A method for preparing fatty acid alkanolamide and its application

Abstract

The invention discloses a method and application for preparing fatty acid alkanolamide, comprising the following steps: adding a catalyst to alkanolamine, stirring and heating to 90°C to dissolve, and matching an atmospheric distillation device; taking another constant pressure dropping funnel with insulation, and loading the melted fatty acid therein; continuing to heat the alkanolamine system to a specified temperature and then starting to drip fatty acid, and water will be continuously evaporated during the dripping process; after dripping, keep warm until no water is discharged and start sampling to measure the acid value control, and the acid value can be terminated when it is lower than 3, cool to 90°C, add appropriate amount of water and 90°C to separate, collect the oil layer negative pressure to evaporate a small amount of water and alkanolamine, pour it into a tray while hot to cool and form, and slice to obtain fatty acid alkanolamide solid. The present invention uses boric acid as a catalyst to realize the one-step preparation of fatty acid alkanolamide by fatty acid and alkanolamine, and the process is simple and convenient for large-scale production. There are fewer by-products in the preparation process, and the production cost is low. The prepared fatty acid alkanolamide is used as a surfactant and is green and environmentally friendly.

Description

Technical Field

[0001] The invention relates to a preparation method and application of fatty acid alkanolamide, and particularly to the use of a boric acid catalyst, which greatly improves the problem of long reaction time in traditional processes. Background Art

[0002] Fatty acid monoethanolamide is a yellowish waxy nonionic surfactant. Due to the presence of amide bonds in its molecules, it has good chemical stability, excellent dispersing, solubilizing, thickening and lubricating effects in a wide pH range. Among them, the widely used lauric acid monoethanolamide (LMEA) can be widely used in various detergents such as shampoo, bath gel, dishwashing, cosmetics, textile printing and dyeing auxiliaries, and medicine, rubber industry and other fields. The biodegradation rate is over 98%. LMEA is also one of the main ingredients of tablet detergents, whose consumption in the European market is on the rise. Studies have shown that the free diethanolamine contained in the fatty acid diethanolamide series surfactants, which are widely used in liquid detergents, has obvious carcinogenic activity. As a similar alkanolamide, LMEA should become a substitute for diethanolamide surfactants. Fatty acid diethanolamide products (6501, 6502) in my country have long been produced and used on a large scale. Although LMEA has also been developed and studied, the process conditions and product quality of industrial production are not mature enough.

[0003] There are three main routes for the synthesis of LMEA at home and abroad: 1. Direct reaction of oil and monoethanolamine. This route is not completely reacted, and the generated glycerol will form a series of by-products. 2. After the oil is methylated, it is reacted with monoethanolamine under the action of an alkaline catalyst. The process is relatively complicated. Due to the presence of methanol in the reaction process, labor protection and fire and explosion protection conditions are required to be high. 3. Direct reaction of fatty acids with monoethanolamine. This method is one of the more mature synthesis processes. Its advantages are simple process and low cost. However, if the operating conditions are not properly controlled, in addition to the generation of LMEA, more by-products such as amino esters and amide esters will be produced. The amide ester in the by-product can be quickly aminolyzed into alkanolamide by monoethanolamine under the action of an alkaline catalyst, while it is more difficult for amino esters to be further aminolyzed. At present, the manufacturers of LMEA sold on the market basically use the first or second route for synthesis. In addition to the high production cost, the content of by-products such as amino esters in the product is also high, and it is more irritating to the skin when used in the daily chemical industry. Therefore, it is very important to develop a method for preparing alkanolamide surfactants that is both efficient and environmentally friendly.

[0004] In view of the above-mentioned technical problems, it is necessary to provide a new technical solution. Summary of the invention

[0005] In order to solve at least one of the technical problems existing in the prior art, and in view of the important position of alkanolamide surfactants and the urgent needs of the current market, our company has invented a method for preparing fatty acid monoethanolamide and fatty acid isopropanolamide and its application. The method uses boric acid as a catalyst to realize the one-step preparation of fatty acid alkanolamide from fatty acid and alkanolamine. The specific scheme is as follows:

[0006] In one aspect, the present invention provides a method for preparing fatty acid alkanolamides, comprising the steps of:

[0007] S1: Add the catalyst to the alkanolamine, stir and heat to 90°C to dissolve, and use an atmospheric distillation device;

[0008] S2: Take another constant pressure dropping funnel with insulation and add the melted fatty acid into it;

[0009] S3: Continue to heat the alkanolamine system to a specified temperature and then start to drip fatty acids. Water will evaporate continuously during the dripping process. After dripping, keep the temperature until no water is produced and start sampling to measure the acid value. The acid value can be stopped when it is lower than 3. Cool down to 90°C, add appropriate amount of water at 90°C, separate the layers, collect a small amount of water and alkanolamine evaporated by negative pressure in the oil layer, and pour them into a tray while they are hot to cool and form. Slice to obtain fatty acid alkanolamide solid.

