I have questions about extractants for everyone
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I would like to ask my colleagues from Sichuan: I need to separate two components, A and B, from a near-boiling-range mixture, where A has a lower boiling point and is therefore a more volatile component. To separate A and B, I plan to use an extractant C. I wonder whether the addition of this extractant will necessarily change the volatility of the original components Does adding an extractant necessarily cause the B substance with a high boiling point to become a volatile component and emerge from the top of the tower?
Extraction is a separation method that takes advantage of the difference in solubility of two substances in an extractant, and it has nothing to do with volatile components
The compound is transferred from one solvent to another by taking advantage of the difference in its solubility or distribution coefficient in two immiscible (or slightly soluble) solvents. After repeated extractions, the vast majority of the compounds were extracted. During extraction, the greater the difference in distribution coefficients of various components between the two-phase solvents, the higher the separation efficiency.
Let me introduce a special case related to the supercritical state: Supercritical fluid extraction is the most advanced physical extraction technique available worldwide, abbreviated as SFE (supercritical fluid extraction). At lower temperatures, as the pressure of the gas is increased, the gas transforms into a liquid. As the pressure rises further, the volume of the liquid increases. For any given substance, there exists a critical temperature (Tc) and a critical pressure (Pc); above these values, the substance will neither be in a liquid nor a gas state. This point is known as the critical point. In the range above the critical point, the state of matter lies between gas and liquid; the fluid in this range is known as a supercritical fluid (SF). Supercritical fluids possess strong penetration similar to that of gases, as well as high density and solubility similar to those of liquids; they have excellent solvent properties and can be used as solvents for extraction and the separation of monomers. Supercritical fluid extraction is a high-tech method that has emerged in modern chemical separation processes. SFE combines traditional distillation with organic solvent extraction, taking advantage of the excellent solvating power of supercritical CO2 to effectively separate, extract, and purify the matrix from the extract. SFE uses supercritical CO2 to extract materials. CO2 is a safe, non-toxic, and inexpensive liquid. Supercritical CO2 possesses a diffusion coefficient similar to that of a gas, as well as the solvating power of a liquid; it has zero surface tension, allowing it to penetrate solid materials rapidly in order to extract their essential components. It features high efficiency, resistance to oxidation, being natural in origin, and containing no chemical pollutants. Supercritical fluid extraction and separation technology takes advantage of the fact that the solvating power of supercritical fluids is closely related to their density; by changing the pressure or temperature, the density of these supercritical fluids can be altered significantly. In the supercritical state, the supercritical fluid is brought into contact with the substance to be separated, allowing it to selectively extract components with different polarities, boiling points, and relative molecular masses one after another.
The original poster has mixed up the definitions! ! ! ! ! !
I’m only looking at the aspect of distillation with extraction; after adding an extractant, the high-boiling-point substances come out from the top of the tower
Thank you very much. While reviewing literature on extractive distillation, I found that with the addition of an extractant, the high-boiling-point substances came out of the top of the tower, while the low-boiling-point substances and the extractant remained in the bottom of the tower