The effect of Zn on side-chain alkylation of toluene with methanol over KX zeolite was investigated. It was found that the addition of Zn with a low content over KX could enhance toluene conversion significantly. In addition, the results showed that the conversion of toluene over ZnKX (0.8 wt. %) catalyst was almost twice as high as that over KX. The catalysts were characterized by X-ray diffraction (XRD), N2 physisorption, NH3-temperature-programmed desorption (TPD), pyridine absorption infrared (IR) spectroscopy, CO2-TPD, X-ray photoelectron spectroscopy (XPS) and IR adsorption of reactants. The TPD and XPS results showed that the existence of Zn species could increase the strength of basic sites. The IR adsorption of reactants results suggested that the introduction of Zn could decrease the chemisorbed toluene and increase the relative amounts of unidentate formate. The results indicated that an excellent balance between the acid-base properties of the catalyst and the sorption stoichiometry of methanol-toluene could be achieved, leading to the improvement of catalytic activity.
side-chain alkylation; X zeolites; toluene; methanol
