Catalytic Air Pollution Control E-Book

Ronald M. Heck

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Veröffentlichungsjahr: 2012

Beschreibung

Catalytic Air Pollution Control: Commercial Technology is the primary source for commercial catalytic air pollution control technology, offering engineers a comprehensive account of all modern catalytic technology. This Third Edition covers all the new advances in technology in automotive catalyst control technology, diesel engine catalyst control technology, small engine catalyst control technology, and alternate sustainable fuels for auto and diesel.

Leseprobe

Contents

Cover

Half Title page

Title page

Copyright page

Dedication

Preface

Acknowledgments

Acknowledgments, First Edition

Acknowledgments, Second Edition

Part I: Fundamentals

Chapter 1: Catalyst Fundamentals

1.1 Introduction

1.2 Catalyzed Versus Noncatalyzed Reactions

1.3 Catalytic Components

1.4 Selectivity

1.5 Promoters and their Effect on Activity and Selectivity

1.6 Dispersed Model for Catalytic Component on Carrier: Pt on Al2O3

1.7 Chemical and Physical Steps in Heterogeneous Catalysis

1.8 Practical Significance of Knowing the Rate-Limiting Step

References

Chapter 1 Questions

Chapter 2: The Preparation of Catalytic Materials: Carriers, Active Components, and Monolithic Substrates

2.1 Introduction

2.2 Carriers

2.3 Making the Finished Catalyst

2.4 Nomenclature for Dispersed Catalysts

2.5 Monolithic Materials as Catalyst Substrates

2.6 Preparing Monolithic Catalysts

2.7 Catalytic Monoliths

2.8 Catalyzed Monolith Nomenclature

2.9 Precious Metal Recovery from Monolithic Catalysts

References

Chapter 2 Questions

Chapter 3: Catalyst Characterization

3.1 Introduction

3.2 Physical Properties of Catalysts

3.3 Chemical and Physical Morphology Structures of Catalytic Materials

3.4 Techniques for Fundamental Studies

References

Chapter 3 Questions

Chapter 4: Monolithic Reactors for Environmental Catalysis

4.1 Introduction

4.2 Chemical Kinetic Control

4.3 The Arrhenius Equation and Reaction Parameters

4.4 Bulk Mass Transfer

4.5 Reactor Bed Pressure Drop

4.6 Summary

References

Chapter 4 Questions

Chapter 5: Catalyst Deactivation

5.1 Introduction

5.2 Thermally Induced Deactivation

5.3 Poisoning

5.4 Washcoat Loss

5.5 General Comments on Deactivation Diagnostics in Monolithic Catalysts for Environmental Applications

References

Chapter 5 Questions

Part II: Mobile Sources

Chapter 6: Automotive Catalyst

6.1 Emissions and Regulations

6.2 The Catalytic Reactions for Pollution Abatement

6.3 The Physical Structure of the Catalytic Converter

6.4 First-Generation Converters: Oxidation Catalyst (1976–1979)

6.5 NOx, CO and HC Reduction: The Second Generation: The Three-Way Catalyst (1979–1986)

6.6 Vehicle Test Procedures (U.S., European, and Japanese)

6.7 NOx, CO, and HC Reduction: The Third Generation (1986–1992)

6.8 Palladium TWC Catalyst: The Fourth Generation (Mid-1990s)

6.9 Low-Emission Catalyst Technologies

6.10 Modern TWC Technologies for the 2000s

6.11 Toward a Zero-Emission Stoichiometric Spark-Ignited Vehicle

6.12 Engineered Catalyst Design

6.13 Lean-Burn Spark-Ignited Gasoline Engine

References

Chapter 6 Questions

Chapter 7: Automotive Substrates

7.1 Introduction to Ceramic Substrates

7.2 Requirements for Substrates

7.3 Design/Sizing of Substrates

7.4 Physical Properties of Substrates

7.5 Physical Durability

7.6 Advances in Substrates

7.7 Commercial Applications

7.8 Summary

References

Appendix

References

Chapter 7 Questions

Chapter 8: Diesel Engine Emissions

8.1 Introduction

8.2 Worldwide Diesel Emission Standards

8.3 NOx-Particulate Trade-Off

8.4 Analytical Procedures for Particulates

8.5 Particulate Removal

8.6 NOx Reduction Technologies

8.7 2007 Commercial System Designs (PM Removal Only)

