Due to increasing atmospheric carbon dioxide (CO 2 ) concentration, energy sources that release smaller amounts of CO 2 to the atmosphere are of considerable interest. Attention is also now being paid to sequestering CO 2 from the combustion process and eliminating discharge to the atmosphere from the major source points. Chemical-looping combustion (CLC) is a promising concept that can be used in power generation, which integrates power production and CO 2 capture. In the present study, a commercially obtained iron ore was used as an oxygen carrier and the associated reduction reaction kinetics parameters have been estimated based on isothermal thermogravimetric analysis (TGA) in reducing environments. The iron oxide in the ore, which is initially Fe 2 O 3 , proceeds through a sequence of reaction steps and can ultimately end up as metallic iron. The reduction mechanism for the first stage reaction (i.e., Fe 2 O 3 to Fe 3 O 4 ) was evaluated using a number of different gas− solid reaction models. The results indicate that the Avrami−Erofe'ev model can be successfully applied to the experimental data. Through this approach, it was confirmed that the initial reaction stage is phase-boundary-controlled, which gradually transitions to diffusion control. The apparent activation energy was estimated and compared with values from the literature data.

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CoOx inhibits Pd oxidation in CH₄ combustion in the wet feed.

The work assesses the effect of hydrothermal ageing on the kinetic parameters of lean methane combustion catalyzed by cobalt oxide supported on ceria. The reactions are performed at model conditions relevant to the exhaust of natural gas vehicles, that is, at temperatures between 200 C-550 C with 0.05 mL/mL (5 vol%) and 0.10 mL/mL (10 vol%) of water in the feed, as well as in the dry feed. The addition of 0.05 mL/mL (5 vol%) of water results in a double decrease of the rate constant, which is not affected by further water increase to 0.10 mL/mL (10 vol%). The reactions in the dry and wet feeds show zero order to water and first order to methane; the activation energy of 73 kJ/mol is the same for all conditions for the supported and unsupported cobalt oxide catalysts. After 100 hours on stream, the supported catalyst shows the same methane conversion as the fresh catalyst.