Chemical use of carbon dioxide as C1 building block in conjunction with use of predominantly regenerative energy

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© Copyright: Lehrstuhl fuer Technische Thermodynamik der RWTH Aachen

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Kai Leonhard

Group Leader Molecular Systems Engineering

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+49 241 80 98174

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Within the framework of the CO2RRECT project the use of carbon dioxide as a feedstock for chemical industry in conjunction with mainly renewable energy shall be investigated. The goal is bind the carbon dioxide, which has been captured in power plants, sustainably in plastics.

As methane currently is used as the primary feedstock for plastic production, the alternative route investigated in this work could lower the need for fossil primary energy sources.

For the production of isocyanates (such as MDI), used as a educt for the polyaddition reaction that produces polyurethane, amoung others hydrogen and carbon monoxide are needed. Thus in the CO2RRECT project the three following pathways will be investigated which could yield the needed hydrogen, H2, and carbon monoxide, CO:

Reverse Water-Gas-Shift CO2 + H2 --> CO + H2O
Dry Reforming CO2 + CH4 --> 2CO + 2H2
CO2 Hydrierung CO2 + H2 --> HCOOH

As the reaction equations show, carbon dioxide is added as a educt in all of the reaction pathways. The chemical activation of the very stable carbon dioxide is achieved mainly by addition of hydrogen, which is provided by an electrolysis. Part of the produced H2 is also needed directly for the production of isocyanates. As an electrolysis is used to generate the hydrogen, it is possible to produce hydrogen from primarily renewable energy sources. Since these energy sources mainly consist of fluctuating energy carriers (e.g. wind energy), it is necessary to be able to operate the electrolysis on partially load. However the chemical processes are optimized for a constant energy supply, leading to the conclusion that energy has to be stored in form of hydrogen. Thus another important goal of the CO2RRECT project is to identify a suitable hydrogen storage.

Goal of the work at the LTT in AP 4.3 is the selection of suitable solvents for the formic acid production in order to realize the two phase reactor concept presented in the figure below. In the presented reactor concept, the solvents will have a dramatic effect on the efficiency of the process. Thus to find the optimal solvent combination a systematical screening will be performed with regard to extraction potential and miscibility of the two solvents. This screening will be performed using the predictive thermodynamical model COSMO RS. In addition process simulations will be performed and necessary tools will be developed.