Fuel production by reduction of CO2 using concentrated sunlight - A material study

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 Redox-material groups for this thermochemical cycle were identified with the aid of thermochemical calculations and comprehensively presented in an Ellingham diagram in previous project stages. Ceria-based materials were found to be the most promising candidate to undergo experimental investigations. In the recent project phase, zirconia-doped ceria materials were synthesized and characterized by means of XRD and SEM. The performance dependency on the zirconia-content was investigated in lab-scale experiments, mainly thermo-gravimetric experiments. The maximum yields of O2 and CO will be discussed as well as the achieved improvements of conducting and analyzing thermo-gravimetric experiments.