Glucose Oxidation into Gluconic Acid: From Batch to Trickle Bed Reactor Dissertation for the academic degree of Doctor of Science Faculty of Chemistry and Biochemistry of Ruhr-Universität Bochum Alessia Padovani Born on 13.12.1988 in Verona, Italy Bochum December 2016 The present work was made in the period from December 2012 to December 2015 in the Department of heterogeneous catalysis at Max Planck Institute für Kohlenforschung in Mülheim an der Ruhr , headed by Prof. Dr. Ferdi Schuth . Supervisor: Prof. Dr. Ferdi Schüth Co-supervisor: Prof. Dr. Wolfgang Grünert For my Parents “Above all, don't fear difficult moments. The best comes from them.” “The body does whatever it wants. I am not my body; I am my mind”. Rita Levi-Montalcini “Nothing in life is to be feared, it is only to be understood.” Marie Curie Acknowledgements At the end of this challenging experience, I would like to thank all the people who were involved in this PhD research work. First of all, I am really thankful to Prof. Dr. Ferdi Schüth for the great opportunity to work in his Group, for his supervision on this PhD work and for the academic independence and autonomy he gave me. Thanks to Prof. Dr. Wolfgang Grünert for the co-supervision and for the interest in my research. I would like to thank the HPLC department, especially Heike Hinrichs and Marie Sophie Sterling for the many measurements, for their evaluation and useful discussion. Thanks to Inge Springer for the ICP analysis and Silvia Palm for the EDX measurements. Big thanks go to Bernd Spliethoff for patiently teaching me how to use the TEM and for the help in evaluating the images. Thanks to Wolfgang Kersten and Knut Gräfenstein from the Workshop for the great technical support, especially in the construction and repair of the batch reactor used in this PhD work. Thanks to the Glassblowing, especially for the trickle bed reactors. I would like to thank also Andre Pommerin and Laila Sahraoui for the practical support in the laboratory and for their effort in keeping the laboratories clean and functional. Thanks to Annette Krappweis and Kirsten Kalischer for helping me in my move to Germany and for all the support in all the organizational matters. In the success and enjoyment of the work, my officemates played an important role. Heartfelt thanks to Valentina Nese, Dr. Mariem Meggouh, Dr. Tobias Grewe, Jean Pascal Schulte and Xiaohui Deng for our daily chats and leisure activities outside the Institut. Thanks to Vale and Mariem for our friendship, to Tobi for all the laughs and also for helping me with the design of the trickle bed reactor. Thanks to JP, for sharing his precious fume hood with me and for the time we spent together in the laboratory. Infinite thanks go to my parents Antonio and Cristina, for all the support during both my academic studies and my PhD work, for their trust and for their encouragement to always pursue and achieve my goals. Last but not least, I would like to deeply thank my boyfriend Daniel for the endless patience and fondness he always showed me and for all the support he gave me. Big thanks the Max Planck Society for financial support. Abstract The central point of this work is the metal catalyzed liquid phase oxidation of glucose to gluconic acid. During recent years, this reaction has indeed received much attention, since gluconic acid is a fine chemical which finds many industrial applications, mainly as water soluble cleansing agent and as additive for food and beverages. In this study, the glucose oxidation is performed starting from an alkaline sugar solution. However, no basic solution (NaOH for example) is added to the reaction mixture to maintain the pH at a fixed value; the reaction is therefore carried out at uncontrolled pH. The reaction is first performed in a batch reactor. Au, Pd and Pt nanoparticles immobilized on metal oxides, resins and porous carbons are used as catalysts; among them, carbon supported metal materials, mainly prepared according to the sol immobilization procedure [1], are the most used ones. After performing the glucose oxidation with varying temperature, pressure and oxidizing agent (pure O2 or air), it can be observed that, at 70°C and 3 bar pure O2, SX carbon supported Au(1wt%) catalyst shows the best performance. Indeed, already after 30 minutes, glucose is almost fully converted into gluconic acid (98% yield). As the maximum gluconic acid formation is achieved in a very short time, the carbon supported Au catalyst might be successfully used also in a continuous system, i.e. in a trickle bed reactor (TBR). However, as powdered catalysts like Au(1wt%)/SX are difficult to handle in TBRs, a “in home” carbon (IHC) in grain form is chosen as support for the Au(1wt%) catalyst for use in the TBR. The glucose oxidation is performed with varying liquid and gas flow rate, temperature and initial glucose concentration; the optimal reaction conditions, which allow to achieve 81.5% yield of gluconic acid, are 20 ml/h (1.2 minutes as average residence time) and 575 ml/min as liquid and gas flow rate, respectively, 70°C and 5wt% starting concentration of glucose. Both under batch conditions and in the trickle bed reactor, with carbon supported Au catalysts, high gluconic acid yields were obtained in a very short time and without pH control during the reaction. Contents 1. Introduction .................................................................................................................... 