Marinelli, Marco; Verona-Rinati, G. [Dip. di Ingegneria Industriale, Università di Roma “Tor Vergata,” Via del Politecnico 1, I-00133 Roma (Italy); Ciccognani, W.; Colangeli, S.; Limiti, E. [Dip. di Ingegneria Elettronica, Università di Roma “Tor Vergata,” Via del Politecnico 1, I-00133 Roma (Italy)

    2016-07-14

    We report on a comparative study of transfer doping of hydrogenated single crystal diamond surface by insulators featured by high electron affinity, such as Nb{sub 2}O{sub 5}, WO{sub 3}, V{sub 2}O{sub 5}, and MoO{sub 3}. The low electron affinity Al{sub 2}O{sub 3} was also investigated for comparison. Hole transport properties were evaluated in the passivated hydrogenated diamond films by Hall effect measurements, and were compared to un-passivated diamond films (air-induced doping). A drastic improvement was observed in passivated samples in terms of conductivity, stability with time, and resistance to high temperatures. The efficiency of the investigated insulators, as electron accepting materials in hydrogenated diamond surface, is consistent with their electronic structure. These surface acceptor materials generate a higher hole sheet concentration, up to 6.5 × 10{sup 13} cm{sup −2}, and a lower sheet resistance, down to 2.6 kΩ/sq, in comparison to the atmosphere-induced values of about 1 × 10{sup 13} cm{sup −2} and 10 kΩ/sq, respectively. On the other hand, hole mobilities were reduced by using high electron affinity insulator dopants. Hole mobility as a function of hole concentration in a hydrogenated diamond layer was also investigated, showing a well-defined monotonically decreasing trend.

  5. Catalytic Hydrogenation of the Sweet Principles of Stevia rebaudiana, Rebaudioside B, Rebaudioside C, and Rebaudioside D and Sensory Evaluation of Their Reduced Derivatives

    Science.gov (United States)

    Prakash, Indra; Campbell, Mary; Chaturvedula, Venkata Sai Prakash

    2012-01-01

    Catalytic hydrogenation of rebaudioside B, rebaudioside C, and rebaudioside D; the three ent-kaurane diterpene glycosides isolated from Stevia rebaudiana was carried out using Pd(OH)2. Reduction of steviol glycosides was performed using straightforward synthetic chemistry with the catalyst Pd(OH)2 and structures of the corresponding dihydro derivatives were characterized on the basis of 1D and 2D nuclear magnetic resonance (NMR) spectral data indicating that all are novel compounds being reported for the first time. Also, the taste properties of all reduced compounds were evaluated against their corresponding original steviol glycosides and sucrose. PMID:23203115

  6. Isotactic and Syndiotactic Alternating Ethylene/Propylene Copolymers Obtained Through Non-Catalytic Hydrogenation of Highly Stereoregular cis-1,4 Poly(1,3-diene)s.

    Science.gov (United States)

    Ricci, Giovanni; Boccia, Antonella Caterina; Leone, Giuseppe; Pierro, Ivana; Zanchin, Giorgia; Scoti, Miriam; Auriemma, Finizia; De Rosa, Claudio

    2017-05-06

    The homogeneous non-catalytic hydrogenation of cis -1,4 poly(isoprene), isotactic cis -1,4 poly(1,3-pentadiene) and syndiotactic cis -1,4 poly(1,3-pentadiene) with diimide, formed by thermal decomposition of para -toluenesulfonylhydrazide, is examined. Perfectly alternating ethylene/propylene copolymers having different tacticity (i.e., isotactic and syndiotactic), which are difficult to synthesize by stereospecific copolymerization of the corresponding monomers, are obtained. Both isotactic and syndiotactic alternating ethylene/propylene copolymers are amorphous, with very low glass transition temperatures.

  7. Metal-Free Catalytic Asymmetric Fluorination of Keto Esters Using a Combination of Hydrogen Fluoride (HF) and Oxidant: Experiment and Computation

    KAUST Repository

    Pluta, Roman

    2018-02-09

    A chiral iodoarene organocatalyst for the catalytic asymmetric fluorination has been developed. The catalyst was used in the asymmetric fluorination of carbonyl compounds, providing the products with a quaternary stereocenter with high enantioselectivities. Chiral hypervalent iodine difluoride intermediates were generated in situ by treatment of the catalyst with an oxidant and hydrogen fluoride as fluoride source. As such, the α-fluorination of a carbonyl compound was achieved with a nucleophilic fluorine source. A combined computational and experimental approach provided insight into the reaction mechanism and the origin of enantioselectivity.

  8. Catalytic Hydrogenation of the Sweet Principles of Stevia rebaudiana, Rebaudioside B, Rebaudioside C, and Rebaudioside D and Sensory Evaluation of Their Reduced Derivatives

    Directory of Open Access Journals (Sweden)

    Mary Campbell

    2012-11-01

    Full Text Available Catalytic hydrogenation of rebaudioside B, rebaudioside C, and rebaudioside D; the three ent-kaurane diterpene glycosides isolated from Stevia rebaudiana was carried out using Pd(OH2. Reduction of steviol glycosides was performed using straightforward synthetic chemistry with the catalyst Pd(OH2 and structures of the corresponding dihydro derivatives were characterized on the basis of 1D and 2D nuclear magnetic resonance (NMR spectral data indicating that all are novel compounds being reported for the first time. Also, the taste properties of all reduced compounds were evaluated against their corresponding original steviol glycosides and sucrose.

  9. Redox-inactive metal ions promoted the catalytic reactivity of non-heme manganese complexes towards oxygen atom transfer.

    Science.gov (United States)

    Choe, Cholho; Yang, Ling; Lv, Zhanao; Mo, Wanling; Chen, Zhuqi; Li, Guangxin; Yin, Guochuan

    2015-05-21

    Redox-inactive metal ions can modulate the reactivity of redox-active metal ions in a variety of biological and chemical oxidations. Many synthetic models have been developed to help address the elusive roles of these redox-inactive metal ions. Using a non-heme manganese(II) complex as the model, the influence of redox-inactive metal ions as a Lewis acid on its catalytic efficiency in oxygen atom transfer was investigated. In the absence of redox-inactive metal ions, the manganese(II) catalyst is very sluggish, for example, in cyclooctene epoxidation, providing only 9.9% conversion with 4.1% yield of epoxide. However, addition of 2 equiv. of Al(3+) to the manganese(II) catalyst sharply improves the epoxidation, providing up to 97.8% conversion with 91.4% yield of epoxide. EPR studies of the manganese(II) catalyst in the presence of an oxidant reveal a 16-line hyperfine structure centered at g = 2.0, clearly indicating the formation of a mixed valent di-μ-oxo-bridged diamond core, Mn(III)-(μ-O)2-Mn(IV). The presence of a Lewis acid like Al(3+) causes the dissociation of this diamond Mn(III)-(μ-O)2-Mn(IV) core to form monomeric manganese(iv) species which is responsible for improved epoxidation efficiency. This promotional effect has also been observed in other manganese complexes bearing various non-heme ligands. The findings presented here have provided a promising strategy to explore the catalytic reactivity of some di-μ-oxo-bridged complexes by adding non-redox metal ions to in situ dissociate those dimeric cores and may also provide clues to understand the mechanism of methane monooxygenase which has a similar diiron diamond core as the intermediate.

  10. Enantioselective Iridium Catalyzed Carbonyl Allylation from the Alcohol Oxidation Level via Transfer Hydrogenation: Minimizing Pre-Activation for Synthetic Efficiency

    Science.gov (United States)

    Han, Soo Bong; Kim, In Su; Krische, Michael J.

    2010-01-01

    Existing methods for enantioselective carbonyl allylation, crotylation and tert-prenylation require stoichiometric generation of pre-metallated nucleophiles and often employ stoichiometric chiral modifiers. Under the conditions of transfer hydrogenation employing an ortho-cyclometallated iridium C,O-benzoate catalyst, enantioselective carbonyl allylations, crotylations and tert-prenylations are achieved in the absence of stoichiometric metallic reagents or stoichiometric chiral modifiers. Moreover, under transfer hydrogenation conditions, primary alcohols function dually as hydrogen donors and aldehyde precursors, enabling enantioselective carbonyl addition directly from the alcohol oxidation level. PMID:20024203

  11. Natural spectroscopic hydrogen isotope transfer in alcohol dehydrogenase-catalysed reduction

    International Nuclear Information System (INIS)

    Ben-Li Zhang; Pionnier, S.

    2002-01-01

    The enantiomeric purity of natural α-mono deuterated enantiomers, (R) and (S)ethanol-1-d 1 , in the alcohol produced by sugar fermentation with yeast was studied by 2 H NMR using their esters derived from optical mandelic acid. The results of isotope tracing experiments show that the transfer pathways of the two eantiotopic hydrogens of the methylene group are different. It was observed that (S)-deuterium comes only from the medium water. The (R)-deuterium transferred by NADH in alcohol dehydrogenase reduction of the acetaldehyde is complex origin. Some of them originates from carbon bound hydrogen of the sugar, especially from C(4) position of glucose and most of them comes from water. Only a small portion of the NADH deuterium is incorporated indirectly from water through enzyme catalysed exchange between the pro-S site of NADH and flavin. When a carbonyl compound (ethyl acetoacetate) was reduced under the same conditions during the alcoholic fermentation, among the NADH-transferred deuterium, only a small portion comes from water while most comes from the unexchangeable positions of the glucose. (author)

  12. High Surface Area Tungsten Carbides: Synthesis, Characterization and Catalytic Activity towards the Hydrogen Evolution Reaction in Phosphoric Acid at Elevated Temperatures

    DEFF Research Database (Denmark)

    Tomás García, Antonio Luis; Li, Qingfeng; Jensen, Jens Oluf

    2014-01-01

    Tungsten carbide powders were synthesized as a potential electrocatalyst for the hydrogen evolution reaction in phosphoric acid at elevated temperatures. With ammonium metatungstate as the precursor, two synthetic routes with and without carbon templates were investigated. Through the intermediate...... nitride route and with carbon black as template, the obtained tungsten carbide samples had higher BET area. In 100% H3PO4 at temperatures up to 185°C, the carbide powders showed superior activity towards the hydrogen evolution reaction. A deviation was found in the correlation between the BET area...... and catalytic activity; this was attributed to the presence of excess amorphous carbon in the carbide powder. TEM imaging and TGA-DTA results revealed a better correlation of the activity with the carbide particle size....

  13. Understanding the role of water in aqueous ruthenium-catalyzed transfer hydrogenation of ketones.

    Science.gov (United States)

    Pavlova, Anna; Meijer, Evert Jan

    2012-10-22

    We report an accurate computational study of the role of water in transfer hydrogenation of formaldehyde with a ruthenium-based catalyst using a water-specific model. Our results suggest that the reaction mechanism in aqueous solution is significantly different from that in the gas phase or in methanol solution. Previous theoretical studies have shown a concerted hydride and proton transfer in the gas phase (M. Yamakawa, H. Ito, R. Noyori, J. Am. Chem. Soc. 2000, 122, 1466-1478;J.-W. Handgraaf, J. N. H. Reek, E. J. Meijer, Organometallics 2003, 22, 3150-3157; D. A. Alonso, P. Brandt, S. J. M. Nordin, P. G. Andersson, J. Am. Chem. Soc. 1999, 121, 9580-9588; D. G. I. Petra, J. N. H. Reek, J.-W. Handgraaf, E. J. Meijer, P. Dierkes, P. C. J. Kamer, J. Brussee, H. E. Schoemaker, P. W. N. M. van Leeuwen, Chem. Eur. J. 2000, 6, 2818-2829), whereas a delayed, solvent-mediated proton transfer has been observed in methanol solution (J.-W. Handgraaf, E. J. Meijer, J. Am. Chem. Soc. 2007, 129, 3099-3103). In aqueous solution, a concerted transition state is observed, as in the previous studies. However, only the hydride is transferred at that point, whereas the proton is transferred later by a water molecule instead of the catalyst. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Sensitive non-radioactive determination of aminotransferase stereospecificity for C-4' hydrogen transfer on the coenzyme.

    Science.gov (United States)

    Jomrit, Juntratip; Summpunn, Pijug; Meevootisom, Vithaya; Wiyakrutta, Suthep

    2011-02-25

    A sensitive non-radioactive method for determination of the stereospecificity of the C-4' hydrogen transfer on the coenzymes (pyridoxal phosphate, PLP; and pyridoxamine phosphate, PMP) of aminotransferases has been developed. Aminotransferase of unknown stereospecificity in its PLP form was incubated in (2)H(2)O with a substrate amino acid resulted in PMP labeled with deuterium at C-4' in the pro-S or pro-R configuration according to the stereospecificity of the aminotransferase tested. The [4'-(2)H]PMP was isolated from the enzyme protein and divided into two portions. The first portion was incubated in aqueous buffer with apo-aspartate aminotransferase (a reference si-face specific enzyme), and the other was incubated with apo-branched-chain amino acid aminotransferase (a reference re-face specific enzyme) in the presence of a substrate 2-oxo acid. The (2)H at C-4' is retained with the PLP if the aminotransferase in question transfers C-4' hydrogen on the opposite face of the coenzyme compared with the reference aminotransferase, but the (2)H is removed if the test and reference aminotransferases catalyze hydrogen transfer on the same face. PLP formed in the final reactions was analyzed by LC-MS/MS for the presence or absence of (2)H. The method was highly sensitive that for the aminotransferase with ca. 50 kDa subunit molecular weight, only 2mg of the enzyme was sufficient for the whole test. With this method, the use of radioactive substances could be avoided without compromising the sensitivity of the assay. Copyright © 2011 Elsevier Inc. All rights reserved.

  15. Some recent results on μ-transfer in systems with bound hydrogen

    International Nuclear Information System (INIS)

    Knight, J.D.; Mausner, L.F.; Orth, C.J.; Schillaci, M.E.; Naumann, R.A.; Schmidt, G.

    1977-01-01

    Preliminary results are given for two sets of experiments conducted in order to obtain information on the role of bound hydrogen in possible μ transfer processes by comparisons of muonic Lyman spectra. Muonic x-ray intensity patterns of Cl in CCl 4 , CH 2 Cl 2 and a CCl 4 + C 8 H 18 mixture. Secondly the same type of experiment was performed but with F as the test element. Muonic x-ray spectra of the normal and deutero forms of a compound were compared

  16. Intramolecular hydrogen bond in molecular and proton-transfer forms of Schiff bases

    Energy Technology Data Exchange (ETDEWEB)

    Filarowski, A.; Koll, A.; Karpfen, A.; Wolschann, P

    2004-02-16

    The force field and structural parameters modifications upon the formation of intramolecular hydrogen bond and proton transfer reaction in N-methyl-2-hydroxybenzylidene amine (HBZA) are determined on the basis of ab initio and DFT calculations. Reliability of the calculations is verified by comparing of the theoretical vibrational spectra with those experimentally determined in the gas phase. A model of resonance interactions is applied and the quantitative contribution of ortho-quinoid structure in the particular conformers is estimated. A comparison is also made to the systems without {pi}-electron coupling (Mannich bases)

  17. Ionization and Charge Transfer of Atomic Hydrogen by Highly Charged Ions

    Science.gov (United States)

    Ding, Bao-Wei; Hu, Bi-Tao

    2010-04-01

    Cross sections for charge transfer and ionization of atomic hydrogen by highly charged ions Aq+ (q = 6-9) are evaluated using a simple and classical method based on the previous works by Bohr and Lindhard [K. Dan. Vidensk. Selsk. Mat. Fys. Medd 28 (1954) No 7], Brandt [Nucl. Instrum. Methods Phys. Res. 214 (1983) 93] and Ben-Itzhak et al. [J. Phys. B: At. Mol. Opt. Phys. 26 (1993) 1711]. It is proved that the present calculations are feasible to some extent in comparison with available experimental data and quantum calculations.

  18. Bane of Hydrogen-Bond Formation on the Photoinduced Charge-Transfer Process in Donor–Acceptor Systems

    KAUST Repository

    Alsam, Amani Abdu

    2017-03-14

    Controlling the ultrafast dynamical process of photoinduced charge transfer at donor acceptor interfaces remains a major challenge for physical chemistry and solar cell communities. The process is complicated by the involvement of other complex dynamical processes, including hydrogen bond formation, energy transfer, and solvation dynamics occurring on similar time scales. In this study, we explore the remarkable impact of hydrogen-bond formation on the interfacial charge transfer between a negatively charged electron donating anionic porphyrin and a positively charged electron accepting pi-conjugated polymer, as a model system in solvents with different polarities and capabilities for hydiogen bonding using femtosecond transient absorption spectroscopy. Unlike the conventional understanding of the key role of hydrogen bonding in promoting the charge-transfer process, our steadystate and time-resolved results reveal that the intervening hydrogen-bonding environment and, consequently, the probable longer spacing between the donor and acceptor molecules significantly hinders the charge-transfer process between them. These results show that site-specific hydrogen bonding and geometric considerations between donor and acceptor can be exploited to control both the charge-transfer dynamics and its efficiency not only at donor acceptor interfaces but also in complex biological systems.

  19. Microscopic models for proton transfer in water and strongly hydrogen-bonded complexes with a single-well proton potential

    DEFF Research Database (Denmark)

    Kuznetsov, A.M.; Ulstrup, Jens

    2004-01-01

    A new mechanism and formalism for proton transfer in donor-acceptor complexes with long hydrogen bonds introduced recently [1], is applied to a proton transfer in liquid water. "Structural diffusion" of hydroxonium ions is regarded as totally adiabatic process, with synchronous hindered translation...... of two closest water molecules to and from the reaction complex as crucial steps. The water molecules induce a "gated" shift of the proton from the donor to the acceptor in the double-well potential with simultaneous breaking/formation of hydrogen bonds between these molecules and the proton donor...... and acceptor. The short-range and long-range proton transfer as "structural diffusion" of Zundel complexes is also considered. The theoretical formalism is illustrated with the use of Morse, exponential, and harmonic molecular potentials. This approach is extended to proton transfer in strongly hydrogen...

