Catalysts, methods of making catalysts, and methods of use

KAUST Repository

Renard, Laetitia; El Eter, Mohamad; Caps, Valerie; Basset, Jean-Marie

2014-01-01

Embodiments of the present disclosure provide for catalysts, methods of making catalysts, methods of using catalysts, and the like. In an embodiment, the method of making the catalysts can be performed in a single step with a metal nanoparticle precursor and a metal oxide precursor, where a separate stabilizing agent is not needed.

Catalysts, methods of making catalysts, and methods of use

KAUST Repository

Renard, Laetitia

2014-03-06

Embodiments of the present disclosure provide for catalysts, methods of making catalysts, methods of using catalysts, and the like. In an embodiment, the method of making the catalysts can be performed in a single step with a metal nanoparticle precursor and a metal oxide precursor, where a separate stabilizing agent is not needed.

Development of Ni-Based Catalysts Derived from Hydrotalcite-Like Compounds Precursors for Synthesis Gas Production via Methane or Ethanol Reforming

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Ya-Li Du

2017-02-01

Full Text Available As a favorably clean fuel, syngas (synthesis gas production has been the focus of concern in past decades. Substantial literatures reported the syngas production by various catalytic reforming reactions particularly in methane or ethanol reforming. Among the developed catalysts in these reforming processes, Ni-based catalysts from hydrotalcite-like compounds (HTLcs precursors have drawn considerable attention for their preferable structural traits. This review covers the recent literature reporting syngas production with Ni-based catalysts from HTLc precursors via methane or ethanol reforming. The discussion was initiated with catalyst preparation (including conventional and novel means, followed by subsequent thermal treatment processes, then composition design and the addition of promoters in these catalysts. As Ni-based catalysts have thermodynamic potential to deactivate because of carbon deposition or metal sintering, measures for dealing with these problems were finally summarized. To obtain optimal catalytic performances and resultantly better syngas production, based on analyzing the achievements of the references, some perspectives were finally proposed.

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

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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.

Sodium citrate-assisted anion exchange strategy for construction of Bi2O2CO3/BiOI photocatalysts

International Nuclear Information System (INIS)

Song, Peng-Yuan; Xu, Ming; Zhang, Wei-De

2015-01-01

Highlights: • Heterostructured Bi 2 O 2 CO 3 /BiOI microspheres were prepared via anion exchange. • Sodium citrate-assisted anion exchange for construction of composite photocatalysts. • Bi 2 O 2 CO 3 /BiOI composites show high visible light photocatalytic activity. - Abstract: Bi 2 O 2 CO 3 /BiOI heterojuncted photocatalysts were constructed through a facile partial anion exchange strategy starting from BiOI microspheres and urea with the assistance of sodium citrate. The content of Bi 2 O 2 CO 3 in the catalysts was regulated by modulating the amount of urea as a precursor, which was decomposed to generate CO 3 2− in the hydrothermal process. Citrate anion plays a key role in controlling the morphology and composition of the products. The Bi 2 O 2 CO 3 /BiOI catalysts display much higher photocatalytic activity than pure BiOI and Bi 2 O 2 CO 3 towards the degradation of rhodamine B (RhB) and bisphenol A (BPA). The enhancement of photocatalytic activity of the heterojuncted catalysts is attributed to the formation of p–n junction between p-BiOI and n-Bi 2 O 2 CO 3 , which is favorable for retarding the recombination of photoinduced electron-hole pairs. Moreover, the holes are demonstrated to be the main active species for the degradation of RhB and BPA

Influence of Cobalt Precursor on Efficient Production of Commercial Fuels over FTS Co/SiC Catalyst

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Ana Raquel de la Osa

2016-07-01

Full Text Available β-SiC-supported cobalt catalysts have been prepared from nitrate, acetate, chloride and citrate salts to study the dependence of Fischer–Tropsch synthesis (FTS on the type of precursor. Com/SiC catalysts were synthetized by vacuum-assisted impregnation while N2 adsorption/desorption, XRD, TEM, TPR, O2 pulses and acid/base titrations were used as characterization techniques. FTS catalytic performance was carried out at 220 °C and 250 °C while keeping constant the pressure (20 bar, space velocity (6000 Ncm3/g·h and syngas composition (H2/CO:2. The nature of cobalt precursor was found to influence basic behavior, extent of reduction and metallic particle size. For β-SiC-supported catalysts, the use of cobalt nitrate resulted in big Co crystallites, an enhanced degree of reduction and higher basicity compared to acetate, chloride and citrate-based catalysts. Consequently, cobalt nitrate provided a better activity and selectivity to C5+ (less than 10% methane was formed, which was centered in kerosene-diesel fraction (α = 0.90. On the contrary, catalyst from cobalt citrate, characterized by the highest viscosity and acidity values, presented a highly dispersed distribution of Co nanoparticles leading to a lower reducibility. Therefore, a lower FTS activity was obtained and chain growth probability was shortened as observed from methane and gasoline-kerosene (α = 0.76 production when using cobalt citrate.

Alkaline ionic liquids applied in supported ionic liquid catalyst for selective hydrogenation of citral to citronellal

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Eero eSalminen

2014-02-01

Full Text Available The challenge in preparation of ionic liquids containing a strong alkaline anion is to identify a suitable cation which can tolerate the harsh conditions induced by the anion. In this study, a commercial quaternary ammonium compound (quat benzalkonium [ADBA] (alkyldimethylbenzylammonium was used as a cation in the synthesis of different alkaline ionic liquids. In fact, the precursor, benzalkonium chloride, is a mixture of alkyldimethylbenzylammonium chlorides of various alkyl chain lengths and is commonly used in the formulation of various antiseptic products. The prepared ionic liquids were utilized as Supported Ionic Liquid Catalysts (SILCAs. Typically, a SILCA contains metal nanoparticles, enzymes or metal complexes in an ionic liquid layer which is immobilized on a solid carrier material such as an active carbon cloth (ACC. The catalysts were applied in the selective hydrogenation of citral to citronellal which is an important perfumery chemical. Interestingly, 70 % molar yield towards citronellal was achieved over a catalyst containing the alkaline ionic liquid benzalkonium methoxide.

Alkaline ionic liquids applied in supported ionic liquid catalyst for selective hydrogenation of citral to citronellal

Science.gov (United States)

Salminen, Eero; Virtanen, Pasi; Mikkola, Jyri-Pekka

2014-01-01

The challenge in preparation of ionic liquids containing a strong alkaline anion is to identify a suitable cation which can tolerate the harsh conditions induced by the anion. In this study, a commercial quaternary ammonium compound (quat) benzalkonium [ADBA] (alkyldimethylbenzylammonium) was used as a cation in the synthesis of different alkaline ionic liquids. In fact, the precursor, benzalkonium chloride, is a mixture of alkyldimethylbenzylammonium chlorides of various alkyl chain lengths and is commonly used in the formulation of various antiseptic products. The prepared ionic liquids were utilized as Supported Ionic Liquid Catalysts (SILCAs). Typically, a SILCA contains metal nanoparticles, enzymes, or metal complexes in an ionic liquid layer which is immobilized on a solid carrier material such as an active carbon cloth (ACC). The catalysts were applied in the selective hydrogenation of citral to citronellal which is an important perfumery chemical. Interestingly, 70% molar yield toward citronellal was achieved over a catalyst containing the alkaline ionic liquid benzalkonium methoxide. PMID:24790972

Methanol Reforming over Cobalt Catalysts Prepared from Fumarate Precursors: TPD Investigation

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Eftichia Papadopoulou

2016-02-01

Full Text Available Temperature-programmed desorption (TPD was employed to investigate adsorption characteristics of CH3OH, H2O, H2, CO2 and CO on cobalt-manganese oxide catalysts prepared through mixed Co-Mn fumarate precursors either by pyrolysis or oxidation and oxidation/reduction pretreatment. Pyrolysis temperature and Co/Mn ratio were the variable synthesis parameters. Adsorption of methanol, water and CO2 was carried out at room temperature. Adsorption of H2 and H2O was carried out at 25 and 300 °C. Adsorption of CO was carried out at 25 and 150 °C. The goal of the work was to gain insight on the observed differences in the performance of the aforementioned catalysts in methanol steam reforming. TPD results indicated that activity differences are mostly related to variation in the number density of active sites, which are able to adsorb and decompose methanol.

Fabrication of CdS nanowires with increasing anionic precursor by SILAR method

Science.gov (United States)

Dariani, R. S.; Salehi, F.

2016-05-01

CdS nanowires were fabricated on glass substrate at room temperature by SILAR method with cadmium nitrate cationic and sodium sulfide anionic precursors. The deposition were done at different S:Cd concentration ratios of 1:1, 3:1, 5:1, and 7:1. Nanowires growth procedure was studied in the mentioned concentrations. The number of immersion cycles was kept constant at 15 cycles. EDX analysis showed that in all stoichiometric ratios, S/Cd composition ratio remains at about unity. Our results indicated that S:Cd concentration ratio of 7:1 had the longest nanowires with hexagonal structure. The main objective of this paper was to produce CdS nanowires with increasing concentration of sulfur.

Crystallization of an amorphous B-C-N precursor with a Li-B-N catalyst at high pressures and temperatures

Energy Technology Data Exchange (ETDEWEB)

Li Dongxu; Yu Dongli; Wang Peng; Li Yingmei; He Julong; Xu Bo; Liu Zhongyuan [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, Hebei Province (China); Tian Yongjun, E-mail: fhcl@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, Hebei Province (China)

2009-11-15

An orthorhombic B-C-N compound was synthesized using an amorphous B-C-N precursor and a Li-B-N catalyst at 6 GPa and 1773 K. The results of energy dispersive spectrometry and electronic energy loss spectrometry suggest a stoichiometry of B:C:N = 1:3.3:1. In addition, the Li-B-N catalyst improves the crystallizations of the B-C-N compound, graphite and BN and therefore might be a profitable catalyst in ultrahigh pressure experiments.

Crystallization of an amorphous B-C-N precursor with a Li-B-N catalyst at high pressures and temperatures

International Nuclear Information System (INIS)

Li Dongxu; Yu Dongli; Wang Peng; Li Yingmei; He Julong; Xu Bo; Liu Zhongyuan; Tian Yongjun

2009-01-01

An orthorhombic B-C-N compound was synthesized using an amorphous B-C-N precursor and a Li-B-N catalyst at 6 GPa and 1773 K. The results of energy dispersive spectrometry and electronic energy loss spectrometry suggest a stoichiometry of B:C:N = 1:3.3:1. In addition, the Li-B-N catalyst improves the crystallizations of the B-C-N compound, graphite and BN and therefore might be a profitable catalyst in ultrahigh pressure experiments.

Recent Advances in Solid Catalysts Obtained by Metalloporphyrins Immobilization on Layered Anionic Exchangers: A Short Review and Some New Catalytic Results

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Shirley Nakagaki

2016-02-01

Full Text Available Layered materials are a very interesting class of compounds obtained by stacking of two-dimensional layers along the basal axis. A remarkable property of these materials is their capacity to interact with a variety of chemical species, irrespective of their charge (neutral, cationic or anionic. These species can be grafted onto the surface of the layered materials or intercalated between the layers, to expand or contract the interlayer distance. Metalloporphyrins, which are typically soluble oxidation catalysts, are examples of molecules that can interact with layered materials. This work presents a short review of the studies involving metalloporphyrin immobilization on two different anionic exchangers, Layered Double Hydroxides (LDHs and Layered Hydroxide Salts (LHSs, published over the past year. After immobilization of anionic porphyrins, the resulting solids behave as reusable catalysts for heterogeneous oxidation processes. Although a large number of publications involving metalloporphyrin immobilization on LDHs exist, only a few papers have dealt with LHSs as supports, so metalloporphyrins immobilized on LHSs represent a new and promising research field. This work also describes new results on an anionic manganese porphyrin (MnP immobilized on Mg/Al-LDH solids with different nominal Mg/Al molar ratios (2:1, 3:1 and 4:1 and intercalated with different anions (CO32− or NO3−. The influence of the support composition on the MnP immobilization rates and the catalytic performance of the resulting solid in cyclooctene oxidation reactions will be reported.

Recent Advances in Solid Catalysts Obtained by Metalloporphyrins Immobilization on Layered Anionic Exchangers: A Short Review and Some New Catalytic Results.

Science.gov (United States)

Nakagaki, Shirley; Mantovani, Karen Mary; Machado, Guilherme Sippel; Castro, Kelly Aparecida Dias de Freitas; Wypych, Fernando

2016-02-29

Layered materials are a very interesting class of compounds obtained by stacking of two-dimensional layers along the basal axis. A remarkable property of these materials is their capacity to interact with a variety of chemical species, irrespective of their charge (neutral, cationic or anionic). These species can be grafted onto the surface of the layered materials or intercalated between the layers, to expand or contract the interlayer distance. Metalloporphyrins, which are typically soluble oxidation catalysts, are examples of molecules that can interact with layered materials. This work presents a short review of the studies involving metalloporphyrin immobilization on two different anionic exchangers, Layered Double Hydroxides (LDHs) and Layered Hydroxide Salts (LHSs), published over the past year. After immobilization of anionic porphyrins, the resulting solids behave as reusable catalysts for heterogeneous oxidation processes. Although a large number of publications involving metalloporphyrin immobilization on LDHs exist, only a few papers have dealt with LHSs as supports, so metalloporphyrins immobilized on LHSs represent a new and promising research field. This work also describes new results on an anionic manganese porphyrin (MnP) immobilized on Mg/Al-LDH solids with different nominal Mg/Al molar ratios (2:1, 3:1 and 4:1) and intercalated with different anions (CO₃(2-) or NO₃(-)). The influence of the support composition on the MnP immobilization rates and the catalytic performance of the resulting solid in cyclooctene oxidation reactions will be reported.

Hydrodeoxygenation of coal using organometallic catalyst precursors

Science.gov (United States)

Kirby, Stephen R.

2002-04-01

coals. Trends within the data were similar to those reported by other authors. Based on the conclusions from both the model compound studies and the coal analysis, predictions were made of the catalyst precursors' performance in the HDO of the three selected coals. It was concluded that CoMo-T2 is a desirable catalyst precursor for the HDO of coals (particularly low-rank coals), but that an optimum set of conditions must be determined to take full advantage of its HDO ability. (Abstract shortened by UMI.)

Halloysite-derived nitrogen doped carbon electrocatalysts for anion exchange membrane fuel cells

Science.gov (United States)

Lu, Yaxiang; Wang, Lianqin; Preuß, Kathrin; Qiao, Mo; Titirici, Maria-Magdalena; Varcoe, John; Cai, Qiong

2017-12-01

Developing the low-cost, highly active carbonaceous materials for oxygen reduction reaction (ORR) catalysts has been a high-priority research direction for durable fuel cells. In this paper, two novel N-doped carbonaceous materials with flaky and rod-like morphology using the natural halloysite as template are obtained from urea nitrogen source as well as glucose (denoted as GU) and furfural (denoted as FU) carbon precursors, respectively, which can be directly applied as metal-free electrocatalysts for ORR in alkaline electrolyte. Importantly, compared with a benchmark Pt/C (20wt%) catalyst, the as-prepared carbon catalysts demonstrate higher retention in diffusion limiting current density (after 3000 cycles) and enhanced methanol tolerances with only 50-60mV negative shift in half-wave potentials. In addition, electrocatalytic activity, durability and methanol tolerant capability of the two N-doped carbon catalysts are systematically evaluated, and the underneath reasons of the outperformance of rod-like catalysts over the flaky are revealed. At last, the produced carbonaceous catalysts are also used as cathodes in the single cell H2/O2 anion exchange membrane fuel cell (AEMFC), in which the rod-like FU delivers a peak power density as high as 703 mW cm-2 (vs. 1106 mW cm-2 with a Pt/C benchmark cathode catalyst).

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

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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.

Precursor Mediated Synthesis of Nanostructured Silicas: From Precursor-Surfactant Ion Pairs to Structured Materials.

Science.gov (United States)

Hesemann, Peter; Nguyen, Thy Phung; Hankari, Samir El

2014-04-11

The synthesis of nanostructured anionic-surfactant-templated mesoporous silica (AMS) recently appeared as a new strategy for the formation of nanostructured silica based materials. This method is based on the use of anionic surfactants together with a co-structure-directing agent (CSDA), mostly a silylated ammonium precursor. The presence of this CSDA is necessary in order to create ionic interactions between template and silica forming phases and to ensure sufficient affinity between the two phases. This synthetic strategy was for the first time applied in view of the synthesis of surface functionalized silica bearing ammonium groups and was then extended on the formation of materials functionalized with anionic carboxylate and bifunctional amine-carboxylate groups. In the field of silica hybrid materials, the "anionic templating" strategy has recently been applied for the synthesis of silica hybrid materials from cationic precursors. Starting from di- or oligosilylated imidazolium and ammonium precursors, only template directed hydrolysis-polycondensation reactions involving complementary anionic surfactants allowed accessing structured ionosilica hybrid materials. The mechanistic particularity of this approach resides in the formation of precursor-surfactant ion pairs in the hydrolysis-polycondensation mixture. This review gives a systematic overview over the various types of materials accessed from this cooperative ionic templating approach and highlights the high potential of this original strategy for the formation of nanostructured silica based materials which appears as a complementary strategy to conventional soft templating approaches.

Transition metal sulfide promoted molybdenum or tungsten sulfide catalysts and their uses for hydroprocessing

International Nuclear Information System (INIS)

Jacobson, A.J.; Chianelli, R.R.; Pecoraro, T.A.

1987-01-01

A process is described for hydrorefining a hydrocarbon feed which comprises contacting the feed at a temperature of at least about 150 0 C and in the presence of hydrogen with a catalyst obtained by heating one or more precursor salts at elevated temperature of at least about 150 0 C, in the presence of sulfur or one or more sulfur-bearing compounds and under oxygen-free conditions for a time sufficient to form the catalyst. The precursor salt contains a tetrathiometallate anion of Mo, W or mixture thereof and a cation comprising one or more divalent promoter metals which are chelated by at least one neutral, nitrogen-containing polydentate ligand. The divalent promoter metal is selected from the group consisting of Ni, Co, Zn, Cu and mixture thereof. The contacting occurs for a time sufficient to hydrorefine at least a portion of the feed

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.

Precursor Mediated Synthesis of Nanostructured Silicas: From Precursor-Surfactant Ion Pairs to Structured Materials

Directory of Open Access Journals (Sweden)

Peter Hesemann

2014-04-01

Full Text Available The synthesis of nanostructured anionic-surfactant-templated mesoporous silica (AMS recently appeared as a new strategy for the formation of nanostructured silica based materials. This method is based on the use of anionic surfactants together with a co-structure-directing agent (CSDA, mostly a silylated ammonium precursor. The presence of this CSDA is necessary in order to create ionic interactions between template and silica forming phases and to ensure sufficient affinity between the two phases. This synthetic strategy was for the first time applied in view of the synthesis of surface functionalized silica bearing ammonium groups and was then extended on the formation of materials functionalized with anionic carboxylate and bifunctional amine-carboxylate groups. In the field of silica hybrid materials, the “anionic templating” strategy has recently been applied for the synthesis of silica hybrid materials from cationic precursors. Starting from di- or oligosilylated imidazolium and ammonium precursors, only template directed hydrolysis-polycondensation reactions involving complementary anionic surfactants allowed accessing structured ionosilica hybrid materials. The mechanistic particularity of this approach resides in the formation of precursor-surfactant ion pairs in the hydrolysis-polycondensation mixture. This review gives a systematic overview over the various types of materials accessed from this cooperative ionic templating approach and highlights the high potential of this original strategy for the formation of nanostructured silica based materials which appears as a complementary strategy to conventional soft templating approaches.

Directed deposition of silicon nanowires using neopentasilane as precursor and gold as catalyst

Directory of Open Access Journals (Sweden)

Britta Kämpken

2012-07-01

Full Text Available In this work the applicability of neopentasilane (Si(SiH34 as a precursor for the formation of silicon nanowires by using gold nanoparticles as a catalyst has been explored. The growth proceeds via the formation of liquid gold/silicon alloy droplets, which excrete the silicon nanowires upon continued decomposition of the precursor. This mechanism determines the diameter of the Si nanowires. Different sources for the gold nanoparticles have been tested: the spontaneous dewetting of gold films, thermally annealed gold films, deposition of preformed gold nanoparticles, and the use of “liquid bright gold”, a material historically used for the gilding of porcelain and glass. The latter does not only form gold nanoparticles when deposited as a thin film and thermally annealed, but can also be patterned by using UV irradiation, providing access to laterally structured layers of silicon nanowires.

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

Uniformly active phase loaded selective catalytic reduction catalysts (V_2O_5/TNTs) with superior alkaline resistance performance

International Nuclear Information System (INIS)

Wang, Haiqiang; Wang, Penglu; Chen, Xiongbo; Wu, Zhongbiao

2017-01-01

Highlights: • VOSO_4 exhibited better synergistic effect with titanate nanotubes than NH_4VO_3. • Ion-exchange reaction occurs between VOSO_4 and titanate nanotubes. • Ion-exchange resulting in uniformly vanadium distribution on titanate nanotubes. • VOSO_4-based catalyst exhibited impressive SCR activity and alkaline resistance. - Abstract: In this work, protonated titanate nanotubes was performed as a potential useful support and different vanadium precursors (NH_4VO_3 and VOSO_4) were used to synthesize deNO_x catalysts. The results showed that VOSO_4 exhibited better synergistic effect with titanate nanotubes than NH_4VO_3, which was caused by the ion-exchange reaction. Then high loading content of vanadium, uniformly active phase distribution, better dispersion of vanadium, more acid sites, better V"5"+/V"4"+ redox cycles and superior oxygen mobility were achieved. Besides, VOSO_4-based titanate nanotubes catalysts also showed enhanced alkaline resistance than particles (P25) based catalysts. It was strongly associated with its abundant acid sites, large surface area, flexible redox cycles and oxygen transfer ability. For the loading on protonated titanate nanotubes, active metal with cation groups was better precursors than anion ones. V_2O_5/TNTs catalyst was a promising substitute for the commercial vanadium catalysts and the work conducted herein provided a useful idea to design uniformly active phase loaded catalyst.

Microwave plasma enhanced chemical vapor deposition growth of few-walled carbon nanotubes using catalyst derived from an iron-containing block copolymer precursor

International Nuclear Information System (INIS)

Wang Peng; Lu, Jennifer; Zhou, Otto

2008-01-01

The microwave plasma enhanced chemical vapor deposition (MPECVD) method is now commonly used for directional and conformal growth of carbon nanotubes (CNTs) on supporting substrates. One of the shortcomings of the current process is the lack of control of the diameter and diameter distribution of the CNTs due to difficulties in synthesizing well-dispersed catalysts. Recently, block copolymer derived catalysts have been developed which offer the potential of fine control of both the size of and the spacing between the metal clusters. In this paper we report the successful growth of CNTs with narrow diameter distribution using polystyrene-block-polyferrocenylethylmethylsilane (PS-b-PFEMS) as the catalyst precursor. The study shows that higher growth pressure leads to better CNT growth. Besides the pressure, the effects on the growth of CNTs of the growth parameters, such as temperature and precursor gas ratio, are also studied

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.

Development of Ni-Based Catalysts Derived from Hydrotalcite-Like Compounds Precursors for Synthesis Gas Production via Methane or Ethanol Reforming

OpenAIRE

Ya-Li Du; Xu Wu; Qiang Cheng; Yan-Li Huang; Wei Huang

2017-01-01

As a favorably clean fuel, syngas (synthesis gas) production has been the focus of concern in past decades. Substantial literatures reported the syngas production by various catalytic reforming reactions particularly in methane or ethanol reforming. Among the developed catalysts in these reforming processes, Ni-based catalysts from hydrotalcite-like compounds (HTLcs) precursors have drawn considerable attention for their preferable structural traits. This review covers the recent literature r...

Petroleum residue upgrading with dispersed catalysts. Part 1. Catalysts activity and selectivity

Energy Technology Data Exchange (ETDEWEB)

Panariti, N.; Del Bianco, A.; Del Piero, G. [ENITECNOLOGIE S.p.A, Via Maritano 26, 20097 San Donato Mil. (Italy); Marchionna, M. [SNAMPROGETTI S.p.A, Via Maritano 26, 20097 San Donato Mil. (Italy)

2000-12-04

The results of a study aimed at the identification of the relevant chemical aspects involved in the process of upgrading heavy feedstocks in the presence of dispersed catalysts are discussed. The catalytic activity of different compounds was compared in terms of products yields and quality. Moreover, a detailed and systematic characterization of the catalysts recovered at the end of the reactions was achieved. The experimental work provided quite a large set of data, allowing to investigate the factors that may affect catalyst activity (precursor solubility, rate of activation, degree of dispersion, presence of promoters, etc.). The results of this study demonstrate that the best performances are obtained by the microcrystalline molybdenite generated in situ by oil-soluble precursors. The nature of the organic ligand does not play a very relevant role in influencing the hydrogenation activity. The presence of phosphorus, however, significantly enhances hydrodemetallation, at least in terms of vanadium removal. Bimetallic precursors show a slight synergistic effect towards the hydrodesulfurization reaction. Microsized powdered catalyst precursors have a much lower catalytic activity compared to the oil-soluble ones.

Anions in Cometary Comae

Science.gov (United States)

Charnley, Steven B.

2011-01-01

The presence of negative ions (anions) in cometary comae is known from Giotto mass spectrometry of IP/Halley. The anions 0-, OH-, C-, CH- and CN- have been detected, as well as unidentified anions with masses 22-65 and 85-110 amu (Chaizy et al. 1991). Organic molecular anions are known to have a significant impact on the charge balance of interstellar clouds and circumstellar envelopes and have been shown to act as catalysts for the gas-phase synthesis of larger hydrocarbon molecules in the ISM, but their importance in cometary comae has not yet been explored. We present details of the first attempt to model the chemistry of anions in cometary comae. Based on the combined chemical and hydro dynamical model of Rodgers & Charnley (2002), we investigate the role of large carbon-chain anions in cometary coma chemistry. We calculate the effects of these anions on coma thermodynamics, charge balance and examine their impact on molecule formation.

Phosphazene-promoted anionic polymerization

KAUST Repository

Zhao, Junpeng

2014-01-01

In the recent surge of metal-free polymerization techniques, phosphazene bases have shown their remarkable potential as organic promoters/catalysts for the anionic polymerization of various types of monomers. By complexation with the counterion (e.g. proton or lithium cation), phosphazene base significantly improve the nucleophilicity of the initiator/chain-end resulting in rapid and usually controlled anionic/quasi-anionic polymerization. In this review, we will introduce the general mechanism, i.e. in situ activation (of initiating sites) and polymerization, and summarize the applications of such a mechanism on macromolecular engineering toward functionalized polymers, block copolymers and complex macromolecular architectures.

DOE Award No. DE-FC36-03GO13108 NOVEL NON-PRECIOUS METAL CATALYSTS FOR PEMFC: CATALYST SELECTION THROUGH MOLECULAR MODELING AND DURABILITY STUDIES Final Report (September 2003 – October 2008)

Energy Technology Data Exchange (ETDEWEB)

Branko N. Popov

2009-02-20

The objective of this project is to develop novel non-precious metal electrocatalysts for oxygen reduction reaction (ORR), and demonstrate the potential of the catalysts to perform at least as good as conventional Pt catalysts currently in use in polymer electrolyte membrane fuel cell (PEMFC) with a cost at least 50 % less than a target of 0.2 g (Pt loading)/peak kW and with durability > 2,000 h operation with less than 10 % power degradation. A novel nitrogen-modified carbon-based catalyst was obtained by modifying carbon black with nitrogen-containing organic precursor in the absence of transition metal precursor. The catalyst shows the onset potential of approximately 0.76 V (NHE) for ORR and the amount of H2O2 of approximately 3% at 0.5 V (NHE). Furthermore, a carbon composite catalyst was achieved through the high-temperature pyrolysis of the precursors of transition metal (Co and Fe) and nitrogen supported on the nitrogen-modified carbon-based catalyst, followed by chemical post-treatment. This catalyst showed an onset potential for ORR as high as 0.87 V (NHE), and generated less than 1 % of H2O2. The PEM fuel cell exhibited a current density of 2.3 A cm-2 at 0.2 V for a catalyst loading of 6.0 mg cm-2. No significant performance degradation was observed for 480 h continuous operation. The characterization studies indicated that the metal-nitrogen chelate complexes decompose at the temperatures above 800 oC. During the pyrolysis, the transition metals facilitate the incorporation of pyridinic and graphitic nitrogen groups into the carbon matrix, and the carbon surface modified with nitrogen is active for ORR. In order to elucidate the role of transition metal precursor played in the formation of active sites in the non-precious metal catalysts, a novel ruthenium-based chelate (RuNx) catalyst was synthesized by using RuCl3 and propylene diammine as the Ru and N precursors, respectively, followed by high-temperature pyrolysis. This catalyst exhibited comparable

DOE Award No. DE-FC36-03GO13108 NOVEL NON-PRECIOUS METAL CATALYSTS FOR PEMFC: CATALYST SELECTION THROUGH MOLECULAR MODELING AND DURABILITY STUDIES Final Report (September 2003 – October 2008)

Energy Technology Data Exchange (ETDEWEB)

Branko N. Popov

2009-03-03

The objective of this project is to develop novel non-precious metal electrocatalysts for oxygen reduction reaction (ORR), and demonstrate the potential of the catalysts to perform at least as good as conventional Pt catalysts currently in use in polymer electrolyte membrane fuel cell (PEMFC) with a cost at least 50 % less than a target of 0.2 g (Pt loading)/peak kW and with durability > 2,000 h operation with less than 10 % power degradation. A novel nitrogen-modified carbon-based catalyst was obtained by modifying carbon black with nitrogen-containing organic precursor in the absence of transition metal precursor. The catalyst shows the onset potential of approximately 0.76 V (NHE) for ORR and the amount of H2O2 of approximately 3% at 0.5 V (NHE). Furthermore, a carbon composite catalyst was achieved through the high-temperature pyrolysis of the precursors of transition metal (Co and Fe) and nitrogen supported on the nitrogen-modified carbon-based catalyst, followed by chemical post-treatment. This catalyst showed an onset potential for ORR as high as 0.87 V (NHE), and generated less than 1 % of H2O2. The PEM fuel cell exhibited a current density of 2.3 A cm-2 at 0.2 V for a catalyst loading of 6.0 mg cm-2. No significant performance degradation was observed for 480 h continuous operation. The characterization studies indicated that the metal-nitrogen chelate complexes decompose at the temperatures above 800 oC. During the pyrolysis, the transition metals facilitate the incorporation of pyridinic and graphitic nitrogen groups into the carbon matrix, and the carbon surface modified with nitrogen is active for ORR. In order to elucidate the role of transition metal precursor played in the formation of active sites in the non-precious metal catalysts, a novel ruthenium-based chelate (RuNx) catalyst was synthesized by using RuCl3 and propylene diammine as the Ru and N precursors, respectively, followed by high-temperature pyrolysis. This catalyst exhibited comparable

exchanged Mg-Al hydrotalcite catalyst

Indian Academy of Sciences (India)

) catalysts, ... The catalyst can be easily separated by simple filtration ... surface area by the single-point N2 adsorption method ... concentration of carbonate anions (by treating the cat- .... hydrotalcite phase along with copper hydroxide and.

Pt/XC-72 catalysts coated with nitrogen-doped carbon (Pt/XC-72@C–N) for methanol electro-oxidation

Energy Technology Data Exchange (ETDEWEB)

Cao, Jun; Chu, Yuanyuan; Tan, Xiaoyao, E-mail: cestanxy@aliyun.com

2014-03-01

Pt/XC-72 catalysts coated with N-doped carbon (denoted as Pt/XC-72@C–N) for the electro-oxidation of methanol are prepared through a combined microwave-assisted polyol with in-situ carbonization of N-doped carbon coating process using polyvinylpyrrolidone (PVP), 1-vinyl-3-ethylimidazolium nitrate (VEIN) or 1-ethyl-3-methylimidazolium dicyanamide (EMID) ionic liquid as the N-doped carbon precursor. X-ray diffraction, energy dispersive of X-ray, transmission electron microscopy, X-ray photoelectron spectroscopy, cyclic voltammograms and accelerated aging test techniques are applied to characterize the structure and the electro-catalytic activity of the catalysts. The results show that the Pt particles with the average size of around 2.5 nm are highly dispersed in face-centered cubic crystal structure in the carbon support. The structure of the N-doped carbon coating precursor has considerable influence on the electro-catalytic performance of the catalysts. The resultant catalyst with EMID ionic liquid as the N-doped carbon source exhibits 115.9 m{sup 2} g{sup −1}Pt electrochemical surface area (ESA) and 0.66 A mg{sup −1}Pt catalytic activity towards the electro-oxidation of methanol, which are 1.37 times the ESA and 1.35 times the catalytic activity of the PVP-derived catalyst, and 2.02 times the electrochemical surface area and 1.94 times the catalytic activity of the VEIN-derived catalyst. The appropriate amount of the EMID ionic liquid used in the catalyst synthesis process is around 10 uL for 100 mg XC-72 support so as to obtain the highest electro-catalytic activity. - Highlights: • N-doped carbon coated Pt/C catalyst is prepared for methanol electro-oxidation. • Pt/XC-72@C–N exhibits excellent electrocatalytic activity over uncoated catalysts. • Ionic liquid with anionic cyano groups is most suitable as N-doped carbon precursor. • The appropriate amount of ionic liquid for coating is around 10 μL for 100 mg carbon.

Uniformly active phase loaded selective catalytic reduction catalysts (V{sub 2}O{sub 5}/TNTs) with superior alkaline resistance performance

Energy Technology Data Exchange (ETDEWEB)

Wang, Haiqiang; Wang, Penglu [Key Laboratory of Environment Remediation and Ecological Health, Ministry of Education, College of Environmental & Resources Science, Zhejiang University, 310058 Hangzhou (China); Zhejiang Provincial Engineering Research Center of Industrial Boiler & Furnace Flue Gas Pollution Control, Hangzhou 310027 (China); Chen, Xiongbo [South China Institute of Environmental Sciences, Ministry of Environmental Protection, Guangzhou 510655 (China); Wu, Zhongbiao, E-mail: zbwu@zju.edu.cn [Key Laboratory of Environment Remediation and Ecological Health, Ministry of Education, College of Environmental & Resources Science, Zhejiang University, 310058 Hangzhou (China); Zhejiang Provincial Engineering Research Center of Industrial Boiler & Furnace Flue Gas Pollution Control, Hangzhou 310027 (China)

2017-02-15

Highlights: • VOSO{sub 4} exhibited better synergistic effect with titanate nanotubes than NH{sub 4}VO{sub 3}. • Ion-exchange reaction occurs between VOSO{sub 4} and titanate nanotubes. • Ion-exchange resulting in uniformly vanadium distribution on titanate nanotubes. • VOSO{sub 4}-based catalyst exhibited impressive SCR activity and alkaline resistance. - Abstract: In this work, protonated titanate nanotubes was performed as a potential useful support and different vanadium precursors (NH{sub 4}VO{sub 3} and VOSO{sub 4}) were used to synthesize deNO{sub x} catalysts. The results showed that VOSO{sub 4} exhibited better synergistic effect with titanate nanotubes than NH{sub 4}VO{sub 3}, which was caused by the ion-exchange reaction. Then high loading content of vanadium, uniformly active phase distribution, better dispersion of vanadium, more acid sites, better V{sup 5+}/V{sup 4+} redox cycles and superior oxygen mobility were achieved. Besides, VOSO{sub 4}-based titanate nanotubes catalysts also showed enhanced alkaline resistance than particles (P25) based catalysts. It was strongly associated with its abundant acid sites, large surface area, flexible redox cycles and oxygen transfer ability. For the loading on protonated titanate nanotubes, active metal with cation groups was better precursors than anion ones. V{sub 2}O{sub 5}/TNTs catalyst was a promising substitute for the commercial vanadium catalysts and the work conducted herein provided a useful idea to design uniformly active phase loaded catalyst.

High-performance oxygen reduction catalysts in both alkaline and acidic fuel cells based on pre-treating carbon material and iron precursor

Energy Technology Data Exchange (ETDEWEB)

Song, Ping; Barkholtz, Heather M.; Wang, Ying; Xu, Weilin; Liu, Dijia; Zhuang, Lin

2017-12-01

We demonstrate a new and simple method for pre-treating the carbon material and iron precursor to prepare oxygen reduction reaction (ORR) catalysts, which can produce super-high performance and stability in alkaline solution, with high performance in acid solution. This strategy using cheap materials is simply controllable. Moreover, it has achieved smaller uniform nanoparticles to exhibit high stability, and the synergetic effect of Fe and N offered much higher performance in ORR than commercial Pt/C, with high maximum power density in alkaline and acid fuel cell test. So it can make this kind of catalysts be the most promising alternatives of Pt-based catalysts with best performance/price.

Co-Assembled Supported Catalysts: Synthesis of Nano-Structured Supported Catalysts with Hierarchic Pores through Combined Flow and Radiation Induced Co-Assembled Nano-Reactors

Directory of Open Access Journals (Sweden)

Galip Akay

2016-05-01

Full Text Available A novel generic method of silica supported catalyst system generation from a fluid state is presented. The technique is based on the combined flow and radiation (such as microwave, thermal or UV induced co-assembly of the support and catalyst precursors forming nano-reactors, followed by catalyst precursor decomposition. The transformation from the precursor to supported catalyst oxide state can be controlled from a few seconds to several minutes. The resulting nano-structured micro-porous silica supported catalyst system has a surface area approaching 300 m2/g and X-ray Diffraction (XRD-based catalyst size controlled in the range of 1–10 nm in which the catalyst structure appears as lamellar sheets sandwiched between the catalyst support. These catalyst characteristics are dependent primarily on the processing history as well as the catalyst (Fe, Co and Ni studied when the catalyst/support molar ratio is typically 0.1–2. In addition, Ca, Mn and Cu were used as co-catalysts with Fe and Co in the evaluation of the mechanism of catalyst generation. Based on extensive XRD, Scanning Electron Microscopy (SEM and Transmission Electron Microscopy (TEM studies, the micro- and nano-structure of the catalyst system were evaluated. It was found that the catalyst and silica support form extensive 0.6–2 nm thick lamellar sheets of 10–100 nm planar dimensions. In these lamellae, the alternate silica support and catalyst layer appear in the form of a bar-code structure. When these lamellae structures pack, they form the walls of a micro-porous catalyst system which typically has a density of 0.2 g/cm3. A tentative mechanism of catalyst nano-structure formation is provided based on the rheology and fluid mechanics of the catalyst/support precursor fluid as well as co-assembly nano-reactor formation during processing. In order to achieve these structures and characteristics, catalyst support must be in the form of silane coated silica nano

Catalytic oxidation of n-hexane promoted by Ce{sub 1−x}Cu{sub x}O{sub 2} catalysts prepared by one-step polymeric precursor method

Energy Technology Data Exchange (ETDEWEB)

Araújo, Vinícius D., E-mail: dantas@ursa.ifsc.usp.br [Instituto de Física, Universidade de São Paulo – USP, 13560-970 São Carlos, SP (Brazil); Lima, Maurício M. de [Instituto de Ciencia de los Materiales, Universidad de Valencia, E-46071 Valencia (Spain); Fundación General, Universitat de Valencia, Valencia (Spain); Cantarero, Andrés [Instituto de Ciencia de los Materiales, Universidad de Valencia, E-46071 Valencia (Spain); Bernardi, Maria I.B. [Instituto de Física, Universidade de São Paulo – USP, 13560-970 São Carlos, SP (Brazil); Bellido, Jorge D.A. [CAP-Engenharia Química, Universidade Federal de São João Del-Rei – UFSJ, São João Del-Rei, MG (Brazil); Assaf, Elisabete M. [Instituto de Química, Universidade de São Paulo – USP, 13560-970 São Carlos, SP (Brazil); Balzer, Rosana; Probst, Luiz F.D. [Departamento de Química, Universidade Federal de Santa Catarina – UFSC, 88040-900 Florianópolis, SC (Brazil); Fajardo, Humberto V. [Departamento de Química, Universidade Federal de Ouro Preto – UFOP, 35400-000 Ouro Preto, MG (Brazil)

2013-11-01

Ceria-supported copper catalysts (Ce{sub 1−x}Cu{sub x}O{sub 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{sub 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{sub 1−x}Cu{sub x}O{sub 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{sub 0.97}Cu{sub 0.03}O{sub 2} and Ce{sub 0.99}Cu{sub 0.01}O{sub 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{sub 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.

In situ Generated Ruthenium Catalyst Systems Bearing Diverse N-Heterocyclic Carbene Precursors for Atom-Economic Amide Synthesis from Alcohols and Amines.

Science.gov (United States)

Cheng, Hua; Xiong, Mao-Qian; Cheng, Chuan-Xiang; Wang, Hua-Jing; Lu, Qiang; Liu, Hong-Fu; Yao, Fu-Bin; Chen, Cheng; Verpoort, Francis

2018-02-16

The transition-metal-catalyzed direct synthesis of amides from alcohols and amines is herein demonstrated as a highly environmentally benign and atom-economic process. Among various catalyst systems, in situ generated N-heterocyclic carbene (NHC)-based ruthenium (Ru) halide catalyst systems have been proven to be active for this transformation. However, these existing catalyst systems usually require an additional ligand to achieve satisfactory results. In this work, through extensive screening of a diverse variety of NHC precursors, we discovered an active in situ catalyst system for efficient amide synthesis without any additional ligand. Notably, this catalyst system was found to be insensitive to the electronic effects of the substrates, and various electron-deficient substrates, which were not highly reactive with our previous catalyst systems, could be employed to afford the corresponding amides efficiently. Furthermore, mechanistic investigations were performed to provide a rationale for the high activity of the optimized catalyst system. NMR-scale reactions indicated that the rapid formation of a Ru hydride intermediate (signal at δ=-7.8 ppm in the 1 H NMR spectrum) after the addition of the alcohol substrate should be pivotal in establishing the high catalyst activity. Besides, HRMS analysis provided possible structures of the in situ generated catalyst system. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Influence of Ce-precursor and fuel on structure and catalytic activity of combustion synthesized Ni/CeO2 catalysts for biogas oxidative steam reforming

International Nuclear Information System (INIS)

Vita, Antonio; Italiano, Cristina; Fabiano, Concetto; Laganà, Massimo; Pino, Lidia

2015-01-01

A series of nanosized Ni/CeO 2 catalysts were prepared by Solution Combustion Synthesis (SCS) varying the fuel (oxalyldihydrazide, urea, carbohydrazide and glycerol), the cerium precursor (cerium nitrate and cerium ammonium nitrate) and the nickel loading (ranging between 3.1 and 15.6 wt%). The obtained powders were characterized by X-ray Diffraction (XRD), N 2 -physisorption, CO-chemisorption, Temperature Programmed Reduction (H 2 -TPR) and Scanning Electron Microscopy (SEM). The catalytic activity towards the Oxy Steam Reforming (OSR) of biogas was assessed. The selected operating variables have a strong influence on the nature of combustion and, in turn, on the morphological and structural properties of the synthesized catalysts. Particularly, the use of urea allows to improve nickel dispersion, surface area, particle size and reducibility of the catalysts, affecting positively the biogas OSR performances. - Highlights: • Synthesis of Ni/CeO 2 nanopowders by quick and easy solution combustion synthesis. • The fuel and precursor drive the structural and morphological properties of the catalysts. • The use of urea as fuel allows to improve nickel dispersion, surface area and particle size. • Ni/CeO 2 (7.8 wt% of Ni loading) powders synthesized by urea route exhibits high performances for the biogas OSR process

Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction

Energy Technology Data Exchange (ETDEWEB)

Chunshan, Song; Kirby, S.; Schmidt, E. [Pennsylvania State Univ., University Park, PA (United States)] [and others

1995-12-31

The objective of this project is to explore bimetallic dispersed catalysts for more efficient coal liquefaction. Coal liquefaction involves cleavage of methylene, dimethylene and ether bridges connecting various aromatic units and the reactions of various oxygen functional groups. This paper describes recent results on (1) hydrodeoxygenation of O-containing polycyclic model compounds using novel organometallic catalyst precursors; and (2) activity and selectivity of dispersed Fe catalysts from organometallic and inorganic precursors for hydrocracking of 4-(1-naphthylmethyl) bibenzyl. The results showed that some iron containing catalysts have higher activity in the sulfur-free form, contrary to conventional wisdom. Adding sulfur to Fe precursors with Cp-ligands decreased the activity of the resulting catalyst. This is in distinct contrast to the cases with iron pentacarbonyl and superfine Fe{sub 2}O{sub 3}, where S addition increased their catalytic activity substantially. A positive correlation between sulfur addition and increased activity can be seen, but a reversed trend between Fe cluster size and hydrocracking conversion could be observed, for carbonyl-type Fe precursors. It is apparent that the activity and selectivity of Fe catalysts for NMBB conversion depends strongly on both the type of ligand environment, the oxidation state and the number of intermetal bonds in the molecular precursor.

Treatment of a non-azo dye aqueous solution by CWAO in continuous reactor using a Ni catalyst derived from hydrotalcite-like precursor

International Nuclear Information System (INIS)

Vallet, Ana; Besson, Michèle; Ovejero, Gabriel; García, Juan

2012-01-01

Highlights: ► Ni supported over hydrotalcite calcined precursors as catalyst. ► Catalytic wet air oxidation in trickle bed reactor for Basic Yellow 11 removal. ► Dye removal depends on temperature, initial dye concentration and flow rate. ► The catalyst proved to be stable and efficient for the dye degradation. - Abstract: Catalytic wet air oxidation (CWAO) of a Basic Yellow 11 (BY11) aqueous solution, chosen as a model of a hardly biodegradable non-azo dye was carried out in a continuous-flow trickle-bed reactor, using nickel supported over hydrotalcite precursor calcined at 550 °C. An increase in the reaction temperature (120–180 °C), and a decrease in dye concentration (1000–3000 ppm) or liquid flow rate (0.1–0.7 mL min −1 ) enhanced the CWAO performance in a 30 and 19% for the variation of the temperature and concentration respectively. After a small leaching observed within the first hours, the catalyst proved to be very stable during the 65-day reaction. The CWAO process was found to be very efficient, achieving BY11 conversion up to 95% and TOC conversion up to 85% at 0.1 mL min −1 and 180 °C under 5 MPa air.

A Molecular Precursor to Phosphaethyne and Its Application in Synthesis of the Aromatic 1,2,3,4-Phosphatriazolate Anion

Energy Technology Data Exchange (ETDEWEB)

Transue, Wesley J.; Velian, Alexandra; Nava, Matthew; Martin-Drumel, Marie-Aline; Womack, Caroline C.; Jiang, Jun; Hou, Gao-Lei; Wang, Xue-Bin; McCarthy, Michael C.; Field, Robert W.; Cummins, Christopher C.

2016-06-01

Dibenzo-7-phosphanorbornadiene Ph₃PC(H)PA (1, A = C₁₄H₁₀, anthracene) is reported as a molecular precursor to phosphaethyne (HC≡P), produced together with anthracene and triphenylphosphine. HCP generated by thermolysis of 1 has been characterized by molecular beam mass spectrometry (MBMS), laser-induced fluorescence (LIF), microwave spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy. In toluene, fragmentation of 1 has been found to proceed with activation parameters of ΔH ^‡ = 25.5 kcal/mol and ΔS^‡ = ₋2.43 e.u., and is accompanied by formation of an orange insoluble precipitate. Results from computational studies of the mechanism of HCP generation are in good agreement with experimental data. This high temperature method of HCP generation has pointed to new reaction chemistry with azide anion to produce the 1,2,3,4-phosphatriazolate anion, HCPN3^- , for which structural data have been obtained in a single-crystal Xray diffraction study. Negative ion photoelectron spectroscopy has shown the adiabatic detachment energy for this anion to be 3.555(10) eV. The aromaticity of HCPN3^- has been assessed using nucleus-independent chemical shift (NICS), quantum theory of atoms in molecules (QTAIM), and natural bond orbital (NBO) methods.

Influence of Ce-precursor and fuel on structure and catalytic activity of combustion synthesized Ni/CeO{sub 2} catalysts for biogas oxidative steam reforming

Energy Technology Data Exchange (ETDEWEB)

Vita, Antonio, E-mail: antonio.vita@itae.cnr.it; Italiano, Cristina; Fabiano, Concetto; Laganà, Massimo; Pino, Lidia

2015-08-01

A series of nanosized Ni/CeO{sub 2} catalysts were prepared by Solution Combustion Synthesis (SCS) varying the fuel (oxalyldihydrazide, urea, carbohydrazide and glycerol), the cerium precursor (cerium nitrate and cerium ammonium nitrate) and the nickel loading (ranging between 3.1 and 15.6 wt%). The obtained powders were characterized by X-ray Diffraction (XRD), N{sub 2}-physisorption, CO-chemisorption, Temperature Programmed Reduction (H{sub 2}-TPR) and Scanning Electron Microscopy (SEM). The catalytic activity towards the Oxy Steam Reforming (OSR) of biogas was assessed. The selected operating variables have a strong influence on the nature of combustion and, in turn, on the morphological and structural properties of the synthesized catalysts. Particularly, the use of urea allows to improve nickel dispersion, surface area, particle size and reducibility of the catalysts, affecting positively the biogas OSR performances. - Highlights: • Synthesis of Ni/CeO{sub 2} nanopowders by quick and easy solution combustion synthesis. • The fuel and precursor drive the structural and morphological properties of the catalysts. • The use of urea as fuel allows to improve nickel dispersion, surface area and particle size. • Ni/CeO{sub 2} (7.8 wt% of Ni loading) powders synthesized by urea route exhibits high performances for the biogas OSR process.

From 5-Hydroxymethylfurfural (HMF) to Polymer Precursors : Catalyst Screening Studies on the Conversion of 1,2,6-hexanetriol to 1,6-hexanediol

NARCIS (Netherlands)

Buntara, Teddy; Noel, Sébastien; Phua, Pim Huat; Melián-Cabrera, Ignacio; Vries, Johannes G. de; Heeres, Hero J.

1,6-hexanediol (1) is an important polymer precursor for the polyester industry. In this paper, exploratory catalyst screening studies on the synthesis of 1 from 1,2,6-hexanetriol (2) are described via two different routes. The latter is available by a two-step procedure from 5-hydroxymethylfurfural

Co3O4 nanowires as efficient catalyst precursor for hydrogen generation from sodium borohydride hydrolysis

Science.gov (United States)

Wei, Lei; Cao, Xurong; Ma, Maixia; Lu, Yanhong; Wang, Dongsheng; Zhang, Suling; Wang, Qian

Hydrogen generation from the catalytic hydrolysis of sodium borohydride has many advantages, and therefore, significant research has been undertaken on the development of highly efficient catalysts for this purpose. In our present work, Co3O4 nanowires were successfully synthesized as catalyst precursor by employing SBA-15 as a hard template. For material characterization, high-resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (XRD), fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and N2 adsorption isotherms were employed, respectively. To measure the catalyst activity, typical water-displacement method was carried out. Using a reaction solution comprising 10wt.% NaBH4 and 2wt.% NaOH, the hydrogen generation rate (HGR) was observed to be as high as 7.74L min-1 g-1 at 25∘C in the presence of Co3O4 nanowires, which is significantly higher than that of CoB nanoparticles and commercial Co3O4 powder. Apparent activation energy was calculated to be 50.9kJ mol-1. After recycling the Co3O4 nanowires six times, HGR was decreased to be 72.6% of the initial level.

A Pd/C-CeO2 Anode Catalyst for High-Performance Platinum-Free Anion Exchange Membrane Fuel Cells.

Science.gov (United States)

Miller, Hamish A; Lavacchi, Alessandro; Vizza, Francesco; Marelli, Marcello; Di Benedetto, Francesco; D'Acapito, Francesco; Paska, Yair; Page, Miles; Dekel, Dario R

2016-05-10

One of the biggest obstacles to the dissemination of fuel cells is their cost, a large part of which is due to platinum (Pt) electrocatalysts. Complete removal of Pt is a difficult if not impossible task for proton exchange membrane fuel cells (PEM-FCs). The anion exchange membrane fuel cell (AEM-FC) has long been proposed as a solution as non-Pt metals may be employed. Despite this, few examples of Pt-free AEM-FCs have been demonstrated with modest power output. The main obstacle preventing the realization of a high power density Pt-free AEM-FC is sluggish hydrogen oxidation (HOR) kinetics of the anode catalyst. Here we describe a Pt-free AEM-FC that employs a mixed carbon-CeO2 supported palladium (Pd) anode catalyst that exhibits enhanced kinetics for the HOR. AEM-FC tests run on dry H2 and pure air show peak power densities of more than 500 mW cm(-2) . © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Catalyst of a metal heteropoly acid salt that is insoluble in a polar solvent on a non-metallic porous support and method of making

Science.gov (United States)

Wang, Yong [Richland, WA; Peden, Charles H. F. [West Richland, WA; Choi, Saemin [Richland, WA

2002-10-29

The present invention includes a catalyst having (a) a non-metallic support having a plurality of pores; (b) a metal heteropoly acid salt that is insoluble in a polar solvent on the non-metallic support; wherein at least a portion of the metal heteropoly acid salt is dispersed within said plurality of pores. The present invention also includes a method of depositing a metal heteropoly acid salt that is insoluble in a polar solvent onto a non-metallic support having a plurality of pores. The method has the steps of: (a) obtaining a first solution containing a first precursor of a metal salt cation; (b) obtaining a second solution containing a second precursor of a heteropoly acid anion in a solvent having a limited dissolution potential for said first precursor; (c) impregnating the non-metallic support with the first precursor forming a first precursor deposit within the plurality of pores, forming a first precursor impregnated support; (d) heating said first precursor impregnated support forming a bonded first precursor impregnated support; (e) impregnating the second precursor that reacts with the precursor deposit and forms the metal heteropoly acid salt.

Treatment of a non-azo dye aqueous solution by CWAO in continuous reactor using a Ni catalyst derived from hydrotalcite-like precursor

Energy Technology Data Exchange (ETDEWEB)

Vallet, Ana, E-mail: avallet@quim.ucm.es [Grupo de Catalisis y Procesos de Separacion (CyPS), Departamento de Ingenieria Quimica, Facultad de Ciencias Quimicas, Universidad Complutense de Madrid, Avda. Complutense s/n, 28040 Madrid (Spain); Besson, Michele, E-mail: michele.besson@ircelyon.univ-lyon1.fr [IRCELYON, Institut de recherches sur la catalyse et l' environnement de Lyon, UMR5256 CNRS-Universite Lyon1, 2 Avenue Albert Einstein, F-69626 Villeurbanne Cedex (France); Ovejero, Gabriel; Garcia, Juan [Grupo de Catalisis y Procesos de Separacion (CyPS), Departamento de Ingenieria Quimica, Facultad de Ciencias Quimicas, Universidad Complutense de Madrid, Avda. Complutense s/n, 28040 Madrid (Spain)

2012-08-15

Highlights: Black-Right-Pointing-Pointer Ni supported over hydrotalcite calcined precursors as catalyst. Black-Right-Pointing-Pointer Catalytic wet air oxidation in trickle bed reactor for Basic Yellow 11 removal. Black-Right-Pointing-Pointer Dye removal depends on temperature, initial dye concentration and flow rate. Black-Right-Pointing-Pointer The catalyst proved to be stable and efficient for the dye degradation. - Abstract: Catalytic wet air oxidation (CWAO) of a Basic Yellow 11 (BY11) aqueous solution, chosen as a model of a hardly biodegradable non-azo dye was carried out in a continuous-flow trickle-bed reactor, using nickel supported over hydrotalcite precursor calcined at 550 Degree-Sign C. An increase in the reaction temperature (120-180 Degree-Sign C), and a decrease in dye concentration (1000-3000 ppm) or liquid flow rate (0.1-0.7 mL min{sup -1}) enhanced the CWAO performance in a 30 and 19% for the variation of the temperature and concentration respectively. After a small leaching observed within the first hours, the catalyst proved to be very stable during the 65-day reaction. The CWAO process was found to be very efficient, achieving BY11 conversion up to 95% and TOC conversion up to 85% at 0.1 mL min{sup -1} and 180 Degree-Sign C under 5 MPa air.

Colloidal nanoparticles as catalysts and catalyst precursors for nitrite hydrogenation

NARCIS (Netherlands)

Zhao, Yingnan

2015-01-01

The most distinguished advantage to use colloidal methods for catalyst preparation is that the size and the shape of nanoparticles can be manipulated easily under good control, which is normally difficult to achieve by using traditional methods, such as impregnation and precipitation. This

Self-assembled 3D-hierarchical structure Cu2ZnSnS4 photocathodes by tuning anion ratios in precursor solution

International Nuclear Information System (INIS)

Wen, Xin; Shao, Hansen; Fu, Gao; Zhou, Yong; Zou, Zhigang; Luo, Wenjun; Guan, Zhongjie

2016-01-01

Cu 2 ZnSnS 4 (CZTS) is one of the most promising light capture materials for solar cells or solar fuels. Construction of 3D hierarchical structure is very important for efficient optoelectronic devices. It is challenging to directly fabricate 3D hierarchical structure CZTS film by a facile solution method. Herein, we present a one-step sol–gel method for fabrication of CZTS thin films with 3D hierarchical structures. For the first time, it is found that the morphologies of thin films can be adjusted between dense, porous and 3D hierarchical structures by tuning anion ratios of Cl − /Ac − in precursor solution. Further analysis suggests the formation of intermediate phases of SnO 2 nanoparticles and SnS 2 nanosheets by tuning ratios of Cl − /Ac − in precursor solution, which has important effects on the formation of different nanostructures of CZTS. This study can deepen understanding of anion’ effect on morphologies of samples using a solution method and forms a reference to prepare novel nanostructures of other materials. (paper)

Synthesis of biodiesel using local natural zeolite as heterogeneous anion exchange catalyst

Science.gov (United States)

Hartono, R.; Wijanarko, A.; Hermansyah, H.

2018-04-01

Production of biodiesel using homogen catalyst: alkaline catalysts, acid catalysts, biocatalysts, and supercritical methanol are very inefficient, because these catalysts have a very high cost production of biodiesel and non-ecofriendly. The heterogeneous catalyst is then used to avoid adverse reaction of biodiesel production. The heterogeneous catalysts used is ion exchanger using natural zeolit catalists bayah banten (ZABBrht) and macroporous lewatit that can be used to produce biodiesel in the solid phase so that the separation is easier and can be used repeatedly. The results of biodiesel reach its optimum in engineering ion exchange catalyst natural zeolit bayah and macroporous lewatit which has been impregnated and calcinated at temperature 60 °C at reaction time 2 hours, are 94.8% and 95.24%, using 100 gr.KOH/100 mL Aquadest.

Preparation of highly dispersed Ru-Sn bimetallic supported catalysts from the single source precursors Cp(PPh32Ru-SnX3 (X = Cl or Br

Directory of Open Access Journals (Sweden)

Ana Cláudia Bernardes Silva

2003-06-01

Full Text Available In this work highly dispersed Ru-Sn bimetallic catalysts have been prepared from organobimetallic Cp(PPh32Ru-SnX3 (X = Cl or Br complexes. These single source precursors can be easily impregnated in high surface area supports, such as activated carbon and sol-gel SiO2, and upon controlled thermal treatment the ligands are released as volatile products resulting in the formation of the bimetallic system Ru-Sn. Catalytic reactions, such as hydrodechlorination of CCl4 and chlorobenzene and TPR (Temperature Programmed Reduction experiments carried out with these RuSn catalysts suggested a strong interaction between Ruthenium and Tin. Mössbauer measurements showed that these materials when exposed to air are immediately oxidized to form Sn (IV. It was shown that upon controlled reduction conditions with H2 it is possible to reduce selectively Sn to different oxidation states and different phases. The Sn oxidation state showed significant effect on the catalytic hydrogenation of 1,5-cyclooctadiene. The use of these single source precursors with a controlled decomposition/reduction procedure allows the preparation of unique catalysts with an intimate interaction between the components ruthenium and tin and the possibility of varying the Sn oxidation state around the Ru metal.

Nanoparticular metal oxide/anatase catalysts

DEFF Research Database (Denmark)

2010-01-01

The present invention concerns a method of preparation of nanoparticular metal oxide catalysts having a narrow particle size distribution. In particular, the invention concerns preparation of nanoparticular metal oxide catalyst precursors comprising combustible crystallization seeds upon which...... the catalyst metai oxide is co-precipitated with the carrier metal oxide, which crystallization seeds are removed by combustion in a final calcining step. The present invention also concerns processes wherein the nanoparticular metal oxide catalysts of the invention are used, such as SCR (deNOx) reactions...

Cooperative research in coal liquefaction. Final report, May 1, 1991--April 30, 1992

Energy Technology Data Exchange (ETDEWEB)

Huffman, G.P. [ed.

1996-03-01

Extensive research continued on catalysts based on novel anion-treated (mainly sulfated) oxides and oxyhydroxides of iron [Fe{sub x}O{sub y}/SO{sub 4}]. In addition, sulfated oxides of tin as well as molybdenum promoted iron oxides were used. Incorporation of small amounts of sulfate, molybdate, or tungstate anions by wet precipitation/impregnation methods was found to increase the surface acidic character of iron oxides; more importantly, it reduced the grain sizes significantly with corresponding increases in specific surface areas. These anion-treated iron and tin oxides were more active for direct coal liquefaction and coal-heavy oil coprocessing than their untreated counterparts. With these catalyst systems, higher conversion levels are obtained as compared to the soluble precursors of iron and molybdenum at the same catalyst metalloading (3500 ppm iron and 50 ppm molybdenum with respect to coal). Sulfated iron oxides and oxyhydroxides were equally active as coal liquefaction catalysts. The sulfate, molybdate, and tungstate anions were found to have similar promotional effects on the properties and activities of iron oxides. One step in the synthesis of anion-treated iron and tin oxides is precipitation as hydroxides using either urea or ammonium hydroxide. The catalysts prepared using urea as a precipitation agent were more reproducible than those using ammonium, hydroxide in terms of activities and properties. These catalysts/catalyst precursors were characterized by several techniques to determine their physical (size and structure related) and chemical (acidity) properties. Sulfated and molybdated iron oxides were found to have grain sizes as small as 10-20 nm. An attempt was made to correlate the physicochemical properties of these catalysts with their activity for coal liquefaction.

Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Final report

Energy Technology Data Exchange (ETDEWEB)

Chunshan Song; Schobert, H.H.; Parfitt, D.P. [and others

1997-11-01

Development of new catalysts is a promising approach to more efficient coal liquefaction. It has been recognized that dispersed catalysts are superior to supported catalysts for primary liquefaction of coals, because the control of initial coal dissolution or depolymerization requires intimate contact between the catalyst and coal. This research is a fundamental and exploratory study on catalytic coal liquefaction, with the emphasis on exploring novel bimetallic dispersed catalysts for coal liquefaction and the effectiveness of temperature-programmed liquefaction using dispersed catalysts. The primary objective of this research was to explore novel bimetallic dispersed catalysts from organometallic molecular precursors, that could be used in low concentrations but exhibit relatively high activity for efficient hydroliquefaction of coals under temperature-programmed conditions. We have synthesized and tested various catalyst precursors in liquefaction of subbituminous and bituminous coals and in model compound studies to examine how do the composition and structure of the catalytic precursors affect their effectiveness for coal liquefaction under different reaction conditions, and how do these factors affect their catalytic functions for hydrogenation of polyaromatic hydrocarbons, for cleavage of C-C bonds in polycyclic systems such as 4-(1-naphthylmethyl)bibenzyl, for hydrogenolysis of C-O bond such as that in dinaphthylether, for hydrodeoxygenation of phenolic compounds and other oxygen-containing compounds such as xanthene, and for hydrodesulfurization of polycyclic sulfur compounds such as dibenzothiophene. The novel bimetallic and monometallic precursors synthesized and tested in this project include various Mo- and Fe-based compounds.

Novel Fragmentation Pathways of Anionic Adducts of Steroids Formed by Electrospray Anion Attachment Involving Regioselective Attachment, Regiospecific Decompositions, Charge-Induced Pathways, and Ion-Dipole Complex Intermediates

Science.gov (United States)

Rannulu, Nalaka S.; Cole, Richard B.

2012-09-01

The analysis of several bifunctional neutral steroids, 5-α-pregnane diol (5-α-pregnane-3α-20βdiol), estradiol (3,17α-dihydroxy-1,3,5(10)-estratriene), progesterone (4-pregnene-3,20-dione), lupeol (3β-hydroxy-20(29)-lupene), pregnenolone (5-pregnen-3β-ol-20-one), and pregnenolone acetate (5-pregnen-3β-ol-20-one acetate) was accomplished by negative ion electrospray mass spectrometry (ESI-MS) employing adduct formation with various anions: fluoride, bicarbonate, acetate, and chloride. Fluoride yielded higher abundances of anionic adducts and more substantial abundances of deprotonated molecules compared with other investigated anions. Collision-induced dissociation (CID) of precursor [M + anion]- adducts of these steroids revealed that fluoride adduct [M + F]- precursors first lose HF to produce [M - H]- and then undergo consecutive decompositions to yield higher abundances of structurally-informative product ions than the other tested anions. In addition to charge-remote fragmentations, the majority of CID pathways of estradiol are deduced to occur via charge-induced fragmentation. Most interestingly, certain anions exhibit preferential attachment to a specific site on these bifunctional steroid molecules, which we are calling "regioselective anion attachment." Regioselective anion attachment is evidenced by subsequent regiospecific decomposition. Regioselective attachment of fluoride (and acetate) anions to low (and moderate) acidity functional groups of pregnenolone, respectively, is demonstrated using deuterated compounds. Moreover, the formation of unique intermediate ion-dipole complexes leading to novel fragmentation pathways of fluoride adducts of pregnenolone acetate, and bicarbonate adducts of d4-pregnenolone, are also discussed.

Characterization of CaSn(OH6 and CaSnO3 Nanostructures Synthesized by a New Precursor

Directory of Open Access Journals (Sweden)

S. Moshtaghi

2015-04-01

Full Text Available In this paper, calcium stannate nanoparticles were synthesized by a fast and simple co-precipitation procedure. For CaSnO3 preparation ammonia was used as precipitation agent. The effect of various surfactants such as cationic, anionic and neutral on the morphology of the products was investigated. By changing in Ca(Sal2 as a new precursor different morphologies were obtained. Ligand as a capping agent with steric hindrance leads to preparation of product with lower particle size. These semiconductor nanostructures have photo-catalyst activities and can degrade organic dyes as water pollution. The synthesized materials were characterized by X-ray diffraction (XRD technique, scanning electron microscopy (SEM Fourier transform infrared (FT-IR and UV-visible spectroscopy.

[Pd(NH{sub 3}){sub 4}]MoO{sub 4} as a precursor for Pd–Mo-containing catalysts: Thermal behavior, X-ray analysis of the thermolysis products and related catalytic studies

Energy Technology Data Exchange (ETDEWEB)

Gubanov, Alexander I., E-mail: gubanov@niic.nsc.su [Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, Akad. Lavrentiev Prospekt 3, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, Pirogova str. 2, 630090 Novosibirsk (Russian Federation); Filatov, Eugeny Yu.; Semitut, Eugeny Yu.; Smolentsev, Anton I. [Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, Akad. Lavrentiev Prospekt 3, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, Pirogova str. 2, 630090 Novosibirsk (Russian Federation); Snytnikov, Pavel V.; Potemkin, Dmitry I. [Novosibirsk State University, Pirogova str. 2, 630090 Novosibirsk (Russian Federation); Boreskov Institute of Catalysis, Siberian Branch of the Russian Academy of Sciences, Akad. Lavrentiev Prospekt 5, 630090 Novosibirsk (Russian Federation); Korenev, Sergey V. [Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, Akad. Lavrentiev Prospekt 3, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, Pirogova str. 2, 630090 Novosibirsk (Russian Federation)

2013-08-20

Highlights: • [Pd(NH{sub 3}){sub 4}]MoO{sub 4} as a precursor for Pd–Mo-containing catalysts. • Different products are formed depending on atmosphere of thermal decomposition. • Thermolysis in He atmosphere affords finely mixed two-phase nanosized system Pd–MoO{sub 2}. • Pd–MoO{sub 2} system can be a promising catalyst both in pure and supported form. - Abstract: Compound [Pd(NH{sub 3}){sub 4}]MoO{sub 4} (1) has been synthesized and characterized by IR spectroscopy, analytical data, powder and single-crystal X-ray crystallography. Thermal properties of 1 have been examined by thermogravimetry. Powder X-ray diffraction has been applied to investigate the nanosized products of thermal decomposition of the precursor in hydrogen (Pd–Mo) and helium (Pd–MoO{sub 2}) atmospheres. Pd–Mo catalysts supported with γ-Al{sub 2}O{sub 3} have been tested in oxidation of CO and H{sub 2} mixtures.

Topotactic Synthesis of Porous Cobalt Ferrite Platelets from a Layered Double Hydroxide Precursor and Their Application in Oxidation Catalysis.

Science.gov (United States)

Ortega, Klaus Friedel; Anke, Sven; Salamon, Soma; Özcan, Fatih; Heese, Justus; Andronescu, Corina; Landers, Joachim; Wende, Heiko; Schuhmann, Wolfgang; Muhler, Martin; Lunkenbein, Thomas; Behrens, Malte

2017-09-12

Monocrystalline, yet porous mosaic platelets of cobalt ferrite, CoFe 2 O 4 , can be synthesized from a layered double hydroxide (LDH) precursor by thermal decomposition. Using an equimolar mixture of Fe 2+ , Co 2+ , and Fe 3+ during co-precipitation, a mixture of LDH, (Fe II Co II ) 2/3 Fe III 1/3 (OH) 2 (CO 3 ) 1/6 ⋅m H 2 O, and the target spinel CoFe 2 O 4 can be obtained in the precursor. During calcination, the remaining Fe II fraction of the LDH is oxidized to Fe III leading to an overall Co 2+ :Fe 3+ ratio of 1:2 as required for spinel crystallization. This pre-adjustment of the spinel composition in the LDH precursor suggests a topotactic crystallization of cobalt ferrite and yields phase pure spinel in unusual anisotropic platelet morphology. The preferred topotactic relationship in most particles is [111] Spinel ∥[001] LDH . Due to the anion decomposition, holes are formed throughout the quasi monocrystalline platelets. This synthesis approach can be used for different ferrites and the unique microstructure leads to unusual chemical properties as shown by the application of the ex-LDH cobalt ferrite as catalyst in the selective oxidation of 2-propanol. Compared to commercial cobalt ferrite, which mainly catalyzes the oxidative dehydrogenation to acetone, the main reaction over the novel ex-LDH cobalt is dehydration to propene. Moreover, the oxygen evolution reaction (OER) activity of the ex-LDH catalyst was markedly higher compared to the commercial material. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preparation and characterization of anode catalysts for the direct alcohol fuel cells (DAFC): methanol and ethanol

CSIR Research Space (South Africa)

Modibedi, M

2007-11-01

Full Text Available and M2 precursor solutions followed by reduction of the precursors. Catalysts prepared were: Pt-M1-M2/C (M1=Sn or Ru, M2= Ir). Phosphorus was deposited on these catalysts and their electrochemical activities were compared. The prepared catalysts were...

Supported transition metal sulfide promoted molybdenum or tungsten sulfide catalysts and their uses for hydroprocessing

International Nuclear Information System (INIS)

Ho, T.C.; Chianelli, R.R.; Jacobson, A.J.; Young, A.R.

1987-01-01

A process is described for hydrotreating a hydrocarbon feed which comprises contacting the feed at a temperature of at least about 150 0 C and heating the composite at elevated temperature of at least about 150 0 C, in the presence of sulfur and under oxygen-free conditions for a time sufficient to form the catalyst. The precursor salt contains a tetrathiometallate anion of Mo, W or mixture thereof and a cation comprising one or more divalent promoter metals which are chelated by at least one neutral, nitrogen-containing polydentate ligand L. The divalent promoter metal is selected from the group consisting of Ni, Co, Zn, Cu and mixture thereof. The contacting occurs for a time sufficient to hydrotreat at least a portion of the feed

Precursor effect on the property and catalytic behavior of Fe-TS-1 in butadiene epoxidation

Science.gov (United States)

Wu, Mei; Zhao, Huahua; Yang, Jian; Zhao, Jun; Song, Huanling; Chou, Lingjun

2017-11-01

The effect of iron precursor on the property and catalytic behavior of iron modified titanium silicalite molecular sieve (Fe-TS-1) catalysts in butadiene selective epoxidation has been studied. Three Fe-TS-1 catalysts were prepared, using iron nitrate, iron chloride and iron sulfate as precursors, which played an important role in adjusting the textural properties and chemical states of TS-1. Of the prepared Fe-TS-1 catalysts, those modified by iron nitrate (FN-TS-1) exhibited a significant enhanced performance in butadiene selective epoxidation compared to those derived from iron sulfate (FS-TS-1) or iron chloride (FC-TS-1) precursors. To obtain a deep understanding of their structure-performance relationship, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Temperature programmed desorption of NH3 (NH3-TPD), Diffuse reflectance UV-Vis spectra (DR UV-Vis), Fourier transformed infrared spectra (FT-IR) and thermal gravimetric analysis (TGA) were conducted to characterize Fe-TS-1 catalysts. Experimental results indicated that textural structures and acid sites of modified catalysts as well as the type of Fe species influenced by the precursors were all responsible for the activity and product distribution.

Ni/SiO2 Catalyst Prepared with Nickel Nitrate Precursor for Combination of CO2 Reforming and Partial Oxidation of Methane: Characterization and Deactivation Mechanism Investigation

Directory of Open Access Journals (Sweden)

Sufang He

2015-01-01

Full Text Available The performance of Ni/SiO2 catalyst in the process of combination of CO2 reforming and partial oxidation of methane to produce syngas was studied. The Ni/SiO2 catalysts were prepared by using incipient wetness impregnation method with nickel nitrate as a precursor and characterized by FT-IR, TG-DTA, UV-Raman, XRD, TEM, and H2-TPR. The metal nickel particles with the average size of 37.5 nm were highly dispersed over the catalyst, while the interaction between nickel particles and SiO2 support is relatively weak. The weak NiO-SiO2 interaction disappeared after repeating oxidation-reduction-oxidation in the fluidized bed reactor at 700°C, which resulted in the sintering of metal nickel particles. As a result, a rapid deactivation of the Ni/SiO2 catalysts was observed in 2.5 h reaction on stream.

Simple preparation of Fenton catalyst@bacterial cellulose for waste water treatment

Science.gov (United States)

Wibowo, Arie; Febi Indrawan, Radian; Triadhi, Untung; Hasdi Aimon, Akfiny; Iskandar, Ferry; Ardy, Husaini

2018-02-01

Heterogeneous fenton catalyst is one of the attractive technologies for destruction of persistent and non-biodegradable pollutant in wastewater, because it can be used in wide range of pH and recyclable. Herein, commercial bacterial celluloses (BCs) were used as an alternative support of fenton catalyst to improve their catalytic activity. Scanning Electron Microscope (SEM) observations indicated that the presence of BCs and decreasing precursor concentration might promote formation of smaller particle sizes of catalyst from 3.5 μm of bare catalyst to 0.7 μm of catalyst@BC. UV-vis measurement showed that fast degradation of dyes with half-time degradation at around 25 min was observed in sample using catalyst@BCs with precursor concentration of 0.01 M. Successful preparation of heterogeneous fenton catalyst with smaller particle size and better catalytic activity is important for their application in wastewater treatment.

Remarkable promotion effect of trace sulfation on OMS-2 nanorod catalysts for the catalytic combustion of ethanol.

Science.gov (United States)

Zhang, Jie; Zhang, Changbin; He, Hong

2015-09-01

OMS-2 nanorod catalysts were synthesized by a hydrothermal redox reaction method using MnSO4 (OMS-2-SO4) and Mn(CH3COO)2 (OMS-2-AC) as precursors. SO4(2-)-doped OMS-2-AC catalysts with different SO4(2-) concentrations were prepared next by adding (NH4)2SO4 solution into OMS-2-AC samples to investigate the effect of the anion SO4(2-) on the OMS-2-AC catalyst. All catalysts were then tested for the catalytic oxidation of ethanol. The OMS-2-SO4 catalyst synthesized demonstrated much better activity than OMS-2-AC. The SO4(2-) doping greatly influenced the activity of the OMS-2-AC catalyst, with a dramatic promotion of activity for suitable concentration of SO4(2-) (SO4/catalyst=0.5% W/W). The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma optical emission spectroscopy (ICP-OES), NH3-TPD and H2-TPR techniques. The results showed that the presence of a suitable amount of SO4(2-) species in the OMS-2-AC catalyst could decrease the Mn-O bond strength and also enhance the lattice oxygen and acid site concentrations, which then effectively promoted the catalytic activity of OMS-2-AC toward ethanol oxidation. Thus it was confirmed that the better catalytic performance of OMS-2-SO4 compared to OMS-2-AC is due to the presence of some residual SO4(2-) species in OMS-2-SO4 samples. Copyright © 2015. Published by Elsevier B.V.

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

Continuous-Flow O-Alkylation of Biobased Derivatives with Dialkyl Carbonates in the Presence of Magnesium-Aluminium Hydrotalcites as Catalyst Precursors.

Science.gov (United States)

Cattelan, Lisa; Perosa, Alvise; Riello, Piero; Maschmeyer, Thomas; Selva, Maurizio

2017-04-10

The base-catalysed reactions of OH-bearing biobased derivatives (BBDs) including glycerol formal, solketal, glycerol carbonate, furfuryl alcohol and tetrahydrofurfuryl alcohol with non-toxic dialkyl carbonates (dimethyl and diethyl carbonate) were explored under continuous-flow (CF) conditions in the presence of three Na-exchanged Y- and X-faujasites (FAUs) and four Mg-Al hydrotalcites (HTs). Compared to previous etherification protocols mediated by dialkyl carbonates, the reported procedure offers substantial improvements not only in terms of (chemo)selectivity but also for the recyclability of the catalysts, workup, ease of product purification and, importantly, process intensification. Characterisation studies proved that both HT30 and KW2000 hydrotalcites acted as catalyst precursors: during the thermal activation pre-treatments, the typical lamellar structure of the hydrotalcite was broken down gradually into a MgO-like phase (periclase) or rather a magnesia-alumina solid solution, which was the genuine catalytic phase. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fischer-Tropsch Synthesis over Iron Manganese Catalysts: Effect of Preparation and Operating Conditions on Catalyst Performance

Directory of Open Access Journals (Sweden)

Ali A. Mirzaei

2009-01-01

molar basis which is the most active catalyst for the conversion of synthesis gas to light olefins. The effects of different promoters and supports with loading of optimum support on the catalytic performance of catalysts are also studied. It was found that the catalyst containing 50%Fe/50%Mn/5 wt.%Al2O3 is an optimum-modified catalyst. The catalytic performance of optimal catalyst has been studied in operation conditions such as a range of reaction temperatures, H2/CO molar feed ratios and a range of total pressures. Characterization of both precursors and calcined catalysts is carried out by powder X-ray diffraction (XRD, scanning electron microscopy (SEM, BET specific surface area and thermal analysis methods such as TGA and DSC.

Boron-containing catalysts for dry reforming of methane to synthesis gas

KAUST Repository

Takanabe, Kazuhiro; Basset, Jean-Marie; Park, Jung-Hyun; Samal, Akshaya Kumar; Alsabban, Bedour

2018-01-01

The present invention uses a cobalt catalyst for carbon dioxide reforming of lower alkanes to synthesis gas having a cobalt catalyst on an oxide support where the supported cobalt catalyst has been modified with a boron precursor. The boron

Epoxidation of Alkenes with Aqueous Hydrogen Peroxide and Quaternary Ammonium Bicarbonate Catalysts

DEFF Research Database (Denmark)

Mielby, Jerrik Jørgen; Kegnæs, Søren

2013-01-01

A range of solid and liquid catalysts containing bicarbonate anions were synthesised and tested for the epoxidation of alkenes with aqueous hydrogen peroxide. The combination of bicarbonate anions and quaternary ammonium cations opens up for new catalytic systems that can help to overcome...

Catalyst dispersion and activity under conditions of temperature-staged liquefaction

Energy Technology Data Exchange (ETDEWEB)

Davis, A.; Schobert, H.H.; Mitchell, G.D.; Artok, L.

1993-02-01

This research program involves the investigation of the use of highly dispersed catalyst precursors for the pretreatment of coals by mild hydrogenation. During the course of this effort solvent preswelling of the coal was evaluated as a means of deeply impregnating catalysts into coal, active phases of catalysts under reaction conditions were studied and the impact of these techniques were evaluated during pretreatment and temperature-staged liquefaction. Two coals, a Texas subbituminous and a Utah high volatile A bituminous, were used to examine the effects of solvent swelling pretreatment and catalyst impregnation on conversion behavior at 275[degrees]C, representative of the first, low-temperature stage in a temperature-staged liquefaction reaction. Ferrous sulfate, iron pentacarbonyl, ammonium tetrathiomolybdate, and molybdenum hexacarbonyl were used as catalyst precursors. Without swelling pretreatment, impregnation of both coals increased conversion, mainly through increased yields of preasphaltenes.

Chemical Hydrogen Storage Using Polyhedral Borane Anions and Aluminum-Ammonia-Borane Complexes

Energy Technology Data Exchange (ETDEWEB)

Hawthorne, M. Frederick; Jalisatgi, Satish S.; Safronov, Alexander V.; Lee, Han Beak; Wu, Jianguo

2010-10-01

Phase 1. Hydrolysis of borohydride compounds offer the potential for significant hydrogen storage capacity, but most work to date has focused on one particular anion, BH4-, which requires high pH for stability. Other borohydride compounds, in particular polyhedral borane anions offer comparable hydrogen storage capacity without requiring high pH media and their long term thermal and hydrolytic stability coupled with non-toxic nature make them a very attractive alternative to NaBH4. The University of Missouri project provided the overall program focal point for the investigation of catalytic hydrolysis of polyhedral borane anions for hydrogen release. Due to their inherent stability, a transition metal catalyst was necessary for the hydrolysis of polyhedral borane anions. Transition metal ions such as cobalt, nickel, palladium and rhodium were investigated for their catalytic activity in the hydrolysis of nido-KB11H14, closo-K2B10H10, and closo-K2B12H12. The rate of hydrolysis follows first-order kinetics with respect to the concentration of the polyhedral borane anion and surface area of the rhodium catalyst. The rate of hydrolysis depends upon a) choice of polyhedral borane anion, c) concentration of polyhedral borane anion, d) surface area of the rhodium catalyst and e) temperature of the reaction. In all cases the yield of hydrogen was 100% which corresponds to ~7 wt% of hydrogen (based on material wt%). Phase 2. The phase 2 of program at the University of Missouri was focused upon developing aluminum ammonia-boranes (Al-AB) as chemical hydrogen storage materials, specifically their synthesis and studies of their dehydrogenation. The ammonia borane molecule (AB) is a demonstrated source of chemically stored hydrogen (19.6 wt%) which meets DOE performance parameters except for its regeneration from spent AB and elemental hydrogen. The presence of an aluminum center bonded to multiple AB residues might combine the efficiency of AB dehydrogenation with an aluminum

Effect of the nickel precursor on the impregnation and drying of γ-Al2O3 catalyst bodies: a UV-vis and IR micro-spectroscopic study

NARCIS (Netherlands)

Espinosa Alonso, L.; de Jong, K.P.; Weckhuysen, B.M.

2008-01-01

The elemental preparation steps of impregnation and drying of Ni/g-Al2O3 catalyst bodies have been studied by combining UV-vis and IR microspectroscopy. The influence of the number of chelating ligands in [Ni(en)x(H2O)6-2x]2+ precursor complexes (with en ) ethylenediamine and x ) 0-3) has been

Formation of carbon nanosheets via simultaneous activation and catalytic carbonization of macroporous anion-exchange resin for supercapacitors application.

Science.gov (United States)

Peng, Hui; Ma, Guofu; Sun, Kanjun; Mu, Jingjing; Zhang, Zhe; Lei, Ziqiang

2014-12-10

Two-dimensional mesoporous carbon nanosheets (CNSs) have been prepared via simultaneous activation and catalytic carbonization route using macroporous anion-exchange resin (AER) as carbon precursor and ZnCl2 and FeCl3 as activating agent and catalyst, respectively. The iron catalyst in the skeleton of the AER may lead to carburization to form a sheetlike structure during the carbonization process. The obtained CNSs have a large number of mesopores, a maximum specific surface area of 1764.9 m(2) g(-1), and large pore volume of 1.38 cm(3) g(-1). As an electrode material for supercapacitors application, the CNSs electrode possesses a large specific capacitance of 283 F g(-1) at 0.5 A g(-1) and excellent rate capability (64% retention ratio even at 50 A g(-1)) in 6 mol L(-1) KOH. Furthermore, CNSs symmetric supercapacitor exhibits specific energies of 17.2 W h kg(-1) at a power density of 224 W kg(-1) operated in the voltage range of 0-1.8 V in 0.5 mol L(-1) Na2SO4 aqueous electrolyte, and outstanding cyclability (retains about 96% initial capacitance after 5000 cycles).

Degradation of anionic surfactants using the reactor based on dielectric barrier discharge

Directory of Open Access Journals (Sweden)

Aonyas Munera Mustafa

2016-01-01

Full Text Available Two anionic surfactants (sodium lauryl sulfate - SDS and sodium dodecylbenzenesulfonate - SDBS were treated with dielectric barrier discharge. Loss of surfactant activity, decrease of chemical oxygen demand and total organic carbon as well as lower toxicity of degradation products were determined. Effects of catalysts - hydrogen peroxide and iron (II, on parameters mentioned above, were determined. Catalysts affect the degradation of SDBS and in the case of SDS catalysts have no effect on degradation. Both catalysts induce the decrease of COD and TOC values. Toxicity of solutions after the plasma treatment is lower in all the systems tested. [Projekat Ministarstva nauke Republike Srbije, br. OI 172030

Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Technical progress report, October--December 1993

Energy Technology Data Exchange (ETDEWEB)

Schmidt, E.; Kirby, S.; Song, Chunshan; Schobert, H.H.

1994-04-01

Development of new catalysts is a promising approach to more, efficient coal liquefaction. It has been recognized that dispersed catalysts can be superior to supported catalysts for primary liquefaction of coals, because the control of initial coal dissolution or depolymerization requires infinite contact between the catalyst and coal. The primary objective of this research is to explore the potential of bimetallic dispersed catalysts from heterometallic molecular precursors in their use in model compound liquefaction reactions. This quarterly report describes the use of three precursors in model compound reactions. The first catalyst is a heterometallic complex consisting of two transition metals, Mo and Ni, and sulfur in a single molecule. The second is a thiocubane type complex consisting of cobalt, molybdenum and sulfur. The third is a thiocubane type cluster consisting of iron and sulfur and the fourth, the pure inorganic salt ammonium tetrathiomolybdate (ATM). It was found that the structure and the ligands in the model complexes affect the activity of the resulting catalyst significantly. The optimum reaction at a pressure of 6.9 MPa hydrogen gas varied for different catalysts. The bimetallic catalysts generated in situ from the organometallic precursor are more active than monometallic catalysts like ATTM and the thiocubane type cluster Fe{sub 4}. Main products are hydrogenated phenanthrene derivatives, like DBP, THP, sym-OHP, cis- and trans-unsym-OHP with minor isomerization products such as sym-OHA. Our results indicate that other transition metal and ligand combinations in the organometallic precursors and the use of another model compound could result in substantially higher conversion activity.

The effect of anion on the magnetic properties of nanocrystalline NiO synthesized by homogeneous precipitation

International Nuclear Information System (INIS)

Ranga Rao Pulimi, V.; Jeevanandam, P.

2009-01-01

The effect of using different anions (nitrate, chloride, sulfate, and acetate) during the precursor synthesis, by homogeneous precipitation, on the magnetic properties of the final product (nanocrystalline NiO), has been studied. The precursors and the oxide were characterized by various analytical techniques including powder X-ray diffraction, FT-IR spectroscopy, thermal gravimetry (TGA), and magnetic measurements. The synthesized NiO samples possess crystallite size in the range, ∼2-6 nm, depending on the anion of the nickel salt. The nickel oxide nanoparticles exhibit superparamagnetic behavior. Acetate and sulfate anions lead to NiO with higher saturation magnetization (∼1.2-1.8 emu/g), while chloride and nitrate anions lead to NiO nanoparticles with lower saturation magnetization (∼0.1-0.4 emu/g) values. The observed magnetic behavior has been attributed to the size effect.

The effect of anion on the magnetic properties of nanocrystalline NiO synthesized by homogeneous precipitation

Energy Technology Data Exchange (ETDEWEB)

Ranga Rao Pulimi, V. [Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee 247667 (India); Jeevanandam, P. [Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee 247667 (India)], E-mail: jeevafcy@iitr.ernet.in

2009-09-15

The effect of using different anions (nitrate, chloride, sulfate, and acetate) during the precursor synthesis, by homogeneous precipitation, on the magnetic properties of the final product (nanocrystalline NiO), has been studied. The precursors and the oxide were characterized by various analytical techniques including powder X-ray diffraction, FT-IR spectroscopy, thermal gravimetry (TGA), and magnetic measurements. The synthesized NiO samples possess crystallite size in the range, {approx}2-6 nm, depending on the anion of the nickel salt. The nickel oxide nanoparticles exhibit superparamagnetic behavior. Acetate and sulfate anions lead to NiO with higher saturation magnetization ({approx}1.2-1.8 emu/g), while chloride and nitrate anions lead to NiO nanoparticles with lower saturation magnetization ({approx}0.1-0.4 emu/g) values. The observed magnetic behavior has been attributed to the size effect.

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.

Scalable synthesis of palladium nanoparticle catalysts by atomic layer deposition

International Nuclear Information System (INIS)

Liang Xinhua; Lyon, Lauren B.; Jiang Yingbing; Weimer, Alan W.

2012-01-01

Atomic layer deposition (ALD) was used to produce Pd/Al 2 O 3 catalysts using sequential exposures of Pd(II) hexafluoroacetylacetonate and formalin at 200 °C in a fluidized bed reactor. The ALD-prepared Pd/alumina catalysts were characterized by various methods including hydrogen chemisorption, XPS, and TEM, and compared with a commercially available 1 wt% Pd/alumina catalyst, which was also characterized. The content of Pd on alumina support and the size of Pd nanoparticles can be controlled by the number of ALD-coating cycles and the dose time of the Pd precursor. One layer of organic component from the Pd precursor remained on the Pd particle surface. The ALD 0.9 wt% Pd/alumina had greater active metal surface area and percent metal dispersion than the commercial 1 wt% Pd/alumina catalyst. The ALD and commercial catalysts were subjected to catalytic testing to determine their relative activities for glucose oxidation to gluconic acid in aqueous solution. The ALD 0.9 wt% Pd/alumina catalyst had comparable activity as compared to the commercial 1 wt% Pd catalyst. No noticeable amount of Pd leaching was observed for the ALD-prepared catalysts during the vigorously stirred reaction.

Effect of pretreatment temperature on catalytic performance of the catalysts derived from cobalt carbonyl cluster in Fischer-Tropsch Synthesis

Directory of Open Access Journals (Sweden)

Byambasuren O

2017-02-01

Full Text Available The monometallic cobalt-based catalysts were prepared by pretreating the catalysts derived from carbonyl cluster precursor (CO6Co2CC(COOH2 supported on γ-Al2O3 with hydrogen at 180, 220, and 260°C respectively. The temperature effect of the pretreatments on the structure evolution of cluster precursors and the catalytic performance of the Fischer-Tropsch (F-T synthesis was investigated. The pretreated catalyst at 220°C with unique phase structure exhibited best catalytic activity and selectivity among three pretreated catalysts. Moreover, the catalysts exhibited high dispersion due to the formation of hydrogen bonds between the cluster precursor and γ-Al2O3 support.

Propene Hydroformylation by Supported Aqueous-phase Rh-NORBOS Catalysts

DEFF Research Database (Denmark)

Riisager, Anders; Eriksen, Kim Michael; Hjortkjær, Jes

2003-01-01

The gas-phase hydroformylation reaction of propene using supported aqueous-phase (SAP) Rh-NORBOS modified catalysts in a continuous flow reactor has been examined. SAP catalysts supported on six different support materials were made by wet impregnation using solutions of the precursor complex Rh(...

Heterogenization of Homogeneous Catalysts: the Effect of the Support

Energy Technology Data Exchange (ETDEWEB)

Earl, W.L.; Ott, K.C.; Hall, K.A.; de Rege, F.M.; Morita, D.K.; Tumas, W.; Brown, G.H.; Broene, R.D.

1999-06-29

We have studied the influence of placing a soluble, homogeneous catalyst onto a solid support. We determined that such a 'heterogenized' homogeneous catalyst can have improved activity and selectivity for the asymmetric hydrogenation of enamides to amino acid derivatives. The route of heterogenization of RhDuPhos(COD){sup +} cations occurs via electrostatic interactions with anions that are capable of strong hydrogen bonding to silica surfaces. This is a novel approach to supported catalysis. Supported RhDuPhos(COD){sup +} is a recyclable, non-leaching catalyst in non-polar media. This is one of the few heterogenized catalysts that exhibits improved catalytic performance as compared to its homogeneous analog.

Alternative alkali resistant deNOx catalysts

DEFF Research Database (Denmark)

Putluru, Siva Sankar Reddy; Kristensen, Steffen Buus; Due-Hansen, Johannes

2012-01-01

by onepot sol–gel method. All catalysts were characterized by BET, XRPD and NH3-TPD. Initial SCR activities of 8 out of 9 catalysts showed higher NO conversion at least at one temperature in the temperature range 300–500 ◦C compared to the conventional V2O5-WO3/TiO2 catalyst. After potassium poisoning (100......Alternative alkali resistant deNOx catalysts were prepared using three different supports ZrO2, TiO2 and Mordenite zeolite. The majority of the catalysts were prepared by incipient wetness impregnation of a commercial support, with vanadium, copper or iron precursor, one catalyst was prepared......–130 µmol of K/g of catalyst) the relative drop in SCR activity and acidity was lower for all the alternative catalysts compared to the industrial V2O5-WO3/TiO2 catalyst. Furthermore, Cu/MOR and Nano-V2O5/Sul-TiO2 catalysts showed 8–16 times higher SCR activities than the conventional even after high...

Catalyst dispersion and activity under conditions of temperature-staged liquefaction. Final report

Energy Technology Data Exchange (ETDEWEB)

Davis, A.; Schobert, H.H.; Mitchell, G.D.; Artok, L.

1993-02-01

This research program involves the investigation of the use of highly dispersed catalyst precursors for the pretreatment of coals by mild hydrogenation. During the course of this effort solvent preswelling of the coal was evaluated as a means of deeply impregnating catalysts into coal, active phases of catalysts under reaction conditions were studied and the impact of these techniques were evaluated during pretreatment and temperature-staged liquefaction. Two coals, a Texas subbituminous and a Utah high volatile A bituminous, were used to examine the effects of solvent swelling pretreatment and catalyst impregnation on conversion behavior at 275{degrees}C, representative of the first, low-temperature stage in a temperature-staged liquefaction reaction. Ferrous sulfate, iron pentacarbonyl, ammonium tetrathiomolybdate, and molybdenum hexacarbonyl were used as catalyst precursors. Without swelling pretreatment, impregnation of both coals increased conversion, mainly through increased yields of preasphaltenes.

Slat templated formation of efficient oxygen reduction electrocatalyst with a fluidic precursor

Science.gov (United States)

Tan, Yao

2018-05-01

Development of cost-effective and efficient oxygen reduction catalyst is critical for the commercialization of proton exchange membrane fuel cell. Metal and nitrogen co-doped carbon is recognized as a promising alternative to traditional platinum-based oxygen reduction catalyst. Herein, we report a novel metal and nitrogen co-doped carbon catalyst with an ionic liquid precursor. Salt template, which can be easily removed with mild treatment after the synthesis, is used to generate abundant mesopores in the resulting catalyst. We show that the novel catalyst shows a superior activity comparable to commercial Pt/C catalyst. Furthermore, the important role of the mesopore for the activity of the catalyst is demonstrated.

Domain growth of carbon nanotubes assisted by dewetting of thin catalyst precursor films

Energy Technology Data Exchange (ETDEWEB)

Srivastava, Alok Kumar [Defence Materials and Stores R and D Establishment (DRDO), GT Road, Kanpur 208013 (India); Department of Chemical Engineering, Indian Institute of Technology, Kanpur 208016 (India); Sachan, Priyanka; Samanta, Chandan [Department of Chemical Engineering, Indian Institute of Technology, Kanpur 208016 (India); Mukhopadhyay, Kingsuk [Defence Materials and Stores R and D Establishment (DRDO), GT Road, Kanpur 208013 (India); Sharma, Ashutosh, E-mail: ashutos@iitk.ac.in [Department of Chemical Engineering, Indian Institute of Technology, Kanpur 208016 (India)

2014-01-01

We explore self-organized dewetting of ultrathin films of a novel metal complex as a one step surface patterning method to create nanoislands of iron, using which spatially separated carbon nanostructures were synthesized. Dewetting of ultrathin metal complex films was induced by two different methods: liquid solvent exposure and thermal annealing to engender surface patterning. For thermal dewetting, thin films of the iron oleate complex were dewetted at high temperature. In the case of liquid solvent assisted dewetting, the metal complex, mixed with a sacrificial polymer (polystyrene) was spin coated as thin films (<40 nm) and then dewetted under an optimal solution mixture consisting of methyl ethyl ketone, acetone and water. The carrier polymer was then selectively removed to produce the iron metal islands. These metal islands were used for selective growth of discrete patches of multiwall CNTs and CNFs by a chemical vapor deposition (CVD) process. Solvent induced dewetting showed clear advantages over thermal dewetting owing to reduced size of catalyst domains formed by dewetting, an improved control over CNT growth as well as in its ability to immobilize the seed particles. The generic solution mediated dewetting and pattern generation in thin films of various catalytic precursors can thus be a powerful method for selective domain growth of a variety of functional nanomaterials.

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....

Effect of Cobalt Source on the Catalyst Reducibility and Activity of ...

African Journals Online (AJOL)

The effect of cobalt precursor (nitrate, acetate and chloride salts) on the catalyst reducibility and dispersion, ... balt catalysts (>5.0 wt%) prepared using ammonium cobalt ... heated from 323 K to 1073 K using a heating ramp of 10 K min–1.

Preparation of supported heterogeneous catalysts by pulse impregnation: Application to Ru[sub 3](CO)[sub 12]/2,2[prime]-bipyridine/SiO[sub 2] catalyst

Energy Technology Data Exchange (ETDEWEB)

Haukka, M.; Pakkanen, T.A. (Univ. of Joensuu (Finland))

1994-07-01

In this paper, the authors introduce pulse impregnation, a method for preparing supported heterogeneous catalysts by successive impregnation cycles. Pulse impregnation is a method for preparing supported heterogeneous catalysts from the liquid phase. In the pulse-impregnation technique the catalyst surface is grown gradually in consecutive cycles, with each cycle consisting of separate deposition and activation steps. During the deposition step, the catalyst precursor or precursors are deposited onto the support from a suitable solvent. The actual chemically bonded catalyst phase is formed during the activation step (e.g., thermal activation). Pulse impregnation was tested in the separate deposition of 2,2[prime]-bipyridine and Ru[sub 3](CO)[sub 12] onto a silica support, and in the preparation of Ru[sub 3](CO)[sub 12]/2,2[prime]-bipyridine/SiO[sub 2] catalyst, in a column-type reactor system. Macroscopically uniform deposition was achieved with both 2,2[prime]-bipyridine and Ru[sub 3](CO)[sub 12]. Various solvent systems were used to control the amount of solute adsorbed during deposition. In the preparation of the Ru[sub 3](CO)[sub 12]/2,2[prime]-bipyridine/SiO[sub 2] catalyst, the ruthenium content increased nearly linearly with the number of preparation cycles. The effects of the preparation method on the catalyst activity was also tested in 1-hexane hydroformylation. 31 refs., 7 figs., 1 tab.

Development physicochemical and catalytic characteristics of Mo-containing catalysts for hydrotreatment based on various supports. 1. Adsorption of molybdate anions on the support surface

International Nuclear Information System (INIS)

Lur'e, M.A.; Kurest, I.Z.; Krasnopol'skaya, S.M.; Reznikov, S.A.; Babikov, A.F.; Shmidt, F.K.

1994-01-01

The amounts of basic OH-groups were determined by means of exchange by F-ions and the adsorption of Mo from acid and alkali ammonium paramolybdate (APM) solutions was investigated on the surface of hydrated titanium dioxide, γ-Al 2 O 3 and palygorskite-montmorillonite clay. The process is adequately described by the exchange equation at pH value of APM solution in excess of the isoelectric point (IEP) of the surface. At opposite correlation between pH of the solution and IEP the Langmuir model is adaptable. They concluded, on experimental data, that in the latter case OH-groups replaced by molybdate-anion stage of synthesis of catalyst. 22 refs., 3 figs

Nanostructured manganese oxides as highly active water oxidation catalysts: a boost from manganese precursor chemistry.

Science.gov (United States)

Menezes, Prashanth W; Indra, Arindam; Littlewood, Patrick; Schwarze, Michael; Göbel, Caren; Schomäcker, Reinhard; Driess, Matthias

2014-08-01

We present a facile synthesis of bioinspired manganese oxides for chemical and photocatalytic water oxidation, starting from a reliable and versatile manganese(II) oxalate single-source precursor (SSP) accessible through an inverse micellar molecular approach. Strikingly, thermal decomposition of the latter precursor in various environments (air, nitrogen, and vacuum) led to the three different mineral phases of bixbyite (Mn2 O3 ), hausmannite (Mn3 O4 ), and manganosite (MnO). Initial chemical water oxidation experiments using ceric ammonium nitrate (CAN) gave the maximum catalytic activity for Mn2 O3 and MnO whereas Mn3 O4 had a limited activity. The substantial increase in the catalytic activity of MnO in chemical water oxidation was demonstrated by the fact that a phase transformation occurs at the surface from nanocrystalline MnO into an amorphous MnOx (1catalysts has been proposed by determining the amount of accessible manganese centers. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermal effects in highly dispersed iron catalysts

International Nuclear Information System (INIS)

Alvarez, A.M.; Cagnoli, M.V.; Gallegos, N.G.; Marchetti, S.G.; Yeramian, A.A.; Mercader, R.C.

1994-01-01

The Moessbauer spectra of three Fe/SiO 2 catalysts with 5 wt% iron content show the presence of several Fe species and display different magnetic behaviours when the precursors are subjected to various thermal treatments. Based on the Moessbauer parameters and CO chemisorption measurements, the average crystal sizes of the catalysts are estimated and discussed in connection with the thermal pretreatment severity and magnetic properties of the samples. (orig.)

Striking difference between alkane and olefin metathesis using the well-defined precursor [≡Si-O-WMe5]: Indirect evidence in favour of a bifunctional catalyst W alkylidene-hydride

KAUST Repository

Riache, Nassima; Callens, Emmanuel; Espinas, Jeff; Dé ry, Alexandre; Samantaray, Manoja; Dey, Raju; Basset, Jean-Marie

2015-01-01

Metathesis of linear alkanes catalyzed by the well-defined precursor (≡Si-O-WMe5) affords a wide distribution of linear alkanes from methane up to triacontane. Olefin metathesis using the same catalyst and under the same reaction conditions gives a very striking different distribution of linear α-olefins and internal olefins. This shows that olefin and alkane metathesis processes occur via very different pathways.

Iridium-catalyst-based autonomous bubble-propelled graphene micromotors with ultralow catalyst loading.

Science.gov (United States)

Wang, Hong; Sofer, Zdeněk; Eng, Alex Yong Sheng; Pumera, Martin

2014-11-10

A novel concept of an iridium-based bubble-propelled Janus-particle-type graphene micromotor with very high surface area and with very low catalyst loading is described. The low loading of Ir catalyst (0.54 at %) allows for fast motion of graphene microparticles with high surface area of 316.2 m(2)  g(-1). The micromotor was prepared with a simple and scalable method by thermal exfoliation of iridium-doped graphite oxide precursor composite in hydrogen atmosphere. Oxygen bubbles generated from the decomposition of hydrogen peroxide at the iridium catalytic sites provide robust propulsion thrust for the graphene micromotor. The high surface area and low iridium catalyst loading of the bubble-propelled graphene motors offer great possibilities for dramatically enhanced cargo delivery. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preparation of electrocatalysts by reduction of precursors with sodium citrate

OpenAIRE

Briskeby, Stein Trygve; Tsypkin, Mikhail; Tunold, Reidar; Sunde, Svein

2014-01-01

In this work synthesis of Pt/C catalysts by reduction of H2PtCl6 with sodium citrate has been investigated. The strong pH-dependence of citrate as a reducing and stabilizing agent has been explored, and an optimum pH range for production of well dispersed catalysts is proposed. To achieve stabilizing and reducing conditions, the presence of both citrate anions and protonated citrates are required. This is achieved in an intermediate pH range between pKa2 and pKa3 (4.76 and 6.4) of citric acid...

Mulliken-Hush elucidation of the encounter (precursor) complex in intermolecular electron transfer via self-exchange of tetracyanoethylene anion-radical

International Nuclear Information System (INIS)

Rosokha, S.V.; Newton, M.D.; Head-Gordon, M.; Kochi, J.K.

2006-01-01

The paramagnetic [1:1] encounter complex (TCNE) 2 -dot is established as the important precursor in the kinetics and mechanism of electron-transfer for the self-exchange between tetracyanoethylene acceptor (TCNE) and its radical-anion as the donor. Spectroscopic observation of the dimeric complex (TCNE) 2 -dot by its intervalence absorption band at the solvent-dependent wavelength of λ IV ∼1500nm facilitates the application of Mulliken-Hush theory which reveals the significant electronic interaction extant between the pair of cofacial TCNE moieties with the sizable coupling of H DA =1000cm -1 . The transient existence of such an encounter complex provides the critical link in the electron-transfer kinetics by lowering the classical Marcus reorganization barrier by the amount of H DA in this strongly adiabatic system. Ab initio quantum-mechanical methods as applied to independent theoretical computations of both the reorganization energy (λ) and the electronic coupling element (H DA ) confirm the essential correctness of the Mulliken-Hush formalism for fast electron transfer via strongly coupled donor/acceptor encounter complexes

Boron-containing catalysts for dry reforming of methane to synthesis gas

KAUST Repository

Takanabe, Kazuhiro

2018-01-04

The present invention uses a cobalt catalyst for carbon dioxide reforming of lower alkanes to synthesis gas having a cobalt catalyst on an oxide support where the supported cobalt catalyst has been modified with a boron precursor. The boron-treated cobalt catalyst systems as described herein show significant increases in the conversion of CH4 and CO2 during the dry reforming of methane (DRM) reaction as compared to traditional catalysts. Described herein are supported catalysts and methods of using the catalysts for the dry reforming of methane to synthesis gas, with the supported catalysts in the present invention include a boron-treated cobalt catalyst disposed on an oxide support. Also described herein are processes for preparing the supported catalysts.

Palladium catalyst system comprising zwitterion and/or acid-​functionalized ionic liquid

DEFF Research Database (Denmark)

2011-01-01

The present invention concerns a catalyst system in particular a catalyst system comprising Palladium (Pd), a zwitterion and/or an acid-functionalized ionic liquid, and one or more phosphine ligands, wherein the Pd catalyst can be provided by a complex precursor, such as Pd(CH3COO)2, PdCI2, Pd(CH3...... methyl methacrylate and/or methacrylic acid. Catalyst systems according to the invention are suitable for reactions forming separable product and catalyst phases and supported ionic liquid phase SILP applications....

Identification of inorganic anions by gas chromatography/mass spectrometry.

Science.gov (United States)

Sakayanagi, Masataka; Yamada, Yaeko; Sakabe, Chikako; Watanabe, Kunio; Harigaya, Yoshihiro

2006-03-10

Inorganic anions were identified by using gas chromatography/mass spectrometry (GC/MS). Derivatization of the anions was achieved with pentafluorobenzyl p-toluenesulphonate (PFB-Tos) as the reaction reagent and a crown ether as a phase transfer catalyst. When PFB-Br was used as the reaction reagent, the retention time of it was close to those of the derivatized inorganic anions and interfered with the analysis. In contrast, the retention time of PFB-Tos differed greatly from the PFB derivatives of the inorganic anions and the compounds of interest could be detected without interference. Although the PFB derivatives of SO4, S2O3, CO3, ClO4, and ClO3 could not be detected, the derivatives of F, Cl, Br, I, CN, OCN, SCN, N3, NO3, and NO2 were detected using PFB-Tos as the derivatizing reagent. The inorganic anions were detectable within 30 ng approximately, which is of sufficient sensitivity for use in forensic chemistry. Accurate mass number was measured for each PFB derivative by high-resolution mass spectrometry (HRMS) within a measurement error of 2 millimass units (mmu), which allowed determination of the compositional formula from the mass number. In addition, actual analysis was performed successively by our method using trial samples of matrix.

Alternative SILP-SCR Catalysts based on Guanidinium Chromates

DEFF Research Database (Denmark)

Due-Hansen, Johannes; Riisager, Anders; Ståhl, Kenny

There is an increasing global concern about human caused emissions of pollutants like sulfur and nitrogen oxides to the atmosphere leading to, e.g. smog and acid rain damaging to the human health and the environment. Selective catalytic reduction (SCR) of NOx with ammonia as reductant is the most...... duct. There is therefore a demand for alkali-resistant SCR catalysts more flexible regarding temperature of operation and position in the duct. Supported ionic liquid phase (SILP) catalysts with 1,1,3,3-Tetramethylguanidinium (TMGH+) and a chromium oxide anion supported on anatase have exhibited...

An optimization study of PtSn/C catalysts applied to direct ethanol fuel cell: Effect of the preparation method on the electrocatalytic activity of the catalysts

Science.gov (United States)

Almeida, T. S.; Palma, L. M.; Leonello, P. H.; Morais, C.; Kokoh, K. B.; De Andrade, A. R.

2012-10-01

The aim of this work was to perform a systematic study of the parameters that can influence the composition, morphology, and catalytic activity of PtSn/C nanoparticles and compare two different methods of nanocatalyst preparation, namely microwave-assisted heating (MW) and thermal decomposition of polymeric precursors (DPP). An investigation of the effects of the reducing and stabilizing agents on the catalytic activity and morphology of Pt75Sn25/C catalysts prepared by microwave-assisted heating was undertaken for optimization purposes. The effect of short-chain alcohols such as ethanol, ethylene glycol, and propylene glycol as reducing agents was evaluated, and the use of sodium acetate and citric acid as stabilizing agents for the MW procedure was examined. Catalysts obtained from propylene glycol displayed higher catalytic activity compared with catalysts prepared in ethylene glycol. Introduction of sodium acetate enhanced the catalytic activity, but this beneficial effect was observed until a critical acetate concentration was reached. Optimization of the MW synthesis allowed for the preparation of highly dispersed catalysts with average sizes lying between 2.0 and 5.0 nm. Comparison of the best catalyst prepared by MW with a catalyst of similar composition prepared by the polymeric precursors method showed that the catalytic activity of the material can be improved when a proper condition for catalyst preparation is achieved.

Characterization of steam-reforming catalysts

Directory of Open Access Journals (Sweden)

Santos D. C. R.M.

2004-01-01

Full Text Available The effect of the addition of Mg and Ca to Ni/ a-Al2O3 catalysts was investigatedstudied, aiming to detail the promotion mechanismaddress their role as promoters in the steam reforming reaction. Temperature- programmed reduction and H2 and CO temperature-programmed desorption experiments indicated that Mg interacts with the metallic phase. Mg-promoted catalysts showed a greater difficulty for Ni precursors reduction besides different probe molecules (H2 and CO adsorbed states. In the conversion of cyclohexane, Mg inhibited the formation of hydrogenolysis products. Nonetheless, the presence of Ca did not influence the metallic phase.

Anion-Regulated Selective Generation of Cobalt Sites in Carbon: Toward Superior Bifunctional Electrocatalysis

Energy Technology Data Exchange (ETDEWEB)

Wan, Gang [State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Ding-xi Road Shanghai 200050 P. R. China; University of Chinese Academy of Sciences, Beijing 100049 P. R. China; Yang, Ce [Chemical Science and Engineering Division, Argonne National Laboratory, 9700 Cass Avenue Lemont IL 60439 USA; Zhao, Wanpeng [State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Ding-xi Road Shanghai 200050 P. R. China; University of Chinese Academy of Sciences, Beijing 100049 P. R. China; Li, Qianru [State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Ding-xi Road Shanghai 200050 P. R. China; University of Chinese Academy of Sciences, Beijing 100049 P. R. China; Wang, Ning [State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Ding-xi Road Shanghai 200050 P. R. China; University of Chinese Academy of Sciences, Beijing 100049 P. R. China; Li, Tao [X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, 9700 Cass Avenue Lemont IL 60439 USA; Zhou, Hua [X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, 9700 Cass Avenue Lemont IL 60439 USA; Chen, Hangrong [State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Ding-xi Road Shanghai 200050 P. R. China; Shi, Jianlin [State Key Laboratory of High Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Ding-xi Road Shanghai 200050 P. R. China

2017-11-06

The introduction of active transition metal sites (TMSs) in carbon enables the synthesis of noble-metal-free electrocatalysts for clean energy conversion applications, however, there are often multiple existing forms of TMSs, which are of different natures and catalytic models. Regulating the evolution of distinctive TMSs is highly desirable but remains challenging to date. Anions, as essential elements involved in the synthesis, have been totally neglected previously in the construction of TMSs. Herein, the effects of anions on the creation of different types of TMSs is investigated for the first time. It is found that the active cobalt-nitrogen sites tend to be selectively constructed on the surface of N-doped carbon by using chloride, while metallic cobalt nanoparticles encased in protective graphite layers are the dominant forms of cobalt species with nitrate ions. The obtained catalysts demonstrate cobalt-sites-dependent activity for ORR and HER in acidic media. And the remarkably enhanced catalytic activities approaching that of benchmark Pt/C in acidic medium has been obtained on the catalyst dominated with cobalt-nitrogen sites, confirmed by the advanced spectroscopic . Our finding demonstrates a general paradigm of anion-regulated evolution of distinctive TMSs, providing a new pathway for enhancing performances of various targeted reactions related with TMSs.

Anionic Palladium(0) and Palladium(II) Ate Complexes.

Science.gov (United States)

Kolter, Marlene; Böck, Katharina; Karaghiosoff, Konstantin; Koszinowski, Konrad

2017-10-16

Palladium ate complexes are frequently invoked as important intermediates in Heck and cross-coupling reactions, but so far have largely eluded characterization at the molecular level. Here, we use electrospray-ionization mass spectrometry, electrical conductivity measurements, and NMR spectroscopy to show that the electron-poor catalyst [L 3 Pd] (L=tris[3,5-bis(trifluoromethyl)phenyl]phosphine) readily reacts with Br - ions to afford the anionic, zero-valent ate complex [L 3 PdBr] - . In contrast, more-electron-rich Pd catalysts display lower tendencies toward the formation of ate complexes. Combining [L 3 Pd] with LiI and an aryl iodide substrate (ArI) results in the observation of the Pd II ate complex [L 2 Pd(Ar)I 2 ] - . © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

La2O3/CaO CATALYSTS AND ITS APPLICATION IN THE OXIDATIVE COUPLING OF METHANE

OpenAIRE

Garrido-Schaeffer, A.; Dedios Yenque, G.; Ponce Alvaréz, S.

2014-01-01

La2O3/CaO catalysts were prepared at different weight percentages of La2O3.Por the coprecipitation method described porRaO, CaCO3 is prepared and then it was impregnated in a solution of La (NO) 3.6H2O thus obtaining the catalyst precursor . precursors dried at 393K and calcined at 973K, obtaining 0-15% La2O3/CaO catalysts. XRF elemental qualitative analysis was performed. By FTIR carbonates adsorbed species was observed. The presence of La2O3 and CaO phases was confirmed by XRD and BET surfa...

Moessbauer investigations of the Fe-Cu-Mn catalysts for Fischer-Tropsch synthesis

International Nuclear Information System (INIS)

Spanu, V.; Filoti, G.; Ilie, I.; Zamfirescu, E.

1990-01-01

In the selective process of the syngas conversion to synthetic gasoline a bifunctional catalytic system has to be used. It was obtained by combination a Fischer-Tropsch catalyst with the HZSM-5 zeolite. The phase compositions of the precursor and the fresh catalyst were established as well as the optimum thermal treatment. The catalyst was reduced in pure H 2 or in a H 2 +CO mixture. The influence of the reduction and reaction conditions on the catalyst structure was investigated. (orig.)

Role of Precursor-Conversion Chemistry in the Crystal-Phase Control of Catalytically Grown Colloidal Semiconductor Quantum Wires.

Science.gov (United States)

Wang, Fudong; Buhro, William E

2017-12-26

Crystal-phase control is one of the most challenging problems in nanowire growth. We demonstrate that, in the solution-phase catalyzed growth of colloidal cadmium telluride (CdTe) quantum wires (QWs), the crystal phase can be controlled by manipulating the reaction chemistry of the Cd precursors and tri-n-octylphosphine telluride (TOPTe) to favor the production of either a CdTe solute or Te, which consequently determines the composition and (liquid or solid) state of the Bi x Cd y Te z catalyst nanoparticles. Growth of single-phase (e.g., wurtzite) QWs is achieved only from solid catalysts (y ≪ z) that enable the solution-solid-solid growth of the QWs, whereas the liquid catalysts (y ≈ z) fulfill the solution-liquid-solid growth of the polytypic QWs. Factors that affect the precursor-conversion chemistry are systematically accounted for, which are correlated with a kinetic study of the composition and state of the catalyst nanoparticles to understand the mechanism. This work reveals the role of the precursor-reaction chemistry in the crystal-phase control of catalytically grown colloidal QWs, opening the possibility of growing phase-pure QWs of other compositions.

{gamma} alumina- and HY zeolite-supported molybdenum catalysts: characterisation of the oxidic and sulfided phases; Catalyseurs a base de molybdene supporte sur alumine {gamma} et zeolithe HY: caracterisation des phases oxydes et sulfures

Energy Technology Data Exchange (ETDEWEB)

Plazenet, G

2001-10-01

Oxidic precursors of hydro-treatment catalysts (Co)Mo/alumina or zeolite were characterised by Raman spectroscopy, NMR and EXAFS at the Mo and Co K-edges. The formation of an Anderson-type alumino-molybdate compound upon impregnation of the support with an ammonium hepta-molybdate solution was confirmed for alumina, and also observed for the HY zeolitic support, with consumption of the amorphous alumina of the zeolite. In absence of the latter, ammonium hepta-molybdate precipitates. The species are conserved upon drying; upon calcination, the alumino-molybdate evolves into a surface aluminium molybdate type phase, whereas the hepta-molybdate transforms into MoO{sub 3}. The species formed upon impregnation are located in the inter-granular porosity whereas MoO{sub 3} vapor-condensation leads to formation of dimers located inside the zeolitic structure. The study of the cobalt-promoted precursors showed that the evolution of the molybdenum is the same in the case of co-impregnation preparation. Impregnation with cobalt-molybdate prevents the formation of the alumino-molybdate anion and thus enables the preservation of the Mo-Co interaction but, whatever the precursor, the leveling effect of the calcination-re-hydration steps was demonstrated. An EXAFS study at different sulfur coverages of the MoS{sub 2} platelets in the alumina-supported sulfided catalysts showed the limitations of EXAFS for size determination of MoS{sub 2} crystallites, a parameter that can be reached by AWAXS, which also conveys information about sheet-stacking. The EXAFS study of sulfided (Co)Mo/HY systems revealed incomplete sulfidation of the samples and the very high dispersion of the active phase. The absence of an observable Mo-Co interaction whatever the preparation of the promoted catalysts is consistent with the absence of promoting effect in toluene hydrogenation. (author)

Catalyst containing oxygen transport membrane

Science.gov (United States)

Christie, Gervase Maxwell; Wilson, Jamie Robyn; van Hassel, Bart Antonie

2012-12-04

A composite oxygen transport membrane having a dense layer, a porous support layer and an intermediate porous layer located between the dense layer and the porous support layer. Both the dense layer and the intermediate porous layer are formed from an ionic conductive material to conduct oxygen ions and an electrically conductive material to conduct electrons. The porous support layer has a high permeability, high porosity, and a high average pore diameter and the intermediate porous layer has a lower permeability and lower pore diameter than the porous support layer. Catalyst particles selected to promote oxidation of a combustible substance are located in the intermediate porous layer and in the porous support adjacent to the intermediate porous layer. The catalyst particles can be formed by wicking a solution of catalyst precursors through the porous support toward the intermediate porous layer.

Ammonia synthesis over multi-promoted iron catalysts obtained by high-energy ball-milling

DEFF Research Database (Denmark)

Jacobsen, C.J.H.; Jiang, Jianzhong; Mørup, Steen

1999-01-01

The feasibility of producing ammonia synthesis catalysts from high-energy ball-milling of a simple mixture of the constituent oxides has been investigated. The effect of ball-milling the fused oxidic precursor of the industrial KM1 ammonia synthesis catalyst has also been studied. The results show...

The impact of copper in LaNi{sub 1-x}Cu{sub x}O{sub 3} perovskite-like structures used as catalyst precursors for dry reforming of methane

Energy Technology Data Exchange (ETDEWEB)

Vlach, K.; Hoang, D.L.; Armbruster, U.; Martin, A. [Leibniz-Institut fuer Katalyse e.V. an der Universitaet Rostock (Germany)

2013-11-01

This work deals with the synthesis of perovskite-like catalyst precursors (LaNi{sub 1-x}Cu{sub x}O{sub 3} with x = 0, 0.2, 0.5, 0.8, 1). These precursors were used to catalyse the dry reforming of methane (DRM) reaction carried out at 973 K, CH{sub 4}/CO{sub 2} = 1 and a GHSV = 18,000 ml/g/h. The precursors were transformed during the course of the reaction to give Ni-Cu/La{sub 2}O{sub 3} solids. We found out that the activity increases with raising Ni content but small Cu admixture suppresses the coke formation substantially. XRD and TEM measurements showed that the transformation led to the formation of small metallic Ni and/or Cu particles. In addition also alloying can be observed. The best catalytic system with respect to activity and suppressed carbon deposition was Ni{sub 0.8}-Cu{sub 0.2}/La{sub 2}O{sub 3} (X{sub CH4} = 61%, X{sub CO2} = 67%). (orig.)

Low temperature catalyst-assisted pyrolysis of polymer precursors to ...

Indian Academy of Sciences (India)

2017-11-15

Nov 15, 2017 ... convert the organic compounds into high-performance car- bon. PAN is one of the ... yield, RF organic gel is also identified as a widely used precursor to produce ..... sis were applied to estimate radius of gyration (Rg) and surface ... pyrolysis approach without compromising the yield and qual- ity of the final ...

The Dependence of CNT Aerogel Synthesis on Sulfur-driven Catalyst Nucleation Processes and a Critical Catalyst Particle Mass Concentration.

