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CO Adsorption (co + adsorption)

Distribution by Scientific Domains

Chemistry	91%

Selected Abstracts

Platinum Sintering on H-ZSM-5 Followed by Chemometrics of CO Adsorption and 2D Pressure-Jump IR Spectroscopy of Adsorbed Species,

ANGEWANDTE CHEMIE, Issue 4 2010
Mickaël Rivallan Dr.
Zwei Welten: 2D-IR-Drucksprung-Spektroskopie von adsorbiertem CO lieferte Informationen über die Umgebung und Lage von Platin-Nanopartikeln auf Zeolith-Trägern und das Verhalten der Pt-Atome nach thermischer Behandlung (Aktivierung, katalytische Reaktion, Sinterung). In den Mesoporen und auf der äußeren Oberfläche des Trägers werden unterschiedliche Arten von Sintermechanismen beobachtet (siehe Bild; HF/LF=Hoch- bzw. Tieffrequenz). [source]

Ab initio Simulation of Lewis Sites in Mordenite and Comparative Study of the Strength of Active Sites via CO Adsorption.

CHEMINFORM, Issue 45 2004
L. Benco
No abstract is available for this article. [source]

Variable-Temperature Infrared Spectroscopy Studies on the Thermodynamics of CO Adsorption on the Zeolite Ca,Y

CHEMPHYSCHEM, Issue 12 2008
Barbara Bonelli Dr.
Abstract Variable temperature FT,IR spectroscopy (in the range of 298,380 K) is used to study the thermodynamics of formation of Ca2+,,,CO carbonyl species upon CO adsorption on the faujasite-type zeolite Ca,Y, and also the (temperature-dependent) isomerization equilibrium between carbonyl and isocarbonyl (Ca2+,,,OC) species. The standard enthalpy and entropy changes involved in formation of the monocarbonyl species resulted to be ,H0=,50.3 (±0.5) kJ,mol,1 and ,S0=,186 (±5) J,mol,1,K,1, respectively. Isomerization of the (C-bonded) Ca2+,,,CO carbonyl to yield the (O-bonded) Ca2+,,,OC isocarbonyl involves an enthalpy change =+11.4 (±1.0) kJ,mol,1. These results are compared with previously reported data for the CO/Sr,Y system; and also, a brief analysis of enthalpy,entropy correlation for CO adsorption on zeolites and metal oxides is given. [source]

CO Adsorption on a LaNi5 Hydrogen Storage Alloy Surface: A Theoretical Investigation

CHEMPHYSCHEM, Issue 11 2008
Song Han Dr.
Abstract Density functional theory calculations are carried out to study CO adsorption on the (001) surface of a LaNi5 hydrogen storage alloy. At low coverages, CO favors adsorption on NiNi bridge sites. With an increase in CO coverage, the decrease in the adsorption energy is much larger for NiNiCO bridge adsorption than that for NiCO on-top adsorption. Thus, the latter sites in the relatively stable adsorption structure are preferentially utilized at high CO coverages. The nature of the bonding between CO and the LaNi5 (001) surface is analyzed in detail. [source]

Ethanol and Acetaldehyde Adsorption on a Carbon-Supported Pt Catalyst: A Comparative DEMS Study

FUEL CELLS, Issue 1-2 2004
H. Wang
Abstract The adsorption of ethanol and acetaldehyde on carbon Vulcan supported Pt fuel cell catalyst and the electrochemical desorption of the adsorption products were studied, using electrochemical measurements and differential electrochemical mass spectrosmetry (DEMS), under continuous flow conditions. Faradaic current adsorption transients at different constant adsorption potentials, which also include CO adsorption for comparison, show pronounced effects of the adsorption potential and the nature of the reactant molecule. Acetaldehyde adsorption is much faster than ethanol adsorption at all potentials. Pronounced Had induced blocking effects for ethanol adsorption are observed at very cathodic adsorption potentials, < 0.16,V, while for acetaldehyde adsorption this effect is much less significant. Comparison of the adsorption charge for CO adsorption with the H-upd charge allows differentiation between H-displacement and double-layer charging effects. Continuous bulk oxidation is observed for both reactants at potentials > 0.31,V; for acetaldehyde adsorption, increasing bulk reduction is found at low potentials. Based on the electron yield per CO2 molecule formed and on the similarity with the CO stripping characteristics the dominant stable adsorbate is CO, coadsorbed with smaller amounts of (partly oxidized) hydrocarbon decomposition fragments, which are also oxidized at higher potentials (> 0.85,V) and which can be reductively desorbed as methane or, to a very small extent, as ethane. The presence of small amounts of adsorbed C2 species and the oxidative dissociation of these species in the main CO oxidation potential range is clearly demonstrated by increased methane desorption after a potential shift to 0.85,V. The data demonstrate that the Pt/Vulcan catalyst is very reactive for C-C bond breaking upon adsorption of these reactants. [source]

