JPS591251B2 - How to separate naphthoquinone and phthalic acid - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for producing naphthoquinone.

More specifically, the oxidation reaction product gas obtained in the catalytic gas phase oxidation reaction of naphthalene is washed with water, naphthoquinone and phthalic acid are collected as an aqueous slurry, and naphthoquinone is extracted from the slurry using a water-immiscible solvent. It relates to extraction and separation methods. Conventionally, there is a method for producing naphthoquinone as disclosed in JP-A-50-47937.
Contact air oxidation reaction gas of naphthalene is contacted with water to collect the main oxidation products, naphthoquinone and phthalic anhydride, as an aqueous slurry of naphthoquinone and phthalic acid, and the slurry is heated to 60-95°C. A method has been proposed in which, after dissolving phthalic acid, naphthoquinone is extracted and separated by contacting it with an organic solvent having a boiling point of 80 to 145°C, immiscible with water, and having a different specific gravity, and then concentrated to dryness. There is.

When carrying out such a process industrially, when crude naphthalene is used as the naphthalene, the catalytic gas phase oxidation product is
In addition to naphthoquinone and phthalic anhydride, a small amount of sulfuric anhydride is produced by the oxidation of sulfur compounds such as maleic anhydride and thionaphthene, which are contained as impurities in naphthalene.
In addition, in the method of producing naphthoquinone by catalytic gas phase oxidation of naphthalene, there is a method of catalytic oxidation in the presence of sulfur or sulfur compounds (Japanese Patent Application Laid-open No. 4935369), and generally the presence of sulfuric anhydride in the reaction product gas is known. I can't avoid it.

In particular, when the method of JP-A-50-47937 is carried out industrially, a process for producing a large amount of phthalic acid as a by-product is required, and in practice, an aqueous slurry consisting of phthalic acid and naphthoquinone is heated. A process is adopted in which phthalic acid is dissolved in water, naphthoquinone is extracted and separated using a solvent, the resulting aqueous phase is cooled to crystallize phthalic acid, and the crystals are separated by filtration.

In this case, a large amount of phthalic acid is still dissolved in the waste liquid, and in order to efficiently recover phthalic acid, a process is adopted to recycle the waste liquid, which results in by-product sulfuric acid and maleic acid. The operation is carried out at a point where the concentrations of sulfuric acid and maleic acid in the naphthoquinone slurry each reach several percent. As mentioned above, in the process of co-producing naphthoquinone and phthalic acid, when the method described in JP-A-50-47937 is carried out using crude naphthalene as a raw material, the purity yield of the naphthoquinone produced gradually decreases, In some cases, relatively low quality products with a purity of 93% can be obtained.

The present inventors investigated the deterioration of naphthoquinone as described above and found that naphthoquinone decomposes violently in an aqueous solution of a strong acid, particularly in the presence of sulfuric acid, at a temperature of 70° C. or higher.

That is, for example, 2.4% naphthoquinone and 6% phthalic acid.
Add 1.4% maleic acid and predetermined amounts of sulfuric acid to a 5% aqueous slurry, and set the treatment temperature to 8'C (line B) and 90°C (
When the A line) was stirred for 4 hours, the results shown in FIG. 1 were obtained. As is clear from these results, the presence of sulfuric acid significantly contributes to the decomposition of naphthoquinone, and surprisingly, in the absence of sulfuric acid, virtually no decomposition of naphthoquinone occurs regardless of the presence of maleic acid and phthalic acid. I knew it wouldn't happen.

Therefore, in order to neutralize the sulfuric acid contained, sodium hydroxide was added to adjust the pH of the test solution from 1.0 to 2.1, and stirring treatment was performed at 80°C for 4 hours. was found to inhibit the decomposition of naphthoquinone. (
(Point C in Figure 1) Also, in the step of heating the aqueous slurry of naphthoquinone and phthalic acid to dissolve the phthalic acid and bringing it into contact with an organic solvent to extract the naphthoquinone,
It is carried out at 110°C, preferably about 70 to 100°C.

