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ISBN:
Category :
Languages : en
Pages : 52
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The work performed during this project focused on the identification of materials capable of providing high activity and selectivity for the selective catalytic reduction of nitric oxide with ammonia. The material surface characteristics were correlated with the catalytic behavior of our catalysts to increase our understanding and to help improve the DeNO(subscript x) efficiency. The catalysts employed in this study include mixed oxide composite powders (TiO2-Cr2O3, TiO2-ZrO2, TiO2-WO3, TiO2-SiO2, and TiO2-Al2O3) loaded with varying amounts of V2O5, along with 5 different commercial sources of TiO2. V2O5 was added to the commercial sources of TiO2 to achieve monolayer coverage. Since the valence state of vanadium in the precursor solution during the impregnation step significantly impacted catalytic performance, catalysts were synthesized from both V{sup +4} and V{sup +5} solutions explain this phenomenon. Specifically, the synthesis of catalysts from V{sup 5+} precursor solutions yields lower-performance catalysts compared to the case of V{sup 4+} under identical conditions. Aging the vanadium precursor solution, which is associated with the reduction of V{sup 5+} to V{sup 4+} (VO2 --> VO{sup 2+}), prior to impregnation results in catalysts with excellent catalytic behavior under identical activation and operating conditions. This work also added vanadia to TiO2-based supports with low crystallinity. These supports, which have traditionally performed poorly, are now able to function as effective SCR catalysts. Increasing the acidity of the support by incorporating oxides such as WO3 and Al2O3 significantly improves the SCR activity and nitrogen selectivity. It was also found that the supports should be synthesized with the simultaneous precipitation of the corresponding precursors. The mixed oxide catalysts possess Broensted and Lewis acid sites of comparable strength over a wide range of temperatures. Catalysts prepared from aged vanadium precursor solutions also demonstrated a wider temperature window for optimum operation.
Author: Jeffrey Archer
Publisher: DIANE Publishing
ISBN: 0788173928
Category :
Languages : en
Pages : 1694
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Book Description
Author: United States. Congress. House. Committee on Science. Subcommittee on Energy and Environment
Publisher:
ISBN:
Category : Political Science
Languages : en
Pages : 1050
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Author:
Publisher:
ISBN:
Category : Economic assistance, Domestic
Languages : en
Pages : 894
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Book Description
Identifies and describes specific government assistance opportunities such as loans, grants, counseling, and procurement contracts available under many agencies and programs.
Author: Süheyda Atalay
Publisher: Springer
ISBN: 3319289500
Category : Science
Languages : en
Pages : 69
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Book Description
This brief summarizes the role of certain catalysts and associated processes that are involved in the reduction or elimination of hazardous substances from wastewater and the exploitation of renewable raw materials. The authors begin by providing a summary of the most recent developments in catalysts used in the advanced oxidation of organic pollutants in aqueous phase. Advanced Oxidation Processes (AOPS) are described in terms of homogeneous and heterogeneous catalysts. Some emphasis is placed on the role nanocatalysts, perovskite-type catalysts, and green catalysts play in several AOPs such as Fenton Chemistry, photocatalytic oxidation, and the hybrid technologies that combine different processes. Catalyst preparation, characterization, reaction chemistry, and process technology are described. Specific wastewater case studies which illustrate the role of these catalysts in AOPs completes the brief.
