The course is located at the end of the study paths of Chemical, Environment and Land and/or Energy Engineering students and has the ambition to provide some notions on the industrial processes of CO2 treatment in order to obtain products for consumers or to realize its storage. However, the main result that we intend to pursue is not exclusively related to the acquisition of these skills, but also to provide an alternative point of view on the possibility of re-activating the carbon dioxide molecule in the natural carbon cycle. The lessons present problems and examples of practical nature that follow the brief basic notions illustrated; in such problems, the engineering approach that recalls wide-ranging skills that the student is supposed to possess must be used to give precise answers on the practical feasibility of the analyzed process solutions. By attending the course, the student must acquire: - knowledge of the nature and chemistry of the natural carbon cycle on the planet; - the peculiar properties of the CO2 molecule and the consequent poor chemical reactivity; - the carbon dioxide capture processes; - the possibility of chemical reactivation through the use of renewable energy and H2 as an energy vector; - the possibility of CO2 entrapment in “end-of-life” compounds, such as carbonates.

The student who accesses this course must know general chemistry, in particular the concepts of chemical equilibrium, stoichiometry, thermodynamics and transport phenomena of heat and mass. She/He must master mass and energy balances on closed and flowing systems, know thermal machines and the principles underlying the processes of energy transformation in its various forms. It is desirable that she/he is able to carry out bibliographic searches on sources in English.

The carbon cycle: the transfer of CO2 between the different sources and geological deposits on a planetary level is characterized by natural and anthropogenic dynamics. The relative kinetics of the various phenomena is the main reason for concern by the scientific community, in relation to the concentration of CO2 in the atmosphere of our planet. The main greenhouse gases: carbon dioxide, methane, nitrous oxide. Plant sources (industrial and biogenic) and measurement methods. Relationship between polluting gases and greenhouse gases. CO2 sequestration: the CO2 capture processes are divided into absorption and adsorption, which differ in the capture phase (liquid or solid, respectively). The choice between the two systems is made based on the streams containing the CO2, in terms of flow rate, composition, operating conditions, presence of contaminants, plant costs, environmental compatibility. Seizure will be treated for stationary applications, but the potential of mobile systems will also be explored. CO2 conversion processes: In this module, the different chemical and biological options of CO2 capture and sequestration (CCS) or reuse (CCU) for the production of compounds and fuels will be developed. • Synthesis of urea: the urea synthesis process is an example of a classic process that has CO2 as its reagent. • Dry reforming: dry reforming represents a process of great interest as a transition stage between the use of fossil fuels (methane) and the reactivation of CO2, with the aim of producing CO, a key molecule for synthesis of carbon-based products of interest. • Conversion of CO2 into inorganic carbonates (carbonation of minerals and industrial residues) and organic ones: CO2 can be converted into chemical compounds, both as a long-term storage strategy (in deposits, through the carbonation of minerals) and medium term (for the production of consumer products): among the latter, there are inorganic carbonates, such as calcium carbonate, which can be used as fillers for cementitious materials. Organic carbonates, on the other hand, are materials that can penetrate the plastics industry (polycarbonates), eliminating dangerous reagents such as phosgene. • Power-to-X chemical and biological processes: in these processes the activation of CO2 derives from reductive processes using hydrogen, obtained from renewable sources by electrolysis of water / steam and / or co-electrolysis of steam and CO2. The multiplicity of CO2 reduction products (collectively referred to as X) includes a broad spectrum of compounds: methane, methanol, di-methyl-ether, short-chain olefins (for the plastics sector) and medium ones (for chemistry), liquid hydrocarbons (covering the similar oil cuts of gasoline, kerosene up to diesel). The reduction of CO2 to hydrocarbon products can take place indirectly (conversion of CO2 to CO and subsequent hydrogenation of CO according to consolidated processes) or directly in the chemical or biological reactor (conversion of CO2 to final products). In this context, the reaction intermediates follow mechanisms similar to the Fischer-Tropsch process or the production of methanol, depending on the catalytic system. • Photo-catalytic processes: in these processes the activation of CO2 occurs by sunlight irradiation. The fundamentals of photocatalytic systems and the materials including sunlight radiation absorption and the systems for coupling with the catalytic system mechanisms will be described. The main challenges towards the application of this kind of technology will be addressed. • Electro-catalytic processes: in these processes, CO2 is converted into final valuable products like fuels or chemicals, without with the direct and in-situ production of H+ intermediates in the catalyst surface (without the intermediation of H2 in gaseous form) and allow the direct exploitation of renewable electricity resources. The fundamentals and engineering challenges of electrochemical systems to achieve this reduction process will be described. • Photo-synthetic processes: in these processes, CO2 is converted into microalgae by the action of light. Depending on the type of migroalgae grown, the final use of biomass is different: nutraceuticals, pharmaceuticals, cosmetics, chemicals are some examples. Process environmental sustainability: the process calculations relating to the different CO2 reactivation approaches will be functional to estimate its competitiveness compared to existing processes, as well as energy and environmental sustainability.

The course will be organized as a mix of lectures (45 hours) and tutorials (12 hours as class exercises and 3 hours as laboratory experiences), order to consolidate the theoretical notions throughout practical activities. The numerical calculations will allow to analyze in detail the processes of CO2 fixation and to assess the sustainability of the different proposed approaches.

Literature and slides provided by the course teachers

Lecture slides; Lecture notes; Exercises; Video lectures (previous years);

Exam: Written test; Computer-based written test in class using POLITO platform;

The exam has the aim to verify the acquisition of theoretical and practical knowledge delivered during the course. Theoretical questions and numerical exercises will be asked. Theoretical open- and closed-ended questions and exercises to be performed in the Exam platform, using personal laptos brought by the students the day of the exam, in physical presence. The exam lasts 1.5 h, with around 15 questions as detailed before. It is not allowed to bring any teaching material during the exam, the use of calculator is admitted. The maximum mark is 30 with laude.

In addition to the message sent by the online system, students with disabilities or Specific Learning Disorders (SLD) are invited to directly inform the professor in charge of the course about the special arrangements for the exam that have been agreed with the Special Needs Unit. The professor has to be informed at least one week before the beginning of the examination session in order to provide students with the most suitable arrangements for each specific type of exam.