Commercial AEI (Si/Al ratio = 10) and CHA (Si/Al ratio = 9) zeolites have been tested in NH3 -SCR for NOx removal, after lab-scale Cu-exchange (Cu ~ 2 wt.%). Both structures showed very high structural stability after hydrothermal aging at 900°C for 1h. The great deNOx performance and high N2 selectivity are attributed to similarities observed between the two frameworks (e.g. an equivalent distribution of Al and Si). The high deNOx performance after hydrothermal aging at 900°C is attributed to the presence of a significant quantity of Z 2 -CuII species (~35% of all present Cu species), attesting to their very high stability in the d6r of the two frameworks. CuOx clusters were formed after hydrothermal aging (10% H2O) at 900°C for 1h. Despite showing higher quantities of CuOx than its equivalent CHA, NOx conversion rates at T> 500°C were higher on AEI HTA-900.

Diesel particulate filters (DPFs) are commonly employed in modern passenger cars to comply with current particulate matter (PM) emission standards. DPFs requires periodic regeneration to remove the accumulated matter. During the process, high-concentration particles, in both nucleation and accumulation modes, are emitted. Here, we report new information on particle morphology and chemical composition of fine (FPs) and ultrafine particles (UFPs) measured downstream of the DPF during active regeneration of two Euro 5 passenger cars. The first vehicle was equipped with a close-coupled diesel oxidation catalyst (DOC) and noncatalyzed DPF combined with fuel borne catalyst and the second one with DOC and a catalyzed-diesel particle filter (CDPF). Differences in PM emission profiles of the two vehicles were related to different after treatment design, regeneration strategies, and vehicle characteristics and mileage. Particles in the nucleation mode consisted of ammonium bisulfate, sulfate and sulfuric acid, suggesting that the catalyst desulfation is the key process in the formation of UFPs. Larger particles and agglomerates, ranging from 90 to 600 nm, consisted of carbonaceous material (soot and soot aggregates) coated by condensable material including organics, ammonium bisulfate and sulfuric acid. Particle emission in the accumulation mode was due to the reduced filtration efficiency (soot cake oxidation) throughout the regeneration process.

Diesel Exhaust Fluid (DEF) like Adblue (R) is a urea/water solution injected upstream from the SCR catalyst. Urea decomposes into ammonia (NH3) which acts as reducing agent in the de-NOx reaction process. However, incomplete decomposition of urea can lead to unwanted deposits formation, thereby resulting into backpressure increase, loss of NOx reduction efficiency, and durability issues. The phenomenon is aggravated at low temperatures and can lead to restriction or stop of DEF injection below certain exhaust temperatures. This paper focuses on the influence of the additivation of DEF on deposits formation in a passenger car close-coupled SCR on filter Diesel exhaust line installed in a laboratory flow bench test. The behavior of two different additivated DEF was compared to Adblue (R) in terms of deposits formation on the mixer and SCRF canning at different temperatures comprised between 240 degrees C and 165 degrees C, and different air flows. The influence of the DEF additivation on the cooling effect of the fluid and the surface temperature of the exhaust line downstream from the injector were also investigated.

The N2O formation during NOx selective catalytic reduction by NH3 is often attributed to NH4NO3 intermediate decomposition. Thermal decomposition of NH4NO3 has been extensively studied owing to the combination of its wide use as fertilizer and its dangerous properties. However, the decomposition of NH4NO3 in the presence of a catalyst has generated less attention. The decomposition of NH4NO3 may yield NxOy-type products such as NO, NO2, N2O, N-2 as well as HNO3 and H2O. This work focuses on the emissions of N2O. The deposition of NH4NO3 onto a Fe-zeolite catalyst was carried out by dry impregnation, by using a dilute solution of NH4NO3, and by a mechanical mixture. In the absence of catalyst, the release of N2O strongly depends on the conditions of the experiment (static or dynamic). The presence of a catalyst and the method of mixing ammonium nitrate into it affects its decomposition. Nitrogen formation is much more significant for the impregnated sample. For the mechanically mixed sample, the ammonium nitrate is mainly decomposed into N2O and NO2. N2O from ammonia oxidation was also detected in the presence of a catalyst.

