JPH02270830A - Production of phenols and hydroxybenzoic acids - Google Patents

Abstract

PURPOSE:To obtain hydroxybenzoic acids by bringing tar prepared by carbonization of coal into contact with an aqueous solution containing an alkali sulfate, etc., in the presence of Ca(OH)2 under heating to give phenols as alkaline metal salts and reacting the phenols with CO2. CONSTITUTION:Tar prepared by carbonization of coal, preferably after concentration of phenols by a means such as distillation, is brought into contact with an aqueous solution containing at least one selected from an alkali sulfate, an alkali sulfite and an alkali hydrogensulfite in the presence of Ca(OH)2 at 30 deg.C - the boiling point for 30 minutes to 5 hours to give phenols as alkali metal salts. Then the phenols are reacted with CO2 and hydroxybenzoic acids are extracted as alkali metal salts. The reaction products are precipitated with an acid by adding sulfuric acid and/or sulfurous acid and the phenols, the hydroxybenzoic acids, the alkali sulfate, etc., are recovered. The aimed substances can be formed readily and inexpensively.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention has a wide range of uses as a disinfectant, a raw material for synthetic resins, a raw material for plasticizers, and a raw material for pharmaceuticals and paints. The present invention relates to a method for producing phenol, cresol, xylenol, etc.) and hydroxybenzoic acids (p-hydroxybenzoic acid, salicylic acid, etc.).

<Prior Art> Phenols are contained in tar obtained by carbonization of coal. When this tar is distilled, phenols are distilled out along with naphthalene. This naphthalene fraction contains about 5 to 20% of phenols, although it varies depending on the properties of the raw material coal, carbonization temperature, distillation conditions, etc.

Conventionally, the following methods have been widely used to produce phenols from this naphthalene fraction. First, the naphthalene fraction is brought into contact with an aqueous solution of alkali hydroxide such as sodium hydroxide to convert the phenols into alkali metal salts.

This is extracted into an aqueous solution and separated from the oil layer.

Next, the extracted alkali metal salts of phenols are decomposed with acid to recover phenols.

In such a method for producing phenols, the generation of an emulsion is observed when the oil layer and the aqueous alkali metal salt solution of extracted phenols are separated. For this reason, it is necessary to use a multi-stage decanter for this liquid-liquid separation, or to leave it standing for a long time. Furthermore, this method consumes a large amount of expensive alkali hydroxide (sodium hydroxide, etc.). Therefore, in order to reduce the amount of alkali hydroxide used, the following measures are being taken. That is, alkali metal salts of phenols are decomposed by carbon dioxide gas to generate alkali metal carbonates (sodium carbonate, etc.) and free phenol. Next, the alkali hydroxide is recovered by reacting the alkali metal carbonate with calcium hydroxide.

In addition, as a method for producing alkali metal salts of phenol,
Alkali metal salts of sulfite (Special Publication No. 40-3767, Special Publication No. 22970/1972) and alkali sulfate (Special Publication No. 43-22970)
-15808, JP-A-48-28445) is heated and brought into contact with phenol in the presence of calcium hydroxide.

<Problem that the invention seeks to solve> The conventional method for producing phenols is as described above.

In the method of producing phenols while recovering alkali hydroxide, the alkali metal salt of phenol is not completely decomposed with carbon dioxide gas, and further decomposition with sulfuric acid is required to recover the phenol. , the process becomes quite complicated. Even if such recovery is performed, there are many problems, such as the proportion of alkali hydroxide in the raw material cost still being high.

The present invention has been made in view of the above facts, and provides a method for producing phenols and hydroxybenzoic acids from tar obtained by carbonization of coal without using expensive alkali hydroxides (sodium hydroxide, etc.). With the goal.

Means for Solving the Problems〉 The conventional method for producing an alkali metal salt of phenol is to heat and heat an alkali metal salt of sulfite or an alkali metal salt of sulfuric acid with phenol in the presence of calcium hydroxide.
The method for obtaining an alkali metal salt of phenol by contacting is as follows:
When the naphthalene fraction of tar obtained by carbonization of coal (hereinafter referred to as coal tar) is used as a raw material, the phenols (active ingredients such as phenol, cresol, and xylenol) contained in the naphthalene fraction of coal tar are ), but it was unclear whether alkali metal salts could be formed by these methods. but,
It was thought that if it was possible to form alkali metal salts of phenols using this method, the phenols contained in the naphthalene fraction of coal tar could be easily recovered at low cost.

Therefore, the present inventors investigated extracting phenols from the naphthalene fraction of coal tar using an aqueous solution of an alkali metal salt of sulfite and an alkali metal salt of sulfuric acid in the presence of calcium hydroxide. As a result, it was found that cresol, xylenol, etc., together with phenol, form their alkali metal salts, and that these can be easily obtained in high yield. Furthermore, the present invention was completed based on the discovery that emulsion, which is a problem during liquid-liquid separation, does not occur at all.

