In situ synthesis of P-type zeolite membranes on porous α-alumina supports

P-type zeolite membranes were hydrothermally synthesized on porous α-alumina supports by the in situ crystallization method. Permselectivity as high as 102 was obtained for H₂/SF₆ by the P zeolite membrane. At room temperature, the permselectivities for H₂/Ar and CH₄/Ar are respectively 5.29 and 2.36 and the corresponding permeance of H₂ is 5.71×10^-7 mol m^-2 s^-1 Pa^-1. The apparent activation energies for permeation of H₂, CH₄, and Ar through the P-type zeolite membranes in 25-65 °C were estimated to be 11.1, 9.1, and 15.2 kJ/mol, respectively. In a dry atmosphere, the crystalline structure of the zeolite layer gradually transforms from the cubic to tetragonal phase at temperatures higher than 65 °C. The transformation does not result in drastic changes in gas permeance and permselectivity, indicating that the P-type zeolite films are still continuous. The P-type zeolite membranes are more stable in a humid atmosphere.