Pure-silica MFI zeolite membrane by cooperative templating approach for ethanol-water separation

Pure-silica MFI zeolite membrane composed of intergrown four prism crystals was fabricated by using tetrabutylammonium (TBA + ) and tetraethylammonium (TEA + ) as cooperating templates and the induced function of MFI seeds under synthesis solution with molar composition of 1TEOS:0.2TBAOH:0.2TEABr:180H 2 O. The ethanol/water separation factor was 64 with a flux of 1.40 kg m −2 hr −1 for 5 wt% ethanol/water mixture at 60°C. In contrast, single TBAOH and TEAOH template led to formation of uncontinuous MEL and MFI membrane respectively, without ethanol-selectivity. The behavior of quaternary ammonium (TBA + and TEA + ) varied in different system: (a) In “TBA + + TEA + ” system, TBA + and TEA + were incorporated into MFI zeolite channel simultaneously; (b) In “TPA + + M + ” system (M = TEA or TBA), either TEA + or TBA + could not be occluded into channel, however, appropriate amount of TBA + could accelerate membrane crystallization, meanwhile increase in TEA + slowed down crystallization rate of MFI membrane. This work extends the alternative preparation approaches of ethanol perm-selective MFI membrane.