Supercritical CO2

What is supercritical CO2 ?

Carbon dioxide (CO2) is known to the general public as a component of the air we breathe. It is also found as a gas in aerated water and soft drinks. Dry ice is CO2 in solid form and is used to keep medicines at a temperature of about -80°C during transport. Liquid CO2 is also used in everyday life in fire extinguishers and preservation of food. Carbon dioxide is widely used in the three known phase states: gas, liquid and solid. However, there is a fourth phase state that we can use: the supercritical state.
When carbon dioxide has a temperature above 31 °C and a pressure above 73.8 bar it is in a supercritical phase. In this phase CO2 has the properties of both gas and liquid. 
As a gas, supercritical CO2 will expand until the container it is in is completely filled. It also has the viscosity of a gas which allows supercritical CO2 to flow through the smallest pores. 
As a liquid, supercritical CO2 has the ability to absorb chemical components. This allows it to be used as a solvent for certain chemicals just like hexane, for example.

Compared to conventional solvents (e.g. hexane), supercritical CO2 has the advantage of being considered a green solvent. Carbon dioxide is considered safe because it is non-flammable and has a high chemical inertness. It is a relatively inexpensive product that is also easy to recycle. It is also ideally suited for extraction of temperature- and oxidation-sensitive substances.

What is supercritical CO2 extraction?

Supercritical CO2-extraction is the process of using supercritical CO2 to extract certain substances. This is done using a purpose-built extractor. 

1     The central part of the

extractor is the extraction vessel. It contains the material from which one wants to extract. 


2    The extraction vessel is located in an oven or is heated directly to the correct temperature.



3   The pump brings the gas from the CO2 storage to the extraction vessel and the pressure regulator (on the back of the extraction vessel) is used to place the CO2 at the correct pressure. 

4    Once the temperature and pressure in the extraction vessel are high enough, the CO2 will be in a supercritical state and the extract can be absorbed by the CO2.

5    The CO2 with the extract leaves the extraction vessel at the other end. After the pressure regulator, the pressure of CO2 is lowered causing it to go back into gas state. 

6     The extract is released and left behind in a collection tank. After extraction, the CO2 gas can be captured for reuse.


Equipment

The platform currently has two installations in operation.

The Waters MV10-ASFE is a computer-controlled extractor on an analytical scale. The extraction vessels have volumes of 10 mL and 25 mL, making the extraction process short. Extracts are collected directly or dissolved in a solvent for immediate analysis. The MV10-ASFE is very suitable for exploratory research and process optimisation.
The SFT-150 from Supercritical Fluids is a laboratory-scale extractor. The extraction vessels have volumes from 100mL to 2L. Because of the larger volumes, the extractions take longer, but the quantity of extract is also larger. Therefore, the extracts can be used for further research or development.

The combination of these two devices makes it possible to develop upscaling models.

In addition to these two devices for extraction, the platform has the necessary techniques and equipment for sample preparation and analysis of the extracts.

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