Catalytic performance and characterization of RhVO₄/SiO ₂ for hydroformylation and CO hydrogenation

Effect of addition of vanadium oxide (vanadia) to Rh/SiO₂ in hydroformylation of ethylene and CO hydrogenation was investigated. In the hydroformylation of ethylene, the addition of vanadia enhanced hydroformylation activity and selectivity; especially the selectivity for 1-propanol formation was drastically promoted. The promoting effect was observed more significantly on the catalyst calcined at higher temperature such as 973 K. It is found that the effect is related to the formation of the RhVO₄ phase, and it is suggested that the active site consists of Rh metal and partially reduced VO_x, which is formed by the reduction of RhVO₄. This can make the interaction between Rh and VO_x more intimate. This catalyst was also effective for the alcohol formation in CO hydrogenation. Based on the catalyst characterization by means of the adsorption measurements of H ₂ and CO, H₂-D₂ exchange rate under the presence of CO, temperature-programmed desorption (TPD) of CO, temperature-programmed reduction (TPR) with H₂ and temperature-programmed surface reaction (TPSR) of adsorbed CO with H ₂, it is suggested that the sites for H₂ activation, which cannot be inhibited by the presence of CO, play an important role in the promotion of alcohol formation in hydroformylation and CO hydrogenation.