Molecular Dynamics Investigations Into Role of EDTA Bisamide in CO2-CH4 Exchange in NGHs in Presence of Flue and Noble Gases

S Singh and M Sharma, ADVANCED THEORY AND SIMULATIONS, 8 (2025).

DOI: 10.1002/adts.202500649

Additives, such as hydrate promoters or inhibitors, play a crucial role in hydrate growth by altering the thermodynamics or kinetics during the formation of hydrates. Ethylenediaminetetracetic acid (EDTA) bisamide can act as methane hydrate promoter or inhibitor based on length of alkyl side group due to shorter or longer alkyl chains, respectively. Molecular dynamics simulations effect of EDTA bisamide are reported with longer alkyl (n-heptyl) side group on selective sequestration of carbon dioxide during CH4-CO2 exchange in natural gas hydrates in a ternary-gas system with different third gas species (N2, H2S, Ar, Kr, and Xe). The results show there is formation of gas cluster in bulk liquid region due to hydrophobic tails of EDTA bisamide. The lifetime of Xe and CH4 clusters is the longest among the reported systems due to favorable interactions between Xe and CH4. The carbon dioxide sequestration in the newly formed sI-hydrate cages is the highest for Xe(3:1) system, followed by N2(2:2), and is the poorest in Ar(2.5:1.5) and H2S(2:2) systems. Xe and Ar show reverse trends in sequestration of carbon dioxide in presence of EDTA bisamide as compared to the earlier reported simulations in a ternary-gas system in the absence of additives (PCCP, 2023, 25, 30211-3022).

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