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Development of an Economically and Environmentally Sustainable Method for the Oxidation of Rice Bran Wax

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Development of an Economically and Environmentally Sustainable Method for the Oxidation of Rice Bran Wax Technische Universität München Professur für Molekulare Katalyse Development of an Economically and Environmentally Sustainable Method for the Oxidation of Rice Bran Wax Tommy Alfred Hofmann 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: Prof. Dr. Klaus Köhler Prüfer der Dissertation: 1. Prof. Dr. Fritz E. Kühn 2. Prof. Dr. Kai-Olaf Hinrichsen Die Dissertation wurde am 14.05.2018 bei der Technischen Universität München eingereicht und durch die Fakultät für Chemie am 13.06.2018 angenommen. „Dem Anwenden muss das Erkennen vorausgehen." (Max Planck) I Die vorliegende Arbeit wurde von August 2015 bis Mai 2018 an der Professur für Molekulare Katalyse der Technischen Universität München angefertigt. Mein ganz besonderer Dank gilt meinem Doktorvater Professor Dr. Fritz E. Kühn Vielen Dank für die Aufnahme in Ihren Arbeitskreis, die Themenauswahl zu Beginn meiner Masterarbeit und die anschließende Übernahme als Doktorand. Die hervorragenden Bedingungen in Ihrem Arbeitskreis, Ihre direkte und unkomplizierte Betreuung sowie das in mich gesetzte Vertrauen ermöglichten den Erfolg dieser Arbeit. Sollte sich in der Zukunft die Gelegenheit zu erneuter Zusammenarbeit ergeben, so würde ich mich darüber sehr freuen. II III Danksagung (Acknowledgements) Ich danke meinem Mentor Dr. Nicolai Nagorny sowie der Kahl GmbH & Co. KG für die produktive Zusammenarbeit und die grundsätzliche Fragestellung. Dem BMBF danke ich für die Bewilligung und Finanzierung des Projekts. Vielen Dank an Tilo Rauchhaus für die umgehende Beantwortung verschiedener verwaltungstechnischer Fragen. Dem Fakultätsgraduiertenzentrum Chemie danke ich für die gegebenen Möglichkeiten und besonders für die Finanzierung meine Konferenzteilnahme in Rochester, NY. Vielen Dank an Dr. Markus Drees für die Beantwortung so mancher Frage. Vielen Dank an die helfenden Hände im Hintergrund. Den Sekretärinnen, insbesondere Irmgard Grötsch und Ulla Hifinger , für die Handhabung von Formularen, Verträgen und sonstigen Verwaltungsaufgaben. Vielen Dank unseren Technikern und Werkstätten für die Hilfe bei den großen und kleinen technischen Problemen. Speziell danke ich Jürgen Kudermann für die Hilfe bei allen Fragen und Hürden im Zusammenhang mit der GC-Analytik. Vielen Dank allen Mitgliedern der Molekularen Katalyse. Die erheiternden Kaffeeraum- und Feierabend-Diskussionen waren die ideale Abwechslung und Ergänzung zum Laboralltag. Vielen Dank den beiden Michis, Dr. Michael Wilhelm und Dr. Michael Anthofer für die Betreuung meines ersten Forschungspraktikums, dem Bekanntmachen mit dem Arbeitskreis und dem leichten Pushen, es sei „noch eine“ Katalyse nötig. Meinen Laborkollegen (in alphabetischer Reihenfolge) Dr. Markus Anneser , Andreas Hinterberger , Benjamin Hofmann , Dr. Özden Karaca , Dr. Anja Lindhorst und Dr. Robert Reich danke ich für das herzliche Laborklima, die gute Zusammenarbeit und den ehrlichen Meinungsaustausch. Liebe Anja , Deine Rufe nach weniger Pfeifen meinerseits und mehr Stille habe ich zuletzt schon ein wenig vermisst, aber der Anblick der „vererbten“ Pflanze hilft immer wieder darüber hinweg. Lieber Robert , vielen Dank für die gemeinsame Zeit, zunächst Rücken-an-Rücken und später Seite-an-Seite an den Abzügen. Dein unermüdliches Abzugsschließen, sobald ich den Abzug für zwei Sekunden verlassen hatte, und Dein Streben nach Ordnung in Labor und Kaffeeraum bewundere ich noch heute. Als Du Deinen Platz räumtest, war ich zunächst besorgt, wer Dein Platznachfolger sei und ob das „Zusammenleben“ genauso gut sein würde. IV V Diese Sorge erwies sich als unbegründet, denn mit Andreas erhielt ich einen ebenso guten Laborkollegen. Lieber Andreas , vielen Dank für Deine ruhige Art, unproblematische Platzaufteilung und den inoffiziellen Wettkampf, wer die größeren Ansätze macht (Deinen Versuch mich mit dem „Notduschen-Ansatz“ zu schlagen, halte ich immer noch für fragwürdig, zumal Du Unterstützung von Jonas hattest). Zusammen mit Andreas möchte ich auch meinem anderen „Industriekollegen“ Dr. Florian Groche danken. Vielen Dank Euch beiden für die guten Diskussionen mit dem „leicht anderen Blickwinkel“ auf die Chemie. Unseren unermüdlichen Kaffee- und Süßigkeiten-Organisatoren „King und Queen Candy“, Florian Groche und Carolin Obermayer danke ich für den immer gut ausgestatteten Vorrat an Nervennahrung, sowie den allmonatlichen Brainteaser, unter welchem Namen ich wohl dieses Mal meine Striche vermerken darf. Für den Abbau überschüssiger Kalorien und Ausgleich zum Labor danke ich meinen Fitness- und Schwimmkollegen, insbesondere Pauline Fischer , Elisabeth