A kind of preparation method of sodium lactate

Abstract

The present invention provides a method for preparing sodium lactate, and belongs to the technical field of organic chemical synthesis. The method for preparing sodium lactate of the present invention comprises the following steps: (1) esterification reaction is carried out with lactic acid and alcohol compounds in the presence of a modified solid acid catalyst to generate lactic acid ester compounds; (2) saponification reaction is carried out with the lactic acid ester compounds and sodium hydroxide solution to obtain a sodium lactate semi-finished product; (3) the sodium lactate semi-finished product is heated to 80-100 degrees Celsius, and kept warm for a period of time to obtain a sodium lactate finished product. The present invention adjusts the esterification reaction temperature and the esterification reaction efficiency by adding a modified solid acid catalyst, avoids the occurrence of yellowing of the sodium lactate product, removes the alcohol compounds remaining in the sodium lactate semi-finished product by a heating distillation method, and controls the reaction process by optimizing the ratio and concentration of lactic acid, alcohol compounds and alkaline solution, as well as reaction conditions, thereby improving the reaction efficiency and the quality of the sodium lactate product.

Description

Technical Field

[0001] The invention relates to the technical field of organic chemical synthesis, and in particular to a method for preparing sodium lactate. Background Art

[0002] Sodium lactate is a chemical substance with the molecular formula C3H5O3Na and a molecular weight of 112.06. It is a colorless or slightly yellow transparent syrupy liquid with strong water absorption capacity. It is miscible with water, ethanol, and glycerin. It is odorless or has a slightly special smell and a slightly salty and bitter taste. It is widely used in the industry. In the meat and poultry food processing industry, it can be used as an emulsifier, moisturizer, flavor improver, quality improver, antioxidant enhancer, and pH adjuster. It can enhance flavor, inhibit the growth of pathogenic bacteria in food, and extend the shelf life of products. In the medical field, sodium lactate can relieve dehydration caused by diarrhea and poisoning caused by diabetes and gastritis, or be used to supplement body fluids or electrolytes in parenteral / solutions. Sodium lactate is also widely used as Ringer's solution to prepare injections for the treatment of metabolic acidosis or skin dysfunction. Sodium lactate is a natural moisturizing factor. One quarter of the human skin stratum corneum is sodium lactate. Sodium lactate has unique pH regulating and moisturizing functions and is widely used in a variety of daily chemical products, such as bath products, skin care products, hair care products and oral care products.

[0003] At present, there are several methods for preparing sodium lactate: 1) direct neutralization method, such as the patent application No. 201210279918.5, entitled "A method for preparing 60-65% sodium lactate", which uses lactic acid and sodium hydroxide to directly react and generate sodium lactate. The advantages of this method are simple equipment and mild reaction conditions. The disadvantages are that the product has high requirements on the quality of raw materials and requires the use of high-purity lactic acid, resulting in high production costs; 2) calcium lactate and sodium carbonate double decomposition reaction method, such as the patent application No. 200910188147.7, entitled "A method for producing sodium lactate", which adds sodium carbonate to the calcium lactate fermentation broth. 3) direct fermentation production method, such as application number 2011100793086, named as a method for directly preparing sodium lactate from fermented liquid, the patent uses sodium hydroxide solution to neutralize lactic acid produced by fermentation, directly produces sodium lactate, although this method can reduce production cost, but the strain has low osmotic pressure resistance, low lactic acid fermentation yield, low sodium lactate preparation efficiency, and long process distance, high production cost. In addition, esterification method can also prepare sodium lactate, but esterification reaction belongs to typical exothermic reaction, the heat released in the reaction process easily makes lactic acid oxidized to pyruvic acid at a higher temperature, and the generated pyruvic acid is easily decomposed into yellow impurities under illumination, resulting in yellowish color of sodium lactate produced, affecting the color and quality of sodium lactate product. Summary of the invention

[0004] In view of this, the present invention provides a method for preparing sodium lactate, comprising the following steps:

[0005] (1) subjecting lactic acid and an alcohol compound to an esterification reaction in the presence of a modified solid acid catalyst to generate a lactic acid ester compound;

[0006] (2) subjecting the lactic acid ester compound to a saponification reaction with a sodium hydroxide solution to obtain a sodium lactate semi-finished product;

[0007] (3) heating the sodium lactate semi-finished product to 80-100 degrees Celsius and keeping the temperature for a period of time to obtain a sodium lactate finished product.

