Abstract:

Shape-selective catalysts for alkylation of biphenyl with cyclohexanol were prepared by modification of MCM-22 zeolite using chemical liquid deposition (CLD) process with tetraethyl orthosilicate (TEOS). The modified MCM-22 catalysts were characterized by X-ray diffraction (XRD), N₂ physical adsorption-desorption, NH₃ temperature-programmed desorption (NH₃-TPD), and adsorbed pyridine infrared spectroscopy (Py-IR). The results showed that SiO₂ was mainly deposited on the external zeolite surfaces, with no significant structural changes observed in the MCM-22 zeolite after modification. The deposited SiO₂ could reduce the number of external Br?nsted acid sites of the zeolites, without noticeably reducing the total amount of acid sites. Shape-selective alkylation of biphenyl with cyclohexanol was carried out over the synthesized catalysts. The selectivity of 4-cyclohexylbiphenyl (4-CBP) and 4, 4'-cyclohexylbiphenyl (4, 4'-DCBP) reached a maximum of 80.4% and 63.7%, respectively, when the reaction was carried out for 200 min at 190℃ under atmospheric pressure. The characterization data indicated that the isomerization reactions at the external Br?nsted acid sites were diminished effectively. In addition, the catalytic activity of the used zeolites was almost recovered by calcination.

Key words: Biphenyl, Shape-selective alkylation, MCM-22, Cyclohexyl biphenyl, Chemical liquid deposition