A Study of Oxide-Supported Homogeneous Catalysts

摘要

The analog of RhCl(CO)(PPh3)2 was supported on both silica and alumina. Infrared and ESCA were used to study changes which occur when the complex reacts with CO. On silica, initially a square planar dicarbonyl complex is formed and at higher CO pressures a dimeric species. On alumina both the square planar and penta-coordinated dicarbonyls are formed. Dimeric species are formed from each kind of dicarbonyl and can be distinguished by their infrared spectra. The supported complex listed above was used to study the liquid phase hydroformylation of 1-hexene. The observed activity and selectivity correlate with the nature of the Rh species on both silica and aluminum supports, as characterized by ESCA and IR. Under mild hydroformylation conditions the concurrent isomerization of olefin is catalyzed by the Rh complex and not by the support. Free phosphene in solution completely eliminates isomerization. The support influences the species that initiates the hydroformylation reaction and consequently influences the products of the reaction.