Method for the combined production of polyols in the presence of an inorganic base
The present invention relates to a process for simultaneously consecutive preparation of polyols by base-catalyzed reaction of at least two different mid-chain aldehydes with formaldehyde. The simultaneous consecutive mode of operation makes it possible to achieve high conversions and high selectivities for both aldehydes, with additional achievement of a distinct reduction in the amount of unreacted formaldehyde remaining. This leads to improved process economics, since the energy costs for workup of the formaldehyde stream are distinctly reduced.
1. A process for simultaneously consecutive preparation of at least two different polyols by reaction of aliphatic aldehydes with formaldehyde in the presence of an inorganic base, characterized in that, in a 1st process step, an aliphatic C2-C9 aldehyde is reacted with formaldehyde in the presence of an inorganic base and, without workup of the reaction solution, in a 2nd process step, the reaction solution from the 1st process step is converted further with addition of at least one aliphatic C2-C9 aldehyde other than the aldehyde from the 1st process step.
2. The process according to claim 1 , wherein, in the 1st process step, an aliphatic C2-C9 aldehyde unbranched in the 2 position is reacted, and, in the 2nd process step, an aliphatic C2-C9 aldehyde branched in the 2 position.
3. The process according to claim 1 , wherein the aldehyde used in the 1st process step is selected from the group consisting of n-propanal, n-butanal, valeraldehyde, and the aldehyde used in the 2nd process step is i-butanal.
4. The process according to claim 1 , wherein the 1st and 2nd process step are conducted at a temperature of greater than or equal 10° C. and less than or equal 105° C.
5. The process according to claim 1 , wherein, in the 2nd process step, an inorganic base is additionally added to the reaction solution.
6. The process according to claim 5 , wherein the same inorganic base is used in the 1st and 2nd process step.
7. The process according to claim 1 , wherein the inorganic base is selected from the group consisting of NaOH, KOH, Ca(OH) 2 or mixtures thereof.
8. The process according to claim 1 , wherein the molar ratio of inorganic base to aliphatic aldehyde in the two process steps is greater than or equal 1:1 and less than or equal 1.6:1.
9. The process according to claim 1 , wherein the formaldehyde is added in the 1st process step in the form of an aqueous formaldehyde solution having a formaldehyde content of greater than or equal 5% by weight and less than or equal 50% by weight.
10. The process according to claim 1 , wherein the molar ratio of formaldehyde to aliphatic aldehyde in the first process step is greater than or equal 3.1:1 and less than or equal 12:1 and the molar ratio of formaldehyde to aliphatic aldehyde in the 2nd process step is greater than or equal 2.1:1 and less than or equal 7:1.
11. The process according to claim 1 , wherein formaldehyde is added only in the 1st process step.
12. The process according to claim 1 , wherein the addition of at least one reactant in the 1st and/or in the 2nd process step is effected stepwise.
13. The process according to claim 12 , wherein the aliphatic aldehyde in the 1st process step is added stepwise to the reaction mixture.
14. The process according to claim 1 , wherein the conversion of aldehyde in the reaction mixture at the end of the 1st process step is greater than or equal 50%.
15. The process according to claim 1 , wherein the reactant volume throughput per unit reactor volume and time (V/Vh) in the two process steps is greater than or equal 0.3 and less than or equal 4.0.
16. The process according to claim 2 , wherein an inorganic base is additionally added to the reaction solution in the 2nd process step.
17. The process according to claim 2 , wherein the molar ratio of inorganic base to aliphatic aldehyde in the two process steps is greater than or equal 1:1 and less than or equal 1.6:1.
18. The process according to claim 2 , wherein formaldehyde is added only in the 1st process step.
19. The process according to claim 2 , wherein the aliphatic aldehyde in the 1st process step is added stepwise to the reaction mixture.
20. The process according to claim 1 , wherein formaldehyde is added only in the 1st process step; the aliphatic aldehyde in the 1st process step is selected from the group consisting of n-propanal, n-butanal, and valeraldehyde and is added stepwise to the reaction mixture; the aliphatic aldehyde in the 2 nd process step is i-butanal; an inorganic base is additionally added to the reaction solution in the 2nd process step; the molar ratio of inorganic base to aliphatic aldehyde in the two process steps is greater than or equal 1:1 and less than or equal 1.6:1; and the reactant volume throughput per unit reactor volume and time (V/Vh) in the two process steps is greater than or equal 0.3 and less than or equal 4.0.