Preparation method of fatty alcohol potassium phosphate with high monoester content

Abstract

The invention discloses a preparation method of fatty alcohol potassium phosphate with high monoester content, which comprises the following steps: esterifying fatty alcohol by using polyphosphoric acid as a phosphorylation reagent, dissolving by using a mixed organic solvent consisting of an oxygen-containing polar solvent and a non-polar solvent, washing with water, dropwise adding a potassium hydroxide solution, and reacting to obtain the fatty alcohol potassium phosphate with high monoester content. The high-quality fatty alcohol potassium phosphate can be obtained. According to the fatty alcohol potassium phosphate product obtained through the preparation method, the residual amount of phosphoric acid is lower than 500 ppm, the residual amount of fatty alcohol is lower than 0.5%, and the preparation method is mild in reaction condition, short in reaction time, high in selectivity, high in conversion rate, environmentally friendly, easy to operate, simple in process route and easy to control.

Description

Technical Field

[0001] The invention relates to a surfactant, in particular to a method for preparing a potassium salt of fatty alcohol phosphate. Background Art

[0002] Monofatty alcohol phosphate and its salt are one of the important varieties of anionic surfactants. The structure is shown in Formula II, where R 1 = aliphatic alkyl, R 2 =H or K.

[0003]

[0004] Since monoalcohol phosphate is similar to natural lecithin in structure and physiological function, it has low toxicity, low irritation, and very good affinity to the skin. After neutralization into salt, it has the characteristics of general anionic surfactants, such as water solubility, emulsification, etc., and has a certain detergency ability, but it does not degrease. It is a mild surfactant and is very suitable for skin cleaning. It has excellent antistatic properties, softening and conditioning properties, and emulsification and dispersibility. It is less irritating, mild, easy to rinse, has rich and delicate foam, and leaves a smooth feeling after washing. It is widely used in skin care products.

[0005] Alkyl phosphate products are usually prepared by esterification reaction between phosphating agents and fatty alcohols. Commonly used phosphating agents include phosphorus pentoxide, polyphosphoric acid, phosphoric acid, phosphorus oxychloride, phosphorus trichloride, etc. A large number of intermediates are produced in the esterification process, so it is difficult to selectively control monoalkyl, dialkyl, and trialkyl molecules. Alkyl phosphate salts are prepared by neutralization reaction of phosphate esters with alkali. Reducing the residual fatty alcohol and phosphoric acid is also necessary to improve the quality of this type of surfactant, but there are usually problems such as cumbersome processes and high production costs.

[0006] Chinese patent application CN107337689A discloses a method for preparing alkyl phosphate monoesters using a mixed phosphating agent (phosphorus pentoxide and phosphoric acid). The reaction rate of this method is improved and the amount of catalyst used is reduced, but it still has limitations such as long reaction time and high vacuum requirements.

[0007] Chinese patent application CN117866007A discloses a method for preparing hexadecyl phosphate monoester, using hexadecyl alcohol and polyphosphoric acid as raw materials in a solvent, using activated carbon supported phosphotungstic acid (HPW / C) as a catalyst, oil bath heating reflux for phosphoesterification reaction, filtering out HPW / C after the reaction, concentrating and removing the solvent, and obtaining a high-yield, high-purity hexadecyl phosphate monoester. This technology requires the use of a specific catalyst, the reaction conditions are relatively harsh, and the catalyst needs to be recovered later, and the residual phosphoric acid and hexadecyl alcohol are high.

