Activity and Thermal Aging Stability of La<sub>1−x</sub>Sr<sub>x</sub>MnO<sub>3</sub> (x = 0.0, 0.3, 0.5, 0.7) and Ir/La<sub>1−x</sub>Sr<sub>x</sub>MnO<sub>3</sub> Catalysts for CO Oxidation with Excess O<sub>2</sub>
Catherine Drosou,
Ersi Nikolaraki,
Vasilios Nikolaou,
Evangelia Koilia,
Georgios Artemakis,
Antonios Stratakis,
Antigoni Evdou,
Nikolaos D. Charisiou,
Maria A. Goula,
Vasilios Zaspalis,
Ioannis V. Yentekakis
Affiliations
Catherine Drosou
Laboratory of Physical Chemistry & Chemical Processes, School of Chemical and Environmental Engineering, Technical University of Crete, 73100 Chania, Crete, Greece
Ersi Nikolaraki
Laboratory of Physical Chemistry & Chemical Processes, School of Chemical and Environmental Engineering, Technical University of Crete, 73100 Chania, Crete, Greece
Vasilios Nikolaou
Laboratory of Physical Chemistry & Chemical Processes, School of Chemical and Environmental Engineering, Technical University of Crete, 73100 Chania, Crete, Greece
Evangelia Koilia
Laboratory of Physical Chemistry & Chemical Processes, School of Chemical and Environmental Engineering, Technical University of Crete, 73100 Chania, Crete, Greece
Georgios Artemakis
Laboratory of Physical Chemistry & Chemical Processes, School of Chemical and Environmental Engineering, Technical University of Crete, 73100 Chania, Crete, Greece
Antonios Stratakis
School of Mineral Resources Engineering, Technical University of Crete, 73100 Chania, Crete, Greece
Antigoni Evdou
Department of Chemical Engineering, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
Nikolaos D. Charisiou
Department of Chemical Engineering, University of Western Macedonia, 50100 Koila, Kozani, Greece
Maria A. Goula
Department of Chemical Engineering, University of Western Macedonia, 50100 Koila, Kozani, Greece
Vasilios Zaspalis
Department of Chemical Engineering, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
Ioannis V. Yentekakis
Laboratory of Physical Chemistry & Chemical Processes, School of Chemical and Environmental Engineering, Technical University of Crete, 73100 Chania, Crete, Greece
The catalytic oxidation of CO is probably the most investigated reaction in the literature, for decades, because of its extended environmental and fundamental importance. In this paper, the oxidation of CO on La1−xSrxMnO3 perovskites (LSMx), either unloaded or loaded with dispersed Ir nanoparticles (Ir/LSMx), was studied in the temperature range 100–450 °C under excess O2 conditions (1% CO + 5% O2). The perovskites, of the type La1−xSrxMnO3 (x = 0.0, 0.3, 0.5 and 0.7), were prepared by the coprecipitation method. The physicochemical and structural properties of both the LSMx and the homologous Ir/LSMx catalysts were evaluated by various techniques (XRD, N2 sorption–desorption by BET-BJH, H2-TPR and H2-Chem), in order to better understand the structure–activity–stability correlations. The effect of preoxidation/prereduction/aging of the catalysts on their activity and stability was also investigated. Results revealed that both LSMx and Ir/LSMx are effective for CO oxidation, with the latter being superior to the former. In both series of materials, increasing the substitution of La by Sr in the composition of the perovskite resulted to a gradual suppression of their CO oxidation activity when these were prereduced; the opposite was true for preoxidized samples. Inverse hysteresis phenomena in activity were observed during heating/cooling cycles on the prereduced Ir/LSMx catalysts with the loop amplitude narrowing with increasing Sr-content in LSMx. Oxidative thermal sintering experiments at high temperatures revealed excellent antisintering behavior of Ir nanoparticles supported on LSMx, resulting from perovskite’s favorable antisintering properties of high oxygen storage capacity and surface oxygen vacancies.
