JPH0761966B2 - Method for purifying para-hydroxybenzaldehyde - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a method for recovering para-hydroxybenzaldehyde in a high yield from a reaction mixture obtained by oxidizing para-cresol with oxygen or an oxygen-containing gas in a solvent in the presence of a cobalt compound and a base. Parahydroxybenzaldehyde is a useful substance as an intermediate raw material for medicines, agricultural chemicals, and fragrances, and the demand for it is increasing year by year.

[Prior art]

A method for producing a para-hydroxybenzaldehyde derivative by oxidizing a para-cresol derivative with oxygen or an oxygen-containing gas in a solvent in the presence of a cobalt compound and a base is disclosed in Japanese Patent Application Laid-Open
No. 55-81832. This method is an excellent method in that the para-cresol derivative is oxidized to selectively produce the para-hydroxybenzaldehyde derivative in a high yield, but it is not always satisfactory in the following points. In other words, in the same publication, isolation and purification of the desired product is carried out by concentrating the reaction mixture, acidification of the residual liquid, extraction with an organic solvent, concentration of the extract, residual, etc., and distillation of the parahydroxybenzaldehyde derivative. If it is not possible, there is a description that a method such as recrystallization or sublimation is taken. In the examples of the publication, a method of distilling off the solvent methanol from the reaction mixture under reduced pressure, adding dilute hydrochloric acid to make it acidic, and extracting with ethyl acetate is described.

[Problems to be Solved by the Invention]

However, the para-cresol reaction rate in the oxidation reaction process was 92%.
If it is less than 1, there is a drawback that tar is formed in the distillation and purification step of parahydroxybenzaldehyde and the recovery rate of the target substance is significantly reduced. On the other hand, in order to separate parahydroxybenzaldehyde from the reaction mixture, a method of crystallizing as a sodium salt of parahydroxybenzaldehyde after desolvation,
A method in which acid precipitation is performed, extraction with a solvent and crystallization as parahydroxybenzaldehyde are considered. However, these methods also have drawbacks such as poor separation of unreacted para-cresol, para-methoxymethylphenol by-produced in the reaction, and tar-like substances, low recovery rate of para-hydroxybenzaldehyde, and poor purity. The present inventors have completed the present invention as a result of continuing diligent research in order to solve these problems.

[Means for solving problems]

