Mitigation Of Sulfur Effects On A Lean Nox Trap Catalyst By Sorbate Reapplication
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Mitigation Of Sulfur Effects On A Lean Nox Trap Catalyst By Sorbate Reapplication
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Author :
language : en
Publisher:
Release Date : 2007
Mitigation Of Sulfur Effects On A Lean Nox Trap Catalyst By Sorbate Reapplication written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with categories.
Lean NOx trap catalysis has demonstrated the ability to reduce NOx emissions from lean natural gas reciprocating engines by>90%. The technology operates in a cyclic fashion where NOx is trapped on the catalyst during lean operation and released and reduced to N2 under rich exhaust conditions; the rich cleansing operation of the cycle is referred to as "regeneration" since the catalyst is reactivated for more NOx trapping. Natural gas combusted over partial oxidation catalysts in the exhaust can be used to obtain the rich exhaust conditions necessary for catalyst regeneration. Thus, the lean NOx trap technology is well suited for lean natural gas engine applications. One potential limitation of the lean NOx trap technology is sulfur poisoning. Sulfur compounds directly bond to the NOx trapping sites of the catalyst and render them ineffective; over time, the sulfur poisoning leads to degradation in overall NOx reduction performance. In order to mitigate the effects of sulfur poisoning, a process has been developed to restore catalyst activity after sulfur poisoning has occurred. The process is an aqueous-based wash process that removes the poisoned sorbate component of the catalyst. A new sorbate component is reapplied after removal of the poisoned sorbate. The process is low cost and does not involve reapplication of precious metal components of the catalyst. Experiments were conducted to investigate the feasibility of the washing process on a lean 8.3-liter natural gas engine on a dynamometer platform. The catalyst was rapidly sulfur poisoned with bottled SO2 gas; then, the catalyst sorbate was washed and reapplied and performance was re-evaluated. Results show that the sorbate reapplication process is effective at restoring lost performance due to sulfur poisoning. Specific details relative to the implementation of the process for large stationary natural gas engines will be discussed.
Performance Of A Perovskite Based Lean Nox Trap Catalyst And Effects Of Thermal Degradation And Sulfur Poisoning
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Author : Crystle Constantinou
language : en
Publisher:
Release Date : 2012
Performance Of A Perovskite Based Lean Nox Trap Catalyst And Effects Of Thermal Degradation And Sulfur Poisoning written by Crystle Constantinou and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.
Increases in vehicle exhaust emission regulations have led to research, development and improvements in catalytic converter technologies for gasoline-powered vehicles since the 1970s. Nowadays, there are strict regulations and standards for diesel engines as well, and one of the regulated species is nitrogen oxides (NOX). The lean NOX trap (LNT) catalyst has been studied and developed for use in lean burn (of which diesel is an example) engine exhaust as a technology to reduce NOX to N2. Typical LNT catalysts contain Pt, which catalyzes NO oxidation and NOX reduction, and an alkali or alkaline earth material for NOX storage via nitrate formation. The catalyst is operated in a cyclic mode, with one phase of the cycle under oxidizing conditions where NOX is trapped, and a second phase, which is reductant-rich relative to O2, where stored NOX is reduced to N2. A recently developed catalyst uses a perovskite material as part of the LNT formulation for the oxidation reactions thereby eliminating the need for Pt in a LNT. This catalyst does include Pd and Rh, added to accommodate hydrocarbon oxidation and NO reduction, respectively. Ba was used as the trapping component, and Ce was also part of the formulation. NO oxidation kinetics over the fully-formulated and bare perovskite material were determined, with NO, O2 and NO2 orders being at or near 1, 1 and -1, respectively for both samples. The fully-formulated sample, which contains Ba supported on the perovskite, was evaluated in terms of NOX trapping ability and NOX reduction as a function of temperature and reduction phase properties. Trapping and overall performance increased with temperature to 375°C, primarily