Catalytic combustion of diesel soot particles on copper catalysts supported on TiO2. Effect of potassium promoter on the activity

We have prepared a TiO2 supported copper catalyst and studied the effect of potassium on its activity in the oxidation of soot particles. The catalysts, with a K/Cu atomic ratio varying between 0 and 2, were calcined at 1073 K. They were characterized by BET surface area measurements, X-ray diffraction and temperature-programmed reduction under hydrogen. The catalytic activity was measured in a microbalance by means of temperature-programmed oxidation in air or argon. The catalytic activity of copper was enhanced by the presence of potassium. This effect was attributed to the formation of mixed KTi oxides which inhibit the sintering of the TiO2 support and thus increases the surface area of the catalyst. Although a redox mechanism can explain the catalytic combustion, no correlation could be established between the reducibility of the different solids and their activity in soot combustion.