KINETICS AND INTERACTIONS OF THE SIMULTANEOUS CATALYTIC HYDRODENITROGENATION OF PYRIDINE AND HYDRODESULFURIZATION OF THIOPHENE by JOHN A. WILKENS B.S., Cornell University (1969) Master of Engineering (Chemical), Cornell University (1971) Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY August, 1977 Signature of Author: Dpartment of Chemical Engineering If A Certified by: Professor C. N. Satterfield ' Thesis Supervisor __ __ -- Professor M. Modell Thesis Supervisor Accepted by: Chairman, Departmental Committee otr~a-dua te Theses SEP 21 197 #rII%* k i Abstract KINETICS AND INTERACTIONS OF THE SIMULTANEOUS CATALYTIC HYDRODENITROGENATION OF PYRIDINE AND HYDRODESULFURIZATION OF THIOPHENE by JOHN A. WILKENS Submitted to the Department of Chemical Engi- neering in August, 1977, in partial fulfillment of the requirements for the degree of Doctor of Philosophy Interactions between the simultaneous catalytic hydrodenitrogenation (HDN) of pyridine and hydrodesulfur- ization (HDS) of thiophene were investigated in a con- tinuous-flow, packed-bed microreactor using a sulfided NiMo/A12 03 catalyst. The reactions were carried out in the vapor phase at total pressures from 150 to 1000 psig (1.1 to 7.0 MPa), and temperatures from 150 to 4100 C. Pyridine and thiophene partial pressures ranged from 93 to 186 torr (12 to 25 kPa). Thiophene HDS was severely inhibited by the presence of pyridine under all reaction conditions studied. Butylamine caused the same degree of inhibition as did pyridine. A Langmuir-Hinshelwood kinetic analysis showed a pyridine adsorption strength greater than that of thiophene on active catalytic sites. Hydrogen sulfide, present as a product of thiophene hydrogenolysis, appeared to be more weakly adsorbed than thiophene. At temperatures above 3500 C, thermodynamic equilibrium was established between pyridine and its saturated reaction intermediate, piperidine, at all pressures studied. Higher hydrogen partial pressures shift the equilibrium composition toward piperidine. Complete conversion of pyridine to piperidine was achieved at the higher pressures. The presence of thiophene inhibited the hydrogenation of pyridine at temperatures below 3500 C. Above 350°C, thiophene enhanced the pyridine hydrogenation, giving con- versions greater than those of the pure-pyridine feed reactions. The concentration of piperidine decreased greatly with the addition of thiophene, caused by both the inhibition of pyridine hydrogenation and the enhancement of piperidine hydrogenolysis. This enhancement was most likely due to increased catalytic activity caused by the sulfiding action and acidity of hydrogen sulfide, a pro- duct of thiophene HDS. In the presence of thiophene, piperidine did not reach its equilibrium concentration under any reaction conditions studied. The overall con- version of pyridine to products beyond piperidine was enhanced by the presence of thiophene for temperatures greater than 300°C at the higher pressures. Kinetic analysis showed piperidine to compete with pyridine for catalytic sites with an adsorption strength equal to or slightly greater than that of pyridine. Ammonia adsorption was equal to or weaker than that of pyridine. The activity of the sulfided NiMo/Al 03 was strongly dependent upon the state of sulfiding of he catalyst. The addition of thiophene to the reactor feed maintained the catalyst activity in the presence of pyridine, a basic nitrogen compound. Thesis Supervisors: C. N. Satterfield Professor of Chemical Engineering M. Modell Professor of Chemical Engineering Department of Chemical Engineering Massachusetts Institute of Technology Cambridge, Massachusetts 02139 August, 1977 Professor Irving Kaplan Secretary of the Faculty Massachusetts Institute of Technology Cambridge, Massachusetts 02139 Dear Professor Kaplan: In accordance with the regulations of the Faculty, I herewith submit a thesis, entitled "Kinetics and Interactions of the Simultaneous Catalytic Hydrode- nitrogenation of Pyridine and Hydrodesulfurization of Thiophene", in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemical Engineering at the Massachusetts Institute of Tech- nology. Respectfully submitted, John A. Wilkens This Thesis is Dedicated to my Family ACKNOWLEDGEMENTS First, I am grateful to my thesis advisors, Professor Charles N. Satterfield and Professor Michael Modell, for their support, guidance, and enhancement of my professional development. I wish to acknowledge the U.S. Environmental Protection Agency for providing financial support for part of my M.I.T. career, and to thank Prof. Glenn Williams for arranging Departmental support for some of the remaining times. Monsieur Claude Declerck deserves special thanks for his excellent advice on gas chromatographic separations; and for providing, through the Solvay Company of Brussels, Belgium, the catalyst analyses presented in this thesis. His uplifting spirits were also greatly appreciated. The mass spectrometric analysis was carried out by Mr. Robert