Descarga Introduction to Chemical Reaction Engineering And Kinetics

28Jun/081

Introduction to Chemical Reaction Engineering And Kinetics – Ronald W. Misen

Introduction to Chemical Reaction Engineering And Kinetics
Ronald W. Misen

1 . INTRODUCTION 1
1.1 Nature and Scope of Chemical Kinetics 1
1.2 Nature and Scope of Chemical Reaction Engineering
1.3 Kinetics and Chemical Reaction Engineering 2
1.4 Aspects of Kinetics 3
1.4.1 Rate of Reaction-Definition 3
1.4.2 Parameters Affecting Rate of Reaction: The Rate Law
1.4.3 Measurement of Rate of Reaction-Preliminary 5
1.4.4 Kinetics and Chemical Reaction Stoichiometry 6
1.4.5 Kinetics and Thermodynamics/Equilibrium 14
1.4.6 Kinetics and Transport Processes 15
1.5 Aspects of Chemical Reaction Engineering 15
1.5.1 Reactor Design and Analysis of Performance 15
1.5.2 Parameters Affecting Reactor Performance 16
1.5.3 Balance Equations 16
1.5.4 An Example of an Industrial Reactor 18
1.6 Dimensions and Units 19
1.7 Plan of Treatment in Following Chapters 21
1.7.1 Organization of Topics 21
1.7.2 Use of Computer Software for Problem Solving 21
1.8 Problems for Chapter 1 22
2 . KINETICS AND IDEAL REACTOR MODELS 25
2.1 Time Quantities 25
2.2 Batch Reactor (BR) 26
2.2.1 General Features 26
2.2.2 Material Balance; Interpretation ri of 27
2.3 Continuous Stirred-Tank Reactor (CSTR) 29
2.3.1 General Features 29
2.3.2 Material Balance; Interpretation of ri 31
2.4 Plug-Flow Reactor (PFR) 33
2.4.1 General Features 33
2.4.2 Material Balance; Interpretation ri of 34
2.5 Laminar-FIow Reactor (LFR) 36
2.6 Smnmary of Results for Ideal Reactor Models 38
2.7 Stoichiometric Table 39
2.8 Problems for Chapter 2 40
3 l EXPERIMENTAL METHODS IN KINETICS: MEASUREMENT OF RATE OF REACTION
3.1 Features of a Rate Law: Introduction 42
3.1.1 Separation of Effects 42
3.1.2 Effect of Concentration: Order of Reaction 42
3.1.3 Effect of Temperature: Arrhenius Equation; Activation Energy 44
3.2 Experimental Measurements: General Considerations 4 5
3.3 Experimental Methods to Follow the Extent of Reaction 46
3.3.1 Ex-situ and In-situ Measurement Techniques 46
3.3.2 Chemical Methods 46
3.3.3 Physical Methods 47
3.3.4 Other Measured Quantities 48
3.4 Experimental Strategies for Determining Rate Parameters 48
3.4.1 Concentration-Related Parameters: Order of Reaction 49
3.4.2 Experimental Aspects of Measurement of Arrhenius Parameters A and EA
3.5 Notes on Methodology for Parameter Estimation 57
3.6 Problems for Chapter 3 6 1
4 . DEVELOPMENT OF THE RATE LAW FOR A SIMPLE SYSTEM 64
4.1 The Rate Law 6 4
4.1.1 Form of Rate Law Used 64
4.1.2 Empirical versus Fundamental Rate Laws 65
4.1.3 Separability versus Nonseparability of Effects 66
4.2 Gas-Phase Reactions: Choice of Concentration Units 66
4.2.1 Use of Partial Pressure 66
4.2.2 Rate and Rate Constant in Terms of Partial Pressure 67
4.2.3 Arrhenius Parameters in Terms of Partial Pressure 68
4.3 Dependence of Rate on Concentration 6 9
4.3.1 First-Order Reactions 69
4.3.2 Second-Order Reactions 71
4.3.3 Third-Order Reactions 72
4.3.4 Other Orders of Reaction 75
4.35 Comparison of Orders of Reaction 75
4.3.6 Product Species in the Rate Law 78
4.4 Dependence of Rate on Temperature 7 9
4.4.1 Determination of Arrhenius Parameters 79
