Organic structure-directing agent-free synthesis for *Bea-type zeolite membrane

Membrane separation has drawn attention as a novel-energy saving separation process. Zeolite membranes have great potential for hydrocarbon separation in petroleum and petrochemical fields because of their high thermal, chemical, and mechanical strength. A *BEA-type zeolite is an interesting membrane material because of its large pore size and wide Si/Al range. This manuscript presents a protocol for *BEA membrane preparation by a secondary growth method that does not use an organic structure-directing agent (OSDA). The preparation protocol consists of four steps: pretreatment of support, seed preparation, dip-coating, and membrane crystallization. First, the *BEA seed crystal is prepared by conventional hydrothermal synthesis using OSDA. The synthesized seed crystal is loaded on the outer surface of a 3 cm long tubular α-Al₂O₃ support by a dip-coating method. The loaded seed layer is prepared with the secondary growth method using a hydrothermal treatment at 393 K for 7 days without using OSDA. A *BEA membrane having very few defects is successfully obtained. The seed preparation and dip-coating steps strongly affect the membrane quality.