Influencia de la cantidad de K sobre el mecanismo de reacción de la combustión catalítica de hollín

MARTÍN GROSS; MARÍA A. ULLA; CARLOS A. QUERINI

Buenos Aires - Argentina

Congreso; XVI Congreso Argentino de Catálisis; 2009

The aim of this work is to understand the reaction mechanism of catalytic soot combustion with K(x)/CeO2 catalysts. Catalysts activity were determined by temperature programmed oxidation techniques (TPO) over catalyst:soot mixtures. By correct design of these experiments it was possible to observe transient phenomena which suggest that the oxidation mechanism involve several steps. It was found that the reaction rate keep increasing at constant temperature (for a group of catalysts formulation and certain temperatures values). Soot is burnt by oxygenated species such as peroxides and superoxides as observed by FTIR, not by molecular oxygen, but the last is necessary to complete the redox cycle in which CeO2 is involved. When potassium is added to ceria, on one hand it favor the contact between soot and catalyst by formation of species with high mobility, and on the other it promotes the formation of such oxygenated species. It was found that there exists an optimal relationship between ceria and potassium ratio that make the catalyst activity maximum. By characterization techniques like FTIR, SEM, XRD, XPS and high frequency CO2 pulses, enough information was gathered in order to propose a reaction mechanism. With the kinetic model that correspond to this mechanism it was possible to satisfactorily simulate a series of complete and partial combustions in conditions completely different to those that had been used to obtain the kinetic parameters.