摘要
采用晶种诱导法合成相组成接近的MFI/MOR和BEA/MOR共生沸石;用碱-酸联合处理法对共生沸石进行介孔改性。用X-射线衍射(XRD)、N2吸附-脱附、扫描/透射电镜(SEM/TEM)和感应耦合等离子体光谱(ICP-AES)表征合成和改性材料的组成和结构。结果表明,共生沸石骨架硅铝物质的量比和相组成受合成胶硅铝物质的量比和晶化条件(温度、时间、pH)的影响;改性共生沸石均为结晶性多级孔材料,其中BEA/MOR(t)具有较窄介孔尺度分布。孔结构性质和相组成变化与所含沸石相的结构稳定性密切相关。初级晶粒较小、骨架稳定性较低的沸石相优先被溶蚀,MFI和BEA质量分数下降,改性沸石骨架硅铝物质的量比因酸洗而提高。
Intergrowth zeolites,i.e.MFI/MOR and BEA/MOR with approximate phase compositions,were hydrothermally synthesized using seed-mediated growth method.The two series of intergrowths were treated by combined alkali-acid treatments for introduction of mesoporous structure.The compositional and structural properties of both synthesized and modified materials were characterized upon the methods of X-ray diffraction（XRD）,N_2 adsorption-desorption at 77 K,scanning and transmission electron microscopes（SEM/TEM）,and inductively coupled plasma-atomic emission spectroscopy（ICP-AES）.As a result,the changes in initial SiO_2/Al_2O_3 ratio and crystallization conditions concerning T/K,t/h and pH affected the framework Si/Al ratio and phase composition of zeolite intergrowths,and the modified intergrowths were shown to have crystalline hierarchical porous structures,especially for BEA/MOR（t）featuring of the narrower mesopore size distribution.The porous structure properties and phase composition were related to the structural stability of zeolite phases in both intergrowths.Moreover,the zeolite phases related to small primary crystal size and low framework stability were etched preferentially by alkaline media,leading to reductions in weight fraction of MFI and BEA phases.In addition,framework Si/Al ratios of modified zeolites were increased due to final acid extraction.
出处
《石油化工高等学校学报》
CAS
2017年第1期8-13,35,共7页
Journal of Petrochemical Universities
基金
国家自然科学基金项目(21171083)
关键词
水热合成
共生沸石
相组成
介孔改性
多级孔结构
Hydrothermal synthesis
Zeolite intergrowth
Phase composition
Mesoporous modification
Hierarchical porous structure
