摘要
采用水热法制备了环状、薄片、类球状聚集体和小晶粒4种不同形貌和尺寸的纳米ZSM-5分子筛,用XRD、SEM、BET、MAS-NMR和NH3-TPD对所合成分子筛进行了表征,并考察分子筛形貌对苯和乙醇烷基化性能的影响.实验结果表明:在相近的硅铝比下,不同形貌的分子筛具有相似的弱酸峰强度,短b轴和中空结构的存在会降低分子筛的强酸峰强度,分子筛的强酸峰强度直接影响烷基化性能;分子筛颗粒形貌对催化烷基化性能有较大影响,4种形貌分子筛催化苯和乙醇烷基化性能优劣顺序为:薄片ZSM-5＞环状ZSM-5＞类球状团聚体ZSM-5＞小晶粒ZSM-5.其中,具有薄片结构的H-ZSM-5分子筛在烷基化反应过程中表现出相对较好的催化性能.综合对比结果表明:较低的强酸强度、较大的比表面积和孔容、较多的直形孔道占比下,分子筛的烷基化性能较好,产物乙苯的选择性越高.
Abstract
In this paper,four kinds of nano-ZSM-5 zeolites with different morphologies and sizes,including cyclic,lamelliform,spheroidal aggregates,and small particles,were prepared by hydrothermal methods.The synthesized zeolites were characterized by X-ray diffraction(XRD),scanning electron microscope(SEM),Brauer-emmett-teller(BET),solid state nuclear magnetic resonance(MAS-NMR)and ammonia temperature programmed desorption(NH3-TPD),and the effects of the morphology on the alkylation properties of benzene and ethanol were investigated.The experimental results showed that zeolites with different morphologies had similar weak acid peak strengths at the similar Si/Al ratio.The presence of short B-axes and hollow structures reduces the strength of the strong acid peak in zeolite,which directly affects the alkylation performance.The catalytic alkylation performance of the four zeolite forms decreased in the order of lamellar ZSM-5,cyclic ZSM-5,spheroidal aggregates ZSM-5,and small particle ZSM-5.Under the conditions of lower acid strength,larger specific surface area and pore volume,and more straight pores,the best alkylation performance of zeolite and the greater selectivity of ethylbenzene were achieved.
基金项目
Key Research and Development Plan of Shaanxi Province(2023-YBGY-290)
Research Project of Shaanxi Yanchang Petroleum(Group)Co.,Ltd(ycsy2023ky-B-81)
NETL
NSTL
万方数据