Experimental Measurement of the Adsorption Equilibrium and Kinetics of CO2 in Chromium-Based Metal-Organic Framework MIL-101

Abstract

A series of MIL-101 samples with hierarchical pore structures and different surface areas (2000-4800 m2/g) was synthesized by hydrothermal method and characterized by X-ray diffraction, thermogravimetric analysis and 77-K N2 adsorption isotherm. The adsorption equilibrium and kinetics of CO2 were studied at 288, 298 and 308 K within a pressure range of 0-5 MPa by a volumetric method. The adsorption heat, mass-transfer constant, diffusion coefficient and diffusion activation energy were also investigated in this work. The results showed that the chromium-based MIL-101 adsorbent exhibited an impressive selectivity for CO2 over N2, and had an adsorption capacity of 20 mmol/g of CO2 at 298 K and 5.0 MPa, which was much better than that of other conventional adsorbents (e.g. SBA-15, MCM-41, SG-A). The adsorption heat of CO2 on MIL-101 was in the range of 21-45 kJ/mol, which decreased with the loading of CO2. The mass-transfer constants and diffusion coefficients increased with the temperature and decreased wit...