The Heterogeneous And Homogeneous Hybird L-Rh/SiO₂ Catalysts For Olefins Hydroformylation

The field of catalysis is mainly divided into heterogeneous one and homogeneous one. The former has the advantage of easy separation of catalysts from the products; the latter can be operated under mild conditions with high activity and selectivity, especially in the olefins hydroformylation process. However, homogeneous catalysts are difficult to be recovered from hydroformylation products. In this paper, a kind of new catalysts for olefins hydroformylation was studied.For the first time, an idea of organic-inorganic hybrid catalysis leads to the originality of a hybrid of heterogeneous and homogeneous catalysts. The organic phosphine ligands (L) were directly used to modify the Rh/SiO2 to prepare L-Rh/SiO2 catalysts for olefins hydroformylation. The results showed that the catalytic performances of hydroformylation over L-Rh/SiO2 catalyst were higher than those of Rh/SiO2 catalyst, and were comparable to those of the corresponding homogeneous catalysts. The TOF of 1-hexene hydroformylation over P(OPh)3-Rh/SiO2 catalyst was up to 51841h-1, which was hundreds of times as many as that of Rh/SiO2 catalyst.By means of TG, 31PMAS NMR, XPS, TPD and FTIR techniques for the characterization of L-Rh/SiO2 catalysts, the coordination bond between phosphine ligands and Rh atom and the valence state of the surfacial Rh are made clear before and after the CO/H2 adsorbed on the PPh3-Rh/Si02. Through the IR characterization of adsorption state of CO, H2 and C2L4 on PPh4-Rh/SiO2 under reaction conditions,it is found that linearly CO bonded on Rh coordinated with PPh3 ligands is the catalytic active site of PPh3-Rh/SiO2 catalyst for ethylene hydroformylation under gas-solid phase conditions.The water-soluble TPPTS ligand is employed to coordinate Rh/SiO2 to prepare the TPPTS-Rh/SiO2 catalyst, which is usble in water-oil biphasic and supported aqueous-phase catalysis system. Finally, The combined supported metal and supported aqueous-phase (SAP/M-SiO2) catalysts were prepared by immobilizing the homogeneous catalytic phase in the pores of supported metal catalysts. Synergistic assistance of heterogeneous component for SAP component on SAP/M-SiO2 catalysts was also investigated.