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

Abstract

AbstractPure‐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:180H2O. 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.