Combination of LNT and SCR for NOx reduction in passenger car applications

• Autorzy: Maunula T.
• Języki publikacji: EN

Abstrakty

EN

The removal of NO_x and particulate emissions in light-duty diesel vehicles will require the use of aftertreatment methods like Diesel Particulate Filters (DPF) and Selective Catalytic Reduction (SCR) with urea and Lean NO_x Trap (LNT) (Euro 6 and beyond). A new concept is the combination of LNT + SCR, which enables on-board synthesis of ammonia (NH₃), which reacts with NO_x on the SCR catalyst. The main application for this kind system will be lighter passenger cars, where LNTs may be used instead of full urea-SCR system. That particular combinatory system was investigated by developing platinum (Pt) and rhodium (Rh) containing LNTs and SCR catalysts in this study. In the use conditions, the maximum temperature may reach temperatures up to 800°C and NO_x reduction reactions should proceed without NO₂ assistance in the SCR position after LNT and DPF. PtRh/LNT with the total loadings of 85 g/cft (2.8 g/L) and higher resulted in a high NO_x efficiency above 80–90% with a broad operation window in the laboratory simulations. In the experimental conditions, a higher NH₃ concentration after LNT was essential to simulate well the operation of SCR catalysts. The developed Cu-SCR catalyst showed a high hydrothermal durability up to the ageing temperature of 800°C and a wide operation window without the NO₂ assistance (NO only in feed). Fe-SCR and V-SCR catalysts were more dependent on NO₂. A studied concept had an air injection after LNT to keep SCR condition always in lean side, where the SCR reaction was promoted by oxygen resulting in high reduction selectivity to nitrogen (N₂) without NH₃ emissions. The simulations in reaction conditions and system design resulted in the proposals for the optimal design and main reaction mechanism in DOC + DPF + LNT + SCR systems.

Słowa kluczowe

EN

NOx; Selective Catalytic Reduction; SCR; LNT; catalysts; diesel

PL

selektywna redukcja katalityczna; katalizator; diesel

• Wydawca: Polskie Towarzystwo Naukowe Silników Spalinowych
• Czasopismo: Combustion Engines
• Rocznik: 2014
• Tom: R. 53, nr 2
• Strony: 60--67
• Opis fizyczny: Bibliogr. 17 poz., tab., wykr.

Twórcy

autor

Maunula T.

• Dinex Ecocat Oy, Catalyst development, Typpitie 1, FI-90620 Oulu, Finland

Bibliografia

• [1] Johnson T.: Vehicular Emissions in Review. SAE Int. J. Engines 2014 (3) Nr 7, SAE Paper 2014-01-1491.
• [2] Guo G., Dobson D., Warner J., Ruona W., Lambert C.: Advanced Urea SCR System Study with a Light Duty Diesel Vehicle. SAE Technical Paper 2012-01-0371.
• [3] Ramsbottom M., Birkby N., Khadiya N., Beesley S.: Development of a thermal enhancer™ for combined partial range burning and hydrocarbon dosing on medium and heavy duty engine applications. SAE Technical Paper 2011-01-0298.
• [4] Gandhi H., Cavataio J., Hammerle R., Cheng Y.: Catalyst system for the reduction of NOx and NH3 emissions. US Pat. 2011/0005200, filed 2004.
• [5] Snow R., Cavatatio G., Dobson D., Minttreuil C., Hammerle R.,:Calibration of a LNT + SCR diesel aftertreatment system. SAE Technical Paper 2007-01-1244.
• [6] Chen H-Y., Weigert E.C., Fedeyko J.M., Cox J.P., Andersen P.J.: Advanced catalysts for combined (NAC + SCR) emission control systems. SAE Technical Paper 2010-01-0302.
• [7] Nanjundaswamy H., Tomazic D., Severin C., Kolbeck A., Korfer T., Wittka T., Schnorbu T.: Further improvements of conventional diesel NOx aftertreatment concepts as pathways for SULEV. DEER Conference, 5 Oct 2011, Detroit.
• [8] Maunula T.: Intensification of catalytic aftertreatment systems for mobile applications. SAE Technical Paper 2013-01-0513.
• [9] Maunula T.: NOx reduction with the combination of LNT and SCR in diesel applications. SAE Int. J. Mater. Manuf., 2014 (7), SAE Technical Paper 2013-24-0161.
• [10] Maunula T., Vakkilainen A., Heikkinen R., Härkönen M.,:NOx storage and reduction on differentiated chemistry catalysts for lean gasoline applications. SAE Technical Paper 2001-01-3665.
• [11] Maunula T., Savimäki A., Viitanen A., Kinnunen T., Kanniainen K.: Thermally durable vanadium-SCR catalysts for diesel applications. SAE Technical Paper 2013-01-0796.
• [12] Wittka T., Holderbaum B., Maunula T., Weissner M.: Development and demonstration of LNT + SCR system for passenger car diesel application. SAE Int. J. Engines 7(2014), Nr 3, SAE Technical Paper 2014-01-1537.
• [13] Prikhodko V.Y., Parks J.E., Pihl J.A., Toops T.J.: Ammonia generation over TWC for passive SCR NOx control for lean gasoline engines. SAE Technical Paper 2014-01-1505.
• [14] Breen J.P., Burch R., Lingaiah N.: An investigation of catalysts for the on board synthesis of NH3. A possible route to low temperature NOx reduction for lean-burn engines. Catal. Lett., 79 (2002), Nr 1-4, 171.
• [15] Koci P., Kubicek M., Marek M., Maunula T., Härkönen M.: Modelling of catalytic monolith converters with low- and high temperature NOx storage compounds and differentiated washcoat. Chem. Eng. J. 97, 131-139, 2004.
• [16] Chatterjee D., Koci P., Schmeisser V., Marek M., Weibel M.: Modelling of NOx storage + SCR exhaust gas aftertreatment system with internal generation of ammonia. SAE Technical Paper 2010-01-0887.
• [17] Maunula T., Ahola J., Hamada H.: Reaction Mechanism and Kinetics of NOx Reduction by Propene on Co/Alumina Catalysts in Lean Conditions. Appl. Catal. B 26 (2000) 3, 173-192.