The efficiency and the selectivity of a model platinum based catalyst supported on a modified ceria-zirconia oxide was evaluated in the NO storage-reduction (NSR) process at four catalytic scales: powder, (0.5 '' x 1.5 '') flow-through monolith (FTM) system, small size (1 '' x 2 '') and full size (5.66 '' x 10 '') catalysed Diesel Particulate Filter (DPF).The washcoating of the active phase over FTM affects both the NOx storage properties and the NOx reduction step. The reduction step efficiency is especially decreased at low temperatures. It is associated with an incomplete regeneration of the storage sites and with a strong NOx desorption peak during the rich pulses of the NSR process for the FTM supported system. The NOx reduction selectivity is also strongly affected by the upscale, with an important N2O selectivity detected over FTM. The recorded NOx profiles during NSR cycles indicate a probable diffusion limitation. However, same trends were observed for both powder and FTM systems concerning the effect of the reductant mixture, for both NSR efficiency and N-compounds selectivity.After incorporation of the active phase in the porosity of the DPF, a sharp drop in NOx storage properties and subsequently in NSR efficiency are observed. Supplementary tests suggest that the diffusion from the platinum oxidizing sites to the storage sites is again very affected by the upscale. Finally, the engine bench tests confirm the low DeNO(x) activity of the DPF system. (C) 2014 Elsevier B.V. All rights reserved.

Selective catalytic reduction by ethanol on silver-based catalysts was proved to be very effective to abate the nitrogen oxides emitted at the exhaust of an automotive engine. Moreover, the selectivity to ammonia of this reaction may be exploited to further enhance the NOx reduction using a dedicated transition metal exchanged zeolite catalyst. This coupling between HC– and NH3–SCR is called Dual SCR. In order to control the silver-based catalyst efficiency via ethanol injection, a NOx sensor is located downstream of it, as usually done for urea–SCR on series vehicles. Furthermore, based on the cross-sensitivity of this NOx sensor, large amounts of ammonia were estimated that would help to reduce the remaining NOx on the zeolite based catalyst. However, when measured by FTIR technique, the concentrations of ammonia produced by the HC–SCR catalyst were surprisingly not as high as expected, while large amounts of acetaldehyde were detected and, in a lesser extent, formaldehyde and hydrogen cyanide. NOx were partly reduced over the iron-exchanged zeolite catalyst, improving the overall deNOx efficiency by up to 15 points, while acetaldehyde to formaldehyde ratio reversed and ammonia concentration remains unchanged. The cross-sensitivity of the NOx sensor was further investigated on synthetic gas bench. If its partial dependence on the ammonia concentration is rather well known, the influence of aldehydes and hydrogen cyanide in presence of ammonia had not yet been investigated. The NOx sensor’s signal remains unchanged whatever the aldehydes concentration and a strong sensitivity to the hydrogen cyanide was highlighted.

The challenge for decreasing the emissions of compression ignition engines now remains mainly on NOx control. If the Lean NOx Trap (LNT) and Selective Catalytic Reduction by Urea (Urea-SCR) are very efficient, their extra-cost and management are a major issue for the OEMs. In that context, the selective catalytic reduction by hydrocarbons (HC-SCR) appears to be an interesting alternative solution, with a more limited NOx conversion efficiency but an easier packaging (diesel fuel as a reductant) and a limited price (reasonable coating cost /no PGM).In the framework of the RedNOx project, a prototype catalyst made of 2% silver on Alumina coated on cordierite was manufactured and tested on a synthetic gas bench. In parallel, an exhaust implementation study has been led to ensure the most suited conditions for injection. Thanks to SGB and simulation results, adapted engine tests have been designed and performed.If the results on SGB are consistent with the literature with a maximum NOx conversion reaching about 70% and an operating range between 300 and 500 degrees C, first engine results were very disappointing showing efficiencies lower than 15% for all the operating points. Three guidelines for improving these results were identified and studied:The way the reductant is introduced in the exhaust, especially the discontinued HC delivery due to the injection patternThe gas velocity: unusual small GHSV values for automotive applications are needed to ensure a good NOx conversion rate.The nature of the used reductant. Diesel fuel (ULSD) compared with decane lowers the efficiency, but synthetic Diesel fuel (SD) and, moreover, ethanol, largely improve it, especially for high GHSV.

