A detailed surface reaction mechanism for CO oxidation on Pt
01 Jan 2000-Vol. 28, Iss: 1, pp 1331-1339
TL;DR: In this article, a detailed surface reaction mechanism for oxidation of CO on polycrystalline Pt surfaces, capable of predicting various available experimental features, has been developed using a multistep methodology.
Abstract: A detailed surface reaction mechanism for oxidation of CO on polycrystalline Pt surfaces, capable of predicting various available experimental features, has been developed using a multistep methodology. First, thermodynamically consistent, coverage-dependent activation energies and heats of reactions were derived from the application of the unity bond index-quadratic exponential potential formulation. Next, initial estimates of pre-exponentials were obtained from transition state theory or available experiments. Important feature identification analysis was performed to determine key reaction parameters for each experiment. Model responses were then parameterized in terms of these important parameters by simple polynomials and factorial design techniques and subsequently used in simultaneous optimization through simulated annealing against different sets of literature and new experimental data from our laboratory. Model validation with independent experiments shows that the proposed surface reaction mechanism performs very well. The potential of our approach for developing surface reaction mechanisms for catalytic combustion of more complex fuels is also discussed.
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15 Apr 2009
TL;DR: In this paper, the authors present an overview of the chemical properties of catalysts and their application in the industrial domain of catalytic cycle and show that they can be classified into three classes: simple binary oxides, complex multicomponent oxides and metal catalysts.
Abstract: The article contains sections titled:
1. Introduction
1.1. Types of Catalysis
1.2. Catalysis as a Scientific Discipline
1.3. Industrial Importance of Catalysis
1.4. History of Catalysis
2. Theoretical Aspects
2.1. Principles and Concepts
2.1.1. Sabatier's Principle
2.1.2. The Principle of Active Sites
2.1.3. Surface Coordination Chemistry
2.1.4. Modifiers and Promoters
2.1.5. Active Phase – Support Interactions
2.1.6. Spillover Phenomena
2.1.7. Phase-Cooperation and Site-Isolation Concepts
2.1.8. Shape-Selectivity Concept
2.1.9. Principles of the Catalytic Cycle
2.2. Kinetics of Heterogeneous Catalytic Reactions
2.2.1. Concepts of Reaction Kinetics (Microkinetics)
2.2.2. Application of Microkinetic Analysis
2.2.3. Langmuir – Hinshelwood – Hougen – Watson Kinetics
2.2.4. Activity and Selectivity
2.3. Molecular Modeling in Heterogeneous Catalysis
2.3.1. Density Functional Theory
2.3.2. Kinetic Monte Carlo Simulation
2.3.3. Mean-Field Approximation
2.3.4. Development of Multistep Surface Reaction Mechanisms
3. Development of Solid Catalysts
4. Classification of Solid Catalysts
4.1. Unsupported (Bulk) Catalysts
4.1.1. Metal Oxides
4.1.1.1. Simple Binary Oxides
4.1.1.2. Complex Multicomponent Oxides
4.1.2. Metals and Metal Alloys
4.1.3. Carbides and Nitrides
4.1.4. Carbons
4.1.5. Ion-Exchange Resins and Ionomers
4.1.6. Molecularly Imprinted Catalysts
4.1.7. Metal – Organic Frameworks
4.1.8. Metal Salts
4.2. Supported Catalysts
4.2.1. Supports
4.2.2. Supported Metal Oxide Catalysts
4.2.3. Surface-Modified Oxides
4.2.4. Supported Metal Catalysts
4.2.5. Supported Sulfide Catalysts
4.2.6. Hybrid Catalysts
4.2.7. Ship-in-a-Bottle Catalysts
4.2.8. Polymerization Catalysts
4.3. Coated Catalysts
5. Production of Heterogeneous Catalysts
5.1. Unsupported Catalysts
5.2. Supported Catalysts
5.2.1. Supports
5.2.2. Preparation of Supported Catalysts
5.3. Unit Operations in Catalyst Production
6. Characterization of Solid Catalysts
6.1. Physical Properties
6.1.1. Surface Area and Porosity
6.1.2. Particle Size and Dispersion
6.1.3. Structure and Morphology
6.1.4. Local Environment of Elements
6.2. Chemical Properties
6.2.1. Surface Chemical Composition
6.2.2. Valence States and Redox Properties
6.2.3. Acidity and Basicity
6.3. Mechanical Properties
6.4. Characterization of Solid Catalysts under Working Conditions
6.4.1. Temporal Analysis of Products (TAP Reactor)
6.4.2. Use of Isotopes
6.4.3. Use of Substituents, Selective Feeding, and Poisoning
6.4.4. Spatially Resolved Analysis of the Fluid Phase over a Catalyst
6.4.5. Spectroscopic Techniques
7. Design and Technical Operation of Solid Catalysts
7.1. Design Criteria for Solid Catalysts
7.2. Catalytic Reactors
7.2.1. Classification of Reactors
7.2.2. Laboratory Reactors
7.2.3. Industrial Reactors
7.2.4. Special Reactor Types and Processes
7.2.5. Simulation of Catalytic Reactors
7.3. Catalyst Deactivation and Regeneration
7.3.1. Different Types of Deactivation
7.3.2. Catalyst Regeneration
7.3.3. Catalyst Reworking and Disposal
8. Industrial Application and Mechanisms of Selected Technically Relevant Reactions
8.1. Synthesis Gas and Hydrogen
8.2. Ammonia Synthesis
8.3. Methanol and Fischer – Tropsch Synthesis
8.3.1. Methanol Synthesis
8.3.2. Fischer – Tropsch Synthesis
8.4. Hydrocarbon Transformations
8.4.1. Selective Hydrocarbon Oxidation Reactions
8.4.1.1. Epoxidation of Ethylene and Propene
8.4.1.2. Ammoxidation of Hydrocarbons
8.4.2. Hydroprocessing Reactions
8.5. Environmental Catalysis
8.5.1. Catalytic Reduction of Nitrogen Oxides from Stationary Sources
8.5.2. Automotive Exhaust Catalysis
176 citations
TL;DR: In this article, the authors present three examples of ethylene hydrogenation, ammonia synthesis, and hydrogen oxidation to assess the thermodynamic validity of literature mechanisms and demonstrate various methods to ensure thermodynamic consistency.
