A method for directly synthesizing fatty acyl alanine salts from fatty acids

Abstract

The invention discloses a method for directly synthesizing fatty acid acyl alanine salt from fatty acid, wherein solid base, alanine and fatty acid are sequentially added to a reactor, the reactor is sealed, the gas in the reactor is replaced, and the pressure in the reactor is maintained; the temperature is gradually increased and reacted; the obtained product is post-treated to obtain the finished fatty acyl alanine salt. The invention adopts a specific feeding sequence and reaction form, so that during the reaction process, alanine and fatty acid are contacted and reacted at the solid-liquid interface, and the solid base penetrates to the reaction interface through alanine to catalyze and participate in the reaction; alanine separates the fatty acid from the solid base, avoiding the direct contact of the fatty acid with the base to saponify into a byproduct fatty acid salt, reducing the saponification side reaction of the fatty acid, thereby obtaining a high-quality fatty acyl alanine salt product.

Description

Technical Field

[0001] The invention belongs to the technical field of fine chemical industry, relates to the synthesis of fatty acyl alanine salts, and in particular to a method for directly synthesizing fatty acyl alanine salts from fatty acids, which can improve product quality, reduce production costs and eliminate production safety hazards. Background Art

[0002] Surfactants have a series of physical and chemical properties and related applications such as wetting, emulsification, foaming, solubilization, and decontamination. The development of the field of surfactants at home and abroad has always been green and functional, focusing on the safety of product processes and raw materials and the high-efficiency and high-quality development of products. Amino acid surfactants are products that adapt to the development of the times. Fatty acyl amino acid salts are a type of amino acid anionic surfactants with good wetting, emulsification, foaming, decontamination, corrosion inhibition and other properties; the reactants are all components of organisms, easy to biodegrade, and the product is safe, which is in line with the development direction of the times.

[0003] At present, the synthesis methods of fatty acyl amino acid salts mainly include chemical synthesis, enzyme synthesis and chemical-enzyme synthesis. The enzyme method is not suitable for large-scale production, and the chemical synthesis method is still the main idea for synthesizing fatty acyl amino acid salts. The chemical synthesis method mainly includes direct dehydration condensation of fatty acids, amidation of fatty anhydrides, hydrolysis and acylation of fatty nitriles, carbonyl addition of fatty amides, amidation of ester compounds and amidation reaction of fatty acid chlorides, i.e., the Schotten-Baumann condensation process. At present, the industrial production of fatty acyl amino acid salts mainly adopts the Schotten-Baumann condensation process, that is, under alkaline conditions, the amidation reaction of fatty acid chlorides with amino acid salts in a mixed solvent of water / organic solvents is prepared. The use of organic solvents in this process and the raw material fatty acid chlorides bring about an equimolar amount of sodium chloride by-products, which requires cumbersome post-treatment to remove solvents and by-products, thereby bringing high economic costs and a large amount of industrial wastewater. At the same time, the easy hydrolysis of fatty acid chlorides will increase the fatty acid salt by-products of the product. This process has many disadvantages, including high by-product content, high economic cost, and production safety issues caused by organic solvents. Solving the above problems by improving the synthesis method or process route has very important practical significance for the development of fatty acyl amino acid salt products.

[0004] There are a few reports on the use of fatty acids as raw materials to replace fatty acid chlorides to synthesize fatty acyl amino acid salts. Zeng et al. used lauric acid and sodium methyl taurate as raw materials, and synthesized sodium lauroyl methyl taurate in liquid paraffin with boric acid as a catalyst. However, the high proportion of liquid paraffin and boric acid required complex post-treatment removal, which brought high economic costs and was not promoted. Patent CN106588710A uses a special synthesis method, namely microwave heating to synthesize fatty acyl methyl taurate. At present, reports on the direct synthesis of fatty acyl amino acid salts using fatty acids as raw materials are only found in the synthesis of acyl methyl taurate products, and the synthesis of other amino acid salts has not been reported. Summary of the invention

[0005] The purpose of the present invention is to provide a method for directly synthesizing fatty acyl alanine salts from fatty acids. The method avoids the side reaction of direct saponification of fatty acids and alkalis through a specific feeding sequence, thereby obtaining high-quality products. Solid alkalis are directly used for reaction without removing solvents. The pH and solid content of the products obtained by solvent-free reaction can be adjusted according to customer needs, thereby making the product application more convenient.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for directly synthesizing fatty acyl alanine salts from fatty acids comprises the following steps:

[0008] 1) Adding solid base, alanine and fatty acid into the reactor in sequence;

[0009] 2) Close the reactor, replace the gas in the reactor, and maintain the pressure in the reactor;

[0010] 3) gradually increase the temperature and react;

[0011] 4) The obtained product is post-treated to obtain the finished fatty acyl alanine salt.

