RU2417981C1 - METHOD OF PRODUCING N-2-ETHYLHEXYL-N'-PHENYL-p-PHENYLENEDIAMINE - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing N-2-ethylhexyl-N'-phenyl-n-phenylenediamine. The method is realised through alkylation of n-aminophenyl-amine with a potassium alcoholate solution in 2-ethylhexanol, added continuously in equal portions into molten n-aminophenyl-amine. Alcohol azeotrope is distilled with water through a fractionating column in which temperature is kept at 90-110°C by returning the condensed hot alcohol into the reaction zone. The end product is separated from the organic layer after aqueous extraction of the reaction mass. Temperature of the added potassium alcoholate solution is kept at 135-160°C. Before adding the potassium alcoholate solution, molten n-aminophenyl-amine is heated to 200-209°C, and addition is carried out until achieving 95% conversion of n-aminophenyl-amine, after which temperature in the reactor is raised to 231-237°C in order to complete alkylation.

EFFECT: short duration of the alkylation step, low power consumption during alkylation, low specific consumption of 2-ethylhexanol, high quality of the product.

4 cl, 1 tbl, 6 ex

Description

The invention relates to the chemical industry, in particular to a technology for producing N-alkyl-N'-phenyl substituted p-phenylenediamines (PFDA), which are widely used as antioxidants for polymers, rubbers and rubbers.

Known methods for producing N-2-ethylhexyl-N'-phenyl-p-phenylenediamine and other PFDA by alkylation of p-aminodiphenylamine (PADA) with aliphatic alcohols at elevated temperatures on a Nickel-Raney catalyst (ed. St. USSR N 150521, publ. BI N 8, 1965; ed. St. USSR N 157693, publ. BI N 19, 1963; ed. St. USSR N 159854, publ. BI N 2, 1964; ed. St. USSR N 159855, publ. BI N 2, 1964; ed. St. USSR N 163625, publ. BI N 13, 1964; ed. St. USSR N 163626, publ. BI N 13, 1964; ed. St. USSR N 164294, publ. BI N 15, 1964; ed. St. USSR N 164295, publ. 13.08.64, BI N 15, 1964).

A common disadvantage of these methods is the fire hazard of the process, due to the pyrophoricity of Nickel-Raney and, accordingly, lack of manufacturability.

There is a method involving the use of potassium hydroxide as a catalyst and neutralization of the reaction mass after alkylation with a 25% aqueous solution of sulfuric acid (L.A. Skripko, V.L. Trostyanetskaya and others J. "Chemical Industry" N 3, 1985 g., from 18-20).

The disadvantages of this method include the high energy intensity and low technology, due to energy costs for the continuous distillation of alcohol and an azeotrope of alcohol with water from the reaction mass and the circulation in a closed cycle of a mixture of alcohol vapor and an 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.

Reducing energy costs for obtaining the target products according to the above method (L.A. Skripko, V.L. Trostyanetskaya and others J. "Chemical Industry" N 3, 1985, from 18-20) is achieved by distillation of the alcohol- water "through a heated reflux condenser with a coolant temperature in the jacket within 115-125 ° C, which allows you to return alcohol to the reaction mass without additional heating, while to neutralize the reaction mass, oxalic acid is used (RU 2169137, class C07C 211/50, C07C 211/55, C07C 209/16, 06/20/2001).

A further reduction in energy consumption during alkylation is achieved by the method in which distillation of alcohol and the alcohol-water azeotrope is carried out through a reflux condenser with a temperature of 126-145 ° C, followed by separation of the azeotrope in the separator and the continuous return of hot alcohol to the synthesis reactor through a reflux condenser, while neutralizing sulfuric, phosphoric or hydrochloric acid is used in the reaction mass, and to reduce the alkylation time before the end of the reaction, the potassium salt of the alkylating alcohol is introduced into the reaction mass stve 10-20 wt.% of potassium hydroxide source (RU 2293077, Cl. 211/51 S07S, S07S 211/55, 10.02.2007).

This method, however, does not provide sufficient full use of the alcohol loaded into the reactor and does not sufficiently reduce the completion time of the limiting stage — the alkylation of the amine with alcohols.

A known method of producing N-2-ethylhexyl-N'-phenyl-p-phenylenediamine and other PFDA, in which the alkylation of PADA with aliphatic alcohols of the C ₇ -C ₉ fraction, or a mixture thereof, or individually 2-ethylhexanol (2EG), in the presence of caustic potassium lead at a temperature of 170-235 ° C, while the alcohol-water azeotrope enters the heat exchanger, where it condenses and merges into the water separator, from where the separated alcohol is passed through a tubular film evaporator heated by a heat carrier with a temperature not lower than 175 ° C, and then return to the alkylation step . Under these conditions, the temperature rise in the reactor occurs both due to external heating through the jacket, and due to the heat of the first exothermic reaction stage - the formation of potassium alcoholate (RU 2268878, class C07C 211/51, C07C 211/55, 01/27/2006 )

In the description of the above invention, examples of the method in semi-industrial reactors such as pilot plants with a volume of 1 m ^{3 are given} . However, when switching to industrial reactors with a volume of 3 m ³ or more as a result of a side reaction of decomposition of an intermediate product - potassium alcoholate at a temperature above 170 ° С, the synthesis of the target product proceeds 10-30 times slower than in laboratory ones, it is poorly controlled, sometimes it stops and it requires additional loading of caustic potassium and / or alcohol and is highly dependent on the conditions of mass and heat transfer in the reactor.