[0008] Preferably, the molar ratio of lactic acid to alcohol compound in step (1) is 2-7:10.

[0009] Preferably, the preparation method of the modified solid acid catalyst described in step (1) comprises: mixing a template, water and ammonium nitrate, stirring for 1-3 hours, adding a silicon source and an aluminum source, stirring at room temperature for 18-24 hours, crystallizing, cooling, filtering, washing, drying and calcining to obtain a modified solid acid catalyst.

[0010] Preferably, the amount of the modified solid acid catalyst in step (1) is 1%-5% of the mass of the lactic acid.

[0011] Preferably, the temperature of the esterification reaction in step (1) is 15-35 degrees Celsius.

[0012] Preferably, the esterification reaction time in step (1) is 1-3 hours.

[0013] Preferably, the volume ratio of the lactic acid ester compound to the sodium hydroxide solution in step (2) is 1:1.

[0014] Preferably, the concentration of the sodium hydroxide solution in step (2) is 45-55wt%.

[0015] Preferably, the temperature of the saponification reaction in step (2) is controlled at 50-150 degrees Celsius, and the saponification reaction time is 1-4 hours.

[0016] Preferably, step (3) is kept warm until the alcohol compounds are completely removed, and then the keeping warm ends.

[0017] The present invention also provides a sodium lactate product prepared according to the method.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The invention adjusts the esterification reaction temperature and improves the esterification reaction efficiency by adding a modified solid acid catalyst, thereby avoiding the occurrence of yellowing of the sodium lactate product.

[0020] The invention removes the alcohol compounds remaining in the sodium lactate semi-finished product by a heating distillation method.

[0021] The invention optimizes the ratio and concentration of lactic acid, alcohol compounds and alkaline solution, as well as reaction conditions, controls the reaction process, and improves the reaction efficiency and the quality of the sodium lactate product. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a comparison chart of the chromaticity values ​​of sodium lactate of Examples 1-3 of the present invention and Comparative Examples 1-3. DETAILED DESCRIPTION

[0023] The present invention provides a method for preparing sodium lactate, comprising the following steps:

[0024] (1) subjecting lactic acid and an alcohol compound to an esterification reaction in the presence of a modified solid acid catalyst to generate a lactic acid ester compound;

[0025] (2) subjecting the lactic acid ester compound to a saponification reaction with a sodium hydroxide solution to obtain a sodium lactate semi-finished product;

[0026] (3) heating the sodium lactate semi-finished product to 80-100 degrees Celsius and keeping the temperature for a period of time to obtain a sodium lactate finished product.

[0027] In some embodiments, the molar ratio of lactic acid to alcohol compound in step (1) is 2-7:10. More preferably, the molar ratio of lactic acid to alcohol compound in step (1) is 3:10.

[0028] In some embodiments, the alcohol compound in step (1) is selected from at least one of methanol and ethanol.

[0029] In some embodiments, the preparation method of the modified solid acid catalyst in step (1) includes: mixing the template, water, and ammonium nitrate, stirring for 1-3 hours, adding a silicon source and an aluminum source, stirring at room temperature for 18-24 hours, crystallizing, cooling, filtering, washing, drying, and calcining to obtain a modified solid acid catalyst.

[0030] In some embodiments, the preparation method of the modified solid acid catalyst in step (1) is specifically as follows: 3.8 g of tetramethylammonium hydroxide, 3.6 mL of deionized water and 0.5 g of ammonium nitrate are mixed, stirred for 1-3 h, 5.5 g of white carbon black and 0.079 g of pseudo-boehmite are added, stirred at room temperature for 24 h, transferred to a crystallization kettle, crystallized at 150 degrees Celsius for 55 h, cooled to room temperature, filtered, washed with water until neutral, dried at 120°C, and calcined at 500°C for 8 h to obtain a modified solid acid catalyst.

