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Impact of OH Radical Generator Involvement in the Gas‐Phase Radical Reaction Network on the Oxidative Coupling of Methane—A Simulation Study
Author(s) -
Li Duanxing,
Baslyman Walaa S.,
Sarathy S. Mani,
Takanabe Kazuhiro
Publication year - 2020
Publication title -
energy technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.91
H-Index - 44
eISSN - 2194-4296
pISSN - 2194-4288
DOI - 10.1002/ente.201900563
Subject(s) - chemistry , selectivity , dehydrogenation , yield (engineering) , methane , oxidative coupling of methane , radical , reaction rate constant , hydrogen atom abstraction , hydroxyl radical , photochemistry , medicinal chemistry , kinetics , organic chemistry , catalysis , thermodynamics , physics , quantum mechanics
The impact of OH • generation during the oxidative coupling of methane (OCM) is simulated using state‐of‐the‐art gas‐phase chemistry and a comprehensive chemical kinetic model. The inclusion of the quasi‐equilibrated formation of OH • from a H 2 O–O 2 mixture into the combustion chemistry network enhances the CH 4 conversion rate and C 2 selectivity, consistent with the previously proposed mechanism involving catalytically generated OH • . The OH‐pathway increases theCH 3 •concentration resulting in an enhanced transformation rate fromCH 3 •to C 2 H 6 (second order inCH 3 • ) more than CO (first order inCH 3 • ). Relative to other H‐abstracting radical species, the OH • weakens the sensitivity of the H abstraction rate constant to C—H bond energy, or lowersk C 2 H 6/ k CH 4, which comparatively slows the C 2 H 6 conversion rate relative to CH 4 , thus enhancing C 2 selectivity. Concurrent dehydrogenation of C 2 H 6 to C 2 H 4 maximizes the C 2 H 4 selectivity even after O 2 depletion. With the involvement of the OH • ‐mediated pathway, this study addresses the effects of temperature and CH 4 /O 2 ratio on the achievable C 2 selectivity and C 2 H 4 yield. The maximum C 2 H 4 yield reaches 32% at a CH 4 /O 2 ratio of 3, temperature of 1100–1200 °C, and total pressure of 1 atm.