For modern automotive applications, after-treatment systems have become essential to respect the new emission standards. All the automotive world's attention is focused on catalysis systems because they seem to be one of the best ways to reach the future standards. As a result, after-treatment issues are more and more significant in the cost of the whole engine and vehicle development process. For example, the Euro 6 Diesel after-treatment line might for some applications be composed of nothing less than five distinct after-treatment bricks. This complex architecture implies developing advanced tools to help the exhaust line conception and also the design of associated control strategies. The present paper demonstrates that zero-dimensional (0D) simulation can be a relevant approach to develop exhaust line simulators compatible with accuracy and CPU time required performances. This paper proposes an original zero-dimensional model of the monolith. This approach is based on resistive and capacitive elements according to the bond graph theory [Karnopp D.C., Margolis D.L., Rosenberg R.C. (1990) Systems dynamics: a unified approach, Second Edition, John Wiley & Sons, New-York]. The described dynamic model takes into account the pneumatic flow and the thermal behaviour of the monolith. Models of several catalysts are built by plugging this monolith model with some well-known simplified chemical reaction schemes [Koltsakis G.C., Konstandinis P.A., Stamatelos A.M. (1997) Development and application range of mathematical models for 3-way catalytic converters, Appl. Catal. B: Environ. 12, 161-191]. Splitting a monolith model into several elementary zero-dimensional blocks in series allows having a good representation of the specific internal dynamic of one catalyst and to access some local information as in conventional well-known one-dimensional models with low CPU time cost [Koltsakis G.C., Konstandinis P.A., Stamatelos A.M. (1997) Development and application range of mathematical models for 3-way catalytic converters, Appl. Catal. B: Environ. 12, 161-191]. Such an approach can be used as a way to get a phenomenological understanding of the catalytic system, which is known to be a very complex multi-physical system. It also represents a relevant simulation tool for the definition of after-treatment line architecture and pollutant emission control. The approach's potential to deal with all modern after-treatment bodies is illustrated by results for a Three-Way Catalyst (3WC), a Diesel Oxidation Catalyst (DOC), a Lean NOx Trap (LNT) system, a Selective Catalyst Reduction of NOx (SCR) system and a Diesel Particulate Filter (DPF). This ability to give, with a good compromise between accuracy/low CPU time cost, some interesting information to help the development of more and more complex exhaust system makes zero-dimensional simulation relevant.

Diesel oxidation catalysts of 16 Euro 4 passenger cars were analyzed and tested on an engine bench to attempt to correlate composition and structure to real-life performances. Particular low temperature behavior was evidenced, which was further studied using simplified gas mixtures on a synthetic gas bench. The long chain hydrocarbons are efficiently trapped, while NO2 plays a major role in CO abatement before the activation of the catalytic oxidation by O2.

Analysis of Particles Emitted by Combustion in Engines — Diesel engine particulate mat- ter (PM) emissions are nowadays globally regulated and limited through a driving cycle measurement. Thus, a known flow of diluted exhaust gases is sampled and filtered. The weighing of the filter before and after the test allows the determination of the soot mass emitted by the vehicle. If these values are useful to limit the pollution of the vehicles, they do not make it possible to the researchers to answer all their interrogations. Indeed, those need more precise information on the nature and the composition of the particles so, for example, to better understand and simulate the phenomena governing their formation. This information also makes it possible to know their toxicity, to compare in a finer way the emissions of various types of engines, Diesel or spark ignited, or to evaluate the influence of the fuel, the lubricant or the after-treatment system. These data are useful for both the car manufacturer and petroleum industry and also for professionals of health and those of environment. The various methods of sampling and analyses here described make it possible to obtain this more complete information on the particles such as the volatile or soluble compound contents, the content of sulphates, polycyclic aromatic compounds, metal, etc. Trace Analysis in the Petroleum Industry / Analyse de traces dans l'industrie petroliere