Application of N, N-diisopropylethylamine in preparation of dimethyl sulfate

Abstract

The invention relates to an application of N, N-diisopropylethylamine as an organic acid binding agent in preparation of dimethyl sulfate, N, N-diisopropylethylamine is used for purifying a crude dimethyl sulfate product into a dimethyl sulfate product, N, N-diisopropylethylamine is added into the crude dimethyl sulfate product, stirring reaction is carried out, and the N, N-diisopropylethylamine is obtained. And carrying out reduced pressure distillation or reduced pressure rectification purification to obtain a dimethyl sulfate product. According to the method, N, N-diisopropylethylamine is used as an organic acid-binding agent, so that various acidic residues in the crude dimethyl sulfate product can be effectively removed, the acidity of the dimethyl sulfate product is reduced, and the product quality is correspondingly improved. And moreover, the residual liquid amount of dimethyl sulfate can be reduced, the treatment amount of three wastes is reduced, and the method is suitable for industrial production of high-purity dimethyl sulfate.

Description

Technical Field

[0001] The present application relates to the technical field of the synthesis of dimethyl sulfate, specifically to the use of N,N-diisopropylethylamine in the preparation of dimethyl sulfate, and more specifically to the use of N,N-diisopropylethylamine as an organic acid-binding agent in the preparation of dimethyl sulfate. Background Art

[0002] Dimethyl sulfate is an important chemical raw material and is a good methylation agent in organic synthesis. It has wide applications in industries such as chemical engineering, medicine, pesticides, military industry, dyes, spices, rubber, and leather. And high-purity dimethyl sulfate plays an important role as a methylation agent in high-end pharmaceutical synthesis.

[0003] Currently, the production of dimethyl sulfate in China mainly uses traditional production processes and catalysts, that is, directly using sulfuric acid for etherification. Its production process is roughly as follows:

[0004] 1. Preparation of catalyst: sulfuric acid + methanol → methyl bisulfate;

[0005] 2. Etherification: methyl bisulfate + methanol → dimethyl ether;

[0006] 3. Esterification: dimethyl ether + sulfur trioxide → dimethyl sulfate;

[0007] In the production process of this process, the consumption of methanol and sulfuric acid is high. The chemical reaction between dimethyl ether and sulfur trioxide in the reactor not only generates crude dimethyl sulfate, but also generates many other by-products, such as acidic by-products containing a small amount of methyl bisulfate, sulfuric acid, dimethyl sulfite, sulfur trioxide, sulfur dioxide, etc. These residues cannot be completely removed by distillation or rectification. The by-products distilled out with dimethyl sulfate will continuously increase and thus exist in subsequent reactions, which not only brings a heavy burden to distillation or rectification, consumes a large amount of energy, but also increases the acidity of dimethyl sulfate, affecting the product yield and product quality. Moreover, these acidic substances are likely to corrode the reaction equipment and reduce the service life of the reactor. Finally, the untreated dimethyl sulfate residue liquid is not only toxic but also highly corrosive. If directly discharged, it will cause serious environmental pollution.

[0008] Therefore, solving the problem of acidic by-products in the production of dimethyl sulfate is an urgent technical problem to be solved for the production of high-purity dimethyl sulfate. Summary of the Invention

[0009] Aiming at the deficiencies of the prior art, the present invention provides the use of N,N-diisopropylethylamine in the preparation of dimethyl sulfate, specifically the use of N,N-diisopropylethylamine as an organic acid-binding agent in the preparation of dimethyl sulfate, especially for purifying crude dimethyl sulfate into dimethyl sulfate products.

[0010] For the use according to the present invention, the acidity of crude dimethyl sulfate is ≤ 2.5%, specifically such as 2.5%, 2%, 1.8%, etc. Controlling the acidity of crude dimethyl sulfate enables the raw material sulfur trioxide to react as completely as possible. First, it avoids waste of the raw material sulfur trioxide. Second, it is beneficial to reduce the content of acidic by-products entering the subsequent purification stage and relieve the pressure of post-treatment.

