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Preparation of WO[sub]3 aerogel catalysts using supercritical CO[sub]2Zoran Novak,
Petra Kotnik,
Željko Knez, 2004, original scientific article
Abstract: Single tungsten oxide aerogels (WO3), binary oxide aerogels (WO3-Al2O3) and ternary oxide aerogels (WO3-SiO2-Al2O3) were prepared using standard sol-gel route. Tungsten oxide tetraethoxide (WO(OCH2CH3)4) was used as the sol-gel precursor. The excellent properties of the gels obtained by the sol-gel synthesis were preserved upon supercritical drying with CO2. After supercritical drying at 40 °C and 100 bar, all aerogels were calcined to 800 °C. The influence of the synthesis parameters on the catalytic activity of WO3as supported on silica andžor alumina aerogels was investigated through thetransformation of N-(phosphonomethyl)iminodiacetic acid to N-(phosphonomethyl)glycine. Despite including WO3 into single and mixed silicaand alumina aerogels, high specific surface areas (284-653 m2 g-1) were preserved. Higher conversion was obtained for catalysts with higher ratios of WO3 in the mixed silica-alumina aerogels that were calcined at 800 °C.
Keywords: chemical processing, aerogels, catalysts, tungsten oxides, preparation of aerogels, characterisation of aerogels, supercritical CO2, supercritical drying, high pressure technology
Published in DKUM: 01.06.2012; Views: 2113; Downloads: 49
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