Boosting pervaporation separation of m-xylene from m/p-xylene isomers mixture through silicalite-1/PVA composite membrane

Silicalite-1 zeolites/polymer composite membranes are among the most reliable materials for the pervaporation separation of m-X from xylene isomers. However, the separation factors of the present silicalite-1 zeolites/ polymer composite membrane are low. This work has succeeded in fabricating dense and defect-free silicalite-1/ PVA composite membrane for first improving the pervaporation separation performance of m-X/p-X isomers. The silicalite-1/PVA composite membrane was prepared by combining solution scraping and vacuum thermal crosslinking methods with fumaric acid as a crosslinker (denoted as silicalite-1/PVA-V). The silicalite-1/PVA-V composite membrane with a thickness of 15.3 mu m, prepared with a fumaric acid/monomeric unit of PVA molar ratio of 0.05 after vacuum thermal crosslinking at 160 degrees C for 2 h, exhibited dense and defect-free structure with extremely low xylene swelling degree, good structural stability and mechanical properties as well as excellent pervaporation separation performance. Compared to the pure PVA membrane, the silicalite-1/PVA-V composite membrane exhibited better selective separation performance of m-X isomer. The temperature, amount of fumaric acid, crosslinking degree and membrane thickness significantly influenced the pervaporation separation performance. The optimum selective separation factor of m-X/p-X isomers and the corresponding total permeate flux were about 9.85 and 59.15 g center dot m-2 center dot h-1 (60 degrees C), respectively. The pervaporation experiments of long-time and repetitively prepared membrane demonstrated that the silicalite-1/PVA-V composite membrane had long-term structural stability and reproducibility. To demonstrate scalability, we showed that our strategy could produce large-size silicalite-1/PVA-V composite membrane with an area of 1000 cm2, which exhibited m-X separation performance similar to that of small membrane coupons. The present work provided a potentially scalable method for producing high-quality silicalite-1/PVA composite membrane for enhancing the pervaporation separation performance of m-X from xylene isomers.