[0012] In the present invention, solid base, alanine and fatty acid are used as raw materials, and the solid base permeates and catalyzes the reaction by itself, and fatty acyl alanine salt is prepared by amidation. Taking the reaction of lauric acid, L-alanine and sodium hydroxide as an example, the reaction equation is as follows: Figure 2 shown.

[0013] The key to the invention is to adopt a specific adding sequence. First, solid alkali is added to the bottom of the reactor, then alanine is added, and finally fatty acid is added. The reaction condition is to increase the temperature step by step, so that during the reaction, alanine and fatty acid are contacted and reacted at the solid-liquid interface, and the solid alkali penetrates into the reaction interface through alanine to catalyze and participate in the reaction; alanine separates the fatty acid from the solid alkali, thereby avoiding direct contact between the fatty acid and the alkali and saponification to form a by-product fatty acid salt, reducing the saponification side reaction of the fatty acid, and thus obtaining a high-quality fatty acyl alanine salt product; by increasing the temperature step by step, the reaction is carried out more slowly, so that the amidation reaction rate is adapted to the penetration rate of the solid alkali, and other side reactions are prevented from being generated by excessively high temperature, so that the color of the product becomes darker.

[0014] As a preferred embodiment of the present invention, in step 1), the molar ratio of fatty acid, alanine and solid base is 1.0:1.0-1.5:1.0-1.5.

[0015] As a preferred embodiment of the present invention, the fatty acid includes C8~C 18 Natural fatty acids or mixtures thereof.

[0016] As a preferred embodiment of the present invention, the fatty acid includes one or more combinations of caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid or coconut oleic acid.

[0017] As a preferred embodiment of the present invention, the solid alkali is flaky or granular solid sodium hydroxide or solid potassium hydroxide.

[0018] As a preferred embodiment of the present invention, in step 2), nitrogen is introduced to replace the gas in the reactor to maintain the pressure in the reactor at 0.01-0.05 MPa.

[0019] Nitrogen is introduced to replace the atmosphere so as to create an oxygen-free environment in the reactor to prevent the high temperature from causing the raw material to darken in color; nitrogen is continued to be introduced to continuously remove the water generated in the reaction to promote the reaction.

[0020] As a preferred embodiment of the present invention, in step 3), the stepwise heating is to heat to 100°C for reaction for 2h, then continue to heat to 120°C for reaction for 2h, then continue to heat to 140°C for reaction for 2h, and finally heat to 160°C for reaction for 10h until the reaction is complete.

[0021] As a preferred embodiment of the present invention, in step 4), the post-treatment includes decolorization, pH adjustment and solid content adjustment.

[0022] The pH value can be adjusted by using hydrochloric acid, sulfuric acid, citric acid, sodium hydroxide or potassium hydroxide, etc. The pH value of the final product can be adjusted to 6-12 according to the customer's requirements, and the solid content can be adjusted to 30-60% according to the customer's requirements.

[0023] As a preferred embodiment of the present invention, the decolorizing agent used for decolorization is hydrogen peroxide.

[0024] As a preferred embodiment of the present invention, the pH regulator used for pH adjustment includes one of hydrochloric acid, sulfuric acid, citric acid, sodium hydroxide or potassium hydroxide.

[0025] Compared with the current industrial Schotten-Bowman condensation process for synthesizing fatty acyl alanine salts, the present invention has the following beneficial effects:

[0026] 1) The present invention uses green fatty acid raw materials to replace fatty acid chloride, which not only solves the problem of poor environmental friendliness of the source of acyl chloride, but also the price of fatty acid is much lower than that of fatty acid chloride;

[0027] 2) The present invention uses fatty acids as raw materials to avoid the byproduct sodium chloride in the product, and no multiple separation and purification processes are required, and no industrial waste is generated in the entire synthesis process;

[0028] 3) The present invention adopts a specific addition sequence and reaction form, that is, the solid base is separated by alanine to prevent the saponification side reaction of fatty acids and bases, so that the fatty acid salt content is only 0.2-0.4%, the yield of fatty acyl alanine salt can reach 98%, and the product quality is much higher than the market products;

[0029] 4) The present invention adopts a solvent-free method to avoid the use of organic solvents, which not only increases the single-pot output, but also improves the greenness and safety of the production process and saves solvent recovery costs;

[0030] 5) The solid content of the fatty acyl alanine salt solid product obtained by the solvent-free method of the present invention can be adjusted according to customer needs, so as to facilitate its application in the formulation of daily chemical products. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is the infrared spectrum of sodium lauroyl alanine synthesized in Example 1 of the present invention.

