JP2007269658A - Method for producing dialkylimidazole and dialkyl imidazole obtained thereby - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing dialkylimidazole of high purity by effectively removing impurities and provide the dialkylimidazole obtained thereby. <P>SOLUTION: In this production method, ammonia, primary amine, aldehyde and glyoxal are allowed to react with one another and the resultant crude dialkylimidazole is distilled to produce dialkylimidazole. In this case, the crude dialkylimidazole is treated with heat at a temperature higher than 60°C before the distillation. The heat-treated crude dialkylimidazole is separated into the aqueous layer and the oil layer, then the oil layer is distilled to obtain the dialkylimidazole of high purity. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a dialkylimidazole for the purpose of obtaining a dialkylimidazole with few impurities by effectively removing impurities produced during the production of the dialkylimidazole, and a dialkylimidazole obtained thereby.

  Dialkylimidazole is a compound that is expected to be useful in various organic drug fields, such as an intermediate for pharmaceuticals or as a catalyst for various resins. It is known that the dialkylimidazole is produced, for example, by reacting ammonia, a primary amine, an aldehyde compound, and glyoxal.

  In the production method described above, by-products such as alkyl imidazole are produced in addition to the target dialkyl imidazole, usually, dialkyl imidazole is obtained by purification by distillation of the crude dialkyl imidazole containing these by-products. Has been done.

  However, the crude dialkylimidazole contains an alkylimidazole having a boiling point close to that of the dialkylimidazole, and the alkylimidazole cannot be completely removed in a normal distillation step, resulting in a dialkylimidazole containing impurities. Become. In addition to the alkyl imidazolium, there are also impurities such as imidazole having no alkyl group and impurities that cause the product to be colored over time. Therefore, although it has transparency immediately after distillation, it has resulted in a discoloration to black brown over time, and it was very difficult to obtain a high-purity dialkylimidazole.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for producing a dialkylimidazole capable of effectively removing impurities and obtaining a high-purity dialkylimidazole, and a dialkylimidazole obtained thereby. And

  In order to achieve the above object, the present invention provides a method for producing a dialkylimidazole by distilling a crude dialkylimidazole obtained by reacting ammonia, a primary amine, an aldehyde and glyoxal. The manufacturing method of the dialkylimidazole which heat-processes at the temperature of 60 degreeC or more is made into the 1st summary.

  And let the dialkyl imidazole obtained by the manufacturing method of the said dialkyl imidazole be a 2nd summary.

  Furthermore, a third gist is a dialkylimidazole having an APHA (Hazen unit color number) of 200 or less after being left at 25 ° C. for 2 months.

  That is, the present inventors have made extensive studies on a method for effectively removing impurities in the crude dialkylimidazole. Impurities that turn blackish brown over time are not colored immediately after production and are difficult to separate and remove in that state, so a method for early coloring and removing the impurities should be determined. Further research was done. As a result, the crude dialkylimidazole can be heated at a temperature of 60 ° C. or higher before the distillation step, thereby facilitating the coloring of the causative substance (impurities) that turn blackish brown over time. I found it. Then, after the heating, the impurities colored by the heat treatment can be easily removed by distillation, and as a result, it has been found that it is possible to obtain a high-purity dialkylimidazole containing very little impurities. The invention has been reached.

  Thus, in the present invention, when dialkylimidazole is produced by distilling crude dialkylimidazole, the crude dialkylimidazole is heat-treated at 60 ° C. or higher prior to distillation. For this reason, impurities that were difficult to extract by conventional methods can be colored before distillation, and can be easily removed by distillation. The dialkylimidazole thus obtained is a high-purity dialkylimidazole with a low content of impurities which is a by-product during the production of the dialkylimidazole.

  When the heat treatment is performed in the presence of a caustic substance, impurities can be easily colored even when the heating temperature is set low, and impurities can be effectively separated and removed by distillation. High purity dialkylimidazole can be obtained.

  Moreover, when the blending amount of the caustic substance is set in the range of 1 to 40 mol% with respect to the crude dialkylimidazole, the amount of water mixed in the distilled distillate is also adjusted, and the 1,2-higher purity 1,2- Dialkylimidazoles can be obtained.

  In this way, a high-purity dialkylimidazole having an APHA of 200 or less after standing at 25 ° C. for 2 months is obtained.

