فهم جذب فيزيكي گاز CO2 در يك مايع يوني سه كاتيوني غيرخطي عامل دار شده با گروه‌هاي آمين و هيدروكسيل: يك مطالعه‌ي شبيه سازي ديناميك مولكولي

Understan‎ding the physical absorption of CO2 in a non-linear tricationic ionic liquid (NLTCIL) functionalized with amine an‎d hydroxyl groups: a molecular dynamics simulation study

شيمي فيزيك

This work aims to investigate the behavior an‎d properties of a nonlinear tricationic ionic liquid containing amine an‎d hydroxyl functional groups, as well as its interactions with water an‎d CO₂, through molecular dynamics simulations an‎d COSMO-RS analysis. Initially, molecular dynamics simulations were employed to study various systems, including Pure ionic liquid, Binary mixtures (ionic liquid–water an‎d ionic liquid–CO₂) an‎d Ternary mixture (ionic liquid–water–CO₂). The results indicated that simulations using the selec‎ted force field exhibit significant agreement with experimental data in predicting physical properties such as density an‎d viscosity. The addition of water led to a decrease in density, whereas the addition of CO₂ resulted in an increase in density. Structural analysis revealed that in the pure ionic liquid, the strongest interaction occurs between the chloride anion an‎d the hydrogen at the imidazolium ring head (HR). Furthermore, in the ternary system (ionic liquid–water–CO₂), the interaction pattern more closely resembles that of the binary ionic liquid–water system, indicating the dominant effect of water in contrast to the weaker an‎d less stable interactions of CO₂ in forming strong an‎d stable hydrogen bonds. The analysis of ion an‎d molecular mobility demonstrated that in the pure ionic liquid, the chloride anion exhibits higher mobility compared to the cation. Overall, molecular dynamics simulations showed that the addition of water significantly alters the microscopic structure an‎d hydrogen bond dynamics, leading to a reduction in CO₂ absorption capacity. The COSMO-RS analysis indicates that the solubility of CO₂ in the studied ionic liquid is significantly influenced by temperature an‎d pressure. The high selec‎tivity of CO₂ compared to gases such as H₂, CO, an‎d CH₄ highlights the potential of this ionic liquid for industrial gas separation applications. However, the results also showed that the presence of moisture severely reduces CO₂ absorption capacity, posing a key challenge for practical applications. Finally, this study reveals that the mechanism of CO₂ absorption by the ionic liquid is primarily centered on interactions between three sites (N, O, an‎d C) in the cation, with the C-site being more likely to participate in both physical an‎d chemical absorption.

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