摘要:
采用巨正则蒙特卡洛方法研究C2H6, CO2和CH4三种气体在两种沸石类咪唑骨架材料(ZIF)--ZIF-2和ZIF-71中的吸附与分离性能.考察了C2H6, CO2和CH4三种气体在ZIF-2和ZIF-71中的单组分吸附等温线、吸附热；C2H6-CH4, CO2-CH4与C2H6-CO2等摩尔二元混合物的分离；以及C2H6-CO2-CH4三元体系的分离性能.研究结果表明：低压下不同气体的吸附量大小与其吸附热关系紧密；而高压下因有限的孔空间,尺寸较小的气体分子吸附量增长趋向更快；多组分吸附分离中,低压下能量效应通常占据主导, ZIF优先吸附作用力较强的组分；高压下堆积效应影响显著, ZIF会优先吸附尺寸较小的组分. ZIF-2和ZIF-71对这3种二元体系的分离性能良好.对于三元混合物吸附分离,在常温下3000-4000 kPa范围内, ZIF-2具有良好的天然气净化性能,可有效地分离出天然气中的C2H6和CO2.
Abstract:
Grand canonical Monte Carlo simulations were employed to investigate the adsorption and separation of C2H6, CO2 and CH4 on two zeolitic imidazolate frameworks (ZIF-2 and ZIF-71). The adsorption isotherm and isosteric heat of pure gas, the separation performance of C2H6-CH4, CO2-CH4 and C2H6-CO2 binary mixtures and C2H6-CO2-CH4 ternary mixtures on two ZIFs were simulated and discussed. For single component gas adsorption at a low pressure, the adsorption amount depended on isosteric heat;at a high pressure, due to the limited pore volume, ZIFs preferably adsorbed smaller size gas molecules. For gas mixture separation, energetic effect dominated at low pressure, therefore, ZIFs selectively adsorbed gas component with strong interactions;packing effect usually played an important role at high pressures, consequently, smaller size component would be more entropically favorable. Results demonstrated that both ZIF-2 and ZIF-71 were of good separation performance for these three binary mixtures. For the ternary mixture separation, it was found that ZIF-2 cowld effectively separate C2H6 and CO2 from CH4 at 3000-4000 kPa and room temperature.
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