How do you model supercritical fluid properties for extraction or reaction applications?

Supercritical fluids (T > Tc, P > Pc) have properties between liquid and gas: liquid-like density and dissolving power, gas-like diffusivity and viscosity. Modeling approach: cubic EOS (PR, SRK) with appropriate parameters, including binary interaction parameters fitted to high-pressure data. Solubility modeling: use fugacity coefficient from EOS, often correlated with density. Key considerations: strong pressure sensitivity near critical, CO2 co-solvent effects, temperature crossover behavior (solubility may increase or decrease with T depending on P). Applications: supercritical CO2 extraction (caffeine, essential oils), supercritical water oxidation, and particle formation (RESS, SAS). Validate against high-pressure experimental data.