原位干胶合成Ni/SAPO-11催化剂中硅含量及配位环境的调控

用原位干胶法合成Ni/SAPO-11双功能催化剂，通过改变初始凝胶中硅添加量调控分子筛骨架硅含量及配位环境，实现对催化剂酸性质的控制。采用XRD、TEM、XPS、SEM、MAS NMR及NH₃-TPD等手段对所得催化剂进行表征，并以正己烷为模型化合物对其异构化性能进行评价。结果表明：增加初始凝胶中的硅添加量对Ni/SAPO-11催化剂的形貌、孔道结构、金属物种类型及分散度并无显著影响，但可促进Si通过SMⅢ同晶取代进入SAPO-11分子筛骨架，硅含量上升，且硅岛结构增多，这使Ni/SAPO-11的酸量在初始凝胶中SiO₂/Al₂O₃摩尔比为0.6时出现最大值。Ni/SAPO-11酸量的增加显著提高了其在正己烷临氢异构化中的活性及异构烃收率，表现出优于Pt/SAPO-11催化剂的异构化性能。

Regulation of Silicon Content and Coordination Environments Over Ni/SAPO-11Catalyst Synthesized via In-Situ Dry Gel Conversion Method

The Ni/SAPO-11 catalyst was prepared via an in-situ dry gel conversion method in this work. The content and coordination environments of silicon (Si) were regulated to tune acidity of the catalyst by controlling Si content in the initial synthesis gel. The physicochemical properties of the obtained catalysts were characterized by XRD, TEM, XPS, SEM, MAS NMR and NH₃-TPD, and the catalytic behavior was tested by hydroisomerization of n-hexane. Increasing the Si content in the initial gel had no significant effect neither on morphology and pore structure nor on chemical environments and dispersion of nickel species over the obtained Ni/SAPO-11 catalyst. It also enhanced SMⅢ isomorphous substitution for the incorporation of Si into framework of SAPO-11 molecular sieve, which increased Si content and promoted formation of Si islands. Thus, the catalyst synthesized with a mole ratio of SiO₂ and Al₂O₃ of 0.6 in the initial gel showed the highest acid density. The enhanced acidity increased activity and products selectivity for the Ni/SAPO-11 catalyst in n-hexane hydroisomerization and the resulting catalyst exhibited better catalytic performance than the Pt/SAPO-11 catalyst.