RU2463289C2 - METHOD OF PRODUCING N-2-ETHYLHEXYL-N'-PHENYL-p-PHENYLENEDIAMINE - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to an improved method of producing N-2-ethylhexyl-N'-phenyl-p-phenylenediamine by reacting p-aminodiphenylamine with 2-ethylhexanol in the presence of potassium hydroxide, at temperature 170-235°C with simultaneous distillation of the alcohol azeotrope with water through a heated refluxer and returning the condensed hot alcohol into the reaction zone, separating the end product from the organic layer after aqueous extraction. The mixture of 2-ethylhexanol and potassium hydroxide is preheated to 90-140°C fed into the reaction mass in two steps, at the first step at temperature of the p-aminodiphenylamine not lower than 100°C, 50-90 wt % of the calculated amount of the mixture of 2-ethylhexanol and potassium hydroxide is fed, and the remaining amount is continuously fed until temperature of the reaction mass reaches 200-235°C.

EFFECT: method cuts the duration of the alkylation step and increases efficiency of the equipment.

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Description

The invention relates to the chemical industry, in particular to a technology for producing N-alkyl-N'-phenyl substituted p-phenylenediamine (PFDA) and can be used in the manufacture of antioxidants for polymeric materials.

A known method of producing PFDA by alkylation of p-aminodiphenylamine (PADA) with aliphatic alcohols at elevated temperatures, using potassium hydroxide as a catalyst and neutralizing the reaction mass after alkylation with a 25% aqueous solution of sulfuric acid (L.A. Skripko, V.L. Trostyanetskaya et al., J. "Chemical Industry" No. 3, 1985, from 18-20).

The disadvantages of this method include the high energy intensity and low technological process due to the energy consumption for the continuous distillation from the reaction mass and the circulation in a closed cycle of a mixture of alcohol vapor and the alcohol-water azeotrope. To separate the alcohol from the mixture and return it to the reactor, cooling the mixture and subsequent heating of the alcohol are required.

A known method, including the alkylation of p-aminodiphenylamine or p-phenylenediamine with C ₅ -C ₁₀ aliphatic alcohols at a temperature of 240-260 ° C, in the presence of potassium hydroxide, with simultaneous distillation during the synthesis of a mixture of alcohol vapors and an alcohol-water azeotrope through heated a reflux condenser with a coolant temperature of 115-125 ° C and the return of condensed vapors of alcohol to the reaction zone through a reflux condenser and neutralization of the reaction mixture with crystalline oxalic acid (patent RU No. 2169137, IPC ⁷ C07C 211/50, C07C 211/55, C07C 209/16 o. 06/20/2001).

The disadvantage of this method is the high temperature of the alkylation process (240-260 ° C), at which by-products are formed from alcohols - fatty acids (valerianic, nylon, caprylic, 2-ethylhexanoic, etc.), resulting in an amine: alcohol molar ratio: the catalyst is broken and the process slows down. To restore the required molar ratio of the reactants and bring the reaction to the end, it is necessary to introduce an additional amount of alcohol and catalyst into the reaction mass. The excess of oxalic acid used in the specified method for the isolation of the target products is involved in side reactions (it binds the potassium hydroxide used and thereby worsens the process), leading to the formation of free organic acids in the reaction mass that are closely boiling with alcohols. As a result, the alcohols distilled off during the reaction contain a significant amount of acids closely boiling with alcohols and cannot be reused in the process without further purification. In addition, oxalic acid has a high corrosive effect, and when used at the stage of neutralization of the reaction mixture at high temperature (120-140 ° C), it may contact the surface of the enameled apparatus, which can cause corrosion.

There is a method according to which the alkylation of p-aminodiphenylamine with aliphatic alcohols in the presence of potassium hydroxide is carried out at a temperature of 170-235 ° C, while the alcohol-water azeotrope enters a heat exchanger where alcohol and water are condensed and merged into a water separator, from which the separated alcohol is passed through a tubular film evaporator heated by a coolant with a temperature of at least 175 ° C, and then returned to the stage of alkylation, and the target product is isolated from the organic layer after water extraction of the reaction mass (Patent RU No. 2268878, IPC С07С 211/51, С07С 211/55, С07С 209/16, op. 27.01.2006). The description of the patent provides examples of the method in semi-industrial reactors such as pilot plants with a volume of 1 m ³ .

This method has several disadvantages:

- an additional operation of heating in a film evaporator of alcohol, previously separated from the water of the azeotrope, and returning it to the reactor, causes additional energy consumption and complicates the process;

- when carrying out the process in industrial reactors, the volume of which exceeds 1 m ³ , the ratio of the volume of the reaction mass to its surface area approximately linearly increases with increasing diameter of the reactor, while the conditions of heat and mass transfer significantly worsen, which increases the duration of the alkylation reaction (5- 6 times for a reactor volume of 5 m ³ );

- due to the long time of the alkylation reaction in the reaction mass, a large number of by-products of this reaction accumulate in the form of potassium salts of fatty acids, esters of used alcohols and fatty acids formed as a by-product, along with the residual amount of potassium hydroxide.