  20. Design and assembly of a catalyst bed gas generator for the catalytic decomposition of high concentration hydrogen peroxide propellants and the catalytic combustion of hydrocarbon/air mixtures

    Science.gov (United States)

    Lohner, Kevin A. (Inventor); Mays, Jeffrey A. (Inventor); Sevener, Kathleen M. (Inventor)

    2004-01-01

    A method for designing and assembling a high performance catalyst bed gas generator for use in decomposing propellants, particularly hydrogen peroxide propellants, for use in target, space, and on-orbit propulsion systems and low-emission terrestrial power and gas generation. The gas generator utilizes a sectioned catalyst bed system, and incorporates a robust, high temperature mixed metal oxide catalyst. The gas generator requires no special preheat apparatus or special sequencing to meet start-up requirements, enabling a fast overall response time. The high performance catalyst bed gas generator system has consistently demonstrated high decomposition efficiency, extremely low decomposition roughness, and long operating life on multiple test articles.

  1. Porphyrin Cobalt(III “Nitrene Radical” Reactivity; Hydrogen Atom Transfer from Ortho-YH Substituents to the Nitrene Moiety of Cobalt-Bound Aryl Nitrene Intermediates (Y = O, NH

    Directory of Open Access Journals (Sweden)

    Monalisa Goswami

    2016-02-01

    Full Text Available In the field of cobalt(II porphyrin-catalyzed metallo-radical reactions, organic azides have emerged as successful nitrene transfer reagents. In the pursuit of employing ortho-YH substituted (Y = O, NH aryl azides in Co(II porphyrin-catalyzed nitrene transfer reactions, unexpected hydrogen atom transfer (HAT from the OH or NH2 group in the ortho-position to the nitrene moiety of the key radical-intermediate was observed. This leads to formation of reactive ortho-iminoquinonoid (Y = O and phenylene diimine (Y = NH species. These intermediates convert to subsequent products in non-catalyzed reactions, as is typical for these free organic compounds. As such, the observed reactions prevent the anticipated cobalt-mediated catalytic radical-type coupling of the nitrene radical intermediates to alkynes or alkenes. Nonetheless, the observed reactions provide valuable insights into the reactivity of transition metal nitrene-radical intermediates, and give access to ortho-iminoquinonoid and phenylene diimine intermediates from ortho-YH substituted aryl azides in a catalytic manner. The latter can be employed as intermediates in one-pot catalytic transformations. From the ortho-hydroxy aryl azide substrates both phenoxizinones and benzoxazines could be synthesized in high yields. From the ortho-amino aryl azide substrates azabenzene compounds were obtained as the main products. Computational studies support these observations, and reveal that HAT from the neighboring OH and NH2 moiety to the nitrene radical moiety has a low energy barrier.

  2. Agro-industrial waste-mediated synthesis and characterization of gold and silver nanoparticles and their catalytic activity for 4-nitroaniline hydrogenation

    Energy Technology Data Exchange (ETDEWEB)

    Dauthal, Preeti; Mukhopadhyay, Mausumi [S.V. National Institute of Technology, Surat (India)

    2015-05-15

    The biosynthesis of gold (Au-NPs) and silver nanoparticles (Ag-NPs) using agro-industrial waste Citrus aurantifolia peel extract as a bio-reducing agent is reported. Catalytic activity of nanoparticles (NPs) was evaluated for hydrogenation of anthropogenic pollutant 4-nitroaniline (4-NA). Both synthesized NPs were nearly spherical and distributed in size range of 6-46 and 10-32 nm for Au-NPs and Ag-NPs, respectively. XRD analysis revealed face centered cubic (fcc) structure of both NPs. ζ potential value obtained from colloidal solution of Au-NPs and Ag-NPs was −28.0 and −26.1mV, respectively, indicating the stability of the NPs in colloidal solution. FTIR spectra supported the role of citric and ascorbic acids of peel extract for biosynthesis and stabilization of NPs. The biosynthesized NPs exhibited excellent catalytic activity for hydrogenation of 4-NA in the presence of NaBH{sub 4}.

  3. Dependence of Vibronic Coupling on Molecular Geometry and Environment: Bridging Hydrogen Atom Transfer and Electron–Proton Transfer

    Science.gov (United States)

    2016-01-01

    The rate constants for typical concerted proton-coupled electron transfer (PCET) reactions depend on the vibronic coupling between the diabatic reactant and product states. The form of the vibronic coupling is different for electronically adiabatic and nonadiabatic reactions, which are associated with hydrogen atom transfer (HAT) and electron–proton transfer (EPT) mechanisms, respectively. Most PCET rate constant expressions rely on the Condon approximation, which assumes that the vibronic coupling is independent of the nuclear coordinates of the solute and the solvent or protein. Herein we test the Condon approximation for PCET vibronic couplings. The dependence of the vibronic coupling on molecular geometry is investigated for an open and a stacked transition state geometry of the phenoxyl-phenol self-exchange reaction. The calculations indicate that the open geometry is electronically nonadiabatic, corresponding to an EPT mechanism that involves significant electronic charge redistribution, while the stacked geometry is predominantly electronically adiabatic, corresponding primarily to an HAT mechanism. Consequently, a single molecular system can exhibit both HAT and EPT character. The dependence of the vibronic coupling on the solvent or protein configuration is examined for the soybean lipoxygenase enzyme. The calculations indicate that this PCET reaction is electronically nonadiabatic with a vibronic coupling that does not depend significantly on the protein environment. Thus, the Condon approximation is shown to be valid for the solvent and protein nuclear coordinates but invalid for the solute nuclear coordinates in certain PCET systems. These results have significant implications for the calculation of rate constants, as well as mechanistic interpretations, of PCET reactions. PMID:26412613

  4. Hydrogen production from cheese whey by catalytic steam reforming: Preliminary study using lactose as a model compound

    International Nuclear Information System (INIS)

    Remón, J.; Laseca, M.; García, L.; Arauzo, J.

    2016-01-01

    Highlights: • Steam reforming of lactose: a promising strategy for cheese whey management. • Thermodynamic and experimental analyses of the effect of the operating conditions. • Reaction pathway showing the formation of the most important gas and liquid products. • Technical/energetic assessment: H 2 rich gas, C-free liquid and neutral energy process. - Abstract: Cheese whey is a yellowish liquid by-product of the cheese making process. Owing to its high BOD and COD values, this feedstock should not be directly discharged into the environment without appropriate treatment. Before dealing with real cheese whey, this work addresses the production of a rich hydrogen gas from lactose (the largest organic constituent of this waste) by catalytic steam reforming. This reforming process has been theoretically and experimentally studied. The theoretical study examines the effect of the temperature (300–600 °C), lactose concentration (1–10 wt.%) and N 2 (0–80 cm 3 STP/min) and liquid flow (0.1–0.5 mL/min) rates on the thermodynamic composition of the gas. The results show that the temperature and lactose concentration exerted the greatest influence on the thermodynamics. The experimental study, conducted in a fixed bed reactor using a Ni-based catalyst, considers the effect of the temperature (300–600 °C), lactose concentration (1–10 wt.%) and spatial time (4–16 g catalyst min/g lactose) on the global lactose conversion, product distribution on a carbon basis (gas, liquid and solid) and the compositions of the gas and liquid phases. Complete lactose conversion was achieved under all the experimental conditions. The carbon converted into gas, liquid and solid was 2–97%, 0–66% and 0–94%, respectively. The gas phase was made up of a mixture of H 2 (0–70 vol.%), CO 2 (20–70 vol.%), CO (2–34 vol.%) and CH 4 (0–3 vol.%). The liquid phase consisted of a mixture of aldehydes, ketones, carboxylic acids, sugars, furans, alcohols and phenols

  5. Excitation and charge transfer in low-energy hydrogen atom collisions with neutral oxygen

    Science.gov (United States)

    Barklem, P. S.

    2018-02-01

    Excitation and charge transfer in low-energy O+H collisions is studied; it is a problem of importance for modelling stellar spectra and obtaining accurate oxygen abundances in late-type stars including the Sun. The collisions have been studied theoretically using a previously presented method based on an asymptotic two-electron linear combination of atomic orbitals (LCAO) model of ionic-covalent interactions in the neutral atom-hydrogen-atom system, together with the multichannel Landau-Zener model. The method has been extended to include configurations involving excited states of hydrogen using an estimate for the two-electron transition coupling, but this extension was found to not lead to any remarkably high rates. Rate coefficients are calculated for temperatures in the range 1000-20 000 K, and charge transfer and (de)excitation processes involving the first excited S-states, 4s.5So and 4s.3So, are found to have the highest rates. Data are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/vizbin/qcat?J/A+A/610/A57. The data are also available at http://https://github.com/barklem/public-data

  6. Electrochemical catalytic reforming of oxygenated-organic compounds: a highly efficient method for production of hydrogen from bio-oil.

    Science.gov (United States)

    Yuan, Lixia; Chen, Yaqiong; Song, Chongfu; Ye, Tongqi; Guo, Qingxiang; Zhu, Qingshi; Torimoto, Youshifumi; Li, Quanxin

    2008-11-07

    A novel approach to produce hydrogen from bio-oil was obtained with high carbon conversion (>90%) and hydrogen yield (>90%) at Tcatalytic reforming of oxygenated-organic compounds over 18%NiO/Al(2)O(3) reforming catalyst; thermal electrons play important promoting roles in the decomposition and reforming of the oxygenated-organic compounds in the bio-oil.

  7. Catalytic mechanisms of direct pyrrole synthesis via dehydrogenative coupling mediated by PNP-Ir or PNN-Ru pincer complexes: Crucial role of proton-transfer shuttles in the PNP-Ir system

    KAUST Repository

    Qu, Shuanglin

    2014-04-02

    Kempe et al. and Milstein et al. have recently advanced the dehydrogenative coupling methodology to synthesize pyrroles from secondary alcohols (e.g., 3) and β-amino alcohols (e.g., 4), using PNP-Ir (1) and PNN-Ru (2) pincer complexes, respectively. We herein present a DFT study to characterize the catalytic mechanism of these reactions. After precatalyst activation to give active 1A/2A, the transformation proceeds via four stages: 1A/2A-catalyzed alcohol (3) dehydrogenation to give ketone (11), base-facilitated C-N coupling of 11 and 4 to form an imine-alcohol intermediate (18), base-promoted cyclization of 18, and catalyst regeneration via H2 release from 1R/2R. For alcohol dehydrogenations, the bifunctional double hydrogen-transfer pathway is more favorable than that via β-hydride elimination. Generally, proton-transfer (H-transfer) shuttles facilitate various H-transfer processes in both systems. Notwithstanding, H-transfer shuttles play a much more crucial role in the PNP-Ir system than in the PNN-Ru system. Without H-transfer shuttles, the key barriers up to 45.9 kcal/mol in PNP-Ir system are too high to be accessible, while the corresponding barriers (<32.0 kcal/mol) in PNN-Ru system are not unreachable. Another significant difference between the two systems is that the addition of alcohol to 1A giving an alkoxo complex is endergonic by 8.1 kcal/mol, whereas the addition to 2A is exergonic by 8.9 kcal/mol. The thermodynamic difference could be the main reason for PNP-Ir system requiring lower catalyst loading than the PNN-Ru system. We discuss how the differences are resulted in terms of electronic and geometric structures of the catalysts and how to use the features in catalyst development. © 2014 American Chemical Society.

  8. Intermolecular hydrogen transfer catalyzed by a flavodehydrogenase, bakers' yeast flavocytochrome b2

    International Nuclear Information System (INIS)

    Urban, P.; Lederer, F.

    1985-01-01

    Bakers yeast flavocytochrome b2 is a flavin-dependent L-2-hydroxy acid dehydrogenase which also exhibits transhydrogenase activity. When a reaction takes place between [2- 3 H]lactate and a halogenopyruvate, tritium is found in water and at the halogenolactate C2 position. When the halogenopyruvate undergoes halide ion elimination, tritium is also found at the C3 position of the resulting pyruvate. The amount tau of this intermolecular tritium transfer depends on the initial keto acid-acceptor concentration. At infinite acceptor concentration, extrapolation yields a maximal transfer of 97 +/- 11%. This indicates that the hydroxy acid-derived hydrogen resides transiently on enzyme monoprotic heteroatoms and that exchange with bulk solvent occurs only at the level of free reduced enzyme. Using a minimal kinetic scheme, the rate constant for hydrogen exchange between Ered and solvent is calculated to be on the order of 10(2) M-1 S-1, which leads to an estimated pK approximately equal to 15 for the ionization of the substrate-derived proton while on the enzyme. It is suggested that this hydrogen could be shared between the active site base and Flred N5 anion. It is furthermore shown that some tritium is incorporated into the products when the transhydrogenation is carried out in tritiated water. Finally, with [2-2H]lactate-reduced enzyme, a deuterium isotope effect is observed on the rate of bromopyruvate disappearance. Extrapolation to infinite bromopyruvate concentration yields DV = 4.4. An apparent inverse isotope effect is determined for bromide ion elimination. These results strengthen the idea that oxidoreduction and elimination pathways involve a common carbanionic intermediate

  9. Catalytic Layer Optimization for Hydrogen Permeation Membranes Based on La5.5WO11.25-δ/La0.87Sr0.13CrO3-δComposites.

    Science.gov (United States)

    Escolástico, Sonia; Solı S, Cecilia; Kjølseth, Christian; Serra, Jose Manuel

    2017-10-18

    (LWO/LSC) composite is one of the most promising mixed ionic-electronic conducting materials for hydrogen separation at high temperature. However, these materials present limited catalytic surface activity toward H 2 activation and water splitting, which determines the overall H 2 separation rate. For the implementation of these materials as catalytic membrane reactors, effective catalytic layers have to be developed that are compatible and stable under the reaction conditions. This contribution presents the development of catalytic layers based on sputtered metals (Cu and Pd), electrochemical characterization by impendace spectroscopy, and the study of the H 2 flow obtained by coating them on 60/40-LWO/LSC membranes. Stability of the catalytic layers is also evaluated under H 2 permeation conditions and CH 4 -containing atmospheres.

  10. The analysis of mixtures of ortho and para-hydrogen and the catalytic conversion o.H2 → p.H2

    International Nuclear Information System (INIS)

    Botter, F.; Dirian, G.

    1956-01-01

    This report describes experiments undertaken to measure the catalytic activity at - 195 deg. C of different types of absorbents for the heterogeneous conversion o.H 2 → p.H 2 . The analytical method employed is a differential measurement of the thermal conductivity of the gas. In contrast to the classic method of FARKAS we have worked at room temperature (the difference of several per cent between the thermal conductivities of ortho and para-hydrogen at this temperature being found sufficiently great) and with a continuously recording system. The gas is at atmospheric pressure. We have investigated also the possibilities of an industrial katharometer which would allow a great extension to be given to this method of analysis. The instrument proved satisfactory. It has been checked that the paramagnetic conversion obeys first order kinetics. A certain number of absorbing substances were tested and amongst them, the active carbons, often used in the laboratory for the production of para-hydrogen, were shown to be the least active. A chromium oxide-aluminium oxide catalyst prepared from data available in the literature had a very great activity. In addition, some observations of the influence of adsorbed gases on the catalytic activity are reported: the comparison with the literature data is not easy due to the uncertainty in the physico-chemical nature of the absorbents used in the two cases. Finally, some bibliographic data relative to the properties of the two forms of hydrogen, their measurement, and the different mechanisms of interconversion are given. (author) [fr

  11. Experimental and Numerical Evaluation of the By-Pass Flow in a Catalytic Plate Reactor for Hydrogen Production

    DEFF Research Database (Denmark)

    Sigurdsson, Haftor Örn; Kær, Søren Knudsen

    2011-01-01

    increases. The numerical results are in good agreement with experimental data. The study improves the understanding of the underlying transport phenomena in these reactors and shows that the flow maldistribution in a catalytic plate reactor using a coated wire mesh has to be considered....

  12. In Situ Catalytic Upgrading of Heavy Crude with CAPRI: Influence of Hydrogen on Catalyst Pore Plugging and Deactivation due to Coke

    Directory of Open Access Journals (Sweden)

    Abarasi Hart

    2018-03-01

    Full Text Available Heavy crude oil is known to have low hydrogen-to-carbon ratios compared to light oil. This is due to the significant content of carbon-rich species such as resins and asphaltenes; hence their upgrading is commonly through carbon-rejection. However, carbon-rejection promotes rapid fouling of catalyst and pore plugging, yielding low upgraded oil and consequently low fuel distillate fractions when distilled. The roles of hydrogen-addition on in situ catalytic upgrading were investigated at pre-established conditions (425 °C, LHSV 11.8 h−1, and 20–40 bars using a simulated fixed-bed reactor that mimics the annular sheath of catalyst (CAPRI surrounding the horizontal producer well of the Toe-to-Heel Air Injection (THAI process. It was found that with H-addition, the upgraded oil American Petroleum Institute (API gravity increased to about 5° compared to 3° obtained with N2 above 13° (THAI feed oil. The fuel distillate fractions increased to 62% (N2, 20 bar, 65% (H2, 20 bar, and 71.8% (H2, 30 bar relative to 40.6% (THAI feed oil; while the coke contents of the catalyst after experiments were 35.3 wt % (N2, and 27.2 wt % (H2. It was also found that catalyst pore plugging and deactivation due to coke was significantly lower under hydrogen than with nitrogen; hence the catalyst is less susceptible to coke fouling when the upgrading reaction is carried out under hydrogen. The coke fouling further decreases with increasing hydrogen pressure while the API gravity of the upgraded oil marginally increases by 0.3° for every 10 bar increase in pressure from 20 to 40 bar.

  13. Catalytic Hydrogenation of Levulinic Acid in Water into g-Valerolactone over Bulk Structure of Inexpensive Intermetallic Ni-Sn Alloy Catalysts

    Directory of Open Access Journals (Sweden)

    Rodiansono Rodiansono

    2015-07-01

    Full Text Available A bulk structure of inexpensive intermetallic nickel-tin (Ni-Sn alloys catalysts demonstrated highly selective in the hydrogenation of levulinic acid in water into g-valerolactone. The intermetallic Ni-Sn catalysts were synthesized via a very simple thermochemical method from non-organometallic precursor at low temperature followed by hydrogen treatment at 673 K for 90 min. The molar ratio of nickel salt and tin salt was varied to obtain the corresponding Ni/Sn ratio of 4.0, 3.0, 2.0, 1.5, and 0.75. The formation of Ni-Sn alloy species was mainly depended on the composition and temperature of H2 treatment. Intermetallics Ni-Sn that contain Ni3Sn, Ni3Sn2, and Ni3Sn4 alloy phases are known to be effective heterogeneous catalysts for levulinic acid hydrogenation giving very excellence g-valerolactone yield of >99% at 433 K, initial H2 pressure of 4.0 MPa within 6 h. The effective hydrogenation was obtained in H2O without the formation of by-product. Intermetallic Ni-Sn(1.5 that contains Ni3Sn2 alloy species demonstrated very stable and reusable catalyst without any significant loss of its selectivity. © 2015 BCREC UNDIP. All rights reserved. Received: 26th February 2015; Revised: 16th April 2015; Accepted: 22nd April 2015  How to Cite: Rodiansono, R., Astuti, M.D., Ghofur, A., Sembiring, K.C. (2015. Catalytic Hydrogenation of Levulinic Acid in Water into g-Valerolactone over Bulk Structure of Inexpensive Intermetallic Ni-Sn Alloy Catalysts. Bulletin of Chemical Reaction Engineering & Catalysis, 10 (2: 192-200. (doi:10.9767/bcrec.10.2.8284.192-200Permalink/DOI: http://dx.doi.org/10.9767/bcrec.10.2.8284.192-200  

  14. Flow injection determination of hydrogen peroxide using catalytic effect of cobalt(II) ion on a dye formation reaction.

