Sonication mediated hydrothermal process – an efficient method for the rapid synthesis of DDR zeolite membranes

Abstract

The formation and growth of a DDR zeolite membrane was developed on the low cost indigenous clay–alumina substrate for separation of H₂ from H₂–CO₂ mixture by selective deposition of oriented seed crystals, followed by secondary growth method with sonication mediated hydrothermal technique. The formation of free radicals by ultrasonic irradiation in the sonochemical method enhances the rate of nucleation which ultimately reduces the DDR zeolite crystallization time. Surface seeding not only accelerates the zeolite crystallization on the support surface but also enhances the formation of an homogenous zeolite membrane layer. The DDR seeds were synthesized by a sonication mediated hydrothermal technique within a short crystallization time i.e. 2 days and used to provide nucleation for the membrane growth. Accordingly DDR zeolite membranes were synthesized on seeded substrate within 5 days. The membrane thickness was found to be ∼26 μm. The synthesized membranes along with seed crystals were characterized by XRD, FTIR, FESEM and EDAX analysis. The performance of the membrane formed was evaluated by single gas as well as mixture gas permeation measurement for H₂ and CO₂. The H₂–CO₂ separation selectivity of the membrane increased up to 3.7 at room temperature which is more than the reported values. To the best of our knowledge, there is no report on the synthesis of a DDR zeolite membrane within 7 (2 days for seed crystal and 5 days for membrane synthesis) days by a secondary growth technique.