Extracting Kinetic Information from Complex Gas–Solid Reaction Data

Abstract

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.