Mechanistic study of the hydroformylation of propene over silica-supported Rh and Pd catalysts: Effect of added sodium cation

Abstract

The mechanism of the hydroformylation of propene over silica-supported Rh and Pd catalysts was studied by isotope tracer technique with microwave spectroscopy and infrared spectroscopic technique as well as kinetic investigation. The rate-determining steps in the hydroformylation process were different over the two metals: hydrogenation of surface acyl species on Rh catalysts and CO insertion into surface propyl species on Pd catalysts. The structure and the reactivity of the surface propyl intermediates were determined by analyzing the isotope distribution of monodeuteropropene formed during C 3H 6D 2CO reaction with microwave spectroscopy. It was revealed that n-propyl species is more reactive for CO insertion than s-propyl species. Promotion effect of sodium cations on hydroformylation was also investigated in detail and different roles of sodium cations were demonstrated for Rh and Pd catalysts.