高温X-射线衍射法考察分子筛的热稳定性——Ⅰ、硅磷酸铝分子筛(SAPO)

Examination of Thermal Stability of Molecular Sieves by High Temperature XRD I.Molecular Sieves SAPO

用高温X-射线衍射法考察了四种具有不同孔径SAPO型分子筛的热稳定性。结果表明,具有较大孔径的SAPO-5与SAPO-11在1000℃时骨架仍没有明显破坏,其热稳定性优于具有较小孔径的SAPO-34与SAPO-20;由Zn或Mg杂原子取代SAPO-34骨架上的Si原子后,其热稳定性明显下降;ZSM-5,ALPO_4-5以及SAPO-5三种具有孔径大小相近分子筛的热稳定性依次下降。此外,分子筛在低角区的XRD峰强度对吸附水汽十分敏感。

The thermal stabilities of molecular sieves SAPO of four different pore diameters have beenexamined by the method of high temperature XRD. It is shown that the frameworks of molecu-lar sieves SAPO-5 and TAPO-11 have not been changed at 1000℃. So their thermal stabilitiesare higher than those of the molecular sieves SAPO-20 and SAPO-34. Replacing the silcon byZinc or Magnesium atoms at the framework of the molecular sieves SAPO-34, the thermal stabilitydecreases apparently. The thermal stabilities of the molecular sieves are decreased in the order ofZSM-5, AlPO_4-5 and SAPO-5. In addition, the intensities of low angle XRD peaks are sensitiveto adsorption of water vapor on molecular sieves