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Author: Richard Lyon Publisher: ISBN: Category : Languages : en Pages : 33
Book Description
Presently available technologies for control of engine NOx are not applicable to diesel engines and numerous research projects are in progress in both the U.S. and Japan to find a practical method of catalytically reducing NOx in diesel exhaust. This report describes the laboratory scale testing of two possible methods of doing this. Tests were done with gas mixtures which simulated diesel exhaust. Of the two NOx control methods tested, one was found unpromising while the other gave promising results when propane was used as the NOx reducing agent. Since, however, the results with diesel fuel as the reducing agent were not promising, further development did not seem justified. It appears likely that the need to use diesel fuel as the NOx reductant in any practical system will be an issue in the other research projects now ongoing.
Author: Richard Lyon Publisher: ISBN: Category : Languages : en Pages : 33
Book Description
Presently available technologies for control of engine NOx are not applicable to diesel engines and numerous research projects are in progress in both the U.S. and Japan to find a practical method of catalytically reducing NOx in diesel exhaust. This report describes the laboratory scale testing of two possible methods of doing this. Tests were done with gas mixtures which simulated diesel exhaust. Of the two NOx control methods tested, one was found unpromising while the other gave promising results when propane was used as the NOx reducing agent. Since, however, the results with diesel fuel as the reducing agent were not promising, further development did not seem justified. It appears likely that the need to use diesel fuel as the NOx reductant in any practical system will be an issue in the other research projects now ongoing.
Author: Umit S. Ozkan Publisher: ISBN: Category : Languages : en Pages :
Book Description
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: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Significant work has been done by the investigators on the cerium oxide-copper oxide based sorbent/catalysts for the combined removal of sulfur and nitrogen oxides from the flue gases of stationary sources. Evaluation of these sorbents as catalysts for the selective reduction of NO[sub x] gave promising results with methane. Since the replacement of ammonia by methane is commercially very attractive, in this project, the effect of promoters on the activity and selectivity of copper oxide/cerium oxide-based catalysts and the reaction mechanism for the SCR with methane was investigated. Unpromoted and promoted catalysts were investigated for their SCR activity with methane in a microreactor setup and also, by the temperature-programmed desorption (TPD) technique. The results from the SCR experiments indicated that manganese is a more effective promoter than the other metals (Rh, Li, K, Na, Zn, and Sn) for the supported copper oxide-ceria catalysts under study. The effectiveness of the promoter increased with the increase in Ce/Cu ratio. Among the catalysts tested, the Cu1Ce3 catalyst promoted with 1 weight% Mn was found to be the best catalyst for the SCR of NO with methane. This catalyst was subjected to long-term testing at the facilities of our industrial partner TDA Research. TDA report indicated that the performance of this catalyst did not deteriorate during 100 hours of operation and the activity and selectivity of the catalyst was not affected by the presence of SO[sub 2]. The conversions obtained by TDA were significantly lower than those obtained at Hampton University due to the transport limitations on the reaction rate in the TDA reactor, in which 1/8th inch pellets were used while the Hampton University reactor contained 250-425-[micro]m catalyst particles. The selected catalyst was also tested at the TDA facilities with high-sulfur heavy oil as the reducing agent. Depending on the heavy oil flow rate, up to 100% NO conversions were obtained. The temperature programmed desorption studies a strong interaction between manganese and cerium. Presence of manganese not only enhanced the reduction rate of NO by methane, but also significantly improved the N[sub 2] selectivity. To increase the activity of the Mn-promoted catalyst, the manganese content of the catalyst need to be optimized and different methods of catalyst preparation and different reactor types need to be investigated to lower the transport limitations in the reactor.
Author: J. van Ham Publisher: Springer Science & Business Media ISBN: 9780792361992 Category : Nature Languages : en Pages : 670
Book Description
In the climate change discussion, non-CO2 greenhouse gases (NCGGs) received official political recognition for the first time in 1997, when agreement was reached on the Kyoto Protocol. As a result methane, nitrous oxide, HFCs, PFCs and SF6 now provide attractive options for detailing the national targets for the reduction of greenhouse gas emissions meant to control climate change. This book is the second volume in this area and addresses three main topics. Firstly, it documents progress with respect to our knowledge of the sources and sinks of NCGGs. Information on this subject is essential in order to reduce the uncertainties in national emissions inventories which serve as the reference values for commitments of countries in the framework of the Kyoto Protocol. Secondly, this volume deals with the control options for the NCGGs and contains a wealth of information in this area. Emerging technologies here provide business opportunities, in particular in connection with the flexible mechanisms for mitigation projects in developing countries which have been agreed in Kyoto. Thirdly, the book treats the policy implementation of mitigation options for greenhouse gas emissions. Tools for control policies, both on the national and international level, and for different sectors of industry are discussed. National integrated approaches, including the ones from the United States Environmental Protection Agency and the Netherlands Ministry of Environment which both sponsored the conference, provide guidance for defining the most effective greenhouse gases mitigation plans in different situations. This volume is being published in support of the IPCC Process and will serve as a reference for IPCC's Third Assessment Report.
