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

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.