[0011] For the use according to the present invention, the mass fraction of N,N-diisopropylethylamine in crude dimethyl sulfate is 1% - 4%, specifically such as 1%, 2%, 2.5%, 3%, 4%, etc. The dosage of N,N-diisopropylethylamine only needs to achieve the purpose of treating acidic by-products. Excessive N,N-diisopropylethylamine not only wastes raw materials but also increases the amount of post-treatment.

[0012] For the use according to the present invention, stirring reaction is carried out after the feeding of N,N-diisopropylethylamine. Stirring can not only promote the reaction between N,N-diisopropylethylamine and acidic by-products and quickly and effectively remove various acidic residues in crude dimethyl sulfate, but also reduce the temperature of the freshly produced crude dimethyl sulfate.

[0013] For the use according to the present invention, the time of the stirring reaction is 0.5 - 2 h, specifically such as 0.5 h, 1 h, 1.5 h, 2 h, etc.

[0014] For the use according to the present invention, after the feeding and reaction of N,N-diisopropylethylamine, dimethyl sulfate product is prepared by purification through vacuum distillation or vacuum rectification. The temperature of vacuum distillation is controlled at 120 - 140 °C, specifically such as 120 °C, 130 °C, 140 °C, etc., and the temperature of vacuum rectification is controlled at 90 - 125 °C, specifically such as 90 °C, 100 °C, 120 °C, 125 °C, etc. The vacuum degree of both vacuum distillation and vacuum rectification is controlled at -0.095 - -0.1 MPa.

[0015] For the use according to the present invention, crude dimethyl sulfate can directly come from the reaction of dimethyl ether and sulfur trioxide, or can come from the reaction of sulfuric acid and methanol to form methyl bisulfate, then methyl bisulfate reacts with methanol to form dimethyl ether, and finally dimethyl ether reacts with sulfur trioxide, etc. As long as the by-products generated in the reaction produce acidic by-products, they can be used as the source reaction of crude dimethyl sulfate, and the present invention does not make strict restrictions.

[0016] The beneficial effects brought by the technical solution provided in this application include:

[0017] The embodiments of the present application provide a use of dimethyl sulfate residue, specifically for purifying crude dimethyl sulfate into dimethyl sulfate product. By adding N,N-diisopropylethylamine with a mass fraction of 1% - 4% into crude dimethyl sulfate with an acidity ≤ 2.5%, stirring and reacting for 0.5 - 2 h, and then purifying by vacuum distillation or vacuum rectification to obtain dimethyl sulfate product. In the present invention, N,N-diisopropylethylamine is used as an organic acid-binding agent, which can effectively remove various acidic residues in crude dimethyl sulfate, reduce the acidity of dimethyl sulfate product, and correspondingly improve the product quality. Moreover, it can reduce the amount of dimethyl sulfate residue and the amount of three wastes treatment, and is applicable to the industrial production of high-purity dimethyl sulfate. Detailed Embodiments

[0018] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the following specifically illustrates various aspects and features of the present invention through preferred embodiments. Those skilled in the art should understand that these embodiments are only for illustrative purposes and do not limit the scope of the present invention. The protection scope of the present invention is only limited by the claims. Without departing from the scope of the claims. Those skilled in the art can make various modifications and improvements to various aspects of the present invention, and these modifications and improvements also belong to the protection scope of the present invention.

[0019] Example 1: 3

[0020] Weigh 200 g of crude dimethyl sulfate (acidity 1.86%, ester content 92.05%) into a three-necked flask, add 5.2 g of N,N-diisopropylethylamine, stir and react for 1.5 h, and then perform vacuum distillation (temperature 125 °C, -0.095 MPa) to obtain 191.6 g of dimethyl sulfate product (acidity 0.053%, ester content 99.62%).

[0021] Example 2:

[0022] Weigh 200 g of crude dimethyl sulfate (acidity 1.52%, ester content 93.22%) into a three-necked flask, add 5.2 g of N,N-diisopropylethylamine, stir and react for 1 h, and then perform vacuum distillation (temperature 130 °C, -0.095 MPa) to obtain 192.3 g of dimethyl sulfate product (acidity 0.042%, ester content 99.66%).