8.8 2010 Commercial System Approaches under Development (PM and NOx Removal)

8.9 Retrofit and Off-Highway

8.10 Natural Gas Engines

References

Chapter 8 Questions

Chapter 9: Diesel Catalyst Supports and Particulate Filters

9.1 Introduction

9.2 Health Effects of Diesel Particulate Emissions

9.3 Diesel Oxidation Catalyst Supports

9.4 Design/Sizing of a Diesel Particulate Filter

9.5 Regeneration Techniques

9.6 Physical Properties and Durability

9.7 Advances in Diesel Filters

9.8 Applications

9.9 Summary

References

Chapter 9 Questions

Chapter 10: Ozone Abatement within Jet Aircraft

10.1 Introduction

10.2 Ozone Abatement

10.3 Deactivation

10.4 Analysis of In-Flight Samples

10.5 New Technology

References

Chapter 10 Questions

Part III: Stationary Sources

Chapter 11: Volatile Organic Compounds

11.1 Introduction

11.2 Catalytic Incineration

11.3 Halogenated Hydrocarbons

11.4 Food Processing

11.5 Wood Stoves

11.6 Process Design

11.7 Deactivation

11.8 Regeneration of Deactivated Catalysts

References

Chapter 11 Questions

Chapter 12: Reduction of NOx

12.1 Introduction

12.2 Nonselective Catalytic Reduction of NOx

12.3 Selective Catalytic Reduction of NOx

12.4 Commercial Experience

12.5 Nitrous Oxide (N2O)

12.6 Catalytically Supported Thermal Combustion

References

Chapter 12 Questions

Chapter 13: Carbon Monoxide and Hydrocarbon Abatement from Gas Turbines: Chapter 14

13.1 Introduction

13.2 Catalyst for CO Abatement

13.3 Non-Methane Hydrocarbon (NMHC) Removal

13.4 Oxidation of Reactive Hydrocarbons

13.5 Oxidation of Unreactive Light Paraffins

13.6 Catalyst Deactivation

References

Chapter 13 Questions

Chapter 14: Small Engines

14.1 Introduction

14.2 Emissions

14.3 EPA Regulations

14.4 Catalyst for Handheld and Nonhandheld Engines

14.5 Catalyst Durability

References

Chapter 14 Questions

Part IV: New and Emerging Technologies

Chapter 15: Ambient Air Cleanup

15.1 Introduction

15.2 Premair® Catalyst Systems

15.3 Other Approaches

References

Chapter 15 Questions

Chapter 16: Fuel Cells and Hydrogen Generation

16.1 Introduction

16.2 Low-Temperature PEM Fuel Cell Technology

16.3 The Ideal Hydrogen Economy

16.4 Conventional Hydrogen Generation

16.5 Hydrogen Generation from Natural Gas for PEM Fuel Cells

16.6 Other Fuel Cell Systems

References

Chapter 16 Questions

Index

CATALYTIC AIR POLLUTION CONTROL

Copyright © 2009 by John Wiley & Sons, Inc. All rights reserved.

Published by John Wiley & Sons, Inc., Hoboken, New JerseyPublished simultaneously in Canada

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Library of Congress Cataloging-in-Publication Data:

Heck, Ronald M., 1943- Catalytic air pollution control : commercial technology / Ronald M. Heck, Robert J. Farrauto, Suresh T. Gulati. - 3rd ed. p.  cm. Includes bibliographical references and index. ISBN 978-0-470-27503-0 (cloth)1. Air-Purification-Equipment and supplies. 2. Catalysts. 3. Automobiles-Catalytic converters. 4. Trucks-Catalytic converters. I. Farrauto, Robert J., 1941- II. Gulati, Suresh T. III. Title. TD889.H43   2009 629.25’28-dc22 2008032182

To my wife, Barbara, whose friendship, support, understanding (especially on lost weekends), humor and selflessness made this endeavor much easier. I’m glad I will have more time for her as this project is finished. Unk for always being there for support; and to Merc and Dutch who were overseeing it all.

Ronald M. Heck

To my wife Olga (Olechka) who has given me love, understanding, focus and a new vision of the wonders of life; my loving daughters Jill Marie and Maryellen and their husbands Glenn and Tom. To my grandchildren Nicholas, Matthew, Kevin, Jillian, Owen and Brendan who represent everything that is beautiful in life.

