Measurements of the dissociation conditions for methane hydrates with various additives of 1,2-epoxybutane, 2,3-dihydrofuran, N-methylformamide, 4-methylmorpholine, or 1-(2-furyl)methylamine

• Main Authors: Wu, TT (Wu, Tsung-Tse), Shao, WC (Shao, Wan-Chun), Chen, YP (Chen, Yan-Ping), Tang, M (Tang, Muoi)
• Other Authors: 化材系
• Format: Article in Journal/Newspaper
• Language: Chinese
• Published: 2020
• Subjects: Methane hydrate; Five additives; Isochoric method; Dissociation conditions; Hydrate plus liquid water plus vapor (H-L-w-V); Phase equilibrium
• Online Access: http://ir.lib.pccu.edu.tw//handle/987654321/46164; http://ir.lib.pccu.edu.tw/bitstream/987654321/46164/2/index.html

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-L-w-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. (C) 2020 Elsevier B.V. All rights reserved.