Preparation method of metal hydroxide catalyst and fatty acid polyoxyethylene ester

Abstract

The invention relates to the technical field of fatty acid polyoxyethylene ester preparation, in particular to a metal hydroxide catalyst and preparation of fatty acid polyoxyethylene ester, and discloses a method for preparing fatty acid polyoxyethylene ester with low free fatty acid content and narrow distribution by using sodium silicate modified fatty acid intercalated metal hydroxide as a catalyst. The problems that in the prior art, the content of free fatty acid is too high, and molecular weight distribution is wide are solved.

Description

Technical Field

[0001] This invention relates to the field of fatty acid polyoxyethylene ester preparation technology, and particularly to a metal hydroxide catalyst and a method for preparing fatty acid polyoxyethylene ester. Background Technology

[0002] Fatty acid polyoxyethylene esters, as an important type of nonionic surfactant, have seen considerable development both domestically and internationally, and are widely used in detergents, cosmetics, textile auxiliaries, pesticides, food processing, plastics, coatings, leather tanning, metal processing, and other industrial sectors. Currently, the invention patent with authorization announcement number CN 104707587 B discloses a method for preparing a composite metal oxide and a method for synthesizing an alcohol ether carboxylic acid ester. The preparation method includes: 1) preparing a composite metal hydroxide; 2) reacting the composite metal hydroxide with fatty acids. Ethoxylation is the mainstream method for synthesizing fatty acid polyoxyethylene esters industrially. However, fatty acid polyoxyethylene esters synthesized using conventional catalysts (alkali metals such as potassium hydroxide and sodium methoxide) still contain a considerable amount of free fatty acids with a wide molecular weight distribution, which has a certain impact on the application of the product. Summary of the Invention

[0003] This invention aims to provide a metal hydroxide catalyst and a method for preparing fatty acid polyoxyethylene esters. Specifically, it is a method for preparing low-free-fatty-content, narrow-distribution fatty acid polyoxyethylene esters using a sodium silicate-modified fatty acid-intercalated metal hydroxide as a catalyst, which solves the problems of excessively high free fatty acid content and wide molecular weight distribution in the prior art.

[0004] The above-mentioned technical objective of the present invention is achieved through the following technical solution: a metal hydroxide catalyst, wherein the general structural formula of the metal hydroxide catalyst is:

[0005]

[0006] In the formula, x = 1 - 11, y = 2 - 15, z = 1, m = 0.1 - 0.6, and n = 1 - 15.

[0007] As a further provision of the present invention, the metal hydroxide catalyst is prepared by the following method:

[0008] S1: Add appropriate proportions of water, alkali solution and fatty acid to the reaction vessel, heat and stir to dissolve, forming solution A;

[0009] S2: Add appropriate proportions of water, divalent magnesium salt and trivalent aluminum salt into the mixing tank, stir to dissolve, and form solution B;

[0010] S3: Add an appropriate proportion of water and ammonia water to the mixing tank and stir evenly to form solution C; the ammonia water is industrial ammonia water with a concentration of about 25%, and the amount of water is to dilute the ammonia water to 15%;

[0011] S4: Add an appropriate proportion of water and sodium silicate to the mixing vessel and stir until homogeneous to form solution D; the sodium silicate has a modulus of 1-3 and its weight is 5-25% of the weight of the fatty acid; the amount of water in S1 is 3-6 times the weight of the fatty acid; the amount of water in S2 is 3-6 times the total weight of the divalent magnesium salt and trivalent aluminum salt; the amount of water in S3 is based on diluting 25% ammonia water to a 15% mass concentration; and the amount of water in S4 is 5-10 times the weight of the sodium silicate.

[0012] S5: Add solutions B and C simultaneously and slowly to solution A to obtain a white suspension, and control the final pH to 8-10; then add solution D slowly and evenly to the above white suspension and stir until homogeneous to obtain a metal hydroxide complex suspension.

[0013] S6: The metal hydroxide complex suspension obtained in step 5 is filtered, washed with water, dried, ground, and granulated to obtain a metal hydroxide catalyst.

[0014] As a further feature of the present invention, the alkaline solution in step S1 includes one or more of sodium hydroxide and potassium hydroxide.

[0015] As a further provision of the present invention, the fatty acid in step S1 includes one or more of lauric acid, myristic acid, oleic acid, and stearic acid.