[0008] Chinese patent application CN1884288A discloses a method for purifying monoalkyl phosphate, which comprises: A. preparing a raw material solution and a neutralization treatment liquid: dissolving the monoalkyl phosphate raw material to be treated in an organic solvent to prepare a raw material solution, wherein the weight ratio of the raw material to the solvent is 1:1-2; preparing a neutralization treatment liquid with alkali and ethanol or isopropanol, wherein the molar ratio of the alkali to the monoalkyl phosphate and the residual acid in the raw material is 1:0.8-1.5, and the weight ratio of ethanol or isopropanol to the monoalkyl phosphate is 0.5-2:1; B. neutralization treatment: slowly adding the prepared neutralization treatment liquid to the raw material solution, and fully stirring it under stirring conditions. The reaction generates a white precipitate and the final slurry is still kept in an acidic state, and the slurry is filtered to obtain the precipitate monoalkyl phosphate monosalt; C, acidification treatment: the precipitate obtained by neutralization treatment is placed in a strong acid dilute solution, and the acidification reaction is carried out under stirring until the precipitate is safely reduced to a phosphate ester; D, extraction: an organic solvent is added to the acidified liquid, and the monoalkyl phosphate is extracted at room temperature or under heating conditions. After the reaction is completed, the slurry is allowed to stand for stratification, and then the oil phase extract is extracted; E, distillation and drying treatment: the extract obtained in step D is distilled to recover the organic solvent, and then the distilled product is dried and crushed to obtain a high-purity monoalkyl phosphate product. Although this method can effectively purify monoalkyl phosphate, the process route is relatively complicated, the equipment requirements are high, the production cost is high, and industrialization is relatively difficult to achieve, and the residual acid content of the purified product is about 0.35-0.5wt%, which is still relatively high.

[0009] As mentioned above, the currently reported methods of using phosphorus pentoxide and mixed phosphating agents have violent reactions, low selectivity, and high risk of industrial production; the phosphoric acid method has a long reaction time, cumbersome process, high requirements for process conditions, and the use of complex reaction procedures or the addition of additional catalysts. Although the yield can be improved, it will inevitably cause other problems, such as expensive catalysts, difficult catalyst recovery, difficult catalyst removal from the product, complex process, and difficulty in industrial operation.

[0010] Therefore, how to obtain high-quality, high-yield and green and environmentally friendly synthetic process of fatty alcohol phosphate potassium salt is still worth exploring. Summary of the invention

[0011] The inventors conducted intensive research and found that high-quality fatty alcohol phosphate potassium salt can be obtained by esterifying fatty alcohol using polyphosphoric acid as a phosphating agent, then dissolving and washing with a mixed organic solvent consisting of an oxygen-containing polar solvent and a non-polar solvent, and then dripping a potassium hydroxide solution, thereby completing the present invention.

[0012] The object of the present invention is to provide a method for preparing potassium salt of fatty alcohol phosphate with high monoester content. The method of the present invention uses polyphosphoric acid as a phosphating agent to esterify fatty alcohol, then uses a mixed organic solvent composed of an oxygen-containing polar solvent and a non-polar solvent to dissolve and wash with water, and then drops a potassium hydroxide solution.

[0013] In the present invention, the structure of the potassium salt of fatty alcohol phosphate is as shown in formula (I),

[0014]

[0015] Among them, R 1 Selected from C 8～22 Aliphatic alkyl; preferably C 12～22 further preferably n-dodecyl, n-hexadecyl or n-docosyl.

[0016] Preferably, the preparation method of the fatty alcohol phosphate potassium salt with high monoester content of the present invention comprises the following steps:

[0017] (1) Esterification: Add fatty alcohol to a reaction vessel, raise the temperature to 60-70°C, add polyphosphoric acid, continue to raise the temperature to 80-120°C, and stir to react;

[0018] (2) Dissolving: adding a mixed organic solvent consisting of an oxygen-containing polar solvent and a non-polar solvent into a reaction container for dissolving;

[0019] (3) washing with water: washing with water to obtain an organic phase solution of fatty alcohol phosphate;

[0020] (4) Salt formation: Heat the organic phase solution of fatty alcohol phosphate to 50-60°C, add potassium hydroxide solution dropwise, cool to crystallize, filter, and dry.

[0021] In a preferred embodiment, in step (1), the fatty alcohol is C 8～22 Fatty alcohol.

[0022] In a preferred embodiment, the molar ratio of fatty alcohol to polyphosphoric acid in step (1) is 1.0:0.9-2.5; the esterification step promotes almost complete reaction conversion of fatty alcohol, and the reaction speed is fast.

[0023] In a further preferred embodiment, the molar ratio of fatty alcohol to polyphosphoric acid in step (1) is 1.0:1.1-2.0.

[0024] In the present invention, in step (1), after the temperature is raised for reaction, the fatty alcohol content in the reaction system is detected, and when the fatty alcohol content is lower than 5 wt %, the reaction is stopped.

