纳米棒插接多级孔ZSM-11分子筛形貌影响因素研究

采用先低温后高温的两段晶化方法在含有四丁基溴化铵的单一模板体系中合成具有插接形貌的ZSM-11分子筛。分别从硅源、铝源、硅铝比、碱源和模板剂的种类对插接形貌形成的影响因素进行分析。结果表明:硅源、铝源以及碱源的种类主要是通过影响解聚-聚合的速率来影响体系的成核以及晶体生长的速率,从而对结晶动力学以及最终产品的晶粒尺寸产生影响,并不会对插接形貌产生大的影响;与固体硅源(硅胶小球)相比,使用液体硅源(硅溶胶和水玻璃)能够在较短时间内得到尺寸较小的分子筛产品;与无机铝源相比,采用异丙醇铝较易在短时间内获得小晶粒产品;与Li+和Na+相比,含有K+的体系中产品分子筛尺寸较大;模板剂的种类直接影响到最终结晶产物的形貌特征,四丁基铵离子的存在是这种插接形貌形成的必要条件。随着合成体系含铝量的减小,插接形貌变得不再明显,铝的存在是这种插接形貌形成的必不可少的影响因素之一。

Factors affecting the intergrowth morphology of hierarchical ZSM-11 microspheres

The hierarchical ZSM-11 microspheres with intergrowth morphology have been synthesized by using tetrabutylammonium bromide (TBABr) as the single template via a two-stage temperature-varying crystallization route. The effects of silica source, aluminum source, SiO₂/Al₂O_3ratio, alkali cations and the organic templates on the formation of intergrowth morphology were investigated. It is found that the silica sources, aluminum sources and the alkali cations mainly influence the rate of nucleation and the crystal growth via the depolymerization-polymerization rate, which affects the crystallization kinetics and the grain size of the final product. And there is no significant influence on the intergrowth morphology. Compared with silica source (silica gel microsphere), using liquid silica source (water glass and silica sol), can obtain smaller sized zeolite microspheres. It is favorable to get smaller crystals in a short period when using aluminiumisopropoxide as aluminum source compared with inorganic aluminum source. Besides, it is found the existence of K⁺ could suppress the fast formation of small crystals relative to the Li⁺ and Na⁺. The formation of the intergrowth morphology of the crystal product is affected directly by the template types, in which the existence of tetrabutylammonium cation is a key factor. It is also found that the intergrowth morphology becomes less evident with the decline of the Al amount in the system. And the presence of Al is one of the necessary factors for this intergrowth morphology.