Insights into the CO Formation Mechanism during Steam Reforming of Dimethyl Ether over NiO/Cu-Based Catalyst

Abstract

Steam reforming of dimethyl ether on Cu-based catalyst was experimentally studied. It is found that formation of H2 and CO2 occurred over Cu/γ-Al2O3/Al, while methanol decomposition to CO and H2 was the main reaction over Cu/Ni/γ-Al2O3/Al in methanol steam reforming (MSR), which is similar to that on metallic Ni. However, XPS results show that nickel species existed as an oxidation state (NiO) over Cu/Ni/γ-Al2O3/Al. Therefore, reaction pathways of MSR over Cu(111) and NiO/Cu(111) were further explored using theoretical density functional theory calculations, and it was found that different reactivities of CH2O* resulted in the distinct product selectivity. On Cu(111), CH2O* reacting with OH* to CH2OOH* is favored, while CH2O* prefers to dehydrogenate to H* and CO* directly on NiO/Cu(111). This provided further evidence on the experimental results and fundamental understanding on the role of NiO species in affecting the MSR mechanism, which was helpful for rational design of selective Cu-based catalysts.