    Science.gov (United States)

    Kurihara, Makoto; Muramatsu, Miyuki; Yamada, Mari; Kitamura, Naoya

    2012-07-15

    A novel flow injection photometric method was developed for the determination of hydrogen peroxide in rainwater. This method is based on a cobalt(II)-catalyzed oxidative coupling of 3-methyl-2-benzothiazolinone hydrazone (MBTH) with N-ethyl-N-(2-hydroxy-3-sulfopropyl)-3,5-dimethoxyaniline (DAOS) as a modified Trinder's reagent to produce intensely colored dye (λ(max)=530nm) in the presence of hydrogen peroxide at pH 8.4. In this method, 1,2-dihydroxy-3,5-benzenedisulfonic acid (Tiron) acted as an activator for the cobalt(II)-catalyzed reaction and effectively increased the peak height for hydrogen peroxide. The linear calibration graphs were obtained in the hydrogen peroxide concentration range 5×10(-8) to 2.2×10(-6)mol dm(-3) at a sampling rate of 20h(-1). The relative standard deviations for ten determinations of 2.2×10(-6) and 2×10(-7)mol dm(-3) hydrogen peroxide were 1.1% and 3.7%, respectively. The proposed method was successfully applied to the determination of hydrogen peroxide in rainwater samples and the analytical results agreed fairly well with the results obtained by different two reference methods; peroxidase method and hydrogen peroxide electrode method. Copyright © 2012 Elsevier B.V. All rights reserved.

  15. Analysis of phosphoinositide 3-kinase inhibitors by bottom-up electron-transfer dissociation hydrogen/deuterium exchange mass spectrometry

    OpenAIRE

    Masson, Glenn R.; Maslen, Sarah L.; Williams, Roger L.

    2017-01-01

    Until recently, one of the major limitations of hydrogen/deuterium exchange mass spectrometry (HDX-MS) was the peptide-level resolution afforded by proteolytic digestion. This limitation can be selectively overcome through the use of electron-transfer dissociation to fragment peptides in a manner that allows the retention of the deuterium signal to produce hydrogen/deuterium exchange tandem mass spectrometry (HDX-MS/MS). Here, we describe the application of HDX-MS/MS to structurally screen in...

  16. Use of Alkyl Ethers as Traceless Hydride Donors in Brønsted Acid-Catalyzed Intramolecular Hydrogen Atom Transfer.

    Science.gov (United States)

    Gandamana, Dhika Aditya; Wang, Bin; Tejo, Ciputra; Bolte, Benoit; Gagosz, Fabien; Chiba, Shunsuke

    2018-03-25

    A new protocol for the deoxygenation of alcohols and the hydrogenation of alkenes under Brønsted acid catalysis has been developed. The method is based on the use of a benzyl or an isopropyl ether as a traceless hydrogen atom donor and involves an intramolecular hydride transfer as a key step that can be achieved in regio- and stereoselective manners. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Mutagenesis Study of the Cytochrome c Subunit Responsible for the Direct Electron Transfer-Type Catalytic Activity of FAD-Dependent Glucose Dehydrogenase

    Directory of Open Access Journals (Sweden)

    Yuki Yamashita

    2018-03-01

    Full Text Available The FAD-dependent glucose dehydrogenase from Burkholderia cepacia (FADGDH is a hetero-oligomeric enzyme that is capable of direct electron transfer (DET with an electrode. The cytochrome c (cyt c subunit, which possesses three hemes (heme 1, heme 2, and heme 3, from the N-terminal sequence, is known to enable DET; however, details of the electron transfer pathway remain unknown. A mutagenesis investigation of the heme axial ligands was carried out to elucidate the electron transfer pathway to the electron mediators and/or the electrode. The sixth axial ligand for each of the three heme irons, Met109, Met263, and Met386 were substituted with His. The catalytic activities of the wild-type (WT and mutant enzymes were compared by investigating their dye-mediated dehydrogenase activities and their DET abilities toward the electrode. The results suggested that (1 heme 1 with Met109 as an axial ligand is mainly responsible for the electron transfer with electron acceptors in the solution, but not for the DET with the electrode; (2 heme 2 with Met263 is responsible for the DET-type reaction with the electrode; and (3 heme 3 with Met386 seemed to be the electron acceptor from the catalytic subunit. From these results, two electron transfer pathways were proposed depending on the electron acceptors. Electrons are transferred from the catalytic subunit to heme 3, then to heme 2, to heme 1 and, finally, to electron acceptors in solution. However, if the enzyme complex is immobilized on the electrode and is used as electron acceptors, electrons are passed to the electrode from heme 2.

  18. A non-adiabatic quantum-classical dynamics study of the intramolecular excited state hydrogen transfer in ortho-nitrobenzaldehyde.

    Science.gov (United States)

    Leyva, Verónica; Corral, Inés; Feixas, Ferran; Migani, Annapaola; Blancafort, Lluís; González-Vázquez, Jesús; González, Leticia

    2011-08-28

    Ab initio surface-hopping dynamics calculations have been performed to simulate the intramolecular excited state hydrogen transfer dynamics of ortho-nitrobenzaldehyde (o-NBA) in the gas phase from the electronic S(1) excited state. Upon UV excitation, the hydrogen is transferred from the aldehyde substituent to the nitro group, generating o-nitrosobenzoic acid through a ketene intermediate. The semiclassical propagations show that the deactivation from the S(1) is ultrafast, in agreement with the experimental measurements, which detect the ketene in less than 400 fs. The trajectories show that the deactivation mechanism involves two different conical intersections. The first one, a planar configuration with the hydrogen partially transferred, is responsible for the branching between the formation of a biradical intermediate and the regeneration of the starting material. The conversion of the biradical to the ketene corresponds to the passage through a second intersection region in which the ketene group is formed.

  19. Efficient and Adaptive Methods for Computing Accurate Potential Surfaces for Quantum Nuclear Effects: Applications to Hydrogen-Transfer Reactions.

    Science.gov (United States)

    DeGregorio, Nicole; Iyengar, Srinivasan S

    2018-01-09

    We present two sampling measures to gauge critical regions of potential energy surfaces. These sampling measures employ (a) the instantaneous quantum wavepacket density, an approximation to the (b) potential surface, its (c) gradients, and (d) a Shannon information theory based expression that estimates the local entropy associated with the quantum wavepacket. These four criteria together enable a directed sampling of potential surfaces that appears to correctly describe the local oscillation frequencies, or the local Nyquist frequency, of a potential surface. The sampling functions are then utilized to derive a tessellation scheme that discretizes the multidimensional space to enable efficient sampling of potential surfaces. The sampled potential surface is then combined with four different interpolation procedures, namely, (a) local Hermite curve interpolation, (b) low-pass filtered Lagrange interpolation, (c) the monomial symmetrization approximation (MSA) developed by Bowman and co-workers, and (d) a modified Shepard algorithm. The sampling procedure and the fitting schemes are used to compute (a) potential surfaces in highly anharmonic hydrogen-bonded systems and (b) study hydrogen-transfer reactions in biogenic volatile organic compounds (isoprene) where the transferring hydrogen atom is found to demonstrate critical quantum nuclear effects. In the case of isoprene, the algorithm discussed here is used to derive multidimensional potential surfaces along a hydrogen-transfer reaction path to gauge the effect of quantum-nuclear degrees of freedom on the hydrogen-transfer process. Based on the decreased computational effort, facilitated by the optimal sampling of the potential surfaces through the use of sampling functions discussed here, and the accuracy of the associated potential surfaces, we believe the method will find great utility in the study of quantum nuclear dynamics problems, of which application to hydrogen-transfer reactions and hydrogen

  20. Hydrogen atom transfer reactions in thiophenol: photogeneration of two new thione isomers.

    Science.gov (United States)

    Reva, Igor; Nowak, Maciej J; Lapinski, Leszek; Fausto, Rui

    2015-02-21

    Photoisomerization reactions of monomeric thiophenol have been investigated for the compound isolated in low-temperature argon matrices. The initial thiophenol population consists exclusively of the thermodynamically most stable thiol form. Phototransformations were induced by irradiation of the matrices with narrowband tunable UV light. Irradiation at λ > 290 nm did not induce any changes in isolated thiophenol molecules. Upon irradiation at 290-285 nm, the initial thiol form of thiophenol converted into its thione isomer, cyclohexa-2,4-diene-1-thione. This conversion occurs by transfer of an H atom from the SH group to a carbon atom at the ortho position of the ring. Subsequent irradiation at longer wavelengths (300-427 nm) demonstrated that this UV-induced hydrogen-atom transfer is photoreversible. Moreover, upon irradiation at 400-425 nm, the cyclohexa-2,4-diene-1-thione product converts, by transfer of a hydrogen atom from the ortho to para position, into another thione isomer, cyclohexa-2,5-diene-1-thione. The latter thione isomer is also photoreactive and is consumed if irradiated at λ atom-transfer isomerization reactions dominate the unimolecular photochemistry of thiophenol confined in a solid argon matrix. A set of low-intensity infrared bands, observed in the spectra of UV irradiated thiophenol, indicates the presence of a phenylthiyl radical with an H- atom detached from the SH group. Alongside the H-atom-transfer and H-atom-detachment processes, the ring-opening photoreaction occurred in cyclohexa-2,4-diene-1-thione by the cleavage of the C-C bond at the alpha position with respect to the thiocarbonyl C[double bond, length as m-dash]S group. The resulting open-ring conjugated thioketene adopts several isomeric forms, differing by orientations around single and double bonds. The species photogenerated upon UV irradiation of thiophenol were identified by comparison of their experimental infrared spectra with the spectra theoretically calculated for

  1. On the role of metal particle size and surface coverage for photo-catalytic hydrogen production; a case study of the Au/CdS system

    KAUST Repository

    Majeed, I.

    2015-09-25

    Photo-catalytic hydrogen production has been studied on Au supported CdS catalysts under visible light irradiation in order to understand the effect of Au particle size as well as the reaction medium properties. Au nanoparticles of size about 2-5 nm were deposited over hexagonal CdS particles using a new simple method involving reduction of Au3+ ions with iodide ions. Within the investigated range of Au (between 1 and 5 wt. %) fresh particles with mean size of 4 nm and XPS Au4f/Cd3d surface ratio of 0.07 showed the highest performance (ca. 1 molecule of H2 / Auatom s−1) under visible light irradiation (>420 nm and a flux of 35 mW/cm2). The highest hydrogen production rate was obtained from water (92%)-ethanol (8%) in an electrolyte medium (Na2S-Na2SO3). TEM studies of fresh and used catalysts showed that Au particle size increases (almost 5 fold) with increasing photo-irradiation time due to photo-agglomeration effect yet no sign of deactivation was observed. A mechanism for hydrogen production from ethanol-water electrolyte mixture is presented and discussed.

  2. When Do Strongly Coupled Diradicals Show Strongly Coupled Reactivity? Thermodynamics and Kinetics of Hydrogen Atom Transfer Reactions of Palladium and Platinum Bis(iminosemiquinone) Complexes.

    Science.gov (United States)

    Conner, Kyle M; Arostegui, AnnaMaria C; Swanson, Daniel D; Brown, Seth N

    2018-03-08

    The 2,2'-biphenylene-bridged bis(iminosemiquinone) complexes ( t BuClip)M [ t BuClipH 4 = 4,4'-di- tert-butyl- N, N'-bis(3,5-di- tert-butyl-2-hydroxyphenyl)-2,2'-diaminobiphenyl; M = Pd, Pt] can be reduced to the bis(aminophenoxide) complexes ( t BuClipH 2 )M by reaction with hydrazobenzene (M = Pd) or by catalytic hydrogenation (M = Pt). The palladium complex with one aminophenoxide ligand and one iminosemiquinone ligand, ( t BuClipH)Pd, is generated by comproportionation of ( t BuClip)Pd with ( t BuClipH 2 )Pd in a process that is both slow (0.06 M -1 s -1 in toluene at 23 °C) and only modestly favorable ( K com = 1.9 in CDCl 3 ), indicating that both N-H bonds have essentially the same bond strength. The mono(iminoquinone) complex ( t BuClipH)Pt has not been observed, indicating that the platinum analogue shows no tendency to comproportionate ( K com < 0.1). The average bond dissociation free energies (BDFE) of the complexes have been established by equilibration with suitably substituted hydrazobenzenes, and the palladium bis(iminosemiquinone) is markedly more oxidizing than the platinum compound, with hydrogen transfer from ( t BuClipH 2 )Pt to ( t BuClip)Pd occurring with Δ G° = -8.9 kcal mol -1 . The palladium complex ( t BuClipH 2 )Pd reacts with nitroxyl radicals in two observable steps, with the first hydrogen transfer taking place slightly faster than the second. In the platinum analogue, the first hydrogen transfer is much slower than the second, presumably because the N-H bond in the monoradical complex ( t BuClipH)Pt is unusually weak. Using driving force-rate correlations, it is estimated that this bond has a BDFE of 55.1 kcal mol -1 , which is 7.1 kcal mol -1 weaker than that of the first N-H bond in ( t BuClipH 2 )Pt. The two radical centers in the platinum, but not the palladium, complex thus act in concert with each other and display a strong thermodynamic bias toward two-electron reactivity. The greater thermodynamic and kinetic coupling in

  3. Concerted hydrogen atom and electron transfer mechanism for catalysis by lysine-specific demethylase.

    Science.gov (United States)

    Yu, Tao; Higashi, Masahiro; Cembran, Alessandro; Gao, Jiali; Truhlar, Donald G

    2013-07-18

    We calculate the free energy profile for the postulated hydride transfer reaction mechanism for the catalysis of lysine demethylation by lysine-specific demethylase LSD1. The potential energy surface is obtained by using combined electrostatically embedded multiconfiguration molecular mechanics (EE-MCMM) and single-configuration molecular mechanics (MM). We employ a constant valence bond coupling term to obtain analytical energies and gradients of the EE-MCMM subsystem, which contains 45 quantum mechanics (QM) atoms and which is parametrized with density functional calculations employing specific reaction parameters obtained by matching high-level wave function calculations. In the MM region, we employ the Amber ff03 and TIP3P force fields. The free energy of activation at 300 K is calculated by molecular dynamics (MD) umbrella sampling on a system with 102,090 atoms as the maximum of the free energy profile along the reaction coordinate as obtained by the weighted histogram analysis method with 17 umbrella sampling windows. This yields a free energy of activation of only 10 kcal/mol, showing that the previously postulated direct hydride transfer reaction mechanism is plausible, although we find that it is better interpreted as a concerted transfer of a hydrogen atom and an electron.

  4. Palladium-Catalyzed Atom-Transfer Radical Cyclization at Remote Unactivated C(sp3 )-H Sites: Hydrogen-Atom Transfer of Hybrid Vinyl Palladium Radical Intermediates.

    Science.gov (United States)

    Ratushnyy, Maxim; Parasram, Marvin; Wang, Yang; Gevorgyan, Vladimir

    2018-03-01

    A novel mild, visible-light-induced palladium-catalyzed hydrogen atom translocation/atom-transfer radical cyclization (HAT/ATRC) cascade has been developed. This protocol involves a 1,5-HAT process of previously unknown hybrid vinyl palladium radical intermediates, thus leading to iodomethyl carbo- and heterocyclic structures. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Kinetics of liquid-phase catalytic heterogeneous protium-tritium isotope exchange with participation of gaseous hydrogen

    International Nuclear Information System (INIS)

    Akulov, G.P.; Snetkova, E.V.; Kayumov, V.G.; Kaminskij, Yu.L.

    1990-01-01

    Reaction rate constants of catalytic (PdO/BaSO 4 (Al 2 O 3 ) catalyst) heterogeneous protium - tritium isotopic exchange D - [1- 3 H] of carbohydrates and gaseous oxygen have been measured. It is ascertained that the rate of isotopic exchange depends on the nature of carbohydrate, catalyst, buffer and medium acidity. The value of concentration of carbohydrate acyclic forms plays the determining role in the process

  6. Protein hydrogen exchange measured at single-residue resolution by electron transfer dissociation mass spectrometry

    DEFF Research Database (Denmark)

    Rand, Kasper D; Zehl, Martin; Jensen, Ole Nørregaard

    2009-01-01

    Because of unparalleled sensitivity and tolerance to protein size, mass spectrometry (MS) has become a popular method for measuring the solution hydrogen (1H/2H) exchange (HX) of biologically relevant protein states. While incorporated deuterium can be localized to different regions by pepsin...... proteolysis of the labeled protein, the assignment of deuteriums to individual residues is typically not obtained, thereby limiting a detailed understanding of HX and the dynamics of protein structure. Here we use gas-phase fragmentation of peptic peptides by electron transfer dissociation (ETD) to measure...... the HX of individual amide linkages in the amyloidogenic protein beta2-microglobulin. A comparison of the deuterium levels of 60 individual backbone amides of beta2-microglobulin measured by HX-ETD-MS analysis to the corresponding values measured by NMR spectroscopy shows an excellent correlation...

  7. Hydrogen transfer experiments and modelization in clay rocks for radioactive waste deep geological repository

    International Nuclear Information System (INIS)

    Boulin, P.

