JPS6039066B2 - Separation method of methyl P-formylbenzoate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating methyl p-formylbenzoate (hereinafter sometimes abbreviated as MPFB) from a mixture containing methyl p-formylbenzoate.

To explain in more detail, from a mixture containing MPFB,
The present invention relates to a method for acetalizing and separating MPFB contained therein. Methyl p-formylbenzoate (MPFB
) is itself useful as a soap aromatic agent, and is also industrially useful as a pharmaceutical intermediate or an intermediate for various industrial chemicals, but there is no known method for producing it at low cost.

Therefore, the present inventors investigated various ways to supply M-yen FB at low cost, and found that it can be used as an intermediate product during the production of dimethyl terephthalate, which has conventionally been industrially produced in large quantities as a raw material for polyester. Noting that it contained some MPFB, we conducted research on methods for separating and recovering it.

In other words, terephthalic acid is produced in large quantities by oxidizing p-xylene in the liquid phase, but the oxidation reaction mixture contains various oxidation intermediates and impurities in addition to terephthalic acid. It is already known that p-formylbenzoic acid is one of the substances. On the other hand, terephthalic acid is converted to dimethyl terephthalate by esterification with excess methanol, but unreacted methanol and dimethyl terephthalate are separated from this esterification reaction mixture. In addition to monomethyl terephthalate, M-FB, which is a methyl ester of p-formylbenzoic acid, is usually contained in an amount of 5 to 2% by weight. On the other hand, dimethyl terephthalate can also be obtained by esterifying terephthalic acid obtained by oxidation of p-xylene with methanol as described above, but dimethyl terephthalate can also be obtained by oxidizing a mixture of p-xylene and methyl p-toluate. A method of obtaining an oxidized mixture mainly consisting of monomethyl terephthalate and esterifying it with methanol to obtain an esterified mixture mainly consisting of methyl p-tholeate and dimethyl terephthalate, and separating dimethyl terephthalate from the esterified mixture. It can also be obtained by This method is known as the so-called Bitten-Hercules method. M-FB is also contained in various residues generated in the Bitten-Hercules process, especially in the distillation residue and/or recrystallization mother liquor concentrate generated when crude dimethyl terephthalate is purified by distillation and/or recrystallization. has been done. Conventionally, as a method for separating aromatic aldehydes from a mixture containing aromatic aldehydes, there has been known a method in which, for example, sodium bisulfite is added to form a salt of aromatic aldehyde and sodium bisulfite. (See Seki No. 50-71640 and No. 50-71641).

In this method, for example, as shown in the following formula, a mixture containing an aromatic aldehyde is brought into contact with an aqueous sodium hydrogen sulfite solution, and the resulting adduct of the aromatic aldehyde and sodium hydrogen sulfite is decomposed with alkali or acid to produce aromatic compounds. This is a method to separate aldehydes. '1} Addition reaction RCHO1NaHS03→RCH04Na [21 Alkali decomposition reaction RCH2S04Na1NaOH→RCHO
10 Na2S03 10 ratio ○■ Acid decomposition reaction 2RCH2S04
Na+day2S04 12RCHO10Na2S0410$0212day20 (In each of the above formulas, R represents an aromatic group) However, the method using alkali decomposition or acid decomposition described above uses large amounts of dangerous chemicals called acids and alkalis. This is not preferable in terms of reaction operation.

Furthermore, it cannot be said to be an economically preferable method since all of the sodium bisulfite, acid, or alkali used in the addition reaction and decomposition reaction is consumed. Furthermore, S02 produced during acid decomposition worsens the working environment, and a great deal of cost is required to dispose of the bitter salt produced as a by-product. On the other hand, it is also known to use hydrogen cyanide instead of sodium bisulfite and decompose it with an alkali. This method also cannot be said to be industrially advantageous compared to the above-mentioned known method. The present inventors conducted research on a method for separating MPFB from a mixture containing MPFB by a method that does not have the disadvantages of the known methods, and as a result, they found that MPFB can be easily separated by acetalizing it with alcohol. Heading This is what has led to the present invention.

