How to separate multi-component substances with similar boiling points?
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There is a multi-component substance whose target component has a melting point of 65 degrees Celsius, and a boiling point of 150 degrees Celsius under reduced pressure (with a pressure of around 2670 Pa). The boiling points of the impurities are 3–5 degrees higher than that of the target component at normal pressure. How should this separation be carried out in industrial production? (Note: The required content of the target component is >99%. Purification can also be achieved using steam distillation in the laboratory, but this method is not suitable for industrial production.) This target component is a pharmaceutical intermediate that remains stable at high temperatures
Try chemical adsorption, reactive removal, or extraction! !
A distillation column should work, though it may require a larger number of trays. If a suitable solvent is available, extraction can also be used. This post was last edited by ThinkfulFish on 2008-2-15 at 16:39.]
Normal distillation won’t work; extractive distillation can be used instead
If industrialization is desired, vacuum distillation can be tried; otherwise, azeotropic distillation would be an option
At atmospheric pressure, the boiling points differ by a few degrees; under reduced pressure, separation is essentially not possible. The melting point is relatively high, and if the tower is too tall, efficient separation cannot be achieved. It is best to first use physical and chemical methods for treatment before proceeding with purification
In industry, to separate substances with similar boiling points, methods such as special distillation, pressure-swapped distillation, adsorption, and pressure-swapped adsorption are used! Among these, adsorption is the one with a simpler operation.
1. Extraction method 2. Membrane separation 3. Adsorption 4. Molecular distillation 5. Absorption and desorption to obtain the target substance
A third medium is introduced: extractive distillation or azeotropic distillation.
I think it’s best to find an extractant and use extractive distillation for separation.
First of all, I would like to express my deepest gratitude to all of you! ! ! ! ! Since the impurities are its isomers or homologs, it’s very difficult to find a solvent suitable for extraction! ! ! I wonder if the steam distillation method will work? ? ? ? :handshake
Vacuum distillation (i.e., short-path distillation) can solve this problem; some manufacturers have already started using this technology. However, membrane separation is the most suitable method for separating substances with close boiling points, but it has not yet been scaled up due to its low flux. Last edited by perfect200 on 2008-2-18 17:15.]
:handshake Thank you! ! !
By how much can the melting point difference be, and can cooling be used?
The melting points are basically the same; the cooling method definitely won’t work! ! ! Additionally, the laboratory also tried the recrystallization method, but it didn’t work! ! !
Since the impurities are either homologs or isomers of the target product, extractive distillation is difficult to implement, and azeotropic distillation is also challenging; the key issue lies in the difficulty of selecting appropriate extractants and azeotropes! Molecular distillation is not widely used in industry at present, and it is mainly applied to the distillation of heat-sensitive substances, **which reduces the time during which the material is exposed to heat. Since your target component is a pharmaceutical intermediate that remains stable at high temperatures, separation can be achieved through conventional distillation; a boiling point difference of 3–5 degrees is sufficient for separation. To obtain a purity of 99%, the following factors need to be considered: 1. The concentration of the target component in the feed mixture, as well as the concentration of substances with similar boiling points. If the concentration of the target component is low while that of similar substances is high, it will be very difficult to obtain a 99% pure product using just one distillation column (the reflux ratio will be high, resulting in high operating costs). On the other hand, it may be possible to achieve this purity with one column. 2. Since the boiling point is 150 degrees Celsius under reduced pressure (with a pressure of about 2670 Pa), it is necessary to minimize the vacuum level during distillation; a packed tower should be used to reduce the pressure drop and thus lower the temperature of the reactor as much as possible. 3. Since the impurities have boiling points similar to those of the target product, reflux is relatively high; therefore, considerations should be given to energy consumption and operational costs: handshake
They’re all experts; I just can’t do it
Thank you for the advice! ! ! The target content of my product is over 95%, and I estimate that one column distillation should be sufficient to achieve this! ! ! ! ! :handshake
Isomers have similar chemical properties; only their physical properties vary slightly. Use vacuum distillation; as long as the tower is tall enough and a packed tower is used, effective separation can still be achieved.