    2008-10-01

    Gases will be generated by corrosion of high radioactive waste containers in deep geological repositories. A gas phase will be generated. Gas pressure will build up and penetrated the geological formation. If gases do not penetrate the geological barrier efficiently, the pressure build up may create a risk of fracturing and of creation of preferential pathways for radionuclide migration. The present work focuses on Callovo-Oxfordian argillites characterisation. An experiment, designed to measure very low permeabilities, was used with hydrogen/helium and analysed using the Dusty Gas Model. Argillites close to saturation have an accessible porosity to gas transfer that is lower than 0,1% to 1% of the porosity. Analysis of the Knudsen effect suggests that this accessible network should be made of 50 nm to 200 nm diameter pores. The permeabilities values were integrated to an ANDRA operating model. The model showed that the maximum pressure expected near the repository would be 83 bar. (author)

  8. CH···π interactions do not contribute to hydrogen transfer catalysis by glycerol dehydratase.

    Science.gov (United States)

    Liu, Yuemin; Gallo, August A; Xu, Wu; Bajpai, Rakesh; Florián, Jan

    2011-10-20

    The role of the nonbonded CH···π interaction in the hydrogen abstraction from glycerol by the coenzyme B(12)-independent glycerol dehydratase (GDH) was examined using the QM/MM (ONIOM), MP2, and CCSD(T) methods. The studied CH···π interaction included the hydrogen atom of the -C(2)H(OH)- group of the glycerol substrate and the tyrosine-339 residue of the dehydratase. A contribution of this interaction to the stabilization of the transition state for the transfer of a hydrogen atom from the adjacent terminal C(1)H(2)(OH) group to cysteine 433 was determined by ab initio HF, MP2, and CCSD(T) calculations with the aug-cc-pvDZ basis set for the corresponding methane/benzene, methanol/phenol, and glycerol radical/phenol subsystems. The calculated CH···π distance, defined as the distance between the H atom and the center of the phenol ring, shortened from 2.62 to 2.52 Å upon going from the ground- to the transition-state of the GDH-catalyzed reaction. However, this shortening was not accompanied by the expected lowering of the CH···π interaction free energy. Instead, this interaction remained weak (about -1 kcal/mol) along the entire reaction coordinate. Additionally, the mutual orientation of the CH group and the phenol ring did not change significantly during the reaction. These results suggest that the phenol group of the tyrosine-339 does not contribute to lowering the activation barrier in the enzyme, but do not exclude the possibility that tyrosine 339 facilitates proper orientation of glycerol for the electrostatic catalysis, or inhibits side-reactions of the reactive glycerol radical intermediate.

  9. Insight into the mechanism revealing the peroxidase mimetic catalytic activity of quaternary CuZnFeS nanocrystals: colorimetric biosensing of hydrogen peroxide and glucose

    Science.gov (United States)

    Dalui, Amit; Pradhan, Bapi; Thupakula, Umamahesh; Khan, Ali Hossain; Kumar, Gundam Sandeep; Ghosh, Tanmay; Satpati, Biswarup; Acharya, Somobrata

    2015-05-01

    Artificial enzyme mimetics have attracted immense interest recently because natural enzymes undergo easy denaturation under environmental conditions restricting practical usefulness. We report for the first time chalcopyrite CuZnFeS (CZIS) alloyed nanocrystals (NCs) as novel biomimetic catalysts with efficient intrinsic peroxidase-like activity. Novel peroxidase activities of CZIS NCs have been evaluated by catalytic oxidation of the peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2). CZIS NCs demonstrate the synergistic effect of elemental composition and photoactivity towards peroxidase-like activity. The quaternary CZIS NCs show enhanced intrinsic peroxidase-like activity compared to the binary NCs with the same constituent elements. Intrinsic peroxidase-like activity has been correlated with the energy band position of CZIS NCs extracted using scanning tunneling spectroscopy and ultraviolet photoelectron spectroscopy. Kinetic analyses indicate Michaelis-Menten enzyme kinetic model catalytic behavior describing the rate of the enzymatic reaction by correlating the reaction rate with substrate concentration. Typical color reactions arising from the catalytic oxidation of TMB over CZIS NCs with H2O2 have been utilized to establish a simple and sensitive colorimetric assay for detection of H2O2 and glucose. CZIS NCs are recyclable catalysts showing high efficiency in multiple uses. Our study may open up the possibility of designing new photoactive multi-component alloyed NCs as enzyme mimetics in biotechnology applications.Artificial enzyme mimetics have attracted immense interest recently because natural enzymes undergo easy denaturation under environmental conditions restricting practical usefulness. We report for the first time chalcopyrite CuZnFeS (CZIS) alloyed nanocrystals (NCs) as novel biomimetic catalysts with efficient intrinsic peroxidase-like activity. Novel peroxidase activities of CZIS NCs have been

  10. Effect of Copper Nanoparticles Dispersion on Catalytic Performance of Cu/SiO2 Catalyst for Hydrogenation of Dimethyl Oxalate to Ethylene Glycol

    Directory of Open Access Journals (Sweden)

    Yajing Zhang

    2013-01-01

    Full Text Available Cu/SiO2 catalysts, for the synthesis of ethylene glycol (EG from hydrogenation of dimethyl oxalate (DMO, were prepared by ammonia-evaporation and sol-gel methods, respectively. The structure, size of copper nanoparticles, copper dispersion, and the surface chemical states were investigated by X-ray diffraction (XRD, transmission electron microscopy (TEM, temperature-programmed reduction (TPR, and X-ray photoelectron spectroscopy (XPS and N2 adsorption. It is found the structures and catalytic performances of the catalysts were highly affected by the preparation method. The catalyst prepared by sol-gel method had smaller average size of copper nanoparticles (about 3-4 nm, better copper dispersion, higher Cu+/C0 ratio and larger BET surface area, and higher DMO conversion and EG selectivity under the optimized reaction conditions.

  11. Acid-Base Bifunctional Zirconium N-Alkyltriphosphate Nanohybrid for Hydrogen Transfer of Biomass-Derived Carboxides

    DEFF Research Database (Denmark)

    Li, Hu; He, Jian; Riisager, Anders

    2016-01-01

    sites, and their catalytic activity in converting biomass-derived carbonyl compounds to corresponding alcohols in 2-propanol. Particularly, a quantitative yield of furfuryl alcohol (FFA) was obtained from furfural (FUR) over organotriphosphate-zirconium hybrid (ZrPN) under mild conditions. The presence...... of Lewis basic sites adjacent to acid sites with an appropriate base/acid site ratio (1:0.7) in ZrPN significantly improved the yield of FFA. Mechanistic studies for the transformation of FUR to FFA with ZrPN in 2-propanol-d(8) evidently indicate CTH reaction proceeding via a direct intermolecular hydrogen...

  12. Ni(0-CMC-Na Nickel Colloids in Sodium Carboxymethyl-Cellulose: Catalytic Evaluation in Hydrogenation Reactions

    Directory of Open Access Journals (Sweden)

    Abdallah Karim

    2011-01-01

    Full Text Available A recyclable catalyst, Ni(0-CMC-Na, composed of nickel colloids dispersed in a water soluble bioorganic polymer, sodium carboxymethylcellulose (CMC-Na, was synthesized by a simple procedure from readily available reagents. The catalyst thus obtained is stable and highly active in alkene hydrogenations.

  13. Synthesis of (R)-BINOL-Derived (Cyclopentadienone)iron Complexes and Their Application in the Catalytic Asymmetric Hydrogenation of Ketones

    NARCIS (Netherlands)

    Gajewski, Piotr; Renom-Carrasco, Marc; Facchini, Sofia Vailati; Pignataro, Luca; Lefort, Laurent; de Vries, Johannes G.; Ferraccioli, Raffaella; Piarulli, Umberto; Gennari, Cesare

    A family of chiral (cyclopentadienone)iron complexes, featuring an (R)-BINOL-derived backbone, and their application in the asymmetric hydrogenation of ketones are described. The complexes differ from each other in the substituents at the 3,3-positions of the binaphthyl residue (H, OH, OR, OCOR,

  14. The Pt-enriched PtNi alloy surface and its excellent catalytic performance in hydrolytic hydrogenation of cellulose.

    Science.gov (United States)

    Liang, Guanfeng; He, Limin; Arai, Masahiko; Zhao, Fengyu

    2014-05-01

    Ni-based catalysts are currently a subject of intense research in the hydrolytic hydrogenation of cellulose. We previously reported that Ni/ZSM-5 catalyst gave high yield of hexitols. However, Ni-based catalysts suffered fast deactivation in hot-compressed water. In this follow-up study we designed highly active Ni-based bimetallic catalysts with excellent hydrothermal stability for the hydrolytic hydrogenation of microcrystalline cellulose. PtNi/ZSM-5 shows a 76.9 % yield of hexitols, which is the best obtained so far in the hydrolytic hydrogenation of microcrystalline cellulose over Ni-based catalysts. Furthermore, the yield of hexitols remained greater than 55 % after the catalyst was reused for 4 times. The results showed that PtNi nanoparticles were formed with a Pt-enriched alloy surface as confirmed by XRD, H2-TPR (temperature-programmed H2 reduction), XPS (X-ray photoelectron spectroscopy), and H2-TPD (temperature-programmed H2 desorption). The surface features of these nano-particles were characterized by CO-TPD (temperature-programmed CO desorption), CO-FTIR (CO adsorption FTIR spectroscopy), HRTEM (high resolution TEM), and O2-TPO (temperature programmed oxidation) and this special surface structure may be responsible for the high activity, selectivity, and stability in the hydrolytic hydrogenation of cellulose in hot-compressed water. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Pinpointing changes in higher-order protein structure by hydrogen/deuterium exchange coupled to electron transfer dissociation mass spectrometry

    DEFF Research Database (Denmark)

    Rand, Kasper Dyrberg

    2013-01-01

    This Feature describes the use of electron transfer dissociation (ETD) to analyze the hydrogen/deuterium exchange (HDX) of proteins at increased spatial resolution down to the level of individual residues. A practical overview of how to couple ETD to the classical bottom-up HDX-MS workflow is given...

  16. Asymmetric Transfer Hydrogenation of Ketones with Modified Grubbs Metathesis Catalysts : On the Way to a Tandem Process

    NARCIS (Netherlands)

    Renom-Carrasco, Marc; Gajewski, Piotr; Pignataro, Luca; de Vries, Johannes G.; Piarulli, Umberto; Gennari, Cesare; Lefort, Laurent

    2016-01-01

    Herein, we report the successful transformation of a 1(st) generation Grubbs metathesis catalyst into an asymmetric transfer hydrogenation (ATH) catalyst. Upon addition of a chiral amine ligand, an alcohol and a base, the 1(st) generation Hoveyda-Grubbs catalyst (HG-I) was found to promote the

  17. Revisiting the Meerwein-Ponndorf-Verley Reduction: A Sustainable Protocol for Transfer Hydrogenation of Aldehydes and Ketones

    Science.gov (United States)

    The metal-catalyzed transfer hydrogenation of carbonyl compounds has received much interest because of the immense number of opportunities that exist to prepare high-value products. This reaction is featured in numerous multi-step organic syntheses and is arguably the most import...

  18. Strong isotope effects on the charge transfer in slow collisions of He2+ with atomic hydrogen, deuterium, and tritium

    NARCIS (Netherlands)

    Stolterfoht, N.; Cabrera-Trujillo, R.; Oehrn, Y.; Deumens, E.; Hoekstra, R.; Sabin, J. R.

    2007-01-01

    Probabilities and cross sections for charge transfer by He2+ impact on atomic hydrogen (H), deuterium (D), and tritium (T) at low collision energies are calculated. The results are obtained using an ab initio theory, which solves the time-dependent Schrodinger equation. For the H target, excellent

  19. Synthetic use of the primary kinetic isotope effect in hydrogen atom transfer 2: generation of captodatively stabilised radicals.

    Science.gov (United States)

    Wood, Mark E; Bissiriou, Sabine; Lowe, Christopher; Windeatt, Kim M

    2013-04-28

    Using C-3 di-deuterated morpholin-2-ones bearing N-2-iodobenzyl and N-3-bromobut-3-enyl radical generating groups, only products derived from the more stabilised C-3, rather than the less stabilised C-5 translocated radicals, were formed after intramolecular 1,5-hydrogen atom transfer, suggesting that any kinetic isotope effect present was not sufficient to offset captodative stabilisation.

  20. A Au/Cu2O-TiO2 system for photo-catalytic hydrogen production. A pn-junction effect or a simple case of in situ reduction?

    KAUST Repository

    Sinatra, Lutfan

    2015-02-01

    Photo-catalytic H2 production from water has been studied over Au-Cu2O nanoparticle deposited on TiO2 (anatase) in order to probe into both the plasmon resonance effect (Au nanoparticles) and the pn-junction at the Cu2O-TiO2 interface. The Au-Cu2O composite is in the form of ∼10 nm Au nanoparticles grown on ∼475 nm Cu2O octahedral nanocrystals with (111) facets by partial galvanic replacement. X-ray Photoelectron Spectroscopy (XPS) Cu2p and Auger L3M4,5M4,5 lines indicate that the surface of Cu2O is mainly composed of Cu+. The rate for H2 production (from 95 water/5 ethylene glycol; vol.%) over 2 wt.% (Au/Cu2O)-TiO2 is found to be ∼10 times faster than that on 2 wt.% Au-TiO2 alone. Raman spectroscopy before and after reaction showed the disappearance of Cu+ lines (2Eu) at 220 cm-1. These observations coupled with the induction time observed for the reaction rate suggest that in situ reduction from Cu+ to Cu0 occurs upon photo-excitation. The reduction requires the presence of TiO2 (electron transfer). The prolonged activity of the reaction (with no signs of deactivation) despite the reduction to Cu0 indicates that the latter takes part in the reaction by providing additional sites for the reaction, most likely as recombination centers for hydrogen atoms to form molecular hydrogen. This phenomenon provides an additional route for enhancing the efficiency and lifetime of Cu2O-TiO2 photocatalytic systems, beyond the usually ascribed pn-junction effect.

  1. Catalytic Dehydrogenative Coupling of Hydrosilanes with Alcohols for the Production of Hydrogen On-demand: Application of a Silane/Alcohol Pair as a Liquid Organic Hydrogen Carrier.

    Science.gov (United States)

    Ventura-Espinosa, David; Carretero-Cerdán, Alba; Baya, Miguel; García, Hermenegildo; Mata, Jose A

    2017-08-10

    The compound [Ru(p-cym)(Cl) 2 (NHC)] is an effective catalyst for the room-temperature coupling of silanes and alcohols with the concomitant formation of molecular hydrogen. High catalyst activity is observed for a variety of substrates affording quantitative yields in minutes at room temperature and with a catalyst loading as low as 0.1 mol %. The coupling reaction is thermodynamically and, in the presence of a Ru complex, kinetically favourable and allows rapid molecular hydrogen generation on-demand at room temperature, under air, and without any additive. The pair silane/alcohol is a potential liquid organic hydrogen carrier (LOHC) for energy storage over long periods in a safe and secure way. Silanes and alcohols are non-toxic compounds and do not require special handling precautions such as high pressure or an inert atmosphere. These properties enhance the practical applications of the pair silane/alcohol as a good LOHC in the automotive industry. The variety and availability of silanes and alcohols permits a pair combination that fulfils the requirements for developing an efficient LOHC. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Analysis of the radical hydrogen transfer pathway for cleaving strong bonds in coal

    Energy Technology Data Exchange (ETDEWEB)

    Autrey, S.T.; Camaioni, D.M.; Ferris, K.F.; Franz, J.A.

    1993-09-01

    Hydrogen transfer processes involving radical intermediates are of key importance in the liquefaction of coal. While the primary function of donor solvents is to transfer H{lg_bullet} to coal-derived radicals that form when weak bonds are cleaved thermolytically, growing evidence suggests that the donor solvent can play a role in promoting cleavage of strong {alpha}-bonds. McMillen and Malhotra have explained the results in terms of a single-step mechanism referred to as radical H-transfer (RHT). Mechanistic kinetic models have been used to suggest the importance of RHT pathways in anthracene- and pyrene-based solvent systems. However, we question the reliability of these approaches because little experimental data exists to support the 16.5 kcal/mol intrinsic barriers they assume for RHT reactions. Unambiguous evidence for RHT is very difficult to obtain experimentally because at the temperatures required to activate the RHT reaction, a suite of multistep reactions can occur, which yield the same products, i.e. H-elimination from hydroaryl radicals followed by ipso addition. For this reason, we have sought to gain insight to barrier heights for RHT from theory. This paper reports our use of Marcus theory in combination with ab initio and semiempirical molecular orbital methods to show how the intrinsic barriers for RHT reactions depend on structural and thermodynamic properties of the reacting partners. In addition, reactions thought to be mediated by RHT are reexamined using mechanistic kinetic modeling (MKM) to determine the extent to which these reactions can be explained by conventional pathways.

  3. Mechanism of Action of Sulforaphane as a Superoxide Radical Anion and Hydrogen Peroxide Scavenger by Double Hydrogen Transfer: A Model for Iron Superoxide Dismutase.

    Science.gov (United States)

    Prasad, Ajit Kumar; Mishra, P C

    2015-06-25

    The mechanism of action of sulforaphane as a scavenger of superoxide radical anion (O2(•-)) and hydrogen peroxide (H2O2) was investigated using density functional theory (DFT) in both gas phase and aqueous media. Iron superoxide dismutase (Fe-SOD) involved in scavenging superoxide radical anion from biological media was modeled by a complex consisting of the ferric ion (Fe(3+)) attached to three histidine rings. Reactions related to scavenging of superoxide radical anion by sulforaphane were studied using DFT in the presence and absence of Fe-SOD represented by this model in both gas phase and aqueous media. The scavenging action of sulforaphane toward both superoxide radical anion and hydrogen peroxide was found to involve the unusual mechanism of double hydrogen transfer. It was found that sulforaphane alone, without Fe-SOD, cannot scavenge superoxide radical anion in gas phase or aqueous media efficiently as the corresponding reaction barriers are very high. However, in the presence of Fe-SOD represented by the above-mentioned model, the scavenging reactions become barrierless, and so sulforaphane scavenges superoxide radical anion by converting it to hydrogen peroxide efficiently. Further, sulforaphane was found to scavenge hydrogen peroxide also very efficiently by converting it into water. Thus, the mechanism of action of sulforaphane as an excellent antioxidant has been unravelled.

  4. Gas cleaning and hydrogen sulfide removal for COREX coal gas by sorption enhanced catalytic oxidation over recyclable activated carbon desulfurizer.

