分子模拟噻吩、苯、正己烷混合物在MFI和MOR中的吸附行为

Adsorption of Mixtures of Thiophene,Benzene and n-hexane in MFI and MOR Using Molecular Simulation

采用GCMC方法模拟了噻吩-苯二元组分和噻吩-苯-正己烷三元组分在MFI和MOR沸石中的吸附分离性能.结果表明,对于噻吩-苯二元体系,在MFI孔道中,噻吩分子比苯分子都优先定位于孔道的交叉部分,当总压升高时,苯的吸附量增加,噻吩的吸附量保持不变,苯分子被噻吩分子“挤”到直型孔道之中,该二元体系符合Clark等提出的竞争吸附模型.而对于在MOR中的吸附,噻吩和苯分子没有表现出明显不同的优先吸附位,符合Clark等提出的体积填充模型.对于噻吩-苯-正己烷三元体系,在MFI沸石中,正己烷的吸附量最大,噻吩和苯的吸附量很小.而对于MOR沸石,噻吩的吸附量最大,苯和正己烷的吸附量小,对于这三种较大尺寸的分子,只能位于MOR主孔道中,当存在着少量的正己烷分子时,就影响到了苯的吸附,而正己烷对噻吩在MOR孔道中填充的影响要比苯小,噻吩的吸附量影响不大.

The adsorption of binary and ternary mixtures of thiophene, benzene, and n-hexane in MFI and MOR zeolites was simulated by using the Monte Carlo technique in grand canonical ensemble. The binary simulation results showed that thiophene molecules took precedence over benzene molecules to occupy the intersection sites in MFI. When the pressure was raised, the loading of benzene increased gradually, whereas the loading of thiophene reached a plateau. Benzene molecules were pushed to the zig-zag or straight channels by thiophene molecules. The binary system in MFI conformed with competition model by Clark et al. However, there were no distinct preferred sites for adsorption of thiophene and benzene on MOR zeolite, and the systems complied with volume filling model. The ternary simulation results showed that the adsorptive amount of n-hexane was the greatest, while the thiophene and benzene are adsorbed very little in MFI zeolite. The adsorptive amount of thiophene was the greatest, while the n-hexane and benzene were adsorbed very little in MOR zeolite. For the molecules with bulker size, they could occupy only the main channel in MOR. A little amount of n-hexane had a stronger effect on the adsorption of benzene than that of thiophene.