High pressure phase equilibria and critical phenomena of water + iso-butane and water + n-butane systems to 695 K and 306 MPa

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• 作者：Tian ; Yiling ; Zhao ; Xuefeng ; Chen ; Li ; Zhu ; Hugang ; Fu ; Huafeng
• 关键词：Critical loci ; High pressure ; iso-Butane ; n-Butane ; Water
• 刊名：The Journal of Supercritical Fluids
• 出版年：2004
• 期刊代码：60_08968446
• 类别：ce
• 出版时间：July, 2004
• 卷：30
• 期：2
• 页码：145-153
• 文件大小：171 K

摘要

The equilibrium surface (x, p, T, V_m) for water+iso-butane was measured and additional equilibrium data for water+n-butane are reported. Mole fractions of water for water+iso-butane from 0.5 to 0.98, pressures up to 306MPa and temperatures up to 695K were studied. Critical curves, represented as the envelope of the isopleths starting at the critical point of water (647K), went through a temperature minimum and then increased at higher pressures and higher temperatures, giving evidence for (gas+gas) equilibria of the third type. The results are compared with the phase equilibrium of previously measured (water+n-alkane) mixtures. The excess molar volumes, V^E, and excess molar Gibbs energies, G^E, for water+n-butane on the phase equilibrium surfaces have been calculated for 600 and 620K from 40 to 200MPa. All the V^E and G^E values were found to be positive.