Science.gov (United States)

Hoecker, Christian; Smail, Fiona; Pick, Martin; Weller, Lee; Boies, Adam M

2017-11-06

The floating catalyst chemical vapor deposition (FC-CVD) process permits macro-scale assembly of nanoscale materials, enabling continuous production of carbon nanotube (CNT) aerogels. Despite the intensive research in the field, fundamental uncertainties remain regarding how catalyst particle dynamics within the system influence the CNT aerogel formation, thus limiting effective scale-up. While aerogel formation in FC-CVD reactors requires a catalyst (typically iron, Fe) and a promotor (typically sulfur, S), their synergistic roles are not fully understood. This paper presents a paradigm shift in the understanding of the role of S in the process with new experimental studies identifying that S lowers the nucleation barrier of the catalyst nanoparticles. Furthermore, CNT aerogel formation requires a critical threshold of Fe x C y  > 160 mg/m 3 , but is surprisingly independent of the initial catalyst diameter or number concentration. The robustness of the critical catalyst mass concentration principle is proved further by producing CNTs using alternative catalyst systems; Fe nanoparticles from a plasma spark generator and cobaltocene and nickelocene precursors. This finding provides evidence that low-cost and high throughput CNT aerogel routes may be achieved by decoupled and enhanced catalyst production and control, opening up new possibilities for large-scale CNT synthesis.

Palladium catalyst system comprising zwitterion and/or acid-functionalized ionic liquid

DEFF Research Database (Denmark)

2011-01-01

The present invention concerns a catalyst system in particular a catalyst system comprising Palladium (Pd), a zwitterion and/or an acid-functionalized ionic liquid, and one or more phosphine ligands, wherein the Pd catalyst can be provided by a complex precursor, such as Pd(CH3COO)2, PdCI2, Pd(CH3......COCHCOCH3), Pd (CF3COO)2, Pd(PPh3)4 or Pd2(dibenzylideneacetone)3. Such catalyst systems can be used for e.g. alkoxycarbonylation reactions, carboxylation reactions, and/or in a co-polymerization reaction, e.g. in the production of methyl propionate and/or propanoic acid, optionally in processes forming...... methyl methacrylate and/or methacrylic acid. Catalyst systems according to the invention are suitable for reactions forming separable product and catalyst phases and supported ionic liquid phase SILP applications....

Studies concerning the anion ex-change resins catalyzed esterification of epichlorohydrin with organic acids

Directory of Open Access Journals (Sweden)

E.I. Muresan

2009-09-01

Full Text Available The paper studies the esterification of carboxylic acids with epichlorohydrin over two macroporous strong base anion exchange resins with different polymer matrix. For both resins, the influence of reaction parameters (temperature, catalyst loading, molar ratio on the reaction rate and the yields of the two isomeric esters were investigated.

Functional Nanoporous Polymers from Block Copolymer Precursors

DEFF Research Database (Denmark)

Guo, Fengxiao

Abstract Self-assembly of block copolymers provides well-defined morphologies with characteristic length scales in the nanometer range. Nanoporous polymers prepared by selective removal of one block from self-assembled block copolymers offer great technological promise due to their many potential...... functionalities remains a great challenge due to the limitation of available polymer synthesis and the nanoscale confinement of the porous cavities. The main topic of this thesis is to develop methods for fabrication of functional nanoporous polymers from block copolymer precursors. A method has been developed......, where living anionic polymerization and atom transfer radical polymerization (ATRP) are combined to synthesize a polydimethylsiloxane-b-poly(tert-butyl acrylate)-b-polystyrene (PDMS-b-PtBA-b-PS) triblock copolymer precursor. By using either anhydrous hydrogen fluoride or trifluoroacetic acid, PtBA block...

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

Science.gov (United States)

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

2016-06-08

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

Characterization of VPO ammoxidation catalysts by in situ methods

Energy Technology Data Exchange (ETDEWEB)

Martin, A.; Luecke, B.; Brueckner, A.; Steinike, U. [Institut fuer Angewandte Chemie Berlin-Adlershof e.V., Berlin (Germany); Brzezinka, K.W. [Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin (Germany); Meisel, M. [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Chemie

1998-12-31

In-situ methods are well known as powerful tools in studying catalyst formation processes, their solid state properties under working conditions and the interaction with the feed, intermediates and products to reveal reaction mechanisms. This paper gives a short overview on results of intense studies using in-situ techniques to reveal VPO catalyst generation processes, interaction of educts, intermediates and products with VPO catalyst surfaces and mechanistic insights. Catalytic data of the ammoxidation of toluene on different VPOs complete these findings. The precursor-catalyst transformation processes were preferently investigated by in-situ XRD, in-situ Raman and in-situ ESR spectroscopy. The interaction of aromatic molecules and intermediates, resp., and VPO solid surfaces was followed by in-situ ESR and in-situ FTIR spectroscopy. Mechanistic information was mainly obtained using in-situ FTIR spectroscopy and the temporal-analysis-of-products (TAP) technique. Catalytic studies were carried out in a fixed-bed microreactor on pure (NH{sub 4}){sub 2}(VO){sub 3}(P{sub 2}O{sub 7}){sub 2}, generated [(NH{sub 4}){sub 2}(VO{sub 3})(P{sub 2}O{sub 7}){sub 2}+V{sub x}O{sub y}] catalysts, having different V{sub x}O{sub y} proportions by use of VOHPO{sub 4} x 1/2H{sub 2}O (V/P=1) and recently studied (VO){sub 3}(PO{sub 4}){sub 2} x 7 H{sub 2}O (V/P=1.5) precursors; the well-known (VO){sub 2}P{sub 2}O{sub 7} was used for comparison. (orig.)

Nitrogen-doped carbon-supported cobalt-iron oxygen reduction catalyst

Science.gov (United States)

Zelenay, Piotr; Wu, Gang

2014-04-29

A Fe--Co hybrid catalyst for oxygen reaction reduction was prepared by a two part process. The first part involves reacting an ethyleneamine with a cobalt-containing precursor to form a cobalt-containing complex, combining the cobalt-containing complex with an electroconductive carbon supporting material, heating the cobalt-containing complex and carbon supporting material under conditions suitable to convert the cobalt-containing complex and carbon supporting material into a cobalt-containing catalyst support. The second part of the process involves polymerizing an aniline in the presence of said cobalt-containing catalyst support and an iron-containing compound under conditions suitable to form a supported, cobalt-containing, iron-bound polyaniline species, and subjecting said supported, cobalt-containing, iron bound polyaniline species to conditions suitable for producing a Fe--Co hybrid catalyst.

Catalyst design for clean and efficient fuels

DEFF Research Database (Denmark)

Šaric, Manuel

cobalt promoted MoS2 catalyst. Reactivity of a series of model molecules, found in oil prior to desulfurization, is studied on cobalt promoted MoS2. Such an approach has the potential to explain the underlying processes involved in the removal of sulfur at each specific site of the catalyst. The goal...... is to identify which sites are active towards specific molecules and in getting insight to what the ideal catalyst should look like in terms of morphology. Dimethyl carbonate is an environmentally benign compound that can be used as a solvent and precursor in chemical synthesis or as a fuel and fuel additive...... processes currently used. It is found that noble metals can be used as electrocatalysts for the synthesis of dimethyl carbonate, significantly lowering the potential when using copper instead of gold. Besides being active, copper was found to be selective towards dimethyl carbonate. A non-selective catalyst...

Graphitised Carbon Nanofibres as Catalyst Support for PEMFC

DEFF Research Database (Denmark)

Yli-Rantala, E.; Pasanen, A.; Kauranen, P.

2011-01-01

(PANI) precursor. The modified surfaces were studied by FTIR and XPS and the electrochemical characterization, including long-term Pt stability tests, was performed using a low-temperature PEMFC single cell. The performance and stability of the G-CNF supported catalysts were compared with a CB supported...

From trash to resource: recovered-Pd from spent three-way catalysts as a precursor of an effective photo-catalyst for H 2 production

KAUST Repository

Gombac, V.; Montini, T.; Falqui, Andrea; Loche, D.; Prato, M.; Genovese, Alessandro; Mercuri, M. L.; Serpe, A.; Fornasiero, P.; Deplano, P.

2016-01-01

The successful production of a nanostructured and highly dispersed Pd-TiO2 photo-catalyst, using [Pd(Me2dazdt)2](I3)2 (Me2dazdt = N,N′-dimethyl-perhydrodiazepine-2,3-dithione) salt, obtained through the selective and safe recovery of palladium from model exhaust three-way catalysts (TWCs), is reported here. The photo-catalyst prepared by the impregnation/photo-reduction of palladium on the support showed improved performance in H2 production from methanol and in glycerol photo-reforming compared to reference photo-catalysts obtained from conventional Pd-salts. The reported results represent a case of successful palladium “recovery and re-employment” and thus constitute an example of green chemistry by providing, in one route, the environmentally friendly recovery of a critical metal and its employment in the renewable energy field.

From trash to resource: recovered-Pd from spent three-way catalysts as a precursor of an effective photo-catalyst for H 2 production

KAUST Repository

Gombac, V.

2016-01-06

The successful production of a nanostructured and highly dispersed Pd-TiO2 photo-catalyst, using [Pd(Me2dazdt)2](I3)2 (Me2dazdt = N,N′-dimethyl-perhydrodiazepine-2,3-dithione) salt, obtained through the selective and safe recovery of palladium from model exhaust three-way catalysts (TWCs), is reported here. The photo-catalyst prepared by the impregnation/photo-reduction of palladium on the support showed improved performance in H2 production from methanol and in glycerol photo-reforming compared to reference photo-catalysts obtained from conventional Pd-salts. The reported results represent a case of successful palladium “recovery and re-employment” and thus constitute an example of green chemistry by providing, in one route, the environmentally friendly recovery of a critical metal and its employment in the renewable energy field.

Fe3C-based oxygen reduction catalysts: synthesis, hollow spherical structures and applications in fuel cells

DEFF Research Database (Denmark)

Hu, Yang; Jensen, Jens Oluf; Zhang, Wei

2015-01-01

We present a detailed study of a novel Fe3C-based spherical catalyst with respect to synthetic parameters, nanostructure formation, ORR active sites and fuel cell demonstration. The catalyst is synthesized by high temperature autoclave pyrolysis using decomposing precursors. Below 500 °C, melamine...

Ultrahighly Dispersed Titanium Oxide on Silica : Effect of Precursors on the Structure and Photocatalysis

OpenAIRE

Yoshida , S.; Takenaka , S.; Tanaka , T.; Funabiki , T.

1997-01-01

The effect of precursor on the dispersion and catalytic performance of titanium oxide supported on silica has ben investigated. The catalysts were prepared by a simple impregnation method with three kinds of titanium complexes of different ligands (bis(isopropyato)-bis(pivaroylmethanato) : DPM, acetylacetonato : ACAC, tetrakis(isopropylato) : IPRO) with the aim of preparing ultrahighly dispersed titanium oxide on silica. The XAFS study revealed that titanium species in the catalyst prepared f...

Schlenk Techniques for Anionic Polymerization

KAUST Repository

Ratkanthwar, Kedar

2015-09-01

Anionic polymerization-high vacuum techniques (HVTs) are doubtlessly the most prominent and reliable experimental tools to prepare polymer samples with well-defined and, in many cases, complex macromolecular architectures. Due to the high demands for time and skilled technical personnel, HVTs are currently used in only a few research laboratories worldwide. Instead, most researchers in this filed are attracted to more facile Schlenk techniques. The basic principle of this technique followed in all laboratories is substantially the same, i.e. the use of alternate vacuum and inert gas atmosphere in glass apparatus for the purification/charging of monomer, solvents, additives, and for the manipulation of air-sensitive compounds such as alkyl metal initiators, organometallic or organic catalysts. However, it is executed quite differently in each research group in terms of the structure of Schlenk apparatus (manifolds, connections, purification/storage flasks, reactors, etc.), the use of small supplementary devices (soft tubing, cannulas, stopcocks, etc.) and experimental procedures. The operational methods are partly purpose-oriented while also featured by a high flexibility, which makes it impossible to describe in detail each specific one. In this chapter we will briefly exemplify the application of Schlenk techniques for anionic polymerization by describing the performance of a few experiments from our own work.

Specific anion effects on copper surface through electrochemical treatment: Enhanced photoelectrochemical CO2 reduction activity of derived nanostructures induced by chaotropic anions

Science.gov (United States)

Navaee, Aso; Salimi, Abdollah

2018-05-01

Copper derivatives are the most prominent CO2 reduction electrocatalyst. Herein, the metallic copper has been electrochemically treated with some of common ionic salts such as N3bar, HPO2bar, S2bar, Fbar, Clbar, Brbar and Ibar based on the dissolution of a metallic working electrode in an aqueous solution to derive the surface roughness incorporated with nanostructures. Diverse surface morphology can be obtained when the ionic radii of anions are changed. Surface study reveals various roughness shapes based on the size and polarity of the anions, where the ions with higher ionic radii have higher impact on the Cu surface. In comparison, polyatomic oxyanion such as HPO2bar even with large ionic radii do not have enough strength to create the surface roughness than that of oxygen-free anions with large ionic radii. The photoelectrochemical behavior of the modified surfaces toward CO2 reduction is studied at a wide potential window in bicarbonate aqueous solution. Based on our investigations, treated surfaces by Ibar, Clbar and S2bargive a more surface roughness, while Ibar and N3bar offer higher catalytic activity toward CO2 reduction due to possible complexing ability of these anions with Cu cations, followed by formation of the co-catalyst semiconductor and facilitate electron transfer. This methodology can be applied to investigate the effect of ions on transition metals along with obtaining different surface morphologies tailored to different applications.

Effect of impregnation protocol in the metallic sites of Pt–Ag/activated carbon catalysts for water denitration

Energy Technology Data Exchange (ETDEWEB)

Aristizábal, A. [Departament d’Enginyeria Química, Universitat Rovira i Virgili, Campus Sescelades, Av. Països Catalans 26, 43007 Tarragona (Spain); Contreras, S., E-mail: sandra.contreras@urv.cat [Departament d’Enginyeria Química, Universitat Rovira i Virgili, Campus Sescelades, Av. Països Catalans 26, 43007 Tarragona (Spain); Divins, N.J.; Llorca, J. [Institut de Tècniques Energètiques i Centre de Recerca en Nanoenginyeria, Universitat Politècnica de Catalunya, Diagonal 647, 08028 Barcelona (Spain); Medina, F. [Departament d’Enginyeria Química, Universitat Rovira i Virgili, Campus Sescelades, Av. Països Catalans 26, 43007 Tarragona (Spain)

2014-04-01

Highlights: • Mean particle size is tuned by the Pt precursor. H{sub 2}PtCl{sub 6} leads to smaller size. • H{sub 2}PtCl{sub 6} leads to higher extent of Pt–Ag particles with a composition richer in silver. • Pt(NH{sub 3}){sub 4}(NO{sub 3}){sub 2} leads to Ag{sup 0} particles and some Pt–Ag ensembles in less extent. • Nitrate and nitrite rates are linearly related to mean metal particle size. • Physical mixture of catalysts enhances N{sub 2} selectivities. - Abstract: The influence of the Pt precursor and the impregnation protocol in the catalytic behavior of 3%Pt–1.5%Ag supported on activated carbon for water denitration in a continuous reactor was studied. Pt(NH{sub 3}){sub 4}(NO{sub 3}){sub 2} and H{sub 2}PtCl{sub 6} were selected as Pt precursors. Five protocols were investigated: sequential impregnations (both sequences), co-impregnation, physical mixture of monometallic catalysts, and physical mixture of a bimetallic catalyst with a Pt monometallic catalyst. The samples were characterized by XRD, XPS, TPR, HRTEM and physisorption. It was found that the catalytic activity strongly depends on the synthesis protocol and the Pt precursor, which modify the particle size. Higher nitrate rates are achieved using H{sub 2}PtCl{sub 6} than Pt(NH{sub 3}){sub 4}(NO{sub 3}){sub 2}; this is mainly related to the smaller metal particle size of the former, evidenced by HRTEM. Nitrate consumption rate is directly related with the mean particle size. The physical mixture of monometallic catalysts resulted in the highest nitrogen rate.

Ethylbenzene dehydrogenation over Mg3Fe0.5−xCoxAl0.5 catalysts derived from hydrotalcites: Comparison with Mg3Fe0.5−yNiyAl0.5 catalysts

KAUST Repository

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

2011-01-01

A series of Mg3Fe0.5-xCoxAl0.5 (x = 0-0.5) catalysts were prepared from hydrotalcite precursors and their activities in the dehydrogenation of ethylbenzene were compared with those of a series of Mg3Fe0.5-yNiyAl0.5 (y = 0-0.5) catalysts also derived

Tungsten Recovery from Spent SCR Catalyst Using Alkaline Leaching and Ion Exchange

Directory of Open Access Journals (Sweden)

Wen-Cheng Wu

2016-10-01

Full Text Available The recovery of tungsten (W from a honeycomb-type spent selective catalytic reduction (SCR catalyst using an alkaline leaching–ion exchange method was investigated. Spent SCR catalyst mainly consists of TiO2 and other oxides (6.37% W, 1.57% vanadium (V, and 2.81% silicon (Si, etc.. The ground catalyst was leached at the optimal conditions, as follows: NaOH concentration of 0.3 kg/kg of catalyst, pulp density of 3%, leaching temperature of 70 °C, particle size of −74 μm, and leaching time of 30 min. In this study, the leaching rate values of V and W under the above conditions were 87 wt %, and 91 wt %, respectively. The pregnant solution was then passed through a strong base anion exchange resin (Amberlite IRA900. At high pH conditions, the use of strong base anion exchange resin led to selective loading of divalent WO42− from the solution, because the fraction of two adjacent positively-charged sites on the IRA900 resin was higher and separate from the coexisting VO43−. The adsorbed W could then be eluted with 1 M NaCl + 0.5 M NaOH. The final concentrated W solution had 8.4 g/L of W with 98% purity. The application of this process in industry is expected to have an important impact on the recovery of W from secondary sources of these metals.

Energetic Mapping of Ni Catalysts by Detailed Kinetic Modeling

DEFF Research Database (Denmark)

Bjørgum, Erlend; Chen, De; Bakken, Mari G.

2005-01-01

Temperature-programmed desorption (TPD) of CO has been performed on supported and unsupported nickel catalysts. The unsupported Ni catalyst consists of a Ni(14 13 13) single crystal which has been studied under ultrahigh vacuum conditions. The desorption energy for CO at low CO surface coverage...... was found to be 119 kJ/mol, and the binding energy of C to the Ni(111) surface of the crystal was 703 kJ/mol. The supported catalysts consist of nickel supported on hydrotalcite-like compounds with three different Mg2+/Al3+ ratios. The experimental results show that for the supported Ni catalysts TPD of CO...... precursor seems to result in more steplike sites, kinks, and defects for carbon monoxide dissociation. A detailed kinetic modeling of the TPO results based on elementary reaction steps has been conducted to give an energetic map of supported Ni catalysts. Experimental results from the ideal Ni surface fit...

Improved Catalysts for Heavy Oil Upgrading Based on Zeolite Y Nanoparticles Encapsulated Stable Nanoporous Host

Energy Technology Data Exchange (ETDEWEB)

Conrad Ingram; Mark Mitchell

2006-09-30

The addition of hydrothermally-aged zeolite Y precursor to an SBA-15 synthesis mixture under a mildly acidic condition resulted in the formation of mesoporous aluminosilicate catalyst, Al-SBA-15, containing strong Broensted acid sites and aluminum (Al) stabilized in a totally tetrahedral coordination. The physicochemical characteristics of the catalyst varied as a function of the synthesis conditions. The catalyst possessed surface areas ranging between 690 and 850 m{sup 2}/g, pore sizes ranging from 5.6 to 7.5 nm, and pore volumes up 1.03 cm{sup 3}, which were comparable to the parent SBA-15 synthesized under similar conditions. Two wt% Al was present in the catalyst that was obtained from the reaction mixture that contained the highest Al content. The Al remained stable in totally tetrahedral coordination after calcination at 550 C. The Al-SBA-15 mesoporous catalyst showed significant catalytic activity for cumene dealkylation, and the activity increased as the amount of zeolite precursor added to the SBA-15 mixture was increased. In preparation for the final phase of the project, the catalyst was embedded into psuedoboemite alumina (catapal B) matrix and then formed into pellets. In the final phase of the project, the pelletized catalyst will be evaluated for the conversion of heavy petroleum feedstocks to naphtha and middle distillates.

Two Iron Complexes as Homogeneous and Heterogeneous Catalysts for the Chemical Fixation of Carbon Dioxide.

Science.gov (United States)

Karan, Chandan Kumar; Bhattacharjee, Manish

2018-04-16

Two new bimetallic iron-alkali metal complexes of amino acid (serine)-based reduced Schiff base ligand were synthesized and structurally characterized. Their efficacy as catalysts for the chemical fixation of carbon dioxide was explored. The heterogeneous version of the catalytic reaction was developed by the immobilization of these homogeneous bimetallic iron-alkali metal complexes in an anion-exchange resin. The resin-bound complexes can be used as recyclable catalysts up to six cycles.

Effects of Cationic Pendant Groups on Ionic Conductivity for Anion Exchange Membranes: Structure Conductivity Relationships

Science.gov (United States)

Kim, Sojeong; Choi, Soo-Hyung; Lee, Won Bo

Anion exchange membranes(AEMs) have been widely studied due to their various applications, especially for Fuel cells. Previous proton exchange membranes(PEMs), such as Nafions® have better conductivity than AEMs so far. However, technical limitations such as slow electrode kinetics, carbon monoxide (CO) poisoning of metal catalysts, high methanol crossover and high cost of Pt-based catalyst detered further usages. AEMs have advantages to supplement its drawbacks. AEMs are environmentally friendly and cost-efficient. Based on the well-defined block copolymer, self-assembled morphology is expected to have some relationship with its ionic conductivity. Recently AEMs based on various cations, including ammonium, phosphonium, guanidinium, imidazolium, metal cation, and benzimidazolium cations have been developed and extensively studied with the aim to prepare high- performance AEMs. But more fundamental approach, such as relationships between nanostructure and conductivity is needed. We use well-defined block copolymer Poly(styrene-block-isoprene) as a backbone which is synthesized by anionic polymerization. Then we graft various cationic functional groups and analysis the relation between morphology and conductivity. Theoretical and computational soft matter lab.

Ultrasound assisted synthesis of iron doped TiO2 catalyst.

Science.gov (United States)

Ambati, Rohini; Gogate, Parag R

2018-01-01

The present work deals with synthesis of Fe (III) doped TiO 2 catalyst using the ultrasound assisted approach and conventional sol-gel approach with an objective of establishing the process intensification benefits. Effect of operating parameters such as Fe doping, type of solvent, solvent to precursor ratio and initial temperature has been investigated to get the best catalyst with minimum particle size. Comparison of the catalysts obtained using the conventional and ultrasound assisted approach under the optimized conditions has been performed using the characterization techniques like DLS, XRD, BET, SEM, EDS, TEM, FTIR and UV-Vis band gap analysis. It was established that catalyst synthesized by ultrasound assisted approach under optimized conditions of 0.4mol% doping, irradiation time of 60min, propan-2-ol as the solvent with the solvent to precursor ratio as 10 and initial temperature of 30°C was the best one with minimum particle size as 99nm and surface area as 49.41m 2 /g. SEM analysis, XRD analysis as well as the TEM analysis also confirmed the superiority of the catalyst obtained using ultrasound assisted approach as compared to the conventional approach. EDS analysis also confirmed the presence of 4.05mol% of Fe element in the sample of 0.4mol% iron doped TiO 2 . UV-Vis band gap results showed the reduction in band gap from 3.2eV to 2.9eV. Photocatalytic experiments performed to check the activity also confirmed that ultrasonically synthesized Fe doped TiO 2 catalyst resulted in a higher degradation of Acid Blue 80 as 38% while the conventionally synthesized catalyst resulted in a degradation of 31.1%. Overall, the work has clearly established importance of ultrasound in giving better catalyst characteristics as well as activity for degradation of the Acid Blue 80 dye. Copyright © 2017 Elsevier B.V. All rights reserved.

Reactions of synthesis gas on silica supported transition metal catalysts

Energy Technology Data Exchange (ETDEWEB)

Niemelae, M. [VTT Chemical Technology, Espoo (Finland). Lab. of Industrial Chemistry

1997-12-31

The effect of catalyst precursor and composition on the activation of CO was investigated using CO hydrogenation as a test reaction. The interrelations of preparation, pretreatment, characteristics and activity were clarified. For Co/SiO{sub 2} catalyst, MgO promotion increased the CO adsorption capacity and the hydrogen uptake, although the extent of reduction for cobalt remained the same or decreased. The conversion per active metallic cobalt site consequently increased in conjunction with MgO promotion, while the effect on overall performance per 1 g of catalyst remained moderate. The precursor affected the performance of Co/SiO{sub 2} considerably. CO was more strongly adsorbed on catalysts of carbonyl origin than on those derived from cobalt nitrate, the activity thus being higher. Although the nitrate derived Co/SiO{sub 2} appeared both to retain its activity and to regain its adsorption capacity better than the catalysts of carbonyl origin, the performance of the latter was superior with time on stream. For tetranuclear cluster based Co-Ru and Co-Rh catalysts, rhodium or ruthenium was in contact with the support and cobalt was enriched on top. On Co-Ru/SiO{sub 2} ruthenium enhanced deactivation, and no benefits in activity or oxygenate selectivity were achieved relative to the monometallic catalysts of cluster origin. The Co-Rh/SiO{sub 2} catalysts were also less active than those derived from monometallic clusters, but they exhibited higher selectivities to oxygenated compounds due to the presence of active sites on the perimeter of the cobalt particles located on rhodium. The highest selectivity to oxygenates was achieved by changing the decomposition atmosphere of Rh{sub 4}(CO){sub 12}/SiO{sub 2} from hydrogen to carbon monoxide. The results also showed two types of active sites to be operative in the formation of oxygenates - one for ethanol and another for aldehydes. (orig.) 69 refs.

Characterization of the impregnated iron based catalyst for direct coal liquefaction by EXAFS

International Nuclear Information System (INIS)

Yang Jianli; Zhun Jisheng; Liu Zhenyu; Zhong Bing

2002-01-01

Catalyst plays an important role in direct coal liquefaction (DCL). Iron catalysts are regarded as the most attractive catalysts for DCL. To maximize catalytic effect and minimize catalysts usage, ultra-fine size catalysts are preferred. The most effective catalysts are found to be those impregnated onto coal because of their high dispersion on coal surface and intimate contact with coal particles. Besides the physical size, chemical form of a catalyst or a catalyst precursor is also important in determination of DCL activity. The expended X-ray absorption fine structure spectroscopy technique were used in this study. It was shown that the catalysts tested are in nanomater range and have structure mainly in the form of γ-FeOOH and FeS, or possibly of Fe/O/S. The presence of γ-FeOOH can be attributed to the interaction between Fe and the oxygen containing groups of coal or oxygen from moisture

Molecular metal catalysts on supports: organometallic chemistry meets surface science.

Science.gov (United States)

Serna, Pedro; Gates, Bruce C

2014-08-19

Recent advances in the synthesis and characterization of small, essentially molecular metal complexes and metal clusters on support surfaces have brought new insights to catalysis and point the way to systematic catalyst design. We summarize recent work unraveling effects of key design variables of site-isolated catalysts: the metal, metal nuclearity, support, and other ligands on the metals, also considering catalysts with separate, complementary functions on supports. The catalysts were synthesized with the goal of structural simplicity and uniformity to facilitate incisive characterization. Thus, they are essentially molecular species bonded to porous supports chosen for their high degree of uniformity; the supports are crystalline aluminosilicates (zeolites) and MgO. The catalytic species are synthesized in reactions of organometallic precursors with the support surfaces; the precursors include M(L)2(acetylacetonate)1-2, with M = Ru, Rh, Ir, or Au and the ligands L = C2H4, CO, or CH3. Os3(CO)12 and Ir4(CO)12 are used as precursors of supported metal clusters, and some such catalysts are made by ship-in-a-bottle syntheses to trap the clusters in zeolite cages. The simplicity and uniformity of the supported catalysts facilitate precise structure determinations, even in reactive atmospheres and during catalysis. The methods of characterizing catalysts in reactive atmospheres include infrared (IR), extended X-ray absorption fine structure (EXAFS), X-ray absorption near edge structure (XANES), and nuclear magnetic resonance (NMR) spectroscopies, and complementary methods include density functional theory and atomic-resolution aberration-corrected scanning transmission electron microscopy for imaging of individual metal atoms. IR, NMR, XANES, and microscopy data demonstrate the high degrees of uniformity of well-prepared supported species. The characterizations determine the compositions of surface metal complexes and clusters, including the ligands and the metal

Functionalized Poly(propylene imine) Dendrimers as Novel Phase Transfer Catalyst in Supercritical Cabon Dioxide

NARCIS (Netherlands)

Goetheer, E.L.V.; Baars, M.W.P.L.; Broeke, van den L.J.P.; Meijer, E.W.; Keurentjes, J.T.F.

2000-01-01

Perfluoro-functionalized poly(propylene imine) dendrimers have been used as reactive extractants for anionic species and as phase transfer catalysts for two types of reactions. Different generations of dendrimers have been used for applications in carbon dioxide. First, the reactive extraction of

Nitrogen–doped graphitized carbon shell encapsulated NiFe nanoparticles: A highly durable oxygen evolution catalyst

Energy Technology Data Exchange (ETDEWEB)

Du, Lei; Luo, Langli; Feng, Zhenxing; Engelhard, Mark; Xie, Xiaohong; Han, Binghong; Sun, Junming; Zhang, Jianghao; Yin, Geping; Wang, Chongmin; Wang, Yong; Shao, Yuyan

2017-09-01

Oxygen evolution reaction (OER) plays a crucial role in various energy conversion devices such as water electrolyzers and metal–air batteries. Precious metal catalysts such as Ir, Ru and their oxides are usually used for enhancing reaction kinetics but are limited by their scarce resource. The challenges associated with alternative non–precious metal catalysts such as transition metal oxides and (oxy)hydroxides etc. are their low electronic conductivity and durability. Herein, we report a highly active (360 mV overpotential at 10 mA cm–2GEO) and durable (no degradation after 20000 cycles) OER catalyst derived from bimetallic metal–organic frameworks (MOFs) precursors. This catalyst consists of NiFe nanoparticles encapsulated by nitrogen–doped graphitized carbon shells. The electron-donation/deviation from Fe and tuned electronic structure of metal cores by Ni are revealed to be primary contributors to the enhanced OER activity, whereas N concentration contributes negligibly. We further demonstrated that the structure and morphology of encapsulating carbon shells, which are the key factors influencing the durability, are facilely controlled by the chemical state of precursors.

Nonalloyed carbon-supported PtRu catalysts for PEMFC applications

NARCIS (Netherlands)

Papageorgopoulos, D.C.; Heer, de M.P.; Keijzer, M.; Pieterse, J.A.Z.; Bruijn, de F.A.

2004-01-01

PtRu(1:1)/C catalysts were prepared by a process that was claimed previously to lead to nonalloyed Pt and Ru particles, using twodifferent precursors, Ru nitrosyl nitrate and Ru chloride hydrate. Both X-ray diffraction and characterization by cyclic voltammetrypoint toward Pt and Ru being present as

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

New magnetic organic-inorganic composites based on hydrotalcite-like anionic clays for drug delivery

Energy Technology Data Exchange (ETDEWEB)

Carja, Gabriela [Department of Physical Chemistry, Faculty of Industrial Chemistry, Technical University of Iasi, 71 Mangeron Boulevard, 700050 Iasi (Romania); Chiriac, Horia [National Institute of Research and Development for Technical Physics, 47 Mangeron Boulevard, 700050 Iasi (Romania)]. E-mail: hchiriac@phys-iasi.ro; Lupu, Nicoleta [National Institute of Research and Development for Technical Physics, 47 Mangeron Boulevard, 700050 Iasi (Romania)

2007-04-15

The structural 'memory effect' of anionic clays was used to obtain layered double hydroxides (LDHs) with tailored magnetic properties, by loading iron oxides and/or spinel structures on iron partially substituted hydrotalcite-like materials. The obtained magnetic layered structures were further used as precursors for new hybrid nanostructures, such as aspirin-hydrotalcite-like anionic clays. Transmission electron microscopy (TEM) analysis shows that small iron oxide or spinel nanoparticles coexist with the fibrous drug particles on the surface of partially aggregated typical clay-like particles. The specific saturation magnetization of the loaded LDHs can be increased up to 70 emu/g by using specific post-synthesis treatments.

New magnetic organic-inorganic composites based on hydrotalcite-like anionic clays for drug delivery

International Nuclear Information System (INIS)

Carja, Gabriela; Chiriac, Horia; Lupu, Nicoleta

2007-01-01

The structural 'memory effect' of anionic clays was used to obtain layered double hydroxides (LDHs) with tailored magnetic properties, by loading iron oxides and/or spinel structures on iron partially substituted hydrotalcite-like materials. The obtained magnetic layered structures were further used as precursors for new hybrid nanostructures, such as aspirin-hydrotalcite-like anionic clays. Transmission electron microscopy (TEM) analysis shows that small iron oxide or spinel nanoparticles coexist with the fibrous drug particles on the surface of partially aggregated typical clay-like particles. The specific saturation magnetization of the loaded LDHs can be increased up to 70 emu/g by using specific post-synthesis treatments

Study on the correlation between the surface active species of Pd/cordierite monolithic catalyst and its catalytic activity

International Nuclear Information System (INIS)

Liao, Hengcheng; Zuo, Peiyuan; Liu, Miaomiao

2016-01-01

Two Pd-loading routes and three Pd-precursor matters were adopted to prepare Pd/(Ce,Y)O_2/γ-Al_2O_3/cordierite monolithic catalyst. The surface active species on the catalyst were characterized by XPS, and its catalytic activity for methane combustion was tested, and the dynamics of the catalytic combustion reaction was also discussed. Pd-loading route and Pd-precursor mass have a significant influence on the catalytic activity and surface active species. The sol dipping method is more advanced than the aqueous solution impregnating method. PN-sol catalyst, by sol dipping combined with Pd(NO_3)_2-precursor, has the best catalytic activity. The physical reason is the unique active Pd phase coexisting with active PdO phase on the surface, and thus the Pd3d_5_/_2 binding energy of surface species and apparent activation energy of combustion reaction are considerably decreased. The catalytic activity index, Pd3d_5_/_2 binding energy and apparent activation energy are highly tied each other with exponential relations.

Nonalloyed carbon-supported PtRu catalysts for PEMFC applications

NARCIS (Netherlands)

Papageorgopoulos, D.C.; De Heer, M.P.; Keijzer, M.; Pieterse, J.A.Z.; de Bruijn, F. A.

2004-01-01

PtRu(1:1)/C catalysts were prepared by a process that was claimed previously to lead to non-alloyed Pt and Ru particles, using two different precursors, Ru nitrosyl nitrate and Ru chloride hydrate. Both X-ray diffraction and characterization by cyclic voltammetry point toward Pt and Ru being present

Nitrogen–doped graphitized carbon shell encapsulated NiFe nanoparticles: A highly durable oxygen evolution catalyst

Energy Technology Data Exchange (ETDEWEB)

Du, Lei; Luo, Langli; Feng, Zhenxing; Engelhard, Mark; Xie, Xiaohong; Han, Binghong; Sun, Junming; Zhang, Jianghao; Yin, Geping; Wang, Chongmin; Wang, Yong; Shao, Yuyan

2017-09-01

Oxygen evolution reaction (OER) plays a crucial role in various energy conversion devices such as water electrolyzers and metal–air batteries. Precious metal catalysts such as Ir, Ru and their oxides are usually used for enhanced reaction kinetics but are limited by their scarce resource. The challenges associated with alternative non–precious metal catalysts such as transition metal oxides and (oxy)hydroxides etc. are their low electronic conductivity and poor durability. Here, we report OER catalysts of NiFe nanoparticles encapsulated by nitrogen–doped graphitized carbon shells derived from bimetallic metal–organic frameworks (MOFs) precursors. The optimal OER catalyst shows excellent activity (360 mV overpotential at 10 mA cm–2GEO) and durability (no obvious degradation after 20 000 cycles). The electron-donation from Fe and tuned electronic structure of metal cores by Ni are revealed to be primary contributors to the enhanced OER activity. We further demonstrated that the structure and morphology of encapsulating carbon shells, which are the key factors influencing the durability, are facilely controlled by chemical state of precursors. Severe metal particle growth probably caused by oxidation of carbon shells and encapsulated nanoparticles is believed to the main mechanism for activity degradation in these catalysts.

Preparation and characterization of stable copper/zinc oxide/alumina catalysts for methanol synthesis

Energy Technology Data Exchange (ETDEWEB)

Hoeppener, R H; Doesburg, E B; Scholten, J J

1986-08-15

A series of Cu/ZnO/Al/sub 2/O/sub 3/ catalysts for the low pressure methanol synthesis has been prepared by coprecipitation with a sodium carbonate solution from solutions of a mixture of the corresponding metal nitrates, followed by drying, calcination and reduction. The catalysts and their precursors were analyzed by techniques like X-ray diffraction, X-ray line broadening, differential thermal analysis, chemical analysis, adsorptive decomposition of N/sub 2/O and B.E.T.-measurements. The catalytic activity for the methanol synthesis was determined in a flow reactor under industrial conditions. Depending on the metal ion ratio in the initial metal nitrate solutions different compounds were formed during coprecipitation, like rosasite, malachite, Cu, Zn-hydrotalcite and a ternary compound which was called roderite. Its structure is unknown and it contains, besides Zn/sup 2+/, up to 28 at% Cu/sup 2+/ and up to 17 at% Al/sup 3+/. Addition of 7 at% Mg/sup 2+/ stabilizes the Cu, Zn-hydrotalcite structure but leads to a drastic decrease in catalytic activity. The rate of methanol production depends on the phase composition of the precursors. Rosasite containing precursors give the highest activity; hydrotalcite proves to be an excellent catalyst stabilizer which evokes the formation of small Cu and ZnO particles. Mg/sup 2+/ inhibits methanol production. 6 figs., 1 tab., 18 refs.

Synthesis of biodiesel from pongamia oil using heterogeneous ion-exchange resin catalyst.

Science.gov (United States)

Jaya, N; Selvan, B Karpanai; Vennison, S John

2015-11-01

Biodiesel is a clean-burning renewable substitute fuel for petroleum. Biodiesel could be effectively produced by transesterification reaction of triglycerides of vegetable oils with short-chain alcohols in the presence of homogeneous or heterogeneous catalysts. Conventionally, biodiesel manufacturing processes employ strong acids or bases as catalysts. But, separation of the catalyst and the by-product glycerol from the product ester is too expensive to justify the product use as an automobile fuel. Hence heterogeneous catalysts are preferred. In this study, transesterification of pongamia oil with ethanol was performed using a solid ion-exchange resin catalyst. It is a macro porous strongly basic anion exchange resin. The process parameters affecting the ethyl ester yield were investigated. The reaction conditions were optimized for the maximum yield of fatty acid ethyl ester (FAEE) of pongamia oil. The properties of FAEE were compared with accepted standards of biodiesel. Engine performance was also studied with pongamia oil diesel blend and engine emission characteristics were observed. Copyright © 2015 Elsevier Inc. All rights reserved.

Catalytic cracking of iso-hexene over sapo-34 catalyst

International Nuclear Information System (INIS)

Nawaz, Z.; Shu, Q.

2009-01-01

The catalytic cracking of model feed compound, iso-hexene (2-methyl-1-pentene) was experimentally studied over 100% pure SAPO-34 zeolite catalyst. The critical focus was given to obtain maximum propylene selectivity. The product distributions were analyzed at temperature between 450-600 degree C. time-on-stream (TOS) from 1 to 5 min. and at WHSV = 7.9 h/sub -1/ The reaction behavior was quantified on both direct and indirect carbenium ion mechanisms owing to catalyst's small pore diameter with respect to 2-methyl-l-pentene kinetic diameter. The propylene yield and selectivity obtained was 41.2% and 43.1% respectively. with higher overall olefins selectivity 90.3%. The small pore size and week surface acid sites of 1000 percent pure SAPO-34 catalyst were found to be suitable for light olefins production and eliminate chances of bimolecular reactions. It was observed that both conversion and selectivity were strongly effected by TOS, as coke precursors become dominant and deactivate catalyst at higher TOS. (author)

Recyclable Aggregates of Mesoporous Titania Synthesized by Thermal Treatment of Amorphous or Peptized Precursors

Directory of Open Access Journals (Sweden)

Maria Cristina Mascolo

2018-03-01

Full Text Available Recyclable aggregates of mesoporous titania with different anatase–rutile ratios have been prepared by thermal treatments of either amorphous or peptized precursors. These last two have been obtained by hydrolysis of either Ti(OC2H54 or of Ti(OC2H54 in mixture with 5 mol % Zr(OC3H74 at room temperature in the presence of NH4OH as a catalyzing agent. The anatase–rutile ratio, the recyclable aggregates of the nano-sized particles, the mesoporosity, the surface area and the crystallinity of the resulting crystallized products of titania can be controlled by the synthesis parameters including: concentration of ammonia catalyst, stirring time and concentration of the peptizing HNO3, drying method of peptized precursors, calcination temperature, and finally the ramp rate up to the titania crystallization temperature. A broad range of synthesis parameters control the crystal sizes of titania particles produced. This allows catalyst preparation with very different crystal size, surface area, anatase to rutile crystal ratio and various mesoporous structures. Drying by lyophilization of precursors reduce the aggregation of the primary particles giving micro-/macroporous structures.

Boehmite-An Efficient and Recyclable Acid-Base Bifunctional Catalyst for Aldol Condensation Reaction.

Science.gov (United States)

Reshma, P C Rajan; Vikneshvaran, Sekar; Velmathi, Sivan

2018-06-01

In this work boehmite was used as an acid-base bifunctional catalyst for aldol condensation reactions of aromatic aldehydes and ketones. The catalyst was prepared by simple sol-gel method using Al(NO3)3·9H2O and NH4OH as precursors. The catalyst has been characterized by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM), UV-visible spectroscopy (DRS), BET surface area analyses. Boehmite is successfully applied as catalyst for the condensation reaction between 4-nitrobenzaldehyde and acetone as a model substrate giving α, β-unsaturated ketones without any side product. The scope of the reaction is extended for various substituted aldehydes. A probable mechanism has been suggested to explain the cooperative behavior of the acidic and basic sites. The catalyst is environmentally friendly and easily recovered from the reaction mixture. Also the catalyst is reusable up to 3 catalytic cycles.

DFT study on the impact of the methylaluminoxane cocatalyst in ethylene oligomerization using a titanium-based catalyst

KAUST Repository

Pasha, Farhan Ahmad; Basset, Jean-Marie; Toulhoat, Hervé ; De Bruin, Theodorus J M

2015-01-01

A computational study within the framework of density functional theory is presented on the oligomerization of ethylene to yield 1-hexene using [(η5-C5H4CMe2C6H5)]TiCl3/MAO] catalyst. This study explicitly takes into account a methylaluminoxane (MAO) cocatalyst model, where the MAO cluster has become an anionic species after having abstracted one chloride anion, yielding a cationic activated catalyst. Hence, the reaction profile was calculated using the zwitterionic system, and the potential energy surface has been compared to the cationic catalytic system. Modest differences were found between the two free energy profiles. However, we show for the first time that the use of a realistic zwitterionic model is required to obtain a Brønsted-Evans-Polanyi relationship between the energy barriers and reaction energies.

DFT study on the impact of the methylaluminoxane cocatalyst in ethylene oligomerization using a titanium-based catalyst

KAUST Repository

Pasha, Farhan Ahmad

2015-01-26

A computational study within the framework of density functional theory is presented on the oligomerization of ethylene to yield 1-hexene using [(η5-C5H4CMe2C6H5)]TiCl3/MAO] catalyst. This study explicitly takes into account a methylaluminoxane (MAO) cocatalyst model, where the MAO cluster has become an anionic species after having abstracted one chloride anion, yielding a cationic activated catalyst. Hence, the reaction profile was calculated using the zwitterionic system, and the potential energy surface has been compared to the cationic catalytic system. Modest differences were found between the two free energy profiles. However, we show for the first time that the use of a realistic zwitterionic model is required to obtain a Brønsted-Evans-Polanyi relationship between the energy barriers and reaction energies.

Improved Catalysts for Heavy Oil Upgrading Based on Zeolite Y Nanoparticles Encapsulated Stable Nanoporous Host

Energy Technology Data Exchange (ETDEWEB)

Conrad Ingram; Mark Mitchell

2007-03-31

The addition of hydrothermally-aged zeolite Y precursor to an SBA-15 synthesis mixture under a mildly acidic condition resulted in the formation of a mesoporous aluminosilicate catalyst, AlSBA-15. The Al-SBA-15 mesoporous catalyst contains strong Br{umlt o}nsted acid sites and aluminum (Al) stabilized in a totally tetrahedral coordination. The physicochemical characteristics of the catalyst varied as a function of the synthesis conditions. The catalyst possessed surface areas ranging between 690 and 850 m{sup 2}/g, pore sizes ranging from 5.6 to 7.5 nm, and pore volumes up 1.03 cm{sup 3}, which were comparable to the parent SBA-15 synthesized under similar conditions. Two wt % Al was present in the catalyst that was obtained from the reaction mixture that contained the highest Al content. The Al remained stable in totally tetrahedral coordination after calcination at a temperature of 550 C. The Al-SBA-15 mesoporous catalyst showed significant catalytic activity for cumene dealkylation, and the activity increased as the amount of zeolite precursor added to the SBA-15 mixture was increased. In preparation for the final phase of the project, the catalyst was embedded into a psuedoboemite alumina (catapal B) matrix and then formed into pellets. In the final phase of the project, the pelletized catalyst is being evaluated for the conversion of a heavy petroleum feedstock to naphtha and middle distillates. This phase was significantly delayed during the past six months due to a serious malfunction of the fume hoods in the Clark Atlanta University's Research Center for Science and Technology, where the project is being conducted. The fume hood system was repaired and the catalyst evaluation is now underway.

Fischer-Tropsch Cobalt Catalyst Activation and Handling Through Wax Enclosure Methods

Science.gov (United States)

Klettlinger, Jennifer L. S.; Yen, Chia H.; Nakley, Leah M.; Surgenor, Angela D.

2016-01-01

Fischer-Tropsch (F-T) synthesis is considered a gas to liquid process which converts syn-gas, a gaseous mixture of hydrogen and carbon monoxide, into liquids of various hydrocarbon chain length and product distributions. Cobalt based catalysts are used in F-T synthesis and are the focus of this paper. One key concern with handling cobalt based catalysts is that the active form of catalyst is in a reduced state, metallic cobalt, which oxidizes readily in air. In laboratory experiments, the precursor cobalt oxide catalyst is activated in a fixed bed at 350 ?C then transferred into a continuous stirred tank reactor (CSTR) with inert gas. NASA has developed a process which involves the enclosure of active cobalt catalyst in a wax mold to prevent oxidation during storage and handling. This improved method allows for precise catalyst loading and delivery into a CSTR. Preliminary results indicate similar activity levels in the F-T reaction in comparison to the direct injection method. The work in this paper was supported by the NASA Fundamental Aeronautics Subsonics Fixed Wing Project.

Topotactic intercalation of a bulky organic anion (thiacalix[4]arene) into LDH through an osmotic swelling/restoration reaction in formamide.

Science.gov (United States)

Huang, Gailing; Ma, Shulan; Zhao, Xinhua; Yang, Xiaojing; Ooi, Kenta

2009-01-21

Utilizing the osmotic swelling of LDH in formamide, for the first time, the bulky thiacalix[4]arene anion is introduced, leading to the recovery of LDH layers, and the hexagonal prism morphology of the precursor is well retained.

Study on the poisoning effect-of non-vanadium catalysts by potassium

Science.gov (United States)

Zeng, Huanmu; Liu, Ying; Yu, Xiaowei; Lin, Yasi

2018-02-01

The poisoning effect of catalyst by alkali metals is one of the problems in the selective catalytic reduction (SCR) of NO by NH3. Serious deactivation by alkali poisoning have been proved to take place in the commercial vanadium catalyst. Recently, non-vanadium catalysts such as copper oxides, manganese oxides, chromium oxides and cerium oxides have attracted special attentions in SCR application. However, their tolerance in the presence of alkali metals is still doubtful. In this paper, copper oxides, manganese oxides, chromium oxides and cerium oxides supported on TiO2 nanoparticle was prepared by impregnating method. Potassium nitrate was chosen as the precursor of poisoner. Catalytic activities of these catalysts were evaluated before and after the addition of potassium. Some characterization methods including X-ray diffraction and temperature programmed desorption was utilized to reveal the main reason of alkali deactivation.

Treatment of a non-azo dye aqueous solution by CWAO in continuous reactor using a Ni catalyst derived from hydrotalcite-like precursor.

Science.gov (United States)

Vallet, Ana; Besson, Michèle; Ovejero, Gabriel; García, Juan

2012-08-15

Catalytic wet air oxidation (CWAO) of a Basic Yellow 11 (BY11) aqueous solution, chosen as a model of a hardly biodegradable non-azo dye was carried out in a continuous-flow trickle-bed reactor, using nickel supported over hydrotalcite precursor calcined at 550°C. An increase in the reaction temperature (120-180°C), and a decrease in dye concentration (1000-3000 ppm) or liquid flow rate (0.1-0.7 mL min(-1)) enhanced the CWAO performance in a 30 and 19% for the variation of the temperature and concentration respectively. After a small leaching observed within the first hours, the catalyst proved to be very stable during the 65-day reaction. The CWAO process was found to be very efficient, achieving BY11 conversion up to 95% and TOC conversion up to 85% at 0.1 mL min(-1) and 180°C under 5 MPa air. Copyright © 2012 Elsevier B.V. All rights reserved.

Synthesis and characterization of a layered double hydroxide containing an intercalated nickel(II) citrate complex

International Nuclear Information System (INIS)

Wang Lianying; Wu Guoqing; Evans, David G.

2007-01-01

The nickel(II) citrate complex anion ([Ni(C 6 H 4 O 7 )] 2- ) may be intercalated into the interlayer galleries of a layered double hydroxide (LDH) host by a process involving ion-exchange with an Mg 2 Al-NO 3 LDH precursor. The powder X-ray diffraction (XRD) pattern confirms that the layered structure is maintained. The thermal decomposition process of the complex anion-intercalated material has been characterized by in situ high temperature powder XRD, thermogravimetry-differential thermal analysis (TG-DTA) and coupled with mass spectrometry (MS). The thermal stability of the nickel(II) citrate complex anion intercalated in LDHs in air is lower than that in the sodium salt. Calcination generates a high degree of nickel(II) oxide dispersion in a matrix of magnesium and aluminium oxide phases which should be an advantage if the materials are used as catalyst precursors. Based on the observed data, a structural model for the [Ni(C 6 H 4 O 7 )] 2- anion intercalated in the galleries of the LDH is proposed

Synthesis of Carbon Nano tubes Using Anadara Granosa Shells as Catalyst Support

International Nuclear Information System (INIS)

Mohd Zobir Hussein; Mohd Zobir Hussein; Salwani Asyikin Zakarya; Siti Halimah Sarijo

2011-01-01

The synthesis of carbon nano tubes (CNTs) by chemical vapor deposition (CVD) method using natural calcite prepared from Anadara granosa shells (CS), as metal catalyst support was studied. Hexane and iron were used as carbon precursor and catalyst, respectively. The as synthesised CNTs was characterized using XRD, TEM and FESEM. From the XRD patterns the CNTs peak can be seen more incisive after purification process and from the FESEM micrographs the CNTs can be seen as a bunch of rope-like structures. (author)

Partial-depth modulation study of anions and neutrals in low pressure silane plasmas

International Nuclear Information System (INIS)

Cozurteille, C.; Dorier, J.L.; Hollenstein, C.; Sansonnens; Howling, A.A.

1995-10-01

Partial-depth modulation of the rf power in a capacitive discharge is used to investigate the relative importance of negative ions and neutral radicals for particle formation in low power, low pressure silane plasmas. For less than 85% modulation depth, anions are trapped indefinitely in the plasma and particle formation ensues, whereas the polymerised neutral flux magnitudes and dynamics are independent of the modulation depth and the powder formation. These observations suggest that negative ions could be the particle precursors in plasma conditions where powder appears many seconds after plasma ignition. Microwave interferometry and mass spectrometry were combined to infer an anion density of ≅7.10 9 cm -3 which is approximately twice the free electron density in these modulated plasmas. (author) 6 figs., tabs., refs

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.

Hydroprocessing with self-promoted molybdenum and tungsten sulfide catalyst

International Nuclear Information System (INIS)

Mc Candish, L.E.; Ho, T.C.

1987-01-01

A hydroprocessing process is described comprising contacting a hydrocarbon feed at elevated temperature of at least about 100 0 C and in the presence of hydrogen with a supported, self-promoted catalyst obtained by compositioning one or more catalyst precursors of the formula (ML) (Mo/sub y/W/sub 1-y/O/sub 4/) with an inorganic refractory oxide support and heating the composition in a non-oxidizing atmosphere in the presence of sulfur at elevated temperature for a time sufficient to form the catalyst. M comprises one or more divalent promoter metals, y is any value ranging from 0 to 1, and wherein L is one or more, neutral, nitrogen-containing ligands at least one of which is a chelating polydentate ligand. The contacting occurs for a time sufficient to convert at least a portion of the feed

Tritium labelling of PACAP-38 using a synthetic diiodinated precursor peptide

DEFF Research Database (Denmark)

Pedersen, Martin Holst Friborg; Baun, Michael

2012-01-01

In the interest of developing efficient methods for tritium labelling peptides, we here demonstrate the successful labelling of PACAP-38 (pituitary adenylate cyclase-activating polypeptide), a 38-mer peptide, using a synthetic diiodinated PACAP-38 precursor. In this example, we employ standard hy...... hydrogenation chemistry with the use of a heterogeneous palladium catalyst and carrier-free tritium gas on a tritium manifold system....

Moessbauer study of CO-precipitated Fischer-Tropsch iron catalysts

International Nuclear Information System (INIS)

Rao, K.R.P.M.; Huggins, F.E.; Mahajan, V.; Huffman, G.P.; Bukur, D.B.; Rao, V.U.S.

1994-01-01

Moessbauer spectroscopy studies of precipitated Fischer-Tropsch (FT) iron catalysts, viz. 100 Fe/5 Cu/4.2 K/x SiO 2 , where x = 0, 8, 16, 24, 25, 40, or 100, have shown that reduction of the oxide precursor in CO gives rise to χ-carbide Fe 5 C 2 whose amount decreases with an increase of SiO 2 content. The χ-carbide is converted into magnetite Fe 3 O 4 while catalyzing the FT synthesis reaction. A correlation between FT activity and the content of χ-carbide in the catalysts was found, which indicated that χ-carbide is active for FT synthesis reaction. (orig.)

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

MoO3/Al2O3 catalyst: Comparison of catalysts prepared by new slurry impregnation with molybdic acid with conventional samples

International Nuclear Information System (INIS)

Spojakina, A.; Kostova, N.; Vit, Z.; Zdrazil, M.

2003-01-01

Alumina-supported molybdena catalysts were prepared by conventional impregnation with (NH 4 ) 6 Mo 7 O 24 (CIM) and by a new slurry impregnation method (SIM). SIM is the reaction of alumina support with a slurry of MoO 3 in water. Two commercial supports were used and the commercial Mo 3 /Al 2 O 3 catalyst was included for comparison. Maximum amount of MoO 3 deposited by SIM was about 19-20 % MoO 3 with the surface area of the support of 260-280 m 2 g -1 and this corresponded to saturation monolayer of similar density as described in literature for CIM catalysts. At the ratios of MoO 3 to Al 2 O 3 in the impregnation slurry below saturation monolayer, the pH of the slurry was 3.5-6 (depending on loading) and chemical erosion of alumina is negligible. However, using the large excess of MoO 3 (35% MoO 3 ) the pH was 2.4-3.4 and chemical erosion of alumina occurred. Silica contained in alumina supports was partly extracted as soluble silicomolybdic anions during SIM. The catalysts were characterized by BET, IR, DRS (UV-vis and NIR), TPR and catalytic activity in hydrodesulfurization of thiophene. Calcination had no significant effect on the properties of SIM catalysts and this proved that calcination is not needed in that method. All catalysts exhibited features of high monolayer dispersion of molybdena and no significant difference in structure and catalytic properties was observed between SIM and CIM catalysts. This confirmed that SIM is a simple, clean and reliable method of preparation of monolayer type MoO 3 /Al 2 O 3 catalysts. (author)

Impregnation of mesoporous silica for catalyst preparation studied with differential scanning calorimetry

NARCIS (Netherlands)

Eggenhuisen, T.M.; van Steenbergen, M.J.; Talsma, H.; de Jongh, P.E.; de Jong, K.P.

2009-01-01

Aqueous impregnation of mesoporous silica as a first step in catalyst preparation was studied to investigate the distribution of the metal-precursor solution over the support. The degree of pore-filling after impregnation was determined using the freezing point depression of confined liquids. A

Investigating the Structure and Reactivity of Azolyl-Based Copper(I)–NHC Complexes: The Role of the Anionic Ligand

KAUST Repository

Trose, Michael; Nahra, Fady; Poater, Albert; Cordes, David B.; Slawin, Alexandra M. Z.; Cavallo, Luigi; Cazin, Catherine S. J.

2017-01-01

A family of copper(I)–NHC azolyl complexes was synthesized and deployed in the hydrosilylation of dicyclo-hexylketone to probe the role of the anionic ligand on catalytic performance. The azolyl ligand is shown to have a crucial role in catalytic activity without the need for additives, and this at very low catalyst loading.

Investigating the Structure and Reactivity of Azolyl-Based Copper(I)–NHC Complexes: The Role of the Anionic Ligand

KAUST Repository

Trose, Michael

2017-11-01

A family of copper(I)–NHC azolyl complexes was synthesized and deployed in the hydrosilylation of dicyclo-hexylketone to probe the role of the anionic ligand on catalytic performance. The azolyl ligand is shown to have a crucial role in catalytic activity without the need for additives, and this at very low catalyst loading.

A Robust Fiber Bragg Grating Hydrogen Gas Sensor Using Platinum-Supported Silica Catalyst Film

OpenAIRE

Marina Kurohiji; Seiji Ichiriyama; Naoki Yamasaku; Shinji Okazaki; Naoya Kasai; Yusuke Maru; Tadahito Mizutani

2018-01-01

A robust fiber Bragg grating (FBG) hydrogen gas sensor for reliable multipoint-leakage monitoring has been developed. The sensing mechanism is based on shifts of center wavelength of the reflection spectra due to temperature change caused by catalytic combustion heat. The sensitive film which consists of platinum-supported silica (Pt/SiO2) catalyst film was obtained using sol-gel method. The precursor solution was composed of hexachloroplatinic acid and commercially available silica precursor...

The Poisoning Effect of Na Doping over Mn-Ce/TiO2 Catalyst for Low-Temperature Selective Catalytic Reduction of NO by NH3

Directory of Open Access Journals (Sweden)

Liu Yang

2014-01-01

Full Text Available Sodium carbonate (Na2CO3, sodium nitrate (NaNO3, and sodium chloride (NaCl were chosen as the precursors to prepare the Na salts deposited Mn-Ce/TiO2 catalysts through an impregnation method. The influence of Na on the performance of the Mn-Ce/TiO2 catalyst for low-temperature selective catalytic reduction of NOx by NH3 was investigated. Experimental results showed that Na salts had negative effects on the activity of Mn-Ce/TiO2 and the precursors of Na salts also affected the catalytic activity. The precursor Na2CO3 had a greater impact on the catalytic activity, while NaNO3 had minimal effect. The characterization results indicated that the significant changes in physical and chemical properties of Mn-Ce/TiO2 were observed after Na was doped on the catalysts. The significant decreases in surface areas and NH3 adsorption amounts were observed after Na was doped on the catalysts, which could be considered as the main reasons for the deactivation of Na deposited Mn-Ce/TiO2.

Anion exchange membrane

Science.gov (United States)

Verkade, John G; Wadhwa, Kuldeep; Kong, Xueqian; Schmidt-Rohr, Klaus

2013-05-07

An anion exchange membrane and fuel cell incorporating the anion exchange membrane are detailed in which proazaphosphatrane and azaphosphatrane cations are covalently bonded to a sulfonated fluoropolymer support along with anionic counterions. A positive charge is dispersed in the aforementioned cations which are buried in the support to reduce the cation-anion interactions and increase the mobility of hydroxide ions, for example, across the membrane. The anion exchange membrane has the ability to operate at high temperatures and in highly alkaline environments with high conductivity and low resistance.

Review of cell performance in anion exchange membrane fuel cells

Science.gov (United States)

Dekel, Dario R.

2018-01-01

Anion exchange membrane fuel cells (AEMFCs) have recently received increasing attention since in principle they allow for the use of non-precious metal catalysts, which dramatically reduces the cost per kilowatt of power in fuel cell devices. Until not long ago, the main barrier in the development of AEMFCs was the availability of highly conductive anion exchange membranes (AEMs); however, improvements on this front in the past decade show that newly developed AEMs have already reached high levels of conductivity, leading to satisfactory cell performance. In recent years, a growing number of research studies have reported AEMFC performance results. In the last three years, new records in performance were achieved. Most of the literature reporting cell performance is based on hydrogen-AEMFCs, although an increasing number of studies have also reported the use of fuels others than hydrogen - such as alcohols, non-alcohol C-based fuels, as well as N-based fuels. This article reviews the cell performance and performance stability achieved in AEMFCs through the years since the first reports in the early 2000s.

