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Analysis and Modeling of NOx Reduction Based on the Reactivity of Cu Active Sites and Brønsted Acid Sites in a Cu-Chabazite SCR Catalyst

Waseda Univ-Yoshihisa Tsukamoto, TAKAO FUKUMA, Jin Kusaka
  • Technical Paper
  • 2019-24-0150
To be published on 2019-09-09 by SAE International in United States
In this study, the NOx purification reactivity of a Cu-chabazite SCR catalyst was analyzed over a wide temperature range based on the NH3-SCR mechanism considering Cu redox reactions and reactions on a Brønsted acid site. It was revealed that the De-NOx reactions on the active site of Cu proceeded in different paths at lower and higher temperatures. This means that the rate-limiting step of SCR reactions was changed as each temperature. The reaction rate of NOx purification on a Cu site less than 200 °C was determined by the reaction rate of oxidation of Cu sites. On the other hand, the NH3 adsorption on Cu sites played a dominant role in NOx purification at temperature range higher than 300°C. Moreover, it was also observed that the Cu reaction site took different states at low and high temperatures during the NOx purification and was estimated that the valence state of a Cu site was changed as the temperature increased. In order to analyze the reaction on a Brønsted acid site of chabazite structure, analysis using an…
 

Analysis of the Emission Conversion Performance of Gasoline Particulate Filters Over Lifetime

Corning GmbH-Dominik Rose, Thorsten Boger
FEV Europe GmbH-Christof Schernus, Michael Görgen, Jim Cox, Martin Nijs, Johannes Scharf
  • Technical Paper
  • 2019-24-0156
To be published on 2019-09-09 by SAE International in United States
Gasoline particulate filters (GPF) recently entered the market, and are already regarded a state-of-the-art solution for gasoline exhaust aftertreatment systems to enable EU6d-TEMP fulfilment and beyond. Due to their rapid market introduction, extensive field experience with GPFs is not yet available. Especially for four-way catalytic converters, the prognosis of the emission conversion performance over lifetime poses an ambitious challenge, which significantly influences future catalyst diagnosis calibrations. In the first part of the paper, experimental GPF ash loading results are presented. Since most of the ash accumulated in the filter results from the combustion of lubricating oil additives, a burner test bench with a purpose-designed oil injection system was chosen for the investigations. The analysis of the backpressure results show that, contrary to high soot loadings, the ash load has a relatively low impact on engine performance and fuel consumption. Regarding the filtration efficiency over time, there is discrepancy between the results obtained during a “COP” (conformity of production) test and the measured values after a run-in mileage of 3,000 km that is required for the…
 

Analysis of TWC Operation Characteristics in a Euro6 Gasoline Light Duty Vehicle

Aristotle University Thessaloniki-Grigorios Koltsakis
Empa-Viola Papetti, Panayotis Dimopoulos Eggenschwiler
  • Technical Paper
  • 2019-24-0162
To be published on 2019-09-09 by SAE International in United States
A Euro6 gasoline light duty vehicle has been tested at the engine dynamometer and the emissions have been analyzed upstream and downstream the Three-Way-Catalyst (TWC) during the WLTP cycle. Catalyst simulations have been used for assessing the processes inside the catalytic converter using a reaction scheme based on 19 brutto reactions (Direct oxidation and reduction, selective catalytic re-ductions with CO, C3H6 and H2, steam reforming, water-gas shift and bulk Ceria as well as surface Ce-ria reactions). The reactions have been parametrized in order to best approximate the measurements. Based on the reactions taken into account, the real vehicle emissions can be predicted with good accu-racy. The simulations show that the cycle emissions are comprising mainly by the cold start contribution as well as discrete emission break-through events during transients. During cold start no reactions are evident in the catalyst before the temperature of the gas entering the catalyst reaches 270°C. Following the light-off, prevailing reactions are direct oxidation for CO and direct oxidation as well as surface ceria reactions for THC. NO reduction during cold…
 

