Oxidative benzene methylation with methane over MCM-41 and zeolite catalysts:: Effect of framework aluminum, SiO2/Al2O3 ratio, and zeolite pore structure

The effect of framework aluminum, SiO2/Al2O3 ratio, and zeolite pore structures on the oxidative methylation of benzene with methane in a high-pressure batch reactor have been studied using a range of MCM-41 samples and zeolites as catalysts. The presence of framework aluminum in MCM-41 has been. shown to be important for providing the required Bronsted acid sites for the reaction. Among the catalysts tested, HZSM-5, CoZSM-5, and H-beta were found to exhibit the best performance, while mordenite was found to be virtually inactive for the reaction. HY and NaY exhibited intermediate performance, but HY, due to its higher acidity, was more active than NaY. H-beta, being more acidic, showed slightly higher activity than the ZSM-5 catalysts due to extra contribution to methylated products formation by cracking of benzene without participation of methane. Differences in the catalytic activities and product selectivities of these catalysts have also been discussed in terms of the variations in the number of available Bronsted acid sites, SiO2/Al2O3 ratios, and zeolite pore structures.