A simple seeding method for MFI zeolite membrane synthesis on macroporous support by microwave heating

摘要

An effective seeding method is a mandatory step to have thin and defect-free zeolite membranes prepared by means of secondary growth method on macroporous tubular supports. The permeation properties of the as-prepared membranes depend strongly on the seeding method of zeolite crystals during which the whole support surface should be covered uniformly and sufficiently. In this work a novel and simple seeding method was designed and developed to prepare seed layer on low-cost macroporous Al2O3 support. This seeding technique includes three steps: (a) pre-modify the support surface by hot dip-coating in large seed (1.2 μm) suspension; (b) rub off the excess large seeds which stick on the support surface; (c) further modify the support by hot dip-coating in another seed (0.4 μm) suspension. After the composite seeding process, silicalite-1 membrane was synthesized by microwave heating (MH) at 423 K for 2 h using the synthesis solution of 1SiO2:0.3TPAOH:80H2O:4C2H5OH. Results showed the as-prepared zeolite membrane was dense and continuous with a thickness of ～4 μm. Moreover, it exhibited high hydrogen permeance of 3.01 x 10~(-6) mol m~(-2) s~(-1) Pa~(-1) and permselectivity of 66 for H2/i-C4H_(10) at room temperature,