Diesel soot and NO sub(x) abatement: K/La sub(2)O sub(3) catalyst stability

• Published in: Applied catalysis. B, Environmental Environmental, 2010-11, Vol.101 (1-2), p.38-44
• Main Authors: Peralta, MA, Ulla, MA, Querini, CA
• Format: Article
• Language: English
• Subjects: Catalysis; Catalysts; Combustion; Diesel; Diesel fuels; Potassium; Soot; Surface chemistry
• ISSN: 0926-3373
• DOI: 10.1016/j.apcatb.2010.08.031

Soot particles and nitrogen oxides are the main pollutants emitted by a diesel engine. In this work, the activity and the stability of the K sub(OH)/La sub(2)O sub(3) catalyst are studied. This catalyst is able to adsorb NO sub(x), which is a good property for the catalyst in order to be used as a NO sub(x) trap. In addition, it is active for soot combustion as determined by temperature-programmed oxidation analyses. FTIR, XRD, CO sub(2)-TPD, Pulses of CO sub(2), and BET techniques are used in order to characterize the catalysts. The catalytic surface composition depends upon the relative partial pressures of H sub(2)O, CO sub(2), NO and O sub(2). Despite the different surface compositions, the catalytic activity remains quite stable, under operation conditions similar to those of a real diesel exhaust. High temperature treatments, such as 800 C, and especially in the presence of water, leads to an irreversible catalyst deactivation due to potassium volatilization. The water condensed on the catalyst, could wash-out a fraction of the potassium from the outer surface, leading to a decrease in activity. However, when the catalyst is treated at 400 C, potassium diffuses from inside the pores to the external surface, thus recovering activity for soot combustion.