That is, the present invention is a method for extracting para-hydroxyhenzaldehyde from a reaction mixture obtained by oxidizing para-cresol with oxygen or an oxygen-containing gas in a reaction solvent in the presence of a cobalt compound and a base. Paracresol reaction rate is 92% or more, (2) step of diluting the reaction mixture with water and filtering (3) step of separating the reaction solvent from the filtrate (4) pH 3 of the aqueous layer after separation of the reaction solvent with acid Step of neutralizing to 6 (hereinafter referred to as neutralization step) (5) Step of extracting the neutralization solution with an extraction solvent (hereinafter referred to as extraction step) or the step of separating the neutralization solution and extracting the aqueous layer with an extraction solvent This is a method for purifying parahydroxybenzaldehyde, which comprises sequentially performing the following steps (hereinafter referred to as “liquid separation extraction step”), and then performing distillation for purification. The present invention will be described in more detail. Paracresol used as a starting material in the present invention is 95.0 to 99.9% by weight.
Is. Further, as the cobalt compound used in the present invention, conventionally known compounds are used, and although not particularly limited in the present invention, examples of the cobalt compound include cobalt fluoride, cobalt chloride, cobalt bromide and iodide. Cobalt and other halogenated cobalt, cobalt acetate, cobalt stearate, cobalt sulphate, cobalt naphthenate and other organic acid cobalt, cobalt nitrate, cobalt sulfate, cobalt borate, cobalt carbonate, cobalt cyanide, cobalt phosphate and other inorganics Examples thereof include cobalt oxides such as cobalt oxide, cobalt monoxide, cobalt trioxide, and cobalt tetraoxide, or cobalt hydroxide and metallic cobalt. Further, a cobalt complex such as a cobalt chelate is also effective. For example, cobalt acetylacetonate, bis (dimethylglyoximato) cobalt, cobaltporphine, NN'-ethylenebis (salicylideneiminato) cobalt and the like. Among the above cobalt compounds, hydrous salts or anhydrides of cobalt chloride, cobalt acetate, cobalt nitrate, cobalt monoxide and the like and metallic cobalt are particularly preferably used. The amount of cobalt compound used is 0.00 relative to para-cresol
There is no particular limitation as long as it is 01 equivalent or more, but preferably 0.0005
Within the range of 0.05 equivalent. The base used in the present invention may be one having a higher basicity than para-cresol, caustic soda, caustic potash,
Metal hydroxides such as lithium hydroxide, magnesium hydroxide, calcium hydroxide, aluminum hydroxide or metal alkoxides such as sodium alkoxide, potassium alkoxide, lithium alkoxide, magnesium alkoxide, calcium alkoxide, aluminum alkoxide (here, The alkoxide is, for example, methoxide, ethoxide, isopropoxide, tert-butoxide, or a metal amide such as lithium amide, sodium amide, potassium amide (wherein, as the amide, for example, unsubstituted amide, ethyl amide, diethyl amide, Such as diisopropylamide). Among the above bases, caustic soda, caustic potash, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, potassium tertiary butoxide, sodium amide and the like are particularly preferably used. The amount of the base used is not particularly limited as long as it is equivalent to or more than paracreezol. It is preferably within the range of 1 to 10 equivalents. Various solvents are used in the reaction of the present invention.
Any substance that is stable to oxygen and has a suitable solubility in a substrate may be used. Suitable solvents include, for example, alcohols, hydrocarbons, ethers, halogenated hydrocarbons, amines, dimethylformamides, dimethylsulfoxides and the like. These can be used alone or in combination of two or more. It can also be used if it contains water. Among the above solvents, alcohols such as methanol, ethanol, isopropanol, normal butanol, isobutanol, secondary butanol, and tert-butanol are particularly preferable. The amount of these solvents used is 1 to 20 times by weight, preferably 1 to 6 times the paracresol.
It is twice the weight. In the case of alcohol solvent, 10% by weight
It can be used even if it contains water, and is economically advantageous for reuse by purifying it by rectification and the like. In the method of the present invention, the oxidant oxygen can be used alone, but a so-called inert gas (for example, nitrogen,
It can also be diluted with argon or the like) and used as an oxygen-containing gas. Air can also be used as the oxygen-containing gas, and a method of blowing it into the reaction solution is generally used, but the method is not limited to this. The pressure of oxygen and the oxygen-containing gas is not particularly limited, but is usually 1 to 100 atm, preferably 1 to 50 atm. However, this should be chosen in conjunction with the oxygen concentration. The reaction temperature is carried out in the range of 0 to 300 ° C, preferably 30 to 100 ° C. As described above, a desired reaction mixture containing para-hydroxybenzaldehyde is obtained, and the reaction mixture is subjected to the steps (1) to (5), which are the features of the present invention, in order to carry out distillation to obtain the desired reaction mixture. It recovers hydroxybenzaldehyde in high yield. Hereinafter, each processing