[0010] Among them, the structure of fatty acid alkanolamide is as follows:

[0011]

[0012] As a preferred embodiment of the method for preparing fatty acid alkanolamides of the present invention, in step S1, the catalyst is boric acid.

[0013] As a preferred embodiment of the method for preparing fatty acid alkanolamides of the present invention, in step S1, the mass ratio of the catalyst to the alkanolamine is 4.5% to 9%.

[0014] As a preferred embodiment of the method for preparing fatty acid alkanolamides of the present invention, in step S1, the mass ratio of the catalyst to the alkanolamine is 6%.

[0015] As a preferred embodiment of the method for preparing fatty acid alkanolamides of the present invention, in steps S1 and S2, the molar ratio of fatty acid to alkanolamine is 1:1.15.

[0016] As a preferred embodiment of the method for preparing fatty acid alkanolamides of the present invention, in step S3, the alkanolamine system is heated to 130-160° C. before the fatty acid is added dropwise.

[0017] As a preferred embodiment of the method for preparing fatty acid alkanolamides of the present invention, in step S3, a small amount of water and alkanolamine are evaporated from the oil layer under negative pressure, and the oil layer is distilled under reduced pressure to 10 mbr and 130° C., and then poured into a tray while hot to cool and form.

[0018] As a preferred embodiment of the method for preparing fatty acid alkanolamides of the present invention, in step S3, the alkanolamine system is heated to 150° C. and then the fatty acid is added dropwise.

[0019] In one aspect, the present invention provides the use of fatty acid alkanolamide prepared by the above method in surfactants.

[0020] Preferably, the fatty acid alkanolamide prepared by the above method is used in a surfactant, and the surfactant is used in a household detergent or a catering detergent.

[0021] Compared with the prior art, the present invention has at least one or more of the following beneficial effects:

[0022] The preparation method of the present invention uses boric acid as a catalyst to prepare fatty acid alkanolamides by a one-step method using fatty acids and alkanolamines, has a simple process and is convenient for large-scale production. There are fewer by-products in the preparation process, and the production cost is low. The prepared fatty acid alkanolamides are green and environmentally friendly when used as surfactants, and have good use effects.

[0023] The use of boric acid catalyst in the preparation method of the present invention can control the amino ester byproduct to less than 1%, and the yield is high. In addition, compared with the traditional process, the use of boric acid catalyst greatly shortens the reaction time, and the reaction can be completed in 5 hours by controlling the amount of catalyst used, which greatly improves the production efficiency and capacity.

[0024] Compared with traditional methods, this method has a relatively low reaction temperature and can be operated at normal pressure in the early stage, thus saving production energy consumption.

[0025] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. DETAILED DESCRIPTION

[0026] The embodiments of the present invention will be described in detail below, and the technical solutions in the embodiments of the present invention will be described clearly and completely. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] The present invention provides a method for preparing fatty acid alkanolamides. The synthetic route of the target compound specifically comprises the following steps:

[0028] S1: Add the catalyst to the alkanolamine, stir and heat to 90°C to dissolve, and use an atmospheric distillation device;

[0029] S2: Take another constant pressure dropping funnel with insulation and add the melted fatty acid into it;

[0030] S3: Continue to heat the alkanolamine system to a specified temperature and then start to drip fatty acids. Water will evaporate continuously during the dripping process. After dripping, keep the temperature until no water is produced and start sampling to measure the acid value. The acid value can be stopped only when it is lower than 3. Cool down to 90°C, add appropriate amount of water at 90°C, separate the layers, collect a small amount of water and alkanolamine evaporated under negative pressure in the oil layer, and pour them into a tray while they are hot to cool and form. Slice to obtain fatty acid alkanolamide white solid.

