Reaction Engineering in Biocatalytic Reactive Distillation Vom Promotionsausschuss der Technischen Universität Hamburg zur Erlangung des akademischen Grades Doktor-Ingenieur (Dr.-Ing.) genehmigte Dissertation von Steffen Kühn aus Marburg (Lahn) 2018 1st Examiner: Prof. Dr. rer. nat. Andreas Liese 2nd Examiner: Prof. Dr.-Ing. Irina Smirnova Day of oral examination: 12.10.2018 For Mum, Dad and Elif ACKNOWLEDGEMENT The presented and discussed results in this work were generated within the time period of May 2014 and September 2017, in which I worked as a scientific coworker at the Institute of Technical Biocatalysis at the Hamburg University of Technology. At this point, I want to take the chance to express my gratitude to all the people, who supported me during that time and finally helped me to realize and set up this work. It has to be mentioned that without all of you, it would not have been possible to finalize this work. First of all, I would like to express my sincerest gratitude to my supervisor, Prof. A. Liese for offering me the position in his institute. I really appreciated not only your excellent scientific support and inspiration in our fruitful discussions at your office, but also your soial dediatio to fo the ITB- fail ad offeig e a geat okig atosphee fo the tie peiod i Haug. I really want to thank you for a fantastic time! I would offer my special thanks to Prof. I. Smirnova for accepting to take over the position of the 2nd examiner and even more for supporting my scientific work with her excellent knowledge in the field of my research topic. Especially, I want to thank you for your valuable feedback and help to successfully exceed in the process of publishing. I have additionally greatly benefited from the support and inspiring ideas by Prof. J.-E. Bäckvall to substantially drive forward with the topic of dynamic kinetic resolution and get an insight into his extraordinary expertise in organic chemistry. Thanks a lot to Prof. S. Heinrich for taking over the lead at the day of examination. I particularly owe my deepest gratitude to Dr. J. Kleber for his excellent support as a group leader, as a friend and his time for intense topic related as well as non-related discussions. I want to thank you for scientific input during proof-reading my thesis, which was pretty important for reflecting writing and to reach the final version. I really appreciate your support! For your extraordinary encouragement, discussions and help, I want to thank all the colleagues, bachelor & master students as well as BTA-applicants & student assistants, who supported this work. Without you, this work would not have been possible! I would show my greatest appreciation to my friends G. Sluyter, M.-A. Christlieb and Dr. R. Heils for their intense discussions and scientific as well as non-scientific input to the topic. Additionally, it was an honor to participate at conferences together! Besides, I would like to offer my special thanks to L. Andersen and A. Bajat for their help during their thesis at the ITB. I want to thank Dr. B. Yang for his incredible support during his stay at the ITB to allow setting up and performing experiments regarding the topic of dynamic kinetic resolution. Beside the great support in the scientific environment of this thesis, I want to express my deepest appreciation to my family although words are never enough to show you my gratitude. Mum and Dad, I want to thank you for everything you did for supporting my time in Hamburg, for your encouragement to manage this thesis and your indispensable help in every situation of my life! Elif, I would like to thank you for your unconditional love and for being the best wife during all situations of my life. You helped me in uncountable moments to finish this thesis – seni seviyorum! 28th of October, 2018 Steffen Kühn Abstract ABSTRACT Reactive distillation is a well-established unit operation in chemical industry incorporating reaction and separation in one device for the synthesis of bulk chemicals. Such an integrated process strategy provides economic advantages compared to serially connected unit operations. In a relatively new approach, substitution of chemical catalysts by enantioselective biocatalysts emerges, which allows a broadened scope of reactions. This idea is especially triggered by the growing interest in more valuable chiral molecules for fine chemical or pharmaceutical synthesis. At first glance, the thermal deactivation of a biocatalyst will cause reduced catalyst lifetimes and requires frequently shutdown procedures for replacing the biocatalyst. However, careful selection of relatively thermostable biocatalysts and their fixation on supporting materials enables reasonable process performance. In this thesis, practicability of Candida