  In the method for producing a dialkylimidazole of the present invention, the crude dialkylimidazole to be purified is produced by reaction and production by a conventionally known method. For example, it is produced by reacting ammonia, primary amine, aldehyde and glyoxal in a reaction medium. The ammonia, primary amine, and glyoxal are usually each subjected to a reaction as an aqueous solution. Specifically, the ammonia is a 5-30 wt% aqueous ammonia solution, and the primary amine is 30-50 wt%. As the aqueous solution, glyoxal is supplied as an aqueous solution of 30 to 50% by weight, preferably about 40% by weight. In the aldehyde, for example, a low-boiling aldehyde compound such as formaldehyde or acetaldehyde is supplied to the reaction as an aqueous solution or a 20 to 80% by weight solution of a lower alcohol such as methanol, ethanol or propanol. For example, a high-boiling aldehyde such as butyraldehyde is supplied to the reaction as it is. Solid aldehydes may be used in the reaction as a solution of lower alcohol or the like.

  The method for adding the raw material components is not particularly limited, and conventionally known methods such as a batch method, a division method, a dropping method, and the like can be mentioned and appropriately selected. The reaction time is usually set to about 30 minutes to 10 hours.

  The reaction medium used in the above reaction is not particularly limited, and usually water is used. If necessary, an organic solvent having compatibility with water such as methanol, ethanol, propanol or the like may be appropriately used. Absent. And the preparation composition of each said raw material component is set in the range of a glyoxal / aldehyde compound / primary amine / ammonia / = 1 / 1-1.5 / 1-4 / 1-1.5 on the molar ratio basis. It is preferable to do.

  And as said crude dialkyl imidazole produced | generated by such reaction, the alkyl imidazole and imidazole which are by-products are contained with the dialkyl imidazole refined | extracted, for example, the said dialkyl imidazole contains the whole crude dialkyl imidazole. In an amount of 50 to 90 mol%, preferably 70 to 90 mol%.

  In the present invention, the method for purifying dialkylimidazole is carried out as follows using the above-mentioned crude dialkylimidazole. That is, the crude dialkylimidazole is heated for a predetermined time to separate into an oil layer containing dialkylimidazole and an aqueous layer, and the aqueous layer is removed. Then, the remaining oil layer is distilled under reduced pressure to obtain high-purity dialkylimidazole.

  The heating conditions for the crude dialkylimidazole need to be set to 60 ° C. or higher, and more preferably set to 120 ° C. or higher. In general, the upper limit of the heating temperature is 300 ° C. That is, when the heating temperature is less than the lower limit, the temperature is too low to color impurities that are difficult to remove by distillation alone, and when the upper limit is exceeded, the N-position substituent of the target imidazole is eliminated. This is because the yield of the target dialkylimidazole is lowered. Moreover, as heating time, it is preferable to set to 20 minutes or more, More preferably, it is 2 to 8 hours.

  Further, the heat treatment of the present invention is carried out under the liquid phase holding pressure of the crude dialkylimidazole solution.

  Further, when the crude dialkylimidazole is subjected to a heat treatment, it is preferable to perform the heat treatment in the presence of a caustic substance. By performing the heat treatment by adding the caustic substance in this way, the effect of promoting the color reaction of the impurities is exerted, so that the impurities can be effectively separated and removed even if the heating temperature is set low, As a result, it becomes possible to obtain a dialkylimidazole of even higher purity. The time for blending the caustic alkali material is not particularly limited, and it may be blended with the crude dialkylimidazole when the heat treatment before distillation is performed.

  Examples of the caustic alkali material include potassium hydroxide and sodium hydroxide. These may be used alone or in combination of two or more. Of these, potassium hydroxide is preferably used from the viewpoint of high solubility in water and difficulty in solidification even when water is distilled off during heating. In addition, when the caustic substance is blended, it may be either solid or aqueous solution, but it is particularly preferable to add it as an aqueous solution from the viewpoint of handling.

  The blending amount of the caustic substance is preferably set in the range of 1 to 40 mol%, particularly preferably 10 to 30 mol%, based on the crude dialkylimidazole. That is, if the amount of caustic alkali material exceeds the upper limit, the amount of water contained in the distilled distillate increases, the purity of the resulting dialkylimidazole decreases, and the amount of caustic alkali that solidifies during distillation. This is because there is a tendency to increase the amount of dialkylimidazole remaining in the distillation residue.

  Furthermore, the heating conditions for the aforementioned crude dialkylimidazole will be described in more detail. That is, the heating conditions can be set finely depending on the presence or absence of a caustic alkali substance during the heat treatment. (1) When a caustic substance is added and heat treatment is performed in the presence of the caustic substance, the heating temperature is preferably set to 60 to 200 ° C, particularly preferably 100 to 150 ° C. (2) When heat treatment is carried out without using caustic substances without using caustic substances, the heating temperature is preferably set to 60 to 300 ° C, particularly preferably 120 to 200 ° C. As described above, the heating temperature can be set lower when the caustic substance is used and the heat treatment is performed in the presence of the caustic substance than when the caustic substance is not used. This is presumably because the coloring reaction of impurities is promoted by the presence of caustic.

