JPH0491053A - Production of aromatic carboxylic acids - Google Patents

Abstract

PURPOSE:To efficiently produce an aromatic carboxylic acid in high yield in oxidizing coal tar pitch with O2 or an O2-containing gas in an aqueous solution of sodium hydroxide by diluting coal tar pitch with a petroleum-based heavy oil followed by oxidizing. CONSTITUTION:Coal tar pitch is used as a raw material, then diluted with a petroleum-based heavy oil, oxidized with oxygen or an oxygen-containing gas in an aqueous solution of sodium hydroxide to economically give an aromatic carboxylic acid. By this method, difficult preliminary treatment is not required, an expensive potassium hydroxide is not used and retention of unreacted pitch can be prevented. The aromatic carboxylic acid is useful as a synthetic raw material for polymers, plasticizers, dye, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing aromatic carboxylic acids. The aromatic carboxylic acids in the present invention refer to aromatic rings of substituted or unsubstituted aromatic hydrocarbons.

Refers to a compound or a mixture thereof in which one or more carboxyl groups are directly bonded.

Specifically, benzoic acid, toluic acid, phthalic acid, isophthalic acid, terephthalic acid, methylbenzenedicarboxylic acid, trimellitic acid, hemimellitic acid, trimesic acid, methylbenzenetricarboxylic acid, merophanic acid, pyromellitic acid, and brenit. acids, substituted or unsubstituted benzenecarboxylic acids such as henzenebentacarboxylic acid and hexacarboxylic acid, biphenylcarboxylic acids such as biphenylmonocarboxylic acid, biphenyldicarboxylic acid, biphenyltricarboxylic acid, 1-naphthoic acid, ? - Substituted or unsubstituted naphthalene carboxylic acids such as naphthoic acid, naphthalenedicarboxylic acid, methylnaphthalenedicarboxylic acid, naphthalenetricarboxylic acid, naphthalenetetracarboxylic acid, phenanthrene monocarboxylic acid, methylphenanthrene monocarboxylic acid, anthracene monocarboxylic acid, methyl Examples include various compounds such as l-substituted or non-substituted tricyclic androaromatic carboxylic acids such as anthracene monocarboxylic acid, or mixtures of some or all of these.

The aromatic carboxylic acids mentioned above can be used as polymers, plasticizers, and dyes.
It is a compound useful as a raw material for synthesis of etc.

BACKGROUND OF THE INVENTION Coal oxidation has been known as a method for producing aromatic carboxylic acids at low cost. In other words, coal is oxidized with nitric acid,
Alternatively, it is obtained as a mixture of various aromatic carboxylic acids by oxygen-strict conditions in an alkaline aqueous solution (for example, Organic Synthesis Research Journal, 17, +09 (1959) and rnd,
Eng, chem, 44.2784 (1952)
).

On the other hand, methods using similarly inexpensive coal tar pitch as a raw material instead of coal are also being considered.
,Am,Che++,Soc, ,61.2398(1
939)), and (2) a method of pre-oxidizing with a resistant agent and then oxidizing with oxygen in an alkaline aqueous solution (US Patent No. 248174).
0), (2) A method of oxidizing coal tar pitch with oxygen in an aqueous sodium hydroxide solution (Japanese Unexamined Patent Publication No. 1-215887), etc. are known.

That is, in (2), pitch was reacted at 250°C for 24 hours in an aqueous potassium hydroxide solution of 17 mol-KOH/kg-H2O under an oxygen partial pressure of 10 kg/cm2, and oxalic acid and aromatic carboxylic acids were reacted at 6 wt% and 30 wt%, respectively.
It is obtained in wt%. In addition, in ■, after preliminary oxidation of Beech 7 with sulfur trioxide, this was mixed with 12.5 mol-NaOH/k
g-H2O (7) in aqueous sodium hydroxide solution, 250°C
Oxygen was introduced to make the total pressure 750 psi, and the reaction was carried out for 4 hours to obtain a mixture of oxalic acid, acetic acid, and aromatic carboxylic acid at 60 wt %. Furthermore, in (1), the concentration of the sodium hydroxide aqueous solution is kept at a relatively low concentration of 1 to 5 /kg-870, thereby suppressing the amount of oxalic acid produced as a by-product.

Problems to be Solved by the Invention When oxidizing coal, oxidation conditions are carefully studied,
Conditions have been found that increase the yield of aromatic carboxylic acids. On the other hand, when coal tar pitch is used as a raw material, the structures of coal and coal tar pitch are quite different, so the reaction conditions when coal is used as a raw material are directly applied to when coal tar pitch is used as a raw material. In addition to this, the above-mentioned conventional methods have many problems from the viewpoint of industrialization. In other words, expensive potassium hydroxide is used in (■). ■ requires difficult preliminary processing. In addition, there was a problem in (1) that unreacted coal tar pitch often remained as a residue.

