Catalytic Carbon Oxidation in The Presence of Cerium Oxide: Experimental Study and Modeling of The Effect of Oxygen Concentration

The catalytic combustion of carbon black (CB) used as a model of diesel soot in tight contact with a commercial ceria (CeO2) was investigated. Oxygen mole fractions of 10, 5, and 1% in the gas phase were tested in order to gain a better understanding of the redox properties of ceria and the mechanism of the catalytic oxidation of carbon black. Both isothermal and temperature programmed runs are performed to extract kinetic parameters, such as activation energy and reaction order with respect to oxygen partial pressure. The experimental data are used to propose a model of CB oxidation in the presence of CeO2 allowing the simulation of carbon oxidation

Reduction of NOx over a NOx-trap catalyst and the regeneration behaviour of adsorbed SO2

International audienc

Reduction of NOx over a NOx-trap catalyst and the regeneration behaviour of adsorbed SO2

A conventional NO-trap catalyst containing platinum, rhodium, barium and lanthanum was conditioned with oxygen at 500 °C, preloaded with NO under standard oxidising conditions and then subjected to regeneration with the reductants H, CO and CH, either alone or as a mixture. Hydrogen is the most efficient reductant in terms of NO conversion efficiency and reductant usage efficiency. There is a temperature optimum for CO between 300 and 400 °C and a catalyst loading optimum (mols reductant added)/(mols NO adsorbed) between 1.5 and 3.0. The behaviour of the catalyst towards sulphur poisoning was examined in supplementary trials with the adsorption of SO in the presence or absence of water vapour. When water is not present in both adsorption and reduction steps, very stable sulphates are formed, unattacked by reductants even at 1000 °C. Sulfates are more easily reduced when water is present in the reductant mixture

Synthèse et caractérisation de catalyseurs de NOx à base de silice mésoporeuse de type MSU contenant de platine et l'acide 12-tungstophosphorique H3PW12O40

Congrès du 22.05.2006 au 25.05.200

Réduction des NOx par le propène sur des catalyseurs à base de silice mésoporeuse organisée contenant PW et Pt incorporés lors de la synthèse

Journée de l'Ecole Doctoral

Réduction des NOx par le propène sur des catalyseurs obtenus par incorporation de H3PW12O40 et Pt dans des silices mésoporeuses de type MSU

Congrès du 22.05.2006 au 25.05.200

A laboratory study of NOx reduction during the rich operating period over a NOx storage catalyst

The behaviour of a NO storage catalyst in powdered form and containing a storage component based on alkaline metal was investigated under rich conditions. Experiments were conducted in a fixed-bed flow reactor with the space velocity set at 45,000 h. From these experiments it was possible to extract the fractional NO reduction and the efficiency of use of the reductant. With 0.9% CO as a reductant at 350°C, complete utilisation of CO was achieved up to 70% NO conversion as treatment time was increased. To obtain 90% NO conversion required longer times, and 23% of the CO did not participate in the reduction of NO. A reductant balance shows that about 40% of the CO added is used to reduce the catalyst surface when the flow is switched from lean to rich. The ranking of efficiencies of different reductant gases at 350°C gave the following sequence: 0.9% H ≈ 0.9% CO > 1285 ppm toluene > 3000 ppm propene ≈ 1125 ppm i-octane > 3000 ppm propane. Thus in an actual exhaust the NO reduction is due mainly to H and CO. A study of the effect of temperature showed that maximum efficiency is obtained in the range 350 to 400°C. A study of the effect of concentration showed that for the injection of a given mass of reductant (CO), it is better to use a shorter burst at higher concentration. The competition for reductant between the NO coming from nitrate decomposition and that needed for catalyst reduction requires a 3:1 excess (i.e. an approximate ratio of two between the quantity of reductant injected and the amount of NO adsorbed during lean phase operations)