Preparation of high performance ZSM-5 zeolite membranes for CO2/H2 separation

High-quality zeolite ZSM-5 zeolite membranes were successfully synthesized on the outer surface of tubular alpha-alumina substrates by manipulating the microstructure of the zeolite layer using a new different-sized seeding in combination with a variable-temperature/time methods. In this method the defects/microcracks in the bottom seed layer, which are filled by smaller seeds, are effectively eliminated using a designed temperature/time profile, resulting in a significant increase in selectivity without scarifying permeance. The effects of number and combination of seed layers, seed particle size, and the synthesis temperature-time profile on the microstructure, N-2/SF6 gas permeation, and H-2/CO2 separation performance of membranes are evaluated in detail. The synthesized ZSM-5 zeolite membranes show the microstructure of thin, fully inter-grown, and densified zeolite layer that is responsible for high selectivity without any negative effect on the permeance. The best synthesized defect-free ZSM-5 zeolite membranes on alumina supports exhibited a very low H-2/CO2 selectivity of 0.1 with CO2 permeance of 3 x 10(-5) molm(-2)s(-1)Pa(-1). (c) 2020 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

Automated summary

High-quality ZSM-5 zeolite membranes were successfully synthesized by manipulating the microstructure of the zeolite layer, resulting in high selectivity without sacrificing permeance. The method effectively eliminated defects/microcracks in the seed layer and achieved excellent separation performance by filling them with smaller seeds.