[0031] Among them, the structure of fatty acid alkanolamide is as follows:

[0032]

[0033] Preferably, in step S1, the catalyst is boric acid.

[0034] Preferably, in step S1, the mass ratio of the catalyst to the alkanolamine is 4.5% to 9%. More preferably, in step S1, the mass ratio of the catalyst to the alkanolamine is 6%.

[0035] Preferably, in steps S1 and S2, the molar ratio of the reaction raw materials fatty acid and alkanolamine is 1:1.15.

[0036] Preferably, in step S3, the fatty acid is added dropwise after the temperature of the alkanolamine system is continued to be raised to 130-160° C. More preferably, in step S3, the fatty acid is added dropwise after the temperature of the alkanolamine system is continued to be raised to 150° C.

[0037] Preferably, in step S3, the oil layer is collected and a small amount of water and alkanolamine is evaporated under negative pressure, and the oil layer is distilled under reduced pressure to 10 mbr and 130° C., and then poured into a tray while hot and cooled to form.

[0038] Preferably, in step S3, an appropriate amount of deionized water is added and stirred at 90° C. to separate the layers, the water layer is removed, and the oil layer is transferred back to the reaction bottle.

[0039] Preferably, in step S3, if the acid ester is measured to be not less than 3, the temperature is kept warm for a period of time, and the acid value is measured again, and the operation is repeated until the acid ester is less than 3.

[0040] The synthesis mechanism of the preparation method of the present invention is as follows:

[0041]

[0042] On the other hand, the fatty acid alkanolamide prepared by the above method provided by the present invention is used as a surfactant.

[0043] Preferably, the fatty acid alkanolamide prepared by the above method is used in a surfactant, and the surfactant is used in a household detergent or a catering detergent.

[0044] Example 1 Synthesis of lauric acid monoethanolamide

[0045] In a 250ml four-necked flask, 40g (655.7mmol) of monoethanolamine and 2.4g (6%) of boric acid were added, and an atmospheric distillation apparatus was set up. A constant temperature and constant pressure dropping funnel was also matched to charge 114g (570.2mmol) of melted lauric acid. The reaction system was heated to 90°C, stirred and dissolved, and then the temperature was continued to rise to 150°C. Lauric acid was added dropwise at this temperature (about 3h to complete the addition). Water was continuously evaporated during the addition. After the addition was completed, the temperature was kept for 2h, and then sampling was started to measure the acid value. After the acid value was less than 3, the temperature was lowered to 90°C, 30g of deionized water was added, stirred at 90°C, and then separated into layers. The water layer was carefully separated, and the oil layer was transferred back to the reaction bottle. After reduced pressure distillation to 10mbr and 130°C, it was poured into a tray while hot and cooled to shape and slice to obtain 136.8g of white flaky solid.

[0046] After testing, the product had a GC content of 97.2%, a chromaticity of 2.0G, and a yield of 96%.

[0047] In this example, the acid number was measured to be 1.75.

[0048] Example 2: Synthesis of lauric acid monoethanolamide

[0049] In a 250ml four-necked flask, 40g (655.7mmol) of monoethanolamine and 1.8g (4.5%) of boric acid were added, and an atmospheric distillation apparatus was set up. A constant temperature and constant pressure dropping funnel was also used to transfer 114g (570.2mmol) of molten lauric acid. The reaction system was heated to 90°C, stirred and dissolved, and then the temperature was continued to rise to 150°C. Lauric acid was added dropwise at this temperature (about 3h to complete the addition). Water was continuously evaporated during the addition. After the addition was completed, the acid value was measured by sampling for 2h and the acid value was 4.7. The acid value was measured by sampling after the temperature was kept warm for 2h and the acid value was 2.2. After the acid value was less than 3, the temperature was lowered to 90°C, 30g of deionized water was added, stirred at 90°C and then separated, the water layer was carefully separated, and the oil layer was transferred back to the reaction bottle. After reduced pressure distillation to 10mbr and 130°C, the mixture was poured into a tray while hot and cooled to shape and slice to obtain 137g of off-white sheet solid.

[0050] After testing, the product had a GC content of 96.5%, a chromaticity of 4.6G, and a yield of 95.4%.