     To the memory of my loving parents who gave me a sense of values that has propelled me to help others.

Robert J. Farrauto

To my wife Teresa whose encouragement and support helped complete this project, my sons Raj and Prem for their genuine support, and my darling daughter Sonya for her “how can I help you, dad?” attitude throughout this project.

Suresh T. Gulati

Preface

Environmental quality is certainly a worldwide concern. Air pollution knows no boundaries, and reducing it is of the utmost importance. Countries are now establishing environmental regulations that must be met by mobile as well as by stationary pollution sources. Exhausts containing volatile organic compounds, carbon monoxide, nitric oxides, ozone, and so forth all can be converted to harmless nonpollutants at reasonable temperatures and with cost-effective systems using heterogeneous catalysts. The use of the right catalyst system converts pollutants to nonpollutants at low-energy requirements and at higher rates, resulting in cost-effective pollution control. The use of catalytic systems for pollution abatement was virtually nonexistent before 1976, but now it is a multibillion-dollar worldwide business that addresses gasoline- and diesel-fueled automobiles and trucks, destruction of volatile organic compounds from stationary sources such as chemical processing plants, reduction of nitric oxides from power plants and stationary engines, decomposition of ozone in high-flying commercial aircraft, pollution from small engines, and so on. The utilization of catalysts for future pollution abatement applications promises to grow at a strong pace over the next decade.

This book is designed to be a stand-alone introductory reference or textbook on the commercially available catalytic systems used today for reducing harmful emissions for both mobile and stationary sources. It is like no other book currently available, because it describes modern catalytic air pollution abatement techniques from a practical point of view. The subjects are discussed in clear and succinct language, with emphasis placed on the real-world catalytic system performance. It is intended to serve as a bridge for academic and industrial catalysis.

Part I has been expanded to include more catalyst fundamentals to give readers a more detailed understanding of kinetics, characterization, and deactivation modes for environmental catalysts. Additionally questions have been added at the end of each chapter to challenge the reader’s knowledge of the material presented. In both of these regards, the book now can serve as an introductory text with special emphasis on the applied aspects of environmental catalysis normally not covered in fundamental textbooks. It is especially useful for newcomers as well as for experienced catalyst scientists and engineers.

Part II discusses the application of catalytic systems for mobile source emission control, the automobile catalytic converter, diesel oxidation catalysts, diesel particulate filters (the newest major application of environmental catalysis), and the decomposition of ozone in high-flying aircraft. The sections on both automotive and diesel have been substantially expanded to reflect the opportunities for catalysis with the new emission standards particularly in diesel.

Part III describes the stationary application of catalysts, including volatile organic compounds, reduction of nitric oxides, and oxidation of gaseous carbon monoxide and hydrocarbons. A new section has been added to small-engine applications as this is a new developing field of catalytic applications.

Finally, Part IV presents new and emerging applications that, if developed, will dramatically change current catalytic technology for environmental control. For this reason, materials for the hydrogen economy including fuel cells have been updated.

* * *

Dr. Ron Heck is president of RMH Consulting where he specializes in consultation on environmental catalysis for auto, diesel, and stationary source; general catalysis; fuel cells; reaction engineering; combustion technology; chemical engineering; and expert witness. He retired as a principal scientist and research manager from Engelhard Corporation in 2003 where he was responsible for developing new catalyst technology for Engelhard Corporation’s worldwide customers in environmental catalysis. He was responsible for developing the PremAir® family of catalysts technologies for removing pollutants from the ambient air and the close-coupled catalyst technology that allowed commercial development of ultra-low-emission systems. Ron was with Engelhard for 31 years and worked on development of catalytic processes for Engelhard in SCR NOx, NSCR NOx, automotive catalyst, diesel catalyst, PremAir® catalyst systems, hydrogenation technology, ozone abatement, volatile organic compound abatement, ammonia oxidation, chemical feedstock purification, and chemical synthesis.

Ron is a member of American Men and Women of Science and Who’s Who in Technology Today. He is a recipient of the Forest R. McFarland Award from the Society of Automotive Engineers for outstanding contributions to this professional society. Ron is an SAE Fellow in recognition of engineering creativity and contributions to the profession and the public at large. With Dr. Gulati, Ron teaches a 2-day course on automotive emission control catalysis and diesel emission control catalysis organized by the Society of Automobile Engineers.

