Catalizadores de tungsteno –zirconia soportado sobre silica para reacciones catalizadas por ácido

C. R. VERA, K. SHIMIZU, C. L. PIECK, J. M. GRAU, M. E. LOVATO, J.M. PARERA

Córdoba, Argentina

Congreso; XIII Congreso Argentino de Catálisis; 2003

The sinthesys of novel complex of tungsten promoted zirconia (WZ)m supported over silica and the study of its actvtity in 1-butene isomerization, n-butane isomerization and isomerization-cracking of n-octane was performed in this work. In order to disperse WZ oversilica, zirconia was first dispersed over silica. Highly dispersed zirconia with a great resistance tosintering was got by controlled hydrolysis of zirconium alkoxide impregnated by incipientwetness. This resistance is crucial for the synthesis of W promoted catalysts which needed to becalcined at 700-800 O C in order to become catalytrcally active. Tungsten promoted catalysts were prepared by impregnation of silica supported Zr(OR)4 with ammonium metatugstate. Catalysts with zirconia contents equal to 1-1.5 monolayers (1 monolayer=30% zirconia in this case) were the most active. Catalysts with lower and higher zirconia contents were less active. For a given zirconia content, the activity increased with tungsten loading. The optimum calcinationtemperature was 750 "C, a value which is similar to that of bdk WZ. The activity of silica supported WZ taken .as a whole (silica -t- WZ) was only in a few cases higher than the activity of bulk WZ. However the activity per unit mass of zirconia was always higher in the case of thesupported catalysts. The activiv in isomerization of n-butane was low (< 1% conversion) while itwas high for isomerization of l-butene and isomerization-cracking of n-octane, indicating thatmost active sites on these catalysts had medium strength In the case of the n-octane reaction, thestability displayed by the new catalysts was higher than the activity of bulk WZ.