Stability of Diesel soot abatement catalysts

M.A. PERALTA; M.A. ULLA; C.A. QUERINI

Rio de Janeiro (Brasil)

Congreso; ENPROMER 2005. 2nd Mercosur Congress on Chemical Engineering and 4th Mercosur Congress on Process Systems Engineering; 2005

Emissions from internal combustion engines are one of the main causes of environmental pollution. Particulate matter (soot) and nitrogen oxides (NOx) are the main pollutants in diesel engine emissions. NOx contribute to acid rain. Because of the soot particulate are so small, they can deeply penetrate into the lungs, thus becoming a potential cancerigenic agent. The aim of this work is the study and development of a catalyst which simultaneously abate both kinds of emissions. In this work the stability of the catalyst is addressed: thermal stability, water and SO2 tolerance are studied. Activity measurements of the catalyst show low and high soot combustion activity from Ba and K respectively. Barium was added because it is a good NOx trap system. The soot burning temperature is higher than the temperature of the small engines exhaust gases and lower than the temperature of the heavy engines exhaust gases. Thermal stability is good up to 700°C. Thermal deactivation is probably due to two facts. A new perovskite phase (BaCeO3) is formed and, on the other hand potassium evaporates. Both, cerium and potassium contribute to soot combustion activity by a synergistic effect, and therefore the lost of any of them led to the decrease in activity. Water modifies the hydroxilation of the surface, as seen by XPS. However, the catalyst is stable in the presence of water at 400°C for a long time (100 h). In the presence of 1000 ppm SO2 the catalyst is deactivated. Cerium, potassium and barium sulfates are formed, and because of this, the activity decreases. The regeneration process of the poisoned catalyst is being studied.