Investigation of Oxygen Storage in Three Way Catalysts PDF Download
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Author: T. Khossusi
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: T. Khossusi
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Jeremias Bickel
Publisher: Logos Verlag Berlin GmbH
ISBN: 3832553827
Category : Technology & Engineering
Languages : en
Pages : 286
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Book Description
The key to achieve optimal emission performance of a modern three-way catalyst (TWC) under transient engine operating conditions is to maintain an optimal oxidation state of the oxygen storage material inside the washcoat of the catalyst. This work demonstrates how simplified kinetic models can be developed that allow for accurately predicting the oxygen storage level under dynamic operation.
Author: Joshua Douglas Cowgill
Publisher:
ISBN:
Category : Oxygen
Languages : en
Pages : 510
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Book Description
Abstract: Three-way catalytic converter oxygen storage control is a topic which has gained increasing interest recently due to the potential additional emissions reduction benefits control could provide to reach SULEV emission standards. To further improve air-to-fuel ratio control strategies, however, accurate three-way catalytic converter models are required to optimally manage oxygen storage. A three-way catalytic converter model depends mostly upon two factors for success. The first of these is, of course, accurate model structure and parameter definition. The second, and possibly more problematic, is accurate measurement data to be used as model inputs. Despite a general trend of increasingly using universal exhaust gas oxygen (UEGO) sensors instead of switching exhaust gas oxygen (EGO) sensors, UEGO sensors are quite susceptible to sensor deception errors particularly present post-catalyst under dynamic conditions. Specifically, the response of the UEGO sensor is significantly effected by the not just the actual exhaust gas air-to-fuel ratio (AFR) but also the concentrations of different components which make up the exhaust gas. To characterize the effect of UEGO sensor measurement error, the specific processes by which measurement error developed was explored. Exhaust gas component concentrations were changed both artificially and through the use of a catalytic converter with the goal of better understanding the UEGO deception phenomenon as a standalone sensor and in its use in conjunction with a catalyst. From the data collected, steady state calibrations were created which allowed for more accurate predictions of true exhaust gas AFR. Furthermore, an ad hoc dynamic calibration was created to indirectly account for additional unmodeled catalytic converter dynamics which significantly affected the post-catalyst UEGO output. The knowledge of UEGO and three-way catalytic converter operation gained was applied to three- way catalytic converter modeling though many methods. Use of the corrected, and thus more accurate, exhaust gas AFR measurements allowed for the accurate determination of parameters necessary for three- way catalytic converter modeling. Understanding of the three-way catalytic converter operation allowed for a detailed analysis, calibration and subsequent improvements of a commonly available three-way catalytic converter model. From this work, the abilities and limitations of a standard three-way catalytic converter model were examined. Within the existing oxygen storage model framework, modified oxygen adsorption and release functions were suggested as well as a means of calibrating them. Furthermore, the work also shows that other unmodeled dynamics are present which are associated with the alteration of the magnitude of the change in hydrogen concentration from pre to post-catalyst possibly caused by catalytic converter deactivation. Unfortunately, while such unmodeled dynamics were noted, the extension of the three-way catalytic converter model to account for these dynamics was beyond the scope of this work. The sensitivity of a current oxygen storage model was numerically investigated by inducing plant and sensor faults and comparing the output of the model with faults against an ideal model output. It is shown in this work that effect of model or plant faults is the slow drifting of the predicted oxygen storage level, as would be expedited, since an integrator-type model is begin used. However it was also determined that, during this drift, the predicted post-catalyst AFR predicted is generally relatively unaffected. In a control application, this slow drift would not be of great concern, as the plant could be regulated around a operating condition which allowed information regarding the current oxygen storage level to be observed in the measurer post-catalyst AFR.
Author: Yuetao Zhang
Publisher:
ISBN:
Category :
Languages : en
Pages : 241
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Book Description
The thesis reports the studies on how the three-way catalytic converters behave under different operation conditions. The main focus of the work is in the oxygen storage capacity of the three-way catalyst. Rich-to-lean air/fuel ratio step-change experiments were carried out to quantify the oxygen storage capacity. Results show that the amount of oxygen stored is dependent on how much oxygen is present in the exhaust. Thus the oxygen storage capacity is not a fixed value, rather it is determined by the equilibrium between the storage sites and the feed stream. A numerical model was developed to characterize the oxygen storage capacity. The model matches well with the experiments. The effects of catalyst age and fuel sulfur content on oxygen storage were measured. The results show that the aging effects and fuel sulfur effects are decoupled. The storage capacity decreases by 10% for every 150ppm increase in fuel sulfur, and it scales with (age−0̇84). Different modes of air/fuel ratio modulations were tested on the catalysts, since such modulation is the practice to keep conversion efficiency high and to increase robustness of the catalyst during transients.
Author: Ronald M. Heck
Publisher: John Wiley & Sons
ISBN: 0470275030
Category : Science
Languages : en
Pages : 548
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Book Description
Catalytic Air Pollution Control: Commercial Technology is the primary source for commercial catalytic air pollution control technology, offering engineers a comprehensive account of all modern catalytic technology. This Third Edition covers all the new advances in technology in automotive catalyst control technology, diesel engine catalyst control technology, small engine catalyst control technology, and alternate sustainable fuels for auto and diesel.
