A meta-analysis and experimental comparison of the deactivation behavior of Mo/H-ZSM-5 and related catalysts under methane dehydroaromatization conditions
Jordy Ramos-Yataco , Xinrui Zhang , Geunho Han , Tobin J. Marks , Justin M. Notestein
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引用次数: 0
Abstract
CH4 exists in great abundance and is used primarily as an energy source. Methane dehydroaromatization (MDA) is a promising route for its direct transformation into liquid hydrocarbons and H2. Mo/H-ZSM-5 is the benchmark catalyst, but it deactivates rapidly by carbonaceous species formation. Here, we evaluated Mo/H-ZSM-5 formulations as a function of MoOx loading, SiO2/Al2O3 ratio, and Mo loading method for their impact on one-pass catalyst deactivation and after cycles of isothermal oxidative regeneration. The profiles of the rate of methane transformation to hydrocarbons vs. contact time show similar values for all catalysts with Mo/Al< 0.5. Similarly, the catalytic profiles of C6H6 selectivity vs. conversion overlap for all the formulations tested, indicating a non-selective deactivation pathway intrinsic to these Mo/H-ZSM-5 and giving the same active sites regardless of preparation method. Similar trends are observed after multiple rounds of isothermal oxidative regeneration. We then reanalyzed results from three decades of MDA studies. C6H6 selectivity vs. conversion profiles are very similar across most studies with Mo/H-ZSM-5 and related supports. While the rate at which catalysts might traverse the induction, activation, and deactivation phases may be highly dependent on materials properties, only a few pre-treatment or reaction conditions gave fundamentally different behavior. Finally, we broaden the scope to review and experimentally test other transition metals on ZSM-5, highlighting the anomalously-high C6H6 selectivities at low CH4 conversion for Zn and Mn under catalytic conditions similar to those of the benchmark Mo/H-ZSM-5 catalyst. This meta-review combined with experimental validation helps identify leads for further investigation with respect to reaction conditions and/or catalyst formulation.
期刊介绍:
Applied Catalysis A: General publishes original papers on all aspects of catalysis of basic and practical interest to chemical scientists in both industrial and academic fields, with an emphasis onnew understanding of catalysts and catalytic reactions, new catalytic materials, new techniques, and new processes, especially those that have potential practical implications.
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