La. Boot et al., IRON-BASED DEHYDROGENATION CATALYSTS SUPPORTED ON ZIRCONIA .1. PREPARATION AND CHARACTERIZATION, Journal of catalysis, 163(1), 1996, pp. 186-194
Zirconia-supported iron oxide catalysts were prepared by incipient wet
ness impregnation, followed by drying and calcination in air. Characte
rization of the catalysts was performed with electron microscopy combi
ned with element analysis (HR-TEM/EDAX), X-ray diffraction (XRD), temp
erature-programmed reduction (TPR), and thermomagnetic analysis. A hom
ogeneous distribution of the iron containing phase can be obtained by
using the metal complexes ammonium iron (III) citrate or ammonium (III
) iron EDTA. A simple salt, such as iron nitrate, proved to be less su
itable for this purpose. By HR-TEM/EDAX, it was shown that coverage of
the zirconia support had been accomplished. XRD showed that crystalli
ne Fe2O3 particles were formed at loadings greater than or equal to 3
wt% Fe. TPR studies point to a bi-modal particle size distribution for
the catalysts with 3 wt% Fe, Above this loading (>3 wt%) bulk propert
ies prevail in TPR, whereas at lower loadings (<3 wt%) no distinct iro
n oxide species could be indicated. Magnetization measurements confirm
ed the results obtained by TPR. Catalysts prepared by coimpregnation o
f iron and potassium were also studied. TEM and XRD results show that
a well-dispersed phase is obtained, but from XRD only potassium carbon
ate and no iron oxide or ferrite is evident, It was also found that th
e presence of potassium increases the onset of reduction of the iron p
hase by about 100 degrees C. (C) 1996 Academic Press, Inc.