Preliminary assessment of SFNM04 perovskite for CO₂ dissociation through Renewable Chemical Looping process

The indications from the Energy Roadmap 2050, various reports and developments worldwide clearly indicate that fossil fuels will continue to be present in the future of Europe and the world and will still be used in many industrial processes. However, the current climate crisis, caused by the continuous and increasing release of CO2 into the atmosphere, has reached a drastic level, in which the changes made by humans on the ecosystem are more and more tangible. In this framework, Carbon Capture Utilization and Storage technologies (CCUS) can play an important role for this transition period, accompanying the current world energy production sector, based on fossil fuels, towards a zero emissions condition driven by renewable resources. CCUS is in fact a hybrid solution in which the CO2 leaving the plants is captured instead of being released into the atmosphere and then stored or reused to produce useful products. This last solution is preferred, as it would allow to transform a product until now discarded with one of commercial value, also allowing a recovering of the costs of capture. Once captured, CO2 can in fact be used to create various useful products: among all stands out the syngas, a mixture of hydrogen and carbon monoxide that is the basic component for the creation of other important chemicals, such as ethanol, methanol and DME. There are several methods for syngas synthesis: among these, the technology of Renewable Chemical Looping is very interesting, because it uses high temperature solar energy (green and clean) from concentrating solar for the splitting of H2O and CO2; the syngas thus created is also called Solar Fuel. Chemical looping is a thermochemical process in which a redox material (also called oxygen carrier) reacts alternately with oxidizing and reducing gas mixtures and returns to the initial composition at the end of the redox cycle, ensuring the repeatability of the process. Different types of chemical looping materials have been studied and tested: in addition to the most common, such as metal oxides and cerium oxides, perovskites are considered very promising materials. In this study, which is part of an international collaboration between the Polytechnic of Turin, Massachusetts Institute of Technology (MIT) and University of Udine, a new type of perovskite, synthesized by the University or Udine, is studied and tested in a microreactor order to analyze its chemical stability and performance within the redox cycle. This material is {Sr}_2Fe{Ni}_{0.4}{Mo}_{0.6}O_{6-\delta} (SFNM04) and has the peculiarity to show an exsolution phenomena of Fe2+ and Ni3+ when reduced, causing the creation of Fe-Ni alloys on the surface of the sample that act as catalyst for the oxidation step and also a larger number of oxygen vacancies in the material, leading to a bigger yield of CO at the end of the cycle. In particular, the aim of this work is to study the behavior of the material while varying the parameters of the process, such as the concentration of the reducing and oxidizing mixtures ( the studied range of H2 is from 5% to 100%, while the CO2 varies between 6% and 100%, both mixed with nitrogen), the temperature for the two steps and reaction times (from 15 up to 120 minutes); temperatures considered have a range from 550°C up to a maximum of 850°C.