Stainless steel wire mesh-supported potassium-doped cobalt oxide catalysts for the catalytic decomposition of nitrous oxide

Abstract

Structured catalysts consisting of potassium-doped cobalt oxide supported on stainless steel wire mesh were tested for the decomposition of N2O under dry and wet conditions. The cobalt oxide catalysts were prepared by the ammonia-evaporation-induced method. Of the several doping procedures tested, dropwise impregnation with potassium carbonate solutions provided the best catalytic results at lower K/Co molar ratios. Kinetic analysis of a potassium-doped catalyst yielded a reaction order on the N2O partial pressure slightly below unity (0.87). The activation energy values and the natural logarithms of the pre-exponentials factors for the different catalysts followed the classical compensation effect. This effect may be the result of a combination of competing reactions on different groups of active centers. Thus, cobalt ions affected by potassium display a low activation energy (∼40kJ/mol), whereas cobalt atoms unaffected by potassium display a higher activation energy equal to that of the undoped catalysts (∼106kJ/mol). The catalytic activity of the catalysts in N2O decomposition increases with the amount of reducible Co3+ ions, although there does not appear to be a direct relation between the amount of Co3+ ions and the textural and crystal properties of the catalysts. The addition of water produces some inhibition of the N2O decomposition reaction on K-doped catalysts, although catalytic activity is completely restored when the water is removed from the reaction stream. The catalysts prepared in this work were found to be among the most active, selective and stable catalysts reported in the literature.