A method for the synthesis of alkanolamides
By using the amidation reaction of γ-stearyl lactone with monoethanolamine or diethanolamine, combined with hydrochloric acid regulation and solvent extraction recrystallization, the problems of low efficiency and poor environmental performance of existing alkanolamide synthesis processes have been solved, achieving efficient and low-cost production of alkanolamides.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SOUTH CHINA UNIV OF TECH
- Filing Date
- 2026-01-12
- Publication Date
- 2026-05-29
AI Technical Summary
Existing alkanolamide synthesis processes suffer from problems such as long reaction times, low production efficiency, easy catalyst residue, high production costs, high energy consumption, complex product purification, and poor environmental friendliness, making it difficult to meet practical application requirements.
The alkanolamide was obtained by amidation reaction of γ-stearyl lactone with monoethanolamine or diethanolamine in ethanol, followed by pH adjustment to 1-3 with hydrochloric acid, extraction with n-butanol and recrystallization with n-hexane to separate the crystals.
This method enables the synthesis of alkanolamides with short reaction time, no catalyst required, high yield, low production cost, low energy consumption, and is green and safe, making it suitable for large-scale industrial applications.
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Figure CN122102935A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of organic synthesis technology, and more specifically to a method for synthesizing alkanolamides. Background Technology
[0002] Alkanolamide surfactants possess excellent emulsifying, dispersing, solubilizing, and foam-stabilizing properties, and are widely used in detergents, cosmetics, textile printing and dyeing, and oil extraction. Alkanolamides are typically produced by the amidation reaction of fatty acids and alkanolamines. However, this preparation process suffers from problems such as long reaction times (more than 2 hours for monoethanolamide synthesis and more than 4 hours for diethanolamide synthesis), low production efficiency, easy catalyst residue (e.g., sodium methoxide, sodium ethoxide), high production costs, high energy consumption, complex product purification procedures, and poor environmental friendliness, making it difficult to meet practical application requirements.
[0003] Therefore, it is of great significance to develop a simple, mild, short reaction time, catalyst-free, high-yield, easy-to-purify, low-cost, low-energy-consumption, green and safe method for synthesizing alkanolamides. Summary of the Invention
[0004] The purpose of this invention is to provide a method for synthesizing alkanolamides.
[0005] The technical solution adopted in this invention is: A method for synthesizing alkanolamide includes the following steps: dispersing γ-stearyl lactone with monoethanolamine or diethanolamine in ethanol for amidation reaction, adding the reaction solution to water and adjusting the pH of the system to 1-3 with hydrochloric acid, extracting with n-butanol, concentrating the organic phase, adding the concentrated product to n-hexane for recrystallization, separating the crystals, washing and drying to obtain alkanolamide.
[0006] Preferably, the molar ratio of γ-stearyl lactone to monoethanolamine is 1:4 to 6, and the corresponding amidation reaction time is 45 min to 75 min.
[0007] Preferably, the molar ratio of γ-stearyl lactone to diethanolamine is 1:7 to 9, and the corresponding amidation reaction time is 90 min to 150 min.
[0008] Preferably, the temperature of the amidation reaction is 110°C to 130°C.
[0009] Preferably, the number of extractions is ≥2.
[0010] Preferably, the volume of n-butanol used in the extraction is 40% to 60% of the volume of the reaction solution to be extracted.
[0011] Preferably, the concentration method is rotary evaporation.
[0012] Preferably, the rotary evaporation is carried out at a temperature of 110℃~130℃ and a vacuum degree of 0.05MPa~0.15MPa.
[0013] Preferably, the ratio of the concentrated product to n-hexane is 1g:5mL to 10mL.
[0014] Preferably, the recrystallization is carried out at room temperature (25°C).
[0015] Preferably, the washing solvent used in the washing process is n-hexane.
[0016] The beneficial effects of the present invention are: the synthesis method of alkanolamide of the present invention has the advantages of simple operation, mild reaction conditions, short reaction time, no need for catalyst, high yield, simple product purification, low production cost, low energy consumption, green and safe, and is suitable for large-scale industrial application.
