Microporous ZIF-8 and ZIF-67 membranes grown on mesoporous alumina substrate for selective propylene transport

Abstract

Defect free microporous ZIF-8 and ZIF-67 membranes were successfully developed from the secondary growth technique to separate propylene from propylene/propane gas mixture. The characterization and gas permeation results demonstrate that ZIF-8 and ZIF-67 membranes have the potential for the separation of propylene from propylene/propane gas mixture with the highest separation factor of 76 and 5, respectively. While ZIF-67 membrane did not perform as expected in term of the selectivity, its permeance was found to be considerably higher than the ZIF-8 membrane. ZIF-67 membrane exhibited the highest propylene permeance of 196 × 10−10 mol·m−2·s−1·Pa−1, whereas ZIF-8 membrane exhibited the highest permeance of 86 × 10−10 mol·m−2·s−1·Pa−1. The difference in the permeation performance was largely due to the better inter-grown grain boundary structure of ZIF-8 membrane than that of ZIF-67 membrane.