Furthermore, in the collection process where the contact gas phase (usually air) oxidation reaction gas of naphthalene is brought into contact with water, the reaction gas temperature is 18
Since the temperature is in the range of 0 to 250 degrees Celsius, there is a possibility that the liquid temperature locally reaches a high temperature. Therefore, the present inventors investigated the influence of temperature on the decomposition of naphthoquinone.

i.e. naphthoquinone 2.401), phthalic acid 6.5
(f), sulfuric acid 1.20! ), when using a test solution consisting of 1.4% maleic acid and without adjusting the pH (Line A), the PH
Figure 2 shows the results of treatment for 4 hours when the pH was adjusted to 1.5 (line B) and when the pH was adjusted to 2.1 (line C). As a result, as shown by line A in FIG. 2, in the presence of sulfuric acid in the naphthoquinone aqueous phthalic acid solution slurry, naphthoquinone decomposes extremely violently when the liquid temperature exceeds 8°C. Therefore, the presence of sulfuric acid in the naphthoquinone slurry significantly accelerates the decomposition of naphthoquinone in the step of collecting water from the reaction gas of catalytic air oxidation of crude naphthalene, dissolving phthalic acid, and extracting naphthoquinone as described above. As a result of various studies on methods for inhibiting the decomposition of naphthoquinone, the present inventors discovered that acid components equivalent to 1 to 2 equivalents of by-produced sulfuric acid and 1 equivalent of maleic acid were oxidized to basic substances, such as hydroxylation. After adjusting the pH of the aqueous naphthoquinone and phthalic acid slurry from 1.2 to 2.5 using an aqueous sodium solution and allowing most of the naphthoquinone to migrate from the aqueous medium to the solvent layer at as low a temperature as possible, the phthalic acid The present invention was completed based on the discovery that the above object can be achieved by heating and dissolving the crystals and separating the naphthoquinone-containing solvent layer.

The present invention involves contacting naphthoquinone, phthalic anhydride, maleic anhydride, and sulfuric anhydride and/or a reaction product gas containing sulfuric acid obtained by catalytic gas phase oxidation of naphthalene with an aqueous medium to convert naphthoquinone and phthalic anhydride into naphthoquinone and phthalic anhydride. After collecting water as an aqueous slurry of phthalic acid and phthalic acid, naphthoquinone is extracted from the slurry using a solvent that is immiscible with water and that dissolves naphthoquinone (excluding linear and/or cyclic saturated hydrocarbon solvents). In the method for separating phthalic acid and phthalic acid, (1) the above aqueous slurry and a solvent are mixed and then heated to dissolve phthalic acid in water and extract naphthoquinone into the solvent to separate the phthalic acid aqueous solution and the naphthoquinone solution. To do, (
2) At least before heating the aqueous slurry as described above, the acid component present in the aqueous slurry or aqueous medium from 1 equivalent of sulfuric acid to substantially equivalent to 2 equivalents of sulfuric acid and 1 equivalent of maleic acid is added to the basic substance. The present invention relates to a method for separating naphthoquinone and phthalic acid.

Conventionally, when separating naphthoquinone and phthalic acid from an aqueous slurry of naphthoquinone and phthalic acid obtained by collecting water from the reaction product gas obtained by catalytic gas-phase oxidation of naphthalene, an alkali is added to separate phthalic acid from phthalic acid. There is a method of separating naphthoquinone by dissolving it as an acid salt.

