Unification of the precarburizing agent and reactant in non-oxidative C1-C3 alkane aromatization over Mo/ZSM-5 for enhanced catalytic performance and process efficiency

Abstract

The direct non-oxidative aromatization of shale gas (consisted of C1-C3 alkanes) is a promising technique for valorizing abundant gas resources without traditional gas fractionation processes that require a large amount of energy input. However, its practical application is hindered by various limitations, including the need for a separate precarburization process, which is required to effectively activate Mo/ZSM-5 catalysts. The use of conventional and well-known precarburizing agents (CH4 or H2) requires an additional gas stream that is unnecessary for the main aromatization reaction, hindering the realization of an efficient process. Therefore, in this study, investigations were conducted to examine the viability of shale gas as a precarburizing feed, which is required to unify the precarburizing gas and main reactant. The use of shale gas reduced the precarburization time, which is determined as the time required for the initial formation of benzene, compared to the use of CH4. Further, precarburization with shale gas enhanced the catalytic performance of Mo/ZSM-5 in the main reaction, and the precarburization temperature had a significant effect. A comprehensive characterization of the precarburized samples revealed that multiple factors were responsible for these findings. Samples precarburized with shale gas at lower temperatures experienced a lower degree of structural disruption and contained adequate Mo carbide (MoCx) species for the reaction, which contributed to their superior activity.