Catalytic aftertreatment of particulate matter

Science and Technology of Advanced Materials, 2007

The European diesel engine industry represents a vital sector across the Continent, with more than 2 million direct work positions and a turnover of over 400 billion Euro. Diesel engines provide large paybacks to society since they are extensively used to transport goods, services and people. In recent years increasing attention has been paid to the emissions from diesel engines which, like gasoline engine emissions, include carbon monoxide (CO), hydrocarbons (HC) and oxides of nitrogen (NO x ). Diesel engines also produce significant levels of particulate matter (PM), which consists mostly of carbonaceous soot and a soluble organic fraction (SOF) of hydrocarbons that have condensed on the soot.

Advanced exhaust after-treatment technology is required for heavy-duty diesel vehicles to achieve stringent Euro VI emission standards. Diesel particulate filter (DPF) is the most efficient system that is used to trap the particulate matter (PM), and particulate number (PN) emissions form diesel engines. The after-treatment system used in this study is catalyzed DPF (CDPF) downstream of diesel oxidation catalyst (DOC) with secondary fuel injection. Additional fuel is injected upstream of DOC to enhance exothermal heat which is needed to raise the CDPF temperature during the active regeneration process.

2005

In this paper a brief overview about diesel emissions and those environmental and health effects are presented. Strategies to control diesel emissions, including engine adjustment, fuel reformulation, and exhaust after-treatment systems are briefly discussed with emphasis on catalytic diesel soot abatement technologies. Types of catalysts reported in literature in the last decades are reviewed. Challenging topics in catalysis of diesel soot oxidation conclude this paper.

Emission Control Science and Technology, 2014

The investigation of the distribution of particulate matter (PM) inside a catalyzed particulate filter (CPF) is studied in this work. The goal was to identify how loading, passive oxidation, active regeneration, and post loading conditions affect the PM distribution. The PM distribution was measured using an Advantest TAS7000 3D Imaging Analysis System, which nondestructively measures the PM distribution. A total of nine experiments were conducted, resulting in three loading scans, four passive oxidation scans, four active regeneration scans, and two post loading scans. The loading experiments were run with two different target PM loadings of 3 and 5 g/L. The passive oxidation experiments were run under two different engine conditions, and four different amounts of PM were oxidized. The active regeneration experiments were run at two target temperatures of 525 and 600°C, and four levels of PM were oxidized. One post loading experiment was completed after a passive oxidation, and one was completed after an active regeneration. The results show that the PM distribution after loading is similar to the model-predicted PM distribution, which is calculated using the wall flow velocity distribution. The amount of PM in the substrate affects the axial distribution uniformity. The amount of PM passively oxidized or actively regenerated affects the axial distribution uniformity as well. The effect of post loading is dependent on whether the PM was passively oxidized or actively regenerated. Passive oxidation Active regeneration O 2 -assisted PM oxidation Post loading PM loading that occurs after a passive oxidation or active regeneration EOC Engine operating condition

Progress in Energy and Combustion Science, 1997

Catalytic exhaust aftertreatment of vehicle engines is increasingly employed to the benefit of the atmosphere quality, especially in the large urban area of the world. Both spark-ignition and compressionignition engines benefit from the application of catalytic converters for the elimination of their main pollutants. Catalysts are further employed in various forms as regeneration aids in particulate filters of diesel engines. The especially demanding exhaust gas conditions prevailing in each engine application pose challenging problems to the emissions control engineer. The attainment of strict emissions regulations requires highly active and durable catalysts, as well as optimized exhaust system design and engine controls. This paper reviews the potential of catalytic systems in automobile emission control. The review covers the catalyst technology applicable in each case, the operating principles and performance characteristics, durability aspects and considerations regarding the interactions between catalyst performance and engine management. The concise presentation of related mathematical model equations provides insight into the catalytic mechanisms and the physical phenomena involved. Further reductions of catalytically controlled automobile emissions may be attained by developing improved and more durable catalysts, by applying a systems approach in designing optimized engine-exhaust aftertreatment configurations, as well as by efficient control of in-use catalytic systems through inspection, maintenance and on-board diagnostics.