He is the co-author of the book with Dr. Farrauto entitled Catalytic Air Pollution Control: Commercial Technology. Ron was a co-editor of the “News-Brief” section of Applied Catalysis B: Environmental and was a member of the Scientific Advisory Board (SAB) for environmental studies for the Strategic Environmental Research & Development Program (SERDP).

Ron and his former research team from Engelhard received the 2004 Thomas Alva Edison Patent Award from the R&D Council of New Jersey for the invention of close-coupled catalyst technology for ultra-low-emission gasoline vehicles.

Ron has been involved in over 80 publications in commercial applications of catalysts and holds 36 U.S. patents on catalytic processes.

Ron received his B.S. in chemical engineering and his Ph.D. from the University of Maryland and his M.A. in theology from the College of Saint Elizabeth.

Dr. Farrauto is a research fellow at the Corporate Research Laboratories of BASF Catalysts LLC (formerly Engelhard) in Iselin, New Jersey. He has worked extensively in the development of catalysts for the environmental, chemical, and alternative energy industries. His major responsibilities have included the development of advanced automobile emission control catalysts for passenger cars. He was technical leader of the Engelhard team that developed diesel oxidation catalysts now commercialized in the United States and Europe for trucks and passenger cars. Currently he is managing a research team investigating hydrogen production for fuel cells to be used for stationary, portable, and vehicular applications.

In addition to the third edition of Catalytic Air Pollution Control: Commercial Technology, he is the co author of Fundamentals of Industrial Catalytic Processes, second edition, published by Wiley. Dr. Farrauto is the author of 85 publications, and 50 U.S. patents, and he served as the North and South American Editor of Applied Catalysis B: Environmental. He is the recipient of the 2008 Ciapetta Lectureship Award sponsored by the North American Catalysis Society and in 2005 received the Catalysis and Reaction Engineering Practice Award in sponsored by the American Institute of Chemical Engineering. He is the recipient of the Canadian Catalysis Foundation (Year 2000–2001) Cross Canada Lectureship Award and in 2001 received the Henry Albert Award for excellence in precious metal catalysis sponsored by the International Precious Metal Institutes. He is an adjunct professor in the Earth and Environmental Engineering Department of Columbia University in New York City where he teaches catalysis courses and supervises graduate students.

He received his B.S. in chemistry from Manhattan College in New York City and a Ph.D. from Rensselaer Polytechnic Institute in Troy, New York.

Dr. Suresh Gulati is a former corporate fellow of Corning Inc. and currently is a consultant to Corning. He has spent 33 years helping Corning develop and optimize ceramic catalyst supports and particulate filters for gasoline- and diesel-powered vehicles. Prior to retiring in 2000, he applied his mechanical engineering background to ensure long-term reliability of glass and ceramic products like space windows, CRT, fiber optics, and liquid crystal displays. He has published extensively in refereed journals, holds 15 U.S. patents, and continues to give talks at conferences organized by the SAE, ASME, and ACerS. He is a fellow of these professional societies. In addition, he is a recipient of two SAE awards: the Lloyd L. Withrow Distinguished Speaker Award in 2000 and the Forest R. McFarland Award in 2003. Both Drs. Gulati and Heck teach a 2-day course on catalytic converters that is organized by the Society of Automobile Engineers.

Dr. Gulati holds a B.S. from the University of Bombay, an M.S. from the Illinois Institute of Technology, and a Ph.D. from the University of Colorado—all in mechanical engineering.

Acknowledgments

The authors want to acknowledge several people who have helped in preparing and reviewing various aspects of the manuscript.

Ron Heck wants to acknowledge the many outside agencies and companies which provided updates on their technology, in particular MECA (Joe Kubsh), EPA (Joe McDonald), Umicore (Bill Staron and Janette Tomes), NGK (Paul Busch), Johnson Matthey (Andy Walker), Caterpillar (Herbert DaCosta), ORNL (Bruce Bunting and Jim Parks), Donaldson Company (Ted Angelo), Ford (Christine Lambert), Cormetech (George Wensell), BASF (Mike Galligan), and Emitec (Klaus Mueller-Hauss).