Author: Alessandro Trovarelli
Publisher: World Scientific
ISBN: 1848169647
Category : Science
Languages : en
Pages : 909
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Book Description
This book follows the 2002 edition of Catalysis by Ceria and Related Materials, which was the first book entirely devoted to ceria and its catalytic properties. In the ten years since the first edition a massive amount of work has been carried out in the field, and ceria has gained a prominent position in catalysis as one of the most valuable material for several applications. This second edition covers fundamental and applied aspects of the latest advances in ceria-based materials with a special focus on structural, redox and catalytic features. Special emphasis is given to nano-engineered and nano-shaped systems which are a key factor in the predictive and rational design of ceria with novel properties.In addition, the book presents recent advances in emerging and traditional large-scale applications of ceria in catalysis, such as the treatment of emissions from mobile sources (including diesel and gasoline engines). The primary readership includes catalysis and material science researchers from academy and industry and postdoctorate and graduate students in chemistry, chemical engineering and physics.
Author: Michail I. Soumelidis
Publisher:
ISBN:
Category :
Languages : en
Pages : 688
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Book Description
Increasingly stringent automotive exhaust emissions legislation demands both advanced catalyst control for super ultra low emission vehicle (SULEV) requirements, and close monitoring of catalyst performance. Modem monitoring and control strategies for three-way catalysts (TWC) are usually based on simplified oxygen storage models. Because such control-oriented models need to be simple in structure, they often fail to capture significant dynamic phenomena that take place inside the TWC. Although several extended oxygen storage models have been recently proposed, often compromising their original simple structure, most of them still appear incomplete. In the study presented in this thesis, the limitations of a conventional control-oriented TWC model, based on the dynamics of oxygen storage, were first investigated. Model validation tests, based on an extensive range of experimental data, suggest that inclusion of the basic kinetics of the governing TWC reactions in some form can be beneficial during the modelling process. A simple chemical model was developed to assist the identification process. The model proved to be accurate and robust in estimating the oxygen storage process and predicting the post-catalyst concentrations of some of the main exhaust gas components. Nonlinear modelling and identification techniques were then employed in order to explore alternative means of modelling the strongly nonlinear dynamic behaviour of TWCs. The polynomial NARMAX model was selected to describe the TWC dynamic system and both its structure and parameters were identified in real-time. Validation tests demonstrated the superior performance of the NARMAX model compared to the oxygen storage model, in predicting the post-catalyst air-fuel ratio (AFR) over a wide range of operating conditions. A nonlinear catalyst model was finally proposed, incorporating four NARMAX models, each optimised for local prediction. The chemical model was ' used to identify the current operating region and select the appropriate local model for prediction. The proposed dynamic model is simple in structure, only requires knowledge of the upstream/downstream AFR values, and could form the basis of an on-board catalyst monitoring and control system.
Author: A. Guerrero-Ruiz
Publisher: Elsevier
ISBN: 0080539742
Category : Technology & Engineering
Languages : en
Pages : 501
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Book Description
"Spillover and Mobility of Species and Solid Surfaces" collects the papers which were presented at the Fifth International Conference Spillover, either as oral or poster contributions, as well as the summaries of the invited lectures. This congress and its publication in the Studies on Surface Science and Catalysis series follow the tradition of previous conferences on spillover, initiated in Lyon, 1983, and continued in Leipzig, 1989, Kyoto 1993 and Dalian, 1997. For the fifth conference, held in S.L. el Escorial (Madrid), the organising committee has attempted to compile representative contributions which illustrate the advances in understanding the spillover phenomenon since 1997. Spillover is a process taking place during the interface of gas reactant molecules (mainly hydrogen and oxygen) on solid surfaces. However, different contributions to the more general area of the chemistry at surfaces, related with the mobility and migration of species, diffusion through membranes, fuel cell catalysts, etc., have also been included. In fact the title of the present volume summarizes this attempt to extend the conference topics towards dynamics at surfaces.Among the 70 contributions received, the 56 accepted papers were selected on the basis of the reports of at least two international reviewers, according to standards comparable to those applied for other specialised journals. These papers are from 21 different countries.
Author: Allen H. Meitzler
Publisher:
ISBN:
Category :
Languages : en
Pages : 9
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Author: Robert Ferrizz
Publisher:
ISBN:
Category :
Languages : en
Pages : 237
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Book Description
Ceria and zirconia are important oxide components of the three-way catalyst (TWC) for automotive emissions control. Simultaneous conversion of harmful exhaust pollutants is enhanced by ceria's ability to store and release oxygen to maintain conditions within a narrow operating window of air-to-fuel ratios. Zirconia increases ceria's effectiveness for oxygen storage, yet a fundamental understanding of this favorable interaction is still lacking. In this thesis, surface-sensitive spectroscopic techniques were used to characterize interactions at ceria-zirconia interfaces and their effect on the activity of model emissions control catalysts. The structure-activity relationships and oxygen transport properties of ceria-based samples were studied primarily using temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Thermal desorption of CO and conversion to CO2 were used as chemical probes of the oxidation and reduction of ceria. NO and CH3OH reactivity on ceria surfaces was used to monitor oxygen vacancy (Ce3+) sites. XPS was used to directly measure the oxidation state of cerium cations. These chemical and spectroscopic probes demonstrated that interactions at the ceria-zirconia interface are responsible for an enhanced reducibility, and therefore enhanced oxygen transport, throughout the ceria layer. This enhanced reducibility results in an increased oxygen storage capacity in the TWC for emissions control.