[0025] In the present invention, step (1) obtains a fatty alcohol phosphate system, in which mono-fatty alcohol phosphate accounts for a high proportion.

[0026] The present invention adopts a mixed organic solvent consisting of an oxygen-containing polar solvent and a non-polar solvent to dissolve the fatty alcohol phosphate obtained in step (1).

[0027] The oxygen-containing polar solvent is selected from esters, ethers or ketones; preferably one or more of ethyl formate, methyl acetate, ethyl acetate, isopropyl acetate, propyl ether, methyl tert-butyl ether, tetrahydrofuran, methyltetrahydrofuran, acetone or 2-hexanone;

[0028] The non-polar solvent is selected from one or more of petroleum ether, n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, n-tridecane, n-tetradecane, n-pentadecane or n-hexadecane.

[0029] The oxygen-containing polar solvent and the non-polar solvent described in the present invention can be combined arbitrarily.

[0030] In the present invention, there is no particular limitation on the amount of oxygen-containing polar solvent and non-polar solvent, but the volume ratio of oxygen-containing polar solvent to non-polar solvent is preferably 4 to 12:1, preferably 4 to 10:1; at this time, the mixed organic solvent can fully dissolve the fatty alcohol phosphate to avoid emulsification, so as to facilitate the subsequent water washing.

[0031] Preferably, in step (2) of the present invention, the amount of the mixed organic solvent is 3 to 15 times the volume of the fatty alcohol phosphate system obtained in step (1).

[0032] In step (3), the polyphosphoric acid in the system is hydrolyzed into phosphoric acid by water washing. The phosphoric acid is soluble in the aqueous phase and can be separated and removed from the organic phase of the fatty alcohol phosphate to prevent acid residue.

[0033] Preferably, in step (3), in order to ensure the hydrolysis washing effect, water washing is stopped when the pH of the water phase is ≥ 2. In practice, it is found that water washing usually requires at least 3 times or more, and the pH of the water phase is ≥ 2.

[0034] In step (4) of the present invention, a potassium hydroxide solution is added dropwise at a temperature of 50 to 60° C. to form a fatty alcohol phosphate potassium salt, and then high-purity fatty alcohol phosphate potassium salt is obtained by cooling and crystallizing.

[0035] The potassium hydroxide solution of the present invention has no particular requirement for its concentration, and preferably has a potassium hydroxide solution with a mass percentage of 5 to 30%, such as a 10% or 20% potassium hydroxide solution.

[0036] The crystallization temperature is preferably 10 to 20°C, more preferably 15°C.

[0037] Beneficial effects of the present invention:

[0038] (1) The present invention uses polyphosphoric acid with stable properties as the phosphating agent, which can react under mild conditions, with a short reaction time and a high conversion rate, thus overcoming the problems of the severe reaction conditions and low selectivity of the phosphorus pentoxide method, and well overcoming the problems of the phosphoric acid method with a long reaction time and a low conversion rate; and the polyphosphoric acid material is relatively stable in properties, unlike phosphorus oxychloride, phosphorus trichloride and the like which have high toxicity;

[0039] (2) The present invention uses a mixed organic solvent consisting of an oxygen-containing polar solvent and a non-polar solvent to dissolve, thereby avoiding emulsification, making it easy to wash the phosphoric acid with water, and effectively removing the phosphoric acid;

[0040] (3) The content of the monofatty alcohol phosphate potassium salt obtained by the present invention is as high as 98% or more;

[0041] (4) The monofatty alcohol phosphate potassium salt obtained by the present invention has excellent quality, with the residual phosphoric acid content being less than 500 ppm and the residual fatty alcohol content being less than 0.5%;

[0042] (5) The method of the present invention is green and environmentally friendly, simple to operate, has a simple process route, and is easy to control. DETAILED DESCRIPTION

[0043] The present invention is further described in detail below by way of examples, but these specific descriptions are only used to illustrate the technical solution of the present invention and do not constitute any limitation to the present invention.

[0044] Example 1

[0045] (1) Esterification: In a 2L four-necked flask, add 100g of dodecanol (lauryl alcohol), heat to 60°C to dissolve, slowly dropwise add 50.31g (1.1eq.) of polyphosphoric acid, heat to 90°C, stir to react for 6h, take samples for testing, lauryl alcohol content ≤2.6%, the reaction is completed, and the temperature is lowered to 60°C.

