Efficient and facile preparation of pure silica CHA zeolite membranes by gel-less method

Abstract

To bring zeolite membranes to commercial application, corresponding preparation technology must solve the following issues like low permeance, poor reproducibility, high manufacturing cost and scale-up etc., which is still a grand challenge. The imhomogeneous slurry-like mother liquor required by the preparation of pure silica CHA membrane makes this challenge even tougher. Herein, we realized facile and efficient preparation of pure silica CHA membrane for the first time. The use of an active silica source, ammonium hexafluorosilicate ((NH4)2SiF6), enabled facile membrane synthesis in a homogeneous mother liquor at mild temperature and ambient pressure. The replacement of conventional imhomogeneous slurry-like mother liquor with homogeneous mother liqour significantly improved the reproducibility of membrane synthesis and favored the formation of thin membrane. The high activity of (NH4)2SiF6 allowed low temperature synthesis at ambient pressure without sacrificing synthesis time. Moreover, gel-less synthesis significantly reduced material waste at no cost of selectivity and permeance. All these factors combined together resulted into a facile and reproducible preparation of thin pure silica CHA membrane with high material efficiency, energy efficiency and low equipment cost. Calcined pure silica CHA membrane exhibited outstanding CO2 permence of 2.9 × 10−6mol/(m2⋅s⋅Pa) and high CO2–CH4 selectivity ∼170. This efficient and facile preparation method has great potential for large scale synthesis.