Simulation of separation of C₂H₆from CH₄using zeolitic imidazolate frameworks

Abstract

Separation of important chemical feedstocks, such as C 2 H 6 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 CH 4 and C 2 H 6 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 C 2 H 6 /CH 4 mixtures at different mole fractions of C 2 H 6 . 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 CH 4 /C 2 H 6 mixture adsorption/separation, the adsorption of CH 4 was confined by the existence of C 2 H 6 . Due to energetic effect, C 2 H 6 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 C 2 H 6 molecules favour sites with strong adsorbent interactions. At high pressures, packing effects played an important role and it became easy for small CH 4 molecules to access the sites with strong adsorbate interactions.

Fine-Tuning the Pore Environment of the Microporous Cu-MOF for High Propylene Storage and Efficient Separation of Light Hydrocarbons

“…Theoretical simulation is a powerful tool enabling us to unveil the adsorption mechanisms and providing us the information on adsorption sites. Hence, GCMC simulations were performed for understanding the interactions and adsorption behaviors of C 3 H 6 in iso-MOF-4 at the molecular level. ,, The density distributions of C 3 H 6 and C 2 H 4 molecules mass center within the structure at 298 K under different pressures were analyzed (Figure a–f). As expected, the potential adsorption sites are located around the paddlewheel secondary building units (SBUs).…”

Computational screening of MOFs for C 2 H 6 /C 2 H 4 and C 2 H 6 /CH 4 separations

“…The bulk gas composition of both mixtures was assumed to be equimolar in all molecular simulations because Guo et al (Guo et al, 2014) recently showed that composition does not strongly affect C 2 H 6 selectivity of a MOF material.…”

“…Bux et al (Bux et al, 2011) used GCMC simulations to estimate single-component adsorption of C 2 H 6 and C 2 H 4 in ZIF-8 and reported a good agreement between simulation results and experimental IRM (infra-red microscopy) results. Guo et al (Guo et al, 2014) carried out GCMC simulations to study adsorption and separation of C 2 H 6 /CH 4 mixtures in IRMOF-1 and four different ZIFs . They showed that compared to MOR zeolite and IRMOF-1, ZIFs exhibit better C 2 H 6 separation performance for different mole fractions of C 2 H 6 /CH 4 mixtures.…”

“…These values are significantly larger than the selectivity of zeolites. Well-known zeolites MOR and MFI were reported to exhibit C 2 H 6 /CH 4 selectivity of 2.5 and 15 from equimolar mixtures at 10 bar, 298 K, respectively (Guo et al, 2014). We again arbitrarily defined a reference performance curve of selectivity×working capacity=30 to qualitatively define a number of promising materials for C 2 H 6 /CH 4 separation.…”

Combined GCMC, MD, and DFT Approach for Unlocking the Performances of COFs for Methane Purification

“…A probe radius of 1.86 Å (kinetic radius of the N 2 molecule) was employed for the calculations of surface area, and the COFs with zero S acc were eliminated so that the gas molecules studied in this work can adsorb into the remaining COFs. CH 4 /H 2 , CH 4 /N 2 , and C 2 H 6 /CH 4 mixtures were assumed to be equimolar as most of the experimental studies in the literature that we compared our results with consider equimolar mixtures. , Moreover, Guo et al , recently showed that composition does not significantly change the simulated C 2 H 6 /CH 4 and CH 4 /H 2 selectivities of ZIFs. To compute the mixture adsorption data in COFs, such as gas uptakes ( N ) and isosteric heat of adsorption ( Q st ), we performed GCMC simulations using the RASPA simulation code .…”