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MAR 0 8 1984 Liranit3 MASSACHUSETTS INSTITUTE of TECHNOLOGY REACTIVITY OF NICKEL PORPHYRINS IN CATALYTIC HYDRODEMETALLATION by ROBERT ADAMS WARE B.S., Worcester Polytechnic Institute (1977) M.S., Cornell University (1979) Submitted to the Department of Chemical Engineering in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF SCIENCE at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY September 1983 i,. - r c q Massachusetts Institute of Tecnology 1983 Signature of Author Department of Chemical Engineering September 15, 1983 Certified by James Wei Thesis Supervisor Accepted by Robert C. Reid Chairman, Departmental Committee on Graduate Students Archives MASSANHETTS 1 'TUE MAR 0 8 1984 LIRAnIt3 MASSACHUSETTS INSTITUTE OF TECHNOLOGY DEPARTMENT OF CHEMICAL ENGINEERING Room number: Cambridge, Massachusetts Telephone: 02139 September 15, 1983 Professor Jack P. Ruina Secretary of the Faculty Massachusetts Institute of Technology Cambridge, MA 02139 Dear Professor Ruina: In accordance with the regulations of the Faculty, I herewith submit a thesis, entitled, "Reactivity of Nickel Porphyrins in Catalytic Hydrodemetallation," in partial fulfillment of the requirements for the degree of Doctor of Science in Chemical Engineering at the Massachusetts Institute of Technology. Respectfully submitted, Robert A. Ware REACTIVITY OF NICKEL PORPHYRINS IN CATALYTIC HYDRODEMETALLATION by ROBERT ADAMS WARE Submitted to the Department of Chemical Engineering on September 15, 1983 in partial fulfillment of the requirements for the Degree of Doctor of Science in Chemical Engineering ABSTRACT The kinetics and reaction network of hydrodemetallation (HDM) reactions and the pattern of metal deposition have been investigated using a model residuum oil, consisting of nickel porphyrins (Ni- etioporphyrin (Ni-EP), Ni-tetraphenylporphyrin (Ni-TPP), and Ni- tetra(3-methylphenyl)porphyrin (Ni-T3MPP)) dissolved in a clean (N and S free) mineral oil. Reactions were carried out over a commercial CoO-MoO./Y-Al 2 03 catalyst at 285 - 345 *C and 4.24 - 10.44 MPa H2 (600 - 1500 psig). The porphyrins react via sequential pathways, first involving hydrogenation of peripheral double bonds to "activate" the porphyrin for the final hydrogenolysis steps which fragment the ring and deposit the metal on the catalyst. The extent of initial hydrogenation, the complexity of the reaction pathway, and the overall rate limiting step for metal removal are dependent on the porphyrin structure. One route to deposition with Ni-T3MPP and Ni-TPP is through a non-porphyrinic nickel intermediate. The behavior of a commercial HDS catalyst in promoting HDM reactions is consistent with the dual functionality concept of hydrogenation activity associated with Co and Mo sites and hydrogenolysis (metal deposition) activity associated with acid sites on the support and Mo. The presence of nitrogen (pyridine) and sulfur (CS 2 , sulfided catalyst) did not change the reaction pathway of Ni-T3MPP during HDM but did alter the hydrogenation/hydrogenolysis reaction selectivity. Pyridine preferentially retarded the hydrogenation steps whereas sulfiding the catalyst selectively enhanced the metal deposition steps. The feasibility of controlling the Ni-T3MPP hydrogenation/ hydrogenolysis (metal deposition) reaction selectivity was demonstrated by doping the CoMo/Al 20 3 catlyst. Changes as dramatic as a shift in the overall rate limiting step were possible. Alkali (Cs, Na) neutralized catalyst acidity and drastically reduced the metal deposition activity with only a marginal reduction in the high hydrogenation activity. Sulfur and halogens (I, Cl) added in a reducing environment resulted in high metal deposition activity attributed to an increase in Bronsted acidity on the surface. Hydrogenation activity became successively lower (S>I>Cl) and rate limiting with the halogens and was interpreted as arising from a strong interaction between Mo vacancies and the halogen which deactivated hydrogenation sites. Nickel deposition profiles obtained under diffusion limited conditions reflect the intrinsic reactivity of the nickel porphyrins. At the reactor entrance all profiles were characterized by an internal maxima in the metal deposition pattern, termed M-shape. These maxima shifted to the edge of the catalyst pellets at the end of the reactor bed. The enhanced metal deposition activity of the sulfided catalyst compared to the oxide catalyst was manifested in steeper, more U-shape metal profiles. Theoretical calculations based on sequential HDM reaction schemes coupled with diffusion successfully interpreted the metal profiles. 