High-Performance FAU Zeolite Membranes Derived from Nano-Seeds for Gas Separation.

In this study, high-performance FAU (NaY type) zeolite membranes were successfully synthesized using small-sized seeds of 50 nm, and their gas separation performance was systematically evaluated. Employing nano-sized NaY seeds and an ultra-dilute reaction solution with a molar composition of 80 NaO: 1AlO: 19 SiO: 5000HO, the effects of synthesis temperature, crystallization time, and porous support (α-AlO or mullite) on the formation of FAU membranes were investigated. The results illustrated that further extending the crystallization time or increasing the synthesis temperature led to the formation of a NaP impurity phase on the FAU membrane layer. The most promising FAU membrane with a thickness of 2.7 µm was synthesized on an α-AlO support at 368 K for 8 h and had good reproducibility. The H permeance of the membrane was as high as 5.34 × 10 mol/(m s Pa), and the H/CH and H/-CH selectivities were 183 and 315, respectively. The CH/CH selectivity of the membrane was as high as 46, with a remarkably high CH permeance of 1.35 × 10 mol/(m s Pa). The excellent separation performance of the membrane is mainly attributed to the thin, defect-free membrane layer and the relatively wide pore size (0.74 nm).