That is, in the present invention, a mixture containing methyl p-formylbenzoate is brought into contact with an alcohol, and p-
- acetalizing methyl formylbenzoate, then separating the acetal of methyl p-formylbenzoate from the acetalization mixture, and then hydrolyzing it to obtain methyl p-formylbenzoate. - A method for separating methyl formylbenzoate.
According to the present invention, there is no disadvantage of the conventional method of using a large amount of a reagent such as sodium bisulfite in an equimolar amount to the aldehyde group, and there is no need to use large amounts of acids or alkalis. Since no S02 is generated, MmFB can be separated advantageously, and since methyl p-formylbenzoate (MPFB) forms acetals with alcohols, especially lower alcohols with 2 or more carbon atoms, conventionally it has been difficult to separate MmFB by distillation. The vapor pressure difference with dimethyl isophthalate, dimethyl terephthalate, dimethyl phthalate, and other mixtures becomes large, and MPFB can be easily separated as an acetal by a simple operation such as vacuum distillation.

By hydrolyzing the separated acetal in the presence of a catalytic amount of acid, M-circle FB of extremely high purity can be easily obtained. Moreover, in some cases, by appropriately selecting the type and amount of alcohol used in the acetalization reaction, the type and amount of solvent, etc., when the acetalization reaction mixture is cooled to about room temperature, dimethyl isophthalate and terephthalate can be formed. A soluble mixture such as dimethyl can be easily separated by filtration or the like, and the acetal can be industrially advantageously recovered by distilling the mother liquor.
'The "mixture containing MPFB" targeted in the present invention is "as long as it contains MPFB, there are no particular restrictions on its origin, content, etc., but in particular, as mentioned above, it is a mixture containing dimethyl terephthalate. Preference is given to various mixtures that occur at the same time.

In particular, it is advantageous to use the distillation residue and/or recrystallization liquid concentrate generated during the distillation and/or recrystallization purification of the crude dimethyl terephthalate obtained in the Bitten-Hercules process. In the method of the present invention, it goes without saying that acetalizing agents such as methyl orthoformate, ethyl orthoformate, methyl orthoacetate, and ethyl orthoacetate can be used to acetalize M-circle FB in the MPFB-containing mixture. It is industrially more advantageous to carry out acetalization directly using alcohol.

As such alcohol, aliphatic, alicyclic or aromatic monoalcohols having 1 to 20 carbon atoms are generally preferably used. Among these, preferred alcohols include aliphatic monoalcohols having 1 to 20 carbon atoms, particularly preferably saturated and unsaturated aliphatic monoalcohols having 2 to 10 carbon atoms, especially saturated aliphatic monoalcohols having 2 to 10 carbon atoms. is preferred. There is no particular restriction on the amount of the alcohol used, but it is generally at least 1 mol, preferably at least 2 mol, particularly preferably at least 2.0 mol, per mole of FBI contained in the mixture.
A range of 5 moles or more is used. On the other hand, the upper limit of the alcohol to be used is not particularly limited, but the reaction can generally proceed sufficiently within 50 moles, particularly preferably within 20 moles, and if desired, within 10 moles, based on the moles of MPFBI contained in the mixture. . The acetalization reaction of the present invention is generally preferably carried out in the presence of a catalyst. As such a catalyst, an acidic catalyst or a strong acid/weakly basic catalyst is generally used. Such catalysts include inorganic acids such as persalt acids, chloric acid, sulfuric acid, sulfurous acid, nitric acid, phosphoric acid, hydrochloric acid, phosphorous acid, hypophosphorous acid, butyl phosphate, and their acid esters: methanesulfonic acid, Organic sulfonic acids represented by ethane sulfonic acid, propane sulfonic acid, decane sulfonic acid, benzene sulfonic acid, p-toluene sulfonic acid, etc.: Organic carboxylic acids such as oxic acid: dimethylamine p-toluene sulfonic acid Strong acid weak basic salts such as ammonia sulfonate ester, diethylamine p-toluene sulfonate ester, etc.: Amberlyst 1
Acidic ion exchange resin such as Amberlite IR-12: Solid acids such as silica alumina, silica, alumina, Amberlite, silica magnesia, silica Zimania, and polyphosphoric acid can be used. The amount of these acids and strong acid weak basic salts used relative to the mol of MPFBI in the starting mixture is generally from 10-6 to 10 mol, preferably from 10-5 to 1 mol, particularly preferably from 5 x 10-
It is 5 to 0.5 mol or less. Although the acetalization can be carried out without removing water produced during the reaction, it is generally desirable to carry out the reaction after removing water using an azeotrope or a dehydrating agent.