That is, the first aspect of the present invention is to produce phenols from tar obtained by carbonization of coal, in which one or more selected from alkali sulfate, alkali sulfite, and alkali hydrogen sulfite are used in the presence of calicylum hydroxide. The present invention provides a method for producing phenols, which is characterized in that phenols are extracted as alkali metal salts by heating and contacting an aqueous solution containing tar with tar.

In addition, the second aspect of the present invention is that when producing hydroxybenzoic acids from tar obtained by carbonization of coal,
In the presence of calcium hydroxide, tar is heated and brought into contact with an aqueous solution containing one or more selected from alkali sulfates, alkali sulfites, and alkali hydrogen sulfites to generate alkali metal salts of phenols. The present invention provides a method for producing hydroxybenzoic acids, which comprises reacting an alkali metal salt of hydroxybenzoic acid with carbon dioxide and extracting the hydroxybenzoic acid as an alkali metal salt.

The present invention will be explained in detail below.

In the present invention, when extracting phenols from coal tar as alkali metal salts, an aqueous solution containing one or more selected from alkali sulfates, alkali sulfites, and alkali hydrogen sulfites is used together with calcium hydroxide.

Examples of the alkali sulfate, alkali sulfite, and alkali hydrogen sulfite include sodium sulfate, potassium sulfate, lithium sulfate, rubidium sulfate, cesium sulfate, sodium sulfite, potassium sulfite, sodium hydrogen sulfite, and potassium hydrogen sulfite. These alone can be 2
It may be a mixture of more than one species. It can be selected as appropriate depending on the purpose of use, the price of metal salts, the ease of manpower, etc. Furthermore, in the method of the present invention, the alkali sulfate, alkali sulfite, and alkali hydrogen sulfite can be recovered from the reaction system, and thus the recovered substances may be reused.

Calcium hydroxide is used in a dissolved or suspended state in water. Therefore, the object of the present invention can be achieved not only by using calcium hydroxide but also by using stalactite or calcium oxide.

Coal tar to be extracted may be produced by carbonization of coal and used as it is, but as with conventional methods, it is better to use it after concentrating the phenols by means such as distillation, which will save the reactor. Preferable for reasons such as size.

The reaction for producing alkali metal salts of phenols involves heating and contacting coal tar containing phenols with an aqueous solution containing one or more selected from alkali sulfates, alkali sulfites, and alkali hydrogen sulfites in the presence of calcium hydroxide. It progresses more easily. Reaction temperature is 30℃
It may be carried out at an appropriate temperature between - boiling point Ili temperature.

At temperatures below 30°C, the reaction is slow and therefore uneconomical. The reaction time is about 30 minutes to 5 hours, depending on the reaction temperature.

As described above, alkali metal salts of phenols are produced using coal tar as a raw material.

The state after the reaction consists of an organic phase, an aqueous phase, and a solid, and the alkali metal salt of phenol is contained in the aqueous phase. Therefore, filtration and phase separation are performed to obtain an aqueous phase.

The first aspect of the present invention is a method for producing phenols, in which acid precipitation is performed by adding sulfuric acid and/or sulfurous acid to the aqueous phase obtained as described above, and together with the phenols, alkali sulfate and sulfite Collect alkali and bisulfite alkali.

Note that acid precipitation can be performed using other acids, but in consideration of reuse of raw materials, it is preferable to use sulfuric acid and/or sulfurous acid.

Phenols obtained by the method of the present invention include phenol, cresol, xylenol, and ethylphenol.

A second aspect of the present invention is a method for producing hydroxybenzoic acids, in which carbon dioxide is reacted with an alkali metal salt of phenol obtained by evaporating water from the aqueous phase obtained as described above. After producing alkali metal salts of hydroxybenzoic acids, acid precipitation is performed by adding sulfuric acid and/or sulfurous acid, and alkali sulfates, alkali sulfites, and alkali hydrogen sulfites are recovered together with hydroxybenzoic acids.

Note that acid precipitation can also be performed using other acids,
Considering the reuse of raw materials, it is preferable to use sulfuric acid and/or sulfurous acid.

The reaction temperature of carbon dioxide is 100°C or higher, preferably 20°C.
0 to 500℃, carbon dioxide pressure is normal pressure to 50kg/cm
2 (G), preferably normal pressure to 15 kg/cm' (G
)And it is sufficient.

The carbon dioxide used in the present invention may be diluted or mixed with a gas that is inert to the raw materials and products under the present reaction conditions, such as nitrogen, hydrogen, helium, argon, and carbon oxide. , hydrocarbons, etc. may be mixed. In addition, blast furnace gas produced as a by-product in steel mills also contains carbon dioxide and can be used economically.

When using such a carbon dioxide mixed gas, the partial pressure of carbon dioxide is normal pressure to 50 kg/cm2 (G),
Preferably, the pressure is normal pressure to 15 kg/C1n' (G).

In the second embodiment of the present invention, the entire process may be carried out either batchwise or continuously, or in a combination of both, although the continuous method is preferred from the viewpoint of industrial significance.