The object of the present invention is to provide a method for economically producing aromatic carboxylic acids using coal tar pitch as a raw material, without difficult pretreatment or using expensive potassium hydroxide, and by preventing the unreacted pitch from remaining. It is about providing.

Means for Solving the Problems The present invention involves diluting coal tar pitch with heavy petroleum oil when producing aromatic carboxylic acids by oxidizing coal tar pitch with oxygen or oxygen-containing gas in sodium hydroxide. 4. Post-oxidation. This is a method for producing aromatic carboxylic acids having a ν characteristic.

As the petroleum heavy oil used in the present invention, atmospheric pressure distillation residue oil, vacuum distillation residue oil, fluid catalytic cracking residue oil, asphalt, etc. can be suitably used.

In the present invention, the dilution ratio of the raw material coal tar pitch with petroleum heavy oil is the weight ratio of coal tar pitch to petroleum heavy oil of 5:1 to 1:5, preferably 3:1 to 1:3.
is within the range of The dilution rate varies depending on the physical properties of coal tar, thi, and petroleum heavy oil, and if the dilution rate is extremely large, oxidation becomes easy, but the yield of the target aromatic carboxylic acids is low and it is not economical. #i If the dissolution rate is too small, oxidation will be difficult to proceed and the amount of unreacted pitch will increase.
On the contrary, the yield of aromatic carboxylic acids decreases.

The concentration of sodium hydroxide in the present invention is 0.5-20
mol/kg-1 (, o, preferably 1 to IO mol
/kg-H70. If the concentration of the sodium hydroxide aqueous solution is lower than 0.5 mol/kg-H2O, the oxidation reaction will be extremely slow midway through, resulting in a low yield of the target aromatic carboxylic acids, which is not economical.
If the concentration is higher than 1/kg-) 1.0, the by-product of carbon dioxide gas will be significant, and the retention of aromatic carboxylic acids will actually decrease.

The reaction temperature in the present invention is in the range of 230°C to 300"C, preferably 240 to 280°C. 230"C
At lower temperatures, the reaction rate is extremely slow and impractical; on the other hand, at high temperatures exceeding 300°C, oxidation to carbon dioxide gas becomes significant and the yield of aromatic carboxylic acids decreases.

In the present invention, coal tar pitch is oxidized with oxygen or an oxygen-containing gas. As the oxygen-containing gas, mixtures of oxygen and inert gases that do not participate in the reaction, such as air, mixtures of nitrogen and oxygen, mixtures of argon and oxygen, etc., can be widely used, but from an economic point of view, Air or a mixture of nitrogen and oxygen is preferable, and the partial pressure of oxygen is between 20 and 80.
kg/c■2 Preferably 30~? It is in the range of Okg/c. Within this range, fluctuations in the results of one reaction will be small, and the purpose of the present invention can be achieved in either case.

In the oxidation reaction of the present invention, one reaction proceeds quickly if the contact efficiency between the coal tar pitch, the petroleum heavy oil mixture, oxygen or oxygen-containing gas, and the sodium hydroxide aqueous solution is good. Therefore, when implementing the method of the present invention,
It is preferable to thoroughly mix the above-mentioned king mixture by stirring or shaking.The reaction time depends on the mixing conditions, but if the mixing is sufficiently efficient, it is usually within 3 hours. However, if the reaction time is longer than this, the reaction performance will deteriorate.

From the reaction mixture thus obtained, the aromatic carboxylic acids targeted by the present invention can be isolated, for example, as follows. That is, the reaction mixture is precipitated with a mineral acid such as hydrochloric acid or sulfuric acid, the resulting aromatic carboxylic acids are extracted with an organic solvent such as ethyl acetate or methyl ethyl ketone, and the extract is concentrated to obtain aromatic carboxylic acids. If oxalic acid is contained, it can be removed in advance by a fractional precipitation separation method or the like.

Function: In the reaction of the present invention, coal tar pitch is oxidized with oxygen by a sodium hydroxide probe to give aromatic carboxylic acids, but since coal tar pitch is mainly composed of polycyclic aromatic hydrocarbons, The intermolecular forces between them are strong, and even if they are stirred during the reaction, their overlapping aromatic rings result in insufficient dispersion at the molecular level, poor contact with alkaline aqueous solutions and oxygen molecules, and a slow oxidation rate.

On the other hand, petroleum-based heavy oils retain more aliphatic structures than coal tar peas and chili, are easily dispersed in alkaline aqueous solutions, and are highly reactive.

Therefore, when coal tar pitch is used as a petroleum-based heavy oil, the intermolecular force between polycyclic aromatic rings is weakened, making it easier to contact with aqueous alkaline solutions and oxygen molecules, and the polycyclic aromatic hydrocarbons in coal tar pitch are It is thought that this makes it easier to oxidize aromatic carboxylic acids, making it possible to efficiently produce aromatic carboxylic acids.

