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CO Oxidation (co + oxidation)
Selected AbstractsControllable Synthesis of Shuttle-Shaped Ceria and Its Catalytic Properties for CO OxidationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 26 2009Chunwen Sun Abstract Shuttle-shaped ceria was obtained in a high yield via a surfactant octadecylamine and urea assisted solvothermal process. The crystalline structure and morphology were characterized with powder X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM). Preliminary catalytic measurement shows that the shuttle-shaped CeO2 exhibits an enhanced activity for CO oxidation, which may be attributed to its higher porosity and more oxygen vacancies.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Highly Active Iron Oxide Supported Gold Catalysts for CO Oxidation: How Small Must the Gold Nanoparticles Be?,ANGEWANDTE CHEMIE, Issue 33 2010Yong Liu Gold? Ja! , Aber in welcher Form? Die im Titel bezeichneten Katalysatoren wurden nach einem Kolloidabscheidungsverfahren erhalten. Rastertransmissionselektronenmikroskopie-Untersuchungen belegen, dass das Vorliegen von Doppelschichten aus etwa 0.5,nm großen Goldclustern nicht zwingend für eine hohe katalytische Aktivität erforderlich ist (siehe Bild). [source] ChemInform Abstract: Hexagonal YFe1-xPdxO3-,: Nonperovskite Host Compounds for Pd2+ and Their Catalytic Activity for CO Oxidation.CHEMINFORM, Issue 3 2009Jun Li Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Increasing the Number of Oxygen Vacancies on TiO2 by Doping with Iron Increases the Activity of Supported Gold for CO OxidationCHEMISTRY - A EUROPEAN JOURNAL, Issue 27 2007Silvio Carrettin Dr. Abstract The addition of iron to high-area TiO2 (Degussa P25, a mixture of anatase and rutile) increases the number of oxygen defect sites that react with O2 to form peroxide and superoxide species. In the presence of gold nanoclusters on the TiO2 surface, the superoxide species become highly reactive, and the activity of the supported gold catalyst for CO oxidation is approximately twice that of the most active comparable catalysts described in the literature. Images of the catalyst obtained by scanning transmission electron microscopy combined with spectra of the catalyst measured in the working state (Raman, extended X-ray absorption fine structure, and X-ray absorption near-edge structure) indicate strong interactions of gold with the support and the presence of iron near the interfaces between the gold clusters and the TiO2 support. The high activity of the catalysts is attributed to the presence of defects in these sites that activate oxygen. [source] Kinetic Evidence for the Influence of Subsurface Oxygen on Palladium Surfaces Towards CO Oxidation at High TemperaturesCHEMISTRY - AN ASIAN JOURNAL, Issue 1 2009Chinnakonda Abstract Transient state kinetics of the catalytic oxidation of CO with O2 on Pd-surfaces has been measured under isothermal conditions by using a molecular beam approach. Systematic studies were carried out as a function of reaction temperature and CO+O2 composition. With sufficient kinetic evidence, we have demonstrated the positive influence of subsurface oxygen towards CO-adsorption and oxidation to CO2 at high temperatures (600,900,K) on Pd-surfaces, and the likely electronic nature of the surface changes with oxygen in the subsurface. These studies also provide a direct proof for CO-adsorption with a significantly reactive sticking coefficient at high temperatures on Pd-surfaces exhibiting a significant subsurface O-coverage. [source] Determination of the Activation Volume for CO Oxidation on Platinum by Pressure ModulationCHEMPHYSCHEM, Issue 13 2010Dr. Han-Chun Wang Highly charged! A pressure-modulation technique is applied to determine the activation volume for CO oxidation on platinum. The negative value obtained suggests the formation of the positively charged transition state [H+,,,O,,,CO], (see figure; grey: Pt; red: O; black: C; blue: H) for which the volume is largely reduced with respect to that of the reactants. [source] Controllable Synthesis of Shuttle-Shaped Ceria and Its Catalytic Properties for CO OxidationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 26 2009Chunwen Sun Abstract Shuttle-shaped ceria was obtained in a high yield via a surfactant octadecylamine and urea assisted solvothermal process. The crystalline structure and morphology were characterized with powder X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM). Preliminary catalytic measurement shows that the shuttle-shaped CeO2 exhibits an enhanced activity for CO oxidation, which may be attributed to its higher porosity and more oxygen vacancies.