Determination and Correlation of Poly(vinylpyrrolidone) Solubility in Subcritical 1,1,1,2-Tetrafluoroethane

Abstract

Poly­(vinylpyrrolidone) (PVP) is most widely used in the process of preparing a drug carrier by subcritical or supercritical fluids impregnation technology, and the design and operation conditions of the subcritical or supercritical fluids impregnation technology are based on the equilibrium solubility of PVP in subcritical or supercritical fluids. In this work, the solubility of PVP with molecular weights of 24 000 and 58 000 in subcritical 1,1,1,2-tetrafluoroethane (R134a) was measured at temperatures from 313 to 333 K and at pressures of 5.0, 7.0, 9.0, 11.0, 13.0, 15.0, and 18.0 MPa. The solubility of PVP in SCCO2 and subcritical R134a at the same experimental temperature and pressure conditions was also compared by calculating the enhancement factor (δ), finding that the solubility of PVP in subcritical R134a is much higher than that in SCCO2. Six semiempirical models (Chrastil, Adachi and Lu, Kumar and Johnston, Sung and Shim, Mendez-Santiago and Teja, and Bartle) were used to correlate PVP solubility in subcritical R134a, and the enthalpy values of PVP, including ΔH total, ΔH sub, and ΔH sol, were estimated through the Chrastil’s and the Bartle’s models.