Nano-thin layer MCM-22 zeolite:Synthesis and catalytic properties of trimethylbenzene isomerization reaction
A nano-thin layer MWW-type zeolite,derived from fumed silica,was dynamically in-situ synthesized at 150 ℃ using a dual-template system of cetyltrimethylammonium bromide(CTAB)and hexamethylene imine(HMI).The effect of CTAB amount on the zeolite was also investigated.The nano-thin layer samples were characterized using powder X-ray diffraction(PXRD),scanning electron microscopy(SEM),N2 adsorption-desorption,ammonia temperature programmed desorption(NH3-TPD),high-resolution transmission electron microscopy(HRTEM),pyri-dine infrared spectroscopy(Py-IR),and 2,6-di-tert-butylpyridine infrared spectroscopy(DTBPy-IR).The results indicated that MWW nanosheets with a thickness of 5-10 nm can be prepared using the double template system.Furthermore,the catalytic performance of the samples was evaluated through the isomerization of the trimethylben-zenes reaction.The catalytic results show that the sample d-MWW-4％CTAB exhibits good catalytic performance,with the conversion of 1,2,4-trimethylbenzene,the yield of 1,3,5-trimethylbenzene,and the selectivity of 1,3,5-trimethylbenzene being 34.97％,22.42％,and 64.09％,respectively.This is primarily attributed to the external sur-face area and interlayer mesoporous structure formed in the nano-thin layer MCM-22.
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