4.4.2 Arrhenius Parameters and Choice of Concentration Units for Gas-Phase
Reactions 80
4.5 Problems for Chapter 4 80
5 . COMPLEX SYSTEMS 87
5.1 Types and Examples of Complex Systems 8 7
51.1 Reversible (Opposing) Reactions 87
5.1.2 Reactions in Parallel 88
5.1.3 Reactions in Series 88
5.1.4 Combinations of Complexities 88
5.1.5 Compartmental or Box Representation of Reaction Network 89
5.2 Measures of Reaction Extent aud Selectivity 90
5.2.1 Reaction Stoichiometry and Its Significance 90
5.2.2 Fractional Conversion of a Reactant 91
5.2.3 Yield of a Product 91
5.2.4 Overall and Instantaneous Fractional Yield 92
5.2.5 Extent of Reaction 93
5.2.6 Stoichiometric Table for Complex System 93
5.3 Reversible Reactions 9 4
5.3.1 Net Rate and Forms of Rate Law 94
5.3.2 Thermodynamic Restrictions on Rate and on Rate Laws 95
5.3.3 Determination of Rate Constants 97
5.3.4 Optimal T for Exothermic Reversible Reaction 99
5.4 Parallel Reactions 100
5.5 Series Reactions 103
5.6 Complexities Combined 106
56.1 Concept of Rate-Determining Step (rds) 106
56.2 Determination of Reaction Network 106
5.7 Problems for Chapter 5 108
6 . FUNDAMENTALS OF REACTION RATES 115
6.1 Prelhninary Considerations 115
6.1.1 Relating to Reaction-Rate Theories 115
6.1.2 Relating to Reaction Mechanisms and Elementary Reactions 116
6.2 Description of Elementary Chemical Reactions 117
6.2.1 Types of Elementary Reactions 117
6.2.2 General Requirements for Elementary Chemical Reactions 120
6.3 Energy in Molecules 120
6.3.1 Potential Energy in Molecules-Requirements for Reaction 120
6.3.2 Kinetic Energy in Molecules 126
6.4 Simple Collision Theory of Reaction Rates 128
6.4.1 Simple Collision Theory (XT) of Bimolecular Gas-Phase Reactions 129
6.4.2 Collision Theory of Unimolecular Reactions 134
6.4.3 Collision Theory of Bimolecular Combination Reactions; Termolecular Reactions 137
6.5 Transition State Theory (TST) 139
6.5.1 General Features of the TST 139
6.5.2 Thermodynamic Formulation 141
6.5.3 Quantitative Estimates of Rate Constants Using TST with Statistical Mechanics 143
6.5.4 Comparison of TST with SCT 145
6.6 Elementary Reactions Involving Other Than Gas-Phase Neutral Species 146
6.6.1 Reactions in Condensed Phases 146
6.6.2 Surface Phenomena 147
6.6.3 Photochemical Elementary Reactions 149
6.6.4 Reactions in Plasmas 150
6.7 Summary 151
6.8 Problems for Chapter 6 152
7 . HOMOGENEOUS REACTION MECHANISMS AND RATE LAWS 154
7.1 Simple Homogeneous Reactions 155
7.1.1 Types of Mechanisms 155
7.1.2 Open-Sequence Mechanisms: Derivation of Rate Law from Mechanism 155
7.1.3 Closed-Sequence Mechanisms; Chain Reactions 157
7.1.4 Photochemical Reactions 163
7.2 Complex Reactions 164
7.2.1 Derivation of Rate Laws 164
7.2.2 Computer Modeling of Complex Reaction Kinetics 165
7.3 Polymerization Reactions 165
7.3.1 Chain-Reaction Polymerization 166
7.3.2 Step-Change Polymerization 168
7.4 Problems for Chapter 7 170
8 . CATALYSIS AND CATALYTIC REACTIONS 176
8.1 Catalysis and Catalysts 176
81.1 Nature and Concept 176
81.2 Types of Catalysis 178
81.3 General Aspects of Catalysis 179
8.2 Molecular Catalysis 182
8.2.1 Gas-Phase Reactions 182
8.2.2 Acid-Base Catalysis 183
8.2.3 Other Liquid-Phase Reactions 186
8.2.4 Organometallic Catalysis 186
8.3 Autocatalysis 187
