Preparation of Cu-γ-Al2O3 Catalyst and Its Performance in Diphenylmethane Synthesis

N. Liangming, H. Jingbin, L. Dongmei and H. Zhongdong

Abstract
γ-Al2O3 has been widely studied as a very promising catalyst for the benzene alkylation reaction. In this study, the γ-Al2O3 support was prepared by the hydrothermal synthesis method, and the Cu-γ-Al2O3 catalyst was prepared by loading Cu through the impregnation treatment method with copper nitrate. Moreover, the Cu-γ-Al2O3 and γ-Al2O3 catalysts were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), specific surface area measurement (BET), ammonia adsorption-desorption (NH3-TPD), and pyridine infrared spectroscopy (Py-FTIR). The characterization results indicate that, compared with the γ-Al2O3 catalyst, the specific surface area, the pore volume and pore diameter of Cu-γ-Al2O3 become smaller, the total acid amount decreases, the amount of Lewis acid (L acid) increases, and the synergistic effect between Brønsted acid (B acid) and Lewis acid is enhanced. Meanwhile, the cases where the mass ratio of Cu-γ-Al2O3 was 3 %, 5 %, 10 %, and 15 % were investigated. Among these catalysts, the Cu-γ-Al2O3 with a mass ratio of 5% exhibited the highest performance in the benzene alkylation reaction. It is worth noting that compared with the previously reported Cu-Al-MCM-41, this catalyst showed a higher selectivity for diphenyl methane (94.8 % vs. 90.1 %).

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Keywords
benzyl alcohol, hydrothermal synthesis, Cu-γ-Al2O3, diphenylmethane, selectivity