Naphthalene in carbon dioxide

The solubility of solids in supercritical fluids is a very sensitive function of temperature and pressure. Unlike liquids, supercritical fluids are highly compressible and minor temperature or pressure changes lead to large changes in density and, therefore, solvent power QJ. The expansion of supercritical solutions, therefore, results in a substantial solubility decrease. The solubility of Naphthalene in carbon dioxide at 45 C, for example, decreases by about two orders of magnitude upon reducing the pressure from 127 to 62 bars (21. If this... 

Tsekhanskaya, Yu. V., M. B. lomtev, and E. V. Mushkina. 1962. Solubility of diphenylamine and naphthalene in carbon dioxide under pressure. Russ. J. Phys. 

Estimate the solubility of naphthalene in carbon dioxide at 35° C and pressures ranging from 1 bar to 60 bar using the virial equation of state with the following values for the second virial coefficient... 

McHugh and Paulaitis [7. Chem. Eng. Data, 25, 326 (1980)] report the following data for the solubility of naphthalene in carbon dioxide at temperatures slightly above the CO2 critical tern- perature and pressures considerably higher than its critical pressure. 

Figure 3 A plot of diffusion coefficient vs. the reciprocal of temperature at constant density for naphthalene in carbon dioxide. The line denoted 7c separates the supercritical region on the left from the subcritical (liquid) region on the right Note that there is no discontinuity when the fluid changes from supercritical to subcritical. The solid lines represent constant densities, from top to bottom of 0.60, 0.70, 0.80, and 0.90gcm , even though temperature is changing continuously from left to right The dashed line indicates a constant pressure line.

Najour, G. C. King, A. D. Solubility of Naphthalene in Compressed Methane, Ethylene, and Carbon Dioxide. Evidence for a Gas-Phase Complex Between Naphthalene and Carbon Dioxide. J. Chem. Phys. 1966, 45, 1915-1921. 

The use of NMR spectroscopy as an analytical technique is well established ( 1 8). In order to quantitate our spin-echo height to the number of protons present, we performed an independent calibration using standard solutions of naphthalene in carbon tetrachloride. Concentrations for the standards were chosen to correspond to the anticipated supercritical C02 solubilities, and all calibration measurements were performed using a sample cell of the same dimensions as the solubility sample cell previously described. The response of our spectrometer to the standard solutions was linear over the concentration range. The reproducibility for independent measurements of the calibration curve was 3 . Throughout the experiment, all spectrometer conditions (pulse lengths, phases, receiver amplifier gain, etc.) were closely monitored, and frequent checks on the calibration of the spectrometer were performed. In this way we were able to obtain the molar solubility of solid naphthalene in supercritical carbon dioxide to an estimated experimental accuracy of 6%. 

The influence of the parameters concentration, pre- and post-expansion pressure and pre- and post-expansion temperature and geometry of the nozzle on the particle size distribution wasn t studied at all. Merely Mohamed [4] examined the influence of concentration, pre- and post-expansion pressure and temperature of the system carbon dioxide - naphthalene. No particle size distribution was measured, only the size of the smallest and biggest particles were measured. For these investigations, anthracene was used as a model substance, while the solubility of anthracene in carbon dioxide [5] is approximately more then 100 times smaler than for naphthalene. 

Figure lQis a graph of naphthalene solubility in carbon dioxide at 45 C (15 C above the critical temperature of carbon dioxide) taken from Reference 17. As is obvious from an examination of the data, the solubility of naphthalene increases dramatically when the pressure is increased beyond the critical pressure of 73 atm. The solubility (given in units of grams/liter in the reference) approaches about 10% (w/w) at a pressure level of 200 atm. 

Figure 14.22 Solubility of naphthalene(l) in carbon dioxide(2) at 308.15 K (35°C). Circles are data. Curves are computed from Eqs. (14.94) and (14.96) under various assumptions...

Figure 5 shows the partial molar volume of naphthalene in supercritical carbon dioxide predicted by theory compared with the data of Eckert et al. (1). Neither naphthalene nor carbon dioxide would be expected to be described quantitatively by the LJ potential. Furthermore, no binary interaction parameter was used with the Lorentz-Berthelot estimates for the CO2-C10H8 interaction. Thus, the degree of agreement between effectively a priori prediction and experiment is judged to be very satisfactory. 

A full report has been published describing the light induced reaction of naphthalene with carbon dioxide in DMF containing amines to give a- and j8-naphthoic acids.The reaction most likely occurs by electron transfer from the amine to the naphthalene excited state followed by coupling of the naphthalene radical ion with carbon dioxide. 

Since naphthalene-SCF mixtures have been so widely studied, it is instructive to consider the solubility behavior of just one of these systems, the naphthalene-C02 system, to highlight the solvent properties of a supercritical fluid solvent. In chapter 1 the effects of pressure and temperature on the solubility of naphthalene in ethylene were described. The solubility behavior is quite similar in carbon dioxide, in trifluoromethane, or even in xenon, although each system achieves its own absolute solubility level of naphthalene. 

Schmitt (1984) verified the entrainer behavior reported by Kurnik and Reid. Schmitt and Reid (1984) show that very small amounts of an entrainer in the SCF-rich phase have very little effect on the solubility of a second component in that phase. This observation is consistent with the work of Kohn and Luks for ternary mixtures at cryogenic temperatures. The data of Kurnik and Reid have been corroborated for the naphthalene-phenanthrene-carbon dioxide system (Gopal et al., 1983). Lemert and Johnston (1989, 1990) also studied the solubility behavior of solids in pure and mixed solvents at conditions close to the upper critical end points. Johnston finds that adding a cosolvent can reduce the temperature and pressure of the UCEP while simultaneously increasing the selectivity of the solid in the SCF-rich phase. In these studies Johnston found the largest effects with a cosolvent capable of hydrogen bonding to the solute. 

Najour, G. C., and A. D. King, Jr. 1966. Solubility of naphthalene in compressed methane, ethylene, and carbon dioxide Evidence for a gas-phase complex between naphthalene and carbon dioxide. J. Chem. Phys. 45 1915. 

We consider application of Eqs. (I.6-16)-(1.6-I8) to (he calculation of the solubility of naphthalene (component 2) in carbon dioxide (component I) at 3S°C and at high pressures. Data for these conditions (Tsekhanskaya et al.T) are shown as open circles in Fig. 1.6-2. Particularly noteworthy is the dramatic enhancement In solubility—several orders of magnitude—that occurs with increasing pressure near foe critical pressure of foe solvent gas. The solubility enhancement, which obtains for temperatures slightly higher than the critical temperature of a solvent gas (the critical temperature of COi is 3l°C), is the basis for certain "supercritical extraction processes ase Paulaitis et a1.Ba for discussions of fols topic. 

Di2 values have been determined for many substances in supercritical CO2, C2H6, CCIF3, SFe, etc. They are normally of the order of 10 cm s (or 10 m s ), and thus much higher than those in liquid solvents. This is of considerable importance for mass transfer in SFE and SFC. A characteristic example is shown in Fig. 29, where values for naphthalene and biphenyl in carbon dioxide at 309 K and 331 K are presented as a function of density / , according to recent measurements by Klask [66]. In the range of the experiments, increases with... 

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