An insight to diesel soot combustion mechanism: unusual reaction rate - temperature relationship

MARTÍN S. GROSS; CARLOS A. QUERINI

Houston - Estados Unidos

Congreso; 20th North American Meeting; 2007

Diesel soot elimination is a very difficult problem.  The catalytic filters seems to be one of the technological alternatives in order to trap and burn the soot, at the exhaust gas temperature.  In order to advance in a rational catalyst design, the reaction mechanism must be understood.  In spite of this need, and even thogh there are many papers in the field, details studies regarding soot combustion mechanism are scarce, and the real kinetic is not typically reported.  Ciambelli et al studied this reaction, and used a power-law rate expression [1,2], to fit the experimental data.  Some other studies also used this type of kinetic law.  However, since the contact between the soot and the catalyst is a major problem in this system, the catalysts formulated 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 on the complex reaction mechanism for this system.  Catalyst characterization was also carried out based on these observations.