Optimization of cesium and potassium promoter loading in alkali-doped Zn0.4Co2.6O4|Al2O3 catalysts for N2O abatement

A series of potassium or cesium doped Zn0.4Co2.6O4|Al2O3 catalysts with different alkali loadings were prepared, characterized with respect to chemical composition (XRF), structure (XRD, RS) morphology (TEM), and the alkali promoter thermal stability. A strong beneficial effect on the deN2O activity of the Zn0.4Co2.6O4|Al2O3 catalyst (decrease in the T50% by about 80 °C) was observed for both promoters at different surface coverages. It was found that in comparison to a rather narrow range of optimal cesium loading (0.5–2 atoms/nm2) a comparable promotional effect of potassium doping was observed for a slightly wider surface concentrations (0.5–3 atoms/nm2). Such difference was attributed to surface dispersion of potassium over the alumina support and the spinel active phase, while cesium was found to be located mainly on the spinel phase. For practical applications, the superiority of potassium over cesium consist in fact that a similar beneficial effect is associated with much higher thermal stability in the temperature range of the catalyst deN2O operation and lower price of the promoter precursor.