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Journal Article

Volume Reduction of SCR Catalyst Using Zeolite-Base Honeycomb Substrate

2010-04-12
2010-01-1170
The method of converting NOx with urea SCR is an effective solution for complying with the stringent NOx emission legislations of the future, particularly in the case of heavy duty diesel vehicles. In order to broaden the freedom of SCR catalyst design and volume design, a honeycomb structure formed with metal ion exchanged zeolite (NCH: New Concept Honeycomb) and for comparison a wash-coat type structure (conventional catalyst) were prepared. The possible range of catalyst volume reduction in NCH was investigated by comparative measurement of NH₃ adsorption distribution, consumption behavior of adsorbed NH₃ within the structures, and of space velocity and NO₂/NOx dependence of NOx conversion efficiency. In addition, from NEDC evaluation in an engine bench, it was found that combining urea injection logic suitable for NCH results in equal or higher NOx conversion efficiency and NH₃ slip characteristics with only 1/2 the volume of conventional catalyst structure.
Journal Article

Catalytic Soot Oxidation: Effect of Ceria-Zirconia Catalyst Particle Size

2016-04-05
2016-01-0968
Catalysts that have been extensively investigated for direct soot oxidation in Catalyzed Diesel Particulate Filters (CDPFs) are very often based on mixed oxides of ceria with zirconia, materials known to assist soot oxidation by providing oxygen to the soot through an oxidation-reduction catalytic cycle. Besides the catalyst composition that significantly affects soot oxidation, other parameters such as morphological characteristics of the catalyst largely determined by the synthesis technique followed, as well as the reagents used in the synthesis may also contribute to the activity of the catalysts. In the present work, two ceria-zirconia catalyst samples with different zirconia content were subjected to different milling protocols with the aim to shift the catalyst particle size distribution to lower values. The produced catalysts were then evaluated with respect to their soot oxidation activity following established protocols from previous works.
Journal Article

Catalytic Nano-structured Materials for Next Generation Diesel Particulate Filters

2008-04-14
2008-01-0417
The increasing need for controlled diesel engine emissions and the strict regulations in the abatement of diesel exhaust products lead to an ever increasing use of Diesel Particulate Filters (DPFs) in OEM applications. The periodic regeneration of DPFs (oxidation of soot particles) demands temperatures that rarely appear during engine operation. It is therefore necessary to employ direct or indirect catalytic measures. In the present work, the development and synthesis via aerosol-based routes, of nanostructured base metal oxides for direct soot oxidation, along with their characterization and their evaluation in engine exhaust is described. The synthesized powders were characterized with respect to their phase composition and morphology. XRD, SEM and TEM analysis have shown the nanostructured character of the powders, while Raman spectroscopy was employed for the preliminary characterization of the materials surface chemistry.
Journal Article

Performance Assessment of a Multi-Functional Reactor Under Conventional and Advanced Combustion Diesel Engine Exhaust Conditions

2011-04-12
2011-01-0606
Current progress in the development of diesel engines substantially contributes to the reduction of NOx and Particulate Matter (PM) emissions but will not succeed to eliminate the application of Diesel Particulate Filters (DPFs) in the future. In the past we have introduced a Multi-Functional Reactor (MFR) prototype, suitable for the abatement of the gaseous and PM emissions of the Low Temperature Combustion (LTC) engine operation. In this work the performance of MFR prototypes under both conventional and advanced combustion engine operating conditions is presented. The effect of the MFR on the fuel penalty associated to the filter regeneration is assessed via simulation. Special focus is placed on presenting the performance assessment in combination with the existing differences in the morphology and reactivity of the soot particles between the different modes of diesel engine operation (conventional and advanced). The effect of aging on the MFR performance is also presented.
Journal Article

Experimental Study of Thermal Aging on Catalytic Diesel Particulate Filter Performance