Development of a dedicated CNG three-way catalyst model in 1-D simulation platforms

FPT Industrial SpA-Stefano Golini, Francesco Giovanni Rutigliano
Istituto Motori CNR-Carlo Beatrice, Valentina Fraioli
  • Technical Paper
  • 2019-24-0074
To be published on 2019-09-09 by SAE International in United States
A growing interest in heavy-duty engines powered with CNG dictated by stringent regulations in terms of emissions, has made it essential to study a specific Three-Way Catalyst (TWC). Oxygen storage phenomena characterize catalytic converter efficiency under real world driving operating conditions and, consequently, during strong dynamics in Air-to-Fuel (A/F) ratio. A numerical “quasi-steady” model has been set-up to simulate the chemical process inside the reactor. A dedicated experimental campaign has been performed in order to evaluate the catalyst response to a defined lambda variation pattern of the engine exhaust stream, thus providing the data necessary for the numerical model validation. In fact, goal of the present research activity was to investigate the effect of very fast composition transitions of the engine exhaust typical of the mentioned driving conditions (including fuel cutoffs etc.) on the catalyst performance and on related emissions at the tailpipe. A surface reactions kinetic mechanism, concerning CH4, CO, H2 oxidation and NO reduction, has been appropriately calibrated with a step-by-step procedure in steady-state in the engine work plan at different A/F ratios…
 

Exhaust Purification Performance Enhancement by Early Activation of Three Way Catalysts for Gasoline Engines Used in Hybrid Electric Vehicles

NE Chemcat Corporation-Makoto Nagata
Waseda Univesity-Toshinori Okajima, Ryota Sone, Xieyang Yan, Ryoya Inoue, Suchitra Sivakumar, Hajime Shingyouchi, Jin Kusaka, Kyohei Yamaguchi
  • Technical Paper
  • 2019-24-0148
To be published on 2019-09-09 by SAE International in United States
Three-way catalyst (TWC) converters are used to purify the toxic substances such as carbon monoxide (CO), nitrogen oxides (NOx), and hydrocarbons (HC) emitted from gasoline engines. However, a large amount of emissions could be emitted before the TWC reaching its light-off temperature during cold start. For hybrid electric vehicles (HEVs) powered by gasoline engines, the emission purification performance by TWC unfortunately become worse caused by mode switching from engine to battery and vice versa, which is possible to generate cold start conditions over and over for TWC In this study, targeting at reducing the emissions from series HEVs by early activation of TWC, numerical simulations with experiments are carried out. A HEV is tested on a chassis dynamometer under Worldwide Light-duty Test Cycle (WLTC) mode; the upstream and downstream gas conditions of the close-coupled catalyst converter are measured. A test piece is taken from the same catalyst and used in model gas experiments for deciding chemical reaction scheme and each corresponding reaction rate parameter. A 1-D numerical simulation TWC model, which includes 13 chemical species…
 

A New Take on Porous Medium Approach for Modelling Monoliths and Other Multiple Channel Devices

Coventry University-Gianluca Padula, Jonathan Saul, Svetlana Aleksandrova, Humberto Medina, Stephen Benjamin
  • Technical Paper
  • 2019-24-0049
To be published on 2019-09-09 by SAE International in United States
Porous medium approach is widely used in modelling high resistance devices such as heat exchangers, automotive catalysts or filters, where details of flow distribution inside the channels are not important. This reduces the computational time considerably, as the whole length of the monolith does not need to be modelled, and the thin boundary layers in each channel do not need to be resolved. The drawback of the approach is compromised accuracy of the flow predictions downstream of the monolith, because the mixing of the individual jets coming out of the monolith channels is not accounted for. Very few studies exist where this issue has been addressed. The methods include artificial turbulence generation, inferring turbulence information from upstream, or using hybrid modelling approach to separate the flow into channels. In this study, a different technique is suggested, where the porous medium model is used simultaneously for imposing the axial flow resistance presented by the monolith, and forming the multiple jet flow downstream of the monolith. The results for a planar diffuser with a catalyst are compared…
 
