Catalytic combustion of diesel soot on perovskite type oxides

Abstract

The combustion of soot particulates is studied on perovskite type oxide catalysts having the general formula: La 0.8 Sr 0.2 Mn 1−x−y B' x Ø y O 3 (B'=Pt, Ru or Pd, x<0.01, and F represents a deficiency in B site, y<0.09). In order to determine the relative activity of various catalytic compositions, TGA and DTA experiments are performed on a mixture of catalyst and soot under air flow. The ignition temperature (Ti), the temperature of the maximum of combustion rate (T m ) and the soot conversion are determined. Soot is simulated either by a mixture of carbon black, fuel and lube oil or by carbon black alone. After a screening, the best catalytic results are obtained for two compositions, i.e. La 0.8 Sr 0.2 Mn 0.999 Pd 0.001 O 3 and La 0.8 Sr 0.2 Mn 0.91 Ø 0.09 O 3 . In both cases, the combustion temperature (T m ) of carbon black is found to be lowered from 650°C to about 440°C. The influence of several parameters, on the catalytic properties of these latter formulations is studied: catalyst preparation method, specific area, ageing carbon black/catalyst ratio.