Fuel production by reduction of CO2 using concentrated sunlight

Abstract

Synthesis gas (syngas, CO:H2 1:2) as an intermediate product is an universal precursor for the production of a very broad variety of chemical substances like gaseous and liquid synthetic fuels, polymers, ammonia, methanol, etc. In order to cover the required heat demand for the generation of carbon monoxide (CO) solely from carbon dioxide (CO2), employing concentrated solar energy may be a viable alternative to the state-of-the-art methods like steam reforming or partial oxidation of fossil resources. This emission-free CO production may be carried out in a two-step thermochemical cycle using an oxide material as the catalyst. The two steps are: Regeneration of the metal oxide (MO) (1200 - 1400 °C): MOox = MOred + O2 Splitting of CO2 into CO (700 to 1000 °C): MOred + CO2 = MOox + CO For this thermochemical cycle, redox materials will be identified, synthesized and tested in lab-scale experiments. Materials for two-step CO2-splitting cycles The criteria of CO2 splitting have been estimated by theoretical considerations and thermo-chemical calculations of simple metal oxide materials yielded suitable material groups for further investigations. Outlook In coming thermo-gravimetric and tube furnace experiments, selected material groups will be tested and optimized in terms of efficiency and long-term stability. Especially, ceria and ferrites seem promising to yield good experimental results. In addition, substrate and reactor technology are crucial for this thermochemical cycle and will be addressed in the second phase of this project.