Kinetics of Catalytic Reactions

ISBN-13: 9780387246499 / Angielski / Twarda / 2005 / 260 str.

M. Albert Vannice

Opis

Heterogeneous catalysis has shaped our past and will shape our future. Already involved in a trillion dollar s worth of gross domestic product, catalysis holds the key to near term impact areas such as improved chemical process efficiency, environmental remediation, development of new energy sources, and new materials. Furthermore, recent advances in understanding and computing chemical reactivity at the quantum level are opening new pathways that will accelerate the design of catalysts for specific functions. This enormous potential will ultimately be turned into reality in laboratory reactors and have its impact on society and the economy in the industrial reactors that lie at the heart of all chemical processes. Because the quanti- tive measure of catalyst performance is the reaction rate, its measurement is central to progress in catalysis. The pages that follow are a comprehensive guide to success for reaction rate measurements and analysis in catalytic systems. The topics chosen, the clarity of presentation, and the liberal use of specific examples illuminate the full slate of issues that must be mastered to produce reliable kinetic results. The unique combination of characterization techniques, thorough disc- sion of how to test for and eliminate heat and mass transfer artifacts, evaluation of and validity tests for rate parameters, and justification of the uniform surface approximation, along with the more standard ideal reactor analyses and development of rate expressions from sequences of elementary steps, will enrich readers from both science and engineering backgrounds."

Spis treści

Foreword Preface List of Symbols 1. Regular Symbols 2. Greek Symbols 3. Subscripts 1: Introduction 2: Definitions and Concepts 2.1 Stoichiometric Coefficients 2.2 Extent of Reaction 2.3 Rate of Reaction 2.4 Turnover Frequency or Specific Activity 2.5 Selectivity 2.6 Structure-Sensitive and Structure4nsensitive Reactions 2.7 Elementary Step and Rate Determining Step (RDS) 2.8 Reaction Pathway or Catalytic Cycle 2.9 Most Abundant Reaction Intermediate (MARI) 2.10 Chain Reactions 2.11 Reaction Rates in Reactors 2.12 Metal Dispersion (Fraction Exposed) 2.13 Meta1Support Interactions (MSI) References 3: Catalyst Characterization 3.1 Total (BET) Surface Area 3.2 Pore Volume and Pore Size Distribution 3.2.1 Hg Porosimetry Method 3.2.2 N2 Desorption Method 3.2.3 Overall Pore Size Distribution 3.3 Metal Surface Area, Crystallite Size, and Dispersion 3.3.1 Transmission Electron Microscopy (TEM) 3.3.2 X-Ray Techniques 3.3.2.1 Line Broadening of X-Ray Diffraction (XRD) Peaks 3.3.2.2 Extended X-Ray Absorption Fine Structure (EXAFS) 3.3.3 Magnetic Measurements 3.3.4 Chemisorption Methods 3.3.4.1 H2 Chemisorption 3.3.4.2 CO Chemisorption 3.3.4.3 02 Chemisorption 3.3.4.4 H2—02 Titration Techniques 3 3.5 Relationships Between Metal Dispersion, Surface Area, and Crystallite Size References Problems 4: Acquisition and Evaluation of Reaction Rate Data 4.1 Types of Reactors 4.1.1 Batch Reactor 4.1.2 Semi-Batch Reactor 4.1.3 Plug-Flow Reactor (PFR) 4.1.4 Continuous Flow Stirred-Tank Reactor (CSTR) 4.2 Heat and Mass Transfer Effects 4.2.1 Interphase (External) Gradients (Damköhler Number) 4.2.1.1 Isothermal Conditions 4.2.1.2 Nonisothermal Conditions 4.2.2 Intraphase (Internal) Gradients (Thiele Modulus) 4.2.1.1 Isothermal Conditions 4.2.2.2Nonisothermal Conditions 4.2.2.3 Determining an Intraphase (Internal) Effectiveness Factor from a Thiele Modulus 4.2.3 Intraphase Gradients (Weisz-Prater Criterion) 4.2.3.1 Gas-Phase or Vapor-Phase Reactions 4.2.3.2 Liquid-Phase Reactions 4.2.4 Other Criteria to Verify the Absence of Mass and Heat Transfer Limitations (The Madon-Boudart Method) 4.2.5 Summary of Tests for Mass and Heat Transfer Effects References Problems 5: Adsorption and Desorption Processes 5.1 Adsorption Rate 5.2 Desorption Rate 5.3 Adsorption Equilibrium on Uniform (Ideal) Surfaces-Langmuir Isotherms 5.3.1 Single-Site (Nondissociative) Adsorption 5.3.2 Dual-Site (Dissociative) Adsorption 5.3.3 Derivation of the Langmuir Isotherm by Other Approaches 5.3.4 Competitive Adsorption 5.4 Adsorption Equilibrium on Nonuniform (Nonideal) Surfaces 5.4.1 The Freundlich Isotherm 5.4.2 The Temkin Isotherm 5.5 Activated Adsorption References Problems 6: Kinetic Data Analysis and Evaluation of Model Parameters for Uniform (Ideal) Surfaces 6.1 Transition-State Theory (TST) or Absolute Rate Theory 6.2 The Steady-State Approximation (SSA) 6.3 Heats of Adsorption and Activation Barriers on Metal Surfaces: BOC-MP/UBI-QEP Method 6.3.1 Basic BOC-MP/UBI-QEP Assumptions 6.3.2 Heats of Atomic Chemisorption 6.3.3 Heats of Molecular Chemisorption 6.3.4 Activation Barriers for Dissociation and Recombination on Metal Surfaces 6.4 Use of a Rate Determining Step (RDS) and/or a Most Abundant Reaction Intermediate (MARl) 6.5 Evaluation of Parameter Consistency in Rate Expressions for Ideal Surfaces References Problems 7: Modeling Reactions on Uniform (Ideal) Surfaces 7.1 Reaction Models with a RDS Unimolecular Surface Reactions 7.2 Reaction Models with a RDS Bimolecular Surface Reactions 7.3 Reaction Models with a RDS Reactions between an Adsorbed Species and a Gas

