CS231911B1 - A method for producing sulphates from spent sulfuric acid - Google Patents

Abstract

The invention solves the production of sulfates from used sulfuric acid containing as impurities HNO^j, HNO2, 3-methylphenol and its nitro-, nitroso- and sulfo-derivatives and inorganic sulfates. In a sulfuric acid solution, nitric acid is reduced by inorganic compounds, preferably metals, or their compounds. The obtained sulfuric acid is neutralized with inorganic hydroxides, oxides, carbonates, sulphite, ammonia, sulphides. The precipitated phenol derivatives are separated from the solution. Soluble phenol derivatives are absorbed or extracted or evaporated. After crystallization, the phenol derivatives are separated from the sulfates by heating to a temperature below the decomposition temperature of the respective sulfates. The invention can be used in the production of sulfates, which find application as mineral fertilizers, in horticulture, or in other industries.

Description

In the sulfuric acid solution, nitric acid is reduced by inorganic compounds, preferably metals, or compounds thereof. The sulfuric acid obtained is neutralized with inorganic hydroxides, oxides, carbonates, sulfites, ammonia, sulfides. The precipitated phenol derivatives are separated from the solution. Soluble phenol derivatives are absorbed or extracted or evaporated. After crystallization, the phenol derivatives are separated from the sulfates by heating to a temperature below the decomposition temperature of the respective sulfates.

The invention can be used in the manufacture of sulphates which find application as mineral fertilizers, in the glass industry or in other sectors.

The invention relates to the production of sulphates from the sulfuric acid used after nitration or oxidation processes. Sulfuric acid, which is eliminated after the nitration, oxidation and sulfonation processes, has a concentration of 20-80% by weight. It contains organic substances, nitric acid, nitrogen oxides, inorganic sulphates and the like. Such auric acid is used in the manufacture of mineral fertilizers (superphosphate, ammonium sulfate, etc.) and in the metallurgy to remove metals.

Methods for removing impurities from the sulfuric acid used are known. Nitrogen oxides are removed in denitration plants or are removed from the acid with acetylene. FedTa patent DD 120 184 removes nitrogen oxides from used sulfuric acid by urea or other carbamides. Sulfuric acid, 70% by weight after nitrosation processes, is concentrated in a Pauling apparatus, oxidizing organic impurities with sulfuric or nitric acid.

The purification of the used sulfuric acid by phenol extraction is described in Soviet author 316 316. certificate 564 260.

A process for purifying spent sulfuric acid after nitration of fluorine-containing aromatic compounds is described in CS 167 207. Alkaline and heavy metal sulphates are separated from dilute sulfuric acid by concentration of sulfuric acid to a concentration of 96-98% by weight. Dilute sulfuric acid is used for the production of calcium, barium, zinc and the like. The production of sulphates contaminated with nitrates from waste sulfuric acid by neutralization is described in MS. AO 208,338.

The sulfuric acid used is often used for the production of mineral fertilizers or some technically important sulphates. The disadvantage is that the mineral fertilizer contains organic substances which in some cases cannot be tolerated in a given concentrate.

The aforementioned drawbacks are eliminated by the process for the production of sulphates from the sulfuric acid used, which contains as impurities 3-methylphenol and its nitro-, nitroso- and sulfoderivatives, nitric acid, nitrogen oxides, alkali sulphates according to the invention. Nitric acid is first reduced with inorganic compounds to nitrogen oxides. It is preferably used for the reduction of metals or their alloys, whereby the corresponding sulphates are formed.

Equations I and II give an example of a reaction medium.

Cu + 8 HNO _{3 -} i. 3 Cu / NO _3/2 + 2 NO + 4 H ₂ 0/1 /

Cu / NO _3/2 + ^H 2 ^SO 4 - _»CuSO4 + 2 HNO _3/11 /

Nitrogen oxides are released from the solution in the form of gases.

After reducing the nitric acid content, the sulfuric acid is further neutralized with hydroxides and / or oxides and / or carbonates and / or sulfites and / or amine and / or sulfides.

The neutralization is preferably carried out so as to form a sulphate solution whose concentration is below that of the saturated solution, wherein the precipitated phenol derivatives are preferably separated by filtration.

The concentration of dissolved phenol derivatives is reduced from the solutions by adsorption and / or extraction and / or evaporation.

From the solutions, the sulfates crystallize in a known manner, and in the crystal the concentration of phenol derivatives is reduced by heating below the decomposition temperature of the sulfates.