step will be described in detail. (1) Regarding the step of diluting with water and filtering; since insoluble substances such as sodium oxalate and tar are present in the reaction mixture obtained by the oxidation reaction, it is insoluble in the reboiler etc. when continuously separating the solvent. Because of the scaling of the material, it is preferred to dilute with water to a parahydroxybenzaldehyde concentration of about 4-11% and filter at a temperature of 30-80 ° C. In this case, any filtration method can be used, and for example, an ultra filter, a Lee filter, a funder back filter, a filter press or the like is used. Further, a center, a decanter or the like can also be used. However, when the solvent is separated by the batch method, it is necessary to dilute with water, but it is not necessary to filter. (2) Step of separating the solvent from the reaction mixture; The method of separating the reaction solvent from the reaction mixture is not particularly limited, but a method of collecting by distillation is preferably used. In this distillation, a wet-wall reboiler is preferable as the heating method in consideration of the thermal stability of parahydroxybenzaldehyde, unreacted paracresol, and other reaction products. The recovered solvent is reused as a reaction solvent again. Considering the solvent recovery rate and the influence in the next step, the solvent concentration in the can solution is preferably 1% by weight or less. (3) Neutralization Step; The acid used in the neutralization step of the present invention may be an inorganic acid such as sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, but is not limited thereto. Further, it is preferable to neutralize the pH to 3-6. The temperature for neutralization is not limited, but usually 50 to 80 ° C is preferable. In the case of this neutralization, the higher the concentration of parahydroxybenzaldehyde, the better the extraction efficiency, but considering the solubility of the inorganic salt produced during neutralization and the liquid separation property during extraction, 11% by weight or less is preferable. When the concentration of para-hydroxybenzaldehyde is low, the liquid separation property is good, but the extraction efficiency is poor,
The parahydroxybenzaldehyde concentration is preferably 4% by weight or more. (4) Extraction step: Solvents used in the extraction step of the present invention include aliphatic halogenated hydrocarbons such as ethylene dichloride and trichloroethylene, monochlorobenzene, dichlorobenzene,
Aromatic halogenated hydrocarbons such as monochloromethylbenzene, aliphatic kents such as methyl isobutyl ketone and methyl isopropyl ketone, aromatic hydrocarbons such as benzene, toluene and xylene, n-propyl ether, isopropyl ether, secondary butyl ether And the like, and fatty acid esters such as methyl acetate, ethyl acetate, and butyl acetate can be used. These extraction solvents can be used alone or in combination of two or more. The amount of the extraction solvent used may be 0.05 to 1.0 times the weight of the neutralized mass in the neutralization step, and the number of extractions may vary depending on the amount of the solvent used.
It is preferable to carry out in a range of 4 times. The extraction method may be a countercurrent or cocurrent batch method, a countercurrent or cocurrent continuous method, or the like. Further, the extraction temperature is not particularly limited as long as it does not cause precipitation of inorganic salt crystals and is not higher than the boiling point of the extraction solvent, but preferably in the range of 40 ° C to 80 ° C. Alternatively, the extraction step can also be performed by the following liquid separation extraction method. The neutralized mass of the neutralization step is separated at a temperature of 40 to 100 ° C. to recover the crude parahydroxybenzaldehyde oil layer, and the unrecovered parahydroxybenzaldehyde contained in the aqueous layer is the solvent used in the extraction step. It is also possible to perform extraction and recovery using the same solvent as. In this case, the amount of the extraction solvent used is 0.05 to 1.0 times the weight of the aqueous layer, and the number of extractions is preferably 1 to 4 times. The extraction method may be a countercurrent or cocurrent batch method, a countercurrent or cocurrent continuous method, or the like. Further, the extraction temperature is not particularly limited as long as it does not cause precipitation of inorganic salt crystals and is not higher than the boiling point of the extraction solvent, but preferably in the range of 40 to 80 ° C. The solvent-extracted parahydroxybenzaldehyde can be obtained by recovering the extraction solvent by an ordinary distillation method and then distilling the parahydroxybenzaldehyde. The recovered extraction solvent can be recycled and reused. Further, crude parahydroxybenzaldehyde separated without solvent and parahydroxybenzaldehyde solvent-extracted from the aqueous layer can also be obtained by removing the light-boiling components by an ordinary distillation method and then distilling parahydroxybenzaldehyde. The distillation method of para-hydroxybenzaldehyde is not particularly limited, but since it is a substance having poor thermal stability, it is preferable to use a wet-wall vacuum evaporator, a thin-film vacuum evaporator, or the like.

