稀土对SO2-4/ZrO2超强酸材料稳定性的影响

SO2 -4/ZrO2 的超强酸酸性与硫酸根含量、氧化锆状态和制备过程有关。在较低温度下ZrO2 由无定形转变成四方晶相 ,在较高温度下由四方晶相转变成单斜晶相。SO2 -4对上述的相变有阻抑作用。对于引入稀土的样品 (Zr/RE摩尔比为 6 0～ 2 4 0 ) ,稀土对ZrO2 在较低温度下由无定形转变成四方晶相的相变无明显的影响 ,但对较高温度下由四方晶相向单斜晶相的相变有明显的阻抑作用 ,因此 ,增强了四方晶态相和酸性中心的热稳定性 ,同时催化剂的活性稳定性也有显著的提高。

EFFECT OF RARE EARTH CATIONS ON THE STABILITY OF SULFATED ZIRCONIA SUPERACID CATALYST

The superacidity of sulfated zirconia cancan be correlated with its sulfate content, zirconia state and preparation procedure. The phase transition of zirconia from amorphous to tetragonal crystalline form occursed at lower temperature, and from tetragonal to monoclinic crystalline form occurred at higher temperature. Sulfate ions inhibited the phase transition of zirconia either from amorphous to tetragonal or from tetragonal to monoclinic crystalline form. For RE containing samples, XRD results showed that the temperature of phase transition from tetragonal to monoclinic crystalline form was higher than that of SO 2- 4/ZrO 2. IR results also showed that the intensity and wave number were relatively stable as compared with that of SO 2- 4/ZrO 2. Thus it increased the thermal stability of tetragonal crystalline form and the superacidic centers and also the stability of increased hexane reaction at the same time.