JPH01106838A - Method for purifying p-hydroxybenzaldehyde - Google Patents

Abstract

PURPOSE:To obtain the titled compound from a specific oxidation reaction mixture of p-cresol in high yield, by specifying a raw material reaction ratio in an oxidation step, successively passing the reaction mixture through steps of dilution with water.filtration step, separation of a solvent, neutralization and extraction, distilling and purifying the resultant product. CONSTITUTION:The titled compound is taken out of a reaction mixture obtained by oxidizing p-cresol with oxygen or an oxygen-containing gas in a solvent in the presence of a cobalt compound and base. In the process, the p-cresol reaction ratio in the oxidation step is adjusted to >=92% and the above- mentioned reaction mixture is successively passed through steps of (i) dilution with water and filtration, (ii) separation of the solvent from the afore-mentioned reaction mixture, (iii) neutralization of an aqueous layer after extracting the above-mentioned solvent to pH 3-6 with an acid and (iv), as necessary, separation of the afore-mentioned neutralized solution and extraction of the separated solution with a solvent. The resultant reaction mixture is then distilled and purified to industrially and readily afford the aimed compound useful as an intermediate for medicines, agricultural chemicals, perfumes, etc., in high yield and purity.

Description

[Detailed description of the invention] [Industrial application field]

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

[Prior art]

A method for producing a parahydroxybenzaldehyde transparent conductor by oxidizing a valacresole derivative with oxygen or an oxygen-containing gas in a solvent in the presence of a cobalt compound and a base is described in JP-A-55-81832. Although this method is an excellent method in that it selectively produces para-hydroxybenzaldehyde derivatives in high yield by oxidizing para-cresol derivatives, it is not necessarily satisfactory in the following points. In other words, the publication states that purification of the target product is carried out by concentration of the reaction mixture, acid precipitation of the residual liquid, extraction with an organic solvent, concentration of the extract, residue, etc., and that when para-hydroxybenzaldehyde derivatives cannot be distilled, There is a description that methods such as recrystallization or sublimation are used. Examples of the same publication describe a method in which the solvent methanol is distilled off from the reaction mixture under reduced pressure, the mixture is made acidic by adding dilute hydrochloric acid, and the mixture is extracted with ethyl acetate.

[Problems to be solved by the invention]

However, the reaction rate of baracresol in the oxidation reaction step was 92
If it is less than %, there is a drawback that the parahydroxybenzaldehyde is turned into tar in the distillation purification process, and the recovery rate of the target substance is significantly reduced. On the other hand, in order to separate parahydroxybenzaldehyde from the reaction mixture, there is a method of removing the solvent and then crystallizing the sodium salt of parahydroxybenzaldehyde.
Possible methods include acid precipitation, extraction with a solvent, and crystallization as parahydroxybenzaldehyde. However, these methods also have drawbacks such as poor separation of unreacted valacresole, paramethquine methylphenol and tar-like substances produced as by-products in the reaction, a low recovery rate of parahydroxybenzaldehyde, and poor purity. The present inventors continued intensive research to solve these problems, and as a result, they completed the present invention.

[Means to solve the problem]

