Solvent-free preparation method for synthesizing 2-methylbutyric acid by using by-product of adiponitrile

Abstract

The invention relates to a solvent-free preparation process for synthesizing 2-methylbutyric acid by using byproducts of adiponitrile, namely 2-methyl-2-butenenitrile and 2-methyl-3-butenenitrile, and belongs to the field of chemical engineering. The technical scheme adopted by the invention is as follows: the solvent-free preparation process for synthesizing an intermediate 2-methylbutyronitrile by hydrogenating byproducts 2-methyl-2-butenenitrile and 2-methyl-3-butenenitrile of adiponitrile and then carrying out hydrolysis reaction to generate the 2-methylbutyric acid is a process which is few in raw materials and auxiliary materials, does not use an organic solvent, is green and environment-friendly, and can be used for preparing the 2-methylbutyric acid. The invention discloses a novel method for turning waste into wealth.

Description

Technical Field

[0001] The invention relates to a solvent-free preparation process for synthesizing 2-methylbutyric acid by utilizing 2-methyl-2-butenenitrile and 2-methyl-3-butenenitrile, by-products of adiponitrile, and belongs to the field of chemical industry. Background Art

[0002] At present, there are three main methods for industrial production of adiponitrile: acrylonitrile electrolysis, adipic acid ammoniation, and butadiene cyanation. The butadiene cyanation method was developed by DuPont in the United States in the early 1970s, replacing the original butadiene hydrochlorination method, with the advantages of low cost, low energy consumption, and low corrosion to equipment. The by-products of this method are mainly composed of 2-pentenenitrile, 3-pentenenitrile, 2-methyl-2-butenenitrile, 2-methyl-3-butenenitrile and other products. Such by-products are treated as combustion waste by the world's largest manufacturers, including Invista and Solvay, and the subsequent treatment costs are very high.

[0003] 2-Methylbutyric acid is an important flavor substance. As an intermediate in the production of flavors and fragrances, it is widely used in various foods, beverages, tobacco, alcohol, and daily necessities. It is very popular in the domestic and foreign markets.

[0004] There are many existing process routes for this product in China: one is the biological fermentation distillation method in CN1621400A and CN1201026A, with a low content of about 98%. The second is that in CN105175247A and CN112552163A, 2-ethyl acrolein and acetone are used as raw materials, and then hydrogenation reduction and oxidation of hydrogen are carried out, and the reaction synthesis involves a variety of catalysts and oxidants, and the process is complicated and difficult to control. The third is that in CN110586195A, tiglic acid is used to carry out catalytic hydrogenation reaction under chiral catalyst conditions, but its chiral catalyst preparation is complicated and difficult, and the price of tiglic acid is too high, which is not suitable for industrial production.

[0005] In view of this, in order to solve the different existing problems in the above methods, the applicant has specially developed a solvent-free preparation process for synthesizing 2-methylbutyric acid using 2-methyl-2-butenenitrile and 2-methyl-3-butenenitrile, the by-products of adiponitrile, which gave rise to this case. Summary of the invention

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present invention is: a solvent-free preparation process of synthesizing the intermediate 2-methylbutyronitrile by hydrogenating the byproducts of adiponitrile 2-methyl-2-butenenitrile and 2-methyl-3-butenenitrile, and then hydrolyzing the resulting 2-methylbutyric acid, a process with few raw and auxiliary materials, no organic solvents, green and environmentally friendly, and a new method of turning waste into treasure. The specific scheme is as follows:

[0007] A solvent-free preparation method for synthesizing 2-methylbutyric acid using a byproduct of adiponitrile comprises the following steps:

[0008] (1) adding a mixture of 2-methyl-2-butenenitrile and 2-methyl-3-butenenitrile into a reaction kettle, adding a palladium-carbon catalyst, starting stirring, replacing with nitrogen and hydrogen, raising the temperature to 70-80° C., reacting for several hours and continuing to keep the temperature and pressure when hydrogen is no longer absorbed;

[0009] (2) Cooling to room temperature, pressing the material into the next reactor through a filter; slowly adding 2-methylbutyronitrile and sulfuric acid solution into the reactor, and heating to 70-80° C. after the feeding is completed; after the temperature is reached, timing the heat preservation reaction, ending the reaction, and taking samples for analysis;

[0010] (3) Continue to add water to hydrolyze, keep the temperature at 80-85°C, terminate the hydrolysis, and take samples for analysis;

[0011] (4) After the hydrolysis, the mixture is allowed to stand for stratification, and the water layer is centrally treated. After washing and dehydration, high-purity by-product ammonium sulfate can be obtained, and the recovered water can be used in the step (1) for preparing sulfuric acid and the step (3) for hydrolysis;

[0012] (5) The oil layer is rectified by a distillation tower, and the dehydrated fraction is collected to obtain the finished product 2-methylbutyric acid.

