Open-cell metallic foams coated by electrodeposition as structured catalysts for energy and environmental applications
Ho, Hoang Phuoc; Palkovits, Regina (Thesis advisor); Fornasari, Giuseppe (Thesis advisor)
Aachen : Erasmus (2018)
Dissertation / PhD Thesis
Dissertation, RWTH Aachen, 2018. - Dissertation, Università di Bologna, 2018
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.