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)

MAGNETO-CHEMICAL CHARACTER STUDIES OF NOVEL Fe CATALYSTS FOR COAL LIQUEFACTION

Energy Technology Data Exchange (ETDEWEB)

Murty A. Akundi; Jian H. Zhang; A.N. Murty; S.V. Naidu

2002-04-01

The objectives of the present study are: (1) To synthesize iron catalysts: Fe/MoO{sub 3}, and Fe/Co/MoO{sub 3} employing two distinct techniques: Pyrolysis with organic precursors and Co-precipitation of metal nitrates; (2) To investigate the magnetic character of the catalysts before and after exposure to CO and CO+H{sub 2} by (a) Mossbauer study of Iron (b) Zerofield Nuclear Magnetic Resonance study of Cobalt, and (c) Magnetic character of the catalyst composite; (3) To study the IR active surface species of the catalyst while stimulating (CO--Metal, (CO+H{sub 2})--Metal) interactions, by FTIR Spectroscopy; and (4) To analyze the catalytic character (conversion efficiency and product distribution) in both direct and indirect liquefaction Process and (5) To examine the correlations between the magnetic and chemical characteristics. This report presents the results of our investigation on (a) the effect of metal loading (b) the effect of intermetallic ratio and (c) the effect of catalyst preparation procedure on (i) the magnetic character of the catalyst composite (ii) the IR active surface species of the catalyst and (iii) the catalytic yields for three different metal loadings: 5%, 15%, and 25% (nominal) for three distinct intermetallic ratios (Fe/Co = 0.3, 1.5, 3.0).

More active and sulfur resistant bimetallic Pd-Ni catalysts

Energy Technology Data Exchange (ETDEWEB)

Betti, Carolina; Carrara, Nicolás; Badano, Juan; Lederhos, Cecilia; Vera, Carlos; Quiroga, Mónica, E-mail: mquiroga@fiq.unl.edu.ar [Instituto de Investigaciones en Catálisis y Petroquímica, INCAPE (FIQ-UNL, CONICET), Santa Fe (Argentina)

2018-02-15

The influence of the kind of metal precursor and the sequence of impregnation on the properties of Pd-Ni catalysts was evaluated during the test reaction of selective hydrogenation of styrene to ethylbenzene by means of physicochemical characterization. The focus was put on the final hydrogenating activity and the resistance to deactivation by sulfide compounds (thiophene). The used techniques of characterization were ICP, XPS, XDR, TPR, CO chemisorption and TEM. XPS results indicated the presence of different Pd species: Pd{sup δ-}, Pd{sup 0} and Pd{sup δ+}. In the case of the Ni containing catalysts, Ni{sup 0} and NiO species were also detected. These palladium and nickel species would be responsible of the variation of activity and sulfur resistance of the catalysts. NiClPd catalysts had a higher resistance to deactivation by sulfur poisoning. This was associated to a higher concentration of Pd{sup η+}Cl{sub x}O{sub y} species that would prevent the adsorption of thiophene by both steric and electronic effects. It could also be due to the lower concentration of Pd{sup 0} and Ni{sup 0} on these catalysts, as compared to those shown by the PdNiCl catalysts. Both the Pd{sup 0} and Ni{sup 0} species are more prone to poisoning because of their higher electronic availability. (author)

Electrical properties of a novel lead alkoxide precursor: Lead glycolate

International Nuclear Information System (INIS)

Tangboriboon, Nuchnapa; Pakdeewanishsukho, Kittikhun; Jamieson, Alexander; Sirivat, Anuvat; Wongkasemjit, Sujitra

2006-01-01

The reaction of lead acetate trihydrate Pb(CH 3 COO) 2 .3H 2 O and ethylene glycol, using triethylenetetramine (TETA) as a catalyst, provides in one step access to a polymer-like precursor of lead glycolate [-PbOCH 2 CH 2 O-]. On the basis of high-resolution mass spectroscopy, chemical analysis composition, FTIR, 13 C-solid state NMR and TGA, the lead glycolate precursor can be identified as a trimer structure. The FTIR spectrum demonstrates the characteristics of lead glycolate; the peaks at 1086 and 1042 cm -1 can be assigned to the C-O-Pb stretchings. The 13 C-solid state NMR spectrum gives notably only one peak at 68.639 ppm belonging to the ethylene glycol ligand. The phase transformations of lead glycolate and lead acetate trihydrate to lead oxide, their microstructures, and electrical properties were found to vary with increasing temperature. The lead glycolate precursor has superior electrical properties relative to those of lead acetate trihydrate, suggesting that the lead glycolate precursor can possibly be used as a starting material for producing electrical and semiconducting ceramics, viz. ferroelectric, anti-ferroelectric, and piezoelectric materials

Local structure of Iridium organometallic catalysts covalently bonded to carbon nanotubes.

Science.gov (United States)

Blasco, J.; Cuartero, V.; Subías, G.; Jiménez, M. V.; Pérez-Torrente, J. J.; Oro, L. A.; Blanco, M.; Álvarez, P.; Blanco, C.; Menéndez, R.

2016-05-01

Hybrid catalysts based on Iridium N-heterocyclic carbenes anchored to carbon nanotubes (CNT) have been studied by XAFS spectroscopy. Oxidation of CNT yields a large amount of functional groups, mainly hydroxyl groups at the walls and carboxylic groups at the tips, defects and edges. Different kinds of esterification reactions were performed to functionalize oxidized CNT with imidazolium salts. Then, the resulting products were reacted with an Ir organometallic compound to form hybrid catalysts efficient in hydrogen transfer processes. XANES spectroscopy agree with the presence of Ir(I) in these catalysts and the EXAFS spectra detected differences in the local structure of Ir atoms between the initial Ir organometallic compound and the Ir complexes anchored to the CNT. Our results confirm that the halide atom, present in the Ir precursor, was replaced by oxygen from -OH groups at the CNT wall in the first coordination shell of Ir. The lability of this group accounts for the good recyclability and the good efficiency shown by these hybrid catalysts.

One-pot synthesis of CuInS2 nanocrystals using different anions to engineer their morphology and crystal phase.

Science.gov (United States)

Tang, Aiwei; Hu, Zunlan; Yin, Zhe; Ye, Haihang; Yang, Chunhe; Teng, Feng

2015-05-21

A simple one-pot colloidal method has been described to engineer ternary CuInS2 nanocrystals with different crystal phases and morphologies, in which dodecanethiol is chosen as the sulfur source and the capping ligands. By a careful choice of the anions in the metal precursors and manipulation of the reaction conditions including the reactant molar ratios and the reaction temperature, CuInS2 nanocrystals with chalcopyrite, zincblende and wurtzite phases have been successfully synthesized. The type of anion in the metal precursors has been found to be essential for determining the crystal phase and morphology of the as-obtained CuInS2 nanocrystals. In particular, the presence of Cl(-) ions plays an important role in the formation of CuInS2 nanoplates with a wurtzite-zincblende polytypism structure. In addition, the molar ratios of Cu to In precursors have a significant effect on the crystal phase and morphology, and the intermediate Cu2S-CuInS2 heteronanostructures are formed which are critical for the anisotropic growth of CuInS2 nanocrystals. Furthermore, the optical absorption results of the as-obtained CuInS2 nanocrystals exhibit a strong dependence on the crystal phase and size.

Single Atomic Iron Catalysts for Oxygen Reduction in Acidic Media: Particle Size Control and Thermal Activation

Energy Technology Data Exchange (ETDEWEB)

Zhang, Hanguang; Hwang, Sooyeon; Wang, Maoyu; Feng, Zhenxing; Karakalos, Stavros; Luo, Langli; Qiao, Zhi; Xie, Xiaohong; Wang, Chongmin; Su, Dong; Shao, Yuyan; Wu, Gang (BNL); (Oregon State U.); (SC); (PNNL); (Buffalo)

2017-09-26

It remains a grand challenge to replace platinum group metal (PGM) catalysts with earth-abundant materials for the oxygen reduction reaction (ORR) in acidic media, which is crucial for large-scale deployment of proton exchange membrane fuel cells (PEMFCs). Here, we report a high-performance atomic Fe catalyst derived from chemically Fe-doped zeolitic imidazolate frameworks (ZIFs) by directly bonding Fe ions to imidazolate ligands within 3D frameworks. Although the ZIF was identified as a promising precursor, the new synthetic chemistry enables the creation of well-dispersed atomic Fe sites embedded into porous carbon without the formation of aggregates. The size of catalyst particles is tunable through synthesizing Fe-doped ZIF nanocrystal precursors in a wide range from 20 to 1000 nm followed by one-step thermal activation. Similar to Pt nanoparticles, the unique size control without altering chemical properties afforded by this approach is able to increase the number of PGM-free active sites. The best ORR activity is measured with the catalyst at a size of 50 nm. Further size reduction to 20 nm leads to significant particle agglomeration, thus decreasing the activity. Using the homogeneous atomic Fe model catalysts, we elucidated the active site formation process through correlating measured ORR activity with the change of chemical bonds in precursors during thermal activation up to 1100 °C. The critical temperature to form active sites is 800 °C, which is associated with a new Fe species with a reduced oxidation number (from Fe3+ to Fe2+) likely bonded with pyridinic N (FeN4) embedded into the carbon planes. Further increasing the temperature leads to continuously enhanced activity, linked to the rise of graphitic N and Fe–N species. The new atomic Fe catalyst has achieved respectable ORR activity in challenging acidic media (0.5 M H2SO4), showing a half-wave potential of 0.85 V vs RHE and leaving only a 30 mV gap with Pt/C (60 μgPt/cm2). Enhanced stability

One-step routes from di- and triblock copolymer precursors to hydrophilic nanoporous poly(acrylic acid)-b-polystyrene

DEFF Research Database (Denmark)

Guo, Fengxiao; Jankova Atanasova, Katja; Schulte, Lars

2008-01-01

Nanoporous polystyrene with hydrophilic pores was prepared from di- and triblock copolymer precursors. The precursor material was either a poly(tert-butyl acryl ate)-b-polystyrene (PtBA-b-PS) diblock copolymer synthesized by atom transfer radical polymerization (ATRP) or a polydimethylsiloxane......-b-poly(tertbutyl acrylate)-b-polystyrene (PDMS-b-PtBA-b-PS) triblock copolymer synthesized by a combination of living anionic polymerization and ATRP. In the latter copolymer, PS was the matrix and mechanically stable component, PtBA was converted by acidic deprotection to hydrophilic poly(acrylic acid) (PAA) providing...

Co, Fe and Ni catalysts supported on coke for direct coal liquefaction

International Nuclear Information System (INIS)

Jimenez, Jose A; Villalba, Oscar A; Rodriguez, Luis I; Hernandez, Orlando; Agamez, Yasmin Y; Dias Jose de Jesus

2008-01-01

Transition metal catalysts supported on coke were prepared by impregnation with a solution of complex of metal-thiourea, that is produced from salt precursors of cobalt chloride, Nickel chloride or iron sulfate and ammonium. sulphide formation on the support surface was generated by decomposition of the metal complex. The catalysts obtained were used in direct coal liquefaction of a medium volatile bituminous coal (Yerbabuena N 1) from Cundinamarca using a 250 Ml, Parr reactor at 723 K and a hydrogen-donor solvent. The catalytic results show, for all samples, both a good coal conversion and an enhancement of the yield of oils, this indicates that the proposed preparation method of catalyst is effective and that eventually the H 2 S sulphidation conventional process could be replaced

Free radicals in an adamantane matrix. XIII. Electron paramagnetic resonance study of sigma* - π* orbital crossover in fluorinated pyridine anions

International Nuclear Information System (INIS)

Yim, M.B.; DiGregorio, S.; Wood, D.E.

1977-01-01

Pentafluoropyridine,2,3,4,6-tetrafluoropyridine, 2,6-difluoropyridine, and 2-fluoropyridine anion radicals were produced by x irradiation of an adamantane matrix which was doubly doped with the aromatic precursors and Me 3 NBH 3 and their EPR spectra obtained. The large fluorine hyperfine splitting constants (hfsc) of penta- and 2,3,4,6-tetrafluoropyridine anions and the small fluorine hfsc's of 2,6-di- and 2-fluoropyridine anions suggest that the former two are sigma radicals while the latter two are π radicals. The sigma*-π* orbital crossover phenomenon observed in these fluorinated pyridine anions is explained in terms of the combined effects of stabilization of sigma* orbitals and destabilization of π* orbitals. The EPR results show that nitrogen has a negligible contribution to the unpaired electron sigma* orbitals. INDO calculations were performed for the various states and the results compared with experiment

Photo-driven electron transfer from the highly reducing excited state of naphthalene diimide radical anion to a CO ₂ reduction catalyst within a molecular triad

Energy Technology Data Exchange (ETDEWEB)

Martinez, Jose F. [Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center; Northwestern University; Evanston; USA; La Porte, Nathan T. [Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center; Northwestern University; Evanston; USA; Mauck, Catherine M. [Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center; Northwestern University; Evanston; USA; Wasielewski, Michael R. [Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center; Northwestern University; Evanston; USA

2017-01-01

The naphthalene-1,4:5,8-bis(dicarboximide) radical anion (NDI^-˙), which is easily produced by mild chemical or electrochemical reduction (-0.5 Vvs.SCE), can be photoexcited at wavelengths as long as 785 nm, and has an excited state (NDI^-˙*) oxidation potential of -2.1 Vvs.SCE, making it a very attractive choice for artificial photosynthetic systems that require powerful photoreductants, such as CO₂ reduction catalysts. However, once an electron is transferred from NDI^-˙* to an acceptor directly bound to it, a combination of strong electronic coupling and favorable free energy change frequently make the back electron transfer rapid. To mitigate this effect, we have designed a molecular triad system comprising an NDI^-˙ chromophoric donor, a 9,10-diphenylanthracene (DPA) intermediate acceptor, and a Re(dmb)(CO)₃carbon dioxide reduction catalyst, where dmb is 4,4'-dimethyl-2,2'-bipyridine, as the terminal acceptor. Photoexcitation of NDI^-˙ to NDI^-˙* is followed by ultrafast reduction of DPA to DPA^-˙, which then rapidly reduces the metal complex. The overall time constant for the forward electron transfer to reduce the metal complex is τ = 20.8 ps, while the time constant for back-electron transfer is six orders of magnitude longer, τ = 43.4 μs. Achieving long-lived, highly reduced states of these metal complexes is a necessary condition for their use as catalysts. The extremely long lifetime of the reduced metal complex is attributed to careful tuning of the redox potentials of the chromophore and intermediate acceptor. The NDI^-˙–DPA fragment presents many attractive features for incorporation into other photoinduced electron transfer assemblies directed at the long-lived photosensitization of difficult-to-reduce catalytic centers.

Biomimetic Catalysts for Oxidation of Veratryl Alcohol, a Lignin Model Compound

Directory of Open Access Journals (Sweden)

Marcelino Maneiro

2013-03-01

Full Text Available Kraft pulp has to be bleached to eliminate the chromophoric structures, which cause a darkening of the pulp. In Nature, an equivalent role is assumed by ligninolytic enzymes such as lignin peroxidases, manganese peroxidases and laccases. The development of low molecular weight manganese peroxidase mimics may achieve environmentally-safe bleaching catalysts for the industry. Herein we report the synthesis and characterization of six manganese(III complexes 1–6, incorporating dianionic hexadentate Schiff base ligands (H2L1-H2L4 and different anions. Complex 4, Mn2L22(H2O2(DCA2 was crystallographically characterized. Complexes 1–4 behave as more efficient mimics of peroxidase in contrast to 5–6. We have studied the use of these complexes as catalysts for the degradation of the lignin model compound veratryl alcohol. The biomimetic catalysts were used in conjunction with chlorine-free inexpensive co-oxidants as dioxygen or hydrogen peroxide. Yields up to 30% of veratryl alcohol conversion to veratraldehyde have been achieved at room temperature in presence of air flow using 0.5% of catalyst.

Chiral pyrrolidinium salts derived from menthol as precursor – synthesis and properties

Directory of Open Access Journals (Sweden)

Janus Ewa

2017-09-01

Full Text Available Six new chiral pyrolidinium salts with chiral substituent at quaternary nitrogen atom were synthesized with high overall yields from (--menthol as cheap chiral precursor and were identified by NMR and HRMS spectroscopy. It was shown that anion type had the effect on chemical shift of protons adjacent to quaternary nitrogen atom and physical properties of these salts. Salts with NTf2 or NPf2 were in a liquid state at room temperature and characterized with the highest thermal stability among others. Furthermore, chiral ionic liquid with NTf2 anion was used as solvent in Diels-Alder reaction and gave higher yield and stereoselectivity than in ionic liquids with achiral cations. Synthesized chiral salts have the potential as chiral solvents in synthesis and auxiliaries in analytical methods to improve chiral recognition.

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.

Tailoring the synthesis of supported Pd catalysts towards desired structure and size of metal particles.

Science.gov (United States)

Suresh, Gatla; Radnik, Jörg; Kalevaru, Venkata Narayana; Pohl, Marga-Martina; Schneider, Matthias; Lücke, Bernhard; Martin, Andreas; Madaan, Neetika; Brückner, Angelika

2010-05-14

In a systematic study, the influence of different preparation parameters on phase composition and size of metal crystallites and particles in Pd-Cu/TiO(2) and Pd-Sb/TiO(2) catalyst materials has been explored. Temperature and atmosphere of thermal pretreatment (pure He or 10% H(2)/He), nature of metal precursors (chlorides, nitrates or acetates) as well as of ammonium additives (ammonium sulfate, nitrate, carbonate) and urea were varied with the aim of tailoring the synthesis procedure for the preferential formation of metal particles with similar size and structure as observed recently in active catalysts after long-term equilibration under catalytic reaction conditions in acetoxylation of toluene to benzylacetate. Among the metal precursors and additives, the chloride metal precursors and (NH(4))(2)SO(4) were most suitable. Upon thermal pretreatment of Pd-Sb or Pd-Cu precursors, chloroamine complexes of Pd and Cu are formed, which decompose above 220 degrees C to metallic phases independent of the atmosphere. In He, metallic Pd particles were formed with both the co-components. In H(2)/He flow, Pd-Cu precursors were converted to core-shell particles with a Cu shell and a Pd core, while Sb(1)Pd(1) and Sb(7)Pd(20) alloy phases were formed in the presence of Sb. Metal crystallites of about 40 nm agglomerate to particles of up to 150 nm in He and to even larger size in H(2)/He.

Automated identification and quantification of glycerophospholipid molecular species by multiple precursor ion scanning

DEFF Research Database (Denmark)

Ejsing, Christer S.; Duchoslav, Eva; Sampaio, Julio

2006-01-01

We report a method for the identification and quantification of glycerophospholipid molecular species that is based on the simultaneous automated acquisition and processing of 41 precursor ion spectra, specific for acyl anions of common fatty acids moieties and several lipid class-specific fragment...... of glycerophospholipids. The automated analysis of total lipid extracts was powered by a robotic nanoflow ion source and produced currently the most detailed description of the glycerophospholipidome....

Modeling of cobalt-based catalyst use during CSS for low-temperature heavy oil upgrading

Science.gov (United States)

Kadyrov, R.; Sitnov, S.; Gareev, B.; Batalin, G.

2018-05-01

One of the methods, which is actively used on deposits of heavy oils of the Upper Kungurian (Ufimian) sandstones of the Republic of Tatarstan, is cyclic steam simulation (CSS). This method consists of 3 stages: injection, soaking, and production. Steam is injected into a well at a temperature of 300 to 340° C for a period of weeks to months. Then, the well is allowed to sit for days to weeks to allow heat to soak into the formation. Finally, the hot oil is pumped out of the well for a period of weeks or months. Once the production rate falls off, the well is put through another cycle. The injection of the catalyst solution before the injection of steam opens the possibility for upgrading the heavy oil in the process of aquathermolysis directly in the reservoir. In this paper, the possibility of using a catalyst precursor based on cobalt for upgrading the hydrocarbons of this field in the process of their extraction is represented. SARA analysis on oil saturated sandstones shows an increase in the proportion of saturated hydrocarbons by 11.1% due to the hydrogenation of aromatic hydrocarbons and their derivatives, the content of resins and asphaltenes are remained practically unchanged. A new method for estimating the adsorption of a catalyst based on taking into account the change in the concentration of the base metal before and after simulation of catalyst injection in the thermobaric conditions of the reservoir is proposed. During the study of catalyst adsorption in the rock, when simulating the CSS process, it is found that almost 28% of the cobalt, which is the main element of the catalyst precursor, is retained in the rock.

Innovative sol–gel route in neutral hydroalcoholic condition to obtain antibacterial cotton finishing by zinc precursor

NARCIS (Netherlands)

Poli, R.; Colleoni, C.; Calvimontes, A.; Polaskova, H.; Dutschk, Victoria; Rosace, G.

2015-01-01

In the present study, a possibility to realize a transparent sol by zinc-based precursors in a neutral medium without acidic or alkaline catalyst was investigated.Moreover, to study the influence of an inorganic–organic hybrid polymer on the proposed antibacterial finishing, the Zn-based sol was

Characterization of deposits formed on catalyst surfaces during hydrotreatment of coal-derived liquids

Energy Technology Data Exchange (ETDEWEB)

Furimsky, E.

1982-04-01

Loss of catalyst activity is attributed to the formation of polynuclear aromatic structures on the surface. Heavy species containing N and O heteroatoms were also present in deposits. Phenols, aromatic and heterocyclic compounds are considered to be the precursors for the formation of the deposits. (16 refs.)

Microemulsion flame pyrolysis for hopcalite nanoparticle synthesis: a new concept for catalyst preparation

OpenAIRE

Kaskel, Stefan; Biemelt, Tim; Wegner, Karl; Teichert, Johannes

2016-01-01

A new route to highly active hopcalite catalysts via flame spray pyrolysis of an inverse microemulsion precursor is reported. The nitrate derived nanoparticles are around 15 nm in diameter and show excellent conversion of CO under ambient conditions, outperforming commercial reference hopcalite materials produced by co-precipitation.

Microemulsion flame pyrolysis for hopcalite nanoparticle synthesis: a new concept for catalyst preparation.

Science.gov (United States)

Biemelt, T; Wegner, K; Teichert, J; Kaskel, S

2015-04-07

A new route to highly active hopcalite catalysts via flame spray pyrolysis of an inverse microemulsion precursor is reported. The nitrate derived nanoparticles are around 15 nm in diameter and show excellent conversion of CO under ambient conditions, outperforming commercial reference hopcalite materials produced by co-precipitation.

Performance of polyethylene based radiation grafted anion exchange membrane with polystyrene-b-poly (ethylene/butylene)-b-polystyrene based ionomer using NiCo2O4 catalyst for water electrolysis

Science.gov (United States)

Gupta, Gaurav; Scott, Keith; Mamlouk, Mohamed

2018-01-01

A soluble anion exchange ionomer with high OH- ion conductivity comparable to that of H+ conductivity of Nafion is synthesised by chloromethylation of polystyrene-b-poly (ethylene/butylene)-b-polystyrene (SEBS) and used with NiCo2O4 electro-catalyst for water electrolysis. The ionomer has an ion exchange capacity of 1.9 mmol g-1 and ionic conductivity of 0.14 S cm-2 at 50 °C. The cell voltage at 20 °C at 100 mA cm-2 is 1.77 and 1.72 V in, 0.1 and 1.0 M NaOH, respectively, for an optimum loading of 10 mg cm-2 NiCo2O4. At 10 mg cm-2 NiCo2O4 electrolyser cell performance is at least equal to or superior to that of IrO2 at 2 mg cm-2 with excellent stability over 1 h. When the catalyst is sprayed on the GDL instead of CCM, the performance is further improved to 1.65 V at 100 mA cm-2 at 60 °C & 0.1 M KOH. The limited AEM electrolyser performance when operating with deionised water in comparison to PEM and alkaline electrolyser arises from the sluggish OER in the AEM environment equivalent to pH of 11.5 and the two orders of magnitude lower HER activity with respect to acid medium combined with the high Tafel slope of 120 mV dec-1.

Synthesis of substituted Calix[6] arene and 18F labeling reaction as catalyst in preparation of 18F-FET

International Nuclear Information System (INIS)

Peng Cheng; Ma Yunchuan; Chen Xiaoxiao; Li Guixia; Li Shilei; Zhang Shuting; He Yong; Qi Chuanmin

2011-01-01

The phase transfer catalyst Substituted Calix[6] arene was prepared and it was used as catalyst to prepare the tumor diagnostic drug 18 F-FET. The results showed that para-sulfonated-calix[6] arene not only catalyzes 19 F substitution reaction, but also catalyzes 18 F labelling reaction with radiochemical yield of 11%. However, para-tert-butyl-calix[6] arene has no catalytic activity for the 19 F substitution reaction nor the 18 F labelling reaction of the precursor of FET. The catalyzing of para-sulfonated-calix[6]arene may be related to it's sulfonate groups, which participated in the coordination reaction and increased the polarity of calyx[6] arene and so on. Although radiochemical yield of the para-sulfonated-calix[6] arene catalyzed 18 F labeling of the precursor of FET was much lower than that obtained by Kryptofix 2. 2. 2, this study still has significant meaning for us to find better substituted Calix[6] arene catalysts by optimizing the reaction conditions. (authors)

Synthesis,Characterization and Application of Benzyl-substituted Cyclopentadienyl lanthanide Complexes as Catalyst Precursors for the Syndiotactic Polymerization of Methyl Methacrylate

Institute of Scientific and Technical Information of China (English)

QIAN,Yan-Long(钱延龙); BALA,Muhammad D.; XIE,Xiao-Min(谢小敏); HUANG,Ji-Ling(黄吉玲)

2004-01-01

Benzyl-substituted cyclopentadienyl lanthanide complexes were synthesized and characterized by elemental analysis, MS and IR spectroscopy. The analytical data point out the formation of monomeric, unsolvated complexes.In conjunction with Al(Et)3 as co-catalyst, the title complexes are efficient catalysts for the syndiotactic polymerization of methyl methacrylate. For the complex (C6H5CH2C5H4)2YCI, under the optimum polymerization conditions (60 ℃, n(MMA):n(catalyst):n(co-catalyst)= 1000:1:10), a predominantly syndiotactic (rr=66%) polymer of high molecular weight (Mη = 105000) was obtained.

Vanadium oxides supported on hydrotalcite-type precursors: the effect of acid-base properties on the oxidation of isopropanol

Directory of Open Access Journals (Sweden)

D. M. Meira

2006-09-01

Full Text Available Vanadium oxide supported on hydrotalcite-type precursors was studied in the oxidation of isopropanol. Hydrotalcites with different y = Mg/Al ratios were synthesized by the method of coprecipitation nitrates of Mg and Al cations with K2CO3 as precipitant. The decomposition of these hydrotalcite precursors at 450°C yielded homogeneous MgyAlOx mixed oxides that contain the Al+3 cations totally incorporated into the MgO framework. The materials were characterized by chemical analysis, BET superficial area, X-ray diffraction, temperature-programmed reduction (TPR and the reaction of isopropanol, a probe molecule used to evaluate the acid-base properties. The results of TPR showed that the reducibility of V+5 decreased with the increase in magnesium loading in catalysts. The X-ray diffraction patterns of Al-rich hydrotalcite precursors showed the presence of crystalline phases of brucite and gibbsite. It was shown that chemical composition, texture, acid-base properties of the active sites and also Mg/Al ratio strongly affect the formation of the products in the oxidation of isopropanol. The Al-rich catalysts were much more active than the Mg-rich ones, converting isopropanol mainly to propylene.

Vanadium oxides supported on hydrotalcite-type precursors: the effect of acid base properties on the oxidation of isopropanol

Energy Technology Data Exchange (ETDEWEB)

Meira, D.M.; Cortez, G.G. [Faculdade de Engenharia Quimica de Lorena, Lorena, SP (Brazil). Dept. de Engenharia Quimica. Lab. de Catalise II]. E-mail: cortez@dequi.faenquil.br; Monteiro, W.R.; Rodrigues, J.A.J. [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Lab. Associado de Combustao e Propulsao]. E-mail: jajr@lcp.inpe.br

2006-07-15

Vanadium oxide supported on hydrotalcite-type precursors was studied in the oxidation of isopropanol. Hydrotalcites with different y = Mg/Al ratios were synthesized by the method of coprecipitation nitrates of Mg and Al cations with K{sub 2}CO{sub 3} as precipitant. The decomposition of these hydrotalcite precursors at 450 deg C yielded homogeneous MgyAlOx mixed oxides that contain the Al{sup +3} cations totally incorporated into the MgO framework. The materials were characterized by chemical analysis, BET superficial area, X-ray diffraction, temperature-programmed reduction (TPR) and the reaction of isopropanol, a probe molecule used to evaluate the acid-base properties. The results of TPR showed that the reducibility of V{sup +5} decreased with the increase in magnesium loading in catalysts. The X-ray diffraction patterns of Al-rich hydrotalcite precursors showed the presence of crystalline phases of brucite and gibbsite. It was shown that chemical composition, texture, acid-base properties of the active sites and also Mg/Al ratio strongly affect the formation of the products in the oxidation of isopropanol. The Al-rich catalysts were much more active than the Mg-rich ones, converting isopropanol mainly to propylene. (author)

Cationic Zn-Porphyrin Polymer Coated onto CNTs as a Cooperative Catalyst for the Synthesis of Cyclic Carbonates.

Science.gov (United States)

Jayakumar, Sanjeevi; Li, He; Chen, Jian; Yang, Qihua

2018-01-24

The development of solid catalysts containing multiple active sites that work cooperatively is very attractive for biomimetic catalysis. Herein, we report the synthesis of bifunctional catalysts by supporting cationic porphyrin-based polymers on carbon nanotubes (CNTs) using the direct reaction of 5,10,15,20-tetrakis(4-pyridyl)porphyrin zinc(II), di(1H-imidazol-1-yl)methane, and 1,4-bis(bromomethyl)benzene in the presence of CNTs. The bifunctional catalysts could efficiently catalyze the cycloaddition reaction of epoxides and CO 2 under solvent-free conditions with porphyrin zinc(II) as the Lewis acid site and a bromine anion as a nucleophilic agent working in a cooperative way. Furthermore, a relative amount of porphyrin zinc(II) and quaternary ammonium bromide could be facilely adjusted for facilitating cooperative behavior. The bifunctional catalyst with a TOF up to 2602 h -1 is much more active than the corresponding homogeneous counterpart and is one of the most active heterogeneous catalysts ever reported under cocatalyst-free conditions. The high activity is mainly attributed to the enhanced cooperation effect of the bifunctional catalyst. With a wide substrate scope, the bifunctional catalyst could be stably recycled. This work demonstrates a new approach for the generation of a cooperative activation effect for solid catalysts.

Eosin Y photoredox catalyzed net redox neutral reaction for regiospecific annulation to 3-sulfonylindoles via anion oxidation of sodium sulfinate salts.

Science.gov (United States)

Rohokale, Rajendra S; Tambe, Shrikant D; Kshirsagar, Umesh A

2018-01-24

An eosin Y photoredox catalyzed net redox neutral process for 3-sulfonylindoles via the anionic oxidation of sodium sulfinate salts and its radical cascade cyclization with 2-alkynyl-azidoarenes was developed with visible light as a mediator. The reaction offers metal and oxidant/reductant free, visible light mediated vicinal sulfonamination of alkynes to 2-aryl/alkyl-3-sulfonylindoles and proceeds via the generation of a sulfur-centered radical through direct oxidation of the sulfinate anion by an excited photocatalyst with a reductive quenching cycle. The mild conditions, use of an organic dye as photo-catalyst, bench stability and easily accessible starting materials make the present approach green and attractive.

Effect of cationic/anionic organic surfactants on evaporation induced self assembled tin oxide nanostructured films

International Nuclear Information System (INIS)

Khun Khun, Kamalpreet; Mahajan, Aman; Bedi, R.K.

2011-01-01

Tin oxide nanostructures with well defined morphologies have been obtained through an evaporation induced self assembly process. The technique has been employed using an ultrasonic nebulizer for production of aersol and its subsequent deposition onto a heated glass substrate. The precursor used for aersol production was modified by introducing cationic and anionic surfactants namely cetyl trimethyl ammonium bromide and sodium dodecyl sulphate respectively. The effect of surfactants on the structural, electrical and optical properties of self assembled tin oxide nanostructures were investigated by using X-ray diffraction, field emission scanning electroscope microscopy, two probe technique and photoluminiscence studies. The results reveal that high concentration of surfactants in the precursor solution leads to reduction in crystallite size with significant changes in the morphology of tin oxide nanostructures. Photoluminiscence studies of the nanostructures show emissions in the visible region which exhibit marked changes in the intensities upon variation of surfactants in the precursor solutions.

Effect of cationic/anionic organic surfactants on evaporation induced self assembled tin oxide nanostructured films

Energy Technology Data Exchange (ETDEWEB)

Khun Khun, Kamalpreet [Material Science Laboratory, Department of Physics, Guru Nanak Dev University, Amritsar 143005 (India); Mahajan, Aman, E-mail: dramanmahajan@yahoo.co.in [Material Science Laboratory, Department of Physics, Guru Nanak Dev University, Amritsar 143005 (India); Bedi, R.K. [Material Science Laboratory, Department of Physics, Guru Nanak Dev University, Amritsar 143005 (India)

2011-01-15

Tin oxide nanostructures with well defined morphologies have been obtained through an evaporation induced self assembly process. The technique has been employed using an ultrasonic nebulizer for production of aersol and its subsequent deposition onto a heated glass substrate. The precursor used for aersol production was modified by introducing cationic and anionic surfactants namely cetyl trimethyl ammonium bromide and sodium dodecyl sulphate respectively. The effect of surfactants on the structural, electrical and optical properties of self assembled tin oxide nanostructures were investigated by using X-ray diffraction, field emission scanning electroscope microscopy, two probe technique and photoluminiscence studies. The results reveal that high concentration of surfactants in the precursor solution leads to reduction in crystallite size with significant changes in the morphology of tin oxide nanostructures. Photoluminiscence studies of the nanostructures show emissions in the visible region which exhibit marked changes in the intensities upon variation of surfactants in the precursor solutions.

Nanostructured CoP: An efficient catalyst for degradation of organic pollutants by activating peroxymonosulfate

Energy Technology Data Exchange (ETDEWEB)

Luo, Rui; Liu, Chao; Li, Jiansheng, E-mail: lijsh@mail.njust.edu.cn; Wang, Jing; Hu, Xingru; Sun, Xiuyun; Shen, Jinyou; Han, Weiqing; Wang, Lianjun

2017-05-05

Highlights: • The CoP/PMS system was first presented for decomposition of pollutants. • CoP exhibited dramatic catalytic activity. • Broadened pH range and favorable anti-interference of anions were achieved. • A possible mechanism for activation of PMS by CoP was proposed. - Abstract: A new catalyst system of CoP/peroxymonosulfate (PMS) is presented, which achieved significant improvement in catalytic activity. Nanostructured CoP, obtained by a simple solid-state reaction, exhibited dramatic catalytic activity with 97.2% degradation of orange II of 100 ppm within 4 min. Moreover, the high efficiency could be reached for other phenolic pollutants, i.e., phenol and 4-chlorophenol. The reaction rate is much higher than the most reported catalysts. Effect of parameters on catalytic activity of the catalyst was studied in detail. Notably, initial pH of the solution had a slight negative effect on the catalytic performance over the pH range 4.07–10.92, suggesting that CoP has the great adaptability of pH. CoP/PMS demonstrated excellent anti-interference performance toward anions (Cl{sup −}, NO{sub 3}{sup −}, and HCO{sub 3}{sup −}). In addition, the pathway of degradation of orange II is proposed by analyzing its intermediates. Based on the XPS spectra of CoP, the identification of the reactive species (·OH and SO{sub 4}·{sup −}) by electron paramagnetic resonance (EPR) analysis and quenching tests, a possible mechanism for activation of PMS by CoP was proposed. Considering the dramatic catalytic activity, a wide range of pH catalyst suited, CoP is believed to provide robust support for the promising industrial application of AOPs.

Hydrophilic cobalt sulfide nanosheets as a bifunctional catalyst for oxygen and hydrogen evolution in electrolysis of alkaline aqueous solution.

Science.gov (United States)

Zhu, Mingchao; Zhang, Zhongyi; Zhang, Hu; Zhang, Hui; Zhang, Xiaodong; Zhang, Lixue; Wang, Shicai

2018-01-01

Hydrophilic medium and precursors were used to synthesize a hydrophilic electro-catalyst for overall water splitting. The cobalt sulfide (Co 3 S 4 ) catalyst exhibits a layered nanosheet structure with a hydrophilic surface, which can facilitate the diffusion of aqueous substrates into the electrode pores and towards the active sites. The Co 3 S 4 catalyst shows excellent bifunctional catalytic activity for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline solution. The assembled water electrolyzer based on Co 3 S 4 exhibits better performance and stability than that of Pt/C-RuO 2 catalyst. Thereforce the hydrophilic Co 3 S 4 is a highly promising bifunctional catalyst for the overall water splitting reaction. Copyright © 2017 Elsevier Inc. All rights reserved.

Silica-Supported Catalyst for Enantioselective Arylation of Aldehydes under Batch and Continuous-Flow Conditions.

Science.gov (United States)

Watanabe, Satoshi; Nakaya, Naoyuki; Akai, Junichiro; Kanaori, Kenji; Harada, Toshiro

2018-05-04

A silica-supported 3-aryl H 8 -BINOL-derived titanium catalyst exhibited high performance in the enantioselective arylation of aromatic aldehydes using Grignard and organolithium reagents not only under batch conditions but also under continuous-flow conditions. Even with a simple pipet reactor packed with the heterogeneous catalyst, the enantioselective production of chiral diarylmethanols could be achieved through a continuous introduction of aldehydes and mixed titanium reagents generated from the organometallic precursors. The pipet reactor could be used repeatedly in different reactions without appreciable deterioration of the activity.

Vapour phase dehydration of glycerol to acrolein over tungstated zirconia catalysts

Science.gov (United States)

Rao Ginjupalli, Srinivasa; Mugawar, Sowmya; Rajan N., Pethan; Kumar Balla, Putra; Chary Komandur, V. R.

2014-08-01

Tetragonal (TZ) and monoclinic (MZ) polymorphs of zirconia supports were synthesised by sol-gel method followed by variation of the calcination temperature. Tungstated (10 wt% WO3) supported on the zirconia polymorphs were prepared by impregnation method by using ammonium metatungstate precursor. The physico-chemical properties of the calcined catalysts were characterised by X-ray diffraction, UV-vis diffused reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), surface area and pore size distribution measurements to gain insight into the effect of morphology of the catalyst textural properties, and structure. The surface acidic properties have been determined by NH3 TPD method and also with FT-IR spectra of pyridine adsorption. Vapour phase dehydration of glycerol to acrolein was employed to investigate the catalytic functionalities. Glycerol conversion and acrolein selectivity was mainly dependent on the fraction of moderate acid sites with majority of them are due to Brønsted acidic sites. Monoclinic zirconia based catalysts have shown the highest activity and acrolein selectivity compared to the corresponding tetragonal zirconia catalysts.

Vapour phase dehydration of glycerol to acrolein over tungstated zirconia catalysts

International Nuclear Information System (INIS)

Rao Ginjupalli, Srinivasa; Mugawar, Sowmya; Rajan, Pethan N.; Kumar Balla, Putra; Chary Komandur, V.R.

2014-01-01

Tetragonal (TZ) and monoclinic (MZ) polymorphs of zirconia supports were synthesised by sol–gel method followed by variation of the calcination temperature. Tungstated (10 wt% WO 3 ) supported on the zirconia polymorphs were prepared by impregnation method by using ammonium metatungstate precursor. The physico-chemical properties of the calcined catalysts were characterised by X-ray diffraction, UV–vis diffused reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), surface area and pore size distribution measurements to gain insight into the effect of morphology of the catalyst textural properties, and structure. The surface acidic properties have been determined by NH 3 TPD method and also with FT-IR spectra of pyridine adsorption. Vapour phase dehydration of glycerol to acrolein was employed to investigate the catalytic functionalities. Glycerol conversion and acrolein selectivity was mainly dependent on the fraction of moderate acid sites with majority of them are due to Brønsted acidic sites. Monoclinic zirconia based catalysts have shown the highest activity and acrolein selectivity compared to the corresponding tetragonal zirconia catalysts.

Vapour phase dehydration of glycerol to acrolein over tungstated zirconia catalysts

Energy Technology Data Exchange (ETDEWEB)

Rao Ginjupalli, Srinivasa; Mugawar, Sowmya; Rajan, Pethan N.; Kumar Balla, Putra; Chary Komandur, V.R., E-mail: kvrchary@iict.res.in

2014-08-01

Tetragonal (TZ) and monoclinic (MZ) polymorphs of zirconia supports were synthesised by sol–gel method followed by variation of the calcination temperature. Tungstated (10 wt% WO{sub 3}) supported on the zirconia polymorphs were prepared by impregnation method by using ammonium metatungstate precursor. The physico-chemical properties of the calcined catalysts were characterised by X-ray diffraction, UV–vis diffused reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), surface area and pore size distribution measurements to gain insight into the effect of morphology of the catalyst textural properties, and structure. The surface acidic properties have been determined by NH{sub 3} TPD method and also with FT-IR spectra of pyridine adsorption. Vapour phase dehydration of glycerol to acrolein was employed to investigate the catalytic functionalities. Glycerol conversion and acrolein selectivity was mainly dependent on the fraction of moderate acid sites with majority of them are due to Brønsted acidic sites. Monoclinic zirconia based catalysts have shown the highest activity and acrolein selectivity compared to the corresponding tetragonal zirconia catalysts.

Electrocatalytic activity of atomic layer deposited Pt-Ru catalysts onto N-doped carbon nanotubes

NARCIS (Netherlands)

Johansson, A.-C.; Larsen, J.V.; Verheijen, M.A.; Haugshøj, K.B.; Clausen, H.; Kessels, W.M.M.; Christensen, L.H.; Thomsen, E.V.

2014-01-01

Pt-Ru catalysts of various compositions, between 0 and 100 at.% of Ru, were deposited onto N-doped multi-walled carbon nanotubes (N-CNTs) by atomic layer deposition (ALD) at 250 C. The Pt and Ru precursors were trimethyl(methylcyclopentadienyl)platinum (MeCpPtMe3) and

Exploration of Cocatalyst Effects on a Bimetallic Cobalt Catalyst System: Enhanced Activity and Enantioselectivity in Epoxide Polymerization

KAUST Repository

Widger, Peter C. B.; Ahmed, Syud M.; Coates, Geoffrey W.

2011-01-01

Organic ionic compounds were synthesized and investigated as cocatalysts with a bimetallic cobalt complex for enantioselective epoxide polymerization. The identities of both the cation and the anion were systematically varied, and the subsequent reactivity was studied. The nature of the ionic cocatalyst dramatically impacted the rate and enantioselectivity of the catalyst system. The ionic cocatalyst [P(N=P(N(CH2)4)3) 4 +][tBuCO2 -] in combination with a bimetallic cobalt complex produced a catalyst system that exhibited the greatest activity and selectivity for a variety of monosubstituted epoxides. © 2011 American Chemical Society.

Exploration of Cocatalyst Effects on a Bimetallic Cobalt Catalyst System: Enhanced Activity and Enantioselectivity in Epoxide Polymerization

KAUST Repository

Widger, Peter C. B.

2011-07-26

Organic ionic compounds were synthesized and investigated as cocatalysts with a bimetallic cobalt complex for enantioselective epoxide polymerization. The identities of both the cation and the anion were systematically varied, and the subsequent reactivity was studied. The nature of the ionic cocatalyst dramatically impacted the rate and enantioselectivity of the catalyst system. The ionic cocatalyst [P(N=P(N(CH2)4)3) 4 +][tBuCO2 -] in combination with a bimetallic cobalt complex produced a catalyst system that exhibited the greatest activity and selectivity for a variety of monosubstituted epoxides. © 2011 American Chemical Society.

CaO Nanocatalyst for Transesterification Reaction of Palm Oil to Biodiesel: Effect of Precursor’s Concentration on the Catalyst Behavior

Science.gov (United States)

Hassan, N.; Ismail, K. N.; Hamid, K. H. Ku; Hadi, Abdul

2018-05-01

Depletion of fossil fuel sources in a few decades due to industrialization and motorization has led to a keen interest in the production of alternative fuels like biodiesel. Research on the development and improvement of more efficient transesterification process for biodiesel production has attain great attention in the last decade. The using of low cost catalyst is one of the main focuses on the biodiesel production. As a basic heterogeneous catalyst, CaO has been examined in the transesterification of vegetable oils for biodiesel production. In this research, calcium oxide (CaO-X) catalysts were prepared by sol-gel method at different Ca2+ precursor concentration (X = 1.0, 1.5, 2.0 M). The crystalline structure and morphology of the synthesized catalysts were characterized by means of x-ray diffraction (XRD) and N2 adsorption-desorption analysis. All the synthesized catalysts were then applied to transesterification reaction of palm oil to produce biodiesel. The characterization by x-ray diffraction demonstrate CaO-1.0 was partially hydrated due to the incomplete reaction during synthesis. As a matter of fact, formation of H2O on the surface of CaO causes lower basic strength of the catalysts, thus responsible in lowering the catalytic activity. It is demonstrated that CaO-2.0 exhibits mesoporous structure with least chemisorb amount of H2O on the catalysts surface has a very active catalytic activity. It was found that 2.0M of calcium precursor has high catalytic activity and 81% FAME yield was obtained within 3h reaction.

Catalysts synthesized by selective deposition of Fe onto Pt for the water-gas shift reaction

Energy Technology Data Exchange (ETDEWEB)

Aragao, Isaias Barbosa; Ro, Insoo; Liu, Yifei; Ball, Madelyn; Huber, George W.; Zanchet, Daniela; Dumesic, James A.

2018-03-01

FePt bimetallic catalysts with intimate contact between the two metals were synthesized by controlled surface reactions (CSR) of (cyclohexadiene)iron tricarbonyl with hydrogen-treated supported Pt nanoparticles. Adsorption of the iron precursor on a Pt/SiO2 catalyst was studied, showing that the Fe loading could be increased by performing multiple CSR cycles, and the efficiency of this process was linked to the renewal of adsorption sites by a reducing pretreatment. The catalytic activity of these bimetallic catalysts for the water gas shift reaction was improved due to promotion by iron, likely linked to H2O activation on FeOx species at or near the Pt surface, mostly in the (II) oxidation state.

ZrO2/bamboo leaves ash (BLA) Catalyst in Biodiesel Conversion of Rice Bran Oil

Science.gov (United States)

Fatimah, Is; Taushiyah, Ana; Badriatun Najah, Fitri; Azmi, Ulil

2018-04-01

Preparation, characterization and catalytic activity of ZrO2/bamboo leaves ash (BLA) catalyst for conversion of rice bran oil to biodiesel have been investigated. The catalyst was prepared by impregnation method of ZrOCl2 as ZrO2 precursor with BLA at a theoretical content of 20% wt. followed by calcination. The physicochemical properties of the catalyst material were characterized by x-ray diffraction (XRD), FTIR and surface acidity measurement. Activity test of materials in biodiesel conversion of rice bran oil was used by reflux method and microwave (MW) assisted method. Reaction variables studied in the investigation were the effect of catalyst weight and time of MW irradiation compared with the use reflux method. The results showed that ZrO2/BLA catalyst exhibited competitively effective and efficient processes for the production of biodiesel. The reflux method demonstrated an higher conversion (%) compared to MW method, however MW method showed the better reusable properties.

Synthesis and optical properties of Mg-Al layered double hydroxides precursor powders

Directory of Open Access Journals (Sweden)

Chia-Hsuan Lin

2017-12-01

Full Text Available The synthesis and optical properties of Mg-Al layered double hydroxide (LDH precursor powders were investigated using X-ray diffraction (XRD, Fourier transform-infrared (FT-IR spectroscopy, transmission electron microscopy (TEM, selected area electron diffraction (SAED, high-resolution TEM (HRTEM, UV-transmission spectrometer, and fluorescence spectrophotometer. The FT-IR results show that the intense absorption at around 1363–1377 cm-1 can be assigned to the antisymmetric ν3 mode of interlayer carbonate anions because the LDH phase contains some CO32-. The XRD results show that all of the Mg-Al LDH precursor powders contain only a single phase of [Mg0.833Al0.167(OH2](CO30.083·(H2O0.75 but have broad and weak intensities of peaks. All of Mg-Al LDHs precursor powders before calcination have the same photoluminescence (PL spectra. Moreover, these spectra were excited at λex = 235 nm, and the broad emission band was in the range 325-650 nm. In the range, there were relatively strong intensity at around 360, 407 and 510 nm, respectively.

Metaloxide--ZrO2 catalysts for the esterification and transesterification of free fatty acids and triglycerides to obtain bio-diesel

Energy Technology Data Exchange (ETDEWEB)

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

2016-09-06

Mixed metal oxide catalysts (ZnO, CeO, La2O3, NiO, Al203, SiO2, TiO2, Nd2O3, Yb2O3, or any combination of these) supported on zirconia (ZrO2) or hydrous zirconia are provided. These mixed metal oxide catalysts can be prepared via coprecipitation, impregnation, or sol-gel methods from metal salt precursors with/without a Zirconium salt precursor. Metal oxides/ZrO2 catalyzes both esterification and transesterification of oil containing free fatty acids in one batch or in single stage. In particular, these mixed metal oxides supported or added on zirconium oxide exhibit good activity and selectivity for esterification and transesterification. The low acid strength of this catalyst can avoid undesirable side reaction such as alcohol dehydration or cracking of fatty acids. Metal oxides/ZrO2 catalysts are not sensitive to any water generated from esterification. Thus, esterification does not require a water free condition or the presence of excess methanol to occur when using the mixed metal oxide catalyst. The FAME yield obtained with metal oxides/ZrO2 is higher than that obtained with homogeneous sulfuric acid catalyst. Metal oxides/ZrO2 catalasts can be prepared as strong pellets and in various shapes for use directly in a flow reactor. Furthermore, the pellet has a strong resistance toward dissolution to aqueous or oil phases.

Oxygen reduction activities compared in rotating-disk electrode and proton exchange membrane fuel cells for highly active Fe-N-C catalysts

International Nuclear Information System (INIS)

Jaouen, F.; Goellner, V.; Lefèvre, M.; Herranz, J.; Proietti, E.; Dodelet, J.P.

2013-01-01

In the past three years, two novel synthesis methods for non-precious metal catalysts resulting in a breakthrough of their activity and performance at the cathode of the proton-exchange membrane fuel cell (PEMFC) have been reported by the group of Prof. Dodelet. While the activity of these novel Fe-based catalysts for the oxygen reduction reaction is very high in PEMFC, our preliminary activity measurements with the rotating disk electrode (RDE) technique on one of them showed an activity being a factor 30–100 lower than the one measured in PEMFC at 80 °C. The present work explains to a large extent this huge difference. Two Fe-N-C catalysts synthesized via our novel approaches and one Fe-N-C catalyst synthesized via our classical approach were investigated in RDE and PEMFC. In both systems, the effect of the ink formulation (Nafion-to-catalyst ratio) was investigated. Optimization of the RDE ink formulation explains a factor between 5 and 10 in the two-decade gap mentioned above. Then, the effect of temperature in the RDE system was investigated. An increase from 20 to 80 °C was found to result in a theoretical maximum twofold increase in activity. However, in practice, decreased O 2 solubility with increased temperature cancels this effect. After taking into account these two parameters, a difference in ORR activity between RDE and PEMFC of ca a factor five still remained for one of the two novel Fe-N-C catalysts investigated here. The lower initial activity measured in RDE for this catalyst is shown to be due to the fast adsorption of anions (HSO 4 − ) from the liquid H 2 SO 4 electrolyte on protonated nitrogen atoms (NH + ) found on its surface. The phenomenon of anion adsorption and associated decreased ORR activity also applies to the other novel Fe-N-C catalyst, but is slower and does not immediately occur in RDE.

TiO2 nanotubes supported NiW hydrodesulphurization catalysts: Characterization and activity

International Nuclear Information System (INIS)

Palcheva, R.; Dimitrov, L.; Tyuliev, G.; Spojakina, A.; Jiratova, K.

2013-01-01

Highlights: ► NiW catalysts supported on TiO 2 nanotubes, titania and alumina. ► The best results are obtained with NiW/TiO 2 nanotubes in hydrodesulfurization (HDS) of thiophene. ► Active phase is Ni-WO x S y . ► Electronic promotion of W by Ti. - Abstract: High surface area TiO 2 nanotubes (Ti-NT) synthesized by alkali hydrothermal method were used as a support for NiW hydrodesulphurization catalyst. Nickel salt of 12-tungstophosphoric acid – Ni 3/2 PW 12 O 40 was applied as oxide precursor of the active components. The catalyst was characterized by S BET , XRD, UV–vis DRS, Raman spectroscopy, XPS, TPR and HRTEM. The results obtained were compared with those for the NiW catalysts prepared over high surface area titania and alumina supports. A polytungstate phase evidenced by Raman spectroscopy was observed indicating the destruction of the initial heteropolyanion. The catalytic experiments revealed two times higher thiophene conversion on NiW catalyst supported on Ti-NT than those of catalysts supported on alumina and titania. Increased HDS activity of the NiW catalyst supported on Ti-NT could be related to a higher amount of W oxysulfide entities interacting with Ni sulfide particles as consequence of the electronic effects of the Ti-NT observed with XPS analysis.

MORE ACTIVE AND SULFUR RESISTANT BIMETALLIC Pd-Ni CATALYSTS

OpenAIRE

Betti, Carolina; Carrara, Nicolás; Badano, Juan; Lederhos, Cecilia; Vera, Carlos; Quiroga, Mónica

2018-01-01

The influence of the kind of metal precursor and the sequence of impregnation on the properties of Pd-Ni catalysts was evaluated during the test reaction of selective hydrogenation of styrene to ethylbenzene by means of physicochemical characterization. The focus was put on the final hydrogenating activity and the resistance to deactivation by sulfided compounds (thiophene). The used techniques of characterization were ICP, XPS, XDR, TPR, CO chemisorption and TEM. XPS results indicated the pr...

Technology development for iron F-T catalysts. Final report

Energy Technology Data Exchange (ETDEWEB)

Frame, R.R.; Gala, H.B.

1994-08-01

The objectives of this work were twofold. The first objective was to design and construct a pilot plant for preparing precipitated iron oxide F-T precursors and demonstrate that the rate of production from this plant is equivalent to 100 lbs/day of dried metal oxide. Secondly, these precipitates were to be used to prepare catalysts capable of achieving 88% CO + H{sub 2} conversion with {le} 5 mole percent selectivity to methane + ethane.

Synthesis and characterization of CNTs using polypropylene waste as precursor

Energy Technology Data Exchange (ETDEWEB)

Bajad, Ganesh S. [Department of Chemical Engineering, Visvesvaraya National Institute of Technology, Nagpur 440010 (India); Tiwari, Saurabh K. [Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076 (India); Vijayakumar, R.P., E-mail: vijayakumarrp@che.vnit.ac.in [Department of Chemical Engineering, Visvesvaraya National Institute of Technology, Nagpur 440010 (India)

2015-04-15

Graphical abstract: - Highlights: • A facile method for producing CNTs from polypropylene waste is proposed. • Optimization of Ni/Mo mole ratio using RSM suggests the adequacy of cubic model. • Process parameters were optimized by RSM using Box–Behnken four factorial design. • Maximum desirability of one suggested that 514% of CNTs would yield over Ni{sub 4}Mo{sub 0.2}MgO{sub 1}. • Increase in Ni/Mo ratio from 0.5 to 20, inner diameter of CNTs decreases from 25 to 2 nm. - Abstract: We study the synthesis of MWCNTs using polypropylene waste as a precursor and Ni/Mo/MgO as a catalyst by the combustion technique. Molar ratios of Ni, Mo and MgO in the Ni/Mo/MgO catalyst were optimized using response surface methodology (RSM) to obtain the maximum yield of CNTs. The mole ratio 4/0.2/1 was found to yield more carbon product. Further, process parameters such as combustion temperature, combustion time, polymer and catalyst weight were optimized by RSM using Box–Behnken three-level and four-factorial design. The best possible combination of process parameters (combustion time of 10 min, combustion temperature of 800 °C, polymer weight of 5 g and catalyst weight of 150 mg) for maximum yield of CNTs was obtained. HRTEM indicates that the diameter of CNTs depends on the catalyst composition used for the synthesis of CNTs. The results of the study indicate a facile method for producing CNTs from polypropylene waste.

Synthesis and characterization of CNTs using polypropylene waste as precursor

International Nuclear Information System (INIS)

Bajad, Ganesh S.; Tiwari, Saurabh K.; Vijayakumar, R.P.

2015-01-01

Graphical abstract: - Highlights: • A facile method for producing CNTs from polypropylene waste is proposed. • Optimization of Ni/Mo mole ratio using RSM suggests the adequacy of cubic model. • Process parameters were optimized by RSM using Box–Behnken four factorial design. • Maximum desirability of one suggested that 514% of CNTs would yield over Ni 4 Mo 0.2 MgO 1 . • Increase in Ni/Mo ratio from 0.5 to 20, inner diameter of CNTs decreases from 25 to 2 nm. - Abstract: We study the synthesis of MWCNTs using polypropylene waste as a precursor and Ni/Mo/MgO as a catalyst by the combustion technique. Molar ratios of Ni, Mo and MgO in the Ni/Mo/MgO catalyst were optimized using response surface methodology (RSM) to obtain the maximum yield of CNTs. The mole ratio 4/0.2/1 was found to yield more carbon product. Further, process parameters such as combustion temperature, combustion time, polymer and catalyst weight were optimized by RSM using Box–Behnken three-level and four-factorial design. The best possible combination of process parameters (combustion time of 10 min, combustion temperature of 800 °C, polymer weight of 5 g and catalyst weight of 150 mg) for maximum yield of CNTs was obtained. HRTEM indicates that the diameter of CNTs depends on the catalyst composition used for the synthesis of CNTs. The results of the study indicate a facile method for producing CNTs from polypropylene waste

High Throughput In Situ XAFS Screening of Catalysts

International Nuclear Information System (INIS)

Tsapatsaris, Nikolaos; Beesley, Angela M.; Weiher, Norbert; Tatton, Helen; Schroeder, Sven L. M.; Dent, Andy J.; Mosselmans, Frederick J. W.; Tromp, Moniek; Russu, Sergio; Evans, John; Harvey, Ian; Hayama, Shu

2007-01-01

We outline and demonstrate the feasibility of high-throughput (HT) in situ XAFS for synchrotron radiation studies. An XAS data acquisition and control system for the analysis of dynamic materials libraries under control of temperature and gaseous environments has been developed. The system is compatible with the 96-well industry standard and coupled to multi-stream quadrupole mass spectrometry (QMS) analysis of reactor effluents. An automated analytical workflow generates data quickly compared to traditional individual spectrum acquisition and analyses them in quasi-real time using an HT data analysis tool based on IFFEFIT. The system was used for the automated characterization of a library of 91 catalyst precursors containing ternary combinations of Cu, Pt, and Au on γ-Al2O3, and for the in situ characterization of Au catalysts supported on Al2O3 and TiO2

Antisolvent Precipitation for the Synthesis of Monodisperse Mesoporous Niobium Oxide Spheres as Highly Effective Solid Acid Catalysts

KAUST Repository

Li, Cheng Chao; Dou, Jian; Chen, Luwei; Lin, Jianyi; Zeng, Hua Chun

2012-01-01

We have developed a low-cost reaction protocol to synthesize mesoporous Nb 2O 5-based solid acid catalysts with external shape control. In the synthesis, monodisperse glycolated niobium oxide spheres (GNOS) were prepared by means of a simple antisolvent precipitation approach and subsequently converted to mesoporous niobium oxide spheres (MNOS) with a large surface area of 312m 2g -1 by means of the hydrothermal treatment. The antisolvent acetone used to obtain GNOS was recovered through distillation at high purity. The obtained mesoporous MNOS were functionalized further with sulfate anions at different temperatures or incorporated with tungstophosphoric acid to obtain recyclable solid acid catalysts. These MNOS-based catalysts showed excellent performance in a wide range of acid-catalyzed reactions, such as Friedel-Crafts alkylation, esterification, and hydrolysis of acetates. As they are monodisperse spheres with diameters in the submicrometer range, the catalysts can be easily separated and reused. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Antisolvent Precipitation for the Synthesis of Monodisperse Mesoporous Niobium Oxide Spheres as Highly Effective Solid Acid Catalysts

KAUST Repository

Li, Cheng Chao

2012-03-20

We have developed a low-cost reaction protocol to synthesize mesoporous Nb 2O 5-based solid acid catalysts with external shape control. In the synthesis, monodisperse glycolated niobium oxide spheres (GNOS) were prepared by means of a simple antisolvent precipitation approach and subsequently converted to mesoporous niobium oxide spheres (MNOS) with a large surface area of 312m 2g -1 by means of the hydrothermal treatment. The antisolvent acetone used to obtain GNOS was recovered through distillation at high purity. The obtained mesoporous MNOS were functionalized further with sulfate anions at different temperatures or incorporated with tungstophosphoric acid to obtain recyclable solid acid catalysts. These MNOS-based catalysts showed excellent performance in a wide range of acid-catalyzed reactions, such as Friedel-Crafts alkylation, esterification, and hydrolysis of acetates. As they are monodisperse spheres with diameters in the submicrometer range, the catalysts can be easily separated and reused. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cluster-derived Ir-Sn/SiO2 catalysts for the catalytic dehydrogenation of propane: A spectroscopic study

KAUST Repository

Gallo, Alessandro

2013-01-01

Ir-Sn bimetallic silica-based materials have been prepared via deposition of the molecular organometallic clusters (NEt4)2[Ir 4(CO)10(SnCl3)2] and NEt 4[Ir6(CO)15(SnCl3)] or via deposition of Sn organometallic precursor Sn(n-C4H9) 4 onto pre-formed Ir metal particles. These solids possess promising properties, in terms of selectivity, as catalysts for propane dehydrogenation to propene. Detailed CO-adsorption DRIFTS, XANES and EXAFS characterization studies have been performed on these systems in order to compare the structural and electronic evolution of systems in relation to the nature of the Ir-Sn bonds present in the precursor compounds and to propose a structural model of the Ir-Sn species present at the silica surface of the final catalyst. © 2013 The Royal Society of Chemistry.