2013-04-08
2013-01-0524
In this paper, a methodology is presented to study the influence of thermal aging on catalytic DPF performance using small scale coated filter samples and side-stream reactor technology. Different mixed oxide catalytic coating families are examined under realistic engine exhaust conditions and under fresh and thermally aged state. This methodology involves the determination of filter physical (flow resistance under clean and soot loaded conditions and filtration efficiency) and chemical properties (reactivity of catalytic coating towards direct soot oxidation). Thermal aging led to sintering of catalytic nanoparticles and to changes in the structure of the catalytic layer affecting negatively the filter wall permeability, the clean filtration efficiency and the pressure drop behavior during soot loading. It also affected negatively the catalytic soot oxidation activity of the catalyzed samples.
Technical Paper

Fundamental Study and Possible Application of New Concept Honeycomb Substrate for Emission Control

2007-04-16
2007-01-0658
To meet the legislation of future diesel emission level, high-performance catalysts are desired. One of the key technologies to realize the catalyst is to highly disperse the precious metal on the catalytic support with high specific surface area. The catalytic support with high specific surface area is directly extruded in honeycomb configuration (New honeycomb substrate) and, as a result, the amount of catalytic support and the surface area reached to around factor of two compared with the conventional catalytic support.
Technical Paper

Study on Catalyzed-DPF for Improving the Continuous Regeneration Performance and Fuel Economy

2007-04-16
2007-01-0919
It is a big challenge how to satisfy both the purification of exhaust gas and the decrease of fuel penalty, that is, carbon-dioxide emission. Regarding the Diesel Particulate Filter (DPF) applied in the diesel after-treatment system, it must be effective for lowering the fuel penalty to prolong the interval and reduce the frequency of the DPF regeneration operation. This can be achieved by a DPF that has high Particulate Matter (PM) mass limit and high PM oxidation performance that is enough to regenerate the DPF continuously during the normal running operation. In this study, the examination of the pore structure of the wall of a DPF that could expand the continuous regeneration region in the engine operation map was carried out. Several porous materials with a wide range of pore structure were prepared and coated with a Mixed Oxide Catalyst (MOC). The continuous regeneration performance was evaluated under realistic conditions in the exhaust of a diesel engine.
Technical Paper

Wall-scale Reaction Models in Diesel Particulate Filters

2007-04-16
2007-01-1130
Following the successful market introduction of diesel particulate filters (DPFs), this class of emission control devices is expanding to include additional functionalities such as gas species oxidation (such as CO, HC and NO), storage phenomena (such as NOx and NH3 storage) to the extent that we should today refer not to DPFs but to Multifunctional Reactor Separators. This trend poses many challenges for the modeling of such systems since the complexity of the coupled reaction and transport phenomena makes any direct general numerical approach to require unacceptably high computing times. These multi-functionalities are urgently needed to be incorporated into system level emission control simulation tools in a robust and computationally efficient manner. In the present paper we discuss a new framework and its application for the computationally efficient implementation of such phenomena.
Technical Paper

Soot Oxidation Kinetics in Diesel Particulate Filters

2007-04-16
2007-01-1129
Direct catalytic soot oxidation is expected to become an important component of future diesel particulate emission control systems. The development of advanced Catalytic Diesel Particulate Filters (CDPFs relies on the interplay of chemistry and geometry in order to enhance soot-catalyst proximity. An extensive set of well-controlled experiments has been performed to provide direct catalytic soot oxidation rates in CDPFs employing small-scale side-stream sample exposure. The experiments are analyzed with a state-of-the-art diesel particulate filter simulator and a set of kinetic parameters are derived for direct catalytic soot oxidation by fuel-borne catalysts as well as by catalytic coatings. The influence of soot-catalyst proximity, on catalytic soot oxidation is found to be excellently described by the so-called Two-Layer model, developed previously by the authors.
Technical Paper

