Abstract: Mesopore modification via framework atom extraction for synthesized TS-1 molecular sieves with various Si/Ti ratios were performed under the identical conditions of sequential alkaline and acid treatments.Effects of initial framework composition variables on the crystal structure, textural mesoporosity and framework desilication selectivity were investigated upon characterization of XRD, FT-IR, UV-vis, N2 adsorption, SEM and EDX.The results reveal that the modified materials are provided with bimodal mesoporous structures feature of concentrated pore size distribution together with preferably structural ordering of TS-1 precursors.As initial Si/Ti molar ratio increases, the BET specific surface area and total specific pore volume are increase by framework desilication for the modified molecular sieves.However, the Si/Ti molar ratio, crystallinity preservation and yield corresponding to modified materials are shown to reduce gradually with the enhanced initial Si/Ti ratio.Moreover, both of the selectivity and efficiency for framework T-atoms removals are correlated with the compositional change of TS-1 precursors.It is demonstrated that the desilication selectivity greatly preponderated over the Ti-removal selectivity for the combined alkaline-acid treatment of TS-1 molecular sieves.With respect to the typical modified sample, the T-atoms removal efficiencies(fT, S-meso and fT, V-meso, T=Si+Ti), are substantiated to arrive at 2.6 m2·g-1·;-1 and 9.4×10-3 m3·g-1·;-1, respectively.

Key words: Mesopore modification via framework atom extraction for synthesized TS-1 molecular sieves with various Si/Ti ratios were performed under the identical conditions of sequential alkaline and acid treatments.Effects of initial framework composition variables on the crystal structure, textural mesoporosity and framework desilication selectivity were investigated upon characterization of XRD, FT-IR, UV-vis, N2 adsorption, SEM and EDX.The results reveal that the modified materials are provided with bimodal mesoporous structures feature of concentrated pore size distribution together with preferably structural ordering of TS-1 precursors.As initial Si/Ti molar ratio increases, the BET specific surface area and total specific pore volume are increase by framework desilication for the modified molecular sieves.However, the Si/Ti molar ratio, crystallinity preservation and yield corresponding to modified materials are shown to reduce gradually with the enhanced initial Si/Ti ratio.Moreover, both of the selectivity and efficiency for framework T-atoms removals are correlated with the compositional change of TS-1 precursors.It is demonstrated that the desilication selectivity greatly preponderated over the Ti-removal selectivity for the combined alkaline-acid treatment of TS-1 molecular sieves.With respect to the typical modified sample, the T-atoms removal efficiencies(fT, S-meso and fT, V-meso, T=Si+Ti), are substantiated to arrive at 2.6 m2·g-1·;-1 and 9.4×10-3 m3·g-1·;-1, respectively.