[0016] As a further feature of the present invention, the molar ratio of alkali solution to fatty acid in step S1 is 1:1, and the reaction temperature is 70-80℃.

[0017] As a further feature of the present invention, the trivalent aluminum salt in step S1 includes one or more of anhydrous aluminum chloride and anhydrous aluminum sulfate.

[0018] As a further feature of the present invention, the molar ratio of aluminum to magnesium in the trivalent aluminum salt and divalent magnesium salt is 1:1-3.

[0019] As a further provision of the present invention, a method for preparing fatty acid polyoxyethylene ester using a metal hydroxide catalyst is characterized by the following preparation method: fatty acid is added to a high-pressure reactor, a metal hydroxide catalyst is added, a vacuum is drawn, nitrogen is used for purging three times, the temperature is raised to 100-110°C for dehydration for half an hour, the temperature is raised to 120-130°C, a specified amount of ethylene oxide is introduced, the reaction is completed, nitrogen is introduced for protection, the temperature is lowered to 80°C, and the product is discharged to obtain fatty acid polyoxyethylene ester.

[0020] As a further feature of the present invention, the mass ratio of the fatty acid, the metal hydroxide catalyst, and ethylene oxide is 1:0.02-0.04:1-20.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. A method for preparing polyoxyethylene esters with low free fatty acid content and narrow distribution of fatty acids using a sodium silicate-modified fatty acid intercalated metal hydroxide as a catalyst, which is used to solve the problems of excessively high free fatty acid content and wide molecular weight distribution in the prior art.

[0023] 2. This invention modifies layered composite metal oxides by intercalation with fatty acids, and finally modifies them with sodium silicate. The fatty acid intercalation occurs simultaneously during the preparation of metal hydroxides. The fatty acid anions combine with the positive charges on the layers, which is called intercalation. This is a novel functional material. Metal ions are water-soluble under acidic conditions but insoluble in water under alkaline conditions (forming precipitates). Fatty acids are insoluble in water under acidic conditions but water-soluble under alkaline conditions. By controlling the reaction conditions, the fatty acids precipitate along with the metal salts due to charge neutralization.

[0024] 3. The fatty acids in this invention are fatty acids containing active hydrogen. The ethoxylation reaction containing active hydrogen is based on the SN2 nucleophilic reaction mechanism. The active hydrogen-containing substances are added stepwise to ethylene oxide. Using high-valence metal salts can yield narrowly distributed fatty acid polyoxyethylene esters. Detailed Implementation

[0025] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] Example 1

[0027] Catalyst preparation:

[0028] 1) Prepare solution A:

[0029] Add 1000 kg of water and 40.1 kg of sodium hydroxide to the reaction vessel, heat to 70-80°C, and add 284.5 kg of stearic acid in batches over 1 hour. Set aside for later use.

[0030] 2) Preparation of solution B:

[0031] Add 4000 kg of water, 570.66 kg of anhydrous magnesium chloride, and 800.04 kg of anhydrous aluminum chloride to the mixing tank and stir until completely dissolved.

[0032] 3) Preparation of solution C:

[0033] Add 1800 kg of water and 2700 kg of ammonia (25%) to the mixing tank and stir well.

[0034] 4) Preparation of solution D:

[0035] Add 36.6 kg of sodium silicate (modulus 2.3) and 270 kg of water to the mixing tank and stir until the sodium silicate is completely dissolved.

[0036] 5) Catalyst Preparation (Part 1):

[0037] Solution A is kept at a temperature of 70-80℃. Solutions B and C are simultaneously and uniformly pumped into solution A using a constant flow pump. The pumping is completed in 2-3 hours. The pH of the system is confirmed to be 9. The system is kept at 70-80℃ for 3 hours. The pH is confirmed to be 9 again, resulting in a white suspension. Solution D is slowly pumped into the white suspension. The system is kept at 70-80℃ for 3 hours to obtain a sodium silicate-modified fatty acid intercalated metal hydroxide complex.

[0038] 6) Catalyst Preparation (II):

[0039] The suspension from step 5 was filtered, washed with water, dried, ground, and granulated to obtain sodium silicate-modified fatty acid-intercalated metal hydroxide, which is the narrow-distribution catalyst for fatty acid ethoxylation.

