A Review of High-Efficient Synthetic Methods for Zeolite Membranes and Challenges of Their Directional Growth Control

ABSTRACT Zeolite membranes are widely used in separation, catalysis, sensors and other fields because of their good diffusion performance, shape selection and catalysis capabilities. However, the slow synthesis rate of zeolite membranes restricts their industrialization process, and the random orientation seriously affects their performance. Therefore, this paper investigates the methods for accelerating the synthesis rate of zeolites and the roles of different methods was explored. The synthesis conditions of oriented zeolite membranes are also summarized. Microwave method can efficiently synthesize oriented zeolite membranes, but it has the defects of harsh synthesis conditions and high equipment requirements. Using physical methods and chemical methods to introduce hydroxyl radicals, which is also an effective method to improve the synthesis rate of zeolites. However, there is a lack of research on how to realize the directional synthesis of zeolite membranes during this process. Synthesis conditions, template and support properties affect the directional synthesis of zeolite membranes. Therefore, while introducing free radicals, adjusting the composition of the synthetic solution or introducing inhibitors that affect the growth direction of zeolite in the synthetic system can realize the efficient directional synthesis of zeolite membrane, which is another potential method to promote the industrialization of directional zeolite membrane besides microwave method. Graphical Abstract