    Science.gov (United States)

    Sun, Tonghua; Shen, Yafei; Jia, Jinping

    2014-02-18

    This paper proposes a novel self-developed JTS-01 desulfurizer and JZC-80 alkaline adsorbent for H2S removal and gas cleaning of the COREX coal gas in small-scale and commercial desulfurizing devices. JTS-01 desulfurizer was loaded with metal oxide (i.e., ferric oxides) catalysts on the surface of activated carbons (AC), and the catalyst capacity was improved dramatically by means of ultrasonically assisted impregnation. Consequently, the sulfur saturation capacity and sulfur capacity breakthrough increased by 30.3% and 27.9%, respectively. The whole desulfurizing process combined selective adsorption with catalytic oxidation. Moreover, JZC-80 adsorbent can effectively remove impurities such as HCl, HF, HCN, and ash in the COREX coal gas, stabilizing the system pressure drop. The JTS-01 desulfurizer and JZC-80 adsorbent have been successfully applied for the COREX coal gas cleaning in the commercial plant at Baosteel, Shanghai. The sulfur capacity of JTS-01 desulfurizer can reach more than 50% in industrial applications. Compared with the conventional dry desulfurization process, the modified AC desulfurizers have more merit, especially in terms of the JTS-01 desulfurizer with higher sulfur capacity and low pressure drop. Thus, this sorption enhanced catalytic desulfurization has promising prospects for H2S removal and other gas cleaning.

  5. Catalytic activity of hydrophobic Pt/C/PTFE catalysts of different PTFE content for hydrogen-water liquid exchange reaction

    International Nuclear Information System (INIS)

    Hu Sheng; Xiao Chengjian; Zhu Zuliang; Luo Shunzhong; Wang Heyi; Luo Yangming; Wang Changbin

    2007-01-01

    10%Pt/C catalysts were prepared by liquid reduction method. PTFE and Pt/ C catalysts were adhered to porous metal and hydrophobic Pt/C/PTFE catalysts were prepared. The structure and size of Pt crystal particles of Pt/C catalysts were analyzed by XRD, and their mean size was 3.1 nm. The dispersion state of Pt/C and PTFE was analyzed by SEM, and they had good dispersion mostly, but PTFE membrane could be observed on local parts of Pt/C/PTFE surface. Because of low hydrophobicity, Pt/C/ PTFE catalysts have low activity when the mass ratio of PTFE and Pt/C is 0.5: 1, and their catalytic activity increases markedly when the ratio is 1:1. When the ratio increases again, more Pt active sites would be covered by PTFE and interior diffusion effect would increase, which result in the decrease of catalytic activity of Pt/C/PTFE. By PTFE pretreatment of porous metal carrier, the activity of Pt/C/PTFE catalysts decreases when the mass ratio of PTFE and Pt/C is 0.5:1, and their activity decreases when the mass ratio is 1:1. (authors)

  6. Use of Heterogenized Metal Complexes in Hydrogenation Reactions: Comparison of Hydrogenation and CTH Reactions.

    Czech Academy of Sciences Publication Activity Database

    Bata, P.; Zsigmond, A.; Gyémánt, M.; Czeglédi, A.; Klusoň, Petr

    2015-01-01

    Roč. 41, č. 12 (2015), s. 9281-9294 ISSN 0922-6168. [Pannonian Symposium on Catalysis /12./. Castle Trest, 16.09.2014-20.09.2014] Institutional support: RVO:67985858 Keywords : catalytic transfer hydrogenation * iron- phthalocyanine catalyst * chemoselectivity Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 1.833, year: 2015

  7. Ruthenium(II) Complexes Containing Lutidine-Derived Pincer CNC Ligands: Synthesis, Structure, and Catalytic Hydrogenation of C-N bonds.

    Science.gov (United States)

    Hernández-Juárez, Martín; López-Serrano, Joaquín; Lara, Patricia; Morales-Cerón, Judith P; Vaquero, Mónica; Álvarez, Eleuterio; Salazar, Verónica; Suárez, Andrés

    2015-05-11

    A series of Ru complexes containing lutidine-derived pincer CNC ligands have been prepared by transmetalation with the corresponding silver-carbene derivatives. Characterization of these derivatives shows both mer and fac coordination of the CNC ligands depending on the wingtips of the N-heterocyclic carbene fragments. In the presence of tBuOK, the Ru-CNC complexes are active in the hydrogenation of a series of imines. In addition, these complexes catalyze the reversible hydrogenation of phenantridine. Detailed NMR spectroscopic studies have shown the capability of the CNC ligand to be deprotonated and get involved in ligand-assisted activation of dihydrogen. More interestingly, upon deprotonation, the Ru-CNC complex 5 e(BF4 ) is able to add aldimines to the metal-ligand framework to yield an amido complex. Finally, investigation of the mechanism of the hydrogenation of imines has been carried out by means of DFT calculations. The calculated mechanism involves outer-sphere stepwise hydrogen transfer to the C-N bond assisted either by the pincer ligand or a second coordinated H2 molecule. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Final Technical Report "Catalytic Hydrogenation of Carbon Monoxide and Olefin Oxidation" Grant number : DE-FG02-86ER13615

    Energy Technology Data Exchange (ETDEWEB)

    Wayland, B.B.

    2009-08-31

    Title: Catalytic Hydrogenation of Carbon Monoxide and Olefin Oxidation Grant No. DE-FG02-86ER13615 PI: Wayland, B. B. (wayland@sas.upenn.edu) Abstract Development of new mechanistic strategies and catalyst materials for activation of CO, H2, CH4, C2H4, O2, and related substrates relevant to the conversion of carbon monoxide, alkanes, and alkenes to organic oxygenates are central objectives encompassed by this program. Design and synthesis of metal complexes that manifest reactivity patterns associated with potential pathways for the hydrogenation of carbon monoxide through metallo-formyl (M-CHO), dimetal ketone (M-C(O)-M), and dimetal dionyl (M-C(O)-C(O)-M) species is one major focus. Hydrocarbon oxidation using molecular oxygen is a central goal for methane activation and functionalization as well as regioselective oxidation of olefins. Discovery of new reactivity patterns and control of selectivity are pursued through designing new metal complexes and adjusting reaction conditions. Variation of reaction media promotes distinct reaction pathways that control both reaction rates and selectivities. Dimetalloradical diporphyrin complexes preorganize transition states for substrate reactions that involve two metal centers and manifest large rate increases over mono-metalloradical reactions of hydrogen, methane, and other small molecule substrates. Another broad goal and recurring theme of this program is to contribute to the thermodynamic database for a wide scope of organo-metal transformations in a range of reaction media. One of the most complete descriptions of equilibrium thermodynamics for organometallic reactions in water and methanol is emerging from the study of rhodium porphyrin substrate reactions in aqueous and alcoholic media. Water soluble group nine metalloporphyrins manifest remarkably versatile substrate reactivity in aqueous and alcoholic media which includes producing rhodium formyl (Rh-CHO) and hydroxy methyl (Rh-CH2OH) species. Exploratory

  9. Experimental, kinetic and numerical modeling of hydrogen production by catalytic reforming of crude ethanol over a commercial catalyst in packed bed tubular reactor and packed bed membrane reactor

    International Nuclear Information System (INIS)

    Aboudheir, Ahmed; Akande, Abayomi; Idem, Raphael

    2006-01-01

    The demand for hydrogen energy has increased tremendously in recent years essentially because of the increase in the word energy consumption as well as recent developments in fuel cell technologies. The energy information administration has projected that world energy consumption will increase by 59% over the next two decades, from 1999 to 2020, in which the largest share is still dominated by fossil fuels (oil, natural gas and coal). Carbon dioxide (CO 2 ) emissions resulting from the combustion of these fossil fuels currently are estimated to account for three-fourth of human-caused CO 2 emissions worldwide. Greenhouse gas emission, including CO 2 , should be limited, as recommended at the Kyoto Conference, Japan, in December 1997. In this regard, hydrogen (H 2 ) has a significant future potential as an alternative fuel that can solve the problems of CO 2 emissions as well as the emissions of other air contaminants. One of the techniques to produce hydrogen is by reforming of hydrocarbons or biomass. Crude ethanol (a form of biomass, which essentially is fermentation broth) is easy to produce, is free of sulphur, has low toxicity, and is also safe to handle, transport and store. In addition, crude ethanol consists of oxygenated hydrocarbons, such as ethanol, lactic acid, glycerol, and maltose. These oxygenated hydrocarbons can be reformed completely to H 2 and CO 2 , the latter of which could be separated from H 2 by membrane technology. This provides for CO 2 capture for eventual storage or destruction. In the case of using crude ethanol, this will result in negative CO 2 , emissions. In this paper, we conducted experimental work on production of hydrogen by the catalytic reforming of crude ethanol over a commercial promoted Ni-based catalyst in a packed bed tubular reactor as well as a packed bed membrane reactor. As well, a rigorous numerical model was developed to simulate this process in both the catalytic packed bed tubular reactor and packed bed membrane

  10. Cu/MgAl(2)O(4) as bifunctional catalyst for aldol condensation of 5-hydroxymethylfurfural and selective transfer hydrogenation.

    Science.gov (United States)

    Pupovac, Kristina; Palkovits, Regina

    2013-11-01

    Copper supported on mesoporous magnesium aluminate has been prepared as noble-metal-free solid catalyst for aldol condensation of 5-hydroxymethylfurfural with acetone, followed by hydrogenation of the aldol condensation products. The investigated mesoporous spinels possess high activity as solid-base catalysts. Magnesium aluminate exhibits superior activity compared to zinc and cobalt-based aluminates, reaching full conversion and up to 81 % yield of the 1:1 aldol product. The high activity can be correlated to a higher concentration of basic surface sites on magnesium aluminate. Applying continuous regeneration, the catalysts can be recycled without loss of activity. Focusing on the subsequent hydrogenation of aldol condensation products, Cu/MgAl2 O4 allows a selective hydrogenation and CO bond cleavage, delivering 3-hydroxybutyl-5-methylfuran as the main product with up to 84 % selectivity avoiding ring saturation. Analysis of the hydrogenation activity reveals that the reaction proceeds in the following order: CC>CO>CO cleavage>ring hydrogenation. Comparable activity and selectivity can be also achieved utilizing 2-propanol as solvent in the transfer hydrogenation, providing the possibility for partial recycling of acetone and optimization of the hydrogen management. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Catalytic hydrogen/oxygen reaction assisted the proton exchange membrane fuel cell (PEMFC) startup at subzero temperature

    Science.gov (United States)

    Sun, Shucheng; Yu, Hongmei; Hou, Junbo; Shao, Zhigang; Yi, Baolian; Ming, Pingwen; Hou, Zhongjun

    Fuel cells for automobile application need to operate in a wide temperature range including freezing temperature. However, the rapid startup of a proton exchange membrane fuel cell (PEMFC) at subfreezing temperature, e.g., -20 °C, is very difficult. A cold-start procedure was developed, which made hydrogen and oxygen react to heat the fuel cell considering that the FC flow channel was the characteristic of microchannel reactor. The effect of hydrogen and oxygen reaction on fuel cell performance at ambient temperature was also investigated. The electrochemical characterizations such as I- V plot and cyclic voltammetry (CV) were performed. The heat generated rate for either the single cell or the stack was calculated. The results showed that the heat generated rate was proportional to the gas flow rate when H 2 concentration and the active area were constant. The fuel cell temperature rose rapidly and steadily by controlling gas flow rate.

  12. New Ru(II)N'NN'-type pincer complexes: synthesis, characterization and the catalytic hydrogenation of CO2 or bicarbonates to formate salts

    International Nuclear Information System (INIS)

    Zengjin Dai; Qi Luo; Hengjiang Cong; Jing Zhang; Tianyou Peng

    2017-01-01

    [RuCl(L1)(MeCN) 2 ]Cl (1) and [RuCl(L2)(MeCN) 2 ]Cl (2) complexes were prepared through the reaction of [RuCl2(p-cymene)] 2 with 2,6-bis(benzimidazole-2-yl)-4-hydroxy-pyridine (L1) or 2,6-bis(benzimidazole- 2-yl) pyridine (L2) in acetonitrile, respectively. The treatment of [Ru(OTf)(L2)(MeCN) 2 ]OTf (3) with 1 equivalent of PPh 3 in ethanol resulted in the formation of [Ru(L2 -1 )(MeCN)(PPh 3 ) 2 ]OTf (4), in which one of the N-H moieties of L2 is deprotonated to give an anionic ligand (L2 -1 ). It was found that complex 1 can catalyze the hydrogenation of CO 2 to formate salts, producing sodium formate in 34.0% yield with a turnover number (TON) of 407 under the optimized conditions. Further investigations revealed that complexes 1-4 can efficiently catalyze the hydrogenation of sodium bicarbonate to sodium formate, and the catalytic activity follows the order 4 ≥ 1 ≥ 2 ≅ 3. In particular, sodium formate was obtained in good yield (77%) with a high TON (1530) when complex 4 was used as the catalyst. The present results illustrate a new example of Ru(II) complexes bearing a rigid N'NN' framework for the efficient hydrogenation of CO 2 to formate salts in a homogeneous system. (authors)

  13. Hydrogenation

    Energy Technology Data Exchange (ETDEWEB)

    Pier, M.

    1943-02-19

    A transcript is presented of a speech on the history of the development of hydrogenation of coal and tar. Apparently the talk had been accompanied by the showing of photographic slides, but none of the pictures were included with the report. In giving the history, Dr. Pier mentioned the dependence of much of the development of hydrogenation upon previous development in the related areas of ammonia and methanol syntheses, but he also pointed out several ways in which equipment appropriate for hydrogenation differed considerably from that used for ammonia and methanol. Dr. Pier discussed the difficulties encountered with residue processing, design of the reaction ovens, manufacture of ovens and preheaters, heating of reaction mixtures, development of steels, and development of compressor pumps. He described in some detail his own involvement in the development of the process. In addition, he discussed the development of methods of testing gasolines and other fuels. Also he listed some important byproducts of hydrogenation, such as phenols and polycyclic aromatics, and he discussed the formation of iso-octane fuel from the butanes arising from hydrogenation. In connection with several kinds of equipment used in hydrogenation (whose pictures were being shown), Dr. Pier gave some of the design and operating data.

  14. Hydrogenation of unactivated enamines to tertiary amines: rhodium complexes of fluorinated phosphines give marked improvements in catalytic activity

    Directory of Open Access Journals (Sweden)

    Sergey Tin

    2015-05-01

    Full Text Available In the hydrogenation of sluggish unactivated enamine substrates, Rh complexes of electron-deficient phosphines are demonstrated to be far more reactive catalysts than those derived from triphenylphosphine. These operate at low catalyst loadings (down to 0.01 mol % and are able to reduce tetrasubstituted enamines. The use of the sustainable and environmentally benign solvent (R-limonene for the reaction is also reported with the amine isolated by acid extraction.

  15. Synthesis of zirconia-immobilized copper chelates for catalytic decomposition of hydrogen peroxide and the oxidation of polycyclic aromatic hydrocarbons

    Czech Academy of Sciences Publication Activity Database

    Baldrian, Petr; Merhautová, Věra; Cajthaml, Tomáš; Nerud, František; Stopka, Pavel; Gorbacheva, O.; Hrubý, Martin; Beneš, Milan J.

    2008-01-01

    Roč. 72, č. 11 (2008), s. 1721-1726 ISSN 0045-6535 R&D Projects: GA AV ČR IBS5020306 Institutional research plan: CEZ:AV0Z50200510; CEZ:AV0Z40320502; CEZ:AV0Z40500505 Keywords : degradation * polycyclic aromatic hydrocarbons * hydrogen peroxide Subject RIV: EE - Microbiology, Virology Impact factor: 3.054, year: 2008

  16. Visible-Light-Enhanced Ring Opening of Cycloalkanols Enabled by Brønsted Base-Tethered Acyloxy Radical Induced Hydrogen Atom Transfer-Electron Transfer.

    Science.gov (United States)

    Zhao, Rong; Yao, Yuan; Zhu, Dan; Chang, Denghu; Liu, Yang; Shi, Lei

    2018-02-16

    A metal-free ring opening/halogenation of cycloalkanols, which combines both PPO/TBAX oxidant system and blue LEDs irradiation, is presented. This method produces diverse γ, δ, and even more remotely halogenated ketones in moderate to excellent yields under mild conditions. Interestingly, experimental and computational studies demonstrate the novel ring size-dependent concerted/stepwise (four-/five- to eight-membered rings) hydrogen atom transfer-electron transfer induced by Brønsted base-tethered acyloxy radical, which indicates distinct advantages brought by the cyclic structure of diacyl peroxides.

  17. Nanoscale Layer Transfer by Hydrogen Ion-Cut Processing: A Brief Review Through Recent U.S. Patents.

    Science.gov (United States)

    Lee, Benjamin T-H

    2017-01-01

    A hydrogen-based Ion-Cut layer-transfer technique, the so-called Ion-Cut or Smart-Cut processing, has been used in transferring a semiconductor membrane onto a desired substrate to reveal unique characteristics on a nanoscale size and to build functional electronic and photonic devices that are used for specific purposes. For example, the sub-100 nm thick silicon membrane transferred onto an insulator became a key substrate for fabricating nanoscale integrated circuit (IC) devices. Recent U.S. patents have exhibited integration of various thinning approaches requiring precision of a few nanometers in fabricating large-area semiconductor nanomembranes, especially for silicon. This paper reviews published patents and work on fabricating sub-100 nm silicon membranes with welldefined features without a chemical-mechanical polishing (CMP) thinning process. This included material analysis leads to ultraprecision thickness in the sub-100 nm region. This paper combines an analysis of peer-reviewed articles and issued patents using focused review keywords of hydrogen implantation, wafer bonding, and layer splitting. The quality of selected patents was appraised based on the authors' 20-year research experience in the field of ultrathin silicon layer-transfer technology. The paper covered more than 10 U.S. patents that have been filed on hydrogen-based Ion-Cut layer-transfer techniques. These patents described approaches for inserting hydrogen ions to split at a well-defined location and then transfer the as-split silicon membrane at the nanoscale thickness onto a desired substrate. Hydrogen-trap sites, implantation energy, and interface of the distinct doped regions could define the layer-split location. The insertion of high-dose hydrogen ions could be thoroughly achieved by ion implantation, plasma ion immersion implantation (PIII), plasma diffusion, and electrolysis. The article concludes with the discussion of the patent-orientated review of layer-transfer techniques

  18. Temperature-dependent kinetics of charge transfer, hydrogen-atom transfer, and hydrogen-atom expulsion in the reaction of CO+ with CH4 and CD4.