[0040] 7) Preparation of fatty acid polyoxyethylene esters:

[0041] 284.5 kg of stearic acid was added to a high-pressure reactor, along with 6 kg of the above-mentioned catalyst. The reactor was then evacuated and purged with nitrogen three times. The temperature was raised to 100-110°C for dehydration for half an hour, then raised to 120-130°C. 440 kg of ethylene oxide was introduced, and the reaction was carried out at 130-140°C for 2 hours. Nitrogen gas was then introduced for protection, and the temperature was lowered to 80°C before the product was discharged.

[0042] Example 2

[0043] Catalyst preparation:

[0044] 1) Prepare solution A:

[0045] Add 1000 kg of water and 40.1 kg of sodium hydroxide to the reaction vessel, heat to 70-80°C, and add 200.32 kg of lauric acid in batches over 1 hour. Set aside for later use.

[0046] 2) Preparation of solution B:

[0047] Add 4000 kg of water, 570.66 kg of anhydrous magnesium chloride, and 800.04 kg of anhydrous aluminum chloride to the mixing tank and stir until completely dissolved.

[0048] 3) Preparation of solution C:

[0049] Add 1800 kg of water and 2700 kg of ammonia (25%) to the mixing tank and stir well.

[0050] 4) Preparation of solution D:

[0051] Add 36.6 kg of sodium silicate (modulus 2.3) and 270 kg of water to the mixing tank and stir until the sodium silicate is completely dissolved.

[0052] 5) Catalyst Preparation (Part 1):

[0053] Solution A is kept at a temperature of 70-80℃. Solutions B and C are simultaneously and uniformly pumped into solution A using a constant flow pump. The pumping is completed in 2-3 hours. The pH of the system is confirmed to be 9. The system is kept at 70-80℃ for 3 hours. The pH is confirmed to be 9 again, resulting in a white suspension. Solution D is slowly pumped into the white suspension. The system is kept at 70-80℃ for 3 hours to obtain a sodium silicate-modified fatty acid intercalated metal hydroxide complex.

[0054] 6) Catalyst Preparation (II):

[0055] The suspension from step 5 was filtered, washed with water, dried, ground, and granulated to obtain sodium silicate-modified fatty acid-intercalated metal hydroxide, which is the narrow-distribution catalyst for fatty acid ethoxylation.

[0056] 7) Preparation of fatty acid polyoxyethylene esters:

[0057] 200.32 kg of lauric acid was added to a high-pressure reactor, along with 6 kg of the above-mentioned catalyst. The reactor was then evacuated and purged with nitrogen three times. The temperature was raised to 100-110°C for dehydration for half an hour, then raised to 120-130°C. 440 kg of ethylene oxide was introduced, and the reaction was carried out at 130-140°C for 2 hours. Nitrogen gas was then introduced for protection, and the temperature was lowered to 80°C before the product was discharged.

[0058] Example 3

[0059] Catalyst preparation:

[0060] 1) Prepare solution A:

[0061] Add 1000 kg of water and 40.1 kg of sodium hydroxide to the reaction vessel, heat to 70-80°C, and add 284.5 kg of stearic acid in batches over 1 hour. Set aside for later use.

[0062] 2) Preparation of solution B:

[0063] Add 4000 kg of water, 570.66 kg of anhydrous magnesium chloride, and 800.04 kg of anhydrous aluminum chloride to the mixing tank and stir until completely dissolved.

[0064] 3) Preparation of solution C:

[0065] Add 1800 kg of water and 2700 kg of ammonia (25%) to the mixing tank and stir well.

[0066] 4) Preparation of solution D:

[0067] Add 36.6 kg of sodium silicate (modulus 1.6) and 270 kg of water to the mixing tank and stir until the sodium silicate is completely dissolved.

[0068] 5) Catalyst Preparation (Part 1):

[0069] Solution A is kept at a temperature of 70-80℃. Solutions B and C are simultaneously and uniformly pumped into solution A using a constant flow pump. The pumping is completed in 2-3 hours. The pH of the system is confirmed to be 9. The system is kept at 70-80℃ for 3 hours. The pH is confirmed to be 9 again, resulting in a white suspension. Solution D is slowly pumped into the white suspension. The system is kept at 70-80℃ for 3 hours to obtain a sodium silicate-modified fatty acid intercalated metal hydroxide complex.

