Comparing porous and dense membranes for the application in membrane reactors

Abstract

The performance of a membrane reactor using two types of membranes has been studied experimentally. A modified Wicke-Kallenbach cell consisting of two well mixed compartments separated by flat membrane discs was used to investigate mass transfer and reaction separately and simultaneously. At first the mass transfer through a porous glass membrane was characterized. Then this membrane was modified with a thin palladium layer by an electroless plating technique. The changes in selectivity and flux were quantified with permeation experiments. Due to remaining defects in the deposited Pd-layer, an appropriate permeation model had to be developed based on the combination of the Dusty Gas Model (DGM) and the Solution Diffusion Model (SDM). Furthermore, the reaction kinetics of the dehydrogenation of cyclohexanol catalyzed by a conventional Pd-catalyst were determined in the slightly modified experimental setup. Finally the separately studied processes were performed simultaneously in the membrane reactor. The experimental results were evaluated using a theoretical model taking into account the observed transport properties of the two membranes and the application of an inert as well as a reactive sweep gas.