For example, 1 Austrian Patent No. 242124 (196
(August 25, 1973) and 2 Japanese Patent Application Publication No. 132042/1973 (December 18, 1972). However, the purpose of both methods is to increase the solubility of phthalic acid in the slurry by converting it into a phthalate salt, and to separate naphthoquinone and phthalic acid at low temperatures, thus efficiently recovering phthalic acid. This clearly differs from the purpose of the present invention, as it is necessary to perform acid precipitation using a mineral acid such as sulfuric acid. That is, the object of the present invention is to use a basic substance to neutralize by-product sulfuric acid or maleic acid, which promotes the decomposition of naphthoquinone when dissolving and extracting phthalic acid at a temperature of 6°C or higher, and to eliminate the decomposition of naphthoquinone. The objective is to suppress this even at temperatures of 60°C or higher. For this purpose, it is sufficient to neutralize only the acid component corresponding to 1 equivalent of sulfuric acid present to 2 equivalents of sulfuric acid and 1 equivalent of maleic acid, in which case the phthalic acid remains unneutralized. Since it exists in the solution, most of the phthalic acid can be separated as crystals by cooling and crystallizing the aqueous layer after extracting naphthoquinone. Furthermore, to be specific, method 1 uses a mixture of naphthoquinone and phthalic anhydride at 80%
'C~ boiling point with water, convert phthalic anhydride to phthalic acid, cool and when cold (5~200C), add ammonia to pH5~
In method 2, an aqueous slurry of naphthoquinone and phthalic acid is neutralized to pH 2 to 5, preferably 3 to 4, using a basic substance. This is a method of separating naphthoquinone by adjusting the temperature to 60°C or less to convert phthalic acid into phthalic acid monosalt and solubilizing it. In the example, 4, which is the pH of phthalic acid monosalt, was used, and the pH was 3 or less. is considered to have little meaning from the purpose of method 2.

The disadvantage of these methods is that the ratio of naphthoquinone and phthalic anhydride obtained by catalytic gas-phase oxidation of naphthalene is equal or higher than that of phthalic anhydride, and a large amount of alkali is required to convert this into a monosalt. Moreover, in order to obtain phthalic acid, a mineral acid is also required for acid decomposition of the phthalic acid monosalt. In addition, the bottom liquid after removing phthalic acid also contains a large amount of salt, making it difficult to reuse in the process, and when discarded, dissolved phthalic acid is lost and the burden of pollution treatment increases.

In contrast, in the method of the present invention, the phthalic acid content is not substantially neutralized, and the amount of basic substance used is extremely small enough to only neutralize acid components such as sulfuric acid that promote the decomposition of naphthoquinone. This is sufficient, and involves heating to dissolve phthalic acid and extracting and separating naphthoquinone, which is different from the previous two methods, but there are differences in the purpose of neutralization, the separation process, and the temperature conditions. Others, large amounts of acid,
There are advantages such as no need for chemicals such as alkalis, and the ability to create a tarose system in which the liquid from the phthalate crystals after separation is recycled to the previous water washing and collection process.

In the method of the present invention, air is usually used as the oxygen-containing gas in the catalytic gas phase oxidation of naphthalene.

The gas produced by this catalytic gas phase oxidation reaction of naphthalene is usually 4
The gaseous naphthoquinone and phthalic anhydride contained in the generated gas are collected as an aqueous slurry of naphthoquinone and phthalic acid while being rapidly cooled. As the aqueous medium, usually the bottom liquid after separating the phthalic acid crystals is used, but water, an organic acid such as phthalic acid, or a salt or sulfate thereof may also be present. The method of contacting the oxidation product gas with the aqueous medium includes known methods such as a method using an atomizer, a method using a scrubber, and a method using submerged injection.

In the method of the invention, first an aqueous slurry of naphthoquinone and phthalic acid is mixed with a solvent.

In this case, a temperature high enough to dissolve the phthalic acid is not necessary, and the temperature is below about 60°C. The mixing method may be a stirring tank or a line mixer. By this mixing, most of the naphthoquinone is dissolved in the solvent, and the phthalic acid coexists as a solution or slurry. This mixture is then heated to a temperature at which the phthalic acid dissolves, but prior to heating, the phthalic acid is not substantially neutralized using a basic substance and is treated with acids stronger than phthalic acid, particularly sulfuric acid and maleic acid. Neutralize etc. Therefore, naphthoquinone, which easily decomposes when exposed to high temperatures above 60°C in an aqueous medium, especially in the presence of strong acids such as sulfuric acid, mostly transfers to the solvent at low temperatures below 60°C, dissolving phthalic acid. It is essentially absent from the aqueous medium at high temperatures when heated. Furthermore, since the sulfuric acid and maleic acid that decompose naphthoquinone in the aqueous medium are neutralized, the decomposition of naphthoquinone can be minimized. Thus, naphthoquinone is dissolved in the solvent and phthalic acid is dissolved in the aqueous medium.
Next, the solvent layer and the aqueous solution layer are separated, and naphthoquinone is produced from the solvent layer by removing the solvent, and phthalic acid is produced from the aqueous solution layer by cooling, crystallization, and filtration in an industrially advantageous manner. can.

