Effect of cobalt precursors on the dispersion, reduction, and CO oxidation of CoOx/γ-Al2O3 catalysts calcined in N2

The present work tentatively investigated the effect of cobalt precursors (cobalt acetate and cobalt nitrate) on the physicochemical properties of CoOx/γ-Al2O3 catalysts calcined in N2. XRD, Raman, XPS, FTIR, and UV–vis DRS results suggested that CoO/γ-Al2O3 was obtained from cobalt acetate precursors and CoO was dispersed on γ-Al2O3 below its dispersion capacity of 1.50 mmol/(100 m2 γ-Al2O3), whereas Co3O4/γ-Al2O3 was obtained from cobalt nitrate precursors and Co3O4 preferred to agglomerate above the dispersion capacity of 0.15 mmol/(100 m2 γ-Al2O3). Compared with Co3O4/γ-Al2O3, CoO/γ-Al2O3 catalysts were difficult to be reduced and easy to desorb oxygen species at low temperatures and presented high activities for CO oxidation as proved by H2-TPR, O2-TPD, and CO oxidation model reaction results. A surface incorporation model was proposed to explain the dispersion and reduction properties of CoO/γ-Al2O3 catalysts.

Graphical abstractThe CoO from cobalt acetate is highly dispersed on γ-Al2O3 while the Co3O4 from cobalt nitrate prefers to agglomerate, which leads to their different redox and CO oxidation properties.Figure optionsDownload full-size imageDownload high-quality image (161 K)Download as PowerPoint slideResearch highlights► CoO was obtained from cobalt acetate with its dispersion capacity of 1.50 mmol/(100 m2 γ-Al2O3). ► Co3O4 was obtain from cobalt nitrate with its dispersion capacity of 0.15 mmol/(100 m2 γ-Al2O3). ► CoO/γ-Al2O3 was more difficult to be reduced and easier to desorb oxygen than Co3O4/γ-Al2O3. ► CoO/γ-Al2O3 were more active for CO oxidation than Co3O4/γ-Al2O3. ► A surface model was proposed to explain the dispersion and reduction properties of CoO/γ-Al2O3.