[0070] 6) Catalyst Preparation (II):

[0071] The suspension from step 5 was filtered, washed with water, dried, ground, and granulated to obtain sodium silicate-modified fatty acid-intercalated metal hydroxide, which is the narrow-distribution catalyst for fatty acid ethoxylation.

[0072] 7) Preparation of fatty acid polyoxyethylene esters:

[0073] 284.5 kg of stearic acid was added to a high-pressure reactor, along with 6 kg of the above-mentioned catalyst. The reactor was then evacuated and purged with nitrogen three times. The temperature was raised to 100-110°C for dehydration for half an hour, then raised to 120-130°C. 440 kg of ethylene oxide was introduced, and the reaction was carried out at 130-140°C for 2 hours. Nitrogen gas was then introduced for protection, and the temperature was lowered to 80°C before the product was discharged.

[0074] Example 4

[0075] Catalyst preparation:

[0076] 1) Prepare solution A:

[0077] Add 1000 kg of water and 40.1 kg of sodium hydroxide to the reaction vessel, heat to 70-80°C, and add 228.38 kg of myristic acid in batches over 1 hour. Set aside for later use.

[0078] 2) Preparation of solution B:

[0079] Add 4000 kg of water, 570.66 kg of anhydrous magnesium chloride, and 800.04 kg of anhydrous aluminum chloride to the mixing tank and stir until completely dissolved.

[0080] 3) Preparation of solution C:

[0081] Add 1800 kg of water and 2700 kg of ammonia (25%) to the mixing tank and stir well.

[0082] 4) Preparation of solution D:

[0083] Add 36.6 kg of sodium silicate (modulus 1.6) and 270 kg of water to the mixing tank and stir until the sodium silicate is completely dissolved.

[0084] 5) Catalyst Preparation (Part 1):

[0085] Solution A is kept at a temperature of 70-80℃. Solutions B and C are simultaneously and uniformly pumped into solution A using a constant flow pump. The pumping is completed in 2-3 hours. The pH of the system is confirmed to be 9. The system is kept at 70-80℃ for 3 hours. The pH is confirmed to be 9 again, resulting in a white suspension. Solution D is slowly pumped into the white suspension. The system is kept at 70-80℃ for 3 hours to obtain a sodium silicate-modified fatty acid intercalated metal hydroxide complex.

[0086] 6) Catalyst Preparation (II):

[0087] The suspension from step 5 was filtered, washed with water, dried, ground, and granulated to obtain sodium silicate-modified fatty acid-intercalated metal hydroxide, which is the narrow-distribution catalyst for fatty acid ethoxylation.

[0088] 7) Preparation of fatty acid polyoxyethylene esters:

[0089] 228.38 kg of myristic acid was added to a high-pressure reactor, along with 6 kg of the above-mentioned catalyst. The reactor was then evacuated and purged with nitrogen three times. The temperature was raised to 100-110°C for dehydration for half an hour, then raised to 120-130°C. 440 kg of ethylene oxide was introduced, and the reaction was carried out at 130-140°C for 2 hours. Nitrogen gas was then introduced for protection, and the temperature was lowered to 80°C before the product was discharged.

[0090] Comparative Example 1

[0091] The difference from Example 1 is that sodium silicate was not added during catalyst preparation.

[0092] Comparative Example 2

[0093] The difference from Example 2 is that the catalyst is the commonly used potassium hydroxide, and the preparation method of fatty acid polyoxyethylene ester is the same.

[0094] Add 200.32 kg of lauric acid to a high-pressure reactor, add 6 kg of potassium hydroxide, evacuate the reactor, purge with nitrogen three times, heat to 100-110℃ to dehydrate for half an hour, heat to 120-130℃, introduce 440 kg of ethylene oxide as specified, react at 130-140℃ for 2 hours, purge with nitrogen for protection, cool to 80℃, and discharge the product.

[0095] The fatty acid polyoxyethylene esters prepared from the catalyst samples obtained in Examples 1-4 and Comparative Examples 1 and 2 were subjected to gel permeation chromatography (GPC) to determine the number-average molecular weight (Mn), weight-average molecular weight (Mw), and molecular weight distribution width (Mw / Mn), as well as the free fatty acid content and emulsifying power.