    Science.gov (United States)

    Melko, Joshua J; Ard, Shaun G; Johnson, Ryan S; Shuman, Nicholas S; Guo, Hua; Viggiano, Albert A

    2014-09-18

    We have determined the rate constants and branching ratios for the reactions of CO(+) with CH4 and CD4 in a variable-temperature selected ion flow tube. We find that the rate constants are collisional for all temperatures measured (193-700 K for CH4 and 193-500 K for CD4). For the CH4 reaction, three product channels are identified, which include charge transfer (CH4(+) + CO), H-atom transfer (HCO(+) + CH3), and H-atom expulsion (CH3CO(+) + H). H-atom transfer is slightly preferred to charge transfer at low temperature, with the charge-transfer product increasing in contribution as the temperature is increased (H-atom expulsion is a minor product for all temperatures). Analogous products are identified for the CD4 reaction. Density functional calculations on the CO(+) + CH4 reaction were also conducted, revealing that the relative temperature dependences of the charge-transfer and H-atom transfer pathways are consistent with an initial charge transfer followed by proton transfer.

  19. Ruthenium(0) nanoclusters stabilized by a Nanozeolite framework: isolable, reusable, and green catalyst for the hydrogenation of neat aromatics under mild conditions with the unprecedented catalytic activity and lifetime.

    Science.gov (United States)

    Zahmakiran, Mehmet; Tonbul, Yalçin; Ozkar, Saim

    2010-05-12

    The hydrogenation of aromatics is a ubiquitous chemical transformation used in both the petrochemical and specialty industry and is important for the generation of clean diesel fuels. Reported herein is the discovery of a superior heterogeneous catalyst, superior in terms of catalytic activity, selectivity, and lifetime in the hydrogenation of aromatics in the solvent-free system under mild conditions (at 25 degrees C and 42 +/- 1 psig initial H(2) pressure). Ruthenium(0) nanoclusters stabilized by a nanozeolite framework as a new catalytic material is reproducibly prepared from the borohydride reduction of a colloidal solution of ruthenium(III)-exchanged nanozeolites at room temperature and characterized by using ICP-OES, XRD, XPS, DLS, TEM, HRTEM, TEM/EDX, mid-IR, far-IR, and Raman spectroscopy. The resultant ruthenium(0) nanoclusters hydrogenate neat benzene to cyclohexane with 100% conversion under mild conditions (at 25 degrees C and 42 +/- 1 psig initial H(2) pressure) with record catalytic activity (initial TOF = 5430 h(-1)) and lifetime (TTO = 177 200). They provide exceptional catalytic activity not only in the hydrogenation of neat benzene but also in the solvent-free hydrogenation of methyl substituted aromatics such as toluene, o-xylene, and mesitylene under otherwise identical conditions. Moreover, they are an isolable, bottleable, and reusable catalyst in the hydrogenation of neat aromatics. When the isolated ruthenium(0) nanoclusters are reused, they retain 92% of their initial catalytic activity even for the third run in the hydrogenation of neat benzene under the same conditions as those of the first run. The work reported here also includes (i) far-infrared spectroscopic investigation of nanozeolite, ruthenium(III)-exchanged-nanozeolite, and ruthenium(0) nanoclusters stabilized by a nanozeolite framework, indicating that the host framework remains intact after the formation of a nanozeolite framework stabilized ruthenium(0) nanoclusters; (ii) the

  20. One-pot Reductive Amination of carbonyl Compounds with Nitro Compounds by Transfer Hydrogenation over Co-Nxas catalyst.

    Science.gov (United States)

    Zhou, Peng; Zhang, Zehui

    2017-05-09

    A new method was developed for the synthesis of secondary amines through the one-pot reductive amination of carbonyl compounds with nitro compounds using formic acid as the hydrogen donor over a heterogeneous non-noble-metal catalyst (Co-N x /C-800-AT, generated by the pyrolysis of the cobalt phthalocyanine/silica composite at 800°C under a N 2 atmosphere and subsequent etching by HF). Both nitrogen and cobalt were of considerable importance in the transfer hydrogenation reactions with formic acid. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Removal of distal protein-water hydrogen bonds in a plant epoxide hydrolase increases catalytic turnover but decreases thermostability

    OpenAIRE

    Thomaeus, Ann; Naworyta, Agata; Mowbray, Sherry L.; Widersten, Mikael

    2008-01-01

    A putative proton wire in potato soluble epoxide hydrolase 1, StEH1, was identified and investigated by means of site-directed mutagenesis, steady-state kinetic measurements, temperature inactivation studies, and X-ray crystallography. The chain of hydrogen bonds includes five water molecules coordinated through backbone carbonyl oxygens of Pro186, Leu266, His269, and the His153 imidazole. The hydroxyl of Tyr149 is also an integrated component of the chain, which leads to the hydroxyl of Tyr1...

  2. Catalytic Hydrogenation of Carbon Dioxide with Ammonia-Borane by Pincer-type Phosphorus Compound: A Theoretical Prediction.

    Science.gov (United States)

    Zeng, Guixiang; Maeda, Satoshi; Taketsugu, Tetsuya; Sakaki, Shigeyoshi

    2016-10-01

    Theoretically designed pincer-type phosphorus compound is found to be active for the hydrogenation of carbon dioxide (CO 2 ) with ammonia-borane. DFT, ONIOM(CCSD(T):MP2), and CCSD(T) computational results demonstrated that the reaction occurs through the phosphorus-ligand cooperative catalysis function, which provides an unprecedented protocol for metal-free CO 2 conversion. The phosphorus compounds with the NNN ligand are more active than those with the ONO ligand. The conjugate and planar ligand considerably improves the efficiency of the catalyst.

  3. Hydrogen.

    Science.gov (United States)

    Bockris, John O'M

    2011-11-30

    The idea of a "Hydrogen Economy" is that carbon containing fuels should be replaced by hydrogen, thus eliminating air pollution and growth of CO₂ in the atmosphere. However, storage of a gas, its transport and reconversion to electricity doubles the cost of H₂ from the electrolyzer. Methanol made with CO₂ from the atmosphere is a zero carbon fuel created from inexhaustible components from the atmosphere. Extensive work on the splitting of water by bacteria shows that if wastes are used as the origin of feed for certain bacteria, the cost for hydrogen becomes lower than any yet known. The first creation of hydrogen and electricity from light was carried out in 1976 by Ohashi et al. at Flinders University in Australia. Improvements in knowledge of the structure of the semiconductor-solution system used in a solar breakdown of water has led to the discovery of surface states which take part in giving rise to hydrogen (Khan). Photoelectrocatalysis made a ten times increase in the efficiency of the photo production of hydrogen from water. The use of two electrode cells; p and n semiconductors respectively, was first introduced by Uosaki in 1978. Most photoanodes decompose during the photoelectrolysis. To avoid this, it has been necessary to create a transparent shield between the semiconductor and its electronic properties and the solution. In this way, 8.5% at 25 °C and 9.5% at 50 °C has been reached in the photo dissociation of water (GaP and InAs) by Kainthla and Barbara Zeleney in 1989. A large consortium has been funded by the US government at the California Institute of Technology under the direction of Nathan Lewis. The decomposition of water by light is the main aim of this group. Whether light will be the origin of the post fossil fuel supply of energy may be questionable, but the maximum program in this direction is likely to come from Cal. Tech.

  4. Porous protein crystals as catalytic vessels for organometallic complexes.

    Science.gov (United States)

    Tabe, Hiroyasu; Abe, Satoshi; Hikage, Tatsuo; Kitagawa, Susumu; Ueno, Takafumi

    2014-05-01

    Porous protein crystals, which are protein assemblies in the solid state, have been engineered to form catalytic vessels by the incorporation of organometallic complexes. Ruthenium complexes in cross-linked porous hen egg white lysozyme (HEWL) crystals catalyzed the enantioselective hydrogen-transfer reduction of acetophenone derivatives. The crystals accelerated the catalytic reaction and gave different enantiomers based on the crystal form (tetragonal or orthorhombic). This method represents a new approach for the construction of bioinorganic catalysts from protein crystals. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Nonsolvent application of ionic liquids: organo-catalysis by 1-alkyl-3-methylimidazolium cation based room-temperature ionic liquids for chemoselective N-tert-butyloxycarbonylation of amines and the influence of the C-2 hydrogen on catalytic efficiency.

    Science.gov (United States)

    Sarkar, Anirban; Roy, Sudipta Raha; Parikh, Naisargee; Chakraborti, Asit K

    2011-09-02

    1-Alkyl-3-methylimidazolium cation based ionic liquids efficiently catalyze N-tert-butyloxycarbonylation of amines with excellent chemoselectivity. The catalytic role of the ionic liquid is envisaged as "electrophilic activation" of di-tert-butyl dicarbonate (Boc(2)O) through bifurcated hydrogen bond formation with the C-2 hydrogen of the 1-alkyl-3-methylimidazolium cation and has been supported by a downfield shift of the imidazolium C-2 hydrogen of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][NTf(2)]) from δ 8.39 to 8.66 in the presence of Boc(2)O in the (1)H NMR and a drastic reduction of the catalytic efficiency with 1-butyl-2,3-dimethylimidazolium ionic liquids that are devoid of the C-2 hydrogen. The differential time required for reaction with aromatic and aliphatic amines has offered means for selective N-t-Boc formation during inter and intramolecular competitions. Preferential N-t-Boc formation with secondary aliphatic amine has been achieved in the presence of primary aliphatic amine. Comparison of the catalytic efficiency for N-t-Boc formation with a common substrate revealed that [bmim][NTf(2)] is superior to the reported Lewis acid catalysts.

  6. Non-typical fluorescence studies of excited and ground state proton and hydrogen transfer

    KAUST Repository

    Gil, Michał

    2017-02-03

    Fluorescence studies of tautomerization have been carried out for various systems that exhibit single and double proton or hydrogen translocation in various environments, such as liquid and solid condensed phases, ultracold supersonic jets, and finally, polymer matrices with single emitters.We focus on less explored areas of application of fluorescence for tautomerization studies, using porphycene, a porphyrin isomer, as an example. Fluorescence anisotropy techniques allow investigations of self-exchange reactions, where the reactant and product are formally identical. Excitation with polarized light makes it possible to monitor tautomerization in single molecules and to detect their three-dimensional orientation. Analysis of fluorescence from single vibronic levels of jet-isolated porphycene not only demonstrates coherent tunneling of two internal protons, but also indicates that the process is vibrational mode-specific. Next, we present bifunctional proton donoracceptor systems, molecules that are able, depending on the environment, to undergo excited state single intramolecular or double intermolecular proton transfer. For molecules that have donor and acceptor groups located in separate moieties linked by a single bond, excited state tautomerization can be coupled to mutual twisting of the two subunits.

  7. Hydrogen Atom Transfer by a High-Valent Nickel-Chloride Complex.

    Science.gov (United States)

    Mondal, Prasenjit; Pirovano, Paolo; Das, Ankita; Farquhar, Erik R; McDonald, Aidan R

    2018-02-07

    Oxo-metal-halide moieties have often been implicated as C-H bond activating oxidants with the terminal oxo-metal entity identified as the electrophilic oxidant. The electrophilic reactivity of metal-halide species has not been investigated. We have prepared a high-valent nickel-halide complex [Ni III (Cl)(L)] (2, L = N,N'-(2,6-dimethylphenyl)-2,6-pyridinedicarboxamide) by one-electron oxidation of a [Ni II (Cl)(L)] - precursor. 2 was characterized using electronic absorption, electron paramagnetic resonance, and X-ray absorption spectroscopies and mass spectrometry. 2 reacted readily with substrates containing either phenolic O-H or hydrocarbon C-H bonds. Analysis of the Hammett, Evans-Polanyi, and Marcus relationships between the determined rate constants and substrate pK a , X-H bond dissociation energy, and oxidation potential, respectively, was performed. Through this analysis, we found that 2 reacted by a hydrogen atom transfer (HAT) mechanism. Our findings shine light on enzymatic high-valent oxo-metal-halide oxidants and open new avenues for oxidative halogenation catalyst design.

  8. Dinuclear Tetrapyrazolyl Palladium Complexes Exhibiting Facile Tandem Transfer Hydrogenation/Suzuki Coupling Reaction of Fluoroarylketone

    KAUST Repository

    Dehury, Niranjan

    2016-07-18

    Herein, we report an unprecedented example of dinuclear pyrazolyl-based Pd complexes exhibiting facile tandem catalysis for fluoroarylketone: Tetrapyrazolyl di-palladium complexes with varying Pd-Pd distances efficiently catalyze the tandem reaction involving transfer hydrogenation of fluoroarylketone to the corresponding alcohol and Suzuki-Miyaura cross coupling reaction of the resulting fluoroarylalcohol under moderate reaction conditions, to biaryl alcohol. The complex with the shortest Pd-Pd distance exhibits the highest tandem activity among its di-metallic analogues, and exceeds in terms of activity and selectivity the analogous mononuclear compound. The kinetics of the reaction indicates clearly that reductive transformation of haloarylketone into haloaryalcohol is the rate determining step in the tandem reaction. Interestingly while fluoroarylketone undergoes the multistep tandem catalysis, the chloro- and bromo-arylketones undergo only a single step C-C coupling reaction resulting in biarylketone as the final product. Unlike the pyrazole based Pd compounds, the precursor PdCl2 and the phosphine based relevant complexes (PPh3)2PdCl2 and (PPh3)4Pd are found to be unable to exhibit the tandem catalysis.

  9. Coumarin or benzoxazinone bearing benzimidazolium and bis(benzimidazolium salts; involvement in transfer hydrogenation of acetophenone derivatives and hCA inhibition

    Directory of Open Access Journals (Sweden)

    Mert Olgun Karataş

    2015-10-01

    Full Text Available Four new salts of benzimidazolium and bis(benzimidazolium which include coumarin or benzoxazinone moieties were synthesized and the structures of the newly synthesized compounds were elucidated on the basis of spectral analyses such as 1H-NMR, 13C-NMR, HSQC, IR, LC-MS and elemental analysis. Benzimidazolium salts were used intensively as N-heterocyclic carbene (NHC precursors in the various catalytic reactions such as transfer hydrogenation (TH, C-H bond activation, Heck, Suzuki reaction etc. With the prospect of potential NHC precursor properties of the synthesized compounds, they were employed in the (TH reaction of p-substitute acetophenones (acetophenone, p-methyl acetophenone, p-chloro acetophenone and good yields were observed. Coumarin compounds are known as inhibitor of carbonic anhydrase and inhibition effects of the synthesized compounds on human carbonic anhydrases (hCA were investigated as in vitro. The in vitro results demonstrated that all compounds inhibited hCA I and hCA II activity. Among the synthesized compounds 1,4-bis(1-((6,8-dimethyl-2H-chromen-2-one-4-ylmethylbenzimidazolium-3-ylbutane dichloride was found to be the most active IC50= 5.55 mM and 6.06 mM for hCA I and hCA II, respectively.

  10. Treatment of printing and dyeing wastewater by catalytic wet hydrogen peroxide oxidation of honeycomb cinder as carrier catalyst

    Science.gov (United States)

    Zhang, D. H.; Yang, H. M.; Ou, Y. J.; Xu, C.; Gu, J. C.

    2017-06-01

    Under the condition of 35 °C, honeycomb cinder was used as the carrier, nickel as the active ingredient, impregnated for 2h, and calcined at 300 °C for 2h. The catalyst was used to Catalytic Wet Peroxide Oxidation of methylene blue simulated printing and dyeing wastewater. The effect of the amount of catalyst, the amount of catalyst, the reaction temperature and the reaction time on the treatment efficiency and the effect of the self-made catalyst on the simulated wastewater with different concentration gradient were studied in the experiment. The results showed that when the reaction conditions were H2O2 8ml/L, catalyst 12g/L and reaction time 1h, the degradation rate of methylene blue reached more than 77% for the wastewater with concentration ranging from 40 mg/L to 200 mg/L. In addition, at a temperature of 30 DEG C, the wastewater, the concentration was 80mg/L, degradation rate was up to 85.70%.

  11. Valorization of Waste Lipids through Hydrothermal Catalytic Conversion to Liquid Hydrocarbon Fuels with in Situ Hydrogen Production

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dongwook; Vardon, Derek R.; Murali, Dheeptha; Sharma, Brajendra K.; Strathmann, Timothy J.

    2016-03-07

    We demonstrate hydrothermal (300 degrees C, 10 MPa) catalytic conversion of real waste lipids (e.g., waste vegetable oil, sewer trap grease) to liquid hydrocarbon fuels without net need for external chemical inputs (e.g., H2 gas, methanol). A supported bimetallic catalyst (Pt-Re/C; 5 wt % of each metal) previously shown to catalyze both aqueous phase reforming of glycerol (a triacylglyceride lipid hydrolysis coproduct) to H2 gas and conversion of oleic and stearic acid, model unsaturated and saturated fatty acids, to linear alkanes was applied to process real waste lipid feedstocks in water. For reactions conducted with an initially inert headspace gas (N2), waste vegetable oil (WVO) was fully converted into linear hydrocarbons (C15-C17) and other hydrolyzed byproducts within 4.5 h, and H2 gas production was observed. Addition of H2 to the initial reactor headspace accelerated conversion, but net H2 production was still observed, in agreement with results obtained for aqueous mixtures containing model fatty acids and glycerol. Conversion to liquid hydrocarbons with net H2 production was also observed for a range of other waste lipid feedstocks (animal fat residuals, sewer trap grease, dry distiller's grain oil, coffee oil residual). These findings demonstrate potential for valorization of waste lipids through conversion to hydrocarbons that are more compatible with current petroleum-based liquid fuels than the biodiesel and biogas products of conventional waste lipid processing technologies.

  12. Steam reformer with catalytic combustor

    Science.gov (United States)

    Voecks, Gerald E. (Inventor)

    1990-01-01

    A steam reformer is disclosed having an annular steam reforming catalyst bed formed by concentric cylinders and having a catalytic combustor located at the center of the innermost cylinder. Fuel is fed into the interior of the catalytic combustor and air is directed at the top of the combustor, creating a catalytic reaction which provides sufficient heat so as to maintain the catalytic reaction in the steam reforming catalyst bed. Alternatively, air is fed into the interior of the catalytic combustor and a fuel mixture is directed at the top. The catalytic combustor provides enhanced radiant and convective heat transfer to the reformer catalyst bed.

