NOx SCR by urea. Integration of the catalyst in particulate filter for compact pollution control system – UreeNOx

The usual SCR catalysts on boarded on heavy duty vehicles are not suitable for an exhaust pipe equipped with a DPF due to the high temperature reached during the DPF regeneration
On other hand, the zeolite-type catalysts, envisaged for light vehicles, are not easily introducible in the porosity of a DPF. The main objectives of the UreeNOx Project are to work both on the improvements of the SCR catalysts (in terms of NOx reduction reactivity and thermal resistance) and their coatability in a SiC particulate filter. Two catalysts technologies will be investigated: non-zeolitic mixed oxides and zeolite catalysts. New catalysts are firstly evaluated as powder in a NH3-NOx test. In addition, an original Urea-SCR test is in development at the laboratory scale.
To have access to reaction mechanisms (a key step to catalyst improvement), specific characterizations, including operando characterizations, will be performed. Interesting catalytic formulations will be then evaluated after coating in a baby DPF, and best ones will be tested on an engine test bench using full size DPF.
Another part of the project concerns the urea spray modelling in the exhaust pipe.

At mi-course, the project is still in a research and development step.
The two reference catalysts, namely a zeolite (Fe/FER) and an oxide (developed by Solvay) have been evaluated and characterized. Results obtained to the different scales (powder, baby-DPF, DPF scale 1) have been compared, and will serve as calibration for new materials development. Among the characterizations, the LCS (Caen) highlighted a possible N2O emission, leading from the decomposition of NH4NO3 intermediate species, formed by NO2 and NH3 adsorption at low temperature. This phenomenon depends from both the ammonia storage capacity and the NO2/NOx ratio of the upstream gas mixture.
In parallel, CTI that works on the catalyst introduction protocol toward DPF wall, has already divided by 5 the pressure drop resulting to the introduction of the zeolite inside the baby-DPF, at constant loading. The extrapolation to the scale 1 will start once catalytic performances checked.
The IFPEN developed some new no- intrusive optical techniques (ICCD camera, YAG laser 355 nm and tracer) to characterize the quality of the incoming mixture in the SCR catalyst, in order to display the impact of a mixer or of the presence of additives in the Adblue, for instance.
Concerning the material synthesis part of the project, partners have work according to the established program. Evolutions of oxides have been presented, with interesting results obtained at low temperature (T <250°C) for NH3=2NOx ratio. The UCCS develops new oxides based on Zr, Ce, W, V elements and the ICGM develops phosphorus silico-aluminates zeolites which present high thermal stability. Finally, some promising results have been presented by the IRCELyon with an original method of direct zeolite germination inside the DPF porosity.

Promising results obtained by the UCCS laboratory guide researches toward the development of optimized synthesis (ultrasonic paths, hydrothermal and sol-gel). The ICGM will pursue the work on zeolites formulation and the synthesis of metal-exchanged materials. The direct-synthesis of zeolite inside DPF wall developped by the IRCELyon will be spread out to a wide kind of structure, potentially more interesting.
The IC2MP has to finish the developpement of the Urea-SCR test, which present a significant technological advance at the laboratory scale. In parralel, the IC2MP also works on the synthesis of new kinds of materials (doped silica-alumina and perovskite)
The LCS has to focus on the deactivation mechanism, and the determination of active sites poisoning after thermal ageing.
Solvay will work on the stability of oxides materials and the scale-up.
Engine tests (IFPEN) restart towards the end of the project with the most promising prototypes.

At this time (07/01/2013), no work valorizations, as publication or communication, were submitted.
However, a patent project about the introduction of zeolite inside the DPF wall is discussed by partners

EURO 6 European regulation should be applied to Diesel light-duty cars from the 1st September 2014. It should lead to a reduction of NOx emission by 50% with respect to EURO 5 regulation (came into effect in 2009) while maintaining a very low threshold of particulate emissions (< 5 mg/km). In parallel, EURO VI regulation for trucks and heavy-duty vehicles aims at reducing NOx emissions by 80% and particulate matter emissions by 66% with respect to EURO V. The severity of the EURO 6/VI regulation imposes to generalize the implementation of specific NOx depollution systems associated with Diesel particulate filters (DPF) for all categories of vehicles. Today, selective catalytic reduction (SCR) of NOx by urea seems to offer several technological advantages (good activity and selectivity to N2) for the depollution of heavy-duty engines (light vehicles or trucks). Contrary to the NOx-trap alternative technology, urea-SCR does not lead to fuel over-consumptions provided that the SCR converter be placed close-to-engine. For efficiency and down-sizing reasons, there should be a decisive advantage to integer the Urea-SCR catalyst inside the DPF. However, soot combustion during DPF regeneration procedures induces exotherms requiring a very high thermal resistance of the SCR catalyst. Today, no catalytic systems exhibit both a high thermal resistance with an easy coating on/in the DPF. In collaboration with PSA Peugeot-Citroen for light-duty vehicles and Volvo Powertrain for trucks, the main objectives of the UreeNOx Project are to work both on the improvements of the SCR catalysts (mainly in terms of thermal resistance) and their coatability in a SiC particulate filter. Two catalysts technologies will be investigated: non-zeolitic mixed oxides and zeolite catalysts. The tasks on the materials synthesis will be entrusted to Rhodia and to Universities of Poitiers and Lille for mixed oxide catalysts and to Universities of Lyon and Montpellier for zeolite catalysts. Catalytic properties in NH3-SCR will be evaluated in Lille and Montpellier while Poitiers University will be in charge of the Urea-SCR tests. To have access to reaction mechanisms (a key step to catalyst improvement), operando characterizations and tests will be performed in Caen and Lille. The PF coating with the most promising powder catalyst will be made at CTI Company in order to test the final catalysts in real conditions (engine bench tests) at IFPEn.
To achieve this challenging project, a consortium of ten major academic and industrial partners of de-NOx technologies has been organized to gather all the necessary skills in materials synthesis and characterization, reaction catalysis, SiC monolith coating and catalyst testing in engine benchs. PSA Peugeot Citroen, Volvo Powertrain, Rhodia and CTI are the industrial partners of this Consortium while the Universities of Poitiers, Lille 1, Caen, Lyon 1, Montpellier as well as IFPEn are the academic partners. The consortium will be coordinated by Poitiers University (LACCO) assisted by Task directors as detailed in the project.