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Peony Seed Oil CO2 Extraction Process

Peony seed oil is a vegetable oil whose main components are unsaturated fatty acids, including linoleic acid, linolenic acid, and oleic acid. In addition, it also contains a variety of vitamins and minerals, such as vitamin E and magnesium.

The peony seed oil has many health benefits, including antioxidant, anti-inflammatory, promoting skin health, reducing wrinkles, and more. It can also help improve cardiovascular health, boost the immune system, regulate blood sugar and blood lipids, and more.

There are many ways to extract peony seed oil, including cold pressing, supercritical extraction and so on. Among them, the cold pressing method is the most commonly used extraction method. It uses mechanical pressing to extract oil from peony seeds, which can retain the nutrients and fragrance in the oil.

peony seed CO2 oil

Supercritical CO2 extraction method

Supercritical CO2 extraction is a common and efficient method for extracting vegetable oil. The following are the general steps to extract oil from peony seeds using supercritical CO2 extraction:

  • Preparation of peony seeds: Fresh peony seeds are dried and ground into powder.
  • Adding the solvent: Put the peony seed powder into the extractor, then add a supercritical fluid solvent (usually carbon dioxide) to mix it with the peony seed powder.
  • Supercritical extraction: Heating and pressurizing the extractor makes the supercritical fluid solvent into a state of high pressure and high temperature, and quickly dissolves the oil in the peony seed powder into the supercritical fluid.
  • Separation: Put the supercritical fluid into another container, then reduce the temperature and pressure to normal temperature and pressure, make the supercritical fluid into a gaseous state, let it volatilize, and leave peony seed oil.
  • Residue removal: The residual solvent in the oil is removed to obtain the final peony seed oil.

Using supercritical CO2 extraction to extract peony seed oil can greatly improve the extraction speed and purity of oil, but the equipment and technology input costs are high. Therefore, it is usually used in the industrial field of large-scale production, rather than domestic oil production.

4 Steps of Peony Seed Oil CO2 Extraction Method

Peony seed oil, also known as peony oil, is a tree nut vegetable oil extracted from peony seeds. It is unique to China. Because of its rich nutrition and uniqueness, it is a treasure among vegetable oils.


First, select fresh, plump, and pest-free peony seeds, dry them at 45°C after removing the hulls with a dehulling machine, and measure the water content of the peony seeds to 3.5%.

Use a pulverizer to crush to certain particle size, and then use a 40-mesh mesh sieve to sieve for use. During the crushing process, the oxidation of the peony seed oil caused by overheating of crushing is prevented.

The process of supercritical CO2 extraction of essential oils

CO2 Extraction

Take one portion (1kg) into a special barrel (120 mesh stainless steel filter screens are used for both the upper and lower barrel), put the barrel into the CO2 extraction vessel, install the sealing ring, and tighten the CO2 extraction vessel cover.

Set the heating temperature of the CO2 extraction vessel, the separation vessel 1, and the CO2 extraction vessel according to the experimental process plan. When the temperature of each vessel reaches the set value, the CO2 high-pressure pump is turned on to pressurize the extraction vessel with the material.

When the CO2 extraction vessel pressure reaches the process setting value, open the stop valve behind the extraction vessel to let CO2 enter the separation vessel 1, and adjust the opening degree of the stop valve to control the CO2 flow to ensure that the extraction pressure is stable at the set value;


When the pressure in separation vessel 1 reaches the process setting value, open the shut-off valve after separation 1 to let CO2 enter the separation vessel 2.

When the pressure in separation vessel 2 reaches the process setting value, close the CO2 cylinder to the system.

Air valve, open the system circulation valve, enter the extraction circulation state, set the circulation time, and start timing.

In the circulation process, can adjust each stop valve to ensure that the pressure of each vessel is stable at the set value, or can set the automatic state to stabilize the pressure by the device.

During the extraction cycle, the extraction products are discharged from the discharge ports of separation vessel 1 and separation vessel 2 every 30 minutes, collected in a special collection bottle, and marked.

Collect the extract

When the cycle time reaches the set value, the device will automatically alarm and stop the high-pressure pump.

After the extraction products in the separation 1 and separation 2 are collected, the CO2 in the extraction kettle and the separation kettle is balanced to the intermediate storage tank, and the pressure in each kettle is balanced After that, close all valves, vent the remaining CO2 in the extraction kettle, take out the material cylinder, and pour out the residue.

The extracted products are collectively weighed and compared with the weight of the input materials to analyze the extraction yield.

3 Important Parameters for CO2 Extraction

Particle size

At an extraction temperature of 45°C, an extraction pressure of 30MPa, a CO2 flow rate of 35L/h, and an extraction time of 160min, the extraction experiments were performed on materials of different particle sizes.

When the particle size of the material is 20-30 mesh, the oil yield after extraction is the highest. Under the condition that other parameters are unchanged, the finer the particle size, the higher the oil yield after extraction.

This is because the finer the particle size of the material, the larger the contact area with the supercritical CO2 fluid, and the more adequate the extraction.

The oil extraction rate of 20-30 mesh and 30-50 mesh is not much different, which are 25.5% and 26%, respectively, indicating that when the material reaches a certain particle size, the material can fully contact the supercritical CO2 fluid, and the particle size is very important for the extraction. The impact of efficiency is getting smaller and smaller.


Under the conditions of extraction pressure of 30MPa, the CO2 flow rate of 35L/h, and extraction time of 160min, the temperature was changed to perform supercritical fluid extraction on the 20-30 mesh materials.

The rate of oil extraction first increased with the increase of temperature and then gradually decreased. The rate of oil extraction was the highest (26%) when the extraction temperature was 45°C.

The influence of temperature on the dissolution of materials in supercritical CO2 fluid is more complicated.

On the one hand, the increase in temperature reduces the density of the fluid, which affects the dissolution of the solute; on the other hand, the increase in temperature increases the volatility of the solute, which is beneficial to the solute.

In this experiment, when the extraction temperature is 40℃, the influence of the latter is greater, so the oil yield will increase when the temperature rises; when the temperature is higher than 47℃, the influence of the former factor will be greater, leading to the oil yield Decrease as the temperature increases.

CO2 pressure

Under the conditions of extraction temperature of 45℃, CO2 circulation flow rate of 35L/h, and extraction time of 160min, different pressures are used for supercritical CO2 extraction of 20-30 mesh materials.

The extraction rate of 15MPa is the lowest. As the pressure increases, The extraction rate of oil continues to increase.

When the extraction pressure reaches 30MPa, the extraction rate of oil is the highest (26%).

This is mainly because the increase in pressure leads to an increase in the density of supercritical CO2, thereby increasing the solubility of solutes. But after more than 30MPa, the extraction capacity does not change much.

Optimum peony seed Oil CO2 Extraction Process

A comprehensive investigation of various factors to obtain the optimization extraction process parameters:

Crush peony seed cuttings to 30 meshes, extraction temperature is 45℃, extraction pressure is 30MPa, separation temperature is 40℃, separation pressure is 10MPa, separation temperature is At 28°C, the second separation pressure is 6MPa, the extraction time is 160min, and the extraction rate of oil is the highest.

Peony Seed Oil CO2 Extraction Process

  • Laboratory equipment: L-06 (5L+1L)
  • Pulverization degree:30 mesh
  • Extraction pressure: 30 MPa
  • Extraction temperature: 45°C
  • Separation pressure I: 10 MPa
  • Separation I temperature: 40°C
  • Separation pressure II: 6 MPa
  • Separation II temperature: 28°C
  • Extraction time: 160 min