Acid–base properties of TiO2-modified MCM-41 mesoporous silica and its catalytic performance for ortho-selective ethylation of phenol with diethyl carbonate

Abstract A series of catalysts were prepared by impregnation of MCM-41 mesoporous silica with TiO 2 . Alkylation of phenol with diethyl carbonate was carried out over the TiO 2 -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 CO 2 and NH 3 temperature programmed desorption. Long-range regularity of the hexagonal arrays of MCM-41 was sustained after TiO 2 modification. As the TiO 2 mass fraction in the catalyst increased, the number of acidic and basic sites also increased, which suggests that TiO 2 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 TiO 2 -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 TiO 2 -modified MCM-41 catalysts were also investigated.