Applied Catalysis A: General, 2016

Highlights • Soot oxidation catalysts exhibit oxidising species with high mobility • Soot oxidation catalysts are dynamic entities • Multifunctional traps for diesel particulate abatement are highly complex systems • The multiscale nature of DPFs lends itself to a models hierarchical organization

Powder Technology, 2008

The next 2008 European legislation on diesel engines will impose the use of specific traps, placed in the car exhaust line, so as to meet very stringent particulate emission limits (0.005 g/km). This paper provides a survey of the status of advancement of R&D in the field of diesel particulate traps for both passenger cars and heavy-duty vehicles. Special emphasis is given to the combined use of traps and catalysts for trap regeneration purposes via catalytic combustion of the collected soot. Issues like trap materials selection (cordierite, SiC, Al 2 O 3 fibers), catalyst development (fuel additives, catalyst coatings, …), catalytic vs. non-catalytic trap performance are addressed, providing a critical analysis on the techno-economical feasibility of the systems currently being developed by several car-components and catalyst manufacturers. Specific highlights of the research in progress at Politecnico di Torino in the framework of several European projects (CATATRAP, ART-DEXA and SYLOC-DEXA) will also be provided.

Industrial & Engineering Chemistry Research, 1999

Initiation of the regeneration of porous ceramic diesel particulate filters at low exhaust gas temperatures and the subsequent control of the soot oxidation rate is necessary in order to allow a wide applicability of filter systems in diesel-powered vehicles. The use of catalysts in this respect, in particular catalytic fuel additives, has been proven to be successful, leading to a minimization of the system's cost and additional fuel consumption. Better understanding and modeling of the catalytic activity at low temperatures necessitates that one takes into account the oxidation not only of dry particulate but also of the volatile hydrocarbons adsorbed on the particulate. In this paper, the oxidation of the hydrocarbons adsorbed on the particulate is modeled, to allow a better understanding of the filter regeneration behavior at very low temperatures (150-300°C). A simplified reaction scheme and tunable kinetics are employed in the description of adsorbed hydrocarbon oxidation. The mechanism is incorporated in an existing mathematical model, and specific computational case studies are invoked to explain and to model regeneration at low temperatures. The results compare well with experimental evidence and indicate certain directions for further research to better understand this complex process which is essential to the successful application of diesel particulate filters.

Industrial & Engineering Chemistry Research, 1997

The diesel particulate filter (DPF) technology with the use of fuel additives as regeneration aids is a promising technology for modern and future low-emissions diesel engines. The development of efficient and reliable DPF systems requires understanding of the regeneration process. Although the role of mathematical models in this respect has been widely recognized, few attempts to model the fuel-additive-assisted regeneration have been presented. In this work, a previously developed simplified authors' model is extended, to allow deeper investigation of the process. The 1D mathematical model of the catalytic regeneration in the channel of the particulate filter is based on a dynamic oxygen storage/release mechanism of additive action, coupled to the transport phenomena occurring in the filter. A previously published set of fullscale measurements is employed to validate the model in a wide range of possible regeneration modes. The advantages of the present 1D model over the previous 0D model are illustrated. It is concluded that, at the present stage, the model can sufficiently describe and explain the main features of the regeneration process. The minor deviations of the model results from reality are attributed to the uncertainties of the reaction kinetics and to nonuniformities regarding flow distribution and soot deposition. The possible explanations are discussed, and directions for future work are suggested. IE970095M X Abstract published in Advance ACS Abstracts, August 15, 1997.

Environment Protection Engineering, 2006

European standards for diesel particulate matter (DPM) emission impose a ban on further use of old-type diesel engines in Poland and other new member countries of European Union. This particularly refers to engines installed in city buses. Based on the well-known theory that diesel soot particulates have the ability to coagulate and aggregate, we propose a simple and cost-effective method of DPM-emission control. We show the results of successful full-scale tests on DPM emission control system in city buses equipped with old-type diesel engines. DPM emitted from diesel engines is collected on a ceramic filter instead of using a conventional exhaust silencer. A simple automatic regeneration system provides complete combustion of the collected material within 0.5-1 minute. Such a design complies with relevant standards and eliminates potential health implications.