Preparation method of glycerol monolaurate

Abstract

The invention discloses a preparation method of glycerol monolaurate, and belongs to the technical field of synthesis and utilization of glycerol monolaurate. According to the method, lauric acid and glycerol are used as raw materials, the glycerol monolaurate is prepared by adopting an acid catalysis esterification method, the reaction temperature and the reaction time of a direct esterification method are reduced by regulating and controlling parameters, and meanwhile, a vacuum device is used for accelerating the reaction and removing generated water. The reaction raw materials have the characteristics of greenness and reproducibility; the preparation process is simple, the reaction temperature is relatively mild, the operation is convenient, and the industrial application prospect is wide.

Description

Technical Field

[0001] The invention belongs to the technical field of laurin synthesis and utilization, and in particular relates to a method for preparing laurin monoglyceride. Background Art

[0002] Fatty acid monoglycerides are nonionic surfactants, among which monolauric acid monoglyceride is an important lipid compound, which is widely used in food, medicine, cosmetics and industrial fields. Its main advantages include excellent emulsifying properties, significant antibacterial and preservative effects, and good biocompatibility and safety. With the increasing demand for natural, safe and efficient additives, the market demand for monolauric acid monoglyceride is also increasing year by year.

[0003] At present, there are many methods for the synthesis of monoglyceride of lauric acid, including direct esterification, lipase catalysis, group protection, alcoholysis and glycidol method. The reaction temperature of the lipase catalysis method is low, but the reaction time usually takes more than 24 hours. In addition, the cost of lipase is high, and it is also difficult to select a suitable lipase. The group protection method is mainly used to prepare monoglyceride of lauric acid of specific position and high purity, and the steps are complicated, the production cost is high, and it is not suitable for industrial production. The alcoholysis method, also known as the ester exchange method, has high requirements on the selection of catalysts and reaction conditions, and the content of monoglyceride in the product is low. The glycidol method, due to the high price of glycidol, limits its application in industrial production. The direct esterification method is the main method for the industrial production of monoglyceride of lauric acid. However, this method has the problem of high reaction temperature (about 220-240°C), and usually requires a water-carrying agent to continuously remove the generated water from the system. Summary of the invention

[0004] In view of the above technical problems, the purpose of the present invention is to reduce the reaction temperature and reaction time of the direct esterification method by regulating parameters, and use a vacuum device to accelerate the reaction and remove the generated water, and propose a method for preparing monolaurin.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing monolaurin comprises the following steps:

[0007] Add lauric acid and glycerin into a vacuum reactor, raise the temperature to 45-55°C, turn on the condenser, and stir mechanically until the mixture is evenly mixed;

[0008] The system is heated to 70-80°C, and a catalyst is added. When the temperature reaches 80-85°C, the system is decompressed from normal pressure to a pressure of 1-2 cm Hg, and the reaction is carried out for 20-30 minutes under this condition. The system pressure is maintained unchanged, and the temperature is raised to 90-100°C for reaction for 50-60 minutes, and the temperature is further raised to 120-140°C for reaction for 20-30 minutes.

[0009] The system temperature is lowered to 80-90°C, the system pressure is restored to normal pressure, and lauric acid monoglyceride is obtained by separation and purification.

[0010] Furthermore, the molar ratio of lauric acid to glycerol is (1:1)-(1:2).

[0011] Furthermore, the rotation speed of the mechanical stirring is 300-400 rpm.

[0012] Furthermore, the amount of the catalyst used is 1-3% of the mass of the glycerol.

[0013] Furthermore, the catalyst is an acidic catalyst, preferably p-toluenesulfonic acid.

[0014] Compared with the prior art, the present invention has the following advantages and technical effects:

[0015] The invention uses lauric acid and glycerol as raw materials and adopts an acid-catalyzed esterification method to prepare lauric acid monoglyceride. The reaction rate is accelerated and the reaction time is reduced by adjusting parameters and cooperating with a vacuum device. The temperature can also be reduced to 90-140 DEG C and the reaction time is reduced to less than two hours, and no water-carrying agent is required.

