CS248237B1 - Method of hydrochloric acid neutralization] from the production of phenylhydrazine hydrochloride - Google Patents

Abstract

The solution concerns the neutralization of waste) hydrochloric acid from the production of phenylhydrazine hydrochloride with calcium sludge from the production of captax. After neutralization, the resulting pH value is 4 to 7, preferably 4.5 to 6.5. Insoluble substances such as caiptax, pitch-like substances, iron hydroxide, zinc hydroxide, impurities from technical calcium hydroxide are separated, preferably by sedimentation.

Description

248237

BACKGROUND OF THE INVENTION The present invention relates to a process for the neutralization of hydrochloric acid, which is produced by the preparation of phenylhydrazine dihydrochloride.

Phenylhydrazine hydrochloride is produced by zaniline by diazotization with sodium nitrite in excess of hydrochloric acid] and reduction of the resulting ibenzenediazonium chloride with a hydrogen sulfite / sulfite solution and reduction with zinc powder. The phenylhydrazine dihydrochloride is filtered off from the mother hydrochloric acid], which contains impurities such as phenylhydrazine hydrochloride, sodium chloride, sodium sulfate, zinc ions and unreacted aniline. At present, the spent hydrochloric acid is not used and goes to wastewater. Sometimes it is not neutralized with sodium hydroxide or calcium hydroxide prior to discharge. 2-mercaptobenzothiazole (which is most commonly produced by condensation of aniline, sulfur, sulfur, and crude captax is purified with calcium hydroxide. In the purification process, waste calcium lime sludges that contain calcium calcium hydroxide as calcium and calcium carbonate impurities) Lime sludge is not used and stored in a chemical waste dump.

The above drawbacks are alleviated by the process of neutralizing hydrochloric acid from the production of phenylhydrazine hydrochloride. Waste hydrochloric acid is purified by chloride and sodium sulfate, zinc and sometimes iron (II), phenylhydrazine and aniline. The hydrochloric acid is neutralized by waste lye which contains 1 to 40% by weight of calcium hydroxide, 0.1 to 5% by weight of calcium salt of calcium, 1 to 15% by weight of bituminous matter formed in the manufacture of the capta and impurities following from technical calcium hydroxide.

The pH after neutralization is 4 to 7, preferably 4.5 to 6.5. From the sewage sludge, the practically calcium ions pass into solution and precipitation is precipitated. Also insoluble matter remains insoluble. Iron and zinc ions are precipitated from the precipitated hydrochloric acid as hydroxide. The insoluble matter is preferably separated from the suspension by sedimentation. The advantage of the process for the neutralization of hydrochloric acid from the production of phenylhydrazine hydrochloride is that the lime sludge from the production of kappa is used to neutralize it. From the lime sludge, practically all of the calcium that is converted to calcium soluble is used. The lime sludge still has insoluble captax and pitch-like substances, the volume of which is substantially less than the volume of the calcium calcium sludge, thus lowering the cost of storing them in chemical waste. Zinc and ferrous ions are precipitated from the waste acid in hydroxide. Example 1

The flask was charged with waste hydrochloric acid from the production of phenylhydrazine hydrochloride containing: 81 g / l HCl "121 g / l Cl", 152 g / l SO42 ", 98 g / l Na +, 742 mg / l Zn 2+, 940 mg / l of aniline, 5.6 g / l of phenylhyidrazine hydrochloride.

Calcium sludges were used for neutralization, containing: 2.1% by weight calcium hydroxide, 0.2% by weight calcium salt and 1.9% by weight pitch. The resulting pH was 4.8. The resulting pH value after filtration of the insoluble precipitates from the suspension was 4.9. Example 2

Example 1 was followed, except that hydrochloric acid contained: 3.2% by weight HCl, 6.8% by weight Cl-, 6.1% by weight SO42, 3.6% by weight Na +, 226 mg / l Zn2 +, 360 mg / l aniline and 3.1 g / l of phenylhydrazine hydrochloride. Calcium sludges contained: 36.0% by weight calcium hydroxide, 3.9% by weight calcium salt, 13.8% by weight pitch. The resulting pH after neutralization was 6.7. The precipitated impurities were allowed to sediment. The aqueous solution obtained had a pH of 6.7.

The invention is applicable to the neutralization of waste hydrochloric acid, thereby reducing the waste water acidity. For neutralization, waste calcium sludge is used to replace calcium or sodium hydroxide.

Claims (1)

SUBJECT Process for neutralizing hydrochloric acid] from the production of phenylhydrazine hydrochloride contaminated with sodium chloride, sodium sulphate, iron and zinc cations, phenylhydrazine hydrochloride and aniline calcium hydroxides, characterized in that the hydrochloric acid is neutralized by waste calcium hydroxide from the production of 2-mercapto-benzothiazole containing calcium hydroxide, 0.1 to 5% INVENTION the weight of the calcium salt of 2-mercaptobenzothiazole, 1 to 15% by weight of the pitch substances resulting from the production of 2-mercaprobenzothiazole and the impurity from technical calcium hydroxide, the pH of the suspension after neutralization being 4 to 7, preferably 4.5 to 6.5, and insoluble impurities such as 2-mercaptobenzothiazole, ammonium compounds, ferrous hydroxide and zinc hydroxide are separated from the reaction mixture, preferably by sedimentation.