Mok Junghoon, Lim Junkyu, Choi Wonjung, Yun Soyeong, Lee Joonseop, Ko Gyeol, Seo Yongwon
Department of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea.
Phys Chem Chem Phys. 2021 Jul 28;23(29):15693-15701. doi: 10.1039/d1cp02327f.
In this study, a new sI-sII dual hydrate former [chlorodifluoromethane (CHClF2); an important greenhouse gas with a global warming potential of 1810], which forms sI hydrate by itself and forms sII hydrate in the presence of external help guests such as CH4 and N2, was introduced and closely investigated for its potential significance in gas hydrate-based gas separation. The phase equilibria of CHClF2 hydrate, binary CHClF2 (5%) + N2 (95%) hydrate, and binary CHClF2 (5%) + CH4 (95%) hydrate were measured to examine the formation conditions and thermodynamic stability regions of CHClF2 + external guest hydrates. Nuclear magnetic resonance and in situ Raman spectroscopic results confirmed the formation of sII hydrates for CHClF2 + external guest (N2 or CH4) mixtures. Powder X-ray diffraction patterns clearly demonstrated a structural transition of sI to sII hydrates and a preferential incorporation of CHClF2 molecules in the hydrate phase when external guests (N2 or CH4) were involved in CHClF2 hydrate formation. The measured dissociation enthalpy values of CHClF2 hydrate, binary CHClF2 (5%) + N2 (95%) hydrate, and binary CHClF2 (5%) + CH4 (95%) hydrate using a high-pressure micro-differential scanning calorimeter also indicated preferential CHClF2 enclathration. The experimental results provide new insights into the thermodynamic and structural features of the CHClF2 (sI-sII dual hydrate former) + external guest hydrates for understanding and designing the hydrate-based CHClF2 separation process.
在本研究中，引入了一种新型的sI-sII双水合物形成剂[氯二氟甲烷（CHClF2）；一种重要的温室气体，全球变暖潜能值为1810]，其自身可形成sI水合物，在CH4和N2等外部辅助客体存在时可形成sII水合物，并对其在基于气体水合物的气体分离中的潜在意义进行了深入研究。测量了CHClF2水合物、二元CHClF2（5%）+N2（95%）水合物和二元CHClF2（5%）+CH4（95%）水合物的相平衡，以考察CHClF2+外部客体水合物的形成条件和热力学稳定区域。核磁共振和原位拉曼光谱结果证实了CHClF2+外部客体（N2或CH4）混合物形成了sII水合物。粉末X射线衍射图谱清楚地表明，当外部客体（N2或CH4）参与CHClF2水合物形成时，sI水合物向sII水合物发生了结构转变，且CHClF2分子优先进入水合物相。使用高压微差示扫描量热仪测量的CHClF2水合物、二元CHClF2（5%）+N2（95%）水合物和二元CHClF2（5%）+CH4（95%）水合物的解离焓值也表明CHClF2优先被包合。实验结果为理解和设计基于水合物的CHClF2分离工艺，提供了关于CHClF2（sI-sII双水合物形成剂）+外部客体水合物的热力学和结构特征的新见解。