1 1.1. The importance of biomass conversion and catalysis ............................................ 1 1.2. Gluconic Acid ......................................................................................................... 5 1.3. Metal Catalysed Liquid Phase Glucose Oxidation to Gluconic Acid ..................... 9 1.3.1. State of the Art .................................................................................................... 9 1.3.2. Supported Metal Catalysts: Preparation Methods ............................................. 17 1.3.3. Batch and Trickle Bed Reactors ........................................................................ 20 2. Motivation and Aim ...................................................................................................... 22 3. Results and Discussion ................................................................................................. 25 3.1. Glucose Liquid Oxidation in Batch Reactor – Finding the Best Catalyst for the Trickle Bed Reactor ......................................................................................................... 25 3.1.1. Batch Reactor - Metal Oxides as Metal Nanoparticles Supports ...................... 26 3.1.2. Batch Reactor - Resins as Metal Nanoparticles Supports ................................. 36 3.1.3. Batch Reactor - Carbon as Metal Nanoparticles Support ................................. 45 3.1.3.1. IHC-1 and IHC-2 Carbons as Metal Nanoparticles Supports .................... 47 3.1.4. Non Powdered Catalyst: from Batch to Trickle Bed Reactor ........................... 50 3.2. Glucose Liquid Oxidation in Batch Reactor – Optimal Catalyst and Reaction Conditions ........................................................................................................................ 52 3.2.1. Commercial Carbon Supported Metals ............................................................. 53 3.2.2. Ordered Mesoporous CMK-5 Carbon ............................................................... 57 3.2.3. Mesoporous SX carbon ..................................................................................... 62 3.3. Glucose Liquid Oxidation under Oxygen Flow .................................................... 93 3.4. Glucose Liquid Oxidation in Trickle Bed Reactor ................................................ 97 3.4.1. Trickle Bed Reactor – Preliminary Tests .................................................... 103 3.4.2. Trickle Bed Reactor - Effect of the Liquid Flow Rate ................................ 104 3.4.3. Trickle Bed Reactor – Effect of the Gas Flow Rate .................................... 110 3.4.4. Trickle Bed Reactor - Effect of the Temperature ........................................ 112 3.4.5. Trickle Bed Reactor - Effect of the Initial Glucose Concentration ............. 114 3.4.6. Trickle Bed Reactor - Effect of the Reactor Diameter ................................ 117 4. Conclusions ................................................................................................................ 121 5. Experimental Part ...................................................................................................... 128 5.1. Chemicals ........................................................................................................... 128 5.2. Catalyst Synthesis ............................................................................................... 130 5.2.1. Synthesis of Metal Nanoparticles Supported on Commercial Resins ......... 130 5.2.2. Synthesis of Au Nanoparticles supported EGD/DVB Resin ...................... 132 5.2.3. Synthesis of Metal Nanoparticles supported on Different Carbons ............ 133 5.2.4. Evaluation of the Metal Content of the Catalysts ........................................... 138 5.3. Reaction Set-ups ................................................................................................. 141 5.3.1. Glucose Oxidation performed in Batch Reactor ......................................... 141 5.3.2. Glucose Oxidation performed in Continuous Mode ..................................