摘要
分子筛的催化活性与酸性质密切相关,其酸性质与酸中心结构紧密相关。制备不同温度焙烧的脱铝HY分子筛,利用固体核磁共振结合探针分子技术,探讨了脱铝HY型分子筛的酸中心结构(Al的配位状态)、酸性以及两者之间的对应关系。结果表明,在空气中焙烧NH4Y时,焙烧温度越高,形成的非骨架铝物种越多;高温焙烧的脱铝HY分子筛中存在3种非骨架铝物种,分别为四配位、五配位和六配位非骨架铝。铝配位状态决定了酸类型及酸强度,骨架四配位铝对应于B酸位,非骨架六配位、五配位及四配位铝物种均对应于L酸位;非骨架铝物种的存在导致了B酸位的酸性增强。
The catalytic activity of zeolite depends on its acidic properties,its acidic properties are closely related to the structure of acidic center.A series of dealuminated HY zeolites were prepared at different calcination temperatures.Solid-state NMR spectroscopy and probe molecules were employed to investigate the structure of acidic center（coordinate status of aluminum）,acidity and the relationship between them in dealuminated HY zeolites.As it turned out,when the NH4Y sample was calcined in air,the higher the calcination temperature,the more extra-framework aluminum species was formed.Three extra-framework aluminum species are present in dealuminated HY zeolite prepared at high calcination temperature,which are the four-coordinate extra-framework aluminum,the five-coordinate extra-framework aluminum and the six-coordinate extra-framework aluminum,respectively.The coordinate status of aluminum determines the type and strength of acid.The four-coordinate framework aluminum is associated with a Brnsted acid site,while six-coordinate,five-coordinate and four-coordinate extra-framework aluminum species act as the Lewis acid sites.The presence of the extra-framework aluminum species results in the acidity enhancement of the Brnsted acid site.
出处
《石油学报（石油加工）》
EI
CAS
CSCD
北大核心
2012年第2期180-187,共8页
Acta Petrolei Sinica(Petroleum Processing Section)
关键词
固体核磁共振
探针分子
脱铝HY分子筛
非骨架铝物种
L酸
B酸
solid-state NMR
probe molecule
dealuminated HY zeolite
extra-framework aluminum species
Lewis acid
Brnsted acid
