Bio-Ethanol/water separation by fractional distillation becomes a popular industrial process to remove water from ethanol-water mixture. However, the mixture of 95.6wt% ethanol and 4.4 wt% water is an azeotrope and cannot be further purified by distillation. Alternatively, this can be achieved by membrane separation technology since it is not works on vapor-liquid equilibrium but on pervaporation mode.
In this work, real ethanol feeds (rectifier bottom, 40 wt%, PH=3.99 and rectifier overhead, 95wt%, PH=4.54) from Pacific Ethanol Inc. were chosen to test the performance and stability of A type zeolite membrane (2~3um), which supported on novel thin porous Ni sheet substrate (~50um). The preliminary results shows that NaA zeolite membrane was unstable at operation condition (~100C), mainly due to the strong acidity of real ethanol-water biomass feedstock (PH≈4).
However, after neutralized with 0.1M NaOH solution to PH=8.5 or by pass a guard bed filled with weak base ion exchange resin (Amberlite@IRA-93), this novel membrane shows high performance (Water flux >2 kg/m2 h, water/ethanol selectivity > 5000) and stability (>100hrs). ICP analysis result also shows that sodium and sulfur ions will remains in the feed side during the separation process, mainly due to their large hydrated diameter (~7.2 Å for Na+ and ~8.6 Å for SO42-) comparing with the pore size of NaA zeolite membrane. (~4Å)
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