Fabrication of b-oriented MFI zeolite membranes via microwave-assisted secondary growth for xylene isomers separation

The morphology and microstructure of zeolite membranes are crucial for improving their separation performance. This can be achieved by creating a thin and uniform seed layer, which can then be intergrown into a continuous and dense membrane. Herein, we show a simple vacuum-filtration method to provide closely packed MFI zeolite crystal seed layers on porous substrates (α-Al 2 O 3 ). Then, a continuous, dense, and twin free MFI zeolite membrane was rapidly prepared based on the pre-set crystal seed layer using the microwave-assisted secondary growth method. XRD confirmed the high crystallinity of the prepared MFI zeolite membranes, with a crystal preferred orientation (CPO) index of 0.91, demonstrating excellent b -axis orientation. In the pervaporation separation experiments of xylene isomers (PX/OX), the as-prepared membrane exhibited superior separation performance at 90 °C and 90 kPa. The permeation flux and separation factor were 1931.8 g m −2  h −1 and 4.74, respectively, which were significantly better than MFI zeolite membranes prepared by traditional hydrothermal methods. Quantum chemical calculations further revealed the screening mechanism, where PX was more likely to diffuse through the MFI channels due to its smaller molecular size and weaker adsorption energy. This work provides new insights for the development of energy-efficient and high-performance xylene isomer separation membrane materials.