Efficient Pd@MIL-101(Cr) hetero-catalysts for 2-butyne-1,4-diol hydrogenation exhibiting high selectivity

KAUST Repository

Yin, Dongdong

2017-01-05

Pd@MIL-101(Cr) hetero-catalysts have been successfully prepared using the metal-organic chemical vapour deposition (MOCVD) approach, by choosing [Pd(η-CH)(η-CH)] as a volatile precursor, and the hydrothermally stable metal-organic framework, MIL-101(Cr) as a support. The prepared Pd@MIL-101(Cr) hetero-catalysts characterized with various analytical techniques, exhibited highly monodispersed immobilized Pd nanoparticles in the MIL-101(Cr) cavities, while retaining the pristine crystallinity and porosity. The intact hybrid Pd@MIL-101(Cr) has been demonstrated to be an efficient catalyst for 2-butyne-1,4-diol hydrogenation with excellent activity, stability and selectivity (2-butene-1,4-diol (>94%)).

Homogeneous and Supported Niobium Catalysts as Lewis Acid and Radical Catalysts

Energy Technology Data Exchange (ETDEWEB)

Wayne Tikkanen

2006-12-31

The synthesis of tetrachlorotetraphenylcyclopentadienyl group 5 metal complexes has been accomplished through two routes, one a salt metathesis with lithiumtetraphenylcyclopentadiende and the other, reaction with trimethyltintetraphenylcyclopentadiene. The reactants and products have been characterized by {sup 1}H and {sup 13}C({sup 1}H) NMR spectroscopy. The niobium complex promotes the silylcyanation of butyraldehyde. The grafting of metal complexes to silica gel surfaces has been accomplished using tetrakisdimethylamidozirconium as the metal precursor. The most homogeneous binding as determined by CP-MAS {sup 13}C NMR and infrared spectroscopy was obtained with drying at 500 C at 3 mtorr vacuum. The remaining amido groups can be replaced by reaction with alcohols to generate surface bound metal alkoxides. These bound catalysts promote silylcyanation of aryl aldehydes and can be reused three times with no loss of activity.

Efficient Pd@MIL-101(Cr) hetero-catalysts for 2-butyne-1,4-diol hydrogenation exhibiting high selectivity

KAUST Repository

Yin, Dongdong; Li, Chuang; Ren, Hangxing; Shekhah, Osama; Liu, Jinxuan; Liang, Changhai

2017-01-01

Pd@MIL-101(Cr) hetero-catalysts have been successfully prepared using the metal-organic chemical vapour deposition (MOCVD) approach, by choosing [Pd(η-CH)(η-CH)] as a volatile precursor, and the hydrothermally stable metal-organic framework, MIL-101

Cu–Co–O nano-catalysts as a burn rate modifier for composite solid propellants

Directory of Open Access Journals (Sweden)

D. Chaitanya Kumar Rao

2016-08-01

Full Text Available Nano-catalysts containing copper–cobalt oxides (Cu–Co–O have been synthesized by the citric acid (CA complexing method. Copper (II nitrate and Cobalt (II nitrate were employed in different molar ratios as the starting reactants to prepare three types of nano-catalysts. Well crystalline nano-catalysts were produced after a period of 3 hours by the calcination of CA–Cu–Co–O precursors at 550 °C. The phase morphologies and crystal composition of synthesized nano-catalysts were examined using Scanning Electron Microscope (SEM, Energy Dispersive Spectroscopy (EDS and Fourier Transform Infrared Spectroscopy (FTIR methods. The particle size of nano-catalysts was observed in the range of 90 nm–200 nm. The prepared nano-catalysts were used to formulate propellant samples of various compositions which showed high reactivity toward the combustion of HTPB/AP-based composite solid propellants. The catalytic effects on the decomposition of propellant samples were found to be significant at higher temperatures. The combustion characteristics of composite solid propellants were significantly improved by the incorporation of nano-catalysts. Out of the three catalysts studied in the present work, CuCo-I was found to be the better catalyst in regard to thermal decomposition and burning nature of composite solid propellants. The improved performance of composite solid propellant can be attributed to the high crystallinity, low agglomeration and lowering the decomposition temperature of oxidizer by the addition of CuCo-I nano-catalyst.

New way for iron introduction in LDH matrix used as catalysts for Friedel–Crafts reactions

Directory of Open Access Journals (Sweden)

S. Kerchiche

2017-02-01

Full Text Available The alkylation of toluene, reaction employing benzyl chloride as the alkylating agent over basic hydrotalcite materials: Fe–Mg–Al-LDH prepared by different synthesis methods, including the method of co-precipitation, impregnation and a new method called the method of intercalation by anion exchange in the lamellar space of the host structure LDH. Our prepared solids were characterized by chemical analysis, XRD analysis, BET method and thermogravimetric analysis (TGA and tested in the alkylation of toluene by benzyl chloride reaction. Fe–Mg–Al-LDH clay without or with calcination (at 773 K has been investigated. The catalyst derived from the hydrotalcite by its calcination at 773 K shows high catalytic activity for the alkylation of toluene and other aromatic compounds. The catalytically active species present in the catalyst in its most active form are the oxides of iron on the catalyst surface.

OXIDATION OF CYCLOHEXANOL ON PHOSPHOTUNGSTIC ACID ANION INTERCALATED LAYERED DOUBLE HYDROXIDES WITH AQUEOUS H2O2 AS OXIDANT

Directory of Open Access Journals (Sweden)

Xueli Bai

Full Text Available The layered double hydroxides (LDH of Mg2AlNi and Mg3Al pillared by Keggin-type phosphotungstic acid anion (POM, i.e. Mg2AlNi-POM LDH and Mg3Al-POM LDH were synthesized by an ion-exchange method. The synthesized POM intercalated LDH compounds were characterized using various techniques such as FTIR, XRD, TGA and BET. The observed results show that the obtained catalysts retain the layer structure of LDH. Compared with the binary Mg3Al-POM LDH, the ternary Mg2AlNi-POM LDH catalyst indicated a higher thermal and chemical stability. The catalytic activity of the resulting LDH-POM was also assessed in the green oxidation of cyclohexanol with aqueous H2O2 as an oxidant. The Mg2AlNi-POM LDH showed a much higher conversion and selectivity for cyclohexanone than the corresponding Mg3Al-POM LDH catalyst.

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.

CATALYTIC PERFORMANCES OF Fe2O3/TS-1 CATALYST IN PHENOL HYDROXYLATION REACTION

Directory of Open Access Journals (Sweden)

Didik Prasetyoko

2010-07-01

Full Text Available Hydroxylation reaction of phenol into diphenol, such as hydroquinone and catechol, has a great role in many industrial applications. Phenol hydroxylation reaction can be carried out using Titanium Silicalite-1 (TS-1 as catalyst and H2O2 as an oxidant. TS-1 catalyst shows high activity and selectivity for phenol hydroxylation reaction. However, its hydrophobic sites lead to slow H2O2 adsorption toward the active site of TS-1. Consequently, the reaction rate of phenol hydroxylation reaction is tends to be low. Addition of metal oxide Fe2O3 enhanced hydrophilicity of TS-1 catalyst. Liquid phase catalytic phenol hydroxylation using hydrogen peroxide as oxidant was carried out over iron (III oxide-modified TS-1 catalyst (Fe2O3/TS-1, that were prepared by impregnation method using iron (III nitrate as precursor and characterized by X-ray diffraction, infrared spectroscopy, nitrogen adsorption, pyridine adsorption, and hydrophilicity techniques. Catalysts 1Fe2O3/TS-1 showed maximum catalytic activity of hydroquinone product. In this research, the increase of hydroquinone formation rate is due to the higher hydrophilicity of Fe2O3/TS-1 catalysts compare to the parent catalyst, TS-1.   Keywords: Fe2O3/TS-1, hydrophilic site, phenol hydroxylation

Cross-Aldol condensation of isobutyraldehyde and formaldehyde using phase transfer catalyst

Directory of Open Access Journals (Sweden)

Azhar Hashmi

2016-09-01

Full Text Available The hydroxypivaldehyde (HPA precursor intermediate for the synthesis of neopentyl glycol (NPG is prepared by novel cross Aldol condensation of isobutyraldehyde and formaldehyde at 20 °C using benzyltrimethylammonium hydroxide, a basic phase transfer catalyst. A feed mole ratio of 1.1:1.0:0.04 (isobutyraldehyde:formaldehyde:benzyltrimethylammonium hydroxide afforded hydroxypivaldehyde as white solid in almost quantitative yield with ∼100% selectivity.

Cross-Aldol condensation of isobutyraldehyde and formaldehyde using phase transfer catalyst

OpenAIRE

Azhar Hashmi

2016-01-01

The hydroxypivaldehyde (HPA) precursor intermediate for the synthesis of neopentyl glycol (NPG) is prepared by novel cross Aldol condensation of isobutyraldehyde and formaldehyde at 20 °C using benzyltrimethylammonium hydroxide, a basic phase transfer catalyst. A feed mole ratio of 1.1:1.0:0.04 (isobutyraldehyde:formaldehyde:benzyltrimethylammonium hydroxide) afforded hydroxypivaldehyde as white solid in almost quantitative yield with ∼100% selectivity.

Fischer-Tropsch Performance of an SiO2-Supported Co-Based Catalyst Prepared by Hydrogen Dielectric-Barrier Discharge Plasma

International Nuclear Information System (INIS)

Fu Tingjun; Huang Chengdu; Lv Jing; Li Zhenhua

2014-01-01

A silica-supported cobalt catalyst was prepared by hydrogen dielectric-barrier discharge (H 2 -DBD) plasma. Compared to thermal hydrogen reduction, H 2 -DBD plasma treatment can not only fully decompose the cobalt precursor but also partially reduce the cobalt oxides at lower temperature and with less time. The effect of the discharge atmosphere on the property of the plasma-prepared catalyst and the Fischer-Tropsch synthesis activity was studied. The results indicate that H 2 -DBD plasma treatment is a promising alternative for preparing Co/SiO 2 catalysts from the viewpoint of energy savings and efficiency

The challenges of treating high strength wastewaters: CWAO using MWNT supported ruthenium catalysts

International Nuclear Information System (INIS)

GarcIa, J.; Gomes, H.T.; Figueiredo, J.L.; Faria, J.L.; Garcia, J.; Serp, P.; Kalck, P.

2005-01-01

High strength wastewaters containing aromatic compounds are normally not efficiently treated by conventional methods, including the common biological treatment. In these cases a more sophisticated approach is necessary to attain the desired levels of purification. Catalytic wet air oxidation (CWAO) using carbon based catalysts is employed worldwide as effective pre-treatment of effluents with these characteristics. Carbon materials are preferred as active catalysts or support for preparing them due to their morphological and structural characteristics. In the last 10 years, due to a tremendous development in materials production and processing, carbon nano-structures are becoming more accessible and common widening their range of applications [1]. In this context, the scope of the present work is to illustrate a potential use of multi-walled carbon nano-tubes (MWNT) supported ruthenium catalysts for catalytic wet air oxidation of aniline polluted wastewaters. The metal was supported by incipient wetness and excess impregnation, starting from liquid solutions of three different Ru precursors. Impregnation was carried out on modified MWNT, namely on MWNT-COOH (HNO 3 modified) and MWNT-COONa (HNO 3 /Na 2 CO 3 modified). For the 1% weight Ru/MWNT catalysts, the order of activities decreased in the sequence Ru(COD)(COT)≥RuCl 3 ≥Ru(C 5 H 5 ) 2 . The conversion of aniline after 45 min of reaction was 100% for the catalyst prepared with Ru(COD)(COT). The influence of the Ru precursor, preparation method and the support surface modification was studied comparing the conversion of aniline obtained for the different prepared Ru/MWNT catalysts (Figure 1). MWNT as support material, provide a significant metal dispersion with very small Ru nanoparticles (Figure 2) being observed. This will induce an efficient surface contact between the aniline molecule and the active sites [2]. The excellent catalytic performances of Ru/MWNT are explained in terms of the high dispersion of

Removal of both N-nitrosodimethylamine and trihalomethanes precursors in a single treatment using ion exchange resins.

Science.gov (United States)

Beita-Sandí, Wilson; Karanfil, Tanju

2017-11-01

Drinking water utilities are relying more than ever on water sources impacted by wastewater effluents. Disinfection/oxidation of these waters during water treatment may lead to the formation of several disinfection by-products, including the probable human carcinogen N-nitrosodimethylamine (NDMA) and the regulated trihalomethanes (THMs). In this study, the potential of ion exchange resins to control both NDMA and THMs precursors in a single treatment is presented. Two ion exchange resins were examined, a cation exchange resin (Plus) to target NDMA precursors and an anion exchange resin (MIEX) for THMs precursors control. We applied the resins, individually and combined, in the treatment of surface and wastewater effluent samples. The treatment with both resins removed simultaneously NDMA (43-85%) and THMs (39-65%) precursors. However, no removal of NDMA precursors was observed in the surface water with low initial NDMA FP (14 ng/L). The removals of NDMA FP and THMs FP with Plus and MIEX resins applied alone were (49-90%) and (41-69%), respectively. These results suggest no interaction between the resins, and thus the feasibility of effectively controlling NDMA and THMs precursors concomitantly. Additionally, the effects of the wastewater impact and the natural attenuation of precursors were studied. The results showed that neither the wastewater content nor the attenuation of the precursor affected the removals of NDMA and THMs precursors. Finally, experiments using a wastewater effluent sample showed that an increase in the calcium concentration resulted in a reduction in the removal of NDMA precursors of about 50%. Copyright © 2017 Elsevier Ltd. All rights reserved.

Development of CuxFe/Al2O3 catalysts for the hydrogenation of carbon monoxide guided by magnetic methods, Moessbauer and infrared spectroscopy

International Nuclear Information System (INIS)

Boellaard, E.; Geus, J.W.; Bruggen, J.M. van; Kraan, A.M. van der

1993-01-01

A copper-iron catalyst for the hydrogenation of carbon monoxide has been prepared using a supported stoichiometric cyanide complex. Conversion of the cyanide precursor to a metallic catalyst appeared to be a precious process. Copper and iron in the bimetallic particles easily separate by thermal treatment and upon exposure to carbon monoxide, as revealed from Moessbauer and infrared spectroscopy. During Fischer-Tropsch reaction the catalyst exhibits a rapid decline of activity. Magnetisation measurements on spent catalysts indicate that the deactivation is caused by a fast conversion of metallic iron to initially unstable carbides which transform ultimately to more stable carbides. (orig.)

CO{sub 2} REFORMING OF METHANE TO SYNGAS OVER HYDROTALCITES DERRIVED CATALYSTS

Energy Technology Data Exchange (ETDEWEB)

Z. Abdelssadek; F. Touahra; A. Saadi; O. Cherifi; D. Halliche [Laboratoire de Chimie du Gaz Naturel, Faculte de Chimie, El-Alia, Alger (Algeria); K. Bachari [Centre de recherches scientifiques et techniques en analyses physico-chimiques, Alger (Algeria)

2008-09-30

Considerable attention has been paid to the catalytic reforming of CH4 with CO2 to synthesis gas (CH4 + CO2 - 2CO + 2H2 ) in recent years. This reaction has very important environmental implications since both CH4 and CO2 contribute to the green house effect. They are also two of the most important abundant carbon-containing materials. Therefore, converting these two gases into a valuable synthesis gas may not only reduce atmospheric emissions of CO2 and CH4 , but also satisfy the requirement of many synthesis processes. In addition, the synthesis gas produced by this reaction has a high CO content, it is more suitable for the synthesis of valuable oxygenated chemicals then that produced by conventional steam reforming. Great efforts have been focused on the development of catalysts which show high activity and stability. Layered double hydroxides (LDH), are a class of synthetic two-dimensional nanostructured anionic clays catalysts. The catalysts obtained are characterized by ICP method, DRX, FTIR and BET methods. The data obtained from chemical analysis of the calcined catalysts confirmed that the n (M2+) / n(M3+) ratio is close to the intended value of 2. Room temperature FT-IR spectra were recorded in the range 4000 - 400 cm-1 , on a Perkin Elmer spectrometer. Catalysts stability were carried out at 650 C and a 1:1 CO2 / CH4 feed ratio. It was found that performances of catalysts after 6 h in reaction indicates that within this period nor or little deactivation takes place over them: At 650 C, the NiMgAL-HDL, NiMgLa-LDH catalysts reach respectively 54.0%, 69.0%, of methane conversion versus 75.0% 79.3% respectively of CO2 conversion. However, Co- catalysts did not show any catalytic activity in these experiments conditions.

Iron Fischer-Tropsch Catalysts Prepared by Solvent-Deficient Precipitation (SDP: Effects of Washing, Promoter Addition Step, and Drying Temperature

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Kyle M. Brunner

2015-07-01

Full Text Available A novel, solvent-deficient precipitation (SDP method for catalyst preparation in general and for preparation of iron FT catalysts in particular is reported. Eight catalysts using a 23 factorial design of experiments to identify the key preparation variables were prepared. The catalysts were characterized by electron microprobe, N2 adsorption, TEM, XRD, and ICP. Results show that the morphology of the catalysts, i.e., surface area, pore volume, pore size distribution, crystallite sizes, and promoter distribution are significantly influenced by (1 whether or not the precursor catalyst is washed, (2 the promoter addition step, and (3 the drying condition (temperature. Consequently, the activity, selectivity, and stability of the catalysts determined from fixed-bed testing are also affected by these three variables. Unwashed catalysts prepared by a one-step method and dried at 100 °C produced the most active catalysts for FT synthesis. The catalysts of this study prepared by SDP compared favorably in activity, productivity, and stability with Fe FT catalysts reported in the literature. It is believed that this facile SDP approach has promise for development of future FT catalysts, and also offers a potential alternate route for the preparation of other catalysts for various other applications.

Cytotoxic mechanisms of hydrosulfide anion and cyanide anion in primary rat hepatocyte cultures

International Nuclear Information System (INIS)

Thompson, Rodney W.; Valentine, Holly L.; Valentine, William M.

2003-01-01

Hydrogen sulfide and hydrogen cyanide are known to compromise mitochondrial respiration through inhibition of cytochrome c oxidase and this is generally considered to be their primary mechanism of toxicity. Experimental studies and the efficiency of current treatment protocols suggest that H 2 S may exert adverse physiological effects through additional mechanisms. To evaluate the role of alternative mechanisms in H 2 S toxicity, the relative contributions of electron transport inhibition, uncoupling of mitochondrial respiration, and opening of the mitochondrial permeability transition pore (MPTP) to hydrosulfide and cyanide anion cytotoxicity in primary hepatocyte cultures were examined. Supplementation of hepatocytes with the glycolytic substrate, fructose, rescued hepatocytes from cyanide anion induced toxicity, whereas fructose supplementation increased hydrosulfide anion toxicity suggesting that hydrosulfide anion may compromise glycolysis in hepatocytes. Although inhibitors of the MPTP opening were protective for hydrosulfide anion, they had no effect on cyanide anion toxicity, consistent with an involvement of the permeability transition pore in hydrosulfide anion toxicity but not cyanide anion toxicity. Exposure of isolated rat liver mitochondria to hydrosulfide did not result in large amplitude swelling suggesting that if H 2 S induces the permeability transition it does so indirectly through a mechanism requiring other cellular components. Hydrosulfide anion did not appear to be an uncoupler of mitochondrial respiration in hepatocytes based upon the inability of oligomycin and fructose to protect hepatocytes from hydrosulfide anion toxicity. These findings support mechanisms additional to inhibition of cytochrome c oxidase in hydrogen sulfide toxicity. Further investigations are required to assess the role of the permeability transition in H 2 S toxicity, determine whether similar affects occur in other cell types or in vivo and evaluate whether this may

Facile Synthesis of Highly Aligned Multiwalled Carbon Nanotubes from Polymer Precursors

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Catherine Y. Han

2009-01-01

Full Text Available We report a facile one-step approach which involves no flammable gas, no catalyst, and no in situ polymerization for the preparation of well-aligned carbon nanotube array. A polymer precursor is placed on top of an anodized aluminum oxide (AAO membrane containing regular nanopore arrays, and slow heating under Ar flow allows the molten polymer to wet the template through adhesive force. The polymer spread into the nanopores of the template to form polymer nanotubes. Upon carbonization the resulting multi-walled carbon nanotubes duplicate the nanopores morphology precisely. The process is demonstrated for 230, 50, and 20 nm pore membranes. The synthesized carbon nanotubes are characterized with scanning/transmission electron microscopies, Raman spectroscopy, and resistive measurements. Convenient functionalization of the nanotubes with this method is demonstrated through premixing CoPt nanoparticles in the polymer precursors.

Facile synthesis of highly aligned multiwalled carbon nanotubes from polymer precursors.

Energy Technology Data Exchange (ETDEWEB)

Han, C. Y.; Xiao, Z.-L.; Wang, H. H.; Lin, X.-M.; Trasobares, S.; Cook, R. E.; Richard J. Daley Coll.; Northern Illinois Univ.; Univ. de Cadiz

2009-01-01

We report a facile one-step approach which involves no flammable gas, no catalyst, and no in situ polymerization for the preparation of well-aligned carbon nanotube array. A polymer precursor is placed on top of an anodized aluminum oxide (AAO) membrane containing regular nanopore arrays, and slow heating under Ar flow allows the molten polymer to wet the template through adhesive force. The polymer spread into the nanopores of the template to form polymer nanotubes. Upon carbonization the resulting multi-walled carbon nanotubes duplicate the nanopores morphology precisely. The process is demonstrated for 230, 50, and 20 nm pore membranes. The synthesized carbon nanotubes are characterized with scanning/transmission electron microscopies, Raman spectroscopy, and resistive measurements. Convenient functionalization of the nanotubes with this method is demonstrated through premixing CoPt nanoparticles in the polymer precursors.

Enantioselective polymerization of epoxides using biaryl-linked bimetallic cobalt catalysts: A mechanistic study

KAUST Repository

Ahmed, Syud M.

2013-12-18

The enantioselective polymerization of propylene oxide (PO) using biaryl-linked bimetallic salen Co catalysts was investigated experimentally and theoretically. Five key aspects of this catalytic system were examined: (1) the structural features of the catalyst, (2) the regio- and stereoselectivity of the chain-growth step, (3) the probable oxidation and electronic state of Co during the polymerization, (4) the role of the cocatalyst, and (5) the mechanism of monomer enchainment. Several important insights were revealed. First, density functional theory (DFT) calculations provided detailed structural information regarding the regio- and stereoselective chain-growth step. Specifically, the absolute stereochemistry of the binaphthol linker determines the enantiomer preference in the polymerization, and the interaction between the salen ligand and the growing polymer chain is a fundamental aspect of enantioselectivity. Second, a new bimetallic catalyst with a conformationally flexible biphenol linker was synthesized and found to enantioselectively polymerize PO, though with lower enantioselectivity than the binaphthol linked catalysts. Third, DFT calculations revealed that the active form of the catalyst has two active exo anionic ligands (chloride or carboxylate) and an endo polymer alkoxide which can ring-open an adjacent cobalt-coordinated epoxide. Fourth, calculations showed that initiation is favored by an endo chloride ligand, while propagation is favored by the presence of two exo carboxylate ligands. © 2013 American Chemical Society.

Enantioselective polymerization of epoxides using biaryl-linked bimetallic cobalt catalysts: A mechanistic study

KAUST Repository

Ahmed, Syud M.; Poater, Albert; Childers, M. Ian; Widger, Peter C B; Lapointe, Anne M.; Lobkovsky, Emil B.; Coates, Geoffrey W.; Cavallo, Luigi

2013-01-01

The enantioselective polymerization of propylene oxide (PO) using biaryl-linked bimetallic salen Co catalysts was investigated experimentally and theoretically. Five key aspects of this catalytic system were examined: (1) the structural features of the catalyst, (2) the regio- and stereoselectivity of the chain-growth step, (3) the probable oxidation and electronic state of Co during the polymerization, (4) the role of the cocatalyst, and (5) the mechanism of monomer enchainment. Several important insights were revealed. First, density functional theory (DFT) calculations provided detailed structural information regarding the regio- and stereoselective chain-growth step. Specifically, the absolute stereochemistry of the binaphthol linker determines the enantiomer preference in the polymerization, and the interaction between the salen ligand and the growing polymer chain is a fundamental aspect of enantioselectivity. Second, a new bimetallic catalyst with a conformationally flexible biphenol linker was synthesized and found to enantioselectively polymerize PO, though with lower enantioselectivity than the binaphthol linked catalysts. Third, DFT calculations revealed that the active form of the catalyst has two active exo anionic ligands (chloride or carboxylate) and an endo polymer alkoxide which can ring-open an adjacent cobalt-coordinated epoxide. Fourth, calculations showed that initiation is favored by an endo chloride ligand, while propagation is favored by the presence of two exo carboxylate ligands. © 2013 American Chemical Society.

Effect of Gas Flowrate on Nucleation Mechanism of MWCNTs for a Compound Catalyst

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S. Shukrullah

2017-01-01

Full Text Available Activation of the catalyst particles during a CVD process can be anticipated from the carbon feeding rate. In this study, Fe2O3/Al2O3 catalyst was synthesized with uniformly dispersed iron over alumina support for onward production of multiwalled carbon nanotubes (MWCNTs in a fluidized bed chemical CVD reactor. The effect of the ethylene flowrate on catalytic activity of the compound catalyst and morphology of the as-grown MWCNTs was also investigated in this study. The dispersed active phases of the catalyst and optimized gas flowrate helped in improving the tube morphology and prevented the aggregation of the as-grown MWCNTs. The flowrates, below 100 sccm, did not provide sufficient reactants to interact with the catalyst for production of defect-free CNT structures. Above 100 sccm, concentration of the carbon precursor did not show notable influence on decomposition rate of the gas molecules. The most promising results on growth and structural properties of MWCNTs were gained at ethylene flowrate of 100 sccm. At this flowrate, the ratio of G and D intensity peaks (IG/ID was deliberated about 1.40, which indicates the growth of graphitic structures of MWCNTs.

Ação promotora do berílio em catalisadores da síntese do estireno Promotor action of beryllium in catalysts for styrene production

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Mário Nilo Mendes Barbosa

1997-10-01

Full Text Available The catalytic dehydrogenation of ethylbenzene in presence of steam is the main commercial route to produce styrene. The industrial catalysts are potassium- and chromia-doped hematite which show low surface areas leading to bad performance and short life. In order to develop catalysts with high areas, the effect of beryllium on the textural properties and on the catalytic performance of this iron oxide was studied. The influence of the amount of the dopant, the starting material and the calcination temperature were also studied. In sample preparations, iron and beryllium salts (nitrate or sulfate were hydrolyzed with ammonia and then calcinated. The experiments followed a factorial design with two variables in two levels (Fe/Be= 3 and 7; calcination temperature= 500 and 700ºC. Solids without any dopant were also prepared. Samples were characterized by elemental analysis, infrared spectroscopy, surface area and porosity measurements, X-ray diffraction, DSC and TG. The catalysts were tested in a microreactor at 524ºC and 1 atm, by using a mole ratio of steam/ ethylbenzene=10. The selectivity was measured by monitoring styrene, benzene and toluene formation. It was found that the effect of beryllium on the characteristics of hematite and on its catalytic performance depends on the starting material and on the amount of dopant. Surface areas increased due to the dopant as well as the nature of the precursor; samples produced by beryllium sulfate showed higher areas. Beryllium-doped solids showed a higher catalytic activity when compared to pure hematite, but no significant influence of the anion of starting material was noted. It can be concluded that beryllium acts as both textural and structural promoter. Samples with Fe/Be= 3, heated at 500ºC, lead to the highest conversion and were the most selective. However, catalysts prepared from beryllium sulfate are the most promising to ethylbenzene dehydrogenation due to their high surface area which

Modelling the transport of carbonic acid anions through anion-exchange membranes

International Nuclear Information System (INIS)

Nikonenko, V.; Lebedev, K.; Manzanares, J.A.; Pourcelly, G.

2003-01-01

Electrodiffusion of carbonate and bicarbonate anions through anion-exchange membranes (AEM) is described on the basis of the Nernst-Planck equations taking into account coupled hydrolysis reactions in the external diffusion boundary layers (DBLs) and internal pore solution. The model supposes local electroneutrality as well as chemical and thermodynamic equilibrium. The transport is considered in three layers being an anion exchange membrane and two adjoining diffusion layers. A mechanism of competitive transport of HCO 3 - and CO 3 2- anions through the membrane which takes into account Donnan exclusion of H + ions is proposed. It is predicted that the pH of the depleting solution decreases and that of the concentrating solution increases during electrodialysis (ED). Eventual deviations from local electroneutrality and local chemical equilibrium are discussed

Development of high-speed reactive processing system for carbon fiber-reinforced polyamide-6 composite: In-situ anionic ring-opening polymerization

International Nuclear Information System (INIS)

Kim, Sang-Woo; Seong, Dong Gi; Yi, Jin-Woo; Um, Moon-Kwang

2016-01-01

In order to manufacture carbon fiber-reinforced polyamide-6 (PA-6) composite, we optimized the reactive processing system. The in-situ anionic ring-opening polymerization of ε-caprolactam was utilized with proper catalyst and initiator for PA-6 matrix. The mechanical properties such as tensile strength, inter-laminar shear strength and compressive strength of the produced carbon fiber-reinforced PA-6 composite were measured, which were compared with the corresponding scanning electron microscope (SEM) images to investigate the polymer properties as well as the interfacial interaction between fiber and polymer matrix. Furthermore, kinetics of in-situ anionic ring-opening polymerization of ε-caprolactam will be discussed in the viewpoint of increasing manufacturing speed and interfacial bonding between PA-6 matrix and carbon fiber during polymerization.

Development of high-speed reactive processing system for carbon fiber-reinforced polyamide-6 composite: In-situ anionic ring-opening polymerization

Energy Technology Data Exchange (ETDEWEB)

Kim, Sang-Woo; Seong, Dong Gi; Yi, Jin-Woo; Um, Moon-Kwang [Composites Research Division, Korea Institute of Materials Science (KIMS), Changwon, Gyeongnam, 642–831 (Korea, Republic of)

2016-05-18

In order to manufacture carbon fiber-reinforced polyamide-6 (PA-6) composite, we optimized the reactive processing system. The in-situ anionic ring-opening polymerization of ε-caprolactam was utilized with proper catalyst and initiator for PA-6 matrix. The mechanical properties such as tensile strength, inter-laminar shear strength and compressive strength of the produced carbon fiber-reinforced PA-6 composite were measured, which were compared with the corresponding scanning electron microscope (SEM) images to investigate the polymer properties as well as the interfacial interaction between fiber and polymer matrix. Furthermore, kinetics of in-situ anionic ring-opening polymerization of ε-caprolactam will be discussed in the viewpoint of increasing manufacturing speed and interfacial bonding between PA-6 matrix and carbon fiber during polymerization.

pH-dependent release of trace elements including platinum group elements (PGEs) from gasoline and diesel catalysts

Science.gov (United States)

Sucha, Veronika; Mihaljevic, Martin; Ettler, Vojtech; Strnad, Ladislav

2014-05-01

The release of trace metals and platinum group elements (PGEs) from automobile exhaust catalysts represents a remarkable source of higly dispersed environmental contamination. Especially, PGEs have shown increasing research interest due to their possible bioaccessibility. In our research, we focused on leaching behaviour of trace metals from gasoline and diesel automobile catalysts. While catalysts for gasoline engines contain a mixture of Pt-Pd-Rh or Pd-Rh, catalysts for diesel engines are composed only of Pt. We used dust from two crushed gasoline and two crushed diesel catalysts (new and aged). The dust of gasoline catalysts contains significant concentrations of Pt (700 mg.kg-1), Pd (11 000 mg.kg-1) and Rh (700 mg.kg-1). And the dust of diesel catalysts are composed of Pt (3 900 mg.kg-1) and they contains negligible amounts of Pd dan Rh (leaching of trace metals from dust we used pH-stat leaching test according to the European standard CEN/TS 14997. The concentrations of cations: PGEs (Pt, Pd a Rh), K, Na, Ca, Mg, Al, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb, La and Ce were determined by inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectrometry (AAS), and anions: F-, Cl-, SO42- and NO3- by high-performance liquid chromatography. Although the dusts from catalysts were relatively stable to acid/base influence, the leaching of trace metals from catalysts showed a dependence on pH. Generally, the highest concentrations were released under acidic conditions. The leaching of PGEs was higher for Pt in diesel catalysts and for Pd and Rh in gasoline catalysts. The highest concentrations of Zn and Pb were observed in old catalysts. The rare earth metals were released more from gasoline catalysts. Catalysts particles represent health risk especially with respect to their PGEs contents.

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.

Multi-Directional Growth of Aligned Carbon Nanotubes Over Catalyst Film Prepared by Atomic Layer Deposition

Directory of Open Access Journals (Sweden)

Zhou Kai

2010-01-01

Full Text Available Abstract The structure of vertically aligned carbon nanotubes (CNTs severely depends on the properties of pre-prepared catalyst films. Aiming for the preparation of precisely controlled catalyst film, atomic layer deposition (ALD was employed to deposit uniform Fe2O3 film for the growth of CNT arrays on planar substrate surfaces as well as the curved ones. Iron acetylacetonate and ozone were introduced into the reactor alternately as precursors to realize the formation of catalyst films. By varying the deposition cycles, uniform and smooth Fe2O3 catalyst films with different thicknesses were obtained on Si/SiO2 substrate, which supported the growth of highly oriented few-walled CNT arrays. Utilizing the advantage of ALD process in coating non-planar surfaces, uniform catalyst films can also be successfully deposited onto quartz fibers. Aligned few-walled CNTs can be grafted on the quartz fibers, and they self-organized into a leaf-shaped structure due to the curved surface morphology. The growth of aligned CNTs on non-planar surfaces holds promise in constructing hierarchical CNT architectures in future.

A Novel Synthesis of Gold Nanoparticles Supported on Hybrid Polymer/Metal Oxide as Catalysts for p-Chloronitrobenzene Hydrogenation

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Cristian H. Campos

2017-01-01

Full Text Available This contribution reports a novel preparation of gold nanoparticles on polymer/metal oxide hybrid materials (Au/P[VBTACl]-M metal: Al, Ti or Zr and their use as heterogeneous catalysts in liquid phase hydrogenation of p-chloronitrobenzene. The support was prepared by in situ radical polymerization/sol gel process of (4-vinyl-benzyltrimethylammonium chloride and 3-(trimethoxysilylpropyl methacrylate in conjunction with metal-alkoxides as metal oxide precursors. The supported catalyst was prepared by an ion exchange process using chloroauric acid (HAuCl4 as gold precursor. The support provided the appropriate environment to induce the spontaneous reduction and deposition of gold nanoparticles. The hybrid material was characterized. TEM and DRUV-vis results indicated that the gold forms spherical metallic nanoparticles and that their mean diameter increases in the sequence, Au/P[VBTACl]-Zr > Au/P[VBTACl]-Al > Au/P[VBTACl]-Ti. The reactivity of the Au catalysts toward the p-CNB hydrogenation reaction is attributed to the different particle size distributions of gold nanoparticles in the hybrid supports. The kinetic pseudo-first-order constant values for the catalysts in the hydrogenation reaction increases in the order, Au/P[VBTACl]-Al > Au/P[VBTACl]-Zr > Au/P[VBTACl]-Ti. The selectivity for all the catalytic systems was greater than 99% toward the chloroaniline target product. Finally the catalyst supported on the hybrid with Al as metal oxide could be reused at least four times without loss in activity or selectivity for the hydrogenation of p-CNB in ethanol as solvent.

Dual Tuning of Ni-Co-A (A = P, Se, O) Nanosheets by Anion Substitution and Holey Engineering for Efficient Hydrogen Evolution.

Science.gov (United States)

Fang, Zhiwei; Peng, Lele; Qian, Yumin; Zhang, Xiao; Xie, Yujun; Cha, Judy J; Yu, Guihua

2018-04-18

Seeking earth-abundant electrocatalysts with high efficiency and durability has become the frontier of energy conversion research. Mixed-transition-metal (MTM)-based electrocatalysts, owing to the desirable electrical conductivity, synergistic effect of bimetal atoms, and structural stability, have recently emerged as new-generation hydrogen evolution reaction (HER) electrocatalysts. However, the correlation between anion species and their intrinsic electrocatalytic properties in MTM-based electrocatalysts is still not well understood. Here we present a novel approach to tuning the anion-dependent electrocatalytic characteristics in MTM-based catalyst for HER, using holey Ni/Co-based phosphides/selenides/oxides (Ni-Co-A, A = P, Se, O) as the model materials. The electrochemical results, combined with the electrical conductivity measurement and DFT calculation, reveal that P substitution could modulate the electron configuration, lower the hydrogen adsorption energy, and facilitate the desorption of hydrogen on the active sites in Ni-Co-A holey nanostructures, resulting in superior HER catalytic activity. Accordingly we fabricate the NCP holey nanosheet electrocatalyst for HER with an ultralow onset overpotential of nearly zero, an overpotential of 58 mV, and long-term durability, along with an applied potential of 1.56 V to boost overall water splitting at 10 mA cm -2 , among the best electrocatalysts reported for non-noble-metal catalysts to date. This work not only presents a deeper understanding of the intrinsic HER electrocatalytic properties for MTM-based electrocatalyst with various anion species but also offers new insights to better design efficient and durable water-splitting electrocatalysts.

Application of New Electrolyte Model to Phase Transfer Catalyst (PTC) Systems

DEFF Research Database (Denmark)

Hyung Kim, Sun; Anantpinijwatna, Amata; Kang, Jeong Won

2015-01-01

Abstract Phase transfer catalyst (PTC) is used to transfer the desirable active form of an anion from the aqueous phase to organic phase where the reaction occurs. One of major challenges for process design of the PTC system is to establish a reliable thermodynamic model capable of describing pha...... in PTC systems, thereby, extending the application range of the PTC-system model. The solubility of PTC in organic solvents, which is a key factor for strategy of PTC and solvent selection, has been calculated using the e-NRTL-SAC model....

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

Structure of alumina supported vanadia catalysts for oxidative dehydrogenation of propane prepared by flame spray pyrolysis

DEFF Research Database (Denmark)

Høj, Martin; Jensen, Anker Degn; Grunwaldt, Jan-Dierk

2013-01-01

.%. The catalysts were subsequently characterized by BET surface area, X-ray diffraction (XRD), Raman, UV–vis diffuse reflectance and X-ray absorption spectroscopy (XAS) as well as measurement of the catalytic performance. The catalysts had specific surface areas from 143 to 169 m2/g corresponding to average......A series of five vanadia on alumina catalysts for oxidative dehydrogenation of propane to propene were synthesized by flame spray pyrolysis (FSP) using vanadium(III)acetylacetonate and aluminium(III)acetylacetonate dissolved in toluene as precursors. The vanadium loading was 2, 3, 5, 7.5 and 10wt...... X-ray absorption near edge structure (XANES) spectroscopy showed that the vanadia can be reduced when operating at low oxygen concentrations. The catalyst performance was determined in fixed bed reactors with an inlet gas composition of C3H8/O2/N2=5/25/70. The main products were propene, CO and CO2...

Geomaterials: their application to environmental remediation

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Hirohisa Yamada, Kenji Tamura, Yujiro Watanabe, Nobuo Iyi and Kazuya Morimoto

2011-01-01

Full Text Available Geomaterials are materials inspired by geological systems originating from the billion years long history of the Earth. This article reviews three important classes of geomaterials. The first one is smectites—layered silicates with a cation-exchange capacity. Smectites are useful for removing pollutants and as intercalation compounds, catalysts and polymer nanocomposites. The second class is layered double hydroxides (LDHs. They have an anion-exchange capacity and are used as catalysts, catalyst precursors, sorbents and scavengers for halogens. The third class of geomaterials is zeolites—microporous materials with a cation-exchange capacity which are used for removing harmful cations. Zeolite composites with LDHs can absorb ammonium and phosphate ions in rivers and lakes, whereas zeolite/apatite composites can immobilize the radioactive iodine. These geomaterials are essential for environmental remediation.

Geomaterials: their application to environmental remediation

Science.gov (United States)

Yamada, Hirohisa; Tamura, Kenji; Watanabe, Yujiro; Iyi, Nobuo; Morimoto, Kazuya

2011-01-01

Geomaterials are materials inspired by geological systems originating from the billion years long history of the Earth. This article reviews three important classes of geomaterials. The first one is smectites—layered silicates with a cation-exchange capacity. Smectites are useful for removing pollutants and as intercalation compounds, catalysts and polymer nanocomposites. The second class is layered double hydroxides (LDHs). They have an anion-exchange capacity and are used as catalysts, catalyst precursors, sorbents and scavengers for halogens. The third class of geomaterials is zeolites—microporous materials with a cation-exchange capacity which are used for removing harmful cations. Zeolite composites with LDHs can absorb ammonium and phosphate ions in rivers and lakes, whereas zeolite/apatite composites can immobilize the radioactive iodine. These geomaterials are essential for environmental remediation. PMID:27877455

Manganese catalysts with bulky bipyridine ligands for the electrocatalytic reduction of carbon dioxide: eliminating dimerization and altering catalysis.

Science.gov (United States)

Sampson, Matthew D; Nguyen, An D; Grice, Kyle A; Moore, Curtis E; Rheingold, Arnold L; Kubiak, Clifford P

2014-04-09

With the goal of improving previously reported Mn bipyridine electrocatalysts in terms of increased activity and reduced overpotential, a bulky bipyridine ligand, 6,6'-dimesityl-2,2'-bipyridine (mesbpy), was utilized to eliminate dimerization in the catalytic cycle. Synthesis, electrocatalytic properties, X-ray diffraction (XRD) studies, and infrared spectroelectrochemistry (IR-SEC) of Mn(mesbpy)(CO)3Br and [Mn(mesbpy)(CO)3(MeCN)](OTf) are reported. Unlike previously reported Mn bipyridine catalysts, these Mn complexes exhibit a single, two-electron reduction wave under nitrogen, with no evidence of dimerization. The anionic complex, [Mn(mesbpy)(CO)3](-), is formed at 300 mV more positive potential than the corresponding state is formed in typical Mn bipyridine catalysts. IR-SEC experiments and chemical reductions with KC8 provide insights into the species leading up to the anionic state, specifically that both the singly reduced and doubly reduced Mn complexes form at the same potential. When formed, the anionic complex binds CO2 with H(+), but catalytic activity does not occur until a ~400 mV more negative potential is present. The Mn complexes show high activity and Faradaic efficiency for CO2 reduction to CO with the addition of weak Brønsted acids. IR-SEC experiments under CO2/H(+) indicate that reduction of a Mn(I)-CO2H catalytic intermediate may be the cause of this unusual "over-reduction" required to initiate catalysis.

Supramolecular Chemistry of Selective Anion Recognition for Anions of Environmental Relevance

International Nuclear Information System (INIS)

Sessler, Jonathan L.

2007-01-01

The major thrust of this project, led by the University of Kansas (Prof. Kristin Bowman-James), entails an exploration of the basic determinants of anion recognition and their application to the design, synthesis, and testing of novel sulfate extractants. A key scientific inspiration for the work comes from the need, codified in simple-to-appreciate terms by the Oak Ridge National Laboratory component of the team (viz. Dr. Bruce Moyer), for chemical entities that can help in the extractive removal of species that have low solubilities in borosilicate glass. Among such species, sulfate anion, has been identified as particularly insidious. Its presence interferes with the vitrification process, thus rendering the remediation of tank waste from, e.g., the Hanford site far more difficult and expensive. The availability of effective extractants, that would allow for the separation of separating sulfate from the major competing anions in the waste, especially nitrate, could allow for pre-vitrification removal of sulfate via liquid-liquid extraction. The efforts at The University of Texas, the subject of this report, have thus concentrated on the development of new sulfate receptors. These systems are designed to increase our basic understanding of anion recognition events and set the stage for the development of viable sulfate anion extractants. In conjunction with the Oak Ridge National Laboratory (ORNL) members of the research team, several of these new receptors were studied as putative extractants, with two of the systems being shown to act as promising synergists for anion exchange.

Hydrophobic catalyst applications in the nuclear field and in environmental studies

International Nuclear Information System (INIS)

Ionita, Gheorghe; Popescu, Irina; Stefanescu, Ioan; Varlam, Carmen

2002-01-01

The paper presents methods of preparation and applications of hydrophobic platinum catalysts in nuclear field and environmental protection. These catalysts allow the transport of gaseous reactants and reaction products to and from catalytic active centers since the pore blocking by water is avoided. Hence the activity and stability of the catalysts increase and isotopic exchange columns with simpler internal structure can be achieved. The aim of the paper is: 1. to give a data base regarding the preparation methods of the optimal catalyst type; 2. to indicate the utilization and operation procedures of hydrophobic catalysts with mixed and simple packings; 3. to evaluate the performances and applications of hydrophobic catalysts. Over one hundred of hydrophobic catalysts of the active metal/support type were prepared in our laboratory. Hydrophobic features were obtained by different methods like these: - coating a hydrophilic conventional catalyst with a hydrophobic agent such as silicone or teflon; - supporting the active metal directly into the pores of a hydrophobic support; - mixing the teflon powder with a hydrophilic conventional catalyst; coating the support with teflon followed by the impregnation with the precursor of the active metal. The most important application of these catalysts is detritiation of the heavy water used as moderator and coolant in CANDU type reactors. Build-up of tritium in heavy water following the neutron capture by deuterium leads to a reduction in the moderating properties and at the same time leads to a contamination hazard for both operation personnel and environment. Tritium recovery leads this way to both improving the moderating qualities of the heavy water and obtaining valuable pure tritium of high importance in fusion research and other laboratory studies. One gram of tritium costs about USD 10,000. The physical chemical process is water-hydrogen catalyzed isotopic exchange. Also discussed in the paper is the separation of

Solar-Driven Hydrogen Peroxide Production Using Polymer-Supported Carbon Dots as Heterogeneous Catalyst

Science.gov (United States)

Gogoi, Satyabrat; Karak, Niranjan

2017-10-01

Safe, sustainable, and green production of hydrogen peroxide is an exciting proposition due to the role of hydrogen peroxide as a green oxidant and energy carrier for fuel cells. The current work reports the development of carbon dot-impregnated waterborne hyperbranched polyurethane as a heterogeneous photo-catalyst for solar-driven production of hydrogen peroxide. The results reveal that the carbon dots possess a suitable band-gap of 2.98 eV, which facilitates effective splitting of both water and ethanol under solar irradiation. Inclusion of the carbon dots within the eco-friendly polymeric material ensures their catalytic activity and also provides a facile route for easy catalyst separation, especially from a solubilizing medium. The overall process was performed in accordance with the principles of green chemistry using bio-based precursors and aqueous medium. This work highlights the potential of carbon dots as an effective photo-catalyst.

Precursor type affecting surface properties and catalytic activity of sulfated zirconia

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Zarubica Aleksandra R.

2007-01-01

Full Text Available Zirconium-hydroxide precursor samples are synthesized from Zr-hydroxide, Zr-nitrate, and Zr-alkoxide, by precipitation/impregnation, as well as by a modified sol-gel method. Precursor samples are further sulphated for the intended SO4 2- content of 4 wt.%, and calcined at 500-700oC. Differences in precursors’ origin and calcination temperature induce the incorporation of SO4 2- groups into ZrO2 matrices by various mechanisms. As a result, different amounts of residual sulphates are coupled with other structural, as well as surface properties, resulting in various catalytic activities of sulphated zirconia samples. Catalyst activity and selectivity are a complex synergistic function of tetragonal phase fraction, sulphates contents, textural and surface characteristics. Superior activity of SZ of alkoxide origin can be explained by a beneficial effect of meso-pores owing to a better accommodation of coke deposits.

Oxidation of cyclohexanol on phosphotungstic acid anion intercalated layered double hydroxides with aqueous H{sub 2}O{sub 2} as oxidant

Energy Technology Data Exchange (ETDEWEB)

Bai, Xueli; Xue, Dandan; Sun, Huiyan; Huang, Xin; Zhao, Yongxiang; Zhang, Yue, E-mail: zyue@sxu.edu.cn [School of Chemical Engineering, Shanxi University, Shanxi (China); Bai, Zhaoyang [Shanxi Agricultural University, Shanxi (China)

2018-01-15

The layered double hydroxides (LDH) of Mg{sub 2}AlNi and Mg{sub 3}Al pillared by Keggin-type phosphotungstic acid anion (POM), i.e. Mg{sub 2}AlNi-POM LDH and Mg{sub 3}Al-POM LDH were synthesized by an ion-exchange method. The synthesized POM intercalated LDH compounds were characterized using various techniques such as FTIR, XRD, TGA and BET. The observed results show that the obtained catalysts retain the layer structure of LDH. Compared with the binary Mg{sub 3}Al-POM LDH, the ternary Mg{sub 2}AlNi-POM LDH catalyst indicated a higher thermal and chemical stability. The catalytic activity of the resulting LDH-POM was also assessed in the green oxidation of cyclohexanol with aqueous H{sub 2}O{sub 2} as an oxidant. The Mg{sub 2}AlNi-POM LDH showed a much higher conversion and selectivity for cyclohexanone than the corresponding Mg{sub 3}Al-POM LDH catalyst. (author)

Preparation and application of zirconium sulfate supported on SAPO-34 molecular sieve as solid acid catalyst for esterification

Energy Technology Data Exchange (ETDEWEB)

Xu, Dongyan, E-mail: xdy0156@sina.com; Ma, Hong; Cheng, Fei

2014-05-01

Graphical abstract: - Highlights: • SAPO-34 supported zirconium sulfate solid acid catalyst was prepared. • Esterification of acetic acid with ethanol can be catalyzed by ZS/SAPO-34. • The hydration of ZS is vital to the acidic property and catalytic performance. • The ZS/SAPO-34 catalyst treated at 200 °C shows good reusability. - Abstract: Zirconium sulfate (ZS) was supported on SAPO-34 molecular sieve by using an incipient wetness impregnation method with zirconium sulfate as the precursor. The as-prepared catalysts were used as solid acid catalyst for esterification reaction of acetic acid with ethanol. The influence of calcination temperature on the acidic property, catalytic activity, and reusability of ZS/SAPO-34 catalysts were mainly investigated. FT-IR, SEM, EDS and TG analysis have been carried out to demonstrate the characteristics of ZS/SAPO-34 catalysts. It was found that the 30 wt%ZS/SAPO-34 catalysts display the property of superacid irrespective of calcination temperature. The ZS/SAPO-34 catalyst treated at 200 °C can enhance the interaction between the supported ZS and SAPO-34 and keep the catalyst remaining substantially active after several reaction cycles. However, further increasing calcination temperature will cause the transfer of ZS from hydrate to anhydrous phase, and thus the decrease of activity.

Preparation and application of zirconium sulfate supported on SAPO-34 molecular sieve as solid acid catalyst for esterification

International Nuclear Information System (INIS)

Xu, Dongyan; Ma, Hong; Cheng, Fei

2014-01-01

Graphical abstract: - Highlights: • SAPO-34 supported zirconium sulfate solid acid catalyst was prepared. • Esterification of acetic acid with ethanol can be catalyzed by ZS/SAPO-34. • The hydration of ZS is vital to the acidic property and catalytic performance. • The ZS/SAPO-34 catalyst treated at 200 °C shows good reusability. - Abstract: Zirconium sulfate (ZS) was supported on SAPO-34 molecular sieve by using an incipient wetness impregnation method with zirconium sulfate as the precursor. The as-prepared catalysts were used as solid acid catalyst for esterification reaction of acetic acid with ethanol. The influence of calcination temperature on the acidic property, catalytic activity, and reusability of ZS/SAPO-34 catalysts were mainly investigated. FT-IR, SEM, EDS and TG analysis have been carried out to demonstrate the characteristics of ZS/SAPO-34 catalysts. It was found that the 30 wt%ZS/SAPO-34 catalysts display the property of superacid irrespective of calcination temperature. The ZS/SAPO-34 catalyst treated at 200 °C can enhance the interaction between the supported ZS and SAPO-34 and keep the catalyst remaining substantially active after several reaction cycles. However, further increasing calcination temperature will cause the transfer of ZS from hydrate to anhydrous phase, and thus the decrease of activity

Characterization of a surface modified carbon cryogel and a carbon supported Pt catalyst

Directory of Open Access Journals (Sweden)

BILJANA M. BABIĆ

2007-08-01

Full Text Available A carbon cryogel, synthesized by carbonization of a resorcinol/formaldehyde cryogel and oxidized in nitric acid, was used as catalyst support for Pt nano-particles. The Pt/C catalyst was prepared by a modified polyol synthesis method in an ethylene glycol (EG solution. Characterization by nitrogen adsorption showed that the carbon cryogel support and the Pt/C catalyst were mesoporous materials with high specific surface areas (SBET > 400 m2 g-1 and large mesoporous volumes. X-Ray diffraction of the catalyst demonstrated the successful reduction of the Pt precursor to metallic form. TEM Images of the Pt/C catalyst and Pt particle size distribution showed that the mean Pt particle size was about 3.3 nm. Cyclic voltammetry (CV experiments at various scan rates (from 2 to 200 mV s-1 were performed in 0.5 mol dm-3 HClO4 solution. The large capacitance of the oxidized carbon cryogel electrode, which arises from a combination of the double-layer capacitance and pseudocapacitance, associated with the participation of surface redox-type reactions was demonstrated. For the oxidized carbon cryogel, the total specific capacitance determined by 1/C vs. ν0.5 extrapolation method was found to be 386 F g-1. The hydrogen oxidation reaction at the investigated Pt/C catalyst proceeded as an electrochemically reversible, two-electron direct discharge reaction.

Ni-SiO2 Catalysts for the Carbon Dioxide Reforming of Methane: Varying Support Properties by Flame Spray Pyrolysis

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Emma C. Lovell

2015-03-01

Full Text Available Silica particles were prepared by flame spray pyrolysis (FSP as a support for nickel catalysts. The impact of precursor feed rate (3, 5 and 7 mL/min during FSP on the silica characteristics and the ensuing effect on catalytic performance for the carbon dioxide, or dry, reforming of methane (DRM was probed. Increasing the precursor feed rate: (i progressively lowered the silica surface area from ≈340 m2/g to ≈240 m2/g; (ii altered the silanol groups on the silica surface; and (iii introduced residual carbon-based surface species to the sample at the highest feed rate. The variations in silica properties altered the (5 wt % nickel deposit characteristics which in turn impacted on the DRM reaction. As the silica surface area increased, the nickel dispersion increased which improved catalyst performance. The residual carbon-based species also appeared to improve nickel dispersion, and in turn catalyst activity, although not to the same extent as the change in silica surface area. The findings illustrate both the importance of silica support characteristics on the catalytic performance of nickel for the DRM reaction and the capacity for using FSP to control these characteristics.

Hydrocracking for oriented conversion of heavy oils. Recent trends for catalyst development

Energy Technology Data Exchange (ETDEWEB)

Bertoncini, F.; Bonduelle, A.; Simon, L.J. [IFP Energies nouvelles, Lyon Establishment, Solaize (France). Catalysis and separation Division; Raybaud, P.; Dulot, H. [IFP Energies nouvelles, Lyon Establishment, Solaize (France). Process Desing Modeling Division

2011-07-01

As a result of the global economic crisis since the end of 2008, HCK operators have been looking to increase the profitability of the unit by processing heavier feed streams, including sourer VGO. These feeds present the drawbacks of increased H{sub 2} consumption, lower products yields and quality, and reduction in cycle lengths. Along with optimised process parameters, catalysts manufacturers are also investigating novel formulations to deal with challenging feeds. This lecture briefly summarizes the market trends (fuel demand, refinery's product specification) and the driving forces for HCK catalyst development in order to face these new challenges. Finally, this lecture highlights the innovating trends for HCK catalyst's development. Overview of various ideas developed recently in our research laboratory about (i) rational approaches for the atomic scale design of active phases (morphology, preparation, inhibitor effects), (ii) new preparations of transition metal sulphides for maximising the hydrogenating function (precursors, activation,.), (iii) rational approaches of HCK acidic supports for maximizing the selectivity and (iv) better understanding of HCK reactions. These improvements will be discussed in term of improvement of activity and selectivity of HCK catalyst to cope with future market needs. (orig.)

The challenges of treating high strength wastewaters: CWAO using MWNT supported ruthenium catalysts

Energy Technology Data Exchange (ETDEWEB)

GarcIa, J.; Gomes, H.T.; Figueiredo, J.L.; Faria, J.L. [Porto Univ., Lab. de Catalise e Materiais, Dept. de Engenharia Quimica, Faculdade de Engenharia (Portugal); Garcia, J. [Madrid Univ. Complutense, Grupo de Catalisis y Operaciones de Separacion, Dept. de Ingenieria Quimica, Facultad de Ciencias (Spain); Serp, P.; Kalck, P. [Ecole Nationale Superieure des Ingenieurs en Arts Chimiques et Technologiques, Lab. de Catalyse, Chimie Fine et Polymeres, 31 - Toulouse (France)

2005-07-01

High strength wastewaters containing aromatic compounds are normally not efficiently treated by conventional methods, including the common biological treatment. In these cases a more sophisticated approach is necessary to attain the desired levels of purification. Catalytic wet air oxidation (CWAO) using carbon based catalysts is employed worldwide as effective pre-treatment of effluents with these characteristics. Carbon materials are preferred as active catalysts or support for preparing them due to their morphological and structural characteristics. In the last 10 years, due to a tremendous development in materials production and processing, carbon nano-structures are becoming more accessible and common widening their range of applications [1]. In this context, the scope of the present work is to illustrate a potential use of multi-walled carbon nano-tubes (MWNT) supported ruthenium catalysts for catalytic wet air oxidation of aniline polluted wastewaters. The metal was supported by incipient wetness and excess impregnation, starting from liquid solutions of three different Ru precursors. Impregnation was carried out on modified MWNT, namely on MWNT-COOH (HNO{sub 3} modified) and MWNT-COONa (HNO{sub 3}/Na{sub 2}CO{sub 3} modified). For the 1% weight Ru/MWNT catalysts, the order of activities decreased in the sequence Ru(COD)(COT){>=}RuCl{sub 3}{>=}Ru(C{sub 5}H{sub 5}){sub 2}. The conversion of aniline after 45 min of reaction was 100% for the catalyst prepared with Ru(COD)(COT). The influence of the Ru precursor, preparation method and the support surface modification was studied comparing the conversion of aniline obtained for the different prepared Ru/MWNT catalysts (Figure 1). MWNT as support material, provide a significant metal dispersion with very small Ru nanoparticles (Figure 2) being observed. This will induce an efficient surface contact between the aniline molecule and the active sites [2]. The excellent catalytic performances of Ru/MWNT are explained

Formation and Yield of Multi-Walled Carbon Nanotubes Synthesized via Chemical Vapour Deposition Routes Using Different Metal-Based Catalysts of FeCoNiAl, CoNiAl and FeNiAl-LDH

Directory of Open Access Journals (Sweden)

Mohd Zobir Hussein

2014-11-01

Full Text Available Multi-walled carbon nanotubes (MWCNTs were prepared via chemical vapor deposition (CVD using a series of different catalysts, derived from FeCoNiAl, CoNiAl and FeNiAl layered double hydroxides (LDHs. Catalyst-active particles were obtained by calcination of LDHs at 800 °C for 5 h. Nitrogen and hexane were used as the carrier gas and carbon source respectively, for preparation of MWCNTs using CVD methods at 800 °C. MWCNTs were allowed to grow for 30 min on the catalyst spread on an alumina boat in a quartz tube. The materials were subsequently characterized through X-ray diffraction, Fourier transform infrared spectroscopy, surface area analysis, field emission scanning electron microscopy and transmission electron microscopy. It was determined that size and yield of MWCNTs varied depending on the type of LDH catalyst precursor that is used during synthesis. MWCNTs obtained using CoNiAl-LDH as the catalyst precursor showed smaller diameter and higher yield compared to FeCoNiAl and FeNiAl LDHs.

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.

Modification by SiO2 of Alumina Support for Light Alkane Dehydrogenation Catalysts

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Giyjaz E. Bekmukhamedov

2016-10-01

Full Text Available Due to the continuously rising demand for C3–C5 olefins it is important to improve the performance of catalysts for dehydrogenation of light alkanes. In this work the effect of modification by SiO2 on the properties of the alumina support and the chromia-alumina catalyst was studied. SiO2 was introduced by impregnation of the support with a silica sol. To characterize the supports and the catalysts the following techniques were used: low-temperature nitrogen adsorption; IR-spectroscopy; magic angle spinning 29Si nuclear magnetic resonance; temperature programmed desorption and reduction; UV-Vis-, Raman- and electron paramagnetic resonance (EPR-spectroscopy. It was shown that the modifier in amounts of 2.5–7.5 wt % distributed on the support surface in the form of SiOx-islands diminishes the interaction between the alumina support and the chromate ions (precursor of the active component. As a result, polychromates are the compounds predominantly stabilized on the surface of the modified support; under thermal activation of the catalyst and are reduced to the amorphous Cr2O3. This in turn leads to an increase in the activity of the catalyst in the dehydrogenation of isobutane.

