Silicon carbide membranes for gas separation applications

SiC microporous membranes were prepared by the pyrolysis of thin allyl-hydridopolycarbosilane (AHPCS) films coated, using a combination of slip-casting and dip-coating techniques, on tubular silicon carbide macroporous supports. Combining slip-casting with dip-coating significantly improved the reproducibility in preparing high quality membranes. The membranes prepared, so far, exhibited an ideal H2/CO2 selectivity in the range of 42–96, and a H2/CH4 ideal selectivity in the range of 29–78. Separation factors measured with the same membranes, using equimolar binary mixtures of H2 in CO2 and H2 in CH4, were similar to the ideal selectivity values. Steam stability experiments with the membranes lasting 21 days, using an equimolar flowing mixture of He/H2O at 200 °C, indicated some initial decline in the permeance of He, after which the permeance became stable at these conditions.