What are extractive distillation and azeotropic distillation?
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What are extractive distillation and azeotropic distillation?
Extractive distillation is a commonly used experimental method in chemistry for separating liquid mixtures. Its principle relies on the difference in solubility or distribution coefficients of compounds in two immiscible (or slightly soluble) solvents, allowing the compounds to be transferred from one solvent to another. After multiple extractions, the vast majority of the compounds were extracted. When the relative volatilities of the components in the solution are similar, a third component (referred to as a carrier or separator) is added to form a new minimum azeotrope with one of the components in the original mixture, thereby increasing the relative volatilities between the components. As a result, a new minimum azeotrope and another component are obtained at the top and bottom of the column, allowing the original mixture to be separated.
Azeotropic distillation is a type of multi-component distillation for non-ideal solutions, in which an azeotrope-forming agent S is added to the original solution so as to form a minimum (maximum) azeotrope with at least one component in the solution, thereby increasing the difference in relative volatility between the original components. The boiling point remains unchanged. Extractive distillation is used when two solutions are difficult to separate; an extractant is added during distillation, and this extractant carries away one of the solutions, thereby achieving separation. Then just separate the extractant from that solution. The key is the selection of the extractant
Azeotropic distillation is a type of multi-component distillation for non-ideal solutions, in which an azeotrope-forming agent S is added to the original solution so as to form a minimum (maximum) azeotrope with at least one component in the solution, thereby increasing the difference in relative volatility between the original components. The boiling point remains unchanged. Extractive distillation is used when two solutions are difficult to separate; an extractant is added during distillation, and this extractant carries away one of the solutions, thereby achieving separation. Then just separate the extractant from that solution. The key is the selection of the extractant