Process for the production of diglycerol

• US 5,710,350 A
• Filed: 09/25/1995
• Issued: 01/20/1998
• Est. Priority Date: 03/25/1993
• Status: Expired due to Fees

• Current Assignee: Cognis Deutschland GmbH & Co. KG (BASF SE)
• Original Assignee: Henkel KGaA (Henkel AG & Co KGaA)
• Inventors: Gutsche, Bernhard, Jordan, Volkmar, Jeromin, Lutz, Bunte, Reinhard
• Primary Examiner(s): Cintins, Marianne M.
• Assistant Examiner(s): Jones, Dwayne C.
• Application Number:
  US08/522,387
• Time in Patent Office: 848 Days
• Field of Search: 568/870, 568/869, 568/868
• US Class Current: 568/869
• CPC Class Codes: C07C 41/09 by dehydration of compounds containing hydroxy groups
• CPC Class Codes: C07C 41/42 by distillation
• CPC Class Codes: C07C 43/132 both carbon chains being substituted by hydroxy or O-metal groups

Abstract

A process for preparing diglycerol in high concentrations and high yields by partially reacting glycerol in the presence of an alkaline catalyst to form a reaction mixture containing from 10 to 15% by weight of diglycerol and separating the unreacted glycerol from the reaction mixture in a wiped film or short path first distillation zone at a reduced pressure of 0.5 to 5 mbar and distilling a bottoms product from the first distillation zone in a second distillation zone which is a short path distillation zone at a pressure of 0.05 to 0.3 mbar to obtain a second bottom product containing at least 90% by weight diglycerol. Diglycerol of higher purity can be obtained by recovering diglycerol as a distillate from a third distillation zone.

Claims

1. A process for the production of diglycerol by condensation of glycerol in the presence of a basic catalyst, at a reaction temperature of from 200°

C. to 275°

C. and concentration of the diglycerol by distillation, which comprises;

a) partially reacting glycerol, in a reaction zone, to form a reaction mixture containing 10% to 15% by weight of diglycerol;

b) terminating the reaction by cooling the reaction mixture to a temperature below 200°

C.;

c) distilling the reaction mixture in a first distillation zone which comprises a distillation zone selected from the group consisting of a wiped film evaporator zone and a short-path evaporator zone, at a pressure of 0.5 to 5 mbar and a bottom temperature of the distillation zone of 125°

C. to 170°

C. to form a first bottom product; and

d) distilling the first bottom product in a second distillation zone comprising a short path evaporator zone at a pressure of 0.05 to 0.3 mbar and a bottom temperature of 140°

C. to 170°

C. to obtain a second bottom product containing more than 90% by weight of diglycerol.

2. The process as claimed in claim 1, wherein the reaction is carried out continuously in a tube reactor containing a fixed bed of catalyst.

3. The process as claimed in claim 1 wherein the reaction is carried out continuously in a tube reactor containing inert packing elements.

4. The process as claimed in claim 2 wherein the reaction mixture is dried before distillation in the first distillation zone.

5. The process as claimed in claim 1, wherein the reaction is carried out in a stirred tank reactor.

6. The process as claimed in claim 1 wherein a distillate from the first distillation zone is returned to the reaction zone.

7. The process as claimed in claim 1 wherein a distillate from the second distillation zone is returned to the first distillation zone.

8. The process as claimed in claim 1 wherein the second bottom product from the second distillation zone is distilled in a third distillation zone comprising a short-path evaporator under a pressure not higher than 0.05 mbar and a temperature of 185°

C. to 215°

C. to obtain a distillate containing more than 95% by weight of diglycerol.

9. The process of claim 1 wherein the pressure in the first distillation zone is from 1 to 2 mbar.

10. The process of claim 1 wherein the bottom temperature in the first distillation zone is from 130°

C. to 140°

C.

11. The process of claim 1 wherein the reaction temperature is from 220°

C. to 240°

C.

12. The process of claim 1 wherein the catalyst comprises at least one member selected from the group consisting of sodium hydroxide and potassium hydroxide.

13. The process of claim 1 wherein the pressure in the second distillation zone is from 0.1 to 0.2 mbar.

14. The process of claim 1 wherein the first distillation zone comprises a wiped film evaporator.

15. The process of claim 3 wherein the reaction mixture is dried before distillation in the first distillation zone.

16. The process of claim 2 wherein a distillate from the first distillation zone is returned to the reaction zone.

17. The process of claim 3 wherein a distillate from the first distillation zone is returned to the reaction zone.

18. The process of claim 2 wherein a distillate from the second distillation zone is returned to the first distillation zone.

19. The process of claim 3 wherein a distillate from the second distillation zone is returned to the first distillation zone.

20. The process of claim 2 wherein the second bottom product is distilled in a third distillation zone comprising a short path evaporator at a pressure not higher than 0.05 mbar and a temperature of 185°

C. to 215°

C. to obtain a distillate containing more than 95% by weight of diglycerol.