CO₂ splitting by thermo-chemical looping based on ZrₓCe₁ₓO₂ oxygen carriers for synthetic fuel generation
2012
Abanades, Stéphane | Le Gal, Alex
The thermochemical CO₂ splitting via cerium-based mixed oxides is considered. This process targets the recycling and upgrading of CO₂ emissions for the production of solar fuels. The CO₂ reduction is achieved by thermochemical looping using ceria–zirconia solid solutions as oxygen carriers: (1) the mixed oxide is first reduced by thermal activation for releasing some oxygen from its lattice, (2) the reduced oxide is then oxidized with CO₂ for producing carbon monoxide and the initial metal oxide that is recycled to the first step. Reactive cerium-based mixed oxides were first synthesized as nanopowders by different soft chemical routes. Their reactivity was then investigated experimentally by thermogravimetry analysis to demonstrate that the produced nanoparticles react efficiently with CO₂. The two-step process consisting of thermal activation and CO₂-splitting reaction was able to produce CO repeatedly. The influence of the synthesis method, the Zr content in ZrₓCe₁₋ ₓO₂, and the temperature of the CO₂ reduction reaction was investigated. The material was reduced at 1400°C in flowing Ar and the CO₂ reduction was performed below this temperature (typically in the range of 700–1200°C). Both the CO production and the material cyclability were improved when decreasing the Zr content, although the reduction extent was lessened. The Ce₀.₇₅Zr₀.₂₅O₂ and Ce₀.₉Zr₀.₁O₂ redox catalysts withstood repeated cycles without any noticeable sintering and reactivity losses. The most reactive material was the powder synthesized via the Pechini method (242μmol CO/g at 1000°C).
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