CONTENTS

Front Matter

Title Page, Preface and Acknowledgements
About the Author
Status, History, Issues and Updates
Complementary Textbooks
Teaching Notes and Resources
A Note about Numerical Solutions

Course Units

I. Chemical Reactions
1. Stoichiometry and Reaction Progress
2. Reaction Thermochemistry
3. Reaction Equilibrium
II. Chemical Reaction Kinetics
A. Rate Expressions
4. Reaction Rates and Temperature Effects
5. Empirical and Theoretical Rate Expressions
6. Reaction Mechanisms
7. The Steady State Approximation
8. Rate-Determining Step
9. Homogeneous and Enzymatic Catalysis
10. Heterogeneous Catalysis
B. Kinetics Experiments
11. Laboratory Reactors
12. Performing Kinetics Experiments
C. Analysis of Kinetics Data
13. CSTR Data Analysis
14. Differential Data Analysis
15. Integral Data Analysis
16. Numerical Data Analysis
III. Chemical Reaction Engineering
A. Ideal Reactors
17. Reactor Models and Reaction Types
B. Perfectly Mixed Batch Reactors
18. Reaction Engineering of Batch Reactors
19. Analysis of Batch Reactors
20. Optimization of Batch Reactor Processes
C. Continuous Flow Stirred Tank Reactors
21. Reaction Engineering of CSTRs
22. Analysis of Steady State CSTRs
23. Analysis of Transient CSTRs
24. Multiple Steady States in CSTRs
D. Plug Flow Reactors
25. Reaction Engineering of PFRs
26. Analysis of Steady State PFRs
27. Analysis of Transient PFRs
E. Matching Reactors to Reactions
28. Choosing a Reactor Type
29. Multiple Reactor Networks
30. Thermal Back-Mixing in a PFR
31. Back-Mixing in a PFR via Recycle
32. Ideal Semi-Batch Reactors
IV. Non-Ideal Reactions and Reactors
A. Alternatives to the Ideal Reactor Models
33. Axial Dispersion Model
34. 2-D and 3-D Tubular Reactor Models
35. Zoned Reactor Models
36. Segregated Flow Models
37. Overview of Multi-Phase Reactors
B. Coupled Chemical and Physical Kinetics
38. Heterogeneous Catalytic Reactions
39. Gas-Liquid Reactions
40. Gas-Solid Reactions

Supplemental Units

S1. Identifying Independent Reactions
S2. Solving Non-differential Equations
S3. Fitting Linear Models to Data
S4. Numerically Fitting Models to Data
S5. Solving Initial Value Differential Equations
S6. Solving Boundary Value Differential Equations

Unit 9. Homogeneous and Enzymatic Catalysis

This website provides learning and teaching tools for a first course on kinetics and reaction engineering. The course is divided into four parts (I through IV). Here, in Part II of the course, the focus is on chemical reaction kinetics, and more specifically, on rate expressions, which are mathematical models of reaction rates. As you progress through Part II, you will learn how rate expressions are generated from experimental kinetics data.

This first section of Part II of the course focuses upon the selection of an equation to be tested as a rate expression. The equation to be tested can be chosen simply for its mathematical convenience. Alternatively, theory can be used to select the mathematical form of the equation to be tested. For some reactions, theory can be applied directly. In other cases the reaction must be described in terms of a group of reactions that comprise what is known as a reaction mechanism. In the latter case theory can be applied to the reactions in the mechanism which are then combined to get the mathematical form of the equation to be tested.

A mathematical expression for the rate of a non-elementary reaction can be generated from its mechanism, using methods described in the last three units. However, when the reaction mechanism involves charged species, enzymes or homogeneous catalysts, those methods must be modified to account for the conservation of charge or catalyst. This is the subject of Unit 9.

Learning Resources

Teaching Resources

Practice Problems

1. Setty and Prengle (Ind. Eng. Chem. Fund. 3(4), 300, 1964.) studied reaction (1a) and proposed the mechanism given in reactions (1b) through (1e). The reaction was catalyzed by AlCl3, which was added to the system by dissolving a known amount of it in nitromethane and injecting the resulting solution. As reaction (1b) indicates, some of the AlCl3 complexes with the nitromethane, and this complex is the catalytically active entity. Derive an expression for the rate of consumption of hexene on the basis of this mechanism. In doing so, you may assume that nitromethane will always be present in sufficient quantity to permit easy measurement of its concentration.

  C6H12 + C6H6 ↔ phenylhexanes (1a)  
  AlCl3 + CH3NO2 ↔ AlCl3:NO2CH3 (1b)  
  C6H12 + AlCl3:NO2CH3 ↔ C6H12-AlCl3:NO2CH3 (1c)  
  C6H6 + C6H12-AlCl3:NO2CH3 ↔ 2-phenylhexane + AlCl3:NO2CH3 (1d)  
  C6H6 + C6H12-AlCl3:NO2CH3 ↔ 3-phenylhexane + AlCl3:NO2CH3 (1e)  

(Problem Statement as .pdf file)

2. Suppose that enzyme E requires a cofactor, C, in order to catalyze the conversion of its substrate, S, to the product, P. If the overall reaction is given by equation (2a) and the mechanism is given by equations (2b) through (2d) with reaction (2d) being irreversible, derive an acceptable expression for the overall rate of reaction. The free cofactor concentration is easy to measure, so it is acceptable for its concentration to appear in the rate expression.

  S → P (2a)  
  E + C ↔ EC (2b)  
  EC + S ↔ ECS (2c)  
  ECS → EC + P (2d)  

(Problem Statement as .pdf file)

3. Suppose the combination of substrate A, SA, and substrate B, SB, to form the product P, reaction (3a), is catalyzed by an enzyme, E, according to the mechanism given in reactions (3b) through (3d). Reactions (3b) and (3d) are reversible. Compare the rate expression that results if reaction (3c) is effectively irreversible to the rate expression that results if reaction (3c) is rate-determining.

  SA + SB → P (3a)  
  SA + E ↔ E-SA (3b)  
  E-SA + SB → E-P (3c)  
  E-P ↔ E + P (3d)  

(Problem Statement as .pdf file)