That is, the present invention provides a method for extracting parahydroxybenzaldehyde from a reaction mixture obtained by oxidizing paracresol with oxygen or an oxygen-containing gas in a solvent in the presence of a cobalt compound and a base. The reaction rate is 92% or more, (2) diluting with water and filtering (3) separating the solvent from the reaction mixture (4) the aqueous layer after the solvent extraction is added to p) 13 to 6 with an acid. A step of neutralizing (hereinafter referred to as neutralization step) (5) a step of extracting the neutralized liquid with a solvent (referred to as extraction step) or a step of extracting with a solvent after liquid separation (hereinafter referred to as liquid separation extraction step) is performed sequentially. This is a method for purifying rose hydroxybenzaldehyde, which is characterized by purification by distillation. To explain the present invention in more detail, para-cresol used as a starting material in the present invention has a temperature of 95° to 99°.
It is 9% by weight. Furthermore, conventionally known cobalt compounds can be used in the present invention, and the present invention is not particularly limited to such cobalt compounds. For example, cobalt compounds include cobalt fluoride, cobalt chloride, cobalt bromide, and Cobalt halides such as cobalt, cobalt organic acids such as cobalt acetate, cobalt stearate, cobalt nitrate, cobalt naphthenate, cobalt nitrate, cobalt sulfate, cobalt borate), cobalt carbonate, cobalt cyanide,
These include inorganic acid cobalt such as cobalt phosphate, cobalt oxide or cobalt hydroxide such as -cobalt oxide, cobalt sesquioxide, and tricobalt tetroxide, and metal cobalt. Cobalt complexes such as cobalt chelates are also effective. Examples include cobalt acetylacetonate, cobalt bis(dimethylglyoximato), cobalt porphine, and cobalt NNI-ethylenebis(salicylideniminato). Among the above cobalt compounds, hydrated salts or anhydrides such as cobalt chloride, cobalt acetate, cobalt nitrate, and cobalt oxide, and metallic cobalt are particularly preferably used. The amount of cobalt compound used is 0.0% relative to para-cresol.
There is no particular restriction as long as it is 0.0001 equivalent or more, but it is preferably within the range of 0.0005 to 0.05 equivalent. The base used in the present invention may be any base that is more basic than para-cresol, such as sodium hydroxide, potassium hydroxide,
Metal hydroxides such as lithium hydroxide, magnesium hydroxide, calcium hydroxide, and aluminum hydroxide, or metal alkoxides such as sodium alkoxide, potassium alkoxide, lithium alkoxide, magnesium alkoxide, calcium alkoxide, and aluminum alkoxide (herein, alkoxide Examples include ethoxide, ethoxide, isobroboquine,
tertiary butoxide) or metal amides such as lithium amide, sodium amide, potassium amide (herein, the amide includes, for example, unsubstituted amide, ethylamide, diethylamide, diisopropylamide, etc.). Among the above bases, hydric soda,
Caustic potash, sodium ethoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, potassium tertiarybutkind, sodium amide, and the like are particularly preferably used. The amount of base used is not particularly limited as long as it is equivalent or more to balacresol. Preferably it is within the range of 1 to 10 equivalents. Various solvents can be used in the reaction of the present invention. Any material that is stable to oxygen and has appropriate solubility in the 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 even if it contains water. Among the above solvents, alcohols such as methanol, ethanol, impropatol, normal butanol, imbutanol, secondary butamer, tertiary butanol and the like are particularly preferred. The amount of these solvents to be used is 1 to 20 times by weight, preferably 1 to 20 times the weight of Baracresol.
It is 6 times I. Furthermore, in the case of an alcohol solvent, it can be used even if it contains up to 10% by weight of water, and it is economically advantageous to purify it by rectification or the like and reuse it. In the method of the present invention, the oxidizing agent oxygen can be used alone, but so-called inert gases (e.g. nitrogen,
It can also be diluted with argon, etc.) and used as an oxygen-containing gas. Air can also be used as the oxygen-containing gas, and is generally blown into the reaction solution, but is not limited to this method. The pressure of oxygen and oxygen-containing gas is not particularly limited, but is usually 1 to 100 atm, preferably 1 to 50 atm. However, this should be selected in conjunction with the oxygen concentration, etc. The reaction temperature is carried out in the range of 0 to 300°C, preferably 30 to 100°C. Through the above steps, a reaction mixture containing the desired rose hydroxybenzaldehyde is obtained, and the reaction mixture is purified by distillation by sequentially carrying out the steps (1) to (5) described above, which are the characteristics of the present invention, to obtain the desired rose hydroxybenzaldehyde. Quinbenzaldehyde is recovered in high yield. Each of these processing steps will be explained in detail below. C1) 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 necessary to remove the insoluble substances in a boiler etc. when continuously separating the solvent. scales, so the barahydroquine benzaldehyde concentration is approximately 4