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Graphene Lid Extends Photoemission Electron Microscopy to Liquids

  • Magazine Article
  • TBMG-34753
Published 2019-07-01 by Tech Briefs Media Group in United States

By capping liquids with graphene (an ultrathin sheet of pure carbon), researchers can easily image and analyze liquid interfaces and the surface of nanometer-scale objects immersed in liquids. In the imaging technique known as photoemission electron microscopy (PEEM), ultraviolet light or X-rays bombard a sample, stimulating the material to release electrons from a region at or just beneath its surface. Electric fields act as lenses, focusing the emitted electrons to create an image.

 
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The Effect of NO2/NOx Ratio on the Performance of a SCR Downstream of a SCR Catalyst on a DPF

SAE International Journal of Fuels and Lubricants

Michigan Technological University, USA-Venkata Rajesh Chundru, Gordon G. Parker, John H. Johnson
  • Journal Article
  • 04-12-02-0008
Published 2019-06-14 by SAE International in United States
Different aftertreatment systems consisting of a combination of selective catalytic reduction (SCR) and SCR catalyst on a diesel particulate filter (DPF) (SCR-F) are being developed to meet future oxides of nitrogen (NOx) emissions standards being set by the Environmental Protection Agency (EPA) and the California Air Resources Board (CARB). One such system consisting of a SCRF® with a downstream SCR was used in this research to determine the system NOx reduction performance using experimental data from a 2013 Cummins 6.7L ISB (Interact System B) diesel engine and model data. The contribution of the three SCR reactions on NOx reduction performance in the SCR-F and the SCR was determined based on the modeling work. The performance of a SCR was simulated with a one-dimensional (1D) SCR model. A NO2/NOx ratio of 0.5 was found to be optimum for maximizing the NOx reduction and minimizing NH3 slip for the SCR for a given value of ammonia-to-NOx ratio (ANR). The SCRF® + SCR system was simulated using the 2D SCR-F + 1D SCR system model. For all the…
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Scientists 3D Print All-Liquid ‘Lab on a Chip’

  • Magazine Article
  • TBMG-34552
Published 2019-06-01 by Tech Briefs Media Group in United States

Researchers at DOE's Lawrence Berkeley National Laboratory (Berkeley Lab) have 3D printed an all-liquid device that, with the click of a button, can be repeatedly reconfigured on demand to serve a wide range of applications — from making battery materials to screening drug candidates.

 

Deposit Reduction in SCR Aftertreatment Systems by Addition of Ti-Based Coordination Complex to UWS

Southwest Research Institute-Cary Henry, Scott Eakle
University of Texas-San Antonio-Ryan Hartley, Zachary Tonzetich
Published 2019-04-02 by SAE International in United States
Formation of urea-derived deposits in selective catalytic reduction (SCR) aftertreatment systems continues to be problematic at temperatures at and below 215 °C. Several consequences of deposit formation include: NOx and NH3 slip, exhaust flow maldistribution, increased engine backpressure, and corrosion of aftertreatment components. Numerous methods have been developed to reduce deposit formation, but to date, there has been no solution for continuous low-temperature dosing of Urea-Water Solution (UWS). This manuscript presents a novel methodology for reducing low-temperature deposit formation in SCR aftertreatment systems. The methodology described herein involves incorporation and dissolution of an HNCO hydrolysis catalyst directly into the UWS. HNCO is a transient species formed by the thermolysis of urea upon injection of UWS into the aftertreatment system. Ideally HNCO undergoes hydrolysis to form NH3 and CO2, but under certain conditions HNCO may polymerize or react with other constituents in the exhaust. Reaction of HNCO with species other than water generally results in the formation of deposits in the aftertreatment system. Addition of an HNCO hydrolysis catalyst directly into the UWS provides maximum contact…
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