Fast synthesis of thin SSZ-13 membranes by a hot-dipping method

Abstract

Among zeolite membranes with CHA structure, SSZ-13 membrane has certain advantages over all-silica CHA and SAPO-34 membranes, like easy synthesis, good stability and insensitivity to moisture, however, its separation performance is not satisfactory. In this study, SSZ-13 membranes were prepared by a hot-dipping method, where the hot contact of seeded support and mother liquor at synthesis temperature resulted into fast crystallization kinetics and thin membranes. The obtained sub-micron SSZ-13 membranes exhibited outstanding CO2–CH4 mixture separation performance, CO2 permeance ~28 × 10−7 mol/(m2 s Pa) and CO2–CH4 selectivity ~180 at 0.14 MPa and room temperature. The hot-dipping method achieved the complete separation of seeding and crystallization (or membrane growth) by preventing the contact of mother liquor and seeded support before reaching synthesis temperature. This treatment avoids any undesirable change of the seed layer before membrane growth, which may help us to correlate the membrane performance with the properties of seed layer, like seed density, thickness and seed size. On the contrary, the CHA seed layer might be dissolved partially by mother liquor during the heating process of conventional membrane synthesis, which led to thick membranes due to unsatisfactory seeding. This method could be used for the synthesis of other zeolite membranes.