La/ZSM-5分子筛热稳定性及镧存在形态研究  

Investigation on the Thermal Stability of La/ZSM-5 Zeolite and the La^(3+) Species

作　　者：杨刚[1] 王妍[1] 周丹红[1] 庄建勤[1] 刘宪春[1] 韩秀文[1] 包信和[1] 

机构地区：[1]中国科学院大连化学物理研究所,大连116023

出　　处：《物理化学学报》2004年第1期60-64,共5页Acta Physico-Chimica Sinica

基　　金：中国科学院知识创新项目(KGCX2-208-3)资助~~

摘　　要：借助密度泛函方法,从理论上证实了当催化裂解工艺的催化剂(ZSM-5分子筛)中引入少量镧离子时,其热稳定性得到了显著的提高,主要是由于镧离子与分子筛之间发生了强的相互作用,使得最易发生断裂的键(Al-O键)变得更加牢固,从而有效地延缓了脱铝进程.La(OH)+2的降解产物中,LaO(OH)的形成几率最大.LaO(OH)和分子筛作用可形成两种稳定的结构Z-La(OH)+2和Z-LaO(OH).其中Z-La(OH)+2是常温下的稳定构型,而Z-LaO(OH)是温度较高时的稳定构型,此构型中的镧离子可提供L酸作为反应的活性中心,为探索催化反应机理提供了有力的理论依据.By density functional calculations,it was confirmed that for the reaction of RSCC (residual oil selective catalytic cracking),the catalysts such as zeolite ZSM 5 will endure an enhanced thermal stability when some La3+ ions are introduced.Due to the strong interaction between La3+ and the zeolite,the Al- O bond,which would have been easily broken,gets stronger and the process of dealumination is thus effectively retarded.Through the reduction of when heated,LaO(OH) is most likely formed,which can interact with zeolite ZSM 5 and turns out to the structure of Z- or Z LaO(OH) after geometrical optimization.Z- remains stable under normal conditions;however,as the temperature is raised,it will change slowly into Z LaO(OH),which stays stable at high temperature.The La3+ ion in Z LaO(OH) can offer Lewis acid as the active site for reactions,we believe that this result can provide valuable insight into the elucidation of catalytic mechanism.

关 键 词：ZSM-5分子筛 热稳定性 镧 存在形态 密度泛函 催化剂 

分 类 号：O643.3[理学—物理化学]