Zirconia‐Supported Cobalt Catalysts: Activity and Selectivity in NO Reduction by CO

Cobalt catalysts supported on tetragonal and monoclinic zirconia were prepared using a one‐pot procedure through the incorporation of a Co3O4 colloidal suspension during the support synthesis and evaluated in the reaction of NO reduction by CO. A better dispersion of the active phase was obtained by this method when compared to the conventional impregnation one. Furthermore, the crystalline phase of zirconia in the supports had a crucial effect in the dispersion of the cobalt species, being that the pure tetragonal phase led to a higher dispersion of the active phase. The one‐pot prepared tetragonal zirconia led to cobalt active species that consisted in well‐dispersed small agglomerates of Co3O4 and Co2+ species as oxo‐ions which displayed the best catalytic performance among the studied catalysts, with the highest NO conversion (75%) and high selectivity to N2 (85%) at 300 °C. These results show that the one‐pot methodology employed in this work has a strong potential to produce suitable catalysts for the abatement of NOx emissions. Tuning N2 selectivity: The incorporation of a colloidal suspension of Co3O4 in the ZrO2 preparation (one‐pot method) improved the Co dispersion as small agglomerates of cobalt oxide and cobalt species as oxo‐ions. These features led to a marked increase in the selective reduction of NO to N2 using CO as reducing agent. Better dispersion of Co3O4 and selectivity to N2 was achieved combining the one‐pot method with a pure tetragonal zirconia phase.