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Author : Sharmilah Kuppusami
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (96 download)
Download or read book The Development of Lanthanide Doped Cobalt Based Catalysts Towards NOx Reduction written by Sharmilah Kuppusami and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Wilson D. Shafer
Publisher : MDPI
ISBN 13 : 303928388X
Total Pages : 414 pages
Book Rating : 4.0/5 (392 download)
Download or read book Iron and Cobalt Catalysts written by Wilson D. Shafer and published by MDPI. This book was released on 2020-06-23 with total page 414 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the turn of the last century when the field of catalysis was born, iron and cobalt have been key players in numerous catalysis processes. These metals, due to their ability to activate CO and CH, haev a major economic impact worldwide. Several industrial processes and synthetic routes use these metals: biomass-to-liquids (BTL), coal-to-liquids (CTL), natural gas-to-liquids (GTL), water-gas-shift, alcohol synthesis, alcohol steam reforming, polymerization processes, cross-coupling reactions, and photocatalyst activated reactions. A vast number of materials are produced from these processes, including oil, lubricants, waxes, diesel and jet fuels, hydrogen (e.g., fuel cell applications), gasoline, rubbers, plastics, alcohols, pharmaceuticals, agrochemicals, feed-stock chemicals, and other alternative materials. However, given the true complexities of the variables involved in these processes, many key mechanistic issues are still not fully defined or understood. This Special Issue of Catalysis will be a collaborative effort to combine current catalysis research on these metals from experimental and theoretical perspectives on both heterogeneous and homogeneous catalysts. We welcome contributions from the catalysis community on catalyst characterization, kinetics, reaction mechanism, reactor development, theoretical modeling, and surface science.
Author : Swee Kuan Yen
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (957 download)
Download or read book Catalytic Activity, Structural and Textural Studies of Doped Cobalt-based Catalysts Towards CO Oxidation written by Swee Kuan Yen and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Luca Lietti
Publisher : Royal Society of Chemistry
ISBN 13 : 1788013239
Total Pages : 514 pages
Book Rating : 4.7/5 (88 download)
Download or read book NOx Trap Catalysts and Technologies written by Luca Lietti and published by Royal Society of Chemistry. This book was released on 2018-06-13 with total page 514 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book will be the first to comprehensively present the current research on catalysts used for NOx abatement in lean exhausts.
Author : Wenfeng Shangguan
Publisher : Springer
ISBN 13 : 9811072663
Total Pages : 138 pages
Book Rating : 4.8/5 (11 download)
Download or read book Simultaneous Catalytic Removal of Diesel Soot and NOx written by Wenfeng Shangguan and published by Springer. This book was released on 2018-06-28 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book not only explores catalysis processes in redox reactions but also proposes a potential after-treatment strategy. Summarizing the authors’ major works, it offers a guidebook for those working on environmental and industrial catalysis. It presents insights into reaction kinetics in a variety of materials and analyzes the external conditions influencing the reaction. As such it is of particular interest to engineers and scientists in the field of material chemistry, chemical engineering and automobile industry. With novel images and illustrations, it provides a new perspective for interpreting soot abatement material and understanding the reaction process and inspires scientists to design new catalysts with moderate redox capacity.
