Abstract: Acidity and accessibility of three commercial zeolites (HY, HMOR, Hβ) were characterized by using in situ FTIR spectroscopy with pyridine (Py), 2,6-dimethylpyridine (DMPy) and 2,6-di-tertbutylpyridine (DTPy) as the probing molecules. The results indicate that the surface acid density of HY molecular sieve is the highest, and there are abundant strong B acid centers, strong L acid centers, and many weak B acid centers. However, the surface acid density of HMOR and Hβ is low, and it is mainly the strong B acid center and the strong L acid center. The accessibility index of B -acid center is calculated by changing the hydroxyl group of Si-Al bridge. The results show that the order of accessibility of macromolecule probes to Br-nsted acid sites in these three type of zeolites is HMOR＞Hβ＞HY.

Key words: In situ FTIR, 12-Ring channels zeolite, Acid site density, Accessibility, Macromolecule probe

摘要： 采用原位红外光谱技术,以吡啶(Py)、2,6-二甲基吡啶(DMPy)、2,6-二叔丁基吡啶(DTPy)为探针分子,考察了HY、HMOR、Hβ3种12元环孔道结构分子筛的表面酸性及其孔道内B酸中心的可接近性。结果表明, HY 分子筛表面酸密度最大,存在丰富的强B酸中心、强L酸中心,以及较多的弱B酸中心,而HMOR和Hβ分子筛表面酸密度较低,且主要为强B酸中心和强L酸中心;以孔道内硅铝桥羟基的变化规律计算B酸中心可接近性指数,结果发现,3种分子筛孔道内B酸中心对大分子碱性探针的可接近性顺序为HMOR> Hβ> HY。

关键词: 原位红外光谱, 12元环分子筛, 酸密度, 可接近性, 大分子探针