In addition, the reaction between the alkali metal salt of phenol and carbon dioxide after water is removed is preferably performed with stirring, and in order to improve contact between the contents, high-speed rotation and/or vigorous shaking is performed. It is more preferable, and it is even more preferable to use conditions that generate turbulent flow.

The hydroxybenzoic acids obtained by the method of the present invention include p-hydroxybenzoic acid, salicylic acid,
These include 3,5-dimethyl-4-hydroxybenzoic acid and methylsalicylic acids.

Note that these hydroxybenzoic acids can be selectively produced mainly by selecting the type of alkali metal. For example, if phenols are recovered as potassium salts, p-hyroxybenzoic acid can be selectively obtained, and if phenols are recovered as sodium salts, salicylic acid and methylsalicylic acids can be obtained.

<Example> EXAMPLES The present invention will be specifically explained below with reference to Examples.

(Example 1) Naphthalene fraction of coal carbonization tar (in 1 kg, phenol 275 mmol, cresol 312 mmol 1,
xylenol (116 mmol) 263 g, calcium hydroxide 16.3 g, potassium bisulfite 240 g
, put 200 mfl of water into a glass round bottom flask,
Reflux with stirring for an hour. When the product was filtered, the filtrate was separated into two layers, and no emulsion was observed. The organic phase of the filtrate was separated and removed, and the aqueous phase was acidified and analyzed. The yields of phenol, cresol, and xylenol were 90%, 80%, and 5%, respectively.
4%, and the total failure rate of phenols reached 78%.

(Example 2) Same as Example 1, to 90g of naphthalene fraction of carbonized tar,
Calcium hydroxide 21g 1 Potassium sulfate 4.7g Water 5
0ml was added and refluxed for 1 hour with stirring. No emulsion was observed, and when analyzed in the same manner as in Example 1, the yields of phenol, cresol, and xylenol were 76%, 41%, and 17%, respectively, and the total loss rate of phenols was 53%. Ta.

(Example 3) The reaction was carried out in the same manner as in Example 2, except that the reaction was carried out at 90°C and irradiated with ultrasonic waves. No emulsion was observed, and when analyzed in the same manner as in Example 1, the yields of phenol, cresol, and xylenol were each 82%.
, 49% and 24%, and the total failure rate for phenols was 59%.
%Met.

(Example 4) Water was evaporated from the aqueous solution of the potassium salt of phenols obtained in Example 1, and the solution was dried. NeoSK-1400 was added to 28 g of the potassium salt of phenols thus obtained.
(manufactured by Souken Kagaku Co., Ltd.), and using a 100 m1 glass separable flask, 200 m1/200 m2 of carbon dioxide was added.
The reaction was carried out at 300° C. for 1 hour while flowing the mixture at a rate of 1.5 min. When the product was dissolved in water, acidified, and analyzed, it was found that p-hydroxybenzoic acid was produced in a yield of 75% (based on potassium phenol).

<Effects of the Invention> The method for producing phenols from coal tar according to the present invention includes conventional extraction with sodium hydroxide (first stage reaction) and recovery of phenols by acid precipitation (second stage reaction).
, extraction with an aqueous solution containing calcium hydroxide and one or more selected from alkali sulfate, alkali sulfite, and alkali hydrogen sulfite for the three-step process of recovering sodium hydroxide with calcium hydroxide (third-stage reaction) A simpler two-step process consisting of recovery of phenols by acid precipitation and recovery of one or more types selected from the alkali sulfate, alkali sulfite, and alkali hydrogen sulfite (second reaction). This process makes it possible to easily produce important chemicals such as phenol, cresol, and xylenol according to the present invention.

In addition, the method for producing phenols from coal tar according to the present invention does not use expensive sodium hydroxide, etc., as in conventional methods, but uses inexpensive calcium hydroxide and alkali sulfate, which can be recovered from the system and recycled. , alkali sulfite, and alkali hydrogen sulfite, the present invention allows important chemical products such as phenol, cresol, and xylenol to be produced at low cost.

Similarly, according to the present invention, hydroxybenzoic acids such as p-hydroxybenzoic acid and salicylic acid can be easily produced at low cost.

Claims (2)

[Claims] (1) When producing phenols from tar obtained by carbonization of coal, the tar is heated and brought into contact with an aqueous solution containing one or more selected from alkali sulfate, alkali sulfite, and alkali hydrogen sulfite in the presence of calcium hydroxide. A method for producing phenols, which comprises extracting phenols as alkali metal salts. (2) When producing hydroxybenzoic acids from tar obtained by carbonization of coal, the tar is heated and brought into contact with an aqueous solution containing one or more selected from alkali sulfate, alkali sulfite, and alkali hydrogen sulfite in the presence of calcium hydroxide. Production of hydroxybenzoic acids, which is characterized in that the alkali metal salts of phenols are produced by reacting the alkali metal salts of phenols with carbon dioxide, and the hydroxybenzoic acids are extracted as alkali metal salts. Method.