2 Diffusivities for the nickel species were on the order of 10-6 cm /sec with the hydrogenated intermediates having diffusion coefficients 2 to 3.5 times larger than the starting porphyrin. The impact of the variations in Ni-T3MPP reaction selectivity obtained by doping the catalyst was apparent in metal deposition profiles generated under diffusion limited conditions. Thesis Supervisor: Dr. James Wei Department Head and Warren K. Lewis Professor of Chemical Engineering In Loving Memory of Rosemary J. Wojtowicz Our life together was painfully short yet during this time we lived life to its fullest, enjoying so much in each others company. She brought a special joy and happiness into my life that I would have otherwise not known. The beloved memories of what we did and shared together will always have a special place in my heart. I dedicate this work to Rosie. The example of her accomplishments and the thought of her constant encouragement and companionship have been a continuing source of inspiration for me. As she now lives, so too shall my memories of her. "Blessed are the pure in heart: for they shall see God." Matthew 5:8 ACKNOWLEDGEMENTS I would first like to express my gratitude to my thesis advisor, Professor James Wei. His guidance, encouragement, and interest in this project and in my professional development over the past years is sincerely appreciated. Thanks are also extended to Professors Michael P. Manning and Charles N. Satterfield for their helpful suggestions during the course of this work and for serving on my thesis committee. The financial support of the Department of Chemical Engineering and the National Science Foundation is gratefully acknowledged. Much of this work would not have been possible were it not for the technical assistance and cooperation of others. Special thanks are extended to Drs. Dave Green and Chi Wen Hung of Chevron Research Company for their contributions of time and talent in serving as the liaisons in the collaborative aspects of this project with Chevron Research Company. Their assistance along with Mr. Jack Gilmore and Mr. Mark Meiser of Chevron Research Company in providing the electron microprobe measurements in this thesis is especially appreciated. Thanks are also extended to Dr. Rene LaPierre and Mr. Paul Brigandi of Mobil Research and Development Corporation for providing the ammonia desorption characterization of the modified catalysts in the latter stages of this work. The assistance of Mr. William Dark of Waters Associates in providing technical advice on HPLC and his generosity in providing the liquid chromatographic columns is appreciated. The discussions on porphyrin chemistry with Dr. Peter Hambright of Howard University and the numerous porphyrin samples he provided were most beneficial. The analytical assistance of several colleagues at MIT including Jim Bentsen of the Chemistry Department for the IR results, Art Lafleur of the Mass Spectrometry Facility for the HPLC UV-vis scans, and John Martin of the Surface Analysis Central Facility for the XPS results, are all acknowledged. My education at MIT would have been incomplete were it not for the friendships, lively discussions, and reckless times shared with my fellow graduate students. To my many labmates, Ian A. Webster, Shan Hsi Yang, George A. Huff, Harvey G. Stenger, Thomas M. Bartos, Robert Summerhayes, C. Morris Smith, Margaret Ingalls, Robert T. Hanlon, and David K. Matsumoto, a sincere thanks for the great memories. The good times we shared over the past years will be hard to match. I am pleased to have shared four years as a research colleague and comrade with Ian Webster. His intellect, intriguing personality, and Scottish brogue left never a dull moment. I wish him all the best. To Norman Margolus, thanks for contributing to the great memories at 13D. The concern and moral support of many, but most especially The Wojtowicz Family, Suzanne Strempek, Mary Koss, Peggy Murphy, and Debbie Luper, at a time of great personal loss and grief in my life is greatly appreciated. I look forward to maintaining these friendships. Finally, no words of thanks can express my appreciation to my parents, Mr. and Mrs. Charles L. Ware, Jr., and my sisters Wendy and Kathy for their love, understanding, and constant encouragement throughout my entire education and most especially during the past year. For all in life you have provided me, I will forever be grateful. - 7 - TABLE OF CONTENTS Page CHAPTER I. INTRODUCTION 16 I.A. Background and Motivation 16 I.B. Characterization of Nickel and Vanadium Compounds in Petroleum 21 I.C. Hydrodemetallation of Petroleum Residua 29 I.D. Model Compound Hydrodemetallation Studies 38 I.E. Thesis Objectives 42 CHAPT ER II. APPARATUS AND EXPERIMENTAL PROCEDURES 45 II.A. Materials 45 II.A.l. Metalloporphyrins 45 II.A.2. Oil 48 II.A.3. Preparing Nickel Porphyrins in Mineral Oil 54 II.A.4. Catalyst 55 II.B. Reactor Design 61 II.C. Reactor Operating Procedure 71 II.D. Analytical Procedures 77 II.D.l. Liquid Samples 77 II.D.2. Catalyst Samples 89 II.E. Initial Transient Behavior of the Catalyst 93 CHAPTER III. PORPHYRIN REACTIVITY IN CATALYTIC HYDRODEMETALLATION 98 III.A. Intrinsic Kinetics on the Oxide Catalyst 98 III.A.l. Ni-Etio 98 III.A.2. Ni-T3MPP 108 III.A.3. Ni-TPP 133 III.B. Discussion of Porphyrin Reactivity 133 III.C. Demetallation Reactions Under Diffusion Limited Conditions 137 III.C.l. Metal Deposition Profiles 137 III.C.2. Metal Profile Model Development and Discussion 141 - 8 - Page CHAPTER IV. HYDRODEMETALLATION OF NI-T3MPP IN THE PRESENCE OF NITROGEN AND SULFUR COMPOUNDS 153 IV.A. Demetallation in the Presence of Pyridine 153 IV.B.
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