Investigation of SFNM-04 Perovskite Supported Composite Oxides for Chemical Looping CO2 Dissociation

The persistent increase of the average temperature of the Earth indicates that global warming is the main problem to be solved in the next years, since it affects both planet and human health. The principal cause of global warming is the continuous use of fossil fuel plants to satisfy the ever-increasing energy demand. One possible alternative to counteract global warming is to investigate CCUS (Carbon Capture Utilization and Storage) technologies for capturing CO2 already generated by current fossil fuel energy systems and develop methods to convert CO2 into useful chemicals or combustible gases. Among the possible methods, one of the most promising is the renewable chemical looping process (R-CLR) for two-step thermochemical CO2 splitting: heat at high temperature provided by a renewable energy system (typically a Concentrated Solar Power CSP system) is imposed on the looping material that alternates between a reduced and an oxidized state producing syngas (CO + H2) as a useful product starting from CO2 and H2O. The aim of this dissertation is to investigate the feasibility to perform chemical looping processes for syngas production using a new perovskite-based oxygen carrier for the conversion of the captured carbon dioxide CO2 to carbon monoxide CO. The Master Thesis and Stage project is carried out at CO2 Circle Lab inside the Environment Park located at Parco Dora, Turin, Italy in collaboration with University of Udine and Massachusetts Institute of Technology (M.I.T.), Boston, USA. More detailed, the material under investigation is Sr_2 Fe Ni_0.4 Mo_0.6 O_(6-δ) (SFNM-04) and it was synthetized by University of Udine; its redox ability and stability is comprehensively analyzed performing microreactor tests. The experimental section of this Master Thesis project is focused on the CO production achieved during the oxidation reactions in which a gas mixture containing different concentrations of carbon dioxide reacts with the SFNM-04 sample. The chemical looping test bench is composed by a gas delivery system with three Bronkhorst mass flow controllers used to automatically send a certain gas flow mixture, a horizontal alumina reactor positioned inside a tubular furnace that guarantees an isothermal environment up to 1600 °C and a quadruple real-time Emerson X-stream gas analyser (multichannel NDIR/UV/TCD) used to analyse the outlet gas composition. The variables that change during the oxidation and reduction experimental procedures are the operating temperatures (from 550 °C to 850 °C) gas mixture compositions (from 6% to 100% of CO2 during the oxidation step and from 5% to 100% of H2 during the reduction step in a N2-based gas mixture), and reaction times (from 15 to 120 minutes) in order to assess the perovskite response and the consequent CO global yield and CO maximum production rate in percentage and in [μmol⁄(g/s)]. In conclusion, it is useful to remark the aim of this master thesis project: it is a preliminary study useful to determine the reproducibility of redox cycles for SFNM-04 perovskite to produce CO starting from CO2. To give a concrete application of this work, it is possible to assert that it points out the necessity of developing new CCUS technologies and materials aimed to successfully complete the energy transition path and to reach the sustainable goals evidenced by the United Nations and UE within the 2030.