Preparation In Enlargement And Application Of Zeolite T Membranes

Pervaporation (PV) is an effective and energy-efficient technique for separating azeotropic or close-boiling liquid mixtures. NaA zeolite membranes have been commercialized in the past decade, which exhibited excellent separation performance in organic dehydration. However, the application was limited to neutral systems due to the low acid resistance for NaA zeolite membranes. Zeolite T membranes showed a relatively low permeation flux as compared with NaA zeolite membranes while remaining acid-resistant. There is no doubt that zeolite T membranes have a broad application prospect in the field of organic solvents containing acid dehydration.In this paper, high performance zeolite T membranes were prepared on coarse macroporous supports. Also, the pervaporation performances in separating organic/water mixtures of the as-prepared zeolite T membranes was tested. The major reseach contents and results are given below:(1) Zeolite T with 2 μn and 0.4 μm was synthesized by the formulation 1SiO2:0.055Al2O3:0.23Na2O:0.0825K2O:xTMAOH:11.68H2O (x=0.045 or 0.1).The high quality of seed layer was obtained by varying-temperature hot dip-coating method on the cheap macroporous support. Zeolite T membranes were synthesized with the formulation of 1SiO2:0.055Al2O3:0.23Na2O:0.08K2O:30H2O. The influences of preparation conditions, such as crystallization temperature and crystallization time on the preparation of zeolite T membranes were studied. The results indicated that the ideal preparation conditions were 150℃ for 4h. The as-synthesized membranes have high performance with the water flux up to 2.84 kg·m-2·h-1 and the separation factor was 1766 for 90wt.%IPA/water.(2) Zeolite T membranes of being prepared under ideal conditions showed high PV performances in various organics dehydration. Acid immersion test showed that high concentrations acid corroded zeolite T membranes. The PV test for pH=490wt.%IPA/water showed the flux was kept at 1.00 kg·m-2·h-1. The as-synthesized membranes exhibited good acid resistance.(3) Zeolite T membranes was prepared in enlargement on 80 cm-long Al2O3, which indicated that spinning crystallization for 170℃,6h was the best conditions. The PV performances of as-synthesized membranes for 90wt.%IPA/water was high with water flux over 1.50 kg·m-2·h-1 and the separation factor over 10000. The operating conditions (feeding flux, feeding temperature, feeding concentration) influenced the PV performance of the as-synthesized 80cm-long membranes to different degrees. The isopropyl alcohol feed was dehydrated from 10wt.% to 0.5wt.% under continuous high temperature PV operating. The zeolite T membrane showed average water flux of 1.90 kg·m-2·h-1 with separation factor over 3000.