8.4 Surface Catalysis: Intrinsic Kinetics 191
8.4.1 Surface-Reaction Steps 191
8.4.2 Adsorption Without Reaction: Langmuir Adsorption Isotherm 192
8.4.3 Langmuir-Hinshelwood (LH) Kinetics 195
8.4.4 Beyond Langmuir-Hinshelwood Kinetics 197
8.5 Heterogeneous Catalysis: Kinetics in Porous Catalyst Particles 198
8.5.1 General Considerations 198
8.5.2 Particle Density and Voidage (Porosity) 199
8.5.3 Modes of Diffusion; Effective Diffusivity 199
8.5.4 Particle Effectiveness Factor 77 201
8.5.5 Dependence of n on Temperature 210
8.5.6 Overall Effectiveness Factor Q 212
8.6 Catalyst Deactivation and Regeneration 214
8.6.1 Fouling 214
8.6.2 Poisoning 215
8.6.3 Sintering 215
8.6.4 How Deactivation Affects Performance 216
8.6.5 Methods for Catalyst Regeneration 216
8.7 Problems for Chapter 8 218
9 MULTIPHASE REACTING SYSTEMS 224
9.1 Gas-Solid (Reactant) Systems 224
9.1.1 Examples of Systems 224
9.1.2 Constant-Size Particle 225
9.1.3 Shrinking Particle 237
9.2 Gas-Liquid Systems 239
9.2.1 Examples of Systems 239
9.2.2 Two-Film Mass-Transfer Model for Gas-Liquid Systems 240
9.2.3 Kinetics Regimes for Two-Film Model 242
9.3 Intrinsic Kinetics of Heterogeneous Reactions Involving Solids 255
9.4 Problems for Chapter 9 257
10 BIOCHEMICAL REACTIONS: ENZYME KINETICS 261
10.1 Enzyme Catalysis 261
10.1.1 Nature and Examples of Enzyme Catalysis 261
10.1.2 Experimental Aspects 263
10.2 Models of Enzyme Kinetics 264
10.2.1 Michaelis-Menten Model 264
10.2.2 Briggs-Haldane Model 266
10.3 Estimation of K,,, and V,, 267
10.3.1 Linearized Form of the Michaelis-Menten Equation 267
10.3.2 Linearized Form of the Integrated Michaelis-Menten Equation 269
10.3.3 Nonlinear Treatment 269
10.4 Inhibition and Activation in Enzyme Reactions 269
10.4.1 Substrate Effects 270
10.4.2 External Inhibitors and Activators 272
10.5 Problems for Chapter 10 276
11 . PRELIMINARY CONSIDERATIONS IN CHEMICAL REACTION ENGINEERING 279
11.1 Process Design and Mechanical Design 279
11.1.1 Process Design 279
11.1.2 Mechanical Design 283
11.2 Examples of Reactors for Illustration of Process Design Considerations 283
11.2.1 Batch Reactors 283
11.2.2 Stirred-Tank Flow Reactors 284
11.2.3 Tubular Flow Reactors 284
11.2.4 Fluidized-Bed Reactors 290
11.2.5 Other Types of Reactors 291
11.3 Problems for Chapter 11 292
12 BATCH REACTORS (BR) 294
12.1 Uses of Batch Reactors 294
12.2 Batch Versus Continuous Operation 295
12.3 Design Equations for a Batch Reactor 296
12.3.1 General Considerations 296
12.3.2 Isothermal Operation 300
12.3.3 Nonisothermal Operation 304
12.3.4 Optimal Performance for Maximum Production Rate 307
12.4 Semibatch and Semicontinuous Reactors 309
12.4.1 Modes of Operation: Semibatch and Semicontinuous Reactors 309
12.4.2 Advantages and Disadvantages (Semibatch Reactor) 310
12.4.3 Design Aspects 311
12.5 Problems for Chapter 12 313
13 . IDEALFLOW 317
13.1 Terminology 317
13.2 Types of Ideal Flow; Closed and Open Vessels 318
13.2.1 Backmix Flow (BMF) 318
13.2.2 Plug Flow (PF) 318
13.2.3 Laminar Flow (LF) 318
13.2.4 Closed and Open Vessels 318
13.3 Characterization of Fiow By Age-Distribution Functions 319
13.3.1 Exit-Age Distribution Function E 319
13.3.2 Cumulative Residence-Time Distribution Function F 321