Preferably, it is diluted with water to ~11% and filtered at a temperature of 30-80°C. In this case, any filtration method can be used, and for example, an ultra filter, a leaf filter, a Funderbank filter, a filter press, etc. can be used. It is also possible to use a center, decanter, etc. However, when the solvent is separated by a batch method, dilution with water is necessary, but filtration is not necessary. (2) Regarding the step of separating the solvent from the reaction mixture; the method for separating the reaction solvent from the reaction mixture is not particularly limited, but preferably a method of recovering by distillation is used. In this distillation, a wet wall reboiler is preferable as the heating method, taking into consideration the thermal stability of barahydroquine benzaldehyde, unreacted baracresol, and other reaction products. The recovered solvent is recycled and used again as a reaction solvent. The solvent concentration in the can liquid is preferably 1% by weight or less, considering the solvent recovery rate and the influence on the next process. (3) Regarding the neutralization step; As the acid used in the neutralization step of the present invention, inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid can be used, but are not limited to these. Moreover, it is preferable to neutralize the pH to 3-6. There is no limit to the neutralization temperature, but 50 to 80°C is usually preferred. In the case of neutralization, the higher the concentration of hydroxybenzaldehyde, the better the extraction efficiency, but in consideration of the solubility of inorganic salts produced during neutralization and the liquid separation properties during extraction, it is preferably 11% by weight or less. As the concentration of parahydroquine benzaldehyde becomes lower, the liquid separation property improves, but the extraction efficiency deteriorates, so the concentration of parahydroquine benzaldehyde is preferably 4% by weight or more. (4) Regarding the extraction step; The solvent used in the extraction step of the present invention includes aliphatic halogenated hydrocarbons such as ethylene dichloride and trichloroethylene, monochlorobenzene, dichlorobenzene,
Aromatic halogenated hydrocarbons such as monochloromethylbenzene, aliphatic hydrocarbons such as methyl isobutyl ketone and methyl isopropyl ketone, aromatic hydrocarbons such as benzene, toluene, and xylene, n-propyl ether, inpropyl ether, and secant Aliphatic ethers such as IJ-7' thyl ether, 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 extraction solvent used can be 0.05 to 1.0 times the weight of the neutralized mass in the neutralization step, and the number of extractions varies depending on the amount of solvent used.
It is preferable to carry out in the range of 1 to 4 times. Further, 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 is below the boiling point of the extraction solvent and the temperature at which crystals of the inorganic salt do not precipitate, but a range of 40°C to 80°C is preferable. Alternatively, the extraction step can also be carried out by the following liquid separation extraction method. After separating the neutralized mass in the neutralization process at a temperature of 40 to 100°C and recovering the oil layer, which is crude para-hydroxybenzaldehyde, the unrecovered para-hydroxybenzaldehyde contained in the aqueous layer is extracted with the solvent used in the extraction process. It is also possible to extract and recover using the same solvent. The amount of extraction solvent used at this time is 0.05 to 1.
0 times by weight, and the number of extractions is preferably 1 to 4 times. Further, the extraction method may be a countercurrent or cocurrent batch method, a countercurrent or cocurrent continuous method, or the like. Furthermore, the extraction temperature is not particularly limited as long as it is below the boiling point of the extraction solvent and the temperature at which crystals of the inorganic salt do not precipitate, but it is preferably in the range of 40 to 80°C. Solvent-extracted rosehydroquine benzaldehyde can be obtained by recovering the extraction solvent using a conventional distillation method and then distilling the rosehydroquine benzaldehyde. The recovered extraction solvent can be recycled and reused. Further, crude rose hydroxybenzaldehyde separated without a solvent and rose hydroxybenzaldehyde extracted with a solvent from the aqueous layer can also be obtained by removing light boiling components by a conventional distillation method, and then distilling rose hydroquine benzaldehyde. There are no particular restrictions on the method of distilling barahydroquine benzaldehyde, but since it is a substance with poor thermal stability, it is preferable to use a wet wall vacuum evaporator, a thin film vacuum evaporator, or the like.

