Isostructural and cage-specific replacement occurring in sII hydrate with external CO2/N2 gas and its implications for natural gas production and CO2 storage
Isostructural and cage-specific replacement occurring in sII hydrate with external CO2/N2 gas and its implications for natural gas production and CO2 storage
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DOI：
10.1016/j.apenergy.2016.06.072
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发表时间：
2016-09
期刊：
影响因子：
11.2
通讯作者：
Youngjoo Seo;Seongmin Park;Hyery Kang;Yun-Ho Ahn;Dongwook Lim;Se-Joon Kim;Jaehyoun Lee;J. Lee
中科院分区：
文献类型：
--
作者：
Youngjoo Seo;Seongmin Park;Hyery Kang;Yun-Ho Ahn;Dongwook Lim;Se-Joon Kim;Jaehyoun Lee;J. Lee
替代技术被认为是从天然气水合物中开采CH 4和将CO2封存到深海储层中的一种有前途的策略。大多数研究都集中在替代反应发生在硅水合物，由于其在天然气水合物的普遍性。然而，自然界中的sII型水合物也在一些地区被发现，并且sII型水合物中的置换机制与sI型水合物中的置换机制显著不同。在这项研究中，我们通过外部注入CO2/N2（50：50）气体混合物深入研究了sII（C3 H8 + CH 4）水合物的置换反应，主要关注粉末X射线衍射、拉曼光谱、核磁共振光谱和气相色谱分析。特别是首次证实了注入CO2/N2气体置换C3 H8 + CH 4水合物过程中没有发生结构转变，表明没有发生sII水合物分解后生成sI水合物的现象。此外，C3 H8 + CH 4水合物的笼特异性替换模式显示，CH 4替换与N2在小笼的sII比C3 H8替换与CO2在大笼的sII更显着。通过NMR和GC分析交叉检查C3 H8 + CH 4水合物的总置换程度，发现约为54%。与用CO2/N2气体置换CH 4水合物相比，用CO2/N2气体置换C3 H8 + CH 4水合物的程度较低，这归因于大笼中C3 H8的持续存在和原料气中较低的N2含量。在C3 H8 + CH 4水合物与外部CO2/N2气体中观察到的结构可持续性和特定于笼的替换将对建议目标天然气水合物储层和理解天然气水合物中安全天然气生产和长期CO2封存的客体交换的确切性质具有重要意义。
A replacement technique has been regarded as a promising strategy for both CH4exploitation from gas hydrates and CO2sequestration into deep-ocean reservoirs. Most research has been focused on replacement reactions that occur in sI hydrates due to their prevalence in natural gas hydrates. However, sII hydrates in nature have been also discovered in some regions, and the replacement mechanism in sII hydrates significantly differs from that in sI hydrates. In this study, we have intensively investigated the replacement reaction of sII (C3H8+ CH4) hydrate by externally injecting CO2/N2(50:50) gas mixture with a primary focus on powder X-ray diffraction, Raman spectroscopy, NMR spectroscopy, and gas chromatography analyses. In particular, it was firstly confirmed that there was no structural transformation during the replacement of C3H8+ CH4hydrate with CO2/N2gas injection, indicating that sII hydrate decomposition followed by sI hydrate formation did not occur. Furthermore, the cage-specific replacement pattern of the C3H8+ CH4hydrate revealed that CH4replacement with N2in the small cages of sII was more significant than C3H8replacement with CO2in the large cages of sII. The total extent of the replacement for the C3H8+ CH4hydrate was cross-checked by NMR and GC analyses and found to be approximately 54%. Compared to the replacement for CH4hydrate with CO2/N2gas, the lower extent of the replacement for the C3H8+ CH4hydrate with CO2/N2gas was attributable to the persistent presence of C3H8in the large cages and the lower content of N2in the feed gas. The structural sustainability and cage-specific replacement observed in the C3H8+ CH4hydrate with external CO2/N2gas will have significant implications for suggesting target gas hydrate reservoirs and understanding the precise nature of guest exchange in gas hydrates for both safe natural gas production and long-term CO2sequestration.