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Method for purifying methacrylic acid

A technology of methacrylic acid and crude methacrylic acid, applied in the direction of organic chemistry, can solve the problems of complex purification process, unfavorable large-scale use, and affecting product purity and chroma

Active Publication Date: 2009-10-28
SHANGHAI HUAYI NEW MATERIAL
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

These impurities will affect the purity and color of the product, especially the trace amount of colored impurities such as furfural and 1,4-butanedione, which makes the appearance of methacrylic acid products yellow, and these trace amounts cannot be effectively removed by traditional rectification methods. Colored impurities
[0003] The current solution to the purification and decolorization of crude methacrylic acid is mainly to achieve the purpose of purification and decolorization by adding some compounds that can chemically react with impurities such as trace aldehydes and ketones, such as adding a certain amount of aromatic diamine (CN 88104811.9 ), bisulfite (JP 252446 / 1985), mercaptan (JP6635 / 1985) or resorcinol, α-naphthol (JP 130546 / 1985) and other compounds, but the effect is not satisfactory
The impurity removal effect of aromatic diamine is average, and it is expensive and toxic, which is not conducive to large-scale use
Bisulfite and mercaptan are not effective in removing impurities and must be used in large quantities. Such decolorizers will cause secondary pollution and make the purification process more complicated

Method used

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  • Method for purifying methacrylic acid

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1～4

[0012] Embodiment 1~4 (batch distillation)

[0013] The reaction gas obtained by gas-phase catalytic oxidation of tert-butanol is cooled and absorbed to obtain an aqueous solution of methacrylic acid, which is then extracted with a solvent and then rectified. Respectively get 500g of delight component tower [2] tower kettle feed liquid as raw material, add and account for the decolorizer of 0.1% of raw material total amount, the mixture enters deheavy component tower [3] and carries out rectification under reduced pressure, and tower kettle temperature is 90 °C, the impurity content in the feed liquid before and after distillation is shown in Table 1. When no decolorizing agent is added, the color of the product after distillation is greater than 50. After adding a decolorizing agent for distillation, almost all impurities such as aldehydes and ketones in the crude methacrylic acid can be removed, and the color value of the product is <10.

[0014] Table 1 Addition of differ...

Embodiment 5～8

[0016] Embodiment 5~8 (batch distillation)

[0017] Carry out rectification under vacuum in the same way as in Example 1, the difference is that the amount of decolorizing agent 1,2-ethylenediamine is changed in the rectifying process (the amount of decolorizing agent is the multiple of the total amount of impurities such as aldehydes and ketones), and distillation The content of impurities in the feed liquid before and after is shown in Table 2.

[0018] Comparing the data in Table 2, it can be seen that when the amount of decolorizing agent added is greater than 10 times the total amount of impurities such as aldehydes and ketones, the impurities such as aldehydes and ketones in the product can be basically completely removed, and the color value of the product is <10.

[0019] Table 2 The impact of the amount of decolorizing agent 1,2-ethylenediamine on the impurity content and product chromaticity in the feed liquid before and after distillation (unit: ppm)

[0020] ...

Embodiment 9～12

[0021] Embodiment 9~12 (batch distillation)

[0022] Carry out rectification under vacuum in the same manner as in Example 1, except that the temperature of the deheavy component tower [3] is changed, and the content of impurities in the feed liquid before and after distillation is as shown in Table 3.

[0023] Comparing the data in Table 3, it can be seen that when the temperature of the tower kettle is higher than 80°C, impurities such as aldehydes and ketones in the product can be basically completely removed, and the product chromaticity value is <10. As the temperature of the tower bottom rises, the polymerization tendency of the bottom liquid increases, so the temperature of the tower bottom should be less than 100°C.

[0024] Table 3 The influence of the tower still temperature on the impurity content in the feed liquid before and after distillation (unit: ppm)

[0025] name

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Abstract

The invention provides a method for purifying methacrylic acid, which can effectively remove impurities such as trace ketones and aldehydes contained in the product, and achieve the purpose of purification and decolorization. The methacrylic acid product obtained by gas-phase catalytic oxidation of isobutene or tert-butanol contains trace impurities such as ketones and aldehydes. These impurities will cause the methacrylic acid product to appear yellow, and it is difficult to remove it by traditional rectification methods. The present invention adds a decolorizing agent to chemically react with impurities such as aldehydes or ketones in the rectification and purification process of methacrylic acid, and the generated high boiling point substances are discharged along with the heavy components, thereby achieving the purpose of purification and decolorization. The chromaticity value of the obtained product is <10.

Description

technical field [0001] The invention relates to a method for removing impurities such as aldehydes and ketones from crude methacrylic acid obtained by gas-phase catalytic oxidation of isobutene or tert-butanol, so as to achieve the purpose of purification and decolorization. Background technique [0002] The gas-phase catalytic oxidation of isobutene or tert-butanol to produce methacrylic acid has been recorded in some patents. Compared with the traditional acetone cyanohydrin method, this method has the advantages of wide source of raw materials, less waste, and low production cost. economic benefits. In addition to the target product methacrylic acid, the reaction gas product obtained by this synthesis method also contains a certain amount of by-products, such as acetaldehyde, 1,4-butanedione, furfural, benzaldehyde, maleic acid, propionic acid , isobutyric acid, benzoic acid, terephthalic acid, acetic acid and acrylic acid, etc. These impurities will affect the purity a...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C07C57/07C07C57/05C07C57/04
Inventor 刘汉勇张庆怀刘书举马建学张春雷
Owner SHANGHAI HUAYI NEW MATERIAL