SHAPE SELECTIVITY IN METHANE DEHYDROAROMATIZATION OVER Mo/MCM-22 CATALYSTS DURING A LIFETIME EXPERIMENT

摘要

Currently, a great challenge and intriguing problem in heterogeneous catalysis is the catalytic conversion of methane to higher hydrocarbons and aromatic compounds as alternative feedstock for the petrochemical induslry. Since the methane dehydroaromatization (MDA) to benzene on Mo/ZSM-5 reported in 1993, many catalysts have been studied in conjunction with their reactivity, reaction mechanism and catalyst characterization. Another interesting catalyst, Mo/MCM-22 reported by Bao et al. features a higher benzene ratio and a lower naphthalene yield in comparison with Mo/ZSM-5. Many researchers have investigated coke deposition on catalysts, but the samples to be characterized are the catalysts that were reacted for only several hours. The main data is also only about the weight of the coke deposition, and the operation and observation of long lifetime tests of the steady state are still in infancy. In this paper, we use BET, Benzene-TPD, TG, and TPO techniques to investigate deposited coke and the changes in the Mo/MCM-22 catalyst as a function of time on stream for 100 hours, and bring forward that there is a critical value for coke capacity based on the shape selectivity of benzene.