Exploring Oxygen Delivery Strategies for Oxidative Coupling of Methane
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Date
2017-05
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Publisher
The Ohio State University
Abstract
A myriad of metal oxide catalysts have been explored for upgrading methane into
higher hydrocarbons in a process called oxidative coupling of methane (OCM). Because
of the ramifications of utilizing methane as a chemical feedstock, efforts to optimize the
reactor design and catalyst for OCM process have been ongoing since 1980. Catalytic
oxygen carriers (COCs) used for cycling oxygen to the reactant gas in OCM reaction
processes have shown distinct advantages over cofeeding reaction schemes. Manganese
based COCs have exhibited multiple oxidation states that function in the cyclic reduction
oxidation reactions of OCM. This study aims to elucidate the different forms of oxygen
delivery strategies that can be leveraged from a deeper understanding of how these COC
oxidation states effect product distributions. The COC particles used to facilitate this
oxygen transfer in this study were Mg6MnO8 and Li0.2Mg5.8MnO8. Thermogravimetric
analysis and fixed bed experiments were performed to characterize the effects of the
Mn4+ and Mn3+ oxidation states on methane conversion and C2+ selectivity. The Mn4+
oxidation state was shown to experience higher reduction rates, higher conversion, and
lower selectivity than the Mn3+ oxidation state. Li doping of the manganese oxide was
shown to reduce reduction rates, lowering conversion and raising selectivity. This study
showed that reduction rate and ultimately product distribution can be tuned by adjusting
the oxidation state of manganese based COCs.
Description
Keywords
OCM, Redox, Natural gas