Modeling and Simulation of Heterogeneous Catalytic Reactions E-Book

• Herausgeber: Wiley-VCH
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 679

Veröffentlichungsjahr: 2013

Beschreibung

The Nobel Prize in Chemistry 2007 awarded to Gerhard Ertl for his groundbreaking studies in surface chemistry highlighted the importance of heterogeneous catalysis not only for modern chemical industry but also for environmental protection. Heterogeneous catalysis is seen as one of the key technologies which could solve the challenges associated with the increasing diversification of raw materials and energy sources. It is the decisive step in most chemical industry processes, a major method of reducing pollutant emissions from mobile sources and is present in fuel cells to produce electricity. The increasing power of computers over the last decades has led to modeling and numerical simulation becoming valuable tools in heterogeneous catalysis. This book covers many aspects, from the state-of-the-art in modeling and simulations of heterogeneous catalytic reactions on a molecular level to heterogeneous catalytic reactions from an engineering perspective. This first book on the topic conveys expert knowledge from surface science to both chemists and engineers interested in heterogeneous catalysis. The well-known and international authors comprehensively present many aspects of the wide bridge between surface science and catalytic technologies, including DFT calculations, reaction dynamics on surfaces, Monte Carlo simulations, heterogeneous reaction rates, reactions in porous media, electro-catalytic reactions, technical reactors, and perspectives of chemical and automobile industry on modeling heterogeneous catalysis. The result is a one-stop reference for theoretical and physical chemists, catalysis researchers, materials scientists, chemical engineers, and chemists in industry who would like to broaden their horizon and get a substantial overview on the different aspects of modeling and simulation of heterogeneous catalytic reactions.

Leseprobe

Contents

Cover

Related Titles

Title Page

Copyright

Preface

List of Contributors

Chapter 1: Modeling Catalytic Reactions on Surfaces with Density Functional Theory

1.1 Introduction

1.2 Theoretical Background

1.3 The Electrocatalytic Oxygen Reduction Reaction on Pt(111)

1.4 Conclusions

References

Chapter 2: Dynamics of Reactions at Surfaces

2.1 Introduction

2.2 Theoretical and Computational Foundations of Dynamical Simulations

2.3 Interpolation of Potential Energy Surfaces

2.4 Quantum Dynamics of Reactions at Surfaces

2.5 Nondissociative Molecular Adsorption Dynamics

2.6 Adsorption Dynamics on Precovered Surfaces

2.7 Relaxation Dynamics of Dissociated H2 Molecules

2.8 Electronically Nonadiabatic Reaction Dynamics

2.9 Conclusions

References

Chapter 3: First-Principles Kinetic Monte Carlo Simulations for Heterogeneous Catalysis: Concepts, Status, and Frontiers

3.1 Introduction

3.2 Concepts and Methodology

3.3 A Showcase

3.4 Frontiers

3.5 Conclusions

References

Chapter 4: Modeling the Rate of Heterogeneous Reactions

4.1 Introduction

4.2 Modeling the Rates of Chemical Reactions in the Gas Phase

4.3 Computation of Surface Reaction Rates on a Molecular Basis

4.4 Models Applicable for Numerical Simulation of Technical Catalytic Reactors

4.5 Simplifying Complex Kinetic Schemes

4.6 Summary and Outlook

References

Chapter 5: Modeling Reactions in Porous Media

5.1 Introduction

5.2 Modeling Porous Structures and Surface Roughness

5.3 Diffusion

5.4 Diffusion and Reaction

5.5 Pore Structure Optimization: Synthesis

Conclusion

References

Chapter 6: Modeling Porous Media Transport, Heterogeneous Thermal Chemistry, and Electrochemical Charge Transfer

6.1 Introduction

6.2 Qualitative Illustration

6.3 Gas-Phase Conservation Equations

6.4 Ion and Electron Transport

6.5 Charge Conservation

6.6 Thermal Energy

6.7 Chemical Kinetics

6.8 Computational Algorithm

6.9 Button Cell Example

6.10 Summary and Conclusions

References

Chapter 7: Evaluation of Models for Heterogeneous Catalysis

7.1 Introduction

7.2 Surface and Gas-Phase Diagnostic Methods

7.3 Evaluation of Hetero/Homogeneous Chemical Reaction Schemes

7.4 Evaluation of Transport

7.5 Conclusions

References

Chapter 8: Computational Fluid Dynamics of Catalytic Reactors

8.1 Introduction

8.2 Modeling of Reactive Flows

8.3 Coupling of the Flow Field with Heterogeneous Chemical Reactions

8.4 Numerical Methods and Computational Tools

8.5 Reactor Simulations

8.6 Summary and Outlook

References

Chapter 9: Perspective of Industry on Modeling Catalysis

9.1 The Industrial Challenge

9.2 The Dual Approach

9.3 The Role of Modeling

9.4 Examples of Modeling and Scale-Up of Industrial Processes

9.5 Conclusions

References

Chapter 10: Perspectives of the Automotive Industry on the Modeling of Exhaust Gas Aftertreatment Catalysts

