JP2906189B2 - Production method of β-hydroxy ketones - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing β-hydroxy ketones. More specifically, the present invention relates to an improvement in a method for producing β-hydroxyketones by reacting formaldehyde generated from formaldehyde or paraformaldehyde with ketones.

[0002]

2. Description of the Related Art β-Hydroxy ketones are known as intermediates for physiologically active substances, medicines, fragrances and the like, and as starting materials which give alkenyl ketones as polymer raw materials by dehydration. For example, Japanese Patent Publication No. 57-27,09
No. 6 discloses 4-hydroxy- as an example of β-hydroxyketones.
It is known that 2-butanone can be a raw material of 4- (4-hydroxyphenyl) -2-butanone, which is a kind of fragrance. The compound is easily dehydrated into alkenyl ketones, and this is shown to be a raw material for a photo-degradable synthetic resin.

[0003] Such β-hydroxyketones are obtained by a condensation reaction between ketones and formaldehyde generated from formaldehyde or paraformaldehyde as shown in the following reaction formula.

[0004]

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(Wherein, R ³ represents a linear or branched alkyl group, and R ⁴ represents hydrogen or a linear or branched alkyl group)

Various attempts have been made in the past to prepare 4-hydroxy-methacrylate, for example, by subjecting (a) acetone to formaldehyde in an aqueous solution (generally containing 37% formaldehyde) in the presence of a basic catalyst. Method for producing 2-butanone (JP-B-60-5)
0,774, JP-A-49-86,315), (b)
A method for producing 4-hydroxy-3-methyl-2-butanone by subjecting methyl ethyl ketone and formaldehyde in an aqueous solution to a condensation reaction (JP-A-49-86,315, GB
774,934) and (c) a method for producing 4-hydroxy-3-methyl-2-butanone by bringing methyl ethyl ketone into contact with paraformaldehyde as a formaldehyde generating source (US Pat. No. 3,009,005). I have.

However, such a conventional manufacturing method has the following problems. That is, in the methods (a) and (b) using an aqueous formaldehyde solution such as formalin as a formaldehyde source, it is difficult to control the reaction because the aqueous solution usually contains methanol that suppresses the condensation reaction. Accordingly, condensation of ketones easily occurs, and a high-boiling compound is also easily generated, so that purification after the reaction becomes difficult, and there is a problem that the yield of the target product is reduced. Further, there is a disadvantage that water in the aqueous formaldehyde solution becomes a large amount of wastewater.

On the other hand, the method (c) in which paraformaldehyde is used as a source of formaldehyde has the drawback that ketones are converted into polymethylol and the yield of the target product is reduced, and furthermore, when continuous condensation is carried out. Has a particle size of usually available paraformaldehyde of 1.5 to 2 m
In some cases, the supply operation of the slurry containing this is difficult, and there is a disadvantage in industrial implementation.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to overcome the above-mentioned disadvantages of the prior art, to operate easily in a batch process and a continuous process without substantially generating wastewater, An object of the present invention is to provide a method capable of producing β-hydroxyketones in a high yield by suppressing the reaction.

[0010]

In order to achieve the above object, the present invention has the following arrangement. (1) In the presence of a basic catalyst, formaldehyde and a general formula

[0011]

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(Wherein, R ¹ represents a linear or branched alkyl group having 5 or less carbon atoms, and R ² represents hydrogen or a linear or branched alkyl group) The condensation reaction is carried out in the presence of

[0013]

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(Wherein R ¹ and R ² have the same meanings as described above). In the process for producing β-hydroxyketones, paraformaldehyde is obtained by thermal decomposition of the above formaldehyde and ketones. Using a mixture obtained by diluting the obtained formaldehyde gas with a ketone gas and then condensing and trapping, and reacting the formaldehyde and the ketone in the presence of water having a solubility of 2% or more and less than the solubility of the ketone. Β-
A method for producing hydroxyketones.

(2) In the presence of a basic catalyst, formaldehyde and a compound of the general formula

[0016]

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(Wherein R ¹ represents a linear or branched alkyl group having 5 or less carbon atoms, and R ² represents hydrogen or a linear or branched alkyl group) The condensation reaction is carried out in the presence of

[0018]

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(Wherein, R ¹ and R ² have the same meanings as described above). In the method for producing β-hydroxyketones, paraformaldehyde is dissolved in the ketones as the formaldehyde and the ketone. Characterized in that the reaction between formaldehyde and ketones is carried out by using a mixed solution that has generated formaldehyde by heating and in the presence of water having a solubility of 2% or more and less than the solubility in ketones.
A method for producing hydroxyketones.