  Next, the above-mentioned crude dialkylimidazole is heat-treated under predetermined conditions, and then allowed to stand to separate into an oil layer and an aqueous layer, and the aqueous layer is removed. Subsequently, the target dialkylimidazole can be obtained by distilling the oil layer under reduced pressure.

  The distillation under reduced pressure of the oil layer can be carried out by a conventionally known method. For example, distillation at a temperature of 60 to 180 ° C., particularly preferably 250 to 7000 Pa and a temperature of 60 to 130, under a reduced pressure of 250 to 14000 Pa. Distillation at 0 ° C. allows the impurities to be distilled off to obtain the desired high-purity dialkylimidazole.

  The dialkylimidazole thus obtained has a high purity with the total content of impurities being less than 2.5% by weight. Note that a gas chromatograph with a flame ionization detector is usually used as a quantitative determination of the total content of impurities, that is, purity.

  As the dialkylimidazole thus obtained, a dialkylimidazole having a concentration of 99% or more and an APHA (Hazen unit color number) of 200 or less after standing at 25 ° C. for 2 months is obtained. Preferably, APHA (Hazen unit color number) after standing at 25 ° C. for 2 months is 100 or less. The APHA (Hazen unit color number) is a color determination method, which is the Hazen unit color number in JIS K0071-1, and conforms to ISO 6271.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to a following example, unless the summary is exceeded. Hereinafter, “%” is based on weight.

[KOH use + heating temperature 120 ° C]
40% aqueous solution of glyoxal (145.0 g, 1 mol), 40% aqueous solution of methylamine (77.8 g, 1 mol), 25% aqueous solution of ammonia (68.0 g, 1 mol) and 70% aqueous solution of acetaldehyde (75.5 g, 1.2 mol) Was reacted at 50 ° C. for 3 hours to obtain a yellow solution (crude dialkylimidazole solution). And as a result of quantifying the reaction mixture which is the said yellow solution with a gas chromatograph, 87g (yield 90%) of 1, 2- dimethylimidazole was contained. To the obtained yellow solution, 10 mol% of potassium hydroxide was added to the crude 1,2-dimethylimidazole and concentrated under normal pressure, and the mixture was refluxed for 2 hours when the temperature of the concentrated solution reached 120 ° C. Next, this is left standing to separate into a lower aqueous layer and an upper oil layer, and after removing the lower aqueous layer, the remaining oil layer is distilled under reduced pressure (conditions: 2670 Pa, 90 to 130 ° C.). This was obtained as 79 g of 1,2-dimethylimidazole having a purity of 99.8% (yield 82%, charged glyoxal) as a slightly yellow solid (APHA in the melt was 40). The obtained 1,2-dimethylimidazole was allowed to stand at 25 ° C. for 2 months and then visually observed. As a result, the color degree was slightly changed, and the APHA at that time was 50.

  In addition, a gas chromatograph was used for the measurement of the yield, and in detail, column: HP-WAX 0.53 mm × 30 m × 1.0 μm manufactured by Agilent, column temperature: from 70 ° C. to 220 ° C. at 10 ° C./min. The temperature was raised and held at 220 ° C. for 10 minutes, the inlet: 220 ° C., detector (hydrogen flame ionization detector): 250 ° C., carrier gas: helium 20 mL / min.

  The purity was measured using a gas chromatograph, and in detail, the area% of the chromatochromatogram obtained by measuring melted 1,2-dimethylimidazole under the same measurement conditions as the yield was defined as the purity. .

  The APHA was measured by performing colorimetry with the APHA standard solution.

[KOH use + heating temperature 60 ° C]
40% aqueous solution of glyoxal (145.0 g, 1 mol), 40% aqueous solution of methylamine (77.8 g, 1 mol), 25% aqueous solution of ammonia (68.0 g, 1 mol) and 70% aqueous solution of acetaldehyde (75.5 g, 1.2 mol) Was reacted at 50 ° C. for 3 hours to obtain a yellow solution (crude dialkylimidazole solution). And as a result of quantifying the reaction mixture which is the said yellow solution with a gas chromatograph, 87g (yield 90%) of 1, 2- dimethylimidazole was contained. To the obtained yellow solution, 30 mol% of potassium hydroxide was added to the crude 1,2-dimethylimidazole, concentrated under reduced pressure at 6670 Pa, and refluxed for 8 hours when the temperature reached 60 ° C. Next, this is left standing to separate into a lower aqueous layer and an upper oil layer, and after removing the lower aqueous layer, the remaining oil layer is distilled under reduced pressure (conditions: 2670 Pa, 90 to 130 ° C.). , 99.1% of 1,2-dimethylimidazole (yield 78%, charged glyoxal), a pale yellow solid (APHA in the melt was 50). The obtained 1,2-dimethylimidazole was allowed to stand at 25 ° C. for 2 months and then visually observed. As a result, the color degree was slightly advanced, and the APHA at that time was 70.