Closest to the proposed invention in essential features and the achieved result is a method comprising obtaining N-2-ethylhexyl-N'-phenyl-p-phenylenediamine by alkylation of p-aminodiphenylamine at a temperature of 170-235 ° C, using an alcohol solution as the alkylating agent potassium salt of 2-ethylhexanol (alcoholate), which is continuously dosed into the melt of the starting p-aminodiphenylamine, preheated to 210-230 ° C while distilling the azeotrope of alcohol with water through a reflux condenser, in which the temperature is 90-110 ° C, the return of the condensed hot alcohol to the reaction zone, the selection of the target product from the organic layer after water extraction of the reaction mixture (RU 2373190, IPC С07С 211/51, С07С 211/55, С07С 209/56, publ. 27.06 .2009).

The disadvantage of this method is the high duration of the process and, as a consequence, the low productivity of the equipment.

The present invention solves the problem of reducing the duration of the alkylation stage and increasing the productivity of the equipment.

This problem is solved in that in the method for producing N-2-ethylhexyl-N'-phenyl-p-phenylenediamine by the interaction of p-aminodiphenylamine with 2-ethylhexanol in the presence of potassium hydroxide, at a temperature of 170-235 ° C, while the alcohol azeotrope is distilled off with water through a heated reflux condenser and returning the condensed hot alcohol to the reaction zone, isolating the target product from the organic layer after water extraction according to the invention, the mixture of 2-ethylhexanol with potassium hydroxide is preheated to 90-140 ° C and put into the reaction mass in two stages, at the first stage, at a temperature of p-aminodiphenylamine of at least 100 ° C, 50-90 wt.% of the calculated amount of a mixture of 2-ethylhexanol with potassium hydroxide is loaded, and the remaining amount is dosed continuously when the temperature of the reaction mass reaches 200 -235 ° C.

Reducing the temperature of p-aminodiphenylamine below 100 ° C before loading the mixture of 2-ethylhexanol with potassium hydroxide, as well as the temperature of the loading mixture below 90 ° C, reducing the amount of loaded mixture of 2-ethylhexanol with potassium hydroxide in the first stage below 50% and increasing its amount above 90% increase the duration of the process. An increase in the temperature of the charged mixture of 2-ethylhexanol and potassium hydroxide above 140 ° C leads to the loss and excessive consumption of alcohol. The invention is illustrated by the following examples:

Example 1

In a three-necked flask with a capacity of 0.5 l, equipped with a stirrer, a thermometer, a heated reflux condenser with a downward refrigerator, an allonge, a receiver and a tray column with the number of plates 2 installed between the bulb and the reflux condenser, so that the vapors from the reaction mass heat the column, load 121 , 0 g of technical (98.6%) p-aminodiphenylamine (PADA) is heated to 140 ° C. A mixture of 120.3 g of 2-ethylhexanol 11.6 g of 95% potassium hydroxide is prepared, heated to 100 ° C and 60 wt.% Of the total amount of the resulting mixture is loaded into a PADA flask with stirring.

In a reflux condenser, a temperature of 90-95 ° C is maintained using a coolant (glycerin), cold water is supplied to the refrigerator, the reaction mass is heated for 3 hours to a temperature of 220-230 ° C. When the temperature reaches 175-180 ° C, the azeotropic alcohol-water mixture begins to be distilled off, while the bulk of 2-ethylhexanol is condensed in a reflux condenser and returned to the reaction flask, and the water formed as a result of the reaction in the form of vapors with 2-ethylhexanol enters the refrigerator , condenses and drains into the water separator. The separated alcohol is constantly returned through the dish column to the reaction mass. When the temperature reaches 230 ° C, gradual dosing is started for 0.5 hour of the remaining amount of the mixture of 2-ethylhexanol and potassium hydroxide and distillation is continued. The duration of the alkylation reaction is 4.5 hours. The total amount of distilled water is 48 ml. The content in the reaction mass of residual PADA 0.8%.

Isolation of the target product: in a three-necked flask with a capacity of 0.5 dm ³ equipped with a stirrer and reflux condenser, 140 ml of water are charged and the reaction mixture is poured from the stage of alkylation (alkylate) with a temperature of 150-230 ° С. The temperature of the resulting reaction mass is maintained in the range of 90-95 ° C. with stirring for 30 minutes, after which it is allowed to stand for 30 minutes at the same temperature and with the stirrer turned off. In this case, the aqueous and organic layers are separated: the upper, organic, contains 2-ethylhexanol (2-EHS) and the alkylation product, the lower, aqueous, contains the potassium salt of 2-ethylhexanoic acid (2-EHC). The aqueous layer is separated. The organic layer is additionally washed with 140 ml of water, stirred for 30 minutes at 90-95 ° C, allowed to stand for one hour at this temperature and with the stirrer turned off. After distillation of 2-EHS, 193.9 g of the expected product is obtained in the form of an oily mass of dark brown with a content of p-aminodiphenylamine of 1.3%, which does not contain additional impurities (2-EHS, an ester based on 2-EHS and 2-EGA ) The yield was 98.7% in terms of p-aminodiphenylamine. The distilled 2-EHS from the stage of alkylation and from the stage of isolation of the target product in the amount of 81.39 g (40.9% of the loaded) is returned to the next alkylation operation.

