Le but de cette étude est de trouver un matériau catalytique pour la réduction catalytique sélective des NOx par les hydrocarbures (HC-SCR) dans l’échappement Diesel par une approche haut débit (HTE : high throughput experiments). Ce matériau doit être actif à basse température et stable hydrothermiquement à hautes températures. Une bibliothèque de 150 catalyseurs a été synthétisée. Les catalyseurs sont constituées d’Ag, Au, Cu supportés sur Al2O3, TiO2, ZrO2, CeO2 qui peuvent être dopés (Ga, Mo…). Ceux-ci sont testés en parallèle dans un dispositif constitué de 16 réacteurs (SWITCH-16) au cours réaction à température programmée (TPR) avec un flux modèle (100ppm NO / 350ppm C3H6 / 15% O2 /11% H2O). Le meilleur catalyseur 5%Ag/1%P/Al2O3, testé plus avant, montre une température de light-off de 50°C en dessous de celle d’un catalyseur commercial de référence et celui-ci est stable après un vieillissement de 16h à 750°C en présence d’eau. Ce catalyseur est ensuite enduit par voie sol-gel sur un monolithe (1*2 pouces et 300 cpsi) et testé sur un mini-pilote. Les tendances obtenues en réacteur à lit fixe montés en parallèle sont confirmées sur mini-pilote. En parallèle une approche microcinétique expérimentale des étapes élémentaires de surface impliquées dans la HC-SCR du NO sur un catalyseur Ag/Al2O3 a été utilisée pour déterminer les étapes élémentaires contrôlant la conversion du NO en prenant en compte l’adsorption compétitive entre NO et CO présent dans le gaz d’échappement Diesel. Nous avons identifié l’élimination des espèces Oads adsorbées sur des sites Ag° comme étape limitante pour la production de N2 et suggéré une nouvelle orientation possible pour l’étude HTE. / The aim of this study was to discover a catalytic material for NOx reduction by HC-SCR in Diesel exhaust which is active at the lowest temperatures and hydro thermally stable at high temperatures by using High Throughtput experiments (HTE). A library of 150 catalysts was synthesized. Catalysts are supported Ag, Au, Cu on Al2O3, TiO2, ZrO2, CeO2 and further doped with different dopants (Ga, Mo, …). They were tested in a 16-parallel reactor (SWITCH-16) using a Temperature Program Reaction (TPR) protocol with a model feed (100ppm NO / 350ppm C3H6 / 15% O2 /11% H2O). The best catalyst formulation 5%Ag/1%P/Al2O3, which was further improved, exhibits a light off temperature of 50°C lower than a reference commercial catalyst and is stable after ageing at 750°C in presence of water for 16 hrs. For pilot testing, the best catalyst was deposited by sol-gel method on a 1x2 inch monolith (300 cpsi). We showed the consistency of catalytic results obtained in the parallel fixed beds match with monolith bench testing. In parallel a experimental microkinetic approach of surface elementary steps involved in the HC-SCR of NO on Ag/Al2O3 catalyst has been performed to reveal the elementary steps controlling the conversion of the NO reactant taking into account the competitive chemisorption between NO and CO that is present in an exhaust gas. We identified the elimination of Oads species adsorbed on Ag° sites as the limiting step for the N2 production and suggested a new orientation of a HTE study.

The depletion of fossil fuels together with growing environmental concerns have created incitement for developing a more energy-efficient and environmentally-friendly vehicle fleet. The development towards cleaner heavy-duty vehicles started already in the 80’s with the introduction of emission legislations. Initially, engine optimization was enough for reaching the legislated levels of emissions. However, at present engine optimization is not enough but exhaust aftertreatment has become an essential part of heavy-duty vehicles, in order to meet the emission standards. Today, the total emissions are targeted which means that there is an interest in decreasing the idling emissions as well as the emissions during operation. To reduce the overall emissions several states in the USA have introduced idling legislations. Due to the limitations in idling time alternative solutions for power generation during rests are requested. A possible alternative is a fuel cell auxiliary power unit, combining a fuel cell with a fuel reformer (FC-APU).  The focus of this thesis is the development of the fuel reformer for an FC-APU, in which the hydrogen to the fuel cell is generated from diesel in a high-temperature catalytic process. The produced hydrogen can also be used in other heavy-duty vehicle applications i.e. selective catalytic reduction of NOx (HC-SCR), where addition of hydrogen is essential for reaching high conversion at low temperatures. The effect of using hydrogen from a fuel reformer in HC-SCR is included in this work. The catalytic material development is focused on developing promoted materials with lower rhodium content but with catalytic activity comparable to that of materials with higher rhodium content. This includes evaluation and extensive characterization of both fresh and aged promoted materials. The work also includes reactor design where a micro reactor with multiple air inlets is evaluated. This work has contributed to increased knowledge of catalytic materials suitable for reforming of diesel. By changing the support material from the traditionally used alumina to ceria-zirconia, increased H2 yield was achieved. In addition, the ceria-zirconia supported material was less prone to coke. By promoting the material with cobalt or lanthanum it was possible to decrease the rhodium content by 2/3 with enhanced catalytic performance. It was also discovered that promotion with lanthanum decreased the tendency for coking even further. Additionally, the lanthanum-promoted material had higher thermal stability as well as a stable highly dispersed rhodium phase. Furthermore, the work has contributed to an increased knowledge concerning the fuel reformer’s effect on HC-SCR. The work displays clear evidence of benefits with using hydrogen-rich gas from a fuel reformer instead of pure hydrogen. The benefits are derived from the content of low molecular weight hydrocarbons present in the hydrogen-rich gas, which are strong reducing agents increasing the NOx reduction. This finding proves that fuel reforming in combination with HC-SCR is a viable option for NOx abatement. / <p>QC 20150202</p>