[0046] (2) Dissolution: Add 400 mL of ethyl acetate and 100 mL of n-hexane and stir until completely dissolved.

[0047] (3) Water washing: Add 200 mL of water, stir for 1 h, let stand to separate the liquids, and wash the organic phase three times. The pH of the aqueous phase is 2.9.

[0048] (4) Salt formation: The organic phase was heated to 60°C, 115.7 g of 20% potassium hydroxide aqueous solution was slowly added dropwise, the temperature was controlled at 55±5°C and stirred for 2 h, the temperature was slowly lowered to 15°C, and after stirring at 15±5°C for 3 h, the mixture was filtered while keeping warm, and the filter cake was washed with 200 mL of ethyl acetate to obtain 186.28 g of a wet product.

[0049] (5) Drying: 186.28 g of the wet product was placed in a clean and dry enamel dish and vacuum dried at 85° C. until the moisture content was ≤1% w / w to obtain 158.79 g of potassium lauryl phosphate with a yield of 97.2% (based on lauryl alcohol). The quality test results are shown in Table 1.

[0050] Table 1

[0051] project Test results Appearance White powder pH 7.2 Lauryl alcohol content 0.2％ Phosphate content 300ppm Potassium Monolauryl Phosphate Content 99.0％

[0052] Example 2

[0053] (1) Esterification: In a 2L four-necked flask, add 100g of hexadecanol (cetyl alcohol), heat to 65°C to dissolve, slowly drop 63.26g (1.8eq.) of polyphosphoric acid, heat to 120°C, stir to react for 8h, take samples for testing, the hexadecanol content is ≤2.8%, the reaction is completed, and the temperature is lowered to 60°C.

[0054] (2) Dissolution: Add 1000 mL of isopropyl acetate and 100 mL of petroleum ether and stir until completely dissolved.

[0055] (3) Washing with water: Add 400 mL of water, stir for 1 h, and then stand to separate the liquids. After the organic phase is washed 4 times, the pH value of the aqueous phase is 2.7.

[0056] (4) Salt formation: The organic phase was heated to 60°C, 115.7 g of 20% potassium hydroxide aqueous solution was slowly added dropwise, the temperature was controlled at 55±5°C and stirred for 2 h, the temperature was slowly lowered to 15°C, and after stirring at 15±5°C for 3 h, the mixture was filtered while keeping warm, and the filter cake was washed with 200 mL of isopropyl acetate to obtain 192.28 g of a wet product.

[0057] (5) Drying: 192.28 g of the wet product was placed in a clean and dry enamel dish and vacuum dried at 85° C. until the moisture content was ≤1% w / w, to obtain 145.43 g of potassium cetyl phosphate with a yield of 97.8% (based on cetyl alcohol). The quality test is shown in Table 2.

[0058] Table 2

[0059] project Test results Appearance White powder pH 7.4 Hexadecanol content 0.1％ Phosphate content 324ppm Potassium Monocetyl Phosphate Content 98.0％

[0060] Example 3

[0061] (1) Esterification: In a 2L four-necked flask, add 100g of n-docosanol (behenyl alcohol), heat to 70°C to dissolve, slowly drop 52.18g (2.0eq.) of polyphosphoric acid, heat to 110°C, stir to react for 8h, take samples for testing, behenyl alcohol ≤3.5%, the reaction is complete, and cool to 60°C.

[0062] (2) Dissolution: Add 650 mL of 2-hexanone and 100 mL of n-pentane and stir until completely dissolved.

[0063] (3) Washing with water: Add 80 mL of water, stir for 1 h, and then stand to separate the liquids. After the organic phase is washed 5 times, the pH of the aqueous phase is 3.0.

[0064] (4) Salt formation: The organic phase was heated to 50°C, 180.6 g of 10% potassium hydroxide aqueous solution was slowly added dropwise, the temperature was controlled at 55±5°C and stirred for 2 h, the temperature was slowly lowered to 15°C, stirred at 15±5°C for 3 h, the mixture was filtered while keeping the temperature, and the filter cake was washed with 250 mL of 2-hexanone to obtain 162.58 g of a wet product.

