Solubility of Sulfur in Supercritical Propane-Butane Mixture

The phase equilibrium of the propane-butane-sulfur system is studied using a high-pressure optical cell in the temperature range 403-443 K and pressure from 5.3 to 24.5 MPa, and the phase behavior is found to be of type V. The solubility of sulfur in a supercritical propane-butane mixture is estimated from the characteristics of the vapor branch of the phase equilibrium of the propane-butane-sulfur system and described by the Peng-Robinson equation of state in combination with the Mukhopadhyay-Rao mixing rule. It is determined that the propane-butane mixture in the supercritical fluid (SCF) state not only has good extraction properties but also allows us to desulfurize commercial hydrocarbons. For example, reducing the pressure from 25 to 7 MPa makes it possible to decrease the sulfur content in the product by 50% in the 413 K isotherm and by a factor of 10 in the 443 K isotherm.