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Preparation method for dimethyl malonate

A technology of dimethyl malonate and cyanoacetic acid, which is applied in the chemical industry, can solve the problems of consumption of sulfuric acid acid waste water, easy decomposition of cyanoacetic acid, and decomposition of cyanoacetic acid, and achieve the goals of improving heating uniformity, simple operation, and improving dispersion performance Effect

Inactive Publication Date: 2017-03-15
内蒙古紫光化工有限责任公司
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0008] The shortcoming that this method exists is: the reaction process of synthesizing cyanoacetic acid produces a large amount of inorganic salt sodium chloride, and the mixture of cyanoacetic acid and salt carries out esterification reaction after being concentrated, but cyanoacetic acid is easily decomposed in the late stage of concentration, and because there is A large amount of sodium chloride, sulfuric acid reacts with sodium chloride during esterification, consumes a large amount of sulfuric acid and produces a large amount of acidic wastewater
This method still has the phenomenon of decomposition of cyanoacetic acid due to local uneven heating in the process of secondary concentration and desalination

Method used

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  • Preparation method for dimethyl malonate
  • Preparation method for dimethyl malonate

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Embodiment 1

[0040] A preparation method of dimethyl malonate includes the following steps:

[0041] 1) Neutralization reaction: 445 kg of chloroacetic acid (mass content 98%, 4.62 kmol) is stirred and dissolved with 620 kg of water, and then neutralized with a saturated aqueous sodium carbonate solution to pH=6.5-7.0 to generate sodium chloroacetate.

[0042] 2) Cyanide reaction: transfer the sodium chloroacetate obtained in step 1) into the cyanide reactor, heat up to 50°C, and then drop 765 kg of sodium cyanide aqueous solution with a mass concentration of 30% (the aqueous solution contains 4.68 kmol sodium cyanide ), when the reaction temperature reaches 85-90° C., stop heating and start cooling. When the reaction temperature reaches 105° C. (the later period is a strong exothermic reaction), the reaction ends, cool to room temperature, and prepare a sodium cyanoacetate aqueous solution.

[0043] 3) Acidification reaction: transfer the sodium cyanoacetate aqueous solution prepared in step 2) ...

Embodiment 2

[0051] A preparation method of dimethyl malonate includes the following steps:

[0052] 1) Neutralization reaction: 445 kg of chloroacetic acid (mass content 98%, 4.62 kmol) is stirred and dissolved with 620 kg of water, and then neutralized with a saturated aqueous sodium carbonate solution to pH=6.5-7.0 to generate sodium chloroacetate.

[0053] 2) Cyanation reaction: transfer the sodium chloroacetate obtained in step (1) into the cyanide reactor, heat up to 50°C, and then drop 792kg (4.85kmol) of sodium cyanide aqueous solution with a mass concentration of 30%, when the reaction temperature After reaching 85-90° C., stop heating and start cooling. When the reaction temperature reaches 105° C., the reaction ends, cool to room temperature, and prepare sodium cyanoacetate aqueous solution.

[0054] 3) Acidification reaction: The sodium cyanoacetate aqueous solution prepared in step 2) is transferred to the acidification reactor, stirred, and hydrogen chloride gas is introduced to pH=...

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Abstract

The invention provides a preparation method for dimethyl malonate, wherein the preparation method comprises the following steps: 1) acidification reaction: adding an acid or hydrogen chloride gas to sodium cyanoacetate, and carrying out reaction to prepare a cyanoacetic acid aqueous solution; 2) concentration and salt removal: adding dimethyl malonate to the cyanoacetic acid aqueous solution prepared in the step 1), carrying out distillation concentration, and removing inorganic salts in the reaction solution; and 3) esterification reaction: adding methanol to the reaction solution after salt removal in the step 2), and under an acidic condition, carrying out esterification reaction to prepare dimethyl malonate. Sulfuric acid and sodium chloride are prevented from undergoing reaction in the esterification process, the dispersion performance and heating uniformity of the materials in the reaction system are improved, cyanoacetic acid is prevented from being decomposed during concentration dewatering, and the product yield is improved.

Description

Technical field [0001] The invention relates to the field of chemical engineering, in particular to a method for preparing dimethyl malonate. Background technique [0002] Dimethyl malonate is an intermediate of medicines, pesticides and dyes. At present, there are many production methods at home and abroad. The main domestic cyanide esterification method is to use chloroacetic acid, sodium cyanide and methanol as raw materials. , Cyanidation, acidification and esterification process to obtain dimethyl malonate. [0003] The common synthesis methods are as follows: [0004] 1. Direct esterification of cyanoacetic acid [0005] [0006] [0007] [0008] The disadvantage of this method is that the reaction process of synthesizing cyanoacetic acid produces a large amount of inorganic salt sodium chloride. The mixture of cyanoacetic acid and salt is concentrated and then esterified. However, the cyanoacetic acid is easily decomposed in the later stage of concentration, and the reaction ...

Claims

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Application Information

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IPC IPC(8): C07C253/34C07C255/23C07C67/22C07C69/38
CPCC07C67/22C07C253/14C07C253/34C07C255/23C07C69/38
Inventor 刘佳丁永良邓建伟唐大家刘文枚刘兵
Owner 内蒙古紫光化工有限责任公司
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