Investigation on zeolite membrane performance deterioration during separation processes

我们制备了亲水性和疏水性的各种沸石膜。每个膜主要在渗透蒸发模式下进行评估，使用我们通过拨款购买的实时气体分析仪。它揭示了每种膜的性能衰减曲线。性能衰减是由于沸石晶体通过水解形成疏水沸石膜（对于疏水沸石膜）或沸石晶体通过离子交换形成亲水沸石膜（对于亲水沸石膜）。对于我们所测试的亲水膜，如菲利石、美利钠石和恰辉石，沸石骨架在弱酸（如乙酸）接触时保持不变，而与强质子酸（如磺酸）密切接触会使骨架恶化。只要通过离子交换过程维持膜的结构，膜的性能就可以可逆地恢复。在这种情况下，由于沸石在与酸性溶液密切接触的渗透蒸发过程中形成质子化晶体，导致膜性能下降。

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.