Synthesis Of TS-1 Zeolite Membrane With Template Removal Via Microwave-assisted Fenton Oxidation Method

Titanium silicalite-1 membranes have been regarded as an outstanding inorganic membrane material not only for their unique MFI topology structure, but also their excellent catalytic performance in the selective oxidation of organic compounds using H2O2 as the oxidant, which promises their encouraging prospects in the area of separation and membrane reactors. Although some advances have been achieved in the research work on preparation of TS-1 membrane on bench scale, the large-scale industrial application of TS-1 membranes are still limited by the low repeatability of the current preparation technology and existence of defects in the membranes. Hence, it is eagerly desirable to improve the preparation technology and reduce the formation of defects in the synthesis process.In this work, titanium silicalite-1 membranes were successfully prepared by secondary growth on the porous ?-Al2O3 substrates using tetrapropylammonium hydroxide(TPAOH) as structure-directing agents. The SEM, XRD, FT-IR, UV-vis and contact angle measurements were used to characterize the structure, surface morphology and performance of the synthesized membranes. The results showed that the membranes were dense and well inter-grown after hydrothermal reaction at 453 K in the presence of synthesis solution, and no obvious defects such as cracks, pinholes or intercrystalline boundary gaps were observed in the membranes. Compared with the in-situ hydrothermal synthesis method, the preparation method has good repeatability.The organic molecules were trapped within the zeolite membrane and must be removed from the zeolite pores after synthesis. Here we presented a new approach for mild template removal from the TS-1 zeolite membrane, based on the liquid Fenton oxidation. Before that, we studied the oxidation properties of Fenton reagent for oxidation of TPAOH in the aqoeous solution. The results indicated that it was effective for the Fenton reagent to decompose the organic template TPAOH in the solution, and the removal efficiency was up to 91.6%. The combination of the advanced Fenton oxidation and microwave radiation technology was employed to remove the organic template from the as-prepared TS-1 membrane. The results demonstrated that the organic molecules distributed in the ultra-thin zeolite membranes could be effectively removed by the microwave assisted Fenton oxidation method in low temperature, and while the amount of the oxidant was excessive, factors such as the reaction temperature, heating mode and thickness of the membranes had a great influence on the template removal efficiency. The SEM characterization and the pore size distribution showed that no large cracks or gaps formed in the membrane after low temperature template removal by the microwave assisted Fenton method. In order to characterize the quality and performance of the activated membranes, they were successfully applied in the separation of CH4/i-C4H10 binary 1:1 mixtures and pervaporation separation of ethanol/water mixtures, the results indicated that the detemplated TS-1 membranes had good density and separation performance.