Performance of Bifunctional ZnZr/ZSM-5 Catalysts in the Alkylation of Benzene with Syngas

A novel alkylation process of benzene with syngas was successfully developed to produce toluene and xylene over a bifunctional catalyst containing zinc oxide (ZnO), zirconium oxide (ZrO2) and ZSM-5 zeolite. Different characterizations, such as: SEM, TEM, XRD, XPS, FT-IR, NH3-TPD and N-2 adsorption-desorption were used to measure the structure of Zn/Zr samples. ZnO was identified as the active component for the synthesis of methanol while ZrO2 was the promoting component which helped the good dispersion of ZnO in the system. The sample with 0.75 Zn/Zr molar ratio calcined at 500 degrees C exhibited the best catalytic performance, resulting in benzene conversion of 34.7%, toluene and xylene selectivity of 68.8% and 18.0% at 450 degrees C under 3.2MPa. Based on the experimental results, the reaction mechanism was proposed as following: methanol was firstly formed on the surface of ZnO/ZrO2 from syngas, then it migrated onto ZSM-5 zeolite and reacted with benzene to form toluene. Furthermore, xylene was obtained through consecutive reaction. [GRAPHICS] .