Recycle CO2 with the help of renewable sources

The Politecnico di Milano is studying the processes of recycling and reuse of CO2: “A valid alternative, because instead of hiding CO2 under the carpet, it is reused to create new products”. Carlo Giorgio Visconti, tenured researcher at the Politecnico di Milano, tells of the new project born from the collaboration with Maire Tecnimont, to study ways of recover carbon dioxide using it as a raw material for the petrochemical industry. In the process, an important role also for the renewable energy sources.

1) What is the goal of your project?

To develop a technology capable of converting, by reaction with hydrogen, CO2 into light olefins such as ethylene, propylene and butenes, molecules are of great interest in the chemical industry as fundamental building blocks for the synthesis of a wide range of products such as polymers, plastics, synthetic rubbers, solvents, additives for automotive fuels, medicines, cosmetics, detergents, etc. CO2 it would come like this recycled to create new products now obtained from petroleum or derivatives, reducing therefore at the same time consumption and polluting emissions associated with the phases of extraction, transport and refining of the same. Hence a substantial decrease in emissions of CO2 and a notable environmental and economic benefit.

Born from the collaboration between Politecnico di Milano and Maire Tecnimont, the project aims to develop a process for eliminate CO2 produced thus avoiding to release it into the atmosphere. With the same objective, there are also CO2 Capture and Storage (CCS) processes, i.e. the capture of CO2 and its storage in an underground or submarine environment.

2) There is talk of "renewable hydrogen" coming from the electrolysis of water as an alternative to the conventional "steam reforming" hydrocarbon system: why this choice and what follows?

The conversion of carbon dioxide into olefins requires that the molecule of CO2 react with hydrogen. With a view to containment of CO2 emissions, the necessary hydrogen cannot be produced according to conventional technologies with processes that would lead to the production of large quantities of CO2. The production of hydrogen from carbon-free raw materials solves this problem. Water is the raw material par excellence, from this point of view. The electrolysis of the H 2O molecule for the production of hydrogen, however, is a process that requires not a little energy: for this reason we plan to use renewable energies, able to produce hydrogen without producing CO2.

3) How do renewable sources come into play? How could the chemical production system change then?

One of the biggest problems ofrenewable electricity is that, unlike fossil energy, we can hardly regulate its availability on the market and even the energy demand from users cannot be controlled. The need to prevent users from running out of energy means that there is always more energy on the network than is actually consumed. This excess of energy is not only not used, but as a result of the impossibility of accumulating electricity in large quantities, it is systematically lost, dissipated. Just this energy could be used to make hydrogen to be used for the conversion of CO2. The olefins produced, therefore, are no longer just a chemical product of industrial interest due to their chemical reactivity, but also become a tool with which to make a chemical storage of excess energy. In all those circumstances in which I have excess energy, I use it to produce hydrogen from water, and with this hydrogen I convert CO 2 into light olefins.

4) What are the project times? How many people involved?

The activities will last 3 years and will be conducted at the Laboratory of Catalysis and Catalytic Processes of the Energy Department of the Politecnico di Milano. The team of teachers involved in the activities includes the prof. Pio Forzatti, the prof. Luca Lietti and theing. Carlo Giorgio Visconti. At least one doctoral student and one post-doc will also be involved in the project, as well as students of the bachelor's and master's degree courses in Chemical and Energy Engineering of the Politecnico di Milano, engaged in thesis or internship activities.

5) In general, what are the consequences of the accumulation of CO2 in the troposphere?

The number of scientific data showing a direct relationship between the increase in the concentration of CO2 in the troposphere and climate change is constantly growing. But this, in my opinion, should not be the only stimulus to contain carbon dioxide emissions. In addition to polluting less, recycling means reducing the consumption of raw materials. Recycle CO2, in particular, it means reducing our needs for carbon, or fossil fuels. And as we all know, the depletion of oil, coal and natural gas sources is an equally relevant issue than the containment of CO2 emissions, which can change the fate of future generations just as drastically.

6) What are the effects of the CO2 “capture” and storage processes, mainly geological and CO2 deep in the sea? Why is public opinion opposed to such practices?

The seizure of the CO2 in deep deposits is a technology to which significant funding has been dedicated in recent years. Expert colleagues on the subject ensure that storing CO2 is possible and, if the sites and operating methods have been appropriately chosen, it is sustainable and safe, even if obviously “zero risk” does not exist. Public opinion is often not adequately informed, neither about the advantages nor about the risks deriving from new technological solutions, and this generally means that often unsubstantiated fears arise from voices that are not authoritative or scientifically unprepared. It is certain that one of the problems associated with the capture and seizure processes of the CO2 are the costs, currently unsustainable if not in the face of important incentives. The processes of recycling and reuse of CO2 are a valid alternative: instead of hiding "under the carpet" the CO2, it is reused to create new products.

7) What does CO2 mean in practice by rethinking CO2 as a basic raw material? In which transformation processes would it be inserted? With what environmental benefits?

I believe that in the next few decades the CO2 can become an important building-block for the chemical industry. The increasing availability of renewable energy, in fact, opens up a whole series of perspectives that appeared to be not very rational thinking of satisfying the energy needs of the conversion processes starting from fossil sources. It should be borne in mind that once it has been "activated", or rendered as a reactant, by the CO2 it is theoretically possible to reconstruct all organic chemistry. There is therefore room for drastically reduce CO2 emissions, going far beyond the limits that Italy, along with many other countries, has committed to respecting by joining the Kyoto protocol.

Video: Recycling CO in. Navy with SMR Small Modular Reactors - Don Larson (January 2022).