reactive distillation

Normal distillation separates and extracts substances based on differences in temperature rise and relative volatility, whereas reactive distillation uses chemical reactions for separation and extraction

Reactive distillation: A distillation method that involves chemical reactions; in some cases, distillation is used to accelerate the reaction, while in other cases, the reaction is used to facilitate distillation. Using distillation to promote the reaction means continuously removing the products of the reaction through distillation, in order to increase the reaction conversion rate and yield. The esterification reaction in which an alcohol reacts with an acid to produce an ester and water is a reversible reaction; when this reaction is carried out in a distillation tower, the chemical reaction takes place simultaneously with distillation, allowing the resulting ester and water to be separated in a timely manner. This allows the reaction to proceed continuously in the direction of esterification. This type of distillation carries out the chemical reaction and the separation of the product within the same equipment, thereby significantly reducing equipment investment and operating costs. However, certain conditions must be met to use this method: ① The boiling point of the product must be higher or lower than that of the reactants ； ②It does not cause an increase in adverse effects such as side reactions at the distillation temperature. Currently, it is mainly used in industry for the production of esters (such as ethyl acetate). 　　Reaction-assisted distillation involves adding a substance (a third component) to the mixture that can undergo a reversible chemical reaction with the components to be separated, in order to increase their relative volatility and facilitate the distillation process. If sodium isopropylphenate is added to mixed xylene, it reacts with p-xylene and m-xylene to form sodium p-xylenate and sodium m-xylenate. The equilibrium constants for these reactions differ significantly, which allows the relative volatility of p-xylene and m-xylene to increase greatly. This method is quite effective in increasing the relative volatility. However, its application is limited due to the difficulty in recovering and recycling the third component.