Determination of crossover pressure for cedarwood oil in carbon dioxide

Abstract

Solubility experiments were conducted to determine the crossover pressure for cedarwood oil (CWO) in CO2. A stirred reactor with an in-line loop connected to a GC was used. Two temperatures (25 °C and 85 °C) with nine pressures (6.9, 10.3, 13.8, 17.2, 20.7, 24.1, 27.6, 31.0, and 34.5 MPa) were tested. The GC-FID counts were used to measure CWO solubility and composition. Below 20.7 MPa, the solubility of CWO was higher in liquid CO2 (25 °C) than supercritical CO2 (85 °C). The crossover pressure for CWO in CO2 was calculated to be 23.7 MPa. The solubility isotherms for CWO in CO2 were similar to those for triglycerides in CO2, although the crossover pressure for CWO was much lower. An experiment was also conducted monitoring CWO extracted from Eastern red cedar sawdust spiked with CWO. The calculated crossover pressure from these extractions was significantly lower (18.5 MPa) than that determined from the stirred reactor experiments.