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首页> 外文期刊>Chemistry: A European journal >Enthalpy of Solution of 1,4-Naphthoquinone in CO_2+n-Pentane in the Critical Region of the Binary Mixtures:Mechanism of Solubility Enhancement
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Enthalpy of Solution of 1,4-Naphthoquinone in CO_2+n-Pentane in the Critical Region of the Binary Mixtures:Mechanism of Solubility Enhancement

机译：二元混合物临界区1,4-萘醌在CO_2 +正戊烷中的溶液焓：增溶机理

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The enthalpy of solution (DELTA_(solv)H_m)) and solubility of 1,4-naphthoquinone in CO_2+n-pentane were measured at 308.15 K in the critical region of the binary fluid.In order to study the effect of phase behavior of the mixed solvent on DELTA_(solv)H_m,the experiments were carried out in the supercritical (SC) and subcritical region of the binary solvent.The density of the mixed solvent in different conditions was determined.The isothermal compressibility (K_T) of the mixed solvent,and partial molar volume (V_(n-pentane)) of n-pentane in the solution were calculated.It was demonstrated that the DELTA_(solv)H_m was negative in all conditions.DELTA_(solv)H_m is nearly independent of pressure or density in all the solvents in a high-density region,in which compressibility of the solvent is very small;this indicates that the intermolecular interaction between the solvent and the solute is similar to that for liquid solutions.It is very interesting that DELTA_(solv)H_m in the mixed SC fluid differs from the DELTA_(solv)H_m in mixed subcritical fluids.The absolute value of DELTA_(solv)H_m in the mixed SC fluid is close to that in pure SC CO_2 in the high-density region,and is much lower than that in pure SC CO_2 in the low-density region.In the mixed subcritical fluids,the DELTA_(solv)H_m is also close to that in the pure CO_2 in the high-density region.However,at the same density,the absolute value of DELTA_(solva)H_m in the binary subcritical fluids is larger than that in pure CO_2 in the high-compressible region of the mixed solvent.The main reason for this is that the degree of clustering in the SC solutions is small at the density in which the degree of clustering is large in the subcritical solutions.It can be concluded that solubility enhancement by n-pentane in the mixed SC fluid is entropy driven.In contrast,the solubility enhancement by n-pentane in subcritical fluids is enthalpy driven.The intermolecular interaction in the SC solutions and subcritical solutions can be significantly different even if their densities are the same.
机译：在二元流体的关键区域，在308.15 K下测量了溶液的焓（DELTA_（solv）H_m）和1,4-萘醌在CO_2 +正戊烷中的溶解度。在DELTA_（solv）H_m上混合溶剂，在二元溶剂的超临界（SC）和亚临界区域进行实验，确定了不同条件下混合溶剂的密度。混合后的等温压缩性（K_T）计算溶剂和溶液中正戊烷的部分摩尔体积（V_（n-戊烷））。证明DELTA_（solv）H_m在所有条件下均为负值.DELTA_（solv）H_m几乎与压力无关或高密度区域中所有溶剂的密度，其中溶剂的可压缩性很小;这表明溶剂与溶质之间的分子间相互作用类似于液体溶液中的分子间相互作用。非常有趣的是DELTA_（混合SC流感中的solv）H_m id与混合亚临界流体中的DELTA_（solv）H_m不同。混合SC流体中的DELTA_（solv）H_m的绝对值在高密度区域中接近于纯SC CO_2中的绝对值，但远低于在低密度区域中，纯SC CO_2。在混合亚临界流体中，DELTA_（solv）H_m也接近高密度区域中的纯CO_2。但是，在相同密度下，DELTA_的绝对值在混合溶剂的高压缩区域中，二元亚临界流体中的（solva）H_m大于纯CO_2中的（solva）H_m。其主要原因是，SC溶液中的聚集度在密度较小的情况下较小。亚临界溶液的团聚度很大。可以得出结论，正戊烷在混合SC流体中的溶解度增强是由熵驱动的。相反，正戊烷在亚临界流体中的溶解度增强是焓驱动的。在SC解决方案和亚临界溶液中即使ns的密度相同，它们也可以有很大不同。

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