RU2126789C1 - Process for preparing n,n-diphenyl-p-phenylene diamine - Google Patents

Abstract

FIELD: technology of organic synthesis. SUBSTANCE: -n-- diphenyl-p-phenylene diamine is prepared by condensation of hydroquinone with aniline in presence of catalyst. Catalyst is 85-89% phosphoric acid. Hydroquinone, aniline and phosphoric acid are mixed at molar ratio of 1:(1.2-1.35): (0.018-0.10), respectively. Reaction mixture is heated to 205-210 C. Azeotropic distillation of the resulting water is carried out at elevated temperature of 235-240 C for 1.5-2.5 h, condensate is separated into aqueous and aniline phases and aniline phase is directed for recycling. Aniline is then added to reaction mixture for 2-8 h till hydroquinone: aniline moles ratio of 1: (2.05-2.5), respectively is achieved. This operation is simultaneously accompanied with azeotropic distillation of the resulting water, said process being carried out for 2-8 h indicated above at elevated temperature at rate of 3-10 C/h. Reaction mixture is then maintained at attained temperature for 1.5-3 h, and unreacted aniline is removed. -n-- diphenyl-p-phenylene diamine is recovered from the remaining reaction mixture. The process makes it possible to attain high and stable yield of the desired product at optimum combination of technological modes of the claimed process and optimum concentrations of the ingredients used. EFFECT: more efficient preparation process. 8 cl, 2 ex

Description

 The invention relates to organic synthesis technology, in particular, to a method for producing a secondary aromatic amine - N, N'-diphenyl-n-phenylenediamine.

 N, N'-diphenyl-n-phenylenediamine is a widely used stabilizer of synthetic rubbers of general purpose, protects rubbers based on these rubbers from thermal oxidative aging and destruction during repeated deformations, passivates the action of metals of variable valency, is a heat stabilizer of polyethylene and polyamides, an inhibitor of polymerization of unsaturated esters carboxylic acids, stabilizer of rocket fuels and lubricants.

 N, N'-diphenyl-n-phenylenediamine (DPPD) is obtained by condensation of hydroquinone with aniline in the presence of a catalyst.

Как следует из приведенной схемы, конденсация гидрохинона с анилином в присутствии катализатора идет в две стадии: вначале образуется n-гидроксидифениламин, который, вступая в реакцию со второй молекулой анилина, дает ДФФД. Так же протекает побочная реакция образования дифениламина.The main reactions for the production of DFFD proceed as follows:

As follows from the above scheme, the condensation of hydroquinone with aniline in the presence of a catalyst proceeds in two stages: first, n-hydroxydiphenylamine is formed, which, reacting with the second aniline molecule, gives DPPD. An adverse reaction of the formation of diphenylamine also proceeds.

A known method of producing DFFD by condensation of hydroquinone with aniline in the presence of a process catalyst - zinc chloride with azeotropic distillation of reaction water. Hydroquinone, aniline and zinc chloride are taken in a molar ratio of 1: 4: 0.7, respectively, condensation is carried out at a temperature of 185-230 ^o C for 10 hours with continuous boiling of the reaction mass. The surfactant OP-10 (ethoxylated alkyl phenol with a degree of hydroxyethylation of 9-10) is added to the aqueous suspension of the reaction mixture, which prevents the product from sticking together, after which excess aniline is distilled off with steam and the product is treated with an aqueous alkali solution. Receive DFFD with a yield of 63% of theoretical in terms of hydroquinone, the melting point of DFFD is 144 ^o C. (A.S. USSR N 168710).

 The disadvantage of this method is the use of high concentrations of aniline and zinc chloride, as well as the insufficiently high yield of the target product - DFFD.

The most effective catalysts for the condensation of hydroquinone with aniline are substances that take away water, such as zinc, calcium, aluminum and iron chlorides. However, metal chlorides have several disadvantages: above 200 ^o C under the reaction conditions, they decompose with the formation of ammonium chloride, which is distilled off from the reaction mass together with aniline. The catalyst is completely separated only after repeated washing with water, which leads to the formation of a large amount of wastewater.

 The use of hydrochloric, sulfuric, boric and phosphoric acids, as well as oxalates, sulfates and phosphates as catalysts for the condensation of hydroquinone with aniline is indicated (Gorbunov E.N. et al. Chemistry and technology of stabilizers of polymeric materials, M. Chemistry, 1981, p. 56.

