CN115745773A

CN115745773A - Method for preparing fatty acid by using fatty acid monomethyl ester

Info

Publication number: CN115745773A
Application number: CN202211511697.XA
Authority: CN
Inventors: 孟永财; 孟爱国
Original assignee: Individual
Current assignee: Individual
Priority date: 2022-11-29
Filing date: 2022-11-29
Publication date: 2023-03-07

Abstract

The application relates to a method for preparing fatty acid by using fatty acid monomethyl ester, which comprises the following steps: 1) Reacting monomethyl ester of a fatty acid with water by heating in the presence of a catalyst consisting of p-toluenesulfonic acid and sulfuric acid to produce fatty acid and methanol; 2) The reaction was driven to completion by addition of water and removal of methanol. The method can obtain the fatty acid by catalyzing the hydrolysis of the fatty acid monomethyl ester under normal pressure with a very small amount of catalyst, has high reaction rate, can obtain the fatty acid with high yield and high purity, has simple process for preparing the fatty acid by utilizing the fatty acid monomethyl ester, can recycle the catalyst and the methanol, and greatly reduces the process cost.

Description

Method for preparing fatty acid by using fatty acid monomethyl ester

Technical Field

The application belongs to the technical field of fatty acid preparation, and particularly relates to a method for preparing fatty acid by using fatty acid monomethyl ester.

Background

Fatty acid is an important chemical raw material, is one of basic raw materials of a surfactant, can be used as a starting raw material to prepare various anionic, nonionic, cationic and amphoteric surfactants, is widely applied to industries such as light textile, washing, rubber, cosmetics, plastics, paper making, medicine, food, petroleum, synthetic fibers, leather making, mineral separation, machinery and the like, and has an increasing demand.

In the prior art, hydrolysis of triglycerides (i.e. of oils and fats of vegetable and animal origin) has become a major source of fatty acid production, and methods of fat hydrolysis can be divided into gap and continuous methods in the manner of operation; whether or not there is a catalyst can be divided into non-catalytic and catalytic (using acid, alkali, enzyme, etc.); according to the operating pressure, the hydrolysis method can be divided into a low pressure (170-190 ℃, 0.8-1.2 MPa), a medium pressure (230 ℃,2.5 MPa) and a high pressure (250-260 ℃, 5.5-6.0 MPa). At present, the low-pressure gap hydrolysis method is mainly used in China, but the method has the problems of high energy consumption, long hydrolysis time, unstable process, poor product quality and the like.

In order to prepare fatty acids by hydrolysis of fatty acid alkyl esters, in particular fatty acid monomethyl esters, the prior art has prevented equilibrium build-up by evaporating the methanol formed from the reaction mixture, the process operating at low pressures, e.g. ambient pressure, in the temperature range of, e.g., 70 to 150 ℃, as a result of these low reaction temperatures it being necessary to catalytically accelerate the reaction in order to obtain the desired high conversions on the basis of industry standard reaction times and residence times. However, the method for preparing fatty acid by using fatty acid methyl ester in the prior art uses a large amount of catalyst and has a complex preparation process, thereby resulting in high cost for preparing fatty acid.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the method for preparing the fatty acid by utilizing the fatty acid monomethyl ester is provided for solving the defects that the method for preparing the fatty acid by utilizing the fatty acid monomethyl ester uses a large amount of catalysts and the preparation process is complex, so that the cost for preparing the fatty acid is high.

The technical scheme adopted by the invention for solving the technical problem is as follows:

a method for preparing fatty acid by using fatty acid monomethyl ester comprises the following steps:

1) Reacting monomethyl ester of a fatty acid with water by heating in the presence of a catalyst consisting of p-toluenesulfonic acid and sulfuric acid to produce fatty acid and methanol;

2) The reaction was driven to completion by addition of water and removal of methanol.

Preferably, the reaction mixture is carried out at 95 to 100 ℃ by heating.

Preferably, after the reaction is completed, the reaction solution is kept still and cooled to be layered, the lower aqueous solution with the catalyst is discharged, and the upper aqueous solution is rectified to obtain the fatty acid.

