Abstract
CO and/or NO adsorption on reduced Rh-2/SiO2 and Rh-2-v/SiO2 catalysts has been studied by in situ infrared spectroscopy. the catalysts were prepared from Rh-2(CO)(4)Cl-2 as a precursor. three kinds of Rh sites are identified by CO adsorption corresponding to absorbance bands at 2085, and 2028cm(-1) (Rh-I(CO)(2)), 2060cm(-1) ((RhCO)-C-II), 1867cm(-1) ((Rh2CO)-C-III), respectively. IR bands of NO adsorption of Rh sites appears at 1748 and 1648cm(-1), which can be assigned to Rh.NO and Rh-No-delta species, respectively. Addition of vanadium oxide to Rh-2/SiO2 catalyst, decreases remarkly the number of Rh-II and Rh-III sites, and enhances the bond energy of Rh-I(CO)(2). the vanadium promotion is suggested as due to the electron transfer form Rh-0 to vanadium ions on Rh-2-V/SiO2 catalyst. The results obtained from CO and NO adsorption on supported Rh and Rh-V catalysts derived from cluster and metal salt precursors, i. e.,Rh-2(CO)(4)Cl-2 and RhCl3, have been compared. It is found that the intensity of linear adsorbed CO on Rh-2/SiO2 catalyst is more intense than that on Rh/SiO2 catalyst, this indicated that more Rh-0 sites were produced on Rh-2/SiO2 catalyst. Rh-2-V/SiO2 catalyst exhibits stronger electronic interaction between Rh metal and vanadium ions than that on Rh-V/SiO2 catalyst.
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