Basic substances used in the method of the invention include basic alkali metal compounds, ammonia or its basic compounds, such as alkali metal oxides such as sodium oxide, potassium oxide; Alkali metal hydroxides such as; alkali metal carbonates such as sodium carbonate and potassium carbonate; alkali metal bicarbonates such as sodium bicarbonate and potassium bicarbonate; alkali salts of organic acids such as sodium phthalate and potassium maleate; Examples include weak acid salts such as aqueous ammonia, ammonia or its carbonates, and organic acid salts.

In addition, organic bases such as triethylamine can also be used if necessary. These basic substances can be used in a form suitable for the process, such as an aqueous solution or a powder, but it is usually preferable to use them as an aqueous solution.

In the method of the present invention, the amount of the basic substance added is at least 1 equivalent to 2 equivalents of by-produced sulfuric acid (1/2 mole to 1 mole of the sulfuric acid) and 1 equivalent of maleic acid (1/2 mole of the maleic acid). The amount required to neutralize the acid component equivalent to 2 moles) is sufficient, but it is of course possible to add an amount that also slightly neutralizes the phthalic acid component.

However, in the case where the phthalic acid content is neutralized, an extra base is used and the amount of circulating phthalic acid increases, which is disadvantageous. Figure 3 shows a study of the amount of basic substance added within the pH range. That is, FIG. 3 shows the relationship between the pH of an aqueous naphthoquinone slurry containing sulfuric acid, phthalic acid, and maleic acid and the decomposition rate of naphthoquinone. That is, the test liquid (a mother liquor obtained by cooling a hot phthalic acid aqueous solution after extracting and separating naphthoquinone and separating the crystallized phthalic acid), whose liquid composition was 1.5% phthalic acid, 1.4% maleic acid, 1.2% sulfuric acid) using an aqueous sodium hydroxide solution, PHL. O, l. 2.l. 5,l
．． 9,2. After adjusting the test solution to 2.4% naphthoquinone and 5.0 (!) phthalic acid, the test solutions were heated and stirred at 80° C. for 4 hours. As a result, PHL. 2. The decomposition of naphthoquinone can be achieved by adding an alkali to a pH value of 2.5 or more, especially when the pH value is 2.5 when neutralizing the acid equivalent to 2 equivalents of sulfuric acid and 1 equivalent of maleic acid present. In addition, it was found that alterations such as polycondensation such as dimerization and trimerization can be substantially suppressed. Therefore, the pH range to be neutralized is selected from 1.2 to 2.5, preferably 1.5 to 2.2. The basic substance can be added anywhere before the step of heating to dissolve the phthalic acid.

For example, methods include adding the bottom liquid after phthalic acid crystal separation before circulating it to the water collection process, or adding it to the aqueous slurry discharged from the collection process. An industrially convenient method is to cool the aqueous layer from which naphthoquinone has been extracted and separated, that is, the phthalic acid aqueous solution, and separate the phthalic acid crystals that crystallize by filtering or centrifugation. PHL in advance. 5 to 2.5, and then the adjusted solution is recycled and used as an aqueous medium in the water collection step. By adopting this method, the sulfur content in the raw material crude naphthalene is usually 1% or less, so even if the adjusted liquid is used in the water collection process, there will be no sudden change in the pH in this process. The method of the present invention can be said to be an extremely preferred method. In the method of the present invention, the temperature for neutralizing sulfuric acid and/or maleic acid or adjusting the pH value is selected from the range of 0 to 70°C, preferably 20 to 60°C. Organic solvents used in the method of the present invention include solvents that are immiscible with water and have a specific gravity different from that of the aqueous phthalic acid solution (excluding chain and/or cyclic saturated hydrocarbon solvents), such as aromatic solvents. Hydrocarbons can be freely selected from hydrocarbons or their derivatives, but if you take into account the temperature conditions in the extraction process, the solubility of naphthoquinone, the separability from an aqueous phthalic acid solution, or the ability to remove solvent from a naphthoquinone solution, it is recommended that the boiling point is 80. ~145°C hydrocarbons such as benzene, toluene or xylene are preferred;
Usually xylene is used.