(3) In the presence of a basic catalyst, formaldehyde and a compound of the general formula

[0021]

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(Wherein R ¹ represents a linear or branched alkyl group having 5 or less carbon atoms, and R ² represents hydrogen or a linear or branched alkyl group) The condensation reaction is carried out in the presence of

[0023]

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(Wherein, R ¹ and R ² have the same meanings as described above). In a method for producing β-hydroxyketones represented by the formula: The dispersion thus obtained is used as a source of formaldehyde and ketones, and the presence of water having a solubility of 2% or more and less than the solubility of the ketones and the reaction of the ketones with the ketones are performed. A process for producing a characteristic β-hydroxyketone.

According to the present invention, prior to the reaction, a mixture of formaldehyde and ketones or a dispersion of paraformaldehyde and ketones which are made into fine particles and easily formaldehyde-prone (hereinafter, these are collectively referred to as a mixture etc.) There is a major feature in the preparation of (sometimes), but such preparation is performed as follows.

That is, in the method described in the above item (1), the preparation of the mixed solution is suitably performed by, for example, the apparatus shown in FIG. In the apparatus shown in FIG.
Paraformaldehyde of 5 to 2 mm is quantitatively supplied from a hopper 1 to a heater 2 equipped with a conveying means such as a screw feeder, where it is heated to 100 to 200 ° C. to depolymerize to generate formaldehyde. On the other hand, ketones sent from the ketone tank 5 to the outlet of the pyrolyzer 2 are quantitatively supplied, and the above-mentioned formaldehyde gas is diluted with the evaporated gas. The diluted mixed gas is then led to the condenser 3 where it is condensed and trapped, and is obtained in the receiver 4 as a mixture having a constant molar ratio.

Next, in the method described in item (2), the mixed solution was prepared by adding the same paraformaldehyde to ketones, adjusting the resulting suspension to pH 8 to 10 with a base, and then adjusting the temperature to 2
It is obtained by stirring at 0-50 ° C. That is,
This is because paraformaldehyde is easily depolymerized by the stirring to formaldehyde. When the pH is lower than 8, the depolymerization rate becomes extremely slow. When the pH is higher than 10, the condensation reaction between the generated formaldehyde and ketones starts, and it becomes difficult to control the reaction in the next step. Not preferred.

In the method described in item (3), the dispersion obtained by adding the same paraformaldehyde to ketones is circulated through a pulverizer so that the particle size of paraformaldehyde can be reduced. It is possible to obtain a dispersion having a mesh size of 100 to 500 mesh.

In any of the above methods, the molar ratio of formaldehyde or paraformaldehyde to ketones must be 1: 1 to 100, preferably 1: 5 to 50. When the molar ratio of the ketones is less than 1, dimethylol of the ketones or a high-boiling substance due to polymethylolation is formed to lower the yield of the target product. This is not preferable because the volumetric efficiency of the product decreases.

When carrying out the thermal decomposition method of (1) and the dissolution method of (2), 1 to 20% of water is added to the mixed solution to prevent polymerization of formaldehyde in the obtained mixed solution. It is preferred to add.

The paraformaldehyde used in the present invention is not particularly limited in concentration, particle size and the like as long as it has the ability to give formaldehyde by decomposition.
1% products, 85% products, 95% products, etc. are widely suitable.

The mixed solution prepared as described above is then subjected to a condensation reaction. For example, in the case of a batch method, the condensation reaction is started by charging a mixed solution or the like into a reactor equipped with a stirrer, heating and adding a basic catalyst. The reaction can be controlled at the temperature of the kettle, and after the reaction is completed, the reaction solution is neutralized with a neutralizing agent. In the case of the continuous method, it is preferable to insert a filler such as a ring into the reaction tower in order to mix the mixed solution and the catalyst and make the contact uniform. Further, the mixing of the basic catalyst is preferably carried out by a method of instantaneous diffusion using an orifice or a venturi. After completion of the reaction, the reaction solution is similarly neutralized with a neutralizing agent. The desired β-hydroxyketones are obtained by distilling off excess ketones, water and low boiling by simple distillation after the above neutralization,
High purity can be obtained by subjecting it to rectification.