Advanced Catalyst Coatings for Diesel Particulate Filters

2008-04-14
2008-01-0483
Novel catalytic coatings with a variety of methods based on conventional and novel synthesis routes are developed for Diesel Particulate Filters (DPFs). The developed catalytic composition exhibits significant direct soot oxidation as evaluated by reacting mixtures of diesel soot and catalyst powders in a thermogravimetric analysis apparatus (TGA). The catalyst composition was further deposited on oxide and non-oxide porous filter structures that were evaluated on an engine bench with respect to their filtration efficiency, pressure drop behavior and direct soot oxidation activity under realistic conditions. The effect of the catalyst amount on the filtration efficiency of non-oxide filters was also investigated. Evaluation of the indirect soot oxidation was conducted on non-oxide catalytic filters coated with precious metal.
Technical Paper

Advanced High Porosity Ceramic Honeycomb Wall Flow Filters

2008-04-14
2008-01-0623
A new platform of advanced ceramic composite filter materials for diesel particulate matter and exhaust gas emission control has been developed. These materials exhibit high porosity, narrow pore-size distribution, robust thermo-mechanical strength, and are extruded into high cell density honeycomb structures for wall-flow filter applications. These new high porosity filters provide a structured filtration surface area and a highly connected wall pore space which is fully accessible for multi-phase catalytic reactions. The cross-linked microstructure (CLM™) pore architecture provides a large surface area to host high washcoat/catalyst loadings, such as those required for advanced multi-functional catalysts (4-way converter applications).
Technical Paper

Improving of the Filtration and Regeneration Performance by the Sic-DPF with the Layer Coating of PM Oxidation Catalyst

2008-04-14
2008-01-0621
DPF has become widely known as an indispensable after-treatment component for the purification of the particulate matter in the diesel exhaust gas. But, in order to correspond to further regulation strengthening such as carbon dioxide emission regulation and number-based particulate matter emission regulation, it must be necessary also for DPF to keep improving its performance. In this study, it was examined how to improve both the filtration efficiency and the oxidation efficiency of PM regarding the catalyzed DPF. SiC-made 10mil/300cpsi-OctoSquare asymmetric cell structure was chosen for the DPF substrate and PM oxidation catalyst was coated on the surface of the filter wall as a layer with the device of the coating method. As a result, it was found that the layer coated DPF has advantage on the filtration efficiency without soot accumulation and efficiency was similar to an uncoated one with 0.1 g/l soot loading.
Technical Paper

Multi-Functional Reactor for Emission Reduction of Future Diesel Engine Exhaust

2009-04-20
2009-01-0287
Future diesel emission control systems have to effectively operate under non-conventional low-temperature combustion engine operating conditions. In this work the research and development efforts for the realization of a Multi-Functional catalyst Reactor (MFR) for the exhaust of the upcoming diesel engines is presented. This work is based on recent advances in catalytic nano-structured materials synthesis and coating techniques. Different catalytic functionalities have been carefully distributed in the filter substrate microstructure for maximizing the direct and indirect (NO2-assisted) soot oxidation rate, the HC and CO conversion efficiency as well as the filtration efficiency. Moreover, a novel filter design has been applied to enable internal heat recovery capability by the implementation of heat exchange between the outlet and the inlet to the filter flow paths.
Technical Paper

Ash Storage Capacity Enhancement of Diesel Particulate Filter

2004-03-08
2004-01-0949
The life of DPF would be decided by ash durability because pressure loss of DPF is increased by accumulation of ash that is produced when soot is burnt in the DPF. We could succeed to increase maximum ash capacity and extend the life of the DPF by an approach from the filter design, making inlet cell volume larger than outlet cell. Furthermore, when the inlet cell is designed octagon, we found that slanted wall blocking the inlet cells is functional worked for soot filtration. As the results, we could improve to manage both transient pressure loss while the soot is collected and the ash durability by the cell shape with (inlet cell/outlet cell) = (octagon/square).
Technical Paper