Preferably, before the upper solution is rectified, the upper solution is washed by water, and the washed aqueous solution and the lower aqueous solution are mixed to obtain the aqueous solution with the catalyst for reuse.

Preferably, the carbon chain of the fatty acid moiety of the fatty acid monomethyl ester contains from 6 to 10 carbon atoms; further, the fatty acid monomethyl ester is preferably at least one of monomethyl caproate, monomethyl caprylate and monomethyl caprate.

Preferably, the mass ratio of the p-toluenesulfonic acid to the sulfuric acid is 1.

Preferably, in step 1), the catalyst is used in an amount of at least 0.1wt%, preferably 0.1wt% to 0.3wt%, based on the weight of the fatty acid monomethyl ester.

Preferably, in step 1), the molar ratio of water to fatty acid monomethyl ester is 1.

Preferably, a rotameter is used to control the flow of make-up water so that the amount of make-up water equals the amount of water consumed during the reaction.

The invention has the beneficial effects that:

the method can obtain the fatty acid by catalyzing the hydrolysis of the fatty acid monomethyl ester under normal pressure with a very small amount of catalyst, has high reaction rate, can obtain the fatty acid with high yield and high purity, has simple process for preparing the fatty acid by utilizing the fatty acid monomethyl ester, can recycle the catalyst and the methanol, and greatly reduces the process cost.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.

The technical solution of the present application will be described in detail with reference to the following examples.

Example 1

This example provides a method for preparing hexanoic acid from monomethyl hexanoate, comprising the following steps:

1) Adding 5421 kg of monomethyl hexanoate and 1500 kg of water into a reaction kettle with a rectifying tower, and adding 8132 g of catalyst under the stirring condition to form a reaction mixture; the catalyst is a mixture of p-toluenesulfonic acid and sulfuric acid with the mass ratio of 1; heating the reaction mixture to 95-100 ℃ to react the fatty acid monomethyl ester with water to produce fatty acid and methanol;

2) Removing methanol by a rectifying tower in the reaction process, supplementing water into a reaction system in time, and controlling the flow of the supplemented water by adopting a rotameter so that the added water amount is equal to the consumption of water in the reaction process; stopping the reaction when no methanol is generated, wherein the reaction time is 1 hour;

3) Standing and cooling the reaction solution to layer the reaction solution, discharging a lower layer aqueous solution with a catalyst, washing an upper layer solution twice by using clear water, wherein the washed upper layer solution contains caproic acid and a small amount of unreacted monomethyl caproate, and analyzing to obtain the yield of the caproic acid which reaches 98.5%; rectifying the washed upper layer solution to obtain caproic acid with the content of 99.5%, and mixing the water solution after washing the upper layer solution with the lower layer water solution to obtain the water solution with the catalyst for reuse.

Example 2

This example provides a method for preparing caprylic acid from monomethyl caprylate, comprising the steps of:

1) 2637 kg of monomethyl octanoate and 1500 kg of water were introduced into a reaction vessel equipped with a rectification column, and 5274 g of catalyst were added with stirring to form a reaction mixture; the catalyst is a mixture of p-toluenesulfonic acid and sulfuric acid with the mass ratio of 2; heating the reaction mixture to 95-100 ℃ to react the monomethyl octanoate with water to produce octanoic acid and methanol;

2) Removing methanol by a rectifying tower in the reaction process, supplementing water into a reaction system in time, and controlling the flow of the supplemented water by adopting a rotameter so that the added water amount is equal to the consumption of water in the reaction process; stopping the reaction when no methanol is generated, wherein the reaction time is 1.2 hours;

3) Standing and cooling the reaction solution to layer the reaction solution, discharging a lower layer aqueous solution with a catalyst, washing an upper layer solution twice by using clear water, wherein the washed upper layer solution contains caproic acid and a small amount of unreacted monomethyl caprylate, and the yield of the caprylic acid is up to 98.9% by analysis; rectifying the washed upper layer solution to obtain caprylic acid with the content of 99.7%, and mixing the water solution after washing the upper layer solution with the lower layer water solution to obtain the water solution with the catalyst for reuse.

