Effect of Pd content on the isomerization performance over Pd-S₂O₈ ²⁻/ZrO₂-Al₂O₃ catalyst

Abstract

The effect of Pd content on the performance of the Pd-S₂O₈ ²⁻/ZrO₂-Al₂O₃ solid superacid catalyst was studied using n-pentane isomerization as a probe reaction, and the catalysts were characterized by FTIR, BET, TG-DTA, H₂-TPR, NH₃-TPD and XPS. The results showed that an appropriate amount of Pd could promote the formation of acid sites, enhance the acidity of catalyst, improve the redox properties of the catalyst, and delay the decomposition of S₂O₈ ²⁻ effectively. The Pd-S₂O₈ ²⁻/ZrO₂-Al₂O₃ catalyst with 0.05 wt % Pd exhibited the best catalytic activity for n-pentane isomerization. At the reaction temperature of 200 °C, reaction pressure of 2.0 MPa, weight hourly space velocity of 1.0 h⁻¹, H₂/n-pentane molar ration of 4.0, the n-pentane conversion, iso-pentane selectivity and yield reached 61.1, 96.7, and 59.1 %, respectively, the isopentane yield with the Pd-S₂O₈ ²⁻/ZrO₂-Al₂O₃ increased by 39.1 % compared to S₂O₈ ²⁻/ZrO₂-Al₂O₃, and no obvious catalyst deactivation was observed within 100 h.