Bauer und Jakob Schneider . Für die Unterstützung während Studium und Promotion, sowie die interessanten Gespräche danke ich Heike Hofmann und Ihren Eltern Drs. Bernhard und Ingrid Hofmann . Für Eure Art, offene Ohren, moralische oder sonstige Unterstützung jedweder Art danke ich all meinen Freunden, insbesondere Dr. Daniel Betz , Dr. Felix Kaiser , Christian Merfels , Hans-Christian Busch und Alyssa Scherer . Zu guter Letzt danke ich meiner Familie für ihre Unterstützung in jedweder Art und Weise. Ohne Euch wäre sicherlich einiges anders verlaufen, und wahrscheinlich nicht so gut, wie es jetzt ist. VI VII Meinem Großvater und besten Kumpel Alfred. VIII IX Abstract In today’s society waxes play important yet for most people unknown roles. They are used as polishes for shoes, cars and floors, as coating agents for medicine, sweets and chewing gums and as components in cosmetic products like lip sticks. Depending on the intended use different requirements have to be met by the wax and also different sources of wax origin are favoured. For food, cosmetic and pharmaceutical applications the price of the wax is of low importance but it needs to be biocompatible and most important without any doubt non-hazardous to humans. For polishes and other industrial applications such standards and social requirements are less prone making price and physical and chemical properties more important. For many of the latter applications Montan Wax (MW) is used as a cheap yet hard wax derived from lignite. In its raw form it is a dark, hard substance mainly consisting of long chained aliphatic esters. Processed by bleaching with chromosulfuric acid it becomes a white, still hard substance with long chained aliphatic acids as its main component. The bleaching serves several purposes. By degrading undesired organic compounds, it bleaches the colour and erases any unpleasant odour of the wax, furthermore aliphatic acids are set free by splitting esters and further acids are formed by oxidation of the alkyl parts of the esters. Already used alternatives to this fossil resource are for example carnauba wax, bees wax and rice bran wax (RBW). Especially interesting is RBW due to being a side-product of the food industry, namely the production of white rice and rice oil. Thus, RBW is not only rather inexpensive but it could also be produced in amounts necessary to replace MW without competing against food crops or natural habitats. Untreated RBW shows many similar properties to raw MW, like high hardness, a high melting point of app. 80 °C and consisting of long chained aliphatic esters. Yet RBW has the advantages of being only slightly yellow coloured and only slightly smelling like rice. In order to gain similar properties to bleached MW RBW only has to be split and oxidized without the need to degrade unwanted organic compounds. In principle the same process utilizing chromosulfuric acid could be applied upon RBW to achieve these results. Yet there are some obstacles in the oxidation of RBW. First of all, RBW is not composed exactly the same as MW and is less easily oxidized by chromosulfuric acid as MW (possibly due to its higher ester content and therefore higher hydrophobicity). Secondly, if RBW was processed unaltered to some recent patents of oxidizing MW, this process would be highly inefficient regarding atom stoichiometry. It would be a waste of resources and generate unnecessary high amounts of waste products. Furthermore, the use of Cr(VI) compounds is restricted by REACH and should in general be replaced by environmentally more friendly processes. The purpose of this work was therefore to develop an environmentally friendlier process for the oxidation of RBW. To reach this intention raw RBW was analysed and a model substrate developed. Literature-known procedures were evaluated and adapted on small scale experiments (1 g) with the model substrate and RBW, finally developing a method with which 1 kg of oxidized RBW could easily be produced in the research laboratory. Always keeping in mind the intended implementation to industrial scales, the developed process is not only X environmentally friendlier as the compared chromosulfuric acid process, but also economically more favourable, lowering the costs of chemical reagents to far less than one third of the chromosulfuric acid process. The process is free of organic solvent or transition metals and is designed as a one-pot-synthesis with high yield per reaction volume. XI Kurzzusammenfassung In unserer heutigen Gesellschaft erfüllen Wachse wichtige, jedoch für Laien oftmals unbekannte Aufgaben in Industrie und Haushalt. Verwendung finden sie in Polituren für Schuhe, Autos und Böden, als Überzugsmaterial von Kaugummis, Süßigkeiten und Medikamenten sowie als Bestandteile von Kosmetika wie etwa Lippenstiften. Je nach Einsatzgebiet
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