In the condensation reaction system, water must be present in an amount of 2% or more based on the ketones and within a range not exceeding the solubility in the ketones used. In addition, the above-mentioned solubility means solubility at a reaction temperature in ketones used in the reaction. If the water content is lower than 2%, the reaction proceeds, but the diffusion of the basic catalyst becomes poor, so that high-boiling products increase and the yield with respect to formaldehyde decreases, which is not preferable. In addition, the presence of water at a level higher than the solubility is not preferable because the reaction system has two layers. The water here is simultaneously recovered when excess ketones are distilled off, and can be used as the water in the next reaction. Therefore, the amount discharged as wastewater to the outside of the system is small.

The basic catalyst may be the same as that used in the preparation of the mixed solution and the like. Usually, a hydroxide of an alkali metal, for example, sodium hydroxide, potassium hydroxide, lithium hydroxide or the like is used. In addition, organic acid salts and carbonates of alkali metals, hydroxides of alkaline earth metals, and basic ion exchange resins are also effective. The amount of the catalyst used is 1 × 10 ⁻⁵ to 1 × 10 ⁻² per mole of formaldehyde.
Mol, preferably 1 × 10 ⁻⁴ to 1 × 10 ⁻³ mol.
When the amount of the catalyst is less than the above range, the reaction rate becomes slow and is not practical, and when the amount of the catalyst is more than the above range, low boiling is generated due to condensation of ketones.

The reaction temperature must be preferably 30 ° C. or higher and a temperature not causing boiling. Reaction temperature is 30
If the temperature is lower than 0 ° C., the main reaction rate becomes slow, but the high-boiling reaction rate becomes relatively high, the amount of high-boiling products increases, and the yield of the target compound with respect to formaldehyde decreases, which is not preferable. Further, if boiling occurs, the required molar ratio cannot be maintained stably, which is not preferable. In addition, the boiling temperature here is that under a mixed or azeotropic composition containing ketones, formaldehyde, water, etc. in the condensation reaction system, and the value is based on ketones at atmospheric pressure. In the case of a mixture, it depends on the boiling point of the ketones used, and naturally becomes higher than the above case under pressure or when a large amount of high-boiling components are present.

The condensation reaction time is not uniform according to the reaction conditions, for example, the molar ratio, the reaction temperature, the type and amount of the catalyst, the content of the third component such as water, and the type of the ketone used. Since the shorter the reaction time is, the higher the yield of the target compound with respect to formaldehyde is, the reaction time is generally preferably within 30 minutes, particularly preferably within 10 minutes. If the reaction time is long, a polymethylolated ketone having a high boiling point is formed,
The yield of β-hydroxyketones, which is the target substance, relative to formaldehyde and ketone is reduced. Examples of the neutralizing agent to be added to the solution after the completion of the condensation reaction include organic acids such as acetic acid, citric acid and tartaric acid. In addition, inorganic salts such as sulfuric acid and acidic ion exchange resins can also be used.

In the present invention, ketones which are one of the raw materials for the condensation reaction are those wherein R ¹ in the above general formula is a lower alkyl group such as a methyl group, an ethyl group or an isopropyl group, and R ² is the same alkyl group as R ^1. It is represented by a group or hydrogen, and specific examples thereof include acetone, methyl ethyl ketone, diethyl ketone, and isopropyl methyl ketone. Corresponding to these, β-hydroxyketones produced according to the present invention include the following. That is, 4-hydroxy-2-
Butanone, 4-hydroxy-3-methyl-2-butanone, 1-hydroxy-3-pentanone, 1-hydroxy-2-methyl-3-pentanone, 3,3-dimethyl-4
-Hydroxy-2-butanone and the like.

[0038]

The present invention will be described in more detail with reference to the following examples. In each example and comparative example, “%” is used.
Means% by weight unless otherwise specified, except for those relating to the yield.

