(628e) Fabrication and Optimization of SAPO-34 Membranes for Efficient Separation of CO2/CH4 Gas Mixture

Zeolites are crystalline materials with angstrom scale pores and channels. Zeolite powders have been widely used as shape-selective catalysts, ion exchangers and adsorbents. Zeolite membranes, as emerging membrane materials in recent years, can offer a great potential for a variety of applications such as gas and liquid separation, membrane catalysis, chemical sensor, corrosion-resistant coating and micro-electronic device. The ways to manipulate the membrane microstructure, including grain shape and intergrowth, thickness, crystal orientation, and even defect minimization, are quite important for its performance improvement. Oriented zeolite membranes usually exhibit superior performances compared with randomly oriented counterparts. For example, the appropriate orientation of crystals can effectively enhance mass transport within the membranes, which is closely related to separation and catalysis. Despite great efforts made over the past decade, challenges still exist to fabricate high-quality oriented zeolite membranes.

In the present work, a thin seed layer was prepared the α-Al₂O₃ substrate by spin-coating by using ca. 400 nm-sized SAPO-34 crystals, based on which preferentially oriented and thin SAPO-34 membrane were synthesized under microwave irradiation. The fabrication process was optimized by changing a variety of parameters, including heating method, water content, aging time, crystallization temperature, and even the mixing order in preparing for the synthesis solution.

Without doubt, the preferentially oriented SAPO-34 membranes could be synthesized using the seeded growth method under microwave irradiation. Under the optimized condition in this study, the synthesized SAPO-34 membrane was only ca. 1.5 μm thick with a preferential (h0l)-orientation. This membrane exhibited a very satisfactory CO₂/CH₄ separation performance, through which a CO₂ permeance of 1.8×10^-6 mol/(m²â–ªsâ–ªPa) with the selectivity of 89 was achieved for the 50/50 CO₂/CH₄ gas mixture under 138 kPa feed pressure and 303 K. The results we obtained were among the best ones compared with the counterparts in the literature. It seemed that both the preferential orientation and thickness of the membrane played an important role for its separation performance.

This work was supported by the National Natural Science Foundation of China (21476171).