Resumo

GUERRERO FAJARDO, Carlos Alberto; SANCHEZ CASTELLANOS, Francisco José; ROGER, Anne-Cécile  e  COURSON, Claire. Sol-gel synthesis of iron catalysers supported on silica and titanium for selectively oxidising methane to formaldehyde. Ing. Investig. [online]. 2008, vol.28, n.1, pp.72-80. ISSN 0120-5609.

Iron materials supported on silica were prepared by the method sol-gel for to evaluate the catalytic activity in the selective oxidation of methane to formaldehyde. We prepare four (4) catalysts, one of them corresponding to the silica support (catalyst 1S), other one for the titania support (catalyst 1T) and two more with iron loads of 0.5% in weight, for the supported on silica (catalyst 2FS) and the other one supported on titania (catalyst 2FT). The higher areas BET are of the order of 659 and 850 m²/g for the catalysts 1S and 2FS, respectively while the catalysts 1T and 2FT displayed areas of 65 and 54 m²/g respectively. The scanning and transmission electronic microscopy displayed amorphous structure in the silica supported materials while the titania supported materials displayed dense materials with defined structure. The rays X diffraction confirms the amorphous structure of the silica in the 1S and 2FS catalysts and displayed the anatase structure for the 1T and 2FT catalysts. The programmed temperature reduction for the 1S and 2FS catalysts didn’t display reducible species while for the 1T and 2FT catalysts displayed peaks of hydrogen consumption related to the Fe₃O₄ reduction until α-Fe through Fe_xO way. The rays X photo electronic spectroscopy confirm the Fe(III) specie with binding energy 710.6 e.V for the both 2FS and 2FT catalysts. The catalytic activity is carried out to atmospheric pressure in quartz reactor, reaction mixture CH₄/O₂/N₂ =7.5/1/4, interval of temperature 400- 800°C. The reaction products are analysed by gases chromatography with Hayesep R and T columns and molecular tamis of 5 Å. The best response for the methane selective oxidation to formaldehyde is displayed for 2FS catalyst with methane conversion percentage of 3.4 mol % at 650°C, formaldehyde selectivity of 11.9%mol and yield of 0.0211 g HCHO/Kg catalyst.

Palavras-chave : catalysts Fe/SiO₂; catalysts Fe/TiO₂; formaldehyde; selective oxidation; sol-gel.

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