Example 1 A commercially available paraformaldehyde (purity: 91%, average particle size: 1.5 to 2 mm) was fed at a decomposition temperature of 160 ° C. using the apparatus shown in FIG. Hr and acetone were supplied to the pyrolyzer at a feed rate of 2240 g / Hr to generate an acetone-formaldehyde mixed gas,
Then, the mixture was condensed and trapped to obtain a mixed solution having a molar ratio of 40, to which was added water of acetone 4%. Separately, a 200-mL four-necked flask having a content of 200 mL was prepared, and the acetone-formaldehyde-water mixed solution 80 obtained above was added thereto.
g of the mixture was heated to 50 ° C., and 1.6 g of a 0.5% aqueous sodium hydroxide solution was added thereto to carry out a condensation reaction. The molar ratio between sodium hydroxide and formaldehyde is 5.7 × 10 ⁻³ . The reaction was completed in 1 minute, and then the reaction solution was neutralized with a 40% aqueous citric acid solution. The resulting neutralized reaction solution was analyzed and quantified by gas chromatography under the following conditions using ethylene glycol as an internal standard.
Detector: FID, column: PEG20M 2m, column temperature: 140 ° C. As a result of the analysis, the conversion of formaldehyde was 99% or more, the yield of 4-hydroxy-2-butanone based on formaldehyde was 96.7%, and the yield based on acetone was 94.3%. The by-product amount of diacetone alcohol was 1.7% based on 4-hydroxy-2-butanone.

Example 2 Except that the molar ratio of potassium hydroxide to formaldehyde was changed to 6.5 × 10 ⁻³ by using 2.5 g of a 1% aqueous potassium hydroxide solution instead of 1.6 g of an aqueous 0.5% sodium hydroxide solution. In the same manner as in Example 1, the condensation reaction of acetone and formaldehyde, the neutralization of the reaction solution, and the analysis were performed. As a result of the analysis, the conversion of formaldehyde was 99% or more, the yield of 4-hydroxy-2-butanone based on formaldehyde was 90.5%, and the yield based on acetone was 88.4%. The by-product amount of diacetone alcohol was 5.7% based on 4-hydroxy-2-butanone.

Example 3 Using the acetone-formaldehyde mixed solution containing 4% of water (molar ratio: 40) prepared in Example 1, a continuous condensation reaction was carried out in a continuous reaction apparatus shown in FIG. That is, volume 1L
The acetone-formaldehyde mixed solution sent from the stock tank 6 for the mixed solution and heated to 50 ° C. at a flow rate of 400 g / min and sent from the basic catalyst stock tank 10 to the packed reaction tower 8 % Sodium hydroxide was supplied through the diffuser 7 at a flow rate of 3.28 g / min, and a condensation reaction was performed under mixing. At that time, the molar ratio between sodium hydroxide and formaldehyde was 4.8 × 10 ^−3.
Met. The reaction was completed in 2 minutes, and the reaction solution was then cooled by the cooler 9 and sent to the neutralization tank 11, where it was neutralized with a 40% aqueous citric acid solution. The obtained neutralized reaction solution was analyzed and quantified in the same manner as in Example 1. As a result, the conversion of formaldehyde was 99% or more, the yield of 4-hydroxy-2-butanone based on formaldehyde was 75%, and the yield based on acetone was the same. Was 72.5%. The by-product amount of diacetone alcohol was 3.5% based on 4-hydroxy-2-butanone.

Example 4 362.5 g of acetone, 11.86 g of water, commercially available paraformaldehyde (purity: 91%, average particle size: 1.5 to 2 m)
m) 5.15 g was charged into a 1-L flask, and 0.4 g of a 0.1% aqueous sodium hydroxide solution was further added to p.
After adjusting H to 10, the mixture was stirred at 40 ° C. to dissolve paraformaldehyde to obtain an acetone-formaldehyde mixed solution. The dissolution time required 10 hours. Content 20
153 g of the obtained acetone-formaldehyde mixed solution (molar ratio: 40) was charged into a 0 mL four-necked flask, and
After heating to 0 ° C., 0.3 g of a 1% aqueous sodium hydroxide solution was added to carry out a condensation reaction. The molar ratio between sodium hydroxide and formaldehyde is 1.1 × 10 ⁻³ . The reaction was completed in 4 minutes, after which the reaction solution was neutralized with a 40% aqueous citric acid solution. The obtained neutralized reaction solution was analyzed and quantified in the same manner as in Example 1. As a result, the conversion of formaldehyde was 99% or more, the yield of 4-hydroxy-2-butanone based on formaldehyde was 74%, and the yield based on acetone was the same. Is 7
2.8%. The by-product amount of diacetone alcohol was 3.6% based on 4-hydroxy-2-butanone.