13.3.3 Washout Residence-Time Distribution Function W 322
13.3.4 Internal-Age Distribution Function I 322
13.3.5 Holdback H 322
13.3.6 Summary of Relationships Among Age-Distribution Functions
13.3.7 Moments of Distribution Functions 323
13.4 Age-Distribution Functions for Ideai Fiow 325
13.4.1 Backmix Flow (BMF) 325
13.4.2 Plug Flow (PF) 327
13.4.3 Laminar Flow (LF) 330
13.4.4 Summary of Results for Ideal Flow 332
13.5 Segregated Fiow 332
13.6 Problems for Chapter 13 333
14 . CONTINUOUS STIRRED-TANK REACTORS (CSTR) 335
14.1 Uses of a CSTR 336
14.2 Advantages and Disadvantages of a CSTR 336
14.3 Design Equations for a Single-Stage CSTR 336
14.3.1 General Considerations; Material and Energy Balances 336
14.3.2 Constant-Density System 339
14.3.3 Variable-Density System 344
14.3.4 Existence of Multiple Stationary States 347
14.4 Multistage CSTR 355
14.4.1 Constant-Density System; Isothermal Operation 351
14.4.2 Optimal Operation 358
14.5 Problems for Chapter 14 361
15 . PLUG FLOW REACTORS (PFR) 365
15.1 Uses of a PFR 365
15.2 Design Equations for a PFR 366
15.2.1 General Considerations; Material, Energy and Momentum Balances 366
15.2.2 Constant-Density System 370
152.3 Variable-Density System 376
15.3 Recycle Operation of a PFR 380
15.3.1 Constant-Density System 381
153.2 Variable-Density System 386
15.5 Problems for Chapter 15 389
16 . LAMINAR FLOW REACTORS (LFR) 393
16.1 Uses of an LFR 393
16.2 Design Equations for an LFR 394
16.2.1 General Considerations and Material Balance 394
16.2.2 Fractional Conversion and Concentration (Profiles) 395
16.2.3 Size of Reactor 397
16.2.4 Results for Specific Rate Laws 397
16.2.5 Summary of Results for LFR 399
16.2.6 LFR Performance in Relation to SFM 400
16.3 Problems for Chapter 16 400
17 . COMPARISONS AND COMBINATIONS OFIDEAL REACTORS 402
17.1 Single-Vessel Comparisons 402
17.1.1 BR and CSTR 402
17.1.2 BR and PFR 404
17.1.3 CSTR and PFR 405
17.1.4 PFR, LFR, and CSTR 406
17.2 Multiple-Vessel Contigurations 408
17.2.1 CSTRs in Parallel 409
17.2.2 CSTRs in Series: RTD 410
17.2.3 PFR and CSTR Combinations in Series 413
17.3 Problems for Chapter 17 418
18 . COMPLEX REACTIONS IN IDEAL REACTORS
18.1 Reversible Reactions 422
18.2 Parallel Reactions 426
18.3 Series Reactions 429
18.3.1 Series Reactions in a BR or PFR 429
18.3.2 Series Reactions in a CSTR 430
18.4 Choice of Reactor and Design Considerations 432
18.4.1 Reactors for Reversible Reactions 433
18.4.2 Reactors for Parallel-Reaction Networks 435
18.4.3 Reactors for Series-Reaction Networks 437
18.4.4 Reactors for Series-Parallel Reaction Networks 441
18.5 Problems for Chapter 18 445
19 . NONIDEAL FLOW 453
19.1 General Features of Nonideal Flow 453
19.2 Miig: Macromixing and Micromixing 454
19.3 Characterization of Nonideal Flow in Terms of RTD 455
19.3.1 Applications of RTD Measurements 455
19.3.2 Experimental Measurement of RTD 455
19.4 One-Parameter Models for Nonideal Plow 471
19.4.1 Tanks-in-Series (TIS) Model 471
19.4.2 Axial Dispersion or Dispersed Plug Flow (DPF) Model
19.4.3 Comparison of DPF and TIS Models 490
19.5 Problems for Chapter 19 490
20 . REACTOR PERFORMANCE WITH NONIDEAL FLOW 495
20.1 Tanks-in-Series (TIS) Reactor Model 495
20.2 Axial Dispersion Reactor Model 499
20.3 Segregated-Plow Reactor Model (SPM) 501