[0031] In some embodiments, the amount of the modified solid acid catalyst in step (1) is 1%-5% of the mass of the lactic acid. More preferably, the amount of the modified solid acid catalyst in step (1) is 3% of the mass of the lactic acid.

[0032] The solid catalyst used in the present invention is low in price and can be easily separated from the reaction product.

[0033] In some embodiments, the temperature of the esterification reaction in step (1) is 15-35 degrees Celsius. More preferably, the temperature of the esterification reaction in step (1) is 25 degrees Celsius.

[0034] In some embodiments, the esterification reaction time in step (1) is 1-3 hours. More preferably, the esterification reaction time in step (1) is 2 hours.

[0035] In some embodiments, the volume ratio of the lactic acid ester compound to the sodium hydroxide solution in step (2) is 1:1.

[0036] In some embodiments, the concentration of the sodium hydroxide solution in step (2) is 45-55 wt %. More preferably, the concentration of the sodium hydroxide solution in step (2) is 50 wt %.

[0037] In some embodiments, the temperature of the saponification reaction in step (2) is controlled at 50-150 degrees Celsius, and the saponification reaction time is 1-4 hours. More preferably, the temperature of the saponification reaction in step (2) is controlled at 80 degrees Celsius, and the saponification reaction time is 2 hours.

[0038] In some embodiments, step (3) is kept warm until the alcohol compound is completely removed, and then the keeping warm ends.

[0039] The present invention does not impose strict restrictions on the method for determining whether the alcohol compounds are completely removed, and any commonly used method on the market is applicable, including but not limited to rotary evaporation recovery, gas chromatography, high performance liquid chromatography, and ultraviolet visible spectrophotometry.

[0040] In some embodiments, the present invention also provides a sodium lactate product prepared according to the above method.

[0041] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0042] The experimental methods or test methods described in the following examples are conventional methods unless otherwise specified; the raw materials and auxiliary agents are obtained from conventional commercial channels or prepared by conventional methods unless otherwise specified.

[0043] Example 1

[0044] A method for preparing sodium lactate, the specific steps are as follows:

[0045] (1) 2.7 g of lactic acid and 3.2 g of methanol were mixed, 0.081 g of a modified solid acid catalyst was added, and an esterification reaction was carried out at 25 degrees Celsius for 3 hours. After the reaction was completed, a lactic acid ester compound was obtained;

[0046] (2) mixing the lactic acid ester compound with a sodium hydroxide solution having a concentration of 50 wt % in a volume ratio of 1:1, and performing a saponification reaction at 80 degrees Celsius for 2 hours to obtain a sodium lactate semi-finished product;

[0047] (3) heating the sodium lactate semi-finished product to 80 degrees Celsius and keeping the temperature until the alcohol compounds are completely removed, cooling to room temperature after the heat preservation is completed, and obtaining a sodium lactate finished product;

[0048] The preparation method of the modified solid acid catalyst in step (1) is as follows: 3.8 g of tetramethylammonium hydroxide, 3.6 mL of deionized water and 0.5 g of ammonium nitrate are mixed, stirred for 1-3 h, 5.5 g of white carbon black and 0.079 g of pseudo-boehmite are added, stirred at room temperature for 24 h, transferred to a crystallization kettle, crystallized at 150 degrees Celsius for 55 h, cooled to room temperature, filtered, washed with water until neutral, dried at 120°C, and calcined at 500°C for 8 h to obtain a modified solid acid catalyst.