[0016] The invention has simple preparation process, low reaction temperature, short reaction time, easy-to-control reaction conditions, relatively high yield of the prepared lauric acid monoglyceride, which is above 450%, and is suitable for industrial production. DETAILED DESCRIPTION

[0017] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0018] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0019] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0020] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0021] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0022] The invention aims to solve the technical problems of the complicated preparation process and high production cost of the existing lauric acid monoglyceride. The present invention uses lauric acid and glycerol as raw materials and adopts an acid-catalyzed esterification method to prepare lauric acid monoglyceride. The present invention expands the preparation method of lauric acid monoglyceride. The reaction raw materials are lauric acid and glycerol, which are green and renewable; the preparation process is simple and the reaction temperature is relatively mild; and an environmentally friendly petroleum ether-ethyl acetate mixed solution is used in the post-treatment process. The process of the present invention is simple, easy to operate, and has broad prospects for industrial application.

[0023] A method for preparing monolaurin comprises the following steps:

[0024] (1) Weighing lauric acid and glycerol in a molar ratio of (1:1) to (1:2), first adding glycerol into a vacuum reactor and stirring, then adding lauric acid, slowly heating to 45-55° C., turning on a condenser at the same time, dissolving lauric acid, and mechanically stirring (stirring speed 300-400 rpm) until the mixture is uniformly mixed;

[0025] (2) The system temperature is raised to 70-80° C., a catalyst is added, the catalyst amount is 2-3% of the mass of glycerol, the reaction temperature is raised to 80-85° C., the system is decompressed to a pressure of 1-2 cm of mercury, and the reaction is carried out for 20-30 minutes under this pressure range; then the system pressure is maintained unchanged, the temperature is raised to 90-100° C., the reaction is carried out for 50-60 minutes, and the temperature is raised to 120-140° C., and the reaction is carried out for 20-30 minutes;

[0026] (3) Lowering the system temperature to 80-90° C. and restoring the system pressure to normal pressure, separating and purifying to obtain lauric acid monoglyceride, and tracking by TLC until the lauric acid is completely reacted.

[0027] In the following examples, the heating rate in the heating process is 2°C / min, and the cooling rate in the cooling process is 2°C / min.

[0028] The raw materials used in the present invention are all purchased from the market.

[0029] The normal pressure described in the present invention refers to 760 mm of mercury.

[0030] The technical solution of the present invention is further illustrated by the following embodiments.

[0031] Example 1

[0032] A method for preparing monolaurin comprises the following steps:

[0033] (1) 1000 g of lauric acid (5 mol) and 690 g of glycerol (7.5 mol) were added to a vacuum reactor, and a condenser was turned on at the same time, and the mixture was stirred at 50° C. and 350 rpm until the lauric acid was dissolved and the raw materials were uniformly mixed;

[0034] (2) The system temperature was raised to 75° C., 13.8 g of p-toluenesulfonic acid catalyst was added (the catalyst dosage was 2% of the mass of glycerol), and when the system temperature was raised to 80° C., the system pressure was reduced to 2 cm of mercury, and the reaction was carried out for 20 min in this pressure range; then the system pressure was maintained unchanged, the temperature was raised to 100° C., the reaction was carried out for 50 min, and then the temperature was further raised to 120° C. and the reaction was carried out for 30 min;

[0035] (3) The system temperature is lowered to 80° C., the system pressure is restored to normal pressure, and the product is separated and purified (petroleum ether-ethyl acetate mixed solution) to obtain lauric acid monoglyceride.

[0036] The reaction of lauric acid was completely tracked by TLC, and the conversion rate of lauric acid was 99.3% and the yield of lauric acid monoglyceride was 47.2% according to the determination method of national standard GB / T 22328-2008.