The amount of hydrocarbon solvent used is 2
It is more than twice the weight, preferably 3 to 10 times the weight. The amount of water in the aqueous naphthoquinone and phthalic acid slurry in the method of the invention is between 60 and 110, preferably between 70 and 100.
The amount of phthalic acid that can be completely dissolved when heated to ℃, and the amount that is appropriate for separating naphthoquinone from an organic solvent solution during extraction of naphthoquinone, usually 7 to 30 mol of phthalic acid to be dissolved. twice, preferably 10 to 20 times by weight.

As water in this case, water or an aqueous medium normally used in the collection step is used as is. In the method of the present invention, the temperature at which phthalic acid is dissolved and naphthoquinone is extracted is the temperature at which the entire amount of phthalic acid present is dissolved, usually 60°C.
A temperature range from 'C to 110°C is chosen.

In the method of the present invention, it has become possible to raise the extraction temperature to 110° C. by transferring most of the naphthoquinone to the solvent at a low temperature.

Therefore, the concentration of the naphthoquinone solution or the phthalic acid aqueous solution can be higher than before. In order to efficiently recover phthalic acid, it is desirable to increase the concentration of phthalic acid, and therefore the higher the treatment temperature, the more preferable it is. The following will be adopted. On the other hand, below 6'C, the solubility of phthalic acid decreases and is not practical. Preferably 60 to 110°C, particularly preferably 70 to 1
It is 00°C. The naphthoquinone solution obtained in the present invention can be used as it is in the next step, for example, the anthraquinone production step by the Ziels-Alder method, or can be separated and obtained by cooling crystallization or distilling off the solvent.

On the other hand, since some naphthoquinone remains in the phthalic acid aqueous solution, it is usually brought into contact with a freshly supplied solvent, preferably in countercurrent, to extract the naphthoquinone component, and then phthalic acid is obtained from the resulting aqueous solution by a known method. Phthalic anhydride can be produced by conventional methods.

By carrying out the method of the present invention as described above, naphthoquinone and phthalic acid can be effectively produced industrially from the gas produced by catalytic gas-phase oxidation of naphthalene while preventing decomposition and deterioration of naphthoquinone using only a small amount of chemicals. can be advantageously separated and acquired.

The method of the present invention will be specifically explained using Examples.

Unless otherwise specified, "parts" and "%" used in the examples represent parts by weight and % by weight, respectively. Example 1 1.6 parts of naphthoquinone obtained by washing and collecting the reaction product gas obtained from the catalytic gas phase oxidation reaction of naphthalene, 4.0 parts of phthalic acid, 0.81 part of maleic acid, and 0.77 parts of sulfuric acid.
1.5 parts of a 4% aqueous sodium hydroxide solution was added dropwise to a slurry of naphthoquinone and phthalic acid (PHl.O) consisting of 1.5 parts and 40 parts of water with stirring at a liquid temperature of 30°C.

The pH was 1.5. Next, 4.6 parts of xylene is added to the slurry, the temperature is raised to 60 degrees Celsius, and the mixture is stirred to extract most of the naphthoquinone. The temperature of the slurry is raised to 95°C to completely dissolve the phthalic acid, and the xylene layer is separated.
The aqueous layer was then subjected to countercurrent extraction using 2 parts of xylene, combined with the previous xylene layer, washed with hot water, and then vacuumed to a degree of 60T0r.
Concentrate under reduced pressure and dry at r700C to give naphthoquinone 1.6
I got the department. The purity of this naphthoquinone was 97.00/). Comparative Example 1 In Example 1, pH was adjusted with 4% sodium hydroxide aqueous solution.
The same procedure was carried out except that no adjustment was made.