[0096] Determination of free fatty acids: Referring to GB5009.229-2016 Determination of acid value in food, the free fatty acid value of the fatty acid polyoxyethylene ester prepared from the catalyst sample was determined by titration.

[0097] Emulsifying power test method: Add 40ml of deionized water and 40ml of white oil (No. 3) to a 250ml stoppered conical flask, weigh 0.5g of sample (accurate to 0.01g), tighten the stoppered conical flask cap, place it on a constant temperature shaker, and shake and mix at 300r / min for 5min. After shaking and mixing, transfer the mixture to a 100ml stoppered graduated cylinder and tighten the stopper cap. Place it in a constant temperature oven and age it at 60℃ for 1h. After aging, read the readings of the liquid precipitated from the upper and lower layers of the graduated cylinder. The molecular weight distribution width, free fatty acids, and emulsifying power test results are shown in Table 1.

[0098] Table 1. Results of Molecular Weight Distribution Width, Free Fatty Acids, and Emulsifying Power Tests

[0099]

Claims

1. A metal hydroxide catalyst, characterized in that: The general structural formula of the metal hydroxide catalyst is: In the formula, x = 1 - 11, y = 2 - 15, z = 1, m = 0.1 - 0.6, and n = 1 - 15.

2. The metal hydroxide catalyst according to claim 1, characterized in that: The metal hydroxide catalyst is prepared by the following method: S1: Add appropriate proportions of water, alkali solution and fatty acid to the reaction vessel, heat and stir to dissolve, forming solution A; S2: Add appropriate proportions of water, divalent magnesium salt and trivalent aluminum salt into the mixing tank, stir to dissolve, and form solution B; S3: Add an appropriate proportion of water and ammonia into the mixing tank and stir until homogeneous to form solution C; S4: Add an appropriate proportion of water and sodium silicate into the mixing tank and stir until homogeneous to form solution D; S5: Add solutions B and C simultaneously and slowly to solution A to obtain a white suspension, and control the endpoint pH to 8-10. Then, slowly and uniformly add solution D to the above white suspension and stir until homogeneous to obtain a metal hydroxide complex suspension; S6: The metal hydroxide complex suspension obtained in step 5 is filtered, washed with water, dried, ground, and granulated to obtain a metal hydroxide catalyst.

3. The metal hydroxide catalyst according to claim 2, characterized in that: The alkaline solution in step S1 includes one or more of sodium hydroxide and potassium hydroxide.

4. The metal hydroxide catalyst according to claim 2, characterized in that: The fatty acids in step S1 include one or more of lauric acid, myristic acid, oleic acid, and stearic acid.

5. A metal hydroxide catalyst according to claim 22, characterized in that: In step S1, the molar ratio of alkali solution to fatty acid is 1:1, the amount of water is 3-6 times the weight of fatty acid, and the reaction temperature is 70-80℃.

6. The metal hydroxide catalyst according to claim 2, characterized in that: In step S1, the trivalent aluminum salt includes one or more of anhydrous aluminum chloride and anhydrous aluminum sulfate.

7. The metal hydroxide catalyst according to claim 2, characterized in that: The divalent magnesium salt in step S2 includes one or more of anhydrous magnesium chloride and anhydrous magnesium sulfate.

8. The metal hydroxide catalyst according to claim 2, characterized in that: In step S2, the molar ratio of aluminum to magnesium in the trivalent aluminum salt and divalent magnesium salt is 1:1-3, and the amount of water is 3-6 times the total weight of the divalent magnesium salt and trivalent aluminum salt.

9. A method for preparing fatty acid polyoxyethylene ester using any one of the metal hydroxide catalysts described in claims 1-8, characterized in that: The following preparation method is used: fatty acids are added to a high-pressure reactor, a metal hydroxide catalyst is added, a vacuum is drawn, nitrogen is used for purging three times, the temperature is raised to 100-110℃ for dehydration for half an hour, the temperature is raised to 120-130℃, a specified amount of ethylene oxide is introduced, the reaction is completed, nitrogen is introduced for protection, the temperature is lowered to 80℃, and the product is discharged to obtain fatty acid polyoxyethylene ester.

10. The method for preparing a fatty acid polyoxyethylene ester according to claim 9, characterized in that: The mass ratio of the fatty acid, metal hydroxide catalyst, and ethylene oxide is 1:0.02-0.04:1-20.

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