  13. Synthesis of ruthenium(II) complexes containing hydroxymethylphosphines and their catalytic activities for hydrogenation of supercritical carbon dioxide.

    Science.gov (United States)

    Kayaki, Yoshihito; Shimokawatoko, Yoshiki; Ikariya, Takao

    2007-07-09

    Ligand substitution of RuCl2[P(C6H5)3]3 and Cp*RuCl(isoprene) (Cp*=1,2,3,4,5-pentamethylcyclopentadienyl) complexes with hydroxymethylphosphines was investigated to develop new catalyst systems for CO2 hydrogenation. A reaction of P(C6H5)2CH2OH with RuCl2[P(C6H5)3]3 in CH2Cl2 gave Ru(H)Cl(CO)[P(C6H5)2CH2OH]3 (1), which was characterized by NMR spectroscopy and X-ray crystallographic analysis. An isotope labeling experiment using P(C6H5)213CH2OH indicated that the carbonyl moiety in complex 1 originated from formaldehyde formed by degradation of the hydroxymethylphosphine. Elimination of formaldehyde from PCy2CH2OH (Cy=cyclohexyl) was also promoted by treatment of RuCl2[P(C6H5)3]3 in ethanol to give RuCl2(PHCy2)4 under mild conditions. On the other hand, the substitution reaction using Cp*RuCl(isoprene) with the hydroxymethylphosphine ligands proceeded smoothly with formation of Cp*RuCl(L)2 [2a-2c; L=P(C6H5)2CH2OH, PCy(CH2OH)2, and P(CH2OH)3] in good yields. The isolable hydroxymethylphosphine complexes 1 and 2 efficiently catalyzed the hydrogenative amidation of supercritical carbon dioxide (scCO2) to N,N-dimethylformamide (DMF).

  14. Hydrogen production with short contact time. Catalytic partial oxidation of hydrocarbons and oxygenated compounds: Recent advances in pilot- and bench-scale testing and process design

    Energy Technology Data Exchange (ETDEWEB)

    Guarinoni, A.; Ponzo, R.; Basini, L. [ENI Refining and Marketing Div., San Donato Milanese (Italy)

    2010-12-30

    ENI R and D has been active for fifteen years in the development of Short Contact Time - Catalytic Partial Oxidation (SCT-CPO) technologies for producing Hydrogen/Synthesis Gas. From the beginning the experimental work addressed either at defining the fundamental principles or the technical and economical potential of the technology. Good experimental responses, technical solutions' simplicity and flexibility, favourable techno-economical evaluations promoted the progressive widening of the field of the investigations. From Natural Gas (NG) the range of ''processable'' Hydrocarbons extended to Liquefied Petroleum Gas (LPG) and Gasoils, including those characterised by high levels of unsaturated and sulphurated molecules and, lately, to other compounds with biological origin. The extensive work led to the definition of different technological solutions, grouped as follows: Technology 1: Air Blown SCT-CPO of Gaseous Hydrocarbons and/or Light Compounds with biological origin Technology 2: Enriched Air/Oxygen Blown SCT-CPO of Gaseous Hydrocarbons and/or Light Compounds with biological origin Technology 3: Enriched Air/Oxygen Blown SCT-CPO of Liquid Hydrocarbons and/or Compounds with biological origin Recently, the licence rights on a non-exclusive basis for the commercialisation of SCT-CPO based processes for H{sub 2}/Synthesis gas production from light hydrocarbons with production capacity lower than 5,000 Nm{sup 3}/h of H{sub 2} or 7,500 Nm3/h of syngas have been assigned to two external companies. In parallel, development of medium- and large-scale plant solutions is progressing within the ENI group framework. These last activities are addressed to the utilisation of SCT-CPO for matching the variable Hydrogen demand in several contexts of oil refining operation. This paper will report on the current status of SCT-CPO with a focus on experimental results obtained, either at pilot- and bench- scale level. (orig.)

  15. How Formaldehyde Inhibits Hydrogen Evolution by [FeFe]-Hydrogenases: Determination by ¹³C ENDOR of Direct Fe-C Coordination and Order of Electron and Proton Transfers.

    Science.gov (United States)

    Bachmeier, Andreas; Esselborn, Julian; Hexter, Suzannah V; Krämer, Tobias; Klein, Kathrin; Happe, Thomas; McGrady, John E; Myers, William K; Armstrong, Fraser A

    2015-04-29

    Formaldehyde (HCHO), a strong electrophile and a rapid and reversible inhibitor of hydrogen production by [FeFe]-hydrogenases, is used to identify the point in the catalytic cycle at which a highly reactive metal-hydrido species is formed. Investigations of the reaction of Chlamydomonas reinhardtii [FeFe]-hydrogenase with formaldehyde using pulsed-EPR techniques including electron-nuclear double resonance spectroscopy establish that formaldehyde binds close to the active site. Density functional theory calculations support an inhibited super-reduced state having a short Fe-(13)C bond in the 2Fe subsite. The adduct forms when HCHO is available to compete with H(+) transfer to a vacant, nucleophilic Fe site: had H(+) transfer already occurred, the reaction of HCHO with the Fe-hydrido species would lead to methanol, release of which is not detected. Instead, Fe-bound formaldehyde is a metal-hydrido mimic, a locked, inhibited form analogous to that in which two electrons and only one proton have transferred to the H-cluster. The results provide strong support for a mechanism in which the fastest pathway for H2 evolution involves two consecutive proton transfer steps to the H-cluster following transfer of a second electron to the active site.

  16. Crystallography aided by atomic core-level binding energies: proton transfer versus hydrogen bonding in organic crystal structures.

    Science.gov (United States)

    Stevens, Joanna S; Byard, Stephen J; Seaton, Colin C; Sadiq, Ghazala; Davey, Roger J; Schroeder, Sven L M

    2011-10-10

    Ionic bond or hydrogen bridge? Brønsted proton transfer to nitrogen acceptors in organic crystals causes strong N1s core-level binding energy shifts. A study of 15 organic cocrystal and salt systems shows that standard X-ray photoelectron spectroscopy (XPS) can be used as a complementary method to X-ray crystallography for distinguishing proton transfer from H-bonding in organic condensed matter. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Salt-assisted clean transfer of continuous monolayer MoS2 film for hydrogen evolution reaction

    Science.gov (United States)

    Cho, Heung-Yeol; Nguyen, Tri Khoa; Ullah, Farman; Yun, Jong-Won; Nguyen, Cao Khang; Kim, Yong Soo

    2018-03-01

    The transfer of two-dimensional (2D) materials from one substrate to another is challenging but of great importance for technological applications. Here, we propose a facile etching and residue-free method for transferring a large-area monolayer MoS2 film continuously grown on a SiO2/Si by chemical vapor deposition. Prior to synthesis, the substrate is dropped with water- soluble perylene-3, 4, 9, 10-tetracarboxylic acid tetrapotassium salt (PTAS). The as-grown MoS2 on the substrate is simply dipped in water to quickly dissolve PTAS to yield the MoS2 film floating on the water surface, which is subsequently transferred to the desired substrate. The morphological, optical and X-ray photoelectron spectroscopic results show that our method is useful for fast and clean transfer of the MoS2 film. Specially, we demonstrate that monolayer MoS2 film transferred onto a conducting substrate leads to excellent performance for hydrogen evolution reaction with low overpotential (0.29 V vs the reversible hydrogen electrode) and Tafel slope (85.5 mV/decade).

  18. Hydrogen

    Directory of Open Access Journals (Sweden)

    John O’M. Bockris

    2011-11-01

    Full Text Available The idea of a “Hydrogen Economy” is that carbon containing fuels should be replaced by hydrogen, thus eliminating air pollution and growth of CO2 in the atmosphere. However, storage of a gas, its transport and reconversion to electricity doubles the cost of H2 from the electrolyzer. Methanol made with CO2 from the atmosphere is a zero carbon fuel created from inexhaustible components from the atmosphere. Extensive work on the splitting of water by bacteria shows that if wastes are used as the origin of feed for certain bacteria, the cost for hydrogen becomes lower than any yet known. The first creation of hydrogen and electricity from light was carried out in 1976 by Ohashi et al. at Flinders University in Australia. Improvements in knowledge of the structure of the semiconductor-solution system used in a solar breakdown of water has led to the discovery of surface states which take part in giving rise to hydrogen (Khan. Photoelectrocatalysis made a ten times increase in the efficiency of the photo production of hydrogen from water. The use of two electrode cells; p and n semiconductors respectively, was first introduced by Uosaki in 1978. Most photoanodes decompose during the photoelectrolysis. To avoid this, it has been necessary to create a transparent shield between the semiconductor and its electronic properties and the solution. In this way, 8.5% at 25 °C and 9.5% at 50 °C has been reached in the photo dissociation of water (GaP and InAs by Kainthla and Barbara Zeleney in 1989. A large consortium has been funded by the US government at the California Institute of Technology under the direction of Nathan Lewis. The decomposition of water by light is the main aim of this group. Whether light will be the origin of the post fossil fuel supply of energy may be questionable, but the maximum program in this direction is likely to come from Cal. Tech.

  19. Role of aromatic structure in pathways of hydrogen transfer and bond cleavage in coal liquefaction: Theoretical studies

    Energy Technology Data Exchange (ETDEWEB)

    Franz, J.A.; Autrey, T.; Camaioni, D.M. [Pacific Northwest Lab., Richland, WA (United States); Watts, J.D.; Bartlett, R.J. [Univ. of Florida, Gainesville, FL (United States). Quantum Theory Project

    1995-09-01

    The mechanisms by which strong carbon-carbon bonds between aromatic rings and side chains are cleaved under hydropyrolysis conditions remain a subject of wide interest to fuel science. Recently, the authors have studied in detail an alternate pathway for hydrogen atom transfer to {pi}-systems, radical hydrogen transfer (RHT). RHT is the direct, bimolecular transfer of hydrogen from the {beta}-position of an organic radical to the target {pi}-system. In the initial theoretical study, they examined the reaction ethyl radical + ethylene = ethylene + ethyl at the spin-projected UMP2/6-31G** level of theory. Recently, they have used a calibrated ROHF-MNDO-PM3 method to predict thermoneutral RHT barriers for hydrogen transfer between hydroaryl radicals and the corresponding arene. Because of the inherent limitations of semiempirical methods such as ROHF-MNDO-PM3, they have extended the initial work with the ethyl + ethylene study to examine this reaction at the ROHF-MBPT[2]-6-31G** and ROHF-CCSD[T]-6-31G** levels of ab initio theory. The primary objective was to determine how intrinsic RHT barriers change with conjugative stabilization of the radicals. The spin-restricted ROHF approach has been applied to study several RHT reactions, and they present completed ROHF results for the ethyl + ethylene system and preliminary results for the methallyl + butadiene system. The methallyl + butadiene system serves as a model for highly stabilized hydroaryl radicals: the methallyl radical exhibits a C-H bond strength of 46.5 kcal/mol compared to 9-hydroanthracenyl, 43.1 kcal/mol.

  20. Stepwise vs concerted excited state tautomerization of 2-hydroxypyridine: Ammonia dimer wire mediated hydrogen/proton transfer

    Energy Technology Data Exchange (ETDEWEB)

    Esboui, Mounir, E-mail: mounir.esboui@fst.rnu.tn [Laboratoire de Spectroscopie Atomique, Moléculaire et Applications, Département de Physique, Faculté des Sciences de Tunis, 2092 Tunis (Tunisia); Technical and Vocational Training Corporation, Hail College of Technology, P.O. Box 1960, Hail 81441 (Saudi Arabia)

    2015-07-21

    The stepwise and concerted excited state intermolecular proton transfer (PT) and hydrogen transfer (HT) reactions in 2-hydroxypyridine-(NH{sub 3}){sub 2} complex in the gas phase under Cs symmetry constraint and without any symmetry constraints were performed using quantum chemical calculations. It shows that upon excitation, the hydrogen bonded in 2HP-(NH{sub 3}){sub 2} cluster facilitates the releasing of both hydrogen and proton transfer reactions along ammonia wire leading to the formation of the 2-pyridone tautomer. For the stepwise mechanism, it has been found that the proton and the hydrogen may transfer consecutively. These processes are distinguished from each other through charge translocation analysis and the coupling between the motion of the proton and the electron density distribution along ammonia wire. For the complex under Cs symmetry, the excited state HT occurs on the A″({sup 1}πσ{sup ∗}) and A′({sup 1}nσ{sup ∗}) states over two accessible energy barriers along reaction coordinates, and excited state PT proceeds mainly through the A′({sup 1}ππ{sup ∗}) and A″({sup 1}nπ{sup ∗}) potential energy surfaces. For the unconstrained complex, potential energy profiles show two {sup 1}ππ{sup ∗}-{sup 1}πσ{sup ∗} conical intersections along enol → keto reaction path indicating that proton and H atom are localized, respectively, on the first and second ammonia of the wire. Moreover, the concerted excited state PT is competitive to take place with the stepwise process, because it proceeds over low barriers of 0.14 eV and 0.11 eV with respect to the Franck-Condon excitation of enol tautomer, respectively, under Cs symmetry and without any symmetry constraints. These barriers can be probably overcome through tunneling effect.

  1. Preparation of MoSex>3/Mo-NPs catalytic films for enhanced hydrogen evolution by pulsed laser ablation of MoSe2 target

    Science.gov (United States)

    Fominski, V. Yu.; Romanov, R. I.; Fominski, D. V.; Shelyakov, A. V.

    2018-02-01

    The peculiarities of pulsed laser ablation of MoSe2 targets which caused the formation of a complex plume containing atoms (Mo and Se) and Mo nanoparticles (Mo-NPs) have been studied. Investigations of the composition, structure, and catalytic activity toward the hydrogen evolution reaction (HER) for MoSex/Mo-NPs films prepared by pulsed laser deposition (PLD) in a vacuum and in a buffer He gas were carried out. For He pressure of 30 Pa, a shock wave could be the dominant mechanism of material transport, resulting in the deposition of an Se-enriched flux of chemically active atoms and leading to the growth of amorphous films with an increased Se content. Mo nanoparticles allowed for a larger surface area of the MoSex∼3.1/Mo-NPs catalyst deposited 5 cm from the target. However, for deposition in He at 10 cm, the amount of Mo NPs in the film appreciably decreased. Factors that could impact on the transport of nanoparticles through a buffer gas were considered. The amorphous MoSex∼3.1/Mo-NPs films prepared by PLD in He gas exhibited excellent HER performance. Quasicrystal MoSex<2/Mo-NPs films obtained by vacuum PLD were obviously inferior to amorphous films. Despite the formation of edge-oriented MoSe2 nanocrystals, the vacuum-deposited films had a large majority of metallic Mo and a deficiency of Se, which could adversely affect their HER performance.

  2. Selective catalytic hydrogenation of the N-acyl and uridyl double bonds in the tunicamycin family of protein N-glycosylation inhibitors.

    Science.gov (United States)

    Price, Neil Pj; Jackson, Michael A; Vermillion, Karl E; Blackburn, Judith A; Li, Jiakun; Yu, Biao

    2017-12-01

    Tunicamycin is a Streptomyces-derived inhibitor of eukaryotic protein N-glycosylation and bacterial cell wall biosynthesis, and is a potent and general toxin by these biological mechanisms. The antibacterial activity is dependent in part upon a π-π stacking interaction between the tunicamycin uridyl group and a specific Phe residue within MraY, a tunicamycin-binding protein in bacteria. We have previously shown that reducing the tunicamycin uridyl group to 5,6-dihydrouridyl (DHU) significantly lowers its eukaryotic toxicity, potentially by disrupting the π-stacking with the active site Phe. The present report compares the catalytic hydrogenation of tunicamycin and uridine with various precious metal catalysts, and describe optimum conditions for the selective production of N-acyl reduced tunicamycin or for tunicamycins reduced in both the N-acyl and uridyl double bonds. At room temperature, Pd-based catalysts are selective for the N-acyl reduction, whereas Rh-based catalysts favor the double reduction to provide access to fully reduced tunicamycin. The reduced DHU is highly base-sensitive, leading to amide ring opening under mild alkaline conditions.

  3. Reaction mechanisms and evaluation of effective process operation for catalytic oxidation and coagulation by ferrous solution and hydrogen peroxide

    Energy Technology Data Exchange (ETDEWEB)

    Lee, S.H.; Moon, H.J.; Kim, Y.M. [Dept. of Environmental Engineering, Sangmyung Univ., Cheonan (Korea); Bae, W.K. [Dept. of Civil and Environmental Engineering, Hanyang Univ., Ansan, Kyounggi (Korea)

    2003-07-01

    This research was carried out to evaluate the removal efficiencies of COD{sub cr} and colour for the dyeing wastewater by ferrous solution and the different dosage of H{sub 2}O{sub 2} in Fenton process. In the case of H{sub 2}O{sub 2} divided dosage, 7:3 was more effective than 3:7 to remove COD{sub cr} and colour. The results showed that COD was mainly removed by Fenton coagulation, where the ferric ions are formed in the initial step of Fenton reaction. On the other hand colour was removed by Fenton oxidation rather than Fenton coagulation. This paper also aims at pursuing to investigate the effective removal mechanisms using ferrous ion coagulation, ferric ion coagulation and Fenton oxidation process. The removal mechanism of COD{sub cr} and colour was mainly coagulation by ferrous ion, ferric ion and Fenton oxidation. The removal efficiencies were dependent on the ferric ion amount at the beginning of the reaction. However the final removal efficiency of COD and colour was in the order of Fenton oxidation, ferric ion coagulation and ferrous ion coagulation. The reason of the highest removal efficiency by Fenton oxidation can be explained by the chain reactions with ferrous solution, ferric ion and hydrogen peroxide. (orig.)

  4. Ultrathin Coating of Confined Pt Nanocatalysts by Atomic Layer Deposition for Enhanced Catalytic Performance in Hydrogenation Reactions.