The aqueous layer, which is an aqueous solution of potassium hydroxide and potassium salt of 2-ethylhexanoic acid is directed to the allocation of 2-EGC.

Examples 2-6

The process is carried out analogously to example 1. The process conditions and the results are shown in the table.

Example 7 Comparative

In a three-necked flask with a capacity of 0.5 l, equipped with a stirrer, thermometer, heated by a reflux condenser with a downward refrigerator, allonge, receiver and plate column, 121.0 technical 98.6% PADA and a pre-prepared mixture of 199.2 g 99% 2-ethylhexanol and 19 , 2 g of 95% potassium hydroxide.

The reaction mass is heated to a temperature of 220-230 ° C. Every 0.5 hours, the content in the reaction mass of residual PADA is determined. The reaction time is 5 hours. The total amount of distilled water is 48 ml. The content in the reaction mass of residual PADA 0.8%.

The selection of the target product is carried out analogously to example 1. Get 193.8 g of the target product in the form of an oily mass of dark brown color with a content of p-aminodiphenylamine 1.3%, not containing additional impurities (2-EHS, an ester based on 2-EHS and 2-EGC). The yield was 98.7% in terms of p-aminodiphenylamine.

Example 8

In an industrial reactor with a volume of 5 m ³ , equipped with a stirrer, reflux condenser, reflux condenser, thermometer and dispenser, 7270 kg of the melt of technical 98.6% PADA are loaded and heated to 140 ° C, then a pre-prepared mixture of 1550 kg of 99% 2-ethylhexanol is loaded ( 1860 dm ³ ) and 142 kg of 95% potassium hydroxide, heated to 100 ° C.

The reaction mass is heated with stirring to 225 ° C with distillation of the azeotrope of alcohol and reaction water, maintaining the temperature in the reflux condenser 90-100 ° C. Then they load a mixture of 525 kg of 2-ethylhexanol (630 dm ³ ) and 48 kg of potassium hydroxide, heated to 100 ° C.

Alkylation is carried out to a residual PADA content in the reaction mass of not more than 0.5%. The total alkylation time is 20 hours.

The reaction mass from the stage of alkylation with nitrogen pressure is transferred to a 6.3 m ³ jacketed reactor equipped with a stirrer. 1400 L of water are pre-added to the reactor. The extraction of potassium 2-ethylhexanoate (2-EHC) is carried out at 90-100 ° C for one hour. After extraction is complete, the aqueous layer containing 2-EHC, as well as the residues of unreacted potassium hydroxide, are separated from the organic layer. The latter is directed to distillation of the alcohol under vacuum and to the isolation of the target product, N-2-ethylhexyl-N'-phenyl-p-phenylenediamine. The amount of the target product is 1940 kg, the residual PADA content is 0.74%, the yield of 100% PADA is 99.4%. The amount of recycled 2-ethylhexanol is 738 kg, the actual consumption of 1254 kg, that is 646.5 kg of 2-ethylhexanol per ton of product C8.

Example 9 (prototype)

In an industrial reactor with a volume of 5 m ³ , equipped with a stirrer, reflux condenser, reflux condenser, thermometer and dispenser, and then 1210 kg of PADA melt and heated to 140 ° C, 2075 kg of 2-ethylhexanol (2500 dm ³ ) containing 190 kg of potassium hydroxide were charged .

The reaction mass is heated with stirring to 225 ° C with distillation of the azeotrope of alcohol and reaction water, maintaining the temperature in the reflux condenser 90-100 ° C.

Alkylation is carried out to the content of residual PADA in the reaction mass of 0.5%. The total alkylation time is 25 hours.

The selection of the target product is carried out analogously to example 8. The amount of the target product is 1935 kg, the residual PADA content is 0.75%, the yield of 100% PADA is 99.1%. The amount of recycled 2-ethylhexanol is 730 kg, the actual consumption of 1260 kg, i.e. 651.2 kg of 2-ethylhexanol per ton of product C8.

Data on the above examples are presented in the table.

Claims (1)

The method of producing N-2-ethylhexyl-N'-phenyl-p-phenylenediamine by the interaction of p-aminodiphenylamine with 2-ethylhexanol in the presence of potassium hydroxide at a temperature of 170-235 ° C while distilling the azeotrope of alcohol with water through a heated reflux condenser and returning the condensed hot alcohol in the reaction zone, the selection of the target product from the organic layer after aqueous extraction, characterized in that the mixture of 2-ethylhexanol with potassium hydroxide is preheated to 90-140 ° C and introduced into the reaction mass in two stages, at the first stage at a temperature of p-aminodiphenylamine is not less than 100 ° C is charged with 50-90 wt.% of the calculated amount of a mixture of 2-ethylhexanol with potassium hydroxide, and the remainder is metered continuously when the reaction mass temperature of 200-235 ° C.