Separation of carbon dioxide from methane is an important issue in the processing of low-quality natural gas. Conventional technology in the natural gas industry uses amines to selectively remove CO2. However recovery of the CO2 and solvent is energy-intensive. Pressure swing adsorption (PSA) based on porous materials are widely considered as a more energy-efficient and economical process for CO2 capture. Considerable attention has been given to the development of PSA processes that are mostly based on differences in adsorption equilibrium.
In this study, we will present the first study attempting to separate CO2 from CH4 in a microporous metal-organic framework (MMOF) by kinetic effect. In order to demonstrate the effect of accessible pore size on the kinetic selectivity, we measured diffusion rate of CO2 and CH4 in MOF-177 (~10.8 Å), MOF-5 (~7.7 Å), zeolite 5A (~4.4 Å), and Cu(hfipbb)(H2hfipbb)0.5 (~3.5 Å). Both the adsorption equlibria and kinetics were measured at 278 K, 298 K and 318 K and pressure up to 800 mmHg. Diffusion time constants of CO2 and CH4 were investigated from the adsorption uptake curves as a function of time by a micropore diffusion model. An overall selectivity of 20+ was obtained in Cu(hfipbb)(H2hfipbb)0.5. The result shows this MMOF of interest is a promising adsorbent for adsorptive separation of CO2/CH4 mixture.
See more of this Group/Topical: Topical 1: Separation Needs for Energy Independence and Environmental Sustainability