Solubility, in supercritical carbon dioxide, of paraffin waxes used as binders for low-pressure injection molding

Paraffin waxes, commonly used as binders in ceramic-forming processes, can be removed from ceramic bodies with supercritical carbon dioxide. Therefore, the solubility of three industrial paraffin waxes (melting at 42, 52, and 62 degrees C, respectively) in supercritical CO2 was investigated. The concentrations of these paraffin waxes in the solvent-rich phase in equilibrium with the paraffin-rich phase were measured at 343 Kin the pressure range 12-30 MPa by using infrared absorption spectroscopy. Some n-alcane-CO2 binaries were also investigated. A model was developed by analogy with polydisperse polymers in solvents. It relates the concentration of the paraffin waxes to the concentration of the pure n-alcanes for n-alcane-CO2 binary systems. This model gives accurate overall concentration values for paraffin-CO2 mixtures and reproduces the n-alcane distribution in the solvent-rich phase.