[0049] Example 2

[0050] A method for preparing sodium lactate, the specific steps are as follows:

[0051] (1) 4.5 g of lactic acid and 3.2 g of methanol were mixed, 0.18 g of a modified solid acid catalyst was added, and an esterification reaction was carried out at 15 degrees Celsius for 2 hours. After the reaction was completed, a lactic acid ester compound was obtained;

[0052] (2) mixing the lactic acid ester compound with a sodium hydroxide solution having a concentration of 45 wt % in a volume ratio of 1:1, and performing a saponification reaction at 50 degrees Celsius for 4 hours to obtain a sodium lactate semi-finished product;

[0053] (3) heating the sodium lactate semi-finished product to 100 degrees Celsius and keeping the temperature until the alcohol compounds are completely removed, cooling to room temperature after the heat preservation is completed, and obtaining a sodium lactate finished product;

[0054] The preparation method of the modified solid acid catalyst in step (1) is as follows: 3.8 g of tetramethylammonium hydroxide, 3.6 mL of deionized water and 0.5 g of ammonium nitrate are mixed, stirred for 1-3 h, 5.5 g of white carbon black and 0.079 g of pseudo-boehmite are added, stirred at room temperature for 24 h, transferred to a crystallization kettle, crystallized at 150 degrees Celsius for 55 h, cooled to room temperature, filtered, washed with water until neutral, dried at 120°C, and calcined at 500°C for 8 h to obtain a modified solid acid catalyst.

[0055] Example 3

[0056] A method for preparing sodium lactate, the specific steps are as follows:

[0057] (1) 6.3 g of lactic acid and 3.2 g of methanol were mixed, 0.126 g of a modified solid acid catalyst was added, and an esterification reaction was carried out at 35 degrees Celsius for 1 hour. After the reaction was completed, a lactic acid ester compound was obtained;

[0058] (2) mixing the lactic acid ester compound with a sodium hydroxide solution having a concentration of 55 wt % in a volume ratio of 1:1, and performing a saponification reaction at 150 degrees Celsius for 1 hour to obtain a sodium lactate semi-finished product;

[0059] (3) heating the sodium lactate semi-finished product to 90 degrees Celsius and keeping the temperature until the alcohol compounds are completely removed, cooling to room temperature after the heat preservation is completed, and obtaining a sodium lactate finished product;

[0060] The preparation method of the modified solid acid catalyst in step (1) is as follows: 3.8 g of tetramethylammonium hydroxide, 3.6 mL of deionized water and 0.5 g of ammonium nitrate are mixed, stirred for 1-3 h, 5.5 g of white carbon black and 0.079 g of pseudo-boehmite are added, stirred at room temperature for 24 h, transferred to a crystallization kettle, crystallized at 150 degrees Celsius for 55 h, cooled to room temperature, filtered, washed with water until neutral, dried at 120°C, and calcined at 500°C for 8 h to obtain a modified solid acid catalyst.

[0061] Comparative Example 1

[0062] A method for preparing sodium lactate, the specific steps are as follows:

[0063] (1) 2.7 g of lactic acid and 3.2 g of methanol were mixed and subjected to esterification reaction at 65°C for 3 h. After the reaction was completed, a lactic acid ester compound was obtained;

[0064] (2) mixing the lactic acid ester compound with a sodium hydroxide solution having a concentration of 50 wt % in a volume ratio of 1:1, and performing a saponification reaction at 80 degrees Celsius for 2 hours to obtain a sodium lactate semi-finished product;

[0065] (3) heating the sodium lactate semi-finished product to 80 degrees Celsius and keeping the temperature until the alcohol compounds are completely removed, cooling the product to room temperature to obtain a sodium lactate product.

[0066] Comparative Example 2

[0067] A method for preparing sodium lactate, the specific steps are as follows:

[0068] (1) 2.7 g of lactic acid and 3.2 g of methanol were mixed, 0.081 g of a solid acid catalyst was added, and an esterification reaction was carried out at 65 degrees Celsius for 3 hours. After the reaction was completed, a lactic acid ester compound was obtained;

[0069] (2) mixing the lactic acid ester compound with a sodium hydroxide solution having a concentration of 50 wt % in a volume ratio of 1:1, and performing a saponification reaction at 80 degrees Celsius for 2 hours to obtain a sodium lactate semi-finished product;