due to improved NO oxidation, as NO2 is more readily trapped, or better diffusion of nitrates away from the initial trapping sites. At higher temperatures nitrate stability decreased, thus decreasing the trapping ability. At these higher temperatures, a more significant amount of unreduced NOX formed during the reduction phase, primarily due to nitrate instability and decomposition and the relative rates of the NOX and oxygen storage (OS) components reduction reactions. Most of the chemistry observed was similar to that observed over Pt-based LNT catalysts. However, there were some distinct differences, including a stronger nitrate diffusion resistance at low temperature and a more significant reductant-induced nitrate decomposition reaction. The perovskite-based lean NOX trap (LNT) catalyst was also evaluated after thermal aging and sulfur exposure. NO oxidation, NOX trapping ability and NOX reduction as a function of temperature and reduction phase properties were evaluated. Similar overall performance trends were seen before and after degradation, however lower performance after thermal aging and sulfur exposure were seen due to sintering effects and possible build-up of S species. Although performance results show that most of the sulfur was removed after desulfation, some sulfur remained affecting the trapping and reduction capabilities as well as the water gas shift (WGS) extent at lower temperatures. The Oxygen storage capacity (OSC) on the other hand was maintained after the catalyst was exposed to thermal aging and sulfur poisoning then desulfation, all of which suggest that the perovskite or Pd components were irreversibly poisoned to some extent.
Diesel Emissions And Their Control 2nd Edition
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Author : W. Addy Majewski
language : en
Publisher: SAE International
Release Date : 2023-12-20
Diesel Emissions And Their Control 2nd Edition written by W. Addy Majewski and has been published by SAE International this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023-12-20 with Technology & Engineering categories.
Engineers, applied scientists, students, and individuals working to reduceemissions and advance diesel engine technology will find the secondedition of Diesel Emissions and Their Control to be an indispensablereference. Whether readers are at the outset of their learning journey orseeking to deepen their expertise, this comprehensive reference bookcaters to a wide audience.In this substantial update to the 2006 classic, the authors have expandedthe coverage of the latest emission technologies. With the industryevolving rapidly, the book ensures that readers are well-informed aboutthe most recent advances in commercial diesel engines, providing acompetitive edge in their respective fields. The second edition has alsostreamlined the content to focus on the most promising technologies.This book is rooted in the wealth of information available on DieselNet.com, where the “Technology Guide” papers offer in-depth insights. Eachchapter includes links to relevant online materials, granting readers accessto even more expertise and knowledge.The second edition is organized into six parts, providing a structuredjourney through every aspect of diesel engines and emissions control: Part I: A foundational exploration of the diesel engine, combustion, andessential subsystems. Part II: An in-depth look at emission characterization, health andenvironmental impacts, testing methods, and global regulations. Part III: A comprehensive overview of diesel fuels, covering petroleumdiesel, alternative fuels, and engine lubricants. Part IV: An exploration of engine efficiency and emission controltechnologies, from exhaust gas recirculation to engine control. Part V: The latest developments in diesel exhaust aftertreatment,encompassing catalyst technologies and particulate filters. Part VI: A historical journey through the evolution of dieselengine technology, with a focus on heavy-duty engines in the NorthAmerican market. (ISBN 9781468605693, ISBN 9781468605709, ISBN 9781468605716, DOI: 10.4271/9781468605709)
Sulfur Management Of Nox Adsorber Technology For Diesel Light Duty Vehicle And Truck Applications
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Author : C. Z. Wan
language : en
Publisher:
Release Date : 2003
Sulfur Management Of Nox Adsorber Technology For Diesel Light Duty Vehicle And Truck Applications written by C. Z. Wan and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003 with categories.
