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

P-type zeolite membranes were hydrothermally synthesized on porous alpha-alumina supports by the in situ crystallization method. Permselectivity as high as 102 was obtained for H-2/SF6 by the P zeolite membrane, At room temperature, the permselectivities for H-2/Ar and CH4/Ar are respectively 5.29 and 2.36 and the corresponding permeance of H-2 is 5.71 x 10(-7) mol m(-2) s(-1) Pa-1. The apparent activation energies for permeation of H-2, CH4, and Ar through the P-type zeolite membranes in 25-65 degrees 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 degrees 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.