10.1 Introduction

10.2 Emission Legislation

10.3 Exhaust Gas Aftertreatment Technologies

10.4 Modeling of Catalytic Monoliths

10.5 Modeling of Diesel Particulate Filters

10.6 Selective Catalytic Reduction by NH3 (Urea-SCR) Modeling

10.7 Diesel Oxidation Catalyst, Three-Way Catalyst, and NOx Storage and Reduction Catalyst Modeling

10.8 Modeling Catalytic Effects in Diesel Particulate Filters

10.9 Determination of Global Kinetic Parameters

10.10 Challenges for Global Kinetic Models

10.11 System Modeling of Combined Exhaust Aftertreatment Systems

10.12 Conclusion

References

Index

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Preface

The Nobel Prize in Chemistry 2007 awarded to Gerhard Ertl for his groundbreaking studies in surface chemistry highlighted the importance of heterogeneous catalysis not only for modern chemical industry but also for environmental protection. Today, heterogeneous catalysis is also expected to be the key technology to solve the challenges associated with the increasing diversification of raw materials and energy sources. Heterogeneous catalysis is the decisive step in most chemical industry processes, it is the major way to reduce pollutant emissions from mobile sources, and it is present in fuel cells to produce electricity and in many systems for the use of solar energy (photocatalysis).

With the increasing power of computers over the past decades and the development of numerical algorithms to solve highly coupled, nonlinear, and stiff equation systems, modeling and numerical simulation also have developed into valuable tools in heterogeneous catalysis. These tools were applied to study the molecular processes in very detail by quantum mechanical computations, density functional theory (DFT), molecular dynamics, and Monte Carlo simulations, but often neglecting the engineering aspects of catalytic reactors such as the interaction of chemistry and mass and heat transfer on one side. On the other side, mixing, flow structures, and heat transport in technical reactors and processes have been analyzed by computational fluid dynamics (CFD) in very detail, neglecting, however, the details of the microkinetics.

One objective of this book is to span bridges over the still existing gaps between both communities regarding modeling of heterogeneous catalytic reactions. In the past years, quite frequently, research proposal and programs on catalysis claim to work on bridging those gaps between surface science and industrial catalysis and indeed some progress has been made. Surface science studies, in experiment, theory, and simulation, more and more include technically relevant conditions. Reaction engineering of technical processes now often tries to understand the underlying molecular processes and even include quantum mechanical simulations in the search and development of new catalysts and catalytic reactors. However, convergence here is a slow process. One major reason is the gap between the high complexity of catalysts used in practice and the many approximations still to be made in molecular simulations. Furthermore, using kinetic data derived from numerical simulations in scale-up of technical systems might indeed become risky if the engineer does not take into account the simplifying assumptions and the computational uncertainties of the numerical simulations. Actually, this warning holds for all simulations relevant for heterogeneous catalysis, from DFT to CFD. In many chapters of this book, the authors will lead the reader not only to the potentials but also to the limitations of the modeling approaches and show where the use of the models presented are beneficial and where they are rather risky.

In this book, the state of the art in modeling and simulations of heterogeneous catalytic reactions will be discussed on a molecular level and from an engineering perspective. Special attention is given to the potentials and – even more important – to the limitations of the approaches used. The reader will become familiar not only with the principal ideas of modeling in heterogeneous catalysis but also with the benefits, challenges, and still open issues. The book is organized as follows: from chapter to chapter, time- and length scales as well as complexity increase on the expense of details of the molecular processes bridging all the way from the surface science to the industrial view on modeling heterogeneous catalytic reactions (Figure 1).

Figure 1 Organization of the book.

