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In this paper, alumina and metatungstate were added simultaneously in order to promote the acidity and stability of SO4/ZrO2 catalysts which were prepared by optimized impregnation-deposition method.
The powder was impregnated with solution of ammonium metatungstate, then filtered and dried at 110 AoC for 12 h.
The chemicals employed for the synthesis of W[O.sub.3] microcrystals were ammonium metatungstate hydrate ([(N[H.sub.4]).sub.6][H.sub.2][W.sub.12][O.sub.40] x x[H.sub.2]O, Sigma-Aldrich, 99.99%) and hydrochloric acid (HCl, NORDIC 37%, 12 M).
1.23 g of ammonium metatungstate hydrate (AMT) was dissolved in 20 mL of water under constant stirring.
SEM measurements revealed that the morphology of the W[O.sub.3] (W[O.sub.3]-AMT) microcrystals synthesized from ammonium metatungstate hydrate was of star-like type (Figure 3).
In this method, 3.0 wt.% of Ni in nickel nitrate, 15 wt.% of tungsten in ammonium metatungstate and 2.5 wt.% of phosphorus in phosphoric acid in water were impregnated onto the alumina support.
Ten grams of air-dried soil was placed in a centrifuge tube with 20 mL sodium metatungstate solution (density 1.75 g/[cm.sup.3]).