Study on the Solid-Liquid Equilibrium of Triphenylphosphine in Four Mono-Solvents and Two Mixed Solvents

The gravimetric method was used to determine the solubility of triphenylphosphine in four mono-solvents (acetonitrile, tetrahydrofuran, cyclohexane, ethyl acetate) and two binary mixed solvents (acetonitrile + tetrahydrofuran, ethyl acetate + tetrahydrofuran) at normal pressure and temperature range (288.15 K-328.15 K). The results show that the solubility of triphenylphosphine in the selected solvent increased with the increase of temperature within the temperature range studied. In the binary mixed solvent (ethyl acetate + tetrahydrofuran, acetonitrile + tetrahydrofuran), the solubility of triphenylphosphine increased with the increase of the mass fraction of tetrahydrofuran. In addition, the Hansen solubility parameter (HSP) was used to explain the dissolution behavior of triphenylphosphine. The solubility data were fitted by the modified Apelblat equation, van't Hoff equation, λh equation, Apelblat-Sun equation and NRTL model. The results show that the modified Apelblat equation and van't Hoff equation have a better fitting effect on the solubility data of triphenylphosphine in the mono-solvents used in the experiment, and the modified Apelblat equation has a better fitting effect on the solubility data of triphenylphosphine in the binary mixed solvent used in the experiment. The fitting results can provide some basic data for the optimization of the crystallization process of triphenylphosphine. The thermodynamic properties of the dissolution process of triphenylphosphine in the selected solvent were calculated and discussed by van't Hoff equation, and the thermodynamic properties of the solution (ΔdisH, ΔdisS and ΔdisG) were all positive values, which increased that the mixing and dissolution of triphenylphosphine in the selected solvent are endothermic and entropy-driven. This study can provide basic thermodynamic data for the crystallization and industrial separation of triphenylphosphine.