Several Fe Ga mixed oxide samples denoted as Fe1-xGaxOy (x = 0, 0.20, 0.25, 0.50, 0.80, 0.90) have been synthesised by a conventional coprecipitation method at controlled pH, dried at 90 degrees C for 24 hours and calcined at 400 y 800 degrees C for 3 hours. All samples were characterised by X-ray diffraction, chemical analyses and thermogravimetry and differential thermal analysis (TG-DTA) and FT-IR and UV-VIS spectroscopies. It was found all materials formed a solid solution, alpha-(Fe,Ga)(2)O-3, in the entire Fe/Ga compositional range until 400 degrees C. Samples calcined at 800 degrees C gave rise to biphasic samples for x > 0.5 due to different structure of the beta-Ga2O3 with respect to the alpha-Fe2O3 one. Surface acidity of samples was studied by pivalonitrile molecule adsorption on the pressed pellet of each material, founding weak Lewis acid in all cases and not being possible distinguish both cation sites on the surface and Bronsted one that increased by increasing Ga content. Methanol molecule was also adsorbed, showing an increase of reactivity for those samples with a little bit of Ga content.
A FT-IR study of the FeGa mixed oxide surface by probe molecule adsorption
BUSCA, GUIDO
2000-01-01
Abstract
Several Fe Ga mixed oxide samples denoted as Fe1-xGaxOy (x = 0, 0.20, 0.25, 0.50, 0.80, 0.90) have been synthesised by a conventional coprecipitation method at controlled pH, dried at 90 degrees C for 24 hours and calcined at 400 y 800 degrees C for 3 hours. All samples were characterised by X-ray diffraction, chemical analyses and thermogravimetry and differential thermal analysis (TG-DTA) and FT-IR and UV-VIS spectroscopies. It was found all materials formed a solid solution, alpha-(Fe,Ga)(2)O-3, in the entire Fe/Ga compositional range until 400 degrees C. Samples calcined at 800 degrees C gave rise to biphasic samples for x > 0.5 due to different structure of the beta-Ga2O3 with respect to the alpha-Fe2O3 one. Surface acidity of samples was studied by pivalonitrile molecule adsorption on the pressed pellet of each material, founding weak Lewis acid in all cases and not being possible distinguish both cation sites on the surface and Bronsted one that increased by increasing Ga content. Methanol molecule was also adsorbed, showing an increase of reactivity for those samples with a little bit of Ga content.
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