Abstract:
A series of WO
3-ZrO
2 solid acids were synthesized by calcining the equilibrium adsorbed peroxotungstic acid/hydrated zirconia precursors. The influences of peroxotungstic acid concentration and calcination temperature on the composition, structure and acidity of the obtained solid acids were evaluated by using XRD, UV-vis and NH
3-TPD. Pt/WO
3-ZrO
2 catalysts were prepared by impregnation method and characterized by BET, H
2-TPR and H
2-TPD. The catalytic performance in the hydroisomerization of
n-pentane was investigated. It was found that under the same calcination temperature, both the support acidity and the catalyst surface area first increase and then decrease with the increase of peroxotungstic acid concentration, and are maximized when the peroxotungstic acid concentration reaches 82 mmol W/L. When the peroxotungstic acid possesses the same concentration of 59 mmol W/L, the tetragonal zirconia fraction, support acidity and the catalyst surface area decrease with the increase of calcination temperature. When the peroxotungstic acid concentration and the calcination temperature of the support are 82 mmol W/L and 700℃ respectively, the obtained catalyst shows the best catalytic performance. The yield of isopentane reaches 57.7% under the reaction condition of ambient pressure, 250℃,
n(H
2)/
n(
n-C
5H
12)=3 and WHSV=1.0 h
-1.