Zeolite membranes: Synthesis and applications

Membrane-based technology has attracted considerable attention owing to its low energy consumption, mild operating conditions, and high efficiency. Polymeric membranes are widely utilized in different separation processes for their low cost and highly reproducible preparation. Fouling and the trade-off between permeability and selectivity represent the main drawbacks in the polymeric membrane field. These problems could be overcome by using inorganic membranes that are less prone to fouling due to their hydrophilic nature, high chemical stability, and high permeability and selectivity. Zeolite membranes, a type of inorganic membranes, can separate liquid and gas species (with very similar size and shape) thanks to their defined pore size at a molecular level and high adsorption property. They are studied in different separation processes as gas separation, pervaporation, and desalination. However, they find application, at the industrial level, only for alcohol dehydration by pervaporation process. Indeed, although 30 years are passed since the first scientific papers about the zeolite membrane preparation, many problems are still unsolved, as reproducibility of the synthesis, defects into the zeolite layer, and high manufacturing costs, which caused a limitation to their application on a large scale. In this review, the main zeolite membrane preparation methods and the novelty in their developing and fabricating have been analyzed. Their application in pervaporation and desalination has been discussed. The effect of zeolite membrane topology and chemical composition on natural gas purification has been presented in detail. The application of zeolite membrane reactors in different interesting processes has been discussed. Concluding remarks and future perspective have been also suggested.