Synthesis of Hierarchically Porous Zeolite Ti-MWW with Different Hard Templates and Their Application in Allyl Alcohol Conversion

Abstract

Diffusion limitation caused by microporous molecular sieves has always been a bottleneck problem in liquid phase epoxidation. In this study, several different carbon sources were used as hard templates to prepare hierarchically porous zeolite Ti-MWW (cTi-MWW) successfully. Compared with conventional Ti-MWW, cTi-MWW has an additional hierarchically porous structure and abundant pore structure distribution. Especially, the cTi-MWW prepared with polyethylene glycol1540 (PEG) as the hard template not only has a multiple hierarchically porous structure, but also exhibits small crystal size and good hydrophobicity properties studied by TEM and in situ FT-IR. At the same time, the cTi-MWW prepared with PEG exhibits better activity than the conventional Ti-MWW in the selective epoxidation reaction of allyl alcohol (AAL) with H2O2 as oxidant and the conversion is improved by 11% (Si/Ti = 20). And a higher efficiency and longer catalyst life in fixed-bed catalytic reactor were exhibited by using cTi-MWWPEG as catalyst. The physicochemical properties of cTi-MWW prepared with different hard templates were systematically studied by SEM, XPS, UV–Vis, XRD and N2 absorption–desorption techniques. This method is effective for the synthesis of cTi-MWW and significant for the preparation of hierarchically porous zeolites in industrial production. A hierarchically porous zeolite Ti-MWW prepared with different hard templates successfully. With the hierarchically porous structure, which have better adsorption, diffusion, and reactivity in liquid phase epoxidation, thus improving the catalytic activity. Especially, the hierarchically porous zeolite Ti-MWW prepared with polyethylene glycol exhibits small crystal size and good hydrophobicity properties.