Effect of the dispersants on Pd species and catalytic activity of supported palladium catalyst

Energy Technology Data Exchange (ETDEWEB)

Hu, Yue [Key Laboratory for Green Chemical Process of Ministry of Education, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan 430205 (China); Yang, Xiaojun, E-mail: 10100201@wit.edu.cn [Key Laboratory for Green Chemical Process of Ministry of Education, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan 430205 (China); Cao, Shuo, E-mail: cao23@email.sc.edu [North America R& D Center, Clariant BU Catalysts, Louisville, 40209, KY (United States); Zhou, Jie [Key Laboratory for Green Chemical Process of Ministry of Education, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan 430205 (China); Wu, Yuanxin [Key Laboratory for Green Chemical Process of Ministry of Education, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan 430205 (China); School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Han, Jinyu [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Yan, Zhiguo [Key Laboratory for Green Chemical Process of Ministry of Education, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan 430205 (China); Zheng, Mingming [Oil Crops Research Institute, Chinese Academy of Agricultural Sciences, Hubei Key Laboratory of Oilcrops Lipid Chemistry and Nutrition, Wuhan 430062 (China)

2017-04-01

Highlights: • Polyvinyl alcohol (PVA) inhibited the sintering and reduction of Pd nanoparticles. • Activity was improved for supported Pd catalysts with PVA modified method. • PVA modified method minimized the catalyst deactivation. • This work provides an insight of the regeneration strategies for Pd catalysts. - Abstract: A series of supported palladium catalysts has been prepared through the precipitation method and the reduction method, using polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) as dispersants. The effects of the dispersants on the properties of catalysts were evaluated and the catalytic performance of the new materials was investigated for the oxidative carbonylation of phenol to diphenyl carbonate (DPC). The catalysts as prepared were also characterized by the X-ray diffraction (XRD), transmission electron microscope (TEM), Brunner-Emmet-Teller (BET) measurements and X-ray photoelectron spectroscopy (XPS) techniques. The results show that the addition of the dispersants had no effect on the crystal phase of the catalysts. However, the dispersion of Pd particles was improved when the dispersants were used. Moreover, the particle sizes of Pd nanoparticles modified by PVA were smaller than those modified by PVP. The catalysts prepared using the dispersants gave better yields of DPC than the catalysts prepared without the dispersants. The highest yield of DPC was 17.9% with the PVA-Red catalyst. The characterization results for the used catalysts showed that the Pd species in the PVA-Red catalyst remained mostly divalent and the lattice oxygen species were consumed during the reaction, which could lead to the higher catalytic activity of the PVA-Red catalyst. The experimental results confirm that PVA effectively inhibited the sintering and reduction of active Pd species in the oxidative carbonylation of phenol.

Heterogeneous catalysis in the liquid-phase oxidation of olefins--3. The activity of supported vanadium-chromium binary oxide catalyst for the oxidation of cyclohexene

Energy Technology Data Exchange (ETDEWEB)

Takehira, K; Hayakawa, T; Ishikawa, T

1979-03-01

The activity of supported vanadium-chromium binary oxide catalyst for the oxidation of cyclohexene to 1-cyclohexenyl hydroperoxide, 2-cyclohexene-1-one, 2-cyclohexene-1-ol, and cyclohexene oxide was due to the interaction between the metal oxides and the carriers. The oxidation reaction was carried out in benzene at 60/sup 0/C for four hours with the binary oxide supported on (GAMMA)-alumina or silica; three series of catalysts were prepared by combining the vanadium and chromium oxide components with alumina hydrate or silica sol by a kneading method. The silica-supported catalysts had the greatest activity, the highest being the V/sub 2/O/sub 5//SiO/sub 2/ system, which lost its activity quickly during the reaction. This was followed in activity by the Cr/sub 2/O/sub 3//SiO/sub 2/ system, containing the chromium(V) species. The Cr/sub 2/O/sub 3//Al/sub 2/O/sub 3/ system also had high activity and the chromium(V) species. The vanadium and chromium metal ions are probably coordinated tetrahedrally on the support, and these complexes catalyze cyclohexene autoxidation by decomposing 1-cyclohexenyl hydroperoxide.

Oxidative desulfurization of benzothiophene and thiophene with WOx/ZrO2 catalysts: effect of calcination temperature of catalysts.

Science.gov (United States)

Hasan, Zubair; Jeon, Jaewoo; Jhung, Sung Hwa

2012-02-29

Oxidative desulfurization (ODS) of model fuel containing benzothiophene (BT) or thiophene (Th) has been carried out with WO(x)/ZrO2 catalyst, which was calcined at various temperatures. Based on the conversion of BT in the model fuel, it can be shown that the optimum calcination temperature of WOx/ZrO2 catalyst is around 700 °C. The most active catalyst is composed of tetragonal zirconia (ZrO2) with well dispersed polyoxotungstate species and it is necessary to minimize the contents of the crystalline WO3 and monoclinic ZrO2 for a high BT conversion. The oxidation rate was interpreted with the first-order kinetics, and it demonstrated the importance of electron density since the kinetic constant for BT was higher than that for Th even though the BT is larger than Th in size. A WOx/ZrO2 catalyst, treated suitably, can be used as a reusable active catalyst in the ODS. Copyright © 2012 Elsevier B.V. All rights reserved.

Lithium chemistry of lithium doped magnesium oxide catalysts used in the oxidative coupling of methane

NARCIS (Netherlands)

Korf, S.J.; Roos, J.A.; de Bruijn, N.A.; van Ommen, J.G.; Ross, J.R.H.

1990-01-01

Active sites are created on the surface of a Li/MgO catalyst used for the selective oxidation of methane by the gradual loss of carbon dioxide from surface carbonate species in the presence of oxygen. Decomposition of the carbonate species in the absence of oxygen is detrimental to the activity of

Oxidation catalysts on alkaline earth supports

Science.gov (United States)

Mohajeri, Nahid

2017-03-21

An oxidation catalyst includes a support including particles of an alkaline earth salt, and first particles including a palladium compound on the support. The oxidation catalyst can also include precious metal group (PMG) metal particles in addition to the first particles intermixed together on the support. A gas permeable polymer that provides a continuous phase can completely encapsulate the particles and the support. The oxidation catalyst may be used as a gas sensor, where the first particles are chemochromic particles.

Heterogeneous Metal Catalysts for Oxidation Reactions

Directory of Open Access Journals (Sweden)

Md. Eaqub Ali

2014-01-01

Full Text Available Oxidation reactions may be considered as the heart of chemical synthesis. However, the indiscriminate uses of harsh and corrosive chemicals in this endeavor are threating to the ecosystems, public health, and terrestrial, aquatic, and aerial flora and fauna. Heterogeneous catalysts with various supports are brought to the spotlight because of their excellent capabilities to accelerate the rate of chemical reactions with low cost. They also minimize the use of chemicals in industries and thus are friendly and green to the environment. However, heterogeneous oxidation catalysis are not comprehensively presented in literature. In this short review, we clearly depicted the current state of catalytic oxidation reactions in chemical industries with specific emphasis on heterogeneous catalysts. We outlined here both the synthesis and applications of important oxidation catalysts. We believe it would serve as a reference guide for the selection of oxidation catalysts for both industries and academics.

High activity PtRu/C catalysts synthesized by a modified impregnation method for methanol electro-oxidation

International Nuclear Information System (INIS)

Ma Liang; Liu Changpeng; Liao Jianhui; Lu Tianhong; Xing Wei; Zhang Jiujun

2009-01-01

A modified impregnation method was used to prepare highly dispersive carbon-supported PtRu catalyst (PtRu/C). Two modifications to the conventional impregnation method were performed: one was to precipitate the precursors ((NH 4 ) 2 PtCl 6 and Ru(OH) 3 ) on the carbon support before metal reduction; the other was to add a buffer into the synthetic solution to stabilize the pH. The prepared catalyst showed a much higher activity for methanol electro-oxidation than a catalyst prepared by the conventional impregnation method, even higher than that of current commercially available, state-of-the-art catalysts. The morphology of the prepared catalyst was characterized using TEM and XRD measurements to determine particle sizes, alloying degree, and lattice parameters. Electrochemical methods were also used to ascertain the electrochemical active surface area and the specific activity of the catalyst. Based on XPS measurements, the high activity of this catalyst was found to originate from both metallic Ru (Ru 0 ) and hydrous ruthenium oxides (RuO x H y ) species on the catalyst surface. However, RuO x H y was found to be more active than metallic Ru. In addition, the anhydrous ruthenium oxide (RuO 2 ) species on the catalyst surface was found to be less active.

Impacts of acid gases on mercury oxidation across SCR catalyst

International Nuclear Information System (INIS)

Zhuang, Ye; Laumb, Jason; Liggett, Richard; Holmes, Mike; Pavlish, John

2007-01-01

A series of bench-scale experiments were completed to evaluate acid gases of HCl, SO 2 , and SO 3 on mercury oxidation across a commercial selective catalytic reduction (SCR) catalyst. The SCR catalyst was placed in a simulated flue gas stream containing O 2 , CO 2 , H 2 O, NO, NO 2 , and NH 3 , and N 2 . HCl, SO 2 , and SO 3 were added to the gas stream either separately or in combination to investigate their interactions with mercury over the SCR catalyst. The compositions of the simulated flue gas represent a medium-sulfur and low- to medium-chlorine coal that could represent either bituminous or subbituminous. The experimental data indicated that 5-50 ppm HCl in flue gas enhanced mercury oxidation within the SCR catalyst, possibly because of the reactive chlorine species formed through catalytic reactions. An addition of 5 ppm HCl in the simulated flue gas resulted in mercury oxidation of 45% across the SCR compared to only 4% mercury oxidation when 1 ppm HCl is in the flue gas. As HCl concentration increased to 50 ppm, 63% of Hg oxidation was reached. SO 2 and SO 3 showed a mitigating effect on mercury chlorination to some degree, depending on the concentrations of SO 2 and SO 3 , by competing against HCl for SCR adsorption sites. High levels of acid gases of HCl (50 ppm), SO 2 (2000 ppm), and SO 3 (50 ppm) in the flue gas deteriorate mercury adsorption on the SCR catalyst. (author)

Isotope exchange in oxide-containing catalyst

Science.gov (United States)

Brown, Kenneth G. (Inventor); Upchurch, Billy T. (Inventor); Hess, Robert V. (Inventor); Miller, Irvin M. (Inventor); Schryer, David R. (Inventor); Sidney, Barry D. (Inventor); Wood, George M. (Inventor); Hoyt, Ronald F. (Inventor)

1989-01-01

A method of exchanging rare-isotope oxygen for common-isotope oxygen in the top several layers of an oxide-containing catalyst is disclosed. A sample of an oxide-containing catalyst is exposed to a flowing stream of reducing gas in an inert carrier gas at a temperature suitable for the removal of the reactive common-isotope oxygen atoms from the surface layer or layers of the catalyst without damaging the catalyst structure. The reduction temperature must be higher than any at which the catalyst will subsequently operate. Sufficient reducing gas is used to allow removal of all the reactive common-isotope oxygen atoms in the top several layers of the catalyst. The catalyst is then reoxidized with the desired rare-isotope oxygen in sufficient quantity to replace all of the common-isotope oxygen that was removed.

Nature of nitrogen specie in coke and their role in NOx formation during FCC catalyst regeneration

International Nuclear Information System (INIS)

Babich, I.V.; Seshan, K.; Lefferts, L.

2005-01-01

NO x emission during the regeneration of coked fluid catalytic cracking (FCC) catalysts is an environmental problem. In order to follow the route to NO x formation and try to find ways to suppress it, a coked industrial FCC catalyst has been prepared using model N-containing compounds, e.g., pyridine, pyrrole, aniline and hexadecane-pyridine mixture. Nitrogen present in the FCC feed is incorporated as polyaromatic compounds in the coke deposited on the catalyst during cracking. Its functionality has been characterized using XPS. Nitrogen specie of different types, namely, pyridine, pyrrolic or quaternary-nitrogen (Q-N) have been discriminated. Decomposition of the coke during the catalyst regeneration (temperature programmed oxidation (TPO) and isothermal oxidation) has been monitored by GC and MS measurements of the gaseous products formed. The pyrrolic- and pyridinic-type N specie, present more in the outer coke layers, are oxidized under conditions when still large amount of C or CO is available from coke to reduced NO x formed to N 2 . ''Q-N'' type species are present in the inner layer, strongly adsorbed on the acid sites on the catalyst. They are combusted last during regeneration. As most of the coke is already combusted at this point, lack of reductants (C, CO, etc.) results in the presence of NO x in the tail gas

Novel metalloporphyrin catalysts for the oxidation of hydrocarbons

Energy Technology Data Exchange (ETDEWEB)

Showalter, M.C.; Nenoff, T.M.; Shelnutt, J.A.

1996-11-01

Work was done for developing biomimetic oxidation catalysts. Two classes of metalloporphyrin catalysts were studied. The first class of catalysts studied were a novel series of highly substituted metalloporphyrins, the fluorinated iron dodecaphenylporphyrins. These homogeneous metalloporphyrin catalysts were screened for activity as catalysts in the oxidation of hydrocarbons by dioxygen. Results are discussed with respect to catalyst structural features. The second type of catalysts studied were heterogeneous catalysts consisting of metalloporphyrins applied to inorganic supports. Preliminary catalytic testing results with these materials are presented.

Catalytic partial oxidation of methane over porous silica supported VO{sub x} catalysts

Energy Technology Data Exchange (ETDEWEB)

Pirovano, C.; Schoenborn, E.; Kalevaru, V.N.; Wohlrab, S.; Luecke, B.; Martin, A. [University Rostock e.V., Rostock (Germany). Leibniz Inst. for Catalysis

2011-07-01

High surface area mesoporous siliceous MCM-41 and SBA-15 materials have been used as supports to disperse vanadium oxide species using wet impregnation and incipient wetness impregnation methods. These materials were used as catalysts for the partial oxidation of methane (POM) to formaldehyde. The physico-chemical properties of the solids were studied by means of BET, DR-UV/Vis spectroscopy, Py-FTIR and TEM. The influence of support and the preparation method on the dispersion of VOx is also investigated. The catalytic properties of the catalysts were examined in a fixed bed stainless steel reactor at 923 K. So far a maximum production of formaldehyde can be detected on SBA-15 supported VOx-catalysts prepared by incipient wetness impregnation. On this V/SBA-15 material a covalent attachment of catalytic active molecular vanadium species dominates, which in turn leads to a lower activation temperature and thereby reduced over-oxidation. From the best case, the space time yield of HCHO could be reached close to 775 g{sub HCHO} Kg{sub cat}{sup -1} h{sup -1}. (orig.)

Tin-antimony oxide oxidation catalysts

Energy Technology Data Exchange (ETDEWEB)

Berry, Frank J. [Open University, Department of Chemistry (United Kingdom)

1998-12-15

Tin-antimony oxide catalysts for the selective oxidation of hydrocarbons have been made by precipitation techniques. The dehydration of the amorphous dried precipitate by calcination at increasingly higher temperatures induces the crystallisation of a rutile-related tin dioxide-type phase and the segregation of antimony oxides which volatilise at elevated temperatures. The rutile-related tin dioxide-type phase contains antimony(V) in the bulk and antimony(III) in the surface. Specific catalytic activity for the oxidative dehydrogenation of butene to butadiene is associated with materials with large concentrations of antimony(III) in the surface.

Oxidative dehydrogenation of ethane on rare-earth oxide-based catalysts

Energy Technology Data Exchange (ETDEWEB)

Buyevskaya, O.; Baerns, M. [Institut fuer Angewandte Chemie Berlin-Adlershof e.V., Berlin (Germany)

1998-12-31

Results on the oxidative dehydrogenation of ethane on rare-earth oxide (REO) based catalysts (Na-P-Sm-O, Sm-Sr(Ca)-O, La-Sr-O and Nd-Sr-O) are described. Oxygen adsorption was found to be a key factor which determines the activity of this type of catalysts. Continuous flow experiments in the presence of catalysts which reveal strong oxygen adsorption showed that the reaction mixture is ignited resulting in an enhanced heat generation at the reactor inlet. The heat produced by the oxidative reactions was sufficient under the conditions chosen for the endothermic thermal pyrolysis which takes place preferentially in the gas phase. Ignition of the reaction mixture is an important catalyst function. Contrary to non-catalytic oxidative dehydrogenation, reaction temperatures above 700 C could be achieved without significant external heat input. Ethylene yields of up to 34-45% (S=66-73%) were obtained on REO-based catalysts under non-isothermal conditions (T{sub max}=810-865 C) at contact times in the order of 30 to 40 ms. (orig.)

Oxidative desulfurization of benzothiophene and thiophene with WO{sub x}/ZrO{sub 2} catalysts: Effect of calcination temperature of catalysts

Energy Technology Data Exchange (ETDEWEB)

Hasan, Zubair; Jeon, Jaewoo [Department of Chemistry and Green-Nano Materials Research Center, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Jhung, Sung Hwa, E-mail: sung@knu.ac.kr [Department of Chemistry and Green-Nano Materials Research Center, Kyungpook National University, Daegu 702-701 (Korea, Republic of)

2012-02-29

Highlights: Black-Right-Pointing-Pointer Oxidative desulfurization was studied with WO{sub x}/ZrO{sub 2} calcined at different temp. Black-Right-Pointing-Pointer The importance of the phases of zirconia and tungsten oxide was suggested. Black-Right-Pointing-Pointer The catalyst was analyzed thoroughly with Raman and XRD techniques. Black-Right-Pointing-Pointer The importance of electron density on S was confirmed with the kinetics of oxidation. - Abstract: Oxidative desulfurization (ODS) of model fuel containing benzothiophene (BT) or thiophene (Th) has been carried out with WO{sub x}/ZrO{sub 2} catalyst, which was calcined at various temperatures. Based on the conversion of BT in the model fuel, it can be shown that the optimum calcination temperature of WO{sub x}/ZrO{sub 2} catalyst is around 700 Degree-Sign C. The most active catalyst is composed of tetragonal zirconia (ZrO{sub 2}) with well dispersed polyoxotungstate species and it is necessary to minimize the contents of the crystalline WO{sub 3} and monoclinic ZrO{sub 2} for a high BT conversion. The oxidation rate was interpreted with the first-order kinetics, and it demonstrated the importance of electron density since the kinetic constant for BT was higher than that for Th even though the BT is larger than Th in size. A WO{sub x}/ZrO{sub 2} catalyst, treated suitably, can be used as a reusable active catalyst in the ODS.

Electro-oxidation of Ethanol on Carbon Supported PtSn and PtSnNi Catalysts

Directory of Open Access Journals (Sweden)

Nur Hidayati

2016-03-01

Full Text Available Even though platinum is known as an active electro-catalyst for ethanol oxidation at low temperatures (< 100 oC, choosing the electrode material for ethanol electro-oxidation is a crucial issue. It is due to its property which easily poisoned by a strong adsorbed species such as CO. PtSn-based electro-catalysts have been identified as better catalysts for ethanol electro-oxidation. The third material is supposed to improved binary catalysts performance. This work presents a study of the ethanol electro-oxidation on carbon supported Pt-Sn and Pt-Sn-Ni catalysts. These catalysts were prepared by alcohol reduction. Nano-particles with diameters between 2.5-5.0 nm were obtained. The peak of (220 crystalline face centred cubic (fcc Pt phase for PtSn and PtSnNi alloys was repositioned due to the presence of Sn and/or Ni in the alloy. Furthermore, the modification of Pt with Sn and SnNi improved ethanol and CO electro-oxidation. Copyright © 2016 BCREC GROUP. All rights reserved Received: 10th November 2015; Revised: 1st February 2016; Accepted: 1st February 2016 How to Cite: Hidayati, N., Scott, K. (2016. Electro-oxidation of Ethanol on Carbon Supported PtSn and PtSnNi Catalysts. Bulletin of Chemical Reaction Engineering & Catalysis, 11 (1: 10-20. (doi:10.9767/bcrec.11.1.394.10-20 Permalink/DOI: http://dx.doi.org/10.9767/bcrec.11.1.394.10-20

Ir catalysts: Preventing CH3COOH formation in ethanol oxidation

Science.gov (United States)

Miao, Bei; Wu, Zhipeng; Xu, Han; Zhang, Minhua; Chen, Yifei; Wang, Lichang

2017-11-01

Current catalysts used for ethanol oxidation reaction (EOR) cannot effectively prevent CH3COOH formation, and thus become a major hindrance for direct ethanol fuel cell applications. We report an Ir catalyst that shows great promise for a complete EOR based on density functional theory calculations using PBE functional. The reaction barrier on Ir(1 0 0) was found to be 2.10 eV for CH3COOH formation, which is much higher than currently used Pd and Pt, and 0.57 eV for Csbnd C bond cleavage in CHCO species, which are comparable to Pd and Pt. The result suggests future directions for studying optimal complete EOR catalysts.

Water oxidation catalysts and methods of use thereof

Energy Technology Data Exchange (ETDEWEB)

Hill, Craig L.; Gueletii, Yurii V.; Musaev, Djamaladdin G.; Yin, Qiushi; Botar, Bogdan

2017-12-05

Homogeneous water oxidation catalysts (WOCs) for the oxidation of water to produce hydrogen ions and oxygen, and methods of making and using thereof are described herein. In a preferred embodiment, the WOC is a polyoxometalate WOC which is hydrolytically stable, oxidatively stable, and thermally stable. The WOC oxidized waters in the presence of an oxidant. The oxidant can be generated photochemically, using light, such as sunlight, or electrochemically using a positively biased electrode. The hydrogen ions are subsequently reduced to form hydrogen gas, for example, using a hydrogen evolution catalyst (HEC). The hydrogen gas can be used as a fuel in combustion reactions and/or in hydrogen fuel cells. The catalysts described herein exhibit higher turn over numbers, faster turn over frequencies, and/or higher oxygen yields than prior art catalysts.

Activity of molybdenum-containing oxide catalysts in the reaction of ethane oxidation

International Nuclear Information System (INIS)

Konovalov, V.I.; Ehpova, T.I.; Shchukin, V.P.; Averbukh, A.Ya.

1977-01-01

Investigation results concerning the catalytic activity of molybdenum-containing catalysts in ethane oxidation reaction are presented. It has been found that the greatest activity in the temperature range from 450 to 600 deg C is exhibited by cobalt-molybdenum catalyst; at 600 deg C bismuth-molybdenum catalyst is the most active. Nickel-molybdenum catalyst is selective and active with respect to ethylene. Iron- and manganese-molybdenum catalysts do not show high ethane oxidation rates and their selectivity is insignificant

ZIF-67-derived hollow nanocages with layered double oxides shell as high-Efficiency catalysts for CO oxidation

Science.gov (United States)

Kong, Wenpeng; Li, Jing; Chen, Yao; Ren, Yuqing; Guo, Yonghua; Niu, Shengli; Yang, Yanzhao

2018-04-01

Constructing non-precious hybrid metal oxides with specific morphology as cost-effective and highly efficient catalysts is a promising way for the automotive exhaust purification. In this work, we report a facile strategy for the fabrication of a unique hollow Co-Ni layered double oxides (HLDO) nanocages by using zeolitic imidazole frameworks (ZIFs) as template. The synthesis of intermediate core-shell and hollow Co-Ni layered double hydroxides (HLDH) nanoflakes as well as the corresponding Co-Ni oxides products were successfully controlled, and the formation process was also explained. Among ZIF-67-derived oxides, HLDO exhibits excellent catalytic activities (complete conversion of CO into CO2 at 118 °C) and long-term stability for CO oxidation. The remarkable catalytic activities of HLDO can be attributed to high surface area (258 m2 g-1) inherited from the HLDH, which could provide more active sites for CO oxidation. In addition, active oxygen species indicated by the O 1 s XPS spectrum and improved synergistic effect between NiO and Co3O4 reflected by H2-TPR, further explain the enhanced performance of the HLDO catalysts. The presented strategy for controlled design and synthesis of hollow multicomponent metal oxides will provide prospects in developing highly effective catalysts.

Chemical engineering design of CO oxidation catalysts

Science.gov (United States)

Herz, Richard K.

1987-01-01

How a chemical reaction engineer would approach the challenge of designing a CO oxidation catalyst for pulsed CO2 lasers is described. CO oxidation catalysts have a long history of application, of course, so it is instructive to first consider the special requirements of the laser application and then to compare them to the characteristics of existing processes which utilize CO oxidation catalysts. All CO2 laser applications require a CO oxidation catalyst with the following characteristics: (1) active at stoichiometric ratios of O2 and CO, (2) no inhibition by CO2 or other components of the laser environment, (3) releases no particulates during vibration or thermal cycling, and (4) long lifetime with a stable activity. In all applications, low consumption of power is desirable, a characteristic especially critical in aerospace applications and, thus, catalyst activity at low temperatures is highly desirable. High power lasers with high pulse repetition rates inherently require circulation of the gas mixture and this forced circulation is available for moving gas past the catalyst. Low repetition rate lasers, however, do not inherently require gas circulation, so a catalyst that did not require such circulation would be favorable from the standpoint of minimum power consumption. Lasers designed for atmospheric penetration of their infrared radiation utilize CO2 formed from rare isotopes of oxygen and this application has the additional constraint that normal abundance oxygen isotopes in the catalyst must not exchange with rare isotopes in the gas mixture.

Catalysts for oxidation of mercury in flue gas

Science.gov (United States)

Granite, Evan J [Wexford, PA; Pennline, Henry W [Bethel Park, PA

2010-08-17

Two new classes of catalysts for the removal of heavy metal contaminants, especially mercury (Hg) from effluent gases. Both of these classes of catalysts are excellent absorbers of HCl and Cl.sub.2 present in effluent gases. This adsorption of oxidizing agents aids in the oxidation of heavy metal contaminants. The catalysts remove mercury by oxidizing the Hg into mercury (II) moieties. For one class of catalysts, the active component is selected from the group consisting of iridium (Ir) and iridum-platinum (Ir/Pt) alloys. The Ir and Ir/Pt alloy catalysts are especially corrosion resistant. For the other class of catalyst, the active component is partially combusted coal or "Thief" carbon impregnated with Cl.sub.2. Untreated Thief carbon catalyst can be self-activating in the presence of effluent gas streams. The Thief carbon catalyst is disposable by means of capture from the effluent gas stream in a particulate collection device (PCD).

Plasma and catalyst for the oxidation of NOx

DEFF Research Database (Denmark)

Jõgi, Indrek; Erme, Kalev; Levoll, Erik

2018-01-01

. In the case of indirect oxidation, only ozone could reach the catalyst surface and improve the oxidation of NO2 to N2O5. The effect of catalyst at different experimental conditions was quantitatively described with the aid of simple global chemical kinetic models derived for the NO x oxidation either...... by plasma or ozone. The models allowed to compare the effect of different catalysts and to analyze the limitations for the efficiency improvement by catalyst....... to NO mediated by O radicals in plasma. Indirect NO oxidation by plasma produced ozone allows to circumvent the back-reaction and further oxidize NO2 to N2O5 but the slow reaction rate for the latter process limits the efficiency of this process. Present paper gives an overview of the role of metal...

Improvement of sulfur resistance of Pd/Ce-Zr-Al-O catalysts for CO oxidation

Science.gov (United States)

Shin, Haebin; Baek, Minsung; Ro, Youngsoo; Song, Changyeol; Lee, Kwan-Young; Song, In Kyu

2018-01-01

Two kinds of mesoporous ceria-zirconia-alumina supports were prepared by a single-step epoxide-driven sol-gel method (SGCZA) and by a co-precipitation method (PCZA). Palladium catalysts supported on these materials were then prepared by a wet impregnation method (Pd/SGCZA and Pd/PCZA). The prepared catalysts were applied to the CO oxidation reaction before and after sulfur aging. XRD and N2 adsorption-desorption analyses revealed that these two catalysts retained different physicochemical properties. Pd/SGCZA had higher surface area and larger pore volume than Pd/PCZA before and after sulfur aging. TPR (Temperature-programmed reduction), CO chemisorption, FT-IR, and XPS analyses showed that the catalysts were differently influenced by sulfur species. Pd/SGCZA formed less sulfate and retained higher palladium dispersion than Pd/PCZA after sulfur aging. In the CO oxidation, Pd/PCZA showed better activity than Pd/SGCZA before sulfur aging. However, Pd/SGCZA showed higher CO conversion than Pd/PCZA after sulfur aging. We concluded that Pd/SGCZA was less poisoned by sulfur species than Pd/PCZA.

Mechanism of 1, 1-d2 propene oxidation over oxide catalysts

International Nuclear Information System (INIS)

Portefaix, J.L.; Figueras, F.; Forissier, M.

1980-01-01

CD 2 CHCH 3 was oxidized over bismuth molybdate, tin-antimony mixed oxides and supported molybdenum and vanadium oxide catalysts. The deuterium retention is high ( > 90%) in the recovered propene. Percentage retentions of deuterium in the acrolein agree with literature data when bismuth molybdate is used as catalyst. On Sb-Sn-O and supported Mo and V oxides, no isotope effect is noticed for the abstraction of the second hydrogen from the olefin. The slow step of the reaction may therefore be different for the oxidation of propene on Bi-Mo-O and Sb-Sn-O. The ethanal produced by oxidation of CD 2 CHCH 3 contains only minor amounts of deuterium, whatever the catalyst used. It is suggested that partial oxidation of propene to acrolein and C-C bond rupture are parallel reactions which involve different intermediates. Possible mechanisms adapted from organic chemistry are presented to explain these findings. 4 tables

Sol-gel based oxidation catalyst and coating system using same

Science.gov (United States)

Watkins, Anthony N. (Inventor); Leighty, Bradley D. (Inventor); Oglesby, Donald M. (Inventor); Patry, JoAnne L. (Inventor); Schryer, Jacqueline L. (Inventor)

2010-01-01

An oxidation catalyst system is formed by particles of an oxidation catalyst dispersed in a porous sol-gel binder. The oxidation catalyst system can be applied by brush or spray painting while the sol-gel binder is in its sol state.

V{sub 2}O{sub 5}-ZrO{sub 2} catalysts for the oxidative dehydrogenation of propane - influence of the niobium oxide doping

Energy Technology Data Exchange (ETDEWEB)

Albrecht, S.; Hallmeier, K.H.; Wendt, G. [Leipzig Univ. (Germany). Fakultaet fuer Chemie und Mineralogie; Lippold, G. [Leipzig Univ. (Germany). Fakultaet fuer Physik und Geowissenschaften

1998-12-31

The oxidative dehydrogenation (ODH) of light alkanes is an alternative way for the production of olefins. A wide variety of catalytic systems has been investigated. Vanadium oxide based catalysts were described in the literature as effective catalysts for the ODH of propane. The catalytic activity and selectivity depend on the kind of support material, the kind of dopants and the formation of complex metal oxide phases. In recent papers it was claimed that both orthovanadate and/or pyrovanadate species are selective for the ODH of propane. Niobia based materials were investigated as catalysts for acidic and selective oxidation type reactions. In the ODH of propane niobia exhibited a high selectivity to propene but the conversion of propane was low. V{sub 2}O{sub 5}-Nb{sub 2}O{sub 5} catalysts proved to be catalytically active and selective and showed no formation of oxygenates. In the present study the influence of the niobia dopant of the catalytic properties of V{sub 2}O{sub 5}-ZrO{sub 2} catalysts in the ODH of propane was examined. The structural and textural properties of the catalysts were investigated using several methods. (orig.)

Ionic Liquids in Selective Oxidation: Catalysts and Solvents.

Science.gov (United States)

Dai, Chengna; Zhang, Jie; Huang, Chongpin; Lei, Zhigang

2017-05-24

Selective oxidation has an important role in environmental and green chemistry (e.g., oxidative desulfurization of fuels and oxidative removal of mercury) as well as chemicals and intermediates chemistry to obtain high-value-added special products (e.g., organic sulfoxides and sulfones, aldehydes, ketones, carboxylic acids, epoxides, esters, and lactones). Due to their unique physical properties such as the nonvolatility, thermal stability, nonexplosion, high polarity, and temperature-dependent miscibility with water, ionic liquids (ILs) have attracted considerable attention as reaction solvents and media for selective oxidations and are considered as green alternatives to volatile organic solvents. Moreover, for easy separation and recyclable utilization, IL catalysts have attracted unprecedented attention as "biphasic catalyst" or "immobilized catalyst" by immobilizing metal- or nonmetal-containing ILs onto mineral or polymer supports to combine the unique properties of ILs (chemical and thermal stability, capacity for extraction of polar substrates and reaction products) with the extended surface of the supports. This review highlights the most recent outcomes on ILs in several important typical oxidation reactions. The contents are arranged in the series of oxidation of sulfides, oxidation of alcohols, epoxidation of alkenes, Baeyer-Villiger oxidation reaction, oxidation of alkanes, and oxidation of other compounds step by step involving ILs as solvents, catalysts, reagents, or their combinations.

Second-Order Biomimicry: In Situ Oxidative Self-Processing Converts Copper(I)/Diamine Precursor into a Highly Active Aerobic Oxidation Catalyst.

Science.gov (United States)

McCann, Scott D; Lumb, Jean-Philip; Arndtsen, Bruce A; Stahl, Shannon S

2017-04-26

A homogeneous Cu-based catalyst system consisting of [Cu(MeCN) 4 ]PF 6 , N , N '-di- tert -butylethylenediamine (DBED), and p -( N , N -dimethylamino)pyridine (DMAP) mediates efficient aerobic oxidation of alcohols. Mechanistic study of this reaction shows that the catalyst undergoes an in situ oxidative self-processing step, resulting in conversion of DBED into a nitroxyl that serves as an efficient cocatalyst for aerobic alcohol oxidation. Insights into this behavior are gained from kinetic studies, which reveal an induction period at the beginning of the reaction that correlates with the oxidative self-processing step, EPR spectroscopic analysis of the catalytic reaction mixture, which shows the buildup of the organic nitroxyl species during steady state turnover, and independent synthesis of oxygenated DBED derivatives, which are shown to serve as effective cocatalysts and eliminate the induction period in the reaction. The overall mechanism bears considerable resemblance to enzymatic reactivity. Most notable is the "oxygenase"-type self-processing step that mirrors generation of catalytic cofactors in enzymes via post-translational modification of amino acid side chains. This higher-order function within a synthetic catalyst system presents new opportunities for the discovery and development of biomimetic catalysts.

Supramolecular water oxidation with rubda-based catalysts

KAUST Repository

Richmond, Craig J.

2014-11-05

Extremely slow and extremely fast new water oxidation catalysts based on the Rubda (bda = 2,2′-bipyri-dine-6,6′-dicarboxylate) systems are reported with turnover frequencies in the range of 1 and 900 cycless"1, respectively. Detailed analyses of the main factors involved in the water oxidation reaction have been carried out and are based on a combination of reactivity tests, electrochemical experiments, and DFT calculations. These analyses give a convergent interpretation that generates a solid understanding of the main factors involved in the water oxidation reaction, which in turn allows the design of catalysts with very low energy barriers in all the steps involved in the water oxidation catalytic cycle. We show that for this type of system p-stacking interactions are the key factors that influence reactivity and by adequately controlling them we can generate exceptionally fast water oxidation catalysts.

Hydrous titanium oxide-supported catalysts

International Nuclear Information System (INIS)

Dosch, R.G.; Stohl, F.V.; Richardson, J.T.

1990-01-01

Catalysts were prepared on hydrous titanium oxide (HTO) supports by ion exchange of an active metal for Na + ions incorporated in the HTO support during preparation by reaction with the parent Ti alkoxide. Strong active metal-HTO interactions as a result of the ion exchange reaction can require significantly different conditions for activation as compared to catalysts prepared by more widely used incipient wetness methods. The latter catalysts typically involve conversion or while the HTO catalysts require the alteration of electrostatic bonds between the metal and support with subsequent alteration of the support itself. In this paper, the authors discuss the activation, via sulfidation or reduction, of catalysts consisting of Co, Mo, or Ni-Mo dispersed on HTO supports by ion exchange. Correlations between the activation process and the hydrogenation, hydrodeoxygenation, and hydrodesulfurization activities of the catalysts are presented

Nitrogen oxides storage catalysts containing cobalt

Science.gov (United States)

Lauterbach, Jochen; Snively, Christopher M.; Vijay, Rohit; Hendershot, Reed; Feist, Ben

2010-10-12

Nitrogen oxides (NO.sub.x) storage catalysts comprising cobalt and barium with a lean NO.sub.x storage ratio of 1.3 or greater. The NO.sub.x storage catalysts can be used to reduce NO.sub.x emissions from diesel or gas combustion engines by contacting the catalysts with the exhaust gas from the engines. The NO.sub.x storage catalysts can be one of the active components of a catalytic converter, which is used to treat exhaust gas from such engines.

The kinetics and mechanism of methanol oxidation on Pt and PtRu catalysts in alkaline and acid media

Directory of Open Access Journals (Sweden)

JELENA LOVIC

2007-07-01

Full Text Available The kinetic of methanol electrochemical oxidation for a series of platinum and platinum–ruthenium catalysts was investigated. A correlation between the beginning of OHad adsorption and methanol oxidation was demonstarated on Pt single crystals and Pt nanocatalyst. The activity of the nano-structured Pt catalyst was compared with single crystal platinum electrodes assuming the Kinoshita model of nanoparticles. The ruthenium-containing catalysts shifted the onset of methanol oxidation to more negative potentials. The effect was more pronounced in acid than in alkaline media. Based on the established diagnostic criteria, the reaction between COad and OHad species according to the Langmuir–Hinshelwood mechanism was proposed as the rate determining step in alkaline and acid media on Pt and PtRu catalysts.

Revisiting the electrochemical oxidation of ammonia on carbon-supported metal nanoparticle catalysts

International Nuclear Information System (INIS)

Li, Zhe-Fei; Wang, Yuxuan; Botte, Gerardine G.

2017-01-01

Highlights: • A procedure to pretreat electrocatalysts to study the ammonia oxidation is provided. • N ads and O/OH ads were identified as the major deactivation species that prevent ammonia oxidatoin. • The electrocatalytic activity, thermodynamics, and possible deactivation mechanisms for ammonia oxidation were elucidated. • The onset potential for ammonia oxidation is related to the hydrogen binding energy of the catalyst. • Ammonia electro-oxidation involves a complex decoupled electron and proton transfer process. - Abstract: The ammonia electro-oxidation reaction (AOR) has been studied due to its promising applications in ammonia electrolysis, wastewater remediation, direct ammonia fuel cells, and sensors. However, it is difficult to compare and analyze the reported electrocatalytic activity of AOR reliably, likely due to the variation in catalyst synthesis, electrode composition, electrode morphology, and testing protocol. In this paper, the electro-oxidation of ammonia on different carbon-supported precious metal nanoparticle catalysts was revisited. The effect of experimental conditions, electrochemical test parameters, electrocatalytic activity, thermodynamics, and possible deactivation mechanism of the catalysts were investigated. Pt/C catalyst possesses the highest electrocatalytic activity, while Ir/C and Rh/C show lower overpotential. The onset potential of the AOR is related to the hydrogen binding energy of the catalyst. N ads is one major cause of deactivation accompanied with the formation of surface O/OH ads at high potentials. The coulombic efficiency of N ads formation on Pt is about 1% initially and gradually decreases with reaction time. Increase in ammonia concentration leads to increase in current density, while increase in hydroxyl ions concentration can enhance the current density and reduce the overpotential simultaneously. The slopes of AOR onset potential and hydrogen adsorption/desorption potential of Pt/C as a function of p

An improved method of preparation of nanoparticular metal oxide catalysts

DEFF Research Database (Denmark)

2014-01-01

The present invention concerns an improved method of preparation of nanoparticular vanadium oxide/anatase titania catalysts having a narrow particle size distribution. In particular, the invention concerns preparation of nanoparticular vanadium oxide/anatase titania catalyst precursors comprising...... combustible crystallization seeds upon which the catalyst metal oxide is coprecipitated with the carrier metal oxide, which crystallization seeds are removed by combustion in a final calcining step....

Performance of diesel particulate filter catalysts in the presence of biodiesel ash species

DEFF Research Database (Denmark)

Hansen, Brian Brun; Jensen, Anker Degn; Jensen, Peter Arendt

2013-01-01

The utilization of bio-fuels, such as biodiesel, is expected to contribute significantly towards the planned 10% of renewable energy within the EU transport sector by 2020. Increased biodiesel blend percentages may change engine exit flue gas ash composition and affect the long-term performance...... of cleaning technologies, such as oxidation catalysts and diesel particulate filters. In this work the performance of a commercial catalyst has been studied for conversion of diesel particulate matter (SRM 2975) at 10% O2, in the presence of salts simulating ash species derived from engine oil and biodiesel...... the temperature at which the oxidation rate peaked from 662 ± 1 °C to 526 ± 19 °C. The introduction of biodiesel ash species such as Na2CO3, K2CO3 or K3PO4 decreased the peak conversion temperature further (422 ± 12; 404 ± 4 and 423 ± 7 °C), with a limited dependence on ash concentration. A deterioration...

Role of the acid-base properties of gallium-antimony oxide catalyst in oxidative ammonolysis of propane to acrylonitrile (AN)

Energy Technology Data Exchange (ETDEWEB)

Osipova, Z.G.; Sokolovskii, V.D.

1979-07-01

The role of the acid-base properties of gallium-antimony oxide catalyst in oxidative ammonolysis of propane to acrylonitrile (AN) was studied in a differential flow reactor at 550/sup 0/C, with the reaction mixture containing 5 3< by vol propane, 6 3< ammonia, and 18.6Vertical Bar3< oxygen diluted in helium, over ebulliated beds of a 5Vertical Bar3< Ga/Sb or a 1:3:1.5:1 Ga/Sb/Ni/P catalysts, the basicity of which was varied by adding 5 mole Vertical Bar3< of an alkaline earth metal (added as the nitrate and calcined). Both the rate of propane conversion and that of AN formation increased with increasing concentration of the basic sites (determined by back titration with benzoic acid) on both types of the catalysts and linearly correlated with the amount of nitrous oxide desorbed from the catalysts after the reaction. The presence of ammonia in the reaction mixture increased the activity and selectivity of the catalysts and the concentration of the active basic sites. Apparently, the reaction rate is limited by proton abstraction from a propane molecule with the formation of a carbanion stabilized on alkaline-earth metal cations. The rate-determining proton abstraction occurs on nucleophile basic sites, formed by dissociative adsorption of ammonia to form species such as NH, NH/sub 2/, and HNO, which are then oxidized to N/sub 2/ and N/sub 2/O.

A DRIFTS study of the partial oxidation of ethanol on Rh catalysts; Estudo da oxidacao parcial do etanol em catalisadores de Rh por DRIFTS

Energy Technology Data Exchange (ETDEWEB)

Oliveira, Raquel Lima; Passos, Fabio Barboza, E-mail: fbpassos@vm.uff.br [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Departamento de Engenharia Quimica e de Petroleo

2013-09-01

The partial oxidation of ethanol on {gamma}-Al{sub 2}O{sub 3}, CeO{sub 2}, ZrO{sub 2} and Ce{sub x}Zr{sub 1-x}O{sub 2} supported rhodium catalysts was investigated by Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). The catalysts were characterized by temperature-programmed reduction (TPR) and cyclohexane dehydrogenation. DRIFTS studies on the partial oxidation of ethanol showed that ethanol is adsorbed dissociatively, through O-H bond breaking, with the formation of ethoxy species, followed by successive dehydrogenation to acetaldehyde and acetyl species. Further oxidation to acetate and carbonate species lead to the formation of CO, CH{sub 4} and H{sub 2} by decomposition. The presence of CeO{sub 2} in the catalysts favored the oxidation steps due to its oxygen storage capacity. (author)

Metal Phosphate-Supported Pt Catalysts for CO Oxidation

Directory of Open Access Journals (Sweden)

Xiaoshuang Qian

2014-12-01

Full Text Available Oxides (such as SiO2, TiO2, ZrO2, Al2O3, Fe2O3, CeO2 have often been used to prepare supported Pt catalysts for CO oxidation and other reactions, whereas metal phosphate-supported Pt catalysts for CO oxidation were rarely reported. Metal phosphates are a family of metal salts with high thermal stability and acid-base properties. Hydroxyapatite (Ca10(PO46(OH2, denoted as Ca-P-O here also has rich hydroxyls. Here we report a series of metal phosphate-supported Pt (Pt/M-P-O, M = Mg, Al, Ca, Fe, Co, Zn, La catalysts for CO oxidation. Pt/Ca-P-O shows the highest activity. Relevant characterization was conducted using N2 adsorption-desorption, inductively coupled plasma (ICP atomic emission spectroscopy, X-ray diffraction (XRD, transmission electron microscopy (TEM, CO2 temperature-programmed desorption (CO2-TPD, X-ray photoelectron spectroscopy (XPS, and H2 temperature-programmed reduction (H2-TPR. This work furnishes a new catalyst system for CO oxidation and other possible reactions.

In situ FTIRS study of ethanol electro-oxidation on anode catalysts in direct ethanol fuel cells

Energy Technology Data Exchange (ETDEWEB)

Wang, Q.; Sun, G.; Jiang, L.; Zhu, M.; Yan, S.; Wang, G.; Xin, Q. [Chinese Academy of Sciences, Dalian (China). Dalian Inst. of Chemical Physics; Chen, Q.; Li, J.; Jiang, Y.; Sun, S. [Xiamen Univ., Xiamen (China). State Key Lab. for Physical Chemistry of Solid Surfaces

2006-07-01

The low activation of ethanol oxidation at lower temperatures is an obstacle to the development of cost-effective direct ethanol fuel cells (DEFCs). This study used a modified polyol method to prepare carbon-supported platinum (Pt) based catalysts. Carbon supported Pt-based catalysts were fabricated by a modified polyol method and characterized through transmission electron spectroscopy (TEM) and X-ray diffraction (XRD). Results of the study showed that the particles in the Pt/C and PtRu/C and PtSn/C catalysts were distributed on the carbon support uniformly. Diffraction peaks of the Pt shifted positively in the PtRu/C catalysts and negatively in the PtSn/C catalysts. In situ Fourier Transform Infra-red spectroscopy (FTIR) was used to investigate the adsorption and oxidation process of ethanol on the catalysts. Results showed that the electrocatalytic activity of ethanol oxidation on the materials was enhanced. Linear bonded carbon monoxide (CO) was the most strongly absorbed species, and the main products produced by the catalysts were carbon dioxide (CO{sub 2}), acetaldehyde, and acetic acid. Results showed that the PtRu/C catalyst broke the C-C bond more easily than the Pt/C and PtSn/C compounds. However, the results of a linear sweep voltammogram analysis showed that ethanol oxidation of the PtSn/C was enhanced. Bands observed on the compound indicated the formation of acetic acid and acetaldehyde. It was concluded that the enhancement of PtSn/C for ethanol oxidation was due to the formation of acetic acid and acetaldehyde at lower potentials. 4 refs., 1 fig.

Phosphate-Doped Carbon Black as Pt Catalyst Support: Co-catalytic Functionality for Dimethyl Ether and Methanol Electro-oxidation

DEFF Research Database (Denmark)

Yin, Min; Huang, Yunjie; Li, Qingfeng

2014-01-01

). The supported Pt catalysts show significant improvement in catalytic activity towards the direct oxidation of methanol and DME, attributable to the enhanced adsorption and dehydrogenation of methanol and DME, as well as the presence of activated OH species in the catalysts. The latter is demonstrated......Niobium-phosphate-doped (NbP-doped) carbon blacks were prepared as the composite catalyst support for Pt nanoparticles. Functionalities of the composite include intrinsic proton conductivity, surface acidity, and interfacial synergistic interactions with methanol and dimethyl ether (DME...... to facilitate the removal of CO intermediates formed during the oxidation reactions....

Mesoporous Mn promoted Co3O4 oxides as an efficient and stable catalyst for low temperature oxidation of CO

Science.gov (United States)

Liu, Changxiang; Gong, Lei; Dai, Runying; Lu, Meijuan; Sun, Tingting; Liu, Qian; Huang, Xigen; Huang, Zhong

2017-09-01

Mesoporous Mn-doped Co3O4 catalysts were successfully prepared via a dry soft reactive grinding method based on solid state reaction, and their catalytic performances on CO oxidation were evaluated at a high space velocity of 49,500 mL g-1 h-1. A significant promoted effect was observed once the atomic ratios of Mn/(Co+Mn) were lower than 10%, for instance, the temperature for 50% conversion decreased to about -60 °C, showing superior catalytic performance compared to the single metal oxide. Especially, the Mn-promoted Co3O4 catalyst with a Mn/(Co+Mn) molar ratio of 10% could convert 100% CO after 3000 min of time-on-steam without any deactivation at room temperature. As prepared catalysts were characterized by XRD, N2-adsorption/desorption, TEM, H2-TPR, O2-TPD and CO-titration analysis. The significant enhancement of performance for oxidation of CO over Mn-Co-O mixed oxides was associated with the high active oxygen species concentrations formed during the pretreatment in O2 atmosphere.

Bimetallic catalysts for continuous catalytic wet air oxidation of phenol.

Science.gov (United States)

Fortuny, A; Bengoa, C; Font, J; Fabregat, A

1999-01-29

Catalytic wet oxidation has proved to be effective at eliminating hazardous organic compounds, such as phenol, from waste waters. However, the lack of active long-life oxidation catalysts which can perform in aqueous phase is its main drawback. This study explores the ability of bimetallic supported catalysts to oxidize aqueous phenol solutions using air as oxidant. Combinations of 2% of CoO, Fe2O3, MnO or ZnO with 10% CuO were supported on gamma-alumina by pore filling, calcined and later tested. The oxidation was carried out in a packed bed reactor operating in trickle flow regime at 140 degrees C and 900 kPa of oxygen partial pressure. Lifetime tests were conducted for 8 days. The pH of the feed solution was also varied. The results show that all the catalysts tested undergo severe deactivation during the first 2 days of operation. Later, the catalysts present steady activity until the end of the test. The highest residual phenol conversion was obtained for the ZnO-CuO, which was significantly higher than that obtained with the 10% CuO catalyst used as reference. The catalyst deactivation is related to the dissolution of the metal oxides from the catalyst surface due to the acidic reaction conditions. Generally, the performance of the catalysts was better when the pH of the feed solution was increased.

Composite catalyst for carbon monoxide and hydrocarbon oxidation

Science.gov (United States)

Liu, Wei; Flytzani-Stephanopoulos, Maria

1996-01-01

A method and composition for the complete oxidation of carbon monoxide and/or hydrocarbon compounds. The method involves reacting the carbon monoxide and/or hydrocarbons with an oxidizing agent in the presence of a metal oxide composite catalyst. The catalyst is prepared by combining fluorite-type oxygen ion conductors with active transition metals. The fluorite oxide, selected from the group consisting of cerium oxide, zirconium oxide, thorium oxide, hafnium oxide, and uranium oxide, and may be doped by alkaline earth and rare earth oxides. The transition metals, selected from the group consisting of molybdnum, copper, cobalt, maganese, nickel, and silver, are used as additives. The atomic ratio of transition metal to fluorite oxide is less than one.

Mitigation of hydrogen by oxidation using nitrous oxide and noble metal catalysts

International Nuclear Information System (INIS)

Britton, M.D.

1995-01-01

This test studied the ability of a blend of nuclear-grade, noble-metal catalysts to catalyze a hydrogen/nitrous oxide reaction in an effort to mitigate a potential hydrogen (H 2 ) gas buildup in the Hanford Site Grout Disposal Facility. For gases having H 2 and a stoichiometric excess of either nitrous oxide or oxygen, the catalyst blend can effectively catalyze the H 2 oxidation reaction at a rate exceeding 380 μmoles of H 2 per hour per gram of catalyst (μmol/h/g) and leave the gas with less than a 0.15 residual H 2 Concentration. This holds true in gases with up to 2.25% water vapor and 0.1% methane. This should also hold true for gases with up to 0.1% carbon monoxide (CO) but only until the catalyst is exposed to enough CO to block the catalytic sites and stop the reaction. Gases with ammonia up to 1% may be slightly inhibited but can have reaction rates greater than 250 μmol/h/g with less than a 0.20% residual H 2 concentration. The mechanism for CO poisoning of the catalyst is the chemisorption of CO to the active catalyst sites. The CO sorption capacity (SC) of the catalyst is the total amount of CO that the catalyst will chemisorb. The average SC for virgin catalyst was determined to be 19.3 ± 2.0 μmoles of CO chemisorbed to each gram of catalyst (μmol/g). The average SC for catalyst regenerated with air was 17.3 ± 1.9 μmol/g

Progress on the mechanistic understanding of SO2 oxidation catalysts

DEFF Research Database (Denmark)

Lapina, Olga B.; Bal'zhinimaev, B.S.; Boghosian, Soghomon

1999-01-01

Production, Goskhimizdat (in Russian), Moscow, 1954, p. 348]. In recent years these catalysts have also been used to clean flue gases and other SO; containing, industrial off-gases. In spite of the importance and long utilization of these industrial processes, the catalytic active species and the reaction......For almost a century vanadium oxide based catalysts have been the dominant materials in industrial processes for sulfuric acid production. A vast body of information leading to fundamental knowledge on the catalytic process was obtained by Academician [G.K. Boreskov, Catalysis in Sulphuric Acid...... mechanism. A multiinstrumental investigation that combine the efforts of four groups from four different countries has been carried out on the model system as well as on working industrial catalysts. Detailed information has been obtained on the complex and on the redox chemistry of vanadium. Based on this...

