Ceramic-zeolite composite membranes and their application for separation of vapor/gas mixtures (original) (raw)

Ceramic-zeolite composite membranes were prepared by in-situ synthesis of a thin ( _ 10 pm) polycrystalline silicalite-1 layer on the inner surface of an alumina membrane tube. The inner surface is a y-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 Nz permeance by a factor of 5, but it decreased the n-C4Hu, permeance by a factor of 190, and n-C.,H10 appeared to adsorb on the membrane. At room temperature, the permeante ratio of n-C4H,,-,/i-C4Hlo was one for the alumina membrane, but it was 3 for the zeolite membrane. Methanol was separated from HZ and from CH4 at 373 K and pressures from 110 to 1100 kPa by preferentially permeating CH30H through the zeolite membrane. For some conditions the CH30H/H2 separation factor was greater than 1000, and the CHsOH/CH4 separation factor was 190. Apparently, CH30H adsorbs and blocks the pores for H2 or CH4 permeation.