Development of Improved Catalysts for the Selective Catalytic Reduction of Nitrogen Oxides with Hydrocarbons PDF Download
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Languages : en
Pages : 74
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Author:
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Languages : en
Pages : 74
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Category :
Languages : en
Pages : 5
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Novel bifunctional catalysts combining two active phases, typically Cu-ZSM-5 and a modifier, were prepared and tested for the selective catalytic reduction of nitrogen oxides using propylene in order to overcome the hindering effects of water typically seen for single-phase catalysts such as Cu-ZSM-5. The catalysts were made by typical preparation techniques, but parameters could be varied to influence the catalyst. The physical characterization of the materials showed that the modification phase was added strictly to the external surface of the zeolite without hindering any internal surface area. Chemical characterization by temperature programmed reactions, DRIFTS and x-ray absorption spectroscopy indicated strong interaction between the two phases, primarily producing materials that exhibited lower reduction temperatures. Two improvements in NOx reduction activity (1000 ppm NO, 1000 ppm C3H6, 2% O2, 30,000 hr-1 GHSV) were seen for these catalysts compared with Cu- ZSM-5: a lower temperature of maximum NOx conversion activity (as low at 250 C), and an enhancement of activity when water was present in the system. The use of a second phase provides a way to further tune the properties of the catalyst in order to achieve mechanistic conditions necessary to maximize NOx remediation.
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Languages : en
Pages : 10
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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: Oliver Kröcher
Publisher: MDPI
ISBN: 3038973645
Category : Science
Languages : en
Pages : 281
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This book is a printed edition of the Special Issue "Selective Catalytic Reduction of NO
x" that was published in Catalysts
Author: Pascal Granger
Publisher: Elsevier
ISBN: 0080554059
Category : Technology & Engineering
Languages : en
Pages : 419
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Book Description
This book offers an overview of the state of the art in the field of DeNOx catalysis in order to focus novel orientations, new technological developments, from laboratory to industrial scale. A particular attention has been paid towards the implementation of catalytic processes for minimising NOx emissions either from stationary or mobile sources under lean condition to meet future standard regulations of NOx emissions. In the first part of this book, critical aspects reported in the literature which usually make difficult the achievement of efficient catalytic technologies in those conditions are summarised and analysed in order two separate new perspectives. The second part deals with fundamental aspects at molecular level. A better understanding of the reactions involved under unsteady-state conditions is probably a pre-requisite step for improving the performances of the actual processes or developing original ones. The development of powerful in situ spectroscopic techniques is of fundamental interest for kinetic modelling. Correlations between spectroscopic and kinetic data with those obtained from theoretical calculations are reported. Some illustrations emphasise the fact that these comparisons may help in determining the nature of the catalytic active sites and building predictive tools for simulations under running conditions. The latter part of this book will be illustrated by different practical approaches covering various aspects related to the catalysts preparation and the development of alternative technologies which include industrial considerations.- New technological developments for investigating catalytic reactions in transient conditions (in situ and operando spectroscopic techniques)- Concerted approaches in DeNOx catalysis - How academic aspects (kinetic, in situ spectroscopic measurements) can provide useful information for practical applications- Comparison of different approaches provided by academic and industrial partners
Author:
Publisher: DIANE Publishing
ISBN: 1428902805
Category :
Languages : en
Pages : 57
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Author: Stephen Grenville Masters
Publisher:
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Category :
Languages : en
Pages :
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Author: K. Fujimoto
Publisher: Elsevier
ISBN: 0080887708
Category : Science
Languages : en
Pages : 457
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The spillover effect is one of the most promising factors in the enhancement of catalytic reaction rates. The spillover phenemenon was found in the 1960s by several research groups independently. It was defined at the previous International Symposium on Spillover as follows Spillover involves the transport of active species which are adsorbed or formed on a first phase onto another phase that does not adsorb or form the species under the same condition. However, this effect appears typically in the dynamic state, i.e., during reactions, which advance with a considerable reaction rate. This makes it difficult to elucidate the spillover effect through static methods. Therefore, more fundamental investigations are necessary. The development of alternative energy sources and protection of the environment demands highly selective and very rapid catalytic reactions at deviating conditions. To achieve these goals new concepts, such as the spillover effect, are needed. This proceedings book, which comprises 80 papers, contains methods for preparing catalysts in order to realize spillover effects and suggests the most probable mechanisms to explain these non-linear phenomena. It also contains studies on applications of the spillover effect to improve industrial catalytic processes.The book will be invaluable in the development of industrial catalysts and for solving energy and environmental protection problems.
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Category :
Languages : en
Pages : 41
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Book Description
A flow trough type catalytic reactor system was adequately modified for NO related catalytic and adsorption measurements, including the on-line connection of a digital chemiluminescent NO-NO(subscript x) analyzer to the reactor outlet system. Moreover, we have largely completed the installation of an FTIR coupled catalytic system containing a HTEC cell for high temperature DRIFT studies. Three different barium cuprate samples, Ba2CuO3, BaCuO2, and Ba2Cu3O5 were synthesized and characterized by powder XRD for catalytic tests. Prior to catalytic studies over these cuprates, a new, liquid indium based supported molten metal catalyst (In-SMMC) was tested in the reduction of NO by various reductants. In the presence of excess O2 and H2O, the In-SMMC proved to be more active for the selective catalytic reduction (SCR) of NO to N2 by ethanol than most other catalysts. Using C1-C3 alcohols as reductants, self sustained periodic oscillations observed in the NO(subscript x) concentrations of reactor effluents indicated the first time that radical intermediates can be involved in the SCR of NO by alcohols. Further, In-SMMC is the only effective and water tolerant SCR catalyst reported thus far which contains SiO2 support. Thus, this novel catalyst opens up a promising new alternative for developing an effective and durable catalyst for NO(subscript x) abatement in stack emission.
Author:
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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.
