Preparation of MFI-type zeolite membranes and their use in separating n-butane and i-butane

Abstract

MFI-type zeolite membranes were synthesized by hydrothermal reaction on the surface of porous α-alumina support tubes with different pore sizes. The zeolite membranes consisted of three zones: The top zone was a polycrystalline zeolite layer and the inner zone was a layer of α-alumina macropores, partially filled with deposits. The intermediate zone was a mixture of alumina particles and deposits. The morphology of the zeolite membranes was dependent on the substrates. The permeance of zeolite membranes formed on the substrate possessing pores of 150 - 170 nm under identical conditions ranged over two orders of magnitude. There was no definite relationship between n-butane/i-butane (n-C4H10/i-C4H10) permselectivity and permeance, although permeance was affected by the substrates. The n-C4H10/i-C4H10 permselectivity calculated from single-component permeances was in the range of 1.5∼12 at 100° C, and the activation energy for the permeances was 11 kJ·mol-1. The selectivity increased in the case of n-C4H10 separation from a mixture containing a small amount of i-C4H10. The zeolite membranes thus served as molecular-sieving for C4 isomers.