Pervaporation through TS-1 membrane

Titanium-substituted silicalite (TS-1) membranes were synthesized onto the surface of a tubular mullite support by in situ crystallization using tetraethyl orthosilicate (TEOS), titanium tetrabutoxide (TBOT) and tetrapropylammonium hydroxide (TPAOH) as silica, titanium source and organic structure directing agent. The typical molar composition was 1SiO2:0.02TiO2:0.17TPAOH:120H2O. X-ray diffraction (XRD) patterns and Fourier transformed infrared (FT-IR) spectra of zeolite powders and membranes confirmed that the titanium was isomorphously incorporated into the MFI framework. The outer surface of the porous support was completely covered with randomly oriented, intergrown TS-1 crystals and the thickness of the membrane was about 10–20 μm, judging from the scanning electron microscopy observation. The membrane prepared at 200 °C for 16 h showed high ethanol selectivity for an ethanol/water mixture. For example, the separation factor and total flux through this TS-1 membrane were 127 and 0.77 kg/m2 h for 5 wt.% ethanol feed concentration at 60 °C, respectively.