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The regulations for mobile applications will become stricter in Euro 6 and further emission levels and require the use of active aftertreatment methods for NOX and particulate matter. SCR and LNT have been both used commercially for mobile NOX removal. An alternative system is based on the combination of these two technologies. Developments of catalysts and whole systems as well as final vehicle demonstrations are discussed in this study. The small and full-size catalyst development experiments resulted in PtRh/LNT with optimized noble metal loadings and Cu-SCR catalyst having a high durability and ammonia adsorption capacity. For this study, an aftertreatment system consisting of LNT plus exhaust bypass, passive SCR and engine independent reductant supply by on-board exhaust fuel reforming was developed and investigated. The concept definition considers NOX conversion, CO2 drawback and system complexity.

Catalyst coated silicon carbide filters were developed and applied for light-duty and heavy-duty diesel applications. This catalyst coating is suitable also for industrial applications and to be used on cordierite or sintered metal filters. Development activities yield solgel type coating for particulate filters with properties allowing very thin coating, containing metal oxides interacting with active sites, e.g. precious metals (Pt, Pd). A tailored catalyst composition was developed for the catalytic activity and durability in oxidation and soot regeneration reactions. The combination of thermal and catalytic particulate oxidation by oxygen and NO2 was investigated using different regeneration strategies in engine exhaust and laboratory conditions. The passive regeneration by NO2 initiated around 310°C with CPF only. One of the main targets was to lengthen the intervals between active regeneration phases by catalyzed particulate filters which enhance passive regeneration properties.

As the Diesel Particulate Filter (DPF) technology is nowadays established, research is currently focusing on meeting the emission and durability requirements by proper system design. This paper focuses on the optimum combination between the catalytic coating and substrate structural properties using experimental and simulation methodologies. The application of these methodologies will be illustrated for the case of SiC substrates coated with innovative sol-gel coatings. Coated samples are characterized versus their uncoated counterparts. Multi-dimensional DOC and DPF simulation models are used to study several effects parametrically and increase our understanding on the governing phenomena. The comparative analysis of DOC/DPF systems covers filtration – pressure drop characteristics, CO/HC/NO oxidation performance, effect of washcoat amount and catalyst dispersion on oxidation activity and finally passive regeneration performance.

One of the first alternative fuels have been fossil crude oil based containing a small amount of biomass derived compounds (bioethanol or biodiesel). Biofuels usually contain oxygenated hydrocarbons such as alcohols or esters. The increasing use of alternative fuels will occur at the same time when various after-treatment systems (oxidation catalysts, filters, SCR catalysts) will be commercialized world-widely between 2010 and 2020. The effects of biofuels on emissions and emission catalysts were reviewed widely in this study. The change in raw emissions has effects on the selection, performance and durability of catalytic systems. Bioethanol has been used widely with emission catalysts since 1990's in Brazil. The results with three-way catalysts (TWC) were analyzed in those conditions. PtRh catalysts showed the better performance and durability than Pd containing TWCs.

NOx storage and reduction (NSR) catalysts are a widely investigated solution for lean gasoline applications. Open coating on metallic substrates gives a new opportunity to combine low and high temperature NSR catalysts into a converter by using differentiated chemistry on separate foils. A wide operation window for NOx conversion between 200-600°C was reached with alumina based NSR catalyst in appropriate conditions. Differentiation on separate foils can be made by NOx adsorption compounds, active metals (Pt, Rh), exhaust gas conditions or desulfation strategy. The desulfation, particularly from potassium-containing high temperature NSR catalysts, was decreased by 100°C by the addition of a small amount of TiO2. The combination of 3-way and NSR catalyst was designed by the size and lean-rich timings in laboratory and engine conditions. Low OSC PdRh (7:1) catalysts with higher loadings were used as 3-way catalysts.

The latest emission regulations for mobile and stationary applications require the use of aftertreatment methods for NOx and diesel particulate filters (DPF) for particulate matter (PM). SCR catalysts were evaluated by laboratory experiments and the most promising SCR catalysts were also scaled up to full-size. Development with copper (Cu) and iron (Fe) on zeolitic materials (Beta, ZSM-5, SAPO, chabazite) has resulted in the new generation of thermally durable SCR (selective catalytic reduction) catalysts, which have also an improved sulfur tolerance and a low N2O formation tendency. Opposite to Cu on Beta and ZSM-5, Cu on chabazite and SAPO showed clearly lower N2O formation. Cu-SCR catalysts had a low dependency on NO2/NOx but Fe-SCR catalysts required a higher NO2/NOx ratio (>0.3) to keep a high NOx efficiency.

The tightening pollutant emission limits require the use of active aftertreatment methods for NOx and particulate matter (PM). Diesel particulate filter (DPF) is a part of commercial aftertreatment system (ATS). PM accumulated in DPF is continuously passively or periodically actively regenerated with the assistance of efficient diesel oxidation catalysts (DOC) having a high efficiency and durability in hydrocarbon (HC), NO and CO oxidation reactions. A high HC concentration during fuel feeding in active regeneration is demanding for DOC. The deactivation in air, hydrothermal, sulfation and active regeneration conditions were evaluated with platinum (Pt-) and platinum-palladium (PtPd)-DOCs by laboratory simulations using the ageing temperature and time as primary variables. The oxidizing conditions with a high oxygen concentration without HCs were deactivating DOCs clearly more than active regeneration conditions with a low oxygen and high HC concentration at 700-800°C.

