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-C₁₄H₁₀ separation from a mixture containing a small amount of i-C₄H₁₀. The zeolite membranes thus served as molecular-sieving for C₄ isomers.