Effect of catalyst preparation on the yield of carbon nanotube growth

International Nuclear Information System (INIS)

Escobar, Mariano; Rubiolo, Gerardo; Candal, Roberto; Goyanes, Silvia

2009-01-01

Multi-wall carbon nanotubes (MWCNTs) were synthesized by catalytic chemical vapor deposition (CVD) on catalytic iron nanoparticles dispersed in a silica matrix, prepared by sol gel method. In this contribution, variation of gelation condition on catalyst structure and its influence on the yield of carbon nanotubes growth was studied. The precursor utilized were tetraethyl-orthosilicate and iron nitrate. The sols were dried at two different temperatures in air (25 or 80 deg. C) and then treated at 450 deg. C for 10 h. The xerogels were introduced into the chamber and reduced in a hydrogen/nitrogen (10%v/v) atmosphere at 600 deg. C. MWCNTs were formed by deposition of carbon atoms from decomposition of acetylene at 700 deg. C. The system gelled at RT shows a yield of 100% respect to initial catalyst mass whereas the yield of that gelled at 80 deg. C was lower than 10%. Different crystalline phases are observed for both catalysts in each step of the process. Moreover, TPR analysis shows that iron oxide can be efficiently reduced to metallic iron only in the system gelled at room temperature. Carbon nanotubes display a diameter of about 25-40 nm and several micron lengths. The growth mechanism of MWCNTs is base growth mode for both catalysts.

Effect of catalyst preparation on the yield of carbon nanotube growth

Energy Technology Data Exchange (ETDEWEB)

Escobar, Mariano, E-mail: mescobar@df.uba.a [Dep. Quimica Inorganica, Analitica y Quimica Fisica, FCEyN, UBA, Ciudad Universitaria (1428), Bs As (Argentina); LP and MC, Dep. Fisica, FCEyN, UBA (Argentina); Rubiolo, Gerardo [Unidad de Actividad Materiales, CNEA, Av Gral Paz 1499, San Martin (1650), Bs As (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET) (Argentina); Candal, Roberto [Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET) (Argentina); Instituto de Fisico-quimica de Materiales, Ambiente y Energia (INQUIMAE), CONICET - UBA (Argentina); Goyanes, Silvia [LP and MC, Dep. Fisica, FCEyN, UBA (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET) (Argentina)

2009-10-01

Multi-wall carbon nanotubes (MWCNTs) were synthesized by catalytic chemical vapor deposition (CVD) on catalytic iron nanoparticles dispersed in a silica matrix, prepared by sol gel method. In this contribution, variation of gelation condition on catalyst structure and its influence on the yield of carbon nanotubes growth was studied. The precursor utilized were tetraethyl-orthosilicate and iron nitrate. The sols were dried at two different temperatures in air (25 or 80 deg. C) and then treated at 450 deg. C for 10 h. The xerogels were introduced into the chamber and reduced in a hydrogen/nitrogen (10%v/v) atmosphere at 600 deg. C. MWCNTs were formed by deposition of carbon atoms from decomposition of acetylene at 700 deg. C. The system gelled at RT shows a yield of 100% respect to initial catalyst mass whereas the yield of that gelled at 80 deg. C was lower than 10%. Different crystalline phases are observed for both catalysts in each step of the process. Moreover, TPR analysis shows that iron oxide can be efficiently reduced to metallic iron only in the system gelled at room temperature. Carbon nanotubes display a diameter of about 25-40 nm and several micron lengths. The growth mechanism of MWCNTs is base growth mode for both catalysts.

Oxidation catalyst

Science.gov (United States)

Ceyer, Sylvia T.; Lahr, David L.

2010-11-09

The present invention generally relates to catalyst systems and methods for oxidation of carbon monoxide. The invention involves catalyst compositions which may be advantageously altered by, for example, modification of the catalyst surface to enhance catalyst performance. Catalyst systems of the present invention may be capable of performing the oxidation of carbon monoxide at relatively lower temperatures (e.g., 200 K and below) and at relatively higher reaction rates than known catalysts. Additionally, catalyst systems disclosed herein may be substantially lower in cost than current commercial catalysts. Such catalyst systems may be useful in, for example, catalytic converters, fuel cells, sensors, and the like.

Catalytic Combustion of Low Concentration Methane over Catalysts Prepared from Co/Mg-Mn Layered Double Hydroxides

Directory of Open Access Journals (Sweden)

Hongfeng Liu

2014-01-01

Full Text Available A series of Co/Mg-Mn mixed oxides were synthesized through thermal decomposition of layered double hydroxides (LDHs precursors. The resulted catalysts were then subjected for catalytic combustion of methane. Experimental results revealed that the Co4.5Mg1.5Mn2LDO catalyst possessed the best performance with the T90=485°C. After being analyzed via XRD, BET-BJH, SEM, H2-TPR, and XPS techniques, it was observed that the addition of cobalt had significantly improved the redox ability of the catalysts whilst certain amount of magnesium was essential to guarantee the catalytic activity. The presence of Mg was helpful to enhance the oxygen mobility and, meanwhile, improved the dispersion of Co and Mn oxides, preventing the surface area loss after calcination.

Densification of Silica Spheres: A New Pathway to Nano-Dimensioned Zeolite-Based Catalysts.

Science.gov (United States)

Machoke, Albert Gonche Fortunatus; Apeleo Zubiri, Benjamin; Leonhardt, Rainer; Marthala, Venkata Ramana Reddy; Schmiele, Martin; Unruh, Tobias; Hartmann, Martin; Spiecker, Erdman; Schwieger, Wilhelm

2017-08-16

Nanosized materials are expected to play a unique role in the development of future catalytic processes. Herein, pre-prepared and geometrically well-defined amorphous silica spheres are densified into silica-rich zeolites with nanosized dimensions. After the densification, the obtained nanosized zeolites exhibit the same spherical morphology like the starting precursor but characterized by a drastically reduced size, higher density, and high crystallinity. The phase transformation into crystalline zeolite material and the densification effect are achieved through a well-controlled steam-assisted treatment of the larger precursor particles so that the transformation process proceeds always towards the center of the spheres, just like a shrinking process. Furthermore, this procedure is applicable also to commercially available silica particles, as well as aluminum-containing systems (precursors) leading to acidic nano-catalysts with improved catalytic performance. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Production of Jet Fuel-Range Hydrocarbons from Hydrodeoxygenation of Lignin over Super Lewis Acid Combined with Metal Catalysts

International Nuclear Information System (INIS)

Wang, Hongliang; Wang, Huamin; Kuhn, Eric; Tucker, Melvin P.; Yang, Bin

2017-01-01

Super Lewis acids containing the triflate anion [e.g., Hf(OTf) 4 , Ln(OTf) 3 , In(OTf) 3 , Al(OTf) 3 ] and noble metal catalysts (e.g., Ru/C, Ru/Al2O 3 ) formed efficient catalytic systems to generate saturated hydrocarbons from lignin in high yields. In such catalytic systems, the metal triflates mediated rapid ether bond cleavage through selective bonding to etheric oxygens while the noble metal catalyzed subsequent hydrodeoxygenation (HDO) reactions. Near theoretical yields of hydrocarbons were produced from lignin model compounds by the combined catalysis of Hf(OTf)4 and ruthenium-based catalysts. When a technical lignin derived from a pilot-scale biorefinery was used, more than 30 wt % of the hydrocarbons produced with this catalytic system were cyclohexane and alkylcyclohexanes in the jet fuel range. Super Lewis acids are postulated to strongly interact with lignin substrates by protonating hydroxyl groups and ether linkages, forming intermediate species that enhance hydrogenation catalysis by supported noble metal catalysts. Meanwhile, the hydrogenation of aromatic rings by the noble metal catalysts can promote oxygenation reactions catalyzed by super Lewis acids.

Production of Jet Fuel-Range Hydrocarbons from Hydrodeoxygenation of Lignin over Super Lewis Acid Combined with Metal Catalysts

Energy Technology Data Exchange (ETDEWEB)

Wang, Hongliang [Department of Biological Systems Engineering, Washington State University, Richland WA 99354 USA; Current address: Center of Biomass Engineering/College of Agronomy and Biotechnology, China Agricultural University, Beijing 100193 PR China; Wang, Huamin [Pacific Northwest National Laboratory, 902 Battelle Boulevard Richland WA 99354 USA; Kuhn, Eric [National Bioenergy Center, National Renewable Energy Laboratory, 15013 Denver West Parkway Golden CO 80401 USA; Tucker, Melvin P. [National Bioenergy Center, National Renewable Energy Laboratory, 15013 Denver West Parkway Golden CO 80401 USA; Yang, Bin [Department of Biological Systems Engineering, Washington State University, Richland WA 99354 USA

2017-11-14

Super Lewis acids containing the triflate anion (e.g. Hf(OTf)4, Ln(OTf)3, Al(OTf)3) and noble metal catalysts (e.g. Ru/C, Ru/Al2O3) formed efficient catalytic systems to generate saturated hydrocarbons from lignin in high yields. In such catalytic systems, the metal triflates mediated rapid ether bond cleavage via selective bonding to etheric oxygens while the noble metal catalysed subsequent hydrodeoxygenation (HDO) reactions. Near theoretical yields of hydrocarbons were produced from lignin model compounds by the combined catalysis of Hf(OTf)4 and ruthenium-based catalysts. When a technical lignin derived from a pilot-scale biorefinery was used, more than 30 wt% of the hydrocarbons produced with this catalytic system were cyclohexane and alkylcyclohexanes in the jet fuel range. Super Lewis acids are postulated to strongly interact with lignin substrates via protonating hydroxyls and ether linkages, forming intermediate species that enhance hydrogenation catalysis by supported noble metal catalysts. Meanwhile, the hydrogenation of aromatic rings by the noble metal catalysts can promote oxygenation reactions catalysed by super Lewis acids.

Graphitic Layer Encapsulated Iron Based Non‐precious Catalysts for the Oxygen Reduction Reaction

DEFF Research Database (Denmark)

Zhong, Lijie

consisting of uniform metallic nanoparticles encapsulated in graphitic layers. The thesis work is conducted aiming at three major objectives: further optimization of the pyrolysis to achieve improved performance of catalysts, investigation of the complex Fe-containing components, and exploration...... of the nitrogen functionalities. Two anions in the electrolyte are used to probe the iron containing active sites towards the ORR, cyanide (CN-) in alkaline and thiocyanate (SCN-) in acidic medium, which seem supporting the above conclusions. These findings provide new insights to the encapsulation structure...

Crosslinked anion exchange membranes with primary diamine-based crosslinkers for vanadium redox flow battery application

Science.gov (United States)

Cha, Min Suc; Jeong, Hwan Yeop; Shin, Hee Young; Hong, Soo Hyun; Kim, Tae-Ho; Oh, Seong-Geun; Lee, Jang Yong; Hong, Young Taik

2017-09-01

A series of polysulfone-based crosslinked anion exchange membranes (AEMs) with primary diamine-based crosslinkers has been prepared via simple a crosslinking process as low-cost and durable membranes for vanadium redox flow batteries (VRFBs). Chloromethylated polysulfone is used as a precursor polymer for crosslinked AEMs (CAPSU-x) with different degrees of crosslinking. Among the developed AEMs, CAPSU-2.5 shows outstanding dimensional stability and anion (Cl-, SO42-, and OH-) conductivity. Moreover, CAPSU-2.5 exhibits much lower vanadium ion permeability (2.72 × 10-8 cm2 min-1) than Nafion 115 (2.88 × 10-6 cm2 min-1), which results in an excellent coulombic efficiency of 100%. The chemical and operational stabilities of the membranes have been investigated via ex situ soaking tests in 0.1 M VO2+ solution and in situ operation tests for 100 cycles, respectively. The excellent chemical, physical, and electrochemical properties of the CAPSU-2.5 membrane make it suitable for use in VRFBs.

Improvement of activated carbons as oxygen reduction catalysts in neutral solutions by ammonia gas treatment and their performance in microbial fuel cells

KAUST Repository

Watson, Valerie J.; Nieto Delgado, Cesar; Logan, Bruce E.

2013-01-01

Commercially available activated carbon (AC) powders from different precursor materials (peat, coconut shell, coal, and hardwood) were treated with ammonia gas at 700 C to improve their performance as oxygen reduction catalysts in neutral p

A novel process for heavy residue hydroconversion using a recoverable pseudo-homogenous catalyst PHC system

Energy Technology Data Exchange (ETDEWEB)

Romocki, S.M.; Rhodey, W.G. [Mobis Energy Inc., Calgary, AB (Canada)

2008-10-15

This paper described a pseudo-homogenous catalyst (PHC) designed to refine heavy hydrocarbon residues containing sulfur, nitrogen, metals, and asphaltene impurities known to clog pores and deactivate traditional hydrocrackers. The heavy residue hydroconversion (HRH) process incorporated a single particle, chemically generated PHC uniformly distributed in the feed. Thermal decomposition within the reaction system of a water-in-oil emulsion containing ammonium paramolybdate was used to form molybdenum oxide, which was then sulfided within the feed in order to create an ultra-dispersed suspension of catalytically active molybdenum disulfide particles measuring between 2 and 9 nm. A proprietary online catalyst recovery and regeneration step was used to maintain high catalyst activity. The molybdenum was then recovered from a purge stream and then reintroduced to the catalyst preparation area as a catalyst precursor. After being conditioned, the feed was combined with hydrogen and a water-oil catalyst emulsion and introduced into a furnace. Heavy components were cracked, hydrogenated and converted to lighter products. The high performance catalyst system was able to convert 95 per cent of residues at pressures below 7.3 Mpa and at reaction temperatures ranging between 400 and 460 degrees C. The catalyst was tested at a pilot plant using Athabasca vacuum bottoms. It was concluded that the HRH process is now being successfully used to produce 200 barrels of heavy oil per day. Designs for commercial installations are now being prepared. 4 refs., 2 tabs., 2 figs.

Dispersed catalysts for transforming extra heavy crude oil into transportable upgraded crude: phase identification

Energy Technology Data Exchange (ETDEWEB)

Martinez, S.; Canizales, E.; Machin, I. [Gerencia Depttal de Investigacion Estrategica en Refinacion PDVSA Intevep (Venezuela); Segovia, X.; Rivas, A.; Lopez, E.; Pena, J.P.; Rojas, J.D.; Sardella, R. [Gerencia Depttal de Infraestructura y Mejoramiento en Faja Petrolifera PDVSA Intevep (Venezuela)

2011-07-01

A new technology to convert extra heavy crude oil into transportable upgraded crude has been developed. A water/oil emulsion composed of steam and catalyst precursors is introduced in the feed which then generates unsupported dispersed catalyst in situ under thermal decomposition. The aim of this paper is to characterize the particles. The study was conducted in a laboratory and on a pilot scale on three different vacuum residues using high resolution transmission electron microscopy and a transmission electron microscope. Results showed that the particles were formed by oxides and inorganic sulphur based in transition metals and their sizes ranged between 5 and 120 nm; in addition, good dispersion was observed. This study demonstrated that the process involved in the generation of dispersed catalyst is extremely complex and showed that further work with heavy crude oils and its residua is required to understand the mechanisms involved.

Synthesis, characterization and optimization of platinum-alloy nanoparticle catalysts in proton exchange membrane fuel cells

Science.gov (United States)

Srivastava, Ratndeep

Renewable hydrogen-fuelled proton exchange membrane (PEMFC) fuel cells have consistently demonstrated great promise as a future source of energy due to their high conversion efficiency, lower temperature of operation and lack of greenhouse emissions. One of the major impediments in the commercialization of polymer electrolyte membrane fuel cells is the insufficient catalytic reactivity and higher cost of Pt electrocatalysts which are utilized for the electroreduction of oxygen from air. This dissertation focuses primarily on a family of Pt alloy fuel cell electrocatalysts referred to as de-alloyed core-shell electrocatalysts. These materials are bimetallic or multimetallic nanoparticles, mostly supported on conductive supports which were first described in a dissertation by Dr. S. Koh earlier in 2009.1 De-alloyed Pt nanoparticle electrocatalysts are formed from base metal rich binary Pt-M and ternary Pt-M1-M 2 (M, M1, M2 = Cu, Co, Ni, Fe and Cr) alloy nanoparticle precursors. The precursors are transformed and activated by electrochemical selective dissolution of the less noble metal component of the precursors (de-alloying). They have shown exceptional activity for oxygen reduction reaction (ORR) in idealized electrochemical half cell measurements, in particular rotating disk electrode experiments. However, these materials were never tested or implemented in realistic Membrane Electrode Assemblies (MEA) and single PEM fuel cells. The objective of this work was to implement de-alloyed Pt particle catalysts in realistic fuel cell electrode layers as well as a detailed characterization of their behavior and stability. The major challenges of MEA implementation consists of the behavior of the new nanostructured electrocatalysts inside the complex three-phase interface of polymer membrane ionomer, liquid water, metal catalyst, support, and reactant gas. Activity measurements were followed by medium and long-term durability analysis by potential cycling of the membrane

Efficient Dual-Site Carbon Monoxide Electro-Catalysts via Interfacial Nano-Engineering

Science.gov (United States)

Liu, Zhen; Huang, Zhongyuan; Cheng, Feifei; Guo, Zhanhu; Wang, Guangdi; Chen, Xu; Wang, Zhe

2016-01-01

Durable, highly efficient, and economic sound electrocatalysts for CO electrooxidation (COE) are the emerging key for wide variety of energy solutions, especially fuel cells and rechargeable metal−air batteries. Herein, we report the novel system of nickel−aluminum double layered hydroxide (NiAl-LDH) nanoplates on carbon nanotubes (CNTs) network. The formulation of such complexes system was to be induced through the assistance of gold nanoparticles in order to form dual-metal active sites so as to create a extended Au/NiO two phase zone. Bis (trifluoromethylsulfonyl)imide (NTf2) anion of ionic liquid electrolyte was selected to enhance the CO/O2 adsorption and to facilitate electro-catalyzed oxidation of Ni (OH)2 to NiOOH by increasing the electrophilicity of catalytic interface. The resulting neutral catalytic system exhibited ultra-high electrocatalytic activity and stability for CO electrooxidation than commercial and other reported precious metal catalysts. The turnover frequency (TOF) of the LDH-Au/CNTs COE catalyst was much higher than the previous reported other similar electrocatalysts, even close to the activity of solid-gas chemical catalysts at high temperature. Moreover, in the long-term durability testing, the negligible variation of current density remains exsisting after 1000 electrochemistry cycles. PMID:27650532

Preparation of a Ni-MgO-Al2O3 catalyst with high activity and resistance to potassium poisoning during direct internal reforming of methane in molten carbonate fuel cells

Science.gov (United States)

Jang, Won-Jun; Jung, You-Shick; Shim, Jae-Oh; Roh, Hyun-Seog; Yoon, Wang Lai

2018-02-01

Steam reforming of methane (SRM) is conducted using a series of Ni-MgO-Al2O3 catalysts for direct internal reforming (DIR) in molten carbonate fuel cells (MCFCs). Ni-MgO-Al2O3 catalysts are prepared by the homogeneous precipitation method with a variety of MgO loading amounts ranging from 3 to 15 wt%. In addition, each precursor concentrations are systemically changed (Ni: 1.2-4.8 mol L-1; Mg: 0.3-1.2 mol L-1; Al: 0.4-1.6 mol L-1) at the optimized composition (10 wt% MgO). The effects of MgO loading and precursor concentration on the catalytic performance and resistance against poisoning of the catalyst by potassium (K) are investigated. The Ni-MgO-Al2O3 catalyst with 10 wt% MgO and the original precursor concentration (Ni: 1.2 mol L-1; Mg: 0.3 mol L-1; Al: 0.4 mol L-1) exhibits the highest CH4 conversion and resistance against K poisoning even at the extremely high gas space velocity (GHSV) of 1,512,000 h-1. Excellent SRM performance of the Ni-MgO-Al2O3 catalyst is attributed to strong metal (Ni) to alumina support interaction (SMSI) when magnesium oxide (MgO) is co-precipitated with the Ni-Al2O3. The enhanced interaction of the Ni with MgO-Al2O3 support is found to protect the active Ni species against K poisoning.

Novel synthesis of highly durable and active Pt catalyst encapsulated in nitrogen containing carbon for polymer electrolyte membrane fuel cell

Science.gov (United States)

Lee, Hyunjoon; Sung, Yung-Eun; Choi, Insoo; Lim, Taeho; Kwon, Oh Joong

2017-09-01

Novel synthesis of a Pt catalyst encapsulated in a N-containing carbon layer for use in a polymer electrolyte membrane fuel cell is described in this study. A Pt-aniline complex, formed by mixing Pt precursor and aniline monomer, was used as the source of Pt, C, and N. Heat treatment of the Pt-aniline complex with carbon black yielded 5 nm Pt nanoparticles encapsulated by a N-containing carbon layer originating from aniline carbonization. The synthesized Pt catalyst exhibited higher mass specific activity to oxygen reduction reaction than that shown by conventional Pt/C catalyst because pyridinic N with graphitic carbon in the carbon layer provided active sites for oxygen reduction reaction in addition to those provided by Pt. In single cell testing, initial performance of the synthesized catalyst was limited because the thick catalyst layer increased resistance related to mass transfer. However, it was observed that the carbon layer successfully prevented Pt nanoparticles from growing via agglomeration and Ostwald ripening under fuel cell operation, thereby improving durability. Furthermore, a mass specific performance of the synthesized catalyst higher than that of a conventional Pt/C catalyst was achieved by modifying the synthesized catalyst's layer thickness.

Formation, precursors, control, and occurrence of nitrosamines in drinking water: a review.

Science.gov (United States)

Krasner, Stuart W; Mitch, William A; McCurry, Daniel L; Hanigan, David; Westerhoff, Paul

2013-09-01

This review summarizes major findings over the last decade related to nitrosamines in drinking water, with a particular focus on N-nitrosodimethylamine (NDMA), because it is among the most widely detected nitrosamines in drinking waters. The reaction of inorganic dichloramine with amine precursors is likely the dominant mechanism responsible for NDMA formation in drinking waters. Even when occurrence surveys found NDMA formation in chlorinated drinking waters, it is unclear whether chloramination resulted from ammonia in the source waters. NDMA formation has been associated with the use of quaternary amine-based coagulants and anion exchange resins, and wastewater-impaired source waters. Specific NDMA precursors in wastewater-impacted source waters may include tertiary amine-containing pharmaceuticals or other quaternary amine-containing constituents of personal care products. Options for nitrosamine control include physical removal of precursors by activated carbon or precursor deactivation by application of oxidants, particularly ozone or chlorine, upstream of chloramination. Although NDMA has been the most prevalent nitrosamine detected in worldwide occurrence surveys, it may account for only ≈ 5% of all nitrosamines in chloraminated drinking waters. Other significant contributors to total nitrosamines are poorly characterized. However, high levels of certain low molecular weight nitrosamines have been detected in certain Chinese waters suspected to be impaired by industrial effluents. The review concludes by identifying research needs that should be addressed over the next decade. Copyright © 2013 Elsevier Ltd. All rights reserved.

The many ways of making anionic clays

Indian Academy of Sciences (India)

Together with hydrotalcite-like layered double hydroxides, bivalent and trivalent metal hydroxides and their hydroxy salts are actually anionic clays consisting of positively charged hydroxide layers with anions intercalated in the interlayer region. The anionic clays exhibit anion sorption, anion diffusion and exchange ...

Steady state and transient simulation of anion exchange membrane fuel cells

Science.gov (United States)

Dekel, Dario R.; Rasin, Igal G.; Page, Miles; Brandon, Simon

2018-01-01

We present a new model for anion exchange membrane fuel cells. Validation against experimental polarization curve data is obtained for current densities ranging from zero to above 2 A cm-2. Experimental transient data is also successfully reproduced. The model is very flexible and can be used to explore the system's sensitivity to a wide range of material properties, cell design specifications, and operating parameters. We demonstrate the impact of gas inlet relative humidity (RH), operating current density, ionomer loading and ionomer ion exchange capacity (IEC) values on cell performance. In agreement with the literature, high air RH levels are shown to improve cell performance. At high current densities (>1 A cm-2) this effect is observed to be especially significant. Simulated hydration number distributions across the cell reveal the related critical dependence of cathode hydration on air RH and current density values. When exploring catalyst layer design, optimal intermediate ionomer loading values are demonstrated. The benefits of asymmetric (cathode versus anode) electrode design are revealed, showing enhanced performance using higher cathode IEC levels. Finally, electrochemical reaction profiles across the electrodes uncover inhomogeneous catalyst utilization. Specifically, at high current densities the cathodic reaction is confined to a narrow region near the membrane.

Catalytic conversion of 11CO2 and 11CO into synthesis precursors for 11C labelling

International Nuclear Information System (INIS)

Patt, J.T.

1994-03-01

The positron emitter carbon-11 (T 1/2 =20.3 min) is an ideal radio nuclide for tracers in positron emission tomography (PET). In this study catalytic methods for the synthesis of [ 11 C]alcohols have been investigated. The formation of [ 11 C]methanol has been studied on Pd/Al 2 O 3 and Cu/ZnO/Al 2 O 3 catalysts with respect to CO and CO 2 carrier addition to the synthesis gas. Carbon monoxide was identified as the precursor of methanol formation on the Pd/Al 2 O 3 -catalyst. In contrast on the Cu/ZnO/Al 2 O 3 -catalyst methanol was formed on a reaction pathway via an adsorbed CO 2 -species. A n.c.a.-[ 11 C]methanol synthesis basing on the Cu/ZnO/Al 2 O 3 -catalyst has been developed by substitution of the oxygen containing components CO and CO 2 in the synthesis gas by N 2 O. The radiochemical yield, the low selectivity of [ 11 C]methanol production and the rather slow kinetics of this process were arguments against the practical use of this process in the synthesis of 11 C-labelling agents. (orig.)

Revealing the Formation of Copper Nanoparticles from a Homogeneous Solid Precursor by Electron Microscopy

DEFF Research Database (Denmark)

van den Berg, Roy; Elkjær, Christian Fink; Gommes, Cedric J.

2016-01-01

The understanding of processes leading to the formation of nanometer-sized particles is important for tailoring of their size, shape and location. The growth mechanisms and kinetics of nanoparticles from solid precursors are, however, often poorly described. Here we employ transmission electron...... microscopy (TEM) to examine the formation of copper nanoparticles on a silica support during the reduction by H2 of homogeneous copper phyllosilicate platelets, as a prototype precursor for a coprecipitated catalyst. Specifically, time-lapsed TEM image series acquired of the material during the reduction...... process provide a direct visualization of the growth dynamics of an ensemble of individual nanoparticles and enable a quantitative evaluation of the nucleation and growth of the nanoparticles. This quantitative information is compared with kinetic models and found to be best described by a nucleation...

New Ir Bis-Carbonyl Precursor for Water Oxidation Catalysis

Energy Technology Data Exchange (ETDEWEB)

Huang, Daria L. [Department of Chemistry, Yale University, 225; Beltrán-Suito, Rodrigo [Department of Chemistry, Yale University, 225; Thomsen, Julianne M. [Department of Chemistry, Yale University, 225; Hashmi, Sara M. [Department of Chemical and Environmental; Materna, Kelly L. [Department of Chemistry, Yale University, 225; Sheehan, Stafford W. [Catalytic Innovations LLC, 70 Crandall; Mercado, Brandon Q. [Department of Chemistry, Yale University, 225; Brudvig, Gary W. [Department of Chemistry, Yale University, 225; Crabtree, Robert H. [Department of Chemistry, Yale University, 225

2016-02-05

This paper introduces IrI(CO)2(pyalc) (pyalc = (2-pyridyl)-2-propanoate) as an atom-efficient precursor for Ir-based homogeneous oxidation catalysis. This compound was chosen to simplify analysis of the water oxidation catalyst species formed by the previously reported Cp*IrIII(pyalc)OH water oxidation precatalyst. Here, we present a comparative study on the chemical and catalytic properties of these two precursors. Previous studies show that oxidative activation of Cp*Ir-based precursors with NaIO4 results in formation of a blue IrIV species. This activation is concomitant with the loss of the placeholder Cp* ligand which oxidatively degrades to form acetic acid, iodate, and other obligatory byproducts. The activation process requires substantial amounts of primary oxidant, and the degradation products complicate analysis of the resulting IrIV species. The species formed from oxidation of the Ir(CO)2(pyalc) precursor, on the other hand, lacks these degradation products (the CO ligands are easily lost upon oxidation) which allows for more detailed examination of the resulting Ir(pyalc) active species both catalytically and spectroscopically, although complete structural analysis is still elusive. Once Ir(CO)2(pyalc) is activated, the system requires acetic acid or acetate to prevent the formation of nanoparticles. Investigation of the activated bis-carbonyl complex also suggests several Ir(pyalc) isomers may exist in solution. By 1H NMR, activated Ir(CO)2(pyalc) has fewer isomers than activated Cp*Ir complexes, allowing for advanced characterization. Future research in this direction is expected to contribute to a better structural understanding of the active species. A diol crystallization agent was needed for the structure determination of 3.

New Ag(I)-iminophosphorane coordination polymers as efficient catalysts precursors for the MW-assisted Meyer-Schuster rearrangement of propargylic alcohols in water.

Science.gov (United States)

García-Álvarez, Joaquín; Díez, Josefina; Vidal, Cristian; Vicent, Cristian

2013-06-03

Treatment of the N-thiophosphorylated iminophosphorane ligands (PTA)═NP(═S)(OR)2 [PTA = 1,3,5-triaza-7-phosphaadamantane, 3a and 3b] and (DAPTA)═NP(═S)(OR)2 [DAPTA = 3,7-diacetyl-1,3,7-triaza-5-bicyclo[3.3.1]nonane, 4a and 4b] with an equimolecular amount of AgSbF6 leads to high-yield formation of the new one-dimensional coordination polymers [Ag{μ(2)-N,S-(PTA)═NP(═S)(OR)2}]x[SbF6]x (5a and 5b) and [Ag{μ(2)-O,S-(DAPTA)═NP(═S)(OR)2}]x[SbF6]x (6a and 6b), respectively. These new (iminophosphorane)silver(I) coordination polymers are efficient catalyst precursors for the Meyer-Schuster isomerization of both terminal and internal alkynols. Reactions proceeded in water, under aerobic conditions and using microwave irradiation as heating source, to afford the corresponding α,β-unsaturated carbonyl compounds in excellent yields, without the addition of any cocatalyst. Remarkably, it should be noted that this catalytic system can be recycled up to 10 consecutive runs (1st cycle 45 min, 99%; 10th cycle 6 h, 97%). ESI-MS analysis of 5a in water has been carried out providing valuable insight into the monomeric active species responsible for catalytic activity in water.

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.

Sulfonic-based precursors (SAPs for silica mesostructures: Advances in synthesis and applications

Directory of Open Access Journals (Sweden)

Sadegh Rostamnia*

2016-01-01

Full Text Available Sulfonic acid-based precursors (SAP play an important role in tailoring mesoporous silica’s and convert them to a solid acid catalyst with a Bronsted-type nature. These kinds of solid acids contribute to sustainable and green chemistry by their heterogeneous, recyclable, and high efficiency features. Therefore, knowing the properties and reactivity of SAPs can guide us to manufacture a sulfonated mesostructures compatible with reaction type and conditions. In the present review, some of the important SAPs, their reactivity and mechanism of functionalization are discussed.

Novel precursors for the deposition of rare earth oxides; Neuartige Precursor zur Abscheidung von Selten-Erd-Oxiden

Energy Technology Data Exchange (ETDEWEB)

Ahlers, Mareike

2010-02-22

During this work rare earth solvates with nitrate and perchlorate anions have been investigated. All compounds have been structurally characterized and analyzed using thermal gravimetric analysis. The decomposition residues were analyzed using powder diffraction methods. Almost all compounds showed a characteristically intense exothermic decomposition step during the thermal decomposition, most likely caused by an intramolecular redox reaction between the nitrate or perchlorate anion respectively and the organic solvent molecules. The nitrates RE(NO{sub 3}){sub 3}(CH(OCH{sub 3}){sub 3}){sub 2} (RE = Sm, Eu) were isolated and characterized for the first time as the intermediate of the dehydration reaction with trimethyl orthoformate. The known compound group of dimethoxyethane solvates was then expanded with RE(NO{sub 3}){sub 3}(O{sub 2}C{sub 4}H{sub 10}) (RE = La, Sm, Eu). Considering the possible use as precursor material the already described neodymium compound is also discussed. The thermal decomposition of these compounds yields the respective cubic rare earth oxide and shows the typical intense exothermic decomposition reaction. A variety of different precursor system based on nitrate solvates for the deposition of rare earth oxide layers on a silicon surface was developed and investigated in collaboration with the group of Prof. Dr. Al-Shamery (Univ. Oldenburg). Ultra thin films on a H-Si(111) surface were obtained via the deposition of the precursor, which was dissolved in organic solvents. An oxide layer was detected after the heating of the sample. The film thickness was measured as < 10 nm, whereas the thickness of the film was controlled by the concentration of the precursor solution. Sm(ClO{sub 4}){sub 3}(CH(OCH{sub 3}){sub 3}){sub 3} was isolated and characterized for the first time as the intermediate of the dehydration reaction with trimethyl orthoformate. Eu(ClO{sub 4}){sub 3}(CH(OCH{sub 3}){sub 3}){sub 2}(MeOH){sub 2} was obtained without

Supramolecular Chemistry of Environmentally Relevant Anions

International Nuclear Information System (INIS)

Bowman-James, Kristin; Moyer, B.A.; Sessler, Jonathan L.

2003-01-01

The goal of this project is the development of highly selective extractants for anions targeting important and timely problems of critical interest to the EMSP mission. In particular, sulfate poses a special problem in cleaning up the Hanford waste tanks in that it interferes with vitrification, but available technologies for sulfate removal are limited. The basic chemical aspects of anion receptor design of functional pH independent systems as well as design of separations strategies for selective and efficient removal of targeted anions have been probed. Key findings include: (1) some of the first synthetic sulfate-selective anion-binding agents; (2) simple, structure-based methods for modifying the intrinsic anion selectivity of a given class of anion receptors; and (3) the first system capable of extracting sulfate from acidic, nitrate-containing aqueous media. Receptor design, structural influences on anion binding affinities, and findings from liquid-liquid extraction studies will be discussed

Crystalline mesoporous zirconia catalysts having stable tetragonal pore wall structure

Science.gov (United States)

Sachtler, W.M.H.; Huang, Y.Y.

1998-07-28

Methods are disclosed for the preparation of new sulfated mesoporous zirconia materials/catalysts with crystalline pore walls of predominantly tetragonal crystal structure, characterized by nitrogen physical sorption measurement, X-ray diffraction, transmission electron microscopy and catalytic tests using n-butane isomerization to iso-butane and alkylation of 1-naphthol with 4-tert-butylstyrene as probe reactions. Sulfate deposition is preferred for the transformation of a mesoporous precursor with amorphous pore walls into a material with crystalline pore walls maintaining the mesoporous characteristics. 17 figs.

Hydration of a Large Anionic Charge Distribution - Naphthalene-Water Cluster Anions

Science.gov (United States)

Weber, J. Mathias; Adams, Christopher L.

2010-06-01

We report the infrared spectra of anionic clusters of naphthalene with up to three water molecules. Comparison of the experimental infrared spectra with theoretically predicted spectra from quantum chemistry calculations allow conclusions regarding the structures of the clusters under study. The first water molecule forms two hydrogen bonds with the π electron system of the naphthalene moiety. Subsequent water ligands interact with both the naphthalene and the other water ligands to form hydrogen bonded networks, similar to other hydrated anion clusters. Naphthalene-water anion clusters illustrate how water interacts with negative charge delocalized over a large π electron system. The clusters are interesting model systems that are discussed in the context of wetting of graphene surfaces and polyaromatic hydrocarbons.

Novel catalysts and photoelectrochemical system for solar fuel production

Science.gov (United States)

Zhang, Yan

spectroscopy (XAS). The photocatalytic activities of as-made nanoparticles were investigated using a well-studied visible light driven [Ru(bpy)3]2+-persulfate system. In both Clark electrode and reactor/gas chromatography (GC) systems, Mn-substituted Co3O 4 nanoparticles exhibited the highest turnover frequency (TOF) among all the three kinds of catalysts. The data presented in this paper suggest that the photocatalytic oxygen evolution activity of Co3O 4 spinel catalyst can be further enhanced by Mn3+ substitution at the octahedral sites. The second part of this piece of work was carried out to further investigate cobalt oxide based photocatalytic oxygen evolution catalyst. A new strategy was developed to synthesize nonsupported cobalt oxide nanocubanes through an in situ phase transformation mechanism using a layered Co(OH)(OCH3) precursor. Under sonication, the precursor was exfoliated and transformed into cobalt oxide nanocubanes in the presence of NaHCO 3-Na2SiF6 buffer solution. The resulting cobalt catalyst with an average particle size less than 2 nm exhibited a turnover frequency of 0.0023 per second per cobalt in photocatalytic oxygen evolution reaction. X-ray absorption results suggested that a unique nanocubane structure, where 13 cobalt atoms fully coordinated with oxygen atoms and hydroxide groups in an octahedral arrangement to form 8 Co4O4 cubanes, may be responsible for the exceptionally high oxygen evolution catalysis activity. This thesis work is completed with the development of a photoanode-driven photoelectrochemical cell for CO2 reduction. A NiOx decorated Si photoanode and nanoporous Ag cathode were employed. With an external bias of 2.0 V, a current density at cathode of 10 mA/cm2 and Faradaic efficiency of 70% for CO2 to CO was achieved. Compared to a normal electrochemical cell, the photoelectrochemical cell saves 0.4 V electrical energy by absorbing photo-energy. In addition, post-test photoanodes were carefully characterized by SEM, XAS, and XPS

Supramolecular Chemistry of Selective Anion Recognition for Anions of Environmental Relevance

International Nuclear Information System (INIS)

Bowman-James, K.; Wilson, G.; Moyer, B. A.

2004-01-01

This project involves the design and synthesis of receptors for oxoanions of environmental importance, including emphasis on high level and low activity waste. Target anions have included primarily oxoanions and a study of the basic concepts behind selective binding of target anions. A primary target has been sulfate because of its deleterious influence on the vitrification of tank wastes

Characterization and evaluation of Pt-Ru catalyst supported on multi-walled carbon nanotubes by electrochemical impedance

Energy Technology Data Exchange (ETDEWEB)

Ocampo, A.L.; Miranda-Hernandez, M.; Sebastian, P.J. [Centro de Investigacion en Energia-UNAM, Temixco, 62580 Morelos (Mexico); Morgado, J.; Montoya, J.A. [IMP, Eje Central Lazaro Cardenas 152, 07730 D.F. Mexico (Mexico)

2006-10-06

In this work the authors present the results of a systematic characterization and evaluation of the carbon nanotube supported Pt-Ru (Pt-Ru/CNT) for its use as methanol oxidation catalyst. Its activity was compared with that of Pt and Pt-Ru catalysts supported on Vulcan and synthesized from carbonyl precursors, and another commercial Pt-Ru catalyst. The cyclic voltammetry, CO stripping and electrochemical impedance techniques were employed to determine the electrocatalytic activity of the catalysts. The electrochemical studies were performed in 0.5M H{sub 2}SO{sub 4} containing different concentrations of methanol (0.05-1M). The results showed a noticeable influence of the catalyst support (CNT) on the performance of the catalyst for CO oxidation. The electrochemical impedance studies allowed us to separate the different steps in the methanol oxidation reaction and to control these steps or reactions by varying the applied potential and the methanol concentration. At low methanol concentration and potentials the de-hydrogenation of methanol predominated. But, at high potential and methanol concentrations, the CO oxidation predominated. These results allowed us to clearly describe at what potential and concentration ranges the bi-functional effect of Ru becomes evident. Our results indicated that the CO oxidation occurs both on Pt and Ru. Compared to other catalysts, Pt-Ru supported on carbon nanotubes showed superior catalytic activity for CO and methanol oxidation. (author)

New organometallic salts as precursors for the functionalization of carbon nanotubes with metallic nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Alonso-Nunez, G., E-mail: galonso@cnyn.unam.mx; Garza, L. Morales de la; Rogel-Hernandez, E.; Reynoso, E. [Universidad Nacional Autonoma de Mexico, Centro de Nanociencias y Nanotecnologia (Mexico); Licea-Claverie, A.; Felix-Navarro, R. M. [Instituto Tecnologico de Tijuana, Centro de Graduados e Investigacion (Mexico); Berhault, G. [UMR 5256 CNRS-Universite de Lyon, Institut de Recherches sur la Catalyse et l' Environnement de Lyon (France); Paraguay-Delgado, F. [Centro de Investigacion en Materiales Avanzados S. C. (Mexico)

2011-09-15

New organometallic salts were synthesized in aqueous solution and were used as precursors for the functionalization of carbon nanotubes (CNT) by metallic nanoparticles. The precursors were obtained by reaction between HAuCl{sub 4}, (NH{sub 4}){sub 2}PtCl{sub 6}, (NH{sub 4}){sub 2}PdCl{sub 6}, or (NH{sub 4}){sub 3}RhCl{sub 6} with cetyltrimethylammonium bromide (CTAB). The as-obtained (CTA){sub n}Me{sub x}Cl{sub y} salts (with Me = Au, Pt, Pd, Rh) were characterized by Fourier-transform infra-red (FTIR) spectroscopy, {sup 1}H nuclear magnetic resonance (NMR) spectroscopy, and thermogravimetric analysis. These precursors were then used to synthesize metallic nanoparticles of Au, Pt, Pd, and Rh over multiwalled carbon nanotubes (MWCNT). Characterization by scanning transmission electron microscopy (STEM) and thermogravimetric analysis under air reveals that the CNT-supported catalysts exhibit high loading and good dispersion of the metallic nanoparticles with small average particle sizes. The present preparation procedure therefore allows obtaining high densities of small metallic nanoparticles at the surface of MWCNT.

Layer-by-layer self-assembly of polyimide precursor/layered double hydroxide ultrathin films

International Nuclear Information System (INIS)

Chen Dan; Huang Shu; Zhang Chao; Wang Weizhi; Liu Tianxi

2010-01-01

The layer-by-layer (LBL) self-assembly has been extensively used as a simple and effective method for the preparation of polyelectrolyte multilayer films. In this work, we utilized this unique method to prepare polyimide precursor/layered double hydroxide (LDH) ultrathin films. Well-crystallized Co-Al-CO 3 LDH and subsequent anion exchanged Co-Al-NO 3 LDH were prepared and characterized by scanning electron microscopy and X-ray diffraction (XRD). By vigorous shaking of the as-prepared Co-Al-NO 3 LDH, positively charged and exfoliated LDH nanosheets were obtained. Atomic force microscopy and XRD investigations indicated the delamination of LDH nanosheets. The precursor of polyimide, poly(amic acid) tertiary amine salt (PAS) was prepared by the polycondensation of dianhydride and diamine, and subsequent amine salt formation. By using the LBL method, heterogeneous ultrathin films of PAS and LDH were prepared. The formation of the ordered nanostructured assemblies was confirmed by the progressive enhancement of UV absorbance and the XRD results.

Comparison of Cobalt based Catalysts Supported on MWCNT and SBA-15 Supporters for Fischer-tropsch Synthesis by Using Novel Vortex Type Reactor

International Nuclear Information System (INIS)

Yakubov, A.; Shahrun, M.S.; Kutty, M.G.; Hamid, S.B.A.; Piven, V.

2011-01-01

10 and 40 wt% Co/ Multi wall Carbon Nano tubes (MWCNT) and 10 and 40 wt% Co/ Santa Barbara Amorphous-15 (SBA) catalysts were prepared via incipient wetness impregnation and characterized by Scanning Electron Microscopy equipped with Energy Dispersive X-ray Spectroscopy (SEM and EDX), N 2 adsorption-desorption (BET), X-ray Diffractometry (XRD), Transmission Electron Microscopy (TEM) and Temperature- Programmed Reduction and H 2 desorption TPD/RO. Co(NO 3 ) 2 * 6H 2 O was used as a cobalt precursor. 200 ml hastelloy autoclave reactor was implemented to see the performance of the catalysts. This report presents details about the catalyst synthesis and reactor study. (author)

Controllable synthesis of Co3O4 nanocrystals as efficient catalysts for oxygen reduction reaction

Science.gov (United States)

Li, Baoying; Zhang, Yihe; Du, Ruifeng; Liu, Lei; Yu, Xuelian

2018-03-01

The electrochemical oxygen reduction reaction (ORR) has received great attention due to its importance in fuel cells and metal-air batteries. Here, we present a simple approach to prepare non-noble metal catalyst-Co3O4 nanocrystals (NCs). The particle size and shape were simply controlled by different types and concentrations of metal precursor. Furthermore, different sizes and shapes of Co3O4 NCs are explored as electrocatalysts for ORR, and it has been observed that particles with a similar shape, and smaller particle size led to greater catalytic current densities because of the greater surface area. For particles with a comparable size, the shape or crystalline structure governed the activity of the electrocatalytic reactions. Most importantly, the 9 nm-Co3O4 were demonstrated to act as low-cost catalysts for the ORR with a similar performance to that of Pt catalysts.

Green Synthesis of Three-Dimensional Hybrid N-Doped ORR Electro-Catalysts Derived from Apricot Sap

Directory of Open Access Journals (Sweden)

Ramesh Karunagaran

2018-01-01

Full Text Available Rapid depletion of fossil fuel and increased energy demand has initiated a need for an alternative energy source to cater for the growing energy demand. Fuel cells are an enabling technology for the conversion of sustainable energy carriers (e.g., renewable hydrogen or bio-gas into electrical power and heat. However, the hazardous raw materials and complicated experimental procedures used to produce electro-catalysts for the oxygen reduction reaction (ORR in fuel cells has been a concern for the effective implementation of these catalysts. Therefore, environmentally friendly and low-cost oxygen reduction electro-catalysts synthesised from natural products are considered as an attractive alternative to currently used synthetic materials involving hazardous chemicals and waste. Herein, we describe a unique integrated oxygen reduction three-dimensional composite catalyst containing both nitrogen-doped carbon fibers (N-CF and carbon microspheres (N-CMS synthesised from apricot sap from an apricot tree. The synthesis was carried out via three-step process, including apricot sap resin preparation, hydrothermal treatment, and pyrolysis with a nitrogen precursor. The nitrogen-doped electro-catalysts synthesised were characterised by SEM, TEM, XRD, Raman, and BET techniques followed by electro-chemical testing for ORR catalysis activity. The obtained catalyst material shows high catalytic activity for ORR in the basic medium by facilitating the reaction via a four-electron transfer mechanism.

Green Synthesis of Three-Dimensional Hybrid N-Doped ORR Electro-Catalysts Derived from Apricot Sap.

Science.gov (United States)

Karunagaran, Ramesh; Coghlan, Campbell; Shearer, Cameron; Tran, Diana; Gulati, Karan; Tung, Tran Thanh; Doonan, Christian; Losic, Dusan

2018-01-28

Rapid depletion of fossil fuel and increased energy demand has initiated a need for an alternative energy source to cater for the growing energy demand. Fuel cells are an enabling technology for the conversion of sustainable energy carriers (e.g., renewable hydrogen or bio-gas) into electrical power and heat. However, the hazardous raw materials and complicated experimental procedures used to produce electro-catalysts for the oxygen reduction reaction (ORR) in fuel cells has been a concern for the effective implementation of these catalysts. Therefore, environmentally friendly and low-cost oxygen reduction electro-catalysts synthesised from natural products are considered as an attractive alternative to currently used synthetic materials involving hazardous chemicals and waste. Herein, we describe a unique integrated oxygen reduction three-dimensional composite catalyst containing both nitrogen-doped carbon fibers (N-CF) and carbon microspheres (N-CMS) synthesised from apricot sap from an apricot tree. The synthesis was carried out via three-step process, including apricot sap resin preparation, hydrothermal treatment, and pyrolysis with a nitrogen precursor. The nitrogen-doped electro-catalysts synthesised were characterised by SEM, TEM, XRD, Raman, and BET techniques followed by electro-chemical testing for ORR catalysis activity. The obtained catalyst material shows high catalytic activity for ORR in the basic medium by facilitating the reaction via a four-electron transfer mechanism.

PREPARATION, CHARACTERIZATIONS AND MODIFICATION OF Ni-Pd/NATURAL ZEOLITE CATALYSTS

Directory of Open Access Journals (Sweden)

Wega Trisunaryanti

2010-06-01

Full Text Available Preparation, and modification of Ni-Pd/natural zeolite as well as their characterizations had been carried out. The aim of this research for the fututure is to prepare the best characters catalyst for the conversion of waste plastics fraction to gasoline fraction (C5-C12 hydrocarbons. The preparation of catalysts was performed by reacting a natural zeolite with the precursor of Ni(NO32. 9H2O and PdCl2 in an ammonia solution (25%. The modifications were performed by varying the rasio of Ni/Pd loaded to the zeolite, whereas the Pd was previously loaded and total metal content was 1 wt.% based on the zeolite. The characterization of catalysts included determination of acidity gravimetrically by adsorption of ammonia or pyridine vapour  base method, metal content by Atomic Adsorption Spectrophotometer (AAS and X-ray Fluoresence (XRF and crystallinity by X-ray Diffraction (XRD. The treatment of catalysts using Etilene Diamine Tetra Acetic acid  (EDTA was performed to study the metal distribution on the outer or inner surface of the zeolite. The characterization results showed that the loading of metals to the zeolite increased its acidity and decreased its spesific surface area, however, did not defect its crystallnity.  The metals loaded on the zeolite were distributed inside the pore and at outer surface of the zeolite. For all catalyst samples, the acidities determined using ammonia were higher than those of pyridine, and the acidities determined before the EDTA treatment was lower than those after the treatment.  Metal contents of the zeolite before the EDTA treatment were higher than those after the treatment. The EDTA treatment enhanced the crystallinity of the sampel. The relationship between the metal rasio towards the acidity of the catalyst samples were in variation. Catalyst samples produced in this research have good characters, thus promisingly can be used for conversion process of waste plastics to gasoline fraction.    Keywords

Atomic Layer Deposition on Porous Materials: Problems with Conventional Approaches to Catalyst and Fuel Cell Electrode Preparation

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Tzia Ming Onn

2018-03-01

Full Text Available Atomic layer deposition (ALD offers exciting possibilities for controlling the structure and composition of surfaces on the atomic scale in heterogeneous catalysts and solid oxide fuel cell (SOFC electrodes. However, while ALD procedures and equipment are well developed for applications involving flat surfaces, the conditions required for ALD in porous materials with a large surface area need to be very different. The materials (e.g., rare earths and other functional oxides that are of interest for catalytic applications will also be different. For flat surfaces, rapid cycling, enabled by high carrier-gas flow rates, is necessary in order to rapidly grow thicker films. By contrast, ALD films in porous materials rarely need to be more than 1 nm thick. The elimination of diffusion gradients, efficient use of precursors, and ligand removal with less reactive precursors are the major factors that need to be controlled. In this review, criteria will be outlined for the successful use of ALD in porous materials. Examples of opportunities for using ALD to modify heterogeneous catalysts and SOFC electrodes will be given.

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.

Effect of temperature in hydrocracking of light cycle oil on a noble metal-supported catalyst for fuel production

Energy Technology Data Exchange (ETDEWEB)

Gutierrez, A.; Arandes, J.M.; Castano, P.; Olazar, M.; Bilbao, J. [Universidad del Pais Vasco (UPV-EHU), Departamento de Ingenieria Quimica, Bilbao (Spain); Barona, A. [Universidad del Pais Vasco (UPV-EHU), Escuela de Ingenieria, Departamento de Ingenieria Quimica y Medio Ambiente, Alda, Urkijo s/n, Bilbao (Spain)

2012-04-15

The effect of temperature has been studied in hydrocracking of light cycle oil (LCO), byproduct of fluidized catalytic cracking (FCC) units on a bifunctional catalyst (Pt-Pd/HY zeolite). The increase in both temperature and H{sub 2} partial pressure have an important attenuating effect on catalyst deactivation, given that they decrease sulfur equilibrium adsorption and enhance hydrocracking of coke precursors. Therefore, the catalyst maintains significant hydrodesulfurization and hydrocracking activity. As the temperature is increased, hydrocracking conversion and naphtha selectivity increase, although there is no significant dearomatization of the medium distillate fraction in the range of the studied experimental conditions. 400 C is the more suitable temperature for obtaining a high yield of naphtha with a high content of i-paraffins. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

A single source precursor route to group 13 homo- and heterometallic oxides as highly active supports for gold-catalyzed aerobic epoxidation of trans-stilbene

KAUST Repository

Mishra, Shashank K.; Mendez, Violaine; Jeanneau, Erwann; Caps, Valerie; Daniè le, Sté phane

2012-01-01

A new Mitsubishi-type of star-shaped homoleptic derivative of indium(III), In4(mdea)6 (2, mdeaH2 = N-methyldiethanolamine) , was synthesized by the chloro-aminoalkoxo exchange reaction of a heteroleptic complex In6Cl6(mdea)6 (1) and used as a facile single source molecular precursor for the sol-gel preparation of high surface area indium oxide. Successful deposition of gold nanoparticles (1 wt.-%) of average size 3.3 nm on the above metal oxide by using HAuCl4· 3H2O afforded a highly efficient Au/In2O3 catalyst for the aerobic epoxidation of trans-stilbene at low temperature. The above single source precursor approach was further extended to obtain other group 13 homo- and heterometallic oxides, namely, α-Ga2O 3, β-Ga2O3 and Al4Ga 2O9, as highly active supports for gold catalysts. The obtained Au/M2O3 (M = Ga, In) and Au/Al4Ga 2O9 catalysts were thoroughly characterized by using several physicochemical techniques such as XRD, high resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray (EDX) spectroscopy, and X-ray photoelectron spectroscopy (XPS). A comparative study of the above catalysts for the model aerobic oxidation of stilbene in methylcyclohexane was undertaken. Highly efficient catalysts for aerobic oxidation reactions were obtained by depositing gold nanoparticles on group 13 mono- or mixed metal oxides prepared from the hydrolysis of well-characterized homo- and heterometallic N-methyldiethanolaminate derivatives. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A single source precursor route to group 13 homo- and heterometallic oxides as highly active supports for gold-catalyzed aerobic epoxidation of trans-stilbene

KAUST Repository

Mishra, Shashank K.

2012-12-14

A new Mitsubishi-type of star-shaped homoleptic derivative of indium(III), In4(mdea)6 (2, mdeaH2 = N-methyldiethanolamine) , was synthesized by the chloro-aminoalkoxo exchange reaction of a heteroleptic complex In6Cl6(mdea)6 (1) and used as a facile single source molecular precursor for the sol-gel preparation of high surface area indium oxide. Successful deposition of gold nanoparticles (1 wt.-%) of average size 3.3 nm on the above metal oxide by using HAuCl4· 3H2O afforded a highly efficient Au/In2O3 catalyst for the aerobic epoxidation of trans-stilbene at low temperature. The above single source precursor approach was further extended to obtain other group 13 homo- and heterometallic oxides, namely, α-Ga2O 3, β-Ga2O3 and Al4Ga 2O9, as highly active supports for gold catalysts. The obtained Au/M2O3 (M = Ga, In) and Au/Al4Ga 2O9 catalysts were thoroughly characterized by using several physicochemical techniques such as XRD, high resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray (EDX) spectroscopy, and X-ray photoelectron spectroscopy (XPS). A comparative study of the above catalysts for the model aerobic oxidation of stilbene in methylcyclohexane was undertaken. Highly efficient catalysts for aerobic oxidation reactions were obtained by depositing gold nanoparticles on group 13 mono- or mixed metal oxides prepared from the hydrolysis of well-characterized homo- and heterometallic N-methyldiethanolaminate derivatives. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of Precursor-Substrate Distances on the Growth of GaN Nanowires

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Hongbin Cheng

2015-01-01

Full Text Available GaN nanowires were synthesized through the Ni-catalyzed chemical vapor deposition (CVD method using Ga2O3/GaN mixtures as gallium sources, and precursor-substrate distances were investigated as the important factor for the growth of GaN nanowires. The microstructure, composition, and photoluminescence property were characterized by X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, and photoluminescence spectra. The results showed that single crystalline GaN nanowires with the diameter of about 90 nm and the length up to tens of micrometers had been grown thickly across Si (100 substrates with uniform density. Moreover, the variations of the GaN nanowire morphology, density, and size were largely attributed to substrate positions which would influence Ga precursor density in the carrier gas, the saturation degree of gaseous reactants, and the catalyst activity, respectively, in the fabrication of GaN nanowires by the vapour liquid solid mechanism.

Methods and systems for measuring anions

KAUST Repository

Masih, Dilshad; Mohammed, Omar F.; Aly, Shawkat M.; Alarousu, Erkki

2016-01-01

Embodiments of the present disclosure provide for methods for detecting the presence and/or concentration of anions in a solution, systems for detecting the presence and/or concentration of anions in a solution, anion sensor systems, and the like.

Methods and systems for measuring anions

KAUST Repository

Masih, Dilshad

2016-08-18

Embodiments of the present disclosure provide for methods for detecting the presence and/or concentration of anions in a solution, systems for detecting the presence and/or concentration of anions in a solution, anion sensor systems, and the like.

Thermal decomposition and spectroscopic investigation of a new aqueous glycolato(-peroxo) Ti(IV) solution-gel precursor

International Nuclear Information System (INIS)

De Dobbelaere, Christopher; Mullens, Jules; Hardy, An; Van Bael, Marlies K.

2011-01-01

Highlights: → A totally water based glycolato-Ti(IV) precursor is presented and characterized. → The precursors' thermal decomposition profile depends on the ligand to metal ratio. → Titanium is coordinated in an unidentate fashion by the glycolate anion. → Smooth and uniform TiO 2 films can be prepared from the precursor solution. - Abstract: A new aqueous solution-gel precursor based on water soluble glycolato(-peroxo)-Ti(IV) complexes is developed for the preparation of TiO 2 films. With regard to the decomposition of complexes towards oxide formation, it is important to gain insight in the chemical transformations inside the precursor during thermal treatment. Therefore, the thermo-oxidative decomposition pathway of a gel obtained by slow evaporation of the precursor solution is described based on hyphenated thermogravimetric analysis with Fourier transform infrared spectroscopy (TGA-FTIR) and mass spectrometry (TGA-MS). Pure glycolic acid is used as a reference system for this study. By varying the molar glycolic acid to Ti(IV) ratio, the thermal decomposition of the gel can be drastically shortened and the profile's course changed. Gel structure and chemical changes in the gel upon heating are also studied by means of off-line FTIR. A unidentate coordination of the titanium(IV) ion by the carboxylate group of the glycolato ligands and the involvement of the hydroxyl group is confirmed. Phase formation at certain points in the thermal decomposition is studied by X-ray diffraction and Raman spectroscopy. Finally, it is proven that the new precursor is a valuable candidate for the deposition of low carbon containing solution-gel films which can ultimately be converted into smooth and uniform TiO 2 films.

Molecular heterogeneous catalysts derived from bipyridine-based organosilica nanotubes for C-H bond activation.

Science.gov (United States)

Zhang, Shengbo; Wang, Hua; Li, Mei; Han, Jinyu; Liu, Xiao; Gong, Jinlong

2017-06-01

Heterogeneous metal complex catalysts for direct C-H activation with high activity and durability have always been desired for transforming raw materials into feedstock chemicals. This study described the design and synthesis of one-dimensional organosilica nanotubes containing 2,2'-bipyridine (bpy) ligands in the framework (BPy-NT) and their post-synthetic metalation to provide highly active and robust molecular heterogeneous catalysts. By adjusting the ratios of organosilane precursors, very short BPy-NT with ∼50 nm length could be controllably obtained. The post-synthetic metalation of bipyridine-functionalized nanotubes with [IrCp*Cl(μ-Cl)] 2 (Cp* = η 5 -pentamethylcyclopentadienyl) and [Ir(cod)(OMe)] 2 (cod = 1,5-cyclooctadiene) afforded solid catalysts, IrCp*-BPy-NT and Ir(cod)-BPy-NT, which were utilized for C-H oxidation of heterocycles and cycloalkanes as well as C-H borylation of arenes. The cut-short nanotube catalysts displayed enhanced activities and durability as compared to the analogous homogeneous catalysts and other conventional heterogeneous catalysts, benefiting from the isolated active sites as well as the fast transport of substrates and products. After the reactions, a detailed characterization of Ir-immobilized BPy-NT via TEM, SEM, nitrogen adsorption, UV/vis, XPS, and 13 C CP MAS NMR indicated the molecular nature of the active species as well as stable structures of nanotube scaffolds. This study demonstrates the potential of BPy-NT with a short length as an integration platform for the construction of efficient heterogeneous catalytic systems for organic transformations.