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Nitrate-dependent anaerobic carbon monoxide oxidation by aerobic CO-oxidizing bacteriaFEMS MICROBIOLOGY ECOLOGY, Issue 1 2006G.M. King Abstract Two dissimilatory nitrate-reducing (Burkholderia xenovorans LB400 and Xanthobacter sp. str. COX) and two denitrifying isolates (Stappia aggregata IAM 12614 and Bradyrhizobium sp. str. CPP), previously characterized as aerobic CO oxidizers, consumed CO at ecologically relevant levels (<100 ppm) under anaerobic conditions in the presence, but not absence, of nitrate. None of the isolates were able to grow anaerobically with CO as a carbon or energy source, however, and nitrate-dependent anaerobic CO oxidation was inhibited by headspace concentrations >100,1000 ppm. Surface soils collected from temperate, subtropical and tropical forests also oxidized CO under anaerobic conditions with no lag. The observed activity was 25,60% less than aerobic CO oxidation rates, and did not appear to depend on nitrate. Chloroform inhibited anaerobic but not aerobic activity, which suggested that acetogenic bacteria may have played a significant role in forest soil anaerobic CO uptake. [source] Flame-Synthesized Ceria-Supported Copper Dimers for Preferential Oxidation of COADVANCED FUNCTIONAL MATERIALS, Issue 3 2009Richard Kydd Abstract Rapid synthesis of CuCeO2 catalysts by flame spray pyrolysis produces highly active Cu dimer morphologies without the need for additional catalyst pretreatment. The active Cu component is enriched onto the CeO2 surface at concentrations higher than the nominal loading with no evidence of amorphous or crystalline CuO phase. Increasing the Cu content results in a morphological transition from isolated Cu monomers to oxygen-bridged dimers and an associated increase in oxygen vacancy concentration. Dimer-containing CuCeO2 catalysts display high levels of activity and selectivity in the low-temperature preferential oxidation of CO. Experimental measurements and simulations suggest that the geometry of the dimer presents a comparatively ionic CuO bond at the catalyst surface. Further studies indicate that these ionic dimer species promote preferential CO oxidation at lower temperatures than observed for monomeric Cu species. This is the first report to explicitly propose and demonstrate that the structural distortion associated with the formation of Cu dimers directly induces increased bond ionicity at the catalyst surface and that these changes are responsible for improved catalytic activity. [source] Homogeneously Dispersed Ceria Nanocatalyst Stabilized with Ordered Mesoporous AluminaADVANCED MATERIALS, Issue 13 2010Quan Yuan Homogeneously dispersed ceria nanocatalyst can be synthesized and stabilized with ordered mesoporous alumina by a one-step sol,gel method. This novel material possesses high thermal stability and exhibits 100% conversion at room temperature for CO oxidation when loaded with Au. This established approach can be expanded to the controlled synthesis and stabilization of other nanocatalysts with wide applications. [source] Carbon monoxide poisoning of proton exchange membrane fuel cellsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 8 2001J. J. Baschuk Abstract Proton exchange membrane fuel cell (PEMFC) performance degrades when carbon monoxide (CO) is present in the fuel gas; this is referred to as CO poisoning. This paper investigates CO poisoning of PEMFCs by reviewing work on the electrochemistry of CO and hydrogen, the experimental performance of PEMFCs exhibiting CO poisoning, methods to mitigate CO poisoning and theoretical models of CO poisoning. It is found that CO poisons the anode reaction through preferentially adsorbing to the platinum surface and blocking active