STUDIES ON CATALYSTS FOR THE ALKYLBENZENE-STEAM REACTION .13. MECHANISM OF WATER ACTIVATION AND ACTIVITIES FOR STEAM DEALKYLATION OF ALKYLBENZENE OVER THE VARIOUS RH-METAL OXIDE CATALYSTS

The mechanism of H2O activation over Rh catalysts supported on various metal oxides (Al2O3, SiO2, Cr2O3, UO2, VO2, MoO2, and WO2) was studied by the pulse reaction using CO and H2O as reactants, and was discussed in relation to m-xylene—steam reaction. Rh/metal oxide catalysts were generally classified into two groups on the basis of the mechanism of H2O activation. First, in the activation of H20 over Type I catalysts (Rh/Al2O3, Rh/SiO2, and Rh/Cr2O3) surface OH groups are formed (Eq. (4)). Second, in the activation of H2O over Type E catalysts (Rh/UO8, Rh/VO2, Rh/MoO2, and Rh/WO2) the cleavage of HsO molecule into gaseous Ht and surface oxygen atom occurs (Eq. (7)). The resulting surface OH groups (Type I catalyst) and resulting surface oxygen atom (Type H catalyst) were both active for CO oxidation (Eqs. (2) and (6)). The order of the activities for CO oxidation of the Rh/metal oxide catalysts was well correlated to that of the steam-dealkylating activities for m-xylene, which were measured by a flow reaction method. © 1979, The Chemical Society of Japan. All rights reserved.