Synthesis and characterization of catalysts for the selective transformation of biomass-derived materials

Science.gov (United States)

Ghampson, Isaac Tyrone

The experimental work in this thesis focuses on generating catalysts for two intermediate processes related to the thermal conversion of lignocellulosic biomass: the synthesis and characterization of mesoporous silica supported cobalt catalysts for the Fischer-Tropsch reaction, and an exploration of the reactivity of bulk and supported molybdenum-based nitride catalysts for the hydrodeoxygenation (HDO) of guaiacol, a lignin model compound. The first section of the work details the synthesis of a series of silica-supported cobalt Fischer-Tropsch catalysts with pore diameters ranging from 2-23 nm. Detailed X-ray diffraction measurements were used to determine the composition and particle diameters of the metal fraction, analyzed as a three-phase system containing Cofcc, Cohcp and CoO particles. Catalyst properties were determined at three stages in catalyst history: (1) after the initial calcination step to thermally decompose the catalyst precursor into Co3O4, (2) after the hydrogen reduction step to activate the catalyst to Co and (3) after the FT reaction. From the study, it was observed that larger pore diameters supported higher turnover frequency; smaller pore diameters yielded larger mole fraction of CoO; XRD on post-reduction and post-FTS catalyst samples indicated significant changes in dispersivity after reduction. In the next section, the catalytic behaviors of unsupported, activated carbon-, alumina-, and SBA-15 mesoporous silica-supported molybdenum nitride catalysts were evaluated for the hydrodeoxygenation of guaiacol (2-methoxy phenol) at 300°C and 5 MPa. The nitride catalysts were prepared by thermal decomposition of bulk and supported ammonium heptamolybdate to form MoO 3 followed by nitridation in either flowing ammonia or a nitrogen/hydrogen mixture. The catalytic properties were strongly affected by the nitriding and purging treatment as well as the physical and chemical properties of support. The overall reaction was influenced by the

Concerning the Deactivation of Cobalt(III)-Based Porphyrin and Salen Catalysts in Epoxide/CO 2 Copolymerization

KAUST Repository

Xia, Wei

2015-02-05

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Functioning as active catalysts for propylene oxide (PO) and carbon dioxide copolymerization, cobalt(III)-based salen and porphyrin complexes have drawn great attention owing to their readily modifiable nature and promising catalytic behavior, such as high selectivity for the copolymer formation and good regioselectivity with respect to the polymer microstructure. Both cobalt(III)-salen and porphyrin catalysts have been found to undergo reduction reactions to their corresponding catalytically inactive cobalt(II) species in the presence of propylene oxide, as evidenced by UV/Vis and NMR spectroscopies and X-ray crystallography (for cobalt(II)-salen). Further investigations on a TPPCoCl (TPP=tetraphenylporphyrin) and NaOMe system reveal that such a catalyst reduction is attributed to the presence of alkoxide anions. Kinetic studies of the redox reaction of TPPCoCl with NaOMe suggests a pseudo-first order in cobalt(III)-porphyrin. The addition of a co-catalyst, namely bis(triphenylphosphine)iminium chloride (PPNCl), into the reaction system of cobalt(III)-salen/porphyrin and PO shows no direct stabilizing effect. However, the results of PO/CO2 copolymerization by cobalt(III)-salen/porphyrin with PPNCl suggest a suppressed catalyst reduction. This phenomenon is explained by a rapid transformation of the alkoxide into the carbonate chain end in the course of the polymer formation, greatly shortening the lifetime of the autoreducible PO-ring-opening intermediates, cobalt(III)-salen/porphyrin alkoxides. CO2 saves: The deactivation of cobalt(III)-porphyrin and salen catalysts in propylene oxide/carbon dioxide copolymerization is systematically investigated, revealing a proposed mechanism for the catalyst reduction (see scheme).

Concerning the Deactivation of Cobalt(III)-Based Porphyrin and Salen Catalysts in Epoxide/CO 2 Copolymerization

KAUST Repository

Xia, Wei; Salmeia, Khalifah A.; Vagin, Sergei I.; Rieger, Bernhard

2015-01-01

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Functioning as active catalysts for propylene oxide (PO) and carbon dioxide copolymerization, cobalt(III)-based salen and porphyrin complexes have drawn great attention owing to their readily modifiable nature and promising catalytic behavior, such as high selectivity for the copolymer formation and good regioselectivity with respect to the polymer microstructure. Both cobalt(III)-salen and porphyrin catalysts have been found to undergo reduction reactions to their corresponding catalytically inactive cobalt(II) species in the presence of propylene oxide, as evidenced by UV/Vis and NMR spectroscopies and X-ray crystallography (for cobalt(II)-salen). Further investigations on a TPPCoCl (TPP=tetraphenylporphyrin) and NaOMe system reveal that such a catalyst reduction is attributed to the presence of alkoxide anions. Kinetic studies of the redox reaction of TPPCoCl with NaOMe suggests a pseudo-first order in cobalt(III)-porphyrin. The addition of a co-catalyst, namely bis(triphenylphosphine)iminium chloride (PPNCl), into the reaction system of cobalt(III)-salen/porphyrin and PO shows no direct stabilizing effect. However, the results of PO/CO2 copolymerization by cobalt(III)-salen/porphyrin with PPNCl suggest a suppressed catalyst reduction. This phenomenon is explained by a rapid transformation of the alkoxide into the carbonate chain end in the course of the polymer formation, greatly shortening the lifetime of the autoreducible PO-ring-opening intermediates, cobalt(III)-salen/porphyrin alkoxides. CO2 saves: The deactivation of cobalt(III)-porphyrin and salen catalysts in propylene oxide/carbon dioxide copolymerization is systematically investigated, revealing a proposed mechanism for the catalyst reduction (see scheme).

Role of iron catalyst impregnated by solvent swelling method in pyrolytic removal of coal nitrogen

Energy Technology Data Exchange (ETDEWEB)

Hayashi, J.; Kusakabe, K.; Morooka, S.; Nielsen, M.; Furimsky, E. [Kyushu University, Fukuoka (Japan). Dept. of Chemical Science and Technology

1995-11-01

Organometallic iron precursors, ferrocene and ferric acetate, were impregnated into Illinois No. 6 (IL), Wyoming (WY) and Yallourn (YL) coals by solvent swelling technique in THF, ethanol, and a THF/ethanol binary solvent. Then iron-impregnated coals were pyrolyzed in a flow of helium at atmospheric pressure in a fixed bed and a thermobalance. Conversion of coal nitrogen to N{sub 2} was 20, 38 and 30% respectively, for original IL, WY, and YL coals. Iron formed from both precursors lowered the onset temperature of N{sub 2} evolution by 20-100{degree}C. When ferrocene was impregnated in coals at a concentration of 1.7-1.8 wt% as Fe, nitrogen conversion was increased to 52, 71 and 68% for IL, WY and YL coals, respectively. Ferric acetate impregnated into IL coal from THF/ethanol solution increased the nitrogen conversion much more than that from ethanol solution. The expansion of microporous coal structure by the swelling was essential for better dispersion of the catalyst precursor. The evolution of HCN as well as NH{sub 3} was effectively suppressed above 600{degree}C by the presence of iron but not influenced significantly by combinations of catalyst precursors and solvents. The increase in N{sub 2} yield was compensated by the decrease in nitrogen emitted as HCN and NH{sub 3} and in tar and char. The increase in CO evolution from the iron-impregnated IL coal at 600-800{degree}C was explained by catalytic rearrangement of aromatic structure of char, accompanying the removal of nitrogen as N{sub 2}. In a range of 600-750{degree}C, the evolution of CO as well as N{sub 2} from the other coals increased remarkably with a significant decrease in CO{sub 2} gasification in char microproes. 32 refs., 9 figs., 3 tabs.

Production of Jet Fuel-Range Hydrocarbons from Hydrodeoxygenation of Lignin over Super Lewis Acid Combined with Metal Catalysts.

Science.gov (United States)

Wang, Hongliang; Wang, Huamin; Kuhn, Eric; Tucker, Melvin P; Yang, Bin

2018-01-10

Super Lewis acids containing the triflate anion [e.g., Hf(OTf) 4 , Ln(OTf) 3 , In(OTf) 3 , Al(OTf) 3 ] and noble metal catalysts (e.g., Ru/C, Ru/Al 2 O 3 ) formed efficient catalytic systems to generate saturated hydrocarbons from lignin in high yields. In such catalytic systems, the metal triflates mediated rapid ether bond cleavage through selective bonding to etheric oxygens while the noble metal catalyzed subsequent hydrodeoxygenation (HDO) reactions. Near theoretical yields of hydrocarbons were produced from lignin model compounds by the combined catalysis of Hf(OTf) 4 and ruthenium-based catalysts. When a technical lignin derived from a pilot-scale biorefinery was used, more than 30 wt % of the hydrocarbons produced with this catalytic system were cyclohexane and alkylcyclohexanes in the jet fuel range. Super Lewis acids are postulated to strongly interact with lignin substrates by protonating hydroxyl groups and ether linkages, forming intermediate species that enhance hydrogenation catalysis by supported noble metal catalysts. Meanwhile, the hydrogenation of aromatic rings by the noble metal catalysts can promote deoxygenation reactions catalyzed by super Lewis acids. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Novel low temperature NOx storage-reduction catalysts for diesel light-duty engine emissions based on hydrotalcite compounds

International Nuclear Information System (INIS)

Fornasari, G.; Trifiro, F.; Vaccari, A.; Prinetto, F.; Ghiotti, G.; Centi, G.

2002-01-01

A series of Pt and Pt,Cu supported catalysts were prepared by wet impregnation of Mg-Al supports obtained from hydrotalcite-type (HT) precursor compounds. These novel NO x storage-reduction (NO x SR) catalysts show improved performances in NO x storage than Pt,Ba/alumina NO x SR catalysts at reaction temperatures lower than 200C. These catalysts show also improved resistance to deactivation by SO 2 . The effect is attributed to the formation of well dispersed Mg(Al)O particles which show good NO x storage properties. The promoted low temperature activity is explained by the lower basicity of the Mg(Al)O mixed oxide in comparison to BaO, which induces on one hand a lower inhibition on Pt activity (NO to NO 2 oxidation and/or hydrocarbon oxidation) due to electronic effect, and on the other hand a lower thermal stability of the stored NO x . The presence of Cu slightly inhibits activity at low temperature, although improves activity and resistance to deactivation at 300C. On these catalysts FT-IR characterization evidences the formation of a Pt-Cu alloy after reduction

Reactions of laser-ablated Co, Rh, and Ir with CO: Infrared spectra and density functional calculations of the metal carbonyl molecules, cations and anions in solid neon

International Nuclear Information System (INIS)

Zhou, M.; Andrews, L.

1999-01-01

Laser ablation produces metal atoms, cations, and electrons for reaction with CO during condensation in excess neon at 4 K. Infrared spectra are observed for the metal carbonyls, cations, and anions, which are identified from isotopic shifts ( 13 CO, C 18 O) and splittings using mixed isotopic precursors. Density functional calculations with pseudopotentials for Rh and Ir predict the observed carbonyl stretching frequencies within 1--2%. This characterization of the simple RhCO + , RhCO, and RhCO - (and Ir) species over a 350 cm -1 range provides a scale for comparison of larger catalytically active Rh and Ir carbonyl complexes in solution and on surfaces to estimate charge on the metal center. This work provides the first spectroscopic characterization of Rh and Ir carbonyl cations and anions except for the stable tetracarbonyl anions in solution

Synthesis and Electrochemical Evaluation of Carbon Supported Pt-Co Bimetallic Catalysts Prepared by Electroless Deposition and Modified Charge Enhanced Dry Impregnation

Directory of Open Access Journals (Sweden)

John Meynard M. Tengco

2016-06-01

Full Text Available Carbon-supported bimetallic Pt-Co cathode catalysts have been previously identified as higher activity alternatives to conventional Pt/C catalysts for fuel cells. In this work, a series of Pt-Co/C catalysts were synthesized using electroless deposition (ED of Pt on a Co/C catalyst prepared by modified charge enhanced dry impregnation. X-ray diffraction (XRD and scanning transmission electron microscopy (STEM characterization of the base catalyst showed highly dispersed particles. A basic ED bath containing PtCl62− as the Pt precursor, dimethylamine borane as reducing agent, and ethylenediamine as stabilizing agent successfully targeted deposition of Pt on Co particles. Simultaneous action of galvanic displacement and ED resulted in Pt-Co alloy formation observed in XRD and energy dispersive X-ray spectroscopy (XEDS mapping. In addition, fast deposition kinetics resulted in hollow shell Pt-Co alloy particles while particles with Pt-rich shell and Co-rich cores formed with controlled Pt deposition. Electrochemical evaluation of the Pt-Co/C catalysts showed lower active surface but much higher mass and surface activities for oxygen reduction reaction compared to a commercial Pt/C fuel cell catalyst.

Continuous bench-scale slurry catalyst testing direct coal liquefaction rawhide sub-bituminous coal

Energy Technology Data Exchange (ETDEWEB)

Bauman, R.F.; Coless, L.A.; Davis, S.M. [and others

1995-12-31

In 1992, the Department of Energy (DOE) sponsored research to demonstrate a dispersed catalyst system using a combination of molybdenum and iron precursors for direct coal liquefaction. This dispersed catalyst system was successfully demonstrated using Black Thunder sub-bituminous coal at Wilsonville, Alabama by Southern Electric International, Inc. The DOE sponsored research continues at Exxon Research and Development Laboratories (ERDL). A six month continuous bench-scale program using ERDL`s Recycle Coal Liquefaction Unit (RCLU) is planned, three months in 1994 and three months in 1995. The initial conditions in RCLU reflect experience gained from the Wilsonville facility in their Test Run 263. Rawhide sub-bituminous coal which is similar to the Black Thunder coal tested at Wilsonville was used as the feed coal. A slate of five dispersed catalysts for direct coal liquefaction of Rawhide sub-bituminous coal has been tested. Throughout the experiments, the molybdenum addition rate was held constant at 100 wppm while the iron oxide addition rate was varied from 0.25 to 1.0 weight percent (dry coal basis). This report covers the 1994 operations and accomplishments.

PVP-Stabilized Palladium Nanoparticles in Silica as Effective Catalysts for Hydrogenation Reactions

Directory of Open Access Journals (Sweden)

Caroline Pires Ruas

2013-01-01

Full Text Available Palladium nanoparticles stabilized by poly (N-vinyl-2-pyrrolidone (PVP can be synthesized by corresponding Pd(acac2 (acac = acetylacetonate as precursor in methanol at 80°C for 2 h followed by reduction with NaBH4 and immobilized onto SiO2 prepared by sol-gel process under acidic conditions (HF or HCl. The PVP/Pd molar ratio is set to 6. The effect of the sol-gel catalyst on the silica morphology and texture and on Pd(0 content was investigated. The catalysts prepared (ca. 2% Pd(0/SiO2/HF and ca. 0,3% Pd(0/SiO2/HCl were characterized by TEM, FAAS, and SEM-EDS. Palladium nanoparticles supported in silica with a size 6.6 ± 1.4 nm were obtained. The catalytic activity was tested in hydrogenation of alkenes.

HDS, HDN and HDA activities of nickel-molybdenum catalysts supported on alumina

Energy Technology Data Exchange (ETDEWEB)

Dominguez-Crespo, M.A. [Instituto Mexicano del Petroleo, Programa de Tratamiento de Crudo Maya. Avenida Eje Central Lazaro Cardenas No.152, Col. San Bartolo Atepehuacan, 07730, Mexico D. F. (Mexico); Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada (CICATA-Altamira, IPN) Km 14.5 Carretera Tampico-puerto Industrial 89600, Altamira, Tamaulipas (Mexico); Torres-Huerta, A.M.; Ramirez-Meneses, E. [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada (CICATA-Altamira, IPN) Km 14.5 Carretera Tampico-puerto Industrial 89600, Altamira, Tamaulipas (Mexico); Diaz-Garcia, L. [Instituto Mexicano del Petroleo, Programa de Tratamiento de Crudo Maya. Avenida Eje Central Lazaro Cardenas No.152, Col. San Bartolo Atepehuacan, 07730, Mexico D. F. (Mexico); Arce-Estrada, E.M. [Instituto Politecnico Nacional, Departamento de Metalurgia y Materiales. A.P. 75-876, 07300 Mexico, D. F. (Mexico)

2008-08-15

In this work, NiMo-Al{sub 2}O{sub 3} catalysts were prepared by using different alumina precursors. The supports were impregnated by means of the spray at incipient wetness technique in both basic and acid media. Both the supports and fresh catalysts were characterized by the adsorption-desorption isotherms, Temperature-Programmed Reduction (TPR), Thermal Pyridine Adsorption-Desorption (TPD) and X-Ray Diffraction analyses (XRD). After sulfidation, the NiMoS metallic particles were characterized by Transmission Electron Microscopy (TEM). The initial analyses were performed in a trickle-bed reactor by using a real feedstock (Mexican heavy gas oil) and performing hydrotreating reactions (HDS, HDN and HDA) at three different temperatures: 613, 633 and 653 K; and 54 kg cm{sup -} {sup 2}. The catalytic activities are discussed in relation to the physicochemical properties of the NiMo catalysts, alumina phase and pH of the impregnating solution. The catalytic results show an increase in the conversion profiles with temperature. The sulfur conversion was increased from 89 to 99.25%, 91-99%, 90.8-97%, 83-95% and 78-96% when the crystal size of the support varied from 3 to 20 nm, respectively. The nitrogen and aromatic conversions were also increased in the range of 23-45 wt.%. It was found that the {gamma} phase reached a higher catalytic performance than the {eta} phase. The NiMo catalysts synthesized in a basic medium showed a better catalytic performance than that obtained with those prepared in acid solutions. The significance of the kinetic data to compare the catalysts is discussed. The maximum value of the catalytic activity was reached with the catalysts with the smallest particle sizes. (author)

Synthesis and application of new polymer bound catalysts

Energy Technology Data Exchange (ETDEWEB)

Fetterly, Brandon Michael [Iowa State Univ., Ames, IA (United States)

2005-01-01

Nitric acid has been shown to be a weak acid in acetonitrile. It is conceivable that a nitrate salt of a weakly Lewis acidic cation could furnish a ''naked'' nitrate anion as a basic catalyst in a variety of reactions in non-aqueous solvents. Such a nitrate salt could also be bound to a polymeric support via the cation, thereby allowing for reclamation and recycling of the nitrate ion. This subject is dealt with in Chapter 2, wherein my contributions consisted of performing all the reactions with the polymer supported catalyst and carrying out the experiments necessary to shed light on the reaction mechanisms. Chapter 3 contains a description of the structure and catalytic properties of an azidoproazaphosphatrane. This compound is an air-stable versatile catalyst that has proven useful not only homogeneously, but also when bound to a solid support. The synthesis of a polymer bound proazaphosphatrane containing a trivalent phosphorus is presented in Chapter 4. Such a compound has been sought after by our group for a number of years. Not only does the synthesis I have accomplished for it allow for easier separation of proazaphosphatrane catalysts from reaction mixtures, but recycling of the base is made much simpler. Proazaphosphatranes are useful homogeneous catalysts that activate atoms in other reagents, thus enhancing their reactivity. The next chapters deal with two such reactions with aldehydes and ketones, namely silylcyanations with trialkylsilylcyanides (Chapters 5 and 6) and reductions with poly(methylhydrosiloxane), in Chapter 7. In Chapter 5, Zhigang Wang performed the initial optimization and scoping of the reaction, while repetitions of the scoping experiments for reproducibility, determination of diastereomeric ratios, and experiments aimed at elucidating aspects of the mechanism were performed by me. The proazaphosphatrane coordinates to the silicon atom in both cases, thereby allowing the aforementioned reactions to proceed under

Carbon-supported co-pyridine as non-platinum cathode catalyst for alkaline membrane fuel cells

International Nuclear Information System (INIS)

Qiao, Jinli; Xu, Li; Liu, Yuyu; Xu, Pan; Shi, Jingjing; Liu, Shiyao; Tian, Binglun

2013-01-01

Development of high-performance cost-effective electrocatalyts that can replace Pt catalyst have been a central theme in polymer electrolyte membrane fuel cells (PEMFCs) including direct methanol fuel cells (DMFCs). Here we show that carbon-supported pyridine–cobalt nanoparticles (CoPy/C) can generate a high catalytic activity toward the oxygen reduction reaction (ORR). The catalysts are synthesized using cobalt sulfate heptahydrate (CoSO 4 ·7H 2 O) and pyridine (Py) as the Co and N precursors via a solid state reaction by heat-treatment in an inert atmosphere at 800 °C. In particular, the ORR kinetics on these catalyst materials are evaluated using rotating disk electrode (RDE) technique in electrolytes of various KOH concentrations, ranging from 0.05 to 12 M. The Koutecky–Levich equation analyses indicate that the transferred electron number, n, per oxygen molecule on CoPy/C electrode depend on the low negative ovevrpotentials in low KOH concentrations, whereas in high KOH concentrations the values of n for oxygen reduction depend on the high negative overpotentials, and varies between 3.5 and 4.0. These catalysts exhibit the superior methanol tolerance to commercial 40%Pt/C catalyst, and the negative effect of high KOH concentration is much less for CoPy/C than for Pt/C, suggesting the promising utilization of CoPy/C as electrocatalysts for alkaline polymer electrolyte membrane fuel cells

Pt/glassy carbon model catalysts prepared from PS-b-P2VP micellar templates.

Science.gov (United States)

Gu, Yunlong; St-Pierre, Jean; Ploehn, Harry J

2008-11-04

Poly(styrene)-block-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer was used as a micellar template to fabricate arrays of Pt nanoparticles on mica and glassy carbon (GC) supports. Polymer micellar deposition yields Pt nanoparticles with tunable particle size and surface number density on both mica and GC. After deposition of precursor-loaded micelles onto GC, oxygen plasma etching removes the polymer shell, followed by thermal treatment with H2 gas to reduce the Pt. Etching conditions were optimized to maximize removal of the polymer while minimizing damage to the GC. Arrays of Pt nanoparticles with controlled size and surface number density can be prepared on mica (for particle size characterization) and GC to make Pt/GC model catalysts. These model catalysts were characterized by tapping mode atomic force microscopy, X-ray photoelectron spectroscopy, and cyclic voltammetry to measure activity for oxidation of carbon monoxide or methanol. Cyclic voltammetry results demonstrate the existence of a correlation between Pt particle size and electrocatalytic properties including onset potential, tolerance of carbonaceous adsorbates, and intrinsic activity (based on active Pt area from CO stripping voltammetry). Results obtained with Pt/GC model catalysts duplicate prior results obtained with Pt/porous carbon catalysts therefore validating the synthesis approach and offering a new, tunable platform to study catalyst structure and other effects such as aging on proton exchange membrane fuel cell (PEMFC) reactions.

Creating molecular macrocycles for anion recognition

Directory of Open Access Journals (Sweden)

Amar H. Flood

2016-03-01

Full Text Available The creation and functionality of new classes of macrocycles that are shape persistent and can bind anions is described. The genesis of triazolophane macrocycles emerges out of activity surrounding 1,2,3-triazoles made using click chemistry; and the same triazoles are responsible for anion capture. Mistakes made and lessons learnt in anion recognition provide deeper understanding that, together with theory, now provides for computer-aided receptor design. The lessons are acted upon in the creation of two new macrocycles. First, cyanostars are larger and like to capture large anions. Second is tricarb, which also favors large anions but shows a propensity to self-assemble in an orderly and stable manner, laying a foundation for future designs of hierarchical nanostructures.

New Cu-based catalysts supported on TiO2 films for Ullmann SnAr-type C-O coupling reactions

NARCIS (Netherlands)

Benaskar, F.; Engels, V.; Rebrov, E.; Patil, N.G.; Meuldijk, J.; Thuene, P.C.; Magusin, P.C.M.M.; Mezari, B.; Hessel, V.; Hulshof, L.A.; Hensen, E.J.M.; Wheatley, A.E.H.; Schouten, J.C.

2012-01-01

New routes for the preparation of highly active TiO2-supported Cu and CuZn catalysts have been developed for CO coupling reactions. Slurries of a titania precursor were dip-coated onto glass beads to obtain either structured mesoporous or non-porous titania thin films. The Cu and CuZn nanoparticles,

Studies on recycling and utilization of spent catalysts. Preparation of active hydrodemetallization catalyst compositions from spent residue hydroprocessing catalysts

Energy Technology Data Exchange (ETDEWEB)

Marafi, Meena; Stanislaus, Antony [Petroleum Refining Department, Petroleum Research and Studies Center, Kuwait Institute for Scientific Research, P.O. Box 24885, Safat (Kuwait)

2007-02-15

Spent catalysts form a major source of solid wastes in the petroleum refining industries. Due to environmental concerns, increasing emphasis has been placed on the development of recycling processes for the waste catalyst materials as much as possible. In the present study the potential reuse of spent catalysts in the preparation of active new catalysts for residual oil hydrotreating was examined. A series of catalysts were prepared by mixing and extruding spent residue hydroprocessing catalysts that contained C, V, Mo, Ni and Al{sub 2}O{sub 3} with boehmite in different proportions. All prepared catalysts were characterized by chemical analysis and by surface area, pore volume, pore size and crushing strength measurements. The hydrodesulfurization (HDS) and hydrodemetallization (HDM) activities of the catalysts were evaluated by testing in a high pressure fixed-bed microreactor unit using Kuwait atmospheric residue as feed. A commercial HDM catalyst was also tested under similar operating conditions and their HDS and HDM activities were compared with that of the prepared catalysts. The results revealed that catalyst prepared with addition of up to 40 wt% spent catalyst to boehmite had fairly high surface area and pore volume together with large pores. The catalyst prepared by mixing and extruding about 40 wt% spent catalyst with boehmite was relatively more active for promoting HDM and HDS reactions than a reference commercial HDM catalyst. The formation of some kind of new active sites from the metals (V, Mo and Ni) present in the spent catalyst is suggested to be responsible for the high HDM activity of the prepared catalyst. (author)

Relevance of the Physicochemical Properties of Calcined Quail Eggshell (CaO as a Catalyst for Biodiesel Production

Directory of Open Access Journals (Sweden)

Leandro Marques Correia

2017-01-01

Full Text Available The CaO solid derived from natural quail eggshell was calcined and employed as catalyst to produce biodiesel via transesterification of sunflower oil. The natural quail eggshell was calcined at 900°C for 3 h, in order to modify the calcium carbonate present in its structure in CaO, the activity phase of the catalyst. Both precursor and catalyst were characterized using Hammett indicators method, X-ray fluorescence (XRF, X-ray diffraction (XRD, thermogravimetric analysis (TG/DTG, CO2 temperature-programmed desorption (CO2-TPD, X-ray photoelectronic spectroscopy (XPS, Fourier infrared spectroscopy (FTIR, scanning electron microscopy (SEM, N2 adsorption-desorption at −196°C, and distribution particle size. The maximum biodiesel production was of 99.00 ± 0.02 wt.% obtained in the following transesterification reaction conditions: XMR (sunflower oil/methanol molar ratio of 1 : 10.5 mol : mol, XCAT (catalyst loading of 2 wt.%, XTIME (reaction time of 2 h, stirring rate of 1000 rpm, and temperature of 60°C.

Low-temperature conversion of ammonia to nitrogen in water with ozone over composite metal oxide catalyst.

Science.gov (United States)

Chen, Yunnen; Wu, Ye; Liu, Chen; Guo, Lin; Nie, Jinxia; Chen, Yu; Qiu, Tingsheng

2018-04-01

As one of the most important water pollutants, ammonia nitrogen emissions have increased year by year, which has attracted people's attention. Catalytic ozonation technology, which involves production of ·OH radical with strong oxidation ability, is widely used in the treatment of organic-containing wastewater. In this work, MgO-Co 3 O 4 composite metal oxide catalysts prepared with different fabrication conditions have been systematically evaluated and compared in the catalytic ozonation of ammonia (50mg/L) in water. In terms of high catalytic activity in ammonia decomposition and high selectivity for gaseous nitrogen, the catalyst with MgO-Co 3 O 4 molar ratio 8:2, calcined at 500°C for 3hr, was the best one among the catalysts we tested, with an ammonia nitrogen removal rate of 85.2% and gaseous nitrogen selectivity of 44.8%. In addition, the reaction mechanism of ozonation oxidative decomposition of ammonia nitrogen in water with the metal oxide catalysts was discussed. Moreover, the effect of coexisting anions on the degradation of ammonia was studied, finding that SO 4 2- and HCO 3 - could inhibit the catalytic activity while CO 3 2- and Br - could promote it. The presence of coexisting cations had very little effect on the catalytic ozonation of ammonia nitrogen. After five successive reuses, the catalyst remained stable in the catalytic ozonation of ammonia. Copyright © 2017. Published by Elsevier B.V.

Highly efficient silver patterning without photo-resist using simple silver precursors

International Nuclear Information System (INIS)

Byun, Younghun; Hwang, Eoc-Chae; Lee, Sang-Yun; Lyu, Yi-Yeol; Yim, Jin-Heong; Kim, Jin-Young; Chang, Seok; Pu, Lyong Sun; Kim, Ji Man

2005-01-01

Highly efficient method for silver patterning without photo-resist was developed by using high photosensitive organo-silver precursors, which were prepared by a simple reaction of silver salts and excess of amines. The FT-IR and GC-MS spectra were recorded depending on UV exposure time, for (n-PrNH 2 )Ag(NO 3 ).0.5MeCN and (n-PrNH 2 )Ag(NO 2 ).0.5MeCN, to understand the photolysis mechanism. The results indicate not only dissociation of coordinated amine and acetonitrile, but also decomposition of corresponding anion upon UV irradiation. When a precursor thin film was exposed to broadband UV irradiation, a partially reduced and insoluble silver species were formed within several minutes. After development, the irradiated areas were treated with a reducing agent to obtain pure metallic patterns. Subsequently, annealing step was followed at 100-350 deg. C to increase the adhesion of interface and cohesion of silver particles. The line resolution of 5 μm was obtained by the present silver precursors. Film thickness was also controllable from 50 to 250 nm by repetition of the above procedure. The average electrical conductivity was in the range of 3-43 Ω cm, measured by four-point probe technique. AES depth profile of the silver pattern thus obtained showed carbon and oxygen contents are less than 1% through the whole range. Even though sulfur contaminant exists on the surface, it was believed that nearly pure silver pattern was generated

Anion concurrence and anion selectivity in the sorption of radionuclides by organotones

International Nuclear Information System (INIS)

Behnsen, Julia G.

2007-01-01

Some long-lived and radiologically important nuclear fission products, such as I-129 (half-life t 1/2 = 1,6 . 10 7 a), Tc-99 (t 1/2 = 2,1 . 10 5 a), and Se-79 (t 1/2 = 6,5 . 10 4 a) are anionic in aqueous environments. This study focuses on the adsorption of such anions to organoclays and the understanding of the selectivity of the process. The organoclays used in this study were prepared from a bentonite (MX-80) and a vermiculite clay, and the cationic surfactants hexadcylpyridium, hexadecyltrimethylammonium, and benzethonium. Surfactant adsorption to the bentonite exceeds the cation exchange capacity of the clay, with the surplus positive charge being balanced by the co-adsorption of chloride. The interlayer distance of the bentonites is increased sufficiently to contain bi- and pseudotrimolecular structures of the surfactants. Adsorption experiments were carried out using the batch technique. Anion adsorption of iodide, perrhenate, selenite, nitrate, and sulphate is mainly due to ion exchange with chloride. As an additional adsorption mechanism, the incorporation of inorganic ion pairs into the interlayer space of the clay is proposed as a result of experiments showing differences in the adsorption levels of sodium and potassium iodide. Anion adsorption results show a clear selectivity of the organoclays, with the affinity sequence being: ReO - 4 > I - > NO - 3 > Cl - > SO 2- 4 > SeO 2- 3 . This sequence corresponds to the sequence of increasing hydration energies of the anions, thus selectivity could be due to the process of minimization of free energy of the system. (orig.)

Role of the metal oxidation state in the SNS-Cr catalyst for ethylene trimerization: Isolation of Di- and trivalent cationic intermediates

NARCIS (Netherlands)

Jabri, A.; Temple, C.N.; Crewdson, P.; Gambarotta, S.; Korobkov, I.V.; Duchateau, R.

2006-01-01

The reaction of the highly selective [CySCH2CH2N(H)CH2CH2SCy]CrCl3 catalyst precursor with alkyl aluminum activators was examined with the aim of isolating reactive intermediates. Reaction with Me3Al afforded a cationic trivalent chromium alkyl species

Thermal decomposition and spectroscopic investigation of a new aqueous glycolato(-peroxo) Ti(IV) solution-gel precursor

Energy Technology Data Exchange (ETDEWEB)

De Dobbelaere, Christopher, E-mail: christopher.dedobbelaere@uhasselt.be [Hasselt University, Institute for Materials Research, Inorganic and Physical Chemistry, Agoralaan Building D, B-3590 Diepenbeek (Belgium); Mullens, Jules, E-mail: jules.mullens@uhasselt.be [Hasselt University, Institute for Materials Research, Inorganic and Physical Chemistry, Agoralaan Building D, B-3590 Diepenbeek (Belgium); Hardy, An, E-mail: an.hardy@uhasselt.be [Hasselt University, Institute for Materials Research, Inorganic and Physical Chemistry, Agoralaan Building D, B-3590 Diepenbeek (Belgium); IMEC vzw, Division IMOMEC, Agoralaan Building D, B-3590 Diepenbeek (Belgium); Van Bael, Marlies K., E-mail: marlies.vanbael@uhasselt.be [Hasselt University, Institute for Materials Research, Inorganic and Physical Chemistry, Agoralaan Building D, B-3590 Diepenbeek (Belgium); IMEC vzw, Division IMOMEC, Agoralaan Building D, B-3590 Diepenbeek (Belgium)

2011-06-10

Highlights: {yields} A totally water based glycolato-Ti(IV) precursor is presented and characterized. {yields} The precursors' thermal decomposition profile depends on the ligand to metal ratio. {yields} Titanium is coordinated in an unidentate fashion by the glycolate anion. {yields} Smooth and uniform TiO{sub 2} films can be prepared from the precursor solution. - Abstract: A new aqueous solution-gel precursor based on water soluble glycolato(-peroxo)-Ti(IV) complexes is developed for the preparation of TiO{sub 2} films. With regard to the decomposition of complexes towards oxide formation, it is important to gain insight in the chemical transformations inside the precursor during thermal treatment. Therefore, the thermo-oxidative decomposition pathway of a gel obtained by slow evaporation of the precursor solution is described based on hyphenated thermogravimetric analysis with Fourier transform infrared spectroscopy (TGA-FTIR) and mass spectrometry (TGA-MS). Pure glycolic acid is used as a reference system for this study. By varying the molar glycolic acid to Ti(IV) ratio, the thermal decomposition of the gel can be drastically shortened and the profile's course changed. Gel structure and chemical changes in the gel upon heating are also studied by means of off-line FTIR. A unidentate coordination of the titanium(IV) ion by the carboxylate group of the glycolato ligands and the involvement of the hydroxyl group is confirmed. Phase formation at certain points in the thermal decomposition is studied by X-ray diffraction and Raman spectroscopy. Finally, it is proven that the new precursor is a valuable candidate for the deposition of low carbon containing solution-gel films which can ultimately be converted into smooth and uniform TiO{sub 2} films.

Effect of cationic molecules on the oxygen reduction reaction on fuel cell grade Pt/C (20 wt%) catalyst in potassium hydroxide (aq, 1 mol dm(-3)).

Science.gov (United States)

Ong, Ai Lien; Inglis, Kenneth K; Whelligan, Daniel K; Murphy, Sam; Varcoe, John R

2015-05-14

This study investigates the effect of 1 mmol dm(-3) concentrations of a selection of small cationic molecules on the performance of a fuel cell grade oxygen reduction reaction (ORR) catalyst (Johnson Matthey HiSPEC 3000, 20 mass% Pt/C) in aqueous KOH (1 mol dm(-3)). The cationic molecules studied include quaternary ammonium (including those based on bicyclic systems) and imidazolium types as well as a phosphonium example: these serve as fully solubilised models for the commonly encountered head-groups in alkaline anion-exchange membranes (AAEM) and anion-exchange ionomers (AEI) that are being developed for application in alkaline polymer electrolyte fuel cells (APEFCs), batteries and electrolysers. Both cyclic and hydrodynamic linear sweep rotating disk electrode voltammetry techniques were used. The resulting voltammograms and subsequently derived data (e.g. apparent electrochemical active surface areas, Tafel plots, and number of [reduction] electrons transferred per O2) were compared. The results show that the imidazolium examples produced the highest level of interference towards the ORR on the Pt/C catalyst under the experimental conditions used.

Deactivation-resistant catalyst for selective catalyst reduction of NOx

DEFF Research Database (Denmark)

2011-01-01

The present invention relates to a catalyst for selective catalytic reduction of NOx in alkali metal containing flue gas using ammonia as reductant, the catalyst comprising a surface with catalytically active sites, wherein the surface is at least partly coated with a coating comprising at least...... one metal oxide. In another aspect the present invention relates to the use of said catalyst and to a method of producing said catalyst. In addition, the present invention relates to a method of treating an catalyst for conferring thereon an improved resistance to alkali poisoning....

Simultaneous anion and cation mobility in polypyrrole

DEFF Research Database (Denmark)

Skaarup, Steen; Bay, Lasse; Vidanapathirana, K.

2003-01-01

and the expulsion of anions; a broad anodic peak centered at ca. - 0.5 V representing the expulsion of cations; and a second broad peak at +0.2 to +0.5 V corresponding to anions being inserted. Although the motion of cations is the most important, as expected, there is a significant anion contribution, thereby...... complicating reproducibility when employing PPy(DBS) polymers as actuators. When the cation is doubly charged, it enters the film less readily, and anions dominate the mobility. Using a large and bulky cation switches the mechanism to apparently total anion motion. The changes in area of the three peaks...

Synthesis and characterization of novel intermetallic catalysts for hydrogenation of carbon dioxide to methanol

DEFF Research Database (Denmark)

Fiordaliso, Elisabetta Maria; Sharafutdinov, Irek; Chorkendorff, Ib

Novel Ni5Ga3 and Pd2Ga catalysts for CO2 hydrogenation to methanol are prepared by impregnation of aqueous Ni-Ga or Pd-Ga solutions of metal nitrates into high surface area SiO2, followed by drying, calcinations and reduction of the precursor in a H2 flow. Steady state experiments are performed...... in a reactor at atmospheric pressure and stoichiometric CO2/H2 mixture, while reaction products are analyzed by gas chromatography. The results are compared to the highly optimized Cu/ZnO/Al2O3. The activity and selectivity of the novel catalysts is close to that of Cu/ZnO/Al2O3 and the equilibrium conversion...... to CH3OH is found to be higher. XRD and XRF are used to investigate the phase and composition of the supported catalysts at the 5 stages of testing, i.e. after drying, calcination, reduction, CO2 hydrogenation, rapid ageing. SEM and TEM images of the exact same locations are acquired after each of the 5...

Graphene-coated polymeric anion exchangers for ion chromatography

Energy Technology Data Exchange (ETDEWEB)

Zhang, Kai; Cao, Minyi; Lou, Chaoyan [Department of Chemistry, Xixi Campus, Zhejiang University, Hangzhou 310028 (China); Wu, Shuchao, E-mail: wushch2002@163.com [Zhejiang Institute of Geology and Mineral Resources, Hangzhou 310007 (China); Zhang, Peimin [Department of Chemistry, Xixi Campus, Zhejiang University, Hangzhou 310028 (China); Zhi, Mingyu [Hangzhou Vocational & Technical College, Hangzhou, 310018 (China); Zhu, Yan, E-mail: zhuyan@zju.edu.cn [Department of Chemistry, Xixi Campus, Zhejiang University, Hangzhou 310028 (China)

2017-06-01

Carbonaceous stationary phases have gained much attention for their peculiar selectivity and robustness. Herein we report the fabrication and application of a graphene-coated polymeric stationary phase for anion exchange chromatography. The graphene-coated particles were fabricated by a facile evaporation-reduction method. These hydrophilic particles were proven appropriate substrates for grafting of hyperbranched condensation polymers (HBCPs) to make pellicular anion exchangers. The new phase was characterized by zeta potentials, Fourier transform infrared spectroscopy, thermogravimetry and scanning electron microscope. Frontal displacement chromatography showed that the capacities of the anion exchangers were tuned by both graphene amount and HBCPs layer count. The chromatographic performance of graphene-coated anion exchangers was demonstrated with separation of inorganic anions, organic acids, carbohydrates and amino acids. Good reproducibility was obtained by consecutive injections, indicating high chemical stability of the coating. - Highlights: • Graphene-coated polymeric particles were fabricated by a facile method. • Hyperbranched condensation polymers (HBCPs) were grafted from graphene-coated particles to make anion exchangers. • Graphene amount and HBCPs layer count had significant effects on the anion exchange capacities. • Separation of diverse anionic analytes on the anion exchangers was demonstrated. • The prepared anion exchangers exhibited high stability.

Silica-supported (nBuCp)2ZrCl2: Effect of catalyst active center distribution on ethylene-1-hexene copolymerization

KAUST Repository

Atiqullah, Muhammad

2013-08-12

Metallocenes are a modern innovation in polyolefin catalysis research. Therefore, two supported metallocene catalysts-silica/MAO/(nBuCp)2ZrCl2 (Catalyst 1) and silica/nBuSnCl3/MAO/(nBuCp)2ZrCl2 (Catalyst 2), where MAO is methylaluminoxane-were synthesized, and subsequently used to prepare, without separate feeding of MAO, ethylene-1-hexene Copolymer 1 and Copolymer 2, respectively. Fouling-free copolymerization, catalyst kinetic stability and production of free-flowing polymer particles (replicating the catalyst particle size distribution) confirmed the occurrence of heterogeneous catalysis. The catalyst active center distribution was modeled by deconvoluting the measured molecular weight distribution and copolymer composition distribution. Five different active center types were predicted for each catalyst, which was corroborated by successive self-nucleation and annealing experiments, as well as by an extended X-ray absorption fine structure spectroscopy report published in the literature. Hence, metallocenes impregnated particularly on an MAO-pretreated support may be rightly envisioned to comprise an ensemble of isolated single sites that have varying coordination environments. This study shows how the active center distribution and the design of supported MAO anions affect copolymerization activity, polymerization mechanism and the resulting polymer microstructures. Catalyst 2 showed less copolymerization activity than Catalyst 1. Strong chain transfer and positive co-monomer effect-both by 1-hexene-were common. Each copolymer demonstrated vinyl, vinylidene and trans-vinylene end groups, and compositional heterogeneity. All these findings were explained, as appropriate, considering the modeled active center distribution, MAO cage structure repeat units, proposed catalyst surface chemistry, segregation effects and the literature that concerns and supports this study. While doing so, new insights were obtained. Additionally, future research, along the direction

Silica-supported (nBuCp)2ZrCl2: Effect of catalyst active center distribution on ethylene-1-hexene copolymerization

KAUST Repository

Atiqullah, Muhammad; Anantawaraskul, Siripon; Emwas, Abdul-Hamid M.; Al-Harthi, Mamdouh Ahmed; Hussain, Ikram; Ul-Hamid, Anwar; Hossaen, Anwar

2013-01-01

Metallocenes are a modern innovation in polyolefin catalysis research. Therefore, two supported metallocene catalysts-silica/MAO/(nBuCp)2ZrCl2 (Catalyst 1) and silica/nBuSnCl3/MAO/(nBuCp)2ZrCl2 (Catalyst 2), where MAO is methylaluminoxane-were synthesized, and subsequently used to prepare, without separate feeding of MAO, ethylene-1-hexene Copolymer 1 and Copolymer 2, respectively. Fouling-free copolymerization, catalyst kinetic stability and production of free-flowing polymer particles (replicating the catalyst particle size distribution) confirmed the occurrence of heterogeneous catalysis. The catalyst active center distribution was modeled by deconvoluting the measured molecular weight distribution and copolymer composition distribution. Five different active center types were predicted for each catalyst, which was corroborated by successive self-nucleation and annealing experiments, as well as by an extended X-ray absorption fine structure spectroscopy report published in the literature. Hence, metallocenes impregnated particularly on an MAO-pretreated support may be rightly envisioned to comprise an ensemble of isolated single sites that have varying coordination environments. This study shows how the active center distribution and the design of supported MAO anions affect copolymerization activity, polymerization mechanism and the resulting polymer microstructures. Catalyst 2 showed less copolymerization activity than Catalyst 1. Strong chain transfer and positive co-monomer effect-both by 1-hexene-were common. Each copolymer demonstrated vinyl, vinylidene and trans-vinylene end groups, and compositional heterogeneity. All these findings were explained, as appropriate, considering the modeled active center distribution, MAO cage structure repeat units, proposed catalyst surface chemistry, segregation effects and the literature that concerns and supports this study. While doing so, new insights were obtained. Additionally, future research, along the direction

POROUS ALUMINOPHOSPHATES :From Molecular Sieves to Designed Acid Catalysts

Science.gov (United States)

Pastore, H. O.; Coluccia, S.; Marchese, L.

2005-08-01

This review covers the synthesis, characterization, and physico-chemical properties of microporous and mesoporous aluminophosphates and silicoaluminophosphates molecular sieves. Particular emphasis is given to the materials that have found applications as acid catalysts. We consider the evolution of the synthesis procedures from the first discoveries to the current methodologies and give perspectives for new possible synthesis strategies. Emphasis is given to the use of specially prepared precursors/reactants designed for the use as molecular sieves. Experimental (especially MAS-NMR and FTIR spectroscopy) and theoretical approaches to the description of the Si insertion into the ALPO framework and to the acidic properties of SAPOs and MeAPSOs materials are discussed.

N, S co-doped carbon spheres with highly dispersed CoO as non-precious metal catalyst for oxygen reduction reaction

Science.gov (United States)

Chen, Linlin; Guo, Xingpeng; Zhang, Guoan

2017-08-01

It is still a great challenge in preparing non-precious metal catalysts with high activity and long-term stability to substitute for precious metal catalysts for oxygen reduction reaction (ORR) in fuel cells. Herein, we report a novel and facile catalyst-N, S co-doped carbon spheres with highly dispersed CoO (CoO@NS-CSs), where biomass glucose spheres act as carbon precursor and H2S, NH3 derived from the decomposition of thiourea not only provide N, S sources but also can etch carbon spheres to produce nanoporous structure. CoO@NS-CSs catalyst exhibits excellent ORR activity with a high onset potential of 0.946 V vs. RHE (reversible hydrogen electrode) and a half-wave potential of 0.821 V vs. RHE through a four-electron pathway in alkaline solution, which is comparable to commercial Pt/C catalyst (onset potential: 0.926 V vs. RHE, half-wave potential: 0.827 V vs. RHE). Furthermore, both the long-term stability and methanol-tolerance of CoO@NS-CSs catalyst are superior to those of commercial Pt/C catalyst. The excellent ORR performance of CoO@NS-CSs catalyst can be attributed to its micro-mesopore structure, high specific surface area (667 m2 g-1), and highly dispersed CoO. This work manifests that the obtained CoO@NS-CSs catalyst is promising to be applied to fuel cells.

Chemical vapor deposition growth of carbon nanotubes on Si substrates using Fe catalyst: What happens at the nanotube/Fe/Si interface

International Nuclear Information System (INIS)

Chakraborty, Amit K.; Jacobs, J.; Anderson, C.; Roberts, C. J.; Hunt, Michael R. C.

2006-01-01

Direct growth of carbon nanotubes (CNTs) on silicon is of great importance for their potential exploitation in the semiconductor industry. In this article we investigate the chemical vapor deposition growth of CNTs on Si substrates from ethylene precursor using an iron catalyst. We observe that CNTs are produced only at temperatures between 830 and 980 deg. C, and within this narrow temperature window CNT yield initially increases with temperature to reach a maximum around 900 deg. C and then declines. While the requirement of a minimum temperature to initiate CNT growth can be understood by considering the minimum energy necessary to activate the catalyst particles, characterization of the as-grown CNTs by atomic force microscopy and x-ray photoelectron spectroscopy reveals that a loss of catalyst is responsible for the observed decline in CNT yield above 900 deg. C. However, unlike some previous reports suggesting surface silicide formation as the mechanism for catalyst loss, we find that either subsurface diffusion or evaporation is the mechanism for the loss of catalyst material in the current study

Towards Highly Performing and Stable PtNi Catalysts in Polymer Electrolyte Fuel Cells for Automotive Application

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Sabrina C. Zignani

2017-03-01

Full Text Available In order to help the introduction on the automotive market of polymer electrolyte fuel cells (PEFCs, it is mandatory to develop highly performing and stable catalysts. The main objective of this work is to investigate PtNi/C catalysts in a PEFC under low relative humidity and pressure conditions, more representative of automotive applications. Carbon supported PtNi nanoparticles were prepared by reduction of metal precursors with formic acid and successive thermal and leaching treatments. The effect of the chemical composition, structure and surface characteristics of the synthesized samples on their electrochemical behavior was investigated. The catalyst characterized by a larger Pt content (Pt3Ni2/C presented the highest catalytic activity (lower potential losses in the activation region among the synthesized bimetallic PtNi catalysts and the commercial Pt/C, used as the reference material, after testing at high temperature (95 °C and low humidification (50% conditions for automotive applications, showing a cell potential (ohmic drop-free of 0.82 V at 500 mA·cm−2. In order to assess the electro-catalysts stability, accelerated degradation tests were carried out by cycling the cell potential between 0.6 V and 1.2 V. By comparing the electrochemical and physico-chemical parameters at the beginning of life (BoL and end of life (EoL, it was demonstrated that the Pt1Ni1/C catalyst was the most stable among the catalyst series, with only a 2% loss of voltage at 200 mA·cm−2 and 12.5% at 950 mA·cm−2. However, further improvements are needed to produce durable catalysts.

The next generation fuel cells: anion exchange membrane fuel cells (AEMFC)

International Nuclear Information System (INIS)

Tauqir, A.; Zahoor, S.

2013-01-01

Many environmentally friendly alternatives (solar, wind, hydroelectric, and geothermal power) can only be used in particular environments. In contrast, fuel cells can have near-zero emissions, are quiet and efficient, and can work in any environment where the temperature is lower than the cell's operating temperature. Among various types of fuel cells, the AEMFC is the most recent one and has advantages such as excellent performance compared to other candidate fuel cells due to its active O/sub 2/ electrode kinetics and flexibility to use a wide range of electro-catalysts such as silver and nickels contrary to expensive one (Platinum) required for proton exchange membrane fuel cell (PEMFC). Anion exchange membrane (AEM) is a crucial part in AEMFC, determining durability and electrochemical performances of membrane electrode assembly (MEA). The role of an AEM is to conduct hydroxyl ions from cathode to anode. If this conduction is not sufficiently high and selective, the corresponding fuel cell will not find any practical application. One of the major problems associated with AEMFC is much lower conductivities of anion compare to proton conductivity in PEMFCs, even upon similar working condition. Thus AEMs is only practical, if it is chemically and mechanically stable against severe basic operation conditions and highly hydroxyl ions conductive. The conventional AEMs based on animated aliphatic and aromatic hydrocarbon or even fluorinated polymers tend to be attacked by hydroxyl ions, causing the degradation during operation is strongly basic conditions. (author)

Metallocene-catalyzed ethylene−α-olefin isomeric copolymerization: A perspective from hydrodynamic boundary layer mass transfer and design of MAO anion

KAUST Repository

Adamu, Sagir

2015-11-28

This study reports a novel conceptual framework that can be easily experimented to evaluate the effects of hydrodynamic boundary layer mass transfer, methylaluminoxane (MAO) anion design, and comonomer steric hindrance on metallocene-catalyzed ethylene polymerization. This approach was illustrated by conducting homo- and isomeric copolymerization of ethylene with 1-hexene and 4-methyl-1-pentene in the presence of bis(n-butylcyclopentadienyl) zirconium dichloride (nBuCp)2ZrCl2, using (i) MAO anion 1 (unsupported [MAOCl2]−) and pseudo-homogeneous reference polymerization, and (ii) MAO anion 2 (supported Si−O−[MAOCl2]−) and in-situ heterogeneous polymerization. The measured polymer morphology, catalyst productivity, molecular weight distribution, and inter-chain composition distribution were related to the locus of polymerization, comonomer effect, in-situ chain transfer process, and micromixing effect, respectively. The peak melting and crystallization temperatures and %crystallinity were mathematically correlated to the parameters of microstructural composition distributions, melt fractionation temperatures, and average lamellar thickness. These relations showed to be insightful. The comonomer-induced enchainment defects and the eventual partial disruption of the crystal lattice were successfully modeled using Flory and Gibbs–Thompson equations. The present methodology can also be applied to study ethylene−α-olefin copolymerization, performed using MAO-activated non-metallocene precatalysts.

Synthesis, Characterization, and Use of Novel Bimetal Oxide Catalyst for Photoassisted Degradation of Malachite Green Dye

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K. L. Ameta

2014-01-01

Full Text Available This work reports a simple, novel, and cost effective synthesis of nanobimetal oxide catalyst using cerium and cadmium nitrates as metal precursors. The cerium-cadmium oxide nanophotocatalyst was synthesized by coprecipitation method and characterized by X-ray powder diffraction method to analyze the particle size. XRD study reveals a high degree of crystallinity and 28.43 nm particle size. The photocatalytic efficiency of the synthesized nanobimetal catalyst was examined by using it for the photocatalytic degradation of malachite green dye. Experiments were conducted to study the effect of various parameters, such as the pH of the dye solution, concentration of dye, amount of catalyst, and light intensity on the rate of dye degradation. The progress of the dye degradation was monitored spectrophotometrically by taking the optical density of the dye solution at regular intervals. Experimental results indicate that the dye degrades best at pH 8.0 with light intensity 600 Wm−2 and catalyst loading 0.03 g/50 mL of dye solution. The rate constant for the reaction was 7.67 × 10−4 s−1.

Hydrogen Production via Glycerol Dry Reforming over La-Ni/Al2O3 Catalyst

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Kah Weng Siew

2013-12-01

Full Text Available Glycerol (a bio-waste generated from biodiesel production has been touted as a promising bio-syngas precursor via reforming route. Previous studies have indicated that carbon deposition is the major performance-limiting factor for nickel (Ni catalyst during glycerol steam reforming. In the current paper, dry (CO2-reforming of glycerol, a new reforming route was carried out over alumina (Al2O3-supported non-promoted and lanthanum-promoted Ni catalysts. Both sets of catalysts were synthesized via wet co-impregnation procedure. The physicochemical characterization of the catalyst showed that the promoted catalyst possessed smaller metal crystallite size, hence higher metal dispersion compared to the virgin Ni/Al2O3 catalyst. This was also corroborated by the surface images captured by the FESEM analysis. In addition, BET surface area measurement gave 92.05m²/g for non-promoted Ni catalyst whilst promoted catalysts showed an average of 1 to 6% improvement depending on the La loading. Reaction studies at 873 K showed that glycerol dry reforming successfully produced H2 with glycerol conversion and H2 yield that peaked at 9.7% and 25% respectively over 2wt% La content. The optimum catalytic performance by 2%La-Ni/Al2O3 can be attributed to the larger BET surface area and smaller crystallite size that ensured accessibility of active catalytic sites.  © 2013 BCREC UNDIP. All rights reservedReceived: 12nd May 2013; Revised: 7th October 2013; Accepted: 16th October 2013[How to Cite: Siew, K.W., Lee, H.C., Gimbun, J., Cheng, C.K. (2013. Hydrogen Production via Glycerol Dry Reforming over La-Ni/Al2O3 Catalyst. Bulletin of Chemical Reaction Engineering & Catalysis, 8 (2: 160-166. (doi:10.9767/bcrec.8.2.4874.160-166][Permalink/DOI: http://dx.doi.org/10.9767/bcrec.8.2.4874.160-166

Nanostructured Co3O4 grown on nickel foam: An efficient and readily recyclable 3D catalyst for heterogeneous peroxymonosulfate activation.

Science.gov (United States)

Yuan, Ruixia; Hu, Lin; Yu, Peng; Wang, Huaiyuan; Wang, Zhaohui; Fang, Jingyun

2018-05-01

Cobalt-based heterogeneous catalyst has been recognized as one of most efficient activators for peroxymonosulfate (PMS) decomposition, but usually suffers from the poor stability and difficulty to recover and reuse. Here easily recyclable cobalt oxide (Co 3 O 4 ) nanowires and nanoflowers grown on nickel foam (NF) are fabricated by a hydrothermal and calcination method. The prepared 3D Co 3 O 4 /NF catalyst is characterized and applied as a heterogeneous catalyst for PMS activation to generate sulfate radicals for decomposition of Acid Orange 7 (AO7). The results show that the AO7 degradation rate increases with cobalt loading and PMS dosage, but decreases with the increase of solution pH. The Co 3 O 4 /NF catalyst using 2 mM Co(NO 3 ) 2 ·6H 2 O as cobalt source exhibits highest activity, and almost complete decolorization could be achieved within 30 min. The diverse effects of coexisting anions (SO 4 2- , HCO 3 - , NO 3 - and Cl - ) on AO7 degradation are observed and explained. After 10 consecutive runs, excellent catalytic reactivity of the catalyst remains while the level of leached cobalt during the catalyst usage is much lower than the maximum allowable concentration in drinking and natural water. More importantly, the macroscopic Co 3 O 4 /NF catalyst shows advantage of easy recycling after application compared to traditional catalysts. It is believed that the as-prepared Co 3 O 4 /NF is promising to be an effective and green heterogeneous catalyst for PMS activation to degrade organic pollutants for environmental application. Copyright © 2018 Elsevier Ltd. All rights reserved.

System Li2O-MoO3 as a catalyst of oxygen (air) electrode

International Nuclear Information System (INIS)

Gavdzik, A.; Gajda, S.; Sofronkov, A.

2000-01-01

Potential of electrode on the basis of system Li x Mo 2-x O 6 (x 0.1-0.5) in alkaline solution saturated by oxygen was studied by the method of polarization curves recording. It is ascertained that the value of stationary potential characteristic of the electrode described under the conditions mentioned is determined by reversible reaction between oxygen and water molecules, resulting in formation of hydroxyl and hydrogen peroxide anions. Practicability of using the solid solutions on the basis of molybdenum oxide with additions of lithium oxide as a catalyst of oxygen (air) electrode in electrochemical current sources is demonstrated [ru

A tailored catalyst for the sustainable conversion of glycerol to acrolein: mechanistic aspect of sequential dehydration.

Science.gov (United States)

Yun, Danim; Kim, Tae Yong; Park, Dae Sung; Yun, Yang Sik; Han, Jeong Woo; Yi, Jongheop

2014-08-01

Developing a catalyst to resolve deactivation caused from coke is a primary challenge in the dehydration of glycerol to acrolein. An open-macropore-structured and Brønsted-acidic catalyst (Marigold-like silica functionalized with sulfonic acid groups, MS-FS) was synthesized for the stable and selective production of acrolein from glycerol. A high acrolein yield of 73% was achieved and maintained for 50 h in the presence of the MS-FS catalyst. The hierarchical structure of the catalyst with macropores was found to have an important effect on the stability of the catalyst because coke polymerization and pore blocking caused by coke deposition were inhibited. In addition, the behavior of 3-hydroxypropionaldehyde (3-HPA) during the sequential dehydration was studied using density functional theory (DFT) calculations because 3-HPA conversion is one of the main causes for coke formation. We found that the easily reproducible Brønsted acid sites in MS-FS permit the selective and stable production of acrolein. This is because the reactive intermediate (3-HPA) is readily adsorbed on the regenerated acid sites, which is essential for the selective production of acrolein during the sequential dehydration. The regeneration ability of the acid sites is related not only to the selective production of acrolein but also to the retardation of catalyst deactivation by suppressing the formation of coke precursors originating from 3-HPA degradation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The assessment of pellicular anion-exchange resins for the determination of anions by ion chromatography

International Nuclear Information System (INIS)

Pohlandt, C.

1981-01-01

Because pellicular anion-exchange resins suitable for the determination, by ion chromatography, of anions with alkaline eluents were unavailable in South Africa at the inception of this work, an attempt was made to prepare such resins. In this study it is shown that the pellicular resins produced are more efficient than the surface-aminated resins used previously. The simultaneous separation and determination of five common anions is demonstrated. The method was applied to the analysis of uranium leach liquors, effluent samples, and a solid sample of ferric oxide (goethite)

ESTUDIO DE LA ESTABILIDAD ESTRUCTURAL DE ÓXIDOS MIXTOS Zn-Al TIPO HIDROTALCITA EN PRECURSORES CATALÍTICOS CoNiMo FRENTE HDS DE TIOFENO

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Ruth Alvarez

2017-07-01

Full Text Available The oil industry is one of the main sources responsible for atmospheric emissions such as: CO, CO2, SO2, NOX, hydrocarbons and suspended particles, which seeks to mitigate environmental pollution from its refineries using some processes, such as hydrotreatment (HDT. The heart of the HDT is the catalysts used, depending on the catalytic support and the metals used during its formulation. Therefore, this research focused on studying the structural stability of mixed Zn-Al type hydrotalcite (HT oxides in catalysts CoNiMo versus thiophene HDS at a calcination temperature of 450 ° C. Initially, the catalytic support HT was synthesized at varying Zn-Al ratios of 0,00 to 1, 00Al, once the optimal range of HT (0,00-0,33Al was obtained, the catalytic precursors CoMo / NiMo, through two stages of calcination, the first is impregnated the support type hydrotalcite (HT without calcining with the metals CoNi and CoMo, after impregnating with these metals is calcined once only; While in the second stage the solids are calcined before impregnation and after impregnation with the aforementioned metals. The obtained results show an excellent performance for the catalysts with double calcination stage, being CoMo precursors more effective than NiMo; this can be justified by the physicochemical characteristics of the phases of the metals involved and their coordination vacancies.

N-Nitrosodimethylamine (NDMA) and its precursors in water and wastewater: A review on formation and removal.