Advantageously, such a co-weaving agent also serves as a reaction solvent. These include aliphatic hydrocarbons such as butane, bentane, hexane, hebetane, and octane; aliphatic hydrocarbons such as cyclobutane, cyclobentane, cyclohexaso, and methylhexane; benzene, toluene/o-xylene, Aromatic hydrocarbons such as m-xylene, p-xylene, mixed xylene, ethylbenzene, pseudocumene, etc.: methyl acetate, ethyl acetate, propyl acetate, butyl acetate, aluminum acetate, methyl propionate, ethyl propionate,
Esters such as methyl acetate: dimethyl ether, diethyl ether, dif. Ethers such as propyl ether, methyl ethyl ether, dibutyl ether, and tetrahydrofuran; and halogenated hydrocarbons such as monochloromethane, dichloromethitane, chloroform, monochrome ethane, dichloroethaso, clohabenzene, and chlorocyclohexane. Among the above, hydrocarbon solvents and entrainers are particularly preferred. When such solvents and entrainers are used, they are preferably used in a range of 1 to 10 parts by weight per 1 part by weight of the starting mixture.

In this manner, acetalization can be advantageously carried out by using the starting materials, solvents and catalysts in amounts within the above-mentioned ranges and allowing them to escape from the reaction system.

In that case, it is preferable to set the reaction temperature and reaction time to appropriate conditions. Generally, a temperature of at least room temperature, preferably at least 30 oo, particularly preferably at least 40 oo, is used. Although there is no particular upper limit to the reaction temperature, generally from an industrial point of view a temperature of 400° C. or lower, usually 300° C. or lower, is preferably used. It may be advantageous if the reaction temperature in the method of the present invention is set to the boiling point of the azeotropic system with water as a solvent at normal pressure. Furthermore, the reaction pressure can be normal pressure, reduced pressure, or increased pressure. The reaction time varies depending on the temperature and pressure, but is generally 1 minute to 10 G hours, preferably 5 minutes to 1 field hour. The acetals synthesized as described above are separated by distillation under reduced pressure, normal pressure, or increased pressure, or after other substances are filtered through a furnace, the acetals contained in the furnace liquid are separated by distillation or through furnace filtration. Something happens.

The acetal separated by the method of the present invention is hydrolyzed with water in the absence or presence of an acid catalyst to regenerate methyl p-formylbenzoate as shown in formula '4'.

(R: hydrocarbon residue) {4' However, it is generally preferable to carry out the hydrolysis in the presence of an acid catalyst.

Such acid catalysts include chloric acid, perchloric acid, periodic acid,
Iodic acid, sulfuric acid, chloric acid, hydrogen chloride, hydrogen bromide, hydrochloric acid,
Inorganic acids such as nitric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, butyl phosphate, and their acid esters: methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, decanesulfonic acid, benzenesulfonic acid, p-tol Organic sulfonic acids such as phthalic acid, carbonic acid, phthalic acid, and carboxylic acids such as acetic acid are used. By using such acid catalysts, acetal hydrolysis proceeds rapidly in a short period of time, but these acid catalysts generally have a concentration of 10-4 to 1 mole of acetal.
More than 1 mole, preferably more than io-3 moles are used. Particularly preferred is 10-2 mol or more. There is no particular upper limit to the amount of the acid catalyst, but from an industrial standpoint it is 10 mol or less, particularly preferably 1 mol or less. There is no particular limit to the amount of water used in the hydrolysis reaction. ~
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The hull girth is used.

Furthermore, the hydrolysis reaction ranges from 0 to 400oo, preferably 2
0qo to 300q○, particularly preferably 30qo to 250
It can be carried out in a temperature range of 0.000. The reaction time varies depending on the reaction temperature, but generally ranges from 1 second to 10 hours, preferably from 1 to 10 hours. Note that the hydrolysis reaction can be carried out at normal pressure, increased pressure, or reduced pressure.

Although the reaction atmosphere can be carried out in a non-oxidizing atmosphere such as helium, argon, neon nitrogen, etc., the MPFB with higher purity can be obtained, but it can also be carried out in an atmosphere such as air.
The present invention will be described in detail below with reference to Examples. Note that the middle parts of the examples are parts by weight without particular mention. Example 1 (Acetalization) In a method for industrially producing dimethyl terephthalate by oxidizing p-xylene with molecular oxygen or a molecular oxygen-containing gas in the presence of a metal salt catalyst and then esterifying it with methanol. When the obtained crude dimethyl terephthalate was purified by recrystallization, the obtained recrystallization mother liquor concentrate was further distilled (hereinafter referred to as raw material A).
contains 14% methyl p-formylbenzoate.