[0017] Specifically: 1) This invention does not require a catalyst or vacuum distillation. The reaction is carried out under normal pressure and mild conditions, which significantly shortens the reaction time (the amidation reaction time of monoethanolamine is shortened from 2 hours in the traditional process to 45-75 minutes, and the amidation reaction time of diethanolamine is shortened from 4 hours in the traditional process to 90-150 minutes). The production efficiency is significantly improved, and the product yield is high (the yield of monoethanolamide is up to 99.14%, and the yield of diethanolamide is up to 73.90%). At the same time, energy consumption and operational complexity are reduced, and production safety is improved. 2) This invention uses γ-stearic acid lactone, a byproduct of oleic acid hydrogenation isomerization (this byproduct has not been efficiently utilized and is mostly discarded, which not only wastes resources but also increases the pressure on environmental treatment) as raw material, to realize the resource utilization of oleic acid hydrogenation isomerization byproduct, reduce raw material costs, and reduce waste emissions, which is in line with the trend of green chemical development. 3) The present invention adopts a product purification process of "hydrochloric acid removal of alkanolamines - n-butanol extraction - n-hexane recrystallization", which can effectively separate unreacted raw materials and products, improve product purity, and is suitable for large-scale industrial application. Attached Figure Description
[0018] Figure 1 The image shows the infrared spectrum of γ-stearyl lactone.
[0019] Figure 2 The image shows the infrared spectrum of the monoethanolamide prepared in Example 1.
[0020] Figure 3The infrared spectrum of the diethanolamide prepared in Example 8 is shown. Detailed Implementation
[0021] The present invention will be further explained and described below with reference to specific embodiments.
[0022] Example 1: A method for synthesizing monoethanolamide, comprising the following steps: 2.82 g of γ-stearin lactone (white powder; a byproduct of oleic acid hydroisomerization) and 2.44 g of monoethanolamine (γ-stearin lactone and monoethanolamine in a molar ratio of 1:4) were added to 5 mL of ethanol. The stirring speed was adjusted to 120 rpm, and the mixture was heated to 120 °C and refluxed for 60 min. While still hot, the reaction solution was dispersed in 50 mL of deionized water. The pH of the system was adjusted to 2 by slowly adding 37% hydrochloric acid. The mixture was stirred for 10 min (unreacted monoethanolamine formed a salt and dissolved in the aqueous phase). Then, 50 mL of n-butanol was added and the mixture was extracted by shaking for 10 min. After standing and separating the layers, the organic phase was collected, and 30 mL of [the solution] was added. The product was extracted twice with n-butanol, and the three organic phases were combined. The organic phase was then subjected to rotary evaporation for 30 min at 120℃ (near the boiling point of n-butanol, which can quickly remove the solvent without causing the target product to decompose) and a vacuum of 0.1 MPa (to remove n-butanol). The concentrated product (white) was then added to 30 mL of n-hexane while hot and stirred until completely dissolved. The mixture was allowed to stand at room temperature for 2 h (white crystals precipitated), filtered, and the crystals were washed twice with a small amount of n-hexane. The mixture was then vacuum dried for 2 h at 50℃ and a vacuum of 0.08 MPa to obtain monoethanolamide (white powder, yield 99.14%).
[0023] The infrared spectrum of γ-stearyl lactone is shown below. Figure 1 As shown.
[0024] Depend on Figure 1 We know that: 1758cm -1 The peak at this location represents the characteristic peak of the C=O stretching vibration of lactone.
[0025] The infrared spectrum of the monoethanolamide prepared in this embodiment is as follows: Figure 2 As shown.
[0026] Depend on Figure 2 We know that: 3273cm -1 The peak at 1638 cm⁻¹ represents the stretching vibration peak of the amide NH group. -1 The peak at 1050 cm⁻¹ represents the C=O stretching vibration of amides. -1 The peak at this point corresponds to the CO stretching vibration, which is consistent with the structural characteristics of monoethanolamide.
