Aphios Corporation

SuperFluids^TM

SuperFluids™ are based on advanced liquid-liquid technology using supercritical, critical or near-critical fluids such as CO2 and other binary gases. These fluids are normally gases at ambient temperature and pressure conditions and are, at times, utilized with polar cosolvents such as ethanol and methanol. As shown in the phase diagram, a compound becomes supercritical at conditions that equal or exceed both its critical temperature and pressure. These parameters are intrinsic thermodynamic properties of all sufficiently stable pure compounds and mixtures. In these regions, normally gaseous substances become dense phase fluids that exhibit greatly enhanced thermodynamic properties of solvation, selection, penetration and expansion.

Carbon dioxide, for example, becomes supercritical at conditions equal to or exceeding 31°C and 1,050 psig (70 atm). At a pressure of 3,000 psig (204 atm) and a temperature of 40°C, carbon dioxide has a density of approximately 0.8 g/cc and behaves much like a nonpolar organic solvent such as hexane, having a dipole moment of zero debyes. A supercritical fluid uniquely displays a wide spectrum of solvation power, as its density is strongly dependent upon temperature and pressure. Temperature changes of tens of degrees or pressure changes by tens of atmospheres can change a compound's solubility in a supercritical fluid by an order of magnitude or more. This unique feature allows for the fine-tuning of solvation power and the fractionation of mixed solutes. The selectivity of nonpolar supercritical, critical and near-critical fluid solvents can also be enhanced by the addition of cosolvents such as ethanol and methanol.

In addition to their unique solubilization characteristics, supercritical fluids possess other physicochemical properties that add to their attractiveness as solvents. They can exhibit liquid-like density yet still retain gas-like properties of high diffusivity and low viscosity. The latter increases mass transfer rates, significantly reducing processing times. Additionally, the ultra-low surface tension of supercritical fluids allows facile penetration into microporous materials, increasing extraction efficiency and overall yields. While similar in many ways to conventional nonpolar solvents such as hexane, it is well known that these fluids can extract a different spectrum of materials than conventional techniques. Product volatilization and oxidation as well as processing time and organic solvent usage can be significantly reduced with the use of SuperFluids™.