Supercritical Fluid Extraction: A Study of Binary and Multicomponent Solid-Fluid Equilibria by Ronald Ted Kurnik ~ B.S.Ch.E. Syracuse University (1976) M.S.Ch.E. Washington University (1977) SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF SCIENCE at the MASSACHUSETTS INSTITUT.E OF TECHNOLOGY May, 1981 @Massachusetts Institute of Technology, 1981 Signature of Author Signature redacted -------""="--------,------------Department of Chemical Engineering May, 1981 Certified by Signature redacted Robert C. Reid i:cnesis Supervisor / Signature redacted Accepted by ARC~J\'ES (_ ;- . _ . = . _ . .. _ MASSACHUSEIT . Chairman, Departmental OFTECHN&&is7rrurE Committee on Graduate Students OCT 2 8 1981 UBRARlES SUPERCRITICAL FLUID EXTRACTION: A STUDY OF BINARY AND MULTICOMPONENT SOLID-FLUID EQUILIBRIA by RONALD TED KURNIK Submitted to the Department of Chemical Engineering on May 1981, in partial fulfillment of the requirements for the degree of Doctor of Science ABSTRACT Solid-fluid equilibrium data for binary and multicom- ponent systems were determined experimentally using two supercritical fluids -- carbon dioxide and ethylene, and six solid solutes. The data were taken for temperatures between the upper and lower critical end points and for pressures from 120 to 280 bar. The existence of very large (106) enhancement (over the ideal gas value) of solubilities of the solutes in the fluid phase was.observed with these systems. In addition, it was found that the solubility of a species in a multicomponent mixture could be significantly greater (as much as 300 per- cent) than the solubility of that same pure species in the given supercritical fluid (at the same temperature and pressure). Correlation of both pure and multicomponent solid-fluid equilibria was accomplished uiing the Peng-Ronbinson equation of state. In the case of multicomponent solid-fluid equil- ibrium it was necessary to introduce an additional binary solute-solute interaction coefficient. The existence of a maximum in solubility of a solid in a supercritical fluid was observed both theoretically and experimentally. The reason for this maximum was explained. Energy effects in solid-fluid equilibria were studied and it was shown that in the retrograde solidification region that the partial molar enthalphy difference for the solute between the fluid and solid phase is exothermic. Thesis Supervisor: Robert C. Reid Title: Professor of Chemical Engineering Department of Chemical Engineering Massachusetts Institute of Technology Cambridge, Massachusetts 02139 May, 1981 Professor George C. Newton Secretary of the Faculty Massachusetts Institute of Technology Cambridge, Massachusetts 02139 Dear Professor Newton: In accordance with the regulations of the Faculty I herewith submit a thesis entitled "Supercritical Fluid Extraction: A Study of Binary and Multicomponent Solid-Fluid Equilibria" in partial fulfillment of the requirements for the degree of Doctor of Science in Chemical Engineering at the Massachusetts Institute of Technology. Respectfully submitted, Ronald Ted Kurnik 5 ACKNOWLE DGEMENTS The author gratefully acknowledges the support and advice of Professor Robert C. Reid. Many thanks are due to Dr. Val J. Krukonis for his enthusiastic support of this work and for his help in the experimental design of the equipment used in this thesis. The help of Mike Mullins in constructing the equipment is gratefully acknowledged. Dr. Herb Britt, Dr. Joe Boston, Dr. Paul Mathias, Suphat Watanasiri, and Fred Ziegler of the ASPEN project are thanked for their many helpful discussions. The members of my thesis committee, Professor Modell, Professor Longwell, Professor Daniel I. C. Wang and Dr. Charles Apt provided many helpful comments and suggestions. Samuel Holla was helpful in obtaining some of the equil- ibrium data used in this thesis. The Nestle's Company is gratefully acknowledged for their financial support in terms of a three year fellowship. Financial support of the National Science Foundation is appreciated. To my many friends at MIT, especially those in the LNG lab, thanks for good advice, endless encouragement, and many fun filled hours when we were together. I wish you all 6 success, happiness, and lasting friendship in the years to come. Finally, I am most indebted to my brother, parents, and grandmother for their continuous confidence and support throughout my schooling. Ronald Ted Kurnik Cambridge, Massachusetts May, 1981 7 CONTENTS Page 1. SUMMARY 20 1-1 Introduction 20 1-2 Background 22 1-3 Thesis Objectives 27 1-4 Experimental Apparatus and Procedure 28 1-5 Results and Discussion 30 1-6 Recommendations 54 2. INTRODUCTION 57 2-1 Background 57 2-2 Phase Diagrams 85 2-3 Thermodynamic Modelling of Solid-Fluid Equilibria 115 2-4 Thesis