Simulation of separation of C2H6 from CH4 using zeolitic imidazolate frameworks

Abstract

Separation of important chemical feedstocks, such as C2H6 from natural gas, can greatly benefit the petrochemical industry. In this paper, the grand canonical Monte Carlo method has been used to study the adsorption and separation of CH4 and C2H6 in zeolites, isoreticular metal-organic framework-1 (IRMOF-1) and zeolitic imidazolate frameworks (ZIFs) with different topology, including soadlite, gmelinite and RHO topologies. Compared with mordenite zeolite and IRMOF-1, ZIFs and mordenite framework inverted (MFI) zeolite have better separation performance for C2H6/CH4 mixtures at different mole fractions of C2H6. From the study of equilibrium snapshots and density distribution profiles, adsorption sites could be grouped as (1) sites with strong interactions with adsorbent and (2) sites with strong interactions with surrounding adsorbates. The gas molecules occupied the first site and then went on to occupy the second site. In CH4/C2H6 mixture adsorption/separation, the adsorption of CH4 was confined by the existence of C2H6. Due to energetic effect, C2H6 selectivity was affected by temperature at a low-pressure range, but did not change as much in a high-pressure range because of packing effect in micropore. In binary adsorption, large C2H6 molecules favour sites with strong adsorbent interactions. At high pressures, packing effects played an important role and it became easy for small CH4 molecules to access the sites with strong adsorbate interactions.