Modelling CO poisoning and O2 bleeding in a PEM fuel cell anode

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 12 2003
J.J. Baschuk
Abstract Fuel gas containing carbon monoxide severely degrades the performance of a polymer electrolyte membrane (PEM) fuel cell. However, CO poisoning can be mitigated by introducing oxygen into the fuel (oxygen bleeding). A mathematical PEM fuel cell model is developed that simulates both CO poisoning and oxygen bleeding, and obtains excellent agreement with published, experimental data. Modelling efforts indicate that CO adsorption and desorption follow a Temkin model. Increasing operating pressure or temperature mitigates CO poisoning, while use of reformate fuel increases the severity of the poisoning effect. Although oxygen bleeding mitigates CO poisoning, an unrecoverable performance loss exists at high current densities due to competition for reaction sites between hydrogen adsorption and the heterogeneous catalysis of CO. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Theoretical study of the CO catalytic oxidation on Au/SAPO-11 zeolite

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 13 2010
Beulah Griffe
Abstract Quantum chemistry calculations were carried out, using ONIOM2 methodology, to investigate the CO adsorption and oxidation on gold supported on Silicoaluminophospates (SAPO) molecular sieves Au/SAPO-11 catalysts. Two models were studied, one containing one Au atom per site (AuSAPO-11), and the other with two Au atoms per site (Au2SAPO-11). The results reveal that the CO adsorption and oxidation are exothermic on Au/SAPO11 with an ,E of ,41.0 kcal/mol and ,E = ,52.0 kcal/mol, for the adsorption and oxidation, respectively. On the Au2SAPO-11 model, the CO adsorption and oxidation reaction occur, with a ,E of ,29.7 kcal/mol and ,52 kcal/mol, respectively. According to our results, the oxidation reaction exhibits an Eley-Rideal type mechanism with adsorbed CO. The theoretical calculations reveal that this type of material could be interesting to disperse Au and consequently to strengthen its catalytic use for different reactions. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem 110:2573,2582, 2010 [source]

FTIR study of the CO adsorption over Pt/MFI catalysts: Ab initio interpretation

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 10 2006
N. S. Nesterenko
Abstract The state and dispersion of Pt supported on MFI catalysts with different contents have been studied using Fourier transform infrared (FTIR) spectroscopy. Experimentally predicted Pt-containing complexes were simulated by density functional theory (DFT) for CO frequency shift estimation and determination of the relative intensities. According to DFT calculation and experimental data, a new interpretation was proposed. A new approach for estimation of the Pt dispersion based on IR spectra of adsorbed CO has been developed. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [source]

Support-dependent activity of noble metal substituted oxide catalysts for the water gas shift reaction

AICHE JOURNAL, Issue 10 2010
Parag A. Deshpande
Abstract The water gas shift reaction was carried out over noble metal ion substituted nanocrystalline oxide catalysts with different supports. Spectroscopic studies of the catalysts before and after the reaction showed different surface phenomena occurring over the catalysts. Reaction mechanisms were proposed based upon the surface processes and intermediates formed. The dual site mechanism utilizing the oxide ion vacancies for water dissociation and metal ions for CO adsorption was proposed to describe the kinetics of the reaction over the reducible oxides like CeO2. A mechanism based on the interaction of adsorbed CO and the hydroxyl group was proposed for the reaction over ZrO2. A hybrid mechanism based on oxide ion vacancies and surface hydroxyl groups was proposed for the reaction over TiO2. The deactivation of the catalysts was also found to be support dependent. Kinetic models for both activation and deactivation were proposed. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source]

Characterization of the Oxidation States of Supported Gold Species by IR Spectroscopy of Adsorbed CO

CHEMIE-INGENIEUR-TECHNIK (CIT), Issue 6 2007
M. Mihaylov Dr.
Abstract The use of IR spectroscopy of adsorbed CO for determination of gold speciation on supported gold catalysts is reviewed. Different ionic and metallic sites (Au3+, Au+, Au0, and Au,) can be differentiated on the basis of the frequency and stability of their surface carbonyl species formed after CO adsorption. In addition, the study of CO adsorption and reaction with other gases can provide unique information on the mechanisms of catalytic reactions with participation of CO. Finally, results from complementary techniques such as X-ray absorption spectroscopy, also useful for determination of gold oxidation state, are briefly considered. [source]