Robert Farrauto wants to acknowledge the many Engelhard (now BASF Catalysts LLC) scientists and engineers, past and present, who have pioneered in the development of the technologies described in this book. A special thanks to Dr. J. G. Cohn who gave special input to earlier editions. Ron and Bob want to express their deep appreciation for the leadership in environmental catalysis provided by Dr. John Steger. All the authors wish to thank the BASF Materials Characterization team, including Bob Geise, Joanne St. Amanda, Sharon Goresh, John Motylewski, Patricia Nelson, Tom Gegan, James Drozd, Nancy Brungard, George Munzing, Gail Hodges, Scott Hedrick, Beth Nartowicz, and Xinsheng Liu, who `have provided many of the photographs of catalysts used in environmental technology. They are grateful to Maurica Fedors and Arda Argulian who have provided literature and patent searches. Bob would like to express his gratitude to the graduate students at Columbia University whose questions and feedback provided an important contribution to this edition.

Suresh Gulati wants to thank Drs. Pronob Bardhan and Joseph Antos of the Science and Technology Division of Corning Incorporated for their thorough review and valuable suggestions, Linda Newell for preparing figures, and Julie Berman for preparing revisions for the manuscript. Also, special acknowledgment is given to BASF (formerly Engelhard Corporation) and Corning Incorporated for their pioneering development of ceramic substrates and catalysts.

Acknowledgments, First Edition

The authors want to acknowledge several people who have helped in preparing and reviewing various aspects of the manuscript. First and foremost they express their deepest gratitude to Dr. J. Gunther Cohn, who critically reviewed the entire book and offered many helpful suggestions. Special appreciation is extended to Drs. Jennifer Feeley, Jim Chen, John Hochmuth, Michel Deeba, Barry Speronello, Jordan Lampert, Harold Rabinowitz, and Michael Spencer, all of Engelhard R&D, who recommended many changes that have been incorporated into the final manuscript. The authors are indebted to Marisa Fedors of the Technical Information Center of Engelhard for her efforts in searching the literature. Thanks to Denise Lenci, Donna Gallagher, Michel Stryjewski, Jon Lederman, and Terry Lomuntad of Engelhard Corporation’s Communications Department who helped with typing and recommending appropriate photos. The efforts in preparing figures by Dave Antonucci, Ray Tisch, and O. J. Natale of Engelhard are greatly appreciated. The authors are grateful to Drs. Jerry Spivey, John Armor, and Professor Scott Cowley for their many helpful suggestions.

Finally, they would like to acknowledge Engelhard Corporation and many of its employees, past and present, who pioneered in the development of processes and catalysts for treating environmental problems, and who will continue to do so in the future.

Acknowledgments, Second Edition

The authors want to acknowledge several people who have helped in preparing and reviewing various aspects of the manuscript, including Maurica Fedors, Arda Agulian, and Jane Szeg of the Engelhard Technical Information Center for considerable help in literature searching; Bob Ianniello, Joanne St. Amand, Sharon Goresh, John Motylewski, Patricia Nelson, Zeneida Gutierrez, George Munzing, Nancy Brungard, and Tom Gegan who contributed important characterization data; and Bob Womelsdorf, Mike Durilla, Jim Fu, Jim Chen, Rudy Lechelt, Rosto Brezny, and Nick Bayachek for help with documentation.

Robert Farrauto wants to acknowledge the entire fuel processing team at Engelhard with special thanks to Dr. Wolfgang Ruettinger and Dr. Larry Shore who provided proofreading and valuable suggestions. Special thanks to Dr. Ed Wolynic, Dr. Terry Poles, and Dr. Bruce Robertson who have given strong commercial leadership and inspiration to move forward in fuel cell technology.

Ron Heck wants to acknowledge the entire PremAir® team who made new technology possible with special thanks to Dr. Jeff Hoke who provided proofreading and valuable suggestions. Special thanks to Dr. Steger who has been a support in communicating this subject to the world.

Ron Heck and Robert Farrauto want to acknowledge the staff at Engelhard who have pioneered in emission control, and who will continue to advance the technology.

Suresh Gulati wants to acknowledge George Beall, Lou Manfredo, and Daniel Ricoult of Corning S & T, who recommended many changes. The efforts in preparing figures by Nancy Foster of Corning and parts of the manuscript by Virginia Doud, formerly of Corning, are greatly appreciated. Finally, special acknowledgment is made to Engelhard Corporation and Corning Incorporated, who pioneered in the development of substrates and catalysts.