Example 5 288 g of methyl ethyl ketone, 39.7 g of water, commercially available paraformaldehyde (purity 91%, average particle size 1.5 to 1.5%)
2mm) 13.2 g was charged into a 500-mL internal volume flask, and 0.5 g of a 1% aqueous sodium hydroxide solution was added to adjust the pH to 8. Then, the mixture was stirred at 40 ° C. to dissolve paraformaldehyde, and methyl ethyl ketone-formaldehyde was added. A mixture was obtained. The dissolution time required 10 hours. A 200 mL four-necked flask was charged with 100 g of the obtained methyl ethyl ketone-formaldehyde mixed solution (molar ratio: 10), heated to 50 ° C., and then 2.7 g of a 1% aqueous sodium hydroxide solution was added to perform a condensation reaction. .
The molar ratio between sodium hydroxide and formaldehyde is 5.8
× 10 ^-3 . The reaction was completed in 7 minutes, after which the reaction solution was neutralized with a 40% aqueous citric acid solution. The obtained neutralized reaction solution was analyzed and quantified in the same manner as in Example 1. As a result, the conversion of formaldehyde was 99% or more, and the yield of 4-hydroxy-3-methyl-2-butanone based on formaldehyde was 81.2%. The same yield based on methyl ethyl ketone was 8
0.5%. The yield of 1-hydroxy-3-pentanone as a by-product is 6.1%, and the condensation by-product of ketones is 0.65% with respect to 4-hydroxy-3-methyl-2-butanone. there were.

Example 6 50.4 g of commercially available paraformaldehyde (purity: 91%, average particle size: 1.5 to 2 mm), 225.4 g of acetone,
A suspension composed of 164.6 g of water was pulverized in a circulating pulverizer for 2 hours to prepare a dispersion of paraformaldehyde which was finely divided into particles having a particle size of 440 mesh and made easy to generate formaldehyde.
4 g was further added to prepare an acetone-paraformaldehyde dispersion having a molar ratio of 40. Dispersion liquid 15 having a molar ratio of 40 obtained as described above was placed in a 200 mL four-necked flask.
3 g was charged, and after heating to 50 ° C., 0.3 g of a 1% aqueous sodium hydroxide solution was added to carry out a condensation reaction. The molar ratio between sodium hydroxide and formaldehyde is 1.5 × 10 ⁻³ . The reaction was completed in 5 minutes, after which the reaction solution was neutralized with a 40% aqueous citric acid solution. The obtained neutralized reaction solution was used in Example 1.
As a result, the conversion of formaldehyde was 99% or more, the yield of 4-hydroxy-2-butanone based on formaldehyde was 74%, and the yield based on acetone was 72.5%. The by-product amount of diacetone alcohol was 4.4% based on 4-hydroxy-2-butanone.

Example 7 50.4 g of commercially available paraformaldehyde (purity 91%, average particle size 1.5 to 2 mm), methyl ethyl ketone 33
A suspension composed of 0.3 g and 151.9 g of water was pulverized for 2 hours in a circulating pulverizer to prepare a dispersion of paraformaldehyde which was made into fine particles in a 440 mesh pass to make formaldehyde easy to generate. 821 g of methyl ethyl ketone was further added to prepare a methyl ethyl ketone-paraformaldehyde dispersion having a molar ratio of 10. Into a 200 mL four-necked flask was charged 126 g of the dispersion obtained in the above at a molar ratio of 10, and after heating at 50 ° C., 2.3 g of a 1% aqueous sodium hydroxide solution was added to carry out a condensation reaction. The molar ratio between sodium hydroxide and formaldehyde is 3.8 × 10 ⁻³ . The reaction was completed in 5 minutes, after which the reaction solution was neutralized with a 40% aqueous citric acid solution. The obtained neutralized reaction solution was analyzed and quantified in the same manner as in Example 1. As a result, the conversion of formaldehyde was 99% or more, and the yield of 4-hydroxy-3-methyl-2-butanone based on formaldehyde was 82.3%. The same yield based on methyl ethyl ketone was 81%. Also, 1- which is a by-product
The yield of hydroxy-3-pentanone is 8%, and the condensation by-product of the ketones is 4-hydroxy-3-methyl-2.
-0.48% with respect to butanone.

