CS218444B1 - Method of making the 4-aminodiphenylamine - Google Patents

Description

The present invention relates to the preparation of 4-aminodiphenylamine which is used to prepare N-alkyl derivatives, important antiozonants for rubber and other products.

4-Aminodiphenylamine is prepared by reduction of 4-nitrosodiphenylamine by sulfides or catalytic hydrogenation. The hydrogenation is preferably carried out with a solution of the alkali salt of 4-nitrosodiphenylamine obtained by basifying the reaction mixture from rearrangements of N-nitrosodiphenylamine with hydrogen chloride in a medium of a mixture of a non-polar solvent with methanol. Chlorinated or aromatic hydrocarbons serve as non-polar solvents. The 4-nitrosodiphenylamine hydrochloride present in the reaction mixture is converted into an aqueous solution of the alkali salt of 4-nitrosodiphenylamine and sodium or potassium chloride and methanol is also passed into the aqueous phase. In the non-polar solvent phase, the starting N-nitrosodiphenylamine and rearrangement by-products remain unreacted. The aqueous phase containing 4-nitro'sodiphenylamine is hydrogenated at 50 ° to 1010 ° C in the presence of catalysts, most often based on Pd, Pt or Ni, respectively. with the addition of a solvent. The catalyst is filtered off from the hydrogenate and the 4-aminodiphenylamine layer is separated, respectively. a solution thereof, from an aqueous phase containing methanol, chloride and sodium or potassium hydroxide. Me2

It is possible to descramble from the mixture and return it to the process, the remainder being difficult waste. This dark colored wastewater can be freed from most organic matter by biological treatment, but requires acid neutralization of the free alkali. Purified water is discharged into watercourses, where it brings a large amount of salts. The waters resulting from the production of 4-aminodiphenylamine therefore require expensive purification and, in particular, increase the salinity of the watercourses.

The salinity of the waste water can be reduced by precipitation of sodium ions by the action of carbon dioxide to form a sparingly soluble sodium bicarbonate (Author's Certificate No. 208 064). In this way, only about 40% of the salts are removed from the water.

The problem of waste water is solved by a process for the production of 4-aminodiphenylamine by rearrangement of N-nitrosodiphenylamine by treatment with hydrogen chloride in a mixture of non-polar solvent with methanol, extraction of 4-nitrosodiphenylamine formed from the reaction mixture into sodium by separating 4-aminodiphenylamine from the hydrogenation product, evaporating methanol and some of the water to obtain a sodium or potassium hydroxide solution having a weight concentration of 8 to 15% by weight and increasing its concentration to 15 to 23% by adding a concentrated solution of solid hydroxide sodium potassium and used to extract 4-nitrosodiphenylamine from the reaction mixture from the rearrangement of N-nifrosodiphenylamine, precipitating sodium or potassium chloride, which is filtered off and washed and the filtrate obtained is separated into a layer of non-polar solvents and an aqueous layer containing 4-nitrosodiphenylamine which is subjected to catalytic reduction.

The invention solves the problem of waste water completely. Sodium or potassium chloride is obtained in a crystalline form suitable for further use. The purity of the chloride is increased by washing with methanol on the filter. If further application so requires, the chloride can be freed from organic matter by annealing. Sodium chloride can be returned to the electrolysis or used for winter spreading of roads, potassium chloride is particularly suitable as an admixture to combined fertilizers.

The process of the invention saves the acid required to neutralize the free hydroxide, but in addition, the free hydroxide is reused in the process. The sodium salt of 4-nitrosodiphenylamine usually contains from 1.2 to 1.6 moles of alkali hydroxide per mole of nitroso compound, so the savings are considerable.

Whether sodium or potassium hydroxide is used is not critical to the process of the invention. Although potassium chloride is less soluble in sodium 4-nitrosodiphenylamine than sodium chloride, the chloride content has no effect on the hydrogenation process. Sodium hydroxide is cheaper than potassium hydroxide, while the obtained potassium chloride has a greater value.

The reaction of 4-nitrosodiphenylamine hydrochloride with hydroxide produces reaction water and additional water is introduced into the cycle using sodium or potassium hydroxide solutions, which are usually supplied at a concentration of about 40% by weight. Some water may add to the mixture by eventually washing the chloride on the filter with water. All this water must be removed from the wastewater by evaporation before it is recycled. First, methanol is separated from the aqueous layer separated from the hydrogenation reaction mixture, which is returned to the N-nitrosodiphenylamine rearrangement process, and the corresponding water balance amount of 500 to 800 · kg per tonne of aminodiphenylamine is distilled off using 40% by weight. sodium hydroxide solution, less water is applied when solid hydroxides are applied.

After evaporation of the water, an equivalent amount of alkaline hydroxide was added to the solution, based on the amount of hydrogen chloride used in the rearrangement with a small excess of losses. In view of the cost, a 40% by weight hydroxide solution as obtained by electrolysis is most suitable. Using anhydrous hydroxide, less water is distilled off from the returned solution, but in solid form hydroxides are considerably more expensive.

