Modelling partial oxidation of methane over ZSM-5 and Mo6S8 catalysts

Other conference contribution, 2017

Partial oxidation of methane is an interesting but difficult reaction. Experimentally, methane can be partially oxidized to methanol over metal-exchanged zeolites. In particular the ZSM-5 zeolite has been widely studied and has been shown to be active when exchanged with Cu, Ni, Co, and Fe [1-4]. A clear [Cu-O-Cu] 2+ candidate for active site for the methane-to-methanol reaction has been put forth for Cu-ZSM-5 [1,5]. A first question to ask is whether this [Cu-O-Cu] 2+ motif is generic and could work also with Cu interchanged with Ni, Co, or Fe. Herein, we employ first-principles calculations and micro-kinetic modelling to compare the performance of Ni, Co, and Fe in this motif to the Cu one. Our finding is that the methane-to-methanol reaction can only realistically happen for Cu on this motif. Thus, this particular motif can be excluded as an active site candidate for Ni-, Co-, and Fe-ZSM-5 [6]. Another catalyst that is interesting for partial methane oxidation is the Mo6S8 cluster. However, instead of the methane-to-methanol reaction we use H2S as an oxidant and transform methane into hydrogen and CH3SH. Using electronic structure calculations and mean-field micro-kinetic modelling to study this reaction, we successfully capture the experimentally observed trend, i.e. that promoting the Mo 6 S 8 cluster with K increases the selectivity towards CH 3 SH, and Ni enhances the hydrogen formation [7].

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