Kinetic modeling of CO2 splitting reactions using perovskites in chemical looping for syngas production

This work, inserted in an international collaboration project (Politecnico di Torino, Università di Udine and Massachusetts Institute of Technology), has the ambitious intent to suggest a partial solution to face the fulfillment of certain Sustainable Development Goals (SDG) provided by United Nations (more specifically, numbers 7, 9, 11, 13)[1]. The general purpose becomes realized in the specific one: the kinetic and quantitative estimation of the carbon monoxide production from carbon dioxide using a SFNM (Sr2FeNi0.4Mo0.6O6-δ) perovskite through a chemical looping process. The innovation of this study lies in the investigation of the use of this material for this specific application. The study is based on the Thermogravimetric Analysis of the material to support the development of a kinetic model of the reaction with CO2 and in the modeling of the application in a reactor. Decarbonization could be accomplished only if renewable sources facilities will be enhanced. Stocking fuels for electrochemical cells and syngas, to save the unused renewable energy, has interesting perspectives. This pathway has to be followed in order to achieve an ecological development. This brief context is the main theme explained in the first chapter of the present work. In addition, some introductory concepts, related to chemical looping for water and carbon dioxide splitting will be provided. In the same section, it will be inserted a review of the main solutions existing in literature, useful for comparing with the innovation introduced in the actual research, jointly with, in a large-scale, all works to it correlated. The chapter 2 of this work stands for the preparatory step for estimation of the system features. In fact, the Thermogravimetric Analysis is essential for any study which handles properties estimation of a new material. Through this survey, the durability and the cycling of the perovskite has to be confirmed. The core of the dissertation is opened in section 3; in this, basing on results provided by the previous chapter, a first kinetic evaluation is provided. The investigation is carried out using a classical fitting method, which supplies the best model to simulate reactions during oxidation of the studied material. The suitable curve has to be adherent to the theoretical solution, offered by the kinetic reactions theory. On these premises, an evaluation of the characteristic parameters (activation energy and frequency factor) for the rate of reaction estimation can be done using an iterative fitting. Although a first kinetic evaluation is provided, the material performance has to be extrapolated to reactor level with a more well-structured analysis, using a multiphysics simulation software. In chapter 4, a model based on real geometrical and material features of a microreactor where the material will be tested has been developed. The outline is represented by a union of several physics, concerning fluid dynamics and chemical reactions. In the chapter 5, the final experimental phase is carried out and an empirical validation of the models previously developed is accomplished. The summary analysis is performed in the chapter 6, commenting the results obtained, underlying the lack of agreement between the model developed and the measured data in microreactor. The discussion on this aspect, together with the feasible perspectives to reach results in future works, close this master thesis.