Abstract
In this work we report results of NO x adsorption and diesel soot combustion on a noble metal promoted K/La 2O 3 catalyst. The fresh-unpromoted solid is a complex mixture of hydroxide and carbonate compounds, but the addition of Rh favors the preferential formation of lanthanum oxycarbonate during the calcination step. K/La 2O 3 adsorbs NO x through the formation of La and K nitrate species when the solid is treated in NO + O 2 between 70 and 490 °C. Nitrates are stable in the same temperature range under helium flow. However, they become unstable at ca. 360 °C when either Rh and/or Pt are present, the effect of Rh being more pronounced. Nitrates decompose under different atmospheres: NO + O 2, He and H 2. The effect of Rh might be to form a thermally unstable complex (Rh–NO +) which takes part both in the formation of the nitrates when the catalyst is exposed to NO x and in the nitrates decomposition at higher temperatures. Regarding soot combustion, nitrates react with soot with a temperature of maximun reaction rate of ca. 370 °C, under tight contact conditions. This temperature is not affected by the presence of Rh, which indicates that the stability of nitrates has little effect on their reaction with soot.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
