Methanol Carbonylation Catalyzed by Rhodium Complexes Immobilized to Silica via Pyridine Group

Abstract

2-(2-Trimethoxysilylethyl)pyridine (I) was used to prepare a series of rhodium carbonyl complexes bound to silica via pyridine group. The rhodium complex Rh2(CO)4Cl2 (Rh2) was used as a starting compound, and the immobilized complexes were prepared by the following routes: (i) by the reaction of untreated silica with a Rh complex formed from Rh2 and I, (ii) by reaction of Rh2 with a silica functionalized with I, (iii) by treatment of Rh2 with a polycondensate prepared by hydrolysis and condensation of a mixture of I and tetraethoxysilane, and (iv) by sol-gel processing of tetraethoxysilane with a Rh complex formed from Rh2 and I. These complexes were found to be efficient catalysts for the liquid phase methanol carbonylation. Their activity and stability in relation to their synthesis and structure is discussed, along with Rh leaching process.