An advantage of the invention is that the sulphate production according to the invention finds application mainly in the production of ammonium sulphate, which can be enriched with sulphates of trace elements e.g. CuSO4 and ZnSO4 to improve its properties. Ammonium sulphate can be used alone or as a component in combined mineral fertilizers. The phenol derivatives obtained can be used in the production of plant protection products. In the production of sulphates from sulfuric acid having a reduced HNO 2 content, a construction material for apparatuses less demanding than the original sulfuric acid can be used.

Example 1

The flask was charged with 100 ml of used sulfuric acid containing 32.1% HgSO4,

1.7% HNO 3, 0.03% nitrogen oxides, 8.3% NaHSO 4, 0.13% 3-methyl-4-nitrophenol, 0.09% 3-methylphenol and its sulfo- and nitroso derivatives. 3 g of powder medium was added to the solution.

The mixture was heated to 60 ° C and stirred. After cooling, the unreacted reaction was filtered off. The solution contained 33.7 wt% H 2 SO 4 and 0.4 wt% HNO 2. Next, the solution was neutralized with 5% science KOH until the Cu / OH / ₂ formed had dissolved again. The solution was then allowed to stand for 24 hours. The precipitated phenol derivatives were filtered off. Phenol derivatives were extracted from the solution 3 x 50 ml xylene. After extraction! The sulfates were crystallized by evaporation of water. The crystalline sulfates were heated to 300 ° C for 2 hours. After cooling, the phenol derivatives were crushed and determined. Sulphates contained below 0.0001% by weight of 3-methyl-4-nitrophenol, which is the analytical limit for spectrophotometric determination.

Example 2

The procedure of Example 1 was followed except that 3 g of powdered activated carbon was used to reduce HNO 3 and the mixture was heated to 30 ° C. After filtration of the activated carbon, the mixture contained 0.2% HNO4. An 8% aqueous KgCO3 solution was used for neutralization. Dissolved phenol derivatives were adsorbed with 2 g activated bentonite. After bentonite was filtered off, the solution contained 0.002% by weight of 3-methyl-4-nitrophenol.

Example 3

The procedure of Example 1 was followed except that 3 g of powdered brass was used instead of the medium. After filtering off the unreacted brass, the solution contained 0.03% by weight of HNO4. Sulfuric acid was then neutralized with an 8% aqueous solution of NagSO4. The precipitated phenol derivatives were filtered off and 3 g of activated carbon were added to the solution. After filtration of the activated carbon, the solution contained 0.000 7% by weight of 3-ethyl-4-nitrophenol.

Example 4

The procedure of Example 3 was followed except that a 10% ammonia solution was used for neutralization. After filtering off the activated carbon, the sulphate solution contained 0.000 9% by weight of 3-ethyl-4-nitrophenol.

Example 5

The procedure of Example 3 was followed except that a 7% aqueous Na 2 S solution was used for neutralization. After filtration of the activated carbon, the sulphate solution contained 0.000 7% by weight of 3-methyl-4-nitrophenol.

The invention can be used in the production of ammonium sulphate, which serves as a mineral fertilizer, sodium sulphate, which can be used in the glass industry, as well as in the production of other sulphates. The production process uses sulfuric acid, which has not been used so far and flows into the waste line.

Claims (5)

OBJECT OF THE INVENTION 1. A process for the production of sulphurates from used sulfuric acid containing as impurities 3-methylphenol and its nitror, nitroso and sulphoderivatives, duic acid, nitrogen oxides and alkali sulphates, characterized in that the nitric acid content is reduced by reducing the inorganic compounds with: or a compound thereof. 2. A method according to claim 1, characterized in that the sulfuric acid is further neutralized with hydroxides and / or oxides and / or carbonates and / or sulphites and / or ammonia and / or silicas. 3. The method of claims 1 and 2, wherein the neutralization is preferably carried out so as to form a solution of the salts, the concentration of which is slightly saturated under the concentration, wherein the precipitated phenol derivatives are separated. 4. The method according to claims 1 to 3, characterized in that, from the salivary plants, the concentration of the dissolved phenol derivatives is reduced by adsorption and / or extraction and / or evaporation. 5. A method according to any one of claims 1 to 4, characterized in that sulphates crystallize out of the solutions in which the concentration of phenol derivatives is reduced and / or the phenol derivatives are removed by heating below the decomposition temperature of the sulphates.