The book starts with a chapter on density functional theory presenting the concept of theoretical calculations of surface reactions. The electrocatalytic oxygen reduction is used as an example, showing the potential of DFT to study different mechanistic aspects, also including environmental effects. On the basis of the energy diagram derived and the ambient conditions, the likelihood of the realization of a specific reaction pathway can be estimated. Chapter 2 focuses on the computation of the dynamics of reactions at surfaces from first principles. These dynamical simulations reveal the actual trajectory of the movement of a molecule on a catalytic surface but are in general restricted to the computation of this trajectory within few nanoseconds. If the interest is rather in the probability whether or not a certain process (adsorption, diffusion, or reaction) takes place, then Monte Carlos (MC) simulations are the model of choice, which are discussed in Chapter 3. Using information derived from DFT, first-principles kinetic Monte Carlo simulations lead directly to the surface reaction rate as function of ambient conditions and the state of the catalyst. They combine elementary kinetics with statistics to properly evaluate the kinetics of the catalytic particle. The diverse morphology of catalytic particles in technical systems calls for a simpler approach because MC simulations are too expensive to be directly included in simulation of catalytic reactors including mass and heat transfer. Chapter 4 therefore moves from MC simulations to rate equations to estimate surface reaction rates and homogeneous gas-phase reaction rates that also play a role in many catalytic processes. In this so-called mean-field approximation, the details of the molecular process such as diffusion of adsorbates and the dependence of the reaction rate on the crystal phases and defects are not taken directly into account. We now move from the microscopic to the mesoscopic processes. Chapter 5 is then the first part of the book in which the interaction of surface reactions and molecular transport of the reactants and products in the ambience of the catalytic particle is considered. This chapter covers modeling of processes in catalytic porous media and the interaction of diffusion and reactions in those pore structures. The last chapter on fundamentals (Chapter 6) also includes electrochemical charge transfer and couples it with the heterogeneous (thermo-) catalytic reactions and transport in porous media using processes in solid-oxide fuel cells as an illustrating example. Chapter 7 discusses the applicability of molecular-based models, in particular of rate equations, in reactive flow systems and their coupling to the surrounding mass transport processes. The comparison of spatially and temporally resolved species profiles in catalytic laboratory reactors using sophisticated experimental techniques with the profiles computed by coupling chemistry and mass transport models can be used for the evaluation of kinetic schemes developed. The coupling of chemistry and heat and mass transport in catalytic reactors is discussed in Chapter 8, using several multiphase flow systems as examples. Now the book has reached the macroscopic view. The last two Chapters 9 and 10 critically discuss the use, benefits, and limitations of modeling tools in chemical and automobile industry today.

Karlsruhe, August 2011

Olaf Deutschmann

List of Contributors

Josef Anton Universität Ulm Institut für Elektrochemie Albert-Einstein-Allee 47 D-89069 Ulm Germany

Daniel Chatterjee MTU Friedrichshafen GmbH Maybachplatz 1 88045 Friedrichshafen Germany

Olaf Deutschmann Karlsruhe Institute of Technology (KIT) Institute of Chemical Technology and Polymer Chemistry Engesserstr. 20 76131 Karlsruhe Germany

Marcus Frey Daimler AG Department GR/APE HPC 010-G206 70546 Stuttgart Germany

Axel Groß Universität Ulm Institut für Theoretische Chemie Albert-Einstein-Allee 11 89069 Ulm Germany

Timo Jacob Universität Ulm Institut für Elektrochemie Albert-Einstein-Allee 47 D-89069 Ulm Germany

Vinod M. Janardhanan Indian Institute of Technology Ordnance Factory Estate Yeddumailaram 502205 Hyderabad Andhra Pradesh India

Payam Kaghazchi Universität Ulm Institut für Elektrochemie Albert-Einstein-Allee 47 D-89069 Ulm Germany

Robert J. Kee Colorado School of Mines Engineering Division Office BB-306 Golden, CO 80401 USA

Frerich J. Keil Hamburg University of Technology Institute of Chemical Reaction Engineering AB VT 4, FSP 6-05 Eissendorfer Str. 38 21073 Hamburg Germany

John A. Keith Mechanical & Aerospace Engineering Department Princeton University, D320 Engineering Quadrangle Princeton, NJ 08544 USA

Lothar Kunz Karlsruhe Institute of Technology (KIT) Institute of Chemical Technology and Polymer Chemistry Engesserstr. 20 76131 Karlsruhe Germany

Lubow Maier Karlsruhe Institute of Technology (KIT) Institute of Catalysis Research and Technology (IKFT) 76128 Karlsruhe Germany

John Mantzaras Paul Scherrer Institute Combustion Research 5232 Villigen PSI Switzerland

Karsten Reuter Fritz-Haber-Institut der Max-Planck- Gesellschaft Faradayweg 4–6 14195 Berlin Germany

and

Technische Universität München Lehrstuhl für Theoretische Chemie Lichtenbergstr. 4–6 85747 Garching Germany

Jens R. Rostrup-Nielsen Haldor Topsoe A/S R&D Division Nymoellevej 55 2800 Lyngby Denmark

Volker Schmeißer Daimler AG Department GR/APE HPC 010-G206 70546 Stuttgart Germany

Steffen Tischer Karlsruhe Institute of Technology (KIT) Institute of Catalysis Research and Technology (IKFT) 76128 Karlsruhe Germany

Michel Weibel Daimler AG Department GR/APE HPC 010-G206 70546 Stuttgart Germany

Huayang Zhu Colorado School of Mines Engineering Division Office BB-306 Golden, CO 80401 USA