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Technical Paper

Improved Sulfur Resistance of Noble Metal Catalyst for Lean-Burn Natural Gas Applications

2013-09-08
2013-24-0155
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.
Technical Paper

The Effect of a Particle Oxidation Catalyst (POC®) on Particle Emissions of a GDI Car during Transient Engine Operation

2013-04-08
2013-01-0839
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.
Technical Paper

Thermally Durable Vanadium-SCR Catalysts for Diesel Applications

2013-04-08
2013-01-1063
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.
Technical Paper

Design of Durable Vanadium - SCR Catalyst Systems for Heavy - Duty Diesel Applications

2013-01-09
2013-26-0049
The emission regulations for mobile applications become stricter in Euro-IV to Euro-VI levels. Carbon monoxide and hydrocarbon can be removed by efficient Diesel Oxidation Catalysts (DOC) but Particulate Matter (PM) and NOx are more demanding requiring the use of active methods (urea-SCR and DPF) which will be world-wide implemented in the 2010's. Durable, coated V-SCR catalysts are based on stabilized raw materials and tailored preparation methods. Coated V2O5/TiO2-WO3 catalysts (ceramic 300/400 cpsi and metallic 500/600 cpsi) were evaluated by laboratory and engine bench experiments. Traditional V-SCR catalysts are durable up to about 600°C and have a high efficiency at 300°C-500°C. SCR activities were tailored to be higher also at 200°C-300°C or 500°C-600°C. The use of thermal stabilizers or the vanadium loading variation enabled the changes in operation window and stability.
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Performance of Particle Oxidation Catalyst and Particle Formation Studies with Sulphur Containing Fuels

2012-06-18
The aim of this paper is to analyse the quantitative impact of fuel sulphur 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 sulphur, 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 sulphur 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 sulphur level. The Fuel Sulphur 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.
Technical Paper

Particle Oxidation Catalyst (POC®) - From Diesel To GDI - Studies on Particulate Number and Mass Efficiency

2012-04-16
2012-01-0845
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.
Journal Article

Performance of Particle Oxidation Catalyst and Particle Formation Studies with Sulphur Containing Fuels

2012-04-16
2012-01-0366
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.
Technical Paper

Design and Durability of Vanadium-SCR Catalyst Systems in Mobile Off-Road Applications

2011-04-12
2011-01-1316
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.
Technical Paper

Effect of Exhaust Flow Conditions and External Cooling on the Performance of the Particle Oxidation Catalyst (POC)

2010-10-25
2010-01-2158
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.
Journal Article

Effects of Biofuel Blends on Performance of Exhaust Gas Catalyst: Ethanol and Acetaldehyde Reactions

2010-04-12
2010-01-0894
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).
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