添加異白胺酸、甲硫胺酸與賴氨酸對於甲烷及二氧化碳水合物之熱力學與動力學性質量測

Abstract

本研究以等容法來進行甲烷以及二氧化碳水合物系統熱力學條件的量測，通過測量添加胺基酸的系統在不同溫度及壓力下的熱力學條件來得到三種氨基酸 (異白胺酸、賴氨酸、甲硫胺酸) 對於甲烷及二氧化碳水合物相邊界的影響，甲烷水合物實驗溫度為275.49 K - 288.00 K；壓力範圍為3.24 MPa - 12.40 MPa，對於二氧化碳系統，溫度範圍是272.81 K - 281.16 K；壓力則為1.28 MPa - 3.43 MPa。通過實驗可以得知，在0.1 mol%的添加濃度下，胺基酸對甲烷水合物的抑制效果排序為異白胺酸>賴氨酸>甲硫胺酸，異白胺酸具有最好的抑制效果，平均抑制溫度為0.29 K，其中甲硫胺酸對於甲烷水合物的相邊界影響幾乎可以忽略。在二氧化碳水合物系統中，抑制效果排序為異白胺酸>賴氨酸>甲硫胺酸，與甲烷水合物趨勢相同，異白胺酸具有最大抑制溫度，平均抑制溫度0.62 K。 在動力學實驗方面，使用恆溫法及攪拌來進行純水與含有異白胺酸之水合物系統的各項動力學性質，實驗長度為誘導時間後600分鐘，動力學性能通過以下幾點進行綜合比較: 誘導時間、總氣體消耗量、初始消耗速率、90%氣體消耗時間及速率。在二氧化碳系統中，系統所設定的溫度為275.15 K，量測壓力為2.875 MPa，異白胺酸的添加濃度為0.1與0.3 mol%，與純水二氧化碳系統相比，隨著異白胺酸添加濃度的提高，平均誘導時間會由純水的21.74分鐘拉長至0.3 mol%的45.17分鐘，而在總氣體消耗量上，0.1 mol% 異白胺酸具有最好的表現，平均為0.0597 mol，0.3 mol%略小於0.1 mol%，為0.0575 mol，純水則僅為0.0100 mol，在誘導時間與氣體消耗方面，純水與異白胺酸系統表現出了不一樣的抑制/促進趨勢。在甲烷水合物動力學條件方面，溫度設定在280.15 K，壓力設定為10.000 MPa，所添加的添加劑為0.1 mol%的異白胺酸，與二氧化碳系統相似，加入異白胺酸的系統在誘導時間上略長於純水系統，由7.23分鐘延長至9.20分鐘，氣體消耗能力上，純水系統平均為0.0298 mol，0.1 mol%異白胺酸系統為0.1908 mol，這也與二氧化碳系統類似，添加了異白胺酸的系統在誘導時間上皆會延長水合物的成核時間，反之在氣體消耗方面則具有巨大的提升效果。

This study used the isochoric method to measure thermodynamic conditions (phase boundary) of methane and carbon dioxide hydrates in the presence of amino acids. Three amino acids, isoleucine, lysine, and methionine, were chosen in this study. The impact of amino acids on the phase boundaries of methane and carbon dioxide hydrates was determined. For methane hydrate experiments, the temperature ranged from 275.49 to 288.00 K, and the pressure ranged from 3.24 to 12.40 MPa. For the carbon dioxide hydrate systems, the temperature ranged from 272.81 to 281.16 K, and the pressure ranged from 1.28 to 3.43 MPa. The experiments revealed that at an additive concentration of 0.1 mol%, the inhibitory effects of amino acids on methane hydrate were ranked as follows: isoleucine > lysine > methionine. Isoleucine exhibited the best inhibitory effect, with an average inhibition of 0.29 K, whereas the impact of methionine on the phase boundary of methane hydrate was almost negligible. In the carbon dioxide hydrate system, the inhibition ranking was the same as for methane hydrate: isoleucine > lysine > methionine, with isoleucine exhibiting the highest suppression temperature of 0.62 K. For the kinetic experiments, the isothermal method and stirring were used to study the kinetic properties of hydrate formation in the presence/absence of isoleucine. The experiment duration for hydrate formation was 600 minutes after the induction time, and the kinetic performance was compared based on several factors: induction time, total gas consumption, initial consumption rate, and 90% gas consumption time and rate. The experimental temperature in the carbon dioxide system was fixed at 275.15 K, and the initial pressure was chosen at 2.875 MPa. The isoleucine concentrations were 0.1 and 0.3 mol%. Compared to the pure water carbon dioxide system, the average induction time was increased from 21.74 minutes for pure water to 45.17 minutes at 0.3 mol% isoleucine system. Regarding total gas consumption, 0.1 mol% isoleucine had the best performance with an average consumption of 0.0597 mol, while 0.3 mol% was slightly lower at 0.0575 mol, and pure water was only 0.0100 mol. The pure water and isoleucine systems exhibited different trends in induction time and gas consumption. For methane hydrate kinetic conditions, the temperature was set at 280.15 K and the pressure at 10.000 MPa. The additive was 0.1 mol% isoleucine. Like the carbon dioxide system, the induction time in the isoleucine-added system was slightly longer than that in the pure water system, extending from 7.23 minutes to 9.20 minutes. For gas consumption, the pure water system averaged 0.0298 mol, while the 0.1 mol% isoleucine system averaged 0.1908 mol. This is also similar to the carbon dioxide system, where the addition of isoleucine extended the nucleation time of the hydrate in terms of induction time and significantly improved gas consumption.