The emission regulations for mobile off-road applications are following on-road trends by a short delay. The latest Stage 3B and 4 emission limits mean a gradual implementation of oxidation and SCR catalysts as well as particulate filters with off-road machines/vehicles in the 2010s. The driving conditions and test cycles differ from on-road truck applications which have been the first design base for off-road aftertreatment technologies. Aftertreatment systems for Stage 4 were first analyzed and they will include oxidation catalysts, a NOx reduction catalyst (SCR or LNT), a particulate filter and possibly units for urea hydrolysis and ammonia slip removal. The design and durability of V₂O₅/TiO₂-WO₃ catalysts based on metallic substrates were investigated by engine bench and field experiments. NOx emissions were measured with 6.6 and 8.4 liters engines designed for agricultural and industrial machinery.

The emission regulations for mobile applications will become stricter in Euro 4 - 6 levels and require the use of active aftertreatment methods (deNOx and DPF) in addition to passively operating diesel oxidation catalysts (DOC). Vanadium-SCR (V-Selective Catalytic Reduction) catalysts based on stabilized TiO₂-WO₃ raw materials and tailored preparation methods were first evaluated by the laboratory experiments. Conventional V-SCR catalysts were durable up to about 600°C but the developed catalyst stand hydrothermal ageing up to 700°C without losses of activity. Simultaneously, the performance at 250 - 450°C was about the same as with the traditional V-SCR catalyst and the SCR selectivity at 450 - 600°C was high with a low NH₃ oxidation tendency. Coated V₂O₅/TiO₂-WO₃ catalysts (ceramic and metallic substrates) were evaluated with a 4.9 L engine by engine bench experiments.

Stricter emission limitations for NOx and particulates in mobile applications will require the use of active aftertreatment methods like Diesel Particulate Filters (DPF), Selective Catalytic Reduction (SCR) with urea and Lean NOx Trap (LNT) as combinations in the 2010's. Due to the significant total space and required investments, a lot of efforts have been focused recently on the optimization of the combinatory aftertreatment systems (ATS). In this study the possibilities to intensify the catalytic ATS were analyzed and reviewed by the examples and studies with engines, laboratory reactors and simulations. The focus was on diesel applications, where the number of needed ATS units is the widest. The diesel engine modifications on SCR or EGR engines have to be also designed together with ATS. The intensification includes the principles of down-sizing and the integration of ATS units with control systems.

Diesel engines are very popular in European passenger cars and their technology has been developed to have cleaner raw emissions and lower fuel consumption. Therefore the exhaust temperatures are extremely low in urban driving conditions. The current diesel European driving cycle (EDC) and diesel catalyst ageing in different positions (Preturbo, CC and UF) were simulated successfully according to diesel light-duty exhaust gas conditions with laboratory equipment. A small mixer type EcoXcell structure was used in Preturbo position with high Pt loading to enhance in particular CO and hydrocarbon oxidations. The small metal substrated pre and larger main catalyst with active, zeolite containing washcoat were developed to decrease emissions. Both experimental and calculation simulations gave a prediction for grams per kilometer emissions for a single or combined catalyst system. The reaction and ageing rate based design can be used to optimize the diesel aftertreatment system.

The use of biofuels in internal combustion engines changes the composition of the engine exhaust gas. When burning a biofuel blend, significant amounts of oxygenated hydrocarbons such as alcohols, ethers and aldehydes are present in the exhaust gas. It is known, that these compounds influence catalytic processes in exhaust gas converters. In this work we propose a global kinetic model for ethanol and acetaldehyde oxidation on commonly used Pt, PtPd and Pd-based catalytic oxidation converters of automobile exhaust gases. The mechanism is based on two steps: (i) partial oxidation of ethanol to acetaldehyde, and (ii) complete oxidation of acetaldehyde to CO₂ and H₂O. Kinetic parameters of ethanol and acetaldehyde reactions are evaluated on the basis of laboratory light-off experiments with several catalytic monolith samples (noble metal loading 9-140 g/cft; Pt, Pd, and PtPd; at space velocity 30 000-240 000 h-₁).

To reach close to zero tailpipe NOx emissions, a double-SCR (selective catalytic reduction) system is proposed. In that, the first SCR unit would be placed upstream of the diesel particulate filter (DPF) and the second SCR unit downstream of DPF. This study focused on the experiments of the first SCR unit. The experiments were conducted utilizing a new, 4.4-liter heavy duty diesel engine that was connected to a research facility for studying after-treatment systems in controlled environment. Three different SCR’s: a vanadium-based SCR (V-SCR), a copper-based SCR (Cu-SCR) and a vanadium-based SCR including an ammonia slip catalyst (V-SCR+ASC) were studied. Studies were done at different exhaust temperatures from 215°C to 350°C. Emissions of NO, NO2, NH3, N2O, CO, CO2 and hydrocarbons were measured by FTIR. Particulate emissions (PM, PN) were studied as a part of the experiments. The results showed that the three SCR units performed differently.