Synthesis And Performance Of FAU/MFI Composite Molecular Sieves

In this thesis,FAU/MFI composite molecular sieves were synthesized by in-situ synthesis method and gel method.The optimum synthesis conditions were discussed and the samples were characterized by equipment,such as XRD,SEM,FTIR,etc.The prepared molecular sieves were modified to investigate the catalytic properties,and MTA reaction and Fenton reaction were selected to test.（1）The in-situ Y molecular sieve was synthesized by the in-situ synthesis technology of kaolin.The Y@ZSM-5 composite molecular sieve with the core-shell structure was synthesized using the in-situ Y molecular sieve.The amount of matrix,the amount of template,reaction system ratio,time and temperature on the synthesis were investigated.The reaction system ratio was determined as Na₂O:Si O₂:H₂O=1:15:478,the amount of matrix was 51.65%,H₂O/Na₂O ratio was 478,Na₂O/Si O₂ ratio was 0.0659,the reaction time was 72 h,and the reaction temperature was 180℃.The relative crystallinity of Y molecular sieve in the prepared Y@ZSM-5 core-shell molecular sieve was 53.8%,and the relative crystallinity of ZSM-5 molecular sieve was 47.3%.The prepared Y@ZSM-5 core-shell molecular sieve pore size was 2.85 nm and specific surface area was 418 m²/g.（2）Gel Y molecular sieves were synthesized through the gel system,and composite molecular sieves were prepared using Y molecular sieves as the matrix.The amount of matrix,the amount of template,reaction system ratio,reaction time and temperature were also discussed.A composite molecular sieve with special morphology were obtained when the amount of Y molecular sieve matrix was 35.43wt%,the amount of template was9.32wt%,the H₂O/Na₂O ratio was 478,and the Na₂O/Si O₂ ratio was 0.0659.The Y molecular sieve content was 41.59%,and the ZSM-5 molecular sieve content was 50.12%.（3）The prepared molecular sieves were modified with Zn and La to prepare catalysts,and the catalytic performance was tested in methanol aromatization reaction.The maximum BTX selectivity of Y@ZSM-5 core-shell molecular sieve was 26.16%in the aromatization reaction at 470°C and 0.5 MPa,and it had a high selectivity to benzene.The maximum BTX selectivity of composite molecular sieve was 37.22%at 450℃and 0.5 MPa,and it had a high selectivity to toluene and xylene.（4）The performance of composite molecular sieves in degrading organic dyes was explored by Fenton reaction,and composite molecular sieves were modified with Fe and La to prepare catalysts.Indigo carmine was used as the organic waste liquid.The degradation rate of Y@ZSM-5 core-shell molecular sieve was 77.19%in 10 min under the optimal conditions,and the degradation rate after 20 min was 77.19%.The degradation rate of Y/ZSM-5/Silicalite-1 composite molecular sieve was 93.96%in 10 min under optimal conditions,and the dye degradation rate reached 100%after 20 min.The reaction kinetics of the prepared composite molecular sieve catalysts in the Fenton reaction were first-order kinetics.