Synthesis of stable UiO-66 membranes for pervaporation separation of methanol/methyl tert-butyl ether mixtures by secondary growth

Stable UiO-66 membranes were successfully prepared on macroporous alumina tubes by secondary growth and were for the first time applied in the separation of methanol/methyl tert-butyl ether (MTBE) mixtures by pervaporation. Two key factors affecting the growth of the UiO-66 membranes were investigated. It has been found that acetic acid promotes the crystallization of UiO-66 crystals and water favors the intergrowth of UiO-66 crystals, leading to the formation of high-performance UiO-66 membranes. Under the optimized synthesis conditions, a continuous and dense UiO-66 membrane could be obtained, showing a separation factor of nearly 600 and a flux of 1.21 kg m(-2) h(-1) for 5 wt% methanol/MTBE mixtures at 40 degrees C. The effects of operation parameters on PV performance of the UiO-66 membranes were also studied in detail. The results reveal that increasing feed temperature or methanol in feed would enhance permeation flux but reduce separation factor, the permeability of components and membrane selectivity. It is worth mentioning that the UiO-66 membranes show excellent operating stability. This work demonstrates that the UiO-66 membranes have great potential for separation of methanol/MTBE mixtures via pervaporation.