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Method for separating and purifying 2-methylimidazole crystal impurity

A methyl imidazole, separation and purification technology, applied in the direction of organic chemistry, etc., can solve the problems of low product purity, large solvent loss, complex process, etc., and achieve the effects of high purity, few processes, and simple process

Active Publication Date: 2009-10-21
HUBEI HONGYUAN PHARMA +1
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  • Abstract
  • Description
  • Claims
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Problems solved by technology

The main problems in conventional extraction are: the loss of solvent required in the extraction process is relatively large, and the target product needs to be further separated from the solvent, and the cost is high
[0007] Chinese patent CN1030756A discloses adding sulfuric acid and solid alkali to the system of synthesizing 2-methylimidazole from glyoxal, acetaldehyde and ammonia water to adjust the pH value, and then extracting, filtering and crystallizing through chlorinated hydrocarbons to obtain 2-methylimidazole. There are many processes, the process is more complicated, the purity of the product is low, and the product is yellow or dark

Method used

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  • Method for separating and purifying 2-methylimidazole crystal impurity

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Embodiment 1

[0022] according to figure 1 Process flow: take 53.3g of 2-methylimidazole crystalline impurities obtained by the glyoxal method, stir and dissolve in 400ml benzene at 60°C, and after dissolving for about 30 minutes, filter out the filtrate (about 400ml). Add 8 g of granular activated carbon to the filtrate, insulate and stir at 60° C. for 15 minutes, then filter off the insoluble matter, and place the filtrate at room temperature for cooling and crystallization for 4 hours. After centrifugation, the crystals were taken out, dried at 50° C. under vacuum for 3 hours, and weighed to obtain 29.0 g of white crystal 2-methylimidazole. The white 2-methylimidazole crystal has a melting point of 139.1° C., a 2-methylimidazole content of 92%, and a recovery rate of 2-methylimidazole of 71%. The centrifuged liquid obtained after the centrifugation of the aforementioned crystals obtained 285 ml of circulating benzene after standing still.

Embodiment 2

[0024] Take 50.0 g of 2-methylimidazole crystalline impurities obtained by the glyoxal method, stir and dissolve in 380 ml of benzene at 78 ° C, dissolve for about 40 minutes, and filter out the filtrate (about 380 ml). Add 10 g of granular activated carbon to the filtrate, insulate and stir at 60° C. for 10 minutes, then filter off the insoluble matter, and place the filtrate at 10° C. for cooling and crystallization for 10 hours. After centrifugation, the crystals were taken out, dried at 42°C under vacuum for 4 hours, and weighed to obtain 40.1 g of white crystal 2-methylimidazole. The white 2-methylimidazole crystal has a melting point of 140.7° C., a 2-methylimidazole content of 95%, and a recovery rate of 2-methylimidazole of 85%. After the centrifugal liquid obtained after the centrifugation of the aforementioned crystals was left to stand, 262 ml of circulating benzene was obtained.

Embodiment 3

[0026] Take the 2-methylimidazole crystalline impurity obtained by the glyoxal method and dry it at 0.07Mpa vacuum at 60°C for 15 hours; take 53.4g of the dry crude product and dissolve it in 400ml of benzene (or standing and stratified) under stirring at 60°C In circulating benzene), after about 30 minutes to dissolve completely, filter out the solution while hot; discard 13.5 g of dark brown impurities. Add 8 g of granular activated carbon to the filtered solution; after stirring and incubating at 60°C for 15 minutes, filter the insoluble matter while it is hot to obtain 12.8 g of black solid matter; place the filtrate at room temperature to cool and crystallize for 4 hours, and there is a little brown matter at the bottom. 2.3 g of a brown gum at the bottom came out. After centrifugation, the crystals were taken out, dried at 50° C. under vacuum for 3 hours, and weighed to obtain 29.0 g of white crystals. The white 2-methylimidazole crystal has a melting point of 140.7° C....

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Abstract

The invention relates to a method for separating and purifying a 2-methylimidazole crystal impurity. The method comprises the following steps: 1) dissolving the 2-methylimidazole crystal impurity by thermal benzene at a temperature of between 40 and 80 DEG C for 30 to 60 minutes, filtering the mixture to obtain filtrate; 2) passing the filtrate, adsorbing and decoloring the filtrate through active carbon, refiltering the filtrate, and crystallizing the obtained filtrate at low temperature to obtain crystal; and 3) centrifugally separating the crystal, and drying the crystal at a temperature of between 40 and 50 DEG C under a vacuum condition for 1 to 4 hours to obtain crystal 2-methylimidazole. The method has the advantages that the benzene as solvent and the active carbon as a decoloring agent are adopted to remove color elements in a crude product without concentration, the separating and purifying method has few steps, accessible raw materials, simple process, easy realization, low energy consumption and high yield. The benzene can be recycled without distillation, and the 2-methylimdazole is white acicular crystal, has high purity, good chromaticity, melting point of between 137 and 141 DEG C, purity over 92 percent, and the yield reaching over 70 percent.

Description

technical field [0001] The invention belongs to the field of separation and purification of fine chemical and pharmaceutical intermediates, in particular to a method for separation and purification of 2-methylimidazole crystalline impurities crystallized from a solution containing glyoxal, acetaldehyde, oxalic acid and ammonia. Background technique [0002] Pure 2-methylimidazole is a white crystal. At present, 2-methylimidazole produced by glyoxal method is mainly obtained by separating from the synthesized mother liquor, and the separation methods mainly include extraction and recrystallization. [0003] Extraction is a separation process in which organic matter present in a certain phase is leached and dissolved with a solvent, and transferred to another liquid phase, which is divided into liquid-liquid extraction and liquid-solid extraction. This process is realized by utilizing the property that organic matter dissolves and distributes in two phases in a certain propor...

Claims

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Application Information

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IPC IPC(8): C07D233/58
Inventor 丁一刚杨昌炎段小六戢峻丁晓娟
Owner HUBEI HONGYUAN PHARMA
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