Dry synthesis of alumina-supported cobalt catalyst for highly enhanced catalytic oxidation

[Display omitted] •Dry synthesis method for utilizing active sites of cobalt oxides on alumina.•Combined alumina dehydroxylation and solid-state impregnation for dry synthesis.•Active control of hydroxyl groups and Al penta sites over γ-Al2O3 surface.•Enhanced redox property via selectively favored Co3O4 phase formation.•Designing catalyst where strong support-metal interaction has negative effects. Alumina-supported cobalt oxide excels as an oxidation catalyst, however, strong metal-support interactions (SMSI) of cobalt and alumina can lead to inactive phases such as cobalt aluminate. To avoid the formation of the inactive phase, it was hypothesized that reducing the number of hydroxyl group anchoring sites on the alumina would enable a higher ratio of active cobalt oxide than inactive phases. We devised a dry synthesis method combined with alumina dehydroxylation and solid-state impregnation of cobalt. Characterization results including XRD, XPS, and Raman spectroscopy confirm the formation of the desired active phase on the dehydroxylated alumina. The resultant catalysts demonstrate a surprising decrease in the cobalt content (max. tenfold from 20 wt.% to 2 wt.% of cobalt loading) for oxidations of NH3 and CO, respectively, suggesting practically useful synthesis method for highly active supported catalysts.