Synthesis and property of silicalite-1 membranes by restricting growth method with dilute solution

A specific synthesis mode, based on precursor diffusion through the support channels, the restricting growth method (RGM) with ultra-dilute precursor has been designed to prepare silicalite-1 zeolite membranes on seeded macroporous alpha-Al2O3 tubular supports. Several parameters were systematically investigated to evaluate their influence on performance of the membranes, including the H2O/SiO2 ratio, template type and crystallization temperature. X-ray diffraction (XRD), scanning electron microscopy (SEM) and single-gas permeation tests were used to characterize the as-prepared membranes. Results showed the membrane prepared under optimum parameters (H2O/SiO2 ratio of 800, TPAOH as template and crystallization at 443 K) was continuous, dense and with a controllable section thickness almost the same as that of the seed layer. It displayed preferable hydrogen permeance (1.2 x 10(-6) mol m(-2) s(-1) Pa-1) and permselectivity (alpha(H2)/SF6 = 134) at 298 K under 0.1 MPa pressure drop. Moreover, due to the utilization of ultra-dilute precursor, this technique has the advantage of reduced chemical consumption. On the contrary, the uncompacted membranes with poor permeation behavior were obtained by the conventional secondary growth method under the same synthesis parameters. (C) 2009 Elsevier Inc. All rights reserved.