Aluminum Fluoride Modified HZSM-5 Zeolite with Superior Performance in Synthesis of Dimethyl Ether from Methanol

摘要

A series of HZSM-5 catalysts modified with various loadings of aluminum fluoride (A1F_3) were prepared from a mechanical mixture route. Combined characterizations of X-ray diffraction, Fourier transform infrared (FT-IR), ~(27)Al, ~(19)Si, ~(19)"F MAS NMR, N_2 sorption, and NH_3-tempeature-programmed desorption (NH3-TPD) techniques show that the structure, texture, and acidity of HZSM-5 catalysts can be adjusted with the loading of A1F_3. A suitable amount of AlF_3 modification (2 wt %) could increase the framework aluminum content and the surface area of HZSM-5. However, when the loading of AlF_3 came to 3 wt % or more, the contrary results were obtained, which could be ascribed to the dealuminau'on of the zeolitic framework. The catalytic activities for dehydration of methanol to dimethyl ether (DME) show that suitable amount of AlF_3-modified HZSM-5 exhibited much higher activity and better stability than parent HZSM-5. The combination of "tunable" synthesis and "superior" properties is very much valuable in the academic and industry.