In order to achieve the climate targets, research is being carried out into the substitution of fossil resources in process chemistry. One approach is the electrochemical reaction of water with carbon dioxide. The anode compartment, in which the water is oxidized, and the cathode compartment, in which the carbon dioxide is reduced, are separated from each other by a membrane. The aim is for the reaction to mainly produce ethanol at the cathode. 

When aqueous electrolytes are used on the cathode side, mainly hydrogen is produced instead of the desired organic products. This is due to the low solubility and diffusion rate of CO2 in water, which is why the CO2 molecules hardly interact with the active electrode. Previous work has shown that the use of organic electrolytes under increased CO2 pressure can shift the product spectrum towards organic products. However, the electrical conductivity of organic electrolytes is significantly lower than that of aqueous electrolytes. This leads to a lower current density and therefore slower CO2 conversion. The development of new organic electrolytes with high conductivity and simultaneously high CO2 solubility is therefore of interest. Since both the conductivity and the CO2 solubility are largely unknown for most organic electrolytes, these are being investigated for approx. 150 electrolytes as a function of salt concentration, temperature and pressure. For this purpose, a self-developed automatic conductometry for the determination of conductivity and a gravimetric method for the determination of CO2 solubility are used.

The cooperation partner Fraunhofer UMSICHT then carries out the reactions. The compositions of the product streams resulting from the reaction serve as the basis for the subsequent separation process. Early consideration of the separation process is important because its costs are usually very high and can exceed the costs of the reaction. As the reaction is carried out with copper-based catalysts, many different products are usually formed (e.g. alcohols, alkenes, alkanes, hydrogen and water). The separation of these substances is extremely complex, which is why simulation programs such as Aspen Plus and Aspen Adsorption are used. A techno-economic evaluation is carried out based on the simulation of the separation process.