Effect of Ammonia on Methane Hydrate Stability under High-Pressure and High-Temperature Conditions
Effect of Ammonia on Methane Hydrate Stability under High-Pressure and High-Temperature Conditions
复制标题
高压高温条件下氨对甲烷水合物稳定性的影响
DOI：
10.1021/acs.jpca.0c09652
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Yamamoto Yoshitaka
中科院分区：
文献类型：
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作者：
Kadobayashi Hirokazu;Hirai Hisako;Ohfuji Hiroaki;Kawamura Hideaki;Muraoka Michihiro;Yoshida Suguru;Yamamoto Yoshitaka
采用拉曼光谱和同步加速器 X 射线粉末衍射，结合外部加热的金刚石砧池，进行高压实验，研究室温至高温下水-甲烷-氨系统中甲烷水合物 (MH) 的稳定性和相变。结果表明，在室温下，MH 在~1.0 GPa 下经历从 MH-I 到 MH-II 的相变，在~2.0 GPa 下经历从 MH-II 到 MH-III 的相变。这些转变行为与水-甲烷系统中的转变行为一致，这表明氨对 MH 的一系列相变的影响可以忽略不计。相反，连续原位拉曼光谱表明，氨影响了 MH-III 在高压和高温下的稳定性：MH-III 在水-甲烷-氨体系中的解离温度比水-甲烷体系低 10 K 以上。这些发现有助于改进冰体的内部结构模型并估计其大气甲烷的来源。
High-pressure experiments were conducted to investigate the stability and phase transition of methane hydrate (MH) in the water–methane–ammonia system at room-to-high temperatures employing Raman spectroscopy and synchrotron X-ray powder diffraction, in combination with an externally heated diamond anvil cell. The results revealed that, at room temperature, MH undergoes phase transitions from MH-I to MH-II at ∼1.0 GPa and from MH-II to MH-III at ∼2.0 GPa. These transition behaviors are consistent with those in the water–methane system, which indicates that ammonia has a negligible effect on a series of phase transitions of MH. Contrarily, a sequential in situ Raman spectroscopy revealed that ammonia affects the stability of MH-III under high pressure and high temperature: the dissociation temperature of MH-III was more than 10 K lower in the water–methane–ammonia system than in the water–methane system. These findings aid in improving the internal structural models of icy bodies and estimating the origin of their atmospheric methane.