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

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 mu m) 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 mu m) 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 1SiO(2):0.3TPAOH:80H(2)O:4C(2)H(5)OH. Results showed the as-prepared zeolite membrane was dense and continuous with a thickness of similar to 4 mu m. Moreover, it exhibited high hydrogen permeance of 3.01 x 10(-6) mol m(-2) s(-1) Pa-1 and permselectivity of 66 for H-2/i-C4H10 at room temperature. (C) 2010 Elsevier Inc. All rights reserved.