Supercritical CO2 Extraction of Corn Stalk Pyrolysis Oil

Supercritical CO₂ extraction was employed to separate simulated and real bio-oil. Effects of adsorbents on enrichment were investigated for a simulated bio-oil, which is composed of acetic acid (AC), propanoic acid (PA), furfural (FR), acetylacetone (AA) and 2-methoxyphenol (MP). Extraction of spiked bio-oil shows adsorbents are able to influence extraction efficiency and selectivity. Appropriate water content in the simulated bio-oil favors in improving extraction efficiency. Extraction with methanol (or ethanol)-modified CO₂ affords higher extraction efficiency than that with pure CO₂, but might lead to lower extraction selectivities. Using 5A molecular sieve as adsorbent, the extraction efficiencies for MP, FR, PA, AA and AC under 45°C and 20.0 MPa respectively reach up to 100%, 84.9%, 57.8%, 57.1% and 22.8%. In addition, supercritical CO₂ extraction of a real bio-oil showed that water content and acidity of the bio-oil after extraction dropped significantly, suggesting remarkable upgrading in heat value and corrosiveness of the bio-oil.