JPS5811936B2 - Purification method of naphthoquinone - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to naphthoquinone (1,4-naphthoquinone unless otherwise specified, and naphthoquinone is abbreviated as NQ) obtained by catalytic gas phase oxidation of naphthalene.

).

More specifically, NQ obtained by contacting the reaction product gas obtained by catalytic gas-phase oxidation of naphthalene with an aqueous medium and collecting it by washing with water is dissolved in a solvent and brought into contact with an aqueous sodium bicarbonate solution to purify NQ. Regarding how to.

Generally, NQ is produced by contacting the gas produced by the catalytic gas-phase oxidation reaction of naphthalene with an aqueous medium, and extracting only NQ from the resulting aqueous mixture containing by-products such as phthalic acid or by a known method such as filtration. Separated and manufactured.

However, the NQ obtained in this way contains compounds of unknown composition, so-called tar-like polycondensates, in addition to organic acid components such as phthalic acid and benzoic acid, and has a low purity, for example, 90% or less. NQ is often produced.

These organic acid components in NQ are relatively soluble in water, so they can be removed by washing with water or an aqueous medium in a non-alkaline range of pH 7 or less, but other polycondensates remain, so NQ Purity does not improve.

In particular, if an attempt is made to improve the selectivity of NQ in the catalytic gas phase oxidation reaction of naphthalene, the amount of polycondensates increases, and this tendency is remarkable.

The low-purity NQ obtained in this way not only deteriorates its quality as an industrial raw material for diclone and dithianone, but also causes undesirable effects such as a decrease in yield when used as a raw material for anthraquinone in the Ziels-Alder process. yields no results.

The present inventors have conducted extensive studies on a method for effectively removing impurities in NQ without deteriorating the quality of NQ itself.

Conventionally known methods for removing organic acid components such as phthalic acid from NQ include JP-A-51-8256 and JP-A-51-
8257 and USF2.536,833.

However, in these methods, it was thought that if an amount of alkali added in excess of the amount to neutralize the organic acid component was used for washing, NQ would deteriorate significantly, so the amount of alkali relative to the organic acid component was limited to less than the neutralizing amount. In other words, washing is carried out in a non-alkaline region, in the extreme case in the presence of an acid salt of phthalic acid, or washing is carried out at a pH of 7 or less using an aqueous solution of an alkali salt of an organic polybasic acid as in JP-A-51-8257. method was adopted.

However, experiments using these methods have failed to improve the purity of NQ because it is difficult to remove the polycondensate, although most of the organic acid component can be removed.

The present inventors have studied in detail the properties and structures of impurities in NQ.

As a result, 1,2-naphthoquinone (hereinafter referred to as 1,
2-NQ) and dimers such as NQ exist in a few percent,
It was found that most of them had hydroxy groups.

This dimer was isolated and treated with alkali, resulting in a pH of
In addition to those that dissolve when pH is 7 or less, there are those that do not dissolve unless the pH becomes 7 or higher.

Next, 90% pure NQ containing these dimers was converted into orthoxylene (hereinafter abbreviated as OX).

) and add an aqueous solution containing at least the neutralization equivalent of organic acids such as phthalic acid and benzoic acid and a certain proportion of sodium bicarbonate to impurities excluding the organic acid components.
When the mixture was mixed for several minutes at 0 to 60°C, separated, and the NQ OX solution was evaporated to dryness, the purity of the obtained NQ increased by several percent, and the yield decreased by about 1%. .

Furthermore, similar cleaning experiments were conducted with an increased amount of sodium bicarbonate in an alkaline pH of 7 or higher, but surprisingly, NQ was hardly decomposed even in the pH range of 7 or higher, where NQ was conventionally said to decompose. First, the present invention was completed by discovering that a considerable amount of impurities, particularly polymers of NQs (including 1,2-NQ) having hydroxyl groups, can be extracted into an aqueous solution in a short period of time.

The present invention relates to a method for purifying NQ obtained by catalytic gas phase oxidation of naphthalene, in which the NQ is mixed with a solution in which the NQ is dissolved in a solvent that is not miscible with water.
A method of extracting impurities in naphthoquinone into an aqueous solution by contacting it with an aqueous sodium bicarbonate solution capable of retaining H7 or higher at room temperature or below 90°C.
It consists in the purification method of Q.

