科研之友
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摘要
A series of catalysts were prepared by impregnation of MCM-41 mesoporous silica with TiO2. Alkylation of phenol with diethyl carbonate was carried out over the TiO2-modified MCM-41 catalysts for the first time, and the reaction had high ortho-selectivity and a high phenol conversion. The physicochemical properties of the catalysts were characterized by X-ray diffraction, X-ray fluorescence, N-2 adsorption-desorption, Fourier-transform infrared spectroscopy with pyridine adsorption, and CO2 and NH3 temperature programmed desorption. Long-range regularity of the hexagonal arrays of MCM-41 was sustained after TiO2 modification. As the TiO2 mass fraction in the catalyst increased, the number of acidic and basic sites also increased, which suggests that TiO2 modification affects the acid-base properties of MCM-41. The high ortho-selectivity and the high phenol conversion for alkylation of phenol with diethyl carbonate over TiO2-modified MCM-41 could be ascribed to catalytic interaction between adjacent acidic and basic sites on the catalysts. The effects of temperature, feed ratio, reactant contact time and time-on-stream on the conversion of phenol and the selectivity for various products over TiO2-modified MCM-41 catalysts were also investigated.