O autorze

After doing undergraduate work at Michigan State University, and graduate work at Stanford, Dr. Vannice did a post doc at Sun Oil Company before joining Exxon. In 1976 he moved to Pennsylvania State University, where he remains. After holding the M.R. Fenske Professor of Chemical Engineering, he became the W.H. Joyce Chair in Chemical Engineering, which position he holds now.

Dr. Vannice belongs to ACS, AIChE, has served first as Secretary and then as Director of the New York Catalysis Society, and has served on the Board of Directors of, as the Vice-President of, and then as President of the North American Catalysis Society. He spent seven years as an Associate Editor of the Journal of Catalysis, and continues on its Editorial Board.

Dr. Vannice has received numerous honors from his colleagues, including the Emmett Award (North American Catalysis Society), the Humboldt Senior Research Award, and the Senior Fulbright Award.

Dr. Vannice has over 250 publications and 9 patents.

Blurb

This textbook contains all the information needed for graduate students or industrial researchers to design kinetic experiments involving heterogeneous catalysts, to characterize these catalysts, to acquire valid rate data, to verify the absence of mass (and heat) transfer limitations, to propose reaction models, to derive rate expressions based on these models and, finally, to assess the consistency of these rate equations.

Langmuir, Freundlich, and Temkin isotherms are derived and the former are used in Langmuir-Hinshelwood (and Hougen-Watson) models, as well as reaction sequences without a rate-determining step, to obtain rate expressions on uniform surfaces. In addition, rate equations based on non-uniform (Temkin-type) surfaces are examined as an alternative approach. The most recent technique to calculate heats of adsorption and activation barriers on metal surfaces, the BOC-MP approach, is discussed in detail. Methods to measure metal surface areas and crystallite sizes using x-ray diffraction, transmission electron microscopy and various chemisorption techniques are discussed. Different experimental techniques to determine the influence of mass transfer limitations, especially within the pores of a catalyst, are reviewed in detail, with a particular emphasis on liquid-phase reactions.

Many illustrations of these and other topics are provided along with numerous problems and a Solutions Manual for instructors. This book will be applicable to any graduate course in chemical engineering, chemistry or materials science that involves kinetics of catalytic reactions, including those catalyzed by enzymes.