At present, there are no fully developed technologies capable to use CO2 as an input material for the production of chemicals and fuels.
Nevertheless, the most promising technologies for CO2 conversion are: (1) the one-step electroreduction of CO2, and (2) the two-step conversion of CO2 with sustainable H2 production, to produce either olefins or alcohols as products. While the two-step process requires H2 production via water-electrolysis followed by CO2 hydrogenation, the direct CO2 electroreduction can be done in one step. Still both technologies allow to produce similar products.
The CO2 electroreduction technology considers the transference of electrical energy into chemical energy in form of high energy organic compounds (such as olefins and alcohols) using CO2 as a raw material. Gaseous CO2 is introduced in the electrochemical reactor, where it reacts on the cathode catalyst with protons (H+) and high-energy electrons to form high energy products such as ethylene. The protons and electrons are formed at the anode catalyst. The catalysts are required to obtain reasonable production rates and product selectivity. While the positively charged protons are transported from the anode to the cathode catalyst by the electrolyte and the membrane, the negatively charged electrons are transferred separately via an electrical circuit, which adds electrical energy to these electrons. This addition of electrical energy is required to be able to transform the low-energy-content CO2 to high-energy-content products like olefins and alcohols.
Due to the fact that CO2 molecules are very stable, energy and catalyst are needed so that the reaction can take place. By considering the catalyst, the energy change for the catalysed and uncatalysed reactions remains the same. The catalyst, however, allows to decrease the energy barrier for the reaction (“activation energy”), which lead to increase of the reaction rate until the chemical equilibrium is attained. This can be easily seen in the diagram, where high energy reactants (CO2, H2) are converted into more stable products like alkane and water.
Today, the implementation of CO2 electroreduction technologies is mainly limited by the low efficiency of CO2 conversion, but the majority of research in this field has focused on fundamental and mechanistic understanding of the electrochemical reaction and on the development of highly active and selective catalytic materials.
Here there are some interesting links: EnCO2re is enabling CO2 re-use. http://enco2re.climate-kic.org
BioRECO2VER aims to demonstrate the technical feasibility of more energy efficient and sustainable non-photosynthetic biotechnological processes for the capture and conversion of CO2 http://bioreco2ver.eu
Power-to-X” Kopernikus project refers to technologies that convert electricity generated from renewable sources into physical energy stores, energy carriers, and energy-intensive chemical products. https://www.kopernikus-projekte.de/projekte/power-to-x
Oxalic acid from CO2 using electrochemistry at demonstration scale. https://www.spire2030.eu/ocean
Comentarii