Extracting kinetic information from complex gas-solid reaction data

We develop an approach for extracting gas-solid kinetic information from convoluted experimental data and demonstrate it on isothermal carbon dioxide splitting at high-temperature using CoFe₂O₄/Al₂O₃ (i.e., a "hercynite" cycle based on Co-doped FeAl₂O₄) active material. The reaction kinetics equations we derive account for competing side reactions, namely catalytic CO₂ splitting on and O₂ oxidation of doped hercynite, in addition to CO₂ splitting driven by the oxidation of oxygen-deficient doped hercynite. The model also accounts for experimental effects, such as detector dead time and gas mixing downstream of the reaction chamber, which obscure the intrinsic chemical processes in the raw signal. A second-order surface reaction model in relation to the extent of unreacted material and a 2.4th-order model in relation to CO₂ concentration were found to best describe the CO generation of the doped hercynite. Overall, the CO production capacity was found to increase with increasing reduction temperature and CO₂ partial pressure, in accordance with previously predicted behavior. The method outlined in this paper is generally applicable to the analysis of other convoluted gas-solid kinetics experiments.