硅钛比对TS-1骨架脱硅衍生介孔结构的影响

Effect of Si/Ti Molar Ratios on Mesoporous Structure Formed by TS-1 Framework Desilication

在相同碱酸处理条件下,通过骨架原子抽提对合成的不同Si/Ti摩尔比的TS-1分子筛进行介孔改性。用XRD、FT-IR、UV-vis、N_2吸附、SEM和EDX技术,考察骨架组成对改性TS-1晶体结构、织构介孔率和骨架脱硅、脱钛选择性的影响。结果表明,改性材料具有尺度分布集中的双介孔结构,并较好地保持其前体的结构有序性。随起始Si/Ti摩尔比的提高,改性TS-1分子筛BET比表面积和总比孔容增加,相应的Si/Ti摩尔比、结晶度保留率和产率逐渐降低。进一步探究骨架中心原子脱除选择性和介孔生成效率与前体组成的关系。TS-1脱硅选择性远大于脱钛选择性,典型样品T-原子脱除效率(f_(T,S-meso)和f_(T,V-meso),T=Si+Ti)高达2.6 m^2·g^(-1)·%^(-1)和9.4×10^(-3)m^3·g^(-1)·%^(-1)。

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 tile 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 efficieneies （ fT, s and fT, v T = Si ＋ Ti ） , are substantiated to arrive at 2.6 m^2·g^-1·%^-1 and 9.4×10^-3 m^3·g^-1·%^-1 , respectively.