Continuous dehydration of IPA–water mixture by vapor permeation using Y type zeolite membrane in a recycling system

• NaY zeolite membrane was useful to continuous vapor permeation for IPA dehydration.
• A new two-step enriching method proposed enabled to concentrate IPA rapidly.
• Increase in the feed rate by two steps shortened the IPA concentration time.

Industrially alcohol dehydration is carried out by a distillation process, thereby requiring a large amount of energy. In an IPA/water system, since producing an azeotrope, two more distillation towers should be added. Therefore, a large amount of energy saving will be expected when the IPA concentration by applying vapor permeation (VP) with membrane becomes possible. Recently, zeolite membrane separation has been attracting much interest in terms of lower energy consumption and higher separation performance.In this study, a composite type of NaY (Faujasite) zeolite membrane with high dehydration performance was synthesized, and VP tests were carried out for IPA/water mixtures. Furthermore, a continuous recycled VP (CVP) apparatus was set up and operated to analyze the enriching process of IPA. As a result, a two-step method, where two membranes with different performances are exchanged along the concentrating way, or operation temperature or feed rate was increased stepwise, was proposed. It was shown that such a new operation method could shorten the time of concentrating IPA.