[0065] (5) Drying: 162.58 g of the wet product was placed in a clean and dry enamel dish and vacuum dried at 85° C. until the moisture content was ≤1% w / w to obtain 129.34 g of potassium behenyl phosphate with a yield of 94.9% (based on behenyl alcohol). The quality test result is shown in Table 3.

[0066] Table 3

[0067] project Test results Appearance White powder pH 7.6 Behenyl alcohol content 0.4％ Phosphate content 243ppm Potassium Monobehenyl Phosphate Content 98.7％

[0068] Example 4

[0069] In a four-necked flask, add 10g of dodecanol (lauryl alcohol), heat to 60°C to dissolve, slowly drop 5.03g (1.1eq.) of polyphosphoric acid, heat to 100°C, stir to react for 2h, take samples for testing, the lauryl alcohol content is ≤2.8%, the reaction is over, cool to 30-60°C. Then use a single solvent or a mixed solvent as shown in Table 4 to stir until dissolved, add 30mL of water, and stir for 1h. The experimental results are shown in Table 4:

[0070] Table 4

[0071]

[0072]

[0073] It can be seen that when a mixed organic solvent consisting of an oxygen-containing polar solvent and a non-polar solvent is used, emulsification will not occur while ensuring complete dissolution, and the aqueous phase and the organic phase can be effectively separated by stratification.

[0074] The present invention has been described in detail above in conjunction with specific embodiments and / or exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a potassium salt of fatty alcohol phosphate with a high monoester content, wherein the method uses polyphosphoric acid as a phosphating agent to esterify the fatty alcohol, then uses a mixed organic solvent consisting of an oxygen-containing polar solvent and a non-polar solvent to dissolve and wash with water, and then drops a potassium hydroxide solution.

2. The preparation method according to claim 1, characterized in that The structure of the fatty alcohol phosphate potassium salt is shown in formula (I), Where: R1 is selected from C 8～22 Aliphatic alkyl; preferably C 12～22 further preferably n-dodecyl, n-hexadecyl or n-docosyl.

3. The preparation method according to claim 2, characterized in that: The following steps are involved: (1) Esterification: Add fatty alcohol to a reaction vessel, raise the temperature to 60-70°C, add polyphosphoric acid, continue to raise the temperature to 80-120°C, and stir to react; (2) Dissolving: adding a mixed organic solvent consisting of an oxygen-containing polar solvent and a non-polar solvent into a reaction container for dissolving; (3) washing with water: washing with water to obtain an organic phase solution of fatty alcohol phosphate; (4) Salt formation: Heat the organic phase solution of fatty alcohol phosphate to 50-60°C, add potassium hydroxide solution dropwise, cool to crystallize, filter, and dry.

4. The preparation method according to claim 3, characterized in that: In step (1), the molar ratio of fatty alcohol to polyphosphoric acid is 1.0:(0.9-2.5); preferably 1.0:(1.1-2.0).

5. The preparation method according to claim 3, characterized in that: In step (1), after the temperature is raised for reaction, the fatty alcohol content in the reaction system is detected, and when the fatty alcohol content is less than 5%, the reaction is stopped.

6. The preparation method according to claim 3, characterized in that: In step (2), the amount of the mixed organic solvent used is 3 to 15 times the volume of the fatty alcohol phosphate system obtained in step (1).

7. The preparation method according to claim 3, characterized in that: In step (3), when the pH of the aqueous phase is ≥2, water washing is stopped.

8. The preparation method according to claim 3, characterized in that: In step (4), the crystallization temperature is 10-20°C, preferably 15°C.

9. The preparation method according to any one of claims 1 to 8, characterized in that The oxygen-containing polar solvent is selected from esters, ethers or ketones; preferably one or more of ethyl formate, methyl acetate, ethyl acetate, isopropyl acetate, propyl ether, methyl tert-butyl ether, tetrahydrofuran, methyltetrahydrofuran, acetone or 2-hexanone; The non-polar solvent is selected from one or more of petroleum ether, n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, n-tridecane, n-tetradecane, n-pentadecane or n-hexadecane.

10. The preparation method according to claim 9, characterized in that: The volume ratio of the oxygen-containing polar solvent to the non-polar solvent is (4-12):1, preferably (4-10):1.

Images