JPH0627090B2 - Process for producing para-hydroxybenzaldehyde - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved process for making parahydroxybenzaldehyde.

Parahydroxybenzaldehyde is important as a raw material compound in a wide field of organic chemical industry, and its production method is also, for example, a method of oxidizing para-cresol with oxygen or an oxygen-containing gas in the presence of a cobalt compound and a base (JP-A-55). -81832) is well known, and it is also well known to use methanol as a reaction solvent at that time.

In such a case, the methanol used is generally recovered, purified by rectification or the like and reused, but the above reaction method is a reaction solution which produces water as a by-product, and depending on the case, Since dilution water may be added to the oxidation reaction product mixture to facilitate the treatment after the oxidation reaction, when recovering methanol, it will be recovered from hydrous methanol containing a large amount of water. .

By the way, conventionally, in the oxidation reaction, it is considered that the presence of water in the solvent reduces the oxidation reaction rate.
In the conventional method, a solvent having a very low water content is used, and it has been considered preferable to reduce the water content as much as possible even when the recovered methanol is reused.

However, reducing the water content in the recovered methanol causes a large amount of equipment such as a rectification column in the recovery and purification process, and also entails a great amount of energy consumption, thereby increasing the economic burden. is there.

From the above, the present inventors have
As a result of various studies on the influence of the water content in the methanol solvent on the oxidation reaction rate, the oxidation reaction rate was such that up to a certain range of water content in methanol, the water content was about the same as that of methanol (usually about 0.1%). However, it was found that when it exceeds the range, it rapidly decreases, and as a result of further study on a method for industrially producing parahydroxybenzaldehyde, the Invented.

That is, the present invention, in the presence of a cobalt compound and a base, a para-cresol or a para-cresol-containing cresol mixture is oxidized with oxygen or an oxygen-containing gas to produce para-hydroxybenzaldehyde, and 0.5 to 10% by weight as a reaction solvent. The present invention provides a method for producing para-hydroxybenzaldehyde, which comprises using methanol containing water as described above.

The para-cresol used in the present invention may be a single cresol, a synthetic cresol containing meta-cresol, ortho-cresol or the like, or a cresol mixture containing para-cresol such as cresylic acids fractionated from coal tar (hereinafter , P-cresols), but when a mixture is used, the higher the para-cresol pigment, the more preferable. The cobalt compound base used in the present invention may be any conventionally known one and is not particularly limited in the present invention. Examples of the cobalt compound include cobalt fluoride, cobalt chloride, cobalt acetate and naphthene. Examples thereof include cobalt acid cobalt, cobalt nitrate, cobalt borate, cobalt carbonate, cobalt trioxide, and the like, and examples of the base include metal hydroxides such as caustic soda and causticum, metal alkoxides such as sodium alkoxide, potassium alkoxide (here, alkoxide Examples thereof include methoxide, ethoxide, isopropoxide, tert-butoxide, etc.), lithium amide, sodium amide and the like. The amount of these cobalt compounds and bases used is generally paracresol or P.
-The former is 0.0001 times equivalent or more, preferably 0.0005 to 0.05 times equivalent, and the latter is 1 to 10 times equivalent to cresols. As the oxidant, an oxygen gas alone or an oxygen-containing gas such as air or an oxygen gas diluted with an inert gas (eg, nitrogen or argon) is used, and the oxygen or the oxygen-containing gas is generally contained in the reaction solution. Used in the insufflation method, but not specific to this method.

The pressure of oxygen and the oxygen-containing gas is not particularly limited, but is usually 1 atm or more and 100 atm or less, preferably 1 atm to 10 atm.
Atmospheric pressure.

The reaction proceeds at atmospheric pressure or under pressure, and the reaction temperature is usually 0 to 300 ° C, preferably 50 to 100 ° C.

The oxidation reaction is carried out by using para-cresol or P-cresols in a solvent in the presence of a cobalt compound and a base as described above,
The oxygen or oxygen reaction itself basically complies with known methods, but the most important point of the present invention is to use water-containing methanol having a water content of 0.5 to 10% by weight as a reaction solvent in such oxidation reaction. In particular, the present invention is effective when recovering and reusing methanol as a solvent.

