ISSN:
1572-879X
Keywords:
CO2 hydrogenation
;
TiO2 promoted rhodium
;
kinetics of CO2 and CO hydrogenation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract Submonolayer deposits of titania on a Rh foil have been found to increase the rate of CO2 hydrogenation. The primary product, methane, exhibits a maximum rate at a TiO x coverage of 0.5 ML which is a factor of 15 higher than that over the clean Rh surface. The rate of ethane formation displays a maximum which is 70 times that over the unpromoted Rh foil; however, the selectivity for methane remains in excess of 99%. The apparent activation energy for methane formation and the dependence of the rate on H2 and CO2 partial pressure have been determined both for the bare Rh surface and the titania-promoted surface. These rate parameters show very small variations as titania is added to the Rh catalyst. The methanation of CO2 is proposed to start with the dissociation of CO2 into CO(a) and O(a), and then proceed through steps which are identical to those for the hydrogenation of CO. The increase in the rate of CO2 hydrogenation in the presence of titania is attributed to an interaction between the adsorbed CO, released by CO2 dissociation, and Ti3+ ions located at the edge of TiO x islands covering the surface. Differences in the effects of titania promotion on the methanation of CO2 and CO are discussed in terms of the mechanisms that have been proposed for these two reactions.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00764834
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