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A kind of preparation method of 1,3-dimethylcyanoacetylurea

A technology of dimethyl cyanoacetyl urea and dimethyl urea, which is applied in 1 field, can solve problems such as the quality of cyanoacetyl urea, the influence of condensation yield, the decomposition of cyanoacetic acid, and the high level of cyanoacetic acid, so as to save acetic anhydride, eliminate damage, and raw materials The effect of cost reduction

Active Publication Date: 2022-06-14
JILIN SHULAN SYNTHETIC PHARMA
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Problems solved by technology

[0010] 2. Add acetic anhydride directly to cyanoacetic acid with water. Under high temperature conditions, the acetic anhydride added and a small amount of water react quickly and exothermic, resulting in excessive local cyanoacetic acid. Because cyanoacetic acid is unstable, it is easy to cause burning if the temperature is too high The decomposition of cyanoacetic acid will affect the quality and condensation yield of 1,3-dimethylcyanoacetylurea

Method used

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  • A kind of preparation method of 1,3-dimethylcyanoacetylurea
  • A kind of preparation method of 1,3-dimethylcyanoacetylurea
  • A kind of preparation method of 1,3-dimethylcyanoacetylurea

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preparation example Construction

[0027] The present invention provides a kind of preparation method of 1,3-dimethyl cyanacetamide, the method comprises:

[0028] Step 1: carry out vacuum distillation of cyanoacetic acid under heating and negative pressure, and distill out a large amount of water in cyanoacetic acid. More preferably, it is 0.095-0.098MPa;

[0029] Step 2: after the vacuum rectification is completed, add anhydride-containing acetic acid to the cyanoacetic acid after the rectification, and the anhydride-containing acetic acid is obtained by dissolving acetic anhydride in acetic acid, and the content of the acetic anhydride is 3-5 %, utilize the acetic anhydride of content 3~5% in the anhydride-containing acetic acid and the remaining small amount of water to all react to produce acetic acid, then continue to heat negative pressure distillation, carry out acid with water, obtain anhydrous cyanoacetic acid and acetic acid; The temperature is preferably ≤92°C, more preferably 85-90°C, and the vacu...

Embodiment 1

[0037] With 255kg of cyanoacetic acid, heating, negative pressure carry out vacuum distillation, a large amount of water in the cyanoacetic acid is distilled out, the distillation temperature is 85 ℃, and the vacuum degree is 0.095MPa;

[0038] After the vacuum rectification is completed, add 130 L of anhydride-containing acetic acid, utilize 3% acetic anhydride in the anhydride-containing acetic acid and the remaining small amount of water to all react to produce acetic acid, then continue to heat negative pressure distillation, carry out acid with water, and the temperature of the water with water is 85℃, the vacuum degree is 0.095MPa, and 230kg of anhydrous cyanoacetic acid and 110L of acetic acid are obtained;

[0039] After the water-carrying end point, cool down to 38 ℃ and add 196kg of dimethylurea, complete, then adjust the temperature to be 58 ℃ and add 255kg of acetic anhydride to carry out the condensation reaction, and the condensation reaction temperature reaches 9...

Embodiment 2

[0042] 255kg of cyanoacetic acid was heated and subjected to vacuum distillation under negative pressure, and a large amount of water in the cyanoacetic acid was distilled out, and the distillation temperature was 90°C, and the vacuum degree was 0.098MPa;

[0043] After the vacuum rectification is completed, add 150 L of anhydride-containing acetic acid, utilize 5% acetic anhydride in the anhydride-containing acetic acid and a small amount of water to react to produce acetic acid, then continue to heat negative pressure distillation, carry out acid with water, and the temperature of the water is 90℃, the vacuum degree is 0.098MPa, and 235kg of anhydrous cyanoacetic acid and 130L of acetic acid are obtained;

[0044] After the water-carrying end point, cool down to 42 ℃ and add 197kg of dimethylurea, complete, then adjust the temperature to be 62 ℃ and add 256kg of acetic anhydride to carry out the condensation reaction, and the condensation reaction temperature reaches 98 ℃ to ...

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Abstract

The invention provides a preparation method of 1,3-dimethylcyanoacetylurea, which belongs to the technical field of chemical technology. The method carries out vacuum rectification of cyanoacetic acid; after the vacuum rectification is completed, anhydride-containing acetic acid is added to the rectified cyanoacetic acid, and then heating and negative pressure distillation are continued to carry out acid entrainment to obtain anhydrous cyanoacetic acid and acetic acid; After the end of the water, cool down to 38-42°C and add dimethylurea. After completion, heat up to 58-62°C and add acetic anhydride to carry out condensation reaction. The condensation reaction temperature reaches 95-98°C. Open the distillation valve and vacuum distill the anhydride under negative pressure. Acetic acid, the condensation reaction is completed, and 1,3-dimethylcyanoacetylurea is obtained. The yield of the product obtained by the method of the invention is increased by an average of about 0.5%; the properties are changed from the original brownish-red liquid to light brownish-red liquid, and the method saves cost.

Description

technical field [0001] The invention belongs to the technical field of chemical technology, and in particular relates to a preparation method of 1,3-dimethyl cyanacetamide. Background technique [0002] In the caffeine production process, condensation is the first step of the synthesis process, and cyanoacetic acid and dimethylurea act on the dehydrating agent acetic anhydride to obtain the intermediate product 1,3-dimethylcyanoacetylurea through condensation reaction. The condensation reaction needs to be carried out in a condition close to anhydrous (the water content in the cyanoacetic acid in the condensation reactor is required to be less than 1.0%), otherwise, the condensation reaction will be incomplete and the yield of condensation will be affected. The yield and quality of the 1,3-dimethyl cyanacetamide obtained by the condensation reaction play a decisive role in the yield and quality of the final caffeine. In order to ensure that the cyanoacetic acid contains wat...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C07C275/50C07C273/18
CPCC07C273/1854C07C253/34C07C275/50C07C255/23
Inventor 郭跃民齐万良孟祥伟李立冬
Owner JILIN SHULAN SYNTHETIC PHARMA
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