ZIF-8吸附性能的研究

发布时间：2018-05-20 18:26

本文选题：ZIF-8 + 苯系物　；参考：《北京化工大学》2015年硕士论文

【摘要】：沸石一咪唑酯一金属有机骨架结构材料(ZIFs)因其具有的水热稳定性好、比表面积大、高孔容、柔性结构以及官能团丰富等优点,而ZIF-8作为一种具有方钠石结构的新型ZIFs微孔结构材料,不仅具备了上述ZIFs材料的优点,且因其所具有的特殊的旋转门效应,能吸附比自身孔大的多的分子。因此,本文进行了ZIF-8吸附性能的研究。本文考察了在不同条件下ZIF-8对苯系物分子的吸附性能。对在不同温度条件下ZIF-8的吸附性能进行了研究,结果表明：吸附量随着温度的增加而增加；探究了苯系物不同的初始浓度对吸附性能的影响,结果表明具有小孔体积的苯系物分子在ZIF一8中被吸附的更多；还考察了吸附性能随时间的变化及吸附动力学,结果表明,吸附开始时ZIF-8中有大量的可被利用的吸附活性位,但随着吸附时间的增加可利用的吸附活性位逐渐减少直至吸附活性位达到饱和,通过pseudo-second-order来解释吸附量随吸附时间的变化的吸附动力学,实验结果表明,苯系物分子的形状和大小对吸附作用同样起到了重要的影响；还考察了不同PH值对ZIF-8吸附苯系物分子性能的影响,实验结果表明,随着PH值的升高吸附量成递减趋势,这可能归因于静电相互作用不是ZIF-8吸附苯系物分子的主要机理,而ZIF-8上的咪唑酯环、官能团以及苯环上π-π键之间的相互作用应是ZIF一8材料吸附苯系物的主要机理；还探讨了苯系物分子的形状结构对吸附性能的影响,通过实验得到的数据可知,ZIF-8对具有小分子直径的苯、甲苯、乙苯、对二甲苯比相对具有大分子结构的间二甲苯和邻二甲苯具有更高的吸附能力。本文还进行了成型前后的ZIF-8对烃类气体的动态吸附性能的研究,通过不同的压力和温度条件进行了成型前后的ZIF-8的吸附性能的研究,并绘制了穿透曲线。实验结果表明,在低压条件下,系统内的堆积空隙及样品孔隙内的死体积与体系超额吸附量的比值较小,故可以忽略；但是管道阀门内的死体积中所积累的烃类气体的量对吸附量的影响较大,且随着压力的升高,系统内的堆积空隙及样品孔隙内的死体积中堆积的烃类气体的量与超额吸附量的比值增人,均须排除。成型后的ZIF-8的吸附量小于成型前的,这说明成型过程中添加的结构助剂堵塞了一部分孔道。通过实验证明丙烯的吸附量大于乙烯,这说明了烯烃与吸附剂之间为物理吸附,作用力主要为范德华力。本文还进行了不同的外界条件对ZIF-8材料吸附水中污染物氨氮的性能的影响,实验结果证明ZIF-8适合吸附低浓度条件下的NH4+,可考虑将其应用于水中氨氮污染物的后续处理。
[Abstract]:Zeolite-imidazole-metal-organic skeleton structure material (ZIFs) has the advantages of good hydrothermal stability, large specific surface area, high pore volume, flexible structure and rich functional groups. As a new type of ZIFs microporous material with square sodium structure, ZIF-8 not only has the advantages of the above-mentioned ZIFs materials, but also can adsorb much larger molecules than its own pore because of its special rotary gate effect. Therefore, the adsorption properties of ZIF-8 were studied in this paper. In this paper, the adsorption properties of benzene series molecules by ZIF-8 under different conditions have been investigated. The adsorption properties of ZIF-8 at different temperatures are studied. The results show that the adsorption capacity increases with the increase of temperature, and the influence of different initial concentrations of benzene series on the adsorption performance is investigated. The results show that the benzene molecules with small pore volume are adsorbed more in ZIF 8, and the adsorption energy changes with time as well as the adsorption kinetics. The results show that there are a large number of available adsorption active sites in ZIF-8 at the beginning of adsorption. However, with the increase of adsorption time, the available adsorption sites gradually decreased until the adsorption sites reached saturation. The adsorption kinetics of adsorption capacity with adsorption time was explained by pseudo-second-order. The shape and size of benzene series molecules also played an important role in the adsorption, and the effects of different PH values on the adsorption properties of benzene series compounds by ZIF-8 were also investigated. The experimental results showed that the adsorption amount decreased with the increase of PH value. This may be attributed to the fact that electrostatic interaction is not the main mechanism of adsorption of benzenes by ZIF-8, while the interaction between imidazolyl ester rings, functional groups and 蟺-蟺 bonds on ZIF-8 is the main mechanism of adsorption of benzene series by ZIF-8 materials. The influence of the shape and structure of benzene series on the adsorption properties was also discussed. The experimental data showed that ZIF-8 had small molecular diameters of benzene, toluene and ethylbenzene. The adsorption ability of p-xylene is higher than that of m-xylene and o-xylene with macromolecular structure. The dynamic adsorption of hydrocarbon gases by ZIF-8 before and after molding was also studied. The adsorption properties of ZIF-8 before and after molding were studied under different pressure and temperature conditions, and the penetrating curves were drawn. The experimental results show that under the low pressure conditions, the ratio of the dead volume in the system and the dead volume in the sample pores to the excess adsorption capacity of the system is small, so it can be neglected. However, the amount of hydrocarbon gas accumulated in the dead volume of the pipe valve has a great effect on the adsorption capacity, and with the increase of pressure, Both the accumulation void in the system and the ratio of the accumulation of hydrocarbon gas in the dead volume of the sample pore to the excess adsorption should be eliminated. The adsorption amount of ZIF-8 after molding is smaller than that before molding, which indicates that some pore channels are blocked by adding structural auxiliaries in the molding process. The experimental results show that the adsorption capacity of propylene is larger than that of ethylene, which indicates that the adsorption between olefins and adsorbents is physical, and the main force is van der Waals force. The effects of different external conditions on the adsorption properties of ammonia nitrogen in water by ZIF-8 materials were also studied. The experimental results show that ZIF-8 is suitable for the adsorption of NH4 at low concentration and can be applied to the subsequent treatment of ammonia nitrogen pollutants in water.
【学位授予单位】：北京化工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X703;TQ424.3

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