Science.gov (United States)

Sgroi, Massimiliano; Vagliasindi, Federico G A; Snyder, Shane A; Roccaro, Paolo

2018-01-01

This review summarizes major findings over the last decade related to N-Nitrosodimethylamine (NDMA) in water and wastewater. In particular, the review is focused on the removal of NDMA and of its precursors by conventional and advanced water and wastewater treatment processes. New information regarding formation mechanisms and precursors are discussed as well. NDMA precursors are generally of anthropogenic origin and their main source in water have been recognized to be wastewater discharges. Chloramination is the most common process that results in formation of NDMA during water and wastewater treatment. However, ozonation of wastewater or highly contaminated surface water can also generate significant levels of NDMA. Thus, NDMA formation control and remediation has become of increasing interest, particularly during treatment of wastewater-impacted water and during potable reuse application. NDMA formation has also been associated with the use of quaternary amine-based coagulants and anion exchange resins. UV photolysis with UV fluence far higher than typical disinfection doses is generally considered the most efficient technology for NDMA mitigation. However, recent studies on the optimization of biological processes offer a potentially lower-energy solution. Options for NDMA control include attenuation of precursor materials through physical removal, biological treatment, and/or deactivation by application of oxidants. Nevertheless, NDMA precursor identification and removal can be challenging and additional research and optimization is needed. As municipal wastewater becomes increasingly used as a source water for drinking, NDMA formation and mitigation strategies will become increasingly more important. The following review provides a summary of the most recent information available. Copyright © 2017 Elsevier Ltd. All rights reserved.

Perspective: Electrospray photoelectron spectroscopy: From multiply-charged anions to ultracold anions

International Nuclear Information System (INIS)

Wang, Lai-Sheng

2015-01-01

Electrospray ionization (ESI) has become an essential tool in chemical physics and physical chemistry for the production of novel molecular ions from solution samples for a variety of spectroscopic experiments. ESI was used to produce free multiply-charged anions (MCAs) for photoelectron spectroscopy (PES) in the late 1990 s, allowing many interesting properties of this class of exotic species to be investigated. Free MCAs are characterized by strong intramolecular Coulomb repulsions, which create a repulsive Coulomb barrier (RCB) for electron emission. The RCB endows many fascinating properties to MCAs, giving rise to meta-stable anions with negative electron binding energies. Recent development in the PES of MCAs includes photoelectron imaging to examine the influence of the RCB on the electron emission dynamics, pump-probe experiments to examine electron tunneling through the RCB, and isomer-specific experiments by coupling PES with ion mobility for biological MCAs. The development of a cryogenically cooled Paul trap has led to much better resolved PE spectra for MCAs by creating vibrationally cold anions from the room temperature ESI source. Recent advances in coupling the cryogenic Paul trap with PE imaging have allowed high-resolution PE spectra to be obtained for singly charged anions produced by ESI. In particular, the observation of dipole-bound excited states has made it possible to conduct vibrational autodetachment spectroscopy and resonant PES, which yield much richer vibrational spectroscopic information for dipolar free radicals than traditional PES

Catalyst Design Using Nanoporous Iron for the Chemical Vapor Deposition Synthesis of Single-Walled Carbon Nanotubes

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Tarek M. Abdel-Fattah

2013-01-01

Full Text Available Single-walled carbon nanotubes (SWNTs have been synthesized via a novel chemical vapor deposition (CVD approach utilizing nanoporous, iron-supported catalysts. Stable aqueous dispersions of the CVD-grown nanotubes using an anionic surfactant were also obtained. The properties of the as-produced SWNTs were characterized through atomic force microscopy and Raman spectroscopy and compared with purified SWNTs produced via the high-pressure CO (HiPCO method as a reference, and the nanotubes were observed with greater lengths than those of similarly processed HiPCO SWNTs.

Efficient Air Desulfurization Catalysts Derived from Pig Manure Liquefaction Char

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Rajiv Wallace

2017-11-01

Full Text Available Biochar from the liquefaction of pig manure was used as a precursor of H2S desulfurization adsorbents. In its inorganic matter, it contains marked quantities of calcium, magnesium and iron, which are known as hydrogen sulfide oxidation catalysts. The char was used either as-received or mixed with 10% nanographite. The latter was added to increase both the content of the carbon phase and conductivity. ZnCl2 in two different ratios of char to an activation agent (1:1 and 1:2 was used to create the porosity in the carbon phase. The content of the later was between 18–45%. The activated samples adsorbed 144 mg/g H2S. Sulfur was the predominant product of reactive adsorption. Its deposition in the pore system and blockage of the most active pores ceased the materials’ activity. The presence of the catalytic phase was necessary but not sufficient to guarantee good performance. The developed porosity, which can store oxidation products in the resulting composite, is essential for the good performance of the desulfurization process. The surface of the composite with nanographite showed the highest catalytic activity, similar to that of the commercial Midas® carbon catalyst. The results obtained indicate that a high quality reactive adsorbent/catalyst for H2S removal can be obtained from pig manure liquefaction wastes.

A Study of Iron-Nitrogen-Carbon Fuel Cell Catalysts: Chemistry - Nanostructure - Performance

Science.gov (United States)

Workman, Michael J., Jr.

Fuel cells have the potential to be a pollution-free, low-cost, and energy efficient alternative to the internal combustion engine for transportation and small-scale stationary power applications. The current state of fuel cell technology has already achieved two of these three lofty goals. The remaining barrier to wide-scale deployment is the high cost, which is primarily caused by dependence on large amounts of platinum to catalyze the energy conversion reactions. To overcome this barrier and facilitate the integration of fuel cells into mainstream applications, research into a new class of catalyst materials that do not require platinum is needed. There has been a significant amount of research effort directed toward the development of platinum-group metal free (PGM-free) catalysts, yet there is a lack of consensus on both the engineering parameters necessary to improve the technology and the fundamental science that would facilitate rational design. I have engaged in research on PGM-free catalysts based on inexpensive and abundant reagents, specifically: nicarbazin and iron. Catalysts made from these precursors have previously proven to be among the best PGM-free catalysts, but their continued advancement suffered from the same lack of understanding that besets all catalysts in this class. The work I have performed address both engineering concerns and fundamental underlying principles. I present results demonstrating correlations between physical structure, chemical speciation, and synthesis parameters, as well as addressing active site chemistry and likely locations. My research presented herein introduces new morphology analysis techniques and elucidates several key structure-to-property characteristics of catalysts derived from iron and nicarbazin. I discuss the development and application of a new length-scale specific surface analysis technique that allows for analysis of well-defined size ranges from a few nm to several microns. The existing technique of

Molybdenum acetate like precursor of molybdenum carburized supported on alumina: a catalyst for hydrogenation reactions

International Nuclear Information System (INIS)

Petkovic, Lucia M; Parra, Ruben D; Marquez Manuel; Larsen, Gustavo

1994-01-01

The stability of the Al203 supported dimers under relatively high temperatures and hydrocarbon/H2 (carburizing) atmospheres is reported also, it has been developed a new method for Mo2 loading of the support based on the wet impregnation of the latter. Since carbided Mo is active for hydrogenations, the isobutene/H2 has been chosen as the probe reaction. Al203 supported Mo2(Ac)4 results in a catalyst active for isobutene hydrogenation after treatment with a H2/C2H6 2:1 mixture at 753 k

[In situ diffuse reflectance FTIR spectroscopy study of CO adsorption on Ni2P/mesoporous molecule sieve catalysts].

Science.gov (United States)

Liu, Qian-qian; Ji, Sheng-fu; Wu, Ping-yi; Hu, Lin-hua; Huang, Xiao-fan; Zhu, Ji-qin; Li, Cheng-yue

2009-05-01

Abstract The supported nickel phosphate precursors were prepared by incipient wetness impregnation using nickel nitrate as nickel source, diammonium hydrogen phosphate as phosphorus source, and MCM-41, MCM-48, SBA-15 and SBA-16 as supports, respectively. Then, the supported Ni2 P catalysts were prepared by temperature-programmed reduction in flowing Hz from their nickel phosphate precursors. The in situ diffuse reflectance FTIR spectroscopy (DRIFTS) analysis with the probe molecule CO was carried out to characterize the surface properties. The results indicated that there were significant differences in the spectral features of the samples. The upsilon(CO) absorbances observed for adsorbed CO on mesoporous molecule sieve was attributed to weak physical adsorption. There are four different kinds of upsilon(CO) absorbances observed for adsorbed CO on Ni2 P/MCM-41 catalyst with the following assignments: (1) the formation of Ni(CO)4 at 2055 cm(-1). (2) CO terminally bonded to cus Ni(delta+) (0catalysts. The absorbance observed at 2051-2055 cm(-1) for CO adsorption on Ni2P/MCM-48, Ni2P/SBA-15 and Ni2P/SBA-16 catalysts is due to the formation of Ni(CO)4 species. The other upsilon absorbances observed at 2093-2096 cm(-1) was attributed to CO terminally bonded to cus Ni(delta+) (0

Synthesis and characterizations of anion exchange organic-inorganic hybrid materials based on poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)

International Nuclear Information System (INIS)

Zhang Shaoling; Wu Cuiming; Xu Tongwen; Gong Ming; Xu Xiaolong

2005-01-01

A series of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)-based organic-inorganic hybrid materials for anion exchange were prepared through sol-gel process of polymer precursors PPO-Si(OCH 3 ) 3 . PPO-Si(OCH 3 ) 3 were obtained from the reaction of bromomethylated PPO with 3-aminopropyl-trimethoxysilane (A1110). These polymer precursors then underwent hydrolysis and condensation with additional A1110 to generate hybrid materials. The reaction to produce polymer precursors was identified by FTIR; while FTIR, TGA, XRD, SEM, as well as conventional ion exchange capacity (IEC) measurements were conducted for the structures and properties of the prepared hybrids. TGA results show that this series of hybrid materials possess high thermal stability; XRD and SEM indicate that the prepared hybrid materials are amorphous and the inorganic and organic contents show good compatibility if the ratio between them is proper. The IEC values of the hybrid materials due to the amine groups range from 1.13 mmol/gBPPO (material i) to 4.80 mmol/gBPPO (material iv)

Advanced oxidation of rhodamine B with hydrogen peroxide over ZnCr layered double hydroxide catalysts

Directory of Open Access Journals (Sweden)

Nguyen Tien Thao

2017-09-01

Full Text Available Zn/Cr layered zinc hydroxide materials with different molar ratios of Cr/Zn have been synthesized through the coprecipitation method at pH of 9.0–9.5. At high Cr/Zn molar ratios of 0.5/1–1/3, the materials possess some layered structure with carbonate anions between the interlayer galleries. The catalysts present uniform particle sizes and quite high surface area. An isomorphous substitution of Zn2+ by Cr3+ in the brucite-like sheets makes the layered Cr-doped zinc hydroxides potential catalysts for efficient oxidation of rhodamine B with H2O2 solution. The experimental results indicated that the intra-lattice Cr3+ ions are more active than Cr2O3 components in the oxidative removal of rhodamine B. The degradation efficiency is dependent on the intra lattice Cr3+ contents and reaction variables. The Cr/Zn LDH gave a high decolorization (99% of rhodamine B at near neutral pH and room temperature.

Oligomerization of ethylene catalysed by nickel complexes associated with nitrogen ligands in ionic liquids; Oligomerisation de l'ethylene catalysee par des complexes du nickel associes a des ligands azotes dans les liquides ioniques

Energy Technology Data Exchange (ETDEWEB)

Lecocq, V.

2003-09-01

We report here the use of a new class of catalytic systems based on a nickel active center associated with nitrogen ligands, such as di-imines, or imino-pyridines, for the oligomerization of ethylene in a biphasic medium using ionic liquids as the catalyst solvent. The nickel catalyst is immobilized in the ionic liquid phase in which the olefinic reaction products are poorly miscible. This biphasic system makes possible an easy separation and recycle of the catalyst. Numerous di-imine and imino-pyridine ligands with different steric and electronic properties have been synthesized and their corresponding nickel complexes isolated and characterized. Different ionic liquids, based on chloro-aluminates or non-chloro-aluminates anions, have also been prepared and characterized. The effect of the nature of the ligand, the ionic liquid, the nickel precursor and its mode of activation have been studied and correlated with the selectivity and activity of the transformation of ethylene. (author)

Catalysts for liquid phase oxidation of olefins and sulfur compounds; Catalyseurs pour l'oxydation en phase liquide d'olefines et de composes soufres

Energy Technology Data Exchange (ETDEWEB)

Palomeque Santiago, J.F.

2002-07-01

Several basic, acid and acid-base catalysts were studied for the epoxidation of olefins activated or not and dibenzo-thiophene.Hydrotalcite activation by thermic treatment and in situ re-hydration improves catalytic activity for 2-cyclohexene-1-one and isophorone. Bronsted basic sites were found to be more active than Lewis sites. Total conversion of 2-cyclohexene-1-one is reached in 1.5 h in polar solvents. W{sub 7}O{sub 24}{sup 6-} Iso-poly-anion was exchanged onto a meixnerite by a new preparation method, A meso-porous solid was obtained with good catalytic properties for cyclohexene epoxidation 100% selective to epoxide. W{sub 7}O{sub 24}{sup 6-} and WO{sub 5}{sup 2-} anions and phenyl and dodecyl-phospho-tungstates were grafted on hydrotalcites. Due to the acid-base characteristics of these solid catalysts, cyclohexene yields products of allylic reactions. Mg-La, and Mg-Al-La mixed oxides were synthesized and mixed phases were gotten. Their basic characteristics account for hydrogen peroxide decomposition which prevents DBT oxidation reaction to sulfone. On the contrary, Mg-Al re-hydrated hydrotalcites are very active for this reaction and remove 100% of sulfur compounds in 1 hour. New catalyst W-ZrO{sub 2} were synthesized with high acid properties. stable structure with temperature and high DBT conversion in less than 5 minutes of reaction. These catalytic systems can be applied for hydrocarbon desulfurization of fuels like naphtha, gas oil and kerosene. (author)

Effect of Drying Temperature on Iron Fischer-Tropsch Catalysts Prepared by Solvent Deficient Precipitation

Directory of Open Access Journals (Sweden)

Michael K. Albretsen

2017-01-01

Full Text Available A novel solvent deficient precipitation (SDP method to produce nanoparticles was studied for its potential in Fischer-Tropsch synthesis (FTS catalysis. Using Fe(NO33·9H2O as the iron-containing precursor, this method produces ferrihydrite particles which are then dried, calcined, reduced, and carbidized to form the active catalytic phase for FTS. Six different drying profiles, including final drying temperatures ranging between 80 and 150°C, were used to investigate the effect of ammonium nitrate (AN, a major by-product of reaction between Fe(NO33·9H2O and NH4HCO3 in the SDP method. Since AN has two phase-transitions within this range of drying temperatures, three different AN phases can exist during the drying of the catalyst precursors. These AN phases, along with physical changes occurring during the phase transitions, may affect the pore structure and the agglomeration of ferrihydrite crystallites, suggesting possible reasons for the observed differences in catalytic performance. Catalysts dried at 130°C showed the highest FTS rate and the lowest methane selectivity. In general, better catalytic performance is related to the AN phase present during drying as follows: phase III > phase II > phase I. However, within each AN phase, lower drying temperatures led to better catalytic properties.

An introduction to catalyst

International Nuclear Information System (INIS)

Jeon, Hak Je

1988-11-01

This book explains basic conception of catalyst such as definition, velocity of chemical reaction and velocity of catalyst reaction, absorption with absorption energy and chemical absorption, pore structure with the role of pore and measurement of pore structure, catalyst activity on solid structure, electrical property on catalyst activity, choice and design of catalyst, catalytic reaction with reaction velocity and chemical equilibrium and reaction velocity model, measurement of reaction velocity and material analysis, catalyst for mixed compound, catalyst for solid acid and catalyst for supported metal.

Process for removing sulfate anions from waste water

Science.gov (United States)

Nilsen, David N.; Galvan, Gloria J.; Hundley, Gary L.; Wright, John B.

1997-01-01

A liquid emulsion membrane process for removing sulfate anions from waste water is disclosed. The liquid emulsion membrane process includes the steps of: (a) providing a liquid emulsion formed from an aqueous strip solution and an organic phase that contains an extractant capable of removing sulfate anions from waste water; (b) dispersing the liquid emulsion in globule form into a quantity of waste water containing sulfate anions to allow the organic phase in each globule of the emulsion to extract and absorb sulfate anions from the waste water and (c) separating the emulsion including its organic phase and absorbed sulfate anions from the waste water to provide waste water containing substantially no sulfate anions.

Production of propylene from 1-butene on highly active "bi-functional single active site" catalyst: Tungsten carbene-hydride supported on alumina

KAUST Repository

Mazoyer, Etienne

2011-12-02

1-Butene is transformed in a continuous flow reactor over tungsten hydrides precursor W-H/Al2O3, 1, giving a promising yield into propylene at 150 °C and different pressures. Tungsten carbene-hydride single active site operates as a "bi-functional catalyst" through 1-butene isomerization on W-hydride and 1-butene/2-butenes cross-metathesis on W-carbene. This active moiety is generated in situ at the initiation steps by insertion of 1-butene on tungsten hydrides precursor W-H/Al2O3, 1 followed by α-H and β-H abstraction. © 2011 American Chemical Society.

Effect of different nickel precursors on capacitive behavior of electrodeposited NiO thin films

Energy Technology Data Exchange (ETDEWEB)

Kore, R. M.; Ghadge, T. S.; Ambare, R. C.; Lokhande, B. J., E-mail: bjlokhande@yahoo.com [School of Physical Sciences, Solapur University, Solapur-413 255, M.S. (India)

2016-04-13

In the present study, the effect of nickel precursors containing different anions like nitrate, chloride and sulphate on the morphology and pseudocapacitance behavior of NiO is investigated. The NiO samples were prepared by using a potentiondynamic electrodeposition technique in the three electrode cell. Cyclic voltammetry technique was exploited for potentiodynamic deposition of the films. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), etc. The XRD reveals the cubic crystal structure for all samples. The SEM micrograph shows nanoflakelike, up grown nanoflakes and honeycomb like nanostructured morphologies for nitrate, chloride and sulphate precursors respectively. The capacitive behavior of these samples was recorded using cyclic voltammetry (CV), charge-discharge and electrochemical impedance spectroscopy (EIS) in 1 M KOH electrolyte. The specific capacitance values of NiO samples obtained using CV for nitrate, chloride and sulphate precursors were 136, 214 and 893 Fg{sup −1} respectively, at the scan rate of 5 mVs{sup −1}. The charge discharge study shows high specific energy for the sample obtained from sulphate (23.98 Whkg{sup −1}) as compared to chloride (9.67 Whkg{sup −1}) and nitrate (4.9 Whkg{sup −1}), whereas samples of cholride (13.9 kWkg{sup −1} and nitrate (10.5 kWkg{sup −1}) shows comparatively more specific power than samples obtained from sulphate (7.6 kWkg{sup −1}). The equivalent series resistance of NiO samples observed from EIS study are 1.34, 1.29 and 1.27 Ω respectively for nitrate, chloride and sulphate precursors. These results emphasizes that the samples obtained from sulphate precursors provides very low impedance through honeycomb like nanostructured morphology which supports good capacitive behavior of NiO.

Facile synthesis of a platinum-lead oxide nanocomposite catalyst with high activity and durability for ethanol electrooxidation.

Science.gov (United States)

Yang, Wei-Hua; Wang, Hong-Hui; Chen, De-Hao; Zhou, Zhi-You; Sun, Shi-Gang

2012-12-21

Aimed at searching for highly active and stable nano-scale Pt-based catalysts that can improve significantly the energy conversion efficiency of direct ethanol fuel cells (DEFCs), a novel Pt-PbO(x) nanocomposite (Pt-PbO(x) NC) catalyst with a mean size of 3.23 nm was synthesized through a simple wet chemistry method without using a surfactant, organometallic precursors and high temperature. Electrocatalytic tests demonstrated that the as-prepared Pt-PbO(x) NC catalyst possesses a much higher catalytic activity and a longer durability than Pt nanoparticles (nm-Pt) and commercial Pt black catalysts for ethanol electrooxidation. For instance, Pt-PbO(x) NC showed an onset potential that was 30 mV and 44 mV less positive, together with a peak current density 1.7 and 2.6 times higher than those observed for nm-Pt and Pt black catalysts in the cyclic voltammogram tests. The ratio of current densities per unit Pt mass on Pt-PbO(x) NC, nm-Pt and Pt black catalysts is 27.3 : 3.4 : 1 for the long-term (2 hours) chronoamperometric experiments measured at -0.4 V (vs. SCE). In situ FTIR spectroscopic studies revealed that the activity of breaking C-C bonds of ethanol of the Pt-PbO(x) NC is as high as 5.17 times that of the nm-Pt, which illustrates a high efficiency of ethanol oxidation to CO(2) on the as-prepared Pt-PbO(x) NC catalyst.

Ionospheric earthquake precursors

International Nuclear Information System (INIS)

Bulachenko, A.L.; Oraevskij, V.N.; Pokhotelov, O.A.; Sorokin, V.N.; Strakhov, V.N.; Chmyrev, V.M.

1996-01-01

Results of experimental study on ionospheric earthquake precursors, program development on processes in the earthquake focus and physical mechanisms of formation of various type precursors are considered. Composition of experimental cosmic system for earthquake precursors monitoring is determined. 36 refs., 5 figs

Methane coupling reaction in an oxy-steam stream through an OH radical pathway by using supported alkali metal catalysts

KAUST Repository

Liang, Yin

2014-03-24

A universal reaction mechanism involved in the oxidative coupling of methane (OCM) is demonstrated under oxy-steam conditions using alkali-metal-based catalysts. Rigorous kinetic measurements indicated a reaction mechanism that is consistent with OH radical formation from a H 2O-O2 reaction followed by C-H activation in CH 4 with an OH radical. Thus, the presence of water enhances both the CH4 conversion rate and the C2 selectivity. This OH radical pathway that is selective for the OCM was observed for the catalyst without Mn, which suggests clearly that Mn is not the essential component in a selective OCM catalyst. The experiments with different catalyst compositions revealed that the OH.-mediated pathway proceeded in the presence of catalysts with different alkali metals (Na, K) and different oxo anions (W, Mo). This difference in catalytic activity for OH radical generation accounts for the different OCM selectivities. As a result, a high C2 yield is achievable by using Na2WO4/SiO2, which catalyzes the OH.-mediated pathway selectively. Make it methane: A universal reaction mechanism involved in the oxidative coupling of methane is demonstrated under oxy-stream conditions by using alkali-metal-based catalysts. Rigorous kinetic measurements indicated a reaction mechanism that is consistent with OH radical formation from an H2O-O2 reaction, followed by C-H activation in CH4 with an OH radical. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Lanthanum and cerium co-modified Ni/SiO2 catalyst for CO methanation from syngas

Science.gov (United States)

Gong, Dandan; Li, Shuangshuang; Guo, Shaoxia; Tang, Honggui; Wang, Hong; Liu, Yuan

2018-03-01

Sintering of active metal nanoparticles (NPs) and carbon deposition is critical problems for many metal catalysts, such as nickel based catalysts for generating methane from syngas. To improve the resistance to the sintering and carbon deposition, a new scheme was proposed in this work. Lanthanum and cerium co-modified Ni/SiO2 catalysts were synthesized by using perovskite type oxide of La1-xCexNiO3 loaded on SiO2 as the precursor. In a nanocrystallite of La1-xCexNiO3, ions of nickel, lanthanum and cerium are evenly mixed at atomic level and confined in the nanocrystallite, therefore, Ni NPs and the two promoters of La2O3 and CeO2 should be in close contact and highly dispersed on SiO2 after reduction. The catalysts were characterized by using XRD, TEM, BET, H2-TPD, XPS, TG and Raman techniques. Compared with the mono-promoted catalysts, the bi-promoted La0.75Ce0.25NiO3/SiO2 showed much better resistance to carbon deposition, higher resistance to sintering and higher activity for CO methanation, which are attributed to co-eliminating effect of the two promoters for the deposited carbon, confinement of the interacted two promoters for Ni NPs and the higher dispersion of Ni NPs derived from the smaller size of La0.75Ce0.25NiO3.

Infrared spectroscopy of anionic hydrated fluorobenzenes

International Nuclear Information System (INIS)

Schneider, Holger; Vogelhuber, Kristen M.; Weber, J. Mathias

2007-01-01

We investigate the structural motifs of anionic hydrated fluorobenzenes by infrared photodissociation spectroscopy and density functional theory. Our calculations show that all fluorobenzene anions under investigation are strongly distorted from the neutral planar molecular geometries. In the anions, different F atoms are no longer equivalent, providing structurally different binding sites for water molecules and giving rise to a multitude of low-lying isomers. The absorption bands for hexa- and pentafluorobenzene show that only one isomer for the respective monohydrate complexes is populated in our experiment. For C 6 F 6 - ·H 2 O, we can assign these bands to an isomer where water forms a weak double ionic hydrogen bond with two F atoms in the ion, in accord with the results of Bowen et al. [J. Chem. Phys. 127, 014312 (2007), following paper.] The spectroscopic motif of the binary complexes changes slightly with decreasing fluorination of the aromatic anion. For dihydrated hexafluorobenzene anions, several isomers are populated in our experiments, some of which may be due to hydrogen bonding between water molecules

Anion channels: master switches of stress responses.

Science.gov (United States)

Roelfsema, M Rob G; Hedrich, Rainer; Geiger, Dietmar

2012-04-01

During stress, plant cells activate anion channels and trigger the release of anions across the plasma membrane. Recently, two new gene families have been identified that encode major groups of anion channels. The SLAC/SLAH channels are characterized by slow voltage-dependent activation (S-type), whereas ALMT genes encode rapid-activating channels (R-type). Both S- and R-type channels are stimulated in guard cells by the stress hormone ABA, which leads to stomatal closure. Besides their role in ABA-dependent stomatal movement, anion channels are also activated by biotic stress factors such as microbe-associated molecular patterns (MAMPs). Given that anion channels occur throughout the plant kingdom, they are likely to serve a general function as master switches of stress responses. Copyright © 2012 Elsevier Ltd. All rights reserved.

Layered double hydroxide supported gold nanoclusters by glutathione-capped Au nanoclusters precursor method for highly efficient aerobic oxidation of alcohols

Science.gov (United States)

Li, Lun; Dou, Liguang; Zhang, Hui

2014-03-01

M3Al-layered double hydroxide (LDH, M = Mg, Ni, Co) supported Au nanoclusters (AuNCs) catalysts have been prepared for the first time by using water-soluble glutathione-capped Au nanoclusters as precursor. Detailed characterizations show that the ultrafine Au nanoclusters (ca. 1.5 +/- 0.6 nm) were well dispersed on the surface of LDH with a loading of Au below ~0.23 wt% upon synergetic interaction between AuNCs and M3Al-LDH. AuNCs/Mg3Al-LDH-0.23 exhibits much higher catalytic performance for the oxidation of 1-phenylethanol in toluene than Au/Mg3Al-LDH(DP) by the conventional deposition precipitation method and can be applied for a wide range of alcohols without basic additives. This catalyst can also be reused without loss of activity or selectivity. The AuNCs/M(= Ni, Co)3Al-LDH catalysts present even higher alcohol oxidation activity than AuNCs/Mg3Al-LDH. Particularly, AuNCs/Ni3Al-LDH-0.22 exhibits the highest activity (46 500 h-1) for the aerobic oxidation of 1-phenylethanol under solvent-free conditions attributed to its strongest Au-support synergy. The excellent activity and stability of AuNCs/M3Al-LDH catalysts render these materials promising candidates for green base-free selective oxidation of alcohols by molecular oxygen.M3Al-layered double hydroxide (LDH, M = Mg, Ni, Co) supported Au nanoclusters (AuNCs) catalysts have been prepared for the first time by using water-soluble glutathione-capped Au nanoclusters as precursor. Detailed characterizations show that the ultrafine Au nanoclusters (ca. 1.5 +/- 0.6 nm) were well dispersed on the surface of LDH with a loading of Au below ~0.23 wt% upon synergetic interaction between AuNCs and M3Al-LDH. AuNCs/Mg3Al-LDH-0.23 exhibits much higher catalytic performance for the oxidation of 1-phenylethanol in toluene than Au/Mg3Al-LDH(DP) by the conventional deposition precipitation method and can be applied for a wide range of alcohols without basic additives. This catalyst can also be reused without loss of activity

New Trends in Gold Catalysts

Directory of Open Access Journals (Sweden)

Leonarda F. Liotta

2014-07-01

Full Text Available Gold is an element that has fascinated mankind for millennia. The catalytic properties of gold have been a source of debate, due to its complete chemical inertness when in a bulk form, while it can oxidize CO at temperatures as low as ~200 K when in a nanocrystalline state, as discovered by Haruta in the late 1980s [1]. Since then, extensive activity in both applied and fundamental research on gold has been initiated. The importance of the catalysis by gold represents one of the fasted growing fields in science and is proven by the promising applications in several fields, such as green chemistry and environmental catalysis, in the synthesis of single-walled carbon nanotubes, as modifiers of Ni catalysts for methane steam and dry reforming reactions and in biological and electrochemistry applications. The range of reactions catalyzed by gold, as well as the suitability of different supports and the influence of the preparation conditions have been widely explored and optimized in applied research [2]. Gold catalysts appeared to be very different from the other noble metal-based catalysts, due to their marked dependence on the preparation method, which is crucial for the genesis of the catalytic activity. Several methods, including deposition-precipitation, chemical vapor deposition and cation adsorption, have been applied for the preparation of gold catalysts over reducible oxides, like TiO2. Among these methods, deposition-precipitation has been the most frequently employed method for Au loading, and it involves the use of tetrachloroauric (III acid as a precursor. On the other hand, the number of articles dealing with Au-loaded acidic supports is smaller than that on basic supports, possibly because the deposition of [AuCl4]− or [AuOHxCl4−x]− species on acidic supports is difficult, due to their very low point of zero charge. Despite this challenge, several groups have reported the use of acidic zeolites as supports for gold. Zeolites

Carbonate anion controlled growth of LiCoPO4/C nanorods and its improved electrochemical behavior

International Nuclear Information System (INIS)

Gangulibabu; Nallathamby, Kalaiselvi; Meyrick, Danielle; Minakshi, Manickam

2013-01-01

Highlights: ► Carbonate anion controlled growth of LiCoPO 4 nanorods has been prepared. ► Mixture of H 2 CO 3 + (NH 4 ) 2 CO 3 increases the CO 3 2− concentration and acts as an effective growth inhibitor. ► Heating the carbonate rich precursor in an inert atmosphere produces a Co 2 P phase that is conductive. ► Addition of super P carbon resulted in an amorphous carbon coating on LiCoPO 4 particles. ► LiCoPO 4 /C nanorods with a co-existence of Co 2 P exhibit excellent discharge capacity with retention on multiple cycling. -- Abstract: LiCoPO 4 /C nanocomposite with growth controlled by carbonate anions was synthesized via a unique solid-state fusion method. Carbonate anions in the form of H 2 CO 3 or a mixture of H 2 CO 3 + (NH 4 ) 2 CO 3 have been used as a growth inhibiting modifier to produce morphology controlled lithium cobalt phosphate. The presence of cobalt phosphide (Co 2 P) as a second phase improved the conductivity and electrochemical properties of the parent LiCoPO 4. The formation of Co 2 P is found to be achievable only in an inert atmosphere. Super P ® carbon (10 wt.%) provided an adherent carbon coating on pristine LiCoPO 4 resulting in the LiCoPO 4 /C composite cathode. This electrode exhibited enhanced electrochemical properties: capacity of 123 mAh g −1 with excellent capacity retention of 89% after 30 cycles, and reasonable rate capability of up to 5 C rate. The synergistic effect of carbonate anions and formation of Co 2 P under inert atmosphere has influenced the electrochemical behavior of LiCoPO 4 /C cathode through controlling the morphology and increasing the conductivity

Impeded solid state reactions and transformations in ceramic catalysts supports and catalysts

Directory of Open Access Journals (Sweden)

Ernő E. Kiss

2012-12-01

Full Text Available Impeded chemical reactions and impeded polymorphous transformation in materials are discussed, as desired effects, for stabilization of ceramic catalyst supports and ceramic based catalysts. This paper gives a short overview about the possibilities of slowing down the aging processes in ceramic catalyst supports and catalysts. Special attention is given to alumina and titania based catalysts.

The synthesis of higher alcohols from CO2 hydrogenation with Co, Cu, Fe-based catalysts

International Nuclear Information System (INIS)

Ji, Qinqin

2017-01-01

CO 2 is a clean carbon source for the chemical reactions, many researchers have studied the utilization of CO 2 . Higher alcohols are clean fuel additives. The synthesis of higher alcohols from CO hydrogenation has also been studied by many researchers, but there are few literatures about the synthesis of higher alcohols from CO 2 hydrogenation, which is a complex and difficult reaction. The catalysts that used for higher alcohols synthesis need at least two active phases and good cooperation. In our study, we tested the Co. Cu. Fe spinel-based catalysts and the effect of supports (CNTs and TUD-1) and promoters (K, Na, Cs) to the HAS reaction. We found that catalyst CuFe-precursor-800 is beneficial for the synthesis of C2+ hydrocarbons and higher alcohols. In the CO 2 hydrogenation, Co acts as a methanation catalyst rather than acting as a FT catalyst, because of the different reaction mechanism between CO hydrogenation and CO 2 hydrogenation. In order to inhibit the formation of huge amount of hydrocarbons, it is better to choose catalysts without Co in the CO 2 hydrogenation reaction. Compared the functions of CNTs and TUD-1, we found that CNTs is a perfect support for the synthesis of long-chain products (higher alcohols and C2+ hydrocarbons). The TUD-1 support are more suitable for synthesis of single-carbon products (methane and methanol).The addition of alkalis as promoters does not only lead to increase the conversion of CO 2 and H 2 , but also sharply increased the selectivity to the desired products, higher alcohols. The catalyst 0.5K30CuFeCNTs owns the highest productivities (370.7 g.kg -1 .h -1 ) of higher alcohols at 350 C and 50 bar. (author) [fr

Synthesis of Ni2B nanoparticles by RF thermal plasma for fuel cell catalyst

International Nuclear Information System (INIS)

Cheng, Y; Tanaka, M; Watanabe, T; Choi, S Y; Shin, M S; Lee, K H

2014-01-01

The catalyst of Ni 2 B nanoparticles was successfully prepared using nickel and boron as precursors with the quenching gas in radio frequency thermal plasmas. The generating of Ni 2 B needs adequate reaction temperature and boron content in precursors. The quenching gas is beneficial for the synthesis of Ni 2 B in RF thermal plasma. The effect of quenching rate, powder feed rate and boron content in feeding powders on the synthesis of nickel boride nanoparticles was studied in this research. The high mass fraction of 28 % of Ni 2 B nanoparticles can be generated at the fixed initial composition of Ni:B = 2:3. Quenching gas is necessary in the synthesis of Ni 2 B nanoaprticles. In addition, the mass fraction of Ni 2 B increases with the increase of quenching gas flow rate and powder feed rate

Reversible conversion of valence-tautomeric copper metal-organic frameworks dependent single-crystal-to-single-crystal oxidation/reduction: a redox-switchable catalyst for C-H bonds activation reaction.

Science.gov (United States)

Huang, Chao; Wu, Jie; Song, Chuanjun; Ding, Ran; Qiao, Yan; Hou, Hongwei; Chang, Junbiao; Fan, Yaoting

2015-06-28

Upon single-crystal-to-single-crystal (SCSC) oxidation/reduction, reversible structural transformations take place between the anionic porous zeolite-like Cu(I) framework and a topologically equivalent neutral Cu(I)Cu(II) mixed-valent framework. The unique conversion behavior of the Cu(I) framework endowed it as a redox-switchable catalyst for the direct arylation of heterocycle C-H bonds.

N-acetylglyoxylic amide bearing a nitrophenyl group as anion receptors: NMR and X-ray investigations on anion binding and selectivity

Science.gov (United States)

Suryanti, Venty; Bhadbhade, Mohan; Black, David StC; Kumar, Naresh

2017-10-01

N-Nitrophenylglyoxylic amides 1 and 2 in presence of tetrabutylammonium cation (TBA) act as receptors for anions HSO4-, Cl-, Br- and NO3- as investigated by NMR studies. The receptors formed 1:1 host-guest complexes in solution. X-ray structure of 1 along with TBA that bind a chloride anion is reported. Molecule 1 showed the highest selectivity for HSO4- anion over others measured. X-ray structure of the bound Cl- revealed a pocket containing the anion making strong (Nsbnd H⋯Cl) and weak hydrogen bonds (Csbnd H⋯Cl) that contribute to the recognition of the chloride anion. Nsbnd H and Csbnd H hydrogen bonds resulted in a relatively strong binding for chloride ions.

Hydrothermally synthesised Fe{sub 2}O{sub 3} nanoparticles as catalyst precursors for the CVD production of graphitic nanofibres

Energy Technology Data Exchange (ETDEWEB)

Edwards, H K [School of Mechanical, Materials and Manufacturing Engineering, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom); Evans, E [School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom); McCaldin, S [School of Mechanical, Materials and Manufacturing Engineering, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom); Blood, P [School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom); Gregory, D H [School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom); Poliakoff, M [School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom); Lester, E [School of Chemical Engineering and Mining Engineering, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom); Walker, G S [School of Mechanical, Materials and Manufacturing Engineering, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom); Brown, P D [School of Mechanical, Materials and Manufacturing Engineering, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom)

2006-02-22

Graphitic nanofibres (GNFs) have been grown by chemical vapour deposition at 500 deg. C and 700 deg. C, using 6 nm and 20 nm particles of Fe{sub 2}O{sub 3} produced by supercritical water hydrothermal synthesis (scWHS). The morphologies of catalyst and GNFs have been examined using the combined techniques of conventional transmission electron microscopy, high resolution electron microscopy, selected area electron diffraction and powder X-ray diffraction. GNF production varied from well ordered nanofibres with an average diameter of 100 nm, to very large, disordered fibres with diameters ranging from 500 nm to {approx}2 {mu}m. Larger fibres were found to have a compound structure composed of discreet domains of graphite and multiwall nanotubes. 20 nm particles produced by scWHS were associated with significant increases in the yield of GNFs as compared with traditional catalyst precipitation routes.

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.

Olefin polymerization from single site catalysts confined within porous media

Science.gov (United States)

Kasi, Rajeswari M.

Single Site Catalysts (SSCs) have been utilized for olefin polymerization. Altering the metal-ligand architecture in the SSCs, polyolefin properties can be enhanced in a rational manner. This influence of the ligands in the SSC on the property of polyolefins prepared can be referred to as the primary ligand influence. Extending this understanding and subsequent control of the metal-ligand framework to the interaction of SSCs within organic and inorganic supports is vital for the synthesis of polyolefins with tailored properties. The motivation behind this thesis was to explore the support influence on the reactivity of the SSC tethered to a support matrix during ethylene homo and copolymerization. In order to address this question of the support influence on the final polyolefin properties, synthetic routes to covalently bind SSCs on different matrices have been explored. Two distinct supported SSCs have been used to prepare branched polyethylenes. Branched polyethylenes can be prepared by either copolymerization (ethylene and alpha-olefin) or oligomerization/copolymerization processes (ethylene and in situ generated alpha-olefin). Synthetic routes to prepare precursor catalysts to Constrained Geometry Catalysts (CGCs) by silyl elimination chemistry have been developed (Chapter 2). Efficient synthetic protocols to assemble CGCs on aminomethylpolysytrene matrices (Chapter 3) and amine-functionalized mesoporous silica (Chapter 4) are also reported. These supported catalysts, with appropriate cocatalysts have been used to prepare ethylene homo and copolymers, the polymer thermal properties and microstructures were analyzed by various analytical techniques. Branched polyethylenes (LLDPE) can be prepared by copolymerization chemistry. It has been observed is that the influence of the support is seen in the production of lower crystalline forms of high density polyethylene (HDPE, 20--50% crystalline), while homogeneous polymerization of analogous soluble CGCs afford HDPE

Catalyst support structure, catalyst including the structure, reactor including a catalyst, and methods of forming same

Science.gov (United States)

Van Norman, Staci A.; Aston, Victoria J.; Weimer, Alan W.

2017-05-09

Structures, catalysts, and reactors suitable for use for a variety of applications, including gas-to-liquid and coal-to-liquid processes and methods of forming the structures, catalysts, and reactors are disclosed. The catalyst material can be deposited onto an inner wall of a microtubular reactor and/or onto porous tungsten support structures using atomic layer deposition techniques.

SYNGAS PRODUCTION FROM CO2-REFORMING OF CH4 OVER SOL-GEL SYNTHESIZED Ni-Co/Al2O3-MgO-ZrO2 NANOCATALYST: EFFECT OF ZrO2 PRECURSOR ON CATALYST PROPERTIES AND PERFORMANCE

Directory of Open Access Journals (Sweden)

Seyed Mehdi Sajjadi

2015-05-01

Full Text Available Ni-Co/Al2O3-MgO-ZrO2 nanocatalyst with utilization of two different zirconia precursors, namely, zirconyl nitrate hydrate (ZNH and zirconyl nitrate solution (ZNS, was synthesized via the sol-gel method. The physiochemical properties of nanocatalysts were characterized by XRD, FESEM, EDX, BET and FTIR analyses and employed for syngas production from CO2-reforming of CH4. XRD patterns, exhibiting proper crystalline structure and homogeneous dispersion of active phase for the nanocatalyst ZNS precursor employed (NCAMZ-ZNS. FESEM and BET results of NCAMZ-ZNS presented more uniform morphology and smaller particle size and consequently higher surface areas. In addition, average particle size of NCAMZ-ZNS was 15.7 nm, which is close to the critical size for Ni-Co catalysts to avoid carbon formation. Moreover, FESEM analysis indicated both prepared samples were nanoscale. EDX analysis confirmed the existence of various elements used and also supported the statements made in the XRD and FESEM analyses regarding dispersion. Based on the excellent physiochemical properties, NCAMZ-ZNS exhibited the best reactant conversion across all of the evaluated temperatures, e.g. CH4 and CO2 conversions were 97.2 and 99% at 850 ºC, respectively. Furthermore, NCAMZ-ZNS demonstrated a stable yield with H2/CO close to unit value during the 1440 min stability test.

Supramolecular Chemistry of Selective Anion Recognition for Anions of Environmental Relevance

International Nuclear Information System (INIS)

Moyer, Bruce a.; Bostick, Debra A.; Fowler, Christopher J.; Kang, Hyun-Ah; Ruas, Alexandre; Delmau, Laetitia H.; Haverlock, Tamara J.; Llinares, Jose M.; Hossain, Alamgir; Kang, S. O.; Bowman-James, Kristin; Shriver, James A.; Marquez, Manuel; Sessler, Jonathan L.

2005-01-01

The major thrust of this project led by the University of Kansas (Prof. Kristin Bowman-Jones) entails the exploration of the principles of recognition and separation of sulfate by the design, synthesis, and testing of novel sulfate extractants. A key science need for the cleanup of tank wastes at Hanford has been identified in developing methods to separate those bulk waste components that have low solubilities in borosilicate glass. Sulfate has been identified as a particularly difficult and expensive problem in that its concentration in the waste is relatively high, its solubility in glass is especially low, and it interferes with the performance of both vitrification equipment and the glass waste form. The new extractants will be synthesized by the University of Kansas and the University of Texas, Austin. Oak Ridge National Laboratory (ORNL) is subjecting the new extractants to experiments that will determine their properties and effectiveness in separating sulfate from the major competing anions in the waste, especially nitrate. Such experiments will entail primarily liquid-liquid extraction. Current efforts focus on exciting new systems in which the anion receptors act as synergists for anion exchange

Deaminated zeolite, ITQ-6 as heterogeneous catalyst for Friedel crafts alkylation

International Nuclear Information System (INIS)

Zainab Ramli; Noor Ashikin Mohd Yusoff; Halimaton Hamdan

2007-01-01

The ability of ITQ-6, a kind of meso porous zeolitic material to replace microporous zeolite as catalyst has attracted particular attention. In this study, modification of a precursor of microporous ferrierite, PREFER to meso porous material, ITQ-6 was carried out by delamination technique. The XRD results show that the crystalline phase of PREFER diminished for the sample after delamination. Porosity study of the ITQ-6 sample shows formation of homogeneous meso pores in the size between 3.5-4.0 nm. The acidity study indicates that ITQ-6 still contains appreciable amounts of Bronsted and Lewis acidities. Catalytic evaluation of the resulting material, ITQ-6 was carried out in the alkylation of resorcinol with methyl tert-butyl ether which gave 4-tert-butyl resorcinol and 4, 6-di-tert-butyl resorcinol as main products. The conversion of resorcinol when using ITQ-6 was ten times higher than ferrierite, FER with similar selectivity of disubstituted product. It shows that the meso porosity of ITQ-6 was responsible for the higher activity of the catalyst in the reaction. (author)

Gas-Grain Models for Interstellar Anion Chemistry

Science.gov (United States)

Cordiner, M. A.; Charnely, S. B.

2012-01-01

Long-chain hydrocarbon anions C(sub n) H(-) (n = 4, 6, 8) have recently been found to be abundant in a variety of interstellar clouds. In order to explain their large abundances in the denser (prestellar/protostellar) environments, new chemical models are constructed that include gas-grain interactions. Models including accretion of gas-phase species onto dust grains and cosmic-ray-induced desorption of atoms are able to reproduce the observed anion-to-neutral ratios, as well as the absolute abundances of anionic and neutral carbon chains, with a reasonable degree of accuracy. Due to their destructive effects, the depletion of oxygen atoms onto dust results in substantially greater polyyne and anion abundances in high-density gas (with n(sub H2) approx > / cubic cm). The large abundances of carbon-chain-bearing species observed in the envelopes of protostars such as L1527 can thus be explained without the need for warm carbon-chain chemistry. The C6H(-) anion-to-neutral ratio is found to be most sensitive to the atomic O and H abundances and the electron density. Therefore, as a core evolves, falling atomic abundances and rising electron densities are found to result in increasing anion-to-neutral ratios. Inclusion of cosmic-ray desorption of atoms in high-density models delays freeze-out, which results in a more temporally stable anion-to-neutral ratio, in better agreement with observations. Our models include reactions between oxygen atoms and carbon-chain anions to produce carbon-chain-oxide species C6O, C7O, HC6O, and HC7O, the abundances of which depend on the assumed branching ratios for associative electron detachment

Tuning the composition of metastable Co_xNi_yMg_100−x−y(OH)(OCH₃) nanoplates for optimizing robust methane dry reforming catalyst

DEFF Research Database (Denmark)

Fan, Xiaoli; Liu, Zhiting; Zhu, Yi-An

2015-01-01

of the metastable precursor CoxNiyMg100−x−y(OH)(OCH3) derived from solvothermal synthesis. The catalyst composition and reaction conditions have been modulated to achieve maximum coke resistance and catalyst stability. Long-term stability for 1000 h time on stream at 800°C has been achieved for the optimized Co0.......075Ni7.425Mg92.5O catalyst. The role of Co in the catalyst has been disclosed through kinetic measurements and detailed characterization of the spent catalysts. Co is enriched on the Co–Ni alloy surface under reforming conditions and accelerates the gasification of coke intermediates. Co also enhances...

Novel precursors for the deposition of rare earth oxides

International Nuclear Information System (INIS)

Ahlers, Mareike

2010-01-01

During this work rare earth solvates with nitrate and perchlorate anions have been investigated. All compounds have been structurally characterized and analyzed using thermal gravimetric analysis. The decomposition residues were analyzed using powder diffraction methods. Almost all compounds showed a characteristically intense exothermic decomposition step during the thermal decomposition, most likely caused by an intramolecular redox reaction between the nitrate or perchlorate anion respectively and the organic solvent molecules. The nitrates RE(NO 3 ) 3 (CH(OCH 3 ) 3 ) 2 (RE = Sm, Eu) were isolated and characterized for the first time as the intermediate of the dehydration reaction with trimethyl orthoformate. The known compound group of dimethoxyethane solvates was then expanded with RE(NO 3 ) 3 (O 2 C 4 H 10 ) (RE = La, Sm, Eu). Considering the possible use as precursor material the already described neodymium compound is also discussed. The thermal decomposition of these compounds yields the respective cubic rare earth oxide and shows the typical intense exothermic decomposition reaction. A variety of different precursor system based on nitrate solvates for the deposition of rare earth oxide layers on a silicon surface was developed and investigated in collaboration with the group of Prof. Dr. Al-Shamery (Univ. Oldenburg). Ultra thin films on a H-Si(111) surface were obtained via the deposition of the precursor, which was dissolved in organic solvents. An oxide layer was detected after the heating of the sample. The film thickness was measured as < 10 nm, whereas the thickness of the film was controlled by the concentration of the precursor solution. Sm(ClO 4 ) 3 (CH(OCH 3 ) 3 ) 3 was isolated and characterized for the first time as the intermediate of the dehydration reaction with trimethyl orthoformate. Eu(ClO 4 ) 3 (CH(OCH 3 ) 3 ) 2 (MeOH) 2 was obtained without recrystallization. The methanol molecules, formed during the hydrolysis of the trimethyl

Ab initio theoretical study of dipole-bound anions of molecular complexes: (HF)3- and (HF)4- anions

Science.gov (United States)

Ramaekers, Riet; Smith, Dayle M. A.; Smets, Johan; Adamowicz, Ludwik

1997-12-01

Ab initio calculations have been performed to determine structures and vertical electron detachment energy (VDE) of the hydrogen fluoride trimer and tetramer anions, (HF)3- and (HF)4-. In these systems the excess electron is bound by the dipole field of the complex. It was determined that, unlike the neutral complexes which prefer the cyclic structures, the equilibrium geometries of the anions have "zig-zag" shapes. For both complexes the predicted VDEs are positive [210 meV and 363 meV for (HF)3- and (HF)4-, respectively], indicating that the anions are stable systems with respect to the vertical electron detachment. These results were obtained at the coupled-cluster level of theory with single, double and triple excitations [CCSD(T) method; the triple-excitation contribution in this method is calculated approximately using the perturbation approach] with the anion geometries obtained using the second-order Møller-Plesset perturbation theory (MP2) method. The same approach was also used to determine the adiabatic electron affinities (AEA) of (HF)3 and (HF)4. In addition to the electronic contribution, we also calculated the contributions (using the harmonic approximation) resulting from different zero-point vibration energies of the neutral and anionic clusters. The calculations predicted that while the AEA of (HF)3 is positive (44 meV), the AEA for (HF)4 is marginally negative (-16 meV). This suggests that the (HF)3- anion should be a stable system, while the (HF)4- is probably metastable.

Design of heterogeneous catalysts

DEFF Research Database (Denmark)

Frey, Anne Mette

was inspired by a computational screening, suggesting that alloys such as Ni-Fe, Co-Ni, and Co-Fe should show superior activity to the industrially used nickel catalyst. Especially the Ni-Fe system was considered to be interesting, since such alloy catalysts should be both more active and cheaper than the Ni...... catalyst. The results from the screening were experimentally verified for CO hydrogenation, CO2 hydrogenation, and simultaneous CO and CO2 hydrogenation by bimetallic Ni-Fe catalysts. These catalysts were found to be highly active and selective. The Co-Ni and Co-Fe systems were investigated for CO...... well, and the best catalyst prepared had a C5+ yield almost a factor of two higher than a standard air calcined Co catalyst. In the NH3-SCR reaction it is desirable to develop an active and stable catalyst for NOx removal in automotive applications, since the traditionally used vanadium-based catalyst...

Influence of crystallization time on structural and morphological characteristics the precursor of zeolite MCM-22

International Nuclear Information System (INIS)

Barbosa, A.S.; Lima, L.A.; Sousa, B.V.; Santos, Everton R.F. dos; Rodrigues, M.G.F.

2009-01-01

The zeolite MCM-22 has been studied extensively as a promising catalyst because of the high thermal stability and high activity for acid catalysis and selectivity of molecular shape. The synthesis of MCM-22 is carried out by hydrothermal treatment and long times required for complete crystallization gradual growth of crystals of 10-14 days for the synthesis of static. This work aims to synthesize the precursor of zeolite MCM-22 using the method of hydrothermal synthesis with a reduction in crystallization time of 8 and 9 days. The precursor of zeolite MCM-22 was obtained using sources of silica, soda, deionized water and the director of structures hexametilenoimina (HMI). The samples were synthesized at 150° C for 8 to 9 days, with the following molar composition: 0.511 SiO 2 : 0.039 NaOH: 0.024 Al 2 O 3 : 23.06 H 2 O and subjected to characterizations by X-ray diffraction (XRD), scanning electron microscopy ( SEM) and energy dispersive (EDX). According to tests carried out showed that the hydrothermal treatment used to synthesize the precursor of zeolite MCM-22 was effective during times of crystallization of 8 and 9 days. The results for the micrographs showed that the samples consist of clusters and / or aggregates of small crystals. (author)

Application in industry and energy production of active carbon/cobalt catalyst for nitrogen oxide neutralization

International Nuclear Information System (INIS)

Mekhandzhiev, D.; Nikolov, R.; Lyutskanov, L.; Dushanov, D.; Lakov, L.

1997-01-01

A new material for neutralization of nitrogen oxides is presented. Two or three metals containing catalysts with a good activity and selectivity towards NO x have been obtained. Preparation of carbon catalysts by deposition of the active phase precursor on the initial carbon material prior to activation is considered as the most promising method. An active carbon-based catalyst (AC/Co) has been synthesized Apricot shells preliminary impregnated with a water-alcohol solution of Co nitrate have been used as initial carbon material. after drying they have been subjected to one-phase steam pyrolysis using a fix-bed reactor. The catalyst thus obtained has a specific surface area (BET) of 53 m 2 g -1 , a favorable mesopore volume/total volume ratio (about 0.85) determined by nitrogen adsorption, a suitable mesopore distribution, about 70% of the mesopores being characterized by r p larger than 25 A and a high dispersion of the Co oxide phase. In addition the catalyst possesses the necessary mechanical resistance. The catalyst has exhibited a high activity with respect to NO x reduction with CO at low temperatures (at 150-250 o C which are the temperatures of industrial flue gases, nO conversion up to 60-95% occurs) and a high selectivity. No presence of H 2 O has been established over the whole temperature range (100-300 o C). An additional advantage of the catalyst is the fact that the amount of CO above 150 o C is lower than the stoichiometric which indicates parallel participation in the process of both the active phase and the support (active carbon) It is also important that the presented catalyst has a low price due to the use of waste products from agriculture and the elimination of special thermal treatment of the supported Co nitrate. There are possibilities of using of other organic wastes from agriculture as well as wastes obtained during flotation of coal. (author)

Obtaining aluminas from the thermal decomposition of their different precursors: An {sup 27}Al MAS NMR and X-ray powder diffraction studies

Energy Technology Data Exchange (ETDEWEB)

Chagas, L.H.; De Carvalho, G.S.G. [Universidade Federal de Juiz de Fora, Departamento de Química, Grupo de Físico-Química de Sólidos e Interfaces, 36036-330 Juiz de Fora, MG (Brazil); San Gil, R.A.S. [Universidade Federal do Rio de Janeiro, Instituto de Química, 21949-900 Rio de Janeiro, RJ (Brazil); Chiaro, S.S.X. [PETROBRAS-CENPES, 21941-915 Rio de Janeiro, RJ (Brazil); Leitão, A.A. [Universidade Federal de Juiz de Fora, Departamento de Química, Grupo de Físico-Química de Sólidos e Interfaces, 36036-330 Juiz de Fora, MG (Brazil); Diniz, R., E-mail: renata.diniz@ufjf.edu.br [Universidade Federal de Juiz de Fora, Departamento de Química, Grupo de Físico-Química de Sólidos e Interfaces, 36036-330 Juiz de Fora, MG (Brazil)

2014-01-01

Graphical abstract: - Highlights: • We synthesized three precursors of alumina from different methods. • The calcination of the precursors generated several alumina polymorphs. • XRD and NMR were used for structural investigation of the polymorphs. • The synthesis route determines the structural and textural properties of the solids. - Abstract: A commercial sample of Boehmite was used as precursor of alumina polymorphs. For comparison, three other precursors were synthesized from different methods. Particularly, the use of excess of urea promoted a very crystalline form of basic aluminum carbonate. The characteristics of the four precursors were investigated by thermal, vibrational and X-ray powder diffraction (XRD) analysis. Additionally, the nuclear magnetic resonance, with magic angle spinning ({sup 27}Al MAS NMR), was used to verify the coordination of aluminum cations. Each precursor was calcined at various temperatures generating alumina polymorphs, which were structurally analyzed by XRD and {sup 27}Al MAS NMR. Due to interest in catalysis supports, special attention was given to the γ-Al{sub 2}O{sub 3} phase, which in addition to structural investigation was subjected to textural analysis. The results showed that, from different synthesis procedures and common route of calcination, one can obtain materials with the same composition but with different structural and textural properties, which in turn can significantly influence the performance of a supported catalyst.

High Br- Content CsPb(Cl yBr1- y)3 Perovskite Nanocrystals with Strong Mn2+ Emission through Diverse Cation/Anion Exchange Engineering.

Science.gov (United States)

Li, Fei; Xia, Zhiguo; Pan, Caofeng; Gong, Yue; Gu, Lin; Liu, Quanlin; Zhang, Jin Z

2018-04-11

The unification of tunable band edge (BE) emission and strong Mn 2+ doping luminescence in all-inorganic cesium lead halide perovskite nanocrystals (NCs) CsPbX 3 (X = Cl and Br) is of fundamental importance in fine tuning their optical properties. Herein, we demonstrate that benefiting from the differentiation of the cation/anion exchange rate, ZnBr 2 and preformed CsPb 1- x Cl 3 : xMn 2+ NCs can be used to obtain high Br - content Cs(Pb 1- x- z Zn z )(Cl y Br 1- y ) 3 : xMn 2+ perovskite NCs with strong Mn 2+ emission, and the Mn 2+ substitution ratio can reach about 22%. More specifically, the fast anion exchange could be realized by the soluble halide precursors, leading to anion exchange within a few seconds as observed from the strong BE emission evolution, whereas the cation exchange instead generally required at least a few hours; moreover, their exchange mechanism and dynamics process have been evaluated. The Mn 2+ emission intensity could be further varied by controlling the replacement of Mn 2+ by Zn 2+ with prolonged ion exchange reaction time. White light emission of the doped perovskite NCs via this cation/anion synergistic exchange strategy has been realized, which was also successfully demonstrated in a prototype white light-emitting diode (LED) device based on a commercially available 365 nm LED chip.

Metal-Oxide Film Conversions Involving Large Anions

Energy Technology Data Exchange (ETDEWEB)

Pretty, S.; Zhang, X.; Shoesmith, D.W.; Wren, J.C. [The University of Western Ontario, Chemistry Department, 1151 Richmond St., N6A 5B7, London, Ontario (Canada)

2008-07-01

The main objective of my research is to establish the mechanism and kinetics of metal-oxide film conversions involving large anions (I{sup -}, Br{sup -}, S{sup 2-}). Within a given group, the anions will provide insight on the effect of anion size on the film conversion, while comparison of Group 6 and Group 7 anions will provide insight on the effect of anion charge. This research has a range of industrial applications, for example, hazardous radioiodine can be immobilized by reaction with Ag to yield AgI. From the perspective of public safety, radioiodine is one of the most important fission products from the uranium fuel because of its large fuel inventory, high volatility, and radiological hazard. Additionally, because of its mobility, the gaseous iodine concentration is a critical parameter for safety assessment and post-accident management. A full kinetic analysis using electrochemical techniques has been performed on the conversion of Ag{sub 2}O to (1) AgI and (2) AgBr. (authors)

Metal-Oxide Film Conversions Involving Large Anions

International Nuclear Information System (INIS)

Pretty, S.; Zhang, X.; Shoesmith, D.W.; Wren, J.C.

2008-01-01

The main objective of my research is to establish the mechanism and kinetics of metal-oxide film conversions involving large anions (I - , Br - , S 2- ). Within a given group, the anions will provide insight on the effect of anion size on the film conversion, while comparison of Group 6 and Group 7 anions will provide insight on the effect of anion charge. This research has a range of industrial applications, for example, hazardous radioiodine can be immobilized by reaction with Ag to yield AgI. From the perspective of public safety, radioiodine is one of the most important fission products from the uranium fuel because of its large fuel inventory, high volatility, and radiological hazard. Additionally, because of its mobility, the gaseous iodine concentration is a critical parameter for safety assessment and post-accident management. A full kinetic analysis using electrochemical techniques has been performed on the conversion of Ag 2 O to (1) AgI and (2) AgBr. (authors)

Synthesis of a highly active carbon-supported Ir-V/C catalyst for the hydrogen oxidation reaction in PEMFC

International Nuclear Information System (INIS)

Li Bing; Qiao Jinli; Yang Daijun; Zheng Junsheng; Ma Jianxin; Zhang Jiujun; Wang Haijiang

2009-01-01

The active, carbon-supported Ir and Ir-V nanoclusters with well-controlled particle size, dispersity, and composition uniformity, have been synthesized via an ethylene glycol method using IrCl 3 and NH 4 VO 3 as the Ir and V precursors. The nanostructured catalysts were characterized by X-ray diffraction and high-resolution transmission electron microscopy. The catalytic activities of these carbon-supported nanoclusters were screened by applying on-line cyclic voltammetry and electrochemical impedance spectroscopy techniques, which were used to characterize the electrochemical properties of fuel cells using several anode Ir/C and Ir-V/C catalysts. It was found that Ir/C and Ir-V/C catalysts affect the performance of electrocatalysts significantly based on the discharge characteristics of the fuel cell. The catalyst Ir-V/C at 40 wt.% displayed the highest catalytic activity to hydrogen oxidation reaction and, therefore, high cell performance is achieved which results in a maximum power density of 563 mW cm -2 at 0.512 V and 70 deg. C in a real H 2 /air fuel cell. This performance is 20% higher as compared to the commercial available Pt/C catalyst. Fuel cell life test at a constant current density of 1000 mA cm -2 in a H 2 /O 2 condition shows good stability of anode Ir-V/C after 100 h of continuous operation.

Specificity of anion-binding in the substrate-pocket ofbacteriorhodopsin

Energy Technology Data Exchange (ETDEWEB)