Indirect Ammoxidation of Glycerol into Acrylonitrile via the Intermediate Acrolein Von der Fakultät für Mathematik, Informatik und Naturwissenschaften der RWTH Aachen University zur Erlangung des akademischen Grades eines Doktors der Ingenieurwissenschaften genehmigte Dissertation vorgelegt von Diplom-Ingenieur (FH) Carsten Liebig aus Worms Berichter: Universitätsprofessor Dr. Wolfgang F. Hölderich Universitätsprofessor Dr. Andreas Pfennig Tag der mündlichen Prüfung: 10.10.2012 Diese Dissertation ist auf den Internetseiten der Hochschulbibliothek online verfügbar. This work was carried out between February 2010 and September 2012 within a co- tutorial thesis at the Department of Chemical Technology and Heterogeneous Catalysis at RWTH Aachen University, Germany and at the Unité de Catalyse et Chimie du Solide, UMR CNRS 8181, at the Université des Sciences et Technologies de Lille, France. I would like to thank Prof. Dr. Wolfgang Hölderich and Prof. Dr. Sébastien Paul for kindly providing the interesting and challenging research topic, for their critical advice and inspiration as well as the excellent working conditions in Aachen and Lille respectively. Thanks to Prof. Dr. Andreas Pfennig and Prof. Dr. Jacques Vedrine for reviewing this thesis and for accepting their role as referee for this thesis. I am very grateful to the European Union for the financial support of this thesis within the Seventh Framework Program (FP7/2007-2013) under grant agreement n°241718 EuroBioRef. Especially, I would like to thank Prof. Dr. Franck Dumeignil for his support throughout my studies. Furthermore, I owe thanks to Dr. Jean-Luc Dubois of Arkema for the critical discussions and his advices. Moreover, I want to thank Prof. Dr. Gerhard Raabe and Dr. Jacques Kervennal for being examiners of this thesis. Furthermore, I wish to thank Dr. Benjamin Katryniok for his continuous support and many discussions, ideas and advices during my stay in Lille. I would like to thank all technicians in Aachen and Lille for their help - especially Elke Biener, Heike Bergstein, Noah Avraham, Marianne Nägler, Gerard Cambien, Olivier Gardoll and Arnaud Beaurain. Moreover, I would like to thank my colleagues in Aachen and Lille Dr. Moritz Venschott, Kyunghoon Kim, Dr. Raweewan Klaewkla, Dr. Oana Rusu, Dr. Matthias Arend, Yun Chen, Thomas Eschemann, Verena Ritzerfeld, Axel Pyrlik, Anna Matzen, Cyrille Guillon, Jorge Beiramar, Dr. Maryam Safariamin-Karimi, Fangli Jing, Kaew- arpha Thavornprasert and Dr. Svetlana Heyte for their help and many fruitful discussions. I owe thanks to my research students Paulo Schmitz, Sebastian Guski, Jonas Deitermann and Fabrice Tanguy for their active engagement and commitment in this work. Finally, I would like to thank my parents, my sister and my girlfriend Inga for their everlasting support and encouragement during my studies. Abstract Due to the depleting reserves of coal, oil and natural gas and to their negative impact on the environment, the humanity is forced to find renewable alternatives to replace the fossil feedstocks for the production of energy and chemical products. An example for an area of application where renewables are already used to substitute fossil feedstocks is the production of fuels. Biodiesel is one of the most popular biofuels nowadays. It is produced by transesterification of vegetable oils and fats. In this process, glycerol is formed as a by-product (approximately 10 wt.%). Glycerol is a versatile starting material which has up to 2000 applications. One very promising use of glycerol as starting material would be the dehydration of glycerol into acrolein. It could then be further converted into acrylonitrile - one of the most important monomers in the polymer production worldwide - by ammoxidation in the presence of ammonia and oxygen over mixed metal oxide catalysts. Today, acrylonitrile is exclusively synthesized from fossil feedstocks like propene and propane on an industrial scale. Therefore, a process combining the dehydration of glycerol to acrolein and the ammoxidation of the latter to acrylonitrile would be an alternative to the production processes based on fossil feedstocks. Thus, both reaction steps were studied separately at first - with focus on the ammoxidation of acrolein - and connected in a tandem reactor setup finally. For the first step of dehydration of glycerol to acrolein, we used previously optimized WO3/TiO2 catalysts, while oxide catalysts containing antimony, iron, vanadium and molybdenum were developed and used for the second ammoxidation step. Especially, the Sb-Fe-O catalysts were found highly selective and the influence of Sb/Fe ratio was subsequently studied. The presence of a FeSbO4 mixed phase on the synthesized samples was correlated to a high selectivity to acrylonitrile. Further, an increase in selectivity to acrylonitrile with the reaction time was observed, which was explained by the progressive formation of additional amounts of FeSbO4 over the catalysts during the reaction. After optimizing the key reaction parameter (reaction temperature, catalyst amount, NH3/acrolein ratio, O2/acrolein ratio) within a design of experiments, both reaction steps were connected in a tandem reactor. A maximum yield in acrylonitrile of 40 % (based on glycerol) was obtained. Table of Contents 1 Introduction and Aim of Work ................................................................................. 