Author : Guihua Liu
Publisher :
ISBN 13 :
Total Pages : 128 pages
Book Rating : 4.:/5 (112 download)
Download or read book Design of Efficient Cobalt-based Bi-functional Catalysts for Zinc-air Batteries written by Guihua Liu and published by . This book was released on 2019 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to its high theoretical specific energy and low-cost, rechargeable zinc-air batteries have attracted tremendous attention as a promising next-generation energy conversion system. However, there are some challenges that need to overcome before its practical application. One of the key issues is the slow reaction kinetics in the air cathode of the batteries towards the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). This would cause insufficient charge/discharge efficiency and poor cycle stability of the batteries. Therefore, the development of efficient ORR-OER bi-functional electrocatalysts with high catalytic activity and durability is essential for the development of rechargeable zinc-air batteries. In this work, a series of catalyst design strategies have been explored to improve the activity and durability of cobalt-based bi-functional catalysts especially under the oxidative condition of OER reaction. The latter would cause catalyst oxidation and aggregation, and therefore deteriorate the cycling performance of the bi-functional catalysts in zinc-air batteries. In the first study, a surface engineering approach was adopted to prepare efficient bi-functional catalyst consists of mildly oxidized, N-doped Co9S8 catalyst supported on N-doped reduce graphite oxide (O-N-Co9S8@N-RGO). The surface decorated electrocatalyst shows excellent activity for both ORR and OER, and maintains good stability over 900 charge-discharge cycles at 10 mA cm-2 in zinc-air battery. Interestedly, it was found that O-N-Co9S8 nanoparticles responsible for the OER reaction were completely converted into Co3O4 after OER reaction, indicating Co3O4 is the actual active phase for OER. On the basis of this observation, we propose and demonstrate that oxides in-situ generated cobalt oxides during OER reaction are more active than the directly calcined oxides. This work advances fundamental insight and the design of metal chalcogenides-based bi-functional "catalysts". On the recognition of the high catalytic activity of surface-engineered Co9S8 material, a three-dimensionally ordered mesoporous (3DOM) structured surface-engineered Co9S8 catalyst was developed to explore the benefits of the 3DOM structural design for its catalytic performance. Different from the N-RGO supported O-N-Co9S8, the 3DOM-Co9S8 catalyst is self-supported, which contains only an inner carbon layer within its mesoporous structure. Due to the 3D interconnected architecture and large surface area, the air electrode delivers excellent cell performance and cycling durability. However, the partial structure crush of N-Co9S8 after long-time OER testing was observed, demonstrating that the highly oxidative operating condition of rechargeable zinc-air batteries could cause significant structural integrity issues of porous chalcogenide electrocatalysts. Thus, in the last study, a new strategy focusing on the oxidation-resistive catalyst support design using oxygen vacancy (OV)-rich, low-bandgap semiconductor was proposed. The OVs promote the electrical conductivity of the semiconductor support, and at the same time offer a strong metal-support interaction (SMSI). The SMSI enables the catalysts with small metal size, high catalytic activity, and high stability. This strategy is demonstrated by successfully synthesizing ultrafine Co metal decorated 3DOM titanium oxynitride (3DOM-Co@TiOxNy). The catalyst not only exhibits good ORR-OER activities, but also shows excellent cycling stability in alkaline conditions, e.g. less than 1% energy efficiency loss over 900 charge-discharge cycles at 20 mA cm-2. Theoretical calculation confirmed that the high stability of this catalyst is attributed to the strong SMSI between Co and 3DOM-TiOxNy. This study will provide an alternative strategy for the design of efficient and durable non-precious electrocatalysts using OV-rich semiconductors as support materials. In summary, a series of catalyst design strategies for efficient and durable bi-functional ORR-OER catalyst were developed in this work. It was found that NH3 treatment is an effective surface-engineering approach to develop highly active ORR-OER catalysts. The in-situ transformation or oxidation of Co9S8 into Co3O4 observed in post-OER analysis advanced our understanding of the chemical, structural transformation and real catalytic phase for OER "catalyst". Moreover, the results show that the 3DOM design of self-supported Co9S8 catalyst could also benefits the catalytic performance by facilitating the mass and electronic transportation within the 3DOM framework. Finally, based on our up-to-date understanding of the OV in semiconductor physics and heterogeneous catalysis, a novel bi-functional catalyst support design strategy was proposed and demonstrated using OV-rich TiOxNy semiconductor. Excellent cycling stability and activity performance of such semiconductor supported cobalt catalyst in rechargeable zinc-air batteries is achieved.