As the closest analogue, the applicant selected a method for producing DFFD by condensation of hydroquinone with aniline in the presence of trialkyl phosphate (trimethyl or triethyl phosphate) as a catalyst (US Patent No. 2503712). The reaction is carried out in a steel autoclave at 300 ^o C, the molar ratio of hydroquinone: aniline: trialkyl phosphate is 1: 3: (0.02-0.026). The total reaction time is 6-7 hours. The process is carried out in two stages. The time of the first stage is 2 hours, the reaction is carried out with azeotropic distillation of the resulting water, and at the end of the first stage of the reaction, unreacted aniline is distilled off. Aniline and a trialkyl phosphate catalyst are additionally added to the reaction mixture remaining after distillation of aniline, and the second stage of the reaction is carried out for 4.5-5 hours with azeotropic distillation of the resulting water. At the end of the second stage of the reaction, unreacted aniline is distilled off and the target product, DFFD, is separated from the remaining reaction mass by fractional distillation. The yield of DFFD by a known method is 87-87.5% of theoretical.

The disadvantages of this method are:
- carrying out the condensation process in two separate stages with intermediate cooling and fractional distillation of the reaction mass;
- carrying out the condensation process in an autoclave;
- the use of high concentrations of aniline.

 The problem to which the present invention is directed, is the creation of a technological process for the production of N, N'-diphenyl-n-phenylenediamine, repeatedly reproduced in industry, providing a high and stable yield of the target product with an optimal combination of technological regimes, method and concentrations of the ingredients used.

 The problem is solved in a new way to obtain N, N'-diphenyl-n-phenylenediamine (DFFD).

DFPD is obtained by condensation of hydroquinone with aniline in the presence of a catalyst - 85-89% phosphoric acid. Hydroquinone, aniline and phosphoric acid of the specified concentration are mixed in a molar ratio of 1: (1.2-1.35): (0.018-0.10), respectively, the reaction mass is heated to a temperature of 205-210 ^o C and the process is carried out under continuous boiling of the reaction masses. Within 1.5-2.5 hours, an azeotropic distillation of the resulting water is carried out with increasing temperature to 235-240 ^° C. The condensate is separated into the aqueous and aniline phases, and the aniline phase is sent for recirculation. Then, within 2-8 hours, aniline is fractionally added to the reaction mass as it is consumed until the hydroquinone: aniline molar ratio is 1: (2.05-2.5), respectively, with simultaneous azeotropic distillation of the resulting water. The process for the specified 2-8 hours is carried out with a gradual increase in temperature at a rate of (3-10) ^o C / hour to 250-270 ^o C. Then the reaction mass is kept at the temperature reached for 1.5-3 hours.

 During the reaction, the total amount of water, at least 90% of its theoretical yield, is azeotropically distilled off.

 Then unreacted aniline is distilled off, while the flow rate of aniline is controlled by the technological parameters of pressure and temperature.

 After distillation of aniline from the remaining reaction mass, the target product, DFFD, is isolated.

 The selection of DFFD is carried out by conventional conventional methods. It is possible to isolate DFFD from the reaction mixture by fractional distillation, which is expediently carried out under vacuum. During fractional distillation of the reaction mass, diphenylamine is distilled off as the first fraction of the distillate. The second fraction of the distillate contains n-hydroxydiphenylamine mixed with the remaining aniline. And finally, the target product, N, N'-diphenyl-n-phenylenediamine, is distilled off in the form of a third fraction upon distillation of the reaction mixture.

 A shoulder strap containing n-hydroxydiphenylamine in a mixture with aniline is returned to the cycle for re-circulation, which ensures lower raw material costs, in particular, hydroquinone, and a higher yield of the target product - DFFD.

 In addition to fractional distillation, it is possible to isolate DPPD by crystallizing it from various solvents. As solvents, toluene, ethylene glycol, chlorobenzene, o-dichlorobenzene can be used.

 It is preferable to use toluene as a solvent in the isolation of DPPD.

 All the ingredients used in the synthesis of N, N'-diphenyl-n-phenylenediamine are commercially available and are commercially available products.

The resulting N, N'-diphenyl-n-phenylenediamine is a dark gray powder with a melting point of 145-150 ^o C. Combustible, dust fire, T _ign. 870 ^o C, moderately toxic.

 The yield of N, N'-diphenyl-n-phenylenediamine is 82-87%.

 The essence of the present invention is further illustrated by two examples of specific performance. Other examples are obvious to specialists. Therefore, the invention is not limited to these examples, but is limited only by the proposed scope of the claims.