1 2 Basic Knowledge .................................................................................................... 4 2.1 Glycerol ............................................................................................................ 4 2.1.1 Glycerol Production ................................................................................... 4 2.1.2 Uses of Glycerol ........................................................................................ 8 2.2 Acrolein .......................................................................................................... 12 2.2.1 Acrolein Production .................................................................................. 12 2.2.2 Uses of Acrolein ....................................................................................... 15 2.3 Acrylonitrile .................................................................................................... 18 2.3.1 Acrylonitrile Production ............................................................................ 18 2.3.2 Uses of Acrylonitrile ................................................................................. 21 3 Scientific State of the Art ...................................................................................... 24 3.1 Direct Ammoxidation of Glycerol .................................................................... 24 3.2 Indirect Ammoxidation of Glycerol via Acrolein .............................................. 27 3.2.1 Step I: Dehydration of Glycerol ................................................................ 28 3.2.1.1 Intermediate Conclusion for the Dehydration of Glycerol .................. 32 3.2.2 Step II: Ammoxidation of Acrolein ............................................................ 33 3.2.2.1 Mechanism and Kinetics ................................................................... 36 3.2.2.2 Intermediate Conclusion for the Ammoxidation of Acrolein ............... 39 4 Results and Discussion ........................................................................................ 41 4.1 Dehydration of Glycerol ................................................................................. 41 4.1.1 Reactor Setup .......................................................................................... 41 4.1.2 Characterization ....................................................................................... 44 4.1.2.1 Nitrogen Physisorption ...................................................................... 44 4.1.2.2 X-ray Diffraction ................................................................................. 47 4.1.2.3 Temperature Programmed Desorption .............................................. 50 4.1.3 Results ..................................................................................................... 52 4.1.3.1 Catalysts Prepared According to Method I ........................................ 52 4.1.3.2 Catalysts Prepared According to Method II ....................................... 56 4.1.3.3 Combination of Method I and II ......................................................... 58 4.1.3.4 Identification of By-products .............................................................. 59 4.2 Ammoxidation of Acrolein .............................................................................. 60 4.2.1 Reactor Setup .......................................................................................... 60 I 4.2.2 Characterization ....................................................................................... 64 4.2.2.1 Antimony Iron Mixed Oxides ............................................................. 64 4.2.2.2 Antimony Vanadium Mixed Oxides ................................................... 76 4.2.2.3 Additional Ammoxidation Catalysts ................................................... 84 4.2.3 Results ..................................................................................................... 92 4.2.3.1 Preliminary Experiments ................................................................... 92 4.2.3.2 Catalyst Screening ...........................................................................