[0037] Example 2

[0038] A method for preparing monolaurin comprises the following steps:

[0039] (1) 1000 g of lauric acid (5 mol) and 690 g of glycerol (7.5 mol) were added to a vacuum reactor, and a condenser was turned on at the same time, and the mixture was stirred at 50° C. and 350 rpm until the lauric acid was dissolved and the raw materials were uniformly mixed;

[0040] (2) The system temperature was raised to 70° C., 10.35 g of p-toluenesulfonic acid catalyst was added (the catalyst dosage was 1.5% of the mass of glycerol). When the system temperature was raised to 80° C., the system pressure was reduced to 2 cm of mercury, and the reaction was carried out for 20 min in this pressure range. After that, the system pressure was maintained unchanged, the temperature was raised to 90° C., the reaction was carried out for 50 min, and then the temperature was further raised to 120° C. and the reaction was carried out for 20 min.

[0041] (3) The system temperature is lowered to 80° C., the system pressure is restored to normal pressure, and lauric acid monoglyceride is obtained by separation and purification.

[0042] Through TLC tracking, lauric acid was completely reacted. According to the determination method of national standard GB / T 22328-2008, the conversion rate of lauric acid was 99.4%, and the yield of lauric acid monoglyceride was 47.4%.

[0043] Example 3

[0044] Same as Example 2, except that the amount of glycerol added is 920 g (10 mol).

[0045] Through TLC tracking, lauric acid was completely reacted. According to the determination method of national standard GB / T 22328-2008, the conversion rate of lauric acid was 99.1%, and the yield of lauric acid monoglyceride was 46.6%.

[0046] Example 4

[0047] Same as Example 2, except that the amount of glycerol added is 552 g (6 mol).

[0048] Through TLC tracking, lauric acid was completely reacted. According to the determination method of national standard GB / T 22328-2008, the conversion rate of lauric acid was 98.9%, and the yield of lauric acid monoglyceride was 47.2%.

[0049] Example 5

[0050] The same as Example 1, except that, in step (2), before adding the catalyst, the system temperature is adjusted to rise to 80°C.

[0051] Through TLC tracking, lauric acid was completely reacted. According to the determination method of national standard GB / T 22328-2008, the conversion rate of lauric acid was 99.1%, and the yield of lauric acid monoglyceride was 47.4%.

[0052] Example 6

[0053] The same as Example 1, except that in step (2), when the system temperature is raised to 85° C., the system begins to decompress.

[0054] Through TLC tracking, lauric acid was completely reacted. According to the determination method of national standard GB / T 22328-2008, the conversion rate of lauric acid was 99.0%, and the yield of lauric acid monoglyceride was 46.9%.

[0055] Example 7

[0056] Same as Example 1, except that in step (2), 20.7 g of p-toluenesulfonic acid catalyst is added.

[0057] Through TLC tracking, lauric acid was completely reacted. According to the determination method of national standard GB / T 22328-2008, the conversion rate of lauric acid was 99.5%, and the yield of lauric acid monoglyceride was 48.2%.

[0058] Example 8

[0059] The method is the same as Example 1, except that, in step (1), glycerol is added after lauric acid is completely dissolved, and the amount remains unchanged, that is, step (1) is specifically as follows: 1000 g of lauric acid (5 mol) is added to a vacuum reactor, and a condensing device is turned on at 50° C. and 350 rpm, and stirred until the lauric acid is dissolved, and then 690 g of glycerol (7.5 mol) is added and mixed evenly.

[0060] Through TLC tracking, lauric acid was completely reacted. According to the determination method of national standard GB / T 22328-2008, the conversion rate of lauric acid was 98.8%, and the yield of lauric acid monoglyceride was 46.6%.

[0061] Comparative Example 1

[0062] A method for preparing monolaurin comprises the following steps:

[0063] (1) 1000 g of lauric acid (5 mol) and 552 g of glycerol (6 mol) were added to a vacuum reactor, and a condenser was turned on at the same time, and the mixture was stirred at 50° C. and 350 rpm until the lauric acid was dissolved and the raw materials were uniformly mixed;

[0064] (2) The system temperature was raised to 80°C, 11.1 g of concentrated sulfuric acid (the catalyst dosage was 2% of the mass of glycerol) was added, and the system pressure was reduced to 1 cm of mercury. The reaction was carried out for 30 min in this pressure range. After that, the system pressure was maintained unchanged, the temperature was raised to 100°C, and the reaction was carried out for 60 min. After that, the temperature was further raised to 120°C and the reaction was carried out for 30 min.