Chemical nature of catalysts of oxide nanoparticles in environment

Indian Academy of Sciences (India)

Carbon nanostructures (CNS) are often grown using oxide nanoparticles as catalyst in chemical vapour deposition and these oxides are not expected to survive as such during growth. In the present study, the catalysts of cobalt- and nickel oxide-based nanoparticles of sizes varying over a range have been reduced at 575 ...

Effect of catalysts on heterogeneous oxidation of coal

Energy Technology Data Exchange (ETDEWEB)

Glazkova, A P; Kazarova, Yu A; Suslov, A V

1978-01-01

Analyzes the effects of catalysts on the heterogeneous oxidation of coal in deflagration processes of stoichiometric mixtures. The following substances are studied as catalysts: alkali and alkaline-earth metals, and compounds of copper, lead, chromium, iron, and sulfur. In the first case the catalysts are used in the form of nitrates and the nitrate simultaneously plays the role of an oxidizer. In the second case the catalysts are added to stoichiometric mixtures of ammonium nitrate with carbon. It is shown that during carbon oxidation by nitrates the catalytic efficiency of the metals studied forms the following order: sodium > lead > potassium > barium > aluminium > calcium > magnesium > copper. The calculated and experimental parameters of combustion are given. The problem of dependence of combustion rate on combustion heat, the mechanism of the combustion reaction and the catalytic effects of the additives are discussed. Features of heterogeneous catalysis in the oxidation process of carbon by various oxidizers are analyzed. The investigations on the combustion process are important as the process takes place during explosion of coal dust in underground coal mines and during burning of coal in industrial furnaces. (34 refs.) (In Russian)

Mechanism-Based Design of Green Oxidation Catalysts

Energy Technology Data Exchange (ETDEWEB)

Rybak-Akimova, Elena [Tufts Univ., Medford, MA (United States)

2015-03-16

In modern era of scarce resources, developing chemical processes that can eventually generate useful materials and fuels from readily available, simple, cheap, renewable starting materials is of paramount importance. Small molecules, such as dioxygen, dinitrogen, water, or carbon dioxide, can be viewed as ideal sources of oxygen, nitrogen, or carbon atoms in synthetic applications. Living organisms perfected the art of utilizing small molecules in biosynthesis and in generating energy; photosynthesis, which couples carbohydrate synthesis from carbon dioxide with photocatalytic water splitting, is but one impressive example of possible catalytic processes. Small molecule activation in synthetic systems remains challenging, and current efforts are focused on developing catalytic reactions that can convert small molecules into useful building blocks for generating more complicated organic molecules, including fuels. Modeling nature is attractive in many respects, including the possibility to use non-toxic, earth-abundant metals in catalysis. Specific systems investigated in our work include biomimetic catalytic oxidations with dioxygen, hydrogen peroxide, and related oxygen atom donors. More recently, a new direction was been also pursued in the group, fixation of carbon dioxide with transition metal complexes. Mechanistic understanding of biomimetic metal-catalyzed oxidations is critical for the design of functional models of metalloenzymes, and ultimately for the rational synthesis of useful, selective and efficient oxidation catalysts utilizing dioxygen and hydrogen peroxide as terminal oxidants. All iron oxidases and oxygenases (both mononuclear and dinuclear) utilize metal-centered intermediates as reactive species in selective substrate oxidation. In contrast, free radical pathways (Fenton chemistry) are common for traditional inorganic iron compounds, producing hydroxyl radicals as very active, non-selective oxidants. Recent developments, however, changed this

Nanocarbons as catalyst for selective oxidation of acrolein to acrylic acid

Energy Technology Data Exchange (ETDEWEB)

Frank, B.; Blume, R.; Rinaldi, A.; Trunschke, A.; Schloegl, R. [Fritz Haber Institute of the Max Planck Society, Berlin (Germany). Dept. of Inorganic Chemistry

2011-07-01

Selective oxidations are key steps of industrial oil and gas processing for the synthesis of high-value chemicals. Mixed metal oxides based on redox active V or Mo are frequently used for oxidative C-H bond activation. However, multiple processes require precious metals or suffer from low product selectivity demanding an ongoing search for cost-effective alternatives. Recently, the nanostructured carbon was reported to catalyze the metal-free selective alkane activation by oxidative dehydrogenation (ODH). Electron-rich surface carbonyls coordinate this reaction and mimic the active oxygen species in metal oxide catalysts. Here we show that the graphitic carbon, beyond ODH, has the potential to selectively mediate the insertion of an oxygen atom into an organic molecule, i.e., acrolein. Multi-step atom rearrangements considerably exceed the mechanistic complexity of hydrogen abstraction and were so far believed to be the exclusive domain of metal (oxide) catalysis. In the carbon catalyzed process, the nucleophilic oxygen atoms terminating the graphite (0001) surface abstract the formyl hydrogen and the activated aldehyde gets oxidized by epoxide-type mobile oxygen, thus the sp{sup 2} carbon acts as a bifunctional catalyst. Substantial similarities between the metal oxide- and carbon-catalyzed reactions could be identified. Our results shed light on a rarely known facet of applications of nanostructured carbon materials being decorated with diverse oxygen functionalities to coordinate complex catalytic processes. We could successfully transfer the results obtained from the graphite model to carbon nanotubes (CNTs) providing a higher surface area, defect density, and intrinsic activity, to substantially increase the reactivity per catalyst volume. Indeed, low dimensional nanostructured carbon is a highly flexible and robust material which can be modified in a multiple manner to optimize its properties with respect to the intended application. The exploration of

Catalytic activity of oxide cerium-molybdenum-tellurium catalysts in oxidation ammonolysis

International Nuclear Information System (INIS)

Dzhordano, N.; Bart, D.; Madzhori, R.

1984-01-01

A commercial catalyst containing a mixture of Ce-, Mo-, Te oxides deposited on SiO 2 is shown to manifest a high efficiency in oxidative ammonolysis of propylene (C 3 - ) to acrylonitrile (AN). The dependence of the catalytic properties on the catalyst composition and reaction conditions is studied. It is established that three-component mixtures are more active and selective than the systems with a lesser number of components. Using the catalyst with the optimum ratio of constituent oxides in a microreactor at 440 deg enabled one to achieve initial selectivity in terms of AN equal to 82.5% at 97% conversion of C 3 - . Acrolein, acetonitrile, HCN and nitrogen oxides are the reaction by-products. A supposition is made that the reaction proceeds via the formation of π-compleXes on the centres of Te(4). Setective oxidation occurs on oxygen atoms bonded with the Mo(6) ions. Tellurium enhances the molybdenum reducibleness due to delocalization of electrons, whereas the cerium addition to the mixture of tellurium- and molybdenum oxides increases the rate of molybdenum reoxidation and thus enhances the catalytic system stability

Regenerable cobalt oxide loaded magnetosphere catalyst from fly ash for mercury removal in coal combustion flue gas.

Science.gov (United States)

Yang, Jianping; Zhao, Yongchun; Zhang, Junying; Zheng, Chuguang

2014-12-16

To remove Hg(0) in coal combustion flue gas and eliminate secondary mercury pollution of the spent catalyst, a new regenerable magnetic catalyst based on cobalt oxide loaded magnetospheres from fly ash (Co-MF) was developed. The catalyst, with an optimal loading of 5.8% cobalt species, attained approximately 95% Hg(0) removal efficiency at 150 °C under simulated flue gas atmosphere. O2 could enhance the Hg(0) removal activity of magnetospheres catalyst via the Mars-Maessen mechanism. SO2 displayed an inhibitive effect on Hg(0) removal capacity. NO with lower concentration could promote the Hg(0) removal efficiency. However, when increasing the NO concentration to 300 ppm, a slightly inhibitive effect of NO was observed. In the presence of 10 ppm of HCl, greater than 95.5% Hg(0) removal efficiency was attained, which was attributed to the formation of active chlorine species on the surface. H2O presented a seriously inhibitive effect on Hg(0) removal efficiency. Repeated oxidation-regeneration cycles demonstrated that the spent Co-MF catalyst could be regenerated effectively via thermally treated at 400 °C for 2 h.

Reactivation of a tin oxide-containing catalyst

Science.gov (United States)

Upchurch, Billy T. (Inventor); Miller, Irvin M. (Inventor); Brown, Kenneth G. (Inventor); Hess, Robert V. (Inventor); Schryer, David R. (Inventor); Sidney, Barry D. (Inventor); Wood, George M. (Inventor); Paulin, Patricia A. (Inventor)

1989-01-01

A method for the reactivation of a tin oxide-containing catalyst of a CO.sub.2 laser is provided. First, the catalyst is pretreated by a standard procedure. When the catalyst experiences diminished activity during usage, the heated zone surrounding the catalyst is raised to a temperature which is the operating temperature of the laser and 400.degree. C. for approximately one hour. The catalyst is exposed to the same laser gas mixture during this period. The temperature of the heated zone is then lowered to the operating temperature of the CO.sub.2 laser.

Catalytic Oxidation of Cyanogen Chloride over a Monolithic Oxidation Catalyst

National Research Council Canada - National Science Library

Campbell, Jeffrey

1997-01-01

The catalytic oxidation of cyanogen chloride was evaluated over a monolithic oxidation catalyst at temperatures between 200 and 300 deg C in air employing feed concentrations between 100 and 10,000 ppm...

The oxidation of copper catalysts during ethylene epoxidation.

Science.gov (United States)

Greiner, M T; Jones, T E; Johnson, B E; Rocha, T C R; Wang, Z J; Armbrüster, M; Willinger, M; Knop-Gericke, A; Schlögl, R

2015-10-14

The oxidation of copper catalysts during ethylene epoxidation was characterized using in situ photoemission spectroscopy and electron microscopy. Gas chromatography, proton-transfer reaction mass spectrometry and electron-ionization mass spectrometry were used to characterize the catalytic properties of the oxidized copper. We find that copper corrodes during epoxidation in a 1 : 1 mixture of oxygen and ethylene. The catalyst corrosion passes through several stages, beginning with the formation of an O-terminated surface, followed by the formation of Cu2O scale and eventually a CuO scale. The oxidized catalyst exhibits measurable activity for ethylene epoxidation, but with a low selectivity of 8/2500) Cu2O forms and eventually covers the surface.

Influence of promoters and oxidants on propane dehydrogenation over chromium-oxide catalysts

Energy Technology Data Exchange (ETDEWEB)

Lapidus, A.L.; Agafonov, Yu.A.; Shaporeva, N.Yu.; Trushin, D.V.; Gaidai, N.A.; Nekrasov, N.V. [Russian Academy of Sciences, Moscow (Russian Federation). N.D. Zelinsky Inst. of Organic Chemistry

2010-12-30

Possibilities for increasing the efficiency of supported on SiO{sub 2} chromium-oxide catalysts in propane oxidative dehydrogenation in CO{sub 2} presence are investigated: the introduction of Li, Na, K, Ca in catalysts and the addition of O{sub 2} in the reaction mixture. It was been found that the positive role of K - the increase of the selectivity to propene and stability of catalysts at long-duration tests - appeared at the relation of Cr:K=20. It was shown that the presence of little amount of O{sub 2} (2%) in the reaction mixtures of propane and carbon dioxide resulted in the increase of propene yield and catalyst stability. (orig.)

Steam reforming and oxidative steam reforming of methanol over CuO-CeO{sub 2} catalysts

Energy Technology Data Exchange (ETDEWEB)

Udani, P.P.C.; Gunawardana, P.V.D.S.; Lee, Hyun Chan; Kim, Dong Hyun [Department of Chemical Engineering, Kyungpook National University, Daegu 702-701 (Korea)

2009-09-15

Steam reforming (SRM) and oxidative steam reforming of methanol (OSRM) were carried out over a series of coprecipitated CuO-CeO{sub 2} catalysts with varying copper content in the range of 30-80 at.% Cu (= 100 x Cu/(Cu + Ce)). The effects of copper content, reaction temperature and O{sub 2} concentration on catalytic activity were investigated. The activity of CuO-CeO{sub 2} catalysts for SRM and OSRM increased with the copper content and 70 at.% CuO-CeO{sub 2} catalyst showed the highest activity in the temperature range of 160-300 C for both SRM and OSRM. After SRM or OSRM, the copper species in the catalysts observed by XRD were mainly metallic copper with small amount of CuO and Cu{sub 2}O, an indication that metallic copper is an active species in the catalysis of both SRM and OSRM. It was observed that the methanol conversion increased considerably with the addition of O{sub 2} into the feed stream, indicating that the partial oxidation of methanol (POM) is much faster than SRM. The optimum 70 at.% CuO-CeO{sub 2} catalyst showed stable activities for both SRM and OSRM reactions at 300 C. (author)

Selective liquid-phase oxidation of alcohols catalyzed by a silver-based catalyst promoted by the presence of ceria

DEFF Research Database (Denmark)

Beier, Matthias Josef; Hansen, Thomas Willum; Grunwaldt, Jan-Dierk

2009-01-01

simultaneously. When a high catalytic conversion (>30% over 2 h) was found the number of catalyst components was reduced in the following tests. Thereby, a collaborative effect between a physical mixture of ceria nanoparticles and silver-impregnated silica (10 wt.% Ag–SiO2) was found. The catalytic activity...... by in situ XAS experiments. Oxygen species incorporated in the silver lattice appear to be important for the catalytic oxidation of the alcohol for which a preliminary mechanism is presented. The application of the catalyst was extended to the oxidation of a wide range of primary and secondary alcohols....... Compared to palladium and gold catalysts, the new silver catalyst performed similarly or even superior in the presence of CeO2. In addition, the presence of ceria increased the catalytic activity of all investigated catalysts....

Formaldehyde formation in coupled oxidation of methane and methanol over V2O5 and MoO3 silica supported catalysts

International Nuclear Information System (INIS)

Lojewska, J.; Makowski, W.; Fajardo Farre, A.; Dziembaj, R.

2003-01-01

The effect of methanol on partial oxidation of methane has been studied on standard molybdena and vanadia catalysts supported on silica. Prior to catalytic tests the catalysts were characterized by BET, SEM/EDAX and TPR/O methods. Three types of catalytic tests were performed giving temperature and contact time dependence on the catalyst activity and selectivity: partial oxidations of methane, methanol and methane/methanol mixtures. The methanol showed an activating impact on the partial oxidation of methane over all used catalysts samples, but the strongest one over Mo 3 /SiO 2 . In the absence of CH 3 OH the only catalyst, which exhibited HCHO selectivity, was low loaded vanadia catalyst. It has been put forward that methanol may enhance formation of oxygen active species, prerequisites for activating methane molecules, through reducing vanadia cations and causing breakage of vanadium oxygen bonds. (author)

Selective Oxidations using Nanostructured Heterogeneous Catalysts

DEFF Research Database (Denmark)

Mielby, Jerrik Jørgen

and because they produce H2O as the only by-product. Chapter 1 gives a short introduction to basic concepts in heterogeneous catalysis and green chemistry. Furthermore, the chapter gives an overview of the most important strategies to synthesise functional nanostructured materials and highlights how detailed......The aim of this thesis is to investigate and develop new efficient methods to oxidise alcohols and amines using heterogeneous catalysts and either O2 or H2O2 as oxidants. From an economic and environmental point of view, these oxidants are ideal, because they are cheap and readily available...... understanding of size, shape and structure can help in the development of new and more efficient heterogeneous catalysts. The chapter is not intended to give a complete survey, but rather to introduce some of the recent developments in the synthesis of nanostructured heterogeneous catalysts. Finally...

Electrical conductivity of uranium-antimony oxide catalysts

International Nuclear Information System (INIS)

Golunski, S.E.; Nevell, T.G.; Hucknall, D.J.

1985-01-01

The relative ionic and electronic contributions to the electrical conductivity of a uranium-antimony oxide catalyst and of USbO 5 have been determined from measurements of a.c. and d.c. conductance. Under inert atmospheres (390 to 775 K) conduction in the catalyst (predominantly USb 3 O 10 together with small proportions of Sb 2 O 4 and USbO 5 ) is associated with both electronic and effectively charged atomic point defects. Only electronic conduction occurs in USbO 5 . Under oxygen (10 to 70 kPa, 493 to 682 K) both materials are n-type semiconductors at higher temperatures, but at lower temperatures semiconducting behaviour varies with the pressure of oxygen. Heating USbO 5 in oxygen induces an ionic contribution to conductivity. Ionic conduction in the catalyst is eliminated by heating in hydrogen or propene at 470 K but is restored by heating in oxygen. It is suggested that both charged oxygen vacancies and interstitial oxide ions are involved in interactions of gaseous components with uranium-antimony oxides. With alkenes, interstitial oxide ions give rise to the products of selective partial oxidation. (author)

Electrical conductivity of uranium-antimony oxide catalysts

Energy Technology Data Exchange (ETDEWEB)

Golunski, S.E.; Nevell, T.G. (Portsmouth Polytechnic (UK)); Hucknall, D.J. (Southampton Univ. (UK). Dept. of Chemistry)

1985-05-01

The relative ionic and electronic contributions to the electrical conductivity of a uranium-antimony oxide catalyst and of USbO/sub 5/ have been determined from measurements of a.c. and d.c. conductance. Under inert atmospheres (390 to 775 K) conduction in the catalyst (predominantly USb/sub 3/O/sub 10/ together with small proportions of Sb/sub 2/O/sub 4/ and USbO/sub 5/) is associated with both electronic and effectively charged atomic point defects. Only electronic conduction occurs in USbO/sub 5/. Under oxygen (10 to 70 kPa, 493 to 682 K) both materials are n-type semiconductors at higher temperatures, but at lower temperatures semiconducting behaviour varies with the pressure of oxygen. Heating USbO/sub 5/ in oxygen induces an ionic contribution to conductivity. Ionic conduction in the catalyst is eliminated by heating in hydrogen or propene at 470 K but is restored by heating in oxygen. It is suggested that both charged oxygen vacancies and interstitial oxide ions are involved in interactions of gaseous components with uranium-antimony oxides. With alkenes, interstitial oxide ions give rise to the products of selective partial oxidation.

Supramolecular water oxidation with Ru-bda-based catalysts.

Science.gov (United States)

Richmond, Craig J; Matheu, Roc; Poater, Albert; Falivene, Laura; Benet-Buchholz, Jordi; Sala, Xavier; Cavallo, Luigi; Llobet, Antoni

2014-12-22

Extremely slow and extremely fast new water oxidation catalysts based on the Ru-bda (bda=2,2'-bipyridine-6,6'-dicarboxylate) systems are reported with turnover frequencies in the range of 1 and 900 cycles s(-1) , respectively. Detailed analyses of the main factors involved in the water oxidation reaction have been carried out and are based on a combination of reactivity tests, electrochemical experiments, and DFT calculations. These analyses give a convergent interpretation that generates a solid understanding of the main factors involved in the water oxidation reaction, which in turn allows the design of catalysts with very low energy barriers in all the steps involved in the water oxidation catalytic cycle. We show that for this type of system π-stacking interactions are the key factors that influence reactivity and by adequately controlling them we can generate exceptionally fast water oxidation catalysts. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Formic acid oxidation at platinum-bismuth catalysts

Directory of Open Access Journals (Sweden)

Popović Ksenija Đ.

2015-01-01

Full Text Available The field of heterogeneous catalysis, specifically catalysis on bimetallic surfaces, has seen many advances over the past few decades. Bimetallic catalysts, which often show electronic and chemical properties that are distinct from those of their parent metals, offer the opportunity to obtain new catalysts with enhanced selectivity, activity, and stability. The oxidation of formic acid is of permanent interest as a model reaction for the mechanistic understanding of the electrooxidation of small organic molecules and because of its technical relevance for fuel cell applications. Platinum is one of the most commonly used catalysts for this reaction, despite the fact that it shows a few significant disadvantages: high cost and extreme susceptibility to poisoning by CO. To solve this problem, several approaches have been used, but generally, they all consist in the modification of platinum with a second element. Especially, bismuth has received significant attention as Pt modifier. According to the results presented in this survey dealing with the effects influencing the formic acid oxidation it was found that two types of Pt-Bi bimetallic catalysts (bulk and low loading deposits on GC showed superior catalytic activity in terms of the lower onset potential and oxidation current density, as well as exceptional stability compared to Pt. The findings in this report are important for the understanding of mechanism of formic acid electrooxidation on a bulk alloy and decorated surface, for the development of advanced anode catalysts for direct formic acid fuel cells, as well as for the synthesis of novel low-loading bimetallic catalysts. The use of bimetallic compounds as the anode catalysts is an effective solution to overcoming the problems of the formic acid oxidation current stability for long term applications. In the future, the tolerance of both CO poisoning and electrochemical leaching should be considered as the key factors in the development

Synthesis of MoVTeNb Oxide Catalysts with Tunable Particle Dimensions

DEFF Research Database (Denmark)

Kolenko, Yury V.; Zhang, Wei; d'Alnoncourt, Raoul Naumann

2011-01-01

Reliable procedures for the controlled synthesis of phase-pure MoVTeNb mixed oxides with M1 structure (ICSD 55097) and tunable crystal dimensions were developed to study the structure sensitivity of the selective oxidation of propane to acrylic acid. A series of powdered M1 catalysts...... catalysts were studied in the selective oxidation of propane to acrylic acid, revealing that active sites appear on the entire M1 surface and illustrating the high sensitivity of catalyst performance on the catalyst synthesis method....

Oxidation catalysts and process for preparing same

International Nuclear Information System (INIS)

1980-01-01

Compounds particularly suitable as oxidation catalysis are described, comprising specified amounts of uranium, antimony and tin as oxides. Processes for making and using the catalysts are described. (U.K.)

Understanding of catalysis on early transition metal oxide-based catalysts through exploration of surface structure and chemistry during catalysis using in-situ approaches

Energy Technology Data Exchange (ETDEWEB)

Tao, Franklin [Univ. of Kansas, Lawrence, KS (United States). Dept. of Chemical and Petroleum Engineering. Dept. of Chemistry

2015-09-14

Two main categories of heterogeneous catalysts are metal and metal oxide which catalyze 80% chemical reactions at solid-gas and solid-liquid interfaces. Metal oxide catalysts are much more complicated than metal catalysts. The reason is that the cations of the metal atoms could exhibit a few different oxidation states on surface of the same catalyst particle such as Co₃O₄ or change of their oxidation states under different reactive environments. For a metal catalyst, there is only one oxidation state typically. In addition, surface of a metal oxide can be terminated with multiple surface functionalities including O atoms with different binding configurations and OH group. For metal, only metal atoms are exposed typically. Obviously, the complication of surface chemistry and structure of a metal oxide makes studies of surface of an oxide catalyst very challenging. Due to the complication of surface of a meal oxide, the electronic and geometric structures of surface of a metal oxide and the exposed species have received enormous attention since oxide catalysts catalyze at least 1/3 chemical reactions in chemical and energy industries. Understanding of catalytic reactions on early transition metal oxide-based catalysts is fundamentally intriguing and of great practical interest in energy- and environment-related catalysis. Exploration of surface chemistry of oxide-based catalysts at molecular level during catalysis has remained challenging though it is critical in deeply understanding catalysis on oxide-based catalysts and developing oxide-based catalysts with high activity and selectivity. Thus, the overall objective of this project is to explore surface chemistry and structure of early transition metal oxide-based catalysts through in-situ characterization of surface of catalysts, measurements of catalytic performances, and then build an intrinsic correlation of surface chemistry and structure with their catalytic performances in a few

Thief carbon catalyst for oxidation of mercury in effluent stream

Science.gov (United States)

Granite, Evan J [Wexford, PA; Pennline, Henry W [Bethel Park, PA

2011-12-06

A catalyst for the oxidation of heavy metal contaminants, especially mercury (Hg), in an effluent stream is presented. The catalyst facilitates removal of mercury through the oxidation of elemental Hg into mercury (II) moieties. The active component of the catalyst is partially combusted coal, or "Thief" carbon, which can be pre-treated with a halogen. An untreated Thief carbon catalyst can be self-promoting in the presence of an effluent gas streams entrained with a halogen.

Nanosized spinel oxide catalysts for CO-oxidation prepared via CoMnMgAl quaternary hydrotalcite route

Energy Technology Data Exchange (ETDEWEB)

Mokhtar, M., E-mail: mmoustafa@kau.edu.s [Chemistry Department, Faculty of Science, King Abdulaziz University, 21589 Jeddah, P.O. Box 80203 (Saudi Arabia); Basahel, S.N.; Al-Angary, Y.O. [Chemistry Department, Faculty of Science, King Abdulaziz University, 21589 Jeddah, P.O. Box 80203 (Saudi Arabia)

2010-03-18

Catalytic activity of the Co-Mn-Mg-Al mixed oxide spinel catalysts was examined in CO oxidation by O{sub 2}. The prepared catalysts were characterized by chemical analysis (ICP), infrared spectroscopy (FTIR), thermal analysis (TG, DTG), powder X-ray diffraction (XRD), surface area measurements, and scanning electron microscopy (SEM).The calcined hydrotalcite-like precursor was composed of spinel-like Co-Mn-Mg-Al mixed oxide as the only XRD crystalline phases. The nanosized spinel oxide catalysts produced by calcination of hydrotalcites showed higher S{sub BET} than CoMn-hydrotalcite samples as calcination led to dehydroxylation and carbonate decomposition of anions in interlayer spaces. All the catalysts showed 100% CO conversion at high temperature even those calcined at 800 {sup o}C. A catalyst with Co/Mn = 4 and calcined at 500 {sup o}C showed 100% CO conversion at 160 {sup o}C. Moreover, this catalyst exhibited quite good durability without deactivation in 60 h stability test.

Novel synthesis of manganese and vanadium mixed oxide (V2O5/OMS-2) as an efficient and selective catalyst for the oxidation of alcohols in liquid phase

International Nuclear Information System (INIS)

Mahdavi, Vahid; Soleimani, Shima

2014-01-01

Graphical abstract: Oxidation of various alcohols is studied in the liquid phase over new composite mixed oxide (V 2 O 5 /OMS-2) catalyst using tert-butyl hydroperoxide (TBHP). The activity of V 2 O 5 /OMS-2 samples was considerably increased with respect to OMS-2 catalyst and these samples are found to be suitable for the selective oxidation of alcohols. - Highlights: • V 2 O 5 /K-OMS-2 with different V/Mn molar ratios prepared by the impregnation method. • Oxidation of alcohols was studied in the liquid phase over V 2 O 5 /K-OMS-2 catalyst. • V 2 O 5 /K-OMS-2 catalyst had excellent activity for alcohol oxidation. • Benzyl alcohol oxidation using excess TBHP followed a pseudo-first order kinetic. • The selected catalyst was reused without significant loss of activity. - Abstract: This work reports the synthesis and characterization of mixed oxide vanadium–manganese V 2 O 5 /K-OMS-2 at various V/Mn molar ratios and prepared by the impregnation method. Characterization of these new composite materials was made by elemental analysis, BET, XRD, FT-IR, SEM and TEM techniques. Results of these analyses showed that vanadium impregnated samples contained mixed phases of cryptomelane and crystalline V 2 O 5 species. Oxidation of various alcohols was studied in the liquid phase over the V 2 O 5 /K-OMS-2 catalyst using tert-butyl hydroperoxide (TBHP) and H 2 O 2 as the oxidant. Activity of the V 2 O 5 /K-OMS-2 samples was increased considerably with respect to K-OMS-2 catalyst due to the interaction of manganese oxide and V 2 O 5 . The kinetic of benzyl alcohol oxidation using excess TBHP over V 2 O 5 /K-OMS-2 catalyst was investigated at different temperatures and a pseudo-first order reaction was determined with respect to benzyl alcohol. The effects of reaction time, oxidant/alcohol molar ratio, reaction temperature, solvents, catalyst recycling potential and leaching were investigated

The Complete Oxidation of Ethanol at Low Temperature over a Novel Pd-Ce/γ-Al2O3-TiO2 Catalyst

International Nuclear Information System (INIS)

Wang, Yanping; Zhao, Jinshuang; Wang, Xiaoli; Li, Zhe; Liu, Pengfei

2013-01-01

Pd-Ce/γ-Al 2 O 3 -TiO 2 catalysts were prepared by combined sol.gel and impregnation methods. Transmission electron microscopy, X-ray diffraction, H 2 -temperature-programmed reduction, O 2 -temperature-programmed desorption, and ethanol oxidation experiments were conducted to determine the properties of the catalysts. Addition of an optimal amount of Ce improved the performance of the Pd/γ-Al 2 O 3 -TiO 2 catalyst in promoting the complete oxidation of ethanol. The catalyst with 1% Ce exhibited the highest activity, and catalyzed complete oxidation of ethanol at 175 .deg. C; its selectivity to CO 2 reached 87%. Characterization results show that addition of appropriate amount of Ce could enrich the PdO species, and weaken the Pd-O bonds, thus enhancing oxidation ability of the catalyst. Meanwhile, the introduction of CeO 2 could make PdO better dispersed on γ-Al 2 O 3 -TiO 2 , which is beneficial for the improvement of the catalytic oxidation activity

Catalysts with Cu base supported in mixed oxides to generate H2: reformed of methanol in oxidant atmosphere

International Nuclear Information System (INIS)

Aguila M, M.M.; Perez H, R.; Rodriguez L, V.

2006-01-01

In this work, the characterization of Cu supported in CeO 2 -ZrO 2 , for to generate H 2 starting from the one reformed of methanol with water vapor and oxygen is presented. The sol-gel technique and classic impregnation for the obtaining of the supports and catalysts respectively were used. The materials were characterized by XRD, SEM, adsorption- desorption of N 2 and TPR. The catalytic materials presented crystalline phases associated with the zircon (tetragonal and monoclinic phase) and the ceria (cubic phase) depending on the CeO 2 /ZrO 2 relationship. The morphology of the catalysts was analyzed by SEM being observed semispheric particles for the rich materials in ZrO 2 and added planars in the rich materials in CeO 2 . The ceria addition to the zircon favors the specific area of the mixed oxides CeO 2 -ZrO 2 and it promotes the reducibility of the copper oxide at low temperatures. The rich catalysts in ceria also showed high activity in the methanol transformation and bigger selectivity toward the production of H 2 . This result is associated with the presence of copper species that decrease to low temperature present in the rich catalysts in ceria and that they are not present in the rich catalysts in zircon. (Author)

Preparation Effects on the Performance of Silica-Doped Hydrous Titanium Oxide (HTO:Si)-Supported Pt Catalysts for Lean-Burn NOx Reduction by Hydrocarbons; TOPICAL

International Nuclear Information System (INIS)

GARDNER, TIMOTHY J.; MCLAUGHLIN, LINDA I.; MOWERY, DEBORAH L.; SANDOVAL, RONALD S.

2002-01-01

This report describes the development of bulk hydrous titanium oxide (HTO)- and silica-doped hydrous titanium oxide (HTO:Si)-supported Pt catalysts for lean-burn NOx catalyst applications. The effects of various preparation methods, including both anion and cation exchange, and specifically the effect of Na content on the performance of Pt/HTO:Si catalysts, were evaluated. Pt/HTO:Si catalysts with low Na content ( and lt; 0.5 wt.%) were found to be very active for NOx reduction in simulated lean-burn exhaust environments utilizing propylene as the major reductant species. The activity and performance of these low Na Pt/HTO:Si catalysts were comparable to supported Pt catalysts prepared using conventional oxide or zeolite supports. In ramp down temperature profile test conditions, Pt/HTO:Si catalysts with Na contents in the range of 3-5 wt.% showed a wide temperature window of appreciable NOx conversion relative to low Na Pt/HTO:Si catalysts. Full reactant species analysis using both ramp up and isothermal test conditions with the high Na Pt/HTO:Si catalysts, as well as diffuse reflectance FTIR studies, showed that this phenomenon was related to transient NOx storage effects associated with NaNO(sub 2)/NaNO(sub 3) formation. These nitrite/nitrate species were found to decompose and release NOx at temperatures above 300 C in the reaction environment (ramp up profile). A separate NOx uptake experiment at 275 C in NO/N(sub 2)/O(sub 2) showed that the Na phase was inefficiently utilized for NOx storage. Steady state tests showed that the effect of increased Na content was to delay NOx light-off and to decrease the maximum NOx conversion. Similar results were observed for high K Pt/HTO:Si catalysts, and the effects of high alkali content were found to be independent of the sample preparation technique. Catalyst characterization (BET surface area, H(sub 2) chemisorption, and transmission electron microscopy) was performed to elucidate differences between the HTO- and HTO

Catalytic wet air oxidation of aniline with nanocasted Mn-Ce-oxide catalyst.

Science.gov (United States)

Levi, R; Milman, M; Landau, M V; Brenner, A; Herskowitz, M

2008-07-15

The catalytic wet air oxidation of aqueous solution containing 1000 ppm aniline was conducted in a trickle-bed reactor packed with a novel nanocasted Mn-Ce-oxide catalyst (surface area of 300 m2/g) prepared using SBA-15 silica as a hard template. A range of liquid hourly space velocities (5-20 h(-1)) and temperatures (110-140 degrees C) at 10 bar of oxygen were tested. The experiments were conducted to provide the intrinsic performance of the catalysts. Complete aniline conversion, 90% TOC conversion, and 80% nitrogen mineralization were achieved at 140 degrees C and 5 h(-1). Blank experiments yielded relatively low homogeneous aniline (<35%) and negligible TOC conversions. Fast deactivation of the catalysts was experienced due to leaching caused by complexation with aniline. Acidification of the solution with HCI (molar HCI to aniline ratio of 1.2) was necessary to avoid colloidization and leaching of the nanoparticulate catalyst components. The catalyst displayed stable performance for over 200 h on stream.

Chromium–tungsten–titanium mixed oxides solid catalyst for fatty acid methyl ester synthesis from palm fatty acid distillate

International Nuclear Information System (INIS)

Wan, Zuraida; Hameed, B.H.

2014-01-01

Highlights: • Chromium–tungsten–titanium mixed oxides as solid catalyst. • Catalyst used for esterification of palm fatty acid distillate to methyl esters. • The maximum methyl ester content is 83%. • Catalyst has shown good activity and can be recycled for 4 times. - Abstract: Chromium–tungsten–titanium mixed oxides solid catalysts were prepared and evaluated in the esterification of palm fatty acid distillate (PFAD) to produce fatty acid methyl ester (FAME). Esterification was conducted in a batch reactor at 110–200 °C temperature ranges. The catalysts were characterized by several techniques such as BET, TEM, FTIR, TGA, XRD, EDX and SEM. The treatment conditions during catalyst preparation, effect of reaction parameters, leaching of the active species and the recycled use of the catalyst were investigated. The catalyst with formula CrWTiO 2 was found to be the most active with maximum FAME content of 83% obtained at best reaction conditions of 170 °C for 3 h, 2:1 (methanol to oil molar ratio) and 2 wt.% catalyst dosage. The catalyst can be recycled for 4 times. The results revealed CrWTiO 2 good potentials for use in esterification of high acid value oil

Oxidative coupling of methane over alkali-promoted simple molybdate catalysts

International Nuclear Information System (INIS)

Discoll, S.A.; Zhang, L.; Ozkan, U.S.

1992-01-01

The study of various metal oxides and alkali promoted metal oxide catalysts has received much interest in recent years after the earlier reports of ethylene synthesis through oxidative coupling of methane, and of achieving high selectivities over a Li/MgO catalyst under methane and oxygen cofeed conditions. The addition of promoter ions to several oxide catalysts has been studied to determine the effect of the promoter ion on catalytic activity and selectivity. The authors' work has focused on the use of alkali promoters for a simple molybdate catalyst. MnMoO 4 . A study of Na, Li, K, Mg, Ba, Mn, Co, Fe, Cu, Zn, and Ni molybdates by Kiwi et al showed that with the exception of NiMoO 4 , the molybdates were stable for long periods of time under reaction conditions for oxidative coupling. At a conversion level of about 60%, selectivities ranged from 9.8% to 16.6%. The MnMoO 4 and K 2 MnMoO 4 molybdates were the least selective catalysts. Another molybdate, PbMoO 4 , was studied by Baerns et al., with 19% selectivity to C 2 hydrocarbons at 1% conversion. An 11.4% conversion to form aldehyde was also reported. In this paper the authors report the characterization and catalytic behavior of MnMoO 4 catalysts promoted with either Li, Na, or K in oxidative coupling of methane

Research advances in the catalysts for the selective oxidation of ethane to aldehydes

Institute of Scientific and Technical Information of China (English)

ZHANG Zhe; ZHAO Zhen; XU Chunming

2005-01-01

Selective oxidation of ethane to aldehydes is one of the most difficult processes in the catalysis researches of low alkanes. The development of selective oxidation of ethane to aldehydes (formaldehyde, acetaldehyde and acrolein) is discussed. The latest progress of the catalysts, including bulk or supported metal oxide catalysts, highly dispersed and isolated active sites catalysts, and the photo-catalytic ethane oxidation catalysts, partial oxidation of ethane in the gas phase, and the proposed reaction pathways from ethane to aldehydes are involved.

Ni–Ta–O mixed oxide catalysts for the low temperature oxidative dehydrogenation of ethane to ethylene

KAUST Repository

Zhu, Haibo

2015-09-01

The "wet" sol-gel and "dry" solid-state methods were used to prepare Ni-Ta-O mixed oxide catalysts. The resulting Ni-Ta oxides exhibit high activity and selectivity for the low temperature oxidative dehydrogenation of ethane to ethylene. The Ta/(Ni + Ta) atomic ratios (varying from 0 to 0.11 in "wet" sol-gel method, and from 0 to 0.20 in "dry" solid-state method) as well as the preparation methods used in the synthesis, play important roles in controlling catalyst structure, activity, selectivity and stability in the oxidative dehydrogenation of ethane. Electron microscopy characterizations (TEM, EELS mapping, and HAADF-STEM) clearly demonstrate that the Ta atoms are inserted into NiO crystal lattice, resulting in the formation of a new Ni-Ta oxide solid solution. More Ta atoms are found to be located at the lattice sites of crystal surface in sol-gel catalyst. While, a small amount of thin layer of Ta2O5 clusters are detected in solid-state catalyst. Further characterization by XRD, N2 adsorption, SEM, H2-TPR, XPS, and Raman techniques reveal different properties of these two Ni-Ta oxides. Due to the different properties of the Ni-Ta oxide catalysts prepared by two distinct approaches, they exhibit different catalytic behaviors in the ethane oxidative dehydrogenation reaction at low temperature. Thus, the catalytic performance of Ni-Ta-O mixed oxide catalysts can be systematically modified and tuned by selecting a suitable synthesis method, and then varying the Ta content. ©2015 Elsevier Inc. All rights reserved.

Radiation modification of vanadium catalyst for anthracene oxidation

International Nuclear Information System (INIS)

Norek, J.; Vymetal, J.; Mucka, V.; Pospisil, M.; Cabicar, J.

1985-01-01

Vanadium pentoxide on a suitable carrier is often used as catalyst for the oxidation of anthracene in the gaseous phase to 9,10-anthraquinone. The activity and selectivity of the catalyst may be affected by irradiation. The effects were studied of gamma radiation on the properties of the catalyst where the active system was a V 2 O 5 -KOH-K 2 SO 4 mixture on a Al 2 O 3 +SiO 2 carrier. The 60 Co radiation source had an activity of 185 TBq; the carrier of the catalyst was irradiated at a dose rate of 3.05, 1.98 and 0.084 kGy/h to a total dose of 10 kGy. Irradiation increased the selectivity of the catalyst such that in the oxidation temperature optimum of 300 to 400 degC the yield of 9,10-anthraquinone increased by 4.6 to 4.8 %mol. to roughly 90 %mol.; a significant reduction of the content of acid components (phthalanhydride) in the oxidation product also occurred. This effect remained unchanged for 5 months after irradiation. A reduction of selectivity was observed at lower dose rates only in the temperature range between 400 and 480 degC. (A.K.)

CO oxidation on PtSn nanoparticle catalysts occurs at the interface of Pt and Sn oxide domains formed under reaction conditions

KAUST Repository

Michalak, William D.

2014-04-01

The barrier to CO oxidation on Pt catalysts is the strongly bound adsorbed CO, which inhibits O2 adsorption and hinders CO2 formation. Using reaction studies and in situ X-ray spectroscopy with colloidally prepared, monodisperse ∼2 nm Pt and PtSn nanoparticle catalysts, we show that the addition of Sn to Pt provides distinctly different reaction sites and a more efficient reaction mechanism for CO oxidation compared to pure Pt catalysts. To probe the influence of Sn, we intentionally poisoned the Pt component of the nanoparticle catalysts using a CO-rich atmosphere. With a reaction environment comprised of 100 Torr CO and 40 Torr O2 and a temperature range between 200 and 300 C, Pt and PtSn catalysts exhibited activation barriers for CO2 formation of 133 kJ/mol and 35 kJ/mol, respectively. While pure Sn is readily oxidized and is not active for CO oxidation, the addition of Sn to Pt provides an active site for O2 adsorption that is important when Pt is covered with CO. Sn oxide was identified as the active Sn species under reaction conditions by in situ ambient pressure X-ray photoelectron spectroscopy measurements. While chemical signatures of Pt and Sn indicated intermixed metallic components under reducing conditions, Pt and Sn were found to reversibly separate into isolated domains of Pt and oxidic Sn on the nanoparticle surface under reaction conditions of 100 mTorr CO and 40 mTorr O2 between temperatures of 200-275 C. Under these conditions, PtSn catalysts exhibited apparent reaction orders in O2 for CO 2 production that were 0.5 and lower with increasing partial pressures. These reaction orders contrast the first-order dependence in O 2 known for pure Pt. The differences in activation barriers, non-first-order dependence in O2, and the presence of a partially oxidized Sn indicate that the enhanced activity is due to a reaction mechanism that occurs at a Pt/Sn oxide interface present at the nanoparticle surface. © 2014 Published by Elsevier Inc.

Desorption of Furfural from Bimetallic Pt-Fe Oxides/Alumina Catalysts

Directory of Open Access Journals (Sweden)

Gloria Lourdes Dimas-Rivera

2014-01-01

Full Text Available In this work, the desorption of furfural, which is a competitive intermediate during the production of biofuel and valuable aromatic compounds, was studied using pure alumina, as well as alumina impregnated with iron and platinum oxides both individually and in combination, using thermogravimetric analysis (TGA. The bimetallic sample exhibited the lowest desorption percentage for furfural. High-resolution transmission electron microscopy (HRTEM imaging revealed the intimate connection between the iron and platinum oxide species on the alumina support. The mechanism of furfural desorption from the Pt-Fe/Al2O3 0.5%-0.5% sample was determined using physisorbed furfural instead of chemisorbed furfural; this mechanism involved the oxidation of the C=O group on furfural by the catalyst. The oxide nanoparticles on γ-Al2O3 support helped to stabilize the furfural molecule on the surface.

Surface chemistry and catalytic properties of VOX/Ti-MCM-41 catalysts for dibenzothiophene oxidation in a biphasic system

Science.gov (United States)

González, J.; Chen, L. F.; Wang, J. A.; Manríquez, Ma.; Limas, R.; Schachat, P.; Navarrete, J.; Contreras, J. L.

2016-08-01

A series of vanadium oxide supported on Ti-MCM-41 catalysts was synthesized via the incipient impregnation method by varying the vanadia loading from 5 wt% to 10, 15, 20 and 25 wt%. These catalysts were characterized by a variety of advanced techniques for investigating their crystalline structure, textural properties, and surface chemistry information including surface acidity, reducibility, vanadium oxidation states, and morphological features. The catalytic activities of the catalysts were evaluated in a biphasic reaction system for oxidative desulfurization (ODS) of a model diesel containing 300 ppm of dibenzothiophene (DBT) where acetonitrile was used as extraction solvent and H2O2 as oxidant. ODS activity was found to be proportional to the V5+/(V4+ + V5+) values of the catalysts, indicating that the surface vanadium pentoxide (V2O5) was the active phase. Reaction temperature would influence significantly the ODS efficiency; high temperature, i.e., 80 °C, would lead to low ODS reaction due to the partial decomposition of oxidant. All the catalysts contained both Lewis and Brønsted acid sites but the former was predominant. The catalysts with low vanadia loading (5 or 10 wt%V2O5) had many Lewis acid sites and could strongly adsorb DBT molecule via the electron donation/acceptance action which resulted in an inhibition for the reaction of DBT with the surface peroxometallic species. The catalyst with high vanadia loading (25wt%V2O5/Ti-MCM-41) showed the highest catalytic activity and could remove 99.9% of DBT at 60 °C within 60 min.

Oxidations of amines with molecular oxygen using bifunctional gold–titania catalysts

DEFF Research Database (Denmark)

Klitgaard, Søren Kegnæs; Egeblad, Kresten; Mentzel, Uffe Vie

2008-01-01

–titania catalysts can be employed to facilitate the oxidation of amines into amides with high selectivity. Furthermore, we report that pure titania is in fact itself a catalyst for the oxidation of amines with molecular oxygen under very mild conditions. We demonstrate that these new methodologies open up for two......Over the past decades it has become clear that supported gold nanoparticles are surprisingly active and selective catalysts for several green oxidation reactions of oxygen-containing hydrocarbons using molecular oxygen as the stoichiometric oxidant. We here report that bifunctional gold...

Low-temperature abatement of toluene over Mn-Ce oxides catalysts synthesized by a modified hydrothermal approach

Science.gov (United States)

Du, Jinpeng; Qu, Zhenping; Dong, Cui; Song, Lixin; Qin, Yuan; Huang, Na

2018-03-01

Mn-Ce oxides catalysts were synthesized by a novel method combining redox-precipitation and hydrothermal approach. The results indicate that the ratio between manganese and cerium plays a crucial role in the formation of catalysts, and the textual properties as well as catalytic activity are remarked affected. Mn0.6Ce0.4O2 possesses a predominant catalytic activity in the oxidation of toluene, over 70% of toluene is converted at 200 °C, and the complete conversion temperature is 210 °C. The formation of Mn-Ce solid solution markedly improves the surface area as well as pore volume of Mn-Ce oxide catalyst, and Mn0.6Ce0.4O2 possesses the largest surface area of 298.5 m2/g. The abundant Ce3+ and Mn3+ on Mn0.6Ce0.4O2 catalyst facilitate the formation of oxygen vacancies, and improve the transfer of oxygen in the catalysts. Meanwhile, it is found that cerium in Mn-Ce oxide plays a key role in the adsorption of toluene, while manganese is proved to be crucial in the oxidation of toluene, the cooperation between manganese and cerium improves the catalytic reaction process. In addition, the reaction process is investigated by in situ DRIFT measurement, and it is found that the adsorbed toluene could be oxidized to benzyl alcohol as temperature rises around 80-120 °C that can be further be oxidized to benzoic acid. Then benzoic acid could be decomposed to formate and/or carbonate species as temperature rises to form CO2 and H2O. In addition, the formed by-product phenol could be further oxidized into CO2 and H2O when the temperature is high enough.

Oxidative dehydrogenation of ethylbenzene using nitrous oxide over vanadia-magnesia catalysts

NARCIS (Netherlands)

Shiju, N.R.; Anilkumar, M.; Gokhale, S.P.; Rao, B.S.; Satyanarayana, C.V.V.

2011-01-01

A series of V-Mg-O catalysts with different loadings of vanadia were prepared by the wet impregnation method and the effect of the local structure of these catalysts on the oxidative dehydrogenation of ethylbenzene with N2O was investigated. High styrene selectivity (97%) was obtained at 773 K. The

Sulfidation of carbon-supported iron oxide catalysts

NARCIS (Netherlands)

Ramselaar, W.L.T.M.; Hadders, R.H.; Gerkema, E.; Beer, de V.H.J.; Oers, van E.M.; Kraan, van der A.M.

1989-01-01

The sulfidation of carbon-supported iron oxide catalysts was studied by means of in-situ Mössbauer spectroscopy at temperatures down to 4.2 K. The catalysts were dried in two different ways and then sulfided in a flow of 10% H2S in H2 at temperatures between 293 and 773 K. Thiophene

Templating Routes to Supported Oxide Catalysts by Design

Energy Technology Data Exchange (ETDEWEB)

Notestein, Justin M. [Northwestern Univ., Evanston, IL (United States)

2016-09-08

The rational design and understanding of supported oxide catalysts requires at least three advancements, in order of increasing complexity: the ability to quantify the number and nature of active sites in a catalytic material, the ability to place external controls on the number and structure of these active sites, and the ability to assemble these active sites so as to carry out more complex functions in tandem. As part of an individual investigator research program that is integrated with the Northwestern University Institute for Catalysis in Energy Processes (ICEP) as of 2015, significant advances were achieved in these three areas. First, phosphonic acids were utilized in the quantitative assessment of the number of active and geometrically-available sites in MO_x-SiO₂ catalysts, including nanocrystalline composites, co-condensed materials, and grafted structures, for M=Ti, Zr, Hf, Nb, and Ta. That work built off progress in understanding supported Fe, Cu, and Co oxide catalysts from chelating and/or multinuclear precursors to maximize surface reactivity. Secondly, significant progress was made in the new area of using thin oxide overcoats containing ‘nanocavities’ from organic templates as a method to control the dispersion and thermal stability of subsequently deposited metal nanoparticles or other catalytic domains. Similar methods were used to control surface reactivity in SiO₂-Al₂O₃ acid catalysts and to control reactant selectivity in Al₂O₃-TiO₂ photocatalysts. Finally, knowledge gained from the first two areas has been combined to synthesize a tandem catalyst for hydrotreating reactions and an orthogonal tandem catalyst system where two subsequent reactions in a reaction network are independently controlled by light and heat. Overall, work carried out under this project significantly advanced the knowledge of synthesis-structure-function relationships in supported

High-throughput technology for novel SO2 oxidation catalysts

International Nuclear Information System (INIS)

Loskyll, Jonas; Stoewe, Klaus; Maier, Wilhelm F

2011-01-01

We review the state of the art and explain the need for better SO 2 oxidation catalysts for the production of sulfuric acid. A high-throughput technology has been developed for the study of potential catalysts in the oxidation of SO 2 to SO 3 . High-throughput methods are reviewed and the problems encountered with their adaptation to the corrosive conditions of SO 2 oxidation are described. We show that while emissivity-corrected infrared thermography (ecIRT) can be used for primary screening, it is prone to errors because of the large variations in the emissivity of the catalyst surface. UV-visible (UV-Vis) spectrometry was selected instead as a reliable analysis method of monitoring the SO 2 conversion. Installing plain sugar absorbents at reactor outlets proved valuable for the detection and quantitative removal of SO 3 from the product gas before the UV-Vis analysis. We also overview some elements used for prescreening and those remaining after the screening of the first catalyst generations. (topical review)

Highly selective oxidation of styrene to benzaldehyde over a tailor-made cobalt oxide encapsulated zeolite catalyst.

Science.gov (United States)

Liu, Jiangyong; Wang, Zihao; Jian, Panming; Jian, Ruiqi

2018-05-01

A tailor-made catalyst with cobalt oxide particles encapsulated into ZSM-5 zeolites (Co 3 O 4 @HZSM-5) was prepared via a hydrothermal method with the conventional impregnated Co 3 O 4 /SiO 2 catalyst as the precursor and Si source. Various characterization results show that the Co 3 O 4 @HZSM-5 catalyst has well-organized structure with Co 3 O 4 particles compatibly encapsulated in the zeolite crystals. The Co 3 O 4 @HZSM-5 catalyst was employed as an efficient catalyst for the selective oxidation of styrene to benzaldehyde with hydrogen peroxide as a green and economic oxidant. The effect of various reaction conditions including reaction time, reaction temperature, different kinds of solvents, styrene/H 2 O 2 molar ratio and catalyst dosage on the catalytic performance were systematically investigated. Under the optimized reaction condition, the yield of benzaldehyde can achieve 78.9% with 96.8% styrene conversion and 81.5% benzaldehyde selectivity. Such an excellent catalytic performance can be attributed to the synergistic effect between the confined reaction environment and the proper acidic property. In addition, the reaction mechanism with Co 3 O 4 @HZSM-5 as the catalyst for the selective oxidation of styrene to benzaldehyde was reasonably proposed. Copyright © 2018 Elsevier Inc. All rights reserved.

Oxidation of mercury across selective catalytic reduction catalysts in coal-fired power plants

Energy Technology Data Exchange (ETDEWEB)

Constance L. Senior [Reaction Engineering International, Salt Lake City, UT (United States)

2006-01-15

A kinetic model for predicting the amount of mercury (Hg) oxidation across selective catalytic reduction (SCR) systems in coal-fired power plants was developed and tested. The model incorporated the effects of diffusion within the porous SCR catalyst and the competition between ammonia and Hg for active sites on the catalyst. Laboratory data on Hg oxidation in simulated flue gas and slipstream data on Hg oxidation in flue gas from power plants were modeled. The model provided good fits to the data for eight different catalysts, both plate and monolith, across a temperature range of 280-420{sup o}C, with space velocities varying from 1900 to 5000 hr{sup -1}. Space velocity, temperature, hydrochloric acid content of the flue gas, ratio of ammonia to nitric oxide, and catalyst design all affected Hg oxidation across the SCR catalyst. The model can be used to predict the impact of coal properties, catalyst design, and operating conditions on Hg oxidation across SCRs. 20 refs., 9 figs., 2 tabs.

