University of Bologna RWTH Aachen University Department of Industrial Chemistry ITMC Open-cell metallic foams coated by electrodeposition as structured catalysts for energy and environmental applications DOCTORAL THESIS SINCHEM - Sustainable Industrial Chemistry Erasmus Mundus - Joint Doctoral Research Program Cycle XXX of doctoral program in Chemistry Coordinator: Prof. Aldo RODA Supervisor (HOME): Prof. Giuseppe FORNASARI Asst. Prof. Patricia BENITO Supervisor (HOST): Prof. Dr. Regina PALKOVITS PHUOC HOANG HO May 2018 “Open-cell metallic foams coated by electrodeposition as structured catalysts for energy and environmental applications” Von der Fakultät für Mathematik, Informatik und Naturwissenschaften der RWTH Aachen University zur Erlangung des akademischen Grades eines(r) Doktors(in) der Naturwissenschaften oder eines(r) Doktors(in) der Ingenieurwissenschaften genehmigte Dissertation vorgelegt von M.Sc. HỒ HOÀNG PHƯỚC aus BẾN TRE, VIỆT NAM Berichter: Prof. Dr. Regina Palkovits Prof. Dr. Giuseppe Fornasari Tag der mündlichen Prüfung: 2. Mai 2018 Diese Dissertation ist auf den Internetseiten der Universitätsbibliothek online verfügbar. Alma Mater Studiorum – Università di Bologna in cotutela con Università di RWTH Aachen DOTTORATO DI RICERCA IN CHIMICA Ciclo XXXo Settore Concorsuale: 03/C2 Settore Scientifico Disciplinare: CHIM/04 OPEN-CELL METALLIC FOAMS COATED BY ELECTRODEPOSITION AS STRUCTURED CATALYSTS FOR ENERGY AND ENVIRONMENTAL APPLICATIONS Presentata da: Phuoc Hoang Ho Coordinatore Dottorato Supervisore Prof. Aldo Roda Prof. Giuseppe Fornasari Co-supervisore Asst. Prof. Patricia Benito Supervisore Prof. Regina Palkovits Esame finale anno 2018 ACKNOWLEDGEMENTS I would like to thank all people who contributed in some ways to the work described in this thesis as well as to my life during unforgettable three-year Ph.D. in Europe. First and foremost, I would like to appreciate to my academic advisors who have spent almost the time with my work at the University of Bologna, RWTH Aachen University, and Politecnico di Milano – Prof. Patricia Benito and Pr. Giuseppe Fornasari, Prof. Regina Palkovits, Prof. Gianpiero Groppi and Prof. Enrico Tronconi. Special thanks to Patricia for her patient for the guidance and support regarding the electrochemistry and structured catalysts which are new topics to me. She spent a lot of time to engage me in new ideas and to demand a high quality research work and continuous help by the time when we got negative results. I still remembered her concern to my first oral presentation in Natural Gas Conversion Symposium even she just gave a birth in the day before. Many thanks to Prof. Fornasari for his valuable guidance and help with all official documents as well as reviewing my thesis until some last days before the deadline. During my six-month mobility, Regina provided me constructive comments regarding my research. From the inspirational guidance she provided for me, I learned to be strong and confident on my research work. My appreciation was also presented to Professor Groppi and Tronconi for valuable discussion from an engineering point of view as well as their support during my three-month in the Lab at Politecnico di Milano. This thesis cannot be accomplished without the help and support of collaborators and colleagues at the laboratory of catalysis group (UNIBO), catalysis and catalytic processes LCCP (POLIMI), and AK Palkovits (RWTH Aachen). I would like to thank Professor Angelo Vaccari, Professor Fabrizio Cavani and all members of the Catalysis group for their priceless help and support. A very friendly group that I have ever worked in my life. I could not obtain very good characterization results without the help from Dr. Francesca Ospitali almost six hours per week for SEM/EDS, TEM as well as Raman analyses. Special thanks to Dr. Amer i Inayat for his valuble time in translation the abstract of my thesis into German. I would like to appreciate Prof. Domenica Tonelli, Prof. Erika Scavetta, Dr. Marco Monti, Ylea Vlamidis and other members in “analitica Laboratorio” for the help provided during the preparation of the catalysts. I would also thank Matteo Ambrosetti, Pio Giuseffi for giving a great time during my mobility at Politecnico di Milano. Without the help from Professor Regina Palkovits’s group, I could not complete my research mobility at RWTH Aachen University. Special thanks to Chalachew Mebratu for giving nice discussion and “beer” time in Aachen, and my sincere colleague Christian Landini for all things that he supported me from Bologna to Aachen. Thanks to Dr. Magdalena Jablonska for her help in both doing the setup of my experiment and guiding me a new topic of N2O decomposition, and other members of the group for wonderful time with a lot of cakes and of course German beer in the Lab. I am in Johannes Niemeier’s debt for correcting my German abstract more than perfect. I would also like to thank Dr. Stefanie Mersmann and Dr. Stefan Palkovits for their support in the official procedure. In addition, I would like to acknowledge my family and friends who supported me during my time in Europe. Thank