In the present invention, the water content in methanol is 0.5 to 10% by weight.
This is because the range specified in the present invention is most advantageous in terms of both the ease of removing water on an industrial scale in recovered methanol and the effect of water content on the oxidation reaction rate.

That is, the smaller the water content is, the more preferable it is in view of the influence on the oxidation reaction rate, but it is relatively easy to remove the water until the water content in the recovered methanol becomes about 0.5% by weight. If the water content exceeds 10% by weight, the removal of water from the recovered methanol will be easy. Causes a problem that the oxidation reaction rate is significantly reduced. However, if the water content is in the range of 0.5 to 10% by weight, it is easy to remove the water in the recovered methanol, and moreover, the oxidation reaction rate can be maintained at the same level as when using anhydrous methanol, After all, it has been found that the present invention removes water to an extent that is industrially easy to implement without removing water unnecessarily, and thus an effect equivalent to that obtained when water is almost completely removed can be obtained. However, its significance is extremely large.

The amount of water-containing methanol used in the oxidation reaction is usually 1 to 20 relative to para-cresol or P-cresols.
Double parts by weight, preferably 1 to 6 parts by weight.

The oxidation product mixture obtained by such oxidation reaction is treated by means such as methanol recovery, acid precipitation, solvent extraction, distillation or recrystallization or sublimation to isolate para-hydroxybenzaldehyde.

Thus, according to the method of the present invention, the target para-hydroxybenzaldehyde can be produced industrially very advantageously.

Hereinafter, the present invention will be described with reference to examples.

Example-1 Paracresol (84.7 g), divalent cobalt acetate tetrahydrate (0.11 g), caustic soda (67 g) and water content 2% by weight.
Of water-containing methanol (140 g) was charged in a small autoclave, and nitrogen gas containing 6% by volume of oxygen was blown through the pores from the bottom, and the reaction was carried out at a pressure of 6 kg / cm ² and a temperature of 65 ° C. for 6 hours with stirring.

Sampling was performed 6 times during the reaction, unreacted para-cresol was analyzed by a gas chromatograph, and a reaction rate constant k ^{* 1} was calculated based on the data. As a result, k = 0.230 [Hr ^-1 ] was obtained.

After adding 135 g of water to the reaction mixture obtained,
Water content of 2% by weight to reuse methanol for the next reaction
Was recovered and purified as water-containing methanol, but this required rectification with 13 theoretical plates and a reflux ratio of 1.2.

Examples 2 to 5 The reaction was performed in the same manner as in Example 1 except that the water content of methanol was changed as shown in Table 1, and as a result, the reaction rate constant k shown in Table 1 was obtained.

In addition, in order to add 135 g of water to the reaction mixture and recover it as methanol having the same water content as each charged methanol, Table-1
The rectification conditions shown in were required.

Comparative Example-1 A reaction rate constant k 0.235 [Hr ^-1 ] was obtained by following the reaction in the same manner as in Example 1 except that 135 g of industrial methanol (water content 0.08% by weight) was used. Further Example-1
In order to purify and recover methanol with a water content of 0.08% by weight from the same water-injected mixture, rectification with 23 theoretical plates and a reflux ratio of 1.4 was required.

Comparative Example-2 A reaction solution rate constant k was obtained by following the reaction in the same manner as in Example-1, except that 135 g of hydrous methanol containing 15% by weight was used.
Was found to be 0.05 [Hr ^-1 ].

* 1 Reaction rate constant k [Hr ^-1 ] Calculated by the following formula.

dc / dt = kc c: residual ratio of unreacted para-cresol to raw material para-cresol t: reaction time [Hr]

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Manabu Yatata 2200 Tsurusaki, Oita City, Oita Prefecture Sumitomo Chemical Co., Ltd. Incorporated (72) Inventor Yasuhiko Horikawa 3-98 Kasugade, Konohana-ku, Osaka City, Osaka Prefecture Sumitomo Chemical Co., Ltd. (56) Reference JP 62-22740 (JP, A)

Claims (1)

[Claims] 1. A para-cresol or a para-cresol-containing cresol mixture is oxidized with oxygen or an oxygen-containing gas in a solvent in the presence of a cobalt compound and a base to produce para-hydroxybenzaldehyde. Of para-hydroxybenzaldehyde, characterized by using methanol containing 100% water