Catalysis Today, Vol.45, No.1-4, 197-201, 1998
Syngas conversion using RhVO4 and Rh2MnO4 catalysts: Regeneration and redispersion of Rh metal by calcination and reduction treatments
The hydrogenation of CO over mixed oxides (RhVO4, Rh2MnO4) supported on SiO2 has been studied after H-2 reduction at 300 degrees C and at 500 degrees C, and the results compared with those of unpromoted Rh/SiO2 catalysts. Rh was more highly dispersed (40 Angstrom) after the decomposition of RhVO4 by the H-2 reduction than those of Rh2MnO4/SiO2 and unpromoted Rh/SiO2 catalysts. The activity and the selectivity to C-2 oxygenates of the mixed-oxide catalysts after the H-2 reduction were higher than those of the unpromoted Rh/SiO2 catalysts, but the activity of the RhVO4/SiO2 catalyst increased more dramatically after the decomposition by the H-2 reduction at 300 degrees C, and hence the yield of C-2 oxygenates increased. These results suggest that a strong metal-oxide interaction (SMOI) was induced by the decomposition of the mixed oxides after the H-2 reduction. The catalytic activity and selectivity were reproduced repeatedly by the calcination and reduction treatments of the spent (used) catalyst because of the regeneration of RhVO4 and redispersion of Rh metal.
Keywords:PROMOTED RH/SIO2 CATALYSTS;CO HYDROGENATION;OXIDEINTERACTIONS;RHODIUM CATALYSTS;NB;SELECTIVITY;DISPERSION;BEHAVIORS