JPH0469673B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for purifying tar acid produced as a by-product from coal carbonization or coal gasification processes. Tar acid is originally a general term for phenols, cresols, and xylenols, but tar acid also contains basic nitrogen compounds such as aniline, pyridine, picoline, lutidine, and quinoline, which are generally referred to as tar bases. Contains impurities. Tar acid is a wood preservative, insecticide, and
It is also used as a disinfectant, but when used as raw materials for synthetic resins and plasticizers, the above impurities are
Must be removed to around 20ppm. Moreover,
Recently, due to resource considerations, the source of materials such as synthetic resins has been switched from petroleum to coal, so the development of a tar acid purification method has become a major issue. [Prior art] Conventionally, in order to obtain tar acid from the coal carbonization process, the raw materials such as tar light oil, carbol oil, naphthalene oil or absorption oil are washed with a dilute aqueous solution of caustic soda, thereby removing the tar acid in the raw material. The sodium salt is converted into soda salt, which is then subjected to steaming or light oil washing to remove neutral oil and tar base, followed by neutralization and decomposition with sulfuric acid or carbon dioxide gas, and further as necessary. Therefore, methods such as distillation have been adopted. However, in the above method, relatively low boiling point bases such as pyridine are easily removed in the steaming process, but high boiling point bases such as aniline are difficult to remove. A large amount is required and it is not favorable from an economic point of view. [Problems to be Solved by the Invention] In view of the above, the present invention provides a purification method that easily eliminates high-boiling heterocyclic compounds such as aromatic amines and lutidine. [Means for Solving the Problems] The present inventors have discovered that the above problems can be solved by adding concentrated sulfuric acid, an organic sulfuric acid derivative, or a sulfonic acid derivative to tar acid and subjecting it to distillation. Ta. The tar acid referred to in the present invention refers to crude tar acid after neutralization and decomposition of sodium tar acid salt with an acid as described in the conventional method, purified tar acid obtained by dehydrating and/or depitching crude tar acid, and purified tar. Phenol, O-cresol, m・p obtained by distilling acid
-Refers to cresol, xylenol, etc. In other words, it is called tar acid containing 100 ppm or more of basic nitrogen compounds. The concentrated sulfuric acid added to such tar acid is ordinary 98% sulfuric acid, and it is believed that this sulfonates a portion of the tar acid to produce the following sulfonic acid derivatives. As the organic sulfuric acid derivative 1 added in place of this, lauryl sulfuric acid can be mentioned. Further, the sulfonic acid derivative 2 refers to organic sulfonic acids or sulfonate salts such as p-toluenesulfonic acid, laurylbenzenesulfonic acid, and p-phenolsulfonic acid. The amount of the sulfuric acid, organic sulfuric acid or sulfonic acid derivative added is equivalent to or more than the amount of the tar base, particularly the basic nitrogen-containing compound, contained in the tar acid. Once added to the tar acid, stir well and distillation can begin immediately. During the distillation, at the distillation temperature, the tar base and the added sulfuric acid or
It reacts with the derivatives to form high-boiling salts, which are removed as residue on the pitcher without being distilled off. The removal of tar bases according to the present invention takes advantage of the fact that additives and bases form salts that result in high boiling points or high decomposition temperatures. For this reason, it is desirable that the distillation temperature be as low as possible, but in practice it is preferable to distill under normal pressure or reduced pressure with a bottom temperature of 200° C. or lower. [Comparative example] 200 g of crude tar acid having the composition listed in Table 1,
Pour into a 200ml flask, and the bottom temperature under vapor pressure is 180.
Dehydration was performed at ℃ using a distillation column with a theoretical cutoff of 15 stages. That is, first, 33.5 g of water and oil were distilled off from the top of the column.

[Table] Oils include phenols and the like that are distilled out by azeotroping with water. Then, while maintaining the bottom temperature at 180°C, the mixture was subjected to vacuum distillation to reach a final pressure of 30 mmHg. 14g of pit-shaped pot residue remained in the flask, and 144g
Dehydrated and depitched tar acid, in other words, purified tar acid was distilled off. Incidentally, the loss was 8.5 g. [Example] Concentrated sulfuric acid, a sulfuric acid derivative, or a sulfonic acid derivative in an amount equivalent to twice the basic nitrogen compound contained in the crude tar acid listed in Table 1 was added, and the same operation as in the above comparative example was performed to obtain purified tar. The acid was distilled off. The material balance itself is not substantially different from that of the comparative example. The types and contents of basic nitrogen compounds in the distilled purified tar acid, including the raw material crude tar acid, are listed in Table 2 (unit: mg/Kg).

〔Effect of the invention〕

According to the present invention, by adding a small amount of concentrated sulfuric acid, an organic sulfuric acid derivative, or a sulfonic acid derivative equivalent to or twice the amount of the tar base contained,
Almost all of the basic nitrogen compounds in tar acid can be removed by simply distilling at a bottom temperature of 200°C or less.

Claims (1)

[Scope of Claims] 1. A method for purifying tar acid, which comprises adding concentrated sulfuric acid, an organic sulfuric acid derivative, or a sulfonic acid derivative to tar acid and subjecting the mixture to distillation. 2. The tar acid according to claim 1, wherein the amount of concentrated sulfuric acid, organic sulfuric acid derivative, or sulfonic acid derivative added is equivalent to or twice the amount of tar base contained in the tar acid. Purification method. 3. The method for purifying tar acid according to claim 1 or 2, wherein the distillation is carried out at a bottom temperature of 200°C or lower.