焙烧温度对微乳液法负载铂制备的Pt-S2O82-/ZrO2-Al2O3催化剂异构化性能的影响

过微乳液法负载Pt制备了Pt-S₂O₈^2-/ZrO₂-Al₂O₃(Pt-SZA-X) 催化剂,并采用XRD、BET、FT-IR、TPR、TEM等手段对催化剂进行了表征。以正戊烷异构化反应为探针,考察了焙烧温度对催化剂异构化性能的影响。结果表明,焙烧温度对Pt-SZA-X的还原温度影响不大,但催化剂表面S含量随着焙烧温度的升高而下降;焙烧温度为600~650℃时形成O=S=O结构,此时S与催化剂载体结合比较稳定;焙烧温度为650℃时,可得到单一的ZrO₂四方晶相,焙烧温度高于650℃时,比表面积迅速降低,催化剂表面S⁶⁺流失严重。在不同温度下焙烧得到的催化剂中,经650℃焙烧的催化剂具有适宜的超强酸位和比表面积,异构化活性最高。在反应温度为230℃、反应压力2.0 MPa、氢烃物质的量比4:1、质量空速1.0 h^-1时,催化异戊烷产率达到60.8%。

Effect of calcination temperature on isomerization performance of Pt-S2O82-/ZrO2-Al2O3 catalyst prepared by microemulsion

Pt-S₂O₈^2-/ZrO₂-Al₂O₃(Pt-SZA-X) solid superacid catalysts were prepared by microemulsion method and characterized by XRD, BET, FT-IR, TPR and TEM. The effects of calcination temperatures on the isomerization performance were studied by using n-pentane isomerization as a probe reaction. It was found that the calcination temperature has less influence on the reduction temperature of the Pt-SZA-X,but the S content over catalyst decreased with increasing calcination temperature. The O=S=O structure formed at calcination temperature range of 600 to 650℃ and the combination between of S and catalyst support was relatively stable. The pure monoclinic phase of ZrO₂ were observed with sample calcined at 650℃. When the calcination temperature is higher than 650℃, the specific surface area decreases rapidly and the loss of S⁶⁺ on the surface of catalyst is seriously. Among the catalysts obtained at various calcination temperatures, the catalyst calcined at 650℃ has appropriate amount of superacid sites and surface area and the highest isomerization activity. At reaction temperature of 230℃, pressure of 2.0 MPa, hydrogen/hydrocarbon molar ratio of 4:1 and mass hourly space velocity of 1.0 h^-1, the isopentane yield is 60.8%.