[0013] In the step (1), the hydrogen pressure is controlled at 0.2-0.5 MPa.

[0014] The concentration of the sulfuric acid solution in step (2) is 60%.

[0015] In the step (2), the molar ratio of 2-methylbutyronitrile to sulfuric acid solution is 1:1.2 to 1:1.5.

[0016] The molar ratio of the amount of water used for hydrolysis in step (3) to 2-methylbutyronitrile is 1:2 to 1:2.5.

[0017] The amount of washing water used in the step (4) is such that the molar ratio of washing water to 2-methylbutyronitrile is 1:1 to 1:1.5.

[0018] The present invention has the following characteristics:

[0019] First, the method of the present invention is a new green preparation process. The mixture of 2-methyl-2-butenenitrile and 2-methyl-3-butenenitrile used are by-products of adiponitrile, which are currently treated as combustion waste. The waste can be utilized and turned into treasure, and the source of raw materials is very cheap;

[0020] Second, the present invention adopts the preparation means and common equipment of general chemical raw materials, and the production process route is simple and easy to implement;

[0021] Third, the product of the present invention, as a flavor and fragrance, has high purity and cost advantages, and has a greater market advantage in the application of downstream products;

[0022] Fourth, the by-product ammonium sulfate has a wide market. It is an excellent nitrogen fertilizer (commonly known as fertilizer powder), suitable for general soil and crops. It also has many biological uses and is mostly used in protein purification processes. Fifth, no organic solvents are used in the reaction process, and the water used can be recycled, resulting in very little wastewater, low pressure on sewage treatment, and environmentally friendly. DETAILED DESCRIPTION

[0023] Example 1

[0024] A mixture of 81g of 2-methyl-2-butenenitrile and 2-methyl-3-butenenitrile was added into the reactor, and 0.5g of palladium-carbon catalyst was added. Stirring was started, nitrogen was replaced 3 times, hydrogen was replaced 3 times, the hydrogen was controlled at 0.5MPa, the temperature was raised to 70°C, and after 6 hours of reaction, no hydrogen was absorbed, and the temperature and pressure were kept for 2 hours, and the reaction was completed. The temperature was lowered to 25°C, and the material was pressed into a 500mL reaction bottle through a filter, and then 200g of a 60% sulfuric acid solution was slowly added, and then the temperature was raised to 70-80°C, and the reaction was kept warm for 5h. The results were obtained by sampling and analysis: 36g of water was added to the reaction bottle, and the temperature was raised to 80-85°C, and the hydrolysis was kept warm for 8h. After the hydrolysis was terminated, the results were obtained by sampling and analysis; after hydrolysis, the mixture was allowed to stand for stratification, and the water layer was concentrated for treatment. After washing and dehydration, 120.1 of ammonium sulfate was obtained; the oil layer was distilled and dehydrated through a distillation tower, and the main fraction was collected to obtain 96.9g of finished 2-methylbutyric acid with a content of 99.89% and a yield of 94.90%.

[0025] Example 2

[0026] A mixture of 162g of 2-methyl-2-butenenitrile and 2-methyl-3-butenenitrile was added into the reactor, and 1g of palladium-carbon catalyst was added. Stirring was started, nitrogen was replaced 3 times, hydrogen was replaced 3 times, the hydrogen was controlled at 0.5MPa, the temperature was raised to 70°C, and after 6 hours of reaction, no hydrogen was absorbed, and the temperature and pressure were kept constant for 2 hours, and the reaction was completed. The temperature was lowered to 25°C, and the material was pressed into a 1L reaction bottle through a filter, and then 400g of 60% sulfuric acid solution was slowly added, and the temperature was raised to 70-80°C, and the reaction was kept warm for 5h. The results were obtained by sampling and analysis: 72g of water was added to the reaction bottle, and the temperature was raised to 80-85°C, and the hydrolysis was kept warm for 8h. After the hydrolysis was terminated, the results were obtained by sampling and analysis; after hydrolysis, the mixture was allowed to stand and the layers were separated, and the water layer was concentrated and washed and dehydrated to obtain 241.2g of ammonium sulfate; the oil layer was distilled and dehydrated through a distillation tower, and the main fraction was collected to obtain 194.2g of finished 2-methylbutyric acid with a content of 99.88% and a yield of 95.08%.