[0027] Example 2: A method for synthesizing monoethanolamide, comprising the following steps: 2.82 g of γ-stearin and 3.05 g of monoethanolamine (molar ratio of γ-stearin to monoethanolamine 1:5) were added to 5 mL of ethanol. The stirring speed was adjusted to 120 rpm, and the mixture was heated to 120 °C and refluxed for 60 min. While still hot, the reaction solution was dispersed in 50 mL of deionized water. The pH of the system was adjusted to 2 by slowly adding 37% hydrochloric acid. The mixture was stirred for 10 min, and then 50 mL of n-butanol was added for extraction by shaking for 10 min. After standing and separating the layers, the mixture was collected. The organic phase was extracted twice more with 30 mL of n-butanol. The three organic phases were combined and then rotary evaporated at 120 °C and 0.1 MPa for 30 min. The concentrated product (white) was then added to 30 mL of n-hexane while hot and stirred until completely dissolved. The mixture was allowed to stand at room temperature for 2 h (white crystals precipitated), filtered, and the crystals were washed twice with a small amount of n-hexane. The mixture was then vacuum dried at 50 °C and 0.08 MPa for 2 h to obtain monoethanolamide (white powder).
[0028] Infrared spectroscopy analysis revealed that the obtained white powdery product was monoethanolamide, and the yield of monoethanolamide calculated by weighing was 98.54%.
[0029] Example 3: A method for synthesizing monoethanolamide, comprising the following steps: 2.82 g of γ-stearin and 3.66 g of monoethanolamine (molar ratio of γ-stearin to monoethanolamine 1:6) were added to 5 mL of ethanol. The stirring speed was adjusted to 120 rpm, and the mixture was heated to 120 °C and refluxed for 60 min. While still hot, the reaction solution was dispersed in 50 mL of deionized water. The pH of the system was adjusted to 2 by slowly adding 37% hydrochloric acid. The mixture was stirred for 10 min, and then 50 mL of n-butanol was added for extraction by shaking for 10 min. After standing and separating the layers, the mixture was collected. The organic phase was extracted twice more with 30 mL of n-butanol. The three organic phases were combined and then rotary evaporated at 120 °C and 0.1 MPa for 30 min. The concentrated product (white) was then added to 30 mL of n-hexane while hot and stirred until completely dissolved. The mixture was allowed to stand at room temperature for 2 h (white crystals precipitated), filtered, and the crystals were washed twice with a small amount of n-hexane. The mixture was then vacuum dried at 50 °C and 0.08 MPa for 2 h to obtain monoethanolamide (white powder).
[0030] Infrared spectroscopy analysis revealed that the obtained white powdery product was monoethanolamide, and the yield of monoethanolamide calculated by weighing was 94.17%.
[0031] Example 4: A method for synthesizing monoethanolamide, comprising the following steps: 2.82 g of γ-stearin and 2.44 g of monoethanolamine (molar ratio of γ-stearin to monoethanolamine 1:4) were added to 5 mL of ethanol. The stirring speed was adjusted to 120 rpm, and the mixture was heated to 110 °C and refluxed for 60 min. While still hot, the reaction solution was dispersed in 50 mL of deionized water. The pH of the system was adjusted to 2 by slowly adding 37% hydrochloric acid. The mixture was stirred for 10 min, and then 50 mL of n-butanol was added for extraction by shaking for 10 min. After standing and separating the layers, the mixture was collected. The organic phase was extracted twice more with 30 mL of n-butanol. The three organic phases were combined and then rotary evaporated at 120 °C and 0.1 MPa for 30 min. The concentrated product (white) was then added to 30 mL of n-hexane while hot and stirred until completely dissolved. The mixture was allowed to stand at room temperature for 2 h (white crystals precipitated), filtered, and the crystals were washed twice with a small amount of n-hexane. The mixture was then vacuum dried at 50 °C and 0.08 MPa for 2 h to obtain monoethanolamide (white powder).
[0032] Infrared spectroscopy analysis revealed that the obtained white powdery product was monoethanolamide, and the yield of monoethanolamide calculated by weighing was 94.51%.
