Encapsulated HRH(CO)(PPh₃)₃ in microporous and mesoporous supports: novel heterogeneous catalysts for hydroformylation

Abstract

Novel heterogeneous catalysts for hydroformylation of olefins to aldehydes using encapsulation and anchoring methodologies for HRh(CO)(PPh₃)₃ in zeolite Na-Y and MCM-41 and MCM-48 mesoporous materials have been reported. The heterogeneous catalysts were characterized and used for hydroformylation of linear and branched olefins to show high activity and recyclability without leaching of the Rh metal during the course of reactions. Using CP-MAS NMR, FT-IR, TEM, XPS, and powder XRD studies, characterization of the Rh complex inside the porous structures of the heterogeneous catalysts has been investigated. ³¹P CP-MAS NMR spectra of the encapsulated Rh complex catalyst inside zeolite Na-Y and mesoporous MCM-41 and MCM-48 supports showed a possible encapsulation of the Rh complex in the pores. TEM images and the diffraction patterns of the heterogenized Rh complex in mesoporous and zeolitic supports further supported a possible entrapment of the complex inside the porous frameworks. Rhodium is present as Rh(I) in the encapsulated catalysts before and after the experiments, as envisaged by XPS spectra. In contrast to other heterogeneous catalytic systems for hydroformylation, the catalysts reported here are highly stable, easily separable, and recyclable. The TON/TOF values of these catalysts were also found to be significantly higher than those of the previously reported heterogeneous catalysts.