Comparison of Elemental Mercury Oxidation Across Vanadium and Cerium Based Catalysts in Coal Combustion Flue Gas: Catalytic Performances and Particulate Matter Effects.

Science.gov (United States)

Wan, Qi; Yao, Qiang; Duan, Lei; Li, Xinghua; Zhang, Lei; Hao, Jiming

2018-03-06

This paper discussed the field test results of mercury oxidation activities over vanadium and cerium based catalysts in both coal-fired circulating fluidized bed boiler (CFBB) and chain grate boiler (CGB) flue gases. The characterizations of the catalysts and effects of flue gas components, specifically the particulate matter (PM) species, were also discussed. The catalytic performance results indicated that both catalysts exhibited mercury oxidation preference in CGB flue gas rather than in CFBB flue gas. Flue gas component studies before and after dust removal equipment implied that the mercury oxidation was well related to PM, together with gaseous components such as NO, SO 2 , and NH 3 . Further investigations demonstrated a negative PM concentration-induced effect on the mercury oxidation activity in the flue gases before the dust removal, which was attributed to the surface coverage by the large amount of PM. In addition, the PM concentrations in the flue gases after the dust removal failed in determining the mercury oxidation efficiency, wherein the presence of different chemical species in PM, such as elemental carbon (EC), organic carbon (OC) and alkali (earth) metals (Na, Mg, K, and Ca) in the flue gases dominated the catalytic oxidation of mercury.

Selectivity and Activity of Iron Molybdate Catalysts in Oxidation of Methanol

Directory of Open Access Journals (Sweden)

Khalid Khazzal Hummadi

2009-06-01

Full Text Available The selectivity and activity of iron molybdate catalysts prepared by different methods are compared with those of a commercial catalyst in the oxidation of methanol to formaldehyde in a continuous tubular bed reactor at 200-350 oC (473-623 oK, 10 atm (1013 kPa, with a methanol-oxygen mixture fixed at 5.5% by volume methanol: air ratio. The iron(III molybdate catalyst prepared by co-precipitation and filtration had a selectivity towards formaldehyde in methanol oxidation comparable with a commercial catalyst; maximum selectivity (82.3% was obtained at 573oK when the conversion was 59.7%. Catalysts prepared by reacting iron (III and molybdate by kneading or precipitation followed by evaporation, omitting a filtration stage, were less active and less selective. The selectivity-activity relationships of these catalysts as a function of temperature were discussed in relation to the method of preparation, surface areas and composition. By combing this catalytic data with data from the patent literature we demonstrate a synergy between iron and molybdenum in regard to methanol oxidation to formaldehyde; the optimum composition corresponded to an iron mole fraction 0.2-0.3. The selectivity to formaldehyde was practically constant up to an iron mole fraction 0.3 and then decreased at higher iron concentrations. The iron component can be regarded as the activity promoter. The iron molybdate catalysts can thus be related to other two-component MoO3-based selective oxidation catalysts, e.g. bismuth and cobalt molybdates. The iron oxide functions as a relatively basic oxide abstracting, in the rate-controlling step, a proton from the methyl of a bound methoxy group of chemisorbed methanol. It was proposed that a crucial feature of the sought after iron(III molybdate catalyst is the presence of -O-Mo-O-Fe-O-Mo-O- groups as found in the compound Fe2(MoO43 and for Fe3+ well dispersed in MoO3 generally. At the higher iron(III concentrations the loss of

Oxidative desulfurization of synthetic diesel using supported catalysts. Part 3. Support effect on vanadium-based catalysts

Energy Technology Data Exchange (ETDEWEB)

Cedeno-Caero, Luis; Gomez-Bernal, Hilda; Fraustro-Cuevas, Adriana; Guerra-Gomez, Hector D.; Cuevas-Garcia, Rogelio [UNICAT, Facultad de Quimica, Universidad Nacional Autonoma de Mexico, Cd. Universitaria 04510, Mexico D.F. (Mexico)

2008-04-15

Oxidesulfurization (ODS) of benzothiophenic compounds prevailing in diesel was conducted with hydrogen peroxide in presence of various catalysts, using a model diesel and actual diesel fuel. ODS activities of dibenzothiophenes (DBTs) in hexadecane for a series of V{sub 2}O{sub 5} catalysts supported on alumina, titania, ceria, niobia and silica, were evaluated. Results show that the oxidation activity of DBTs depends on the support used. It was observed that the sulfone yield is not proportional to textural properties or V content. For all catalysts, ODS of benzothiophene (BT), dibenzothiophene (DBT), 4-methyl dibenzothiophene (4-MDBT) and 4,6-dimethyl dibenzothiophene (4,6-DMDBT) decreased in the following order: DBT > 4-MDBT > 4,6-DMDBT > BT. This trend does not depend on the catalyst used or the textural properties of the catalysts and supports. In presence of indole ODS activities diminish, except with catalysts supported on alumina-titania mixed oxide, whereas with V{sub 2}O{sub 5}/TiO{sub 2} catalyst the performance is the highest. ODS of Mexican diesel fuel was carried out in presence of this catalyst and S level was diminished in about 99%. (author)

Surface chemistry and catalytic properties of VOX/Ti-MCM-41 catalysts for dibenzothiophene oxidation in a biphasic system

International Nuclear Information System (INIS)

González, J.; Chen, L.F.; Wang, J.A.; Manríquez, Ma.; Limas, R.; Schachat, P.; Navarrete, J.; Contreras, J.L.

2016-01-01

Highlights: • Oxidative desulfurization of model diesel was tested in a biphasic system. • ODS activity was proportional to the V 5+ /(V 4+ + V 5+ ) values of the catalysts. • Lewis acidity was related to vanadium content and catalytic activity. • 99.9% DBT was oxidized using 25%V 2 O 5 /Ti-MCM-41 at 60 °C within 60 min. - Abstract: A series of vanadium oxide supported on Ti-MCM-41 catalysts was synthesized via the incipient impregnation method by varying the vanadia loading from 5 wt% to 10, 15, 20 and 25 wt%. These catalysts were characterized by a variety of advanced techniques for investigating their crystalline structure, textural properties, and surface chemistry information including surface acidity, reducibility, vanadium oxidation states, and morphological features. The catalytic activities of the catalysts were evaluated in a biphasic reaction system for oxidative desulfurization (ODS) of a model diesel containing 300 ppm of dibenzothiophene (DBT) where acetonitrile was used as extraction solvent and H 2 O 2 as oxidant. ODS activity was found to be proportional to the V 5+ /(V 4+ + V 5+ ) values of the catalysts, indicating that the surface vanadium pentoxide (V 2 O 5 ) was the active phase. Reaction temperature would influence significantly the ODS efficiency; high temperature, i.e., 80 °C, would lead to low ODS reaction due to the partial decomposition of oxidant. All the catalysts contained both Lewis and Brønsted acid sites but the former was predominant. The catalysts with low vanadia loading (5 or 10 wt%V 2 O 5 ) had many Lewis acid sites and could strongly adsorb DBT molecule via the electron donation/acceptance action which resulted in an inhibition for the reaction of DBT with the surface peroxometallic species. The catalyst with high vanadia loading (25wt%V 2 O 5 /Ti-MCM-41) showed the highest catalytic activity and could remove 99.9% of DBT at 60 °C within 60 min.

Revealing the Cytotoxicity of Residues of Phosphazene Catalysts Used for Synthesis of Poly(ethylene oxide)

KAUST Repository

Xia, Yening

2017-08-24

We herein report a case study on the toxicity of residual catalyst in metal-free polymer. Eight-arm star-like poly(ethylene oxide)s were successfully synthesized via phosphazene-catalyzed ring-opening polymerization of ethylene oxide using sucrose as an octahydroxy initiator. The products were subjected to MTT assay using human cancer cell lines (MDA-MB-231 and A2780). Comparison between the crude and purified products clearly revealed that the residual phosphazenium salts were considerably cytotoxic regardless of the anionic species, and that the cytotoxicity of more bulky t-BuP4 salt was higher than that of t-BuP2 salt. Such results have therefore put forward the necessity for removal of the catalyst residues from PEO-based polymers synthesized through phosphazene catalysis for bio-related applications, and for the development of less or non-toxic organocatalysts for such polymers.

Revealing the Cytotoxicity of Residues of Phosphazene Catalysts Used for Synthesis of Poly(ethylene oxide)

KAUST Repository

Xia, Yening; Shen, Jizhou; Alamri, Haleema; Hadjichristidis, Nikolaos; Zhao, Junpeng; Wang, Yucai; Zhang, Guangzhao

2017-01-01

We herein report a case study on the toxicity of residual catalyst in metal-free polymer. Eight-arm star-like poly(ethylene oxide)s were successfully synthesized via phosphazene-catalyzed ring-opening polymerization of ethylene oxide using sucrose as an octahydroxy initiator. The products were subjected to MTT assay using human cancer cell lines (MDA-MB-231 and A2780). Comparison between the crude and purified products clearly revealed that the residual phosphazenium salts were considerably cytotoxic regardless of the anionic species, and that the cytotoxicity of more bulky t-BuP4 salt was higher than that of t-BuP2 salt. Such results have therefore put forward the necessity for removal of the catalyst residues from PEO-based polymers synthesized through phosphazene catalysis for bio-related applications, and for the development of less or non-toxic organocatalysts for such polymers.

VO x /SiO 2 Catalyst Prepared by Grafting VOCl 3 on Silica for Oxidative Dehydrogenation of Propane

KAUST Repository

Zhu, Haibo; Ould-Chikh, Samy; Dong, Hailin; Llorens, Isabelle; Saih, Youssef; Anjum, Dalaver H.; Hazemann, Jean Louis; Basset, Jean-Marie

2015-01-01

The VOx/SiO2 catalysts for oxidative dehydrogenation of propane were synthesized by a simple grafting method. The VOCl3 was first grafted at the surface of SiO2, which was dehydrated at different temperature (from 200 to 1000°C). The formed grafted complexes were then calcined in air, leading to the formation of VOx/SiO2 catalysts. The synthesized catalysts were characterized by nitrogen adsorption, SEM, Raman spectroscopy, temperature-programmed reduction, and extended X-ray absorption fine structure analysis. The SiO2 pretreatment temperature has an evident effect on the loading and dispersion of VOx on SiO2, which finally affects their catalytic performance. High SiO2 treatment temperature is beneficial to dispersing the vanadium oxide species at the SiO2 surface. These materials are efficient catalysts for the catalytic oxidative dehydrogenation of propane to propylene. The best selectivity to propylene is achieved on the VOx/SiO2-(1000) catalyst. The high selectivity and activity are well maintained for three days catalytic reaction. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

VO x /SiO 2 Catalyst Prepared by Grafting VOCl 3 on Silica for Oxidative Dehydrogenation of Propane

KAUST Repository

Zhu, Haibo

2015-09-07

The VOx/SiO2 catalysts for oxidative dehydrogenation of propane were synthesized by a simple grafting method. The VOCl3 was first grafted at the surface of SiO2, which was dehydrated at different temperature (from 200 to 1000°C). The formed grafted complexes were then calcined in air, leading to the formation of VOx/SiO2 catalysts. The synthesized catalysts were characterized by nitrogen adsorption, SEM, Raman spectroscopy, temperature-programmed reduction, and extended X-ray absorption fine structure analysis. The SiO2 pretreatment temperature has an evident effect on the loading and dispersion of VOx on SiO2, which finally affects their catalytic performance. High SiO2 treatment temperature is beneficial to dispersing the vanadium oxide species at the SiO2 surface. These materials are efficient catalysts for the catalytic oxidative dehydrogenation of propane to propylene. The best selectivity to propylene is achieved on the VOx/SiO2-(1000) catalyst. The high selectivity and activity are well maintained for three days catalytic reaction. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Solution Structures of Highly Active Molecular Ir Water-Oxidation Catalysts from Density Functional Theory Combined with High-Energy X-ray Scattering and EXAFS Spectroscopy.

Science.gov (United States)

Yang, Ke R; Matula, Adam J; Kwon, Gihan; Hong, Jiyun; Sheehan, Stafford W; Thomsen, Julianne M; Brudvig, Gary W; Crabtree, Robert H; Tiede, David M; Chen, Lin X; Batista, Victor S

2016-05-04

The solution structures of highly active Ir water-oxidation catalysts are elucidated by combining density functional theory, high-energy X-ray scattering (HEXS), and extended X-ray absorption fine structure (EXAFS) spectroscopy. We find that the catalysts are Ir dimers with mono-μ-O cores and terminal anionic ligands, generated in situ through partial oxidation of a common catalyst precursor. The proposed structures are supported by (1)H and (17)O NMR, EPR, resonance Raman and UV-vis spectra, electrophoresis, etc. Our findings are particularly valuable to understand the mechanism of water oxidation by highly reactive Ir catalysts. Importantly, our DFT-EXAFS-HEXS methodology provides a new in situ technique for characterization of active species in catalytic systems.

Nanocasted synthesis of magnetic mesoporous iron cerium bimetal oxides (MMIC) as an efficient heterogeneous Fenton-like catalyst for oxidation of arsenite.

Science.gov (United States)

Wen, Zhipan; Zhang, Yalei; Dai, Chaomeng; Sun, Zhen

2015-04-28

Magnetic mesoporous iron cerium bimetal oxides (MMIC) with large surface area and pore volume was synthesized via the hard template approach. This obtained MMIC was easily separated from aqueous solution with an external magnetic field and was proposed as a heterogeneous Fenton-like catalyst for oxidation of As(III). The MMIC presented excellent catalytic activity for the oxidation of As(III), achieving almost complete oxidation of 1000ppb As(III) after 60min and complete removal of arsenic species after 180min with reaction conditions of 0.4g/L catalyst, pH of 3.0 and 0.4mM H2O2. Kinetics analysis showed that arsenic removal followed the pseudo-first order, and the pseudo-first-order rate constants increased from 0.0014min(-1) to 0.0548min(-1) as the H2O2 concentration increased from 0.04mM to 0.4mM. On the basis of the effects of XPS analysis and reactive oxidizing species, As(III) in aqueous solution was mainly oxidized by OH radicals, including the surface-bound OHads generated on the MMIC surface which were involved in Fe(2+) and Ce(3+), and free OHfree generation by soluble iron ions which were released from the MMIC into the bulk solution, and the generated As(V) was finally removed by MMIC through adsorption. Copyright © 2015 Elsevier B.V. All rights reserved.

The acidic properties of mixed tin and antimony oxide catalysts

Energy Technology Data Exchange (ETDEWEB)

Irving, E.A.; Taylor, D.

1978-01-01

The acidic properties of mixed tin + antimony oxide catalysts were studied in the isomerization of 3,3-dimethyl-1-butene, cyclopropane, 1-butene, and cis-2-butene and the dehydration of isopropanol over the mixed oxides outgassed at room temperature and 698/sup 0/K. Only the zero-order portions of the reaction were used for calculations. With catalysts outgassed at room temperature, weakly acidic sites were present, and all the reactions probably occurred by a carbonium ion mechanism with Broensted acid sites as a source of protons. The rates increased with increasing antimony content to a maximum at approx. 50 at. % and then decreased with further increase in the antimony content. Outgassing of the catalysts at 698/sup 0/K increased the isomerization rate of 3,3-dimethyl-1-butene, but decreased those for cyclopropane and isopropanol due to poisoning by the propylene produced. For 1-butene and cis-2-butene and catalysts outgassed at 698/sup 0/K, only catalysts with less than 50Vertical Bar3< antimony were active. The catalysts were poisoned by treatment with bases or with sodium acetate. A proposed correlation between rates and acidity led to the conclusion that the catalyst composition corresponding to maximum acidity differs from that for maximum selective oxidation activity. Graphs and 10 references.

Studies of Deactivation of Methanol to Formaldehyde Selective Oxidation Catalyst

DEFF Research Database (Denmark)

Raun, Kristian Viegaard; Schumann, Max; Høj, Martin

This work presents a study of the deactivation behavior of Fe-Mo oxide catalyst during selective oxidation of methanol to formaldehyde in a period of 5 days. The structural changes in the catalyst have been investigated in situ for the initial 10 h by Raman spectroscopy, and the structure after 5...

Comparison of Preparation Methods of Copper Based PGMFree Diesel-Soot Oxidation Catalysts

Directory of Open Access Journals (Sweden)

R. Prasad

2011-05-01

Full Text Available CuO-CeO2 systems have been proposed as a promising catalyst for low temperature diesel-soot oxidation. CuO-CeO2 catalysts prepared by various methods were examined for air oxidation of the soot in a semi batch tubular flow reactor. The air oxidation of soot was carried out under tight contact with soot/catalyst ratio of 1/10. Air flow rate was 150 ml/min, soot-catalyst mixture was 110 mg, heating rate was 5 0C/min. Prepared catalysts were calcined at 500 0C and their stability was examined by further heating to 800 0C for 4 hours. It was found that the selectivity of all the catalysts was nearly 100% to CO2 production. It was observed that the activity and stability of the catalysts greatly influenced by the preparation methods. The strong interaction between CuO and CeO2 is closely related to the preparation route that plays a crucial role in the soot oxidation over the CuO-CeO2 catalysts. The ranking order of the preparation methods of the catalysts in the soot oxidation performance is as follows: sol-gel > urea nitrate combustion > Urea gelation method > thermal decomposition > co-precipitation. Copyright © 2011 BCREC UNDIP. All rights reserved.(Received: 27th June 2010, Revised: 7th August 2010; Accepted: 13rd October 2010[How to Cite: R. Prasad, V.R. Bella. (2011. Comparison of Preparation Methods of Copper Based PGMFree Diesel-Soot Oxidation Catalysts. Bulletin of Chemical Reaction Engineering and Catalysis, 6(1: 15-21. doi:10.9767/bcrec.6.1.822.15-21][How to Link / DOI: http://dx.doi.org/10.9767/bcrec.6.1.822.15-21 || or local: http://ejournal.undip.ac.id/index.php/bcrec/article/view/822 | View in 

Effect of drying method on properties of vanadium-molybdenum oxide catalysts

International Nuclear Information System (INIS)

Gorshkova, T.P.; Savchenko, L.A.; Tarasova, D.V.; Tret'yakov, Yu.D.; Olen'kova, I.P.; Nikoro, T.A.; Maksimov, N.G.

1981-01-01

Effect of drying method of molybdenum and vanadium salt solutions on physicochemical and catalytical properties of vanadium-molybdenum catalysts is studied. It is shown that the drying method of solutions determines the completeness of vanadium binding into oxide vanadium-molybdenum compounds and thus effects the activity and selectivity of catalysts in acrolein oxidation into acrylic acid. Besides the drying method determines the porous structure of catalysts [ru

Hydrogen production by ethanol partial oxidation over nano-iron oxide catalysts produced by chemical vapour synthesis

Energy Technology Data Exchange (ETDEWEB)

Ahmed, Wael Ahmed Abou Taleb Sayed

2011-01-13

This work presents the experimental results of the synthesis of unsupported and supported SiC iron oxide nanoparticles and their catalytic activity towards ethanol partial oxidation. For comparison, further unsupported iron oxide phases were investigated towards the ethanol partial oxidation. These {gamma}-Fe{sub 2}O{sub 3} and {alpha}/{gamma}-Fe{sub 2}O{sub 3} phase catalysts were prepared by the CVS method using Fe(CO){sub 5} as precursor, supplied by another author. The {alpha}-Fe{sub 2}O{sub 3} and SiC nanoparticles were prepared by the CVS method using a home made hot wall reactor technique at atmospheric pressure. Ferrocene and tetramethylsilane were used as precursor for the production process. Process parameters of precursor evaporation temperature, precursor concentration, gas mixture velocity and gas mixture dilution were investigated and optimised to produce particle sizes in a range of 10 nm. For Fe{sub 2}O{sub 3}/SiC catalyst series production, a new hot wall reactor setup was used. The particles were produced by simultaneous thermal decomposition of ferrocene and tetramethylsilane in one reactor from both sides. The production parameters of inlet tube distance inside the reactor, precursor evaporation temperature and carrier gas flow were investigated to produce a series of samples with different iron oxide content. The prepared catalysts composition, physical and chemical properties were characterized by XRD, EDX, SEM, BET surface area, FTIR, XPS and dynamic light scattering (DLS) techniques. The catalytic activity for the ethanol gas-phase oxidation was investigated in a temperature range from 260 C to 290 C. The product distributions obtained over all catalysts were analysed with mass spectrometry analysis tool. The activity of bulk Fe{sub 2}O{sub 3} and SiC nanoparticles was compared with prepared nano-iron oxide phase catalysts. The reaction parameters, such as reaction temperature and O{sub 2}/ethanol ratio were investigated. The catalysts

Impacts of halogen additions on mercury oxidation, in a slipstream selective catalyst reduction (SCR), reactor when burning sub-bituminous coal.

Science.gov (United States)

Cao, Yan; Gao, Zhengyang; Zhu, Jiashun; Wang, Quanhai; Huang, Yaji; Chiu, Chengchung; Parker, Bruce; Chu, Paul; Pant, Wei-Ping

2008-01-01

This paper presents a comparison of impacts of halogen species on the elemental mercury (Hg(0)) oxidation in a real coal-derived flue gas atmosphere. It is reported there is a higher percentage of Hg(0) in the flue gas when burning sub-bituminous coal (herein Powder River Basin (PRB) coal) and lignite, even with the use of selective catalytic reduction (SCR). The higher Hg(0)concentration in the flue gas makes it difficult to use the wet-FGD process for the mercury emission control in coal-fired utility boilers. Investigation of enhanced Hg(0) oxidation by addition of hydrogen halogens (HF, HCl, HBr, and HI) was conducted in a slipstream reactor with and without SCR catalysts when burning PRB coal. Two commercial SCR catalysts were evaluated. SCR catalyst no. 1 showed higher efficiencies of both NO reduction and Hg(0) oxidation than those of SCR catalyst no. 2. NH3 addition seemed to inhibit the Hg(0) oxidation, which indicated competitive processes between NH3 reduction and Hg(0) oxidation on the surface of SCR catalysts. The hydrogen halogens, in the order of impact on Hg(0) oxidation, were HBr, HI, and HCl or HF. Addition of HBr at approximately 3 ppm could achieve 80% Hg(0) oxidation. Addition of HI at approximately 5 ppm could achieve 40% Hg(0) oxidation. In comparison to the empty reactor, 40% Hg(0) oxidation could be achieved when HCl addition was up to 300 ppm. The enhanced Hg(0) oxidation by addition of HBr and HI seemed not to be correlated to the catalytic effects by both evaluated SCR catalysts. The effectiveness of conversion of hydrogen halogens to halogen molecules or interhalogens seemed to be attributed to their impacts on Hg(0) oxidation.

Light olefins from synthesis gas using ruthenium on rare earth oxide catalysts

International Nuclear Information System (INIS)

Bruce, L.; Hardin, S.; Hoang, M.; Turney, T.

1988-01-01

The interaction of ruthenium carbonyl, Ru/sub 3/(CO)/sub 12/ with rare earth oxides of high surface area, >50m/sup 2/g/sup -1/, has been studied. [Ru/sub 3/(μ H)(CO)/sub 10/(μ-OM=)] is formed on holmia, but on lanthana only [Ru(CO)/sub 2/]/sub n/ species are observed. Reduction of the carbonyl ligands takes place at <573K to give catalysts for the hydrogenation of carbon monoxide with activity and selectivity dependent on the particular rare earth oxide and pretreatment. Over ceria, the product is up to 55 wt% C2-5 olefins. A similar selectivity is obtained over lanthana only after redispersion through a reduction-oxidation-reduction cycle

Copper oxide as efficient catalyst for oxidative dehydrogenation of alcohols with air

DEFF Research Database (Denmark)

Poreddy, Raju; Engelbrekt, Christian; Riisager, Anders

2015-01-01

The oxidative dehydrogenation of alcohols to carbonyl compounds was studied using CuO nanoparticle catalysts prepared by solution synthesis in buffered media. CuO nanoparticles synthesized in N-cyclohexyl- 3-aminopropanesulfonic acid buffer showed high catalytic activity for the oxidation...... of benzylic, alicyclic and unsaturated alcohols to their corresponding carbonyl compounds with excellent selectivities. The observed trend in activity for conversion of substituted alcohols suggested a β-H elimination step to be involved, thus enabling a possible reaction mechanism for oxidative...... dehydrogenation of benzyl alcohols to be proposed. The use of CuO as an inexpensive and efficient heterogeneous catalyst under aerobic conditions provides a new noble metal-free and green reaction protocol for carbonyl compound synthesis....

Pretreatment of Platinum/Tin Oxide-Catalyst

Science.gov (United States)

Hess, Robert V.; Paulin, Patricia A.; Miller, Irvin M.; Schryer, David R.; Sidney, Barry D.; Wood, George M.; Upchurch, Billy T.; Brown, Kenneth G.

1987-01-01

Addition of CO to He pretreatment doubles catalytic activity. In sealed, high-energy, pulsed CO2 laser, CO and O2 form as decomposition products of CO2 in laser discharge zone. Products must be recombined, because oxygen concentration of more than few tenths of percent causes rapid deterioration of power, ending in unstable operation. Promising low-temperature catalyst for combining CO and O2 is platinum on tin oxide. New development increases activity of catalyst so less needed for recombination process.

Alumina- and titania-based monolithic catalysts for low temperature selective catalytic reduction of nitrogen oxides

International Nuclear Information System (INIS)

Blanco, J.; Avila, P.; Suarez, S.; Martin, J.A.; Knapp, C.

2000-01-01

The selective catalytic reduction of NO+NO 2 (NO x ) at low temperature (180-230C) with ammonia has been investigated with copper-nickel and vanadium oxides supported on titania and alumina monoliths. The influence of the operating temperature, as well as NH 3 /NO x and NO/NO 2 inlet ratios has been studied. High NO x conversions were obtained at operating conditions similar to those used in industrial scale units with all the catalysts. Reaction temperature, ammonia and nitrogen dioxide inlet concentration increased the N 2 O formation with the copper-nickel catalysts, while no increase was observed with the vanadium catalysts. The vanadium-titania catalyst exhibited the highest DeNO x activity, with no detectable ammonia slip and a low N 2 O formation when NH 3 /NO x inlet ratio was kept below 0.8. TPR results of this catalyst with NO/NH 3 /O 2 , NO 2 /NH 3 /O 2 and NO/NO 2 /NH 3 /O 2 feed mixtures indicated that the presence of NO 2 as the only nitrogen oxide increases the quantity of adsorbed species, which seem to be responsible for N 2 O formation. When NO was also present, N 2 O formation was not observed

STUDY OF EPOXIDE DECYCLISATION OF CARYOPHYLENE OXIDE WITH SYNTHETIC ZEOLITE AS CATALYSTS

Directory of Open Access Journals (Sweden)

Winarto Haryadi

2010-06-01

Full Text Available The reaction of epoxide ring opening of caryophillene oxide has been done using zeolite H-Y, H-sodalit, and H-ZSM-5 as catalysts. The reactions were done in two types, there were in dioxane solvent at temperature of 110 oC and without solvent at temperature of 175 oC. The catalyst weight was 10 % from caryophillene oxide weight, and the time of reaction was four hours. The product of reaction was analyzed using GC, FTIR, and GC-MS. The reactions of caryophillene oxide in dioxane solvent with the three kinds of zeolites did not give any targeted product. Whereas, the reactions without solvent gave three main products, there was one compound with one group of secondary hidroxyl (secondary alcohol, and two compounds of ketone from caryophillene. The reaction product of caryophillene oxide obtained without using solvent with the three type of catalysts were then compared. Conversion of three main products produced by H-ZSM-5 catalyst, H-sodalit catalyst and H-Y catalyst were 82.11 %, 54.92 % and 38.53 % respectively. For that reason, the transformation of caryophillene oxide using H-ZSM-5 catalyst was considered to be the best selective product. The alcohol product was resulted from reaction between caryophillene oxide and Bronsted acid, and  the ketone products was resulted from the reaction with Lewis acid in zeolite.   Keywords: Epoxide ring opening, HY, H-sodalit and HZSM-5

Adsorption and oxidation of acetaldehyde on carbon supported Pt, PtSn and PtSn-based trimetallic catalysts by in situ Fourier transform infrared spectroscopy

Science.gov (United States)

Beyhan, Seden; Léger, Jean-Michel; Kadırgan, Figen

2013-11-01

The adsorption and oxidation of acetaldehyde on carbon supported Pt, Pt90Sn10 and Pt80Sn10M10 (M = Ni, Co, Rh, Pd) catalysts have been investigated by using in situ Fourier transform infrared (FTIR) spectroscopy. The result revealed that Pt90Sn10/C catalyst is not very efficient for the conversion of acetaldehyde to CO2 due to the weak adsorption of acetaldehyde in the presence of Sn. However, the addition of a third metal to Pt--Sn facilitates the C-C bond cleavage of acetaldehyde. It seems that acetaldehyde is adsorbed dissociatively on the surface of Pt80Sn10Ni10/C, Pt80Sn10Co10/C, Pt80Sn10Rh10/C catalysts, producing CH3 and CHO adsorbate species, which can be further oxidized to CO2. However, the pathway forming CO2 for Pt80Sn10Pd10/C catalyst mainly originates from the oxidation of CH3CO species. Thus, the presence of third metal in the PtSn catalyst has a strong impact upon the acetaldehyde adsorption behaviour and its reaction products.

Organometallic model complexes elucidate the active gallium species in alkane dehydrogenation catalysts based on ligand effects in Ga K-edge XANES

Energy Technology Data Exchange (ETDEWEB)

Getsoian, Andrew “Bean”; Das, Ujjal; Camacho-Bunquin, Jeffrey; Zhang, Guanghui; Gallagher, James R.; Hu, Bo; Cheah, Singfoong; Schaidle, Joshua A.; Ruddy, Daniel A.; Hensley, Jesse E.; Krause, Theodore R.; Curtiss, Larry A.; Miller, Jeffrey T.; Hock, Adam S.

2016-01-01

Gallium-modified zeolites are known catalysts for the dehydrogenation of alkanes, reactivity that finds industrial application in the aromatization of light alkanes by Ga-ZSM5. While the role of gallium cations in alkane activation is well known, the oxidation state and coordination environment of gallium under reaction conditions has been the subject of debate. Edge shifts in Ga K-edge XANES spectra acquired under reaction conditions have long been interpreted as evidence for reduction of Ga(III) to Ga(I). However, a change in oxidation state is not the only factor that can give rise to a change in the XANES spectrum. In order to better understand the XANES spectra of working catalysts, we have synthesized a series of molecular model compounds and grafted surface organometallic Ga species and compared their XANES spectra to those of gallium-based catalysts acquired under reducing conditions. We demonstrate that changes in the identity and number of gallium nearest neighbors can give rise to changes in XANES spectra similar to those attributed in literature to changes in oxidation state. Specifically, spectral features previously attributed to Ga(I) may be equally well interpreted as evidence for low-coordinate Ga(III) alkyl or hydride species. These findings apply both to gallium-impregnated zeolite catalysts and to silica-supported single site gallium catalysts, the latter of which is found to be active and selective for dehydrogenation of propane and hydrogenation of propylene.

Sulfidation of alumina-supported iron and iron-molybdenum oxide catalysts

NARCIS (Netherlands)

Ramselaar, W.L.T.M.; Crajé, M.W.J.; Hadders, R.H.; Gerkema, E.; Beer, de V.H.J.; Kraan, van der A.M.

1990-01-01

The transition of alumina-supported iron and iron-molybdenum catalysts from the oxidic precursor to the sulfided catalysts was systematically studied by means of in-situ Mössbauer spectroscopy at room temperature. This enabled the adjudgement of various sulfidic phases in the sulfided catalysts. The

Studies of Heterogenous Palladium and Related Catalysts for Aerobic Oxidation of Primary Alcohols

Science.gov (United States)

Ahmed, Maaz S.

Development of aerobic oxidation methods is of critical importance for the advancement of green chemistry, where the only byproduct produced is water. Recent work by our lab has produced an efficient Pd based heterogenous catalyst capable of preforming the aerobic oxidation of a wide spectrum of alcohols to either carboxylic acid or methyl ester. The well-defined catalyst PdBi 0.35Te0.23/C (PBT/C) catalyst has been shown to can perform the aerobic oxidation of alcohols to carboxylic acids in basic conditions. Additionally, we explored this catalyst for a wide range of alcohols and probed the nature of the selectivity of PBT/C for methyl esterification over other side products. Finally, means by which the catalyst operates with respect to oxidation states of the three components, Pd, Bi, and Te, was probed. Carboxylic acids are an important functional group due to their prevalence in various pharmaceutically active agents, agrochemicals, and commodity scale chemicals. The well-defined catalyst PBT/C catalyst was discovered to be effective for the oxidation of a wide spectrum of alcohols to carboxylic acid. The demonstrated substrate scope and functional group tolerance are the widest reported for an aerobic heterogeneous catalyst. Additionally, the catalyst has been implemented in a packed bed reactor with quantitative yield of benzoic acid maintained throughout a two-day run. Biomass derived 5-(hydroxymethyl)furfural (HMF) is also oxidized to 2,5-furandicarboxylic acid (FDCA) in high yield. Exploration of PBT/C for the oxidative methyl esterification was found to exhibit exquisite selectivity for the initial oxidation of primary alcohol instead of methanol, which is the bulk solvent. We explored this selectivity and conclude that it results from various substrate-surface interactions, which are not attainable by methanol. The primary alcohol can outcompete the methanol for binding on the catalyst surface through various interactions between the side chain of the

Application of a mixed metal oxide catalyst to a metallic substrate

Science.gov (United States)

Sevener, Kathleen M. (Inventor); Lohner, Kevin A. (Inventor); Mays, Jeffrey A. (Inventor); Wisner, Daniel L. (Inventor)

2009-01-01

A method for applying a mixed metal oxide catalyst to a metallic substrate for the creation of a robust, high temperature catalyst system for use in decomposing propellants, particularly hydrogen peroxide propellants, for use in propulsion systems. The method begins by forming a prepared substrate material consisting of a metallic inner substrate and a bound layer of a noble metal intermediate. Alternatively, a bound ceramic coating, or frit, may be introduced between the metallic inner substrate and noble metal intermediate when the metallic substrate is oxidation resistant. A high-activity catalyst slurry is applied to the surface of the prepared substrate and dried to remove the organic solvent. The catalyst layer is then heat treated to bind the catalyst layer to the surface. The bound catalyst layer is then activated using an activation treatment and calcinations to form the high-activity catalyst system.

Heterogeneous Catalysts for VOC Oxidation from Red Mud and Bagasse Ash Carbon

Science.gov (United States)

Pande, Gaurav

A range of VOC oxidation catalysts have been prepared in this study from agricultural and industrial waste as the starting point. The aim is to prepare catalysts with non-noble metal oxides as the active catalytic component (iron in red mud). The same active component was also supported on activated carbon obtained from unburned carbon in bagasse ash. Red mud which is an aluminum industry waste and rich in different phases of iron as oxide and hydroxide is used as the source for the catalytically active species. It is our aim to enhance the catalytic performance of red mud which though high in iron concentration has a low surface area and may not have the properties of an ideal catalyst by itself. In one of the attempts to enhance the catalytic performance, we have tried to leach red mud for which we have explored a range of leaching acids for effecting the leaching most efficiently and then precipitated the iron from the leachate as its hydroxide by precipitating with alkali solution followed by drying and calcination to give high surface area metal oxide material. Extensive surface characterization and VOC oxidation catalytic testing were performed for these solids. In a step to further enhance the catalytic activity towards oxidation, copper was introduced by taking another industrial waste from the copper tubing industry viz. the pickling acid. Copper has a more favourable redox potential making it catalytically more effective than iron. To make the mixed metal oxide, red mud leachate was mixed with the pickling acid in a pre-decided ratio before precipitating with alkali solution followed by drying and calcination as was done with the red mud leachate. The results from these experiments are encouraging. The temperature programmed reduction (TPR) of the solids show that the precipitate of red mud leachates show hydrogen uptake peak at a lower temperature than for just the calcined red mud. This could be due to the greatly enhanced surface area of the prepared

Uranium oxide catalysts: environmental applications for treatment of chlorinated organic waste from nuclear industry.

Science.gov (United States)

Lazareva, Svetlana; Ismagilov, Zinfer; Kuznetsov, Vadim; Shikina, Nadezhda; Kerzhentsev, Mikhail

2018-02-05

Huge amounts of nuclear waste, including depleted uranium, significantly contribute to the adverse environmental situation throughout the world. An approach to the effective use of uranium oxides in catalysts for the deep oxidation of chlorine-containing hydrocarbons is suggested. Investigation of the catalytic activity of the synthesized supported uranium oxide catalysts doped with Cr, Mn and Co transition metals in the chlorobenzene oxidation showed that these catalysts are comparable with conventional commercial ones. Physicochemical properties of the catalysts were studied by X-ray diffraction, temperature-programmed reduction with hydrogen (H 2 -TPR), and Fourier transform infrared spectroscopy. The higher activity of Mn- and Co-containing uranium oxide catalysts in the H 2 -TPR and oxidation of chlorobenzene in comparison with non-uranium catalysts may be related to the formation of a new disperse phase represented by uranates. The study of chlorobenzene adsorption revealed that the surface oxygen is involved in the catalytic process.

Perovskite catalysts for oxidative coupling

Science.gov (United States)

Campbell, Kenneth D.

1991-01-01

Perovskites of the structure A.sub.2 B.sub.2 C.sub.3 O.sub.10 are useful as catalysts for the oxidative coupling of lower alkane to heavier hydrocarbons. A is alkali metal; B is lanthanide or lanthanum, cerium, neodymium, samarium, praseodymium, gadolinium or dysprosium; and C is titanium.

Bi-modified Pd/C catalyst via irreversible adsorption and its catalytic activity for ethanol oxidation in alkaline medium

International Nuclear Information System (INIS)

Cai, Jindi; Huang, Yiyin; Guo, Yonglang

2013-01-01

Highlights: • Pd-Bi/C catalysts were easily prepared by irreversible adsorption of Bi on Pd/C surface. • The adsorption of Bi increases the oxygen-containing species obviously on Pd-Bi/C surface. • Only a little amount of Bi on Pd-Bi/C can play a significant role in ethanol oxidation reaction (EOR). • Current density of EOR on Pd-Bi/C (20:1) is 2.4 times higher than that on Pd/C. • Anti-poisoning ability and durability of Pd-Bi/C (20:1) is greatly enhanced. -- Abstract: A facile approach to promote ethanol electro-oxidation on Pd-based catalysts is presented by the modification of Bi on Pd/C catalyst via irreversible adsorption. X-ray diffraction (XRD), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS) measurements show that the modification of Bi has no significant effect on the Pd morphology and particle size distribution. Bi(III) and Pd(0) are the dominant forms in Pd-Bi/C catalyst. Electrochemical tests show that the modification of the appropriate amount of Bi on Pd/C catalyst can remarkably enhance activity toward ethanol oxidation reaction (EOR) up to about 2.4 times higher compared to Pd/C catalyst. The Pd-Bi/C (20:1) catalyst exhibits excellent stability and enhances CO tolerance. The enhanced electrochemical performance of Pd-Bi/C catalyst is attributed to the electronic effect and the bifunctional mechanism. The high exchange current density and the low apparent activation energy on Pd-Bi/C (20:1) catalyst reveal its faster kinetics and higher intrinsic activity compared to Pd/C catalyst

Pd and S binding energies and Auger parameters on a model silica-supported Suzuki–Miyaura catalyst: Insights into catalyst activation

International Nuclear Information System (INIS)

Hanif, Mohammad A.; Ebralidze, Iraklii I.; Horton, J. Hugh

2013-01-01

Model Suzuki–Miyaura reaction catalysts have been developed by immobilizing palladium on a mercaptopropyltrimethoxysilane (MPTMS) functionalized Si substrate. Two types of Pd species were found on the fresh catalysts that may be attributed to a S-bound Pd (II) species and Pd nanoparticles. The binding energy of the nanoparticles is strongly size dependent, and is higher than that of metallic Pd. A sulfur species that has not been previously reported on this class of catalysts has also been observed. A systematic investigation of various palladium/sulfur complexes using XPS was carried out to identify this species, which may be assigned to high oxidation state sulfur formed by oxidation of thiol during the reduction of the Pd(OAc) 2 used to load the catalyst with Pd. Shifts in binding energy observed for both Pd and S spectra of the used catalysts were examined in order to probe the change of electronic environment of reactive palladium center and the thiol ligand during the reaction. Electron and atomic force microscopic imaging of the surfaces demonstrates the formation of Pd nanoparticles on fresh catalysts and subsequent size reduction of the Pd nano-particles following reaction.

Hydrogen-water deuterium exchange over metal oxide promoted nickel catalysts

Energy Technology Data Exchange (ETDEWEB)

Sagert, N H; Shaw-Wood, P E; Pouteau, R M.L. [Atomic Energy of Canada Ltd., Pinawa, Manitoba. Whiteshell Nuclear Research Establishment

1975-11-01

Specific rates have been measured for hydrogen-water deuterium isotope exchange over unsupported nickel promoted with about 20% of various metal oxides. The oxides used were Cr/sub 2/O/sub 3/, MoO/sub 2/, MnO, WO/sub 2/-WO/sub 3/, and UO/sub 2/. Nickel surface areas, which are required to measure the specific rates, were determined by hydrogen chemisorption. Specific rates were measured as a function of temperature in the range 353 to 573 K and as a function of the partial pressure of hydrogen and water over a 10-fold range of partial pressure. The molybdenum and tungsten oxides gave the highest specific rates, and manganese and uranium oxides the lowest. Chromium oxide was intermediate, although it gave the highest rate per gram of catalyst. The orders with respect to hydrogen and water over molybdenum oxide and tungsten oxide promoted nickel were consistent with a mechanism in which nickel oxide is formed from the reaction of water with the catalyst, and then is reduced by hydrogen. Over manganese and uranium oxide promoted catalysts, these orders are consistent with a mechanism in which adsorbed water exchanges with chemisorbed hydrogen atoms on the nickel surface. Chromium oxide is intermediate. It was noted that those oxides which favored the nickel oxide route had electronic work functions closest to those of metallic nickel and nickel oxide.

Propylene oxidation on catalytic Pt-Cu/y alumina. (Part II) chemical Kinetics of catalysts of Pt-Cu/y-alumina in the propylene oxidation

International Nuclear Information System (INIS)

Carballo, Luis M; Zea, Hugo R

1999-01-01

In this work is treated the effect of the composition of catalysts of Pt-Cu/y - alumina on the specific superficial activity corresponding to the total oxidation of propylene. Although the catalyst activity of the Cu in the operation conditions went practically null the specific activity of the catalytic Pt-Cu it incremented with the increase of the contained proportion of Cu in the catalyst. The total global speed by gram of catalyst was also increased with the introduction of Cu, but only to medium and high concentrations of propylene. The specific superficial activity was bigger for the sinterizated catalyst, for a given composition of the bimetallic catalyst, compared with that of the fresh catalyst (non-sinterizated). To explain, the catalytic behavior of the propylene oxidation, on the catalysts here studied, it is postulated that the propylene molecule it absorb with less force on the faces than in the corners or borders of the crystals of the catalyst and that the connection of adsorption on a place of given Pt is affected by the atoms of neighboring Cu on the surface causing changes in the mobility of the absorbed species. The kinetic results reveal a complex dependence between the reaction speed and the concentration of the propylene. In low concentrations of propylene the reaction speed was increased until to reach a maximum, and then to continue with a marked decreasing; and to concentrations. In bigger propylene concentrations, the reaction kinetics is presented as zero order with regard to the propylene, for some given concentrations of oxygen

Low temperature incineration of mixed wastes using bulk metal oxide catalysts

International Nuclear Information System (INIS)

Gordon, M.J.; Gaur, S.; Kelkar, S.; Baldwin, R.M.

1996-01-01

Volume reduction of low-level mixed wastes from former nuclear weapons facilities is a significant environmental problem. Processing of these materials presents unique scientific and engineering problems due to the presence of minute quantities of radionuclides which must be contained and concentrated for later safe disposal. Low-temperature catalytic incineration is one option that has been utilized at the Rocky Flats facility for this purpose. This paper presents results of research regarding evaluation of bulk metal oxides as catalysts for low-temperature incineration of carbonaceous residues which are typical by-products of fluidized bed combustion of mixed wastes under oxygen-lean conditions. A series of 14 metal oxides were screened in a thermogravimetric analyzer, using on-line mass spectrometry for speciation of reaction product gases. Catalyst evaluation criteria focused on the thermal-redox activity of the metals using both carbon black and PVC char as surrogate waste materials. Results indicated that metal oxides which were P-type semiconductor materials were suitable as catalysts for this application. Oxides of cobalt, molybdenum, vanadium, and manganese were found to be particularly stable and active catalysts under conditions specific to this process (T<650C, low oxygen partial pressures). Bench-scale evaluation of these metal oxides with respect to stability to chlorine (HCl) attack was carried out at 550C using a TG/MS system. Cobalt oxide was found to be resistant to metal loss in a HCl/He gaseous environment while metal loss from Mo, Mn, and V-based catalysts was moderate to severe. XRD and SEM/EDX analysis of spent Co catalysts indicated the formation of non-stoichiometric cobalt chlorides. Regeneration of chlorinated cobalt was found to successfully restore the low-temperature combustion activity to that of the fresh metal oxide

Metal oxides modified NiO catalysts for oxidative dehydrogenation of ethane to ethylene

KAUST Repository

Zhu, Haibo

2014-06-01

The sol-gel method was applied to the synthesis of Zr, Ti, Mo, W, and V modified NiO based catalysts for the ethane oxidative dehydrogenation reaction. The synthesized catalysts were characterized by XRD, N2 adsorption, SEM and TPR techniques. The results showed that the doping metals could be highly dispersed into NiO domains without the formation of large amount of other bulk metal oxide. The modified NiO materials have small particle size, larger surface area, and higher reduction temperature in contrast to pure NiO. The introduction of group IV, V and VI transition metals into NiO decreases the catalytic activity in ethane ODH. However, the ethylene selectivity is enhanced with the highest level for the Ni-W-O and Ni-Ti-O catalysts. As a result, these two catalysts show improved efficiency of ethylene production in the ethane ODH reaction. © 2014 Elsevier B.V. All rights reserved.

Influence of phosphorous addition on Bi3Mo2Fe1 oxide catalysts for the oxidative dehydrogenation of 1-butene

KAUST Repository

Park, Jung-Hyun

2016-01-22

Bi3Mo2Fe1Px oxide catalysts were prepared by a co-precipitation method and the influence of phosphorous content on the catalytic performance in the oxidative dehydrogenation of 1-butene was investigated. The addition of phosphorous up to 0.4mole ratio to Bi3Mo2Fe1 oxide catalyst led to an increase in the catalytic performance; however, a higher phosphorous content (above P=0.4) led to a decrease of conversion. Of the tested catalysts, Bi3Mo2Fe1P0.4 oxide catalyst exhibited the highest catalytic performance. Characterization results showed that the catalytic performance was related to the quantity of a π-allylic intermediate, facile desorption behavior of adsorbed intermediates and ability for re-oxidation of catalysts. © 2015 Korean Institute of Chemical Engineers, Seoul, Korea

Influence of phosphorous addition on Bi3Mo2Fe1 oxide catalysts for the oxidative dehydrogenation of 1-butene

KAUST Repository

Park, Jung-Hyun; Shin, Chae-Ho

2016-01-01

Bi3Mo2Fe1Px oxide catalysts were prepared by a co-precipitation method and the influence of phosphorous content on the catalytic performance in the oxidative dehydrogenation of 1-butene was investigated. The addition of phosphorous up to 0.4mole ratio to Bi3Mo2Fe1 oxide catalyst led to an increase in the catalytic performance; however, a higher phosphorous content (above P=0.4) led to a decrease of conversion. Of the tested catalysts, Bi3Mo2Fe1P0.4 oxide catalyst exhibited the highest catalytic performance. Characterization results showed that the catalytic performance was related to the quantity of a π-allylic intermediate, facile desorption behavior of adsorbed intermediates and ability for re-oxidation of catalysts. © 2015 Korean Institute of Chemical Engineers, Seoul, Korea

Catalytic Oxidation of Propene over Pd Catalysts Supported on CeO2, TiO2, Al2O3 and M/Al2O3 Oxides (M = Ce, Ti, Fe, Mn

Directory of Open Access Journals (Sweden)

Sonia Gil

2015-04-01

Full Text Available In the following work, the catalytic behavior of Pd catalysts prepared using different oxides as support (Al2O3, CeO2 and TiO2 in the catalytic combustion of propene, in low concentration in excess of oxygen, to mimic the conditions of catalytic decomposition of a volatile organic compound of hydrocarbon-type is reported. In addition, the influence of different promoters (Ce, Ti, Fe and Mn when added to a Pd/Al2O3 catalyst was analyzed. Catalysts were prepared by the impregnation method and were characterized by ICP-OES, N2 adsorption, temperature-programmed reduction, temperature-programmed oxidation, X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. Catalyst prepared using CeO2 as the support was less easily reducible, due to the stabilization effect of CeO2 over the palladium oxides. Small PdO particles and, therefore, high Pd dispersion were observed for all of the catalysts, as confirmed by XRD and TEM. The addition of Ce to the Pd/Al2O3 catalysts increased the metal-support interaction and the formation of highly-dispersed Pd species. The addition of Ce and Fe improved the catalytic behavior of the Pd/Al2O3 catalyst; however, the addition of Mn and Ti decreased the catalytic activity in the propene oxidation. Pd/TiO2 showed the highest catalytic activity, probably due to the high capacity of this catalyst to reoxidize Pd into PdO, as has been found in the temperature-programmed oxidation (TPO experiments.

Bio-inspired Iron Catalysts for Hydrocarbon Oxidations

Energy Technology Data Exchange (ETDEWEB)

Que, Jr., Lawrence [Univ. of Minnesota, Minneapolis, MN (United States)

2016-03-22

Stereoselective oxidation of C–H and C=C bonds are catalyzed by nonheme iron enzymes. Inspired by these bioinorganic systems, our group has been exploring the use of nonheme iron complexes as catalysts for the oxidation of hydrocarbons using H2O2 as an environmentally friendly and atom-efficient oxidant in order to gain mechanistic insights into these novel transformations. In particular, we have focused on clarifying the nature of the high-valent iron oxidants likely to be involved in these transformations.

Preparation of iron molybdate catalysts for methanol to formaldehyde oxidation based on ammonium molybdoferrate(II precursor

Directory of Open Access Journals (Sweden)

N.V. Nikolenko

2018-03-01

Full Text Available It was demonstrated that iron molybdate catalysts for methanol oxidation can be prepared using Fe(II as a precursor instead of Fe(III. This would allow for reduction of acidity of preparation solutions as well as elimination of Fe(III oxide impurities which are detrimental for the process selectivity. The system containing Fe(II and Mo(VI species in aqueous solution was investigated using UV–Vis spectroscopy. It was demonstrated that three types of chemical reactions occur in the Fe(II–Mo(VI system: (i formation of complexes between Fe(II and molybdate(VI ions, (ii inner sphere oxidation of coordinated Fe(II by Mo(VI and (iii decomposition of the Fe–Mo complexes to form scarcely soluble Fe(III molybdate, Mo(VI hydrous trioxide and molybdenum blue. Solid molybdoferrate(II prepared by interaction of Fe(II and Mo(VI in solution was characterized by EDXA, TGA, DTA and XRD and a scheme of its thermal evolution proposed. The iron molybdate catalyst prepared from Fe(II precursor was tested in methanol-to-formaldehyde oxidation in a continuous flow fixed-bed reactor to show similar activity and selectivity to the conventional catalyst prepared with the use of Fe(III.

Cobalt doped CuMnOx catalysts for the preferential oxidation of carbon monoxide

Science.gov (United States)

Dey, Subhashish; Dhal, Ganesh Chandra; Mohan, Devendra; Prasad, Ram; Gupta, Rajeev Nayan

2018-05-01

Carbon monoxide (CO) is a poisonous gas, recognized as a silent killer for the 21st century. It is produced from the partial oxidation of carbon containing compounds. The catalytic oxidation of CO receives a huge attention due to its applications in different fields. In the present work, hopcalite (CuMnOx) catalysts were synthesized using a co-precipitation method for CO oxidation purposes. Also, it was doped with the cobalt by varying concentration from 1 to 5wt%. It was observed that the addition of cobalt into the CuMnOx catalyst (by the deposition-precipitation method) improved the catalytic performance for the low-temperature CO oxidation. CuMnOx catalyst doped with 3wt% of cobalt exhibited most active performance and showed the highest activity than other cobalt concentrations. Different analytical tools (i.e. XRD, FTIR, BET, XPS and SEM-EDX) were used to characterize the as-synthesized catalysts. It was expected that the introduction of cobalt will introduce new active sites into the CuMnOx catalyst that are associated with the cobalt nano-particles. The order of calcination strategies based on the activity for cobalt doped CuMnOx catalysts was observed as: Reactive calcinations (RC) > flowing air > stagnant air. Therefore, RC (4.5% CO in air) route can be recommended for the synthesis of highly active catalysts. The catalytic activity of doped CuMnOx catalysts toward CO oxidation shows a correlation among average oxidation number of Mn and the position and the nature of the doped cobalt cation.