The final concentration of the hydroxide solution to be used to treat the reaction mixture from the N-nitrosodiphenylamine rearrangement is determined by several circumstances. The most important limiting factor is the solubility of chloride in the respective hydroxide solution, which is particularly important for the potassium salt. Another condition is the concentration of the 4-nitrosodiphenylamine salt obtained; for hydrogenation a content of 17 to 2.2% by weight is suitable. Of 4-nitrosodiphenylamine in solution. These limitations result in a final concentration of 15 to 18 wt%. % NaOH and 15 to 20 wt. KOH.

During total recycling of hydroxides, carbonates accumulate in the solution. To remove them, part of the solution can be removed from the cycle after the methanol has been evaporated and treated as waste water. It is sufficient to remove 10 ·% of the total amount of solution. This also removes part of the accumulated organic substances. Another possibility to reduce the carbonate concentration is a two-step process for dissolving the reaction mixture from rearrangement; first, a regenerated hydroxide solution is added to obtain an approximately neutral reaction and carbon dioxide escapes, then a new hydroxide is added.

Organic substances are also accumulated by recycling the hydroxide solution. However, some of them are trapped in sodium or potassium chloride filtration, some of the organic substances are absorbed on the catalyst and reduce its activity. Catalyst consumption increases by 10 to 30% compared to the known process without recycling the hydroxide solution. This only disadvantage, however, is of little importance in the field of ecology in the process according to the invention in comparison with the saving of raw materials and the reach. Example 1 (comparative experiment)

To a 1000 g solution of N-nitrosodiphenylamine (40 wt%) was added a solution of 107 g HCl in 293 g methanol with stirring at 23 ° C. After 6 hours, the rearrangement of the nitrosamine to 4-nitrosodiphenylamine is complete and the reaction mixture is basified with a solution of 222 g of NaOH in 1006 g of water at 25 ° C. After stirring for 3 minutes, the layers were allowed to separate, the toluene layer containing 20 g of pitch and unreacted nitrosamine, 4-nitrosodifehylamine as the sodium salt was added to the aqueous phase, followed by sodium chloride, excess hydroxide and methanol.

The solution of the sodium salt of 4-nitrosodiphenylamine is hydrogenated in an autoclave at a pressure of 5 MPa and a temperature of 60-80 ° C with the addition of 1 g of catalyst 3% Pd on activated carbon and 40 ml of toluene. Hydrogenation is complete in 30 minutes. The catalyst is filtered off from the reaction mixture and the phases are allowed to separate. The organic layer contains crude 4-aminodiphenylamine, the aqueous layer contains methanol, sodium chloride and hydroxide, and some organic substances. Extraction with a small amount of toluene removes the 4-aminodiphenylamine residue and some other organic matter from the aqueous layer. Then, methanol is distilled off on the column, the residue is from water, containing 171 g of NaCl and 106 g of NaOH. After neutralization and sufficient dilution, this water can be discharged for biological treatment.

Example 2

From the waste water obtained in Example 1 in an amount of 1335 g, 230 g of water were distilled off and 118 g of NaOH as a 40% solution were added. After cooling, the mixture thus obtained is used to basify the reaction mixture of N-nitrosodiphenylamine rearrangement according to Example 1. The precipitated sodium chloride is filtered off and washed with methanol, the filtrate is allowed to separate into toluene and aqueous phases. The aqueous phase, i.e. the sodium salt of 4-nitrosodiphenylamine, is hydrogenated under the conditions of Example 1, the reaction time being noticeably extended.

After the third return of the NaOH solution, the hydrogenation time is increased by 20%.

Crystalline sodium chloride contains some organic substances that it can get rid of by annealing in air.

Example 3

The N-nitrosodiphenylamine rearrangement mixture of Example 1 was basified with a solution of 304 grams of KOH in 1270 g of water. The 4-nitrosodiphenylamine potassium salt solution was hydrogenated according to Example 1 and the reaction mixture was also treated in the same manner. The waste water obtained, total 1690 g, contains 144 g KOH and 225 g KCl is freed from distilled water (300 g) and 162 g KOH is added as a 40% solution. The solution thus obtained is used to basify the reaction mixture of N-nitrosodiphenylamine rearrangement prepared according to Example 1. The precipitated potassium chloride is washed with a small amount of methanol and water, the filtrate is separated into an organic and an aqueous phase. The aqueous layer, i.e. the potassium salt of 4-nitrosodiphenylamine, is hydrogenated as in Example 1.

Crystalline potassium chloride contains a small amount of organic matter and is suitable as such or better after annealing for the preparation of combined fertilizers.

Claims (1)

A process for producing 4-aminodiphenylamine by rearrangement of N-nitrosodiphenylamine by treatment with hydrogen chloride in a mixture of a nonpolar solvent with methanol, extracting the formed 4-nitrosodiphenylamine from the reaction mixture into a sodium or potassium hydroxide solution followed by catalytic reduction with hydrogen. -aminodiphenylamine, evaporate methanol and some of the water to obtain a sodium or potassium hydroxide solution having a concentration of 8 to 15% by weight, whose weight concentration is increased to 15 to 23% by adding a concentrated solution or solid sodium or potassium hydroxide, and to extract the 4-nitrosodiphenylamine from the reaction mixture from the N-nitrosodiphenylamine rearrangement, which precipitates sodium or potassium chloride, which is filtered off and washed, and the filtrate obtained is separated into a non-polar solvent layer and an aqueous layer containing 4-nitrosodiphenylamine, which is subjected to catalytic reduction.