Preparation method of unsaturated aldehyde by aldehyde condensation

Abstract

The invention relates to a preparation process of an unsaturated aldehyde in the field of petroleum chemistry, and in particular relates to a preparation method of the unsaturated aldehyde by aldehyde condensation. The method comprises the following steps: performing chromatographic separation after a reaction mixed substance leaves a reaction region; separating the water phase containing a catalyst from an organic phase; and distilling and separating the organic phase in a distillation region so as to reduce the possibility that the mixed substance circularly undergoes a side reaction, namely cannizzaro reaction, in the process and lighten the load of the distillation region. According to the preparation method of the unsaturated aldehyde by aldehyde condensation, the water phase containing the catalyst is separated from the organic phase, so that the possibility that the mixed substance circularly undergoes the side reaction, namely cannizzaro reaction, is reduced, the reaction mixed substance is subjected to chromatographic separation before entering the distillation region, and only the organic phase is fed into the distillation region for distillation and separation, so that the load of the distillation region is lightened.

Description

technical field [0001] The invention relates to a preparation process of unsaturated aldehyde in the field of petrochemical industry, in particular to a method for preparing unsaturated aldehyde through aldehyde condensation. Background technique [0002] Aldol condensation is a well-known reaction in which when the reactant is a single aldehyde, the resulting product is an unsaturated aldehyde with twice the number of carbon atoms as the starting aldehyde. The aldol condensation reaction can use acid or alkali as a catalyst. In industry, alkali metal hydroxide (such as sodium hydroxide NaOH) is generally used as a catalyst. The reverse process of this reaction is as follows: [0003] [0004] Under the action of alkali catalyst, two molecules of aldehyde undergo dimerization to form aldol, which is further dehydrated to form unsaturated alkenal. For aldehydes with more than four carbon atoms, the reaction is a two-phase reaction due to the low mutual solubility of aldeh...

AI Technical Summary

Problems solved by technology

[0024] This method has some disadvantages: during the distillation process, the catalyst phase is heated at the same time as the organic, which is conducive to the occurrence of Cannizzaro reaction, thereby increasing the loss of raw material aldehyde, reducing the yield, and also increasing energy consumption and equipment. In order to recover the unreacted aldehyde during the distillation process, most of the aldehyde and a large amount of water are evaporated, which also consumes more heat

But there are some following disadvantages in this method: the adiabatic reactor may cause the reactor temperature to be too high, which is beneficial to the Cannizzaro reaction and the reaction that the unsaturated aldehyde of the product generates a high boiler; When the aldehyde evaporates to the top of the tower, a large amount of water and a certain amount of condensation products unsaturated aldehyde or ketone will evaporate to the top of the tower, and the organic phase containing unsaturated aldehyde will be returned to the reaction zone. Aldehydes may react to form high-boiling products, which can reduce yields

Images