Characterization and hydroisomerization performance of SAPO-11 molecular sieves synthesized by dry gel conversion
Characterization and hydroisomerization performance of SAPO-11 molecular sieves synthesized by dry gel conversion
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DOI：
10.1016/j.micromeso.2011.06.019
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发表时间：
2012
影响因子：
5.2
通讯作者：
C. Song;Yi Feng;Liling Ma
中科院分区：
文献类型：
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作者：
C. Song;Yi Feng;Liling Ma
采用干凝胶转化法(DGC)和常规水热法(CHT)合成了SAPO-11分子筛。用X射线衍射仪、X射线荧光光谱仪、扫描电子显微镜、氮气吸附、吡啶红外光谱和29SiMAS核磁共振仪对样品的性能进行了表征。结果表明，二正丙胺(DPA)是制备无杂质SAPO-11的合适结构导向剂(SDA)。SAC和VPT合成的SAPO-11分子筛比CHT法合成的SAPO-11分子筛具有更高的结晶度、更高的硅含量和更强的酸性中心。29SiMAS核磁共振结果表明，两种方法合成的SAPO-11分子筛中含有更多的Si(NaL)(0<；n<；4)物种。这些事实表明，SAC和VPT方法要么有助于Si更好地融入AlPO4骨架，要么有助于更好地分散Si，从而减小硅岛的尺寸，增加酸性中心的数量和强度。正十二烷加氢异构化反应的结果表明，由于分子筛载体的高酸性，SAC合成的铂/SAPO-11催化剂具有最高的加氢转化活性和异构体产率。
SAPO-11 molecular sieves were synthesized by two types of dry gel conversion (DGC) methods, namely, steam-assisted conversion (SAC) and vapor phase transport (VPT), and by conventional hydrothermal (CHT) method. The properties of these samples were characterized by XRD, XRF, SEM, N2-adsorption, Pyridine-IR and29Si MAS NMR methods. The results show that di-n-propylamine (DPA) is a suitable structure-directing agent (SDA) for the preparation of impurity-free SAPO-11. SAPO-11 molecular sieves synthesized by SAC and VPT exhibit higher crystallinity, higher Si content and more strongly acidic sites than that synthesized by CHT.29Si MAS NMR results demonstrated that the two samples obtained by the DGC methods contain more Si(nAl)(0<n<4) species than that obtained by CHT. These facts suggest that the SAC and VPT methods contribute either to better Si incorporation into the AlPO4framework or to better Si dispersal, thus decreasing the size of Si islands and increasing the number and strength of acidic sites. The results from the hydroisomerization of n-dodecane indicate that the Pt/SAPO-11 synthesized by SAC possesses the highest hydroconversion activity and isomer yield among those three catalysts, due to the high acidity of the molecular sieve supporter.