TECHNISCHE UNIVERSITÄT MÜNCHEN Lehrstuhl II für Technische Chemie Reductive cleavage of aromatic ethers by supported metal catalysts Meng Wang Vollständiger Abdruck der von der Fakultät für Chemie der Technischen Universität München zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften (Dr. rer. nat.) genehmigten Dissertation. Vorsitzender: Univ.-Prof. Dr. Tom Nilges Prüfer der Dissertation: 1. Univ.-Prof. Dr. techn. Johannes A. Lercher 2. Prof. Ph.D. Gary L. Haller (Yale University, New Haven, CT, USA) 3. Univ.-Prof. Dr. Roland A. Fischer Die Dissertation wurde am 07.08.2018 bei der Technischen Universität München eingereicht und durch die Fakultät für Chemie am 10.09.2018 angenommen. 大哉一诚天下动，如鼎三足兮，曰知、曰仁、曰勇。 — 江谦 (1876 —1942) The good I stand on is my truth and honesty. — William Shakespeare (1564 — 1616) ‘Henry VIII’, Act 5, Scene 1 Acknowledgement First and foremost I would like to express my sincerest appreciation to my thesis advisor, Prof. Johannes A. Lercher, for offering me the opportunity to work in his group and the endless support throughout my Ph.D., especially for a Chinese student who is working in the US and getting the degree from Germany. I am incredibly fortunate to have been able to work at the Pacific Northwest National Laboratory (PNNL) and enlightened by his guidance, patience, trust and profound knowledge. Being a “stubborn” student, I gained a lot of knowledge from our invaluable scientific group discussion that will help both my scientific and personal growth. I would also like to express my deep appreciation to my mentor Dr. Donald M. Camaioni for guiding me to think and work scientifically and efficiently in PNNL. He is the best go to person I ever had and his thoughtful guidance, warm encouragement and high degree of attention to even the smallest details helped my growth in research. I am greatly grateful for the time and efforts Don has spent to coach me. Then I would like to express a sincere gratitude to my mentor Dr. Oliver Y. Gutierrez for the discussions we had, and for the suggestions he gave me. Thank you for your uncountable assistance in the laboratory and my graduation. I am deeply grateful to Prof. Miroslaw A. Derewinski for his suggestions, encouragement and unfailing assistance in a variety of ways not only about science. I am full of gratitude to John Fulton, with whom I learned XAFS (X-ray absorption fine structure) during our APS (Advanced Photon Source) trips and data analysis. Don, Mirek, John and Oliver have broadened my horizons in and outside the lab and let me have an enriched life in the Pacific Northwest. My heartfelt gratitude to Dr. Jian Zhi Hu for his kind guidance and assistance, the resources I have got and the discussions we have made helped me know the lab regulations and understand how to efficiently make use of characterizations for catalysis. I deeply appreciate the help of Dr. Donghai Mei and his students, Zhibo Ren and Yuntao Zhao, about the theoretical calculations. My sincere thanks go to Dr. John Linehan and Dr. Sarah Burton for their valuable advice and great help. I am also utmost grateful to the people at PNNL who helped me in the field of catalysis and characterization. Especially, the great help of Dr. Abhi Karkamkar, Dr. Mark Bowden, Dr. Molly O’Hagan and Dr. Libor Kovarik is highly appreciated. I am also i incredibly grateful to Dr. Wendy Shaw and Dr. Aaron Appel, who were my managers at PNNL, as well as to the PNNL administrative staff. Next, I would like to thank my lab mates Dr. Hui Shi, Dr. Zizwe Chase, Dr. Aleksei Vjunov, Dr. Sebastian Prodinger, Dr. Jian Zheng and Dr. Feng Chen who have always supported me during my research. Especially the extensive help from Hui Shi at the beginning of my study. My sincere appreciation also goes to Dr. Nianhua Xue, Dr. Yifeng Zhu, Dr. Bo Peng, Dr. Manish Shetty, Dr. Udishnu Sanyal, Dr. Katherine Koh, Laura Meyer, thank all of you for your kind help not only in science. Furthermore, I would like to thank our senior scientists and administrative staff in TCII at TUM, Prof. Andreas Jentys, Dr. Yue Liu, Stefanie Seibold, Kateryna Kryvko, Bettina Federmann and Ulrike Sanwald, who all helped me for my stay at TUM. Moreover, I would like to thank all following colleagues in TUM, Dr. Yuanshuai Liu, Xi Chen, Guanhua Cheng, Takaaki Ikuno, Insu Lee, Wanqiu Luo, Ferdinand Vogelgsang, Manuel Wagenhofer, Yang Zhang and Ruixue Zhao. Thank you for your support and help. Particularly, I would like to thank Prof. Gary L. Haller for the help on my thesis. Finally, I am great indebted to my family, relatives and friends who loved me and I loved. Especially thank my wife Huifang for building our life together and thank our parents’ endless support. Meng Wang July 2018. ii Abstract Abstract The catalytic