[0033] Example 5: A method for synthesizing monoethanolamide, comprising the following steps: 2.82 g of γ-stearin and 2.44 g of monoethanolamine (molar ratio of γ-stearin to monoethanolamine 1:4) were added to 5 mL of ethanol. The stirring speed was adjusted to 120 rpm, and the temperature was raised to 130 °C and refluxed for 60 min. While still hot, the reaction solution was dispersed in 50 mL of deionized water. The pH of the system was adjusted to 2 by slowly adding 37% hydrochloric acid. The mixture was stirred for 10 min, and then 50 mL of n-butanol was added for extraction by shaking for 10 min. After standing and separating the layers, the mixture was collected. The organic phase was extracted twice more with 30 mL of n-butanol. The three organic phases were combined and then rotary evaporated at 120 °C and 0.1 MPa for 30 min. The concentrated product (white) was then added to 30 mL of n-hexane while hot and stirred until completely dissolved. The mixture was allowed to stand at room temperature for 2 h (white crystals precipitated), filtered, and the crystals were washed twice with a small amount of n-hexane. The mixture was then vacuum dried at 50 °C and 0.08 MPa for 2 h to obtain monoethanolamide (white powder).
[0034] Infrared spectroscopy analysis revealed that the obtained white powdery product was monoethanolamide, and the yield of monoethanolamide calculated by weighing was 98.59%.
[0035] Example 6: A method for synthesizing monoethanolamide, comprising the following steps: 2.82 g of γ-stearyl lactone and 2.44 g of monoethanolamine (molar ratio of γ-stearyl lactone to monoethanolamine 1:4) were added to 5 mL of ethanol. The stirring speed was adjusted to 120 rpm, and the mixture was heated to 120 °C and refluxed for 45 min. While still hot, the reaction solution was dispersed in 50 mL of deionized water. The pH of the system was adjusted to 2 by slowly adding 37% hydrochloric acid. The mixture was stirred for 10 min, and then 50 mL of n-butanol was added for extraction by shaking for 10 min. After standing and separating the layers, the mixture was collected. The organic phase was extracted twice more with 30 mL of n-butanol. The three organic phases were combined and then rotary evaporated at 120 °C and 0.1 MPa for 30 min. The concentrated product (white) was then added to 30 mL of n-hexane while hot and stirred until completely dissolved. The mixture was allowed to stand at room temperature for 2 h (white crystals precipitated), filtered, and the crystals were washed twice with a small amount of n-hexane. The mixture was then vacuum dried at 50 °C and 0.08 MPa for 2 h to obtain monoethanolamide (white powder).
[0036] Infrared spectroscopy analysis revealed that the obtained white powdery product was monoethanolamide, and the yield of monoethanolamide calculated by weighing was 95.04%.
[0037] Example 7: A method for synthesizing monoethanolamide, comprising the following steps: 2.82 g of γ-stearyl lactone and 2.44 g of monoethanolamine (molar ratio of γ-stearyl lactone to monoethanolamine 1:4) were added to 5 mL of ethanol. The stirring speed was adjusted to 120 rpm, and the mixture was heated to 120 °C and refluxed for 75 min. While still hot, the reaction solution was dispersed in 50 mL of deionized water. The pH of the system was adjusted to 2 by slowly adding 37% hydrochloric acid. The mixture was stirred for 10 min, and then 50 mL of n-butanol was added for extraction by shaking for 10 min. After standing and separating the layers, the mixture was collected. The organic phase was extracted twice more with 30 mL of n-butanol. The three organic phases were combined and then rotary evaporated at 120 °C and 0.1 MPa for 30 min. The concentrated product (white) was then added to 30 mL of n-hexane while hot and stirred until completely dissolved. The mixture was allowed to stand at room temperature for 2 h (white crystals precipitated), filtered, and the crystals were washed twice with a small amount of n-hexane. The mixture was then vacuum dried at 50 °C and 0.08 MPa for 2 h to obtain monoethanolamide (white powder).