20.4 Maximum-Mixedness Reactor Model (MMM) 502
20.5 Performance Characteristics for Micromixing Models 504
20.6 Problems for Chapter 20 508
21 . FIXED-BED CATALYTIC REACTORS FOR FLUID-SOLID REACTIONS 512
21.1 Examples of Reactions 512
21.2 Types of Reactors and Modes of Operation 514
21.2.1 Reactors for Two-Phase Reactions 514
21.2.2 Flow Arrangement 514
21.2.3 Thermal and Bed Arrangement 514
21.3 Design Considerations 516
21.3.1 Considerations of Particle and Bed Characteristics 516
21.3.2 Fluid-Particle Interaction; Pressure Drop (-AP) 517
21.3.3 Considerations Relating to a Reversible Reaction 519
21.4 A Classification of Reactor Models 523
21.5 Pseudohomogeneous, One-Dimensional, Plug-Plow Model 527
21.51 Continuity Equation 527
21.5.2 Optimal Single-Stage Operation 528
21.5.3 Adiabatic Operation 529
21.5.4 Nonadiabatic Operation 542
21.6 Heterogeneous, One-Dimensional, Plug-Plow Model 544
21.7 One-Dimensional Versus ‘Dvo-Dimensional Models 546
21.8 Problems for Chapter 21 546
22 . REACTORS FOR FLUID-SOLID (NONCATALYTIC) REACTIONS
22.1 Reactions and Reaction Kinetics Models 552
22.2 Reactor Models 553
22.2.1 Factors Affecting Reactor Performance 553
22.2.2 Semicontinuous Reactors 553
22.2.3 Continuous Reactors 554
22.2.4 Examples of Continuous Reactor Models 556
22.2.5 Extension to More Complex Cases 563
22.3 Problems for Chapter 22 566
23 . FLUIDIZED-BED AND OTHER MOVING-PARTICLE REACTORS FOR FLUID-SOLID REACTIONS 23.1 Moving-Particle Reactors 570
23.1.1 Some Types 570
23.1.2 Examples of Reactions 572
23.1.3 Advantages and Disadvantages 573
23.1.4 Design Considerations 574
23.2 Pluid-Particle Interactions 574
23.2.1 Upward Flow of Fluid Through Solid Particles: (-AP) Regimes 575
23.2.2 Minimum Fluidization Velocity ( umf) 575
23.2.3 Elutriation and Terminal Velocity (u,) 577
23.2.4 Comparison umoff and u, 578
23.3 Hydrodynamic Models of Fluidization 579
23.3.1 Two-Region Model (Class (1)) 579
23.3.2 Kunii-Levenspiel (KL) Bubbling-Bed Model (Class (2))
23.4 Fluidized-Bed Reactor Models 584
23.4.1 KL Model for Fine Particles 584
23.4.2 KL Model for Intermediate-Size Particles 592
23.4.3 Model for Large Particles 595
23.4.4 Reaction in Freeboard and Distributor Regions 595
23.5 Problems for CChapter 23 596
24 REACTORS FOR FLUID-FLUID REACTIONS 599
24.1 Types of Reactions 599
24.1.1 Separation-Process Point of View 599
24.1.2 Reaction-Process Point of View 599
24.2 Types of Reactors 600
24.2.1 Tower or Column Reactors 600
24.2.2 Tank Reactors 602
24.3 Choice of Tower or Tank Reactor 602
24.4 Tower Reactors 603
24.4.1 Packed-Tower Reactors 603
24.4.2 Bubble-Column Reactors 608
24.5 Tank Reactors 614
24.5.1 Continuity Equations for Tank Reactors 614
24.5.2 Correlations for Design Parameters for Tank Reactors 615
24.6 Trickle-Bed Reactor: Three-Phase Reactions 618
24.7 Problems for Chapter 24 619
APPENDIX A 623
A.1 Common Conversion Factors for Non-S1 Units to SI Units
A.2 Values of Physicochemical Constants 623
A.3 Standard SI Prefixes 624
APPENDIX B: BIBLIOGRAPHY 625
B.l Books on Chemical Reactors 625
B.2 Books on Chemical Kinetics and Catalysis 626
APPENDIX C: ANSWERS TO SELECTED PROBLEMS 627
APPENDIX D: USE OF E-Z SOLVE FOR EQUATION SOLVING AND
PARAMETER ESTIMATION 635