Supercritical CO2 extraction of thyme essential oil
Process conditions for preparing thyme essential oil by supercritical carbon dioxide
Laboratory equipment: HA120-50-01
Extraction pressure: 25 MPa
Extraction temperature: 40°C
Extraction time: 240 min
The experimental results show that the process conditions for preparing thyme essential oil by supercritical carbon dioxide are: extraction pressure 25 MPa, extraction temperature 40 ℃, and extraction time 4 h. Under these conditions, the extraction yield was 4.2 2%.
Accurately weigh 200g of crushed thyme raw material, put it into the extraction tank, pass CO2 under supercritical state, the flow rate is 25L / min, and change the extraction pressure and extraction time at different temperatures to continuously extract and extract thyme. The material enters the separation tank for separation. After CO2 is vaporized, it is recycled and the extract is released from the bottom of the separation tank. Weigh and calculate the yield.
Results and analysis:
The effect of extraction pressure on the yield of thyme extract at different temperatures The extraction pressure increases, the CO 2 density increases, the solubility of the solute increases, which is beneficial for extraction, but on the other hand, the diffusion coefficient of the solute will decrease, which is not good for Extraction, usually, the former plays a leading role. When the extraction time is 4h and the CO2 flow rate is 25L / min, the effect of extraction pressure on the yield of extracts at different temperatures is shown in Figure 1.
At different temperatures, as the extraction pressure rises, the yield of the extract will increase, but after the pressure rises to a certain level, the increase in the yield of the extract will start to slow down. When it reaches 2 5 MP a, the yield will increase. Basically no more increase, at this time the extraction yield was 4.22%. Under the same extraction pressure, the temperature is high, and the basic yield is also high. When the temperature is 40 ° C, the extract yield is the highest. If the temperature is too high, the yield will decrease. This is because the temperature rise increases the diffusion coefficient of the substance, and the mass transfer speed of the fluid is accelerated, which is conducive to extraction; on the other hand, the temperature rise will cause the density of the fluid to decrease, which will reduce the ability to dissolve organic matter, which is not conducive to extraction. Comprehensive consideration, it is more appropriate to choose an extraction pressure of 25 M Pa and an extraction temperature of 40 ° C.
Effect of extraction time on the extraction effect of thyme:
When the extraction pressure is 25 MPa and the CO2 flow rate is 25 L / min, the effect of extraction time on the yield of the extract is shown in Figure 2.
At the beginning of the extraction, with the extension of the extraction time, the extraction yield showed a rapid increase trend. After 3 h, the yield increase tended to decrease, and after 4 h, the extraction yield basically did not increase, so the extraction time should be 4 h.The SFE-CO 2 method has a simple process, low temperature, strong extraction selectivity, and no solvent residues. Thyme essential oil with pure aroma and excellent performance can be obtained. The product yield can be as high as 4.22%, which has a good application prospect. < p> The experimental results show that the process conditions for preparing thyme essential oil by supercritical carbon dioxide are: extraction pressure 25 MPa, extraction temperature 40 ℃, and extraction time 4 h. Under these conditions, the extraction yield was 4.2 2%.