Stability of K-La2O3 catalyst during the combustion of Diesel soot. High frecuency CO2 pulses and soot-catalyst contacting studies

M.L. PISARELLO; C. SAUX; E.E. MIRÓ; C.A. QUERINI

Toronto - Ontario - Canada

Congreso; 17 North American Catalysis Society Meeting; 2001

The catalysts to be used in the combustion of diesel soot,  must be stable to high temperatures and the presence of other combustion products.  The activity should be high enough at temperatures as low as 200°C for low charge diesel engines, unless an external heating power is supply to the catalytic filter.  In any case, the catalyst stability is a key factor in determining its applicability in a commercial scale.             It is well stablished that the contact between the soot and the catalyst plays a mayor role in the combustion rate.  We have previously found that some promoters, like the potassium, favor the effective contact between the soot and the catalyst, due to its high mobility (1,2).  The potassium supported on La2O3 has good activity, and preliminary results indicated that the catalyst maintain its activity after a thermal treament up to 700°C. However, further studies are needed in order to characterize the stability of the material to treatments at high temperatures.  In this paper we present a simple experimental procedure, namely High Frequency CO2 Pulses, that indicate if the surface of the catalyst change upon a given treatment. The soot-catalyst contacting problem is also addressed, by comparing combustion rates of mechanical mixtures with those measured when K and La are directly deposited on the soot surface.