Dimethylacetamide (DMA) 【Background and Overview】
Dimethylformamide (DMF) is relatively common in chemical production, but there is little introduction about dimethylacetamide (DMA). Dimethylacetamide is N, N-dimethylacetamide, also known as acetamide, dimethylamine acetate, English name Dimethylacetamide (abbreviated as DMAC or DMA). Dimethylacetamide is a colorless and transparent liquid that can be mixed with organic solvents such as water, alcohol, ether, etc. It is a polar solvent. It has the characteristics of high thermal stability, not easy to hydrolyze, low corrosivity, low toxicity, etc. It is an excellent polar solvent for the synthesis of natural resins. It is used for the synthesis of polyimide, polysulfone amide and other polymer compounds, and also for the synthesis Film formation and spinning of resins, and purification of synthetic drugs and crystals of aromatic dicarboxylic acids (such as terephthalic acid). It can also be used as a catalyst in certain organic reactions. Compared with dimethylformamide of the same series, it has high thermal stability, hydrolytic stability, low corrosion and toxicity, and can replace dimethylformamide. At present, China’s annual demand for dimethylacetamide is more than 13 kt, especially in recent years, the demand for pharmaceutical intermediates and pesticides has grown rapidly. The demand for high-quality dimethylacetamide in the electronics industry has also grown significantly, and the market for solvents such as polyacrylonitrile spinning, imine resins and insulating materials is gradually expanding. There are less than 10 DMA manufacturers in China. The total production capacity of the country is 3000t / a, and the actual output is 2000-2500t / a, which can basically meet the needs of the domestic market. The customs does not have statistics on the import and export volume of DMA. Because DMA has good solubility in a variety of resins, it is mainly used as a solvent in heat-resistant fibers, plastic films, coatings, pharmaceuticals, catalysts and acrylonitrile spinning. The market prospect of dimethylacetamide is promising
Dimethylacetamide (DMA) 【Properties and Structure】
Relative molecular weight of dimethylacetamide: 87.12, boiling point: 164-166 ℃ (1xl & Pa), melting point: -20 ℃, flash point (open): 66 ℃, ignition point: 490 ℃, relative density: 0.9429 (20/4 ℃) ), Refractive index: 1.4373. It is a colorless transparent liquid, can be mixed with organic solvents such as water, alcohol, ether, etc. It is a polar solvent. Its thermal stability is good, it is stable and does not decompose even at the boiling point, it can be refined by distillation; it is stable in aqueous solution, but it will promote hydrolysis in the presence of acid and alkali. Dimethylacetamide should be stored in a cool, ventilated and dry place in a sealed place, and avoid water absorption and sunlight, and should not be close to the fire source. Pay attention to handling when handling, and transport in accordance with the provisions of toxic substances. Protective equipment must be worn when operating on site, and rinse with plenty of water after touching the skin.
Dimethylacetamide (DMA)
At present, the production methods of dimethylacetamide mainly include acetic anhydride method, acetyl chloride method and acetic acid method. In addition, ethyl acetate and dimethylamine, acetic acid and ammonia are reacted with methanol to synthesize dimethylacetamide, methyl acetate and diacetate One-step methylamine reaction, trimethylamine / carbon monoxide carbonylation.
Acetic anhydride method
From the reaction of acetic anhydride and dimethylamine to get dimethylacetamide:
First, the dimethylamine aqueous solution is heated to vaporization. After dehydration and purification of the gaseous dimethylamine, it is passed into acetic anhydride at room temperature to carry out the acylation reaction. The reaction is an exothermic reaction. When the reaction temperature no longer rises, it is the acylation end point ( 170 ° C). Then, control the acylation solution at 0-20 ° C, add alkaline solution for neutralization, and react to form sodium acetate. When the pH is 8-9, separate the sodium acetate. After washing the neutralized solution with alkali, add ethyl acetate for azeotropic dehydration. , Rough distillation and then rectification, take 164-166.5 ℃ fractions, that is, finished dimethylacetamide.
2. Acetic acid method
The dimethylacetamide is obtained by the reaction of acetic acid and dimethylamine:
The dimethylamine aqueous solution is heated and vaporized first, and the gaseous dimethylamine is passed into acetic acid to carry out the acylation reaction. The reaction is an exothermic reaction, and the reaction proceeds continuously. The obtained crude product is subjected to rectification, and a 164-166.5 ° C fraction is taken to obtain the finished dimethylacetamide. Domestic direct synthesis using catalytic rectification technology, the reaction heat can be used, the energy consumption in the reaction process is reduced, and because the reaction and rectification are in the same series, the process flow is greatly shortened, and the separation effect and product yield are greatly improved. No three waste emissions.
3. Acetyl chloride method
From the reaction of dimethylamine and acetyl chloride to obtain dimethylacetamide:
Under cooling, dimethylamine was first introduced into diethyl ether, and then the mixture of acetyl chloride and diethyl ether was slowly added, and while stirring, the white solid of dimethylamine hydrochloride was immediately precipitated and filtered out. The filtrate was recovered with ether in a water bath, and then subjected to rectification, collecting 164-16.66.5 ° C fractions to obtain the finished dimethylacetamide.
4. Ethyl acetate method
Diethylacetamide was obtained from the reaction of ethyl acetate and dimethylamine at 30 ° C with a yield of 98%.