Example 3

The embodiment provides a method for preparing decanoic acid by using monomethyl decanoate, which comprises the following steps:

1) 5238 kg of monomethyl decanoate and 1500 kg of water were added to a reaction vessel equipped with a rectification column, and 5238 g of catalyst was added with stirring to form a reaction mixture; the catalyst is a mixture of p-toluenesulfonic acid and sulfuric acid with the mass ratio of 1.5; heating the reaction mixture to 95-100 ℃ to react the monomethyl decanoate with water to produce decanoic acid and methanol;

2) Removing methanol through a rectifying tower in the reaction process, supplementing water into the reaction system in time, and controlling the flow of the supplemented water by adopting a rotameter to ensure that the water addition amount is equal to the water consumption amount in the reaction process; stopping the reaction when no methanol is generated, wherein the reaction time is 1.5 hours;

3) Standing and cooling the reaction solution to layer the reaction solution, discharging a lower layer aqueous solution with a catalyst, washing an upper layer solution twice by using clear water, wherein the washed upper layer solution contains caproic acid and a small amount of unreacted monomethyl decanoate, and the yield of the decanoic acid is up to 98.6% by analysis; rectifying the washed upper layer solution to obtain 99.5% decanoic acid, and mixing the water solution after washing the upper layer solution with the lower layer water solution to obtain the water solution with the catalyst for reuse.

In light of the foregoing description of the preferred embodiments according to the present application, it is to be understood that various changes and modifications may be made by those skilled in the art without departing from the scope of the invention as defined by the appended claims. The technical scope of the present application is not limited to the content of the specification, and must be determined according to the scope of the claims.

Claims

1. A method for preparing fatty acid by using fatty acid monomethyl ester is characterized by comprising the following steps:

1) Reacting fatty acid monomethyl ester with water by heating in the presence of a catalyst comprised of p-toluenesulfonic acid and sulfuric acid to produce fatty acids and methanol;

2. The method for preparing fatty acid using monomethyl fatty acid ester according to claim 1, wherein the reaction mixture is reacted at 95 to 100 ℃ by heating.

3. The method for producing fatty acids from fatty acid monomethyl ester according to claim 1 or 2, characterized in that after completion of the reaction, the reaction solution is allowed to stand and cool to separate into layers, the lower aqueous solution with the catalyst is discharged, and the upper aqueous solution is rectified to obtain fatty acids.

4. The method for preparing fatty acid from fatty acid monomethyl ester according to claim 3, wherein the upper solution is washed with water before rectification, and the washed aqueous solution is mixed with the lower aqueous solution to obtain an aqueous solution with catalyst for reuse.

5. The method for preparing fatty acid by using fatty acid monomethyl ester according to any one of claims 1 to 4, wherein the carbon chain of the fatty acid moiety of the fatty acid monomethyl ester contains 6 to 12 carbon atoms.

6. The method for preparing fatty acid by using fatty acid monomethyl ester according to claim 5, wherein the fatty acid monomethyl ester is at least one of monomethyl caproate, monomethyl caprylate and monomethyl caprate.

7. The method for preparing fatty acid by using fatty acid monomethyl ester according to any one of claims 1 to 6, wherein the mass ratio of p-toluenesulfonic acid to sulfuric acid is 1.

8. The method for preparing fatty acid by using fatty acid monomethyl ester according to any of claims 1-7, wherein the catalyst is used in an amount of at least 0.1wt%, preferably 0.1wt% to 0.3wt%, based on the weight of fatty acid monomethyl ester.

9. The method for preparing fatty acid by using fatty acid monomethyl ester according to any one of claims 1 to 8, wherein in step 1), the molar ratio of water to fatty acid monomethyl ester is 1.

10. The method for producing fatty acids from monomethyl fatty acid esters according to any of claims 1 to 9, wherein the flow rate of the make-up water is controlled by a rotameter so that the amount of water added is equal to the amount of water consumed in the reaction.