[0032] Figure 2 It is the reaction equation of the reaction of lauric acid, L-alanine and sodium hydroxide of the present invention. DETAILED DESCRIPTION

[0033] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 making creative work are within the scope of protection of the present invention.

[0034] Example 1

[0035] The present embodiment provides a method for directly synthesizing fatty acyl alanine salt from fatty acids, wherein 0.1 mol of granular sodium hydroxide, 0.105 mol of alanine and 0.1 mol of lauric acid are sequentially added to a reactor, replaced with nitrogen three times, and the system is kept at a slight positive pressure of 0.01-0.05 MPa, and the temperature is initially raised to 100°C for reaction for 2 hours, then raised to 120°C for reaction for 2 hours, then raised to 140°C for reaction for 2 hours, and finally raised to 160°C for reaction for 10 hours until the reaction is complete, thereby obtaining a crude product of sodium lauroyl alanine. 10 g of 2 wt.% hydrogen peroxide is added, and the product is heat-treated at 65°C for decolorization, a small amount of citric acid is added, the pH is adjusted to 7.5-8.5, and water is added to adjust the solid content to obtain a 50% aqueous solution of sodium lauroyl alanine. The product has a color of 38 degrees, and the by-product fatty acid sodium content is only 0.42%. The infrared spectrum of sodium lauroyl alanine shows Figure 1 .

[0036] Example 2

[0037] The present embodiment provides a method for directly synthesizing fatty acyl alanine salt from fatty acid, wherein 0.1 mol of flaky potassium hydroxide, 0.105 mol of alanine and 0.1 mol of coconut oil acid are sequentially added to a reactor, replaced with nitrogen 3 times, and the system is kept at a slight positive pressure of 0.01-0.05 MPa, and the temperature is initially raised to 100°C for reaction for 2 hours, then raised to 120°C for reaction for 2 hours, then raised to 140°C for reaction for 2 hours, and finally raised to 160°C for insulation reaction for 10 hours until the reaction is complete, thereby obtaining a crude product of potassium cocoyl alanine. 10 g of 2 wt.% hydrogen peroxide is added, and the mixture is heat-insulated and decolorized at 65°C, a small amount of hydrochloric acid is added, the pH value is adjusted to 8.0-9.0, and water is added to adjust the solid content, thereby obtaining a 40% aqueous solution product of potassium cocoyl alanine, the product color is 32 degrees, and the byproduct fatty acid potassium content is only 0.53%.

[0038] Example 3

[0039] The present embodiment provides a method for directly synthesizing fatty acyl alanine salt from fatty acid, wherein 0.1 mol of flaky sodium hydroxide, 0.108 mol of alanine and 0.1 mol of myristic acid are sequentially added to a reactor, replaced with nitrogen 3 times, and the system is kept at a slight positive pressure of 0.01-0.05 MPa, and the temperature is initially raised to 120°C for reaction for 2 hours, then raised to 140°C for reaction for 2 hours, then raised to 160°C for reaction for 2 hours, and finally raised to 180°C for insulation reaction for 10 hours until the reaction is complete, thereby obtaining a crude product of sodium myristoyl alanine. 10 g of 2 wt.% hydrogen peroxide is added, and the mixture is heat-insulated and decolorized at 65°C, a small amount of sodium hydroxide is added, the pH value is adjusted to 10.5-11.5, and water is added to adjust the solid content, thereby obtaining a 30% aqueous solution product of sodium lauroyl alanine, the product color is 28 degrees, and the byproduct fatty acid sodium content is only 0.58%.

