Supercritical Fluid Extraction Machine

Supercritical fluid extraction (SFE) refers to the process of extracting specific components from liquid or solid to achieve extraction and separation by using the characteristics of supercritical fluid with high solubility of solute in supercritical state and low solubility of solute in non supercritical state.

Any pure substance, with the change of temperature and pressure, will correspondingly present three states: solid state, liquid state and gas state, which is called the three states of matter. The temperature and pressure values of the mutual transformation between the three states are called the three-phase point (as shown in the right figure). Each substance with stable chemical properties has an inherent critical point, that is, under this temperature and pressure, the density of the substance is close to its density in the liquid state, but retains the characteristics of the gas. When the temperature and pressure exceed the temperature and pressure of the critical point, the material enters the supercritical state. The material in the supercritical state is neither gas nor liquid, which is called supercritical fluid.

Although there are many substances that can be used as supercritical fluid, only a few solvents meet the requirements in terms of cheap and easy availability, low critical temperature and pressure, low latent heat of evaporation, safety and environmental protection. The substances with critical temperature within 0 ~ 100 ℃, critical pressure within 2 ~ 10MPa and low latent heat of evaporation include carbon dioxide (tc31.1 ℃, pc7.15mpa, latent heat of evaporation 25.25kj/mol), propane (tc96.8 ℃, pc4.12mpa, latent heat of evaporation 15.1kj/mol). Considering the factors of low cost, easy availability and safe use, carbon dioxide is regarded as the most suitable supercritical fluid for extraction.

The density of supercritical fluid is very sensitive to the change of temperature and pressure, and its solubility is proportional to its density within a certain pressure range. Therefore, the solubility of substances in supercritical fluid can be changed by controlling temperature and pressure. Especially near the critical point, small changes in temperature and pressure can lead to several orders of magnitude mutations in solute solubility, this provides a research basis for the feasibility of SFE technology.

Suzhou Pharma Machinery Co.,Ltd.

2022/02/09

David