Example 8 Using the acetone-paraformaldehyde dispersion having a molar ratio of 40 prepared in Example 6 as a starting material, a continuous condensation reaction was carried out in a continuous reactor shown in FIG. That is, volume 2
The acetone-paraformaldehyde dispersion sent from the stock tank 6 containing the mixed solution and heated to 50 ° C. is sent to the L-filled reaction tower 8 at a flow rate of 380 g / min and from the basic catalyst stock tank 10. A 1% aqueous sodium hydroxide solution was supplied through the diffuser 7 at a flow rate of 1.8 g / min, and a condensation reaction was performed under mixing. At that time, the molar ratio between sodium hydroxide and formaldehyde was 1.8 ×
It was 10 ^-3 . The reaction was completed in 4 minutes, and the reaction solution was then cooled by the cooler 9 and sent to the neutralization tank 11, where
Neutralized with aqueous citric acid solution. The obtained neutralized reaction solution was analyzed and quantified in the same manner as in Example 1. As a result, the conversion of formaldehyde was 99% or more, the yield of 4-hydroxy-2-butanone based on formaldehyde was 70%, and the yield based on acetone was the same. Was 69%. The by-product amount of diacetone alcohol was 4.4% based on 4-hydroxy-2-butanone.

COMPARATIVE EXAMPLE 1 In a four-necked flask having an internal volume of 200 mL, acetone was mixed with acetone so that the molar ratio of acetone to formaldehyde was 40.
6 g and 2.54 g of formalin (containing 37% formaldehyde and 8% methanol) were charged, heated to 50 ° C., and then added with 2.0 g of a 0.5% aqueous sodium hydroxide solution to carry out a condensation reaction. The molar ratio between sodium hydroxide and formaldehyde is 8.1 × 10 ⁻³ . The reaction was completed in 3 minutes, after which the reaction solution was neutralized with a 40% aqueous citric acid solution.
The obtained neutralized reaction solution was analyzed and quantified in the same manner as in Example 1. As a result, the conversion of formaldehyde was 99% or more, the yield of 4-hydroxy-2-butanone based on formaldehyde was 79.7%, and the yield based on acetone. The yield was as good as 75%, but the amount of diacetone alcohol by-product was 4-
It showed a very high value of 27.6% with respect to hydroxy-2-butanone.

Comparative Example 2 A four-necked flask having an inner volume of 200 mL was charged with 71.9 g of methyl ethyl ketone and 8.1 g of formalin (containing 37% formaldehyde and 8% methanol) so that the molar ratio of methyl ethyl ketone to formaldehyde was 10. After heating to 50 ° C., 2.0 g of a 0.5% aqueous sodium hydroxide solution was added to carry out a condensation reaction. The molar ratio between sodium hydroxide and formaldehyde is 3.5 × 10 ⁻³ . The reaction was completed in 6 minutes, after which the reaction solution was neutralized with a 40% aqueous citric acid solution. The obtained neutralized reaction solution was analyzed and quantified in the same manner as in Example 1. As a result, the conversion of formaldehyde was 99% or more, but the yield of 4-hydroxy-3-methyl-2-butanone based on formaldehyde was 7
1.5%, the same yield based on methyl ethyl ketone.
At 3%, both values were significantly lower than those of the corresponding Examples 5 and 7. The by-product 1-hydroxy-
The yield of 3-pentanone was 5.7%, and the condensed by-product of ketones was 0.66% of that of 4-hydroxy-3-methyl-2-butanone, and no particular deterioration was observed.

Comparative Example 3 In a four-necked flask having an internal volume of 200 mL, 144 g of methyl ethyl ketone and commercially available paraformaldehyde (purity: 91%)
Product, average particle size 1.5 to 2 mm)
After heating to ° C, 3.0 g of a 0.5% aqueous sodium hydroxide solution was added to carry out a condensation reaction. The molar ratio between sodium hydroxide and formaldehyde is 3.8 × 10 ⁻³ . The reaction is 9
After that, the reaction solution was neutralized with a 40% aqueous citric acid solution. The obtained neutralized reaction solution was analyzed and quantified in the same manner as in Example 1. As a result, the conversion of formaldehyde was 99% or more, but the yield of 4-hydroxy-3-methyl-2-butanone based on formaldehyde was 63.1%, the same yield based on methyl ethyl ketone was 65%, which was significantly lower than the corresponding examples 5 and 7, and the yield of 1-hydroxy-3-pentanone as a by-product was 12.5%.
%, And the condensed by-product of the ketones was 0.8% based on 4-hydroxy-3-methyl-2-butanone, and the former showed a particularly high value.

