Continuous process for the production of lower alkyl esters

• US 5,514,820 A
• Filed: 02/03/1994
• Issued: 05/07/1996
• Est. Priority Date: 09/29/1989
• Status: Expired due to Term

• Current Assignee: Cognis IP Management GmbH (BASF SE)
• Original Assignee: Henkel KGaA (Henkel AG & Co KGaA)
• Inventors: Assmann, Georg, Gutsche, Bernhard, Blasey, Gerhard, Armengaud, Rene, Rigal, Jean, Jeromin, Lutz, Cormary, Bernard
• Primary Examiner(s): Dees, Jose G.
• Assistant Examiner(s): Carr, Deborah D.
• Application Number:
  US08/191,746
• Time in Patent Office: 824 Days
• Field of Search: 554/167
• US Class Current: 554/167
• CPC Class Codes: B01J 19/242 in series
• CPC Class Codes: B01J 2219/00103 in a heat exchanger separate from the reactor
• CPC Class Codes: B01J 2219/00166 controlling the residence time inside the reactor vessel
• CPC Class Codes: B01J 2219/00168 controlling the viscosity
• CPC Class Codes: B01J 2219/00171 controlling the density
• CPC Class Codes: C07C 67/03 by reacting an ester group with a hydroxy group
• CPC Class Codes: C07C 69/24 esterified with monohydroxylic compounds

Abstract

The invention relates to a continuous process for the production of lower alkyl esters at temperatures of up to 100° C. and under pressures of up to 10 bar by reaction of fatty acid triglycerides containing less than 1% free fatty acid with a lower alcohol in two stages in the presence of a homogeneous alkaline catalyst, the glycerol formed being removed after the first stage. To enable the process to be carried out with high yields and with lower maintenance, investment and energy costs than in the prior art, the reaction mixture is passed through a reactor and a following static separator only once in each stage, tube reactors are used as the reactors and the Reynolds number of the flow of the reaction mixture is greater than 2,300.

Claims

1. In a process for the manufacture of lower alkyl esters by the reaction of fatty acid triglycerides containing less than 1% free fatty acid with a lower alcohol at a temperature up to 100°

C. and at a pressure up to 10 bar in the presence of a homogeneous alkaline catalyst, the improvement wherein the reaction mixture is passed through at least two stages in which in each stage the reaction mixture is passed through a single horizontally oriented tubular reactor and a following static separator in which glycerol is removed from the reaction mixture, and wherein the Reynolds number of the flow of the reaction mixture at the entrance of the first tubular reactor is greater than 2,300, the Reynolds number being calculated from the formula ##EQU4## in which Re is the Reynolds number, ζ

is the density of the mixture, v is the average tube velocity, d is the internal tube diameter and η

is the viscosity of the mixture.

2. The process of claim 1 wherein the Reynolds number is greater than 4,000.

3. The process of claim 1 wherein the Reynolds number is greater than 10,000.

4. The process of claim 1 wherein the residence time of the reaction mixture in the static separators is from 0.1 to 5 hours and wherein the reaction mixture is kept at the reaction temperature in the static separators.

5. The process of claim 4 wherein the lower alcohol is methanol and the residence time of the reaction mixture in the static separators is from 1 to 2 hours.

6. The process of claim 1 wherein the static separators are tubular horizontal separators into one end of which the reactor mixture enters, then separates into an ester upper phase and a glycerol lower phase, and the two phases leave separately at the opposite end from which the reaction mixture enters.

7. The process of claim 1 wherein the residence time of the reaction mixture in each tubular reactor is from 1 to 10 minutes.

8. The process of claim 1 wherein the lower alcohol is methanol and the residence time of the reaction mixture in each tubular reactor is from 2 to 5 minutes.

9. The process of claim 1 wherein in each stage the lower alcohol and fatty acid triglycerides are present in a ratio of from 4.5 to 7.5 mols of alcohol per mole of triglycerides.

10. The process of claim 9 wherein the lower alcohol is methanol and said ratio is from 5.1 to 6.9 mols of methanol per mole of triglycerides.

11. The process of claim 1 wherein the total concentration of alkaline catalyst in the at least two stages is less than 0.25% by weight, based on the weight of neutral triglycerides, and wherein the total quantity of alkaline catalyst and lower alcohol used in the process is divided among the stages so that a conversion to lower alkyl ester of at least 85% is obtained in each stage.

12. The process of claim 1 wherein the reaction mixture used in the first stage is mixed prior to use in a static mixer.

13. The process of claim 1 wherein the lower alcohol is methanol;

the Reynolds number is greater than 10,000;

the residence time of the reaction mixture in each tubular reactor is from 2 to 5 minutes and the residence time of the reaction mixture in the static separators is from 1 to 2 hours;

the static separators are tubular horizontal separators; and

the ratio of methanol to triglycerides in each stage is from 5.1 to 6.9 moles of methanol per mole of triglycerides.