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Diffusion Coefficients for Several Dilute Solutes in N-Eicosane, N-Octacosane, and Fischer-Tropsch Wax At 373-533 K - 1988

John Bernard Rodden

Texas A & M University

Cover Page

Abstract

Table of Contents

Section 1
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I

Introduction 1
 

A

Fischer-Tropsch Synthesis 1

B

Overview of Diffusion Research Program 2

C

Additional Accomplishments 4

D

General Outline 5

II

Measurements of Diffusion Coefficients  6
 

A

Types of Diffusion Coefficients 6

B

Techniques for Measuring Diffusion Coefficients 9

C

Taylor Dispersion 10

III

Previous Experimental Work 16

IV

Theory of Predicting Diffusion in Liquids  22
 

A

Hydrodynamic Theory 22

B

Activation Theory 23
C Free Volume Theory 24
D Kinetic Theory 25
E Correlation of Experimental Data with the RHS Theory 31
Section 2
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V

Apparatus and Procedure  35
 

A

Original Apparatus and Procedure 35

B

Potential Sources of Error 39

C

Density From Taylor Dispersion 41

D

Modifications to the Original Apparatus 42

E

Special Considerations with Molten Solvents 48

F

Composition of Solutes and Solvents 49

G

Experimental Conditions 51

VI

Taylor Dispersion Model 52
 

A

Mathematical Description of Model 52

B

Handling of Raw Data 55

C

Model Validation Using Generated Data 56

D

Model Validation Using Experimental Data 58

E

Sensitivity Analyses 64

F

Comparison to Other Analysis Methods 68

G

Comparison of Model Results to Literature Values 71

H

Selection of Operating Flow Rate 72
 

1

Flow Criteria Based on Limitations of Taylor's Solution 73

2

Laminar Flow Criterion 75

3

Coiling Effects 75
Section 3
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VII

Results and Discussion 79
 

A

Diffusion Coefficients Measured During This Work 79

B

Correction of Previously Reported Values 90

C

Solvent Density 91

D

Rough Hard Sphere Correlation 93

E

Validation of Correlation Using Literature Data 107

F

Predicting Diffusion Coefficients in Fischer-Tropsch Wax 111
Section 4
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VIII

Conclusions 119
  Recommendations for Future Work 122
Literature Cited 124
Appendix A:  Fortran Code for Taylor Dispersion Model  130
Appendix B: Example Output from Taylor Dispersion Model  145
B.1 Carbon Dioxide in N-Eicosane at 222 C 146
B.2. N-Dodecane in N-Eicosane at 222 C 152
B.3. N-Octane in N-Octacosane at 100 C 159
Appendix C:  Corrected Diffusion Coefficients in the Solvents N-Heptane, N-Dodecan, and N-Hexadecane 167
Appendix D:  Tabulation of Literature Diffusion Coefficients Versus the Predictions of Equation 7.8 170
Vita 176