The NQ used in the method of the present invention is industrially obtained by catalytic gas phase oxidation of naphthalene with an oxygen-containing gas such as air over a solid catalyst, and then by a suitable separation method.

As suitable separation methods, known methods have already been proposed, such as contacting the oxidation product gas with an aqueous medium containing water and maleic acid, phthalic acid and/or their salts, such as monosodium salts, Collect the contained NQ as an aqueous mixture containing solid NQ, dissolve the organic acid component and filter the NQ, or extract the NQ with a solvent, or if phthalic acid and NQ form a slurry, filter the solid matter. Alternatively, a method may be used in which NQ is extracted with a solvent without filtration.

Alternatively, a method may be adopted in which the oxidation product gas is collected with an organic solvent and then the phthalic anhydride contained therein is extracted with hot water to obtain the NQ bath solution.

In the case of solid NQ, it is used after being dissolved in a solvent.

Generally, the reaction product gas generated by the catalytic gas phase oxidation reaction of naphthalene is collected by washing with water, and NQ is extracted with a solvent from the resulting aqueous mixture containing NQ, preferably at room temperature to 90°C. It is convenient to use the NQ bath solution after washing with water to remove most of the organic acid components.

The effect of removing organic acid components is to reduce the amount of alkali used and prevent foaming due to carbon dioxide gas.

The purity of these NQs is generally about 85-97%, and NQs with many impurities below 95% are particularly 1,2-
NQ, NQ polycondensates, and tar-like substances account for most of the impurities.

By the method of the present invention, part of the polymers and tar-like substances having hydroxyl groups can be removed, and the purity can be increased.

Further, in a method of producing high purity NQ by a method such as solvent recrystallization, the purity can be easily increased.

In the present invention, a solvent is used.

The solvent dissolves NQ and impurities and facilitates the reaction between the alkali and impurities.

The solvent is preferably one that dissolves NQ but is not compatible with water and has no difference in specific gravity with water.

Usually aromatic hydrocarbons such as benzene, toluene,
Xylene etc. are used.

Particularly suitable is xylene.

The NQ bath solution concentration is used up to the solubility at each temperature.

Generally, 10 to 30% is appropriate.

Sodium salts and potassium salts are used as the alkali bicarbonate, but sodium salts are usually used for economic reasons.

Alkali bicarbonate does not easily alter NQ even at pH 7 or higher compared to alkali carbonate or alkali hydroxide.

The concentration of sodium bicarbonate aqueous solution is generally 6% or less,
Use 1% or more.

If the concentration is too dilute, a large amount of liquid must be used,
Therefore, the amount of NQ dissolved increases and is likely to be lost.

If the concentration is too high, impurities may precipitate in the aqueous solution, making it unsuitable for operation.

Therefore, it is preferable to decide by considering the amount of cleaning liquid and the pH.

The amount of cleaning liquid is generally selected from the same amount (by weight or volume) to about 1 to 2% of the NQ bath solution.

From the viewpoint of NQ loss, it is preferable to have less.

In the present invention, the conditions for contacting the NQ bath solution with the aqueous solution of sodium bicarbonate are at a temperature of 90°C, preferably 80°C.
The temperature must be at room temperature or above, and the pH at the time when most of the impurities to be extracted into the aqueous phase has migrated to the aqueous phase is 7 or more, and the pH must be about 8.2 when sodium bicarbonate is present in excess.

In this range, the decomposition of NQ is extremely small, so the contact time can be relatively long, for example about 1 hour, but usually within 30 minutes in a batch method, and within 5 minutes or more than a few seconds in a continuous method. good.

In particular, at temperatures above 80°C, the contact time is preferably short, for example within 20 minutes, particularly about 10 seconds to 5 minutes.

At temperatures above 90°C, purity and yield (refined NQ after treatment relative to pure NQ in raw materials) are shown in Tables 1 and 2.
In particular, the yield (% of pure NQ content) decreases significantly and is in an extremely dangerous range industrially.

