The phase behavior of the carbon dioxide + cycloheptane binary system for which no literature data are available has been examined at temperatures ranging from 292.6 to 372.8 K. Saturation pressures, ranging from 23.9 to 154.8 bar, were acquired by a synthetic and visual method. In concrete terms, an adjustable-volume high-pressure cell was utilized to measure bubble and dew point pressures by visual detection of phase transitions at constant overall composition. A total of 11 different mixtures with mole fractions of carbon dioxide ranging from 0.20 to 0.96 were prepared, and a total of 99 experimental points were reported. The experimental results obtained in this work reveal the absence of liquid–liquid immiscibility in the studied temperature range and make it possible to conclude that the vapor–liquid critical line of the binary system is continuous and uninterrupted between the two pure compounds. Experimental data were correlated with the Peng–Robinson equation of state and classical van der Waals mixing rules with temperature-dependent binary interaction parameters. They were also compared to the PPR78 model, an entirely predictive group contribution method in which the k_ij depends on temperature.

中文翻译：

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二氧化碳 + 环庚烷二元系统的高压相平衡测量

已经在 292.6 至 372.8 K 的温度范围内检查了二氧化碳 + 环庚烷二元系统的相行为，没有可用的文献数据。饱和压力范围为 23.9 至 154.8 bar，通过合成和视觉方法获得。具体而言，通过视觉检测在恒定总成分下的相变，利用可调节体积的高压电池来测量气泡和露点压力。共制备了 11 种不同的二氧化碳摩尔分数范围为 0.20 到 0.96 的混合物，共报告了 99 个实验点。在这项工作中获得的实验结果表明，在所研究的温度范围内不存在液-液不混溶性，并且可以得出结论，二元系统的汽-液临界线在两种纯化合物之间是连续且不间断的。实验数据与 Peng-Robinson 状态方程和经典范德华混合规则与温度相关的二元相互作用参数相关。他们还与 PPR78 模型进行了比较，这是一种完全预测的组贡献方法，其中k _ij取决于温度。