Vapor–liquid equilibria and volume expansion of the tetrahydrofuran/CO2 system: Application to a SAS-atomization process

Using the synthetic method, vapor–liquid equilibria near the critical points of tetrahydrofuran (THF)/carbon dioxide mixtures were determined at 313 K, 323 K and 333 K and at pressures from 6 MPa to 10 MPa. The volume expansion of THF in high-pressure CO2 was measured in a high-pressure view cell at 308 K, 313 K and 318 K and at pressures from 1 MPa to 8 MPa. The correlation of the experimental VLE data with the Peng–Robinson equation of state and the Panagiotopoulos–Reid (P&R) mixing rules described better the experimental data than the same equation of state with the van der Waals one-fluid mixing rules. On the contrary, prediction of volume expansion data with van der Waals mixing rules agreed better with experimental data at low pressures than those predicted with the P&R mixing rules. The hydrogenated palm oil (HPO)/THF/CO2 system was studied to produce particles of HPO using a supercritical antisolvent (SAS) atomization process. Results indicate that the morphology of the produced HPO particles ranged from spheres to fibers. A discussion is presented on the effects of the initial state of the CO2/THF mixture on the particle morphology based on the phase equilibrium behavior around the critical points of the binary THF/CO2 mixtures, the atomization, and a differential scanning calorimetry (DSC) investigation. This discussion suggests that the initial state of the feed mixture determines the morphology of the produced particles—a two-phase vapor–liquid mixture favors the production of spheres due to atomization, whereas a mixture in a SCF state favors the formation of fibers due to crystallization.