Polydimethylsilalkylene-dimethylsiloxanes as advanced membrane materials for thermopervaporative recovery of oxygenates from aqueous reaction media

Abstract

Polydimethylsildimethylene-dimethylsiloxane (PSDMS) and polydimethylsiltrimethylenedimethylsiloxane (PSTMS) have been first studied as pervaporation membrane materials for the recovery of butanol from aqueous media. New synthesis procedures that make it possible to obtain the monomers 2,2,5,5-tetramethyl-1-oxa-2,5-disilacyclopentane (1) and 2,2,6,6-tetramethyl-1-oxa-2,6-disilacyclohexane (2) in high yields and with high purity required for subsequent polymerization have been developed. The optimum concentration of the crosslinking agent (tetraethoxysilane (TEOS)) of 5% has been found, which provides the maximum degree of crosslinking without sacrificing high values of separation factor and permeate flux. It has been shown that the permselectivity of PSDMS or PSTMS for butanol–water is higher by a factor of 1.5 or- almost 2, respectively, than the selectivity of the industrial membrane polymer, PDMS, at comparable values of the butanol permeability coefficient.