Author:
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ISBN:
Category :
Languages : en
Pages :
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Air pollution arising from the emission of nitrogen oxides as a result of combustion taking place in boilers, furnaces and engines, has increasingly been recognized as a problem. New methods to remove NOx emissions significantly and economically must be developed. The current technology for post-combustion removal of NO is the selective catalytic reduction (SCR) of NO by ammonia or possibly by a hydrocarbon such as methane. The catalytic decomposition of NO to give N2 will be preferable to the SCR process because it will eliminate the costs and operating problems associated with the use of an external reducing species. The most promising decomposition catalysts are transition metal (especially copper)-exchanged zeolites, perovskites, and noble metals supported on metal oxides such as alumina, silica, and ceria. The main shortcoming of the noble metal reducible oxide (NMRO) catalysts is that they are prone to deactivation by oxygen. It has been reported that catalysts containing tin oxide show oxygen adsorption behavior that may involve hydroxyl groups attached to the tin oxide. This is different than that observed with other noble metal-metal oxide combinations, which have the oxygen adsorbing on the noble metal and subsequently spilling over to the metal oxide. This observation leads one to believe that the Pt/SnO2 catalysts may have a potential as NO decomposition catalysts in the presence of oxygen. This prediction is also supported by some preliminary data obtained for NO decomposition on a Pt/SnO2 catalyst in the PI's laboratory. The main objective of the research that is being undertaken is the evaluation of the Pt/SnO2 catalysts for the decomposition of NO in simulated power plant stack gases with particular attention to the resistance to deactivation by O2, CO2, and elevated temperatures. Temperature programmed desorption (TPD) and temperature programmed reaction (TPRx) studies on Pt/SnO2 catalysts having different noble metal concentrations and pretreated under different conditions were done. It is also planned to perform NO decomposition tests in a laboratory-size packed-bed reactor to obtain long-term deactivation data. In the previous reporting periods, runs were made with catalysts containing 15% Pt and 10% Pt on SnO2 were done. Catalysts containing 10% Pt resulted in significantly lower actgivities than 15% PT catalysts. Therefore, in the following tests 15% Pt/SnO2 catalysts were used. Runs to elucidate the effects of temperature, oxygen, water vapor, pretreatment temperature, and space velocity on NO dissociation were completed. It was found that the presence of oxygen and water vapor did not affect the activation energy of the NO dissociation reaction indicating the presence of the same rate controlling step for all feed compositions. Activation energy was higher for higher gas velocities suggesting the presence of mass transfer limitations at lower velocities. Presence of oxygen in the feed inhibited the NO decomposition. Having water vapor in the feed did not significantly affect the catalyst activity for catalysts pretreated at 373 K, but significantly reduced catalyst activity for catalysts pretreated at 900 K. In this reporting period, since no release time was available, no laboratory work was undertaken. Focus was on obtaining equilibrium data on various feed mixtures at temperatures up to 1000 K.
Author:
Publisher:
ISBN:
Category : Acid precipitation (Meteorology)
Languages : en
Pages : 744
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Author: John N. Armor
Publisher: American Chemical Society
ISBN:
Category : Nature
Languages : en
Pages : 464
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Book Description
The first comprehensive volume on the major aspects of environmental catalysis. Focuses on NO x removal, mobile engine emission controls, power plant emissions, control of volatile organic compounds, SO x emissions, and waste minimization. Overview chapters introduce each section and provide added perspective and coverage. Includes comprehensive technical reports on automotive and diesel emission control catalysis, NO x removal, and removal of chlorinated hydrocarbons from various process streams.
Author: Xinchen Wang
Publisher: Elsevier
ISBN: 0128190035
Category : Science
Languages : en
Pages : 568
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Book Description
Photocatalytic materials can improve the efficiency and sustainability of processes and offer novel ways to address issues across a wide range of fields—from sustainable chemistry and energy production to environmental remediation. Current Developments in Photocatalysis and Photocatalytic Materials provides an overview of the latest advances in this field, offering insight into the chemistry and activity of the latest generation of photocatalytic materials.After an introduction to photocatalysis and photocatalytic materials, this book goes on to outline a wide selection of photocatalytic materials, not only covering typical metal oxide photocatalysts such as TiO2 but also exploring newly developed organic semiconducting photocatalysts, such as g-C3N4.Drawing on the experience of an expert team of contributors, Current Developments in Photocatalysis and Photocatalytic Materials highlights the new horizons of photocatalysis, in which photocatalytic materials will come to play an important role in our day-to-day lives. - Reviews developments in both organic- and inorganic-based materials for use in photocatalysis - Presents the fundamental chemistry and activity of a broad range of key photocatalytic materials, including both typical and novel materials - Highlights the role photocatalytic materials can play in sustainable applications
Author: National Research Council
Publisher: National Academies Press
ISBN: 0309182751
Category : Nature
Languages : en
Pages : 158
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Book Description
Carbon monoxide (CO) is a toxic air pollutant produced largely from vehicle emissions. Breathing CO at high concentrations leads to reduced oxygen transport by hemoglobin, which has health effects that include impaired reaction timing, headaches, lightheadedness, nausea, vomiting, weakness, clouding of consciousness, coma, and, at high enough concentrations and long enough exposure, death. In recognition of those health effects, the U.S. Environmental Protection Agency (EPA), as directed by the Clean Air Act, established the health-based National Ambient Air Quality Standards (NAAQS) for CO in 1971. Most areas that were previously designated as "nonattainment" areas have come into compliance with the NAAQS for CO, but some locations still have difficulty in attaining the CO standards. Those locations tend to have topographical or meteorological characteristics that exacerbate pollution. In view of the challenges posed for some areas to attain compliance with the NAAQS for CO, congress asked the National Research Council to investigate the problem of CO in areas with meteorological and topographical problems. This interim report deals specifically with Fairbanks, Alaska. Fairbanks was chosen as a case study because its meteorological and topographical characteristics make it susceptible to severe winter inversions that trap CO and other pollutants at ground level.
