(4cc) Understanding the Interaction and Promotional Role of Ag Promoters with Mo/HZSM-5 Catalyst Via Sequential Addition in Methane Dehydroaromatization

Research Interests: catalysis, and reaction engineering, methane dehydroaromatization, catalyst deactivation, coke production

Direct non-oxidative transformation of methane to aromatics over Mo/HZSM-5 catalyst is a reaction that has the great potential to upset a huge part of the synthesis gas-derived chemical industry. However, hampering catalyst activity due to rigorous coking is the main challenge at higher-temperature MDA conditions. This investigation aims to enhance catalytic activity and stability by examining the promoting effect of adding Ag (0.4-0.6 wt.%) via sequential impregnation/co-impregnation method along with 5wt.% loaded Mo/HZSM-5 catalysts. MDA catalytic activity was determined and correlated with an array of physicochemical characterization tools. MDA activity displayed that the Ag-incorporated Mo/HZSM-5 exhibited greater reactivity and constancy related to the reference Mo/HZSM-5 catalyst, with the highest activity unveiled by the co-impregnated Ag-Mo/HZSM-5 with the benzene formation selectivity (70 %) at 120 min on stream. Coke content analysis via TGA confirmed that the addition of Ag with Mo/HZSM-5 greatly controls the coke deposition with a reduced degree of coke formation during the reaction. A synergy between Ag species and Mo is observed, and the characterization results suggested that the enhancement in the catalytic activity of co-impregnated Ag-modified Mo/HZSM-5 catalysts might be due to several factors: acidic sites characterization results suggest that Ag impacts the acidic properties of the catalyst while simultaneously influencing the chemical and electronic state of molybdenum over the zeolite support that enhances the retention of Mo species within the pores with less decreased degree of aggregation. This in turn imparts in enhancing MDA catalytic activity and stability.