An oxidation-resistant indium tin oxide catalyst support for proton exchange membrane fuel cells

Energy Technology Data Exchange (ETDEWEB)

Chhina, H.; Campbell, S. [Ballard Power Systems Inc., 9000 Glenlyon Parkway, Burnaby, BC V5J 5J8 (Canada); Kesler, O. [Department of Mechanical Engineering, University of British Columbia, Vancouver, BC, V6T 1Z4 (Canada)

2006-10-27

The oxidation of carbon catalyst supports causes degradation in catalyst performance in proton exchange membrane fuel cells (PEMFCs). Indium tin oxide (ITO) is considered as a candidate for an alternative catalyst support. The electrochemical stability of ITO was studied by use of a rotating disk electrode (RDE). Oxidation cycles between +0.6 and +1.8V were applied to ITO supporting a Pt catalyst. Cyclic voltammograms (CVs) both before and after the oxidation cycles were obtained for Pt on ITO, Hispec 4000 (a commercially available catalyst), and 40wt.% Pt dispersed in-house on Vulcan XC-72R. Pt on ITO showed significantly better electrochemical stability, as determined by the relative change in electrochemically active surface area after cycling. Hydrogen desorption peaks in the CVs existed even after 100 cycles from 0.6 to 1.8V for Pt on ITO. On the other hand, most of the active surface area was lost after 100 cycles of the Hispec 4000 catalyst. The 40wt.% Pt on Vulcan made in-house also lost most of its active area after only 50 cycles. Pt on ITO was significantly more electrochemically stable than both Hispec 4000 and Pt on Vulcan XC-72R. In this study, it was found that the Pt on ITO had average crystallite sizes of 13nm for Pt and 38nm for ITO. Pt on ITO showed extremely high thermal stability, with only {approx}1wt.% loss of material for ITO versus {approx}57wt.% for Hispec 4000 on heating to 1000{sup o}C. The TEM data show Pt clusters dispersed on small crystalline ITO particles. The SEM data show octahedral shaped ITO particles supporting Pt. (author)

Surface chemistry and catalytic properties of VO{sub X}/Ti-MCM-41 catalysts for dibenzothiophene oxidation in a biphasic system

Energy Technology Data Exchange (ETDEWEB)

González, J. [ESIQIE, Instituto Politécnico Nacional, Av. Instituto Politécnico Nacional s/n, 07738 Col. Zacatenco, Mexico City (Mexico); Chen, L.F., E-mail: lchen@ipn.mx [ESIQIE, Instituto Politécnico Nacional, Av. Instituto Politécnico Nacional s/n, 07738 Col. Zacatenco, Mexico City (Mexico); Wang, J.A.; Manríquez, Ma.; Limas, R. [ESIQIE, Instituto Politécnico Nacional, Av. Instituto Politécnico Nacional s/n, 07738 Col. Zacatenco, Mexico City (Mexico); Schachat, P.; Navarrete, J. [Dirección de Investigación, Instituto Mexicano del Petróleo, Eje Lázaro Cárdenas 152, 07730 México D.F. (Mexico); Contreras, J.L. [Laboratorio de Catálisis y Polímeros, División de Ciencias Básicas e Ingeniería, Universidad Autónoma Metropolitana-A, Av. San Pablo No. 180, 02200 México D.F. (Mexico)

2016-08-30

Highlights: • Oxidative desulfurization of model diesel was tested in a biphasic system. • ODS activity was proportional to the V{sup 5+}/(V{sup 4+} + V{sup 5+}) values of the catalysts. • Lewis acidity was related to vanadium content and catalytic activity. • 99.9% DBT was oxidized using 25%V{sub 2}O{sub 5}/Ti-MCM-41 at 60 °C within 60 min. - Abstract: A series of vanadium oxide supported on Ti-MCM-41 catalysts was synthesized via the incipient impregnation method by varying the vanadia loading from 5 wt% to 10, 15, 20 and 25 wt%. These catalysts were characterized by a variety of advanced techniques for investigating their crystalline structure, textural properties, and surface chemistry information including surface acidity, reducibility, vanadium oxidation states, and morphological features. The catalytic activities of the catalysts were evaluated in a biphasic reaction system for oxidative desulfurization (ODS) of a model diesel containing 300 ppm of dibenzothiophene (DBT) where acetonitrile was used as extraction solvent and H{sub 2}O{sub 2} as oxidant. ODS activity was found to be proportional to the V{sup 5+}/(V{sup 4+} + V{sup 5+}) values of the catalysts, indicating that the surface vanadium pentoxide (V{sub 2}O{sub 5}) was the active phase. Reaction temperature would influence significantly the ODS efficiency; high temperature, i.e., 80 °C, would lead to low ODS reaction due to the partial decomposition of oxidant. All the catalysts contained both Lewis and Brønsted acid sites but the former was predominant. The catalysts with low vanadia loading (5 or 10 wt%V{sub 2}O{sub 5}) had many Lewis acid sites and could strongly adsorb DBT molecule via the electron donation/acceptance action which resulted in an inhibition for the reaction of DBT with the surface peroxometallic species. The catalyst with high vanadia loading (25wt%V{sub 2}O{sub 5}/Ti-MCM-41) showed the highest catalytic activity and could remove 99.9% of DBT at 60 °C within 60 min.

Partial oxidation of methane to syngas on Rh/Al{sub 2}O{sub 3} and Rh/Ce-ZrO{sub 2} catalysts

Energy Technology Data Exchange (ETDEWEB)

Oliveira, Raquel L.; Bitencourt, Isabela G.; Passos, Fabio B., E-mail: fbpassos@vm.uff.br [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Dept. de Engenharia Quimica e Petroleo

2013-01-15

The partial oxidation of methane with {gamma}-Al{sub 2}O{sub 3}-, CeO{sub 2}-, ZrO{sub 2}- and Ce-ZrO{sub 2}-supported rhodium catalysts was investigated. DRIFTS (diffuse reflectance infrared spectroscopy) measurements of adsorbed CO showed the formation of different rhodium species on different supports, which influenced the dispersion of the metal. The effects of the metal dispersion, oxygen storage capacity on the activity of these catalysts for the partial oxidation of methane are discussed. (author)

Highly-dispersed Ta-oxide catalysts prepared by electrodeposition in a non-aqueous plating bath for polymer electrolyte fuel cell cathodes

KAUST Repository

Seo, Jeongsuk; Cha, Dong Kyu; Takanabe, Kazuhiro; Kubota, Jun; Domen, Kazunari

2012-01-01

The Ta-oxide cathode catalysts were prepared by electrodeposition in a non-aqueous solution. These catalysts showed excellent catalytic activity and have an onset potential of 0.92 V RHE for the oxygen reduction reaction (ORR). The highly-dispersed Ta species at the nanometer scale on the carbon black was an important contributor to the high activity. © 2012 The Royal Society of Chemistry.

Electron microscopic studies of natural gas oxidation catalyst – Effects of thermally accelerated aging on catalyst microstructure

DEFF Research Database (Denmark)

Honkanen, Mari; Hansen, Thomas Willum; Jiang, Hua

2017-01-01

Structural changes of PtPd nanoparticles in a natural gas oxidation catalyst were studied at elevated temperatures in air and low-oxygen conditions and in situ using environmental transmission electron microscopy (ETEM). The fresh catalyst shows

Carbon monoxide oxidation over three different states of copper: Development of a model metal oxide catalyst

Energy Technology Data Exchange (ETDEWEB)

Jernigan, Glenn Geoffrey [California Univ., Berkeley, CA (United States). Dept. of Chemistry

1994-10-01

Carbon monoxide oxidation was performed over the three different oxidation states of copper -- metallic (Cu), copper (I) oxide (Cu₂O), and copper (II) oxide (CuO) as a test case for developing a model metal oxide catalyst amenable to study by the methods of modern surface science and catalysis. Copper was deposited and oxidized on oxidized supports of aluminum, silicon, molybdenum, tantalum, stainless steel, and iron as well as on graphite. The catalytic activity was found to decrease with increasing oxidation state (Cu > Cu₂O > CuO) and the activation energy increased with increasing oxidation state (Cu, 9 kcal/mol < Cu₂O, 14 kcal/mol < CuO, 17 kcal/mol). Reaction mechanisms were determined for the different oxidation states. Lastly, NO reduction by CO was studied. A Cu and CuO catalyst were exposed to an equal mixture of CO and NO at 300--350 C to observe the production of N₂ and CO₂. At the end of each reaction, the catalyst was found to be Cu₂O. There is a need to study the kinetics of this reaction over the different oxidation states of copper.

Methanol Oxidation Using Ozone on Titania-Supported Vanadium Catalyst

Science.gov (United States)

Ozone-enhanced catalytic oxidation of methanol has been conducted at mild temperatures of 100 to 250NC using V2O5/TiO2 catalyst prepared by the sol-gel method. The catalyst was characterized using XRD, surface area measurements, and temperature-programmed desorption of methanol. ...

Catalytic Oxidation of Phenol over Zeolite Based Cu/Y-5 Catalyst: Part 1: Catalyst Preparation and Characterization

Directory of Open Access Journals (Sweden)

K. Maduna Valkaj

2015-01-01

Full Text Available The necessity to remove organic pollutants from the industrial wastewater streams has forced the development of new technologies that can produce better results in terms of pollutant removal and process efficiency in combination with low investment and operating costs. One of the new emerging processes with a potential to fulfil these demands is catalytic wet peroxide oxidation, commonly known as the CWPO process. The oxidative effect of the hydrogen peroxide is intensified by the addition of a heterogeneous catalyst that can reduce the operating conditions to atmospheric pressure and temperatures below 383 K. Zeolites, among others, are especially appealing as catalysts for selective oxidation processes due to their unique characteristics such as shape selectivity, thermal and chemical stability, and benign effect on nature and the living world. In this work, catalytic activity, selectivity and stability of Cu/Y-5 zeolite in phenol oxidation with hydrogen peroxide was examined. Catalyst samples were prepared by ion exchange method of the protonic form of commercial zeolite. The catalysts were characterized with powder X-ray diffraction (XRD, scanning electron microscopy (SEM, and AAS elemental analysis, while the adsorption techniques were used for the measurement of the specific surface area. The catalytic tests were carried out in a stainless steel Parr reactor in batch operation mode at the atmospheric pressure and in the temperature range from 323 to 353 K. The catalyst was prepared in powdered form and the mass fraction of the active metal component on the zeolite was 3.46 %. The initial concentration of phenol solution was equal to 0.01 mol dm−3 and the concentration of hydrogen peroxide ranged from 0.01 to 0.10 mol dm−3. The obtained experimental data was tested to a proposed kinetic model for phenol oxidation r = k1 cF cVP and hydrogen peroxide decomposition rHP = k2 cHP. The kinetic parameters were estimated using the Nelder

Selectivity and Activity of Iron Molybdate Catalysts in Oxidation of Methanol

OpenAIRE

Khalid Khazzal Hummadi; Karim H. Hassan; Phillip C.H. Mitchell

2009-01-01

The selectivity and activity of iron molybdate catalysts prepared by different methods are compared with those of a commercial catalyst in the oxidation of methanol to formaldehyde in a continuous tubular bed reactor at 200-350 oC (473-623 oK), 10 atm (1013 kPa), with a methanol-oxygen mixture fixed at 5.5% by volume methanol: air ratio. The iron(III) molybdate catalyst prepared by co-precipitation and filtration had a selectivity towards formaldehyde in methanol oxidation comparable with a c...

Atomic Scale Structure-Chemistry Relationships at Oxide Catalyst Surfaces and Interfaces

Science.gov (United States)

McBriarty, Martin E.

Oxide catalysts are integral to chemical production, fuel refining, and the removal of environmental pollutants. However, the atomic-scale phenomena which lead to the useful reactive properties of catalyst materials are not sufficiently understood. In this work, the tools of surface and interface science and electronic structure theory are applied to investigate the structure and chemical properties of catalytically active particles and ultrathin films supported on oxide single crystals. These studies focus on structure-property relationships in vanadium oxide, tungsten oxide, and mixed V-W oxides on the surfaces of alpha-Al2O3 and alpha-Fe2O 3 (0001)-oriented single crystal substrates, two materials with nearly identical crystal structures but drastically different chemical properties. In situ synchrotron X-ray standing wave (XSW) measurements are sensitive to changes in the atomic-scale geometry of single crystal model catalyst surfaces through chemical reaction cycles, while X-ray photoelectron spectroscopy (XPS) reveals corresponding chemical changes. Experimental results agree with theoretical calculations of surface structures, allowing for detailed electronic structure investigations and predictions of surface chemical phenomena. The surface configurations and oxidation states of V and W are found to depend on the coverage of each, and reversible structural shifts accompany chemical state changes through reduction-oxidation cycles. Substrate-dependent effects suggest how the choice of oxide support material may affect catalytic behavior. Additionally, the structure and chemistry of W deposited on alpha-Fe 2O3 nanopowders is studied using X-ray absorption fine structure (XAFS) measurements in an attempt to bridge single crystal surface studies with real catalysts. These investigations of catalytically active material surfaces can inform the rational design of new catalysts for more efficient and sustainable chemistry.

The oxidative coupling of methane and the oxidative dehydrogenation of ethane over a niobium promoted lithium doped magnesium oxide catalyst

NARCIS (Netherlands)

Swaan, H.M.; Swaan, H.M.; Li, X.; Seshan, Kulathuiyer; van Ommen, J.G.; Ross, J.R.H.; Ross, J.R.H.

1993-01-01

The promoting effect of niobium in a Li/MgO catalyst for the oxidative coupling of methane (OCM) and for the oxidative dehydrogenation of ethane (ODHE) has been studied in some detail. It has been found that a Li/Nb/MgO catalyst with 16 wt % niobium showed the highest activity for the C2 production

The Application of Moessbauer Emission Spectroscopy to Industrial Cobalt Based Fischer-Tropsch Catalysts

International Nuclear Information System (INIS)

Loosdrecht, J. van de; Berge, P. J. van; Craje, M. W. J.; Kraan, A. M. van der

2002-01-01

The application of Moessbauer emission spectroscopy to study cobalt based Fischer-Tropsch catalysts for the gas-to-liquids process was investigated. It was shown that Moessbauer emission spectroscopy could be used to study the oxidation of cobalt as a deactivation mechanism of high loading cobalt based Fischer-Tropsch catalysts. Oxidation was observed under conditions that are in contradiction with the bulk cobalt phase thermodynamics. This can be explained by oxidation of small cobalt crystallites or by surface oxidation. The formation of re-reducible Co 3+ species was observed as well as the formation of irreducible Co 3+ and Co 2+ species that interact strongly with the alumina support. The formation of the different cobalt species depends on the oxidation conditions. Iron was used as a probe nuclide to investigate the cobalt catalyst preparation procedure. A high-pressure Moessbauer emission spectroscopy cell was designed and constructed, which creates the opportunity to study cobalt based Fischer-Tropsch catalysts under realistic synthesis conditions.

Effect of thermal treatment conditions on properties of vanadium molybdenum oxide catalyst in acrolein oxidation reaction to acrylic acid

International Nuclear Information System (INIS)

Gorshkova, T.P.; Tarasova, D.V.; Olen'kova, I.P.; Andrushkevich, T.V.; Nikoro, T.A.

1984-01-01

The effect of thermal treatment conditions (temperature and gas medium) on properties of vanadium molybdenum oxide catalyst in acrolein oxidation reaction to acrylic acid is investigated. It is shown that active and selective catalysts are formed in the course of thermal decomposition of the drying product of ammonium metavanadate and paramolybdate under the conditions ensuring the vanadium ion reduction up to tetravalent state with conservation of molybdenum oxidation degree equal to 6. It is possible to realize it either by treatment of the catalyst calcinated in the air flow at 300 deg by the reaction mixture at the activation stage or by gas-reducer flow treatment at 280 deg. Thermal treatment in the reducing medium of the oxidized catalyst does not lead to complete regeneration of its properties

Catalytic dehydration of ethanol using transition metal oxide catalysts.

Science.gov (United States)

Zaki, T

2005-04-15

The aim of this work is to study catalytic ethanol dehydration using different prepared catalysts, which include Fe(2)O(3), Mn(2)O(3), and calcined physical mixtures of both ferric and manganese oxides with alumina and/or silica gel. The physicochemical properties of these catalysts were investigated via X-ray powder diffraction (XRD), acidity measurement, and nitrogen adsorption-desorption at -196 degrees C. The catalytic activities of such catalysts were tested through conversion of ethanol at 200-500 degrees C using a catalytic flow system operated under atmospheric pressure. The results obtained indicated that the dehydration reaction on the catalyst relies on surface acidity, whereas the ethylene production selectivity depends on the catalyst chemical constituents.

Comparison of direct and indirect plasma oxidation of NO combined with oxidation by catalyst

DEFF Research Database (Denmark)

Jogi, Indrek; Stamate, Eugen; Irimiea, Cornelia

2015-01-01

of the DBD reactor decreased the long-term efficiency of direct plasma oxidation. At the same time, the efficiency of indirect oxidation increased at elevated reactor temperatures. Additional experiments were carried out to investigate the improvement of indirect oxidation by the introduction of catalyst...

Selectivity in the oxidative dehydrogenation of butene on zinc-iron oxide catalyst

Energy Technology Data Exchange (ETDEWEB)

Kung, H.H.; Kundalkar, B.; Kung, M.C.; Cheng, W.H.

1980-02-21

Adsorption, temperature-programed desorption, and pulse reaction studies of cis-2-butene and butadiene on spinel zinc ferrite by previously described methods provided evidence that the selectivity for oxidative dehydrogenation of butenes increases when zinc is added to the iron oxide catalyst because selective oxidation and complete oxidation proceed on separate sites, as they do on pure iron; because the density of sites for selective oxidation is higher and the density of sites for complete combustion is lower than on pure iron oxide; and because the activity of the combustion sites is lower.

Synthesis of highly efficient Mn2O3 catalysts for CO oxidation derived from Mn-MIL-100

Science.gov (United States)

Zhang, Xiaodong; Li, Hongxin; Hou, Fulin; Yang, Yang; Dong, Han; Liu, Ning; Wang, Yuxin; Cui, Lifeng

2017-07-01

In this work, metal-organic frameworks (MOFs) Mn-MIL-100 were first prepared, which were next used as templates to obtain the irregular porous Mn2O3 cubes through calcination with air at different temperature. The catalysts were characterized by N2 adsorption-desorption, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), H2-temperature program reduction (H2-TPR) and X-ray photoelectron spectroscopic (XPS). The catalytic activity for CO oxidation over Mn2O3 catalysts was investigated. It was found that calcination temperature had a strong effect on the structure and catalytic activity of Mn2O3 catalyst. Mn2O3 catalyst obtained by calcined at 700 °C (Mn2O3-700) showed a smaller specific surface area, but displayed a high catalytic activity and excellent stability with a complete CO conversion temperature (T98) of 240 °C, which was attributed to the unique structure, a high quantity of surface active oxygen species, smaller particle size, oxygen vacancies and good low temperature reduction behavior. The effect of water vapor on catalytic activity was also examined. The introduction of water vapor to the feedstock induced a positive effect on CO oxidation over Mn2O3-700 catalyst. Furthermore, no obvious drop is observed in activity over catalysts even in the presence of water vapor during 48 h.

Oxidation of tritium in packed bed of noble metal catalyst for detritiation from system gases

International Nuclear Information System (INIS)

Nishikawa, Masabumi; Takeishi, Toshiharu; Munakata, Kenzo; Kotoh, Kenji; Enoeda, Mikio

1985-01-01

Catalytic oxidation rates of tritium in the bed of the noble metal catalysts are obtained and compared with the oxidation rates observed for the packed bed of spongy copper oxide or hopcalites. Use of Pt- or Pd-aluminia catalysts is recommended in this study because they give effective oxidation rates of tritium in the ambient temperature range. The adsorption performance of tritiated water in the catalyst bed is also discussed. (orig.)

Dehydrogenation of propane in the presence of carbon dioxide over chromium and gallium oxides catalysts

Energy Technology Data Exchange (ETDEWEB)

Lapidus, A.L.; Agafonov, Yu.A.; Gaidai, N.A.; Nekrasov, N.V.; Menshova, M.V.; Kunusova, R.M. [Russian Academy of Sciences, Moscow (Russian Federation). N.D. Zelinsky Inst. of Organic Chemistry

2011-07-01

Effective chromium and gallium oxides supported catalysts were prepared and tested in longduration experiments for propane dehydrogenation in the presence of CO{sub 2}. The optimal concentrations of active metals were found. It was shown that the activity, selectivity and stability of chromium oxides catalysts were higher than these parameters for gallium ones. Mechanism of propane oxidative dehydrogenation was studied over both catalysts using unstationary and spectroscopic methods. The employment of these methods allowed to establish the differences in process mechanism. It was shown that surface hydroxides took participation in propene formation over Cr-catalysts and hydrides - over Ga-ones. Propane and carbon dioxide participated in the reaction from the adsorbed state over both catalysts but they were differed by the adsorption capacity of the reaction components: CO2 was tied more firmly than C{sub 3}H{sub 6} over both catalysts, CO{sub 2} and C{sub 3}H{sub 6} were tied more strongly with Cr-catalysts than with Ga-ones. It was shown that CO{sub 2} took active participation in reverse watergas shift reaction and in oxidation of catalyst surface over chromium oxides catalysts. The main role of CO{sub 2} in propane dehydrogenation over gallium catalysts consisted in a decrease of coke formation. Step-schemes of propene and cracking products formation were proposed on the basis of literature and obtained data: via the redox mechanism over Cr-catalysts and through a heterolytic dissociation reaction pathway over Ga-ones. (orig.)

Iron-tellurium-selenium mixed oxide catalysts for the selective oxidation of propylene to acrolein

International Nuclear Information System (INIS)

Patel, B.M.; Price, G.L.

1990-01-01

This paper reports on iron-tellurium-selenium mixed oxide catalysts prepared by coprecipitation from aqueous solution investigated for the propylene to acrolein reaction in the temperature range 543-773 K. Infrared spectroscopy, electron dispersive X-ray analysis, X-ray diffraction, and isotopic tracer techniques have also been employed to characterize this catalytic system. Properties of the Fe-Te-Se mixed oxide catalysts have been compared with Fe-Te mixed oxides in an effort to deduce the functionality of Se. The selenium in the Fe-Te-Se-O catalyst has been found to be the hydrocarbon activating site. The activation energies for the acrolein and carbon dioxide formation are 71 and 54 kJ/mol, respectively. Reactions carried out with 18 O 2 have shown lattice oxygen to be primarily responsible for the formation of both acrolein and carbon dioxide. The initial and rate-determining step for acrolein formation is hydrogen abstraction as determined by an isotope effect associated with the C 3 D 6 reaction. No isotope effect is observed for carbon dioxide formation from C 3 D 6 suggesting that CO 2 is formed by parallel, not consecutive, oxidation of propylene

Calcium oxide supported gold nanoparticles as catalysts for the selective epoxidation of styrene by t-butyl hydroperoxide.

Science.gov (United States)

Dumbre, Deepa K; Choudhary, Vasant R; Patil, Nilesh S; Uphade, Balu S; Bhargava, Suresh K

2014-02-01

Gold nanoparticles are deposited on basic CaO supports as catalysts for the selective conversion of styrene into styrene oxide. Synthetic methods, gold loading and calcination temperatures are varied to permit an understanding of their influence on gold nanoparticle size, the presence of cationic gold species and the nature of interaction between the gold nanoparticles and the CaO support. Based on these studies, optimal conditions are designed to make the Au/CaO catalyst efficient for the selective epoxidation of styrene. Copyright © 2013 Elsevier Inc. All rights reserved.

Oxidation of 1-butene over uranium oxide (UO3)-antimony oxide (Sb2O3) catalysts

NARCIS (Netherlands)

Simons, T.; Houtman, P.N.; Schuit, G.C.A.

1971-01-01

The oxidative dehydrogenation of butene to butadiene over U-Sb catalysts was investigated. The presence of two compds., (UO2)Sb3O7 and Sb3U3O14, reported by Grasselli and Callahan (1969), was confirmed with (UO2)Sb3O7 being the actual catalyst. The reaction is first order in butene and zero order in

Catalytic wet oxidation of ammonia solution: Activity of the nanoscale platinum-palladium-rhodium composite oxide catalyst

International Nuclear Information System (INIS)

Hung, C.-M.

2009-01-01

Aqueous solutions of 400-1000 mg/L of ammonia were oxidized in a trickle-bed reactor (TBR) in this study of nanoscale platinum-palladium-rhodium composite oxide catalysts, which were prepared by the co-precipitation of H 2 PtCl 6 , Pd(NO 3 ) 3 and Rh(NO 3 ) 3 . Hardly any of the dissolved ammonia was removed by wet oxidation in the absence of any catalyst, whereas about 99% of the ammonia was reduced during wet oxidation over nanoscale platinum-palladium-rhodium composite oxide catalysts at 503 K in an oxygen partial pressure of 2.0 MPa. A synergistic effect exists in the nanoscale platinum-palladium-rhodium composite structure, which is the material with the highest ammonia reduction activity. The nanometer-sized particles were characterized by TEM, XRD and FTIR. The effect of the initial concentration and reaction temperature on the removal of ammonia from the effluent streams was also studied at a liquid hourly space velocity of under 9 h -1 in the wet catalytic processes

Catalytic wet oxidation of ammonia solution: Activity of the nanoscale platinum-palladium-rhodium composite oxide catalyst

Energy Technology Data Exchange (ETDEWEB)

Hung, C.-M. [Department of Industry Engineering and Management, Yung-Ta Institute of Technology and Commerce, 316 Chung-shan Road, Linlo, Pingtung 909, Taiwan (China)], E-mail: hungcm1031@gmail.com

2009-04-15

Aqueous solutions of 400-1000 mg/L of ammonia were oxidized in a trickle-bed reactor (TBR) in this study of nanoscale platinum-palladium-rhodium composite oxide catalysts, which were prepared by the co-precipitation of H{sub 2}PtCl{sub 6}, Pd(NO{sub 3}){sub 3} and Rh(NO{sub 3}){sub 3}. Hardly any of the dissolved ammonia was removed by wet oxidation in the absence of any catalyst, whereas about 99% of the ammonia was reduced during wet oxidation over nanoscale platinum-palladium-rhodium composite oxide catalysts at 503 K in an oxygen partial pressure of 2.0 MPa. A synergistic effect exists in the nanoscale platinum-palladium-rhodium composite structure, which is the material with the highest ammonia reduction activity. The nanometer-sized particles were characterized by TEM, XRD and FTIR. The effect of the initial concentration and reaction temperature on the removal of ammonia from the effluent streams was also studied at a liquid hourly space velocity of under 9 h{sup -1} in the wet catalytic processes.

Catalytic wet oxidation of ammonia solution: activity of the nanoscale platinum-palladium-rhodium composite oxide catalyst.

Science.gov (United States)

Hung, Chang-Mao

2009-04-15

Aqueous solutions of 400-1000 mg/L of ammonia were oxidized in a trickle-bed reactor (TBR) in this study of nanoscale platinum-palladium-rhodium composite oxide catalysts, which were prepared by the co-precipitation of H(2)PtCl(6), Pd(NO(3))(3) and Rh(NO(3))(3). Hardly any of the dissolved ammonia was removed by wet oxidation in the absence of any catalyst, whereas about 99% of the ammonia was reduced during wet oxidation over nanoscale platinum-palladium-rhodium composite oxide catalysts at 503 K in an oxygen partial pressure of 2.0 MPa. A synergistic effect exists in the nanoscale platinum-palladium-rhodium composite structure, which is the material with the highest ammonia reduction activity. The nanometer-sized particles were characterized by TEM, XRD and FTIR. The effect of the initial concentration and reaction temperature on the removal of ammonia from the effluent streams was also studied at a liquid hourly space velocity of under 9 h(-1) in the wet catalytic processes.

Potassium/calcium/nickel oxide catalysts for the oxidative coupling of methane

NARCIS (Netherlands)

Dooley, K.; Dooley, Kerry M.; Ross, J.R.H.; Ross, Julian R.H.

1992-01-01

A series of potassium/calcium/nickel oxides were tested for the oxidative coupling of methane (OCM) at 843–943 K and water addition to the feed at 0–66 mol-%. The K/Ni ratios varied from 0.0–0.6 and Ca/Ni from 0.0–11; catalysts with no nickel were also tested. At least 10% water in the feed and

Catalytic Oxidation of NO over MnOx–CeO2 and MnOx–TiO2 Catalysts

Directory of Open Access Journals (Sweden)

Xiaolan Zeng

2016-11-01

Full Text Available A series of MnOx–CeO2 and MnOx–TiO2 catalysts were prepared by a homogeneous precipitation method and their catalytic activities for the NO oxidation in the absence or presence of SO2 were evaluated. Results show that the optimal molar ratio of Mn/Ce and Mn/Ti are 0.7 and 0.5, respectively. The MnOx–CeO2 catalyst exhibits higher catalytic activity and better resistance to SO2 poisoning than the MnOx–TiO2 catalyst. On the basis of Brunauer–Emmett–Teller (BET, X-ray diffraction (XRD, and scanning transmission electron microscope with mapping (STEM-mapping analyses, it is seen that the MnOx–CeO2 catalyst possesses higher BET surface area and better dispersion of MnOx over the catalyst than MnOx–TiO2 catalyst. X-ray photoelectron spectroscopy (XPS measurements reveal that MnOx–CeO2 catalyst provides the abundance of Mn3+ and more surface adsorbed oxygen, and SO2 might be preferentially adsorbed to the surface of CeO2 to form sulfate species, which provides a protection of MnOx active sites from being poisoned. In contrast, MnOx active sites over the MnOx–TiO2 catalyst are easily and quickly sulfated, leading to rapid deactivation of the catalyst for NO oxidation. Furthermore, temperature programmed desorption with NO and O2 (NO + O2-TPD and in situ diffuse reflectance infrared transform spectroscopy (in situ DRIFTS characterizations results show that the MnOx–CeO2 catalyst displays much stronger ability to adsorb NOx than the MnOx–TiO2 catalyst, especially after SO2 poisoning.

Ozone Decomposition on the Surface of Metal Oxide Catalyst

Directory of Open Access Journals (Sweden)

Batakliev Todor Todorov

2014-12-01

Full Text Available The catalytic decomposition of ozone to molecular oxygen over catalytic mixture containing manganese, copper and nickel oxides was investigated in the present work. The catalytic activity was evaluated on the basis of the decomposition coefficient which is proportional to ozone decomposition rate, and it has been already used in other studies for catalytic activity estimation. The reaction was studied in the presence of thermally modified catalytic samples operating at different temperatures and ozone flow rates. The catalyst changes were followed by kinetic methods, surface measurements, temperature programmed reduction and IR-spectroscopy. The phase composition of the metal oxide catalyst was determined by X-ray diffraction. The catalyst mixture has shown high activity in ozone decomposition at wet and dry O3/O2 gas mixtures. The mechanism of catalytic ozone degradation was suggested.

Process for Making a Noble Metal on Tin Oxide Catalyst

Science.gov (United States)

Davis, Patricia; Miller, Irvin; Upchurch, Billy

2010-01-01

To produce a noble metal-on-metal oxide catalyst on an inert, high-surface-area support material (that functions as a catalyst at approximately room temperature using chloride-free reagents), for use in a carbon dioxide laser, requires two steps: First, a commercially available, inert, high-surface-area support material (silica spheres) is coated with a thin layer of metal oxide, a monolayer equivalent. Very beneficial results have been obtained using nitric acid as an oxidizing agent because it leaves no residue. It is also helpful if the spheres are first deaerated by boiling in water to allow the entire surface to be coated. A metal, such as tin, is then dissolved in the oxidizing agent/support material mixture to yield, in the case of tin, metastannic acid. Although tin has proven especially beneficial for use in a closed-cycle CO2 laser, in general any metal with two valence states, such as most transition metals and antimony, may be used. The metastannic acid will be adsorbed onto the high-surface-area spheres, coating them. Any excess oxidizing agent is then evaporated, and the resulting metastannic acid-coated spheres are dried and calcined, whereby the metastannic acid becomes tin(IV) oxide. The second step is accomplished by preparing an aqueous mixture of the tin(IV) oxide-coated spheres, and a soluble, chloride-free salt of at least one catalyst metal. The catalyst metal may be selected from the group consisting of platinum, palladium, ruthenium, gold, and rhodium, or other platinum group metals. Extremely beneficial results have been obtained using chloride-free salts of platinum, palladium, or a combination thereof, such as tetraammineplatinum (II) hydroxide ([Pt(NH3)4] (OH)2), or tetraammine palladium nitrate ([Pd(NH3)4](NO3)2).

Calcium-based mixed oxide catalysts for methanolysis of Jatropha curcas oil to biodiesel

International Nuclear Information System (INIS)

Taufiq-Yap, Y.H.; Lee, H.V.; Hussein, M.Z.; Yunus, R.

2011-01-01

Calcium-based mixed oxides catalysts (CaMgO and CaZnO) have been investigated for the transesterification of Jatropha curcas oil (JCO) with methanol, in order to evaluate their potential as heterogeneous catalysts for biodiesel production. Both CaMgO and CaZnO catalysts were prepared by coprecipitation method of the corresponding mixed metal nitrate solution in the presence of a soluble carbonate salt at ∼ pH 8-9. The catalysts were characterized by X-ray diffraction (XRD), temperature programmed desorption of CO 2 (CO 2 -TPD), scanning electron microscopy (SEM) and N 2 adsorption (BET). The conversion of JCO by CaMgO and CaZnO were studied and compared with calcium oxide (CaO), magnesium oxide (MgO) and zinc oxide (ZnO) catalysts. Both CaMgO and CaZnO catalysts showed high activity as CaO and were easily separated from the product. CaMgO was found more active than CaZnO in the transesterification of JCO with methanol. Under the suitable transesterification conditions at 338 K (catalyst amount = 4 wt. %, methanol/oil molar ratio = 15, reaction time = 6 h), the JCO conversion of more than 80% can be achieved over CaMgO and CaZnO catalysts. Even though CaO gave the highest activity, the conversion of JCO decreased significantly after reused for forth run whereas the conversion was only slightly lowered for CaMgO and CaZnO after sixth run.

Bioinspired organocatalytic aerobic C-H oxidation of amines with an ortho-quinone catalyst.

Science.gov (United States)

Qin, Yan; Zhang, Long; Lv, Jian; Luo, Sanzhong; Cheng, Jin-Pei

2015-03-20

A simple bioinspired ortho-quinone catalyst for the aerobic oxidative dehydrogenation of amines to imines is reported. Without any metal cocatalysts, the identified optimal ortho-quinone catalyst enables the oxidations of α-branched primary amines and cyclic secondary amines. Mechanistic studies have disclosed the origins of different performances of ortho-quinone vs para-quinone in biomimetic amine oxidations.

Computationally Probing the Performance of Hybrid, Heterogeneous, and Homogeneous Iridium-Based Catalysts for Water Oxidation

Energy Technology Data Exchange (ETDEWEB)

García-Melchor, Max [SUNCAT Center for Interface Science and Catalysis, Department of Chemical Engineering, Stanford University, Stanford CA (United States); Vilella, Laia [Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology (BIST),Tarragona (Spain); Departament de Quimica, Universitat Autonoma de Barcelona, Barcelona (Spain); López, Núria [Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology (BIST), Tarragona (Spain); Vojvodic, Aleksandra [SUNCAT Center for Interface Science and Catalysis, SLAC National Accelerator Laboratory, Menlo Park CA (United States)

2016-04-29

An attractive strategy to improve the performance of water oxidation catalysts would be to anchor a homogeneous molecular catalyst on a heterogeneous solid surface to create a hybrid catalyst. The idea of this combined system is to take advantage of the individual properties of each of the two catalyst components. We use Density Functional Theory to determine the stability and activity of a model hybrid water oxidation catalyst consisting of a dimeric Ir complex attached on the IrO₂(110) surface through two oxygen atoms. We find that homogeneous catalysts can be bound to its matrix oxide without losing significant activity. Hence, designing hybrid systems that benefit from both the high tunability of activity of homogeneous catalysts and the stability of heterogeneous systems seems feasible.

Iron oxide/cassava starch-supported Ziegler-Natta catalysts for in situ ethylene polymerization.

Science.gov (United States)

Chancharoenrith, Sittikorn; Kamonsatikul, Choavarit; Namkajorn, Montree; Kiatisevi, Supavadee; Somsook, Ekasith

2015-03-06

Iron oxide nanoparticles were used as supporters for in situ polymerization to produce polymer nanocomposites with well-dispersed fillers in polymer matrix. Iron oxide could be sustained as colloidal solutions by cassava starch to produce a good dispersion of iron oxide in the matrix. New supports based on iron oxide/cassava starch or cassava starch for Ziegler-Natta catalysts were utilized as heterogeneous supporters for partially hydrolyzed triethylaluminum. Then, TiCl4 was immobilized on the supports as catalysts for polymerization of ethylene. High-density polyethylene (HDPE) composites were obtained by the synthesized catalysts. A good dispersion of iron oxide/cassava starch particles was observed in the synthesized polymer matrix promoting to good mechanical properties of HDPE. Copyright © 2014 Elsevier Ltd. All rights reserved.

Mechanochemical synthesis of graphene oxide-supported transition metal catalysts for the oxidation of isoeugenol to vanillin.

Science.gov (United States)

Franco, Ana; De, Sudipta; Balu, Alina M; Garcia, Araceli; Luque, Rafael

2017-01-01

Vanillin is one of the most commonly used natural products, which can also be produced from lignin-derived feedstocks. The chemical synthesis of vanillin is well-established in large-scale production from petrochemical-based starting materials. To overcome this problem, lignin-derived monomers (such as eugenol, isoeugenol, ferulic acid etc.) have been effectively used in the past few years. However, selective and efficient production of vanillin from these feedstocks still remains an issue to replace the existing process. In this work, new transition metal-based catalysts were proposed to investigate their efficiency in vanillin production. Reduced graphene oxide supported Fe and Co catalysts showed high conversion of isoeugenol under mild reaction conditions using H 2 O 2 as oxidizing agent. Fe catalysts were more selective as compared to Co catalysts, providing a 63% vanillin selectivity at 61% conversion in 2 h. The mechanochemical process was demonstrated as an effective approach to prepare supported metal catalysts that exhibited high activity for the production of vanillin from isoeugenol.

STUDY OF THE EFFECT OF CHLORINE ADDITION ON MERCURY OXIDATION BY SCR CATALYST UNDER SIMULATED SUBBITUMINOUS COAL FLUE GAS

Science.gov (United States)

An entrained flow reactor is used to study the effect of addition of chlorine-containing species on the oxidation of elemental mercury (Hgo)by a selective catalytic reduction (SCR) catalyst in simulated subbituminous coal combustion flue gas. The combustion flue gas was doped wit...

Supramolecular water oxidation with rubda-based catalysts

KAUST Repository

Richmond, Craig J.; Matheu, Roc; Poater, Albert; Falivene, Laura; Benet-Buchholz, Jordi; Sala, Xavier; Cavallo, Luigi; Llobet, Antoni A.

2014-01-01

Extremely slow and extremely fast new water oxidation catalysts based on the Rubda (bda = 2,2′-bipyri-dine-6,6′-dicarboxylate) systems are reported with turnover frequencies in the range of 1 and 900 cycless"1, respectively. Detailed analyses

Magnesium oxide prepared via metal-chitosan complexation method: Application as catalyst for transesterification of soybean oil and catalyst deactivation studies

Science.gov (United States)

Almerindo, Gizelle I.; Probst, Luiz F. D.; Campos, Carlos E. M.; de Almeida, Rusiene M.; Meneghetti, Simoni M. P.; Meneghetti, Mario R.; Clacens, Jean-Marc; Fajardo, Humberto V.

2011-10-01

A simple method to prepare magnesium oxide catalysts for biodiesel production by transesterification reaction of soybean oil with ethanol is proposed. The method was developed using a metal-chitosan complex. Compared to the commercial oxide, the proposed catalysts displayed higher surface area and basicity values, leading to higher yield in terms of fatty acid ethyl esters (biodiesel). The deactivation of the catalyst due to contact with CO2 and H2O present in the ambient air was verified. It was confirmed that the active catalytic site is a hydrogenocarbonate adsorption site.

Enhanced activity and stability of copper oxide/γ-alumina catalyst in catalytic wet-air oxidation: Critical roles of cerium incorporation

Science.gov (United States)

Zhang, Yongli; Zhou, Yanbo; Peng, Chao; Shi, Junjun; Wang, Qingyu; He, Lingfeng; Shi, Liang

2018-04-01

By successive impregnation method, the Ce-modified Cu-O/γ-Al2O3 catalyst was prepared and characterized using nitrogen adsorption-desorption, scanning electron microscopy energy dispersive X-ray analysis (SEM-EDS), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman, and H2-Temperature programming reduction (H2-TPR). In catalytic wet-air oxidation (CWAO) process for the printing and dyeing wastewater (PDW), the effects of Ce addition on performance, mechanism and kinetics of the catalyst were investigated. The Ce addition increases the Brunauer-Emmett-Teller (BET) surface area and pore volume of the catalyst and makes the active components uniformly distributed on the catalyst surface. Formation of a stable CuAl2O4 solid solution by anchoring Cu onto the γ-Al2O3 crystal lattice leads to a significant decrease in metal leaching of the Ce-modified catalyst. The proportion of lattice oxygen in the catalyst substantially increases and the apparent activation energy of Cu-O/γ-Al2O3 catalyst decreases owing to Ce addition. Therefore, the catalytic activity and stability of the Ce-modified catalyst are considerably improved. The scavengers experiments identify the active species existed in the CWAO reaction system, with the order of reactivity: h+ > O2•- > H2O2 > HO•. This novel Cu-Ce-O/γ-Al2O3 catalyst has great potential in applications for treatment of concentrated organic wastewater due to its superior catalytic activity and improved stability.

Mild oxidation of methane to methanol or acetic acid on supported isolated rhodium catalysts

Science.gov (United States)

Shan, Junjun; Li, Mengwei; Allard, Lawrence F.; Lee, Sungsik; Flytzani-Stephanopoulos, Maria

2017-11-01

An efficient and direct method of catalytic conversion of methane to liquid methanol and other oxygenates would be of considerable practical value. However, it remains an unsolved problem in catalysis, as typically it involves expensive or corrosive oxidants or reaction media that are not amenable to commercialization. Although methane can be directly converted to methanol using molecular oxygen under mild conditions in the gas phase, the process is either stoichiometric (and therefore requires a water extraction step) or is too slow and low-yielding to be practical. Methane could, in principle, also be transformed through direct oxidative carbonylation to acetic acid, which is commercially obtained through methane steam reforming, methanol synthesis, and subsequent methanol carbonylation on homogeneous catalysts. However, an effective catalyst for the direct carbonylation of methane to acetic acid, which might enable the economical small-scale utilization of natural gas that is currently flared or stranded, has not yet been reported. Here we show that mononuclear rhodium species, anchored on a zeolite or titanium dioxide support suspended in aqueous solution, catalyse the direct conversion of methane to methanol and acetic acid, using oxygen and carbon monoxide under mild conditions. We find that the two products form through independent pathways, which allows us to tune the conversion: three-hour-long batch-reactor tests conducted at 150 degrees Celsius, using either the zeolite-supported or the titanium-dioxide-supported catalyst, yield around 22,000 micromoles of acetic acid per gram of catalyst, or around 230 micromoles of methanol per gram of catalyst, respectively, with selectivities of 60-100 per cent. We anticipate that these unusually high activities, despite still being too low for commercial application, may guide the development of optimized catalysts and practical processes for the direct conversion of methane to methanol, acetic acid and other useful

Formation of nitrogen compounds from nitrogen-containing rings during oxidative regeneration of spent hydroprocessing catalysts

Energy Technology Data Exchange (ETDEWEB)

Furimsky, E.; Nielsen, M.; Jurasek, P. [CANMET, Ottawa, ON (Canada). Energy Research Laboratories

1995-05-01

Commercial CoMo and NiMo catalysts in an oxidic and sulfided form and a {gamma}-alumina were deposited with pyrrole, pyridine, and quinoline. The deposited catalysts and two spent hydroprocessing catalysts were pyrolyzed and oxidized under conditions typical of regeneration of hydroprocessing catalysts. The formation of NH{sub 3} and HCN, as well as selected cases of N{sub 2}O and NO, was monitored during the experiments. NH{sub 3} and HCN were formed during pyrolysis of pyrrole-deposited catalysts whereas only NH{sub 3} was formed during that of pyridine-and quinoline-deposited catalysts. For all deposited catalysts, both NH{sub 3} and HCN were formed during temperature programmed oxidation in 2% O{sub 2}. For spent catalysts, a small amount of N{sub 2}O was formed in 2 and 4% O{sub 2}. For pyrrole-deposited catalysts, large yields of N{sub 2}O were formed in 4% O{sub 2}. Under the same conditions, N{sub 2}O yields for pyridine- and quinoline-deposited catalysts were very small. 13 refs., 12 figs., 6 tabs.

Catalysts Promoted with Niobium Oxide for Air Pollution Abatement

Directory of Open Access Journals (Sweden)

Wendi Xiang

2017-05-01

Full Text Available Pt-containing catalysts are currently used commercially to catalyze the conversion of carbon monoxide (CO and hydrocarbon (HC pollutants from stationary chemical and petroleum plants. It is well known that Pt-containing catalysts are expensive and have limited availability. The goal of this research is to find alternative and less expensive catalysts to replace Pt for these applications. This study found that niobium oxide (Nb2O5, as a carrier or support for certain transition metal oxides, promotes oxidation activity while maintaining stability, making them candidates as alternatives to Pt. The present work reports that the orthorhombic structure of niobium oxide (formed at 800 °C in air promotes Co3O4 toward the oxidation of both CO and propane, which are common pollutants in volatile organic compound (VOC applications. This was a surprising result since this structure of Nb2O5 has a very low surface area (about 2 m2/g relative to the more traditional Al2O3 support, with a surface area of 150 m2/g. The results reported demonstrate that 1% Co3O4/Nb2O5 has comparable fresh and aged catalytic activity to 1% Pt/γ-Al2O3 and 1% Pt/Nb2O5. Furthermore, 6% Co3O4/Nb2O5 outperforms 1% Pt/Al2O3 in both catalytic activity and thermal stability. These results suggest a strong interaction between niobium oxide and the active component—cobalt oxide—likely by inducing an oxygen defect structure with oxygen vacancies leading to enhanced activity toward the oxidation of CO and propane.

Stepwise mechanism of oxidative ammonolysis of propane to acrylonitrile over gallium-antimony oxide catalysts

Energy Technology Data Exchange (ETDEWEB)

Osipova, Z.G.; Sokolovskii, V.D.

1979-03-01

The stepwise mechanism of oxidative ammonolysis of propane to acrylonitrile over gallium-antimony oxide catalysts GaSb/sub 19/O/sub x/, GaSb/sub 3/Ni/sub 1.5/0/sub x/, and GaSb/sub 2.5/Ni/sub 1.5/PW/sub 0//sub 0.25/O/sub x/ was studied at 450/sup 0/ and 550/sup 0/C by introducing alternating pulses of 0.5Vertical Bar3< propane/0.6Vertical Bar3< ammonia/helium (to reduce the steady-state catalytic surface) and 0.5Vertical Bar3< propane/0.6Vertical Bar3< ammonia/1.86Vertical Bar3< oxygen/helium mixtures into a fluidized-bed catalytic reactor. Over all the catalysts studied, the rates of acrylonitrile formation during the two types of pulses were very similar, but carbon dioxide was formed much faster during the reducing pulses, particularly at 450/sup 0/C. These findings suggested that acrylonitrile is formed by a stepwise redox mechanism involving consecutive interaction of propane and ammonia with the surface oxygen of the catalysts and oxidation of the reduced catalyst surface by gas-phase oxygen. The formation of carbon dioxide proceeds by both stepwise and associative mechanisms, the latter being more important at higher temperatures. The results are similar to published results for ammoxidation of propylene and olefins.

Promotion of catalytic performance by adding W into Pt/ZrO{sub 2} catalyst for selective catalytic oxidation of ammonia

Energy Technology Data Exchange (ETDEWEB)

Sun, Mengmeng [Institute of New Energy and Low-Carbon Technology, Sichuan University, Chengdu 610064, Sichuan (China); Wang, Suning; Li, Yuanshan [College of Chemical Engineering, Sichuan University, Chengdu 610064, Sichuan (China); Xu, Haidi, E-mail: xuhaidi@scu.edu.cn [Institute of New Energy and Low-Carbon Technology, Sichuan University, Chengdu 610064, Sichuan (China); Chen, Yaoqiang, E-mail: nic7501@scu.edu.cn [Institute of New Energy and Low-Carbon Technology, Sichuan University, Chengdu 610064, Sichuan (China); College of Chemical Engineering, Sichuan University, Chengdu 610064, Sichuan (China)

2017-04-30

Highlights: • The tungsten species weaken platinum-oxygen bond strength. • Pt{sup 0} was the active species of ammonia oxidation reaction in the low temperature. • Some PtO species could convert to Pt [111] beside WO{sub 3} species. - Abstract: Pt-WO{sub 3}/ZrO{sub 2} catalyst was prepared by co-impregnation method to improve the ammonia oxidation performance of Pt/ZrO{sub 2}. Differences in textural, structural, surface chemical states, redox properties and acid properties, together with the catalytic performance of Pt/ZrO{sub 2} and Pt-WO{sub 3}/ZrO{sub 2} catalysts were investigated systematically. The results of H{sub 2}-TPR revealed that higher reduction ability was possessed by Pt-WO{sub 3}/ZrO{sub 2} than that of Pt/ZrO{sub 2} due to the influence of tungsten on platinum. The XPS results showed that electron transfer from tungsten to platinum species made higher electron density around platinum. The TEM results revealed that the active lattice plane Pt[111] was obtained by modification of W species. Consequently, Pt-WO{sub 3}/ZrO{sub 2} exhibited obviously better ammonia oxidation performance compared with Pt/ZrO{sub 2}, the light-off temperature of NH{sub 3} shifted from 284 °C to 249 °C, the activation energy decreased from 113.4 kJ mol{sup −1} to 96.2 kJ mol{sup −1}.

Hydrothermal Synthesis of MoO2 and Supported MoO2 Cata-lysts for Oxidative Desulfurization of Dibenzothiophene

Institute of Scientific and Technical Information of China (English)

Wang Danhong; Zhang Jianyong; Liu Ni; Zhao Xin; Zhang Minghui

2014-01-01

A novel method for obtaining spherical MoO2 nanoparticles and SiO2-Al2O3 supported MoO2 by hydrothermal reduction of Mo (VI) species was studied. The obtained MoO2 catalysts show very high catalytic activity in the oxidative desulfurization (ODS) process. The effect of hydrothermal temperature and crystallization temperature on ODS activity was investigated. The ODS activity of supported MoO2 catalysts with various MoO2 contents were also investigated. The mecha-nism for formation of MoO2 involving oxalic acid was proposed.

Pt/SnO2-based CO-oxidation catalysts for long-life closed-cycle CO2 lasers

Science.gov (United States)

Schryer, David R.; Upchurch, Billy T.; Hess, Robert V.; Wood, George M.; Sidney, Barry D.; Miller, Irvin M.; Brown, Kenneth G.; Vannorman, John D.; Schryer, Jacqueline; Brown, David R.

1990-01-01

Noble-metal/tin-oxide based catalysts such as Pt/SnO2 have been shown to be good catalysts for the efficient oxidation of CO at or near room temperature. These catalysts require a reductive pretreatment and traces of hydrogen or water to exhibit their full activity. Addition of Palladium enhances the activity of these catalysts with about 15 to 20 percent Pt, 4 percent Pd, and the balance SnO2 being an optimum composition. Unfortunately, these catalysts presently exhibit significant decay due in part to CO2 retention, probably as a bicarbonate. Research on minimizing the decay in activity of these catalysts is currently in progress. A proposed mechanism of CO oxidation on Pt/SnO2-based catalysts has been developed and is discussed.

Activity of Cu-activated carbon fiber catalyst in wet oxidation of ammonia solution.

Science.gov (United States)

Hung, Chang-Mao

2009-07-30

Aqueous solutions of 200-1000 mg/L of ammonia were oxidized in a trickle-bed reactor using Cu-activated carbon fiber (ACF) catalysts, which were prepared by incipient wet impregnation with aqueous solutions of copper nitrate that was deposited on ACF substrates. The results reveal that the conversion of ammonia by wet oxidation in the presence of Cu-ACF catalysts was a function of the metal loading weight ratio of the catalyst. The total conversion efficiency of ammonia was 95% during wet oxidation over the catalyst at 463 K at an oxygen partial pressure of 3.0 MPa. Moreover, the effect of the initial concentration of ammonia and the reaction temperature on the removal of ammonia from the effluent streams was also studied at a liquid space velocity of less than 3.0 h(-1).