[0038] Infrared spectroscopy analysis revealed that the obtained white powdery product was monoethanolamide, and the yield of monoethanolamide calculated by weighing was 98.47%.
[0039] Example 8: A method for synthesizing diethanolamide, comprising the following steps: 2.82 g of γ-stearyl lactone and 8.40 g of diethanolamine (molar ratio of γ-stearyl lactone to diethanolamine 1:8) were added to 5 mL of ethanol. The stirring speed was adjusted to 120 rpm, and the mixture was heated to 120 °C and refluxed for 120 min. While still hot, the reaction solution was dispersed in 50 mL of deionized water. The pH of the system was adjusted to 2 by slowly adding 37% hydrochloric acid. The mixture was stirred for 10 min, and then 50 mL of n-butanol was added for extraction with shaking for 10 min. After standing and separation, the organic phase was collected. The product was extracted twice with 30 mL of n-butanol. The three organic phases were combined and then the organic phase was rotary evaporated at 120 °C and 0.1 MPa for 30 min. The concentrated product (white) was then added to 30 mL of n-hexane while hot and stirred until completely dissolved. The mixture was allowed to stand at room temperature for 2 h (white crystals precipitated), filtered, and the crystals were washed twice with a small amount of n-hexane. The mixture was then vacuum dried at 50 °C and 0.08 MPa for 2 h to obtain diethanolamide (white powder, yield 73.90%).
[0040] The infrared spectrum of the diethanolamide prepared in this embodiment is as follows: Figure 3 As shown.
[0041] Depend on Figure 3 It can be determined that: 3299cm -1 The peak at 1615 cm⁻¹ represents the stretching vibration peak of amide NH₃. -1 The peak at 1070 cm⁻¹ represents the C=O stretching vibration of amides. -1 The peak at this location corresponds to the CO stretching vibration, which is consistent with the structural characteristics of diethanolamide.
[0042] Example 9: A method for synthesizing diethanolamide, comprising the following steps: 2.82 g of γ-stearin and 7.35 g of diethanolamine (molar ratio of γ-stearin to diethanolamine 1:7) were added to 5 mL of ethanol. The stirring speed was adjusted to 120 rpm, and the mixture was heated to 120 °C and refluxed for 120 min. While still hot, the reaction solution was dispersed in 50 mL of deionized water. The pH of the system was adjusted to 2 by slowly adding 37% hydrochloric acid. The mixture was stirred for 10 min, and then 50 mL of n-butanol was added for extraction by shaking for 10 min. After standing and separating the layers, the mixture was collected. The organic phase was extracted twice more with 30 mL of n-butanol. The three organic phases were combined and then rotary evaporated at 120 °C and 0.1 MPa for 30 min. The concentrated product (white) was then added to 30 mL of n-hexane while hot and stirred until completely dissolved. The mixture was allowed to stand at room temperature for 2 h (white crystals precipitated), filtered, and the crystals were washed twice with a small amount of n-hexane. The mixture was then vacuum dried at 50 °C and 0.08 MPa for 2 h to obtain diethanolamide (white powder).
[0043] Infrared spectroscopy analysis revealed that the obtained white powdery product was diethanolamide, and the yield of diethanolamide calculated by weighing was 71.02%.
[0044] Example 10: A method for synthesizing diethanolamide, comprising the following steps: 2.82 g of γ-stearin and 9.45 g of diethanolamine (molar ratio of γ-stearin to diethanolamine 1:9) were added to 5 mL of ethanol. The stirring speed was adjusted to 120 rpm, and the mixture was heated to 120 °C and refluxed for 120 min. While still hot, the reaction solution was dispersed in 50 mL of deionized water. The pH of the system was adjusted to 2 by slowly adding 37% hydrochloric acid. The mixture was stirred for 10 min, and then 50 mL of n-butanol was added for extraction by shaking for 10 min. After standing and separating the layers, the mixture was collected. The organic phase was extracted twice more with 30 mL of n-butanol. The three organic phases were combined and then rotary evaporated at 120 °C and 0.1 MPa for 30 min. The concentrated product (white) was then added to 30 mL of n-hexane while hot and stirred until completely dissolved. The mixture was allowed to stand at room temperature for 2 h (white crystals precipitated), filtered, and the crystals were washed twice with a small amount of n-hexane. The mixture was then vacuum dried at 50 °C and 0.08 MPa for 2 h to obtain diethanolamide (white powder).
