Selective Synthesis of p-Cresol by Alkylation of Phenol with Methanol over SiO2-Modified HMCM-22 Catalyst

A series of xSiO(2)/HMCM-22 were prepared by chemical liquid deposition of HMCM-22 with tetraethyl orthosilicate and evaluated in the catalytic synthesis of p-cresol by alkylation of phenol with methanol. Several characterization techniques including N-2 adsorption-desorption, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Pyridine-IR, temperature-programmed desorption of NH3 (NH3-TPD) as well as the probe reaction of m-xylene isomerization and 1,3,5-triisopropyl benzene (1,3,5-TIPB) cracking have been used to analyze the physicochemical properties of xSiO(2)/HMCM-22 catalyst. The conversion of phenol decreased with increasing SiO2 loading of xSiO(2)/HCM-22 catalyst; while the selectivity for p-cresol maximized at x=1 %. The 1 %SiO2/HMCM-22 catalyst was identified as the most efficient catalyst, showing the highest p-cresol selectivity for longer than 15 h under optimized reaction conditions. The high p-cresol selectivity of the catalyst is attributed to the fact that SiO2 covered the acid sites of the external surface of the HMCM-22 and preserved the acid sites in the micropores of zeolite.