Rapid synthesis of high-selective Al-rich beta zeolite membrane via an organic template-free route for pervaporation dehydration of water-n-butanol mixtures

Abstract

The high-selective Al-rich beta zeolite membranes were rapidly fabricated on porous α-alumina supports via an organic template-free and fluoride-containing route. The growth process of Al-rich beta zeolite membrane transformed from high-silica beta seed crystals was investigated in details. With the help of NaF, the high-silica seed with a Si/Al ratio of ∼ 25 gradually dissolved into an amorphous layer, and then more AlO4 gathered on the amorphous layer and rearranged with SiO4 to form Al-rich beta crystals with a Si/Al ratio of ∼ 2.7. A continuous and compact membrane layer was obtained for a short crystallization time of 48 h by conventional heating. The synthesized Al-rich beta zeolite membrane with strong hydrophilicity was applied in the dehydration of organic solvents for the first time. The membrane exhibited a permeation flux of 2.84 kg m-2h−1 and a high separation factor of 17,900 for a 90 wt% n-BuOH/H2O mixture at 348 K. Even in a 95 wt% n-BuOH/H2O mixture, the membrane showed a high selectivity together with the water content in permeate of 99.93 wt%, indicating that the Al-rich beta zeolite membrane was a promising candidate for dehydration of organic solvents.