Co-aromatization of light alkanes over Mo/ZSM-5: How the presences of CH4 and C2H6 & C3H8 influence the aromatization of each other

Abstract

The chemical inertness of methane is a significant bottleneck for its direct conversion into value-added light aromatics. However, co-feeding higher hydrocarbons with methane produces intermediates that facilitate the participation of methane in aromatization. This synergistic effect has typically been observed under conditions that do not allow the conversion of methane without any co-reactants (over non-Mo-based catalysts at temperatures below 650 ℃). Therefore, the interaction between methane and higher hydrocarbons remains unexplored under conditions that allow methane activation. In this study, we explored the behavior of co-reactants in the direct aromatization of simulated shale gas (a mixture of methane, ethane, and propane) over Mo/ZSM-5. Our aim was to comprehend the complex co-aromatization system under conditions optimized for rigorous activation of methane, which leads to a considerable production of aromatics. The majority of reaction indices in the shale gas aromatization system were governed by the presence of ethane and propane, which were represented by a rapid catalytic lifetime cycle. Mathematical calculations, based on experimentally derived C and H balances, revealed an unexpected anti-synergy within the components of shale gas where the conversion of methane to aromatics was partially suppressed by the presence of ethane and propane. These findings expand the understanding of the complex yet desirable shale gas aromatization system, and also highlight the need for the development of new catalysts capable of further enhancing the activity of methane among the reactants.