antarctica lipase B applied as the preparation Novozym435® is evaluated for kinetic resolution reactions in reactive distillation. The defined three step approach, including the theoretical preselection of reactions and their experimental characterization in batch reactors as well as the implementation in a solvent-free reactive distillation column, aims at the isolation of the desired chiral target compound with high purity. In the theoretical preselection step, two different chiral starting materials ((R/S)-2-pentanol, (R/S)-3-hydroxy ethyl butyrate) were selected for experimental comparison. Main criteria for the feasibility study were the predetermined biocatalyst temperature range (TRD = 30 – 80 °C) and the theoretical operating window of the individual compounds, defined by their boiling points at reduced column pressures. In the second experimental characterization step, both chiral starting materials were investigated in batch reactions for their feasibility in reactive distillation. The investigated parameters comprise the initial catalytic activity, the enantioselectivity, the determination of present equilibrium limitations and the concentration profiles of the starting materials in a batch reactive distillation setup. During the characterization phase, the results for the kinetic resolution of the chiral alcohol (R/S)-2-pentanol turned out to be more promising. Therefore in the third step, reactive distillation column experiments were carried out with this starting material aiming at excellent optical purity and high molar fractions of the target compound (S)-2-pentanol. In focus of these reactive distillation experiments were the influence of changing the fractional distillation strategy, the spatial distribution of the biocatalyst and the initial molar fractions of the starting material. Finally, successful operation of an integrated batch biocatalytic reactive distillation column is approved by in situ isolation of the chiral target compound -1 (S)-2-pentanol with high purity (x(S)-2-PeOH = 0.95 mol∙mol ) and excellent enantiomeric excess (ee(S)-2-PeOH > 99 %). Moreover, an alternative reaction approach of chemo-enzymatic dynamic kinetic resolution is successfully evaluated in a proof of concept study including a second chemocatalyst. Based on these results, this thesis underlines the possibility to allow the production of fine chemicals or pharmaceuticals in reactive distillation processes in future times. I Kurzzusammenfassung KURZZUSAMMENFASSUNG Der Einsatz von Reaktivrektifikations-Kolonnen repräsentiert einen weltweit etablierten Verfahrensschritt in der chemischen Industrie zur Synthese von bulk-Produkten, welcher die Prozessschritte der chemischen Reaktion sowie die anschließende Auftrennung in einem Apparat vereint. Durch diese integrierte Prozessvariante resultieren ökonomische Vorteile gegenüber herkömmlichen sequentiellen Verfahrenskonzepten. Ein neuer Ansatz beschäftigt sich nun mit der Idee ein erweitertes Reaktionsspektrum für die Reaktivrektifikation verfügbar zu machen, indem der chemische Katalysator durch hochselektive Biokatalysatoren ersetzt wird. Der Hauptgrund für die Substitution des chemischen Katalysators liegt insbesondere in dem steigenden Interesse an chiralen Molekülen zur Synthese von Feinchemikalien oder Intermediaten von pharmazeutischen Produkten. Neben dem Vorteil der hohen Selektivität stellt die größte Herausforderung beim Einsatz von Biokatalysatoren in der Reaktivrektifikation dessen Sensitivität gegenüber moderaten Prozesstemperaturen dar. Dadurch wird eine regelmäßige Erneuerung des Katalysators erforderlich, was ein häufiges An- und Abfahren der Kolonne bedingen würde. Die geeignete Auswahl von Biokatalysatoren mit erhöhter thermischer Belastbarkeit und deren Fixierung in Immobilisierungsverfahren ermöglicht wiederum den Einsatz in der Reaktivrektifikation. Auf dieser Basis wurde im Rahmen der vorliegenden Arbeit der Einsatz von Lipase B aus Candida antarctica in der Reaktivrektifikation in lösungsmittelfreien, kinetischen Racematspaltungen untersucht und bewertet. In einem entwickelten dreistufigen Konzept war das Hauptziel die gewünschte chirale Zielkomponente mit hoher Reinheit am Kopf der Kolonne zu isolieren. Im ersten Schritt erfolgte mittels eines aufgebauten Preselection-Tools die Auswahl von zwei chiralen Substraten ((R/S)-2-Pentanol, (R/S)-Ethyl-3-Hydroxybutyrat). Die Hauptkriterien für die theoretische Machbarkeitsstudie der gewählten Substrate waren der vom Biokatalysator definierte Temperaturbereich für die Reaktivrektifikation (TRD = 30 – 80 °C) und das daraus resultierende Prozessfenster, welches die Siedepunkte beim gewählten reduzierten Kolonnendruck umfasst. Im zweiten Schritt erfolgte die experimentelle Charakterisierung der beiden chiralen