5. Methyl acetate method
By the reaction of methyl acetate and dimethylamine, the reaction temperature is 140-170 ℃, and the pressure is 2.0-2.5 MPa. The method has low corrosiveness, high product yield and low production cost, and now has industrial conditions.
N, N-dimethylacetamide 【application】
1. Pharmaceutical intermediates
Dimethylacetamide is an important pharmaceutical raw material, widely used in the production of amoxicillin, cephalosporins and other drugs. As a solvent or cocatalyst, dimethylacetamide improves product quality and yield compared with traditional organic solvents. In 2000, the demand for dimethylacetamide in the pharmaceutical industry was about 6 kt. The demand for dimethylacetamide in 2006 was about 9.6 kt.

2. Acrylic production

In the production of acrylic fiber, some use dimethylacetamide route. At present, the domestic acrylic fiber production mainly includes sodium thiocyanate two-step method, dimethylformamide one-step method and dimethylacetamide organic wet method according to the solvent. From the process and equipment characteristics, material consumption, environmental impact, product quality, after Many factors such as processing performance, localization rate and foreign development trends have increased application research and promotion. As a comprehensive comparison of dimethylacetamide, sodium thiocyanate two-step method and dimethylacetamide organic wet method are the most With development prospects. At present, there are many acrylic devices in China using the wet process using dimethylacetamide as the solvent.
3. Polymer synthesis
Dimethylacetamide has good dissolving power for various resins, especially polyurethane resins and polyimide resins, and is mainly used as a solvent for heat-resistant synthetic fibers, plastic films, coatings, pharmaceuticals, and acrylonitrile spinning. At present, it is mostly used in the production of polyimide film, soluble polyimide, polyimide-polyfluoroethylene propylene composite film, polyimide film, soluble polyimide molding powder, etc. A good solvent for spinning synthetic fibers and other organic synthesis.
4. Organic pigments

In the production of organic pigments, many devices use dimethylformamide as the solvent, but the chromaticity is quite different from foreign products. After some devices use dimethylacetamide as the solvent, the product quality and chromaticity have been significantly improved Export requirements.
5. Petrochemical
In the petrochemical process, dimethylacetamide is an excellent catalyst, it can accelerate the cyclization, halogenation, cyanation, alkylation and dehydrogenation reactions, and can increase the yield of the main product.
6. Other aspects
There are many solvents for extracting butadiene from ethylene cracking gas, among which there are multiple sets of devices at home and abroad that use dimethylacetamide as the solvent. Dimethylacetamide is widely used as a solvent for separating pure benzene, cyclohexane and cyclohexene in a nylon 66 salt cyclohexanol unit. In the production of pesticides, dimethylacetamide can also be used as a solvent or cocatalyst. Compared with traditional organic solvents, it improves product quality and yield.

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