Author: David Morales-Morales Publisher: Elsevier ISBN: 0080545157 Category : Science Languages : en Pages : 467
Book Description
Pincer complexes are formed by the binding of a chemical structure to a metal atom with at least one carbon-metal bond. Usually the metal atom has three bonds to a chemical backbone, enclosing the atom like a pincer. The resulting structure protects the metal atom and gives it unique properties.The last decade has witnessed the continuous growth in the development of pincer complexes. These species have passed from being curiosity compounds to chemical chameleons able to perform a wide variety of applications. Their unique metal bound structures provide some of the most active catalysts yet known for organic transformations involving the activation of bonds. The Chemistry of Pincer Compounds details use of pincer compounds including homogeneous catalysis, enantioselective organic transformations, the activation of strong bonds, the biological importance of pincer compounds as potential therapeutic or pharmaceutical agents, dendrimeric and supported materials. * Describes the chemistry and applications of this important class of organometallic and coordination compounds* Covers the areas in which pincer complexes have had an impact* Includes information on more recent and interesting pincer compounds not just those that are well-known
Author: Publisher: ISBN: Category : Languages : en Pages : 10
Book Description
The original goal of this program was the identification and design of new noble-metal-based catalysts for the selective catalytic reduction of nitric oxide by hydrocarbons under excess oxygen (i.e., ''lean'') conditions (HC-SCR). Work conducted in the first funding cycle of this award (i.e., 1997-2000) was successful in allowing us to develop an understanding of the fundamental surface chemistry taking place during the adsorption and reaction of nitrogen oxides and propylene on the surface of supported noble metal catalysts. Both experimental results collected in our own group as well as molecular simulation results published by Professor Neurock suggested that in order to improve the performance of the Pt catalysts--in terms of the nitrogen selectivity and the temperature window of operation-- it was necessary to introduce a second metal. However, synthesizing such catalysts with the metals of interest (i.e., Pt-Au, Pt-Ru, Pt-Rh, etc.) with some degree of control of the structure and composition of the resulting supported metal particles is in itself a research challenge. Consequently, the bulk of our efforts during the second funding cycle of this award (covered by this report) was shifted to the use of organometallic cluster precursors for the synthesis on novel bimetallic catalysts. During this time we have also continued to maintain an interest in NOx abatement, but have redirected our efforts from the HC-SCR process to the more promising from a commercial standpoint NOx Storage Reduction (NSR) approach.
Author: Publisher: Newnes ISBN: 0080965296 Category : Science Languages : en Pages : 7694
Book Description
Comprehensive Inorganic Chemistry II, Nine Volume Set reviews and examines topics of relevance to today’s inorganic chemists. Covering more interdisciplinary and high impact areas, Comprehensive Inorganic Chemistry II includes biological inorganic chemistry, solid state chemistry, materials chemistry, and nanoscience. The work is designed to follow on, with a different viewpoint and format, from our 1973 work, Comprehensive Inorganic Chemistry, edited by Bailar, Emeléus, Nyholm, and Trotman-Dickenson, which has received over 2,000 citations. The new work will also complement other recent Elsevier works in this area, Comprehensive Coordination Chemistry and Comprehensive Organometallic Chemistry, to form a trio of works covering the whole of modern inorganic chemistry. Chapters are designed to provide a valuable, long-standing scientific resource for both advanced students new to an area and researchers who need further background or answers to a particular problem on the elements, their compounds, or applications. Chapters are written by teams of leading experts, under the guidance of the Volume Editors and the Editors-in-Chief. The articles are written at a level that allows undergraduate students to understand the material, while providing active researchers with a ready reference resource for information in the field. The chapters will not provide basic data on the elements, which is available from many sources (and the original work), but instead concentrate on applications of the elements and their compounds. Provides a comprehensive review which serves to put many advances in perspective and allows the reader to make connections to related fields, such as: biological inorganic chemistry, materials chemistry, solid state chemistry and nanoscience Inorganic chemistry is rapidly developing, which brings about the need for a reference resource such as this that summarise recent developments and simultaneously provide background information Forms the new definitive source for researchers interested in elements and their applications; completely replacing the highly cited first edition, which published in 1973
Author: Richard Lyon
Author: Richard Lyon
Author: Umit S. Ozkan
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Author: J. van Ham
Author: Oliver Kröcher
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Author: Christopher M. Rodenbush
Author: David Morales-Morales
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