(459a) Pervaporation and Vapor Permeation Separation of Xylene Mixture By Randomly Oriented MFI  Zeolite Membranes

MFI zeolite membranes have attracted much attention for separation of p-xylene from xylene isomer mixture. However, all studies reported were either focused on vapor-permeation or pervaporation separation of xylene separation properties. Furthermore, the vapor permeation studies were conducted under unpractical condtions of quite low xylene activity (<3%). There is lack of a comparative study on xylene separation characteristics of the MFI membranes of different structures in the different operation modes. In this work, randomly oriented MFI zeolite membranes synthesized with and without using organic template on α-alumina support were studied for the separation of xylene isomers by pervaporation and vapor-permeation methods. Vapor permeation selectivity and permeance of binary mixture of p-xylene and o-xylene through MFI zeolite membranes were measured in various p-xylene activity in a wide temperature range. It was found that the separation factor of p-xylene/o-xylene decreases with increasing p-xylene activity. Membranes obtained from template-free precursor exhibit much higher separation factors of p-xylene over o-xylene than the membrane synthesized with template by using both separation methods due to less intercrystalline defects in the former membrane than the latter. The p-xylene/o-xylene separation factor of both membranes in vapor-permeation (with highest of 162) is found to be much higher than that of pervaporation (highest 34) because the latter was operated at highest activity.