Objectives 128 3. EXPERIMENTAL APPARATUS AND PROCEDURE 130 3-1 Review of Alternative Experimental 130 Methods 3-2 Description of Equipment 131 3-3 Operating Procedure 134 3-4 Determination of Solid Mixture Composition 135 3-5 Safety- Considerations 136 4. RESULTS AND DISCUSSION OF RESULTS 137 4-1 Binary Solid-Fliud Equilibrium Data 137 4-2 Ternary solid-Fluid Equilibrium Data 159 4-3 Experimental Proof that T < Tq 189 5. UNIQUE SOLUBILITY PHENOMENA OF SUPERCRITICAL FLUIDS 193 5-1 Solubilitv Minima 193 5-2 Solubility Maxima 194 5-3 A Method to Achieve 100% Solubility of a Solid in a Supercritical Fluid Phase 201 5-4 Entrainers in Supercritical Fluids 202 5-5 Transport Properties of Supercritical Fluids 206 lo I a Page 6. ENERGY EFFECTS 208 6-1 Theoretical Development 208 6-2 Presentation and Discussion of Theoretical Results 210 7. OVERALL CONCLUSIONS 214 217 8. RECOM ENDATIONS FOR FUTURE RESEARCH 8-1 Solid-Fluid Equilibria 217 8-2 Liquid-Fluid Equilibria 218 8-3 Equipment Design 219 APPENDIX I. Partial Molar Volume Using the Peng-Robinson Equation of State 220 APPENDIX II. Derivation of Slope Equality at a Binary Mixture Critical Point 222 APPENDIX III. Derivation of Enthalpy Change of Solvation 225 APPENDIX IV. Freezing Point Data for Multicom- ponent Mixtures 227 APPENDIX V. Physical Properties of Solutes Studied 236 APPENDIX VI. Sources of Physical Properties of Complex Molecules 244 APPENDIX VII. Listings of Pertinent Computer Programs 246 APPENDIX VIII. Detailed Equipment Specifications and Operating Procedures 281 APPENDIX IX. Operating Conditions and Calibra- 286 tions for the Gas Chromatograph 304 APPENDIX X. Sample Calculations Standardization and APPENDIX XI. Equipment 307 Error Analysis Location of Original Data, APPENDIX XII. 314 Computer Programs, and Output NOTATION 315 9 Page LITERATURE CITED 320 BIOGRAPHICAL SKETCH 332 10 LIST OF FIGURES Page 1-1 Equipment Flow Chart 29 1-2 The Pressure-Temperature-Composition Surfaces for Equilibrium Between Two Pure Solid Phases, A Liquid Phase and a Vapor Phase 32 1-3 P-T Projection of a System in Which the Three Phase Line Does Not Cut the Critical Locus 33 1-4 P-T Projection of a System in which the Three Phase Line Cuts the Critical Locus 35 1-5 Solubility of Benzoic Acid in Supercritical Carbon Dioxide 36 1-6 Solubility of 2,3-Dimethylnaphthalene in Supercritical Carbon Dioxide 37 1-7 Solubility of 2,3-Dimethylnaphthalene in Supercritical Ethylene 38 1-8 Solubility of Naphthalene in Supercritical Nitrogen 40 1-9 P-T Projection of a Four Dimensional Surface of Two Solid Phases in Equilibrium with a Fluid Phase 42 1-10 Solubility of Phenanthrene from a Phenanthrene-Naphthalene Mixture in Supercritical Carbon Dioxide 44 1-11 Solubility of Naphthalene from a Phenanthrene-Naphthalene Mixture in Supercritical Carbon Dioxide 45 1-12 Selectivities in the Naphthalene- Phenanthrene-Carbon Dioxide System 47 11 Page 1-13 Solubility of Naphthalene in Supercritical Ethylene-Indicating Solubility Maxima 49 1-14 Experimental Data Confirming Solubility Maxima of Naphthalene in Supercritical Ethylene 51 1-15 Partial Molar Volume of Naphthalene in Supercritical Ethylene 55 2-1 Solubility of Naphthalene in Supercritical Ethylene 65 2-2 Reduced Second Cross Virial Coefficients of Anthracene in C0 2 , C 2 H 4 , C2 H6 , and Temperature 67 CH 4 as a Function of Reduced 2-3 Kerr-McGee Process to De-ash Coal 72 2-4 Phase Diagrams for a Ternary Solvent- Water-Fluid Type I System 75 2-5 Phase Diagrams for a Ternary Solvent- Water-Fluid Type II System 77 2-6 Phase Diagrams for a Ternary Solvent- Water-Fluid Type III System 78 2-7 Phase Equilibrium Diagram for Ethylene- Water-Methyl Ethyl Ketone and Schematic Flowsheet for Ethylene Dehydration of Solvents 2-8 Supercritical Fluid (SCI) Operating Regimes for Extraction Purposes 82 2-9 The Pressure-Temperature-Composition Surfaces for the Equilibrium Between Two Pure Solid Phases, A Liquid Phase and a Vapor Phase 86 2-10 A Pressure Composition Section at a Constant Temperature Lying Between the Melting Points of the Pure Components 88 2-11 A Pressure Composition Section at a 12 Page Constant Temperature above the Melting Point of the Second Component 89 2-12 P-T Projection of a System in Which the Three Phase Line Does Not Cut the Critical Locus 90 2-13 P-T Projection of a System in Which the Three Phase Line Cuts the Critical Locus 93 2-14 A P-T Projection Indicating Where the Isothermal P-x Projections of Figure 2-15 are Located 94 2-15 Isothermal P-x Projections for Solid- Fluid Equilibria 95 2-16 Naphthalene-Carbon Dioxide Solubility Map Calculated from the Peng-Robinson Equation 98 2-17 Solubility of Phenanthrene in Supercritical Carbon Dioxide 99 2-18 Space Model in the Case Where the Critical Locus and the Three Phase Line