以原位碳化蔗糖为硬模板合成多级孔道SAPO-34分子筛

为强化SAPO-34分子筛内传质过程,增强其酸性位的可接近性,以原位碳化的蔗糖为硬模板,采用双结构导向剂(四乙基氢氧化铵、吗啡啉),通过干凝胶方法合成了多级孔道SAPO-34分子筛。使用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)及氮气物理吸附对分子筛结构进行表征,并进行了低密度聚乙烯热解性能考评。结果表明,合成的多级孔道SAPO-34晶体具有纳米尺寸,含有晶内介孔,介孔体积达0.41 cm3/g。四乙基氢氧化铵具有促进成核的作用,使晶体尺寸降低。结晶过程中纳米晶体对碳模板的包裹造成了晶内介孔的形成。该分子筛在低密度聚乙烯热解反应中T50温度显著降低,说明其具有更多可接近的酸性位。

Synthesis of Hierarchical SAP0-34 Zeolite with in-Situ Carbonized Sucrose as Hard Template

To enhance the diffusion in SAP0-34 zeolite and the accessibility to the acid sites, hierarchicalSAP0-34 with intra-crystalline and inter-crystalline mesopores is synthesized in a vapor-phase transportprocess with in-situ carbonized sucrose as a meso-template, where tetraethylammonium hydroxide (TEAOH)in the dry gel and morpholine (MOR) in the vapor work was functioned as structure directing agents. X-raydiffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) andN2-physisorption measurements were used to characterize the structure of the zeolite sieve, and low densitypolyethylene (LDPE) degradation was tested on the molecular sieve. The results indicate that the hierarchicalSAP0-34 zeolite exhibits nano-scale size, and has intracrystalline mesopores with mesopore volume about0.41 cm3/g. Nano-sized SAP0-34 crystals were formed due to the promoted nucleation by TEAOH and itsmesopores were created by the encapsulation of carbon template within crystals during crystallization. Onthe hierarchical SAP0-34, the degradation temperature (Tso) at 50% of LDPE conversion is decreasedremarkably, indicating the increased accessibility to acid sites.