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

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.