【Effect of the invention】

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

【Example】

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but it goes without saying that the present invention is not limited to these Examples. Example-1 23.95 kg of baracresol with a purity of 99.5% by weight and 18% of sodium hydroxide were placed in a 2002 reactor with turbine blades.
゜8 kg, cobalt divalent acetate tetrahydrate 0.016 kg
and Metamer (38.6 kg) were charged, and salt production was carried out for 2 hours with stirring at a temperature of 60 to 80°C. Next, air was blown through a nozzle attached to the bottom of the reactor, and the reaction was carried out for 12 hours with stirring at a reaction temperature of 75° C. and a pressure of 6 kg/crl gauge pressure. The amount of air blown until the end of the reaction was 32.7 Nm', and the amount of oxygen absorbed was 8°5.
It was kg. Thereafter, 52.5 kg of water was charged into the reactor and mixed and diluted to obtain 141.2 kg of oxidation reaction mass. Quantitative analysis of this oxidation reaction mass by gas chromatography and liquid chromatography revealed that balacresol was 0.
08 kg (baracresol reaction rate 99.7%), baracresol 21.55 kg. It contained 2.4 kg of paramethoxymethylphenol, 0.28 kg of parahydroquine benzoic acid, and 0.10 kg of parahydroquine methylphenol. Add 142.3 kg of water to the oxidation reaction mass and dilute it again. Next, the oxidized diluted mass was filtered at 60° C. using an ultra filter covered with Pyrene S#26 filter cloth to remove sodium oxalate and insoluble tar. The oxidation dilution mass was supplied to the 13th stage from the top of the rectification column with wet wall reboiler (16 theoretical plates), and the temperature was 300 Torr and the reflux ratio was 2.
The solvent was removed using 99.8% methanol (37.2% by weight).
kg was collected. The methanol concentration in the bottom liquid was 0.9% by weight. In addition, most of the reaction products were not crushed in this solvent removal step. 18.8 kg of this demethanol mass was kept warm at 50°C,
Add 1.46 kg of 97 wt% sulfuric acid to neutralize and adjust the pH of the demethanol mass to 5.0 (60°C), add 3.98 kg of methyl isobutyl ketone, stir at 60°C for 30 minutes, and let stand for 30 minutes. The mixture was drained to obtain 6.21 kg of oil layer. A second extraction and liquid separation was performed under the same conditions as the first extraction in this extraction step to obtain an oil layer of 4.17 kg. The second oil layer obtained in this extraction step is used as the first extraction solvent in the next extraction step. The above neutralization and extraction were carried out 13 times. 80.8 kg of the methyl isobutyl ketone solution containing rose hydroxybenzaldehyde recovered in the extraction process was distilled at 40 Torr using a wet wall evaporator, and 51.7 kg of 98.5% by weight methyl isobutyl ketone was recovered. The retention rate of hydroxybenzaldehyde in this process was 98.0%, and the concentration of methyl isobutyl ketone in the bottom liquid was 0.8% by weight.
Met. Next, the crude bulk hydroxybenzaldehyde, which is the liquid in the tank, was heated to 6TO using a thin film vacuum evaporator manufactured by Luer.
Distilled at FR, 98.4% by weight, 19.0kgr of hydroxybenzaldehyde
Obtained. The total yield of rose hydroxybenzaldehyde for the entire process is 69.5%. Although this extraction step was carried out by a countercurrent batch method, it can also be carried out by a countercurrent continuous method, and is not limited to the extraction method. Example 2 The entire procedure up to the neutralization step was carried out in the same manner as in Example 1. Next, branching was performed at 60°C to obtain 2.30 kg of 62.5% by weight rose hydroxybenzaldehyde. Aqueous layer 17° Add 3.98 kg of methyl isobutyl ketone to 39 kg, stir at 60°C for 30 minutes, let stand for 30 minutes, then separate the liquids to obtain 4.1.
A 0 kg oil layer was obtained. 3.98 kg of methyl isobutyl ketone was added to 17.27 kg of the water layer obtained here, and the mixture was extracted and separated under the same conditions as the first extraction in the liquid separation and extraction step to obtain 4.05 kg of an oil layer. This oil layer is used as the first extraction solvent in the next liquid separation and extraction step. The above neutralization and liquid separation and extraction were performed 13 times. In this extraction step, almost no intermediate layer was generated. The crude para-hydroxybenzaldehyde and oil layer recovered in the separation and extraction step were delight boiled and treated in the same manner as in Example-1.
Distilled using a thin film vacuum evaporator to obtain 18°8 kg of 98.1% parahydroxybenzaldehyde by weight. The total yield of rose hydroxybenzaldehyde for the entire process is 68.5%. Although this extraction step was performed using a countercurrent batch method, a countercurrent continuous method is also possible, and the extraction method is not limited. Comparative Example-1 23.95 kg of para-cresol with a purity of 99.5% by weight and 18% of sodium hydroxide were placed in a 2001 reactor with turbine blades.
8 kg of cobalt divalent acetate tetrahydrate, and 38.6 kg of methanol 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 into the reactor through a nozzle attached to the bottom of the reactor, and the reaction was carried out at a reaction temperature of 75° C. and a pressure of 5 kg/c++f gauge pressure for 6 hours with stirring. The amount of air blown until the end of the reaction was 29.6Nc++t, and the amount of oxygen absorbed was 7
It was 4 kg. After that, 52.5 kg of water was charged into the reactor, mixed and diluted, and the oxidation reaction mass was 140.6 kg.
I got it. When this oxidation reaction mass was analyzed using gas chromatography and liquid chromatography, it was 2.26 kg of para-cresol (90.5% para-cresol reaction rate).
, parahydroxybenzaldehyde 19.57 kg. It contained 2.17 kg of para-methoxymethyl phenol, 0.25 kg of Balaoquin ben fF acid, and 0.09 kg of para-hydroxymethyl phenol. The oxidation reaction mass was further diluted by adding 142.9 kg of water. When this oxidized diluted mass was treated in the same manner as in Example-1, 98.0
Parahydroxybenzaldehyde in weight% 15.5 kg
I got it. The total yield of the entire process was 56.4%. When the conversion rate of para-cresol is less than 92%, the yield of para-hydroxybenzaldehyde decreases significantly in the distillation process.

Claims (1)

[Claims] A method for extracting para-hydroxybenzaldehyde 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, comprising: (1) para-hydroxybenzaldehyde in the oxidation step; The cresol reaction rate is set to 92% or more, (2) diluting with water and filtering, (3) separating the solvent from the reaction mixture, and (4) adjusting the aqueous layer after the solvent extraction to pH 3 to 6 with acid. Step (5) of extracting the neutralized liquid with a solvent or after liquid separation,
A method for purifying parahydroxybenzaldehyde, which comprises sequentially performing extraction steps with a solvent and purifying it by distillation.