Hydrophobic zeolite–silicone rubber mixed matrix membranes for ethanol–water separation: Effect of zeolite and silicone component selection on pervaporation performance

High-silica ZSM-5 zeolites were incorporated into poly(dimethyl siloxane) (PDMS) polymers to form mixed matrix membranes for ethanol removal from water via pervaporation. Membrane formulation and preparation parameters were varied to determine the effect on pervaporation performance including siloxane chain length, crosslinking agent concentration and density of reactive groups, catalyst level, solvent type, zeolite type and loading, mixing method, and presence of a porous support membrane. Uniform dispersion of zeolite was critical to the achievement of reproducible results and ultrasonication with a probe-type device was found to be effective at particle dispersal. Properties of the vinyl-terminated PDMS and methyl-hydride crosslinking agents in the polymer system had a limited effect on performance while zeolite loading had the greatest effect. The highest observed selectivity of 3.0 was observed with 65 wt% zeolite loading, the highest practicable loading for the polymer system studied. The current results are placed in the context of ZSM-5/PDMS mixed matrix membranes previously reported in the literature for ethanol–water separation.