During the above treatment, the pH is maintained at about 7 or higher.

For this purpose, alkali bicarbonate is generally used in an amount of about 10% to 100% based on the impurities in the NQ solution.

If the pH is below 7, a sufficient increase in purity cannot be expected as shown in Table 1.

A general method of carrying out the present invention is to mix an NQ bath solution with an aqueous solution of alkali bicarbonate, usually economically inexpensive sodium bicarbonate, at room temperature to 90°C using a mixing means such as a stirring tank or line mixer. In reality, it is 50-80℃,
30 minutes or less while maintaining the pH at about 7 or higher, preferably about 1
By contacting for 0 seconds to 5 minutes, most of the removable impurities in the NQ solution, such as polymers such as 1,2-NQ or NQ having hydroxyl groups, are mostly transferred to the aqueous solution phase.

Next, the aqueous NQ bath solution is separated, the NQ bath solution is washed with water or an aqueous nitric acid solution as necessary, and then the solvent is usually removed to obtain the product NQ.

Alternatively, this solution can be used in subsequent steps, such as the production of anthraquinone by the Ziels-Alder process with Butadiens.

Thus, according to the method of the present invention, it is possible to prevent deterioration of NQ, thereby minimizing a decrease in yield and improving the purity of NQ.

In addition, when desolventing the NQ bath solution, polymers and tar-like substances are removed, so when NQ is obtained by desolvation, the evaporation rate of the solvent is accelerated and the resulting product NQ is stored. It can also prevent solidification.

Furthermore, it has the effect of improving the anthraquinone yield in the production of anthraquinone by the Shiels-Alder method.

Hereinafter, it will be explained in detail in Examples.

In the specification, "%" means "% by weight" unless otherwise specified.

Example 1 Organic acids were removed in advance by washing with warm water, and the purity was 91.6.
% of NQ was dissolved in OX to make a solution with a concentration of 20%.

To 100 parts by weight of each of these solutions, 20 parts by weight of aqueous sodium bicarbonate (hereinafter referred to as NaHco3) solutions with different concentrations were added, stirred at a temperature of 90°C for 1 minute, and left to stand to remove the washed aqueous layer. Next, 20 parts by weight of water was added, stirred at the same temperature for 5 minutes, washed with water, and the aqueous layer was allowed to stand to separate.

The oil layer was desolvated at 80° C. under reduced pressure to obtain the treated NQ, and the purity was analyzed using a gas chromatograph.

The results are shown in Table 1 (however, the NQ recovery rate is the percentage of recovered NQ to the pure NQ). Example 2 100 parts by weight of crude NQ with a purity of 89.7% was dissolved in 900 parts by weight of OX, After adding 200 parts by weight of warm water at the same temperature and stirring for 5 minutes, the mixture was allowed to stand to separate the aqueous layer and remove the organic acids.

Take 100 parts by weight of this NQ OX solution and add 1.5% NaH
After adding 20 parts by weight of CO3 aqueous solution and stirring at 60°C for 30 minutes, the washing water layer was separated by standing still, and then 20 parts by weight of water at the same temperature was added.
After adding parts by weight and stirring for 5 minutes, the mixture was left to stand and separated to remove the remaining alkali.

The oil layer was desolvated at 80° C. under reduced pressure to obtain treated NQ.

For the same NQ bath solution, temperature conditions (or NaHC
Repeat the above operation by changing the O3 concentration and time.
The stability of NQ with respect to temperature was investigated.

The results are shown in Table 2.

Note that the analysis was performed by gas chromatography.

Example 3 NQ with different purity was dissolved in OX to make a 20% solution,
Example 2 with 20 parts by weight of hot water per 100 parts by weight of solution.
After washing with water in the same manner as above, the pH of the washing solution was 7 to 8.
After washing with NaHCO3 aqueous solutions with different concentrations as shown in Table 2 for 1 to 5 minutes at a temperature of 60 to 75°C to separate the washed water layer, the oil layer was filtered to remove a small amount of insoluble matter present at the oil-water interface. Regarding the oil layer obtained as a filtrate, see Examples 1 and 2.
The NQ obtained by performing the same post-treatment as above was analyzed by gas chromatography and high pressure liquid chromatography,
Purity was determined and changes in composition due to NaHCO3 washing were investigated.