[0051] Example 3 Synthesis of Lauric Acid Isopropanolamide

[0052] In a 250ml four-necked flask, 40g (532.6mmol) of isopropanolamine and 4.62g (9%) of boric acid were added, and an atmospheric distillation apparatus was set up. A constant temperature and constant pressure dropping funnel was also used to transfer 92.6g (463mmol) of melted lauric acid. The reaction system was heated to 90°C, stirred and dissolved, and then the temperature was continued to rise to 150°C. Lauric acid was added dropwise at this temperature (about 3h to complete the addition). Water was continuously evaporated during the addition. After the addition was completed, the temperature was kept for 2h. Sampling was started to measure the acid value. After the acid value was less than 3, the temperature was lowered to 90°C. 30g of deionized water was added, stirred at 90°C, and then separated into layers. The water layer was carefully separated, and the oil layer was transferred back to the reaction bottle. After being distilled under reduced pressure to 10mbr and 130°C, it was poured into a tray while hot and cooled to shape and slice to obtain 115.3g of white flaky solid.

[0053] After testing, the product had a GC content of 96.2%, a chromaticity of 2.1G, and a yield of 93.2%.

[0054] In this example, the acid value was measured to be 1.2.

[0055] Example 4 Synthesis of palmitic acid monoethanolamide

[0056] In a 250ml four-necked flask, 40g (655.7mmol) of monoethanolamine and 2.4g (6%) of boric acid were added, and an atmospheric distillation apparatus was set up. A constant temperature and pressure dropping funnel was also used to transfer 146g (570.2mmol) of molten palmitic acid. The reaction system was heated to 90°C, stirred and dissolved, and then the temperature was continued to rise to 150°C. Lauric acid was added dropwise at this temperature (about 3h to complete the addition). Water was continuously evaporated during the addition. After the addition was completed, the temperature was kept for 2h. Sampling was started to measure the acid value. After the acid value was less than 3, the temperature was lowered to 90°C, 30g of deionized water was added, stirred at 90°C, and layers were separated. The water layer was carefully separated, and the oil layer was transferred back to the reaction bottle. After reduced pressure distillation to 10mbr and 130°C, the mixture was poured into a tray while hot and cooled to shape and slice to obtain 168.8g of light yellow flaky solid.

[0057] After testing, the product had a GC content of 96.2%, a chromaticity of 4.1G, and a yield of 95.1%.

[0058] In this example, the acid number was measured to be 1.75.

[0059] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A method for preparing fatty acid alkanolamides, characterized in that: The steps include: S1: adding the catalyst to the alkanolamine, stirring and heating to 90°C to dissolve, and using an atmospheric distillation apparatus; wherein the catalyst is boric acid, and the mass ratio of the catalyst to the alkanolamine is 4.5% to 9%; S2: Take another constant pressure dropping funnel with insulation and add the melted fatty acid into it; S3: Continue to heat the alkanolamine system to a specified temperature and then start to drip fatty acids. Water will evaporate continuously during the dripping process. After dripping, keep the temperature until no water is produced and start sampling to measure the acid value. The acid value can be stopped when it is lower than 3. Cool down to 90°C, add appropriate amount of water at 90°C, separate the layers, collect a small amount of water and alkanolamine evaporated by negative pressure in the oil layer, and pour them into a tray while they are hot to cool and form. Slice to obtain fatty acid alkanolamide solid. Among them, the structure of alkanolamine is as follows: The structure of fatty acids is as follows: The structure of fatty acid alkanolamides is as follows:

2. The method for preparing fatty acid alkanolamides according to claim 1, characterized in that: In step S1, the mass ratio of the catalyst to the alkanolamine is 6%.

3. The method for preparing fatty acid alkanolamides according to claim 1, characterized in that: In steps S1 and S2, the molar ratio of fatty acid to alkanolamine is 1:1.

15.

4. The method for preparing fatty acid alkanolamides according to claim 1, characterized in that: In step S3, the temperature of the alkanolamine system is continuously raised to 130-160° C., and then the fatty acid is added dropwise.

5. The method for preparing fatty acid alkanolamides according to claim 1, characterized in that: In step S3, the oil layer is collected and a small amount of water and alkanolamine are evaporated under negative pressure, and the oil layer is distilled under reduced pressure to 10 mbr and 130° C., and then poured into a tray while hot to cool and form.

6. The method for preparing fatty acid alkanolamides according to claim 4, characterized in that: In step S3, the temperature of the alkanolamine system is continued to be raised to 150° C., and then the fatty acid is added dropwise.

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