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

Abstract

Silicalite-1 membranes supported on macroporous alumina (α-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., [ETES] 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:120H2O:[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 M3 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 M3 membrane were 1.55, 0.10, and 1.51kgm−2h−1 towards acetone/H2O, butanol/H2O and ethanol/H2O mixtures, respectively for 3wt.% acetone/water, 2wt.% butanol/water and 5wt.% ethanol/water mixture, respectively and the corresponding separation factor was 211, 150, and 39, respectively.