Potential of Supported Copper and Potassium Oxide Catalysts in the Combustion of Carbonaceous Particles

Different oxide carriers (TiO2 and ZrO2) as supports for low amounts of Cu2+ and K+ species (2 wt % as equivalent oxide) were tested in the catalytic oxidation of carbon black. The K-Cu/oxide catalysts were shown to have a lower soot combustion temperature than K/oxide, Cu/oxide, and pure oxide carriers. The K-Cu/ZrO2 catalyst was found to be the most active; it exhibited activity in a loose contact nearly similar to that obtained in a tight contact mode. Physicochemical characterization by EPR, XPS, and TPR revealed the interaction of K+ species with Cu2+ species and the ZrO2 carrier in K-Cu/ZrO2 as well as a strongly distorted Cu2+ species on the ZrO2 surface. The potassium ions ensure promoting effects towards the contact between the carbon black and the catalyst surface. Although potassium ions were found to lower the reducibility of the cupric oxide species, the oxidation rate of carbon black increased in the presence of K/oxide and K-Cu/oxide.