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Future emissions regulations proposed for the Asian automotive industry (BS VI regulations for India and NS VI regulations for China) are strict and similar to EU VI regulations. As a result, they will require both advanced NOx control as well as advanced Particulate Matter (PM) control. This will drive implementation of full Catalyzed Diesel Particulate Filter (cDPF) and simultaneous NOx control using Selective Catalytic Reduction (SCR) technologies. In this work, we present the performance of various Diesel Oxidation Catalyst (DOC), cDPF, SCR and Ammonia slip catalyst (ASC) systems utilizing the World Harmonized Transient Cycle (WHTC). Aftertreatment Systems (ATS) required for both active and passive filter regeneration applications will be discussed. The sensitivity of key design parameters like catalyst technology, PGM loading, catalyst sizing to meet the regulation limits has been investigated.

For diesel emission control technologies, reduction efficiencies of Particulate Matter (PM) control systems have been traditionally reported based on mass-based criteria. However, particle number-based criteria are now receiving increased attention. In this paper, results of real-time particle size distribution and number based evaluation of the effectiveness of multiple PM control technologies are reported on an HDD engine. An Engine Exhaust Particle Sizer (EEPS) was used for comparative analysis. The technologies that were evaluated included diesel oxidation catalysts (DOC), a DOC with an uncatalyzed wall-flow filter as a continuously regenerating diesel particulate filter (CR-DPF) system, a DOC with a catalytically coated wall-flow filter as a catalyzed CR-DPF (CCR-DPF), and a DOC with a partial filter as a continuously regenerating partial filter (CR-PF).

Selective Catalytic Reduction (SCR) systems have been demonstrated as effective solutions for controlling NOx emissions from Heavy Duty diesel engines. Future HD diesel engines are being designed for higher engine out NOx to improve fuel economy, which will require increasingly higher NOx conversion to meet emission regulations. For future aftertreatment designs, advanced technologies such as SCR coated on filter (SCRF®) and SCR coated on high porous flow through substrates can be utilized to achieve high NOx conversion. In this work, different options were evaluated for achieving high NOx conversion. First, high performance NOx control catalysts were designed by using SCRF unit followed by additional SCR on high porosity substrates. Second, different control strategies were evaluated to understand the effect of reductant dosing strategy and thermal management on NOx conversion. Tests were carried out on a HD engine under transient test cycles.

Selective Catalytic Reduction (SCR) catalysts have been demonstrated as an effective solution for controlling NOx emissions from diesel engines. There is a drive to reduce the overall packaging volume of the aftertreatment system for these applications. In addition, more active SCR catalysts will be needed as the applications become more challenging: e.g. lower temperatures and higher engine out NOx, for fuel consumption improvements. One approach to meet the challenges of reduced volume and/or higher NOx reduction is to increase the active site density of the SCR catalyst by coating higher amount of SCR catalyst on high porosity substrates (HPS). This approach could enable the reduction of the overall packaging volume while maintaining similar NOx conversion as compared to 2010/2013 systems, or improve the NOx reduction performance for equivalent volume and NH3 slip.

Selective Catalytic Reduction (SCR) technology has been widely studied for removal of NOX from the exhaust of diesel engines. To design and optimize diesel engine aftertreatment systems including an SCR catalyst component, a reliable SCR model is a very useful tool, to aid in system integration and control algorithm testing. In this paper, the development of a one-dimensional numerical model for a Fe-Zeolite-based SCR catalyst (hydrothermally aged for 100 hours at 650°C in 10% H₂O in air) is presented, followed by its validation and application. The resulting model is capable of predicting NOX reduction efficiency under various operating conditions as a function of gas hourly space velocity (SV), temperature, NO₂/NOX ratio and NH₃ to NOX (ANR) ratios; NH₃ slip and N₂O formation are also correctly predicted by the model. Extensive validation of the model has been carried out against engine test data for both steady state light-off and the heavy-duty FTP transient cycle (HD-FTP).

The next generation advanced emission regulations have been proposed for the Indian heavy duty automotive industry for implementation from 2020. These BS VI emission regulations will require both advanced NOx control as well as advanced PM (Particulate Matter) control along with Particle Number limitations. This will require implementation of full DPF (Diesel Particulate Filter) and simultaneous NOx control using SCR technologies. DPF technologies have already been successfully implemented in Euro VI and US 10 HDD systems. These systems use low temperature NO2 based passive DPF regeneration as well as high temperature oxygen based active DPF regeneration. Effective DPF and DOC designs are essential to enable successful DPF regeneration (minimize soot loading in the DPF) while operating HDD vehicles under transient conditions. DOC designs are optimized to oxidize engine out NO into NO2, which helps with passive DPF regeneration.

This paper will review several different emission control systems for heavy duty diesel (HDD) applications aimed at future legislations. The focus will be on the (DOC+CSF+SCR+ASC) configuration. As of today, various SCR technologies are used on commercial vehicles around the globe. Moving beyond EuroVI/US10 emission levels, both fuel consumption savings and higher catalyst system efficiency are required. Therefore, significant system optimization has to be considered. Examples of this include: catalyst development, optimized thermal management, advanced urea dosing calibrations, and optimized SCR inlet NO:NO2 ratios. The aim of this paper is to provide a thorough system screening using a range of advanced SCR technologies, where the pros and cons from a system perspective will be discussed. Further optimization of selected systems will also be reviewed. The results suggest that current legislation requirements can be met for all SCR catalysts under investigation.

In recent years, ammonia slip catalysts (ASC) are being used downstream of an SCR system to minimize the ammonia slip. The dual-layer ASC is more attractive for its bi-functionality in reducing the ammonia and NOX emissions. It consists of two layers with the upper layer comprising a component with SCR functionality and the lower layer a PGM containing catalyst with oxidation functionality. Thus, both oxidation and SCR reactions take place in two different layers and are interlinked by the inter-layer mass transfer mechanism. In addition, adsorption and desorption kinetics between the gas and solid phases play a significant role. Mathematically, the overall system is a complex system of mass, momentum and energy transfer equations with temporal and spatial variables in both axial and radial directions. In this work, we focus on devising a suitable, computationally inexpensive model for such ASCs to be efficiently used for design, control and system optimization studies.

The use of vanadia selective catalytic reduction (V-SCR) catalysts for NOX reduction from diesel engine exhaust is well known. These catalysts are also active for hydrocarbon (HC) and particulate matter (PM) oxidation. This dual functionality (oxidation and reduction) of V-SCR catalysts can help certain applications achieve the legislative limits with an improved margin. In this work, NOX reduction, HC and CO oxidation over V-SCR were studied independently and simultaneously in microreactor tests. The effect of various parameters (HC speciation, concentration, ANR, and NO₂/NOX ratio) was investigated and the data was used to develop a kinetic model. Oxidation of CO, C₃H₆, and n-C₁₀H₂₂ is first order in CO/HC, while C₇H₈ oxidation is less than first order in C₇H₈. All these reactions were zero order in O₂. Oxidation activity decreased in order: C₇H₈ ≻ n-C₁₀H₂₂ ≻ C₃H₆ ≻ CO. HC oxidation was inhibited by NH₃.