sites, and that the CO poisoning effect is slow and reversible. There exist three methods to mitigate the effect of CO poisoning: (i) the use of a platinum alloy catalyst, (ii) higher cell operating temperature and (iii) introduction of oxygen into the fuel gas flow. Of these three methods, the third is the most practical. There are several models available in the literature for the effect of CO poisoning on a PEMFC and from the modeling efforts, it is clear that small CO oxidation rates can result in much increased performance of the anode. However, none of the existing models have considered the effect of transport phenomena in a cell, nor the effect of oxygen crossover from the cathode, which may be a significant contributor to CO tolerance in a PEMFC. In addition, there is a lack of data for CO oxidation and adsorption at low temperatures, which is needed for detailed modeling of CO poisoning in PEMFCs. Copyright © 2001 John Wiley & Sons, Ltd. [source] Carbon monoxide and oxidative stress in Desulfovibrio desulfuricans B-1388JOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 2 2004M. Davydova Abstract It has been shown that carbon monoxide (CO) in low concentration may be an active biochemical and physiological regulator of cell function. The bases of CO toxicity and cell protection are not clearly understood. To provide insights into these mechanisms, we measured superoxide production by D. desulfuricans B-1388 incubated anaerobically in Postgate medium with or without 5% CO. D. desulfuricans B-1388 growing with CO in the gas phase produced more superoxide radicals then control cells growing in Ar. When the cells were pregrown with CO, NADH oxidase and peroxidase activities were increased. The increase in peroxidase activities of cells growing under CO (particularly NADH peroxidase) suggested that H2O2 was accumulated in cells. Superoxide dismutase (SOD) activity of cells decreased in exponential growth phase and increased in stationary phase. This may be due to CO concentration fall during CO oxidation by CO dehydrogenase. Altogether, our data suggest that superoxide production is a possible mechanism of CO toxicity. © 2004 Wiley Periodicals, Inc. J Biochem Mol Toxicol 18:87,91, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20011 [source] First-principle calculations on CO oxidation catalyzed by a gold nanoparticleJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 2 2010Hsin-Tsung Chen Abstract We have elucidated the mechanism of CO oxidation catalyzed by gold nanoparticles through first-principle density-functional theory (DFT) calculations. Calculations on selected model show that the low-coordinated Au atoms of the Au29 nanoparticle carry slightly negative charges, which enhance the O2 binding energy compared with the corresponding bulk surfaces. Two reaction pathways of the CO oxidation were considered: the Eley,Rideal (ER) and Langmuir,Hinshelwood (LH). The overall LH reaction O2(ads) + CO(gas) , O2(ads) + CO(ads) , OOCO(ads) , O(ads) + CO2(gas) is calculated to be exothermic by 3.72 eV; the potential energies of the two transition states (TSLH1 and TSLH2) are smaller than the reactants, indicating that no net activation energy is required for this process. The CO oxidation via ER reaction Au29 + O2(gas) + CO(gas) , Au29,O2(ads) + CO(gas) , Au29,CO3(ads) , Au29,O(ads) + CO2(gas) requires an overall activation barrier of 0.19 eV, and the formation of Au29,CO3(ads) intermediate possesses high exothermicity of 4.33 eV, indicating that this process may compete with the LH mechanism. Thereafter, a second CO molecule can react with the remaining O atom via the ER mechanism with a very small barrier (0.03 eV). Our calculations suggest that the CO oxidation catalyzed by the Au29 nanoparticle is likely to occur at or even below room temperature. To gain insights into high-catalytic activity of the gold nanoparticles, the interaction nature between adsorbate and substrate is also analyzed by the detailed electronic analysis. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 [source] Local forcing of a nonlinear surface reaction: CO oxidation on Pt(100)AICHE JOURNAL, Issue 1 2009Daniel Bilbao Abstract A novel spatiotemporal perturbation method for nonlinear surface reactions is reported, thus allowing the creation of new spatially localized structures. Forcing was achieved by dosing reactant gases through a capillary positioned near the catalyst surface, providing control over the local surface coverage and reaction rate. The emergence of localized concentration patterns and oscillations in an otherwise stable system is attributed to a local modification of the catalytic properties of the surface due to external forcing. Based on the spatial orientation, the temporal and thermal stability of the modified surface, as well as the affinity of CO toward the perturbed surface, subsurface O is proposed as a possible source of the observed localized patterning and surface memory effect. © 2008 American Institute of Chemical Engineers AIChE J, 2009 [source] The transient response study of CO, CO2, and O2 adsorption and CO oxidation over La0.4Sr0.6Co0.4Mn0.6O3THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2008Rong Li Abstract The transient behaviour caused by the change of the component concentration for CO oxidation on the perovskite-type catalyst La0.4Sr0.6Co0.4Mn0.6O3 was investigated. Results showed that CO was not adsorbed on the catalyst surface and CO oxidation was carried out between the surface oxygen species and gas phase CO. On the other hand, CO2 can be adsorbed on the catalyst surface but its adsorption site was different from the forming site. On a étudié le comportement transitoire causé parle changement dans la concentration des composantes pour l'oxydation du CO sur un catalyseur de type perovskite La0.4Sr0.6Co0.4Mn0.6O3. Les résultats montrent que le CO n'est pas adsorbé á la surface du catalyseur et que l'oxydation du CO s'est produite entre les espèces d'oxygène de surface et la phase gazeuse du CO. En outre, le CO2 peut être adsorbé sur la surface du catalyseur mais son site d'adsorption est différent du site de formation. [source] Increasing the Number of Oxygen Vacancies on TiO2 by Doping with Iron Increases the Activity of Supported Gold for CO OxidationCHEMISTRY - A EUROPEAN JOURNAL, Issue 27 2007Silvio Carrettin Dr. Abstract The addition of iron to high-area TiO2 (Degussa P25, a mixture of anatase and rutile) increases the number of oxygen defect sites that react with O2 to form peroxide and superoxide species. In the presence of gold nanoclusters on the TiO2 surface, the superoxide species become highly reactive, and the activity of the supported gold catalyst for CO oxidation is approximately twice that of the most active comparable catalysts described in the literature. Images of the catalyst obtained by scanning transmission electron microscopy combined with spectra of the catalyst measured in the working state (Raman, extended X-ray absorption fine structure, and X-ray absorption near-edge structure) indicate strong interactions of gold with the support and the presence of iron near the interfaces between the gold clusters and the TiO2 support. The high activity of the catalysts is attributed to the presence of defects in these sites that activate oxygen. [source] Determination of the Activation Volume for CO Oxidation on Platinum by Pressure ModulationCHEMPHYSCHEM, Issue 13 2010Dr. Han-Chun Wang Highly charged! A pressure-modulation technique is applied to determine the activation volume for CO oxidation on platinum. The negative value obtained suggests the formation of the positively charged transition state [H+,,,O,,,CO], (see figure; grey: Pt; red: O; black: C; blue: H) for which the volume is largely reduced with respect to that of the reactants. [source] New Generation of Gold Catalysts: Nanoporous Foams and Tubes,Is Unsupported Gold Catalytically Active?CHEMPHYSCHEM, Issue 13 2007Masatake Haruta Prof. Dr. Gold fever: Gold turns out to be catalytically very active, provided that either one or two of the three conditions shown in the graphic are fulfilled. In CO oxidation at room temperature even unsupported gold is active in the presence of alkaline water. The active states of gold in the gold catalysts reported so far can be classified into four groups: bulk gold, nanoparticles, clusters or thin layers with specific sizes, and cations. [source] | ||||||||||||||||||||||||||||