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Solid-State Redox Kinetics of $CeO_{2}$ in Two-Step Solar $CH_{4}$ Partial Oxidation and Thermochemical $CO_{2}$ Conversion
| Content Provider | MDPI |
|---|---|
| Author | Nair, Mahesh Abanades, Stéphane |
| Copyright Year | 2021 |
| Description | The $CeO_{2}/CeO_{2−δ}$ redox system occupies a unique position as an oxygen carrier in chemical looping processes for producing solar fuels, using concentrated solar energy. The two-step thermochemical ceria-based cycle for the production of synthesis gas from methane and solar energy, followed by $CO_{2}$ splitting, was considered in this work. This topic concerns one of the emerging and most promising processes for the recycling and valorization of anthropogenic greenhouse gas emissions. The development of redox-active catalysts with enhanced efficiency for solar thermochemical fuel production and $CO_{2}$ conversion is a highly demanding and challenging topic. The determination of redox reaction kinetics is crucial for process design and optimization. In this study, the solid-state redox kinetics of $CeO_{2}$ in the two-step process with $CH_{4}$ as the reducing agent and $CO_{2}$ as the oxidizing agent was investigated in an original prototype solar thermogravimetric reactor equipped with a parabolic dish solar concentrator. In particular, the ceria reduction and re-oxidation reactions were carried out under isothermal conditions. Several solid-state kinetic models based on reaction order, nucleation, shrinking core, and diffusion were utilized for deducing the reaction mechanisms. It was observed that both ceria reduction with $CH_{4}$ and re-oxidation with $CO_{2}$ were best represented by a 2D nucleation and nuclei growth model under the applied conditions. The kinetic models exhibiting the best agreement with the experimental reaction data were used to estimate the kinetic parameters. The values of apparent activation energies (~80 $kJ·mol^{−1}$ for reduction and ~10 $kJ·mol^{−1}$ for re-oxidation) and pre-exponential factors (~2–9 $s^{−1}$ for reduction and ~123–253 $s^{−1}$ for re-oxidation) were obtained from the Arrhenius plots. |
| Starting Page | 723 |
| e-ISSN | 20734344 |
| DOI | 10.3390/catal11060723 |
| Journal | Catalysts |
| Issue Number | 6 |
| Volume Number | 11 |
| Language | English |
| Publisher | MDPI |
| Publisher Date | 2021-06-10 |
| Access Restriction | Open |
| Subject Keyword | Catalysts Concentrated Solar Energy Ceria Oxygen Carriers Thermochemical Redox Cycle Chemical-looping Methane Reforming Syngas Solid-state Kinetics Co2 Utilization |
| Content Type | Text |
| Resource Type | Article |