The composition of this raw material A is shown in Table 1. Table 1 Composition of raw material A Methyl p-formylbenzoate 14. Skin t% Dimethyl terephthalate 10.5 Dimethyl isophthalate 46.2″ Dimethyl phthalate
6.7〃p-Methyl toluate 1.9〃
Unknown items 20.7 total
200 parts of 100% raw material A,
44 parts of n-propyl alcohol, 1 part of benzene as solvent
0 part and 0.0024 parts of sulfuric acid as a catalyst were charged into a 50-board capacity glass Mitsuro flask equipped with a dehydrator, a thermometer, and a competitive layer, and an acetalization reaction was carried out while dehydrating at 87°C for 3 hours. Ta.

Add 2.0 parts of sodium carbonate to the reaction mixture, first remove benzene and n-propyl alcohol by single evaporation, and distill under reduced pressure to obtain methyl p-dipropoxymethylbenzoate.
Two parts (151°C/3 days) were obtained.The purity of this product was 99.6% when analyzed by gas chromatography, and it was colorless at room temperature.The analytical values of this compound are as follows. o Infrared absorption spectrum: Shic Ni〇, Ni 1730 skin-1 Reccoc Ni 1277 (ester), 1105 (acetal) o Highly resolved bear gas mass vector M = 266.1608 Example 2 (Hydrated Decomposition) 2.7 mol % of sulfuric acid was added to methyl p-dipropoxymethylbenzoate obtained as in Example 1, 0.1 part, 0.1 part, and the starting acetal, and 1000% of sulfuric acid was added to the starting acetal.
0 and 1. When the immediate hydrolysis reaction was carried out, the conversion rate of methyl p-dipropoxymethylbenzoate was 100 mol%, 99%.
Methyl p-formylbenzoate was obtained with a selectivity of mol%.

The purity of the obtained product as measured by gas chromatography was almost 100%, and it was pure white in color. Also, the melting point is 6y
It showed o. o Infrared absorbing svector re○ni.

D1728C-.

-C Ni1283o High resolution gas mass vector M1i164.0433 (C9 ratio 03) Example 3 The same equipment as in Example 1 was used, except that the sulfuric acid catalyst was replaced with p-toluenesulfonic acid and the same amount was used. As a result of acetalization and separation in the same machine as in Example 1, 38.6 parts of methyl p-dipropoxymethylbenzoate was obtained.

Example 4 The following raw materials AI Sobe, 27 parts of n-butyl alcohol,
5 parts of benzene as a solvent and 0.001 $ part of p-toluenesulfonic acid as a catalyst were charged into a 10 part glass three-necked frusto equipped with a dehydrator, a thermometer, and a thickener, and the temperature was lowered to bath temperature. The acetalization reaction was carried out while dehydrating at 11,000 for 3 hours.

Add 0.5 part of sodium carbonate to the reaction mixture, first remove benzene and n-butyl alcohol by single evaporation, and then distill under reduced pressure to remove methyl p-dipropoxymethylbenzoate. Foundation (
15g C/2 legs) was obtained. The purity of this product was 99.5 (%) when analyzed by gas chromatography, and it is colorless at room temperature. Examples 5 to 13 In Example 2, acetal hydrolysis reactions were carried out by appropriately changing the acid catalyst, reaction temperature, and reaction time, and the results shown in Table 2 were obtained.

Table 2 Acetal hydrolysis table *Acetal is p-
Methyl dibutoxymethylbenzoate was used.

Claims (1)

[Claims] 1. A mixture containing methyl p-formylbenzoate is brought into contact with an alcohol to acetalize methyl p-formylbenzoate in the mixture, and then methyl p-formylbenzoate is extracted from the acetalized mixture. A method for separating methyl p-formylbenzoate from the above mixture, characterized in that the acetal is separated and then hydrolyzed to obtain methyl p-formylbenzoate. 2. A method for separating methyl p-formylbenzoate according to claim 1, characterized in that the acetal of methyl p-formylbenzoate is separated from the acetalization mixture by distillation.