Catalytic oxidative dehydrogenation (ODH) of low molecular weight alkanes is an attractive and alternative to the direct thermal dehydrogenation route towards the production of the corresponding olefins. In light of the recent shale gas revolution, abundant ethane resources serve as a strong incentive for academic and industrial communities to advance and evolve research strategies for the production of ethylene. Modern catalytic processes for ODH of ethane demand a paradigm shift where efforts are placed to guarantee high selectivity to olefins by improving redox properties, hampering consecutive olefin overoxidation, limiting coke formation, or enhancing in-situ coke removal pathways. Utilizing carbon dioxide as an oxidant has been recognized in recent years as a promising alternative approach that offers an attractive solution to severe total oxidation of ethylene resulting in higher selectivity to desired products. In addition, the in-situ release of the heat of the reaction due to the oxidation of the abstracted hydrogen, the enhanced olefin production through the shift of the equilibrium of alkane conversion due to the consecutive reverse water gas shift, the improved stability of catalytic materials due to CO2 participation in coke removal mechanisms and the generation of H2/CO mixtures through dry reforming comprise additional benefits when CO2 is realized as soft oxidant. Unravelling this complex reaction network toward maximizing olefin selectivity can be achieved by coupling kinetic and spectroscopic measurements, simultaneously, in one single catalytic reactor to establish structure-reactivity relationships. In this work, we will discuss our research efforts to understand competitive pathways occurring during the CO2-assisted oxidative dehydrogenation of ethane over MoOx catalysts supported on reducible CeO2-TiO2 supports. Efforts will be placed on discussing spectrokinetic measurements to investigate reduction and possible reoxidation pathways over the dispersed MoOx sites.

Competitive pathways in alkane oxidative dehydrogenation over metal oxides: A spectrokinetic approach

ACS Fall 2021

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