Sulfur poisoning from engine fuel and lube is one of the most recognizable degradation mechanisms of a NOx adsorber catalyst system for diesel emission reduction. Even with the availability of 15 ppm sulfur diesel fuel, NOx adsorber will be deactivated without an effective sulfur management. Two general pathways are currently being explored for sulfur management: (1) the use of a disposable SOx trap that can be replaced or rejuvenated offline periodically, and (2) the use of diesel fuel injection in the exhaust and high temperature de-sulfation approach to remove the sulfur poisons to recover the NOx trapping efficiency. The major concern of the de-sulfation process is the many prolonged high temperature rich cycles that catalyst will encounter during its useful life. It is shown that NOx adsorber catalyst suffers some loss of its trapping capacity upon high temperature lean-rich exposure. With the use of a disposable SOx trap to remove large portion of the sulfur poisons from the exhaust, the NOx adsorber catalyst can be protected and the numbers of de-sulfation events can be greatly reduced. Spectroscopic techniques, such as DRIFTS and Raman, have been used to monitor the underlying chemical reactions during NOx trapping/ regeneration and de-sulfation periods, and provide a fundamental understanding of NOx storage capacity and catalyst degradation mechanism using model catalysts. This paper examines the sulfur effect on two model NOx adsorber catalysts. The chemistry of SOx/base metal oxides and the sulfation product pathways and their corresponding spectroscopic data are discussed. SAE Paper SAE-2003-01-3245 {copyright} 2003 SAE International. This paper is published on this website with permission from SAE International. As a user of this website, you are permitted to view this paper on-line, download this pdf file and print one copy of this paper at no cost for your use only. The downloaded pdf file and printout of this SAE paper may not be copied, distributed or forwarded to others or for the use of others.
Ley No 4416 Y Su Reglamento De Pesca
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Author :
language : en
Publisher:
Release Date : 1937
Ley No 4416 Y Su Reglamento De Pesca written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1937 with categories.
Diesel Fuel Sulfur Effects On The Performance Of Lean Nox Catalysts
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Author :
language : en
Publisher:
Release Date : 2000
Diesel Fuel Sulfur Effects On The Performance Of Lean Nox Catalysts written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2000 with categories.
Evaluate the effects of diesel fuel sulfur on the performance of low temperature and high temperature Lean-NOx Catalysts. Evaluate the effects of up to 250 hours of aging on the performance of the Lean-NOx Catalysts with different fuel sulfur contents.
Investigation Of Aging Mechanisms In Lean Nox Traps
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Author :
language : en
Publisher:
Release Date : 2010
Investigation Of Aging Mechanisms In Lean Nox Traps written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
Lean NO(subscript x) traps (LNTs) represent a promising technology for the abatement of NO(subscript x) under lean conditions. Although LNTs are starting to find commercial application, the issue of catalyst durability remains problematic. LNT susceptibility to sulfur poisoning is the single most important factor determining effective catalyst lifetime. The NO(subscript x) storage element of the catalyst has a greater affinity for SO3 than it does for NO2, and the resulting sulfate is more stable than the stored nitrate. Although this sulfate can be removed from the catalyst by means of high temperature treatment under rich conditions, the required conditions give rise to deactivation mechanisms such as precious metal sintering, total surface area loss, and solid state reactions between the various oxides present. The principle objective of this project was to improve understanding of the mechanisms of lean NO(subscript x) trap aging, and to understand the effect of washcoat composition on catalyst aging characteristics. The approach utilized involved detailed characterization of model catalysts prior to and after aging, in tandem with measurement of catalyst performance in NO(subscript x) storage and reduction. In this manner, NO(subscript x) storage and reduction characteristics were correlated with the evolution of catalyst physico-chemical properties upon aging. Rather than using poorly characterized proprietary catalysts, or simple model catalysts of the Pt/BaO/Al2O3 type (representing the first generation of LNTs), Pt/Rh/BaO/Al2O3 catalysts were employed which also incorporated CeO2 or CeO2-ZrO2, representing a model system which more accurately reflects current LNT formulations. Catalysts were prepared in which the concentration of each of the main components was systematically varied: Pt (50, 75 or 100 g/ft3), Rh (10 or 20 g/ft3), BaO (15, 30 or 45 g/L), and either CeO2 (0, 50 or 100 g/L) or CeO2-ZrO2 (0, 50 or 100 g/L). A high surface area La-stabilized alumina was used to support the BaO phase. Catalysts were obtained by washcoating onto standard cordierite substrates, the total washcoat loading being set at 260 g/L. La-stabilized alumina was used as the balance. Subsequent to de-greening, the NO(subscript x) storage and reduction characteristics of the catalysts were evaluated on a bench reactor, after which the catalysts were aged on a bench reactor to the equivalent of ca. 75,000 miles of road aging using a published accelerated aging protocol. The aged catalysts were then subjected to the same evaluation proecdure used for the de-greened catalysts. In addition to the use of standard physico-chemical analytical techniques for studying the fresh and aged model catalysts, use was made of advanced analytical tools for characterizing their NO(subscript x) storage/reduction and sulfation/desulfation characteristics, such as Spatially resolved capillary-inlet Mass Spectrometry (SpaciMS) and in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS).
