含不饱和金属位点的金属有机骨架材料对烟道气中SO_2的吸附与分离行为的分子模拟研究

Molecular simulation study on adsorption and separation of SO_2 in flue gas by metal organic frameworks with unsaturated metal sites

MOFs(Metal organic frameworks)材料因具有较高的比表面积和孔隙率、可调的孔道以及良好的热稳定性和化学稳定性等优势,被认为是用于硫化物吸附与分离最有前途的新型多孔材料。采用分子模拟方法研究了含不饱和金属位点的MOFs材料对烟道气中SO_2的吸附与分离行为,揭示影响吸附/分离性能的因素,研究结果表明:低压下,SO_2在MOFs材料中的吸附性能取决于SO_2与MOFs材料之间的相互作用,MOFs材料与SO_2之间的相互作用越强,吸附性能越好;高压下,SO_2在MOFs材料中的吸附性能由材料的比表面积、孔体积决定。金属离子与有机配体构成的角度越大,烟道气中SO_2与M-DOBDCs材料(金属离子MⅡ(Co、Ni、Mg等)和2,5-二羟基-1,4-对苯二甲酸(2,5-dioxido-1,4-benzenedicarboxylate,DOBDC)配体配位形成的微孔材料)中的不饱和金属位点之间接触概率越大,M-DOBDCs材料与烟道气中SO_2之间的相互作用越强,其对烟道气中SO_2的分离性能越佳。烟道气中N2在不同金属离子的M-DOBDCs材料中吸附量相当,不同金属离子对烟道气分离性能差异主要由CO2与SO_2在不同M-DOBDCs中竞争效应不同所致。Zn-DOBDC是可用于烟道气中VSA过程SO_2分离的备选材料。

Metal Organic Frameworks（MOFs）is considered as the most promising material for absorbing and separating sulfide compounds for its advantages of high specific surface area and porosity,adjustable pore size,and good thermodynamics and chemical stability.In this paper,molecular simulation method was employed to study the adsorption and separation of SO2 by MOFs with unsaturated metal sites,to reveal the factors influencing the adsorption/separation properties.The research results suggest that,in case of low pressure,the SO2 absorption property of MOFs depends on the interaction between SO2 and MOFs,and great interaction between SO2 and MOFs means high absorption property;in case of high pressure,the SO2 adsorption property of MOFs is decided by specific surface area and pore volume.The larger the angle between metal ion and organic ligands is,the larger the probability that the SO2 in flue gas contacts the unsaturated metal sites of M-DOBDCs（M-DOBDCs refer to cellular materials formed by metal ions of MⅡ（Co,Ni,Mg,etc.）and 2,5-dioxido-1,4-benzenedicarboxylate（DOBDC）by means of ligand coordination）is,the greater the interaction between M-DOBDCs and SO2 in flue gas is,and the better MDOBDC performs in separating SO2 in flue gas.The M-DOBDCs containing different metal ions are of similar property of absorbing N2 in flue gas,and the difference of M-DOBDCs containing different metal ions in the property of separating flue gas is mainly caused by the difference between CO2 and SO2 in competitive effect in M-DOBDCs.Zn-DOBDC is a good candidate for separating SO2 from flue gas in VSA process.