Micro-Kinetic Study of Reduction of NO on Pt Group Catalysts
TL;DR: In this article, an elementary reaction mechanism based on NO dissociation applicable to Pt group catalysts and simulated with CHEMKIN 4.0.2 using single and multiple PSR (Perfectly Stirred Reactor) model is presented.
Abstract: Catalytic reduction using CO has significant potential for the control of NOx using Pt group catalysts as CO is already present in the exhausts and Pt group catalysts have high durability in the presence of SO2 and H2O. Different reaction mechanisms are given in the literature for this reaction based on NO dissociation, -NCO formation and so on, but the exact reaction mechanism capable of capturing experimentally observed features is as yet unavailable. To determine the kinetics and reaction mechanism, we propose here an elementary reaction mechanism based on NO dissociation applicable to Pt group catalysts and simulated with CHEMKIN 4.0.2 using single and multiple PSR (Perfectly Stirred Reactor) model. The activation energies of the elementary steps are found from the Unity Bond Index-Quadratic Exponential Potential (UBI-QEP) method. Excellent agreement between literature experiments and our simulation results are observed for the NO-CO reaction on Pt and Rh catalysts and for the NO-CO-O2 reaction on Ir catalyst. The effect of temperature on the NO reduction activity is captured well by the model. Additionally the simulations can also point towards importance of particular reactions, selectivity to N2, effects of surface coverage, effects of residence time and catalytic surface area on NO reduction.
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Dissertation•
31 Aug 2011
TL;DR: In this paper, the authors present a table of contents, including table of contents, table of attributes, list of figures, and list of appendices, and chapter headings.
Abstract: ............................................................................................................................iii TABLE OF CONTENTS ....................................................................................................... iv ACKNOWLEDGEMENTS .................................................................................................. vii LIST OF TABLES ................................................................................................................viii LIST OF FIGURES ................................................................................................................ ix LIST OF APPENDICES ......................................................................................................... x NOMENCLATURE ................................................................................................................ xi CHAPTER
10 citations
Cites background from "Micro-Kinetic Study of Reduction of..."
...Most researchers support the L-H mechanism proposed in the 1990s with considerable N2O formation and strong CO adsorption as characteristics of the model [22,148-151,153,160]....
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...In particular, as industry attempts to develop better kinetics as a function of interactions on the surface [15-22], and as indicated by efforts at KU through adaptive kinetics that include metal properties like dispersion and loading, this past data continues to provide insight [23]....
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TL;DR: In this article, a reaction mechanism for the NO-CO system on Pt group catalysts and coupled it with an isothermal PSR model to obtain solutions at atmospheric conditions with the continuation software CONTENT 1.5, at different operating conditions.
Abstract: Due to the importance of the NO-CO reaction in current catalytic converters, reduction of NO by CO on Pt group catalysts is important to study. Various reaction mechanisms have been proposed for the NO-CO reaction on Pt(100), which shows bifurcations, kinetic oscillations and multiple steady states under ultra high vacuum (UHV) conditions due to complex surface dynamics. Some experiments on supported Pt group catalysts reported in literature show oscillations and bistability under atmospheric conditions as well. Industrially relevant conditions require the modelling and detailed analysis of the system at atmospheric pressure. We have proposed a reaction mechanism for the NO-CO system on Pt group catalysts and coupled it with an isothermal PSR model to obtain solutions at atmospheric conditions with the continuation software CONTENT 1.5, at different operating conditions. Simulation results suggest that Pt(111) shows bifurcations at certain operating conditions while Ir(111) shows stable solutions at all the operating conditions studied here.