PART I

Fundamentals

Chapter 1

Catalyst Fundamentals

1.1 INTRODUCTION

Chemical reactions occur by breaking chemical bonds of reactants and by forming new bonds and new compounds. Breaking stable bonds requires the absorption of energy, whereas making new bonds results in the liberation of energy. The combination of these energies results in either an exothermic reaction in which the conversion of reactants to products liberates energy or an endothermic process in which the conversion process requires energy. In the former case, the energy of the product is lower than that of the reactants, with the difference being the heat liberated. In the latter case, the product energy is greater by the amount that must be added to conserve the total energy of the system. Under the same reaction conditions, the heat of reaction (ΔH) being a thermodynamic function does not depend on the path or the rate by which reactants are converted to products. Similarly, the free energy of reaction (ΔG) of the reaction is not dependent on the reaction path because it too is a thermodynamic state function. This will be emphasized once we discuss catalytic reactions. The rate of reaction is determined by the slowest step in a conversion process independent of the energy content of the reactants or products.

1.2 CATALYZED VERSUS NONCATALYZED REACTIONS

A few decades ago, chlorofluorocarbons (i.e., CF2Cl2), emitted primarily from refrigerants, were found to catalyze the destruction of the ozone (O3) layer in the stratosphere necessary to protect us from harmful ultraviolet (UV) radiation and its skin cancer consequences. Fortunately alternative chemicals are now used, and this problem is no longer of great concern. It does, however, serve as an excellent example of a homogeneous gas phase catalytic reaction. First let us consider the very slow noncatalytic reaction between gaseous O3 and O atoms produced by dissociation of O2 by solar radiation in the upper atmosphere:

(1.1)

Chlorine atoms, produced by solar radiation of chlorofluorohydrocarbons, catalyze the decomposition of ozone by reacting with it to form ClO and O2(1.2). The ClO then reacts with the O atoms regenerating Cl and producing more O2(1.3).

(1.2)

(1.3)

Adding both reactions results in Eq. (1.1) and completes the catalytic cycle since the Cl and ClO are both consumed and regenerated in the two reactions. Thus, Cl is a homogeneous catalyst for the destruction of O3. The uncatalyzed reaction is very slow, and its reaction profile can be described kinetically by the Arrhenius profile in which reactants convert to products by surmounting the noncatalytic activation energy barrier (ENC) as shown in Figure 1.1. The rate constant k of the reaction is inversely related to the exponential of the activation energy, where T is the absolute temperature, R is the universal gas constant, and ko is the preexponential constant. The Arrhenius equation (1.4) indicates that the rate constant k decreases the higher the activation energy (E).

FIGURE 1.1. Catalyzed and uncatalyzed reaction energy paths for O3 decomposition to O2. Activation energy for catalyzed reaction EC is lower, and the reaction is faster than the noncatalyzed ENC.

(1.4)

Since the catalyzed reaction has a lower activation energy (EC), its reaction rate is greater. The barrier was lowered by the Cl catalyst providing a chemical shortcut to products. Although the rate is greater for the catalyzed reaction, the enthalpy (ΔH) and free energy (ΔG) are not changed. Similarly the equilibrium constant for both catalyzed and noncatalyzed reactions is not changed since both operate under the same reaction conditions in the stratosphere. The catalyst can only influence the rate of which reactants are converted to products in accordance to the equilibrium constant and cannot make thermodynamically unfavorable reactions occur. In industrial practice, reactions conditions, such as temperature and pressure, are varied to bring the free energy to a desirable value to permit the reaction to occur.

Now we will consider the conversion of carbon monoxide (CO), a known human poison, to CO2, a reaction of great importance to the quality of air we breathe daily. The overall rate of the noncatalytic reaction is controlled by the dissociation of the O2 molecule to O atoms (rate-limiting step), which rapidly react with CO forming CO2. The temperature required to initiate the dissociation of O2 is greater than 700°C, and once provided, the reaction rapidly goes to completion with a net liberation of energy (the heat of reaction is exothermic). The requirement to bring about the O dissociation and ultimately the conversion of CO to CO has an activation energy (E). Reaction occurs when a sufficient number of molecules (O) possess the energy necessary (as determined by the Boltzmann distribution) to surmount the activation energy barrier (E) shown in ). The rate of reaction is expressed in accordance with the Arrhenius . Typically the activation energy for the noncatalytic or thermal conversion of CO to CO is about 40 Kcal/mole.