Abstract The experimental phase equilibrium measurements for the dissociation conditions of methane hydrates in the presence of five additives are reported in this study. The isochoric method was employed to measure the three-phase (hydrate + liquid water + vapor, H-Lw-V) dissociation conditions (the three-phase equilibrium temperatures and pressures) under various concentrations of five additive compounds. These additives include 1,2-epoxybutane that showed a promotion effect up to 2.6 K at a fixed pressure for the formation of methane hydrate. Other additives of 2,3-dihydrofuran N-methylformamide, 4-methylmorpholine and 1-(2-furyl)methylamine, however, all showed the inhibition effect from 1.3 up to 9 K. The possible structures of methane hydrates with these additives were estimated from the Clausius-Clapeyron equation by using the measured equilibrium temperature and pressure data. It is shown that with the additive of 1,2-epoxybutane, a sII hydrate structure might cause the promotion effect. The other four additives with inhibition effect all showed the possible sI structure. This study reports novel phase equilibrium data and verifies a useful screening method to select the available additives for natural gas production or transportation.

中文翻译：

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使用 1,2-环氧丁烷、2,3-二氢呋喃、N-甲基甲酰胺、4-甲基吗啉或 1-(2-呋喃基)甲胺的各种添加剂测量甲烷水合物的解离条件

摘要 本研究报告了在五种添加剂存在下甲烷水合物解离条件的实验相平衡测量。等容法用于测量在不同浓度的五种添加剂化合物下的三相（水合物 + 液态水 + 蒸汽，H-Lw-V）解离条件（三相平衡温度和压力）。这些添加剂包括 1,2-环氧丁烷，它在固定压力下显示出高达 2.6 K 的促进作用，以形成甲烷水合物。然而，2,3-二氢呋喃N-甲基甲酰胺、4-甲基吗啉和1-(2-呋喃基)甲胺等其他添加剂在1.3至9 K范围内均表现出抑制作用。通过使用测量的平衡温度和压力数据，从克劳修斯-克拉珀龙方程估计含有这些添加剂的甲烷水合物的可能结构。结果表明，加入1,2-环氧丁烷后，sII水合物结构可能会产生促进作用。其他四种具有抑制作用的添加剂均表现出可能的sI结构。该研究报告了新的相平衡数据，并验证了一种有用的筛选方法来选择天然气生产或运输的可用添加剂。