Hydro-Solvothermal Synthesis of NaX Zeolite Membranes for the Separation of MeOH/Methyl tert-Butyl Ether Mixtures

Zeolite membranes are emerging as attractive candidates for the separation of methanol/methyl tert-butyl ether (MTBE) mixtures, while the random deposition of silicon aluminum components on the surface of the support can lead to the poor quality of zeolite membranes, restricting the use of zeolite membranes in separation and purification applications. In this study, the deposition process of the silicon aluminum components was controlled, and compact NaX zeolite membranes with great pervaporation performance for methanol/MTBE mixtures were synthesized using water–organic solvent synthesis solutions. Systematic research showed the existence of a stable "liquid film" on the surface of the support controlling the formation environment of zeolite membranes during their synthesis; organic solvents that partly replaced water in the synthesis solution improved the quality of the zeolite membranes. The water–organic solvent system could not only decrease the nucleation and crystallization rate of zeolite particles in the main body of the synthesis solution and reduce the consumption of silicon aluminum components in the main body of the synthesis solution but also promote the migration of silicon aluminum components to the "liquid film" on the surface of the support from the main body of the synthesis solution, thus promoting the growth of zeolite membranes. The zeolite membrane synthesized in the 20(v) % 1,3-propanediol synthesis solution exhibited a MeOH/MTBE separation factor greater than 10,000 with a permeation flux of 1.6 kg·m–2·h–1, indicating that a compact zeolite membrane was grown on the support. In this work, the formation of zeolite membranes was controlled by adding an organic solvent to the synthesis solution to adjust the deposition process of silicon aluminum components to the support and a new method for the preparation of compact membranes was developed.