Abstract
In this study, a new-type of triblock structure directing agent (SDA) with hydrophobic middle part and hydrophilic ends was prepared and used in MFI zeolite synthesis. The SDA with propoxy middle part and quaternary ammonium ends (N3(PO)n-N3，n = 2、32、67) was synthesized by nucleophilic substitution reaction. The effects of the length of SDA on the morphology and catalytic activity of MFI zeolite was investigated by tuning the concentration of SDA with various length of hydrophobic part. In the synthesis of silicalite-1, lamellar structure was obtained by using N3-(PO)67-N3、N3-(PO)32-N3 as SDA, flower-like morphology was formed with N3-(PO)32-N3, and furthermore, self-pillared, intersectional and compressed octahedron was obtained by using N3-(PO)2-N3 as SDA. N2 physisorption isotherm showed that these prepared materials contain slit-type mesopores and zeolitic micropores. In the synthesis of TS-1 & ZSM-5, the self-pillared and intersectional structure of TS-1 was successfully obtained by using N3-(PO)2-N3 as SDA, and lamellar structure of ZSM-5 was also obtained by using N3-(PO)32-N3 as SDA. The hierarchical ZSM-5 has high BET surface area, large pore volume and exhibited much better catalytic activity in Friedel-Craft alkylations as compared to conventional ZSM-5.