Investigation on zeolite membrane performance deterioration during separation processes

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We prepared various kinds of zeolite membranes for hydrophobic nature as well as hydrophilic nature. Each membranes were evaluated mainly in pervaporation mode, using a real-time gas analyzer that we purchased by the grant. It revealed the performance decay profile for each membrane. The performance decay was due to hydrophilic transformation of zeolite crystalline composing the hydrophobic zeolite membrane by hydrolysis (for hydrophobic zeolite membrane) or hydrophilic transformation of zeolite crystalline composing the hydrophilic zeolite membrane by ion exchange (for hydrophilic zeolite membrane). For hydrophilic membrane we tested, such as philipsite, merlinoite, and chabazite, the zeolite framework was maintained during the contact by weak acid such as acetic acid, while close contact with strong protonic acid such as sulfonic acid deteriorated the framework. The membrane performance was recovered reversibly as long as the framework was maintained by ion exchange procedure. In this case, the membrane performance had been deteriorated due to protonated zeolite crystalline formation during the pervaporation operation in close contact with acidic solution.