[0050]

As described above, according to the present invention, in the production of β-hydroxyketones by the condensation reaction of formaldehyde and ketones, the supply of formaldehyde contains methanol, which is a cause of suppressing the condensation reaction, and the wastewater problem is reduced. Instead of the conventional method using paraformaldehyde, which is inevitable for formalin and granular by-products that are difficult to work with, it is difficult to operate.Instead, the pyrolysis gas of paraformaldehyde is diluted with ketones and condensed mixture, and paraformaldehyde is converted to ketones It is a structure that uses a mixed solution dissolved in water or a dispersion liquid in which paraformaldehyde is made into fine particles in ketones, thereby suppressing side reactions by an easy operation without substantially generating wastewater and improving yield. It has become possible to produce β-hydroxy ketones well.

[Brief description of the drawings]

FIG. 1 is a schematic flow chart of a formaldehyde-ketones mixed liquid preparation apparatus applied to one embodiment of the present invention.

FIG. 2 is a schematic flow chart of a continuous condensation reaction apparatus suitable for carrying out the present invention.

[Explanation of symbols]

1: hopper, 2: pyrolyzer, 3: condenser, 4: receiver
5: ketone tank, 6: stock tank for mixed liquid, etc.
7: diffuser, 8: reaction tower, 9: cooler, 10: basic catalyst stock tank, 11: neutralization tank

Continuation of front page (58) Fields investigated (Int.Cl. ⁶ , DB name) C07C 49/17 B01J 23/02 B01J 27/232 C07C 45/75 C07B 61/00 300 WPI / L (QUESTEL)

Claims (3)

(57) [Claims] (1) Formaldehyde and a compound of the general formula (1) in the presence of a basic catalyst: (Wherein, R ¹ represents a straight-chain or branched-chain alkyl group having 5 or less carbon atoms, and R ² represents hydrogen or a straight-chain or branched-chain alkyl group). A condensation reaction is carried out in the presence of (Wherein, R ¹ and R ² have the same meanings as described above). In the method for producing β-hydroxyketones represented by the formula ( ¹ ), as the formaldehyde and the ketone, formaldehyde gas obtained by thermally decomposing paraformaldehyde Is diluted with a gas of ketones and then a mixture obtained by condensation trap is used, and 2% based on ketones
A process for producing β-hydroxyketones, comprising reacting formaldehyde with ketones in the presence of water having a solubility of less than the above. 2. Formaldehyde and a compound of the general formula ## STR3 ## in the presence of a basic catalyst. (Wherein, R ¹ represents a straight-chain or branched-chain alkyl group having 5 or less carbon atoms, and R ² represents hydrogen or a straight-chain or branched-chain alkyl group). A condensation reaction is carried out in the presence of a compound of the general formula Wherein R ¹ and R ² have the same meanings as described above, wherein paraformaldehyde is dissolved in the ketone to formaldehyde as the formaldehyde and the ketone. A method for producing β-hydroxyketones, comprising reacting formaldehyde and ketones using the mixed solution and in the presence of water having a solubility of 2% or more and less than the solubility of ketones. 3. Formaldehyde and a compound of the formula ## STR5 ## in the presence of a basic catalyst. (Wherein, R ¹ represents a straight-chain or branched-chain alkyl group having 5 or less carbon atoms, and R ² represents hydrogen or a straight-chain or branched-chain alkyl group). A condensation reaction is carried out in the presence of a compound of the general formula (Wherein, R ¹ and R ² have the same meanings as described above). In a method for producing β-hydroxyketones, paraformaldehyde is pulverized in ketones to form formaldehyde-prone fine particles. The dispersion thus obtained is used as a source of formaldehyde and ketones, and water having a solubility of 2% or more and less than the solubility of the ketones is present, and the ketones are reacted with the formaldehyde while generating the formaldehyde. A method for producing β-hydroxy ketones.