[0045] Infrared spectroscopy analysis revealed that the obtained white powdery product was diethanolamide, and the yield of diethanolamide calculated by weighing was 72.63%.
[0046] Example 11: A method for synthesizing diethanolamide, comprising the following steps: 2.82 g of γ-stearin and 8.40 g of diethanolamine (molar ratio of γ-stearin to diethanolamine 1:8) were added to 5 mL of ethanol. The stirring speed was adjusted to 120 rpm, and the mixture was heated to 110 °C and refluxed for 120 min. While still hot, the reaction solution was dispersed in 50 mL of deionized water. The pH of the system was adjusted to 2 by slowly adding 37% hydrochloric acid. The mixture was stirred for 10 min, and then 50 mL of n-butanol was added for extraction by shaking for 10 min. After standing and separating the layers, the mixture was collected. The organic phase was extracted twice more with 30 mL of n-butanol. The three organic phases were combined and then rotary evaporated at 120 °C and 0.1 MPa for 30 min. The concentrated product (white) was then added to 30 mL of n-hexane while hot and stirred until completely dissolved. The mixture was allowed to stand at room temperature for 2 h (white crystals precipitated), filtered, and the crystals were washed twice with a small amount of n-hexane. The mixture was then vacuum dried at 50 °C and 0.08 MPa for 2 h to obtain diethanolamide (white powder).
[0047] Infrared spectroscopy analysis revealed that the obtained white powdery product was diethanolamide, and the yield of diethanolamide calculated by weighing was 71.19%.
[0048] Example 12: A method for synthesizing diethanolamide, comprising the following steps: 2.82 g of γ-stearin and 8.40 g of diethanolamine (molar ratio of γ-stearin to diethanolamine 1:8) were added to 5 mL of ethanol. The stirring speed was adjusted to 120 rpm, and the temperature was raised to 130 °C and refluxed for 120 min. While still hot, the reaction solution was stirred and dispersed in 50 mL of deionized water. The pH of the system was adjusted to 2 by slowly adding 37% hydrochloric acid. The mixture was stirred for 10 min, and then 50 mL of n-butanol was added and extracted by shaking for 10 min. After standing and separating the layers, the mixture was collected. The organic phase was extracted twice more with 30 mL of n-butanol. The three organic phases were combined and then rotary evaporated at 120 °C and 0.1 MPa for 30 min. The concentrated product (white) was then added to 30 mL of n-hexane while hot and stirred until completely dissolved. The mixture was allowed to stand at room temperature for 2 h (white crystals precipitated), filtered, and the crystals were washed twice with a small amount of n-hexane. The mixture was then vacuum dried at 50 °C and 0.08 MPa for 2 h to obtain diethanolamide (white powder).
[0049] Infrared spectroscopy analysis revealed that the obtained white powdery product was diethanolamide, and the yield of diethanolamide calculated by weighing was 72.09%.
[0050] Example 13: A method for synthesizing diethanolamide, comprising the following steps: 2.82 g of γ-stearin and 8.40 g of diethanolamine (molar ratio of γ-stearin to diethanolamine 1:8) were added to 5 mL of ethanol. The stirring speed was adjusted to 120 rpm, and the mixture was heated to 120 °C and refluxed for 90 min. While still hot, the reaction solution was dispersed in 50 mL of deionized water. The pH of the system was adjusted to 2 by slowly adding 37% hydrochloric acid. The mixture was stirred for 10 min, and then 50 mL of n-butanol was added for extraction by shaking for 10 min. After standing and separating the layers, the mixture was collected. The organic phase was extracted twice more with 30 mL of n-butanol. The three organic phases were combined and then rotary evaporated at 120 °C and 0.1 MPa for 30 min. The concentrated product (white) was then added to 30 mL of n-hexane while hot and stirred until completely dissolved. The mixture was allowed to stand at room temperature for 2 h (white crystals precipitated), filtered, and the crystals were washed twice with a small amount of n-hexane. The mixture was then vacuum dried at 50 °C and 0.08 MPa for 2 h to obtain diethanolamide (white powder).
