超临界CO_2-共溶剂二元体系溶质的偏摩尔体积及分子间的相互作用

PARTIAL MOLAR VOLUMES OF SOLUTES AND MOLECULAR INTERACTION IN BINARY MIXED CO_2-COSOLVENT SUPERCRITICAL FLUIDS

在 313 5～ 32 3 5K、 7～ 14MPa范围内测定了CO2 及CO2 甲醇、CO2 乙醇、CO2 正丁醛、CO2 异丁醛二元混合流体的表观密度 ,讨论了压力、第 2组分的种类和加入量对CO2 表观密度的影响 ,在此基础上计算了溶质的偏摩尔体积 ,讨论了温度、压力和第 2组分的性质对溶质偏摩尔体积的影响规律 .实验发现 :CO2 共溶剂二元体系在临界点附近溶质的偏摩尔体积出现较大的负值 ,反映了CO2 与共溶剂之间存在较强的相互作用 ,使CO2 分子发生聚集现象 ;CO2 分子聚集程度与共溶剂分子大小及空间结构有关 ,分子越大或越规则 ,CO2 分子聚集程度越强 .

The densities of the binary mixtures of CO2-methanol, CO2-ethanol, CO2-n-butyraldehyde, CO2-i-butyraldehyde were measured at temperature ranging from 313.5 K to 323.5 K under a pressure ranging from 7 MPa to 14 MPa. The partial molar volumes of the solutes were calculated based on the relationship between the concentrations of the solutes and the densities of the mixtures. Intermolecular interaction between CO2 and the solutes was studied based on the partial molar volume data. The partial molar volumes of the solutes were negative and the absolute value decreases with an increasing pressure and the concentration of the cosolvent. Moreover, the partial molar volumes of the solutes were related with molecule size and space structure of the cosolvent.