Complete oxidation of hydrocarbons on YFeO3 and LaFeO3 catalysts

•Synthesis of YFeO3 and LaFeO3 perovskite catalysts via sucrose assisted solution-combustion.•Intensive fluctuation between the different oxidation states of Fe ions suggested with LaFeO3.•More effective activation of hydrocarbon and oxygen molecules on LaFeO3 than on YFeO3. Perovskite catalysts (YF...

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Bibliographic Details
Published in:Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2013-09, Vol.231, p.236-244
Main Authors: Markova-Velichkova, M., Lazarova, T., Tumbalev, V., Ivanov, G., Kovacheva, D., Stefanov, P., Naydenov, A.
Format: Article
Language:English
Subjects:
active sites
adsorption
Catalysis
Catalysts
Catalytic oxidation
Cations
chemical engineering
deformation
Hydrocarbons
ions
Iron
Kinetics
LaFeO3
Methane
Oxidation
oxygen
Perovskites
sucrose
Surface chemistry
Toluene
YFeO3
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Summary:•Synthesis of YFeO3 and LaFeO3 perovskite catalysts via sucrose assisted solution-combustion.•Intensive fluctuation between the different oxidation states of Fe ions suggested with LaFeO3.•More effective activation of hydrocarbon and oxygen molecules on LaFeO3 than on YFeO3. Perovskite catalysts (YFeO3 and LaFeO3, supported on α-Al2O3) were synthesized via sucrose assisted solution-combustion method. The phase composition as well as the surface morphology and catalyst evolution were studied before and after carrying out the reaction using different instrumental methods as XRD, XPS and TPR. Different hydrocarbons (methane, n-hexane and toluene) were tested in reaction of complete oxidation. Considering the case of toluene the kinetics calculations for both catalysts showed as most probable the Langmuir–Hinshelwood mechanisms, which include adsorption of the reagents (toluene and oxygen) on different types of sites and dissociative adsorption of oxygen. With YFeO3 the Mars–van Krevelen mechanism cannot yet be excluded. The presence of small size A-type cation like Y in the perovskite structure leads to structure deformation and makes it relatively unstable and does not permit an intensive transformation of Fe ions into higher or lower oxidation state. On the contrary – the structure of LaFeO3 is very stable and can easily accommodate certain amount of cation and anion defects without structural changes, which promotes more intensive fluctuation between the oxidation states of Fe ions and provides more active sites on the catalyst surface for interaction between hydrocarbon and oxygen molecules.
ISSN:1385-8947
1873-3212
DOI:10.1016/j.cej.2013.07.029