The results are shown in Table 3.

Example 4 1300Kg of crude NQ with purity 92.5% was oxidized to OX5
700Kg and using the apparatus shown in Figure 1, Na
Continuous washing with an aqueous HCO3 solution was performed.

An OX solution of crude NQ maintained at a temperature of 70° C. was supplied from storage tank 1 through line 2 to stirring mixer 3 at a flow rate of 251/min.

At the same time, 1.5% NaHCO3 solution is added from storage tank 4 to line 5.
was supplied to the mixer 3 at a flow rate of 51/min.

After both liquids were stirred and mixed in the mixer 3 for an average residence time of 1.3 minutes, they were extracted from the line 6 and separated in the separator 7.

The lower washing aqueous solution layer was continuously discharged from a line 8 to a washing liquid receiving tank 9.

On the other hand, the upper oil layer is discharged from line 10 and is also supplied to line 10 from line 11 at a flow rate of 51/min.
The mixture was supplied to the mixer 12 together with 0° C. wash water, stirred and mixed at an average residence time of 1.3 minutes, and then supplied to the separator 14 from the line 13.

The water layer is transferred from the bottom of the separator 14 through the line 15 to the wastewater receiving tank 1.
6, and the oil layer was discharged from the upper part through line 17 to treated NQ solution receiving tank 18.

The NQ bath solution obtained in the receiving tank 18 was measured, a sample was taken, and the treated NQ obtained by removing the solvent was analyzed.

The results are shown in Table 4. Comparative Example 1 Example 2 to investigate the purification effect of NQ by hot water washing
The same crude NQ (purity 89.7%) was dissolved in OX, and 2
To make a 0% solution, add 20 parts by weight of warm water to 100 parts by weight of this solution, stir at 90°C for 5 minutes, and then separate the aqueous layer.
To this oil layer, 20 parts of warm water was added again and the above operation was repeated, and the obtained oil layer was desolvated at 80°C under reduced pressure and treated with N.
Q was obtained and analyzed by gas chromatography, but the NQ line purity improved by only 1.9%.

The results are shown in Table 5.

Comparative Example 2 The same NQ (purity 89.7%) as in Example 2 was dissolved in OX to make a 20% solution, and 7.6 parts by weight was added to 100 parts by weight of this solution.
Add 20 parts by weight of % disodium phthalate aqueous solution to 90%
After stirring for 1 minute at °C, the aqueous layer was separated and removed, and then 20 parts by weight of warm water was added and stirred for 5 minutes, then the aqueous layer was removed.

The treated NQ obtained by removing the solvent from the oil layer under reduced pressure at 80° C. was analyzed by gas chromatography.

The NQ line purity improved by only 3.2%.

The results are shown in Table 6.

[Brief explanation of drawings]

FIG. 1 shows one embodiment in which the method of the present invention is carried out continuously. In the figure, 1 is a crude NQ solution storage tank, 4 is an NaHCO3 aqueous solution storage tank, and 3 is a crude NQ solution and Na
A mixer with HCO3 aqueous solution, 7 a separator, 9 a washing waste liquid receiving tank, 12 a mixer with NQ bath solution water, 14 a separator,
16 is a wastewater receiving tank, and 18 is a treated NQ solution receiving tank.

Claims (1)

[Claims] 1. A method for purifying naphthoquinone obtained by catalytic gas-phase oxidation of naphthalene, which includes a solution in which the naphthoquinone is dissolved in a solvent that is not miscible with water and the pH thereof is maintained at 7 or more. A method for purifying naphthoquinone, which comprises bringing the naphthoquinone into contact with a moist aqueous sodium bicarbonate solution at a temperature below 90° C. and above room temperature to extract impurities in the naphthoquinone into the aqueous solution. 2. Consists of contacting a naphthoquinone solution with water at room temperature to 90°C to extract most of the organic acids such as phthalic acid and benzoic acid into water, and then contacting the solution with an aqueous solution containing sodium bicarbonate. A method according to claim 1.