Effect of calcination temperature on isomerization performance of Pt-S₂O₈^2-/ZrO₂-Al₂O₃ catalyst prepared by microemulsion

Pt-S₂O₈^2-/ZrO₂-Al₂O₃(Pt-SZA-X) solid superacid catalysts were prepared by microemulsion method and characterized by XRD, BET, FT-IR, TPR and TEM. The effects of calcination temperatures on the isomerization performance were studied by using n-pentane isomerization as a probe reaction. It was found that the calcination temperature has less influence on the reduction temperature of the Pt-SZA-X,but the S content over catalyst decreased with increasing calcination temperature. The O=S=O structure formed at calcination temperature range of 600 to 650℃ and the combination between of S and catalyst support was relatively stable. The pure monoclinic phase of ZrO₂ were observed with sample calcined at 650℃. When the calcination temperature is higher than 650℃, the specific surface area decreases rapidly and the loss of S⁶⁺ on the surface of catalyst is seriously. Among the catalysts obtained at various calcination temperatures, the catalyst calcined at 650℃ has appropriate amount of superacid sites and surface area and the highest isomerization activity. At reaction temperature of 230℃, pressure of 2.0 MPa, hydrogen/hydrocarbon molar ratio of 4:1 and mass hourly space velocity of 1.0 h^-1, the isopentane yield is 60.8%.