Abstract: The foundation of microkinetic analysis over 10 years ago has drastically changed the way of parametrization of rates of surface-catalyzed reactions. In the initial stages of development, some parameters arose from experimental data whereas others were fitted to experimental data. Semiempirical and first principles quantum mechanical and statistical mechanics simulations nowadays are powerful tools in estimating kinetic parameters. However, even in best cases, some tuning of parameters is typically necessary for quantitative model predictions. During this process, parameters of reaction mechanisms may violate thermodynamics. Here we review thermodynamic constraints of reaction networks and derive expressions applicable to surface reactions. We present three examples of ethylene hydrogenation, ammonia synthesis, and hydrogen oxidation to assess the thermodynamic validity of literature mechanisms. Various methods to ensure thermodynamic consistency are discussed and demonstrated with a specific example of H...
156 citations
TL;DR: In this paper, the gas-phase ignition of fuel-lean hydrogen/air mixtures over platinum was investigated experimentally and numerically in laminar channel-flow configurations, and the differences between measured and predicted homogeneous ignition distances could be substantial (ranging from 8% to 66%, depending on the particular hetero/homogeneous schemes) and were ascribed primarily to the homogeneous reaction pathway.
149 citations
TL;DR: In this article, a comprehensive surface reaction mechanism on Pt is presented that is capable of describing CO oxidation, H2 oxidation, water−gas shift (WGS), preferential oxidation (PROX) of CO, and the promoting role of H2O on CO oxidation reasonably well.
Abstract: A comprehensive surface reaction mechanism on Pt is presented that is capable of describing CO oxidation, H2 oxidation, water−gas shift (WGS), preferential oxidation (PROX) of CO, and the promoting role of H2O on CO oxidation reasonably well. This mechanism consists of a literature CO oxidation model, a surface reaction mechanism for H2 oxidation on Pt developed here, and coupling reactions between the CO and H2 chemistries included for the first time. Thermodynamic consistency, which is shown to be essential for WGS, is ensured in all steps of the entire mechanism. The CO−H2 coupling via the CO + OH reaction, which may involve direct CO2 formation, CO* + OH* ↔ CO2* + H*, as well as an indirect pathway via the carboxyl intermediate, is explored. It is shown that this coupling plays a significant role in capturing the promoting effect of H2O on the CO oxidation-temperature-programmed reaction experiments at low temperatures as well as the overall speed of the WGS and PROX reactions. With the parameters use...
137 citations
TL;DR: In this paper, a multiscale, hierarchical computational framework is presented for modeling homogeneous-heterogeneous reactors, which exhibit a large disparity in length and time scales, ranging from quantum, to atomistic, to mesoscopic, to macroscopic.
134 citations
Cites background or methods from "A detailed surface reaction mechani..."
...Reaction [75] a [140] b [45] c [80] d...
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...A multistep methodology was recently proposed and successfully applied to optimize the pre-factors of MF simulators [44,45]....
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...Additional examples of reaction mechanism limitations for H2 and CO oxidation are given in [39,44,45]....
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TL;DR: This implementation of simulated annealing was used in "Global Optimization of Statistical Functions with Simulated Annealing," Goffe, Ferrier and Rogers, Journal of Econometrics, vol.
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TL;DR: A new global optimization algorithm for functions of continuous variables is presented, derived from the “Simulated Annealing” algorithm recently introduced in combinatorial optimization, which is quite costly in terms of function evaluations, but its cost can be predicted in advance, depending only slightly on the starting point.
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1,598 citations
TL;DR: In this paper, the main lines in the development of the whole field of oscillatory surface reactions are presented, and the phenomenology and mechanisms which give rise to oscillations are presented before the more complicated aspects of spatiotemporal self-organization and chaotic dynamics are discussed.
Abstract: Practically by definition, heterogeneous catalytic reactions represent systems far from thermodynamic equilibrium, and therefore one can observe in such systems rate oscillations, spatiotemporal patterns and chaos--a group of phenomena which has been denoted ``dissipative structures`` by Prigogine. Although oscillatory kinetics in a heterogeneous chemical reaction system had been discovered quite early, it was only about 25 years ago that such phenomena were also found in heterogeneous catalysis by the group of Wicke, who observed rate oscillations in catalytic CO oxidation. Since then, oscillatory surface reactions have developed into a field of very active research. The purpose of the present paper is not to give a full account of all the experimental and theoretical work on oscillatory surface reactions, but to demonstrate the main lines in the development of the whole field. The paper is organized such that first the phenomenology and the mechanisms which give rise to oscillations are presented before the more complicated aspects of spatiotemporal self-organization and chaotic dynamics are discussed. 360 refs.
993 citations