Low temperature diesel soots combustion using copper based catalysts modified by niobium and potassium promoters

Gravimetric temperature programmed oxidation was used to study the combustion of a diesel soot mixed with copper catalysts supported on La2O3 or La2O2CO3. In a first step, different systems associating copper oxide with an other metal oxide were prepared and tested in presence of SO2. The association of copper and niobium was found the most active. The influence of alkali on the activity was also studied. It results that potassium is the most effective in lowering the combustion temperature domain in agreement with literature. Finally, Cu-Nb-K catalysts deposited on lanthanum oxide have an improved catalytic activity at low temperatures compared to Cu-V-K or Cu-Mo-K/TiO2, reported in literature. For this catalyst, the maximum oxidation rate was observed at ca. 300 degrees C with the combustion starting at about 250 degrees C. A similar behaviour is obtained when replacing Nb by Ta or the support La2O3 by either La2O2CO3 or TiO2.