CH4/N2在Zr-MOFs上的吸附分离研究

Adsorption-separation research of CH4/N2 on Zr-MOFs

关键词:  Zr-MOFs,CH₄/N₂分离  吸附等温线  吸附热  分离因子 

Key words:  Zr-MOFs  separation of CH₄/N₂  adsorption isotherms  adsorption heat  separation coefficient

摘要:

以H₄L为配体,与金属离子Zr⁴⁺自组装得到棒状晶体Zr基金属有机框架材料(Zr-MOFs),并借助X射线单晶衍射、N₂吸附脱附、X射线粉末衍射、热重等对其结构进行表征,利用气体吸附仪测量了CH₄和N₂的吸附等温线,采用克-克(Clausius-Clapeyron)方程计算CH₄的吸附热,并运用Ideal Adsorbed Solution Theory(IAST)理论来计算CH₄/N₂的分离因子(SCH₄/N₂)。结果 表明:在273 K、0.1 MPa时,晶体Zr-MOFs对CH₄有较好的吸附效果,吸附量为8.2 cm³/g,对CH₄/N₂的选择性分离因子(S)为6.3,且具有较好的分离效果；对吸附热力学的研究表明,CH₄的吸附热在20 kJ/mol左右,相对分子筛类吸附剂吸附热较小,易于吸附剂的再生。

Abstract:

Using ligands containing methyl and carboxylic acid H₄L self-assemblyed with Zr⁴⁺, the rod-like crystals Zr-MOFs is gotten and characterized by X-ray single crystal diffraction, N₂ adsorption, X-ray powder diffraction to analyze the structure. Adsorption isotherms of CH₄/N₂ are measured by adsorption instrument. The Clausius-Clapeyron equation is used to calculate the adsorption heat of CH₄. The separation coefficient of CH₄/N₂ is calculated from the Ideal Adsorbed Solution Theory(IAST). The results show that Zr-MOFs has good adsorption effect on methane which is about 8.2 cm³/g at 273 K and 0.1 MPa, and the selectivity factor of CH₄/N₂ is 6.3 which means a better separation result. The isosteric heat of adsorption of CH₄ is about 20 kJ/mol. Compared with other zeolite-like adsorbents, the isosteric heat of adsorption is lower, which means an easier regeneration.