[0051] Infrared spectroscopy analysis revealed that the obtained white powdery product was diethanolamide, and the yield of diethanolamide calculated by weighing was 71.84%.
[0052] Example 14: A method for synthesizing diethanolamide, comprising the following steps: 2.82 g of γ-stearin and 8.40 g of diethanolamine (molar ratio of γ-stearin to diethanolamine 1:8) were added to 5 mL of ethanol. The stirring speed was adjusted to 120 rpm, and the mixture was heated to 120 °C and refluxed for 150 min. While still hot, the reaction solution was dispersed in 50 mL of deionized water. The pH of the system was adjusted to 2 by slowly adding 37% hydrochloric acid. The mixture was stirred for 10 min, and then 50 mL of n-butanol was added for extraction by shaking for 10 min. After standing and separating the layers, the mixture was collected. The organic phase was extracted twice more with 30 mL of n-butanol. The three organic phases were combined and then rotary evaporated at 120 °C and 0.1 MPa for 30 min. The concentrated product (white) was then added to 30 mL of n-hexane while hot and stirred until completely dissolved. The mixture was allowed to stand at room temperature for 2 h (white crystals precipitated), filtered, and the crystals were washed twice with a small amount of n-hexane. The mixture was then vacuum dried at 50 °C and 0.08 MPa for 2 h to obtain diethanolamide (white powder).
[0053] Infrared spectroscopy analysis revealed that the obtained white powdery product was diethanolamide, and the yield of diethanolamide calculated by weighing was 71.05%.
[0054] Comparative Example 1: A method for synthesizing diethanolamide, comprising the following steps: Add 2.82 g of γ-stearyl lactone, 8.40 g of diethanolamine (molar ratio of γ-stearyl lactone to diethanolamine 1:8), and 0.141 g of sodium ethoxide to 5 mL of ethanol. Adjust the stirring speed to 120 rpm, heat to 120 °C, and reflux for 120 min. While still hot, disperse the reaction solution in 50 mL of deionized water. Slowly add 37% hydrochloric acid to adjust the pH of the system to 2, stir for 10 min, then add 50 mL of n-butanol and extract with shaking for 10 min. Let stand. After separation, the organic phase was collected, and 30 mL of n-butanol was added for repeated extraction twice. The three organic phases were combined, and the organic phase was then subjected to rotary evaporation at 120 °C and 0.1 MPa for 30 min. The concentrated product (white) was then added to 30 mL of n-hexane while hot and stirred until completely dissolved. The mixture was allowed to stand at room temperature for 2 h (white crystals precipitated), filtered, and the crystals were washed twice with a small amount of n-hexane. The mixture was then vacuum dried at 50 °C and 0.08 MPa for 2 h to obtain diethanolamide (white powder).
[0055] Infrared spectroscopy analysis revealed that the obtained white powdery product was diethanolamide, and the yield of diethanolamide calculated by weighing was 52.20%.
[0056] Compared with Example 8, the yield of diethanolamide in this comparative example decreased significantly. This is because sodium ethoxide is a conventional alkaline catalyst for the synthesis of alkaline amides from fatty acids and alkaline amines. Its role is to promote the activation of the carboxyl group of fatty acids, thereby accelerating the amidation reaction. However, γ-stearyl lactone (a cyclic ester structure) is prone to hydrolysis in the alkaline environment provided by sodium ethoxide to generate γ-hydroxystearic acid, which leads to a reduction in the amount of lactone participating in the amidation reaction. At the same time, the amidation reaction activity of the hydrolyzed γ-hydroxystearic acid with diethanolamine is much lower than that of the nucleophilic addition reaction of γ-stearyl lactone with diethanolamine, and the reaction pathway is complex (accompanied by transesterification side reactions), ultimately resulting in a significant decrease in the yield of diethanolamide.
