Development of voc permselective membranes by using an organic-inorganic hybrid gel

An organic-inorganic hybrid gel having a joint-rod structure was prepared by using the Ashby-Karstedt catalyst. 1,3,5,7-tetramethylcyclohexane is one of siloxane compounds that was employed as a joint molecule. 1, 5-Hexadiene is one of a, (uncoupling dienes that was employed as a rod molecule. Porous y-alumina substrates having pores of 4nm were coated with this gel to obtain toluene permselective membranes. Toluene is one of VOC components. Toluene/N2 permeance ratio was 850 with toluene permeance of 1.55X 10~6molm~2s"'Pa~'. The permeation through this gel membrane is discussed using a novel permeation model. The permeation model consists of two permeation pathways. One is permeation through the thin gel layer, and the other is that through the gap between the gel clusters. Optimum membrane structures can be found through a novel transmission mechanism and by variation of the model parameters.