En raison de l'importance de la reaction entre NO et CO dans les convertisseurs catalytiques habituels, il est important d'etudier la reduction de NO par le CO sur des catalyseurs du groupe Pt. Divers mecanismes de reaction ont ete proposes pour la reaction de NO-CO sur Pt(100), qui montre des bifurcations, des oscillations cinetiques et de multiples etats permanents dans des conditions de vide extreme en raison de la dynamique de surface complexe. Certaines experiences dans la litterature scientifique sur des catalyseurs de groupe Pt supportes montrent en outre des oscillations et une bi-stabilite dans des conditions atmospheriques. Des conditions industrielles pertinentes requierent la modelisation et l'analyse detaillee du systeme a la pression atmospherique. On a propose un mecanisme de reaction pour le systeme de NO-CO sur des catalyseurs de groupe Pt et on l'a couple avec un modele PSR isotherme afin d'obtenir des solutions dans des conditions atmospheriques avec le logiciel de continuation CONTENT 1.5, dans differentes conditions operatoires. Les resultats des simulations suggerent que Pt(111) montre des bifurcations a certaines conditions operatoires, tandis que l'Ir(111) montre des solutions stables a toutes les conditions operatoires etudiees ici.
8 citations
TL;DR: The model results show the temperature of complete NO decomposition decreases with greater media depth, higher fractional area of coverage by the catalyst particles, and with smaller catalyst particle size.
7 citations
TL;DR: In this article, the micro-kinetic model for the reaction on single metals Pt and Rh is simulated for the mixture case in CHEMKIN PRO ®, and it is observed that the mixture maintains the activity while producing less N2O (byproduct of NO þ CO reaction) thus enhancing N2 selectivity inspite of having only half amount of Rh.
Abstract: NO reduction to N2 is the key reaction for effi- cient operation of a three-way catalytic converter (TWC). It is reported that metal catalysts Pt and Rh co-exist as individual metals in a TWC to give synergistic perfor- mance. In this article, we have studied the NO þ CO reaction for a 1:1 physical mixture of silica supported Pt and Rh catalysts using fixed bed experiments and micro- kinetic modeling. The microkinetic model (14) for the reaction on single metals Pt and Rh is simulated for the mixture case in CHEMKIN PRO ® . It is observed that the mixture maintains the activity while producing less N2O (by-product of NO þ CO reaction) thus enhancing N2 selectivity inspite of having only half amount of Rh. Analysis of surface coverages on individual metals in mixture shows that in the presence of Pt, CO poisoning of Rh is reduced at lower temperature leading to better overall conversion and selectivity. This has potential ben- efit in automotive catalysis, as it results in the formation of significantly lower amounts of N2O, an undesirable side-product and greenhouse gas; at a lower cost than if pure Pt/Rh catalysts were used.
6 citations
Cites background or methods from "Micro-Kinetic Study of Reduction of..."
...The microkinetic model [14] for the reaction on single metals Pt and Rh is simulated for the mixture case in CHEMKIN PRO....
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...The PSR model was also demonstrated to be suitable for the modeling of such experiments in earlier work [14]....
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...As shown in earlier work [14] in the group, this reaction mechanism is able to predict the experimental data [17] to good accuracy....
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...Our group [14] has developed a microkinetic model for the NO–CO reaction on Pt- and Rh-based catalysts....
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...Detailed mathematical simulations corresponding to the experiments were performed using the perfectly stirred reactor (PSR) module in CHEMKIN PRO, incorporating the microkinetic model that was earlier developed and validated in the group [14]....
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01 Feb 2021
TL;DR: In this article, the authors considered the measures to suppress emissions of nitrogen and carbon oxides emitted during natural gas combustion, used on the VAZ heat electro-power station territory in Togliatti.
Abstract: The paper considers the measures to suppress emissions of nitrogen and carbon oxides emitted during natural gas combustion, used on the VAZ heat electro-power station territory in Togliatti. The analysis of the quantitative distribution of fuel consumption and pollutant emissions for 2015 - 2019 has been carried out. The description of the process flow diagram of the gas-air duct of the TGME-464 boiler unit (KA No.12) is presented. The possibility of using the method of selective catalytic reduction of nitrogen and carbon oxides on the honeycomb ceramic catalyst surface is considered. The graphical dependences of the volumetric-mass air flow rates, flue gas fuel, specific flow and speed energy on the change in the heat load of the boiler unit are determined. The possibility of using a mathematical model for calculating the change in concentrations and along the length of the catalytic layer depending on the flue gas flow temperature is considered.