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

摘要

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 N-2 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.