2003

Layered-type perovskite catalysts (A2−xA′xB1−yB′yO4±δ, where A, A′=La, K and B, B′=Cu, V), prepared by the citrates method and characterized by BET, XRD, and catalytic activity analysis, proved to be effective in the simultaneous removal of soot and NOx, the two prevalent pollutants in diesel exhaust gases, but only at temperatures as high as 450–500 °C, seldom reached at the exhaust line location unless next to the engine exit (close-coupled system).

Catalytic traps for diesel particulate removal are multifunctional reactors coupling filtration and catalytic combustion of soot. This paper reviews the most recent developments carried out at Politecnico di Torino concerning two different trap types: zirconia-toughened-alumina foams catalysed with Cs-V catalysts, operating according to a deep filtration mechanism, and cordierite or SiC wall-flow filters catalysed with perovskite catalysts (e.g. LaCr 0.9O3), enabling shallow-bed filtration.

As an alternative to previously developed catalytic FeCrAlloy fibre mat burners based on perovskite catalysts, new catalytic burners have been developed based on Pd catalyst on lantana-stabilised Al2O3 and different fibre structures (NIT100A, NIT100S and NIT200S by ACOTECH NV).

Combustion synthesis has been applied to LaMnO3 production with a view to boosting its activity towards natural gas combustion by enhancing its specific surface area. With a highly exothermic and self-sustaining reaction, this oxide can be quickly prepared from an aqueous solution of metal nitrates (oxidisers) and urea (fuel). The favourable conditions for LaMnO3 formation were sought: only fuel-rich mixtures are effective, but carbonaceous deposits are formed when too much urea is used.