Catalytic combustion of carbon particulate at high values of the carbon/catalyst mass ratio

The oxidn. of diesel soot and amorphous carbon black, in the presence of a copper-vanadium-potassium catalyst supported on -alumina, was studied to investigate the influence of the carbon/catalyst initial mass ratio, Rm, on the carbon reactivity. A differential flow reactor was employed to perform kinetic tests. The progress of the catalytic combustion process was followed measuring the concns. of carbon oxides in the product stream at the reactor outlet with online NDIR analyzers. Exptl. results conform to those obtained while operating at relatively low values of Rm for what concerns the influence of oxygen partial pressure and temp. Furthermore, burn-off temps. in the presence of the catalyst were lowered by ca. 300 K, and correspondingly, the apparent activation energy for the catalytic oxidn. was found to be less than half with respect to the uncatalyzed combustion. A strong influence of Rm on the evolution with time of the combustion process was experienced. Specifically, time profiles of reactivity obtained when Rm was higher than 0.1 show a max. whose amplitude increases as Rm increases. This behavior was related to the segregation of a more-or-less large fraction of the total carbon. Following such findings, a kinetic model for carbon catalytic oxidn. was proposed. It is based on the assumption that different carbon portions enter the reaction zone at different times. Model parameters were estd. by a numerical code properly adapted. A good agreement between the model predictions and exptl. results was found for all Rm values.