 Example 1

110.1 g (1 mol) of hydroquinone, 11.7 g (1.2 mol) of aniline and 2.3 g (0.02 mol) of 89% phosphoric acid are charged to the reactor. The reaction mass is heated to boiling (205-210 ^o C) and 16.5 g of water are azeotropically removed over 2.5 hours, while the temperature of the reaction mass rises to 235-240 ^o C. Then, fractionally 102 are added to the reactor over 6 hours , 4 g (1.1 mol) of aniline as it is consumed, while azeotropically removing the resulting water. Over the course of the indicated 6 hours, the temperature of the reaction mass is gradually increased at a rate of 3-4 ^° C / hr to 250-260 ^° C and, at the temperature reached, the mass is held for 2-3 hours. During the reaction, 33 g of water is released (91.7% of its theoretical yield). Unreacted aniline is then distilled off. DFFD is isolated from the remaining reaction mass by fractional distillation in vacuo. 205.5 g of DPPD are obtained with a melting point of 148-150 ^° C. The pregon consisting of n-hydroxydiphenylamine and aniline is recycled, resulting in a yield of DPPD of 220.5 g (84.5%).

 Example 2

110.1 g (1 mol) of hydroquinone, 121 g (1.3 mol) of aniline and 11.5 g (0.1 mol) of 85% phosphoric acid are charged to the reactor. The reaction mass is heated to boiling (205-210 ^o C) and 16-17 g of water are azeotropically removed within 1.5 hours, while the temperature of the reaction mass rises to 235-240 ^o C. Then, in a boiling reaction mass for 3 hours add fractionally 74.5 g (0.8 mol) of aniline as it is consumed, while azeotropically removing the reaction water. Within the specified 3 hours, the temperature of the reaction mass is gradually increased at a speed of 8-10 ^o C / hour to 260-270 ^o C and at the temperature reached, the mass is kept for 1.5 hours. During the reaction, 34 g of water is released (94.4% of its theoretical yield). Unreacted aniline is then distilled off. DFFD is isolated from the remaining reaction mass by crystallization from toluene. For this, the reaction mass is poured into 500 ml of toluene with stirring, kept for 15-20 minutes at a moderate boil, cooled, the precipitate is filtered off, washed twice with toluene and dried. Get 213.5 g of DFFD with a melting point of 145-147 ^o C. The yield of DFFD 82%.

 The presented examples illustrate the manufacturing process of N, N'-diphenyl-n-phenylenediamine, repeatedly reproduced in industry, providing a high and stable yield of the target product with an optimal combination of technological modes of the method and the concentrations of the ingredients used.

Claims (8)

1. A method of producing N, N'-diphenyl-n-phenylenediamine by condensation of hydroquinone with aniline in the presence of a catalyst with azeotropic distillation of the resulting water, and upon completion of the process, by distillation of unreacted aniline and subsequent isolation of N, N'-diphenyl-n-phenylenediamine from the remaining reaction mass, characterized in that the catalyst used is 85 - 89% phosphoric acid, which is mixed with hydroquinone and aniline in a molar ratio of (0.018 - 0.10): 1: (1.2 - 1.35), respectively , the reaction mass is heated to 205 - 210 ^o C for 1.5 - 2.0 hours, an azeotropic distillation of the resulting water is carried out at a temperature increase of 235 - 240 ^o C, the condensate is separated into the aqueous and aniline phases and the aniline phase is recycled, then fractional aniline is added to the reaction mass until it reaches the molar ratio of hydroquinone: aniline 1: (2.05 - 2.5), respectively, with simultaneous azeotropic distillation of the resulting water, and the process for the specified 2 to 8 hours is carried out with increasing temperature at a speed of (3 - 10) ^o C / h, then the reaction mass is maintained when achieved temperature for 1.5 - 3 hours and distilled off the unreacted aniline.  2. The method according to claim 1, characterized in that the azeotropic distillation of the resulting water is carried out until its total amount during the reaction is not less than 90% of the theoretical yield.  3. The method according to claim 1 or 2, characterized in that the allocation of N, N'-diphenyl-n-phenylenediamine from the reaction mass is carried out by fractional distillation.  4. The method according to claim 3, characterized in that during fractional distillation of the reaction mass, diphenylamine is removed as the first fraction of the distillate, n-hydroxydiphenylamine as a second fraction of the distillate mixed with the remaining aniline, followed by isolation of the target product as a third fraction of the distillate - N, N'-diphenyl-n-phenylenediamine.  5. The method according to claim 4, characterized in that the second fraction of the distillate containing n-hydroxydiphenylamine in a mixture with aniline is sent for recycling.  6. The method according to claim 1 or 2, characterized in that the allocation of N, N'-diphenyl-n-phenylenediamine from the reaction mass is carried out by crystallization from a solvent selected from the group consisting of toluene, ethylene glycol, chlorobenzene, o-dichlorobenzene .  7. The method according to claim 6, characterized in that the allocation of N, N'-diphenyl-n-phenylenediamine from the reaction mass is carried out by crystallization from toluene. 8. The method according to any one of claims 1 to 7, characterized in that the allocation of N, N'-phenyl-n-phenylenediamine is carried out when it reaches a solidification temperature of 145 - 150 ^o C.