Producing α,β-unsaturated aldehydes by means of a reaction mixing pump
View Patent ↗The invention relates to a method for producing α,β-unsaturated aldehydes, wherein a catalytic aldol condensation of charged aldehydes is carried out in the presence of an aqueous base within a continuous-flow reactor. The aim of the invention is to provide a method for aldolizing aldehydes that can be carried out in a particularly economical manner. The aim is achieved by using a reaction mixing pump as the reactor.
1. A process for preparing an α,β-unsaturated aldehyde, comprising:
reacting, in a catalytic aldol condensation in a reactor, a starting aldehyde, in presence of an aqueous base, and
maintaining continuous flow through the reactor during reacting,
wherein the reactor is a reaction mixing pump.
2. The process of claim 1 , wherein the reaction mixing pump comprises:
a) a fixed pump housing,
b) an impeller configured to rotate in the pump housing and comprising a plurality of radially extending mixing chambers which are open in a direction of a circumference of the impeller,
c) a mixing channel which encloses the mixing chambers and extends within the pump housing along the circumference of the impeller,
d) an inlet for a reaction starting material,
e) an outlet for a reaction product, the outlet connected to the inlet, thereby allowing fluid flow by the mixing channel, and
f) a motor configured to rotate the impeller.
3. The process of claim 2 , further comprising:
adding the starting aldehyde and the aqueous base through a joint inlet or separate inlets into the mixing channel while the impeller is rotating,
wherein catalytic aldol condensation occurs within the mixing channel and
the α,β-unsaturated aldehyde leaves the mixing channel through the outlet.
4. The process of claim 3 , wherein the catalytic aldol condensation is exclusively within the mixing channel.
5. The process of claim 3 , wherein the impeller rotates at a circumferential velocity greater than an average flow velocity of a reaction mixture along the mixing channel.
6. The process of claim 3 , wherein the catalytic aldol condensation comprises maintaining a temperature in the mixing channel of from 50 to 180° C.
7. The process of claim 3 , wherein a mass ratio of the aqueous base to the starting aldehyde in the inlet is from 20 to 400.
8. The process of claim 3 , wherein a residence time in the reaction mixing pump is from 0.1 to 2 seconds.
9. The process of claim 3 ,
wherein the starting aldehyde comprises a pentenal and the α,β-unsaturated aldehyde comprises a decenal.
10. The process of claim 9 , wherein the starting aldehyde is a C 5 -aldehyde mixture having an n-pentanal content of at least 90% by mass.
11. The process of claim 10 , wherein the starting aldehyde is a C 5 -aldehyde mixture having an n-pentanal content of at least 95% by mass.
12. The process of claim 9 , wherein a temperature in the mixing channel is from 110° C. to 140° C.
13. The process of claim 9 , wherein a mass ratio of the aqueous base to the starting aldehyde in the inlet is from 40 to 240.
14. The process of claim 9 , wherein a residence time in the reaction mixing pump is from 0.1 to 1.5 seconds.
15. The process of claim 9 , further comprising:
phase separating the reaction product at a temperature of from 70 to 120° C.
16. The process of claim 3 , wherein the aqueous base is an alkali metal hydroxide.
17. The process of claim 16 , wherein the aqueous base comprises sodium hydroxide.
18. The process of claim 17 , further comprising:
discharging a portion of the sodium hydroxide of the catalytic aldol condensation to obtain a recycled sodium hydroxide mixture, and
introducing fresh sodium hydroxide and the recycled sodium hydroxide mixture into the reaction mixing pump,
wherein the recycled sodium hydroxide mixture comprises a sodium salt of a carboxylic acid,
the starting aldehyde comprises a pentenal, and
the α,β-unsaturated aldehyde comprises a decenal.
19. The process of claim 9 , wherein a pressure of the catalytic aldol condensation is from 0.1 to 2 MPa.