Influence of aluminum species on the isomerization performance over solid superacid Pt-S₂₈O^2-/ZrO₂-Al₂O₃

A series of Pt-S₂₈O^2-/ZrO₂-Al₂O₃ catalysts were prepared by microemulsion method with pseudo-boehmite, γ-Al₂O₃, Al₂O₃ and Al(NO₃)₃·9H₂O as aluminum source, respectively, and the resulting catalysts were characterized by XRD, FT-IR, BET, H₂-TPR techniques. The influence of aluminum sources on the structure and acidic properties of the catalysts were investigated. The catalytic performance of the Pt-S₂₈O^2-/ZrO₂-Al₂O₃ catalysts was studied using n-petane isomerization as a probe reaction. The results indicated that all the catalysts prepared with different source of aluminum can stabilize the tetrogonal ZrO₂ phase and increase specific surface area of the catalysts. Except for pseudo-boehmite, the redox performance of catalysts prepared with other aluminum source were improved. The catalyst prepared with Al(NO₃)₃·9H₂O as the aluminum source, which possessed the largest specific surface area and more superacid, exhibited the best isomerization performance. At a reaction temperature of 220 ℃, a pressure of 2.0 MPa, a hydrogen/hydrocarbon mol ratio of 4∶1 and a WHSV of 1.0 h^-1, the isopentane yield reaches a maximum of 59.5%.