Acta Phys. -Chim. Sin. ›› 2004, Vol. 20 ›› Issue (01): 60-64.doi: 10.3866/PKU.WHXB20040113

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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

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