Recrystallisation of SBA-15 into ZSM-5/SBA-15 composites

摘要

Micro/mesostructured ZSM-5/SBA-15 composites were prepared by secondary crystallisation of SBA-15 impregnated with a solution of tetrapropylammonium hydroxide and sodium aluminate.The samples were characterised by X-ray diffraction (XRD),nitrogen sorption,infrared spectroscopy (FTIR) and scanning electronic microscopy (SEM).XRD and nitrogen sorption confirmed the partial preservation of the mesoporous structure and the formation of ZSM-5.Formation of ZSM-5 structural units in still X-ray amorphous material was detected by FTIR,which further indicates the incorporation of aluminium into the ZSM-5 structure.However,SEM micrographs showed the mesoporous SBA-15 and the microporous ZSM-5 as segregate particles evidencing that direct transformation of the SBA-15 pore walls into microporous ZSM-5 is unlikely.An enhanced activity in the isomerization of m-xylene on the recrystallised samples was observed.