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Examples Examples 1 to 3 In a stainless steel beaker, 20 g of sodium hydroxide (0,
5 mol) in 100 g of water, 5 go 1-Na
An aqueous sodium hydroxide solution with a concentration of OH/kg-H20 was prepared. 4 g of a mixture of coal tar pitch and petroleum heavy oil asphalt was added to this, and the beaker was placed in an autoclave equipped with a stirrer. The mixing ratio of coal tar pitch and asphalt was as in Example 1.2.
．． 3: 3:1 respectively. After exchanging nitrogen, the autoclave was sealed at a ratio of l:11:3 (weight ratio), and the autoclave was heated and heated while stirring.

The stirring speed was 150 rpm and the reaction temperature was 265.
After raising the temperature to ℃, 50kg/c+w2 of oxygen was injected,
Stir at the same temperature for 3 hours. During this time, if the pressure decreased, oxygen was pumped in to keep the total pressure constant. After cooling to room temperature, the pressure was returned to normal, the reaction mixture was dissolved in water to form a bifurcated solution, and after standing still, the product contained was analyzed by the following method.

(2) Oxalic acid: 50 mm of supernatant liquid was collected and made into a weakly acidic solution of 6 mal/hydrochloric acid. After removing dissolved carbon dioxide, a 20-liter aqueous solution of calcium chloride was added to precipitate. 6 mol of this
/fL ammonia wood 3- is added to make it slightly alkaline, 6
After heating at 0° C. for 1 hour, the precipitate was filtered off. 0.
After washing with 1 layer of/i ammonia water, 1 at 60-70℃
A colored solution was obtained by adding 100% of a 0% aqueous sulfuric acid solution. After decolorizing this with powdered activated carbon, the oxalic acid contained therein was titrated with a 1/3 ON potassium permanganate aqueous solution.

(2) Aromatic carboxylic acids: The supernatant liquid 50- was collected, concentrated hydrochloric acid was added thereto to make it acidic with 1 intestine o1/in hydrochloric acid, and the mixture was heated for 2 to 3 hours. The precipitate that separated out was classified into 1 mol/! ; Washed with L-hydrochloric acid until the solution reached 100 wJl. After the obtained liquid e was saturated with sodium chloride, extraction was repeated with 100 liters of methyl ethyl ketone (MEK) to obtain about 200 liters of the extract. This was concentrated under reduced pressure, and the residue was
K60- was added to remove insoluble matter. 1! The liquid was concentrated under reduced pressure, and the residue was soaked with dry silica gel until constant humidity was reached.
MEK extract was obtained by drying under reduced pressure for ~7 days. Since this is a mixture of aromatic carboxylic acids and oxalic acid, the amount of produced aromatic carboxylic acids was determined by subtracting the amount of oxalic acid. The content of shuchu was determined by dissolving this MEK extract in methanol to make the total amount 25-, and determining the content using the method described above. Table 1 shows the results.

Incidentally, the aromatic carboxylic acids obtained in Examples 1 to 3 are all mixtures of various compounds. This aromatic carboxylic acid was methyl esterified by a conventional method, and its components were analyzed by GC-MS. As a result, it was found that the following compounds were mainly contained.

Benzoic acid, toluic acid, phthalic acid, terephthalic acid, isophthalic acid, methylbenzenedicarboxylic acid, 1-naphthoic acid, 2-naphthoic acid, biphenylcarboxylic acid, trimellitic acid, hemimellitic acid, trimesic acid, methylbenzenedicarboxylic acid, biphenyldicarboxylic acid, naphthalene dicarboxylic acid, methylnaphthalene dicarboxylic acid, pyromellitic acid, brenitic acid, merophane acid, biphenyltricarboxylic acid, phenanthrene monocarboxylic acid, anthracene monocarboxylic acid, naphthalene tricarboxylic acid,
Benzenepentacarboxylic acid, benzenehexacarboxylic acid, methylphenanthrene monocarboxylic acid, methylanthracene monocarboxylic acid.

Comparative Example 1.2 A similar reaction was carried out using only coal tar pitch in Comparative Example 1 and only alphalt in Comparative Example 2 instead of the mixture of coal tar pitch and asphalt in Examples 1 to 3. The results are also listed in Table 1. In Comparative Example 1, 37% of the coal tar pitch remained unreacted, whereas in Examples 1 to 3, the amount was as small as 27% and 5.0%, respectively.

In Comparative Example 2, the yield of the target water-soluble aromatic acid was 3.
The yield is as low as 0%, which is disadvantageous compared to the yields of Examples 1 to 3, which are all 50% or more.

(Hereinafter in the margin) Effects of the Invention By using the method of the present invention, aromatic carboxylic acids can be suitably obtained from coal tar pitch as a raw material.

Claims (1)

[Claims] When producing aromatic carboxylic acids by oxidizing coal tar pitch with oxygen or an oxygen-containing gas in an aqueous sodium hydroxide solution, an aromatic compound characterized by diluting coal tar pitch with petroleum-based heavy oil and then oxidizing it. Method for producing carboxylic acids.