Environment-friendly clean production method of high-purity cyanoacetic acid, cyanoacetate and malonate
A high-purity cyanoacetic acid and cyanoacetate technology, which is applied in chemical instruments and methods, carboxylate/lactone preparation, carboxylate preparation, etc., can solve the problem of cyanoacetic acid purification or high energy consumption and unclean salt separation , cumbersome operation and other problems, to achieve the effect of solving unclean salt separation, saving investment and reducing processing load
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[0056] Example 1: 1159.4kg of sodium cyanoacetate aqueous solution prepared by chloroacetic acid and sodium carbonate in water for neutralization reaction, and sodium cyanide solution for cyanation reaction (containing sodium cyanoacetate 23.33wt%, sodium chloride 12.88% , Water 61.47%), and 31wt% hydrochloric acid 296.4L for acidification reaction to obtain acidification solution containing cyanoacetic acid and sodium chloride (cyanoacetic acid 14.19wt%, sodium chloride 21.18wt%, water 63.43%), add salt precipitation agent The mass ratio of the amount of tert-butanol to the amount of water in the acidified liquid is 0.25:1, and about 80% of the sodium chloride in the acidified liquid is separated and filtered at 25°C. The washing liquid obtained by washing the solid sodium chloride with tert-butanol is used for reuse To the next salt precipitation, the filtrate after separating sodium chloride is about 1453kg (containing cyanoacetic acid 14.64wt%, sodium chloride 4.31wt%, water...
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[0057] Example 2: As in Example 1, the desalinated solution with a salt content of less than 0.05% obtained from the shallow chamber by the above-mentioned electrodialysis desalination treatment was concentrated by vacuum evaporation until the water content of the concentrated solution was about 8wt%, and 1.8 times moles of cyanoacetic acid was added Add an amount of anhydrous methanol, drop an appropriate amount of 98wt% concentrated sulfuric acid catalyst, and control the temperature at 60~70℃ for esterification reaction. After the reaction is completed, the excess methanol is evaporated under negative pressure, and sodium carbonate solution is added for washing, neutralization, phase separation, and refinement. Distillation winner 234.7kg of high-purity methyl cyanoacetate with content ≥99.5%.
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[0058] Example 3: As in Example 1, the desalinated solution with a salt content of less than 0.05% obtained from the desalination chamber by the above-mentioned electrodialysis desalination treatment was subjected to negative pressure evaporation and concentrated to a water content of about 12wt% in the concentrated solution, and 1.85 times moles of cyanoacetic acid was added Add an amount of absolute ethanol, drop an appropriate amount of 98wt% concentrated sulfuric acid catalyst, and control the temperature at 60~70℃ for esterification reaction. After the reaction is completed, the excess ethanol is evaporated under negative pressure, and sodium carbonate solution is added for washing, neutralization, phase separation, and refinement. 264.4kg of high-purity ethyl cyanoacetate with a content of ≥99.5%.
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