Catalytic Combustion of Diesel Soot over K/CeO2 Catalysts: insights in the kinetics.

MARTÍN GROSS; CARLOS QUERINI

Seoul - Korea

Congreso; 14th International Congress on Catalysis; 2008

Diesel soot elimination is a very difficult problem.  The catalytic filters seem to be one of the technological alternatives in order to trap and burn the soot, at the tail pipe gas temperature.  In order to advance in a rational catalyst design, the reaction mechanism must be understood.  Since the contact between the soot and the catalyst is a major problem in this system, catalysts formulation for soot burning typically contains highly mobile species.  For example, eutectic mixtures, volatile compounds, or low melting-point compounds with high mobility were used.  This fact, introduce a different behavior, since it can be expected that active sites are permanently changing, as the mobile compound migrates throughout the surface. In this study, ceria supported catalysts promoted with potassium and sodium, are used for soot combustion.  Temperature programmed oxidation (TPO) analysis are carried out using different ramp rates and final temperatures, to obtain information regarding the reaction rate. The activity data provides new insights in the complex reaction mechanism for this system.  It was found that at constant temperature, the reaction rate increases with time. This phenomenon appears depending upon the precursors, and the temperature.  This quite unusual kinetic behavior is attributed to changes in the contact between soot and the catalytic functions during the reaction.