P. Ciambelli et al., La, Ca and Fe oxide perovskites: preparation, characterization and catalytic properties for methane combustion, APP CATAL B, 33(3), 2001, pp. 193-203
Citations number
23
Categorie Soggetti
Physical Chemistry/Chemical Physics","Environmental Engineering & Energy
La1-xCaxFeO3 (X = 0.1, 0.2, 0.3, 0.4, 0.5) perovskites prepared by citrate
method and calcined at 1073 K have been investigated as catalysts for metha
ne combustion. The formation of the perovskite structure has been shown by
X-ray diffraction (XRD) for all samples. The surface area (SA) values are i
n the range 3-6 m(2) g(-1) for the samples up to x=0.4, whereas SA is 0.7 m
(2) g(-1) for the specimen with x = 0.5. The atomic susceptibility increase
s with increasing in Ca content. The Fe4+/Fe-total ratio has been determine
d by both redox titration and TPR analysis. The amount of Fe4+ enhances wit
h Ca substitution but the Fe4+/Ca2+ ratio is quite constant giving rise to
an increasing formation of oxygen vacancies to preserve charge neutrality.
All perovskites show a similar intrinsic activity in CH4 combustion with ac
tivation energy, E-a, of about 23 kcal mol(-1). A slightly lower value of E
-a is shown by LaFeO3 which, in contrast with Ca substituted samples, exhib
its a small cationic defectivity. Methane reaction order lower than one was
found for all catalysts. (C) 2001 Elsevier Science B.V All rights reserved
.