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摘要
Adsorption isotherms and zero length column (ZLC) desorption curves of alkylbenzene (toluene and isopropylbenzene) in a series of microspherical ZSM-5 zeolites with inter- and intracrystalline mesopores were measured for revealing structural and surface characteristics of the hierarchical zeolites. The isotherms showed that adsorption capacities of toluene and isopropylbenzene increase with increase of mesoporosities in the range of higher relative pressure. Henry's constants (K-H) and initial heats of adsorption (Q(st)) turned out that introduction of mesoporous structure into the zeolites weakens interaction between alkylbenzene molecules and zeolite surface. Moreover, isopropylbenzene and toluene have different adsorption and diffusion behavior in the zeolites. The adsorption capacity, K-H and Q(st) for isopropylbenzene to microporous and mesoporous ZSM-5 zeolites are lower than these for toluene. The effective diffusion time constants (D-eff/R-2) of alkylbenzene from the ZLC desorption curves increase with increase of mesoporosities in the ZSM-5 zeolites, but diffusion activation energy (Ea) expresses a contrary tendency. Due to low interaction between isopropylbenzene and zeolite surface, D-eff/R-2 values of isopropylbenzene with lower activation energy in all ZSM-5 samples are higher than these of toluene. The molecular sizes of two alkylbenzenes are not the key factor for their adsorption and diffusion in the mesozeolites.
- 出版日期2018-11
- 单位太原理工大学