Nox Removal By Lnt Scr Dual Layer Catalysts
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Author : Yi Liu
language : en
Publisher:
Release Date : 2012
Nox Removal By Lnt Scr Dual Layer Catalysts written by Yi Liu and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with Chemical engineering categories.
The increasingly strict emission standards have driven the progress of NOx storage and reduction (NSR) technology. NOx is stored in a lean NOx trap (LNT) catalyst during fuel-lean mode and reduced to N2 during fuel-rich mode. First, we investigated the impact of ceria on NSR in an Pt/Ce LNT catalyst. The physisorbed oxygen over the ceria-containing LNT catalyst led to a spatio-temporal temperature rise in the monolith upstream after the cyclic introduction of H2/CO to a pre-oxidized catalyst. The stored oxygen over ceria enhanced NO storage by in-situ NO2 formation, while it competed with NO2 for storage sites. During the NOx reduction over the Pt/Ceria, the Pt surface purgation was the first step and the oxygen reduction preceded the NOx reduction. Second, we studied the NSR by dual-layer catalysts consisting of a selective catalytic reduction (SCR) catalyst layer on top of a LNT catalyst. During periodic switching between lean and rich feeds, the LNT layer reduced NOx to N2 and NH3. The SCR layer trapped the latter leading to additional NOx reduction. The dual-layer catalysts exhibited high N2 selectivity and low NH3 selectivity over the temperature range of 150-400 oC. The NOx conversion was incomplete due to undesired NH3 oxidation. The dual-layer catalyst has a higher NOx conversion and N2 selectivity than the LNT catalyst when H2O and CO2 were present in the feed. Ceria was used to adjust the dual-layer catalyst performance. The ceria addition increased NOx storage capacity, promoted hydrothermal durability and mitigated CO poisoning. However, ceria decreased the high-temperature NOx conversion by promoting NH3 oxidation. Ceria zoning led to the highest NOx reduction for both low- and high- temperatures due to the beneficial interaction of ceria and H2. The impact of catalyst design and operation strategy was evaluated. The low-temperature NOx conversion of an aged dual-layer catalyst was increased by a high SCR catalyst loading. The ratio of lean to rich feed duration and the total cycle time were optimized to improve the NOx conversion. The results suggest the dual-layer catalyst could be used to reduce precious metal loading and improve the fuel economy.
Tropical Plant Science
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Author : G. K. Berrie
language : en
Publisher: Longman Scientific and Technical
Release Date : 1987
Tropical Plant Science written by G. K. Berrie and has been published by Longman Scientific and Technical this book supported file pdf, txt, epub, kindle and other format this book has been release on 1987 with Science categories.
Sisters Super Creeps And Slushy Gushy Love Songs
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Author : Karen McCombie
language : en
Publisher:
Release Date : 2011
Sisters Super Creeps And Slushy Gushy Love Songs written by Karen McCombie and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with Ally (Fictitious character : McCombie) categories.
Ally knows her super-efficient big sis Linn finds their chaotic family a bit ... exasperating. But when Linn falls for Q, the tearaway lead singer in a local band, all her sensible ways go out of the window. Everyone else can see that Q's a creep, but does Ally have the courage to burst Linn's heart-shaped bubble?