Effect of SiC-DPF with High Cell Density for Pressure Loss and Regeneration

2001-03-05
2001-01-0191
One technology for removing PM discharged from diesel-powered vehicles is the DPF system. The DPF system brings about increases in pressure loss because PM accumulates in the filter. DPF with a high cell density shows low pressure loss when PM accumulates because of the large filtration area, and in addition, it makes it possible to thin the cell wall because it has a high thermal diffusion ability. For the catalyzation of SiC, the pore size and porosity of the base material were changed. Even when a catalyst is borne, pressure loss which DPF changed pore structure hardly changes. This verification was done based on the theory and by means of experimentation.
Technical Paper

Characterization of High Porosity SiC-DPF

2002-03-04
2002-01-0325
The pore diameter and porosity of SiC-DPF has been increased by elaborating its porous structure. Increasing the porosity of DPF decreases its strength and thermal conductivity. It was clarified how these characteristics affect the performance such as filtration characteristics, low pressure loss, maximum soot loading limit, and thermal response characteristics required for DPF. It was found that the basic characteristics of SiC such as high strength and high thermal conductivity play an important role in its high porosity.
Technical Paper

Characterization of Thin Wall SiC-DPF

2003-03-03
2003-01-0377
We examined a filter structure of a SiC-DPF, and found that the reduction in a wall thickness is effective in decreasing a pressure loss. And we made it clear how this reduction in the wall thickness influences the performances of the DPF, that are the filtration efficiency and the accumulated soot mass limit which are important for the DPF. From the results of this study, it can be seen that the filter structure which is suitable for the catalyzed DPF should be controlled in a porosity and the wall thickness in proportion to an amount of catalyst required.
Technical Paper

The Micromechanics of Catalytic Soot Oxidation in Diesel Particulate Filters

2012-04-16
2012-01-1288
Despite the great effort devoted to the modeling of the operation of catalytic DPFs, even today very simple expressions are used for the soot oxidation rate. In the relevant to DPF operation case of a gas phase rich in oxygen, the structure of the soot-catalyst geometry and its evolution during oxidation determines the reaction rate. An extensive set of controlled experiments (isothermal or with linear temperature increase) using fuel borne catalysts and catalytic coatings has been performed in order to obtain corresponding soot oxidation rate-conversion curves. The shape of the resulting curves cannot be described by the typical theories for solid phase reactions posing the need for microstructural models for the micromechanics of soot catalyst interactions.
Technical Paper

Catalytic Filter Systems with Direct and Indirect Soot Oxidation Activity

2005-04-11
2005-01-0670
Diesel Particulate Filters (DPFs) need to be periodically regenerated in order to achieve efficient and safe vehicle operation. Under typical diesel exhaust conditions, this invariably requires the raising of the exhaust gas temperature by active means, up to the point that particulate (soot) oxidation can be self-sustained in the filter. In the present work the development path of an advanced catalytic filter technology is presented. Full scale optimized Catalytic Diesel Particulate Filters (CDPFs) are tested in the exhaust of a light-duty modern diesel engine in line with a Diesel Oxidation Catalyst (DOC). The management of the DOC-CDPF emission control system is facilitated by a virtual soot sensor in order to ensure energy-efficient operation of the emission control system.
Technical Paper

Performance Evaluation of SiC-DPF Sintered with Sintering Additive

2005-04-11
2005-01-0579
SiC is well known as a ceramic with high mechanical strength and thermal conductivity, and the R-SiC-DPF (recrystallized SiC-DPF) used these excellent properties is widely recognized as the substrate material for DPF. DPF system requires the material possessing high thermal shock resistance against an unexpected accident, such as an uncontrolled regeneration. One of the indices indicating the thermal shock resistance of the DPF is soot mass limit, which is an important factor determining the penalty of vehicle fuel consumption. In order to further increase the soot mass limits of R-SiC-DPF, this paper covers the attempts of IBIDEN to promote the sintering of the neck part of a SiC porous body using a sintering additive. Al2O3, well known as a sintering additive for a SiC dense body, was selected as the sintering additive.
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