Investigation of highly efficient adsorbent based on Ni-MOF-74 in the separation of CO₂ from natural gas

Ni-MOF-74 is used in the separation of CO2 from natural gas. However, its low selectivity coefficient for CO2 limits its application. To address this limitation, -CH3, -NH2, -F, and -O-Li groups were introduced to modify Ni-MOF-74. First, the adsorption of pure CO2 on metal-organic frameworks (MOFs) was simulated using the grand canonical Monte Carlo (GCMC) method. The CO2 adsorption capacities of adsorbents modified with -F and -O-Li were respectively 36.5% and 26.95% higher than that of unmodified Ni-MOF-74. The adsorption of a CH4/CO2 mixture on the MOFs was also studied. Ni-MOF-74 modified with -O-Li, denoted as Li-O-Ni-MOE-74, had the highest selectivity coefficient among the modified adsorbents. This was explained based on the analysis of the isosteric heat of adsorption and the electrostatic potential distribution gradient. The specific surface area and pore volume of Li-O-Ni-MOE-74 were respectively 162.03% and 86.42% higher than those of Ni-MOF-74, according to microstructure analysis. This also proved that the modified adsorbent has a higher adsorption capacity. Penetration experiments involving a CO2/CH4 mixture at different flow rates were carried out by an adsorption experiment device. The penetration time and separation factor of Li-O-Ni-MOE-74 were higher than those of Ni-MOF-74. Therefore, an efficient adsorbent based on Ni-MOF-74 for the separation of CO2 from natural gas was identified through GCMC simulation and experimental analysis. This study will help improve the efficiency of natural gas deacidification.