  The above yield and purity were measured in the same manner as in Example 1. Further, the APHA was also measured by performing colorimetry with the APHA standard solution in the same manner as in Example 1.

[KOH use + heating temperature 200 ° C]
40% aqueous solution of glyoxal (145.0 g, 1 mol), 40% aqueous solution of methylamine (77.8 g, 1 mol), 25% aqueous solution of ammonia (68.0 g, 1 mol) and 70% aqueous solution of acetaldehyde (75.5 g, 1.2 mol) Was reacted at 50 ° C. for 3 hours to obtain a yellow solution (crude dialkylimidazole solution). And as a result of quantifying the reaction mixture which is the said yellow solution with a gas chromatograph, 87g (yield 90%) of 1, 2- dimethylimidazole was contained. To the obtained yellow solution, 3 mol% of potassium hydroxide was added to the crude 1,2-dimethylimidazole and concentrated under normal pressure. When the concentrated solution reached 200 ° C., it was refluxed for 2 hours. Then, by distillation under reduced pressure, 98.7% of 1,2-dimethylimidazole was obtained as 61 g (yield 63%, charged glyoxal) as a slightly yellow solid (APHA of the melt was 20). The obtained 1,2-dimethylimidazole was allowed to stand at 25 ° C. for 2 months and then visually observed. As a result, the color degree slightly changed, and the APHA at that time was 50.

  The above yield and purity were measured in the same manner as in Example 1. Further, the APHA was also measured by performing colorimetry with the APHA standard solution in the same manner as in Example 1.

[No KOH + Heating temperature 180 ° C]
40% aqueous solution of glyoxal (145.0 g, 1 mol), 40% aqueous solution of methylamine (77.8 g, 1 mol), 25% aqueous solution of ammonia (68.0 g, 1 mol) and 70% aqueous solution of acetaldehyde (75.5 g, 1.2 mol) Was reacted at 50 ° C. for 3 hours to obtain a yellow solution (crude dialkylimidazole solution). And as a result of quantifying the reaction mixture which is the said yellow solution with a gas chromatograph, 87g (yield 90%) of 1, 2- dimethylimidazole was contained. The resulting yellow solution was concentrated under normal pressure, and refluxed for 8 hours when the temperature of the concentrated solution reached 180 ° C. Subsequently, this was distilled under reduced pressure (conditions: 2679 Pa, 90 to 130 ° C.) to give 64 g of 1,2-dimethylimidazole with a purity of 97.6% (yield 67%, charged glyoxal), slightly yellow solid (melt) APHA was obtained as 90). The obtained 1,2-dimethylimidazole was allowed to stand at 25 ° C. for 2 months and then observed with the naked eye. As a result, the degree of color was slightly changed, but no extreme color change was observed. APHA at that time was 180.

  The above yield and purity were measured in the same manner as in Example 1. Further, the APHA was also measured by performing colorimetry with the APHA standard solution in the same manner as in Example 1.

[No KOH + heating temperature 300 ° C]
40% aqueous solution of glyoxal (145.0 g, 1 mol), 40% aqueous solution of methylamine (77.8 g, 1 mol), 25% aqueous solution of ammonia (68.0 g, 1 mol) and 70% aqueous solution of acetaldehyde (75.5 g, 1.2 mol) Was reacted at 50 ° C. for 3 hours to obtain a yellow solution (crude dialkylimidazole solution). And as a result of quantifying the reaction mixture which is the said yellow solution with a gas chromatograph, 87g (yield 90%) of 1, 2- dimethylimidazole was contained. The obtained yellow solution was concentrated at normal pressure, and when the internal temperature reached 180 ° C., it was sealed in an autoclave and heated at 300 ° C. for 4 hours while adjusting to 850000 to 900,000 Pa. Subsequently, 55 g of 1,2-dimethylimidazole having a purity of 97.8% (yield 57%, charged glyoxal) by distillation under reduced pressure (conditions: 2670 Pa, 90 to 130 ° C.), slightly yellow solid (APHA of the melt was 60 ) Was obtained. The obtained 1,2-dimethylimidazole was allowed to stand at 25 ° C. for 2 months and then visually observed. As a result, although the degree of color was slightly changed, no extreme color change was observed. APHA at that time was 160.

