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Published on: March 20, 2017
Lithium Promotes Acetylide Formation on MgO During Methane Coupling Under Non-Oxidative Conditions
Seraphine B X Y Zhang1, Quentin Pessemesse2, Zachariah J Berkson1
1Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 1-5, 8093, Zürich, Switzerland.
Abstract:
A prototypical material for the oxidative coupling of methane (OCM) is Li/MgO, for which Li is known to be essential as a dopant to obtain high C2 selectivities. Herein, Li/MgO is demonstrated to be an effective catalyst for non-oxidative coupling of methane (NOCM). Moreover, the presence of Li is shown to favor the formation of magnesium acetylide (MgC2 ), while pure MgO promotes coke formation as evidenced by solid-state 13 C NMR, thus indicating that Li promotes C-C bond formation. Metadynamic simulations of the carbon mobility in MgC2 and Li2 C2 at the density functional theory (DFT) level show that carbon easily diffuses as a C2 unit at 1000 °C. These insights suggest that the enhanced C2 selectivity for Li-doped MgO is related to the formation of Li and Mg acetylides.
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