Pervaporation separation of ethanol–water mixtures through B-ZSM-11 zeolite membranes on macroporous supports

• B-ZSM-11 membranes were synthesized by a secondary growth method.
• Cheap macroporous α-Al2O3 tubes were used as supports.
• Boron atom was found to improve growth and hydrophobocity of zeolite MEL membrane.
• PV performance of the obtained membranes was improved.

Boron-substituted silicalite-2 (B-ZSM-11) membranes were prepared on seeded cheap macroporous α-Al2O3 tubes to separate ethanol from water by pervaporation. The incorporation of boron atom into MEL framework was confirmed by XRD and FTIR. The effects of B/Si ratio in the synthesis solution together with PV operation temperature and feed concentration on separation properties of the membranes were investigated. The B-ZSM-11 membrane prepared with B/Si ratio of 0.06 exhibited the highest separation factor of 35.0 with a total flux of 1.51 kg m−2 h−1 for 5 wt% ethanol/water mixtures at 60 °C. The total flux increased with increasing PV temperature from 30 to 75 °C and the separation factor showed the highest value at 60 °C. The separation factor decreased with feed concentration from 1 to 7 wt% and the total flux also showed the highest value for a 5 wt% mixture. It is demonstrated that the incorporation of boron atom into MEL structure improved separation performance of B-ZSM-11 membrane for ethanol/water solutions. On the other hand, the better hydrophobicity of B-ZSM-11 membranes, evidenced by contact angle measurements, is responsible for pervaporation performance for ethanol/water mixtures.

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