[0027] Example 3 (Amplification experiment of Example 1)

[0028] In the enlarged experiment, 810g of a mixture of 2-methyl-2-butenenitrile and 2-methyl-3-butenenitrile was added to the reactor, 5g of palladium-carbon catalyst was added, stirring was started, nitrogen was replaced 3 times, hydrogen was replaced 3 times, the hydrogen was controlled at 0.5MPa, the temperature was raised to 70°C, and after 6 hours of reaction, no hydrogen was absorbed, and the temperature and pressure were kept for 2 hours, and the reaction was completed. The temperature was lowered to 25°C, and the material was pressed into a 5L reaction bottle through a filter, and then 2000g of 60% sulfuric acid solution was slowly added, and the temperature was controlled at 70-80°C by a high-low temperature oil bath, and the reaction was kept warm for 5h, and the results were obtained by sampling and analysis: 360g of water was added to the reaction bottle, and the temperature was raised to 80-85°C, and the hydrolysis was kept warm for 8h, and the hydrolysis was terminated, and the results were obtained by sampling and analysis; after hydrolysis, the mixture was allowed to stand for stratification, and the water layer was concentrated for treatment, and 1210g of ammonium sulfate was obtained after washing and dehydration; the oil layer was distilled and dehydrated by a distillation tower, and the main fraction was collected to obtain 981g of finished 2-methylbutyric acid with a content of 99.90% and a yield of 96.08%.

[0029] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention is described in detail with reference to the preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A solvent-free preparation method for synthesizing 2-methylbutyric acid using a by-product of adiponitrile, characterized in that: The steps include: (1) Add a mixture of 2-methyl-2-butenenitrile and 2-methyl-3-butenenitrile into a reaction kettle, add a palladium-carbon catalyst, start stirring, replace with nitrogen, replace with hydrogen, raise the temperature to 70-80°C, react for several hours and continue to keep the temperature and pressure until hydrogen is no longer absorbed; (2) Cooling to room temperature, pressing the material into the next reactor through a filter; slowly adding 2-methylbutyronitrile and sulfuric acid solution into the reactor, and heating to 70-80°C after the feeding is completed; after the temperature is reached, timing the heat preservation reaction, ending the reaction, and taking samples for analysis; (3) Continue to add water to hydrolyze, keep the temperature at 80-85°C, end the hydrolysis, and take samples for analysis; (4) After hydrolysis, the mixture is allowed to stand for stratification, and the water layer is centrally treated. After washing and dehydration, high-purity by-product ammonium sulfate can be obtained. The recovered water can be used in step (1) for preparing sulfuric acid and step (3) for hydrolysis; (5) The oil layer is distilled in a distillation tower, and the dehydrated fraction is collected to obtain the finished product 2-methylbutyric acid.

2. A solvent-free preparation method for synthesizing 2-methylbutyric acid using a by-product of adiponitrile as claimed in claim 1, characterized in that: In the step (1), the hydrogen pressure is controlled at 0.2-0.5 MPa.

3. The solvent-free preparation method for synthesizing 2-methylbutyric acid using a by-product of adiponitrile as claimed in claim 1, characterized in that: The concentration of the sulfuric acid solution in step (2) is 60%.

4. The solvent-free preparation method for synthesizing 2-methylbutyric acid using a by-product of adiponitrile as claimed in claim 1, characterized in that: In the step (2), the molar ratio of 2-methylbutyronitrile to sulfuric acid solution is 1:1.2 to 1:1.

5.

5. The solvent-free preparation method for synthesizing 2-methylbutyric acid using a by-product of adiponitrile as claimed in claim 1, characterized in that: The amount of water used for hydrolysis in step (3) is such that the molar ratio of water to 2-methylbutyronitrile is 1:2 to 1:2.

5.

6. The solvent-free preparation method for synthesizing 2-methylbutyric acid using a by-product of adiponitrile as claimed in claim 1, characterized in that: The amount of washing water used in step (4) is such that the molar ratio of washing water to 2-methylbutyronitrile is 1:1 to 1:1.5.