【The invention's effect】

According to the method of the present invention, the target parahydroxybenzaldehyde can be easily produced industrially with high yield and high purity, and its industrial significance is extremely large.

【Example】

Hereinafter, the present invention will be described in more detail with reference to Examples, but it goes without saying that the present invention is not limited to these Examples. Example-1 200 reactors having turbine blades were charged with 23.95 kg of 99.5 wt.% Para-cresol, 18.8 kg of caustic soda, 0.016 kg of divalent cobalt acetate tetrahydrate and 38.6 kg of methanol, at 60-80 ° C. Salt formation is carried out for 2 hours with stirring at temperature. Next, air was blown in from the nozzle attached to the bottom of the reactor, and the reaction temperature was 75 ° C and the pressure was 6 kg / cm ² gauge pressure under stirring.
Reacted for hours. The amount of air blown in by the end of the reaction was 32.7
It was Nm ³ , and the oxygen absorption amount was 8.5 kg. Then water 5
2.5 kg was charged into a reactor, mixed and diluted to obtain an oxidation reaction mass of 141.2 kg. Quantitative analysis of this oxidation reaction mass by gas chromatography and liquid chromatography revealed para-cresol 0.08.
It contained kg (paracresol reaction rate 99.7%), parahydroxybenzaldehyde 21.555 kg, paramethoxymethylphenol 2.4 kg, paraoxybenzoic acid 0.28 kg, and parahydroxymethylphenol 0.10 kg. The oxidation reaction mass was diluted again by adding 142.3 kg of water. Next, the oxidized diluted mass was filtered at 60 ° C. using an ultrafilter covered with a filter cloth of Pyrene S # 26 to remove sodium oxalate and insoluble tar. The oxidative dilution mass was supplied to the 13th plate from the top of the rectification column with a wet wall reboiler (16 theoretical plates), the solvent was desolvated at 300 Torr and a reflux ratio of 2 to recover 37.2 kg of 99.8 wt% methanol. The methanol concentration in the can solution was 0.9% by weight. In this desolvation step, most of the reaction products were not crushed. 18.8 kg of this demethanol mass was kept warm at 50 ° C and 97% by weight
Add 1.46 kg of sulfuric acid and adjust the pH of the methanol-free mass to 5.0 (60
℃) to neutralize, add 3.98 kg of methyl isobutyl ketone, stir for 30 minutes at 60 ℃, let stand for 30 minutes, and then separate the oil layer
Obtained 6.21 kg. The second extraction and separation were performed under the same conditions as the first extraction of this extraction step to obtain 4.17 kg of an oil layer. The second oil layer obtained in this extraction step is used as the first extraction solvent in the next extraction step. Perform the above neutralization and extraction 13 times. 80.8 kg of a methyl isobutyl ketone solution containing para-hydroxybenzaldehyde recovered in the extraction step was subjected to 40 Torr using a wet-wall type evaporator.
Distilled at 98.5% by weight of methyl isobutyl ketone 51.7 kg
Was recovered. The para-hydroxybenzaldehyde retention rate in this step was 98.0%, and the methyl isobutyl ketone concentration in the can was 0.8% by weight. Then, crude parahydroxybenzaldehyde as a bottom liquid was distilled at 6 Torr using a thin film vacuum evaporator manufactured by Lure Co. to obtain 19.0 kg of 98.4% by weight of parahydroxybenzaldehyde. The total yield of parahydroxybenzaldehyde is 69.5%. This extraction step was carried out by the countercurrent batch method, but it can also be carried out by the countercurrent continuous method and is not limited to the extraction method. Example-2 The procedure up to the neutralization step was exactly the same as in Example-1. Next, liquid separation was performed at 60 ° C. to obtain 2.30 kg of 62.5% by weight parahydroxybenzaldehyde. Methyl isobutyl ketone (3.98 kg) was added to the aqueous layer (17.39 kg), and the mixture was stirred at 60 ° C for 30 minutes, allowed to stand for 30 minutes, and then separated to obtain 4.10 kg of an oil layer. To 17.27 kg of the aqueous layer obtained here, 3.98 kg of methyl isobruketone was added, and liquid separation was performed under the same conditions as in the first extraction of the liquid separation extraction step to obtain 4.05 kg of an oil layer. This oil layer is used as the first extraction solvent in the next separation / extraction step. The above neutralization and liquid separation extraction are performed 13 times. In this extraction step, almost no intermediate layer was generated. The crude parahydroxybenzaldehyde and oil layer recovered in the liquid separation and extraction step are delightly boiled and treated in the same manner as in Example-1,
Distillation in a thin film vacuum evaporator yielded 18.8 kg of 98.1 wt% para-hydroxybenzaldehyde. The total yield of parahydroxybenzaldehyde is 68.5%. The extraction process was carried out by the countercurrent batch method, but the countercurrent continuous method is also possible and is not limited to the extraction method. Comparative Example-1 Purity 99.5 wt% in a 200 l reactor with turbine blades
Paracresol (23.95 kg), caustic soda (18.8 kg), divalent cobalt acetate tetrahydrate (0.016 kg) and methanol (38.6 kg) are charged, and salt formation is carried out at a temperature of 60 to 80 ° C for 2 hours with stirring. Next, air was blown in from the nozzle attached to the lower part of the reactor, and the reaction temperature was 75 ° C, and the pressure was 6 kg / cm ² gauge pressure.
Reacted for hours. The amount of air blown in by the end of the reaction was 29.6
It was Ncm ³ , and the amount of oxygen inhaled was 7.4 kg. Then water 5
2.5 kg was charged into a reactor, mixed and diluted to obtain 140.6 kg of oxidation reaction mass. Quantitative analysis of the oxidation reaction mass by gas chromatography and liquid chromatography revealed that para-cresol 2.26 kg (para-cresol reaction rate 90.5
%), Para-hydroxybenzaldehyde 19.57kg, para-methoxymethylphenol 2.17kg, para-oxybenzoic acid
It contained 0.25 kg and 0.09 kg of parahydroxymethylphenol. The oxidation reaction mass was further diluted by adding 142.9 kg of water. When this diluted diluted mass was treated as in Example 1, 98.0% by weight of parahydroxybenzaldehyde 1 was obtained.
I got 5.5kg. The total yield of all steps was 56.4%. When the reaction rate of para-cresol is less than 92%, the yield of para-hydroxybenzaldehyde is significantly reduced in the distillation process.

Claims (1)

[Claims] 1. A method for extracting para-hydroxybenzaldehyde from a reaction mixture obtained by oxidizing para-cresol with oxygen or an oxygen-containing gas in a reaction solvent in the presence of a cobalt compound and a base. The cresol reaction rate is 92% or more, and (2) the step of diluting the reaction mixture with water and filtering (3) the step of separating the reaction solvent from the filtrate (4) the pH of the aqueous layer after the reaction solvent separation is adjusted to 3 to 6 with an acid. (5) The step of extracting the neutralized solution with an extraction solvent or the step of separating the neutralized solution and then extracting the aqueous layer with an extraction solvent are sequentially performed, and then purified by distillation. Purification method of hydroxybenzaldehyde.