日本ゼオライト学会　刊行物 Publication of Japan Zeolite Association

Several authors have reported that zeolite membranes are likely to be cracked during the calcination process due to the thermal expansion mismatch between the membrane and the support such as in the case of alumina, zirconia and stainless steel. In this study, a binderless silicalite support for a silicalite membrane has been prepared by the dry gel conversion method to avoid crack formation. An amorphous dry gel powder was prepared by evaporation of a mixture of colloidal silica and tetrapropylammonium hydroxide (TPAOH) as template. The silicalite porous support was obtained by crystallization of the shaped dry gel in water vapor at 180°C for 18 h. The maximum bending strength of the support was obtained at a TPAOH/silica molar ratio of 0.04 in the starting gel. Also, it was shown that the crystal size of the silicalite support increased with tetrapropylammonium bromide (TPABr) contents. The silicalite membrane on the silicalite support was prepared by conventional hydrothermal synthesis. Xylene isomer vapor permeation was carried out by the Wicke-Kallenbach method to examine the quality of the silicalite membrane. The silicalite membrane on the silicalite support has a high p-xylene selectivity for the xylene isomer mixture at temperatures above 150°C. Therefore, it was shown that the silicalite membrane on the silicalite support has little cracks after the calcination process.