[0057] Therefore, it can be seen that the catalyst-free conditions of this invention can avoid the hydrolysis side reaction of γ-stearyl lactone and ensure that the amidation reaction proceeds along a single path, which is a key technical feature for achieving high yield.
[0058] Comparative Example 2: A method for synthesizing diethanolamide, comprising the following steps: Add 2.82 g of γ-stearyl lactone, 8.40 g of diethanolamine (molar ratio of γ-stearyl lactone to diethanolamine 1:8), and 0.282 g of sodium ethoxide to 5 mL of ethanol. Adjust the stirring speed to 120 rpm, heat to 120 °C, and reflux for 120 min. While still hot, disperse the reaction solution in 50 mL of deionized water. Slowly add 37% hydrochloric acid to adjust the pH of the system to 2, stir for 10 min, then add 50 mL of n-butanol and extract with shaking for 10 min. Let stand. After separation, the organic phase was collected, and 30 mL of n-butanol was added for repeated extraction twice. The three organic phases were combined, and the organic phase was then subjected to rotary evaporation at 120 °C and 0.1 MPa for 30 min. The concentrated product (white) was then added to 30 mL of n-hexane while hot and stirred until completely dissolved. The mixture was allowed to stand at room temperature for 2 h (white crystals precipitated), filtered, and the crystals were washed twice with a small amount of n-hexane. The mixture was then vacuum dried at 50 °C and 0.08 MPa for 2 h to obtain diethanolamide (white powder).
[0059] Infrared spectroscopy analysis revealed that the obtained white powdery product was diethanolamide, and the yield of diethanolamide calculated by weighing was 47.29%.
[0060] Compared with Comparative Example 1, the yield of diethanolamide in this comparative example further decreased. This is because: after further increasing the amount of sodium ethoxide, the alkalinity of the system increased, the hydrolysis reaction of γ-stearyl lactone became more intense, the raw material loss rate further increased, and the amidation reaction efficiency further decreased, ultimately leading to a further decrease in the yield of diethanolamide.
[0061] The present invention is a preferred embodiment, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.
Claims
1. A method for synthesizing alkanolamides, characterized in that, Includes the following steps: γ-Stearyl lactone was dispersed in ethanol and subjected to an amidation reaction with monoethanolamine or diethanolamine. The reaction solution was then added to water and the pH of the system was adjusted to 1-3 with hydrochloric acid. The mixture was then extracted with n-butanol, and the organic phase was concentrated. The concentrated product was then added to n-hexane for recrystallization. The crystals were then separated, washed, and dried to obtain alkanolamide.
2. The method for synthesizing alkanolamide according to claim 1, characterized in that: The molar ratio of γ-stearyl lactone to monoethanolamine is 1:4 to 6.
3. The method for synthesizing alkanolamide according to claim 2, characterized in that: The amidation reaction takes 45 to 75 minutes.
4. The method for synthesizing alkanolamide according to claim 1, characterized in that: The molar ratio of γ-stearyl lactone to diethanolamine is 1:7 to 9.
5. The method for synthesizing alkanolamide according to claim 4, characterized in that: The amidation reaction takes 90 to 150 minutes.
6. The method for synthesizing alkanolamide according to any one of claims 1 to 5, characterized in that: The amidation reaction is performed at a temperature of 110°C to 130°C.
7. The method for synthesizing alkanolamide according to any one of claims 1 to 5, characterized in that: The number of extractions is ≥2.
8. The method for synthesizing alkanolamide according to any one of claims 1 to 5, characterized in that: The concentration method is rotary evaporation.
9. The method for synthesizing alkanolamide according to any one of claims 1 to 5, characterized in that: The ratio of the concentrated product to n-hexane is 1g:5mL to 10mL.
10. The method for synthesizing alkanolamide according to any one of claims 1 to 5, characterized in that: The recrystallization is carried out at room temperature.