Activity of Cu-activated carbon fiber catalyst in wet oxidation of ammonia solution

International Nuclear Information System (INIS)

Hung, Chang-Mao

2009-01-01

Aqueous solutions of 200-1000 mg/L of ammonia were oxidized in a trickle-bed reactor using Cu-activated carbon fiber (ACF) catalysts, which were prepared by incipient wet impregnation with aqueous solutions of copper nitrate that was deposited on ACF substrates. The results reveal that the conversion of ammonia by wet oxidation in the presence of Cu-ACF catalysts was a function of the metal loading weight ratio of the catalyst. The total conversion efficiency of ammonia was 95% during wet oxidation over the catalyst at 463 K at an oxygen partial pressure of 3.0 MPa. Moreover, the effect of the initial concentration of ammonia and the reaction temperature on the removal of ammonia from the effluent streams was also studied at a liquid space velocity of less than 3.0 h -1 .

Titania Supported Co-Mn-Al Oxide Catalysts in Total Oxidation of Ethanol

Czech Academy of Sciences Publication Activity Database

Ludvíková, Jana; Jirátová, Květa; Klempa, Jan; Böhmová, Vlasta; Obalová, L.

2012-01-01

Roč. 179, č. 1 (2012), s. 164-169 ISSN 0920-5861 R&D Projects: GA ČR GAP106/10/1762; GA ČR GD203/08/H032 Institutional research plan: CEZ:AV0Z40720504; CEZ:AV0Z30130516 Keywords : mixed oxide catalysts * voc oxidation * titania Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.980, year: 2012

Nanocasted synthesis of magnetic mesoporous iron cerium bimetal oxides (MMIC) as an efficient heterogeneous Fenton-like catalyst for oxidation of arsenite

Energy Technology Data Exchange (ETDEWEB)

Wen, Zhipan [State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092 (China); Zhang, Yalei, E-mail: zhangyalei@tongji.edu.cn [State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092 (China); Dai, Chaomeng [College of Civil Engineering, Tongji University, Shanghai 200092 (China); Sun, Zhen [State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092 (China)

2015-04-28

Highlights: • MMIC with large surface area and pore volume was synthesized via the hard template. • MMIC could be easily separated from aqueous solution with an external magnetic field. • MMIC presented excellent catalytic activity for the oxidation of As(III). • As(III) was mainly oxidized by surface-bound ·OH{sub ads} and free ·OH{sub free} radicals. • MMIC played a dual function role for the arsenic removal in aqueous solution. - Abstract: Magnetic mesoporous iron cerium bimetal oxides (MMIC) with large surface area and pore volume was synthesized via the hard template approach. This obtained MMIC was easily separated from aqueous solution with an external magnetic field and was proposed as a heterogeneous Fenton-like catalyst for oxidation of As(III). The MMIC presented excellent catalytic activity for the oxidation of As(III), achieving almost complete oxidation of 1000 ppb As(III) after 60 min and complete removal of arsenic species after 180 min with reaction conditions of 0.4 g/L catalyst, pH of 3.0 and 0.4 mM H{sub 2}O{sub 2}. Kinetics analysis showed that arsenic removal followed the pseudo-first order, and the pseudo-first-order rate constants increased from 0.0014 min{sup −1} to 0.0548 min{sup −1} as the H{sub 2}O{sub 2} concentration increased from 0.04 mM to 0.4 mM. On the basis of the effects of XPS analysis and reactive oxidizing species, As(III) in aqueous solution was mainly oxidized by ·OH radicals, including the surface-bound ·OH{sub ads} generated on the MMIC surface which were involved in ≡Fe{sup 2+} and ≡Ce{sup 3+}, and free ·OH{sub free} generation by soluble iron ions which were released from the MMIC into the bulk solution, and the generated As(V) was finally removed by MMIC through adsorption.

Studies of vanadium-phosphorus-oxygen selective oxidation catalysts by sup 31 P and sup 51 V NMR spin-echo and volume susceptibility measurements

Energy Technology Data Exchange (ETDEWEB)

Li, Juan.

1991-10-01

The purpose of this work is to characterize the vanadium-phosphorous oxide (V-P-O) catalysts for the selective oxidation of n-butane and 1-butene to maleic anhydride. The utility of solid state nuclear magnetic resonance as an analytical tool in this investigation lies in its sensitivity to the electronic environment surrounding the phosphorous and vanadium nuclei, and proximity of paramagnetic species. Spin-echo mapping NMR of {sup 31}p and {sup 51}v and volume magnetic susceptibility measurements were used as local microscopic probes of the presence of V{sup 5+}, V{sup 4+}, V{sup 3+} species in the model compounds: {beta}-VOPO{sub 4}, {beta}-VOPO{sub 4} treated with n-butane/1-butene, (VO){sub 2}P{sub 2}O{sub 7} treated with n-butane/1-butene; and industrial catalysts with P/V (phosphorus to vanadium) ratio of 0.9, 1.0 and 1.1, before and after treatment with n-butane and 1-butene. The NMR spectra provide a picture of how the oxidation states of vanadium are distributed in these catalysts. 73 refs., 32 figs., 8 tabs.

Aluminum Oxide Formation On Fecral Catalyst Support By Electro-Chemical Coating

Directory of Open Access Journals (Sweden)

Yang H.S.

2015-06-01

Full Text Available FeCrAl is comprised essentially of Fe, Cr, Al and generally considered as metallic substrates for catalyst support because of its advantage in the high-temperature corrosion resistance, high mechanical strength, and ductility. Oxidation film and its adhesion on FeCrAl surface with aluminum are important for catalyst life. Therefore various appropriate surface treatments such as thermal oxidation, Sol, PVD, CVD has studied. In this research, PEO (plasma electrolytic oxidation process was applied to form the aluminum oxide on FeCrAl surface, and the formed oxide particle according to process conditions such as electric energy and oxidation time were investigated. Microstructure and aluminum oxide particle on FeCrAl surface after PEO process was observed by FE-SEM and EDS with element mapping analysis. The study presents possibility of aluminum oxide formation by electro-chemical coating process without any pretreatment of FeCrAl.

Chemoselective Oxidation of Bio-Glycerol with Nano-Sized Metal Catalysts

DEFF Research Database (Denmark)

Li, Hu; Kotni, Ramakrishna; Zhang, Qiuyun

2015-01-01

to selectively oxidize glycerol and yield products with good selectivity is the use of nano-sized metal particles as heterogeneous catalysts. In this short review, recent developments in chemoselective oxidation of glycerol to specific products over nano-sized metal catalysts are described. Attention is drawn...... to various reaction parameters such as the type of the support, the size of the metal particles, and the acid/base properties of the reaction medium which were illustrated to largely influence the activity of the nanocatalyst and selectivity to the target product. - See more at: http...

Synthesis of cerium oxide catalysts supported on MCM-41 molecular sieve

International Nuclear Information System (INIS)

Souza, E.L.S.; Barros, T.R.B.; Sousa, B.V. de

2016-01-01

Porous materials have been widely studied as catalysts and catalyst support. The MCM-41 structure is the one that has been most studied because of its application possibilities in chemical processes. This work aimed to obtain and characterize cerium oxide catalysts supported on MCM-41 molecular sieve. The molecular sieve was synthesized by the conventional method with the following molar composition: 1 SiO2: 0.30 CTABr: NH3 11: 144 H2O. Then, 25% w/w cerium was incorporated into the MCM-41 using the wet impregnation process and the material obtained was activated by calcination. From the XRD patterns was confirmed the structure of the molecular sieve, and were identified the cerium oxide phases in its structure. The textural catalysts characteristics were investigated by isotherms of N2 adsorption/desorption (BET method). (author)

Selective oxidation of propylene to acrolein by silica-supported bismuth molybdate catalysts

DEFF Research Database (Denmark)

Duc, Duc Truong; Ha, Hanh Nguyen; Fehrmann, Rasmus

2011-01-01

Silica-supported bismuth molybdate catalysts have been prepared by impregnation, structurally characterized and examined as improved catalysts for the selective oxidation of propylene to acrolein. Catalysts with a wide range of loadings (from 10 to 90 wt%) of beta bismuth molybdate (β-Bi2Mo2O9) w...

Strategies for catalyst development: possibilities of the ``rational approach`` illustrated with partial oxidation reactions

Energy Technology Data Exchange (ETDEWEB)

Weiss, W.; Schedel-Niedrig, T.; Schloegl, R. [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin (Germany). Abt. Oberflaechenphysik

1998-12-31

The paper discusses two petrochemical selective oxidation reactions namely the practised formation of styrene (STY) and the desired oxidative functionalisation of propane. The present knowledge about the mode of operation of oxide catalysts is critically considered. The dehydrogenation of ethylbenzene (EB) should be described by an oxidehydration with water acting as oxidant. The potential role of the coke formed during catalytic reaction as co-catalyst will be discussed. Selective oxidation is connected with the participation of lattice oxygen mechanism which transforms unselective gas phase oxygen into selective oxygen. The atomistic description of this process is still quite unclear as well as the electron structural properties of the activated oxygen atom. The Role of solid state acidity as compared to the role of lattice oxygen is much less well investigated modern multiphase-multielement oxide (MMO) catalysts. The rationale is that the significant efforts made to improve current MMO systems by chemical modifications can be very much more fruitful when in a first step the mode of action of a catalyst is clarified on the basis of suitable experiments. Such time-consuming experiments at the beginning of a campaign for catalyst improvement pay back their investment in later stages of the project when strategies of chemical development can be derived on grounds of understanding. (orig.)

IR-doped ruthenium oxide catalyst for oxygen evolution

Science.gov (United States)

Valdez, Thomas I. (Inventor); Narayanan, Sekharipuram R. (Inventor)

2012-01-01

A method for preparing a metal-doped ruthenium oxide material by heating a mixture of a doping metal and a source of ruthenium under an inert atmosphere. In some embodiments, the doping metal is in the form of iridium black or lead powder, and the source of ruthenium is a powdered ruthenium oxide. An iridium-doped or lead-doped ruthenium oxide material can perform as an oxygen evolution catalyst and can be fabricated into electrodes for electrolysis cells.

Newly designed PdRuBi/N-Graphene catalysts with synergistic effects for enhanced ethylene glycol electro-oxidation

International Nuclear Information System (INIS)

Li, Tengfei; Huang, Yiyin; Ding, Kui; Wu, Peng; Abbas, Syed Comail; Ghausi, Muhammad Arsalan; Zhang, Teng; Wang, Yaobing

2016-01-01

Graphical abstract: We rationally design and synthesize a ternary PdRuBi/NG catalyst with significantly enhanced catalytic activity with synergetic effect of Ru and Bi towards ethylene glycol electro-oxidation. - Abstract: Palladium (Pd)-based catalysts are appealing electro-catalysts for alcohol oxidation reaction in fuel cell, but still not efficient as the complicated oxidation process and sluggish kinetic. Here we rationally design and synthesize a PdRuBi/NG tri-metallic catalyst with space synergetic effect for enhanced ethylene glycol electro-oxidation, in which both Ru and Bi in the catalyst are synergistic effective in promoting catalytic activity of Pd catalytic interlayer by electronic effect and surface modification mechanism respectively. It shows 4.2 times higher peak current density towards ethylene glycol electro-oxidation than commercial Pd/C catalyst, and the catalytic durability is also greatly improved.

Modelling of the partial oxidation of {alpha}, {beta}-unsaturated aldehydes on Mo-V-oxides based catalysts

Energy Technology Data Exchange (ETDEWEB)

Boehnke, H.; Petzoldt, J.C.; Stein, B.; Weimer, C.; Gaube, J.W. [Technische Univ. Darmstadt (Germany). Inst. fuer Chemische Technologie

1998-12-31

A kinetic model based on the Mars-van Krevelen mechanism that allows to describe the microkinetics of the heterogeneously catalysed partial oxidation of {alpha}, {beta}-unsaturated aldehydes is presented. This conversion is represented by a network, composed of the oxidation of the {alpha}, {beta}-unsaturated aldehyde towards the {alpha}, {beta}-unsaturated carboxylic acid and the consecutive oxidation of the acid as well as the parallel reaction of the aldehyde to products of deeper oxidation. The reaction steps of aldehyde respectively acid oxidation and catalyst reoxidation have been investigated separately in transient experiments. The combination of steady state and transient experiments has led to an improved understanding of the interaction of the catalyst with the aldehyde and the carboxylic acids as well as to a support of the kinetic model assumptions. (orig.)

The Effect of Annealing Temperature on Nickel on Reduced Graphene Oxide Catalysts on Urea Electrooxidation

International Nuclear Information System (INIS)

Glass, Dean E.; Galvan, Vicente; Prakash, G.K. Surya

2017-01-01

Highlights: •Nickel was reduced on graphene oxide and annealed under argon from 300 to 700 °C. •Nickel was oxidized from the removal of oxygen groups on the graphene oxide. •Higher annealed catalysts displayed decreased urea electrooxidation currents. •Micro direct urea/hydrogen peroxide fuel cells were employed for the first time. •Ni/rGO catalysts displayed enhanced fuel cell performance than the bare nickel. -- Abstract: The annealing temperature effects on nickel on reduced graphene oxide (Ni/rGO) catalysts for urea electrooxidation were investigated. Nickel chloride was directly reduced in an aqueous solution of graphene oxide (GO) followed by annealing under argon at 300, 400, 500, 600, and 700 °C, respectively. X-ray Diffraction (XRD) patterns revealed an increase in the crystallite size of the nickel nanoparticles while the Raman spectra displayed an increase in the graphitic disorder of the reduced graphene oxide at higher annealing temperatures due to the removal of oxygen functional groups. The Ni/rGO catalysts annealed at higher temperatures displayed oxidized nickel surface characteristics from the Ni 2p X-ray Photoelectron Spectra (XPS) due to the oxidation of the nickel from the oxygen functional groups in the graphitic lattice. In the half-cell testing, the onset potential of urea electrooxidation decreased while the urea electrooxidation currents decreased as the annealing temperature was increased. The nickel catalyst annealed at 700 °C displayed a 31% decrease in peak power density while the catalyst annealed at 300 °C displayed a 13% increase compared with the unannealed Ni/rGO catalyst in the micro direct urea/hydrogen peroxide fuel cells tests.

Chlorination of antimony and its volatilization treatment of waste antimony-uranium composite oxide catalyst

International Nuclear Information System (INIS)

Sawada, K.; Enokida, Y.

2011-01-01

For the waste antimony-uranium composite oxide catalyst, the chlorination of antimony and its volatilization treatment were proposed, and evaluated using hydrogen chloride gas at 873-1173 K. During the treatment, the weight loss of the composite oxide sample, which resulted from the volatilization of antimony, was confirmed. An X-ray diffraction analysis showed that uranium oxide, U 3 O 8 , was formed during the reaction. After the treatment at 1173 K for 1 h, almost all the uranium contained in the waste catalyst was dissolved by a 3 M nitric acid solution at 353 K within 10 min, although that of the non-treated catalyst was less than 0.1%. It was found that the chlorination and volatilization treatment was effective to separate antimony from the composite oxide catalyst and change uranium into its removable form. (orig.)

Mechanochemical synthesis of graphene oxide-supported transition metal catalysts for the oxidation of isoeugenol to vanillin

Directory of Open Access Journals (Sweden)

Ana Franco

2017-07-01

Full Text Available Vanillin is one of the most commonly used natural products, which can also be produced from lignin-derived feedstocks. The chemical synthesis of vanillin is well-established in large-scale production from petrochemical-based starting materials. To overcome this problem, lignin-derived monomers (such as eugenol, isoeugenol, ferulic acid etc. have been effectively used in the past few years. However, selective and efficient production of vanillin from these feedstocks still remains an issue to replace the existing process. In this work, new transition metal-based catalysts were proposed to investigate their efficiency in vanillin production. Reduced graphene oxide supported Fe and Co catalysts showed high conversion of isoeugenol under mild reaction conditions using H2O2 as oxidizing agent. Fe catalysts were more selective as compared to Co catalysts, providing a 63% vanillin selectivity at 61% conversion in 2 h. The mechanochemical process was demonstrated as an effective approach to prepare supported metal catalysts that exhibited high activity for the production of vanillin from isoeugenol.

Ni–Ta–O mixed oxide catalysts for the low temperature oxidative dehydrogenation of ethane to ethylene

KAUST Repository

Zhu, Haibo; Rosenfeld, Devon C.; Anjum, Dalaver H.; Sangaru, Shiv; Saih, Youssef; Ould-Chikh, Samy; Basset, Jean-Marie

2015-01-01

The "wet" sol-gel and "dry" solid-state methods were used to prepare Ni-Ta-O mixed oxide catalysts. The resulting Ni-Ta oxides exhibit high activity and selectivity for the low temperature oxidative dehydrogenation of ethane to ethylene. The Ta

Reduction and re-oxidation of Cu/Al{sub 2}O{sub 3} catalysts investigated with quick-scanning XANES and EXAFS

Energy Technology Data Exchange (ETDEWEB)

Stoetzel, J; Luetzenkirchen-Hecht, D; Frahm, R [Department of Physics, University of Wuppertal, Gaussstr. 20, D-42097 Wuppertal (Germany); Kimmerle, B; Baiker, A [Department of Chemistry and Applied Biosciences, ETH Zuerich, CH-8093 Zuerich (Switzerland); Nachtegaal, M [Paul Scherrer Institut, CH-5232 Villigen (Switzerland); Beier, M J; Grunwaldt, J-D, E-mail: j.stoetzel@uni-wuppertal.d, E-mail: jdg@kt.dtu.d [Department of Chemical and Biochemical Engineering, Technical University of Denmark, Building 229, DK-2800 Kgs. Lyngby (Denmark)

2009-11-15

In the present study the structure of copper catalysts on alumina support were investigated in situ and time resolved during reduction and re-oxidation at different temperatures with the quick-scanning EXAFS (QEXAFS) technique. Different impregnation times (2 min and 90 min) were chosen for the preparation which resulted in different copper species that show a strong variation in the reduction/re-oxidation behaviour. These dynamic changes as well as possible intermediate phases during the gas atmospheres changes were followed with up to 20 EXAFS spectra per second at the copper K-edge covering an energy range of 450 eV. The high time resolution provided new insights into the dynamics of the catalysts e.g. revealing Cu(I) as intermediate state during re-oxidation. Latest advances in the data acquisition hardware are leading to an improved data quality of spectra collected at the SuperXAS beamline. Thus, not only accurate analysis of the catalysts via XANES but also by EXAFS was possible. This is also due to the recent upgrade to monitor the Bragg angle directly with an encoder during the experiments.

Cyclic catalytic upgrading of chemical species using metal oxide materials

Science.gov (United States)

White, James H; Schutte, Erick J; Rolfe, Sara L

2013-05-07

Processes are disclosure which comprise alternately contacting an oxygen-carrying catalyst with a reducing substance, or a lower partial pressure of an oxidizing gas, and then with the oxidizing gas or a higher partial pressure of the oxidizing gas, whereby the catalyst is alternately reduced and then regenerated to an oxygenated state. In certain embodiments, the oxygen-carrying catalyst comprises at least one metal oxide-containing material containing a composition having the following formulas: (a) Ce.sub.xB.sub.yB'.sub.zB''O.sub..delta., wherein B=Ba, Sr, Ca, or Zr; B'=Mn, Co, and/or Fe; B''=Cu; 0.01Ba, Ca, La, or K; 0.02catalyst material itself or as a support for said unary or binary metal oxides.

Activity of Cu-activated carbon fiber catalyst in wet oxidation of ammonia solution

Energy Technology Data Exchange (ETDEWEB)

Hung, Chang-Mao, E-mail: hungcm1031@gmail.com [Department of Industry Engineering and Management, Yung-Ta Institute of Technology and Commerce, 316 Chung-shan Road, Linlo, Pingtung 909, Taiwan (China)

2009-07-30

Aqueous solutions of 200-1000 mg/L of ammonia were oxidized in a trickle-bed reactor using Cu-activated carbon fiber (ACF) catalysts, which were prepared by incipient wet impregnation with aqueous solutions of copper nitrate that was deposited on ACF substrates. The results reveal that the conversion of ammonia by wet oxidation in the presence of Cu-ACF catalysts was a function of the metal loading weight ratio of the catalyst. The total conversion efficiency of ammonia was 95% during wet oxidation over the catalyst at 463 K at an oxygen partial pressure of 3.0 MPa. Moreover, the effect of the initial concentration of ammonia and the reaction temperature on the removal of ammonia from the effluent streams was also studied at a liquid space velocity of less than 3.0 h{sup -1}.

Highly Efficient Gas-Phase Oxidation of Renewable Furfural to Maleic Anhydride over Plate Vanadium Phosphorus Oxide Catalyst.

Science.gov (United States)

Li, Xiukai; Ko, Jogie; Zhang, Yugen

2018-02-09

Maleic anhydride (MAnh) and its acids are critical intermediates in chemical industry. The synthesis of maleic anhydride from renewable furfural is one of the most sought after processes in the field of sustainable chemistry. In this study, a plate vanadium phosphorus oxide (VPO) catalyst synthesized by a hydrothermal method with glucose as a green reducing agent catalyzes furfural oxidation to MAnh in the gas phase. The plate catalyst-denoted as VPO HT -has a preferentially exposed (200) crystal plane and exhibited dramatically enhanced activity, selectivity and stability as compared to conventional VPO catalysts and other state-of-the-art catalytic systems. At 360 °C reaction temperature with air as an oxidant, about 90 % yield of MAnh was obtained at 10 vol % of furfural in the feed, a furfural concentration value that is much higher than those (<2 vol %) reported for other catalytic systems. The catalyst showed good long-term stability and there was no decrease in activity or selectivity for MAnh during the time-on-stream of 25 h. The high efficiency and catalyst stability indicate the great potential of this system for the synthesis of maleic anhydride from renewable furfural. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Alkaline Ionic Liquid Modified Pd/C Catalyst as an Efficient Catalyst for Oxidation of 5-Hydroxymethylfurfural

Directory of Open Access Journals (Sweden)

Zou Bin

2018-01-01

Full Text Available Conversion of HMF into FDCA was carried out by a simple and green process based on alkaline ionic liquid (IL modified Pd/C catalyst (Pd/C-OH−. Alkaline ionic liquids were chosen to optimize Pd/C catalyst for special hydrophilicity and hydrophobicity, redox stability, and unique dissolving abilities for polar compounds. The Pd/C-OH− catalyst was successfully prepared and characterized by SEM, XRD, TG, FT-IR, and CO2-TPD technologies. Loading of alkaline ionic liquid on the surface of Pd/C was 2.54 mmol·g−1. The catalyst showed excellent catalytic activity in the HMF oxidation after optimization of reaction temperature, reaction time, catalyst amount, and solvent. Supported alkaline ionic liquid (IL could be a substitute and promotion for homogeneous base (NaOH. Under optimal reaction conditions, high HMF conversion of 100% and FDCA yield of 82.39% were achieved over Pd/C-OH− catalyst in water at 373 K for 24 h.

Catalyst for reduction of nitrogen oxides

Science.gov (United States)

Ott, Kevin C.

2010-04-06

A Selective Catalytic Reduction (SCR) catalyst was prepared by slurry coating ZSM-5 zeolite onto a cordierite monolith, then subliming an iron salt onto the zeolite, calcining the monolith, and then dipping the monolith either into an aqueous solution of manganese nitrate and cerium nitrate and then calcining, or by similar treatment with separate solutions of manganese nitrate and cerium nitrate. The supported catalyst containing iron, manganese, and cerium showed 80 percent conversion at 113 degrees Celsius of a feed gas containing nitrogen oxides having 4 parts NO to one part NO.sub.2, about one equivalent ammonia, and excess oxygen; conversion improved to 94 percent at 147 degrees Celsius. N.sub.2O was not detected (detection limit: 0.6 percent N.sub.2O).

Effect of Au Precursor and Support on the Catalytic Activity of the Nano-Au-Catalysts for Propane Complete Oxidation

Directory of Open Access Journals (Sweden)

Arshid M. Ali

2015-01-01

Full Text Available Catalytic activity of nano-Au-catalyst(s for the complete propane oxidation was investigated. The results showed that the nature of both Au precursor and support strongly influences catalytic activity of the Au-catalyst(s for the propane oxidation. Oxidation state, size, and dispersion of Au nanoparticles in the Au-catalysts, surface area, crystallinity, phase structure, and redox property of the support are the key aspects for the complete propane oxidation. Among the studied Au-catalysts, the AuHAuCl4-Ce catalyst is found to be the most active catalyst.

Influence of Gold on Ce-Zr-Co Fluorite-Type Mixed Oxide Catalysts for Ethanol Steam Reforming

Directory of Open Access Journals (Sweden)

Véronique Pitchon

2012-02-01

Full Text Available The effect of gold presence on carbon monoxide oxidation and ethanol steam reforming catalytic behavior of two Ce-Zr-Co mixed oxides catalysts with a constant Co charge and different Ce/Zr ratios was investigated. The Ce-Zr-Co mixed oxides were obtained by the pseudo sol-gel like method, based on metallic propionates polymerization and thermal decomposition, whereas the gold-supported Ce-Zr-Co mixed oxides catalysts were prepared using the direct anionic exchange. The catalysts were characterized using XRD, TPR, and EDXS-TEM. The presence of Au in doped Ce-Zr-Co oxide catalyst decreases the temperature necessary to reduce the cobalt and the cerium loaded in the catalyst and favors a different reaction pathway, improving the acetaldehyde route by ethanol dehydrogenation, instead of the ethylene route by ethanol dehydration or methane re-adsorption, thus increasing the catalytic activity and selectivity into hydrogen.

Effects of p-substituents on electrochemical CO oxidation by Rh porphyrin-based catalysts.

Science.gov (United States)

Yamazaki, Shin-ichi; Yamada, Yusuke; Takeda, Sahori; Goto, Midori; Ioroi, Tsutomu; Siroma, Zyun; Yasuda, Kazuaki

2010-08-21

Electrochemical CO oxidation by several carbon-supported rhodium tetraphenylporphyrins with systematically varied meso-substituents was investigated. A quantitative analysis revealed that the p-substituents on the meso-phenyl groups significantly affected CO oxidation activity. The electrocatalytic reaction was characterized in detail based on the spectroscopic and X-ray structural results as well as electrochemical analyses. The difference in the activity among Rh porphyrins is discussed in terms of the properties of p-substituents along with a proposed reaction mechanism. Rhodium tetrakis(4-carboxyphenyl)porphyrin (Rh(TCPP)), which exhibited the highest activity among the porphyrins tested, oxidized CO at a high rate at much lower potentials (means that CO is electrochemically oxidized by this catalyst when a slight overpotential is applied during the operation of a proton exchange membrane fuel cell. This catalyst exhibited little H(2) oxidation activity, in contrast to Pt-based catalysts.

Aerobic oxidation of aldehydes under ambient conditions using supported gold nanoparticle catalysts

DEFF Research Database (Denmark)

Marsden, Charlotte Clare; Taarning, Esben; Hansen, David

2008-01-01

A new, green protocol for producing simple esters by selectively oxidizing an aldehyde dissolved in a primary alcohol has been established, utilising air as the oxidant and supported gold nanoparticles as catalyst. The oxidative esterifications proceed with excellent selectivities at ambient cond...... conditions; the reactions can be performed in an open flask and at room temperature. Benzaldehyde is even oxidised at a reasonable rate below -70 degrees C. Acrolein is oxidised to methyl acrylate in high yield using the same protocol.......A new, green protocol for producing simple esters by selectively oxidizing an aldehyde dissolved in a primary alcohol has been established, utilising air as the oxidant and supported gold nanoparticles as catalyst. The oxidative esterifications proceed with excellent selectivities at ambient...

Modeling of carbon monoxide oxidation kinetics over NASA carbon dioxide laser catalysts

Science.gov (United States)

Herz, Richard K.

1989-01-01

The recombination of CO and O2 formed by the dissociation of CO2 in a sealed CO2 laser discharge zone is examined. Conventional base-metal-oxide catalysts and conventional noble-metal catalysts are not effective in recombining the low O2/CO ratio at the low temperatures used by the lasers. The use of Pt/SnO2 as the noble-metal reducible-oxide (NMRO), or other related materials from Group VIIIA and IB and SnO2 interact synergistically to produce a catalytic activity that is substantially higher than either componet separately. The Pt/SnO2 and Pd/SnO2 were reported to have significant reaction rates at temperatures as low as -27 C, conditions under which conventional catalysts are inactive. The gas temperature range of lasers is 0 + or - 40 C. There are three general ways in which the NMRO composite materials can interact synergistically: one component altering the properties of another component; the two components each providing independent catalytic functions in a complex reaction mechanism; and the formation of catalytic sites through the combination of two components at the atomic level. All three of these interactions may be important in low temperature CO oxidation over NMRO catalysts. The effect of the noble metal on the oxide is discussed first, followed by the effect of the oxide on the noble metal, the interaction of the noble metal and oxide to form catalytic sites, and the possible ways in which the CO oxidation reaction is catalyzed by the NMRO materials.

Characterization of electro-oxidation catalysts using scanning electrochemical and mass spectral methods

Science.gov (United States)

Jambunathan, Krishnakumar

Low temperature fuel cells have many potential benefits, including high efficiency, high energy density and environmental friendliness. However, logistically appealing fuels for this system, such as reformed hydrocarbons or alcohols, exhibit poor performance because of catalyst poisoning that occurs during oxidation at the anode. This research focuses on the analysis of several model fuels and catalyst materials to understand the impact of catalyst poisoning on reactivity. Two novel experimental tools were developed based upon the local measurement of catalyst performance using scanning, reactivity mapping probes. The Scanning Electrochemical Microscope (SECM) was used to directly measure the rate constant for hydrogen oxidation in the presence and absence of dissolved CO. The Scanning Differential Electrochemical Mass Spectrometer (SDEMS) was exploited to measure the partial and complete oxidation products of methanol and ethanol oxidation. The reactivity of Pt and Pt/Ru catalysts towards the hydrogen oxidation reaction in the absence and presence of adsorbed CO was elucidated using the SECM. Steady state rate constant measurements in the absence of CO showed that the rate of hydrogen oxidation reaction exceeded 1 cms-1 . Steady state rate constant measurements in the presence of CO indicated that the platinum surface is completely inactive due to adsorbed CO. Addition of as little as 6% Ru to the Pt electrode was found to significantly improve the activity of the electrode towards CO removal. SDEMS was used to study the electro-oxidation of methanol on Pt xRuy electrodes at different electrode potentials and temperatures. Screening measurements performed with the SDEMS showed that PtxRu y electrodes containing 6--40% Ru had the highest activity for methanol oxidation. Current efficiencies for CO2 were also calculated under different conditions. SDEMS was also used to study the electro-oxidation of ethanol on Pt xRuy electrodes. The reaction was found to occur

Development and Comparison of the Substrate Scope of Pd-Catalysts for the Aerobic Oxidation of Alcohols

Science.gov (United States)

Schultz, Mitchell J.; Hamilton, Steven S.; Jensen, David R.; Sigman, Matthew S.

2009-01-01

Three catalysts for aerobic oxidation of alcohols are discussed and the effectiveness of each is evaluated for allylic, benzylic, aliphatic, and functionalized alcohols. Additionally, chiral nonracemic substrates as well as chemoselective and diastereoselective oxidations are investigated. In this study, the most convenient system for the Pd-catalyzed aerobic oxidation of alcohols is Pd(OAc)2 in combination with triethylamine. This system functions effectively for the majority of alcohols tested and uses mild conditions (3 to 5 mol % of catalyst, room temperature). Pd(IiPr)(OAc)2(H2O) (1) also successfully oxidizes the majority of alcohols evaluated. This system has the advantage of significantly lowering catalyst loadings but requires higher temperatures (0.1 to 1 mol % of catalyst, 60 °C). A new catalyst is also disclosed, Pd(IiPr)(OPiv)2 (2). This catalyst operates under very mild conditions (1 mol %, room temperature, and air as the O2 source) but with a more limited substrate scope. PMID:15844968

Potassium effects on kinetics of propane oxydehydrogenation on vanadia-titania catalyst

International Nuclear Information System (INIS)

Grabowski, R.; Samson, K.

2003-01-01

Oxidative dehydrogenation of propane (ODH) over V 2 O 5 /TiO 2 and V 2 O 5 /TiO 2 doped with K was carried out by measuring conversions and selectiveness for various feed compositions, contact times and temperatures. The results obtained for both catalysts were interpreted on the basis of the mechanism, in which propene is formed through Eley-Rideal sequence of steps, i.e. without participation of the adsorbed propane species. Kinetic constants (activation energies, pre-exponential factors) for the model of ODH reaction of propane on these catalysts, obtained on the basis of steady-state results, are given. Addition of K to vanadia-titania catalysts leads to decrease of total combustion of propane and consecutive combustion of propene. It has been found that the direct propane total oxidation is 5 - 9 times lower than that of the consecutive propene oxidation and is almost temperature independent for potassium doped catalyst, whereas it quickly decreases with temperature for a non-doped catalyst. Secondly, the addition of K to a vanadia-titania catalyst decreases the activation energies for propene formation (k 1 ), parallel formation of CO x (k 3 ) and reoxidation of the catalyst (k os ). Potassium exhibits a stronger inhibitory effect on the secondary propene combustion, what reflects the lower activity of V 5+ cations modified by the strongly basic alkali oxide species. (author)

Hysteresis Phenomena in Sulfur Dioxide Oxidation over Supported Vanadium Catalysts

DEFF Research Database (Denmark)

Masters, Stephen G.; Eriksen, Kim Michael; Fehrmann, Rasmus

1997-01-01

Catalyst deactivation and hysteresis behavior in industrial SO2-oxidation catalysts have been studied in the temperature region 350-480 C by combined in situ EPR spectroscopy and catalytic activity measurements. The feed gas composition simulated sulfuric acid synthesis gas and wet/dry de......NOx'ed flue gas. The vanadium (IV) compound K4(VO)3(SO4)5 precipitated during all the investigated conditions hence causing catalyst deactivation. Hysteresis behavior of both the catalytic activity and the V(IV) content was observed during reheating....

Synthesis and Evaluation of Nanostructured Gold-Iron Oxide Catalysts for the Oxidative Dehydrogenation of Cyclohexane

Science.gov (United States)

Wu, Peng

Shape-controlled iron oxide and gold-iron oxide catalysts with a cubic inverse spinel structure were studied in this thesis for the oxidative dehydrogenation of cyclohexane. The structure of iron oxide and gold-iron oxide catalysts has no major impact on their oxidative dehydrogenation activity. However, the product selectivity is influenced. Both cyclohexene and benzene are formed on bare iron oxide nanoshapes, while benzene is the only dehydrogenation product in the presence of gold. The selectivity of benzene over CO2 depends strongly on the stability of the iron oxide support and the gold-support interaction. The highest benzene yield has been observed on gold-iron oxide octahedra. {111}-bound nanooctahedra are highly stable in reaction conditions at 300 °C, while {100}-bound nanocubes start to sinter above 250 °C. The highest benzene yield has been observed on gold-iron oxide nanooctahedra, which are likely to have gold atoms, and few-atom gold clusters strongly-bound on their surface. Cationic gold appears to be the active site for benzene formation. An all-organic method to prepare Au-FeOx nano-catalysts is needed due to the inconvenience of the half-organic, half-inorganic synthesis process discussed above. Several methods from the literature to prepare gold-iron oxide nanocomposites completely in organic solvents were reviewed and followed. FeOx Au synthesis procedures in literatures are initially designed for a Au content of over 70%. This approach was tried here to prepare composites with a much lower Au content (2-5 atom. %). Heat treatment is required to bond Au and FeOx NPs in the organic-phase syntheses. Au-FeOx-4 was obtained as a selective catalyst for the ODH of cyclohexane. A Audelta+ peak is observed in the UV-Vis spectrum of sample Au-FeOx-4. This different Au delta+ form may be cationic Au nano-clusters interacting with the FeOx support. It has been demonstrated that cationic gold is responsible for dehydrogenation behavior. Furthermore, the

Cobalt oxide-based catalysts deposited by cold plasma for proton exchange membrane fuel cells

Energy Technology Data Exchange (ETDEWEB)

Kazimierski, P.; Jozwiak, L.; Sielski, J.; Tyczkowski, J., E-mail: jacek.tyczkowski@p.lodz.pl

2015-11-02

In proton exchange membrane fuel cells (PEMFC), both the anodic hydrogen oxidation reaction and the cathodic oxygen reduction reaction (ORR) require appropriate catalysts. So far, platinum-based catalysts are still the best option for this purpose. However, because these catalysts are too expensive for making commercially viable fuel cells, extensive research over the past decade has focused on developing noble metal-free alternative catalysts. In this paper, an approach based on cobalt oxide films fabricated by plasma-enhanced metal-organic chemical vapor deposition is presented. Such a material can be used to prepare catalysts for ORR in PEMFC. The films containing CoO{sub X} were deposited on a carbon paper thereby forming the electrode. Morphology and atomic composition of the films were investigated by scanning electron microscopy and energy-dispersive X-ray spectroscopy, respectively. The possibility of their application as the electro-catalyst for ORR in PEMFC was investigated and the electro-catalytic activities were evaluated by the electrochemical measurements and single cell tests. It was found that the fuel cell with Pt as the anode catalyst and CoO{sub X} deposit as the cathode catalyst was characterized by the open circuit voltage of 635 mV, Tafel slope of approx. 130 mV/dec and the maximum power density of 5.3 W/m{sup 2}. - Highlights: • Cobalt oxide catalyst for proton exchange membrane fuel cells was plasma deposited. • The catalyst exhibits activity for the oxygen reduction reaction. • Morphology and atomic composition of the catalyst were determined.

Low-temperature carbon monoxide oxidation over zirconia-supported CuO–CeO{sub 2} catalysts: Effect of zirconia support properties

Energy Technology Data Exchange (ETDEWEB)

Moretti, Elisa, E-mail: elisa.moretti@unive.it [Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca' Foscari Venezia, INSTM Venice Research Unit, Via Torino 155/B, 30172 Mestre Venezia (Italy); Molina, Antonia Infantes [Departamento de Química Inorgánica, Cristalografía y Mineralogía, Facultad de Ciencias, Universidad de Málaga, Campus de Teatinos, 29071 Málaga (Spain); Sponchia, Gabriele; Talon, Aldo; Frattini, Romana [Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca' Foscari Venezia, INSTM Venice Research Unit, Via Torino 155/B, 30172 Mestre Venezia (Italy); Rodriguez-Castellon, Enrique [Departamento de Química Inorgánica, Cristalografía y Mineralogía, Facultad de Ciencias, Universidad de Málaga, Campus de Teatinos, 29071 Málaga (Spain); Storaro, Loretta [Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca' Foscari Venezia, INSTM Venice Research Unit, Via Torino 155/B, 30172 Mestre Venezia (Italy)

2017-05-01

Highlights: • CuO-CeO{sub 2}/ZrO{sub 2} materials were investigated in the low temperature CO oxidation. • High surface area ZrO{sub 2} synthetized by sol-gel method. • Low ZrO{sub 2} surface area synthetized by fast precipitation. • Sol-gel samples showed, after impregnation, a severe decrease of surface area. • CuO-CeO{sub 2}/ZrO{sub 2} with precipitated ZrO{sub 2} led to a very active catalyst. - Abstract: A study was conducted to investigate the effect of the preparation route of ZrO{sub 2} in CuO–CeO{sub 2}/ZrO{sub 2} catalysts for the oxidation of carbon monoxide at low temperature (COX). Four ZrO{sub 2} supports were synthetized via either type sol-gel methodology or precipitation. The final Cu-Ce-Zr oxide catalysts were prepared by incipient wetness co-impregnation with copper and cerium solutions (with a loading of 6 wt% of CuO and 20 wt% of CeO{sub 2}). The catalyst crystalline phases, texture and active species reducibility were determined by XRD, N{sub 2} physisorption at −196 °C and H{sub 2}-TPR, respectively; meanwhile the surface composition and copper-cerium electronic states were studied by XPS. The catalytic activity was evaluated in the oxidation of CO to CO{sub 2}, in the 40–215 °C temperature range. Catalytic results evidenced that the samples prepared by a sol-gel methodology showed, after the impregnation, a severe decrease of specific surface area and pore volume attributable to a wide degree of pore blockage caused by the presence of metal oxide particles and a collapse of the structure partially burying the active sites. A simple co-impregnation of a zirconia support, obtained through facile and fast precipitation, provided instead a catalyst with very good redox properties and high dispersion of the active phases, which completely oxidizes CO in the range 115–215 °C with T{sub 50} of 65 °C. This higher observed activity was ascribed to the formation of a larger fraction of highly dispersed and easily reducible Cu

A mechanistic study on the oxidative coupling of methane over lithium doped magnesium oxide catalysts

NARCIS (Netherlands)

Geerts, J.W.M.H.; Kasteren, van J.M.N.; Wiele, van der K.; Imarisio, G.; Frias, M.; Berntgen, J.M.

1988-01-01

To elucidate the importance of various reaction steps in the oxidative convers ion of methane, experiments were carried out with three reaction products: ethane, ethylene and carbon monoxide. These products were studied seperately, in oxidation experiments with and without a catalyst. Moreover , the

Room temperature aerobic oxidation of amines by a nanocrystalline ruthenium oxide pyrochlore nafion composite catalyst.

Science.gov (United States)

Venkatesan, Shanmuganathan; Kumar, Annamalai Senthil; Lee, Jyh-Fu; Chan, Ting-Shan; Zen, Jyh-Myng

2012-05-14

The aerobic oxidation of primary amines to their respective nitriles has been carried out at room temperature using a highly reusable nanocrystalline ruthenium oxide pyrochlore Nafion composite catalyst (see figure). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Selective Oxidation of Styrene to Benzaldehyde by Co-Ag Codoped ZnO Catalyst and H2O2 as Oxidant

Directory of Open Access Journals (Sweden)

Abderrazak Aberkouks

2018-01-01

Full Text Available Various ratio of Co-Ag supported on ZnO have been evaluated in the selective catalytic oxidation of styrene to benzaldehyde, using H2O2 as an oxidant. The catalysts were prepared by a sol-gel process and were characterized using XRD, FT-IR, TG-DTG, BET, and SEM/EDX. The performance of the prepared catalyst was investigated under different parameters such as solvent, temperature, substrate/oxidant molar ratios, reaction time, and doping percent. The Zn1−x−yAgxCoyO catalysts exhibit a good activity and a high selectivity towards benzaldehyde (95% with the formation of only 5% of acetophenone.

Influence of vanadium oxidation states on the performance of V-Mg-Al mixed-oxide catalysts for the oxidative dehydrogenation of propane

International Nuclear Information System (INIS)

Schacht, L.; Navarrete, J.; Schacht, P.; Ramirez, M. A.

2010-01-01

V-Mg-Al mixed-oxide catalysts for oxidative dehydrogenation of propane were prepared by thermal decomposition of Mg-Al-layered double hydroxides with vanadium interlayer doping. The obtained catalysts were tested for the oxidative dehydrogenation of propane, obtaining good results in catalytic activity (conversion 16.55 % and selectivity 99.97 %) Results indicated that catalytic performance of these materials depends on how vanadium is integrated in the layered structure, which is determined by the Mg/Al ratio. Vanadium interlayer doping modifies the oxidation state of vanadium and consequently catalytic properties. Surface properties were studied by X-ray photoelectron spectroscopic and diffuse reflectance, UV-visible spectroscopy, and temperature programmed reduction. The analyses provided information about the oxidation state, before and after the reaction. From these results, it is suggested that selectivity to propylene and catalytic activity depend mainly of vanadium oxidation state. (Author)

Influence of vanadium oxidation states on the performance of V-Mg-Al mixed-oxide catalysts for the oxidative dehydrogenation of propane

Energy Technology Data Exchange (ETDEWEB)

Schacht, L. [IPN, Escuela Superior de Fisica y Matematicas, Departamento de Ciencia de Materiales, Av. IPN s/n, Edificio 9, Col. Lindavista, 07738 Mexico D. F. (Mexico); Navarrete, J.; Schacht, P.; Ramirez, M. A., E-mail: pschacha@imp.m [Instituto Mexicano del Petroleo, Programa de Ingenieria Molecular, Eje Central Lazaro Cardenas No. 152, 07730 Mexico D. F. (Mexico)

2010-07-01

V-Mg-Al mixed-oxide catalysts for oxidative dehydrogenation of propane were prepared by thermal decomposition of Mg-Al-layered double hydroxides with vanadium interlayer doping. The obtained catalysts were tested for the oxidative dehydrogenation of propane, obtaining good results in catalytic activity (conversion 16.55 % and selectivity 99.97 %) Results indicated that catalytic performance of these materials depends on how vanadium is integrated in the layered structure, which is determined by the Mg/Al ratio. Vanadium interlayer doping modifies the oxidation state of vanadium and consequently catalytic properties. Surface properties were studied by X-ray photoelectron spectroscopic and diffuse reflectance, UV-visible spectroscopy, and temperature programmed reduction. The analyses provided information about the oxidation state, before and after the reaction. From these results, it is suggested that selectivity to propylene and catalytic activity depend mainly of vanadium oxidation state. (Author)

Methanol oxidation at platinum electrodes in acid solution: comparison between model and real catalysts

Directory of Open Access Journals (Sweden)

A. V. TRIPKOVIC

2006-12-01

Full Text Available Methanol oxidation in acid solution was studied at platinum single crystals, Pt(hkl, as the model catalyst, and at nanostructural platinum supported on high surface area carbon, Pt/C, as the real catalyst. The linear extrapolation method was used to determine the beginning of hydroxyl anion adsorption. Structural sensitivity of the adsorption was proved and a correlation with the onset of the methanol oxidation current was established at all catalysts. Bisulfate and chloride anions were found to decrease the methanol oxidation rate, but probably did not influence the reaction parth. The specific activity for the reaction increased in the sequence Pt(110 < Pt/C < Pt(111, suggesting that the activity of the supported Pt catalyst can be correlated with the activities of the dominating crystal planes on its surface.

Study of ternary-component bismuth molybdate catalysts by 18O2 tracer in the oxidation of propylene to acrolein

International Nuclear Information System (INIS)

Ueda, W.; Moro-oka, Y.; Ikawa, T.

1981-01-01

Participation of lattice oxide ions of ternary-component bismuth molybdate catalysts M-Bi-Mo-O (M = Ni, Co, Mg, Mn, Ca, Sr, Ba, and Pb) was investigated using the 18 O 2 tracer in the selective oxidation of propylene to acrolein. The participation of the lattice oxide ions in the oxidation is prominent on every catalyst but the extent of the participation varies significantly depending on the structure of the catalyst. Only lattice oxide ions in the bismuth molybdate phase are incorporated into the oxidized products on the catalysts (M = Ni, Co, Mg, and Mn) where M have smaller ionic radius than Bi 3+ ; catalyst particles are composed of a shell of bismuth molybdates and a core of MMoO 4 . On the other hand, whole oxide ions in the active particles are involved in the oxidation on catalysts having a scheelite-type structure (M = Ca, Sr, Ba, and Pb) where M has a comparable ionic radius to Bi 3+

New Catalysts for Direct Methanol Oxidation Fuel Cells

Energy Technology Data Exchange (ETDEWEB)

Adzic, Radoslav

1998-08-01

A new class of efficient electrocatalytic materials based on platinum - metal oxide systems has been synthetized and characterized by several techniques. Best activity was found with NiWO{sub 4}-, CoWO{sub 4}-, and RuO{sub 2}- sr¡pported platinum catalysts. A very similar activity at room temperature was observed with the electrodes prepared with the catalyst obtained from International Fuel Cells Inc. for the same Pt loading. Surprisingly, the two tungstates per se show a small activity for methanol oxidation without any Pt loading. Synthesis of NiWO{sub 4} and CoWO{sub 4} were carried out by solid-state reactions. FTIR spectroscopy shows that the tungstates contain a certain amount of physically adsorbed water even after heating samples at 200{degrees}C. A direct relationship between the activity for methanol oxidation and the amount of adsorbed water on those oxides has been found. The Ru(0001) single crystal shows a very small activity for CO adsorption and oxidation, in contrast to the behavior of polycrystalline Ru. In situ extended x-ray absorption fine structure spectroscopy (EXAFS) and x-ray absorption near edge spectroscopy (XANES) showed that the OH adsorption on Ru in the Pt-Ru alloy appears to be the limiting step in methanol oxidation. This does not occur for Pt-RuO{SUB 2} electrocatalyst, which explains its advantages over the Pt-Ru alloys. The IFCC electrocatalyst has the properties of the Pt-Ru alloy.

Oxidation of 4-methoxy-1-naphthol on promoted platinum catalysts

CSIR Research Space (South Africa)

Maphoru, MV

2017-07-01

Full Text Available , July 2017, Volume 58, Issue 4, pp 441–447 Oxidation of 4-methoxy-1-naphthol on promoted platinum catalysts M. V. Maphoru J. Heveling S. Kesavan Pillai Abstract Oxidative coupling of naphthols is a useful method for the formation of new...

Alternative deNOx catalysts and technologies

DEFF Research Database (Denmark)

Due-Hansen, Johannes

The present thesis entitled Alternative deNOx Catalysts and technologies revolves around the topic of removal of nitrogen oxides. Nitrogen oxides, NOx, are unwanted byproducts formed during combustion (e.g. in engines or power plants). If emitted to the atmosphere, they are involved...... in the formation of acid rain and photochemical smog. Some basic concepts and reactions regarding the formation and removal of NOx are presented in chapter 1 and 2. Two approaches are undertaken in the present work to reduce the emission of NOx: by means of catalytic removal, and by NO absorption in ionic liquids....... The commercial catalyst used for the selective catalytic reduction (SCR) of nitrogen oxides exhibits high activity and selectivity towards N2. However, the vanadia-titania-based catalyst used is very sensitive to deactivation by alkali-species (primarily potassium), which are typically present in high amounts...

ENVIRONMENTAL TECHNOLOGY VERIFICATION, TEST REPORT OF MOBILE SOURCE EMISSIONS CONTROL DEVICES/CLEAN DIESEL TECHNOLOGIES FUEL BORNE CATALYST WITH CLEANAIR SYSTEM'S DIESEL OXIDATION CATALYST

Science.gov (United States)

The Environmental Technology Verification report discusses the technology and performance of the Fuel-Borne Catalyst with CleanAir System's Diesel Oxidation Catalyst manufactured by Clean Diesel Technologies, Inc. The technology is a fuel-borne catalyst used in ultra low sulfur d...

[Synergetic effects of silicon carbide and molecular sieve loaded catalyst on microwave assisted catalytic oxidation of toluene].

Science.gov (United States)

Wang, Xiao-Hui; Bo, Long-Li; Liu, Hai-Nan; Zhang, Hao; Sun, Jian-Yu; Yang, Li; Cai, Li-Dong

2013-06-01

Molecular sieve loaded catalyst was prepared by impregnation method, microwave-absorbing material silicon carbide and the catalyst were investigated for catalytic oxidation of toluene by microwave irradiation. Research work examined effects of silicon carbide and molecular sieve loading Cu-V catalyst's mixture ratio as well as mixed approach changes on degradation of toluene, and characteristics of catalyst were measured through scanning electron microscope, specific surface area test and X-ray diffraction analysis. The result showed that the fixed bed reactor had advantages of both thermal storage property and low-temperature catalytic oxidation when 20% silicon carbide was filled at the bottom of the reactor, and this could effectively improve the utilization of microwave energy as well as catalytic oxidation efficiency of toluene. Under microwave power of 75 W and 47 W, complete-combustion temperatures of molecular sieve loaded Cu-V catalyst and Cu-V-Ce catalyst to toluene were 325 degrees C and 160 degrees C, respectively. Characteristics of the catalysts showed that mixture of rare-earth element Ce increased the dispersion of active components in the surface of catalyst, micropore structure of catalyst effectively guaranteed high adsorption capacity for toluene, while amorphous phase of Cu and V oxides increased the activity of catalyst greatly.

Catalytic Activity and Deactivation of SO2 Oxidation Catalysts in Simulated Power Plant Flue Gases

DEFF Research Database (Denmark)

Masters, Stephen G.; Chrissanthopoulos, Asthanassios; Eriksen, Kim Michael

1997-01-01

The catalyst deactivation and the simultaneious formation of compounds in commercial SO2 oxidation catalysts have been studied by combined activity measurements and in situ EPR spectroscopy in the temperature range 350-480 C in wet and dry simulated power plant flue gas.......The catalyst deactivation and the simultaneious formation of compounds in commercial SO2 oxidation catalysts have been studied by combined activity measurements and in situ EPR spectroscopy in the temperature range 350-480 C in wet and dry simulated power plant flue gas....