Author : Nurly Safiza Pathe
Publisher :
ISBN 13 :
Total Pages : 31 pages
Book Rating : 4.:/5 (96 download)
Download or read book Development of Cobalt Oxide Based Catalyst for the Conversion of Carbon Dioxide to Methane written by Nurly Safiza Pathe and published by . This book was released on 2007 with total page 31 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Gregory Brandon Collinge
Publisher :
ISBN 13 :
Total Pages : 351 pages
Book Rating : 4.:/5 (129 download)
Download or read book Surface Reconstruction and Lateral Adsorbate Interactions on Cobalt-Based Catalysts written by Gregory Brandon Collinge and published by . This book was released on 2019 with total page 351 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation deals with the problem of computationally determining the structure and catalytically active phase of cobalt-based Fischer-Tropsch (FT) catalysts driven toward oxygenates. Cobalt-copper based catalysts are examined first using density functional theory calculations. The interactions of carbon monoxide (CO) with cobalt-copper nanoparticle surfaces are analyzed for CO's possible role in restructuring these nanoparticles and subsequent creation of the catalytically active phase. It is shown that cobalt-copper catalysts preferentially form Co Cu core-shell nanoparticles, and that CO can induce up to half of step edge and one quarter of terrace copper atoms to be substituted with cobalt atoms from the core. Cobalt enrichment is limited due to the formation of cobalt subcarbonyl complexes. These complexes are shown to be capable of rupturing and diffusing across the surface, providing the ingredients needed for nanoisland formation and facet reconstruction. This work points to new models that are likely important to cobalt-copper catalyzed FT. New lattice gas (LG) cluster expansion (CE) tools are also developed in this dissertation via the development of the ab initio Mean-field Augmented Lattice Gas Modeling (AMALGM) code. A new theoretical reformulation of the CE formalism, which is more appropriate for the LG paradigm, is detailed. AMALGM is designed to use a newly developed convergent version of the leave-multiple-out cross-validation (LMO-CV) score as the objective function for optimization of LG CEs. A new method for quantifying the errors of the effective cluster interactions of CEs is also developed. This error quantification is shown to capture the uncertainty in CEs due to geometric relaxations in DFT data. AMALGM and these new methods are then utilized to investigate the differences in CO adsorption energetics on the face centered cubic (fcc) and hexagonal close packed (hcp) phases of cobalt relevant to FT. It is shown that the first nearest neighbor (1NN) dominates and is very repulsive in both but significantly more repulsive for fcc cobalt. At high chemical potentials, 1NN CO pairings may be allowed on hcp cobalt where they are still energetically prohibited on fcc cobalt, suggesting a potential source for the reduced activity observed on hcp cobalt catalysts.
Author : Matthew Maurice Yung
Publisher :
ISBN 13 :
Total Pages : 228 pages
Book Rating : 4.:/5 (182 download)
Download or read book Oxidation Catalysis in Environmental Applications written by Matthew Maurice Yung and published by . This book was released on 2007 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: The environmental applications of oxidation catalysis were examined as part of a two-stage strategy for the reduction of nitrogen oxides (NOx) and also for the removal of carbon monoxide from hydrogen streams. Cobalt-based catalysts were examined. Reduction of NOx, Co/TiO2 and Co/ZrO2 were studied for the oxidation of NO to NO2 in excess oxygen. NO oxidation was studied as the first step in a two-step catalytic scheme where NO is oxidized to NO2 and, in turn, NO2 is reduced with CH4 to N2 under lean conditions. Catalysts were prepared by sol-gel and incipient-wetness impregnation techniques. It was found that increasing the calcination temperature had an adverse effect on the activity of the IWI catalysts. Catalyst characterization showed higher activity for NO oxidation on Co/ZrO2 than on Co/TiO2 which was observed to correlate with the formation of the Co3O4 phase. For the preferential oxidation of CO, cobalt on several metal oxide supports were investigated and showed the highest activity on Co/ZrO2. A variety of reaction experiments were performed to examine the effects of reactant concentrations, residence time, and temperature on the CO conversion and O2 selectivity to CO2.
Author : Giuliano GIAMBASTIANI
Publisher : Springer
ISBN 13 : 9789400736177
Total Pages : 268 pages
Book Rating : 4.7/5 (361 download)
Download or read book Olefin Upgrading Catalysis by Nitrogen-based Metal Complexes II written by Giuliano GIAMBASTIANI and published by Springer. This book was released on 2013-07-15 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt: Olefin Upgrading Catalysis by Nitrogen-based Metal Complexes II: State-of-the-art and Perspectives provides a critical review of the state-of-the-art developments in industrially relevant processes connected to efficient and selective olefin upgrading. Specific attention is devoted to catalysts containing imine- and amine-based ligands. All the chapters in this book have been designed to provide a systematic account of the vast amount of information available for this type of catalyst as well as to highlight the factors that ultimately control the catalyst’s performance and productivity. A comprehensive panorama of catalyst precursors is presented, spanning from group 10 α-diimine complexes and iron and cobalt 2,6-bis(imino)pyridine derivatives, to vanadium, chromium, titanium, zirconium and lanthanide complexes supported by nitrogen-containing ligands. The authors of this collective work are currently involved in the development of imine-based catalysts for efficient and selective olefin upgrading and the majority of them have dedicated most of their scientific career to this important field. In writing this book, their major goal is to transfer as many ideas and experiences as possible to the global audience of scientists engaged in this area of research.
