Kinetic Modelling of Co3O4- and Pd/Co3O4-Catalyzed Wet Lean Methane Combustion
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Reaction kinetics of methane combustion is investigated on Co3O4 and Pd/Co3O4 (0.27 wt% Pd) catalysts for a fuel-lean feed. The temperature ranges between 250 and 550 °C in the presence of 5 and 10 vol% water with CH4 concentrations that varied between 1000 and 5000 ppmv. Significant cobalt oxide contribution to the activity of the bimetallic catalyst is observed, especially at higher water concentration and lower temperature (up to 70%). Co3O4 demonstrates first order to CH4, 0 order to H2O and activation energy of 69 kJ/mol. Pd/Co3O4 catalyst shows first order to CH4, negative 0.37 order to H2O and an observed activation energy of 90.7 kJ/mol, which is corrected for water adsorption to 60.6 kJ/mol. The latter is a typical activation energy for Pd/Al2O3 catalyst at similar conditions, indicating that the Co3O4 contribution is not only in performing the methane combustion itself but also in supplying surface oxygen rather than in affecting the activation energy. The kinetic evidence shows that the observed behaviour of Pd/Co3O4 catalyst is not a summation of individual activities of Co3O4 and Pd, but rather the effect of strong metal-support interactions (SMSI).
KeywordsMethane combustion Cobalt oxide Water effect Reaction kinetics Strong metal-support interactions
We thank Dr. Jing Shen for performing the TEM and CO chemisorption analyses.
Financial support was from Natural Sciences and Engineering Research Council of Canada (NSERC Strategic grant STPGP 478979-15).
Compliance with Ethical Standards
- 2.Zasada, F., Janas, J., Piskorz, W., Gorczyńska, M., Sojka, Z.: Total oxidation of lean methane over cobalt spinel nanocubes controlled by the self-adjusted redox state of the catalyst: experimental and theoretical account for interplay between the Langmuir-Hinshelwood and Mars-van Krevelen mechanisms. ACS Catal. 7, 2853–2867 (2017)CrossRefGoogle Scholar
- 4.Piskorz, W., Gryboś, J., Sojka, Z., Indyka, P., Zasada, F., Janas, J.: Reactive oxygen species on the (100) facet of cobalt spinel nanocatalyst and their relevance in 16O2 / 18O2 isotopic exchange, de N2O, and de CH4 processes—a theoretical and experimental account. ACS Catal. 5, 6879–6892 (2015)CrossRefGoogle Scholar
- 10.Willis, J.J., Goodman, E.D., Wu, L., Riscoe, A.R., Martins, P., Tassone, C.J., Cargnello, M.: Systematic identification of promoters for methane oxidation catalysts using size- and composition-controlled Pd-based bimetallic nanocrystals. J. Am. Chem. Soc. 139, 11989–11997 (2017)CrossRefGoogle Scholar
- 23.Thommes, M., Kaneko, K., Neimark, A.V., Olivier, J.P., Rodriquez-Reinoso, F., Rouquerol, J., Sing, K.S.W.: Physisorption of gases, with special reference to the evaluation of surface area and pore size distribution (IUPAC Technical Report). Pure Appl. Chem.; aop. (2015). https://doi.org/10.1515/pac-2014-117
- 28.Zasada, F., Piskorz, W., Cristol, S., Paul, J.-F., Kotarba, A., Sojka, Z.: Periodic density functional theory and atomistic thermodynamic studies of cobalt spinel nanocrystals in wet environment: molecular interpretation of water adsorption equilibria. J. Phys. Chem. C. 114, 22245–22253 (2010)CrossRefGoogle Scholar