Effects of bubbles on the structure and performance of zeolite membranes

Defects in the zeolite layer restricts the applications of the zeolite membrane. In this study, we found that the bubbles in the synthesis solution and the interface between the support and the synthesis solution impeded the movement of the Si/Al active ingredients to the surface of the support during the membrane synthesis process, leading to the formation of defects. Accordingly, we pre-degassed the synthesis solution containing 170-mm-long ceramic tube supports under a vacuum of 0.1 MPa at room temperature before the membrane synthesis. The characterization results showed that the degassing pretreatment drove out the gases in the synthesis solution and the interface between the synthesis solution and the support, and thus eliminated pinhole defects in the zeolite layer. The permselectivity of H2 over C3H8 increased from 8.8 to 20.2 when the synthesis solution was degassing pretreated. In conclusion, the degassing pretreatment clearly eliminated the defects in the membrane.