    Science.gov (United States)

    Wang, Meihua; Gao, Zhe; Zhang, Bin; Yang, Huimin; Qiao, Yan; Chen, Shuai; Ge, Huibin; Zhang, Jiankang; Qin, Yong

    2016-06-13

    Metal-support interfaces play a prominent role in heterogeneous catalysis. However, tailoring the metal-support interfaces to realize full utilization remains a major challenge. In this work, we propose a graceful strategy to maximize the metal-oxide interfaces by coating confined nanoparticles with an ultrathin oxide layer. This is achieved by sequential deposition of ultrathin Al2 O3 coats, Pt, and a thick Al2 O3 layer on carbon nanocoils templates by atomic layer deposition (ALD), followed by removal of the templates. Compared with the Pt catalysts confined in Al2 O3 nanotubes without the ultrathin coats, the ultrathin coated samples have larger Pt-Al2 O3 interfaces. The maximized interfaces significantly improve the activity and the protecting Al2 O3 nanotubes retain the stability for hydrogenation reactions of 4-nitrophenol. We believe that applying ALD ultrathin coats on confined catalysts is a promising way to achieve enhanced performance for other catalysts. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. ARGAZ: a new device for experimental study of the coupling between hydrogen production and hydrogen transfer through saturated Callovian-Oxfordian argillite

    International Nuclear Information System (INIS)

    Imbert, C.; Bataillon, C.; Touze, G.; Vigier, P.; Talandier, J.

    2010-01-01

    Document available in extended abstract form only. A specific experimental device has been designed to produce hydrogen at the metal-argillite interface by electrochemistry. The target is for one hand to reproduce the production of hydrogen occurring when a metal is corroded by the water contained in the porosity of the mud-stone. On the other hand, the transfer of the hydrogen through the mud-stone can be studied. The specific features of the experiment are the following: - Hydrogen is generated inside a cell by electrochemistry, at the interface between the argillite and a metallic surface; no gas injection is required; - Electrochemistry gives the possibility to control the hydrogen production rate; - Hydrogen generation implies water consumption: the water comes from the porosity of the bulk argillite, near the interface; - That one-dimensional experiment has been built around a cylindrical sample of bulk and undamaged argillite coming from the Callovian-Oxfordian formation. Inside the device a cylindrical sample of argillite is placed above a nickel plate. Around the argillite, a ring of compacted bentonite ensures a mechanical confinement. When saturated, the bentonite will apply a swelling pressure close to the total pressure encountered by the sample in the geological formation. The hydrogen is generated at the interface nickel-argillite. The nickel plate is one of the two electrodes required for electrochemistry. At the top face of bentonite, iron electrode is used to close the electrical circuit. The hydrogen produced at the bottom face of the mud-stone is expected to go across the argillite towards the top face. A porous plate connected with a sampling bottle allows the capture of hydrogen. The argillite sample has a diameter of 50 mm, and a height of 50 mm. It is obtained by over-coring a core sample, and by a careful machining leading to a perfect geometry and surface quality. The production rate of hydrogen can be calculated from the current intensity

  6. Magnetic gold nanocatalyst (nanocat-Fe–Au): catalytic applications for the oxidative esterification and hydrogen transfer reactions

    Science.gov (United States)

    An efficient and sustainable protocol is described for the oxidative esterification of aldehydes and the reduction of aromatic nitro compounds that uses magnetically separable and reusable maghemite-supported gold nanocatalyst (nanocat-Fe-Au) under mild conditions. The complex ch...

  7. Role of the sulfonamide moiety of Ru(II) half-sandwich complexes in the asymmetric transfer hydrogenation of 3,4-dihydroisoquinolines

    Czech Academy of Sciences Publication Activity Database

    Matuška, O.; Zápal, J.; Hrdličková, R.; Mikoška, M.; Pecháček, J.; Vilhanová, B.; Václavík, Jiří; Kuzma, M.; Kačer, P.

    2016-01-01

    Roč. 118, č. 1 (2016), s. 215-222 ISSN 1878-5190 Institutional support: RVO:61388963 Keywords : ruthenium * asymmetric transfer hydrogenation * dihydroisoquinolines * sulfonamide Subject RIV: CC - Organic Chemistry Impact factor: 1.264, year: 2016

  8. Heat transfer in pool boiling liquid neon, deuterium and hydrogen, and critical heat flux in forced convection of liquid neon

    International Nuclear Information System (INIS)

    Astruc, J.M.

    1967-12-01

    In the first part, free-convection and nucleate pool boiling heat transfer (up to burn-out heat flux) between a platinum wire of 0.15 mm in diameter in neon, deuterium and hydrogen has been studied at atmospheric pressure. These measurements were continued in liquid neon up to 23 bars (Pc ≅ 26.8 b). Film boiling heat transfer coefficients have been measured in pool boiling liquid neon at atmospheric pressure with three heating wires (diameters 0.2, 0.5, 2 mm). All the results have been compared with existing correlations. The second part is devoted to measurements of the critical heat flux limiting heat transfer with small temperature differences between the wall and the liquid neon flowing inside a tube (diameters 3 x 3.5 mm) heated by joule effect on 30 cm of length. Influences of flow stability, nature of electrical current, pressure, mass flow rate and subcooling are shown. In conclusion, the similarity of the heat transfer characteristics in pool boiling as well as in forced convection of liquid neon and hydrogen is emphasized. (author) [fr

  9. Structural and medium effects on the reactions of the cumyloxyl radical with intramolecular hydrogen bonded phenols. The interplay between hydrogen-bonding and acid-base interactions on the hydrogen atom transfer reactivity and selectivity.

    Science.gov (United States)

    Salamone, Michela; Amorati, Riccardo; Menichetti, Stefano; Viglianisi, Caterina; Bietti, Massimo

    2014-07-03

    A time-resolved kinetic study on the reactions of the cumyloxyl radical (CumO(•)) with intramolecularly hydrogen bonded 2-(1-piperidinylmethyl)phenol (1) and 4-methoxy-2-(1-piperidinylmethyl)phenol (2) and with 4-methoxy-3-(1-piperidinylmethyl)phenol (3) has been carried out. In acetonitrile, intramolecular hydrogen bonding protects the phenolic O-H of 1 and 2 from attack by CumO(•) and hydrogen atom transfer (HAT) exclusively occurs from the C-H bonds that are α to the piperidine nitrogen (α-C-H bonds). With 3 HAT from both the phenolic O-H and the α-C-H bonds is observed. In the presence of TFA or Mg(ClO4)2, protonation or Mg(2+) complexation of the piperidine nitrogen removes the intramolecular hydrogen bond in 1 and 2 and strongly deactivates the α-C-H bonds of the three substrates. Under these conditions, HAT to CumO(•) exclusively occurs from the phenolic O-H group of 1-3. These results clearly show that in these systems the interplay between intramolecular hydrogen bonding and Brønsted and Lewis acid-base interactions can drastically influence both the HAT reactivity and selectivity. The possible implications of these findings are discussed in the framework of the important role played by tyrosyl radicals in biological systems.

  10. Selective catalytic reduction of nitrogen oxides from industrial gases by hydrogen or methane; Reduction catalytique selective des oxydes d'azote (NO{sub x}) provenant d'effluents gazeux industriels par l'hydrogene ou le methane

    Energy Technology Data Exchange (ETDEWEB)

    Engelmann Pirez, M

    2004-12-15

    This work deals with the selective catalytic reduction of nitrogen oxides (NO{sub x}), contained in the effluents of industrial plants, by hydrogen or methane. The aim is to replace ammonia, used as reducing agent, in the conventional process. The use of others reducing agents such as hydrogen or methane is interesting for different reasons: practical, economical and ecological. The catalyst has to convert selectively NO into N{sub 2}, in presence of an excess of oxygen, steam and sulfur dioxide. The developed catalyst is constituted by a support such as perovskites, particularly LaCoO{sub 3}, on which are dispersed noble metals (palladium, platinum). The interaction between the noble metal and the support, generated during the activation of the catalyst, allows to minimize the water and sulfur dioxide inhibitor phenomena on the catalytic performances, particularly in the reduction of NO by hydrogen. (O.M.)

  11. Investigation into mechanism of hydrogen transfer from alcohol to ketone in the presence of RhCl(PPh3)3 and RuCl2(PPh3)3 complexes

    International Nuclear Information System (INIS)

    Sharf, V.Z.; Frejdlin, L.Kh.; Krutij, V.N.

    1977-01-01

    The effect of the concentration of complexes and reacting substrates in reactions of ketone reduction by alcohols is studied. The rate of hydrogen transfer is proportional to the concentration of tris(triphenylphosphine) complexes of ruthenium (2) or rhodium (1) chloride, alkanol and ketone. High ketone concentrations inhibit the process. The ultraviolet spectrum of the product of RhCl(PPh 3 ) 3 reaction with cyclohexane reveals a new absorption band and two isobestic points, which is ascribed to the formation of mono- and diketone forms of the rhodium complex. A mechanism of the catalytic effect of complexes is proposed; it includes ligand dissociation, oxidative addition of alcohol, and coordination of the ketone molecule with the formation of an intermediate six-membered compound

  12. Fabrication of a form- and size-variable microcellular-polymer-stabilized metal nanocomposite using supercritical foaming and impregnation for catalytic hydrogenation

    Science.gov (United States)

    2012-01-01

    This article presents the fabrication of size-controllable and shape-flexible microcellular high-density polyethylene-stabilized palladium nanoparticles (Pd/m-HDPE) using supercritical foaming, followed by supercritical impregnation. These nanomaterials are investigated for use as heterogeneous hydrogenation catalysts of biphenyls in supercritical carbon dioxide with no significant surface and inner mass transfer resistance. The morphology of the Pd/m-HDPE is examined using scanning electron microscopy images of the pores inside Pd/m-HDPE catalysts and transmission electron microscopy images of the Pd particles confined in an HDPE structure. This nanocomposite simplifies industrial design and operation. These Pd/m-HDPE catalysts can be recycled easily and reused without complex recovery and cleaning procedures. PMID:22651135

  13. CATALYTIC KINETIC SPECTROPHOTOMETRIC DETERMINATION ...

    African Journals Online (AJOL)

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    acetylchlorophosphonazo(CPApA) by hydrogen peroxide in 0.10 M phosphoric acid. A novel catalytic kinetic-spectrophotometric method is proposed for the determination of copper based on this principle. Copper(II) can be determined spectrophotometrically ...

  14. Solvent-dependent excited-state hydrogen transfer and intersystem crossing in 2-(2′-hydroxyphenyl)-benzothiazole

    KAUST Repository

    Aly, Shawkat Mohammede

    2015-02-12

    The excited-state intramolecular hydrogen transfer (ESIHT) of 2-(2′-hydroxyphenyl) benzothiazole (HBT) has been investigated in a series of nonpolar, polar aprotic, and polar protic solvents. A variety of state-of-the-art experimental methods were employed, including femto- and nanosecond transient absorption and fluorescence upconversion spectroscopy with broadband capabilities. We show that the dynamics and mechanism of ESIHT of the singlet excited HBT are strongly solvent-dependent. In nonpolar solvents, the data demonstrate that HBT molecules adopt a closed form stabilized by O-H⋯N chelated hydrogen bonds with no twisting angle, and the photoinduced H transfer occurs within 120 fs, leading to the formation of a keto tautomer. In polar solvents, owing to dipole-dipole cross talk and hydrogen bonding interactions, the H transfer process is followed by ultrafast nonradiative deactivation channels, including ultrafast internal conversion (IC) and intersystem crossing (ISC). This is likely to be driven by the twisting motion around the C-C bond between the hydroxyphenyl and thiazole moieties, facilitating the IC back to the enol ground state or to the keto triplet state. In addition, our femtosecond time-resolved fluorescence experiments indicate, for the first time, that the lifetime of the enol form in ACN is approximately 280 fs. This observation indicates that the solvent plays a crucial role in breaking the H bond and deactivating the excited state of the HBT. Interestingly, the broadband transient absorption and fluorescence up-conversion data clearly demonstrate that the intermolecular proton transfer from the excited HBT to the DMSO solvent is about 190 fs, forming the HBT anion excited state.

  15. Rapid hydrogen and oxygen atom transfer by a high-valent nickel-oxygen species

    NARCIS (Netherlands)

    Corona, Teresa; Draksharapu, Apparao; Padamati, Sandeep K; Gamba, Ilaria; Martin-Diaconescu, Vlad; Acuña-Parés, Ferran; Browne, Wesley R; Company, Anna

    2016-01-01

    Terminal high-valent metal-oxygen species are key reaction intermediates in the catalytic cycle of both enzymes (e.g., oxygenases) and synthetic oxidation catalysts. While tremendous efforts have been directed towards the characterization of the biologically relevant terminal manganese-oxygen and

  16. Hydrogen bond strengthening induces fluorescence quenching of PRODAN derivative by turning on twisted intramolecular charge transfer

    Science.gov (United States)

    Yang, Yonggang; Li, Donglin; Li, Chaozheng; Liu, YuFang; Jiang, Kai

    2017-12-01

    Researchers have proposed different effective mechanisms of hydrogen bonding (HB) on the fluorescence of 6-propionyl-2-dimethylaminonaphthalene (PRODAN) and its derivatives. Herein, excited state transition and dynamics analysis confirm that the fluorescence of PD (a derivative of PRODAN with ethyl replaced by 3-hydroxy-2,2-dimethylpropan) emits from the planar intramolecular charge transfer (PICT) state rather than twist ICT (TICT) state, because the fluorescence emission and surface hopping from the TICT state to the twist ground (T-S0) state is energy forbidden. Nevertheless, the strengthening of intramolecular-HB (intra-HB) and intermolecular-HB (inter-HB) of PD-(methanol)2 smooth the pathway of surface hopping from TICT to T-S0 state and the external conversion going to planar ground state by decreasing the energy difference of the two states. This smoothing changes the fluorescence state of PD-(methanol)2 to the TICT state in which fluorescence emission does not occur but surface hopping, leading to the partial fluorescence quenching of PD in methanol solvent. This conclusion is different from previous related reports. Moreover, the inter-HB strengthening of PD-methanol in PICT state induces the cleavage of intra-HB and a fluorescence red-shift of 54 nm compared to PD. This red-shift increases to 66 nm for PD-(methanol)2 for the strengthening of the one intra-HB and two inter-HBs. The dipole moments of PD-methanol and PD-(methanol)2 respectively increase about 10.3D and 8.1D in PICT state compared to PD. The synergistic effect of intra-HB and inter-HB induces partial quenching of PD in methanol solvent by turning on the TICT state and fluorescence red-shift. This work gives a reasonable description on the fluorescence red-shift and partial quenching of PD in methanol solvent, which will bring insight into the study of spectroscopic properties of molecules owning better spectral characteristics.

  17. Enhanced catalytic performance in hydrogen generation from NaBH4 hydrolysis by super porous cryogel supported Co and Ni catalysts

    Science.gov (United States)

    Seven, Fahriye; Sahiner, Nurettin

    2014-12-01

    The neutral 3-D superporous cryogel is prepared from a poly(acrylamide) (p(AAm)) hydrogel network modified with an amidoximation reaction to induce chemical changes to produce superporous amidoximated-p(AAm) (amid-p(AAm)) cryogel. The newly-formed strongly ionizable matrices can readily absorb metal ions such as Co(II) and Ni(II) enabling in situ preparation of corresponding metal nanoparticles by NaBH4 treatments. It is found that the superporous amid-p(AAm)-Co cryogel composite is very effective as a catalyst for H2 generation from hydrolysis of NaBH4 in alkaline medium. Furthermore, it is demonstrated that the metal ion loading capacity and catalytic activity of superporous amid-p(AAm)-Co cryogel composites increased with 2nd and 3rd Co(II) ion loading and reduction cycles. The hydrogen generation rate of p(AAm)-Co metal composites is increased to 1926.3 ± 1.1 from 1130.2 ± 1.5 (mL H2) (min)-1 (g of M)-1. The effect of various parameters such as porosity, metal type, the number of reloading and reduction cycles of the metal ion, and temperature are investigated for the hydrolysis of NaBH4. The kinetic parameters such as energy, enthalpy and entropy are determined as Ea = 39.7 ± 0.2 kJ mol-1, ΔH = 37.2 ± 0.1 kJ mol-1 and ΔS = -171.9 ± 0.5 J mol-1 K-1, respectively.

  18. Technology Development for Hydrogen Propellant Storage and Transfer at the Kennedy Space Center (KSC)

    Science.gov (United States)

    Youngquist, Robert; Starr, Stanley; Krenn, Angela; Captain, Janine; Williams, Martha

    2016-01-01

    The National Aeronautics and Space Administration (NASA) is a major user of liquid hydrogen. In particular, NASA's John F. Kennedy (KSC) Space Center has operated facilities for handling and storing very large quantities of liquid hydrogen (LH2) since the early 1960s. Safe operations pose unique challenges and as a result NASA has invested in technology development to improve operational efficiency and safety. This paper reviews recent innovations including methods of leak and fire detection and aspects of large storage tank health and integrity. We also discuss the use of liquid hydrogen in space and issues we are addressing to ensure safe and efficient operations should hydrogen be used as a propellant derived from in-situ volatiles.

  19. Phonon driven proton transfer in crystals with short strong hydrogen bonds

    NARCIS (Netherlands)

    Fontaine-Vive, F.; Johnson, M.R.; Kearley, G.J.; Cowan, J.A.; Howard, J.A.K.; Parker, S.F.

    2006-01-01

    Recent work on understanding why protons migrate with increasing temperature in short, strong hydrogen bonds is extended here to three more organic, crystalline systems. Inelastic neutron scattering and density functional theory based simulations are used to investigate structure, vibrations, and

  20. Peptide-Driven Charge-Transfer Organogels Built from Synergetic Hydrogen Bonding and Pyrene-Naphthalenediimide Donor-Acceptor Interactions.

    Science.gov (United States)

    Bartocci, Silvia; Berrocal, José Augusto; Guarracino, Paola; Grillaud, Maxime; Franco, Lorenzo; Mba, Miriam

    2018-02-26

    The peptide-driven formation of charge transfer (CT) supramolecular gels featuring both directional hydrogen-bonding and donor-acceptor (D-A) complexation is reported. Our design consists of the coassembly of two dipeptide-chromophore conjugates, namely diphenylalanine (FF) dipeptide conveniently functionalized at the N-terminus with either a pyrene (Py-1, donor) or naphthalene diimide (NDI-1, acceptor). UV/Vis spectroscopy confirmed the formation of CT complexes. FTIR and 1 H NMR spectroscopy studies underlined the pivotal role of hydrogen bonding in the gelation process, and electronic paramagnetic resonance (EPR) measurements unraveled the advantage of preorganized CT supramolecular architectures for charge transport over solutions containing non-coassembled D and A molecular systems. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.