Study On Zn And Fe Modified S₂O₈^2-/ZrO₂-Al₂O₃ Solid Superacid Catalyst

Catalyzed isomerization of light paraffin is one of the important processes in petroleum fields and one of the important technologies for RON improvement in oil refining.It has the advantages of simple operation,low cost and save resources.The S₂O₈^2-/M_xO_y solid superacid catalysts is one important type for isomerization,have attracted much attention of the researchers,due to its strong acidity,improved selectivity,easy to preparation,no pollution and high reusability.After continuous modification,the activity and stability performance of the catalyst were elevated,and the catalyst can be applied to various reaction and industrialization.In this paper,the catalyst support is ZrO₂-Al₂O₃,and high catalytic activity and stability Zn-Fe-S₂O₈^2-/ZrO₂-Al₂O₃（Zn–Fe–SZA）mental-acid bifunctional solid superacid catalysts were prepared by simultaneously introducing the S₂O₈^2-and Zn、Fe into ZrO₂-Al₂O₃support.The catalysts were characterized by XRD,FT-IR,Py-IR,TG-DTA,TPR,BET for the catalyst performance.The effects of the content of Zn and Fe on the performance of catalysts and catalyst deactivation and regeneration performance was studied by using n-pentane isomerization as a probe reaction.Analyses the reason for the catalyst deactivation.The kinetic model of n-pentane isomerization reaction on Fe-Zn-SZA catalyst is proposed on the base of kinetic experiments.The results show that the transition metal Zn and Fe to significantly improve the activity and stability performance of the catalysts,Zn can enhance the activity of the catalyst reduction and decreases significantly the reduced temperature of the catalyst,Metal Fe can facilitate specific surface area of catalyst.And the synergistic interaction between Zn and Fe can provide more acidic sites.The active of catalyst decreases in the order:Zn–Fe–SZA>Zn–SZA>Fe–SZA>SZA.The catalyst with 1.0%of Zn and Fe,respectively,calcinated at 650℃,exhibited the highest activity for isomerization.At reaction temperature of 170^oC,pressure of 2.0 MPa,hydrogen/n-pentane molor ratio of 4:1,and MHSV of 1.0 h-1,the yield and selectivity of isopentane are 67.0%and 99.5%,respectively.Carbon deposit catalyst surface and removal of sulfur entities,which make the decrease of the activity and stability of the catalyst.High temperature calcinate the deactivation catalyst can make recovery the activity,but due removal of sulfur entities,it only can reach the 75%the fresh catalyst activity.Due to supplement of S after resulfating the catalyst,the activity of catalyst can reach 90%the fresh catalyst activity.The kinetic model of n-pentane isomerization reaction on Fe-Zn-SZA catalyst is a first-order reversible kinetic model.The apparent active energy of the forward and reverse reaction is 71.9 kJ/mol and 70.3 KJ/mol,respectively.