Preparation of T-type zeolite membranes using a dip-coating seeding suspension containing colloidal SiO₂

T-type zeolite membranes were prepared on mullite tubes by the secondary growth method with a simple dip-coating seeding approach. Uniform and continuous seed layers were achieved by dip-coating with the addition of colloidal silica into the seed suspension. The seeded substrates could reproducibly induce high-performance T-type zeolite membranes at 378 K for 30-35 h. Typically, a water permeation flux of 1.22 kg·m^-2·h^-1 with a separation factor of 2040 was obtained for pervaporation (PV) dehydration of 90 wt.% ethanol/water mixture at 348 K. T-type zeolite membranes with 80-cm lengths were successfully produced on a pilot scale. The as-synthesized membranes were further evaluated by ethanol dehydration. A formula for estimating the average water permeation flux was derived for a batch separation operation. Two membrane modules (0.1 m² for each) connected in series were continuously operated to dehydrate an industrial propanal solution with pH ∼4 for 1000 h, which produced anhydrous propanal with a water content of <0.1 wt.%.