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Natural gas and biogas alone or in combination with conventional liquid fuels (dual-fuel applications) are advanced alternative solutions to diesel and gasoline in the future. Burning of natural- or biogas produces less CO2 emissions per energy unit, and particulate matter emissions can also be reduced compared to more traditional liquefied fuels. This decrease in engine out emissions can be utilized as a tool to meet tightening emission limits and to improve the air quality locally in the areas with big challenges especially related nitrogen oxide and particulate emissions. In the present study the focus was on the development of catalytic emission control technology for both mobile and stationary lean-burn natural gas applications. Main activities were related to the oxidation catalyst and its improvements towards sulfur poisoning and to enhance methane light-off performance.

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.

Particle emissions have been generally associated to diesel engines. However, spark-ignition direct injection (SI-DI) engines have been observed to produce notable amounts of particulate matter as well. The upcoming Euro 6 legislation for passenger cars (effective in 2014, stricter limit in 2017) will further limit the particulate emissions from SI engines by introducing a particle number emission (PN) limit, and it is not probable that the SI-DI engines are able to meet this limit without resorting to additional aftertreatment systems. In this study, the solid particle emissions of a SI-DI passenger car with and without an installed Particle Oxidation Catalyst (POC®) were studied over the New European Driving Cycle (NEDC) on a chassis dynamometer and over real transient acceleration situations on road. It was observed that a considerable portion of particle number emissions occurred during the transient acceleration phases of the cycle.

The aim of this paper is to analyze the quantitative impact of fuel sulfur content on particulate oxidation catalyst (POC) functionality, focusing on soot emission reduction and the ability to regenerate. Studies were conducted on fuels containing three different levels of sulfur, covering the range of 6 to 340 parts per million, for a light-duty application. The data presented in this paper provide further insights into the specific issues associated with usage of a POC with fuels of higher sulfur content. A 48-hour loading phase was performed for each fuel, during which filter smoke number, temperature and back-pressure were all observed to vary depending on the fuel sulfur level. The Fuel Sulfur Content (FSC) affected also soot particle size distributions (particle number and size) so that with FSC 6 ppm the soot particle concentration was lower than with FSC 65 and 340, both upstream and downstream of the POC.

Legislations worldwide have started imposing stringent emission standards for particulate matter (PM) emitted by diesel engines. The main reason for these actions is the adverse effects on human health caused by particle emissions. Conventional ceramic Diesel Particulate Filters (DPF) have proven exceptionally effective in reducing particulate emissions with efficiencies of 90% or more. However, these filters require regular active regenerations as well as periodical ash removal in order to avoid a blockage of the exhaust line. These procedures are both costly and complex and as a result alternative aftertreatment solutions have been developed. One of these solutions is the Particle Oxidation Catalyst, POC-X. The main aim of the POC-X is not to equal the high efficiencies of the DPF, but to achieve the best possible particle reduction without creating the risk of blocking or the need for complex filter regeneration procedures.

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.

Under on-road driving conditions, the engine load and speed and the cooling effect of ambient air may affect the functioning of exhaust aftertreatment devices. In this paper, we studied the effects of these parameters on the functioning of the combination of a Diesel Oxidation Catalyst and a Particle Oxidation Catalyst (DOC+POC). In the engine tests, the engine load and speed were observed to affect the nonvolatile particle reduction efficiency curve of the DOC+POC; while the nonvolatile core particle (Dp ≺ 15 nm) reduction was high (97-99%) in all the engine test modes, the reduction of soot varied from 57% at low load to 70% at high load. Because the change in engine load and speed affected both the exhaust temperature and flow velocity, the effects of these parameters were measured separately in an aerosol laboratory.

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).

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.

State-of-art light duty diesel vehicles and heavy duty diesel engines are utilized in studying the effect of a novel particle oxidation catalyst (POC®) on particle emission. In addition to the regulated particulate matter (PM) emission measurement, a real time mass emission and particle number size distribution measurements are utilized in testing. The results show that the particle oxidation catalyst can have a significant decreasing effect on the diesel exhaust particle emissions. For example, in light duty applications PM reductions of 55-61% were achieved over the New European Driving Cycle (NEDC) when using a POC of same size as the engine volume. The usage of a DOC in combination with the POC ensures proper regeneration of the POC substrate. The size distribution measurements revealed that the particle number collection efficiency for smaller particles i.e. the nanoparticles was very high, being close to 100 %.

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.

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.