Infrared study of anomalous volume behavior of water–benzene mixtures in the vicinity of the critical region

Abstract

Volume behavior of water–benzene mixtures at temperatures and pressures in the 473–623 K and 100–350 bar ranges, respectively, has been studied by infrared in situ measurements. The densities of the benzene-rich phase were estimated from the spectroscopically determined concentrations of water and benzene and compared with the average densities before mixing, which were calculated using literature densities of neat water and neat benzene at the same temperature and pressure. Anomalously large volume change for mixing has been found in the vicinity of the critical region of the water–benzene mixtures.

Near infrared study of water-benzene mixtures at high temperatures and pressures

“…Figure 10 shows plots of the maximum values at a few temperatures against molar fraction of benzene. The previously reported values for the benzene-rich phase 21 are also plotted in Fig. 10 and prove to be consistent with the present results for the water-rich phase.…”

“…For example, volume expansion on the mixing of water and benzene becomes as large as 300% at 573 K and 100 bar. 21 Similar phenomena have been observed for water-toluene and water-ethylbenzene mixtures. 22 Thus the anomalous volume expansion is considered to be common to the mixing of water and hydrophobic hydrocarbons in the vicinity of the critical region.…”

“…8 has recently been reported by Furutaka et al for the hydrocarbon-rich phase of the waterhydrocarbon mixtures. 21,22 It is proved that the maxima of the volume expansion of both the water-rich and the benzene-rich phases of the mixtures occur at about the same pressure at each temperature of 573, 598, and 623 K. Therefore, the anomalous volumetric behavior should be characteristic of water-hydrocarbon mixtures in the vicinity of the critical region, particularly near the vapor pressure curve of water. This phenomenon may have some relationship with the large excess molar volumes of fluid mixtures of carbon dioxide with ethene and sulfur hexafluoride observed at around room temperature and near the critical pressures of the component fluids.…”

Volumetric behavior of water–methanol mixtures in the vicinity of the critical region

“…Similar volumetric behavior has recently been reported by Wormald and Hodgetts [8] on mixtures of carbon dioxide and sulfur hexafluoride in the near-critical region. Another intriguing pattern of volumetric behavior has been reported by Furutaka and Ikawa [9] and Jin and Ikawa [10] for water-benzene mixtures at high temperatures and pressures. They have estimated molar concentrations of water and benzene in each of the two coexisting two phases of their mixtures by measuring infrared and near-infrared absorption intensities, and found that the relative volume change on mixing becomes anomalously large in the vicinity of the critical region.…”

“…To compare the volumetric behavior of the water-methanol mixtures with that of water-benzene mixtures, we estimate the relative volume change given by the following expression [9,10]:…”