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Methane Coupling Reaction in an Oxy‐Steam Stream through an OH Radical Pathway by using Supported Alkali Metal Catalysts
Author(s) -
Liang Yin,
Li Zhikao,
Nourdine Mohamed,
Shahid Salman,
Takanabe Kazuhiro
Publication year - 2014
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201400018
Subject(s) - catalysis , chemistry , oxidative coupling of methane , alkali metal , selectivity , methane , inorganic chemistry , yield (engineering) , metal , reaction mechanism , photochemistry , radical , hydroxyl radical , organic chemistry , materials science , metallurgy
A universal reaction mechanism involved in the oxidative coupling of methane (OCM) is demonstrated under oxy‐steam conditions using alkali‐metal‐based catalysts. Rigorous kinetic measurements indicated a reaction mechanism that is consistent with OH radical formation from a H 2 O–O 2 reaction followed by CH activation in CH 4 with an OH radical. Thus, the presence of water enhances both the CH 4 conversion rate and the C 2 selectivity. This OH radical pathway that is selective for the OCM was observed for the catalyst without Mn, which suggests clearly that Mn is not the essential component in a selective OCM catalyst. The experiments with different catalyst compositions revealed that the OH . ‐mediated pathway proceeded in the presence of catalysts with different alkali metals (Na, K) and different oxo anions (W, Mo). This difference in catalytic activity for OH radical generation accounts for the different OCM selectivities. As a result, a high C 2 yield is achievable by using Na 2 WO 4 /SiO 2 , which catalyzes the OH . ‐mediated pathway selectively.