Oxidative dehydrogenation of ethane at low temperature over nickel catalysts: influence of morphology and chemical state of the solid during reaction.

摘要

The ODH of ethane over nickel-based catalysts occurs at low temperatures with 50-70 percent selectivities towards ethylene. Magnetic measurements and in situ DRIFT experiments have revealed that little metallic nickel is present in the course of the reaction in unsupported and silica-supported nickel catalysts in contrast to Raney nickel. Furthermore, the latter sample is more active than unsupported catalyst on a unit area basis. Prereduction of Ni/SiO_2 catalysts is beneficial to activity. The active site is supposed to be a mixed species including nickel in the reduced and oxidised state. Selectivity to ethylene is found to vary little with conversion and morphology of nickel catalysts. It is inferred that ethylene is not subsequently oxidised by the catalyst and that the active sites are common to total and selective oxidation.