Abstract This study investigated the influence of feed gas composition on structural transformation and guest exchange behaviors in the replacement of sH (CH4 + methylcyclopentane) hydrate with CO2 + N2 for energy recovery and CO2 sequestration. CO2 + N2 mixtures with three different CO2 concentrations (20, 40, and 60%) were used as replacement gases, and their exchange behaviors were observed with gas chromatography, nuclear magnetic resonance, and powder X-ray diffraction. The experimental results demonstrated that an increase in the CO2 concentration of replacement gases increased the structural transformation of sH to sI, which resulted in the enhancement of both the extent of replacement and the guest exchange rate. However, the highest extent of replacement was observed in the CO2 (40%) and N2 (60%) mixture due to the asymmetrical change in the CO2 and N2 compositions in the replaced hydrates, which was caused by the higher degree of structural transformation in feed gas with a higher CO2 concentration and the larger N2 inclusion in replaced hydrates at the lower CO2 concentration. The experimental results obtained in this study are helpful for accurately understanding the replacement mechanism and guest exchange behaviors in sH hydrate–flue gas replacement.

中文翻译：

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原料气组成对 sH 水合物结构转变和客体交换行为的影响——用于能量回收和 CO2 封存的烟气替代

摘要 本研究研究了在用 CO2 + N2 替代 sH（CH4 + 甲基环戊烷）水合物进行能量回收和 CO2 封存时，原料气组成对结构转变和客体交换行为的影响。以三种不同 CO2 浓度（20%、40% 和 60%）的 CO2 + N2 混合物作为置换气体，并通过气相色谱、核磁共振和粉末 X 射线衍射观察了它们的交换行为。实验结果表明，置换气体中CO2浓度的增加促进了sH向sI的结构转变，从而导致置换程度和客体交换率的提高。然而，在 CO2 (40%) 和 N2 (60%) 混合物中观察到最高程度的置换，这是由于被置换的水合物中 CO2 和 N2 组成的不对称变化，这是由进料气中更高程度的结构转变引起的具有较高的 CO2 浓度和较大的 N2 夹杂物在较低的 CO2 浓度下被置换的水合物中。本研究获得的实验结果有助于准确理解sH水合物-烟气置换过程中的置换机理和客体交换行为。