d-Al2O3 supported La, Mn, Co and Fe contg. catalysts were prepd. by impregnation of d-Al2O3 with citrate-type precursors and calcination at 1073 K. The catalysts were characterized by X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), X-ray absorption spectroscopy (XAS), and BET sp. surface area detn. XRD revealed the presence of d-Al2O3 in all cases and, at 30 wt.% of metal loading, of other single (a-Mn2O3 and a-Fe2O3) or mixed (LaAlO3, LaMnO3, CoAl2O4 and LaFeO3) oxide phases. XAS suggested the formation of some oxide phases also at lower loading. In particular, all Mn and 10 wt.% La-Mn contg. samples revealed the formation of a-Mn2O3, while the 30 wt.% La-Mn bimetallic sample showed the formation of LaMnO3 perovskite. All Co contg. samples revealed the presence of CoAl2O4 spinel. Fe contg. samples showed the formation of a-Fe2O3, while La-Fe contg. ones, that of LaFeO3 perovskite. Catalytic tests of CO oxidn. were performed in the temp. range 300-800 K. The sample contg. 30 wt.% of La and Mn in the form of LaMnO3 perovskite dispersed on d-Al2O3 was found the most active among all the examd. catalysts. Most of the Co contg. catalysts were found active at RT too, but they deactivated rapidly. None of the Fe-based samples was active at RT and these catalysts were found, on av., to be substantially less active than the Mn- and Co-based ones.
LaAl1-xMnxO3 perovskite-type oxide solid solutions: structural,magnetic and electronic properties.
2003-01-01
Abstract
d-Al2O3 supported La, Mn, Co and Fe contg. catalysts were prepd. by impregnation of d-Al2O3 with citrate-type precursors and calcination at 1073 K. The catalysts were characterized by X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), X-ray absorption spectroscopy (XAS), and BET sp. surface area detn. XRD revealed the presence of d-Al2O3 in all cases and, at 30 wt.% of metal loading, of other single (a-Mn2O3 and a-Fe2O3) or mixed (LaAlO3, LaMnO3, CoAl2O4 and LaFeO3) oxide phases. XAS suggested the formation of some oxide phases also at lower loading. In particular, all Mn and 10 wt.% La-Mn contg. samples revealed the formation of a-Mn2O3, while the 30 wt.% La-Mn bimetallic sample showed the formation of LaMnO3 perovskite. All Co contg. samples revealed the presence of CoAl2O4 spinel. Fe contg. samples showed the formation of a-Fe2O3, while La-Fe contg. ones, that of LaFeO3 perovskite. Catalytic tests of CO oxidn. were performed in the temp. range 300-800 K. The sample contg. 30 wt.% of La and Mn in the form of LaMnO3 perovskite dispersed on d-Al2O3 was found the most active among all the examd. catalysts. Most of the Co contg. catalysts were found active at RT too, but they deactivated rapidly. None of the Fe-based samples was active at RT and these catalysts were found, on av., to be substantially less active than the Mn- and Co-based ones.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