[0070] (3) heating the sodium lactate semi-finished product to 80 degrees Celsius and keeping the temperature until the alcohol compounds are completely removed, cooling to room temperature after the heat preservation is completed, and obtaining a sodium lactate finished product;

[0071] The preparation method of the solid acid catalyst in step (1) is as follows: 3.8 g of tetramethylammonium hydroxide and 3.6 mL of deionized water are mixed, stirred for 1-3 h, 5.5 g of white carbon black and 0.079 g of pseudo-boehmite are added, stirred at room temperature for 24 h, transferred to a crystallization kettle, crystallized at 150 degrees Celsius for 55 h, cooled to room temperature, filtered, washed with water until neutral, dried at 120°C, and calcined at 500°C for 8 h to obtain a solid acid catalyst.

[0072] Comparative Example 3

[0073] A method for preparing sodium lactate, the specific steps are as follows:

[0074] (1) 2.7 g of lactic acid and 3.2 g of methanol were mixed, 0.162 g of a modified solid acid catalyst was added, and an esterification reaction was carried out at 25 degrees Celsius for 3 hours. After the reaction was completed, a lactic acid ester compound was obtained;

[0075] (2) mixing the lactic acid ester compound with a sodium hydroxide solution having a concentration of 50 wt % in a volume ratio of 1:1, and performing a saponification reaction at 80 degrees Celsius for 2 hours to obtain a sodium lactate semi-finished product;

[0076] (3) heating the sodium lactate semi-finished product to 80 degrees Celsius and keeping the temperature until the alcohol compounds are completely removed, cooling the product to room temperature to obtain a sodium lactate product.

[0077] The chromaticity values ​​of the sodium lactate products of Examples 1-3 and Comparative Examples 1-3 were tested, and the results are shown in Table 1.

[0078] Table 1

[0079]

[0080]

[0081] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing sodium lactate, characterized in that: The following steps are involved: (1) subjecting lactic acid and an alcohol compound to an esterification reaction in the presence of a modified solid acid catalyst to generate a lactic acid ester compound; (2) subjecting the lactic acid ester compound to a saponification reaction with a sodium hydroxide solution to obtain a sodium lactate semi-finished product; (3) heating the sodium lactate semi-finished product to 80-100 degrees Celsius and keeping the temperature for a period of time to obtain a sodium lactate finished product.

2. The method for preparing sodium lactate according to claim 1, characterized in that: The molar ratio of lactic acid to alcohol compound in step (1) is 2-7:

10.

3. The method for preparing sodium lactate according to claim 1, characterized in that: The preparation method of the modified solid acid catalyst in step (1) comprises: The template, water and ammonium nitrate are mixed, stirred for 1-3 hours, and then silicon source and aluminum source are added. After stirring at room temperature for 18-24 hours, crystallization, cooling, suction filtration, water washing, drying and calcination are performed to obtain a modified solid acid catalyst.

4. The method for preparing sodium lactate according to claim 1, characterized in that: The amount of the modified solid acid catalyst in step (1) is 1%-5% of the mass of the lactic acid.

5. The method for preparing sodium lactate according to claim 1, characterized in that: The temperature of the esterification reaction in step (1) is 15-35 degrees Celsius, and the time of the esterification reaction is 1-3 hours.

6. The method for preparing sodium lactate according to claim 1, characterized in that: In step (2), the volume ratio of the lactic acid ester compound to the sodium hydroxide solution is 1:

1.

7. The method for preparing sodium lactate according to claim 1, characterized in that: The concentration of the sodium hydroxide solution in step (2) is 45-55wt%.

8. The method for preparing sodium lactate according to claim 1, characterized in that: The temperature of the saponification reaction in step (2) is controlled at 50-150 degrees Celsius, and the saponification reaction time is 1-4 hours.

9. The method for preparing sodium lactate according to claim 1, characterized in that: Step (3) is kept warm until the alcohol compounds are completely removed, and the keeping warm ends.

10. Sodium lactate prepared according to the method according to any one of claims 1 to 9.

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