| Zeolite ZSM-5 has been emerging as the one of the most promising active components in many chemical processes,such as catalytic cracking,alkylation and aromatization.However,one key problem remains unresolved in this typical shape-selective zeolite:its small pore size which limits the accessibility of active centers to macromolecules,remains far from application of conversion of large molecules.Therefore,the obtainging of hierarchical ZSM-5 by the introduction of mesoporous structure in the micropores remains a great challenging goal.1.In this article,a hierarchical ZSM-5 zeolite was synthesized by the synergy of crystal seed and bifunctional template(Mesotemp).Specifically,the addition of Mesotemp would lead to the bind formation of silica-aluminum gel with Mesotemp and the obtaining of well-ordered mesophase.On the other hand,the intrinsic ZSM-5 crystals would be inherited from crystal seeds.The intracrystalline mesopores were formed from the anchored Mesotemp.The hierarchical ZSM-5 obtained had a relative crystallinity 93%,total specific surface area 371.2 m27·g-1,mesoporous specific surface area 127.4 m2·g-1 by 1 L amplification under the optimal conditions.2.The hierarchical ZSM-5 zeolite was synthesized using TPABr as microprogen,and LAO as mesoprogen.TPABr determined whether to guide the MFI structure.From XRD and BET studied,it can be seen that adjusting of the mesoporous porosity can be achieved by the introduction of LAO.The hierarchical ZSM-5 obtained had a relative crystallinity 95.6%,total specific surface area 397.8 m2·g-1,mesoporous specific surface area 150.6 m2.g-1.It is very interesting that the mesoporous pore volume increased to 0.10 cm3·g-1,and average pore diameter was 3.5 nm.3.The hierachical zeolite Y with high Si/Al ratio was obtained by dealuminization and silicon supplementation in ammonium fluosilicate.In this strategy,an inverse trend of the relative crystallinity and Si/Al ratio can be observed due to collapse of skeleton in the process of dealuminization.The hierarchical high-silica Y obtained had a relative crystallinity more than 60%,SiO2/Al2O3 ratio 32.8,total specific surface area 450.5 m2·g-1,mesoporous specific surface area 102.3 m2·g-1,and average pore diameter 3.3 nm. |
