# US 5,710,350 A · Process for the production of diglycerol

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- Number: US 5,710,350 A
- Document ID: US5710350A
- Status: Granted
- Kind: A
- Application number: 08/522,387
- Filed: 1995-09-25
- Granted: 1998-01-20
- Earliest claimed: 1993-03-25
- Assignees: Henkel Kommanditgesellschaft auf Aktien
- Inventors: Lutz Jeromin; Bernhard Gutsche; Reinhard Bunte; Volkmar Jordan
- Web page: https://patentgrep.com/patent/US5710350A

## CPC

- C07C 41/42: by distillation
- C07C 41/09: by dehydration of compounds containing hydroxy groups
- C07C: ACYCLIC OR CARBOCYCLIC COMPOUNDS

## 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

### Claim 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.degree. C. to 275.degree. 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.degree. 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.degree. C. to 170.degree. 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.degree. C. to 170.degree. C. to obtain a second bottom product containing more than 90% by weight of diglycerol.

### Claim 2 (depends on 1)

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

### Claim 3 (depends on 1)

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

### Claim 4 (depends on 2)

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

### Claim 5 (depends on 1)

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

### Claim 6 (depends on 1)

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

### Claim 7 (depends on 1)

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

### Claim 8 (depends on 1)

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.degree. C. to 215.degree. C. to obtain a distillate containing more than 95% by weight of diglycerol.

### Claim 9 (depends on 1)

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

### Claim 10 (depends on 1)

The process of claim 1 wherein the bottom temperature in the first distillation zone is from 130.degree. C. to 140.degree. C.

### Claim 11 (depends on 1)

The process of claim 1 wherein the reaction temperature is from 220.degree. C. to 240.degree. C.

### Claim 12 (depends on 1)

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

### Claim 13 (depends on 1)

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

### Claim 14 (depends on 1)

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

### Claim 15 (depends on 3)

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

### Claim 16 (depends on 2)

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

### Claim 17 (depends on 3)

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

### Claim 18 (depends on 2)

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

### Claim 19 (depends on 3)

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

### Claim 20 (depends on 2)

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.degree. C. to 215.degree. C. to obtain a distillate containing more than 95% by weight of diglycerol.