CERAMIC-ZEOLITE COMPOSITE MEMBRANES AND THEIR APPLICATION FOR SEPARATION OF VAPOR GAS-MIXTURES

Ceramic-zeolite composite membranes were prepared by in-situ synthesis of a thin (approximately 10 mum) polycrystalline silicalite-1 layer on the inner surface of an alumina membrane tube. The inner surface is a gamma-alumina coating that has 5-nm diameter pores. X-ray diffraction verified the presence of a pure silicalite phase in the layer, and SEM showed that individual silicalite crystals had grown together to form a continuous silicalite-1 layer. The addition of silicalite to the alumina membrane decreased the N2 permeance by a factor of 5, but it decreased the n-C4H10 permeance by a factor of 190, and n-C4H10 appeared to adsorb on the membrane. At room temperature, the permeance ratio of n-C4H10/i-C4H10 was one for the alumina membrane, but it was 3 for the zeolite membrane. Methanol was separated from H-2 and from CH4 at 373 K and pressures from 110 to 1100 kPa by preferentially permeating CH3OH through the zeolite membrane. For some conditions the CH3OH/H-2 Separation factor was greater than 1000, and the CH3OH/CH4 separation factor was 190. Apparently, CH3OH adsorbs and blocks the pores for H-2 or CH4 permeation.