The Effect of Zinc Content on n -Pentane Isomerisation Over Zn–S 2 O 8 2– /ZrO 2 –Al 2 O 3 Catalyst

A number of Zn–S₂O₈^2–/ZrO₂–Al₂O₃ (Zn(x)–SZA) catalysts with different Zn mass fractions were synthesised and characterised by using X-ray diffraction, the Brunauer–Emmett–Teller method, and H₂ temperature-programmed reduction. The structure and isomerisation performance of Zn(x)–SZA catalysts were studied using n-pentane as a probe reaction. The results showed that a pure tetragonal ZrO₂ phase was formed on Zn(x)–SZA, and the ZrO₂ crystallite sizes of the tetragonal phase increased in the order: Zn(0.5)–SZA < Zn(1.0)–SZA < Zn(1.5)–SZA < Zn(2.0)–SZA < SZA. Zn can strengthen the interaction between persulfate ions and the support, promote the formation of stronger acidity, lead to a better dispersion of sulfate ions on the surface, and improve the redox performance of the catalysts. The Zn(1.0)–SZA catalyst exhibited the best catalytic activity for n-pentane isomerisation. At a temperature of 170 °C, a reaction pressure of 2.0 MPa, a molar H₂/n-pentane ratio of 4:1, and a weight hourly space velocity of 1.0 h⁻¹, the isopentane yield reached 58.0%.