Choline chloride templated CHA zeolite membranes for solvents dehydration with improved acid stability

Four-channel hollow fiber supported CHA zeolite membranes with relatively higher Si/Al ratios (3.6–3.9) were successfully synthesized using cheap choline chloride (CC) as structure directing agent. The influence of synthesis parameters, such as precursor composition, crystallization temperature and duration, on the composition and dehydration performance of CHA zeolite membranes was extensively investigated. TG, EDX and FT-IR results indicated that the template decomposed during membrane synthesis which generated some residue in CHA framework. Interestingly, no thermal treatment was necessary to open water permeating channels of the as-prepared CHA zeolite membranes. The SiO₂/Al₂O₃ ratio and CC content in the precursor significantly affected the separation performance. High-quality CHA zeolite membranes with the Si/Al ratio between 3.6 and 3.9 was prepared from precursor 28 SiO₂: 0.58 Al₂O₃: 4.7–5.7 CC: 11.78 Na₂O: 1260 H₂O at 413 K for 10 h. The as-synthesized membranes showed water permeation flux of 4.7–5.6 kg m⁻² h⁻¹ and separation factor of >2000 for pervaporation (PV) dehydration of 90 wt% ethanol/water mixture at 348 K. Moreover, the membrane showed long-term (>35 h) stability for the acetic acid dehydration.