[0040] Example 4

[0041] The present embodiment provides a method for directly synthesizing fatty acyl alanine salt from fatty acids, wherein 0.1 mol of flaky sodium hydroxide, 0.110 mol of alanine and 0.1 mol of palmitic acid are sequentially added to a reactor, replaced with nitrogen 3 times, and the system is kept at a slight positive pressure of 0.01-0.05 MPa, and the temperature is initially raised to 130°C for reaction for 2 hours, then raised to 150°C for reaction for 2 hours, then raised to 170°C for reaction for 2 hours, and finally raised to 190°C for insulation reaction for 10 hours until the reaction is complete, thereby obtaining a crude product of sodium palmitoyl alanine. 10 g of 2 wt.% hydrogen peroxide is added, and the product is heat-decolorized at 65°C, and a small amount of sodium hydroxide is added to adjust the pH to 10.5-11.5, and water is added to adjust the solid content to obtain a 30% aqueous solution product of sodium palmitoyl alanine, the product color is 36 degrees, and the by-product fatty acid sodium content is only 0.62%.

[0042] Comparative Example 1

[0043] The addition order was changed. 0.105 mol L-alanine, 0.1 mol granular sodium hydroxide and 0.1 mol lauric acid were added to the reactor in sequence. The system was replaced with nitrogen three times, and a slight positive pressure of 0.01-0.05 MPa was maintained in the system. The temperature was gradually raised to 130°C and the reaction was kept warm for 10 hours until the reaction was complete. The sodium fatty acid content was as high as 60%, that is, most of the lauric acid was converted into sodium laurate, indicating that the above addition order was not feasible.

[0044] It can be seen that the present invention adopts a specific feeding sequence and reaction form, so that during the reaction process, alanine and fatty acid are contacted and reacted at the solid-liquid interface, and the solid base penetrates into the reaction interface through the alanine to catalyze and participate in the reaction; the alanine separates the fatty acid from the solid base, thereby avoiding the direct contact of the fatty acid with the base to saponify into a by-product fatty acid salt, reducing the saponification side reaction of the fatty acid, thereby obtaining a high-quality fatty acyl alanine salt product; in the product prepared by the method of the present invention, the fatty acid salt content is only 0.2-0.4%, the yield of the fatty acyl alanine salt can reach 98%, and the product quality is much higher than that of the market product.

[0045] The above is only a preferred embodiment of the present invention, and is not any formal or substantial limitation of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present invention, and these improvements and supplements should also be regarded as the protection scope of the present invention. Any technician familiar with this profession, without departing from the spirit and scope of the present invention, can make some changes, modifications and evolutions of the technical content disclosed above, which are equivalent embodiments of the present invention; at the same time, any changes, modifications and evolutions of any equivalent changes made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for directly synthesizing fatty acyl alanine salts from fatty acids, characterized in that: The following steps are involved: 1) Add solid base, alanine and fatty acid into the reactor in sequence; the molar ratio of fatty acid, alanine and solid base is 1.0:1.0-1.5:1.0-1.5; the fatty acid is selected from C8-C 18 Natural fatty acids or mixtures thereof; 2) Close the reactor, replace the gas in the reactor, and maintain the pressure in the reactor; 3) gradually heating up and reacting; the stepwise heating up is heating up to 100°C for reaction for 2h, then heating up to 120°C for reaction for 2h, then heating up to 140°C for reaction for 2h, and finally heating up to 160°C for reaction for 10h until the reaction is complete; 4) The obtained product is post-treated to obtain the finished fatty acyl alanine salt.

2. The method for directly synthesizing fatty acyl alanine salts from fatty acids according to claim 1, characterized in that: The fatty acid comprises one or more combinations of caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid or coconut oleic acid.

3. The method for directly synthesizing fatty acyl alanine salts from fatty acids according to claim 1, characterized in that: The solid alkali is flaky or granular solid sodium hydroxide or solid potassium hydroxide.

4. The method for directly synthesizing fatty acyl alanine salts from fatty acids according to claim 1, characterized in that: In step 2), nitrogen is introduced to replace the gas in the reactor to maintain the pressure in the reactor at 0.01-0.05 MPa.

5. The method for directly synthesizing fatty acyl alanine salts from fatty acids according to claim 1, characterized in that: In step 4), the post-treatment includes decolorization, pH adjustment and solid content adjustment.

6. The method for directly synthesizing fatty acyl alanine salts from fatty acids according to claim 5, characterized in that: The decolorizing agent used for decolorization is hydrogen peroxide.

7. The method for directly synthesizing fatty acyl alanine salts from fatty acids according to claim 5, characterized in that: The pH adjuster used for pH adjustment includes one of hydrochloric acid, sulfuric acid, citric acid, sodium hydroxide or potassium hydroxide.

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