The Hβ zeolite was modified with different concentrations of citric acid. The textures of the modified Hβ zeolites were characterized by XRD and Ar adsorption, and the acid properties were characterized by NH3⁃TPD and Py⁃FTIR. In addition, the interaction between the pyridine molecules and the active constituent units of the Hβ zeolite was also analyzed by Py⁃FTIR. The results showed that several active sites, such as the Brønsted acid sites associated with the bridging hydroxyl groups (SiOHAl), the weak Lewis acid sites associated with EFAL hydroxyl groups and the strong Lewis acid sites associated with the three⁃coordinated Al hydroxyl species and AlO+ cations were existed in the Hβ zeolite. The synergistic effect between the EFAL and the adjacent bridging hydroxyl groups was found on the adsorption of pyridine. The pyridine molecule which adsorbed in the Lewis acid site and bonded with the adjacent B acid sites was less likely to desorb at high temperature. Pyridine molecules were preferentially adsorbed on the strong acidic bridging hydroxyls and defect sites associated with the three⁃coordinated Al hydroxyl species. It was only weakly interacted with EFAL hydroxyl groups. After citric acid treatment, EFAL hydroxyl groups were selectively removed while the framework aluminum was not severe damaged. The strong Lewis acid sites were preserved in the modified Hβ zeolite after citric acid treatment, and the strong Lewis acid sites may be related to AlO+ and the three⁃coordinated Al species of defect sites.

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.

Adsorption and diffusion behavior of benzene in NaY zeolite are studied by using the frequency response method. The TG/DTG curves and Py FTIR technique are used to analyze the adsorption and diffusion mechanism of benzene on NaY. The results indicate that NaY zeolite contains two kinds of acidic centers, namely, the weak B acid and weak L acid sites. And L acid sites are in a dominant position. There are two adsorption interactions on NaY zeolite at 333 K and 423 K, the adsorption of low frequency through the π electronic interactions and high frequency of adsorption belong to pore filling. Adsorption is still the controlling stepat 573 K. However, diffusion is the controlling step on NaY at 623 K, indicating that weak adsorption results in easier desorption and easier diffusion of aromatic molecules on NaY, there by improving the performance of the hydro cracking reaction.

The isomerization of nhexane over Mo ₂C /Mo O ₂ - Z r O ₂ catalyst was investigated. First, the precursor solid superacid Mo O ₃ - Z r O ₂ was prepared by coprecipitation process, using the mixture of cetyltrimethylammonium bromide and polyethylene glycol 20000 as templates. It can be seen that the precursor samples had applicable surface area, pore diameter and volume from the BET and FTIR characterization of the Mo ₂C/MoO ₂ZrO ₂.The total acid of precursor Mo O ₃ - Z r O ₂had a large decline after carbonized. The conversion and selectivity of Mo ₂C/MZP0.005C0.5 are much more than single auxiliary catalystafter adding catalyst mixed assistant. The conversion rate and selectivity reached 67.5%, 75.2%, respectively.