Acraldehyde recovering method

Abstract

The present invention is a method of separating and recovering unreacted acraldehyde from the reacted liquid of hydrolyzing acraldehyde to prepare 3-hydroxy propionic aldehyde. The recovering process includes preheating an aqueous solution of 3-hydroxy propionic aldehyde with 2-10 wt% of acraldehyde to 50-75 deg.C; and treating in the middle part of a refining tower under the solution speed of 0.1-2.0 m / hr and vacuum degree of 0.066-0.092 MPa while introducing inert gas of 5-25 times the volume of the aqueous solution and heated to 50-75 deg.C from the bottom of the tower; cooling the distrilled liquid from the top of the tower to obtain the aqueous, solution of rich acraldehyde content. The said method can reduce the consumption of acraldehyde and prolong the service life of the catalyst.

Description

Technical field: [0001] The invention relates to a method for separating and recovering unreacted acrolein from the reaction liquid produced in the reaction process of preparing 3-hydroxypropanal by hydration of acrolein. Background technique: [0002] At present, the recovery of acrolein basically adopts traditional fractionation and rectification methods. Due to the active chemical properties of acrolein and 3-hydroxypropanal, the recovery rate is very low. Generally, the acrolein hydration reaction is carried out under the action of an acidic catalyst. The reaction is a reversible reaction. The 3-hydroxypropionaldehyde aqueous solution produced contains about 2-10% unreacted acrolein by weight. If this part of acrolein is not added Recycling will form a variety of by-products in the next step of 3-hydroxypropanal hydrogenation reaction, which will rapidly reduce the activity of the hydrogenation catalyst, affect the life of the hydrogenation catalyst, and increase the con...

AI Technical Summary

Problems solved by technology

Generally, the acrolein hydration reaction is carried out under the action of an acidic catalyst. The reaction is a reversible reaction. The 3-hydroxypropionaldehyde aqueous solution produced contains about 2-10% unreacted acrolein by weight. If this part of acrolein is not added Recovery will form a variety of by-products in the next hydrogenation reaction of 3-hydroxypropionaldehyde, which will rapidly reduce the activity of the hydrogenation catalyst, affect the life of the hydrogenation catalyst, and increase the consumption quota

With the distillation of acrolein, 3-hydroxypropanal will decompose into acrolein and water, and 3-hydroxypropanal is very unstable, and it is easy to undergo polymerization and condensation reactions by itself or with acrolein under heated conditions, resulting in The content of acrolein in the 3-hydroxypropanal hydration solution is difficult to reduce to meet the requirements of hydrogenation, and the separated liquid is not suitable as a raw material for hydrogenation because it contains high polymers, so the existing methods are not suitable for separating acrolein in the aqueous solution of 3-hydroxypropanal acrolein

U.S. Patents US3518310, US5015789, US5093537, and US6140543 all mentioned the use of a thin-film evaporator to separate acrolein in the 3-hydroxypropionaldehyde hydration solution, and shorten the contact time between the hydration solution and the heat source as much as possible to avoid side reactions. The recovery rate of aldehyde has been improved, but the investment of thin-film evaporator equipment required is large, and the operation is also relatively difficult

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