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The Effect of Water on the 2-Propanol Oxidation Activity of Co-Substituted LaFe_1- Co_x O₃ Perovskites.

ABSTRACT: Perovskites are interesting oxidation catalysts due to their chemical flexibility enabling the tuning of several properties. In this work, we synthesized LaFe_1-x Co_x O₃ catalysts by co-precipitation and thermal decomposition, characterized them thoroughly and studied their 2-propanol oxidation activity under dry and wet conditions to bridge the knowledge gap between gas and liquid phase reactions. Transient tests showed a highly active, unstable low-temperature (LT) reaction channel in conversion profiles and a stable, less-active high-temperature (HT) channel. Cobalt incorporation had a positive effect on the activity. The effect of water was negative on the LT channel, whereas the HT channel activity was boosted for x>0.15. The boost may originate from a slower deactivation rate of the Co³⁺ sites under wet conditions and a higher amount of hydroxide species on the surface comparing wet to dry feeds. Water addition resulted in a slower deactivation for Co-rich catalysts and higher activity in the HT channel state.

SUBMITTER: Dreyer M

PROVIDER: S-EPMC9299464 | biostudies-literature | 2021 Dec

REPOSITORIES: biostudies-literature

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The Effect of Water on the 2-Propanol Oxidation Activity of Co-Substituted LaFe1- Cox O3 Perovskites.

Dreyer Maik M Cruz Daniel D Hagemann Ulrich U Zeller Patrick P Heidelmann Markus M Salamon Soma S Landers Joachim J Rabe Anna A Ortega Klaus Friedel KF Najafishirtari Sharif S Wende Heiko H Hartmann Nils N Knop-Gericke Axel A Schlögl Robert R Behrens Malte M

Chemistry (Weinheim an der Bergstrasse, Germany) 20211108 68

Perovskites are interesting oxidation catalysts due to their chemical flexibility enabling the tuning of several properties. In this work, we synthesized LaFe1-x Cox O3 catalysts by co-precipitation and thermal decomposition, characterized them thoroughly and studied their 2-propanol oxidation activity under dry and wet conditions to bridge the knowledge gap between gas and liquid phase reactions. Transient tests showed a highly active, unstable low-temperature ( ...[more]

PMID: 34633707

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Project description:As a model for the energy-efficient aftertreatment of exhaust gas components, we studied microwave-assisted (MW) CO oxidation over a (La,Sr)CoO3-δ (LSC) perovskite oxide catalyst under dry and humidified conditions. We found that the use of a MW-based process can offer multiple advantages over traditional thermocatalysis in this scenario, as the nature of the MW-solid interaction offers quick, adaptive, and energy-efficient heating as well as improved yield and lower light-off temperatures. As found by combined CO and water MW-desorption experiments, the presence of technically relevant amounts of water leads to a competition for surface active sites and thus slows the reaction rate without indications for a fundamental change in the mechanism. Remarkably, the performance loss related to the presence of water was less pronounced in the MW-assisted process. Additionally, while we recorded a temperature-dependent degradation of the reaction rate in extended MW-catalysis experiments both in dry and humidified conditions, it quickly recovered after a short reactivation MW-treatment. Our study confirms that surface reaction can be driven by the use of MW-radiation in a similar magnitude that can be achieved by thermal activation at significantly higher temperatures. The nature of the effect of the MW-treatment on the structural and electronic surface properties of the LSC material was investigated by X-ray absorption (XAS) and X-ray photoelectron spectroscopy (XPS). We found evidence of a significant structural, chemical, and electronic reorganization of the oxide surface, possibly consistent with the occurrence of overheated surfaces or "hotspots" during MW-exposure, which may explain the increased catalytic and heating properties of the LSC after the MW-pretreatment. The good catalytic performance, quick response to MW-heating, and long-term stability of the catalyst all indicate the promising potential of a MW-based process for the energy-efficient exhaust aftertreatment using noble-metal-free oxide catalysts.

Dataset Information

The Effect of Water on the 2-Propanol Oxidation Activity of Co-Substituted LaFe_1- Co_x O₃ Perovskites.

Publications

The Effect of Water on the 2-Propanol Oxidation Activity of Co-Substituted LaFe<sub>1-</sub> Co<sub>x</sub> O<sub>3</sub> Perovskites.

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