Methane dehydrogenation on monomeric Rh center located on (100) γ-alumina — A theoretical study ☆

Abstract The reaction mechanism of methane dehydrogenation on monomeric Rh center located on (100) γ-alumina has been theoretically investigated at the PBE0/cc-pVTZ, SDD level. The (100) face of γ-alumina support is represented by an Al 8 O 26 H 28 cluster, which is cut out from the ideal crystal structure. Then, two model Rh/γ-Al 2 O 3 catalysts, in which Rh center interacts with one oxygen or two oxygen atoms of the (100) surface of γ-Al 2 O 3 , have been compared and denoted as Rh/Al 8 O 26 H 27 and Rh/Al 8 O 26 H 26 , respectively. Toward methane activation, the model catalyst Rh/Al 8 O 26 H 27 exhibits better performance than Rh/Al 8 O 26 H 26 . For the first C H bond cleavage of methane, the lowering of activation barriers on Rh/Al 8 O 26 H 27 is mainly caused by lower substrate activation strain Δ E ≠ strain [substr], which is from substrate equilibrium geometry to the geometry it adopts in the TS, in comparison with that on Rh/Al 8 O 26 H 26 . These results are in qualitative agreement with the experimental results, where the partially reduced Rh + is one of the active sites for methane dissociation.