[0023] Example 3:

[0024] Weigh 200 g of crude dimethyl sulfate (acidity 2.50%, ester content 90.12%) into a three-necked flask, add 8 g of N,N-diisopropylethylamine, stir and react for 2 h, and then perform vacuum distillation (temperature 130 °C, -0.1 MPa) to obtain 189.8 g of dimethyl sulfate product (acidity 0.097%, ester content 99.55%).

[0025] Example 4:

[0026] Weigh 200 g of crude dimethyl sulfate (acidity 1.06%, ester content 93.25%) into a three-necked flask, add 2 g of N,N-diisopropylethylamine, stir and react for 0.5 h, and carry out vacuum distillation (temperature 100 °C, -0.095 MPa) to obtain 190.1 g of dimethyl sulfate product (acidity 0.037%, ester content 99.71%).

[0027] Example 5:

[0028] Weigh 200 g of crude dimethyl sulfate (acidity 1.06%, ester content 93.25%) into a three-necked flask, add 4 g of N,N-diisopropylethylamine, stir and react for 1 h, and carry out vacuum distillation (temperature 90 °C, -0.095 MPa) to obtain 191.7 g of dimethyl sulfate product (acidity 0.031%, ester content 99.68%).

[0029] Comparative Example 1:

[0030] Weigh 200 g of crude dimethyl sulfate (acidity 1.06%, ester content 93.25%) into a three-necked flask, and carry out vacuum distillation (temperature 100 °C, -0.095 MPa) to obtain 188.1 g of dimethyl sulfate product (acidity 0.56%, ester content 99.05%).

[0031] Comparative Example 2:

[0032] Weigh 200 g of crude dimethyl sulfate (acidity 1.06%, ester content 93.25%) into a three-necked flask, add 20 g of N,N-diisopropylethylamine, stir and react for 0.5 h, and carry out vacuum distillation (temperature 100 °C, -0.095 MPa) to obtain 170.1 g of dimethyl sulfate product (acidity 0.96%, ester content 97.54%).

[0033] In the examples of this application, by adding N,N-diisopropylethylamine into the crude dimethyl sulfate, it acts as an organic acid-binding agent, which can reduce the acidic residues in the crude dimethyl sulfate, significantly reduce the acidity of the dimethyl sulfate product (below 0.1%), improve the product quality and yield, and can obtain a pharmaceutical-grade dimethyl sulfate product, which can meet the requirements of high-end pharmaceutical synthesis. For the traditional reaction without adding N,N-diisopropylethylamine, the acidity of the obtained dimethyl sulfate product is higher. However, the addition amount of N,N-diisopropylethylamine cannot be excessive. Excessive addition will increase the collision frequency between reactants, resulting in too fast reaction rate, which may cause incomplete reaction or generate other by-products, and will also affect the quality decline of the dimethyl sulfate product and reduce the yield.

[0034] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art. Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents. The foregoing embodiments and methods described in the present invention may vary based on the capabilities, experience, and preferences of those skilled in the art.

[0035] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be encompassed within the present invention.

[0036] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. Use of N,N - diisopropylethylamine as an organic acid-binding agent in the preparation of dimethyl sulfate.

2. The use according to claim 1, characterized in that, The N,N - diisopropylethylamine is used to purify crude dimethyl sulfate into dimethyl sulfate product.

3. The use according to claim 2, wherein The acidity of the crude dimethyl sulfate is ≤2.5%.

4. The use according to claim 2, characterized in that, The mass fraction of the N,N - diisopropylethylamine in the crude dimethyl sulfate is 1% - 4%.

5. The use according to claim 2, characterized in that, After the N,N - diisopropylethylamine is fed, stirring reaction is carried out.

6. The use according to claim 5, characterized in that, The time of the stirring reaction is 0.5 - 2 h.

7. The use according to claim 5, characterized in that, After the N,N - diisopropylethylamine is fed and reacted, the dimethyl sulfate product is obtained by purification through vacuum distillation or vacuum rectification.