不同季铵盐作用下的CO2水合物相平衡

CO₂气体水合物形成热力学性质是实施海水淡化、沼气纯化、碳捕集和封存、能源利用、天然气储存等技术的关键。采用恒容温度搜索法，在温度272.75~294.35 K，压力0.35~4.50 MPa的范围内，探究了四种季铵盐促进剂对CO₂气体水合物相平衡的影响。结果表明，相同条件下，季铵盐作用下CO₂水合物的相平衡温度由高到低分别为：四丁基氟化铵（TBAF）>四丁基溴化铵（TBAB）>四丁基氯化铵（TBAC）>苄基三乙基氯化铵（TEBAC）。基于Clausius-Clapeyron方程，计算了不同体系的相变潜热，探讨了其对水合物稳定性的影响。可以看出，水合物的相平衡压力对数与温度倒数呈线性关系，其中，TBAF、TBAB作用下的CO₂水合物相变潜热相接近且明显高于其他季铵盐，说明其促进效果最好，所对应的水合物生成条件也最为温和。利用Chen-Guo模型，结合PR状态方程和改进Joshi经验活度模型，分别计算了TBAF、TBAB、TBAC和TEBAC作用下CO₂水合物热力学相平衡数据，计算结果与实验数据吻合良好，最大平均相对误差为7.50%。

Phase equilibrium of CO2 hydrate in the presence of four different quaternary ammonium salts

Thermodynamic properties of CO₂ gas hydrates were essential for the design and operation of seawater desalination, biogas purification, CO₂ capture and storage systems, energy utilization, natural gas storage, etc. In this study, four different quaternary ammonium salts were employed to accelerate the CO₂ hydrate formation in the temperature range from 272.75 K to 294.35 K at pressures 0.35—4.50 MPa by the constant volume temperature search method. The results showed that under the same conditions, the CO₂ hydrate phase equilibrium temperature under the action of quaternary ammonium salt can be summarized as below:tetrabutylammonium fluoride (TBAF) > tetrabutylammonium bromide (TBAB) > tetrabutylammonium chloride (TBAC) > benzyl-triethyl-ammonium chloride (TEBAC). The phase enthalpy of CO₂ hydrate in different quaternary ammonium salt solutions was calculated by using the Clausius-Clapeyron equation, and the influence of its hydrate stability was explored. The logarithm of the pressure versus the reciprocal (absolute) hydrate formation temperature was also found to be nearly linear. The phase enthalpy of CO₂ hydrate under the action of TBAF and TBAB was close to and significantly higher than other quaternary ammonium salts, indicating that its promotion effect was the best, the corresponding hydrate formation conditions were also the mildest. Using the Chen-Guo model, combined with the PR equation of state and the improved Joshi empirical activity model, the thermodynamic phase equilibrium data of CO₂ hydrate under the action of TBAF, TBAB, TBAC and TEBAC were calculated respectively. The calculated results were in good agreement with the experimental data, and the maximum average relative error was 7.50%.