合成方法对合成多级孔SAPO-11分子筛的影响

Effect of Synthetic Methods on Synthesis of Hierarchical Porous SAPO-11

采用以十二烷基三甲基溴化铵(DTAB)作为介孔模板剂和盐酸后处理的方法分别制备了多级孔SAPO-11分子筛。利用X射线衍射、N2吸附–脱附、扫描电子显微镜和透射电子显微镜等分析手段对2种方法合成的多级孔SAPO-11分子筛进行了表征,研究不同合成方法对多级孔SAPO-11结构、形貌等性质的影响。结果表明,介孔模板剂DTAB的含量对SAPO-11的孔结构和外表面积有较大的影响,当n(DTAB):n(Al2O3)=0.4:1.0,原料配比为n(Al2O3):n(P2O5):n(二正丙胺+二异丙胺):n(SiO2):n(H2O)=1.0:1.0:1.0:0.5:50.0的条件下,合成的多级孔SAPO-11外表面积和孔体积最大;盐酸酸洗方法中,当盐酸浓度为0.3 mol/L时得到的多级孔SAPO-11外表面积和孔体积最大;2种合成方法相比,盐酸酸洗破坏了SAPO-11的球形晶貌,孔道除了来源于片状晶粒堆积产生的狭缝孔外,还来源于大量层状结构产生的狭缝孔,而以介孔模板剂合成的多级孔SAPO-11孔道主要来源于片状晶粒堆积产生的狭缝孔,更好地保留了分子筛的晶型结构,增大了比表面积。

A hierarchical porous SAPO-11 zeolite was synthesized via dodecyl trimethylammonium bromide(DTAB)as a mesoporous template and hydrochloric acid post-treatment,respectively.The synthesized samples were characterized by X-ray diffraction,N2 adsorption–desorption,scanning electron microscopy and transmission electron microscopy.The effect of different synthetic methods on the structure and morphology of the hierarchical porous SAPO-11 was investigated.The results indicate that the content of mesoporous template DTAB has a great influence on the pore structure and external surface area of SAPO-11.When n(DTAB):n(Al2O3)=0.4:1.0,the composition of the synthesis system is n(Al2O3):n(P2O5):n(DPA+DIPA):n(SiO2):n(H2O)=1.0:1.0:1.0:0.5:50.0,the external surface area and pore volume of the synthesized hierarchical pore SAPO-11 become the maximum values.For the hydrochloric acid post-treatment,the maximum external surface area and pore volume of hierarchical pore SAPO-11 are obtained when the concentration of hydrochloric acid is 0.3 mol/L.Compared to the two methods,hydrochloric acid treatment can destroy the spherical morphology of SAPO-11.Besides the slit holes produced due to the grain accumulation,the channels also come from the slit holes formed due to the layer structure.The hierarchical holes of SAPO-11 synthesized with mesoporous template DTAB mainly comes from the slit holes formed due to the grain accumulation.The crystal structure of the zeolite retains and the specific surface area increases.