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The preparation method of dimethyl malonate

A technology of dimethyl malonate and cyanoacetic acid, which is applied in the chemical industry, can solve problems such as the easy decomposition of cyanoacetic acid, the consumption of sulfuric acid acidic wastewater, and the decomposition of cyanoacetic acid, and achieve the advantages of simple operation, improved heating uniformity, and improved dispersion performance Effect

Inactive Publication Date: 2019-03-22
内蒙古紫光化工有限责任公司
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  • Abstract
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  • 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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  • The preparation method of dimethyl malonate
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  • The preparation method of dimethyl malonate

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Embodiment 1

[0040] A preparation method for dimethyl malonate, comprising the steps of:

[0041] 1) Neutralization reaction: Add 445kg of chloroacetic acid (98% by mass, 4.62kmol) to 620kg of water and stir to dissolve, then neutralize with saturated aqueous sodium carbonate solution to pH=6.5-7.0 to generate sodium chloroacetate.

[0042] 2) Cyanide reaction: the sodium chloroacetate that step 1) obtains is transferred to the cyanide reaction kettle, is warming up to 50 ℃, then drips the sodium cyanide aqueous solution 765kg that mass concentration is 30% (containing 4.68kmol sodium cyanide in the aqueous solution ), when the reaction temperature reaches 85-90°C, stop heating and start cooling, when the reaction temperature reaches 105°C (the later stage is a strong exothermic reaction), the reaction ends, and it is cooled to room temperature to obtain an aqueous solution of sodium cyanoacetate.

[0043] 3) Acidification reaction: transfer the sodium cyanoacetate aqueous solution obtaine...

Embodiment 2

[0051]A preparation method for dimethyl malonate, comprising the steps of:

[0052] 1) Neutralization reaction: Add 445kg of chloroacetic acid (98% by mass, 4.62kmol) to 620kg of water and stir to dissolve, then neutralize with saturated aqueous sodium carbonate solution to pH=6.5-7.0 to generate sodium chloroacetate.

[0053] 2) Cyanide reaction: the sodium chloroacetate obtained in step (1) is transferred to the cyanide reactor, warming up to 50 DEG C, then dripping 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 and cools down to room temperature to obtain an aqueous solution of sodium cyanoacetate.

[0054] 3) Acidification reaction: transfer the sodium cyanoacetate aqueous solution obtained in step 2) into an acidification reaction kettle, stir, feed hydrogen chloride gas to pH=7.0, after...

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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 industry, in particular to a preparation method of 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. In China, cyanation esterification is mainly used, that is, chloroacetic acid, sodium cyanide and methanol are used as raw materials, and after neutralization , Cyanide, acidification and esterification processes to obtain dimethyl malonate. [0003] Common synthetic methods are as follows: [0004] 1. Direct esterification of cyanoacetic acid [0005] [0006] [0007] [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 ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
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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