[0065] (3) The system temperature is lowered to 80° C., the system pressure is restored to normal pressure, and lauric acid monoglyceride is obtained by separation and purification.

[0066] TLC tracking showed that due to the use of concentrated sulfuric acid as a catalyst, the reaction was not complete and a large amount of lauric acid remained. According to the determination method of national standard GB / T 22328-2008, the conversion rate of lauric acid was 40.4% and the yield of lauric acid monoglyceride was 14.3%.

[0067] Comparative Example 2

[0068] A method for preparing monolaurin comprises the following steps:

[0069] (1) 1000 g of lauric acid (5 mol) and 552 g of glycerol (6 mol) were added to a vacuum reactor, and a condenser was turned on at the same time, and the mixture was stirred at 50° C. and 350 rpm until the lauric acid was dissolved and the raw materials were uniformly mixed;

[0070] (2) The system temperature was raised to 80°C, 13.8 g of concentrated sulfuric acid as a catalyst was added (the catalyst dosage was 2.5% of the mass of glycerol), the system pressure was reduced to 1 cm of mercury, and the reaction was carried out for 30 min in this pressure range; then the system pressure was maintained unchanged, the temperature was raised to 100°C, the reaction was carried out for 120 min, and then the temperature was further raised to 120°C and the reaction was carried out for 30 min;

[0071] (3) The system temperature is lowered to 80° C., the system pressure is restored to normal pressure, and lauric acid monoglyceride is obtained by separation and purification.

[0072] TLC tracking showed that due to the use of concentrated sulfuric acid as a catalyst, the reaction was not complete and a large amount of lauric acid remained. According to the determination method of national standard GB / T 22328-2008, the conversion rate of lauric acid was 55.7% and the yield of lauric acid monoglyceride was 22.2%.

[0073] Comparative Example 3

[0074] A method for preparing monolaurin comprises the following steps:

[0075] (1) 1000 g of lauric acid (5 mol) and 552 g of glycerol (6 mol) were added to a vacuum reactor, and a condenser was turned on at the same time, and the mixture was stirred at 50° C. and 350 rpm until the lauric acid was dissolved and the raw materials were uniformly mixed;

[0076] (2) The system temperature was raised to 65° C., 13.8 g of p-toluenesulfonic acid catalyst was added (the catalyst dosage was 2.5% of the mass of glycerol), the system pressure was reduced to 1 cm of mercury, and the reaction was carried out for 20 min in this pressure range; then the system pressure was maintained unchanged, the temperature was raised to 105° C., the reaction was carried out for 50 min, and then the temperature was further raised to 120° C. and the reaction was carried out for 20 min;

[0077] Through TLC tracking, lauric acid was completely reacted. According to the determination method of national standard GB / T 22328-2008, the conversion rate of lauric acid was 96.7% (a small amount of lauric acid was taken out of the system during this process), and the yield of lauric acid monoglyceride was 43.5%.

[0078] Comparative Example 4

[0079] A method for preparing monolaurin comprises the following steps:

[0080] (1) 1000 g of lauric acid (5 mol) and 552 g of glycerol (6 mol) were added to a vacuum reactor, and a condenser was turned on at the same time, and the mixture was stirred at 50° C. and 350 rpm until the lauric acid was dissolved and the raw materials were uniformly mixed;

[0081] (2) The system temperature was raised to 65° C., 13.8 g of p-toluenesulfonic acid catalyst was added (the catalyst dosage was 2.5% of the mass of glycerol), the system pressure was reduced to 1 cm of mercury, and the reaction was carried out for 20 min in this pressure range; then the system pressure was maintained unchanged, the temperature was raised to 105° C., the reaction was carried out for 40 min, and then the temperature was further raised to 120° C. and the reaction was carried out for 20 min;

[0082] Through TLC tracking, a small amount of lauric acid was not completely reacted. According to the determination method of national standard GB / T 22328-2008, the conversion rate of lauric acid was 93.2%, and the yield of lauric acid monoglyceride was 39.9%.

