采用27Al MAS NMR、N2吸附-脱附、IR等表征技术及XRD Rietveld结构精修的方法,通过清除和交换引入非骨架铝,探讨了USY沸石中非骨架铝的形态。结果表明,27Al MAS NMR化学位移为0的非骨架铝以游离在超笼中的非骨架铝为主,化学位移为30-50...采用27Al MAS NMR、N2吸附-脱附、IR等表征技术及XRD Rietveld结构精修的方法,通过清除和交换引入非骨架铝,探讨了USY沸石中非骨架铝的形态。结果表明,27Al MAS NMR化学位移为0的非骨架铝以游离在超笼中的非骨架铝为主,化学位移为30-50的非骨架铝与沸石骨架存在键合作用;晶体学可识别的离子态非骨架铝存在于方钠石笼的SⅠ′和SⅡ′位置,其中,SⅠ′位置的非骨架铝与沸石骨架3个O3原子及与其配位的三重轴的O形成不稳定的四配位结构,SⅡ′位置的Al不与沸石骨架O形成配位。超笼中未发现可识别的离子态非骨架铝。聚合态非骨架铝的存在将堵塞沸石孔道,影响微孔吸附性能,并掩盖B酸中心。清除非骨架铝后,可以使沸石孔道畅通,使B酸中心得到恢复。展开更多
The Pt-bearing SO42-/ZrO2 superacid catalysts supported on ultra stable Y (USY) zeolite were prepared by impregnation and characterized by X-ray diffracti on, nitrogen adsorption and Hammett indicators. Their catalyti...The Pt-bearing SO42-/ZrO2 superacid catalysts supported on ultra stable Y (USY) zeolite were prepared by impregnation and characterized by X-ray diffracti on, nitrogen adsorption and Hammett indicators. Their catalytic activities were evaluated in the hydroisomerization of n-heptane with an atmospheric fixed-bed r eactor. The catalysts possessed a high surface area, superacidity and well maint ained pore structure of USY support. The supported catalysts with a suitable SO4 2-/ZrO2 loading exhibited a higher catalytic activity and selectivity than the u nsupported SO42-/ZrO2 catalyst or the Pt supported on USY catalyst without super acid. At the reaction temperature of 220 ℃, over the catalyst with a Pt loading of 0.8wt% and ZrO2 loading of 10wt%, the conversion of n-heptane could be as hi gh as 35.2% with a selectivity of 87.9% for isomerization products.展开更多
文摘采用27Al MAS NMR、N2吸附-脱附、IR等表征技术及XRD Rietveld结构精修的方法,通过清除和交换引入非骨架铝,探讨了USY沸石中非骨架铝的形态。结果表明,27Al MAS NMR化学位移为0的非骨架铝以游离在超笼中的非骨架铝为主,化学位移为30-50的非骨架铝与沸石骨架存在键合作用;晶体学可识别的离子态非骨架铝存在于方钠石笼的SⅠ′和SⅡ′位置,其中,SⅠ′位置的非骨架铝与沸石骨架3个O3原子及与其配位的三重轴的O形成不稳定的四配位结构,SⅡ′位置的Al不与沸石骨架O形成配位。超笼中未发现可识别的离子态非骨架铝。聚合态非骨架铝的存在将堵塞沸石孔道,影响微孔吸附性能,并掩盖B酸中心。清除非骨架铝后,可以使沸石孔道畅通,使B酸中心得到恢复。
文摘The Pt-bearing SO42-/ZrO2 superacid catalysts supported on ultra stable Y (USY) zeolite were prepared by impregnation and characterized by X-ray diffracti on, nitrogen adsorption and Hammett indicators. Their catalytic activities were evaluated in the hydroisomerization of n-heptane with an atmospheric fixed-bed r eactor. The catalysts possessed a high surface area, superacidity and well maint ained pore structure of USY support. The supported catalysts with a suitable SO4 2-/ZrO2 loading exhibited a higher catalytic activity and selectivity than the u nsupported SO42-/ZrO2 catalyst or the Pt supported on USY catalyst without super acid. At the reaction temperature of 220 ℃, over the catalyst with a Pt loading of 0.8wt% and ZrO2 loading of 10wt%, the conversion of n-heptane could be as hi gh as 35.2% with a selectivity of 87.9% for isomerization products.