The yield of naphthoquinone is 1.6 parts, and its purity is 93
．． It was 1%. Example 2 A phthalic acid crystallization mother liquor consisting of 1.3 parts of phthalic acid, 1.2 parts of maleic acid, 1.3 parts of sulfuric acid and 70 parts of water was heated to a liquid temperature of 4.
At C, 4% aqueous sodium hydroxide solution was added under stirring to adjust the pH to 1.9.

Next, the reaction product gas containing 5.5 parts of phthalic anhydride and 3.0 parts of naphthoquinone obtained by the catalytic gas phase oxidation reaction of naphthalene was cooled to 180° C. using a gas cooler, and then the above PH adjustment liquid was added. A slurry of naphthoquinone and phthalic acid (PHl. 7) was obtained. 8.5 parts of xylene was added to the slurry, and the temperature was raised to 60°C while stirring to extract most of the naphthoquinone.

Furthermore, the temperature of the slurry was raised to 95°C to completely dissolve the phthalic acid, and the xylene layer was separated. The aqueous layer was countercurrently extracted using 3 parts of xylene, combined with the previously separated xylene layer, and washed with hot water.
The mixture was concentrated to dryness under reduced pressure to obtain 2.6 parts of naphthoquinone. The purity of this naphthoquinone was 97.1%. The aqueous layer was cooled to 40° C. and the crystallized phthalic acid was separated by F. The crystallization mother liquor obtained can be used as a washing liquid for collecting the product gas obtained in the next catalytic gas phase oxidation reaction of naphthalene. Example 3 At a liquid temperature of 40°C, 1.5% ammonia water was added to the phthalic acid crystallization mother liquor used in Example 2 with stirring to give PHL.
Adjusted to 5.

Then, a contact gas phase reaction gas of naphthalene having the same composition and temperature as in Example 2 was introduced into the crystallization mother liquor after the above pH adjustment to obtain a slurry of naphthoquinone and phthalic acid. Thereafter, treatment was performed according to the method in Example 2 to obtain 2.6 parts of naphthoquinone. The purity of this naphthoquinone is 96.4
It was %. Comparative Example 2 The same procedure as in Example 3 was carried out except that the pH was not adjusted.

The yield of the naphthoquinone obtained was 2.5 parts, and its purity was 89.5(f).

[Brief explanation of drawings]

Figure 1 shows the effect of sulfuric acid concentration on the decomposition of naphthoquinone in an aqueous phthalic acid solution.

Claims (1)

[Scope of Claims] 1. A reaction product gas containing naphthoquinone, phthalic anhydride, maleic anhydride, and sulfuric anhydride and/or sulfuric acid obtained by catalytic gas phase oxidation of naphthalene is brought into contact with an aqueous medium, and naphthoquinone and phthalic anhydride are After the acid is collected in water as an aqueous slurry of naphthoquinone and phthalic acid, a solvent that is immiscible with water and that dissolves the naphthoquinone (excluding linear and/or cyclic saturated hydrocarbon solvents) is extracted from the slurry. In the method for separating naphthoquinone and phthalic acid, (1) the above aqueous slurry and a solvent are mixed and then heated to 60 to 110°C to dissolve phthalic acid in water and extract naphthoquinone into the solvent. (2) separating the aqueous acid solution and the naphthoquinone solution; (2) equivalent to substantially 2 equivalents of sulfuric acid and 1 equivalent of maleic acid; A method for separating naphthoquinone and phthalic acid, which is characterized by neutralizing the acid component using a basic substance. 2. The aqueous phase from which naphthoquinone has been extracted and separated, that is, the phthalic acid aqueous solution, is cooled to separate the crystallized phthalic acid crystals, and the resulting filtrate is used as an aqueous medium for water collection of the reactive product gas from the catalytic gas-phase oxidation of naphthalene. The method according to claim 1, wherein the method is used repeatedly as a method. 3. Adjust the pH of the filtrate from which the phthalic acid crystals have been separated from 1.5 to 2.
5. The method according to claim 2, wherein the adjusted liquid is used as an aqueous medium for water collection.