ABSTRACT Carbon monoxide hydrogenation was studied over a γ-alumina-supported 1 wt.% Rh catalyst ... more ABSTRACT Carbon monoxide hydrogenation was studied over a γ-alumina-supported 1 wt.% Rh catalyst by means of kinetic and in situ-Infrared measurements. The study was carried out at 200-300ºC, 0 – 22.5 kPa H2 and 1 – 7.5 kPa CO. The in-situ FTIR scrutiny of catalyst surface shows that adsorbed CO* species and vacancies dominate the Rh surface, while no effect of H2 and H2O pressures on surface coverage was observed at the conditions studied. Kinetic data are consistent with a mechanism in which the C-O bond dissociation is assisted by a double H-addition while H2 dissociative adsorption, CO molecular adsorption and the HCO* formation are quasi-equilibrated steps. A two-parameter Langmuir-Hinshelwood rate expression is deduced for CH4 formation, in agreement with the proposed sequence of elementary steps and kinetic data. The effect of temperature on parameters α and KCO leads to an apparent activation energy of 82.3 kJ·mol-1, an average CO adsorption enthalpy of -14.1 kJ·mol-1 and an entropy change of -17.9 J·mol-1·K-1. In-situ FTIR experiments show a full coverage of Rh surface with adsorbed CO below 200ºC and this CO* coverage decreases as temperature increases in the range 200-300ºC; It is also observed that the heat of CO adsorption on Rh surface decreases with CO* coverage.
ABSTRACT Unconventional oxidants, such as nitric oxide (N2O) and carbon dioxide (CO2), are used t... more ABSTRACT Unconventional oxidants, such as nitric oxide (N2O) and carbon dioxide (CO2), are used to circumvent the main selectivity issue in selective oxidation with molecular oxygen (overoxidation of the desired product) because of their lower oxidizing power and the different nature of the oxygen species they generate. After presenting the most relevant properties on these two oxidants, in this chapter we describe recent advances in the use of N2O as oxidant for different hydrocarbons (propane, propene, isobutene, methanol, methane, aromatics) and on the use of CO2 in the oxidative dehydrogenation (ODH) of light alkanes and ethylbenzene. Besides, CO2 and N2O are being used as gas promoters in ODH with oxygen. Their role to master in situ the dynamic phenomena at the surface of oxides at work, and their oxidation state, is described. Finally, the role of CO2 in ODH (oxidant or shift of dehydrogenation equilibrium) is discussed. Read More: http://www.worldscientific.com/doi/abs/10.1142/9781848167513_0026?queryID=%24%7BresultBean.queryID%7D
ABSTRACT Pd nanoparticles supported on TiO2 and SiO2 (2 wt.%) were synthesized by the water-in-oi... more ABSTRACT Pd nanoparticles supported on TiO2 and SiO2 (2 wt.%) were synthesized by the water-in-oil microemulsion method. Material was characterized by standard physico-chemical methods (XRD, ICP, TEM, BET, XPS), DRIFT in operando mode and tested in gas-phase reaction of oxidation of methanol. The direct formation of methyl formate (MF) from methanol was observed. Supported palladium catalysts produced methyl formate at low temperature (< 100°C) with high selectivity. At higher temperatures methyl formate is not formed anymore and the total oxidation to CO2 occurred. DRIFT-operando study confirmed that methanol is adsorbed mainly in two forms, the un-dissociated gaseous methanol (via H bond) and dissociatively adsorbed methoxy species (CH3O-) on the surface. Methyl formate is formed already at RT with the maximum at about 80°C. Mechanism of the formation of methyl formate from methanol at low temperature is discussed.
Please be patient while the object screen loads. Changez de vue : Choisir un site… UCL FUNDP FUSL... more Please be patient while the object screen loads. Changez de vue : Choisir un site… UCL FUNDP FUSL FUCaM. ...
ABSTRACT Carbon monoxide hydrogenation was studied over a γ-alumina-supported 1 wt.% Rh catalyst ... more ABSTRACT Carbon monoxide hydrogenation was studied over a γ-alumina-supported 1 wt.% Rh catalyst by means of kinetic and in situ-Infrared measurements. The study was carried out at 200-300ºC, 0 – 22.5 kPa H2 and 1 – 7.5 kPa CO. The in-situ FTIR scrutiny of catalyst surface shows that adsorbed CO* species and vacancies dominate the Rh surface, while no effect of H2 and H2O pressures on surface coverage was observed at the conditions studied. Kinetic data are consistent with a mechanism in which the C-O bond dissociation is assisted by a double H-addition while H2 dissociative adsorption, CO molecular adsorption and the HCO* formation are quasi-equilibrated steps. A two-parameter Langmuir-Hinshelwood rate expression is deduced for CH4 formation, in agreement with the proposed sequence of elementary steps and kinetic data. The effect of temperature on parameters α and KCO leads to an apparent activation energy of 82.3 kJ·mol-1, an average CO adsorption enthalpy of -14.1 kJ·mol-1 and an entropy change of -17.9 J·mol-1·K-1. In-situ FTIR experiments show a full coverage of Rh surface with adsorbed CO below 200ºC and this CO* coverage decreases as temperature increases in the range 200-300ºC; It is also observed that the heat of CO adsorption on Rh surface decreases with CO* coverage.
ABSTRACT Unconventional oxidants, such as nitric oxide (N2O) and carbon dioxide (CO2), are used t... more ABSTRACT Unconventional oxidants, such as nitric oxide (N2O) and carbon dioxide (CO2), are used to circumvent the main selectivity issue in selective oxidation with molecular oxygen (overoxidation of the desired product) because of their lower oxidizing power and the different nature of the oxygen species they generate. After presenting the most relevant properties on these two oxidants, in this chapter we describe recent advances in the use of N2O as oxidant for different hydrocarbons (propane, propene, isobutene, methanol, methane, aromatics) and on the use of CO2 in the oxidative dehydrogenation (ODH) of light alkanes and ethylbenzene. Besides, CO2 and N2O are being used as gas promoters in ODH with oxygen. Their role to master in situ the dynamic phenomena at the surface of oxides at work, and their oxidation state, is described. Finally, the role of CO2 in ODH (oxidant or shift of dehydrogenation equilibrium) is discussed. Read More: http://www.worldscientific.com/doi/abs/10.1142/9781848167513_0026?queryID=%24%7BresultBean.queryID%7D
ABSTRACT Pd nanoparticles supported on TiO2 and SiO2 (2 wt.%) were synthesized by the water-in-oi... more ABSTRACT Pd nanoparticles supported on TiO2 and SiO2 (2 wt.%) were synthesized by the water-in-oil microemulsion method. Material was characterized by standard physico-chemical methods (XRD, ICP, TEM, BET, XPS), DRIFT in operando mode and tested in gas-phase reaction of oxidation of methanol. The direct formation of methyl formate (MF) from methanol was observed. Supported palladium catalysts produced methyl formate at low temperature (< 100°C) with high selectivity. At higher temperatures methyl formate is not formed anymore and the total oxidation to CO2 occurred. DRIFT-operando study confirmed that methanol is adsorbed mainly in two forms, the un-dissociated gaseous methanol (via H bond) and dissociatively adsorbed methoxy species (CH3O-) on the surface. Methyl formate is formed already at RT with the maximum at about 80°C. Mechanism of the formation of methyl formate from methanol at low temperature is discussed.
Please be patient while the object screen loads. Changez de vue : Choisir un site… UCL FUNDP FUSL... more Please be patient while the object screen loads. Changez de vue : Choisir un site… UCL FUNDP FUSL FUCaM. ...
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