Molecular mechanisms by which tetrahydrofuran affects CO2 hydrate Growth: Implications for carbon storage
Molecular mechanisms by which tetrahydrofuran affects CO2 hydrate Growth: Implications for carbon storage
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DOI：
10.1016/j.cej.2021.129423
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发表时间：
2021-04-01
影响因子：
15.1
通讯作者：
Striolo, Alberto
中科院分区：
文献类型：
--
作者：
Phan, Anh;Schloesser, Henrik;Striolo, Alberto
天然气水合物由于其在各种技术和环境过程中的重要作用而引起了重大的基础和应用兴趣。最近，天然气水合物显示出在温室气体捕获和储存方面的潜在应用。为了促进后一种应用，在笼形水合物中引入化学添加剂有助于提高水合物的形成/生长速率，前提是气体储存能力不降低。利用平衡分子动力学，我们研究了四氢呋喃 (THF) 对二氧化碳 (CO2) 水合物生长/解离动力学以及水合物 CO2 储存能力的影响。我们的模拟重现了 CO2 和 CO2 + THF 水合物在选定操作条件下的实验数据。模拟结果证实，化学计量浓度的 THF 确实会降低 CO2 储存能力。这不仅是由于 sII 水合物 512 笼中 CO2 捕集的不足，而且还因为由于优先的 THF-水氢键，THF 优先占据水合物笼中。对水合物-液体界面处 CO2 和 THF 的动力学性质的分析表明，与不含 THF 的系统相比，THF 可以加速 CO2 扩散，从而改变有利于 CO2 水合物生长的条件以及对较低压力和较高温度的稳定性。这些模拟结果增强了文献实验观察，因为它们提供了对分子机制所需的见解，可以调整这些分子机制以实现水合物中最佳的二氧化碳储存。
Gas hydrates have attracted significant fundamental and applied interests due to their important role in various technological and environmental processes. More recently, gas hydrates have shown potential applications for greenhouse gas capture and storage. To facilitate the latter application, introducing chemical additives into clathrate hydrates could help to enhance hydrate formation/growth rates, provided the gas storage capacity is not reduced. Employing equilibrium molecular dynamics, we study the impact of tetrahydrofuran (THF) on the kinetics of carbon dioxide (CO2) hydrate growth/dissociation and on the CO2 storage capacity of hydrates. Our simulations reproduce experimental data for CO2 and CO2 + THF hydrates at selected operating conditions. The simulated results confirm that THF in stoichiometric concentration does reduce CO2 storage capacity. This is not only due to the shortage of CO2 trapping in sII hydrate 512 cages, but also because of the favored THF occupancy in hydrate cages due to preferential THF - water hydrogen bonds. An analysis of the dynamical properties for CO2 and THF at the hydrate-liquid interface reveals that THF can expedite CO2 diffusion yielding a shift in the conditions conducive to CO2 hydrate growth and stability to lower pressures and higher temperatures compared to systems without THF. These simulation results augment literature experimental observations, as they provide needed insights into the molecular mechanisms that can be adjusted to achieve optimal CO2 storage in hydrates.