Influence of Preparation Method on HZSM-5 Supported Cerium Catalyst for Alkylation of Phenol with Methanol.

The alkylation of phenol with methanol was studied in vapor phase over 5 wt% cerium supported on HZSM-5 catalyst prepared by three different methods, such as impregnation, ball mixing and solid-state ion-exchange. The catalytic activities are tested in a fixed-bed reactor, and the physicochemical properties of the catalyst are characterized with X-ray powder diffraction, scanning electron microscope, nitrogen physical sorption, Fourier Transform Infrared Spectrometer, Infrared spectra of pyridine adsorption, X-ray photoelectron spectroscopy and temperature-programmed desorption of ammonia. It was found that the dispersion form of cerium was greatly affected by the preparation method, and difference in acidity affects catalytic performance in the alkylation reaction of phenol and methanol. Ball milling method generated greater amount of strong Brønsted acidic sites and lower specific surface area than other catalysts, which led to higher carbon deposition rate and lower catalyst activity. The catalyst prepared by impregnation method yields higher Lewis acid concentration (2.09 μmol/g) and more chemisorbed oxygen due to the increased Ce3+ concentration in the lattice, resulted in an improved o-cresol selectivity of 48%. Furthermore, the catalyst prepared by solid-phase ion-exchange method produces a catalyst with appropriate B/L ratio of 60.6 and large specific surface area of 389.0 m2/g, which yields the highest phenol conversion of 23%. [ABSTRACT FROM AUTHOR]