Author : Samuel D. Lentz
Publisher :
ISBN 13 :
Total Pages : 33 pages
Book Rating : 4.:/5 (429 download)
Download or read book Development and Optimization of NOx Reduction Catalysts Using Statistical Analysis written by Samuel D. Lentz and published by . This book was released on 2009 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt: The second pathway focused on changing the catalytic support from zirconia to ceria on incipient wetness prepared Pd-based catalysts. Ceria has been shown to be more hydrophobic that zirconia and has been active in other catalyzed reactions. Several catalysts were prepared that varied the palladium loading and sulfate loading on the samples to see how these parameters impacted nitrogen dioxide reduction. Results indicated that all samples failed to show activity and further work is being accomplished to change the formulation.
Author : Umit S. Ozkan
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (316 download)
Download or read book Two-stage Catalytic Reduction of NOx with Hydrocarbons written by Umit S. Ozkan and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A two-stage system for the catalytic reduction of NO from lean-burn natural gas reciprocating engine exhaust is investigated. Each of the two stages uses a distinct catalyst. The first stage is oxidation of NO to NO{sub 2} and the second stage is reduction of NO{sub 2} to N{sub 2} with a hydrocarbon. The central idea is that since NO{sub 2} is a more easily reduced species than NO, it should be better able to compete with oxygen for the combustion reaction of hydrocarbon, which is a challenge in lean conditions. Early work focused on demonstrating that the N{sub 2} yield obtained when NO{sub 2} was reduced was greater than when NO was reduced. NO{sub 2} reduction catalysts were designed and silver supported on alumina (Ag/Al{sub 2}O{sub 3}) was found to be quite active, able to achieve 95% N{sub 2} yield in 10% O{sub 2} using propane as the reducing agent. The design of a catalyst for NO oxidation was also investigated, and a Co/TiO{sub 2} catalyst prepared by sol-gel was shown to have high activity for the reaction, able to reach equilibrium conversion of 80% at 300 C at GHSV of 50,000h{sup -1}. After it was shown that NO{sub 2} could be more easily reduced to N{sub 2} than NO, the focus shifted on developing a catalyst that could use methane as the reducing agent. The Ag/Al{sub 2}O{sub 3} catalyst was tested and found to be inactive for NOx reduction with methane. Through iterative catalyst design, a palladium-based catalyst on a sulfated-zirconia support (Pd/SZ) was synthesized and shown to be able to selectively reduce NO{sub 2} in lean conditions using methane. Development of catalysts for the oxidation reaction also continued and higher activity, as well as stability in 10% water, was observed on a Co/ZrO{sub 2} catalyst, which reached equilibrium conversion of 94% at 250 C at the same GHSV. The Co/ZrO{sub 2} catalyst was also found to be extremely active for oxidation of CO, ethane, and propane, which could potential eliminate the need for any separate oxidation catalyst. At every stage, catalyst synthesis was guided by the insights gained through detailed characterization of the catalysts using many surface and bulk analysis techniques such as X-ray diffraction, X-ray photoelectron spectroscopy, Temperature-programmed Reduction, Temperature programmed Desorption, and Diffuse Reflectance InfraRed Fourier Transform Spectroscopy as well as steady state reaction experiments. Once active catalysts for each stage had been developed, a physical mixture of the two catalysts was tested for the reduction of NO with methane in lean conditions. These experiments using a mixture of the catalysts produced N2 yields as high as 90%. In the presence of 10% water, the catalyst mixture produced 75% N{sub 2} yield, without any optimization. The dual catalyst system developed has the potential to be implemented in lean-burn natural gas engines for reducing NOx in lean exhaust as well as eliminating CO and unburned hydrocarbons without any fuel penalty or any system modifications. If funding continues, future work will focus on improving the hydrothermal stability of the system to bring the technology closer to application.
