CS231535B1 - A method of purifying sulfuric acid - Google Patents

Abstract

The invention solves the purification of sulfuric acid], which contains as impurities HNOs, HNO2, 3-methylphenol and its nitro-, nitroso- and sulfo-derivatives, alkali sulfates. In a sulfuric acid solution, nitric acid is reacted by adding 3-methyl-4-nitrosophenol to nitrous acid. Nitric acid is separated from sulfuric acid at an absolute pressure of 50 Pa to 110 kPa and at a temperature of 0 to 200 °C. Nitric acid is decomposed into nitrous gases. The invention can be used in the purification of sulfuric acid, where nitric acid is a problem in large quantities, but other substances that pollute it do not cause problems in its use.

Description

231535

BACKGROUND OF THE INVENTION The present invention relates to the purification of sulfuric acid resulting from nitration or oxidation of 3-methylphenol derivatives.

In nitration, oxidation, sulfonation of aromatic compounds, sulfuric acid of 20 to 80% by weight is omitted, containing organic substances, nitric acid, nitrous acid, inorganic sulfates and the like. The use of such contaminated sulfuric acid in the production of superphosphate is known. sulphonate, in the removal of metal oxides in metallurgy. Known procedures for removing impurities from sulfuric acid. The acid-adherent is removed in denitration plants or removed from the sulfuric acid by acetylene, optionally acetone. DDR NDR Pat. 120,184 are removed from the sulfuric acid used by the nitrogen oxide with urea or other carbamides. The acidic acid at a concentration of 70% by weight of the nitrosating or nitrating processes is concentrated in a Pauling apparatus, oxidizing the organic non-pure with sulfuric acid or acid-free. The purification of sulfuric acid contaminated with organic compounds by extraction with phenols is described in Soviet Patent No. 316 648. Extraction of organic impurities from sulfuric acid with fatty alcohols or aromatic hydroxyl derivatives is described in Soviet Patent No. 416 312. The removal of organic matter from sulfuric acid in the presence of iron sulphates, or by the medium, is described in the Soviet author's certificate number 564 260. The method of purifying the sulfuric acid used after nitration of aromatic compounds and containing fluorine compounds is given in Art. The heavy metal alkaline sulphates and sulphates are separated from the diluted sulfuric acid by concentrating sulfuric acid to a concentration of 90 to 98%. Diluted acid kinase is used to produce calcium, barium, zinc, copper sulfate and the like. Often, organic substances are removed from sulfuric acid by distillation with water, whereby sulfuric acid is diluted with water, which requires an acidic concentration which is energy intensive. We know that nitric acid always contains dissolved nitrogen oxides. The pure nitric acid solutions are stained into rye until reddish brown from the nitrogen dioxide dissolved in it. The equilibrium of concentrated nitric acid can be described (1J 4 HNOs # 4 NOz + 2 H2O + O2 (1)

Nitric acid has strong oxidative properties. For example, hydrogen sulfide, sulfur, sulfur dioxide, sulfuric acid, phosphorus to trihydroxyphosphoric acid are oxidized from inorganic substances. It is usually reduced to nitric oxide by itself (2)

NOs' + 4 H + -j- 3 = # NO + 2 H2O (2J In organic technology, nitric acid is used for nitration, especially aromatic substances, for oxidation and the like).

The aforementioned drawbacks are eliminated by the process of purifying sulfuric acid containing 3-methyl-4-nitrophenol, 3-methylphenol and its nitro nitroso and sulfo derivatives, nitric acid, nitrous acid and alkaline sulphates, the principle of which is based on that nitric acid is reduced with 3-methyl-4-nitrophenol to nitrous acid, which is separated in the form of nitrogen oxides from sulfuric acid. If necessary, the unreacted 3-methyl-4-nitrosophenol can also be separated from the sulfuric acid, if necessary, and the 3-methyl-4-nitro-phenol formed in the form of a suspension by oxidation with nitric acid.

Nitrous acid is separated from the sulfuric acid at an absolute pressure of 50 to 110 kPa.

The nitric acid is separated from the sulfuric acid at 0 to 200 ° C. The advantage of the sulfuric acid purification process of the invention is the ability to reduce the nitric acid in sulfuric acid in a simple manner. Most preferably, the purified sulfuric acid can be used in such production where the presence of nitroso and 3-methylphenol nitro derivatives is not a problem. In particular, the nitrosation of 3-methylphenol and the oxidation of the resulting 3-methyl-4-nitro-phenophenol to 3-methyl-4-nitrophenol. Example 1

The flask was charged with 500 mL of the used acidic acid followed by a 29.6% by weight H2SO4, 1.2% HNO3, 0.1% HNO2, 3.6% NaHSO3, 0.14% 3-methyl-4. n-trophenol and 0.05% 3-methylphenol and its nitroso and sulfoderivative. Sulfuric acid was heated to 40-45 ° C and dosed with 3-methyl-4-nitrosophenol (48.7% by weight), 3-methyl-4-nitrosophenol, at a rate of 45 g of 3-methyl-4-nitrosophenol over a period of 15 minutes. The mixture was then left to react at 40 ° C for three hours. Insoluble 3-methyl-4-nitro-phenol with non-reacted 3-methyl-4-nitrosophenol was filtered off. Sulfuric acid was heated to 100 ° C and after 60 minutes free to cool to 20 ° C. Sulfuric acid contained 0.111% HNO3. Example 2

The procedure of Example 1 was followed, with the exception that after separation of 3-methyl-4-nitrophenol and 3-methyl-4-nitrosophenol, the acid kinase was heated to 153 ° C for 10 minutes. Sulfuric acid, after cooling to 20 ° C, contained 0.06% by weight of HNO3,

Claims (3)

Process for the purification of sulfuric acid containing as impurities 3-methyl-4-nitrophenol, 3-methylphenol and its nitro-, nitroso- and sulphonated derivatives, nitric acid, nitrous acid, alkaline sulphates, characterized in that nitric acid is reduced by 3- methyl 4-nitrosophenol to nitrous acid, which is separated from the sulfuric acid. INVENTION It 2. The process according to claim 1, wherein nitrous acid is separated from the sulfuric acid at an absolute pressure of 50 Pa to 110 kPa. 3. The process of claim 1 wherein the nitrous acid is separated from the sulfuric acid at a temperature of 0 to 200 ° C.