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.