JP2568318B2 - Recovery method of high boiling tar acid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering a high-boiling tar acid, and more particularly to a method for recovering a high-viscosity distillation residue generated from the distillation of tar acid recovered from coal tar. The present invention relates to a method for recovering tar acid.

[0002]

2. Description of the Related Art As a method for recovering tar acid from coal tar, generally, among fractionated oils obtained by distilling coal tar, an oil containing a large amount of tar acid is brought into contact with an aqueous solution of caustic soda to remove tar. The aqueous phase was extracted as an alkali salt of an acid (usually sodium tarate), and this was extracted with carbon dioxide and / or
Alternatively, it is decomposed with sulfuric acid and recovered as a crude tar acid. The resulting crude tar acid is refined and distilled several times to obtain a purified tar acid mainly composed of phenol, cresol and xylenol. The heavy distillation residue generated during this purification distillation contains a high-boiling tar acid such as xylenol, which is a useful component, but has a viscosity of 10 to 10,000.
Since it cannot be recovered by distillation due to its high cP (180 ° C.), it is usually mixed with tar pitch or creosote oil or returned to the coke oven, but in any case, it is economically disadvantageous. There was a problem.

[0003]

A method for recovering a high boiling tar acid from a highly viscous tar acid distillation residue includes the following.
A method of mixing or contacting a distillation residue with a caustic aqueous solution to impart or dissolve fluidity, and then decomposing with mineral acid to reduce the viscosity, followed by distillation, and mixing and contacting the distillation residue with an aromatic hydrocarbon oil to form an oil phase. After the extraction, the oil phase extract is extracted with water with a caustic aqueous solution, the oil phase extract is extracted with water with a caustic aqueous solution, and the water extract is subjected to mineral acid decomposition to reduce the viscosity and distilled. A method in which an aromatic hydrocarbon oil is mixed and contacted with a distillation residue, followed by mixing and contacting with an aqueous solution of caustic alkali to extract an aqueous phase, and the aqueous phase extract is treated with a mineral acid to reduce the viscosity and distillation. A method in which an aromatic hydrocarbon oil is mixed and brought into contact with a distillation residue to extract oil, and then the oil phase extract is distilled.
186) a method of adding a mineral acid to a distillation residue and performing distillation,
(Japanese Patent Application No. 195329/1989) and the like have been proposed. However, in the case of the method described above, there are many steps (-), a large amount of chemicals such as caustic aqueous solution, mineral acid and aromatic hydrocarbon oil are used (-), and aromatic hydrocarbon oil and high boiling tar acid are used. However, there is a problem that it is not economical because it is difficult to completely separate it from (1) and (2) there is a risk of equipment corrosion due to mineral acid.

According to the present invention, useful components in the distillation residue are reduced in a simple manner by pretreating the heavy distillation residue generated during the above-mentioned purification distillation to reduce the viscosity and then distilling the residue. It is an object of the present invention to provide a method for recovering a high boiling tar acid which is economically advantageous.

[0005]

Means for Solving the Problems The present inventors have conducted a study on the high viscosity of the distillation residue, and as a result, have found that the cause is the formation of aggregates caused by sodium tarate. . This is because relatively high-boiling sodium tarate having a hydrophilic group -ONa group forms a colloid in tar acid, which is an organic substance, and the colloid is aggregated to form a micellar form. It thickens. Therefore, the present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, it has been found that the highly viscous distillation residue of tar acid recovered from coal tar is distilled by adding an aqueous solution of iron sulfate or copper sulfate. The present invention has been found to be effective and has led to the present invention.

That is, the present invention provides a method for recovering high-boiling tar acid, which comprises adding an aqueous solution of iron sulfate or copper sulfate to a distillation residue of tar acid recovered from coal tar and performing distillation. is there.

[0007]

The present invention will be described below in more detail.

When the tar acid recovered from the coal tar is purified and distilled, a highly viscous distillation residue is obtained. This distillation residue is composed mainly of a high boiling tar acid such as xylenol,
２０20% by weight of sodium tarate is mixed. The present invention seeks to recover high-boiling tar acids from the distillation residue. In the present invention, distillation is performed after adding iron sulfate or copper sulfate to the distillation residue.

The amount of iron sulfate or copper sulfate added to the distillation residue is sufficient to decompose sodium tarate, which causes the distillation residue to have a high viscosity, and the pH of the distillation residue is 6 or less, preferably 4 or less. Is desirable. Further, the concentration of the aqueous solution of iron sulfate or copper sulfate is desirably small in view of the load of the dehydration operation in the subsequent distillation step. It is desirable to use divalent or trivalent iron sulfate and divalent copper sulfate.

[0010] After the required amount of iron sulfate or copper sulfate is added to the distillation residue, distillation is performed. Distillation is 50-2
When distilled under reduced pressure at 00 mmHg, preferably 100-150 mmHg, about 9% of the initially contained xylenoleic acid
5% by weight or more can be recovered.

[0011]

Next, the present invention will be specifically described based on examples.

Example 1 400 ml of a tar acid distillation residue having a viscosity of 3300 cP (at 180 ° C.) containing 60% by weight of cresol, xylenol and the like and 8% by weight of sodium tarate as raw materials are m and 100 ml of p-cresol
30 ml of a 30% by weight aqueous solution of iron sulfate (FeSO ₄ ) was added to the mixture diluted with the above to adjust the pH to 5;
Distillation at 70% by weight at 100 mmHg resulted in a residual viscosity of 170 cP (at 50 ° C.). The recovery of cresol, xylenol, etc. was about 95% (Invention Example 1). As a comparison, a residue obtained by diluting 400 ml of a tar acid distillation residue, which was not treated at all, with 100 ml of m, p-cresol was distilled under the same conditions. 1) At the time of distillation of 55% by weight, the kettle residue was solidified, and distillation was impossible (Comparative Example 2). The results are summarized in Table 1.

(Example 2) m, p-cresol 10 was added to 400 ml of the tar acid distillation residue used in Example 1 as a raw material.
20 ml of copper sulfate (CuSO ₄ ) added to 0 ml
An aqueous solution (50 ml) was added to adjust the pH to 5, and the simple distillation was performed to distill 70% by weight at 100 mmHg. The viscosity of the kettle became 200 cP (at 50 ° C.). The recovery of cresol, xylenol, etc. was about 95% (Invention Example 2). The results are summarized in Table 1.

[0014]

[0015]

According to the present invention, tar acid having a high boiling point can be obtained from a distillation residue by a simple method with low equipment corrosion and a high yield, so that it can be effectively used industrially. .

Claims (1)

(57) [Claims] 1. A method for recovering a high-boiling tar acid, comprising adding an aqueous solution of iron sulfate or copper sulfate to a distillation residue of tar acid recovered from coal tar and performing distillation.