The ecology of environment nowadays

THE SYNTHESIS OF MESOPOROUS WO3/ZrO2

WITH USING POLYVINIL ALCOHOL AS A TEMPLATE

O.V. Melezhyk, S.V. Prudius, V.V. Brei

Institute of Surface Chemistry, Ukrainian National Academy of Sciences,

Generala Naumova st. 17, 03164 Kyiv, Ukraine

Tungstated zirconia, WO3/ZrO2, is known to be a stable solid superacid. It is widely used for development of efficient catalysts for important processes in petrochemistry, in particular for isomerisation of C4 - C6 alkanes. We have developed a method for synthesis of mesoporous WO3/ZrO2 using polyvinyl alcohol as a template.

It has been shown that coarsening of crystals and collapse of pores can be prevented by use of a template capable to carbonization. After thermal treatment at 600 - 800oC in nonoxidizing atmosphere the mesoporous structure with carbon as a template was formed. Then carbon was burned out at 500° C in air. The materials synthesized are characterised by high surface area (S=200 – 300 m2 g-1) after calcination at 600 – 700° C.

Isotherms of adsorption of methanol and nitrogen were recorded and distributions of pores by size for samples of WO3/ZrO2 was calculated by Kelvin formula. It was found that the average diameter of pores was 24–28A.

With use of X-ray diffraction and UV-Vis Reflectance spectroscopy techniques it has been shown that in the structure of WO3/ZrO2 samples there are phases of tetragonal ZrO2 (2Q=35,3o), on whose surface there are situated clusters of WO3 which are characterised by forbidden gap of E0 = 3,10 – 3,20 eV. It is shown that such samples are characterised by the high catalytic activity in the reaction of n-hexane isomerization.

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