[0083] Comparative Example 5

[0084] A method for preparing monolaurin comprises the following steps:

[0085] (1) 1000 g of lauric acid (5 mol) and 552 g of glycerol (6 mol) were added to a vacuum reactor, and a condenser was turned on at the same time, and the mixture was stirred at 50° C. and 350 rpm until the lauric acid was dissolved and the raw materials were uniformly mixed;

[0086] (2) The system temperature was raised to 65° C., 13.8 g of p-toluenesulfonic acid catalyst was added (the catalyst dosage was 2.5% of the mass of glycerol), the system pressure was reduced to 1 cm of mercury, and the reaction was carried out for 20 min in this pressure range; then the system pressure was maintained unchanged, the temperature was raised to 105° C., the reaction was carried out for 50 min, and then the temperature was further raised to 120° C. and the reaction was carried out for 10 min;

[0087] Through TLC tracking, a small amount of lauric acid was not completely reacted. According to the determination method of national standard GB / T 22328-2008, the conversion rate of lauric acid was 95.8%, and the yield of lauric acid monoglyceride was 43.0%.

[0088] Comparative Example 6

[0089] A method for preparing monolaurin comprises the following steps:

[0090] (1) 1000 g of lauric acid (5 mol) and 552 g of glycerol (6 mol) were added to a vacuum reactor, and a condenser was turned on at the same time, and the mixture was stirred at 50° C. and 350 rpm until the lauric acid was dissolved and the raw materials were uniformly mixed;

[0091] (2) The system temperature was raised to 80° C., 8.28 g of p-toluenesulfonic acid catalyst was added (the catalyst dosage was 1.5% of the mass of glycerol), the system pressure was reduced to 1 cm of mercury, and the reaction was carried out for 20 min in this pressure range; then the system pressure was maintained unchanged, the temperature was raised to 105° C., the reaction was carried out for 50 min, and then the temperature was further raised to 120° C. and the reaction was carried out for 20 min;

[0092] Through TLC tracking, lauric acid was completely reacted. According to the determination method of national standard GB / T 22328-2008, the conversion rate of lauric acid was 92.7%, and the yield of lauric acid monoglyceride was 38.6%.

[0093] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for preparing monolaurin, characterized in that: The following steps are involved: Add lauric acid and glycerin into the vacuum reactor, turn on the condenser, and heat and stir; The system is heated to 70-80°C, and a catalyst is added. When the temperature reaches 80-85°C, the system is decompressed from normal pressure to a pressure of 1-2 cm Hg, and the reaction is carried out for 20-30 minutes under this condition. The system pressure is maintained unchanged, and the temperature is raised to 90-100°C for reaction for 50-60 minutes, and the temperature is further raised to 120-140°C for reaction for 20-30 minutes. The system temperature is lowered to 80-90°C, the system pressure is restored to normal pressure, and lauric acid monoglyceride is obtained by separation and purification.

2. The method for preparing monolaurin according to claim 1, characterized in that: The molar ratio of lauric acid to glycerol is (1:1)-(1:2).

3. The method for preparing monolaurin according to claim 1, characterized in that: The heating and stirring rotation speed is 300-400 rpm, and the temperature is 45-55°C.

4. The method for preparing monolaurin according to claim 1, characterized in that: The amount of the catalyst used is 1-3% of the mass of the glycerol.

5. The method for preparing monolaurin according to claim 4, characterized in that: The catalyst is an acidic catalyst.

6. The method for preparing monolaurin according to claim 5, characterized in that: The catalyst is p-toluenesulfonic acid.