VAPOR PHASE HYDROFORMYLATION OF ETHYLENE AND PROPYLENE ON Rh-V/SiOCATALYSTS

<正> Promoter effects of vanadium on ethylene and propylene hydro-formylation have been studied over Rh-V/SiO2 catalysts.The results werecompared with that of CO hydrogenation for C2-oxygenates.The addition ofthe vanadium promoter remarkably reduced the initial temperature of C2H4 orC3H6 hydroformylation,increased the reaction rates and the ratios of alcoholto aldehyde in the products,and improved the reaction selectivites.The for-mation rates of propanol and propanal in the C2H4 hydroformylation andthose of C2-oxygenates in CO hydrogenation as a function of the amount ofvanadium added showed a good parallel relationship.The promoting action ofvanadium was explained by a model of hydrogen assisted CO activation overrhodium,promoted by lower valence vanadium.The results suggest that ahigh rate of CO insertion is the key factor for the selectivity improvement ofCO hydrogenation to C2-oxygenates,and the rate limiting step of the forma-tion of C2-oxygenates may be the formation of CHx species,or a step relatedto its formation.