Synthesis of silicalite-1 membrane with two silicon source by secondary growth method and its pervaporation performance

Silicalite-1 membranes supported on macroporous alumina (alpha-Al2O3) tubes for pervaporation were successfully prepared by introducing ethyl triethoxysilane (ETES) during the preparation of synthesis solutions. The effects of synthesis parameters (i.e., FETES] content, crystallization time, and crystallization temperature) on the membranes thickness and pervaporation performance were investigated for silicalite-1 membranes grown onto seeded supports. The as-synthesized membranes were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and pervaporation testing. The results indicated that the as-synthesized membranes were typical MFI-type zeolite membranes and the ETES promoted the crystal growth of the silicalite-1 membranes. The optimum molar composition (1TEOS:0.17TPAOH:120H(2)O:[0.02-0.04]ETES:4EtOH), more than 16h crystallization time at low-temperature (413K) was better for obtaining a dense and continuous silicalite-1 membranes with a good pervaporation performance. The M-3 membrane shows a relatively low selectivity for ethanol/water system but a high selectivity for acetone/water and butanol/water systems. The total fluxes of the M-3 membrane were 1.55, 0.10, and 1.51 kg m(-2) h(-1) towards acetone/H2O, butanol/H2O and ethanol/H2O mixtures, respectively for 3 wt.% acetone/water, 2 wt.% butanol/water and 5 wt.% ethanol/water mixture, respectively and the corresponding separation factor was 211, 150, and 39, respectively. (C) 2010 Elsevier B.V. All rights reserved.