【作者】 张国；

【导师】 张红星；

【作者基本信息】 吉林大学 ， 物理化学， 2008， 博士

【摘要】 计算机模拟作为一种有效的方法广泛用于固体材料,尤其是微孔材料的研究中,在结构、热力学、吸附分离和催化等性质的研究中取得巨大成功。本文采用了蒙特卡罗和动力学方法研究了有机分子在MOR和MCM-22分子筛中的吸附和扩散行为。并得到如下结果:1.通过分子模拟得到了噻吩在MOR分子筛中的吸附等温线和吸附热。温度和压力影响吸附等温线,但对吸附热影响较小。对于噻吩和异辛烷的二元混合物,噻吩在MOR分子筛中的吸附能力明显高于异辛烷,说明二元混合物可通过MOR分子筛分离开来。2.噻吩在MCM-22分子筛十元环和超笼中都可以吸附,异辛烷主要吸附在超笼中,温度和压力对其吸附量和吸附位有影响,但对吸附热影响不大。二元混合物间存在竞争吸附,噻吩在MCM-22分子筛中的吸附能力明显大于异辛烷。动力学模拟发现在超笼中异辛烷的扩散速度高于噻吩分子,这与蒙特卡罗模拟结果相对应。因此通过MCM-22分子筛可以将两者很好的分离开来。3.噻吩和苯分子单纯物质在MCM-22分子筛中吸附趋势基本相同,都可以在MCM-22两个独立孔道中吸附,并且扩散主要发生在超笼中。两者的二元混合物存在竞争吸附,噻吩的吸附能力高于苯分子。因此可以通过MCM-22分子筛将两者分离。4. 1-丁烯和正丁烷在MCM-22分子筛两个独立孔道中都可以吸附,并优先吸附在十元环孔道和超笼的底部和顶部;动力学模拟结果显示扩散主要发生在超笼的孔道系统中。1-丁烯和正丁烷在MCM-22分子筛中的催化反应主要发生在十元环孔道和超笼的底部和顶部。更多还原

【Abstract】 Recently, with increasing attention has been paid to the environmental protection, the product of clean fuel has been the focus which people are concerned about. The deep desulfurization of gasoline and incrase of the octane number of lead free gasoline have become the emphosis of investigation. Zeolites are microporous materials that have been found widespread useing in several technological fields. These materials have outstanding properties due to their regular structure and high internal surface areas, and they have been used as catalysts ino exchangers, and adsobents. The adsorption of thiophene in zeolite microporous materials is of great scientific interest in the context of separation and catalysis processes. For instance, the separation of thiophene from gasoline is performed by using selective adsorption in synthetic-type zeolites. MOR and MCM-22 are two kinds of microporous materials. MOR zeolite possesses 12-MR(member rings) channel systems; and MCM-22 zeolite possesses an interesting and unusual framework structure: two independent pore systems formed by interconnected sinusoidal 10-MR(member rings) pores with a 0.41×0.51 nm diameter and an independent 12-MR supercage with 1.82×0.71 nm linked by 10-MR windows with 0.40×0.55 nm diameter. The organic molecules can adsorb and diffuse in two independent pore systems because of their large surface area and the high thermal stability of the framework. It is very important to understand the adsorption and diffusion of the pure organic molecules and the mixture of organic molecules in MCM-22 zeolite. But it is very difficult or impossible to be interpreted by the experimental and theoretical study. It is of great importance to investigate that by molecular simulation techniques.In this paper, we employed Monte Carlo and Dynamic technique to simulate the adsorption and diffusion of thiophene/isooctane, thiophene/benzene and their mixtures, and 1-butene and n-butane in MCM-22 zeolite; and obtained the the adsorption isotherms, the heat of adsorption, mass cloud and diffusion coefficients. Then the located sites and the mainly diffusion channel can be predicted. The fellowing results can be drawn:1. Adsorption of thiophene and thiophene/iso-octane mixtures in MOR zeolite by Monte Carlo simulationAt first, the adsorption isotherm of thiophene in MOR zeolite was studied with CVFF and COMPASS forcefield by Monte Carto simulation. The simulated results showed that the result with compass is more exactly than that with CVFF compared with the reference. Thus, the COMPASS force field was used to simulate. The adsorption of thiophene/iso-octane mixtures in MOR zeolite was studied by Monte Carlo simulation. The results showed that Thiophene and iso-octane can be separated effectively by MOR zeolite.2. Adsorption and diffusion of thiophene and thiophene/iso-octane mixtures in MCM-22 zeolite by Monte Carlo simulation and dynamic simulationThe adsorption isotherm, the heat of adsorption and the located sites of the pure thiophene and iso-octane molecules can be obtained by MC simulation. It can be showed that thiophene can be adsorbed in 10-MR channel and 12-MR supercage system, but iso-octane mainly is adsorbed in supercage system. And the adsorption capacity and the adsorption sites can be affected by the temperature and the pressure. The binary mixtures obey competition classification, and thiophene is adsorbed more strongly than iso-octane. The diffusion coefficients of iso-octane are larger than these of thiophene, and the result is in agreement with that of GCMC simulation. The molecules of thiophene and iso-octane can be segregated by MCM-22 zeolite.3. Adsorpion of thiophene and thiophene/benzene mixture in MCM-22 zeolite by Monte Carlo simulationThe adsorption tendencies of thiophene and benzene are similar in MCM-22 zeolite, which can be adsorbed in two independent channel systems. On the other hand, the binary mixtures have competition adsorption, and thiophene adsorbs more strongly than benzene. The adsorption of the ternary mixtures of thiophene, benzene and iso-octane in MCM-22 was studied by MC simulation. The results showed that the adsorptive capacity of thiophene in MCM-22 zeolite is strongest, and the iso-octane is weakest. Then MCM-22 zeolite is a eximious sorbent of deep desulfurization of gasoline.4. Adsorption and diffusion of 1-butene and n-butane in MCM-22 zeolite were studied by Monte Carlo and Monte Carlo simulationThe adsorption and diffusion of 1-butene and n-butane in MCM-22 zeolite were studied by Monte Carlo and Molecular Dynamic simulation. The calculated results showed that 1-butene and n-butane can be adsorbed in two independent channel systems, and can be preferentially adsorbed in 10-MR channel systems. The dynamic simulation was performed at 400K and 673K, and the two kinds of molecules can diffuse in two independent channel systems and mainly diffuse in the center of the supercage systems. It can be predicted that the catalytic reactions mainly happen in 10-MR channel, and the upper and lower of the supercage systems.更多还原