Laflamme and Prof. Ronald Hites. I wish to thank many people who have contributed to the success of my M.I.T. career in various ways, particularly Mrs. Johanna Bond, Mr. Arthur Clifford, Prof. Richard Donnelly, Mr. Charles Foshey, Mr. John Fresina, Mr. Kent Griffis, Mr. Paul Halloran, Prof. Jack Howard, Mrs. Elenore Kehoe, Dr. Jerry Mayer, Mr. Richard McKay, Mr. Stanley Mitchell, Mr. Hank Prichard, and Prof. John Vivian. It was the close association of fellow students from many parts of the world which made life during these M.I.T. years interesting and enjoyable. Of particular significance, through nearly all of my days in Cambridge, were the friend- ships of Michael van Eek and Fahri Ozel. Of special importance throughout the last several years has been the encouraging and comforting presence of my wife, Lucie. Her contributions to my work have ranged from scholarly advice to the typing of many parts of this thesis. Finally, I wish to thank my parents, grandfather, and brother for nearly three decades of continual development, encouragement, stimulation, and support of my interest in science and technology. It has been their love, patience, and understanding which have helped make this long edu- cational process both possible and enjoyable. John A. Wilkens Cambridge, Massachusetts August, 1977 7- Table of Contents I. Summary 21 I.A. Introduction 21 I.B. Objectives 22 I.C. Literature Review 22 I.D. Experimental Apparatus and Procedure 29 I.E. Results 31 I.E.1. Catalyst Activity 32 I.E.2. Pure Thiophene Hydrodesulfur- 33 ization I.E.3. Thiophene HDS in the Presence of 34 Nitrogen Compounds I.E.4. Pure Pyridine Hydrodenitrogen- 35 ation I.E.5. Pyridine HDN in the Presence of 37 Sulfur Compounds I.F. Discussion of Results 39 I.F.1. Catalyst Activity 39 I.F.2. Pure Thiophene Hydrodesulfur- 40 ization I.F.3. Thiophene HDS in the Presence of 41 Nitrogen Compounds I.F.4. Thiophene HDS: Kinetic Analysis 42 I.F.5. Pure Pyridine Hydrodenitrogen- 45 ation I.F.6. Pyridine HDN: Equilibrium Analysis 47 I.F.7. Pyridine HDN in the Presence of 49 Sulfur Compounds I.F.8. Pyridine HDN: Kinetic Analysis 50 I.F.9. Relative Rates of Thiophene HDS 53 and Pyridine HDN I.G. Conclusions 54 I.G.1. Catalyst Activity 54 I.G.2. Thiophene Hydrodesulfurization 54 I.G.3. Pyridine Hydrodenitrogenation 55 II. Introduction 69 II.A. General Background 69 -8- II.B. Literature Review 73 II.B.1. Desulfurization and Denitro- 73 genation Catalysts II.B.2. Thiophene Hydrodesulfurization 74 II.B.2.a. Thiophene Adsorption 75 II.B. 2.b. Hydrogen Adsorption 77 II.B.2.c. Hydrogen Sulfide Ad- 79 sorption II.B.2.d. Hydrocarbon Adsorption 81 II.B.2.e. Adsorption of Basic 84 Nitrogen Compounds II.B.2.f. Reaction Products of 86 Thiophene HDS II.B.2.g. Thiophene HDS Reaction 87 Mechanism II.B.3. Pyridine Hydrodenitrogenation 92 II.B.3.a. Pyridine HDN: Mechanism, 92 Kinetics, and Compound Adsorptions II.B. 3.b. Pyridine HDN: Equili- 96 brium Limitation II.B. 3.c. Pyridine Hydrogenation: 97 Constant Determination II.B.3.d. Pyridine HDN: Effects 99 of Sulfur Compounds II.C. Thermodynamics of Thiophene HDS and Pyr- 101 idine HDN II.D. Objectives 104 III. Apparatus and Procedure 106 III.A. Reactor Design Considerations 114 III.B. Reactor System 116 III.C. The Catalyst Used, and Catalyst Sulfiding 121 Procedures III.D. Reactant Feed Systems 123 III.E. Reactant Stream Composition Analysis 126 III.F. Safety Considerations 133 III.G. Experimental Procedure 136 IV. Results 140 IV.A. Catalyst Activity 142 IV.B. Thiophene Hydrodesulfurization 149 -9- IV.B.1. Pure Thiophene HDS 150 IV.B.2. Thiophene HDS in the Presence 152 of Nitrogen Compounds IV.B.3. Effect of Methyl Substitution 153 on Thiophene HDS IV.C. Pyridine Hydrodenitrogenation 160 IV.C.1. Pure Pyridine HDN 161 IV.C.2. Pyridine HDN in the Presence 173 of Sulfur Compounds V. Discussion of Results 186 V.A. Catalyst Activity 187 V.B. Thiophene Hydrodesulfurization 190 V.B.1. Pure Thiophene HDS 190 V.B.2. Thiophene HDS in the Presence 191 of Nitrogen Compounds V.B.3. Effect of Methyl Substitution 193 on Thiophene HDS V.B.4. Thiophene HDS: Kinetic Analysis 196 V.C. Pyridine Hydrodenitrogenation 213 V.C.1. Pure Pyridine HDN 213 V.C.2. Pyridine HDN: Equilibrium 219 Analysis V.C.3. Pyridine HDN in the Presence 233 of Sulfur Compounds V.C.4. Pyridine HDN: Kinetic Analysis 241 V.D. Relative Rates of Thiophene HDS and 255 Pyridine HDN V.E. Quality of the Experimental Data 260 VI. Conclusions 266 VI.A. Catalyst Activity 266 VI.B. Thiophene Hydrodesulfurization 266 VI.C. Pyridine Hydrodenitrogenation 267 VII. Recommendations 269 -10- VIII. Appendix 271 VIII.A. Apparatus - Further Details 271 VIII.B. Physical Property Data 278 VIII.C. Run Data Summaries 282 VIII.D. Derivation of Equations and 310 Supporting Principles VIII.D.1. Plug Flow Reactor 310 Parameters VIII.D.2. Conversion of Reactants 312 VIII.D.3. Data Quality - Statistical 316 Determination VIII.D.4. Pyridine-Piperidine Equili- 319 brium - Principles of cal- culation VIII.E.