Self-diffusion coefficients for water and organic solvents in extremely low-density supercritical states
Self-diffusion coefficients for water and organic solvents in extremely low-density supercritical states
复制标题
极低密度超临界状态下水和有机溶剂的自扩散系数
DOI：
10.1016/j.molliq.2008.10.006
复制
发表时间：
2009
期刊：
影响因子：
--
通讯作者：
and M. Nakahara
中科院分区：
文献类型：
--
作者：
K. Yoshida;N. Matubayasi;and M. Nakahara
苯和环己烷的自扩散系数D是通过使用质子脉冲场梯度自旋回波（PGSE）方法在150-400 °C的高温和低密度（苯和环己烷分别为0.007-0.21和0.005-0.15 g cm− 3）的单相区域中测定的。对于苯，在150-400 °C范围内，零密度极限下的密度-扩散系数积除以绝对温度的平方根（ρD）0/T小于硬球模型的结果，并且随着温度的降低而减小，这反映了吸引相互作用的影响。环己烷的（ρD）0/T与硬球值相当，其温度依赖性小于苯，表明苯的吸引作用比环己烷强.通过与我们以前对水的结果进行比较，讨论了氢键的动态效应[J. Chem. Phys.，125，074307（2006）; J. Chem. Phys. 126，089901（2007）]。
Self-diffusion coefficients D for benzene and cyclohexane are determined by using the proton pulsed-field-gradient spin echo (PGSE) method at high temperatures of 150–400 °C and in the low-density (0.007–0.21 and 0.005–0.15 g cm−3for benzene and cyclohexane, respectively), one-phase region. For benzene, the density-diffusivity product in the zero-density limit divided by the square root of the absolute temperature, (ρD)0/T is smaller than that of the hard sphere model at 150–400 °C and decreases with lowering temperature as a reflection of the attractive interaction effect. The (ρD)0/T for cyclohexane is comparable to the hard-sphere value and its temperature dependence is smaller than that for benzene, showing that the effect of the attractive interaction is stronger for benzene than for cyclohexane. The dynamic effect of the hydrogen bonding is discussed through comparison to our previous results on water [J. Chem. Phys., 125, 074307 (2006); J. Chem. Phys. 126, 089901 (2007)].