Technical Principle: Selective Dissolution in the Supercritical State
When carbon dioxide is maintained above its critical point-with a temperature exceeding 31.1°C and pressure above 7.38 MPa-it enters a supercritical fluid state. This unique phase combines the penetrability of a gas with the solvating power of a liquid, allowing it to permeate deep into plant cell structures and selectively dissolve low-molecular-weight aromatic compounds such as terpenes, aromatic esters, and phenols. In contrast, it remains inert toward macromolecular impurities like proteins and polysaccharides. Throughout the process, carbon dioxide acts solely as a physical medium and does not undergo chemical reactions, thereby preserving the natural integrity of the fragrance components.
Carbon dioxide itself meets food-grade safety standards and exhibits properties including chemical inertness, non-flammability, and non-explosiveness. Within a closed-loop system, its recovery rate can exceed 95%, achieving zero solvent residue in the production process and meeting the highest safety requirements for raw materials in the pharmaceutical, food, and cosmetics industries.
Standard Process Flow
1. Raw Material Pretreatment
Raw materials are washed, dried at low temperatures, and then crushed to a particle size of 40–60 mesh. Proper crushing disrupts plant cell wall structures and establishes efficient mass transfer channels. For instance, crushing clove buds increases the exposure rate of their internal oil glands by approximately 70%, significantly reducing the subsequent extraction time.
2. Supercritical Phase Transformation
Liquid carbon dioxide is pressurized by a high-pressure pump and precisely temperature-controlled using a heat exchanger to form a stable supercritical fluid phase within the extraction vessel. The system employs a PID control system to limit parameter fluctuations to within ±0.5°C and ±0.2 MPa, providing a stable phase environment for efficient extraction.
3. Dynamic Circulation Extraction
The supercritical fluid circulates through the raw material bed at a flow rate of 3–5 L/min, conducting continuous extraction for 1–3 hours under mild conditions (35–55°C and 10–30 MPa). During this stage, system pressure is maintained by a back-pressure valve, while the concentration of the outflow is monitored in real time to accurately determine the extraction endpoint.
4. Fractional Separation and Medium Recovery
The fluid containing the target components enters a two-stage separation vessel, where components of different polarities are precipitated stepwise through gradient pressure reduction. The separated carbon dioxide is condensed and liquefied before being returned to the storage tank, completing the medium cycle. The single-cycle loss rate in typical industrial-scale equipment is less than 3%.
Industrial Application Value
This technology offers significant advantages in the field of natural fragrances: For heat-sensitive fragrances (e.g., jasmine absolute and tuberose concrete), the retention rate of aromatic components is over 40% higher than that achieved by traditional distillation methods. In terms of selective extraction, targeted enrichment of specific components can be realized by adjusting pressure and temperature parameters. The entire production process complies with green chemistry principles and generates no wastewater or exhaust emissions.
With the growing consumer demand for "clean label" products, supercritical carbon dioxide extraction technology is rapidly expanding from high-end applications to mainstream markets. This technology not only ensures the natural attributes and safety standards of fragrance products but also provides manufacturers with an industrialized solution that balances economic efficiency and environmental sustainability-representing the future direction of natural product extraction technology.