  The above yield and purity were measured in the same manner as in Example 1. Further, the APHA was also measured by performing colorimetry with the APHA standard solution in the same manner as in Example 1.

[Comparative Example 1]
40% aqueous solution of glyoxal (145.0 g, 1 mol), 40% aqueous solution of methylamine (77.8 g, 1 mol), 25% aqueous solution of ammonia (68.0 g, 1 mol) and 70% aqueous solution of acetaldehyde (75.5 g, 1.2 mol) Was reacted at 50 ° C. for 3 hours to obtain a yellow solution (crude dialkylimidazole solution). And as a result of quantifying the reaction mixture which is the said yellow solution with a gas chromatograph, 87g (yield 90%) of 1, 2- dimethylimidazole was contained. The obtained yellow solution was distilled under reduced pressure (conditions: 2670 Pa, 95-130 ° C.) to obtain 70 g of 1,2-dimethylimidazole having a purity of 95% (yield 73%, charged glyoxal), slightly yellow solid (melting solution) APHA was obtained as 200). The obtained 1,2-dimethylimidazole was allowed to stand at 25 ° C. for 2 months and then visually observed. As a result, the color turned blackish brown. APHA at that time was 1000 or more, and measurement was impossible.

  The above yield and purity were measured in the same manner as in Example 1. The APHA was also colorimetrically compared with the APHA standard solution, as in Example 1.

[Comparative Example 2]
(Heating temperature is 50 ° C)
50% aqueous 40% glyoxal solution (145.0 g, 1 mol), 40% aqueous methylamine solution (77.8 g, 1 mol), 25% aqueous ammonia solution (68.0 g, 1 mol) and 70% aqueous acetaldehyde solution (62.9 g, 1 mol) The reaction was carried out at 0 ° C. for 3 hours to obtain a yellow solution (crude dialkylimidazole solution). And as a result of quantifying the reaction mixture which is the said yellow solution with a gas chromatograph, 87g (yield 90%) of 1, 2- dimethylimidazole was contained. The resulting yellow solution was concentrated under reduced pressure at 6670 Pa, and refluxed for 2 hours when the temperature of the concentrated solution reached 50 ° C. Next, this was allowed to stand to separate into a lower aqueous layer and an upper oil layer, and after removing the lower aqueous layer, the oil layer was distilled under reduced pressure (conditions: 2670 Pa, 95 to 130 ° C.) to obtain a purity of 95. % 1,2-dimethylimidazole (yield 69%, vs. charged glyoxal) as a pale yellow solid (APHA in the melt was 150). The obtained 1,2-dimethylimidazole was allowed to stand at 25 ° C. for 2 months and then visually observed. As a result, it turned blackish brown. APHA at that time was 1000 or more, and measurement was impossible.

  The above yield and purity were measured in the same manner as in Example 1. The APHA was also colorimetrically compared with the APHA standard solution, as in Example 1.

The present invention is a production method for obtaining a high-purity dialkylimidazole useful for, for example, pharmaceutical intermediates, dye intermediates, and catalysts for various resins such as epoxy resins and polyurethane resins.

Claims (7)

  A method for producing a dialkylimidazole by distilling a crude dialkylimidazole obtained by reacting ammonia, primary amine, aldehyde and glyoxal, wherein the crude dialkylimidazole is heat-treated at a temperature of 60 ° C. or higher prior to distillation. A method for producing a dialkylimidazole.   The method for producing a dialkylimidazole according to claim 1, wherein the crude dialkylimidazole contains an alkylimidazole and an imidazole together with the dialkylimidazole, and the dialkylimidazole contains 50 to 90 mol% of the whole crude dialkylimidazole. .   The method for producing a dialkylimidazole according to claim 1 or 2, wherein the heat treatment is performed in the presence of a caustic substance.   The manufacturing method of the dialkyl imidazole of Claim 3 with which the compounding quantity of the said caustic alkali substance is set to the range of 1-40 mol% with respect to crude dialkyl imidazole.   The said heat processing time is 20 minutes or more, The manufacturing method of the dialkylimidazole as described in any one of Claims 1-4.   The dialkylimidazole obtained by the manufacturing method of the dialkylimidazole as described in any one of Claims 1-5.   A dialkylimidazole having an APHA (Hazen unit color number) of 200 or less after standing at 25 ° C. for 2 months.