Effect of Preparation Conditions on the n -Pentane Isomerisation Performance of Pt-S 2 O 8 2– /ZrO 2 –Al 2 O 3 Catalysts Prepared by the Microemulsion Method

Abstract

Pt-promoted S₂O₈^2–/ZrO₂–Al₂O₃ (SZA) catalysts were successfully prepared by the microemulsion (Pt-SZA-M) and impregnation (Pt-SZA-I) methods. The effects of the preparation parameters (surfactant-to-oil ratio, surfactant-to-cosurfactant ratio, types of cosurfactant and oil phase, etc.) on the catalytic activity of Pt-SZA-M catalysts in the isomerisation of n-pentane were investigated. The results showed that the optimal catalyst preparation conditions were: a cetyltrimethylammonium bromide (CTAB)/n-butanol mass ratio of 4:6, a (CTAB + n-butanol)/cyclohexane mass ratio of 3:7, a content of H₂PtCl₆ solution in microemulsion of 3.6 wt% and a N₂H₅OH/H₂PtCl₆ molar ratio of 25:1. A comparison of the isopentane yield for Pt-SZA-M with that for Pt-SZA-I was also performed. The results showed that the microemulsion method led to smaller and more uniform Pt particles (4.5 nm) on the SZA. In comparison with Pt-SZA-I, the isopentane yield for Pt-SZA-M was increased by 13.5% at 180 °C, showing the catalytic performance of Pt-SZA-M at lower temperature was improved significantly. At a reaction temperature of 230 °C, a pressure of 2.0 MPa, a hydrogen/n-pentane molar ratio of 4:1 and a weight hourly space velocity of 1.0 h⁻¹, the yield of isopentane for Pt-SZA-M reached 60.8%.