Author : Shih-yi Lin
Publisher :
ISBN 13 :
Total Pages : 143 pages
Book Rating : 4.:/5 (822 download)
Download or read book Characterization of Cobalt Based Catalysts for Ethanol Steam Reforming written by Shih-yi Lin and published by . This book was released on 2009 with total page 143 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 :
Total Pages : 6 pages
Book Rating : 4.:/5 (316 download)
Download or read book SELECTIVE REDUCTION OF NOX IN OXYGEN RICH ENVIRONMENTS WITH PLASMA-ASSISTED CATALYSIS written by and published by . This book was released on 2003 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: The control of NOx (NO and NO2) emissions from so-called ''lean-burn'' vehicle engines remains a challenge. In recent years, there have been a number of reports that show that a plasma device combined with a catalyst can reduce as high as 90% or more of NOx in simulated diesel and other ''lean-burn'' exhaust. In the case of propylene containing simulated diesel exhaust, the beneficial role of a plasma treatment is now thought to be due to oxidation of NO to NO2, and the formation of partially oxidized hydrocarbons that are more active for the catalytic reduction of NO2 than propylene. Thus, the overall system can be most usefully described as hydrocarbon selective catalytic reduction (SCR) enhanced by 'reforming' the exhaust with a non-thermal plasma (NTP) device. For plasma-enhanced catalysis, both zeolite- and alumina-based materials have shown high activity, albeit in somewhat different temperature ranges, when preceded by an NTP reactor. This paper will briefly describe our research efforts aimed at optimizing the catalyst materials for NTP-catalysis devices based, in part, on our continuing studies of the NTP- and catalytic-reaction mechanisms. Various alkali- and alkaline earth-cation-exchanged Y zeolites have been prepared, their material properties characterized, and they have been tested as catalytic materials for NOx reduction in laboratory NTP-catalysis reactors. Interestingly, NO2 formed in the plasma and not subsequently removed over these catalysts, will back-convert to NO, albeit to varying extents depending upon the nature of the cation. Besides this comparative reactivity, we will also discuss selected synthesis strategies for enhancing the performance of these zeolite-based catalyst materials. A particularly important result from our mechanistic studies is the observation that aldehydes, formed during the plasma treatment of simulated diesel exhaust, are the important species for the reduction of NOx to N2. Indeed, acetaldehyde has been found to be especially effective in the thermal reduction of both NO and NO2 over Ba- and Na-Y zeolite catalysts.
Author : Alicia Boix
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (139 download)
Download or read book Cobalt-Based Catalysts for CO Preferential Oxidation written by Alicia Boix and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work, catalysts based on cobalt supported on ZrO2 and CeO2 and CoCeMnOx were studied for the CO preferential oxidation (COPrOx) in hydrogen-rich stream able to feed fuel cells. Among them, the CoCeMnOx formulation showed the highest CO conversion at low temperatures, while the cobalt oxide supported on ceria presented the best selectivity toward CO2. The Co3O4 spinel was the active phase for the CO preferential oxidation detected in all catalysts. However, the CoOx-CeO2 and CoCeMnOx catalysts resulted more active than cobalt oxide supported on zirconia. The presence of ceria close to cobalt species promotes the redox properties and enhances the catalytic activity. In the CoCeMnOx catalyst prepared by coprecipitation, the incorporation of Mn represented an additional positive effect. The presence of Mn promoted the reoxidation of Co2+ to Co3+ and, consequently, the activity increased at low temperature. By X-ray diffraction (XRD) of CoOx-ZrO2 and the CoOx-CeO2 catalysts, the Co3O4 spinel and ZrO2 or CeO2 were identified in agreement with laser-Raman spectra. At the same time, the CoCeMnOx catalyst, prepared by coprecipitation of precursor salts, showed an incipient development of a new phase (Mn,Co)3O4 mixed spinel, due to the intimate contact between elements.
Author :
Publisher :
ISBN 13 :
Total Pages : 42 pages
Book Rating : 4.:/5 (16 download)
Download or read book Development of a Stable Cobalt-ruthenium Fischer-Tropsch Catalyst written by and published by . This book was released on 1991 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this contract is to examine the relationship between catalytic properties and the function of cobalt Fischer-Tropsch catalysts and to apply this fundamental knowledge to the development of a stable cobalt-based catalyst with a low methane-plus-ethane selectivity for use in slurry reactors. An experimental cobalt catalyst 585R2723 was tested three times in the fixed-bed reactor. The objective of the tests was to identify suitable testing conditions for screening catalyst. The?-alumina was determined to be a suitable diluent medium for controlling the catalyst bed temperature close to the inlet temperature. With 13 g of catalyst and 155 g of diluent, the catalyst maximum temperature were within 2°C from the inlet temperatures. As a result of this work, 210°C and 21 atm were shown to result in low methane selectivity and were used as initial conditions in the catalyst screening test. Ethane, which along with methane is undesirable, is typically produced with low selectivity and follows the same trend as methane. Other work reported here indicated that methane selectivity increases with increasing temperature but is not excessively high at 230°C. Consequently, the catalyst screening test should include an evaluation of the catalyst performance at 230°C. During Run 67, the increase in temperature from 210°C to 230°C was initiated at 30 hours on-stream.
Author : Crystle Constantinou
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (835 download)
Download or read book Performance of a Perovskite-based Lean-NOX-trap Catalyst and Effects of Thermal Degradation and Sulfur Poisoning written by Crystle Constantinou and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