Fe–Co/sulfonated polystyrene as an efficient and selective catalyst in heterogeneous Baeyer–Villiger oxidation reaction of cyclic ketones

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Yingting Wang

2018-02-01

Full Text Available A highly efficient catalyst Fe–Co/sulfonated polystyrene (Fe–Co/SPS was introduced and synthesized, which catalyzed BV oxidation of ketones with aqueous hydrogen peroxide to give the corresponding lactones in high yield and selectivity. Solid acid catalyst of Fe–Co/SPS has been prepared by using the 98-wt% sulfuric acid as the sulfonating agent and CoCl2 combined FeCl3 as sources of metal ions. Various physical–chemical characterizations including FT-IR, XRD, SEM and TGA, revealed that bimetallic ions Fe3+–Co2+ species in the sulfonated polystyrene framework were responsible for the catalytic activities. The BV reaction catalyzed by Fe–Co/SPS highlighted the special effects between metal ions and protonic acids as well as solvent-free heterogeneous catalytic oxidation with excellent conversion.

Structure, activity and kinetics of supported molybdenum oxide and mixed molybdenum-vanadium oxide catalysts prepared by flame spray pyrolysis for propane OHD

DEFF Research Database (Denmark)

Høj, Martin; Kessler, Thomas; Beato, Pablo

2013-01-01

reflectance UV-vis spectroscopy and evaluated as catalysts for the oxidative dehydrogenation (ODH) of propane. The results show that samples with high specific surface areas between 122 and 182 m2/g were obtained, resulting in apparent MoOx and VOx surface densities from 0.7 to 7.7 nm -2 and 1.5 to 1.9 nm-2......, respectively. Raman spectroscopy, UV-vis spectroscopy and XRD confirmed the high dispersion of molybdenum and vanadia species on γ-Al2O3 as the main crystalline phase. Only at the highest loading of 15 wt% Mo, with theoretically more than monolayer coverage, some crystalline molybdenum oxide was observed...

Modifications induced by potassium addition on chromia/alumina catalysts and their influence on the catalytic activity for the oxidative dehydrogenation of propane

International Nuclear Information System (INIS)

Rombi, E.; Gazzoli, D.; Cutrufello, M.G.; De Rossi, S.; Ferino, I.

2010-01-01

The oxidative dehydrogenation of propane was investigated on K-containing chromia/alumina catalysts, with nominal Cr and K loadings of 10 and 0-2 wt%, respectively. Their chemical composition, structure, texture, nature of surface species, redox features and surface acidity were determined. Catalytic behaviour was investigated in a continuous-flow micro-reactor under different conditions. Besides the nature and concentration of the chromium species, potassium addition was found to affect the reducibility of the catalysts as well as their acid surface features. Such modifications were found to condition the catalytic behaviour, which appeared somewhat peculiar in comparison with that of the catalytic systems reported in literature.

Partial oxidation of n- and i-pentane over promoted vanadium-phosphorus oxide catalysts

Energy Technology Data Exchange (ETDEWEB)

Zazhigalov, V.A.; Mikhajluk, B.D.; Komashko, G.A. [AN Ukrainskoj SSR, Kiev (Ukraine). Inst. Fizicheskoj Khimii

1998-12-31

It is known, that the cost of raw materials for catalytic oxidation processes is about 60% of the product price. Cheap initial compounds to produce variety of products and to replace olefins and aromatic hydrocarbons are paraffins. That is why catalytic systems which could be possibly rather efficient in selective oxidation of paraffin hydrocarbons are under very close investigation now. One of such processes in n-pentane oxidation. The obtained results on n-pentane oxidation over VPO catalysts were quite encouraging in respect of possible reach high selectivity and yield of phthalic anhydride. However, in our work it was shown that the main product of n-pentane oxidation in the presence of VPO catalytic system as well as VPMeO was maleic anhydride. Some later our results were confirmed in, where to grow the selectivity towards phthalic anhydride the Co-additive was introduced. On the basis of the proposal made before on the mechanism of paraffins conversion over the vanadyl pyrophosphate surface with their activation at the first and fourth carbon atoms, we assumed possible methylmaleic (citraconic) anhydride forming at n- and i-pentane oxidation. This assumption has been recently supported by both our and other researchers` experimental results. In it was also hypothized possible mechanistic features for phthalic anhydride forming from n-pentane. The present work deals with the results of n- and i-pentane oxidation over VPO catalysts promoted with Bi, Cs, Te, Zr. (orig.)

A Highly Practical Copper(I)/TEMPO Catalyst System for Chemoselective Aerobic Oxidation of Primary Alcohols

Science.gov (United States)

Hoover, Jessica M.; Stahl, Shannon S.

2011-01-01

Aerobic oxidation reactions have been the focus of considerable attention, but their use in mainstream organic chemistry has been constrained by limitations in their synthetic scope and by practical factors, such as the use of pure O2 as the oxidant or complex catalyst synthesis. Here, we report a new (bpy)CuI/TEMPO catalyst system that enables efficient and selective aerobic oxidation of a broad range of primary alcohols, including allylic, benzylic and aliphatic derivatives, to the corresponding aldehydes using readily available reagents, at room temperature with ambient air as the oxidant. The catalyst system is compatible with a wide range of functional groups and the high selectivity for 1° alcohols enables selective oxidation of diols that lack protecting groups. PMID:21861488

Manganese oxide octahedral molecular sieve K-OMS-2 as catalyst in post plasma-catalysis for trichloroethylene degradation in humid air

International Nuclear Information System (INIS)

Nguyen Dinh, M.T.; Giraudon, J.-M.; Vandenbroucke, A.M.; Morent, R.; De Geyter, N.; Lamonier, J.-F.

2016-01-01

Highlights: • Post plasma catalysis: negative DC glow discharge combined with a cryptomelane. • The α-MnO_2 catalyst totally decomposes the NTP generated ozone. • Active oxygen oxidizes the end-up plasma VOC by-products. - Abstract: The total oxidation of trichloroethylene (TCE) in air at low relative humidity (RH = 10%) in the presence of CO_2 (520 ppmv) was investigated in function of energy density using an atmospheric pressure negative DC luminescent glow discharge combined with a cryptomelane catalyst positioned downstream of the plasma reactor at a temperature of 150 °C. When using Non-Thermal Plasma (NTP) alone, it is found a low COx (x = 1–2) yield in agreement with the detection of gaseous polychlorinated by-products in the outlet stream as well as ozone which is an harmful pollutant. Introduction of cryptomelane enhanced trichloroethylene removal, totally inhibited plasma ozone formation and increased significantly the COx yield. The improved performances of the hybrid system were mainly ascribed to the total destruction of plasma generated ozone on cryptomelane surface to produce active oxygen species. Consequently these active oxygen species greatly enhanced the abatement of the plasma non-reacted TCE and completely destroyed the hazardous plasma generated polychlorinated intermediates. The facile redox of Mn species associated with oxygen vacancies and mobility as well as the textural properties of the catalyst might also contribute as a whole to the efficiency of the process.

Manganese oxide octahedral molecular sieve K-OMS-2 as catalyst in post plasma-catalysis for trichloroethylene degradation in humid air

Energy Technology Data Exchange (ETDEWEB)

Nguyen Dinh, M.T. [Université Lille, Sciences et Technologies, Unité de Catalyse et Chimie du Solide UMR CNRS UCCS 8181, 59655 Villeneuve d’Ascq (France); The University of Da-Nang, University of Science and Technology, 54, Nguyen Luong Bang, Da-Nang (Viet Nam); Giraudon, J.-M., E-mail: jean-marc.giraudon@univ-lille1.fr [Université Lille, Sciences et Technologies, Unité de Catalyse et Chimie du Solide UMR CNRS UCCS 8181, 59655 Villeneuve d’Ascq (France); Vandenbroucke, A.M.; Morent, R.; De Geyter, N. [Ghent University, Faculty of Engineering and Architecture, Department of Applied Physics, Research Unit Plasma Technology, Sint-Pietersnieuwstraat 41, 9000 Ghent (Belgium); Lamonier, J.-F. [Université Lille, Sciences et Technologies, Unité de Catalyse et Chimie du Solide UMR CNRS UCCS 8181, 59655 Villeneuve d’Ascq (France)

2016-08-15

Highlights: • Post plasma catalysis: negative DC glow discharge combined with a cryptomelane. • The α-MnO{sub 2} catalyst totally decomposes the NTP generated ozone. • Active oxygen oxidizes the end-up plasma VOC by-products. - Abstract: The total oxidation of trichloroethylene (TCE) in air at low relative humidity (RH = 10%) in the presence of CO{sub 2} (520 ppmv) was investigated in function of energy density using an atmospheric pressure negative DC luminescent glow discharge combined with a cryptomelane catalyst positioned downstream of the plasma reactor at a temperature of 150 °C. When using Non-Thermal Plasma (NTP) alone, it is found a low COx (x = 1–2) yield in agreement with the detection of gaseous polychlorinated by-products in the outlet stream as well as ozone which is an harmful pollutant. Introduction of cryptomelane enhanced trichloroethylene removal, totally inhibited plasma ozone formation and increased significantly the COx yield. The improved performances of the hybrid system were mainly ascribed to the total destruction of plasma generated ozone on cryptomelane surface to produce active oxygen species. Consequently these active oxygen species greatly enhanced the abatement of the plasma non-reacted TCE and completely destroyed the hazardous plasma generated polychlorinated intermediates. The facile redox of Mn species associated with oxygen vacancies and mobility as well as the textural properties of the catalyst might also contribute as a whole to the efficiency of the process.

Reactivation of a Tin-Oxide-Containing Catalyst

Science.gov (United States)

Hess, Robert; Sidney, Barry; Schryer, David; Miller, Irvin; Miller, George; Upchurch, Bill; Davis, Patricia; Brown, Kenneth

2010-01-01

The electrons in electric-discharge CO2 lasers cause dissociation of some CO2 into O2 and CO, and attach themselves to electronegative molecules such as O2, forming negative O2 ions, as well as larger negative ion clusters by collisions with CO or other molecules. The decrease in CO2 concentration due to dissociation into CO and O2 will reduce the average repetitively pulsed or continuous wave laser power, even if no disruptive negative ion instabilities occur. Accordingly, it is the primary object of this invention to extend the lifetime of a catalyst used to combine the CO and O2 products formed in a laser discharge. A promising low-temperature catalyst for combining CO and O2 is platinum on tin oxide (Pt/SnO2). First, the catalyst is pretreated by a standard procedure. The pretreatment is considered complete when no measurable quantity of CO2 is given off by the catalyst. After this standard pretreatment, the catalyst is ready for its low-temperature use in the sealed, high-energy, pulsed CO2 laser. However, after about 3,000 minutes of operation, the activity of the catalyst begins to slowly diminish. When the catalyst experiences diminished activity during exposure to the circulating gas stream inside or external to the laser, the heated zone surrounding the catalyst is raised to a temperature between 100 and 400 C. A temperature of 225 C was experimentally found to provide an adequate temperature for reactivation. During this period, the catalyst is still exposed to the circulating gas inside or external to the laser. This constant heating and exposing the catalyst to the laser gas mixture is maintained for an hour. After heating and exposing for an appropriate amount of time, the heated zone around the catalyst is allowed to return to the nominal operating temperature of the CO2 laser. This temperature normally resides in the range of 23 to 100 C. Catalyst activity can be measured as the percentage conversion of CO to CO2. In the specific embodiment

Perovskite Catalysts—A Special Issue on Versatile Oxide Catalysts

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Yu-Chuan Lin

2014-08-01

Full Text Available Perovskite-type catalysts have been prominent oxide catalysts for many years due to attributes such as flexibility in choosing cations, significant thermal stability, and the unique nature of lattice oxygen. Nearly 90% metallic elements of the Periodic Table can be stabilized in perovskite’s crystalline framework [1]. Moreover, by following the Goldschmidt rule [2], the A- and/or B-site elements can be partially substituted, making perovskites extremely flexible in catalyst design. One successful example is the commercialization of noble metal-incorporated perovskites (e.g., LaFe0.57Co0.38Pd0.05O3 for automotive emission control used by Daihatsu Motor Co. Ltd. [3]. Thus, growing interest in, and application of perovskites in the fields of material sciences, heterogeneous catalysis, and energy storage have prompted this Special Issue on perovskite catalysts. [...

Preferential synthesis of (6,4) single-walled carbon nanotubes by controlling oxidation degree of Co catalyst.

Science.gov (United States)

Xu, Bin; Kaneko, Toshiro; Shibuta, Yasushi; Kato, Toshiaki

2017-09-11

Chirality-selective synthesis of single-walled carbon nanotubes (SWNTs) has been a research goal for the last two decades and is still challenging due to the difficulty in controlling the atomic structure in the one-dimensional material. Here, we develop an optimized approach for controlling the chirality of species by tuning the oxidation degree of Co catalyst. Predominant synthesis of (6,4) SWNTs is realized for the first time. The detailed mechanism is investigated through a systematic experimental study combined with first-principles calculations, revealing that the independent control of tube diameter and chiral angle achieved by changing the binding energy between SWNTs (cap and tube edge) and catalyst causes a drastic transition of chirality of SWNTs from (6,5) to (6,4). Since our approach of independently controlling the diameter and chiral angle can be applied to other chirality species, our results can be useful in achieving the on-demand synthesis of specific-chirality SWNTs.

Fundamental Studies of Butane Oxidation over Model-Supported Vanadium Oxide Catalysts: Molecular Structure-Reactivity Relationships

NARCIS (Netherlands)

Wachs, I.E.; Jehng, J.M.; Deo, G.; Weckhuysen, B.M.; Guliants, V.V.; Benziger, J.B.; Sundaresan, S.

1997-01-01

The oxidation of n-butane to maleic anhydride was investigated over a series of model-supported vanadia catalysts where the vanadia phase was present as a two-dimensional metal oxide overlayer on the different oxide supports (TiO2, ZrO2, CeO2, Nb2O5, Al2O3, and SiO2). No correlation was found

A genetically optimized kinetic model for ethanol electro-oxidation on Pt-based binary catalysts used in direct ethanol fuel cells

Science.gov (United States)

Sánchez-Monreal, Juan; García-Salaberri, Pablo A.; Vera, Marcos

2017-09-01

A one-dimensional model is proposed for the anode of a liquid-feed direct ethanol fuel cell. The complex kinetics of the ethanol electro-oxidation reaction is described using a multi-step reaction mechanism that considers free and adsorbed intermediate species on Pt-based binary catalysts. The adsorbed species are modeled using coverage factors to account for the blockage of the active reaction sites on the catalyst surface. The reaction rates are described by Butler-Volmer equations that are coupled to a one-dimensional mass transport model, which incorporates the effect of ethanol and acetaldehyde crossover. The proposed kinetic model circumvents the acetaldehyde bottleneck effect observed in previous studies by incorporating CH3CHOHads among the adsorbed intermediates. A multi-objetive genetic algorithm is used to determine the reaction constants using anode polarization and product selectivity data obtained from the literature. By adjusting the reaction constants using the methodology developed here, different catalyst layers could be modeled and their selectivities could be successfully reproduced.

Oxidation of Catechol using Titanium Silicate (TS-1 Catalyst: Modeling and Optimization

Directory of Open Access Journals (Sweden)

Sonali Sengupta

2013-12-01

Full Text Available The oxidation of catechol was studied in an eco-friendly process with commercial titanium silicate-1 (TS-1 catalyst and hydrogen peroxide as oxidant in absence of all mass transfer effects. The process was opti-mized by Box-Behnken design in terms of three independent process variables such as reaction tempera-ture, moles of hydrogen peroxide per mole of catechol and catalyst amount whose optimum values of the process variables were found to be 60 °C, 13.2 and 1.24 g respectively for maximum conversion of 75.8 %. The effects of different process parameters such as mole ratio of hydrogen peroxide to catechol, catalyst par-ticle size, catalyst amount, temperature and reaction time were studied. A pseudo first order kinetic model was fitted with the experimental rate data. The apparent activation energy for the reaction was found to be 11.37 kJ/mole.  © 2013 BCREC UNDIP. All rights reservedReceived: 22nd April 2013; Revised: 25th October 2013; Accepted: 1st November 2013[How to Cite: Sengupta, S., Ghosal, D., Basu, J.K. (2013. Oxidation of Catechol using Titanium Silicate (TS-1 Catalyst: Modeling and Optimization. Bulletin of Chemical Reaction Engineering & Catalysis, 8 (2: 167-177. (doi:10.9767/bcrec.8.2.4759.167-177][Permalink/DOI: http://dx.doi.org/10.9767/bcrec.8.2.4759.167-177

Polyethers for biomedical applications. Polymerization of propylene oxide by organozinc/organotin catalysts

NARCIS (Netherlands)

Bots, Jan Gert; van der Does, L.; Bantjes, Adriaan; Broersma, Jaap

1987-01-01

The polymerization of propylene oxide to obtain a high-molecular-weight polymer with an atactic structure required for the application as artificial blood vessels was investigated using combinations of organozinc and organotin compounds as catalyst. The composition of the most active catalyst,

Simple Copper Catalysts for the Aerobic Oxidation of Amines: Selectivity Control by the Counterion.

Science.gov (United States)

Xu, Boran; Hartigan, Elizabeth M; Feula, Giancarlo; Huang, Zheng; Lumb, Jean-Philip; Arndtsen, Bruce A

2016-12-19

We describe the use of simple copper-salt catalysts in the selective aerobic oxidation of amines to nitriles or imines. These catalysts are marked by their exceptional efficiency, operate at ambient temperature and pressure, and allow the oxidation of amines without expensive ligands or additives. This study highlights the significant role counterions can play in controlling selectivity in catalytic aerobic oxidations. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

NO oxidation on Zeolite Supported Cu Catalysts: Formation and Reactivity of Surface Nitrates

Energy Technology Data Exchange (ETDEWEB)

Chen, Hai-Ying; Wei, Zhehao; Kollar, Marton; Gao, Feng; Wang, Yilin; Szanyi, Janos; Peden, Charles HF

2016-04-18

The comparative activities of a small-pore Cu-CHA and a large-pore Cu-BEA catalyst for the selective catalytic reduction (SCR) of NOx with NH3, and for the oxidation of NO to NO2 and the subsequent formation of surface nitrates were investigated. Although both catalysts are highly active in SCR reactions, they exhibit very low NO oxidation activity. Furthermore, Cu-CHA is even less active than Cu-BEA in catalyzing NO oxidation but is clearly more active for SCR reactions. Temperature-programed desorption (TPD) experiments following the adsorption of (NO2 + NO + O2) with different NO2:NO ratios reveal that the poor NO oxidation activity of the two catalysts is not due to the formation of stable surface nitrates. On the contrary, NO is found to reduce and decompose the surface nitrates on both catalysts. To monitor the reaction pathways, isotope exchange experiments were conducted by using 15NO to react with 14N-nitrate covered catalyst surfaces. The evolution of FTIR spectra during the isotope exchange process demonstrates that 14N-nitrates are simply displaced with no formation of 15N-nitrates on the Cu-CHA sample, which is clearly different from that observed on the Cu-BEA sample where formation of 15N-nitrates is apparent. The results suggest that the formal oxidation state of N during the NO oxidation on Cu-CHA mainly proceeds from its original +2 to a +3 oxidation state, whereas reaching a higher oxidation state for N, such as +4 or +5, is possible on Cu-BEA. The authors at PNNL gratefully acknowledge the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Office for the support of this work. The research described in this paper was performed at the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle.

Hydroformylation of 1-Hexene over Rh/Nano-Oxide Catalysts

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Sari Suvanto

2013-03-01

Full Text Available The effect of nanostructured supports on the activity of Rh catalysts was studied by comparing the catalytic performance of nano- and bulk-oxide supported Rh/ZnO, Rh/SiO2 and Rh/TiO2 systems in 1-hexene hydroformylation. The highest activity with 100% total conversion and 96% yield of aldehydes was obtained with the Rh/nano-ZnO catalyst. The Rh/nano-ZnO catalyst was found to be more stable and active than the corresponding rhodium catalyst supported on bulk ZnO. The favorable morphology of Rh/nano-ZnO particles led to an increased metal content and an increased number of weak acid sites compared to the bulk ZnO supported catalysts. Both these factors favored the improved catalytic performance. Improvements of catalytic properties were obtained also with the nano-SiO2 and nano-TiO2 supports in comparison with the bulk supports. All of the catalysts were characterized by scanning electron microscope (SEM, inductively coupled plasma mass spectrometry (ICP-MS, BET, powder X-ray diffraction (PXRD and NH3- temperature-programmed desorption (TPD.

Bio-dissolution of Ni, V and Mo from spent petroleum catalyst using iron oxidizing bacteria.

Science.gov (United States)

Pradhan, Debabrata; Kim, Dong J; Roychaudhury, Gautam; Lee, Seoung W

2010-01-01

Bioleaching studies of spent petroleum catalyst containing Ni, V and Mo were carried out using iron oxidizing bacteria. Various leaching parameters such as Fe(II) concentration, pulp density, pH, temperature and particle size were studied to evaluate their effects on the leaching efficiency as well as the kinetics of dissolution. The percentage of leaching of Ni and V were higher than Mo. The leaching process followed a diffusion controlled model and the product layer was observed to be impervious due to formation of ammonium jarosite (NH(4))Fe(3)(SO(4))(2)(OH)(6). Apart from this, the lower leaching efficiency of Mo was due to a hydrophobic coating of elemental sulfur over Mo matrix in the spent catalyst. The diffusivities of the attacking species for Ni, V and Mo were also calculated.

Methane oxidation over noble metal catalysts as related to controlling natural gas vehicle exhaust emissions

International Nuclear Information System (INIS)

Oh, S.H.; Mitchell, P.J.; Siewert, R.M.

1992-01-01

Natural gas has considerable potential as an alternative automotive fuel. This paper reports on methane, the principal hydrocarbon species in natural-gas engine exhaust, which has extremely low photochemical reactivity but is a powerful greenhouse gas. Therefore, exhaust emissions of unburned methane from natural-gas vehicles are of particular concern. This laboratory reactor study evaluates noble metal catalysts for their potential in the catalytic removal of methane from natural-gas vehicle exhaust. Temperature run-up experiments show that the methane oxidation activity decreases in the order Pd/Al 2 O 3 > Rh/Al 2 O 3 > Pt/Al 2 O 3 . Also, for all the noble metal catalysts studied, methane conversion can be maximized by controlling the O 2 concentration of the feedstream at a point somewhat rich (reducing) of stoichiometry

Kinetics of the reduction of uranium oxide catalysts

International Nuclear Information System (INIS)

Heynen, H.W.G.; Camp-van Berkel, M.M.; Bann, H.S. van der

1977-01-01

The reduction of uranium oxide and uranium oxide on alumina catalysts by ethylbenzene and by hydrogen has been studied in a thermobalance. Ethylbenzene mole fractions between 0.0026 and 0.052 and hydrogen mole fractions between 0.1 and 0.6 were applied at temperatures of 425--530 0 C. During the reduction the uranium oxides are converted into UO 2 . The rate of reduction of pure uranium oxide appears to be constant in the composition region UO/sub 2.6/-UO/sub 2.25/. The extent of this region is independent of the concentration of the reducing agents and of the reaction temperature. The constant rate is explained in terms of a constant oxygen pressure which is in equilibrium with the two solid phases, U 3 O/sub 8-x/ and U 4 O 9 . The reduction rate is first order in hydrogen and zero order in ethylbenzene with activation energies of 120 and 190 kJ mol -1 , respectively. Oxygen diffusion through the lattice is probably not rate limiting. The reduction behavior of uranium oxide on alumina is different from that of pure uranium oxide; the rate of reduction continuously decreases with increasing degree of reduction. An explanation for this behavior has been given by visualizing this catalyst as a set of isolated uranium oxide crystallites with a relative wide variation of diameters, in an alumina matrix. At the beginning of the reduction, carbon dioxide and water are the only reaction products. Thereafter, benzene is found as well and, finally, at U/O ratios below 2.25, styrene also appears in the reactor outlet

Samarium-modified vanadium phosphate catalyst for the selective oxidation of n-butane to maleic anhydride

International Nuclear Information System (INIS)

Wu, Hua-Yi; Wang, Hai-Bo; Liu, Xin-Hua; Li, Jian-Hui; Yang, Mei-Hua; Huang, Chuan-Jing; Weng, Wei-Zheng; Wan, Hui-Lin

2015-01-01

Graphical abstract: The addition of a small amount of Sm into VPO catalyst brought about great changes in its physicochemical properties such as surface area, surface morphology, phase composition and redox property, thus leading to a higher catalytic performance in the selective oxidation of n-butane to maleic anhydride, as compared to the undoped VPO catalyst. - Highlights: • The addition of Sm leads to great changes in the structure of VPO catalyst. • Sm improves performance of VPO for oxidation of n-butane to maleic anhydride. • Catalytic performance is closely related to structure of VPO catalyst. - Abstract: A series of samarium-modified vanadium phosphate catalysts were prepared and studied in selective oxidation of n-butane to maleic anhydride. The catalytic evaluation showed that Sm modification significantly increased the overall n-butane conversion and intrinsic activity. N 2 -adsorption, XRD, SEM, Raman, XPS, EPR and H 2 -TPR techniques were used to investigate the intrinsic difference among these catalysts. The results revealed that the addition of Sm to VPO catalyst can increase the surface area of the catalyst, lead to a significant change in catalyst morphology from plate-like structure into rosette-shape clusters, and largely promote the formation of (VO) 2 P 2 O 7 . All of these were related to the different catalytic performance of Sm-doped and undoped VPO catalysts. The roles of the different VOPO 4 phases and the influence of Sm were also described and discussed

Hydrogenation of carbon monoxide over supported palladium catalysts

Energy Technology Data Exchange (ETDEWEB)

Fujimoto, K.; Hashimoto, H.; Kunugi, T.

1978-03-01

An alumina-supported 2% palladium catalyst had higher activity for carbon monoxide hydrogenation than a silica-supported 2% palladium catalyst, at 250/sup 0/-400/sup 0/C and 1 atm. The addition of lanthanum oxide or thorium oxide, but not of potassium oxide, to the silica-supported catalyst increased the conversion at 350/sup 0/C from 1.1% to 81.0% with a selectivity of 56.1% for methane, 1.4% for C/sub 2/ compounds, 0.1% for C/sub 3/ compounds, and 42.5% for carbon dioxide. Temperature-programed desorption of carbon monoxide in a hydrogen stream showed that of two desorption peaks observed for carbon monoxide, the one at higher temperature corresponded to the carbon monoxide species which hydrogenates to methane and that the area of this peak increased with increasing thorium content of the catalyst. Graphs, tables, and 12 references.

Catalytic wet air oxidation of 2-chlorophenol over sewage sludge-derived carbon-based catalysts

Energy Technology Data Exchange (ETDEWEB)

Tu, Yuting [Institut de recherches sur la catalyse et l’environnement de Lyon (IRCELYON), CNRS – Université Claude Bernard Lyon 1, 2 Avenue Albert Einstein, 69626 Villeurbanne Cedex (France); School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Xiong, Ya; Tian, Shuanghong [School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou 510275 (China); Kong, Lingjun [School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Descorme, Claude, E-mail: claude.descorme@ircelyon.univ-lyon1.fr [Institut de recherches sur la catalyse et l’environnement de Lyon (IRCELYON), CNRS – Université Claude Bernard Lyon 1, 2 Avenue Albert Einstein, 69626 Villeurbanne Cedex (France)

2014-07-15

Highlights: • A sewage sludge derived carbon-supported iron oxide catalyst (FeSC) was prepared. • FeSC exhibited high catalytic activity in the wet air oxidation of 2-chlorophenol. • A strong correlation was observed between the 2-CP conversion, the iron leaching and the pH. • Using an acetate buffer, the iron leaching was suppressed while keeping some catalytic activity. • A simplified reaction pathway was proposed for the CWAO of 2-CP over the FeSC catalyst. - Abstract: A sewage sludge derived carbon-supported iron oxide catalyst (FeSC) was prepared and used in the Catalytic Wet Air Oxidation (CWAO) of 2-chlorophenol (2-CP). The catalysts were characterized in terms of elemental composition, surface area, pH{sub PZC}, XRD and SEM. The performances of the FeSC catalyst in the CWAO of 2-CP was assessed in a batch reactor operated at 120 °C under 0.9 MPa oxygen partial pressure. Complete decomposition of 2-CP was achieved within 5 h and 90% Total Organic Carbon (TOC) was removed after 24 h of reaction. Quite a straight correlation was observed between the 2-CP conversion, the amount of iron leached in solution and the pH of the reaction mixture at a given reaction time, indicating a strong predominance of the homogeneous catalysis contribution. The iron leaching could be efficiently prevented when the pH of the solution was maintained at values higher than 4.5, while the catalytic activity was only slightly reduced. Upon four successive batch CWAO experiments, using the same FeSC catalyst recovered by filtration after pH adjustment, only a very minor catalyst deactivation was observed. Finally, based on all the identified intermediates, a simplified reaction pathway was proposed for the CWAO of 2-CP over the FeSC catalyst.

Direct Synthesis of Methanol by Partial Oxidation of Methane with Oxygen over Cobalt Modified Mesoporous H-ZSM-5 Catalyst

Directory of Open Access Journals (Sweden)

Yuni Krisyuningsih Krisnandi

2015-11-01

Full Text Available Partial oxidation of methane over mesoporous catalyst cobalt modified H-ZSM-5 has been carried out. Mesoporous Na-ZSM-5 (Si/Al = 35.4 was successfully synthesized using double template method which has high surface area (450 m2/g and average pore diameter distribution of 1.9 nm. The as-synthesized Na-ZSM-5 was converted to H-ZSM-5 through multi-exchange treatment with ammonium ion solution, causing decreased crystallinity and surface area, but increased porous diameter, due to dealumination during treatment process. Moreover, H-ZSM-5 was loaded with cobalt (Co = 2.5% w by the incipient impregnation method and calcined at 550 °C. Partial oxidation of methane was performed in the batch reactor with 0.75 bar methane and 2 bar of nitrogen (with impurities of 0.5% oxygen as the input at various reaction time (30, 60 and 120 min. The reaction results show that cobalt species in catalyst has an important role, because H-ZSM-5 cannot produce methanol in partial oxidation of methane. The presence of molecular oxygen increased the percentage of methanol yield. The reaction is time-dependent with the highest methanol yield (79% was acquired using Co/H-ZSM-5 catalyst for 60 min.

Ceramic wash-coat for catalyst support

Science.gov (United States)

Kulkarni, Anand A.; Subramanian, Ramesh; Sabol, Stephen M.

2012-08-14

A wash-coat (16) for use as a support for an active catalyst species (18) and a catalytic combustor component (10) incorporating such wash-coat. The wash-coat is a solid solution of alumina or alumina-based material (Al.sub.2O.sub.3-0-3 wt % La.sub.2O.sub.3) and a further oxide exhibiting a coefficient of thermal expansion that is lower than that exhibited by alumina. The further oxide may be silicon dioxide (2-30 wt % SiO.sub.2), zirconia silicate (2-30 wt % ZrSiO.sub.4), neodymium oxide (0-4 wt %), titania (Al.sub.2O.sub.3-3-40% TiO.sub.2) or alumina-based magnesium aluminate spinel (Al.sub.2O.sub.3-25 wt % MgO) in various embodiments. The active catalyst species may be palladium and a second metal in a concentration of 10-50% of the concentration of the palladium.

Enhanced methanol electro-oxidation reaction on Pt-CoOx/MWCNTs hybrid electro-catalyst

International Nuclear Information System (INIS)

Nouralishahi, Amideddin; Rashidi, Ali Morad; Mortazavi, Yadollah; Khodadadi, Abbas Ali; Choolaei, Mohammadmehdi

2015-01-01

Highlights: • Promoting effects of Cobalt oxide on methanol electro-oxidation over Pt/MWCNTs are investigated. • Higher activity, about 2.9 times, and enhanced stability are observed on Pt-CoO x /MWCNTs. • Electrochemical active surface area of Pt nanoparticles is significantly improved upon CoO x addition. • Bi-functional mechanism is facilitated in presence of CoO x . - Abstract: The electro-catalytic behavior of Pt-CoO x /MWCNTs in methanol electro-oxidation reaction (MOR) is investigated and compared to that of Pt/MWCNTs. The electro-catalysts were synthesized by an impregnation method using NaBH 4  as the reducing agent. The morphological and physical characteristics of samples are examined by XRD, TEM, ICP and EDS techniques. In the presence of CoO x , Pt nanoparticles were highly distributed on the support with an average particle size of 2 nm, an obvious decrease from 5.1 nm for Pt/MWCNTs. Cyclic voltammetry, CO-stripping, Chronoamperometry, and electrochemical impedance spectroscopy (EIS) measurements are used to study the electrochemical behavior of the electro-catalysts. The results revealed a considerable enhancement in the oxidation kinetics of CO ads on Pt active sites by the participation of CoO x . Compared to Pt/MWCNTs, Pt-CoO x /MWCNTs sample has a larger electrochemical active surface area (ECSA) and higher electro-catalytic activity and stability toward methanol electro-oxidation. According to the results of cyclic voltammetry, the forward anodic peak current density enhances more than 89% at the optimum atomic ratio of Pt:Co = 2:1. Furthermore, inclusion of cobalt oxide species causes the onset potential of methanol electro-oxidation reaction to shift 84 mV to negative values compared to that on Pt/MWCNTs. Based on EIS data, dehydrogenation of methanol is the rate-determining step of MOR on both Pt/MWCNTs and Pt-CoO x /MWCNTs, at small overpotentials. However, at higher overpotentials, the oxidation of adsorbed oxygen-containing groups

Ethanol electrooxidation on Pt/C and Pd/C catalysts promoted with oxide

Energy Technology Data Exchange (ETDEWEB)

Xu, Changwei [Department of Chemistry and Institute of Nanochemistry, Jinan University, Guangzhou 510632 (China); State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Shen, Pei kang [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Liu, Yingliang [Department of Chemistry and Institute of Nanochemistry, Jinan University, Guangzhou 510632 (China)

2007-02-10

This research aims to investigate Pd-based catalysts as a replacement for Pt-based catalysts for ethanol electrooxidation in alkaline media. The results show that Pd/C has a higher catalytic activity and better steady-state behaviour for ethanol oxidation than that of Pt/C. The effect of the addition of CeO{sub 2} and NiO to the Pt/C and Pd/C electrocatalysts on ethanol oxidation is also studied in alkaline media. The electrocatalysts with a weight ratio of noble metal (Pt, Pd) to CeO{sub 2} of 2:1 and a noble metal to NiO ration 6:1 show the highest catalytic activity for ethanol oxidation. The oxide promoted Pt/C and Pd/C electrocatalysts show a higher activity than the commercial E-TEK PtRu/C electrocatalyst for ethanol oxidation in alkaline media. (author)

Catalytic oxidation of n-hexane promoted by Ce1−xCuxO2 catalysts prepared by one-step polymeric precursor method

International Nuclear Information System (INIS)

Araújo, Vinícius D.; Lima, Maurício M. de; Cantarero, Andrés; Bernardi, Maria I.B.; Bellido, Jorge D.A.; Assaf, Elisabete M.; Balzer, Rosana; Probst, Luiz F.D.; Fajardo, Humberto V.

2013-01-01

Ceria-supported copper catalysts (Ce 1−x Cu x O 2 , with x (mol) = 0, 0.01, 0.03, 0.05 and 0.10) were prepared in one step through the polymeric precursor method. The textural properties of the catalysts were investigated by X-ray diffraction (XRD), Rietveld refinement, N 2 -physisorption (BET surface area), electron paramagnetic resonance (EPR), UV–visible diffuse reflectance and photoluminescence spectroscopies and temperature-programmed reduction (TPR). In a previous study ceria-supported copper catalysts were found to be efficient in the preferential oxidation of CO. In this study, we extended the catalytic application of Ce 1−x Cu x O 2 systems to n-hexane oxidation and it was verified that the catalysts were highly efficient in the proposed reaction. The best performance (up to 95% conversion) was observed for the catalysts with low copper loads (Ce 0.97 Cu 0.03 O 2 and Ce 0.99 Cu 0.01 O 2 , respectively). The physicochemical characterizations revealed that these behaviors could be attributed to the copper species present in the catalysts and the interaction between CuO and CeO 2 , which vary according to the copper content. - Highlights: • Synthesis of CuO/CeO2 catalysts by the one-step polymeric precursor method. • 95% n-hexane conversion on Ce0.97Cu0.03O2 catalyst. • Redox properties play a key role in the catalytic performance

Oxygen-assisted conversion of propane over metal and metal oxide catalysts

Energy Technology Data Exchange (ETDEWEB)

Laate, Leiv

2002-07-01

An experimental set-up has been build and applied in activity/selectivity studies of the oxygen-assisted conversion of propane over metals and metal oxide catalysts. The apparatus has been used in order to achieve an improved understanding of the reactions between alkanes/alkenes and oxygen. Processes that have been studied arc the oxidative dehydrogenation of propane over a VMgO catalyst and the selective combustion of hydrogen in the presence of hydrocarbons over Pt-based catalysts and metal oxide catalysts. From the experiments, the following conclusions are drawn: A study of the oxidative dehydrogenation of propane over a vanadium-magnesium-oxide catalyst confirmed that the main problem with this system is the lack of selectivity due to complete combustion. Selectivity to propene up to about 60% was obtained at 10% conversion at 500{sup o}C, but the selectivity decreased with increasing conversion. No oxygenates were detected, the only by- products were CO and CO{sub 2}. The selectivity to propene is a strong function of the conversion of propane. The reaction rate of propane was found to be 1.0 {+-} 0.1 order in propane and 0.07 {+-} 0.02 order in oxygen. The kinetic results are in agreement with a Mars van Krevelen mechanism with the activation of the hydrocarbons as the slow step. The rate of propene oxidation to CO{sub 2} was studied and found to be significantly higher than that of propane. Another possible process involves the simultaneous equilibrium dehydrogenation of alkanes to alkenes and combustion of the hydrogen formed to shift the equilibrium dehydrogenation reaction further to the product alkenes. A study of the selective combustion of hydrogen in the presence of propane/propene was found to be possible under certain reaction conditions over some metal oxide catalysts. In{sub 2}O{sub 3}/SiO{sub 2}, unsupported Bi{sub 2}O{sub 3} and ZSM-5 show the ability to combust hydrogen in a gas mixture with propane and oxygen with good selectivity. Bi{sub 2

Influence of Catalyst Acid/Base Properties in Acrolein Production by Oxidative Coupling of Ethanol and Methanol.

Science.gov (United States)

Lilić, Aleksandra; Bennici, Simona; Devaux, Jean-François; Dubois, Jean-Luc; Auroux, Aline

2017-05-09

Oxidative coupling of methanol and ethanol represents a new route to produce acrolein. In this work, the overall reaction was decoupled in two steps, the oxidation and the aldolization, by using two consecutive reactors to investigate the role of the acid/base properties of silica-supported oxide catalysts. The oxidation of a mixture of methanol and ethanol to formaldehyde and acetaldehyde was performed over a FeMoO x catalyst, and then the product mixture was transferred without intermediate separation to a second reactor, in which the aldol condensation and dehydration to acrolein were performed over the supported oxides. The impact of the acid/base properties on the selectivity towards acrolein was investigated under oxidizing conditions for the first time. The acid/base properties of the catalysts were investigated by NH 3 -, SO 2 -, and methanol-adsorption microcalorimetry. A MgO/SiO 2 catalyst was the most active in acrolein production owing to an appropriate ratio of basic to acidic sites. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Supported catalyst systems and method of making biodiesel products using such catalysts

Science.gov (United States)

Kim, Manhoe; Yan, Shuli; Salley, Steven O.; Ng, K. Y. Simon

2015-10-20

A heterogeneous catalyst system, a method of preparing the catalyst system and a method of forming a biodiesel product via transesterification reactions using the catalyst system is disclosed. The catalyst system according to one aspect of the present disclosure represents a class of supported mixed metal oxides that include at least calcium oxide and another metal oxide deposited on a lanthanum oxide or cerium oxide support. Preferably, the catalysts include CaO--CeO.sub.2ZLa.sub.2O.sub.3 or CaO--La.sub.2O.sub.3/CeO.sub.2. Optionally, the catalyst may further include additional metal oxides, such as CaO--La.sub.2O.sub.3--GdOxZLa.sub.2O.sub.3.

Selective oxidation of methane to ethane and ethylene over various oxide catalysts

NARCIS (Netherlands)

Roos, J.A.; Bakker, A.G.; Bosch, H.; van Ommen, J.G.; Ross, J.R.H.

1987-01-01

Preliminary results are reported for the oxidative coupling of methane to give ethane/ethylene mixtures over a series of different catalyst formulations; the temperature range studied is 650–850°C. A comparison is made of the behaviour of lead/alumina and lithium/magnesia materials. It is found that

Study of propane partial oxidation on vanadium-containing catalysts

Energy Technology Data Exchange (ETDEWEB)

Komashko, G.A.; Khalamejda, S.V.; Zazhigalov, V.A. [AN Ukrainskoj SSR, Kiev (Ukraine). Inst. Fizicheskoj Khimii

1998-12-31

The present results indicate that maximum selectivity to acrylic acid can be reached over V-P-Zr-O catalysts. When the hydrocarbon concentration is 5.1 vol.% the selectivity is about 30% at quite high paraffin conversion. Conclusively, some explanations to the observed facts can be given. The V-P-O catalyst promotion with lanthanum by means of mechanochemical treatment is distinguished by the additive uniform spreading all over the matrix surface. Such twophase system is highly active in propane conversion (lanthanum oxide) and further oxidation of the desired products. The similar properties are attributed to V-P-Bi-La-O catalyst. Bismuth, tellurium and zirconium additives having clearly defined acidic properties provoke the surface acidity strengthening and make easier desorption of the acidic product (acrylic acid) from the surface lowering its further oxidation. Additionally, since bismuth and zirconium are able to form phosphates and, according to, to create space limitations for the paraffin molecule movement out of the active group boundaries, this can be one more support in favour of the selectivity increase. With this point of view very interesting results were obtained. It has been shown that the more limited the size of the vanadium unit, the higher the selectivity is. Monoclinic phase AV{sub 2}P{sub 2}O{sub 10} which consists in clusters of four vanadium atoms is sensibly more reactive than the orthorhombic phase consists in V{sub {infinity}} infinite chains. (orig.)

β-cyclodextrin functionalized on glass micro-particles: A green catalyst for selective oxidation of toluene to benzaldehyde

Energy Technology Data Exchange (ETDEWEB)

Tahir, M. Nazir, E-mail: tahir.muhammad_nazir@courrier.uqam.ca [Department of Chemistry and Bioscience, Aalborg University, Frederik Bajers Vej 7H, DK-9220, Aalborg East (Denmark); Department of Chemistry, University of Quebec at Montreal, QC, H3C 3P8 (Canada); Nielsen, Thorbjørn T.; Larsen, Kim L. [Department of Chemistry and Bioscience, Aalborg University, Frederik Bajers Vej 7H, DK-9220, Aalborg East (Denmark)

2016-12-15

Highlights: • Functionalization of βCD onto glass micro-particles (GMP-βCD). • Application of GMP-βCD as a green catalyst for the oxidation of toluene. • 82% yield at room temperature. • Repeated use of the catalyst for several cycles. - Abstract: Oxidation of toluene is considered an important process which often requires high temperatures and specific conditions along with heavy-metals based catalysts. In this study, we have developed a green catalyst by functionalizing beta-cyclodextrin onto glass micro-particle surfaces. All surfaces were characterized by X-ray photoelectron spectroscopy and applied to catalyze the selective oxidation of toluene into benzaldehyde (82% yield) at room temperature. The catalyst was stable and could be used repeatedly for several cycles without losing efficiency.

The influence of Mn species on the SO2 removal of Mn-based activated carbon catalysts

International Nuclear Information System (INIS)

Qu, Yi-Fan; Guo, Jia-Xiu; Chu, Ying-Hao; Sun, Ming-Chao; Yin, Hua-Qiang

2013-01-01

Using Mn(NO 3 ) 2 as precursor, a series of Mn-based activated carbon catalysts were prepared by ultrasound-assisted excessive impregnation method and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and temperature programmed reduction (TPR). The influences of Mn species and nitric acid pretreatment on the removal role of SO 2 were investigated. MnO and Mn 3 O 4 coexist in catalysts calcined at 650 and 800 °C and exhibit best SO 2 removal ability, whereas Mn 2 O 3 formed in the catalyst calcined at 500 °C and shows poor activity. After treatment by nitric acid, the C=O of activated carbon support increases and the crystal size of MnO decreases, resulting in the enhancement of the catalytic activity. During reaction process, manganese oxides are gradually transferred into MnO 2 . And this change directly results in a decrease of activity. But the SO 2 removal rate has been maintained in the range of 30–40%, indicating that MnO 2 still has a certain SO 2 removal ability.

Transformation of Unsaturated Fatty Acids/Esters to Corresponding Keto Fatty Acids/Esters by Aerobic Oxidation with Pd(II)/Lewis Acid Catalyst.

Science.gov (United States)

Senan, Ahmed M; Zhang, Sicheng; Zeng, Miao; Chen, Zhuqi; Yin, Guochuan

2017-08-16

Utilization of renewable biomass to partly replace the fossil resources in industrial applications has attracted attention due to the limited fossil feedstock with the increased environmental concerns. This work introduced a modified Wacker-type oxidation for transformation of unsaturated fatty acids/esters to the corresponding keto fatty acids/esters, in which Cu 2+ cation was replaced with common nonredox metal ions, that is, a novel Pd(II)/Lewis acid (LA) catalyst. It was found that adding nonredox metal ions can effectively promote Pd(II)-catalyzed oxidation of unsaturated fatty acids/esters to the corresponding keto fatty acids/esters, even much better than Cu 2+ , and the promotional effect is highly dependent on the Lewis acidity of added nonredox metal ions. The improved catalytic efficiency is attributed to the formation of heterobimetallic Pd(II)/LA species, and the oxidation mechanism of this Pd(II)/LA catalyst is also briefly discussed.

Enhanced oxidation of naphthalene using plasma activation of TiO2/diatomite catalyst.

Science.gov (United States)

Wu, Zuliang; Zhu, Zhoubin; Hao, Xiaodong; Zhou, Weili; Han, Jingyi; Tang, Xiujuan; Yao, Shuiliang; Zhang, Xuming

2018-04-05

Non-thermal plasma technology has great potential in reducing polycyclic aromatic hydrocarbons (PAHs) emission. But in plasma-alone process, various undesired by-products are produced, which causes secondary pollutions. Here, a dielectric barrier discharge (DBD) reactor has been developed for the oxidation of naphthalene over a TiO 2 /diatomite catalyst at low temperature. In comparison to plasma-alone process, the combination of plasma and TiO 2 /diatomite catalyst significantly enhanced naphthalene conversion (up to 40%) and CO x selectivity (up to 92%), and substantially reduced the formation of aerosol (up to 90%) and secondary volatile organic compounds (up to near 100%). The mechanistic study suggested that the presence of the TiO 2 /diatomite catalyst intensified the electron energy in the DBD. Meantime, the energized electrons generated in the discharge activated TiO 2 , while the presence of ozone enhanced the activity of the TiO 2 /diatomite catalyst. This plasma-catalyst interaction led to the synergetic effect resulting from the combination of plasma and TiO 2 /diatomite catalyst, consequently enhanced the oxidation of naphthalene. Importantly, we have demonstrated the effectiveness of plasma to activate the photocatalyst for the deep oxidation of PAH without external heating, which is potentially valuable in the development of cost-effective gas cleaning process for the removal of PAHs in vehicle applications during cold start conditions. Copyright © 2017 Elsevier B.V. All rights reserved.

Lanthanoid-free perovskite oxide catalyst for dehydrogenation of ethylbenzene working with redox mechanism

Science.gov (United States)

Watanabe, Ryo; Ikushima, Maiko; Mukawa, Kei; Sumomozawa, Fumitaka; Ogo, Shuhei; Sekine, Yasushi

2013-01-01

For the development of highly active and robust catalysts for dehydrogenation of ethylbenzene (EBDH) to produce styrene; an important monomer for polystyrene production, perovskite-type oxides were applied to the reaction. Controlling the mobility of lattice oxygen by changing the structure of Ba1 − xSrxFeyMn1 − yO3 − δ (0 ≤ x ≤ 1, 0.2 ≤ y ≤ 0.8), perovskite catalyst showed higher activity and stability on EBDH. The optimized Ba/Sr and Fe/Mn molar ratios were 0.4/0.6 and 0.6/0.4, respectively. Comparison of the dehydrogenation activity of Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst with that of an industrial potassium promoted iron (Fe–K) catalyst revealed that the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst showed higher initial activity than the industrial Fe–K oxide catalyst. Additionally, the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst showed high activity and stability under severe conditions, even at temperatures as low as 783 K, or at the low steam/EB ratio of 2, while, the Fe–K catalyst showed low activity in such conditions. Comparing reduction profiles of the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ and the Fe–K catalysts in a H2O/H2 atmosphere, reduction was suppressed by the presence of H2O over the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst while the Fe–K catalyst was reduced. In other words, Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst had higher potential for activating the steam than the Fe–K catalyst. The lattice oxygen in perovskite-structure was consumed by H2, subsequently the consumed lattice oxygen was regenerated by H2O. So the catalytic performance of Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ was superior to that of Fe–K catalyst thanks to the high redox property of the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ perovskite oxide. PMID:24790949

Lanthanoid-free perovskite oxide catalyst for dehydrogenation of ethylbenzene working with redox mechanism

Directory of Open Access Journals (Sweden)

Ryo eWatanabe

2013-10-01

Full Text Available For the development of highly active and robust catalysts for dehydrogenation of ethylbenzene (EBDH to produce styrene; an important monomer for polystyrene production, perovskite-type oxides were applied to the reaction. Controlling the mobility of lattice oxygen by changing the structure of Ba1–xSrxFeyMn1–yO3–d(0 ≤ x≤ 1, 0.2 ≤ y≤ 0.8, perovskite catalyst showed higher activity and stability on EBDH. The optimized Ba/Sr and Fe/Mn molar ratios were 0.4/0.6 and 0.6/0.4, respectively. Comparison of the dehydrogenation activity of Ba0.4Sr0.6Fe0.6Mn0.4O3–d catalyst with that of an industrial potassium promoted iron (Fe–K catalyst revealed that the Ba0.4Sr0.6Fe0.6Mn0.4O3–d catalyst showed higher initial activity than the industrial Fe–K oxide catalyst. Additionally, the Ba0.4Sr0.6Fe0.6Mn0.4O3–d catalyst showed high activity and stability under severe conditions, even at temperatures as low as 783 K, or at the low steam/EB ratio of 2, while, the Fe–K catalyst showed low activity in such conditions. Comparing reduction profiles of the Ba0.4Sr0.6Fe0.6Mn0.4O3–d and the Fe–K catalysts in aH2O/H2 atmosphere, reduction was suppressed by the presence of H2O over the Ba0.4Sr0.6Fe0.6Mn0.4O3–d catalyst while the Fe–K catalyst was reduced. In other words, Ba0.4Sr0.6Fe0.6Mn0.4O3–d catalyst had higher potential for activating the steam than the Fe–K catalyst. The lattice oxygen in perovskite-structure was consumed by H2, subsequently the consumed lattice oxygen was regenerated by H2O. So the catalytic performance of Ba0.4Sr0.6Fe0.6Mn0.4O3–d was superior to that of Fe–K catalyst thanks to the high redox property of the Ba0.4Sr0.6Fe0.6Mn0.4O3–d perovskite oxide.

Lanthanoid-free perovskite oxide catalyst for dehydrogenation of ethylbenzene working with redox mechanism

Science.gov (United States)

Watanabe, Ryo; Ikushima, Maiko; Mukawa, Kei; Sumomozawa, Fumitaka; Ogo, Shuhei; Sekine, Yasushi

2013-10-01

For the development of highly active and robust catalysts for dehydrogenation of ethylbenzene (EBDH) to produce styrene; an important monomer for polystyrene production, perovskite-type oxides were applied to the reaction. Controlling the mobility of lattice oxygen by changing the structure of Ba1-xSrxFeyMn1-yO3-d(0 ≤ x≤ 1, 0.2 ≤ y≤ 0.8), perovskite catalyst showed higher activity and stability on EBDH. The optimized Ba/Sr and Fe/Mn molar ratios were 0.4/0.6 and 0.6/0.4, respectively. Comparison of the dehydrogenation activity of Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst with that of an industrial potassium promoted iron (Fe-K) catalyst revealed that the Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst showed higher initial activity than the industrial Fe-K oxide catalyst. Additionally, the Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst showed high activity and stability under severe conditions, even at temperatures as low as 783 K, or at the low steam/EB ratio of 2, while, the Fe-K catalyst showed low activity in such conditions. Comparing reduction profiles of the Ba0.4Sr0.6Fe0.6Mn0.4O3-d and the Fe-K catalysts in aH2O/H2 atmosphere, reduction was suppressed by the presence of H2O over the Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst while the Fe-K catalyst was reduced. In other words, Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst had higher potential for activating the steam than the Fe-K catalyst. The lattice oxygen in perovskite-structure was consumed by H2, subsequently the consumed lattice oxygen was regenerated by H2O. So the catalytic performance of Ba0.4Sr0.6Fe0.6Mn0.4O3-d was superior to that of Fe-K catalyst thanks to the high redox property of the Ba0.4Sr0.6Fe0.6Mn0.4O3-d perovskite oxide.