my grandmother, Mom, Dad, my young sister as well as my cousin Ms. Ho Ngoc Hao and her family in Germany for their constant love and help. Thanks to Ha V. Le my brother and bestie for his instant support in both work and life. It is not a forgettable memory about a twelve-day journey through five fantastic places in summer 2015, and other trips with Dang Khoa and Kim Hoang. I owe a debt of gratitude to all my close friends: my brother Phuoc, Long, Duy, Duc – Trang, Phuc, Thom, Khoa, Trinh, Thang, Canh, Do, Bach for their constant concern. Sincerely thank to Long for processing the format of my thesis; Phuc and Thom for their help in the design of nice images using SOLIDSWORK. Thanks to other friends in Italy: Binh – Nga, Le Hong Lam, Tinh, Nhan, Man, Meggi Quynh and other Vietnamese families in Bologna for an enjoyable time of my life in Italy. ii Finally, I would like to thank SINCHEM program for giving me a great opportunity of study in Europe. How nice is the program! Thanks to Professor Stefania Albonetti – fantastic coordinator of the program. She always takes care me and other students like a mom for all things from the life and academic issues that new students, especially foreigner, usually face at the beginning of Ph.D. study. Thanks to all SINCHEM guys for great time we stay together. I am in debt from all the secretaries and administrative staffs involving in the SINCHEM program at the University of Bologna, RWTH Aachen, and Politecnico di Milano: Marina Grandini, Rosanna Antonino, Angela Maritato, Cristina Caretti, Professor Alessandra Beretta, and Dr. Stefanie Mersmann. Bologna, 18th December 2017. Phuoc Hoang Ho. iii ABSTRACT Structured catalysts based on open-cell metallic foams offer a great potential for process intensification of fast, highly exo-/endothermic and diffusion-controlled catalytic processes. For the development of such structured catalysts, the choice of coating technique used to deposit the active phase on the foam surface is very crucial, as the coating technique strongly influences the properties of the coated layer and in turn the activity/selectivity of the obtained structured catalysts. In this regard, the electro-base generation method has been proposed as a promising option that allows for coating of (even small pore) foams with avoidance of pore clogging which is a common drawback of conventional wash-coating technique. The thesis aims to improve the electrodeposition method and widen its applicability in the preparation of structured catalysts. In this respect, the first part of this thesis focuses on the investigation of the electrochemical processes, taking place during the electrodeposition of Mg-Al hydrotalcite, thereby studying the role of nitrate (of respective cations) concentration and reduction. Understanding the reactions involved in the electrodeposition helps to identify the main steps that determine the properties of the coating, and provides possible solutions to improve the method. In fact, by using a new electrochemical set-up, the control on the electrodeposition is achieved in terms of homogeneity and composition of the coated layer. In the second part of this thesis, a modified method for the electrodeposition of active phase on metallic foams is proposed and its applicability is demonstrated in the preparation of following catalyst systems for the use in energy and environmental catalytic processes: i) Rh/Mg/Al on both FeCrAl and NiCrAl foams for the catalytic partial oxidation of CH4, ii) Pd- CeO2 on FeCrAl foam (different pore sizes) for oxidation of CO, and iii) Rh/Mg/Al, Rh-CeO2, and Co3O4 on FeCrAl foam for catalytic decomposition of N2O. The aforementioned catalyst systems exhibit satisfactory performances in the respective test reactions, thus confirming the potential of using electrodeposition in preparing the structured catalysts. iv SOMMARIO I catalizzatori strutturati basati su schiume metalliche a celle aperte offrono una grande opportunità per l’intensificazione di processi catalitici veloci, fortemente eso/endotermici e controllati dalla diffusione. Per lo sviluppo di tali catalizzatori strutturati, la scelta di una tecnica di ricoprimento, utilizzabile per depositare la fase attiva sulla superficie della schiuma, è cruciale, poiché questa tecnica influisce fortemente sulle proprietà dello strato di ricoprimento e in genere sull’attività/selettività dei catalizzatori strutturati ottenuti. In considerazione di questo, il metodo di elettro-generazione di basi è stato proposto come una promettente opzione, che permette il ricoprimento di schiume (anche a pori piccoli) evitando il blocco dei pori, che è lo svantaggio usuale della tecnica convenzionale di washcoating. Questa tesi ha lo scopo di perfezionare il metodo di elettrodeposizione e ampliarne l’applicabilità nella preparazione dei catalizzatori strutturati. A tal fine, la prima parte di questo lavoro si concentra sull’analisi dei processi elettrochimici, che avvengono durante l’elettrodeposizione di Mg-Al idrotalcite, attraverso lo studio del ruolo della concentrazione e della riduzione dei nitrati (dei rispettivi cationi).