Measurement and Modeling of the Solubility of Tetramethylthiuram Disulfide and 2-Nitrophenyl Disulfide in Compressed Propane

Abstract

The solubility of tetramethylthiuram disulfide (TTDS) and 2-nitrophenyl disulfide (NPDS) in sub-and supercritical propane has been experimentally determined in a static view cell, for temperatures between (347 and 393) K and pressures in the range (4.8 to 12.9) MPa. The solubilities of TTDS varied from (0.09 to 0.67) mg of solute per gram of propane, whereas those of NPDS were from (0.06 to 0.70) mg of solute per gram of propane within the experimental range studied. It was found that larger values of the solubility were obtained at higher pressures. Regarding the temperature effect, for NPDS the solubility rose with increasing values of the variable in the whole experimental range analyzed, while for TTDS higher solubilities were found at 370 K (the critical temperature of propane). The solubility values obtained for these compounds were compared to those of anthracene, carbazole, and dibenzothiophene (DBT) in propane. It was observed that TTDS and NPDS solubilities are similar to those of carbazole and 1 or 2 orders of magnitude smaller than those of anthracene or DBT. These results have been explained taking into account the solute's vapor pressure and the polarity of both the solvent and the solutes. With this purpose, dipole moments of all solutes compared were calculated using the HyperChem computational chemistry package. TTDS and NPDS solubility in propane was modeled by the Peng−Robinson equation of state. Using a set of mixing rules with two parameters a good fitting of the experimental results was attained. Physical properties of TTDS and NPDS required for solubility modeling by the Peng−Robinson equation were calculated using estimation methods previously proposed in the literature.

Compressed isobutane as a solvent of heavy hydrocarbons

“…In this section, we will compare the solubility data of DBT, NPDS, and TTDS in isobutane with those reported for propane by our group in previous works . It should be noticed that in one of these earlier works the solubility of DBT in propane was also compared to that in carbon dioxide, the most widely used supercritical solvent .…”

“…The solid solubilities were determined in an experimental apparatus (model R100CW) supplied by Thar Technology (Pittsburgh, PA). It is schematically shown in Figure and has been described in detail elsewhere . Basically, it consists of a 0.1 L cylindrical view cell with two sapphire windows mounted 90° apart.…”

“…The experimental procedure will be only briefly presented since it has been described in detail elsewhere . A solubility experiment starts by placing the solute in the view cell.…”

“…According to all above, in this article we will report the solubilities of these compounds in isobutane at temperatures between 367 and 413 K and pressures from 3.9 to 7.5 MPa. Following, we will compare the solubility results obtained with isobutane to those reported in the literature for propane and CO 2 . Next, considering that rational process design is entirely dependent on the existence of appropriate thermodynamic models for phase equilibrium calculation at working conditions, the solubility data experimentally obtained will be modeled by the Peng – Robinson equation of state .…”

“…For this purpose, different physical characteristics of the solutes are required, like their critical constants, vapor pressures, or acentric factors. In this work, when these parameters are not found in the scientific literature, they are estimated using widely accepted methods, such as the Pitzer expansion equation for the acentric factors, the method by Wilson and Jasperson for the critical constants, and the Ambrose−Walton corresponding states method for the vapor pressures …”