Lanthanoid-free perovskite oxide catalyst for dehydrogenation of ethylbenzene working with redox mechanism.

Science.gov (United States)

Watanabe, Ryo; Ikushima, Maiko; Mukawa, Kei; Sumomozawa, Fumitaka; Ogo, Shuhei; Sekine, Yasushi

2013-01-01

For the development of highly active and robust catalysts for dehydrogenation of ethylbenzene (EBDH) to produce styrene; an important monomer for polystyrene production, perovskite-type oxides were applied to the reaction. Controlling the mobility of lattice oxygen by changing the structure of Ba1 - x SrxFe y Mn1 - y O3 - δ (0 ≤ x ≤ 1, 0.2 ≤ y ≤ 0.8), perovskite catalyst showed higher activity and stability on EBDH. The optimized Ba/Sr and Fe/Mn molar ratios were 0.4/0.6 and 0.6/0.4, respectively. Comparison of the dehydrogenation activity of Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst with that of an industrial potassium promoted iron (Fe-K) catalyst revealed that the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst showed higher initial activity than the industrial Fe-K oxide catalyst. Additionally, the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst showed high activity and stability under severe conditions, even at temperatures as low as 783 K, or at the low steam/EB ratio of 2, while, the Fe-K catalyst showed low activity in such conditions. Comparing reduction profiles of the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ and the Fe-K catalysts in a H2O/H2 atmosphere, reduction was suppressed by the presence of H2O over the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst while the Fe-K catalyst was reduced. In other words, Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst had higher potential for activating the steam than the Fe-K catalyst. The lattice oxygen in perovskite-structure was consumed by H2, subsequently the consumed lattice oxygen was regenerated by H2O. So the catalytic performance of Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ was superior to that of Fe-K catalyst thanks to the high redox property of the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ perovskite oxide.

Catalytic oxidation of albendazole using molybdenum supported on carbon nanotubes as catalyst

International Nuclear Information System (INIS)

Sun-Kou, Maria del Rosario; Vega Carrasco, Edgar R.; Picasso Escobar, Gino I.

2013-01-01

The catalytic oxidation reaction of the thioether group (-S-) in the structure to the drug albendazole (C 12 H 15 N 3 O 2 S) was studied in order to obtain a pharmacologically active molecule known as albendazole sulfoxide. With this purpose, three heterogeneous catalysts were prepared using molybdenum (Mo) as active phase and carbon nanotubes as a multiple-layer catalyst support. The incorporation of the active phase was performed by wet impregnation, with subsequent calcination for 4 hours at 400 o C. For the catalytic oxidation reaction was employed hydrogen peroxide-urea (H 2 NCONH 2 ·H 2 O 2 ) as oxidizing agent and methanol (CH 3 OH) as reaction medium. The textural and morphology characterization of carbon nanoparticles and catalysts was carried out by adsorption-desorption of N 2 (BET) and scanning electron microscopy (SEM). The identification and quantification of the reaction products were followed by Fourier transform infrared spectroscopy (FTIR) and high performance liquid chromatography (HPLC), respectively. With the yield, selectivity and conversion higher than 90% after 60 minutes of reaction, albendazole sulphoxide was obtained as major product of oxidation reaction. (author)

Bimetallic Ag-Pt Sub-nanometer Supported Clusters as Highly Efficient and Robust Oxidation Catalysts

Energy Technology Data Exchange (ETDEWEB)

Negreiros, Fabio R. [CNR-ICCOM & IPCF, Consiglio Nazionale delle Ricerche, Pisa Italy; Halder, Avik [Materials Science Division, Argonne National Laboratory, Lemont IL USA; Yin, Chunrong [Materials Science Division, Argonne National Laboratory, Lemont IL USA; Singh, Akansha [Harish-Chandra Research Institute, HBNI, Chhatnag Road Jhunsi Allahabad 211019 India; Barcaro, Giovanni [CNR-ICCOM & IPCF, Consiglio Nazionale delle Ricerche, Pisa Italy; Sementa, Luca [CNR-ICCOM & IPCF, Consiglio Nazionale delle Ricerche, Pisa Italy; Tyo, Eric C. [Materials Science Division, Argonne National Laboratory, Lemont IL USA; Pellin, Michael J. [Materials Science Division, Argonne National Laboratory, Lemont IL USA; Bartling, Stephan [Institut für Physik, Universität Rostock, Rostock Germany; Meiwes-Broer, Karl-Heinz [Institut für Physik, Universität Rostock, Rostock Germany; Seifert, Sönke [X-ray Science Division, Argonne National Laboratory, Lemont IL USA; Sen, Prasenjit [Harish-Chandra Research Institute, HBNI, Chhatnag Road Jhunsi Allahabad 211019 India; Nigam, Sandeep [Chemistry Division, Bhabha Atomic Research Centre, Trombay Mumbai- 400 085 India; Majumder, Chiranjib [Chemistry Division, Bhabha Atomic Research Centre, Trombay Mumbai- 400 085 India; Fukui, Nobuyuki [East Tokyo Laboratory, Genesis Research Institute, Inc., Ichikawa Chiba 272-0001 Japan; Yasumatsu, Hisato [Cluster Research Laboratory, Toyota Technological Institute: in, East Tokyo Laboratory, Genesis Research Institute, Inc. Ichikawa, Chiba 272-0001 Japan; Vajda, Stefan [Materials Science Division, Argonne National Laboratory, Lemont IL USA; Nanoscience and Technology Division, Argonne National Laboratory, Lemont IL USA; Institute for Molecular Engineering, University of Chicago, Chicago IL USA; Fortunelli, Alessandro [CNR-ICCOM & IPCF, Consiglio Nazionale delle Ricerche, Pisa Italy; Materials and Process Simulation Center, California Institute of Technology, Pasadena CA USA

2017-12-29

A combined experimental and theoretical investigation of Ag-Pt sub-nanometer clusters as heterogeneous catalysts in the CO -> CO2 reaction (COox) is presented. Ag9Pt2 and Ag9Pt3 clusters are size-selected in the gas phase, deposited on an ultrathin amorphous alumina support, and tested as catalysts experimentally under realistic conditions and by first-principles simulations at realistic coverage. Insitu GISAXS/TPRx demonstrates that the clusters do not sinter or deactivate even after prolonged exposure to reactants at high temperature, and present comparable, extremely high COox catalytic efficiency. Such high activity and stability are ascribed to a synergic role of Ag and Pt in ultranano-aggregates, in which Pt anchors the clusters to the support and binds and activates two CO molecules, while Ag binds and activates O-2, and Ag/Pt surface proximity disfavors poisoning by CO or oxidized species.

Ethylbenzene dehydrogenation over binary FeOx–MeOy/Mg(Al)O catalysts derived from hydrotalcites

KAUST Repository

Balasamy, Rabindran J.; Khurshid, Alam; Al-Ali, Ali A S; Atanda, Luqman A.; Sagata, Kunimasa; Asamoto, Makiko; Yahiro, Hidenori; Nomura, Kiyoshi; Sano, Tsuneji; Takehira, Katsuomi; Al-Khattaf, Sulaiman S.

2010-01-01

A series of FeOx-MeOy/Mg(Al)O catalysts were prepared from hydrotalcite-like compounds as precursors and were tested in the ethylbenzene dehydrogenation to styrene in He atmosphere at 550 °C. The hydrotalcite-like precursors of the metal compositions of Mg3Fe 0.25Me0.25Al0.5 (Me = Cu, Zn, Cr, Mn, Fe, Co and Ni) were coprecipitated from the nitrates of metal components and calcined to mixed oxides at 550 °C. After the calcination, the mixed oxides showed high surface area of 150-200 m2 gcat -1, and were mainly composed of (MgMe)(Fe3+Al)O periclase in the bulk, whereas the surface was enriched by (MgMe)(Fe3+Al)2O 4 pinel. Among the Me species tested, Co2+ was the most effective, followed by Ni2+. Co2+ addition increased the activity of original FeOx/Mg(Al)O catalyst, whereas Ni2+ increased the activity at the beginning of reaction, but deactivated the catalyst during the reaction. The other metals formed isolated MeOx species in the catalyst, resulting in a decrease in the activity compared to the original FeOx/Mg(Al)O catalyst. The active Fe species exists as metastable Fe3+ on the FeOx/Mg(Al)O catalyst. By the addition of Co2+, the reduction-oxidation between Fe3+ and Fe2+ was facilitated and, moreover, the active Fe3+ species was stabilized. It is likely that the dehydrogenation proceeds on the active Fe3+ species via its reduction-oxidation assisted by Co 2+. © 2010 Elsevier B.V.

Ethylbenzene dehydrogenation over binary FeOx–MeOy/Mg(Al)O catalysts derived from hydrotalcites

KAUST Repository

Balasamy, Rabindran J.

2010-12-20

A series of FeOx-MeOy/Mg(Al)O catalysts were prepared from hydrotalcite-like compounds as precursors and were tested in the ethylbenzene dehydrogenation to styrene in He atmosphere at 550 °C. The hydrotalcite-like precursors of the metal compositions of Mg3Fe 0.25Me0.25Al0.5 (Me = Cu, Zn, Cr, Mn, Fe, Co and Ni) were coprecipitated from the nitrates of metal components and calcined to mixed oxides at 550 °C. After the calcination, the mixed oxides showed high surface area of 150-200 m2 gcat -1, and were mainly composed of (MgMe)(Fe3+Al)O periclase in the bulk, whereas the surface was enriched by (MgMe)(Fe3+Al)2O 4 pinel. Among the Me species tested, Co2+ was the most effective, followed by Ni2+. Co2+ addition increased the activity of original FeOx/Mg(Al)O catalyst, whereas Ni2+ increased the activity at the beginning of reaction, but deactivated the catalyst during the reaction. The other metals formed isolated MeOx species in the catalyst, resulting in a decrease in the activity compared to the original FeOx/Mg(Al)O catalyst. The active Fe species exists as metastable Fe3+ on the FeOx/Mg(Al)O catalyst. By the addition of Co2+, the reduction-oxidation between Fe3+ and Fe2+ was facilitated and, moreover, the active Fe3+ species was stabilized. It is likely that the dehydrogenation proceeds on the active Fe3+ species via its reduction-oxidation assisted by Co 2+. © 2010 Elsevier B.V.

Catalyst for Carbon Monoxide Oxidation

Science.gov (United States)

Davis, Patricia; Brown, Kenneth; VanNorman, John; Brown, David; Upchurch, Billy; Schryer, David; Miller, Irvin

2010-01-01

In many applications, it is highly desirable to operate a CO2 laser in a sealed condition, for in an open system the laser requires a continuous flow of laser gas to remove the dissociation products that occur in the discharge zone of the laser, in order to maintain a stable power output. This adds to the operating cost of the laser, and in airborne or space applications, it also adds to the weight penalty of the laser. In a sealed CO2 laser, a small amount of CO2 gas is decomposed in the electrical discharge zone into corresponding quantities of CO and O2. As the laser continues to operate, the concentration of CO2 decreases, while the concentrations of CO and O2 correspondingly increase. The increasing concentration of O2 reduces laser power, because O2 scavenges electrons in the electrical discharge, thereby causing arcing in the electric discharge and a loss of the energetic electrons required to boost CO2 molecules to lasing energy levels. As a result, laser power decreases rapidly. The primary object of this invention is to provide a catalyst that, by composition of matter alone, contains chemisorbed water within and upon its structure. Such bound moisture renders the catalyst highly active and very long-lived, such that only a small quantity of it needs to be used with a CO2 laser under ambient operating conditions. This object is achieved by a catalyst that consists essentially of about 1 to 40 percent by weight of one or more platinum group metals (Pt, Pd, Rh, Ir, Ru, Os, Pt being preferred); about 1 to 90 percent by weight of one or more oxides of reducible metals having multiple valence states (such as Sn, Ti, Mn, Cu, and Ce, with SnO2 being preferred); and about 1 to 90 percent by weight of a compound that can bind water to its structure (such as silica gel, calcium chloride, magnesium sulfate, hydrated alumina, and magnesium perchlorate, with silica gel being preferred). Especially beneficial results are obtained when platinum is present in the

Synthesis of a molecularly defined single-active site heterogeneous catalyst for selective oxidation of N-heterocycles.

Science.gov (United States)

Zhang, Yujing; Pang, Shaofeng; Wei, Zhihong; Jiao, Haijun; Dai, Xingchao; Wang, Hongli; Shi, Feng

2018-04-13

Generally, a homogeneous catalyst exhibits good activity and defined active sites but it is difficult to recycle. Meanwhile, a heterogeneous catalyst can easily be reused but its active site is difficult to reveal. It is interesting to bridge the gap between homogeneous and heterogeneous catalysis via controllable construction of a heterogeneous catalyst containing defined active sites. Here, we report that a molecularly defined, single-active site heterogeneous catalyst has been designed and prepared via the oxidative polymerization of maleimide derivatives. These polymaleimide derivatives can be active catalysts for the selective oxidation of heterocyclic compounds to quinoline and indole via the recycling of -C=O and -C-OH groups, which was confirmed by tracing the reaction with GC-MS using maleimide as the catalyst and by FT-IR analysis with polymaleimide as the catalyst. These results might promote the development of heterogeneous catalysts with molecularly defined single active sites exhibiting a comparable activity to homogeneous catalysts.

Toluene decomposition performance and NOx by-product formation during a DBD-catalyst process.

Science.gov (United States)

Guo, Yufang; Liao, Xiaobin; Fu, Mingli; Huang, Haibao; Ye, Daiqi

2015-02-01

Characteristics of toluene decomposition and formation of nitrogen oxide (NOx) by-products were investigated in a dielectric barrier discharge (DBD) reactor with/without catalyst at room temperature and atmospheric pressure. Four kinds of metal oxides, i.e., manganese oxide (MnOx), iron oxide (FeOx), cobalt oxide (CoOx) and copper oxide (CuO), supported on Al2O3/nickel foam, were used as catalysts. It was found that introducing catalysts could improve toluene removal efficiency, promote decomposition of by-product ozone and enhance CO2 selectivity. In addition, NOx was suppressed with the decrease of specific energy density (SED) and the increase of humidity, gas flow rate and toluene concentration, or catalyst introduction. Among the four kinds of catalysts, the CuO catalyst showed the best performance in NOx suppression. The MnOx catalyst exhibited the lowest concentration of O3 and highest CO2 selectivity but the highest concentration of NOx. A possible pathway for NOx production in DBD was discussed. The contributions of oxygen active species and hydroxyl radicals are dominant in NOx suppression. Copyright © 2014. Published by Elsevier B.V.

Oxidative desulfurization of diesel fuel using amphiphilic quaternary ammonium phosphomolybdate catalysts

Energy Technology Data Exchange (ETDEWEB)

Qiu, Jianghua; Wang, Guanghui; Zeng, Danlin; Tang, Yan [College of Chemical Engineering and Technology, Wuhan University of Science and Technology, Wuhan 430081 (China); Wang, Meng; Li, Yanjun [College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072 (China)

2009-12-15

Phosphomolybdic acid (HPMo) modified respectively with tetramethyl ammonium chloride (TMAC), dodecyl trimethyl ammonium chloride (DTAC) and hexadecyl trimethyl ammonium chloride (HTAC) as the catalysts were prepared and characterized by FT-IR, XRD and SEM. The catalysts were evaluated for the oxidative desulfurization of benzothiophene (BT), dibenzothiophene (DBT) and straight-run diesel using hydrogen peroxide as an oxidant. Results show that all of the catalysts keep the Keggin structures and are finely dispersed with mixing of quaternary ammonium salts. Hexadecyl chains are more favorable to wrap up DBT to the catalytic center and form stable emulsion system with higher conversion rates of DBT. The shorter dodecyl chains can wrap up BT more suitably and bring smaller steric hindrance, which display higher conversion rates of BT. The oxidative reactions fit apparent first-order kinetics, and the apparent activation energies of DBT are much lower than those of BT. The desulfurization rate of straight-run diesel can be up to 84.4% with the recovery rate of 98.1% catalyzed by [HPMo][HTAC]{sub 2} in 2 h. When increasing the extraction times, the desulfurization rates increase, but the recovery rates of diesel decrease significantly. (author)

Use of Graphite Oxide and Graphene Oxide as Catalysts in the Synthesis of Dipyrromethane and Calix[4]pyrrole

Directory of Open Access Journals (Sweden)

Sweta Mishra

2011-08-01

Full Text Available Graphite oxide and graphene oxides have been used as solid catalysts for the synthesis of 5,5-dialkyldipyrromethanes and calix[4]pyrroles in organic and aqueous solutions at room temperature.

Morphological Effect of Pd Catalyst on Ethanol Electro-Oxidation Reaction

Directory of Open Access Journals (Sweden)

Rosalba Fuentes Ramírez

2012-09-01

Full Text Available In the present study, three different structures with preferentially exposed crystal faces were supported on commercial carbon black by the polyol method (nanoparticles (NP/C, nanobars (NB/C and nanorods (NR/C. The electrocatalysts were characterized by XRD, TEM, TGA and cyclic voltammetry at three different ethanol concentrations. Considerable differences were found in terms of catalytic electroactivity. At all ethanol concentrations, the trend observed for the ethanol oxidation peak potential was preserved as follows: NB/C < NP/C< NR/C < commercial Pd/C. This result indicates that, from a thermodynamics point of view, the NB/C catalyst enclosed by Pd(100 facets presented the highest activity with respect to ethanol electro-oxidation among all of the catalysts studied.

A predictive tool for selective oxidation of hydrocarbons: optical basicity of catalysts

Energy Technology Data Exchange (ETDEWEB)

Moriceau, P.; Lebouteiller, A.; Bordes, E.; Courtine, P. [Universite de Technologie de Compiegne, 60 (France). Dept. de Genie Chimique

1998-12-31

Whatever the composition of the catalyst (promoted, supported, multicomponent, etc.) is, it is possible to calculate its electron donor capacity {Lambda}. However, one important question remains: How are the surface and the bulk values of {Lambda} related? Most oxidation catalysts exhibit either a layered structure as V{sub 2}O{sub 5}, and approximately {Lambda}{sub th}{proportional_to}{Lambda}{sub surf}, or a molecular structure as polyoxometallates, and no correction seems to be needed. Work is in progress on that point. Of great importance is also the actual oxidation and coordination states of cations at the stedy state: {Lambda}s have been calculated from the composition determined by XANES and XPS. Finally, the model is able to discriminate between `paraffins` and olefins as reactants. These calibration curves should help to find new catalysts. (orig.)

Cyanide Containing Wastewater Treatment by Ozone Enhanced Catalytic Oxidation over Diatomite Catalysts

Directory of Open Access Journals (Sweden)

Lin Mingguo

2018-01-01

Full Text Available Cyanide containing wastewater that discharged from gold mining process creates environmental problems due to the toxicity of cyanide. As one of the promising advanced oxidation process, catalytic oxidation with ozone is considered to be effective on the purification of cyanide. Diatomite, a natural mineral, was used as catalyst in this study. The effect of O3 dosage, salinity, initial cyanide concentration and initial pH condition were investigated. It was observed that the removal rate of cyanide was much higher in the catalytic oxidation with ozone process than the one in zone alone process. Alkaline condition was especially favorable for cyanide in catalytic oxidation with ozone. The ozone and catalytic oxidation with ozone were simulated by pseudo-first-order kinetics model. The apparent first-order rate constant contribution of the diatomite catalyst was 0.0757 min-1, and the contribution percentage was 65.77%.

Intrinsic Activity of MnOx-CeO2 Catalysts in Ethanol Oxidation

Directory of Open Access Journals (Sweden)

Dimitrios Delimaris

2017-11-01

Full Text Available MnOx-CeO2 mixed oxides are considered efficient oxidation catalysts superior to the corresponding single oxides. Although these oxides have been the subject of numerous studies, their fundamental performance indicators, such as turnover frequency (TOF or specific activity, are scarcely reported. The purpose of the present work is to investigate the effect of catalyst composition on the concentration of active sites and intrinsic activity in ethanol oxidation by the employment of temperature-programmed desorption and oxidation of isotopically-labelled ethanol, 12CH313CH2OH. The transformation pathways of preadsorbed ethanol in the absence of gaseous oxygen refer to dehydrogenation to acetaldehyde followed by its dissociation combined with oxidation by lattice oxygen. In the presence of gaseous oxygen, lattice oxygen is rapidly restored and the main products are acetaldehyde, CO2, and water. CO2 forms less easily on mixed oxides than on pure MnOx. The TOF of ethanol oxidation has been calculated assuming that the amount of adsorbed ethanol and CO2 produced during temperature-programmed oxidation (TPO is a reliable indicator of the concentration of the active sites.

o-Naphthoquinone-Catalyzed Aerobic Oxidation of Amines to (Ket)imines: A Modular Catalyst Approach.

Science.gov (United States)

Goriya, Yogesh; Kim, Hun Young; Oh, Kyungsoo

2016-10-07

A modular aerobic oxidation of amines to imines has been achieved using an ortho-naphthoquinone (o-NQ) catalyst. The cooperative catalyst system of o-NQ and Cu(OAc) 2 enabled the formation of homocoupled imines from benzylamines, while the presence of TFA helped the formation of cross-coupled imines in excellent yields. The current mild aerobic oxidation protocol could also be applied to the oxidation of secondary amines to imines or ketimines with the help of cocatalyst, Ag 2 CO 3 , with excellent yields.

EFFECT OF IMPREGNATION PROCEDURE OF Pt/γ-Al2O3 CATALYSTS UPON CATALYTIC OXIDATION OF CO

Directory of Open Access Journals (Sweden)

Triyono Triyono

2010-06-01

Full Text Available The oxidation of carbon monoxide by oxygen using two catalysts prepared by two different methods has been investigated. In the first method, catalyst prepared by immersing γ-Al2O3 into the hexa-chloroplatinic acid solution at 80oC for 4 h, resulted Pt/γ-Al2O3 catalyst having platinum highly dispersed on the support. While that of immersing γ-Al2O3 in the hexa-chloroplatinic acid solution at room temperature for 12 h, produced Pt/ γ-Al2O3 catalyst where platinum dispersion was much lower. Catalytic activity test showed that platinum well dispersed on the support enhanced the activity of oxidation of carbon monoxide. The platinum impregnated at room temperature resulted in the poor activity.   Keyword: Catalyst, CO Oxidation, Platinum.

Rational design of Mg-Al mixed oxide-supported bimetallic catalysts for dry reforming of methane

Energy Technology Data Exchange (ETDEWEB)

Tsyganok, Andrey I. [Centre for Catalysis Research and Innovation, Department of Chemistry, University of Ottawa, D' Iorio Hall, 10 Marie Curie Street, Ottawa, Ont. (Canada); Inaba, Mieko [Natural Gas Technology Development Team, Teikoku Oil Co., 9-23-30 Kitakarasuyama, Setagaya-ku, Tokyo 157-0061 (Japan); Tsunoda, Tatsuo; Uchida, Kunio; Suzuki, Kunio; Hayakawa, Takashi [Institute for Materials and Chemical Process, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba 305-8565 (Japan); Takehira, Katsuomi [Department of Applied Chemistry, Faculty of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima 739-8527 (Japan)

2005-09-18

A novel synthetic strategy for preparing bimetallic Ru-M (M=Cr, Fe, Co, Ni and Cu) catalysts, supported on Mg-Al mixed oxide, has been introduced. It was based on a 'memory effect', i.e. on the ability of Mg-Al mixed oxide to reconstruct a layered structure upon rehydration with an aqueous solution. By repeated calcinations-rehydration cycles, layered double hydroxide (LDH) precursors of catalysts containing two different metals were synthesized. Bimetallic catalysts were then generated (1) in situ from LDH under methane reforming reaction conditions and (2) from mixed metal oxides obtained by preliminary LDH calcination. Among all the LDH-derived catalysts, a Ru{sup 0.1%}-Ni{sup 5.0%}/MgAlO{sub x} sample revealed the highest activity and selectivity to syngas, a suitable durability and a low coking capacity. A promoting effect of ruthenium on catalytic function of supported nickel was demonstrated. Preliminary LDH calcination was shown to markedly affect the catalytic activity of the derived catalysts and especially their coking properties.

Physico-Chemical and Structural Properties of DeNOx and SO2 Oxidation Catalysts

DEFF Research Database (Denmark)

Masters, Stephen Grenville; Oehlers, Cord; Nielsen, Kurt

1996-01-01

Commercial catalysts for NOx removal and SO2 oxidation and their model systems have been investigated by spectroscopic, thermal, electrochemical and X-ray methods. Structural information on the vanadium complexes and compounds as well as physico-chemical properties for catalyst model systems have...

Power generation using spinel manganese-cobalt oxide as a cathode catalyst for microbial fuel cell applications.

Science.gov (United States)

Mahmoud, Mohamed; Gad-Allah, Tarek A; El-Khatib, K M; El-Gohary, Fatma

2011-11-01

This study focused on the use of spinel manganese-cobalt (Mn-Co) oxide, prepared by a solid state reaction, as a cathode catalyst to replace platinum in microbial fuel cells (MFCs) applications. Spinel Mn-Co oxides, with an Mn/Co atomic ratios of 0.5, 1, and 2, were prepared and examined in an air cathode MFCs which was fed with a molasses-laden synthetic wastewater and operated in batch mode. Among the three Mn-Co oxide cathodes and after 300 h of operation, the Mn-Co oxide catalyst with Mn/Co atomic ratio of 2 (MnCo-2) exhibited the highest power generation 113 mW/m2 at cell potential of 279 mV, which were lower than those for the Pt catalyst (148 mW/m2 and 325 mV, respectively). This study indicated that using spinel Mn-Co oxide to replace platinum as a cathodic catalyst enhances power generation, increases contaminant removal, and substantially reduces the cost of MFCs. Copyright © 2011 Elsevier Ltd. All rights reserved.

Removal of toluene by sequential adsorption-plasma oxidation: Mixed support and catalyst deactivation.

Science.gov (United States)

Qin, Caihong; Huang, Xuemin; Zhao, Junjie; Huang, Jiayu; Kang, Zhongli; Dang, Xiaoqing

2017-07-15

A sequential adsorption-plasma oxidation system was used to remove toluene from simulated dry air using γ-Al 2 O 3 , HZSM-5, a mixture of the two materials or their supported Mn-Ag catalyst as adsorbents under atmospheric pressure and room temperature. After 120min of plasma oxidation, γ-Al 2 O 3 had a better carbon balance (∼75%) than HZSM-5, but the CO 2 yield of γ-Al 2 O 3 was only ∼50%; and there was some desorption of toluene when γ-Al 2 O 3 was used. When a mixture of HZSM-5 and γ-Al 2 O 3 with a mass ratio of 1/2 was used, the carbon balance was up to 90% and 82% of this was CO 2 . The adsorption performance and electric discharge characteristics of the mixed supports were tested in order to rationalize this high CO x yield. After seven cycles of sequential adsorption-plasma oxidation, support and Mn-Ag catalyst deactivation occurred. The support and catalyst were characterized before and after deactivation by SEM, a BET method, XRD, XPS and GC-MS in order to probe the mechanism of their deactivation. 97.6% of the deactivated supports and 76% of the deactivated catalysts could be recovered by O 2 temperature-programmed oxidation. Copyright © 2017 Elsevier B.V. All rights reserved.

Change in activity of catalysts for the oxidation of tritium during a fire event

International Nuclear Information System (INIS)

Iwai, Yasunori; Sato, Katsumi; Yamanishi, Toshihiko

2012-01-01

Highlights: ► We experimentally demonstrated the influence of produced gases from burned low-halogen cable on the activity of catalysts for tritium oxidation. ► At 423 K, no considerable decrease in catalytic activity was observed. ► At 293 K, considerable increase in catalytic activity was initially observed due to the effect of produced hydrogen. Then the temporary decrease was observed due mainly to the effect of produced moisture, however the activity was gradually recovered. - Abstract: The catalytic performance should be maintained in any off normal events. Fire accident is the typical off normal event. In the fusion plant, typical combustibles are evaluated to be polymeric low-halogen cables. Produced gases from burned low-halogen cable may affect the activity of catalysts for the oxidation of tritium. We experimentally demonstrated the influence of produced gases from burned low-halogen cable on the activity of catalyst using tritium gas. Our evaluation showed that ethylene, methane and benzene were major produced gases. The activity of catalysts for the oxidation of tritium during a fire event was evaluated using a commercial hydrophilic Pt/Al 2 O 3 catalyst and a commercial hydrophobic Pt-catalyst. The temperature of catalytic reactor was selected to be 423 and 293 K. At 423 K, no considerable decrease in catalytic activity was observed for both catalysts even in the presence of produced gases from burned low-halogen cable. At 293 K, considerable increase in catalytic activity was initially observed for both catalysts due to the effect of produced hydrogen. Then the temporary decrease was observed, however the catalytic activity was gradually recovered to be the original activity. Consequently, the irreversible decrease in activity of the catalysts during a fire event was not observed.

Tungsten carbide/porous carbon composite as superior support for platinum catalyst toward methanol electro-oxidation

International Nuclear Information System (INIS)

Jiang, Liming; Fu, Honggang; Wang, Lei; Mu, Guang; Jiang, Baojiang; Zhou, Wei; Wang, Ruihong

2014-01-01

Graphical abstract: The WC nanoparticles are well dispersed in the carbon matrix. The size of WC nanoparticles is about 30 nm. It can be concluded that tungsten carbide and carbon composite was successfully prepared by the present synthesis conditions. - Highlights: • The WC/PC composite with high specific surface area was prepared by a simple way. • The Pt/WC/PC catalyst has superior performance toward methanol electro-oxidation. • The current density for methanol electro-oxidation is as high as 595.93 A g −1 Pt. • The Pt/WC/PC catalyst shows better durability and stronger CO electro-oxidation. • The performance of Pt/WC/PC is superior to the commercial Pt/C (JM) catalyst. - Abstract: Tungsten carbide/porous carbon (WC/PC) composites have been successfully synthesized through a surfactant assisted evaporation-induced-assembly method, followed by a thermal treatment process. In particular, WC/PC-35-1000 composite with tungsten content of 35% synthesized at the carbonized temperature of 1000 °C, exhibited a specific surface area (S BET ) of 457.92 m 2 g −1 . After loading Pt nanoparticles (NPs), the obtained Pt/WC/PC-35-1000 catalyst exhibits the highest unit mass electroactivity (595.93 A g −1 Pt) toward methanol electro-oxidation, which is about 2.6 times as that of the commercial Pt/C (JM) catalyst. Furthermore, the Pt/WC/PC-35-1000 catalyst displays much stronger resistance to CO poisoning and better durability toward methanol electrooxidation compared with the commercial Pt/C (JM) catalyst. The high electrocatalytic activity, strong poison-resistivity and good stability of Pt/WC/PC-35-1000 catalyst are attributed to the porous structures and high specific surface area of WC/PC support could facilitate the rapid mass transportation. Moreover, synergistic effect between WC and Pt NPs is favorable to the higher catalytic performance

Critical Surface Parameters for the Oxidative Coupling of Methane over the Mn-Na-W/SiO2 Catalyst.

Science.gov (United States)

Hayek, Naseem S; Lucas, Nishita S; Warwar Damouny, Christine; Gazit, Oz M

2017-11-22

The work here presents a thorough evaluation of the effect of Mn-Na-W/SiO 2 catalyst surface parameters on its performance in the oxidative coupling of methane (OCM). To do so, we used microporous dealuminated β-zeolite (Zeo), or mesoporous SBA-15 (SBA), or macroporous fumed silica (Fum) as precursors for catalyst preparation, together with Mn nitrate, Mn acetate and Na 2 WO 4 . Characterizing the catalysts by inductively coupled plasma-optical emission spectroscopy, N 2 physisorption, X-ray diffraction, high-resolution scanning electron microscopy-energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, and catalytic testing enabled us to identify critical surface parameters that govern the activity and C 2 selectivity of the Mn-Na-W/SiO 2 catalyst. Although the current paradigm views the phase transition of silica to α-cristobalite as the critical step in obtaining dispersed and stable metal sites, we show that the choice of precursors is equally or even more important with respect to tailoring the right surface properties. Specifically, the SBA-based catalyst, characterized by relatively closed surface porosity, demonstrated low activity and low C 2 selectivity. By contrast, for the same composition, the Zeo-based catalyst showed an open surface pore structure, which translated up to fourfold higher activity and enhanced selectivity. By varying the overall composition of the Zeo catalysts, we show that reducing the overall W concentration reduces the size of the Na 2 WO 4 species and increases the catalytic activity linearly as much as fivefold higher than the SBA catalyst. This linear dependence correlates well to the number of interfaces between the Na 2 WO 4 and Mn 2 O 3 species. Our results combined with prior studies lead us to single out the interface between Na 2 WO 4 and Mn 2 O 3 as the most probable active site for OCM using this catalyst. Synergistic interactions between the various precursors used and the phase transition are discussed in

One-step flame synthesis of an active Pt/TiO2 catalyst for SO2 oxidation

DEFF Research Database (Denmark)

Johannessen, Tue; Koutsopoulos, Sotiris

2002-01-01

Flame synthesis as a route for production of composite metal oxides has been employed for the one-step synthesis of a supported noble metal catalyst, i.e. a Pt/TiO2 catalyst, by simultaneous combustion of Ti-isopropoxide and platinum acetylacetonate in a quench-cooled flame reactor. The average...... size of the platinum particles supported on aggregated nano-particles of TiO2 is approximately 2 nm. The high SO2-oxidation activity of the catalyst proves that platinum is not hidden in the titania matrix. The flame-produced catalyst showed catalytic activity similar to samples prepared by wet...

Effects of manganese oxide and sulphate on the olefin selectivity of iron catalysts in the Fischer Tropsch reaction

NARCIS (Netherlands)

Dijk, van W.L.; Niemantsverdriet, J.W.; Kraan, van der A.M.; van der Baan, Hessel

1982-01-01

Although it has been claimed by various authors that the addition of manganese oxide, MnO, to an iron catalyst gives a marked increase in the olefin selectivity of iron catalysts, we have been unable to confirm these claims in Fischer Tropsch experiments at 513 K for an iron manganese oxide catalyst

PdRu/C catalysts for ethanol oxidation in anion-exchange membrane direct ethanol fuel cells

Science.gov (United States)

Ma, Liang; He, Hui; Hsu, Andrew; Chen, Rongrong

2013-11-01

Carbon supported PdRu catalysts with various Pd:Ru atomic ratios were synthesized by impregnation method, and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), electrochemical half-cell tests, and the anion-exchange membrane direct ethanol fuel cell (AEM-DEFC) tests. XRD results suggest that the PdRu metal exists on carbon support in an alloy form. TEM study shows that the bimetallic PdRu/C catalysts have slightly smaller average particle size than the single metal Pd/C catalyst. Lower onset potential and peak potential and much higher steady state current for ethanol oxidation in alkaline media were observed on the bimetallic catalysts (PdxRuy/C) than on the Pd/C, while the activity for ethanol oxidation on the pure Ru/C was not noticeable. By using Pd/C anode catalysts and MnO2 cathode catalysts, AEM-DEFCs free from the expensive Pt catalyst were assembled. The AEM DEFC using the bimetallic Pd3Ru/C anode catalyst showed a peak power density as high as 176 mW cm-2 at 80 °C, about 1.8 times higher than that using the single metal Pd/C catalyst. The role of Ru for enhancing the EOR activity of Pd/C catalysts is discussed.

Supported sub-nanometer Ta oxide clusters as model catalysts for the selective epoxidation of cyclooctene

KAUST Repository

Zwaschka, Gregor; Rondelli, Manuel; Krause, Maximilian; Rö tzer, Marian David; Hedhili, Mohamed N.; Heiz, Ulrich; Basset, Jean-Marie; Schweinberger, Florian; D'Elia, Valerio

2018-01-01

The preparation of organic ligands-free, isolated tantalum oxide atoms (Ta1) and small clusters (Tan>1) on flat silicate supports was accomplished by ultra-high vacuum (UHV) techniques followed by oxidation in air. The resulting surface complexes were thoroughly characterized and tested as supported catalysts for the epoxidation of cycloalkenes. The observed catalytic performance highlights the potential of the applied method for the production of active catalysts and the study of well-defined, ligand-free metal oxide moieties.

Supported sub-nanometer Ta oxide clusters as model catalysts for the selective epoxidation of cyclooctene

KAUST Repository

Zwaschka, Gregor

2018-01-22

The preparation of organic ligands-free, isolated tantalum oxide atoms (Ta1) and small clusters (Tan>1) on flat silicate supports was accomplished by ultra-high vacuum (UHV) techniques followed by oxidation in air. The resulting surface complexes were thoroughly characterized and tested as supported catalysts for the epoxidation of cycloalkenes. The observed catalytic performance highlights the potential of the applied method for the production of active catalysts and the study of well-defined, ligand-free metal oxide moieties.

PILOT TESTING OF MERCURY OXIDATION CATALYSTS FOR UPSTREAM OF WET FGD SYSTEMS

International Nuclear Information System (INIS)

Gary M. Blythe

2002-01-01

The objective of this project is to demonstrate at pilot scale the use of solid honeycomb catalysts to promote the oxidation of elemental mercury in the flue gas from coal combustion. The project is being funded by the U.S. DOE National Energy Technology Laboratory under Cooperative Agreement DE-FC26-01NT41185. EPRI, Great River Energy (GRE), and City Public Service (CPS) of San Antonio are project co-funders. URS Group is the prime contractor. The mercury catalytic oxidation process under development uses catalyst materials applied to honeycomb substrates to promote the oxidation of elemental mercury in the flue gas from coal-fired power plants that have wet lime or limestone flue gas desulfurization (FGD) systems. Oxidized mercury is removed in the wet FGD absorbers and co-precipitates in a stable form with the byproducts from the FGD system. The co-precipitated mercury does not appear to adversely affect the disposal or reuse properties of the FGD byproduct. The current project will test previously identified, effective catalyst materials at a larger, pilot scale and in a commercial form, so as to provide engineering data for future full-scale designs. The pilot-scale tests will continue for up to 14 months at each of two sites to provide longer-term catalyst life data. This is the first full reporting period for the subject Cooperative Agreement. During this period, most of the project efforts were related to project initiation and planning. There is no significant technical progress to report for the current period

Iron carbide on titania surface modified with group VA oxides as Fischer-Tropsch catalysts

International Nuclear Information System (INIS)

Wachs, I.E.; Fiato, R.A.; Chersich, C.C.

1986-01-01

A catalyst is described comprising iron carbide supported on a surface modified titania wherein the support comprises an oxide of a metal selected form the group consisting of niobium, vanadium, tantalum or mixture thereof supported on the titania wherein at least a portion of the supported oxide of niobium, vanandium, tantalum or mixture is in a non-crystalline form. The amount of the supported oxide ranges from about 0.5 to 25 weight percent metal oxide on the titania support based on the total support composition and the catalyst contains at least about 2 milligrams of iron, calculated as Fe/sub 2/O/sub 3/, per square meter of support surface

Uniform Pt Nanoparticles Incorporated into Reduced Graphene Oxides with MoO_3 as Advanced Anode Catalysts for Methanol Electro-oxidation

International Nuclear Information System (INIS)

Hao, Yanfei; Wang, Xudan; Zheng, Yuanyuan; Shen, Jianfeng; Yuan, Junhua; Wang, Ai-jun; Niu, Li; Huang, Shengtang

2016-01-01

Highlights: • Pt nanoparticles were uniformly deposited on graphene with MoO_3. Their size can be tuned by controlling MoO_3 loading. These Pt catalysts are high active on methanol oxidation. They also show high tolerance to CO poisoning. - Abstract: Pt nanoparticles (NPs) were uniformly deposited on the reduced graphene oxides (RGOs) by one-pot thermoreduction strategy with assist of MoO_3. MoO_3 can significantly reduce the size of Pt NPs on RGOs. These Pt NPs can be averaged to be 3.0 to 4.1 nm with MoO_3 loading from 27.4 to 8.8%. Without MoO_3, the size of Pt NPs can reach up to 15.2 nm. In addition, MoO_3 in Pt-MoO_3/RGO catalysts conducts a surface-confined reversible electron transfer. And the Pt-MoO_3/RGO catalysts show strong resistance to CO poisoning and high activity towards methanol oxidation reaction (MOR). Among these Pt-based catalysts, Pt-MoO_3/RGO catalysts with 16.5% MoO_3 loading possess a largest MOR current up to 610 mA mg"−"1 Pt with a smallest deteriorate rate of 0.000425 s"−"1 polarizing for 5000 s at 0.65 V. These results demonstrate commercial feasibility for Pt catalysts to reduce significantly the amount of precious metals Pt in parallel to maintain a high MOR activity and CO tolerance.

Crystalline structure and propylene oxidation in complex bismuth-molybdenum oxide catalysts

International Nuclear Information System (INIS)

Manaila, R.; Ionescu, N.I.; Caldararu, M.

1980-01-01

Complex Bi-Mo oxide catalysts supported on amorphous SiO 2 were prepared by coprecipitation and tested in the reaction of selective oxidation of propylene to acrolein. They consist of a mixture of molybdate phases and excess MoO 3 . The Fe 2 (MoO 4 ) 3 phase was found to have a high concentration of lattice defects, induced by a Mo excess. These defects could be related to the catalytic conversion and to the selectivity to total oxidation by varying the calcination temperature. Calcination above 500 0 C induced also the transition of the metastable modification β-NiMoO 4 to the stable form α, accompanied by a loss of conversion. A complex Bi molybdate with scheelitic structure was found to have a high selectivity to acrolein. (author)

Transesterification of Jatropha curcas crude oil to biodiesel on calcium lanthanum mixed oxide catalyst: Effect of stoichiometric composition

International Nuclear Information System (INIS)

Taufiq-Yap, Yun Hin; Teo, Siow Hwa; Rashid, Umer; Islam, Aminul; Hussien, Mohd Zobir; Lee, Keat Teong

2014-01-01

Highlights: • Biodiesel synthesis from Jatropha curcas oil catalyzed by CaO–La 2 O 3 mixed oxide. • Effects of Ca-to-La ratio, catalyst concentration, methanol/oil ratio and reaction temperature were optimized. • Biodiesel yield >85% was achieved at 65 °C temperature. • CaO–La 2 O 3 catalyst can be easy regenerated. - Abstract: Heterogeneous solid mixed oxide (CaO–La 2 O 3 ) catalysts with different molar ratios of calcium to lanthanum (Ca-to-La) were synthesized by co-precipitation method. The synthesized solid CaO–La 2 O 3 mixed metal oxide catalysts were utilized in transesterification of Jatropha curcus oil as feedstock to produce biodiesel. Under the optimized conditions at 65 °C, 4% catalyst dose with 24:1 MeOH to Jatropha oil molar ratio, the transesterification reaction exhibited 86.51% of biodiesel yield. The prepared catalysts were characterized using various techniques such as X-ray diffraction (XRD), nitrogen sorption with Brunauer–Emmer–Teller (BET) method, temperature-programmed desorption of CO 2 (CO 2 -TPD) and scanning electron microscopy (SEM). Influence of Ca-to-La atomic ratio in the mixed metal oxide catalyst, catalyst amount, methanol to oil molar ratio, reaction time, different oils on the fatty acid methyl ester (FAME) yield were appraised. Different catalyst regeneration procedures were also performed to investigate the reusability of the CaO–La 2 O 3 catalyst

Development of Vanadium Phosphaate Catalysts for Methanol Production by Selective Oxidation of Methane.

Energy Technology Data Exchange (ETDEWEB)

McCormick, R.L.

1997-10-01

This DOE sponsored study of methane partial oxidation was initiated at Amax Research and Development in Golden, CO in October of 1993. Shortly thereafter the management of Amax closed this R&D facility and the PI moved to the Colorado School of Mines. The project was begun again after contract transfer via a novation agreement. Experimental work began with testing of vandyl pyrophosphate (VPO), a well known alkane selective oxidation catalyst. It was found that VPO was not a selective catalyst for methane conversion yielding primarily CO. However, promotion of VPO with Fe, Cr, and other first row transition metals led to measurable yields for formaldehyde, as noted in the summary table. Catalyst characterization studies indicated that the role of promoters was to stabilize some of the vanadium in the V{sup 5+} oxidation state rather than the V{sup 4+} state formally expected for (VO){sub 2}P{sub 2}O{sub 7}.

W-containing oxide layers obtained on aluminum and titanium by PEO as catalysts in thiophene oxidation

Science.gov (United States)

Rudnev, V. S.; Lukiyanchuk, I. V.; Vasilyeva, M. S.; Morozova, V. P.; Zelikman, V. M.; Tarkhanova, I. G.

2017-11-01

W-containing oxide layers fabricated on titanium and aluminum alloys by Plasma electrolytic oxidation (PEO) have been tested in the reaction of the peroxide oxidation of thiophene. Samples with two types of coatings have been investigated. Coatings I contained tungsten oxide in the matrix and on the surface of amorphous silica-titania or silica-alumina layers, while coatings II comprised crystalline WO3 and/or Al2(WO4)3. Aluminum-supported catalyst containing a smallest amount of transition metals in the form of tungsten oxides and manganese oxides in low oxidation levels showed high activity and stability.

Dehydrogenation of Ethylbenzene with Carbon Dioxide as Soft Oxidant over Supported Vanadium-Antimony Oxide Catalyst

Energy Technology Data Exchange (ETDEWEB)

Hong, Do Young; Vislovskiy, Vladislav P.; Yoo, Jin S.; Chang, Jong San [Korea Research Institute of Chemical Technology, Daejeon (Korea, Republic of); Park, Sang Eon [Inha University, Incheon (Korea, Republic of); Park, Min Seok [Mongolia International University, Ulaanbaatar (Mongolia)

2005-11-15

This work presents that carbon dioxide, which is a main contributor to the global warming effect, could be utilized as a selective oxidant in the oxidative dehydrogenation of ethylbenzene. The dehydrogenation of ethylbenzene over alumina-supported vanadium-antimony oxide catalyst has been studied under different atmospheres such as inert nitrogen, steam, oxygen or carbon dioxide as diluent or oxidant. Among them, the addition of carbon dioxide gave the highest styrene yield (up to 82%) and styrene selectivity (up to 97%) along with stable activity. Carbon dioxide could play a beneficial role of a selective oxidant in the improvement of the catalytic behavior through the oxidative pathway.

Nature of active vanadium nanospecies in MCM-41 type catalysts for olefins oxidation

Energy Technology Data Exchange (ETDEWEB)

Chanquía, Corina M., E-mail: cchanquia@cab.cnea.gov.ar [Centro Atómico Bariloche, Comisión Nacional de Energía Atómica (CAB-CNEA). Av. Bustillo 9500, R8402AGP, San Carlos de Bariloche, Río Negro (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Avenida Rivadavia 1917, C1033AAJ, Ciudad Autónoma de Buenos Aires (Argentina); Cánepa, Analía L. [Centro de Investigación y Tecnología Química (CITeQ), Universidad Tecnológica Nacional, Facultad Regional Córdoba (UTN-FRC), Maestro López esq. Cruz Roja Argentina, Ciudad Universitaria, 5016, Córdoba Capital (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Avenida Rivadavia 1917, C1033AAJ, Ciudad Autónoma de Buenos Aires (Argentina); Winkler, Elin L. [Centro Atómico Bariloche, Comisión Nacional de Energía Atómica (CAB-CNEA). Av. Bustillo 9500, R8402AGP, San Carlos de Bariloche, Río Negro (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Avenida Rivadavia 1917, C1033AAJ, Ciudad Autónoma de Buenos Aires (Argentina); and others

2016-06-01

A multi-technique physicochemical investigation including UV–Vis-DRS, Raman spectroscopy, XPS, ESR and FTIRS with pyridine adsorption was performed to analyze the nature of different vanadium nanospecies present on MCM-41 type catalysts. By employing a direct hydrothermal synthesis, vanadium species were incorporated into siliceous structure mainly as tetrahedrally coordinated isolated V{sup δ+} ions, which would be located inside the wall and on the wall surface of the mesoporous channels. The coexistence of both vanadium oxidation states V{sup 4+} and V{sup 5+} was also revealed. Acidity measurements permitted to infer about the majority presence of Lewis acid sites, which increase with vanadium content. The catalytic performance of these materials was evaluated in the reaction of α-pinene oxidation with H{sub 2}O{sub 2}. The highest intrinsic activity of the sample with lower V loading was attributed to the high dispersion and efficiency of the isolated V{sup δ+} species that actuate as active sites. A mixture of reaction products arising from competitive processes of epoxidation and allylic oxidation was found. - Highlights: • Nature of vanadium nanospecies in mesoporous silicates was investigated. • From hydrothermal sol–gel synthesis, isolated V{sup δ+} sites were mainly generated. • The coexistence of both vanadium oxidation states V{sup 4+} and V{sup 5+} was revealed. • The catalytic performance was evaluated in α-pinene oxidation with H{sub 2}O{sub 2}. • The high catalytic activity is attributed to high dispersion of isolated V{sup δ+} ions.

Oxidation of methanol to formaldehyde over a series of Fe1-xAlx-V-oxide catalysts

DEFF Research Database (Denmark)

Häggblad, Robert; Wagner, Jakob Birkedal; Hansen, Staffan

2008-01-01

A series of triclinic Fe1−xAlxVO4 phases with 0x1 were prepared and used in the oxidation of methanol to formaldehyde. The activity measurements revealed that both the activity and especially the selectivity to formaldehyde increased with time of operation for at least 16 h, indicating...... restructuring of the catalysts. Characterisation of the catalysts with XRD, XANES, and electron microscopy after use in methanol oxidation showed that the stability of the bulk phases improved when Al was substituted for Fe in the structure. XRD and XANES of the used FeVO4 showed that it partly transformed...... in methanol oxidation revealed no significant change in the metal composition, in good agreement with the corresponding bulk values, except for a lower Fe value. Steady-state activity data showed a modest increase in specific activity with the Al content, whereas the selectivity to formaldehyde was about 90...

Cobalt nanoparticles as recyclable catalyst for aerobic oxidation of alcohols in liquid phase

Energy Technology Data Exchange (ETDEWEB)

Mondal, Arijit; Mukherjee, Debkumar, E-mail: debkumarmukherjee@rediffmail.com [Ramsaday College, Department of Chemistry (India); Adhikary, Bibhutosh, E-mail: adhikarybibhu@yahoo.com [Indian Institute of Engineering, Sciences and Technology, Shibpur, Department of Chemistry (India); Ahmed, Md Azharuddin [University of Calcutta, Department of Physics (India)

2016-05-15

Cobalt nanoparticles prepared at room temperature from cobalt sulphate and tetrabutyl ammonium bromide as surfactant have been found to be effective oxidation catalysts. Palladium and platinum nanoparticles (average size 4–6 nm) can also be prepared from PdCl{sub 2} and K{sub 2}PtCl{sub 4}, respectively, using the same surfactant but require high temperature (~120 °C) and much longer preparation time. Agglomeration of nanoparticles prepared from metals like palladium and platinum in common solvents, however, restricts their use as catalysts. It is therefore our endeavour to find the right combination of catalyst and solvent that will be beneficial from industrial point of view. Magnetic property measurement of cobalt nanoclusters was made using SQUID to identify their reusability nature. Herein, we report the use of cobalt nanoparticles (average size 90–95 nm) in dichloromethane solvent as effective reusable catalysts for aerobic oxidation of a variety of alcohols.Graphical Abstract.

Chemical nature of catalysts of oxide nanoparticles in environment ...

Indian Academy of Sciences (India)

12

Chemical nature of catalysts of oxide nanoparticles in environment prevailing during growth of carbon nanostructures by CCVD. M. Jana*, A. Sil and S. Ray. †. Department of Metallurgical and Materials Engineering. Indian Institute of Technology Roorkee. Roorkee 247 667, India. Present address: *School of Materials ...

Moessbauer spectroscopy and nuclear inelastic scattering studies on polynuclear oxo-bridged iron catalyst-first results

International Nuclear Information System (INIS)

Rajagopalan, S.; Asthalter, T.; Rabe, V.; Buerck, U. van; Wagner, F. E.; Laschat, S.

2008-01-01

Polynuclear iron catalysts are interesting materials because of their novel properties. In the future they may help to replace high cost and hazardous heavy metal catalysts by efficient, non toxic and economic iron compounds. In this work, we present some preliminary results on a novel polynuclear oxo-bridged iron catalyst. The chemical environment of the metal species (Fe) was studied under Gif-type conditions (Fe catalyst/Zn/O 2 in pyridine/acetic acid) with cyclohexene as substrate. Such Gif-type catalysts are able to catalyse the selective oxidation of alkanes and alkenes. The characterization was done by Moessbauer spectroscopy and nuclear inelastic scattering. In order to identify the intermediate species during the reaction (selective oxidation using molecular O 2 ), a freeze-quench technique was used. This also helps to understand the kinetics of the chemical reaction.

