We performed CO2 hydrogenation over Li-promoted Rh ion-exchanged zeolite ca
talysts (Li/RhY). As the amount of added Li increased, the main product tra
nsformed from methane to CO. Simultaneously, we observed promotion of ethan
ol production, as well as methanol production. Moreover, when 1.8% of CO wa
s mixed with the reactant gas, the selectivity for ethanol was increased to
as high as 13% on Li/RhY (Li/Rh=10), but no influence was observed on Rh i
on-exchanged zeolite catalyst (RhY). We studied the mechanism of the promot
ion effect of Li by means of in situ FT-IR observations. IR spectra of CO/C
O2 adsorption and those for subsequent TPR were observed. On RhY, CO2 molec
ules were adsorbed as terminal CO species which were the same as those foun
d in CO adsorption. However, on Li/RhY, a new peak appeared at 1618 cm(-1)
by CO2 adsorption and relatively stable species were formed on Li/RhY (Li/R
h=10). The results indicate that the Li additives created a new reaction pa
th on the catalyst surface, where CO2 adsorption enhancement as well as sta
bilization of adsorbed CO species occurred. (C) 1998 Elsevier Science B.V.
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