物理化学学报 >> 2004, Vol. 20 >> Issue (01): 60-64.doi: 10.3866/PKU.WHXB20040113

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La/ZSM-5分子筛热稳定性及镧存在形态研究

杨刚;王妍;周丹红;庄建勤;刘宪春;韩秀文;包信和   

  1. 中国科学院大连化学物理研究所,大连　116023; 辽宁师范大学化学系,大连　116029
  • 收稿日期:2003-06-30 修回日期:2003-09-16 发布日期:2004-01-15
  • 通讯作者: 包信和 E-mail:xhbao@dicp.ac.cn

Investigation on the Thermal Stability of La/ZSM-5 Zeolite and the La3＋ Species

Yang Gang;Wang Yan;Zhou Dan-Hong;Zhuang Jian-Qin;Liu Xian-Chun;Han Xiu-Wen;Bao Xin-He   

  1. State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences　116023; Department of Chemistry, Liaoning Normal University, Dalian　116029
  • Received:2003-06-30 Revised:2003-09-16 Published:2004-01-15
  • Contact: Bao Xin-He E-mail:xhbao@dicp.ac.cn

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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.

关键词: ZSM-5, LaO(OH), La(OH)2＋, 密度泛函, 热稳定性

Abstract: 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 La(OH)2＋ when heated, LaO(OH) is most likely formed, which can interact with zeolite ZSM-5 and turns out to the structure of Z－La(OH)2＋ or Z-LaO(OH) after geometrical optimization. Z－La(OH)2＋ 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.

Key words: ZSM-5, LaO(OH), La(OH)2＋, Density functional, 　Thermal stability