Tungsten-Based Mesoporous Silicates W-MMM-E as Heterogeneous Catalysts for Liquid-Phase Oxidations with Aqueous H2O2

Directory of Open Access Journals (Sweden)

Nataliya Maksimchuk

2018-02-01

Full Text Available Mesoporous tungsten-silicates, W-MMM-E, have been prepared following evaporation-induced self-assembly methodology and characterized by elemental analysis, XRD, N2 adsorption, STEM-HAADF (high angle annular dark field in scanning-TEM mode, DRS UV-vis, and Raman techniques. DRS UV-vis showed the presence of two types of tungsten oxo-species in W-MMM-E samples: isolated tetrahedrally and oligomeric octahedrally coordinated ones, with the ratio depending on the content of tungsten in the catalyst. Materials with lower W loading have a higher contribution from isolated species, regardless of the preparation method. W-MMM-E catalyzes selectively oxidize of a range of alkenes and organic sulfides, including bulky terpene or thianthrene molecules, using green aqueous H2O2. The selectivity of corresponding epoxides reached 85–99% in up to 80% alkene conversions, while sulfoxides formed with 84–90% selectivity in almost complete sulfide conversions and a 90–100% H2O2 utilization efficiency. The true heterogeneity of catalysis over W-MMM-E was proved by hot filtration tests. Leaching of inactive W species depended on the reaction conditions and initial W loading in the catalyst. After optimization of the catalyst system, it did not exceed 20 ppm and 3 ppm for epoxidation and sulfoxidation reactions, respectively. Elaborated catalysts could be easily retrieved by filtration and reused several times with maintenance of the catalytic behavior.

Hydroxylation of benzene to phenol over magnetic recyclable nanostructured CuFe mixed-oxide catalyst

CSIR Research Space (South Africa)

Makgwane, PR

2015-03-01

Full Text Available A highly active and magnetically recyclable nanostructured copper–iron oxide (CuFe) catalyst has been synthesized for hydroxylation of benzene to phenol under mild reaction conditions. The obtained catalytic results were correlated with the catalyst...

Advances in Base-Free Oxidation of Bio-Based Compounds on Supported Gold Catalysts

Directory of Open Access Journals (Sweden)

Robert Wojcieszak

2017-11-01

Full Text Available The oxidation of bio-based molecules in general, and of carbohydrates and furanics in particular, is a highly attractive process. The catalytic conversion of renewable compounds is of high importance. Acids and other chemical intermediates issued from oxidation processes have many applications related, especially, to food and detergents, as well as to pharmaceutics, cosmetics, and the chemical industry. Until now, the oxidation of sugars, furfural, or 5-hydroxymethylfurfural has been mainly conducted through biochemical processes or with strong inorganic oxidants. The use of these processes very often presents many disadvantages, especially regarding products separation and selectivity control. Generally, the oxidation is performed in batch conditions using an appropriate catalyst and a basic aqueous solution (pH 7–9, while bubbling oxygen or air through the slurry. However, there is a renewed interest in working in base-free conditions to avoid the production of salts. Actually, this gives direct access to different acids or diacids without laborious product purification steps. This review focuses on processes applying gold-based catalysts, and on the catalytic properties of these systems in the base-free oxidation of important compounds: C5–C6 sugars, furfural, and 5-hydroxymethylfurfural. A better understanding of the chemical and physical properties of the catalysts and of the operating conditions applied in the oxidation reactions is essential. For this reason, in this review we put emphasis on these most impacting factors.

Study of the oxides nature effect of rare and rare earth elements on the aluminium-chromium catalyst properties

International Nuclear Information System (INIS)

Dadashev, B.A.; Abbasov, S.G.; Sarydzhanov, A.A.; AN Azerbajdzhanskoj SSR, Baku. Inst. Neftekhimicheskikh Protsessov)

1975-01-01

Adsorption studies have shown that oxides of rare and rare earth elements REE appreciably influence the structure of aluminium-chrome catalyst. Alkaline promotors, unlike REE, contribute to the formation of developed contact surface. Electrophysical investigations show that oxides of rare elements introduced into the catalyst increase its conductivity and activation energy. As for REE oxides, they decrease the conductivity and increase the activation energy. Catalysts with developed surface and high conductivity are also more active in the reaction of isopentane dehydration

Effect of gasoline composition on oxidative desulfurization using a phosphotungstic acid/activated carbon catalyst with hydrogen peroxide

International Nuclear Information System (INIS)

Xiao, Jing; Wu, Luoming; Wu, Ying; Liu, Bing; Dai, Lu; Li, Zhong; Xia, Qibin; Xi, Hongxia

2014-01-01

Highlights: • Concerned with the question why ODS catalyst is not effective for real gasoline. • Reported the strong inhibiting effect of gasoline composition on ODS for the 1st time. • ODS reactivity is suggested to be determined by partial charge on S atom of thiophene. • Proposed approaches to improve ODS selectivity for real gasoline desulfurization. - Abstract: This work is concerned with the question of why oxidative desulfurization (ODS) catalyst that show good catalytic performance for ODS of model gasoline thiophenic compounds is not effective for real gasoline. For the first time, the effects of gasoline composition on ODS using a phosphotungstic acid/activated carbon (HPW/AC) catalyst with H 2 O 2 were investigated. ODS of thiophene, one of the most difficult thiophenic compounds to be oxidized, was studied in a model fuel system, where a high thiophene conversion rate of 90% could be reached in 2 h at 90 °C. However, when applying the ODS to a real gasoline, the ODS conversion rate decreased to only 32%, suggesting a strong inhibiting effect of gasoline composition on ODS. The ODS studies in different model fuels suggested that the inhibiting effect can be ascribed to the competitive adsorption and oxidation with the presence of the alkenes and alkylated aromatic hydrocarbons in real gasoline. The active pi-electrons in alkenes and alkyl groups in alkylated aromatic hydrocarbons may react with polyoxoperoxo species or peroxo-metallate complexes formed by phosphotungstic acid–H 2 O 2 interaction. Additionally, it was indicated that the ODS selectivity followed the order of benzothiophene > trimethylthiophene > dimethylthiophene ∼ methylthiophene > thiophene, suggesting the partial charge on the electron-rich sulfur atom may play a decisive role for its oxidation reactivity. To mitigate the inhibiting effect of gasoline composition on ODS, we propose (a) implementation of selective separation–oxidation processes; (b) choice of suitable

Influence of ionizing radiation on the catalytic properties of oxide catalysts tested by hydrogen peroxide decomposition

International Nuclear Information System (INIS)

Mucka, V.

1987-01-01

Results of a study of some physical and catalytic properties of different oxide catalysts as affected by ionizing radiation (γ, n, e - ) and tested by the decomposition of hydrogen peroxide in aqueous solution are presented in this paper. The oxidation state of the active component present on the catalyst surface was found to be one of the most sensitive properties to the ionizing radiation. Changes of this state induced by γ-irradiation were found to be positive in most cases; electron pre-irradiation of the oxides leads, as a rule, to negative effects and the effects of neutron irradiation may be positive or negative. On the other hand, changes in the catalytic activity of the oxides after γ-or electron-irradiation seem to be mostly negative and positive, respectively; the effects of fast neutrons seem to vary here. Neither quantitative or qualitative correlation was found between the radiation-induced changes in these two quantities. The results give evidence that ionizing radiation principally affects the surface concentration of the catalytic sites. Both the character and magnitude of the changes in surface oxidation abilities and in catalytic activities of the oxide catalysts seem to be dependent upon the actual state of the catalyst surface. (author)

Synthesis and application of different phthalocyanine molecular sieve catalyst for oxidative desulfurization

International Nuclear Information System (INIS)

Zhao, Na; Li, Siwen; Wang, Jinyi; Zhang, Ronglan; Gao, Ruimin; Zhao, Jianshe; Wang, Junlong

2015-01-01

M 2 (PcAN) 2 (M=Fe, Co, Ni, Cu, Zn and Mn) anchored onto W-HZSM-5 (M 2 (PcAN) 2 –W-HZSM-5) or the M 2 (PcTN) 2 doping W-HZSM-5 (M 2 (PcTN) 2 /W-HZSM-5) were prepared and their catalytic performances were tested for oxidative desulfurization in the presence of oxygen. Thiophene (T), benzothiophene (BT), and dibenzothiophene (DBT) were considered as sulfur compounds. Among zeolite-based catalysts, the Cu 2 (PcAN) 2 –W-HZSM-5 and Cu 2 (PcTN) 2 /W-HZSM-5 showed superior desulfurization performance and the activity of selectivity followed the order: T>BT>DBT. The effects of phthalocyanine concentration were studied by UV–Vis and calcination temperature was obtained by TG-DSC for Cu 2 (PcTN) 2 /W-HZSM-5. Catalysts were characterized by EA, IR, XRD, SEM, TEM, ICP, and N 2 adsorption. Reaction time, temperature and the amount of catalyst were investigated as the important parameters for optimization of the reaction. Furthermore, a possible process of oxidative desulfurization and the reaction products were proposed. - Graphical abstract: The ODS reaction schematic shows the reaction mechanism of ultra-deep desulfurization. The sulfur compounds are oxidized to their corresponding sulfoxides or sulfones through the use of oxygen and catalysts. The reaction process of ultra-deep desulfurization. - Highlights: • A kind of novel catalyst for deep desulfurization was synthesized. • Cu 2 (PcAN) 2 –W-HZSM-5 exhibits excellent catalytic performance for desulfurization. • The reaction conditions that affect desulfurization efficiency are investigated. • The reaction process of model sulfur compounds is proposed

Relating FTS Catalyst Properties to Performance

Science.gov (United States)

Ma, Wenping; Ramana Rao Pendyala, Venkat; Gao, Pei; Jermwongratanachai, Thani; Jacobs, Gary; Davis, Burton H.

2016-01-01

During the reporting period June 23, 2011 to August 31, 2013, CAER researchers carried out research in two areas of fundamental importance to the topic of cobalt-based Fischer-Tropsch Synthesis (FTS): promoters and stability. The first area was research into possible substitute promoters that might be used to replace the expensive promoters (e.g., Pt, Re, and Ru) that are commonly used. To that end, three separate investigations were carried out. Due to the strong support interaction of ?-Al2O3 with cobalt, metal promoters are commonly added to commercial FTS catalysts to facilitate the reduction of cobalt oxides and thereby boost active surface cobalt metal sites. To date, the metal promoters examined have been those up to and including Group 11. Because two Group 11 promoters (i.e., Ag and Au) were identified to exhibit positive impacts on conversion, selectivity, or both, research was undertaken to explore metals in Groups 12 - 14. The three metals selected for this purpose were Cd, In, and Sn. At a higher loading of 25%Co on alumina, 1% addition of Cd, In, or Sn was found to-on average-facilitate reduction by promoting a heterogeneous distribution of cobalt consisting of larger lesser interacting cobalt clusters and smaller strongly interacting cobalt species. The lesser interacting species were identified in TPR profiles, where a sharp low temperature peak occurred for the reduction of larger, weakly interacting, CoO species. In XANES, the Cd, In, and Sn promoters were found to exist as oxides, whereas typical promoters (e.g., Re, Ru, Pt) were previously determined to exist in an metallic state in atomic coordination with cobalt. The larger cobalt clusters significantly decreased the active site density relative to the unpromoted 25%Co/Al2O3 catalyst. Decreasing the cobalt loading to 15%Co eliminated the large non-interacting species. The TPR peak for reduction of strongly interacting CoO in the Cd promoted catalyst occurred at a measurably lower temperature

Aerobic Oxidation of 5-(Hydroxymethyl)furfural in Ionic Liquids with Solid Ruthenium Hydroxide Catalysts

DEFF Research Database (Denmark)

Ståhlberg, Tim Johannes Bjarki; Eyjolfsdottir, Ester; Gorbanev, Yury

2012-01-01

The aerobic oxidation of 5-(hydroxymethyl)furfural was investigated over solid ruthenium hydroxide catalysts in ionic liquids at elevated temperatures and pressures. Several different catalyst supports were tested in combination with various ionic liquids. The best result was obtained in [EMIm...

Optimization of reaction conditions in selective oxidation of styrene over fine crystallite spinel-type CaFe2O4 complex oxide catalyst

International Nuclear Information System (INIS)

Pardeshi, Satish K.; Pawar, Ravindra Y.

2010-01-01

The CaFe 2 O 4 spinel-type catalyst was synthesized by citrate gel method and well characterized by thermogravimetric analysis, atomic absorption spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction and transmission electron microscopy. The crystallization temperature of the spinel particle prepared by citrate gel method was 600 o C which was lower than that of ferrite prepared by other methods. CaFe 2 O 4 catalysts prepared by citrate gel method show better activity for styrene oxidation in the presence of dilute H 2 O 2 (30%) as an oxidizing agent. In this reaction the oxidative cleavage of carbon-carbon double bond of styrene takes place selectively with 38 ± 2 mol% conversion. The major product of the reaction is benzaldehyde up to 91 ± 2 mol% and minor product phenyl acetaldehyde up to 9 ± 2 mol%, respectively. The products obtained in the styrene oxidation reaction were analyzed by gas chromatography and mass spectroscopy. The influence of the catalyst, reaction time, temperature, amount of catalyst, styrene/H 2 O 2 molar ratio and solvents on the conversion and product distribution were studied.

Complex catalysts from self-repairing ensembles to highly reactive air-based oxidation systems

Science.gov (United States)

Craig L. Hill; Laurent Delannoy; Dean C. Duncan; Ira A. Weinstock; Roman F. Renneke; Richard S. Reiner; Rajai H. Atalla; Jong Woo Han; Daniel A. Hillesheim; Rui Cao; Travis M. Anderson; Nelya M. Okun; Djamaladdin G. Musaev; Yurii V. Geletii

2007-01-01

Progress in four interrelated catalysis research efforts in our laboratory are summarized: (1) catalytic photochemical functionalization of unactivated CeH bonds by polyoxometalates (POMs); (2) self-repairing catalysts; (3) catalysts for air-based oxidations under ambient conditions; and (4) terminal oxo complexes of the late-transition metal elements and their...

Catalyst and method for reduction of nitrogen oxides

Science.gov (United States)

Ott, Kevin C [Los Alamos, NM

2008-05-27

A Selective Catalytic Reduction (SCR) catalyst was prepared by slurry coating ZSM-5 zeolite onto a cordierite monolith, then subliming an iron salt onto the zeolite, calcining the monolith, and then dipping the monolith either into an aqueous solution of manganese nitrate and cerium nitrate and then calcining, or by similar treatment with separate solutions of manganese nitrate and cerium nitrate. The supported catalyst containing iron, manganese, and cerium showed 80 percent conversion at 113 degrees Celsius of a feed gas containing nitrogen oxides having 4 parts NO to one part NO.sub.2, about one equivalent ammonia, and excess oxygen; conversion improved to 94 percent at 147 degrees Celsius. N.sub.2O was not detected (detection limit: 0.6 percent N.sub.2O).

Aerobic Oxidation of Xylose to Xylaric acid in Water over Pt Catalysts.

Science.gov (United States)

Saha, Basudeb; Sadula, Sunitha

2018-05-02

Energy-efficient catalytic conversion of biomass intermediates to functional chemicals can enable bio-products viable. Herein, we report an efficient and low temperature aerobic oxidation of xylose to xylaric acid, a promising bio-based chemical for the production of glutaric acid, over commercial catalysts in water. Among several heterogeneous catalysts investigated, Pt/C exhibits the best activity. Systematic variation of reaction parameters in the pH range of 2.5 to 10 suggests that the reaction is fast at higher temperatures but high C-C scission of intermediate C5-oxidized products to low carbon carboxylic acids undermines xylaric acid selectivity. The C-C cleavage is also high in basic solution. The oxidation at neutral pH and 60 C achieves the highest xylaric acid yield (64%). O2 pressure and Pt-amount have significant influence on the reactivity. Decarboxylation of short chain carboxylic acids results in formation of CO2, causing some carbon loss; however such decarboxylation is slow in the presence of xylose. The catalyst retained comparable activity, in terms of product selectivity, after five cycles with no sign of Pt leaching. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spectroelectrochemical Study of Carbon Monoxide and Ethanol Oxidation on Pt/C, PtSn(3:1/C and PtSn(1:1/C Catalysts

Directory of Open Access Journals (Sweden)

Rubén Rizo

2016-09-01

Full Text Available PtSn-based catalysts are one of the most active materials toward that contribute ethanol oxidation reaction (EOR. In order to gain a better understanding of the Sn influence on the carbon monoxide (principal catalyst poison and ethanol oxidation reactions in acidic media, a systematic spectroelectrochemical study was carried out. With this end, carbon-supported PtSnx (x = 0, 1/3 and 1 materials were synthesized and employed as anodic catalysts for both reactions. In situ Fourier transform infrared spectroscopy (FTIRS and differential electrochemical mass spectrometry (DEMS indicate that Sn diminishes the amount of bridge bonded CO (COB and greatly improves the CO tolerance of Pt-based catalysts. Regarding the effect of Sn loading on the EOR, it enhances the catalytic activity and decreases the onset potential. FTIRS and DEMS analysis indicate that the C-C bond scission occurs at low overpotentials and at the same potential values regardless of the Sn loading, although the amount of C-C bond breaking decreases with the rise of Sn in the catalytic material. Therefore, the elevated catalytic activity toward the EOR at PtSn-based electrodes is mainly associated with the improved CO tolerance and the incomplete oxidation of ethanol to form acetic acid and acetaldehyde species, causing the formation of a higher amount of both C2 products with the rise of Sn loading.

Ordered meso- and macroporous perovskite oxide catalysts for emerging applications

DEFF Research Database (Denmark)

Arandiyan, Hamidreza; Wang, Yuan; Sun, Hongyu

2018-01-01

This feature article summarizes the recent progress in porous perovskite oxides as advanced catalysts for both energy conversion applications and various heterogeneous reactions. Recently, research has been focused on specifically designing porous perovskite materials so that large surface areas ...

OXIDATIVE-REFORMING OF METHANE AND PARTIAL OXIDATION OF METHANE REACTIONS OVER NiO/PrO2/ZrO2 CATALYSTS: EFFECT OF NICKEL CONTENT

Directory of Open Access Journals (Sweden)

Y. J. O. Asencios

Full Text Available Abstract In this work the behavior of NiO-PrO2-ZrO2 catalysts containing various nickel loadings was evaluated in the partial oxidation of methane and oxidative-reforming reactions of methane. The catalysts were characterized by X-Ray Diffraction Analysis (in situ-XRD, Temperature Programmed Reduction (H2-TPR, Scanning Electron Microscopy (SEM/EDX and Adsorption-Desorption of nitrogen (BET area. The reactions were carried out at 750 °C and 1 atm for 5 hours. The catalysts were studied with different nickel content: 0, 5, 10 and 15% (related to total weight of catalyst, wt%. In both reactions, the catalyst containing the mixture of the three oxides (NiO/PrO2/ZrO2 with 15% nickel (15NiPrZr catalyst showed the best activity for the conversion of the reactants into Syngas and showed high selectivity for H2 and CO. The results suggest that the promoter PrO2 and the Niº centers are in a good proportion in the catalyst with 15% Ni. Our results showed that low nickel concentrations in the catalyst led to high metallic dispersion; however, very low nickel concentrations did not favor the methane transformation into Syngas. The catalyst containing only NiO/ZrO2 in the mixture was not sufficient for the catalysis. The presence of the promoter PrO2 was very important for the catalysis of the POM.

Selective hydrodeoxygenation of cyclic vicinal diols to cyclic alcohols over tungsten oxide-palladium catalysts.

Science.gov (United States)

Amada, Yasushi; Ota, Nobuhiko; Tamura, Masazumi; Nakagawa, Yoshinao; Tomishige, Keiichi

2014-08-01

Hydrodeoxygenation of cyclic vicinal diols such as 1,4-anhydroerythritol was conducted over catalysts containing both a noble metal and a group 5-7 transition-metal oxide. The combination of Pd and WOx allowed the removal of one of the two OH groups selectively. 3-Hydroxytetrahydrofuran was obtained from 1,4-anhydroerythritol in 72 and 74% yield over WOx -Pd/C and WOx -Pd/ZrO2 , respectively. The WOx -Pd/ZrO2 catalyst was reusable without significant loss of activity if the catalyst was calcined as a method of regeneration. Characterization of WOx -Pd/C with temperature-programmed reduction, X-ray diffraction, and transmission electron microscopy/energy-dispersive X-ray spectroscopy suggested that Pd metal particles approximately 9 nm in size were formed on amorphous tungsten oxide particles. A reaction mechanism was proposed on the basis of kinetics, reaction results with tungsten oxides under an atmosphere of Ar, and density functional theory calculations. A tetravalent tungsten center (W(IV) ) was formed by reduction of WO3 with the Pd catalyst and H2 , and this center served as the reductant for partial hydrodeoxygenation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Acetic Acid Formation by Selective Aerobic Oxidation of Aqueous Ethanol over Heterogeneous Ruthenium Catalysts

DEFF Research Database (Denmark)

Gorbanev, Yury; Kegnæs, Søren; Hanning, Christopher William

2012-01-01

Heterogeneous catalyst systems comprising ruthenium hydroxide supported on different carrier materials, titania, alumina, ceria, and spinel (MgAl2O4), were applied in selective aerobic oxidation ethanol to form acetic acid, an important bulk chemical and food ingredient. The catalysts were...

Effect of oxygen on decomposition of nitrous oxide over various metal oxide catalysts

International Nuclear Information System (INIS)

Satsuma, Atsushi; Maeshima, Hajime; Watanabe, Kiyoshi; Hattori, Tadashi

2001-01-01

The inhibitory effect of oxygen on decomposition of nitrous oxide over various metal oxide catalysts was investigated. The activity of nitrous oxide decomposition significantly decreased over CuO, Co 3 O 4 , NiO, Fe 2 O 3 , SnO 2 , In 2 O 3 and Cr 2 O 3 by reversible adsorption of oxygen onto the active sites. On the contrary to this, there was no or small change in the activity of TiO 2 , Al 2 O 3 , MgO, La 2 O 3 and CaO. A good correlation was observed between the degree of inhibition and the heat of formation of metal oxides. On the basis of kinetic model, the reduction of catalytic activity in the presence of oxygen was rationalized with the strength of oxygen adsorption on the metal oxide surface. (author)

Tungsten carbide/porous carbon composite as superior support for platinum catalyst toward methanol electro-oxidation

Energy Technology Data Exchange (ETDEWEB)

Jiang, Liming [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China); Fu, Honggang, E-mail: fuhg@vip.sina.com [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China); Key Laboratory of Functional Inorganic Material Chemistry, Heilongjiang University, Harbin 150080 (China); Wang, Lei; Mu, Guang; Jiang, Baojiang; Zhou, Wei; Wang, Ruihong [Key Laboratory of Functional Inorganic Material Chemistry, Heilongjiang University, Harbin 150080 (China)

2014-01-01

Graphical abstract: The WC nanoparticles are well dispersed in the carbon matrix. The size of WC nanoparticles is about 30 nm. It can be concluded that tungsten carbide and carbon composite was successfully prepared by the present synthesis conditions. - Highlights: • The WC/PC composite with high specific surface area was prepared by a simple way. • The Pt/WC/PC catalyst has superior performance toward methanol electro-oxidation. • The current density for methanol electro-oxidation is as high as 595.93 A g{sup −1} Pt. • The Pt/WC/PC catalyst shows better durability and stronger CO electro-oxidation. • The performance of Pt/WC/PC is superior to the commercial Pt/C (JM) catalyst. - Abstract: Tungsten carbide/porous carbon (WC/PC) composites have been successfully synthesized through a surfactant assisted evaporation-induced-assembly method, followed by a thermal treatment process. In particular, WC/PC-35-1000 composite with tungsten content of 35% synthesized at the carbonized temperature of 1000 °C, exhibited a specific surface area (S{sub BET}) of 457.92 m{sup 2} g{sup −1}. After loading Pt nanoparticles (NPs), the obtained Pt/WC/PC-35-1000 catalyst exhibits the highest unit mass electroactivity (595.93 A g{sup −1} Pt) toward methanol electro-oxidation, which is about 2.6 times as that of the commercial Pt/C (JM) catalyst. Furthermore, the Pt/WC/PC-35-1000 catalyst displays much stronger resistance to CO poisoning and better durability toward methanol electrooxidation compared with the commercial Pt/C (JM) catalyst. The high electrocatalytic activity, strong poison-resistivity and good stability of Pt/WC/PC-35-1000 catalyst are attributed to the porous structures and high specific surface area of WC/PC support could facilitate the rapid mass transportation. Moreover, synergistic effect between WC and Pt NPs is favorable to the higher catalytic performance.

Synthesis, characterization and application of a nano-manganese-catalyst as an efficient solid catalyst for solvent free selective oxidation of ethylbenzene, cyclohexene, and benzylalcohol

Science.gov (United States)

Habibi, Davood; Faraji, Ali Reza

2013-07-01

The object of this study is to synthesize the heterogeneous Mn-nano-catalyst (MNC) which has been covalently anchored on a modified nanoscaleSiO2/Al2O3, and characterized by FT-IR, UV-Vis, CHN elemental analysis, EDS, TEM, and EDX. The method is efficient for the highly selective oxidation of ethylbenzene, cyclohexene, and benzylalcohol without the need to any solvents, using tert-butyl hydroperoxide (TBHP) as an oxidant. Oxidation of ethylbenzene, cyclohexene, and benzylalcohol gave acetophenone, 2-cyclohexene-1-one and benzaldehyde, respectively, as major products. Reaction conditions have been optimized by considering the effect of various factors such as reaction time, amounts of substrates and oxidant, Mn-nano-catalyst and application of various solvents.

Permanganate oxidation of sulfur compounds to prevent poisoning of Pd catalysts in water treatment processes.

Science.gov (United States)

Angeles-Wedler, Dalia; Mackenzie, Katrin; Kopinke, Frank-Dieter

2008-08-01

The practical application of Pd-catalyzed water treatment processes is impeded by catalyst poisoning by reduced sulfur compounds (RSCs). In this study, the potential of permanganate as a selective oxidant for the removal of microbially generated RSCs in water and as a regeneration agent for S-poisoned catalysts was evaluated. Hydrodechlorination using Pd/Al2O3 was carried out as a probe reaction in permanganate-pretreated water. The activity of the Pd catalysts in the successfully pretreated reaction medium was similar to that in deionized water. The catalyst showed no deactivation behavior in the presence of permanganate at a concentration level or = 0.08 mM, a significant but temporary inhibition of the catalytic dechlorination was observed. Unprotected Pd/Al2O3, which had been completely poisoned by sulfide, was reactivated by a combined treatment with permanganate and hydrazine. However, the anthropogenic water pollutants thiophene and carbon disulfide were resistant against permanganate. Together with the preoxidation of catalyst poisons, hydrophobic protection of the catalysts was studied. Pd/zeolite and various hydrophobically coated catalysts showed a higher stability against ionic poisons and permanganate than the uncoated catalyst. By means of a combination of oxidative water pretreatment and hydrophobic catalyst protection, we provide a new tool to harness the potential of Pd-catalyzed hydrodehalogenation for the treatment of real waters.

Selective catalytic reduction of nitric oxide with acetaldehyde over NaY zeolite catalyst in lean exhaust feed

International Nuclear Information System (INIS)

Schmieg, Steven J.; Cho, Byong K.; Oh, Se H.

2004-01-01

Steady-state selective catalytic reduction (SCR) of nitric oxide (NO) was investigated under simulated lean-burn conditions using acetaldehyde (CH 3 CHO) as the reductant. This work describes the influence of catalyst space velocity and the impact of nitric oxide, acetaldehyde, oxygen, sulfur dioxide, and water on NO x reduction activity over NaY zeolite catalyst. Results indicate that with sufficient catalyst volume 90% NO x conversion can be achieved at temperatures relevant to light-duty diesel exhaust (150-350C). Nitric oxide and acetaldehyde react to form N 2 , HCN, and CO 2 . Oxygen is necessary in the exhaust feed stream to oxidize NO to NO 2 over the catalyst prior to reduction, and water is required to prevent catalyst deactivation. Under conditions of excess acetaldehyde (C 1 :N>6:1) and low temperature ( x conversion is apparently very high; however, the NO x conversion steadily declines with time due to catalytic oxidation of some of the stored (adsorbed) NO to NO 2 , which can have a significant impact on steady-state NO x conversion. With 250ppm NO in the exhaust feed stream, maximum NO x conversion at 200C can be achieved with =400ppm of acetaldehyde, with higher acetaldehyde concentrations resulting in production of acetic acid and breakthrough of NO 2 causing lower NO x conversion levels. Less acetaldehyde is necessary at lower NO concentrations, while more acetaldehyde is required at higher temperatures. Sulfur in the exhaust feed stream as SO 2 can cause slow deactivation of the catalyst by poisoning the adsorption and subsequent reaction of nitric oxide and acetaldehyde, particularly at low temperature

Highly selective oxidative dehydrogenation of ethane with supported molten chloride catalysts

Energy Technology Data Exchange (ETDEWEB)

Gaertner, C.A.; Veen, A.C. van; Lercher, J.A. [Technische Univ. Muenchen (Germany). Catalysis Research Center

2011-07-01

Ethene production is one of the most important transformations in chemical industry, given that C{sub 2}H{sub 4} serves as building block for many mass-market products. Besides conventional thermal processes like steam cracking of ethane, ethane can be produced selectively by catalytic processes. One of the classes of catalysts that have been reported in literature as active and highly selective for the oxidative dehydrogenation of ethane is that of supported molten chloride catalysts, containing an alkali chloride overlayer on a solid support. This work deals with fundamental aspects of the catalytic action in latter class of catalysts. Results from kinetic reaction studies are related to observations in detailed characterization and lead to a comprehensive mechanistic understanding. Of fundamental importance towards mechanistic insights is the oxygen storage capacity of the catalysts that has been determined by transient step experiments. (orig.)

CO2-Free Power Generation on an Iron Group Nanoalloy Catalyst via Selective Oxidation of Ethylene Glycol to Oxalic Acid in Alkaline Media

Science.gov (United States)

Matsumoto, Takeshi; Sadakiyo, Masaaki; Ooi, Mei Lee; Kitano, Sho; Yamamoto, Tomokazu; Matsumura, Syo; Kato, Kenichi; Takeguchi, Tatsuya; Yamauchi, Miho

2014-07-01

An Fe group ternary nanoalloy (NA) catalyst enabled selective electrocatalysis towards CO2-free power generation from highly deliverable ethylene glycol (EG). A solid-solution-type FeCoNi NA catalyst supported on carbon was prepared by a two-step reduction method. High-resolution electron microscopy techniques identified atomic-level mixing of constituent elements in the nanoalloy. We examined the distribution of oxidised species, including CO2, produced on the FeCoNi nanoalloy catalyst in the EG electrooxidation under alkaline conditions. The FeCoNi nanoalloy catalyst exhibited the highest selectivities toward the formation of C2 products and to oxalic acid, i.e., 99 and 60%, respectively, at 0.4 V vs. the reversible hydrogen electrode (RHE), without CO2 generation. We successfully generated power by a direct EG alkaline fuel cell employing the FeCoNi nanoalloy catalyst and a solid-oxide electrolyte with oxygen reduction ability, i.e., a completely precious-metal-free system.

Synthesis of highly efficient Mn{sub 2}O{sub 3} catalysts for CO oxidation derived from Mn-MIL-100

Energy Technology Data Exchange (ETDEWEB)

Zhang, Xiaodong, E-mail: fatzhxd@126.com [Environment and Low-Carbon Research Center, School of Environment and Architecture, University of Shanghai for Science and Technology, Shanghai 200093 (China); Li, Hongxin; Hou, Fulin; Yang, Yang; Dong, Han; Liu, Ning [Environment and Low-Carbon Research Center, School of Environment and Architecture, University of Shanghai for Science and Technology, Shanghai 200093 (China); Wang, Yuxin [Institute of Applied Biotechnology, Taizhou Vocation & Technical College, Taizhou, Zhejiang 318000 (China); Cui, Lifeng, E-mail: lifeng.cui@gmail.com [Environment and Low-Carbon Research Center, School of Environment and Architecture, University of Shanghai for Science and Technology, Shanghai 200093 (China)

2017-07-31

Highlights: • The morphology of porous Mn{sub 2}O{sub 3} cubes was inherited from Mn-MIL-100 template. • Mn{sub 2}O{sub 3} obtained at calcined temperature of 700 °C displayed high activity. • Enhanced activity is attributed to surface active oxygen, and reduction behavior. - Abstract: In this work, metal-organic frameworks (MOFs) Mn-MIL-100 were first prepared, which were next used as templates to obtain the irregular porous Mn{sub 2}O{sub 3} cubes through calcination with air at different temperature. The catalysts were characterized by N{sub 2} adsorption-desorption, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), H{sub 2}-temperature program reduction (H{sub 2}-TPR) and X-ray photoelectron spectroscopic (XPS). The catalytic activity for CO oxidation over Mn{sub 2}O{sub 3} catalysts was investigated. It was found that calcination temperature had a strong effect on the structure and catalytic activity of Mn{sub 2}O{sub 3} catalyst. Mn{sub 2}O{sub 3} catalyst obtained by calcined at 700 °C (Mn{sub 2}O{sub 3}-700) showed a smaller specific surface area, but displayed a high catalytic activity and excellent stability with a complete CO conversion temperature (T{sub 98}) of 240 °C, which was attributed to the unique structure, a high quantity of surface active oxygen species, smaller particle size, oxygen vacancies and good low temperature reduction behavior. The effect of water vapor on catalytic activity was also examined. The introduction of water vapor to the feedstock induced a positive effect on CO oxidation over Mn{sub 2}O{sub 3}-700 catalyst. Furthermore, no obvious drop is observed in activity over catalysts even in the presence of water vapor during 48 h.

Enhanced methanol electro-oxidation reaction on Pt-CoO{sub x}/MWCNTs hybrid electro-catalyst

Energy Technology Data Exchange (ETDEWEB)

Nouralishahi, Amideddin, E-mail: Nouralishahi@ut.ac.ir [Catalysis and Nanostructured Materials Research Laboratory, School of Chemical Engineering, University of Tehran, P.O. Box 11155/4563, Tehran (Iran, Islamic Republic of); Caspian Faculty of Engineering, University of Tehran, P.O. Box 43841-119, Rezvanshahr (Iran, Islamic Republic of); Catalysis and Nanotechnology Research Division, Research Institute of Petroleum Industry (RIPI), P.O. Box 14665-1998, Tehran (Iran, Islamic Republic of); Rashidi, Ali Morad, E-mail: Rashidiam@ripi.ir [Catalysis and Nanotechnology Research Division, Research Institute of Petroleum Industry (RIPI), P.O. Box 14665-1998, Tehran (Iran, Islamic Republic of); Mortazavi, Yadollah, E-mail: Mortazav@ut.ac.ir [Catalysis and Nanostructured Materials Research Laboratory, School of Chemical Engineering, University of Tehran, P.O. Box 11155/4563, Tehran (Iran, Islamic Republic of); Khodadadi, Abbas Ali, E-mail: Khodadad@ut.ac.ir [Catalysis and Nanostructured Materials Research Laboratory, School of Chemical Engineering, University of Tehran, P.O. Box 11155/4563, Tehran (Iran, Islamic Republic of); Choolaei, Mohammadmehdi, E-mail: Choolaeimm@ripi.ir [Catalysis and Nanotechnology Research Division, Research Institute of Petroleum Industry (RIPI), P.O. Box 14665-1998, Tehran (Iran, Islamic Republic of)

2015-04-30

Highlights: • Promoting effects of Cobalt oxide on methanol electro-oxidation over Pt/MWCNTs are investigated. • Higher activity, about 2.9 times, and enhanced stability are observed on Pt-CoO{sub x}/MWCNTs. • Electrochemical active surface area of Pt nanoparticles is significantly improved upon CoO{sub x} addition. • Bi-functional mechanism is facilitated in presence of CoO{sub x}. - Abstract: The electro-catalytic behavior of Pt-CoO{sub x}/MWCNTs in methanol electro-oxidation reaction (MOR) is investigated and compared to that of Pt/MWCNTs. The electro-catalysts were synthesized by an impregnation method using NaBH{sub 4} as the reducing agent. The morphological and physical characteristics of samples are examined by XRD, TEM, ICP and EDS techniques. In the presence of CoO{sub x}, Pt nanoparticles were highly distributed on the support with an average particle size of 2 nm, an obvious decrease from 5.1 nm for Pt/MWCNTs. Cyclic voltammetry, CO-stripping, Chronoamperometry, and electrochemical impedance spectroscopy (EIS) measurements are used to study the electrochemical behavior of the electro-catalysts. The results revealed a considerable enhancement in the oxidation kinetics of CO{sub ads} on Pt active sites by the participation of CoO{sub x}. Compared to Pt/MWCNTs, Pt-CoO{sub x}/MWCNTs sample has a larger electrochemical active surface area (ECSA) and higher electro-catalytic activity and stability toward methanol electro-oxidation. According to the results of cyclic voltammetry, the forward anodic peak current density enhances more than 89% at the optimum atomic ratio of Pt:Co = 2:1. Furthermore, inclusion of cobalt oxide species causes the onset potential of methanol electro-oxidation reaction to shift 84 mV to negative values compared to that on Pt/MWCNTs. Based on EIS data, dehydrogenation of methanol is the rate-determining step of MOR on both Pt/MWCNTs and Pt-CoO{sub x}/MWCNTs, at small overpotentials. However, at higher overpotentials, the

Synthesis and application of different phthalocyanine molecular sieve catalyst for oxidative desulfurization

Energy Technology Data Exchange (ETDEWEB)

Zhao, Na; Li, Siwen; Wang, Jinyi; Zhang, Ronglan [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, Shaanxi Key Laboratory of Physico-Inorganic Chemistry, College of Chemistry & Material Science, Northwest University, Xi’an 710069, Shaanxi (China); Composites Research Institute, Weinan Normal University, Weinan 714000 (China); Gao, Ruimin [Research Institute of Shaanxi Yanchang Petroleum Group Corp. Ltd., Xi’an 710075 (China); Composites Research Institute, Weinan Normal University, Weinan 714000 (China); Zhao, Jianshe, E-mail: jszhao@nwu.edu.cn [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, Shaanxi Key Laboratory of Physico-Inorganic Chemistry, College of Chemistry & Material Science, Northwest University, Xi’an 710069, Shaanxi (China); Composites Research Institute, Weinan Normal University, Weinan 714000 (China); Wang, Junlong [Research Institute of Shaanxi Yanchang Petroleum Group Corp. Ltd., Xi’an 710075 (China); Composites Research Institute, Weinan Normal University, Weinan 714000 (China)

2015-05-15

M{sub 2}(PcAN){sub 2} (M=Fe, Co, Ni, Cu, Zn and Mn) anchored onto W-HZSM-5 (M{sub 2}(PcAN){sub 2}–W-HZSM-5) or the M{sub 2}(PcTN){sub 2} doping W-HZSM-5 (M{sub 2}(PcTN){sub 2}/W-HZSM-5) were prepared and their catalytic performances were tested for oxidative desulfurization in the presence of oxygen. Thiophene (T), benzothiophene (BT), and dibenzothiophene (DBT) were considered as sulfur compounds. Among zeolite-based catalysts, the Cu{sub 2}(PcAN){sub 2}–W-HZSM-5 and Cu{sub 2}(PcTN){sub 2}/W-HZSM-5 showed superior desulfurization performance and the activity of selectivity followed the order: T>BT>DBT. The effects of phthalocyanine concentration were studied by UV–Vis and calcination temperature was obtained by TG-DSC for Cu{sub 2}(PcTN){sub 2}/W-HZSM-5. Catalysts were characterized by EA, IR, XRD, SEM, TEM, ICP, and N{sub 2} adsorption. Reaction time, temperature and the amount of catalyst were investigated as the important parameters for optimization of the reaction. Furthermore, a possible process of oxidative desulfurization and the reaction products were proposed. - Graphical abstract: The ODS reaction schematic shows the reaction mechanism of ultra-deep desulfurization. The sulfur compounds are oxidized to their corresponding sulfoxides or sulfones through the use of oxygen and catalysts. The reaction process of ultra-deep desulfurization. - Highlights: • A kind of novel catalyst for deep desulfurization was synthesized. • Cu{sub 2}(PcAN){sub 2}–W-HZSM-5 exhibits excellent catalytic performance for desulfurization. • The reaction conditions that affect desulfurization efficiency are investigated. • The reaction process of model sulfur compounds is proposed.

Biodiesel production using alkali earth metal oxides catalysts synthesized by sol-gel method

Directory of Open Access Journals (Sweden)

Majid Mohadesi

2014-03-01

Full Text Available Biodiesel fuel is considered as an alternative to diesel fuel. This fuel is produced through transesterification reactions of vegetable oils or animal fat by alcohols in the presence of different catalysts. Recent studies on this process have shown that, basic heterogeneous catalysts have a higher performance than other catalysts. In this study different alkali earth metal oxides (CaO, MgO and BaO doped SiO2 were used as catalyst for the biodiesel production process. These catalysts were synthesis by using the sol-gel method. A transesterification reaction was studied after 8h by mixing corn oil, methanol (methanol to oil molar ratio of 16:1, and 6 wt. % catalyst (based on oil at 60oC and 600rpm. Catalyst loading was studied for different catalysts ranging in amounts from 40, 60 to 80%. The purity and yield of the produced biodiesel for 60% CaO/SiO2 was higher than other catalysts and at 97.3% and 82.1%, respectively.

Sensitization of Nanocrystalline Metal Oxides with a Phosphonate-Functionalized Perylene Diimide for Photoelectrochemical Water Oxidation with a CoOx Catalyst.

Science.gov (United States)

Kirner, Joel T; Finke, Richard G

2017-08-23

A planar organic thin film composed of a perylene diimide dye (N,N'-bis(phosphonomethyl)-3,4,9,10-perylenediimide, PMPDI) with photoelectrochemically deposited cobalt oxide (CoO x ) catalyst was previously shown to photoelectrochemically oxidize water (DOI: 10.1021/am405598w). Herein, the same PMPDI dye is studied for the sensitization of different nanostructured metal oxide (nano-MO x ) films in a dye-sensitized photoelectrochemical cell architecture. Dye adsorption kinetics and saturation decreases in the order TiO 2 > SnO 2 ≫ WO 3 . Despite highest initial dye loading on TiO 2 films, photocurrent with hydroquinone (H 2 Q) sacrificial reductant in pH 7 aqueous solution is much higher on SnO 2 films, likely due to a higher driving force for charge injection into the more positive conduction band energy of SnO 2 . Dyeing conditions and SnO 2 film thickness were subsequently optimized to achieve light-harvesting efficiency >99% at the λ max of the dye, and absorbed photon-to-current efficiency of 13% with H 2 Q, a 2-fold improvement over the previous thin-film architecture. A CoO x water-oxidation catalyst was photoelectrochemically deposited, allowing for photoelectrochemical water oxidation with a faradaic efficiency of 31 ± 7%, thus demonstrating the second example of a water-oxidizing, dye-sensitized photoelectrolysis cell composed entirely of earth-abundant materials. However, deposition of CoO x always results in lower photocurrent due to enhanced recombination between catalyst and photoinjected electrons in SnO 2 , as confirmed by open-circuit photovoltage measurements. Possible future studies to enhance photoanode performance are discussed, including alternative catalyst deposition strategies or structural derivatization of the perylene dye.

DFT studies of the substituent effects of dimethylamino on non-heme active oxidizing species: iron(V)-oxo species or iron(IV)-oxo acetate aminopyridine cation radical species?

Science.gov (United States)

Wang, Fang; Sun, Wei; Xia, Chungu; Wang, Yong

2017-10-01

Through the introduction of dimethylamino (Me 2 N) substituent at the pyridine ring of 2-((R)-2-[(R)-1-(pyridine-2-ylmethyl)pyrrolidin-2-yl]pyrrolidin-1-ylmethyl)pyridine (PDP) ligand, the non-heme Fe II ( Me2N PDP)/H 2 O 2 /AcOH catalyst system was found to exhibit significant higher catalytic activity and enantioselectivity than the non-substituent one in the asymmetric epoxidation experiments. The mechanistic origin of the remarkable substituent effects in these oxidation reactions has not been well established. To ascertain the potent oxidant and the related reaction mechanism, a detailed DFT calculation was performed. Interestingly, a novel Fe(IV)-oxo Me2N PDP cation radical species, [( Me2N PDP) + · Fe IV (O)(OAc)] 2+ ( Me2N 5), with about one spin spreading over the non-heme Me2N PDP ligand was formed via a carboxylic-acid-assisted O-O bond heterolysis, which is reminiscent of Compound I (an Fe(IV)(O)(porphyrin cation radical) species) in cytochrome P450 chemistry. Me2N 5 is energetically comparable with the cyclic ferric peracetate species Me2N 6, while in the pristine Fe(PDP) catalyst system, H 6 is more stable than H 5. Comparison of the activation energy for the ethylene epoxidation promoted by Me2N 5 and Me2N 6, Me2N 5 is supposed as the true oxidant triggering the epoxidation of olefins. In addition, a systematic research on the substituent effects varied from the electron-donating substituent (dMM, the substituents at sites 3, 4, and 5 of the pyridine ring: methyl, methoxyl, and methyl) to the electron-withdrawing one (CF 3 , 2,6-bis(trifluoromethyl)phenyl) on the electronic structure of the reaction intermediates has also been investigated. An alternative cyclic ferric peracetate complex is obtained, indicating that the substituents at the pyridine ring of PDP ligands have significant impacts on the electronic structure of the oxidants.

Partial oxidation of dimethyl ether using the structured catalyst Rh/Al2O3/Al prepared through the anodic oxidation of aluminum.

Science.gov (United States)

Yu, B Y; Lee, K H; Kim, K; Byun, D J; Ha, H P; Byun, J Y

2011-07-01

The partial oxidation of dimethyl ether (DME) was investigated using the structured catalyst Rh/Al2O3/Al. The porous Al2O3 layer was synthesized on the aluminum plate through anodic oxidation in an oxalic-acid solution. It was observed that about 20 nm nanopores were well developed in the Al2O3 layer. The thickness of Al2O3 layer can be adjusted by controlling the anodizing time and current density. After pore-widening and hot-water treatment, the Al2O3/Al plate was calcined at 500 degrees C for 3 h. The obtained delta-Al2O3 had a specific surface area of 160 m2/g, making it fit to be used as a catalyst support. A microchannel reactor was designed and fabricated to evaluate the catalytic activity of Rh/Al2O3/Al in the partial oxidation of DME. The structured catalyst showed an 86% maximum hydrogen yield at 450 degrees C. On the other hand, the maximum syngas yield by a pack-bed-type catalyst could be attained by using a more than fivefold Rh amount compared to that used in the structured Rh/Al2O3/Al catalyst.

Electrocatalytic Reduction-oxidation of Chlorinated Phenols using a Nanostructured Pd-Fe Modified Graphene Catalyst

International Nuclear Information System (INIS)

Shi, Qin; Wang, Hui; Liu, Shaolei; Pang, Lei; Bian, Zhaoyong

2015-01-01

A Pd-Fe modified graphene (Pd-Fe/G) catalyst was prepared by the Hummers oxidation method and bimetallic co-deposition method. The catalyst was then characterized by various characterization techniques and its electrochemical property toward the electrocatalytic reduction-oxidation of chlorinated phenols was investigated by using cyclic voltammetry and differential pulse voltammetry. The results of the characterization show that the Pd-Fe/G catalyst in which the weight proportion of Pd and Fe is 1:1 has an optimal surface performance. The diameter of the Pd-Fe particles is approximately 5.2 ± 0.3 nm, with a uniform distribution on the supporting graphene. This is smaller than the Pd particles of a Pd-modified graphene (Pd/G) catalyst. The Pd-Fe/G catalyst shows a higher electrocatalytic activity than the Pd/G catalyst for reductive dechlorination when feeding with hydrogen gas. The reductive peak potentials of −0.188 V, −0.836 V and −0.956 V in the DPV curves are attributed to the dechlorination of ortho-Cl, meta-Cl, and para-Cl in 2-chlorophenol, 3-chlorophenol and 4-chlorophenol, respectively. In accordance with an analysis of the frontier orbital theory, the order of ease of dechlorination with Pd-Fe/G catalyst is 2-chlorophenol > 3-chlorophenol > 4-chlorophenol. The Pd-Fe/G catalyst has a greater activity than the Pd/G catalyst in accelerating the two-electron reduction of O_2 to H_2O_2, which is attributed to the higher current of the reduction peak at approximately −0.40 V when feeding with oxygen gas. Therefore, the Pd-Fe/G catalyst exhibits a higher electrocatalytic activity than the Pd/G catalyst for the reductive dechlorination and acceleration of the two-electron reduction of O_2 to H_2O_2.

Promotion of Pt-Ru/C catalysts driven by heat treated induced surface segregation for methanol oxidation reaction

International Nuclear Information System (INIS)

Wei Yuchen; Liu Chenwei; Chang Weijung; Wang Kuanwen

2011-01-01

Research highlights: → Thermal treatments on the Pt-Ru/C induce different extents of surface segregation. → O 2 treatment results in obvious Ru segregation and formation of RuO 2 . → Catalysts treated in H 2 have the excellent CO de-poisoning ability. → N 2 treatment suppresses the surface Pt depletion and hence promotes the MOR. - Abstract: Carbon supported Pt-Ru/C (1:1) alloy catalysts supplied by E-TEK are widely used for fuel cell research. Heat treatments in various atmospheres are conducted for the promotion of the methanol oxidation reaction (MOR) and the investigation of the structure-activity relationship (SAR) of the catalysts. The alloy structures, surface compositions, surface species, and electro-catalytic activities of the alloy catalysts are characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV), respectively. The as-received Pt-Ru/C catalysts have a Ru rich in the inner core and Pt rich on the outer shell structure. Thermal treatments on the catalysts induce Ru surface segregation in different extents and thereby lead to their alteration of the alloying degrees. O 2 treatment results in obvious Ru segregation and formation of RuO 2 . Catalysts treated in H 2 have the highest I f /I b value in the CV scans among all samples, indicating the catalysts have the excellent CO de-poisoning ability as evidenced by anodic CO stripping experiments. N 2 treatment may serve as an adjustment process for the surface composition and structure of the catalysts, which can suppress the surface Pt depletion (∼60% Pt on the surface), make the components stable and hence promote the MOR significantly.

Promotion of Pt-Ru/C catalysts driven by heat treated induced surface segregation for methanol oxidation reaction

Energy Technology Data Exchange (ETDEWEB)

Wei Yuchen; Liu Chenwei; Chang Weijung [Institute of Materials Science and Engineering, National Central University, Taoyuan 32001, Taiwan (China); Wang Kuanwen, E-mail: kuanwen.wang@gmail.com [Institute of Materials Science and Engineering, National Central University, Taoyuan 32001, Taiwan (China)

2011-01-12

Research highlights: > Thermal treatments on the Pt-Ru/C induce different extents of surface segregation. > O{sub 2} treatment results in obvious Ru segregation and formation of RuO{sub 2}. > Catalysts treated in H{sub 2} have the excellent CO de-poisoning ability. > N{sub 2} treatment suppresses the surface Pt depletion and hence promotes the MOR. - Abstract: Carbon supported Pt-Ru/C (1:1) alloy catalysts supplied by E-TEK are widely used for fuel cell research. Heat treatments in various atmospheres are conducted for the promotion of the methanol oxidation reaction (MOR) and the investigation of the structure-activity relationship (SAR) of the catalysts. The alloy structures, surface compositions, surface species, and electro-catalytic activities of the alloy catalysts are characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV), respectively. The as-received Pt-Ru/C catalysts have a Ru rich in the inner core and Pt rich on the outer shell structure. Thermal treatments on the catalysts induce Ru surface segregation in different extents and thereby lead to their alteration of the alloying degrees. O{sub 2} treatment results in obvious Ru segregation and formation of RuO{sub 2}. Catalysts treated in H{sub 2} have the highest I{sub f}/I{sub b} value in the CV scans among all samples, indicating the catalysts have the excellent CO de-poisoning ability as evidenced by anodic CO stripping experiments. N{sub 2} treatment may serve as an adjustment process for the surface composition and structure of the catalysts, which can suppress the surface Pt depletion ({approx}60% Pt on the surface), make the components stable and hence promote the MOR significantly.

Characterization of Cu/CeO2/Al2O3 catalysts by temperature programmed reduction and activity for CO oxidation

International Nuclear Information System (INIS)

Cataluna, Renato; Baibich, Ione M.; Dallago, R.M.; Picinini, C.; Martinez-Arias, A.; Soria, J.

2001-01-01

The kinetic parameters for the CO oxidation reaction using copper/alumina-modified ceria as catalysts were determined. The catalysts with different concentrations of the metals were prepared using impregnation methods. In addition, the reduction-oxidation behaviour of the catalysts were investigated by temperature-programmed reduction. The activity results show that the mechanism for CO oxidation is bifunctional: oxygen is activated on the anionic vacancies of ceria surface, while carbon monoxide is adsorbed preferentially on the higher oxidation copper site. Therefore, the reaction occurs on the interfacial active centers. Temperatures-programmed Reduction patterns show a higher dispersion when cerium oxide is present. (author)

METHANOL OXIDATION OVER AU/ γ -AL 2O3 CATALYSTS 149