hydrolysis and hydrogenolysis of aromatic ethers have been explored on supported metal catalysts. Palladium is highly selective for reductive hydrolysis and transetherification in water and alcohols, respectively. Partial hydrogenation of one aromatic ring prior to the insertion of H2O or alcohol has been identified. Kinetic analysis suggests that hydrogenolysis is catalyzed via a (concerted) addition of hydrogen, cleavage of the C-O bond and formation of a phenoxy group, the critical step has being aided by a strong interaction of the ether oxygen with the metal. Kurzzusammenfassung Die katalytische Hydrolyse und Hydrogenolyse von aromatischen Ethern wurden an geträgerten Metallkatalysatoren untersucht. Palladium ist hochselektiv für die reduktive Hydrolyse bzw. Umätherung in Wasser und Alkoholen. Die partielle Hydrierung eines aromatischen Rings vor dem Einbringen von H2O oder Alkohol wurde identifiziert. Die kinetische Analyse deutet, dass die Hydrogenolyse durch (konzertierte) Zugabe von Wasserstoff, Spaltung der C-O-Bindung und Bildung einer Phenoxygruppe katalysiert wird. Der geschwindigkeitsbestimmende Schritt wird durch eine starke Wechselwirkung des Äthersauerstoffs mit dem Metall unterstützt. iii iv Table of contents Table of Contents Acknowledgement ................................................................................................................................... i Abstract .................................................................................................................................................. iii Kurzzusammenfassung .......................................................................................................................... iii Table of Contents .................................................................................................................................... v Chapter 1 Introduction .............................................................................................................. 1 1.1 General background ...................................................................................................................... 2 1.2 Importance of the cleavage of aromatic C-O bonds ...................................................................... 5 1.2.1 Depolymerization of lignin .................................................................................................... 5 1.2.2 Activation of carbon oxygen bond ......................................................................................... 8 1.3 Reaction routes of reductive conversion of aryl ethers ................................................................. 9 1.3.1 Hydrogenolysis .................................................................................................................... 11 1.3.2 Hydrolysis ............................................................................................................................ 14 1.3.3 Hydrogenation ...................................................................................................................... 15 1.3.4 Reactions of phenols ............................................................................................................ 16 1.4 Mechanistic studies ..................................................................................................................... 20 1.5 Scope of this thesis ...................................................................................................................... 22 1.6 References ................................................................................................................................... 24 Chapter 2 Palladium Catalyzed Hydrolytic Cleavage of Aromatic C-O Bonds ................................................................................................................................................. 29 2.1 Introduction ................................................................................................................................. 30 2.2 Experimental ............................................................................................................................... 31 2.2.1 Chemicals and commercial catalysts ................................................................................... 31 2.2.2 Catalyst testing ..................................................................................................................... 31 2.3 Result and discussion .................................................................................................................. 32 2.3.1 Kinetic studies of supported palladium catalysts ................................................................. 32 v Table of contents 2.3.2 Control experiments of