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 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 × 10−6 mol m−2 s−1 Pa−1 and permselectivity of 66 for H2/i-C4H10 at room temperature.

Schematic representation of the formation of seed layers on macroporous supports: (A) and (B) dip-coating method; (C) hot double-layer dip-coating method.Figure optionsDownload as PowerPoint slideResearch highlights
► Three seeding methods were compared to prepare Silicalite-1 membranes.
► A novel seeding method called DRD (dipping-rubbing-dipping) was designed.
► The membrane from DRD seed layer exhibited high permeation performance.
► The effective and simple seeding method can also be used in other zeolite membranes.