The features of the process for producing N-2-ethylhexyl-N'-phenyl-p-phenylenediamine carried out in industrial reactors by the methods indicated above lead to an increase in energy consumption, consumption rates for raw materials, an increase in the content of impurities and an increase in the cost of the target product.

The closest in technical essence and the achieved result, the method of producing N-2-ethylhexyl-N'-phenyl-p-phenylenediamine, the prototype of the present invention, is a method in which the alkylation of PADA is carried out with an 8-40% alcohol solution of potassium alcoholate, uniformly dosed in portions of the PADA introduced into the reaction to the melt, heated to 220-230 ° С, with the azeotrope distillation through a reflux condenser at a temperature of 90-110 ° С and the condensed alcohol is returned to the reaction zone through a column with a nozzle or a plate column heated by steam coming from the reactor (RU 2373190, class С07С 211/51, С07С 211/55, 11/20/2009).

The rate of dosing of the alcoholate in this way is determined by the need to maintain the optimum temperature of the alkylation reaction in the range of 215-230 ° C. In order to further prevent water from entering the reactor, a column (packed or plate) is installed between the reactor and the reflux condenser. At the same time, the use of a heated packed or plate column can further reduce the alkylation time by 1-3 hours (for industrial reactors) due to the better separation of water and the exclusion of water from entering the alkylation reactor.

After completion of the alkylation process, the resulting product is poured onto water, the reaction mass is cooled to 90-95 ° C, subjected to extraction and washing from a water-soluble potassium salt of carboxylic acid. The organic layer containing the target product and residual alcohol is separated from the aqueous layer and sent to distill off the alcohol under vacuum and to isolate the target product.

The described method for producing N-2-ethylhexyl-N'-phenyl-p-phenylenediamine according to the patent RU 2373190 has the following disadvantages:

- an alcoholic solution of potassium alcoholate, which is used to alkylate PADA, is supplied to the PADA melt with a temperature of 100 to 130 ° C, that is, much lower than the temperature in the alkylation reactor (210-230 ° C), which constantly cools the alkylation reactor, the process in which it is endothermic in itself, and requires significant energy consumption to maintain it in this reactor, which has a larger volume in industrial design than the reactor for the preparation of potassium alcoholate;

- at a temperature in the alkylation reactor (210-230 ° C), a side reaction of the monomolecular decomposition of the alcoholate occurs, first to 2-ethylhexanal, and then in a strongly alkaline medium to the potassium salt of 2-ethylhexanoic acid, which leads to an increase in the alkylation time;

- the alkylation under the above conditions does not allow to reduce the concentration of residual PADA in the target product below 1.0%.

In addition, the presence of residual PADA, insoluble, in contrast to the target product N-2-ethylhexyl-N'-phenyl-p-femylenediamine, in aliphatic solvents, when using this product as an antioxidant in the production of a number of synthetic rubbers leads to the accumulation of hard to remove deposits in devices and communications.

The objective of the invention is to develop a method for producing N-2-ethylhexyl-N'-phenyl-p-phenylenediamine with the achievement of the technical result, which consists in reducing the energy consumption for the alkylation, reducing the duration of the alkylation stage, thereby increasing the productivity of the process, reducing the specific consumption 2-ethylhexanol and, as a consequence, in reducing the cost of the target product N-2-ethylhexyl-N'-phenyl-p-phenylenediamine while improving its quality by reducing the content of residual PADA in the reaction mass.

To achieve the technical result, a method is proposed for producing N-2-ethylhexyl-N'-phenyl-p-phenylenediamine by alkylation of p-aminodiphenylamine with a solution of potassium alcoholate in 2-ethylhexanol, dosed and uniformly in portions of the PAD introduced into the reaction to the heated melt, followed by distillation of the azeotrope alcohol with water, aqueous extraction, separation of the organic layer and isolation of the target product from it, characterized in that the heated PADA melt at the initial stage of alkylation is maintained at a temperature of 200-209 ° C and then m, when the PADA conversion of 95% is reached, the dosing of the alcoholate solution is stopped, the temperature is raised to the level of 231-237 ° C and the dosing is resumed, while the temperature of the potassium alcoholate of the potassium alcoholate dosed onto the heated melt is maintained in the range of 135-160 ° C.

As a result, at the first stage of alkylation, the rate of conversion of PADA by bimolecular reaction to the target product is quite high, and the rate of side reaction of the decomposition of the alcoholate to potassium 2-ethylhexanoate is lower than under the prototype under these conditions.

After reaching 95% conversion of PADA, when its concentration in the reaction mass decreases by more than 20-30 times, the temperature rise in the alkylation reactor is 1-7 ° C higher than the upper temperature limit of the prototype and at a higher temperature of the dosed potassium alcoholate compared with the conditions of the prototype, allows you to achieve a deeper degree of conversion of residual PADA, reduce the time of the alkylation operation and reduce energy consumption for the alkylation process in comparison with these indicators by the method selected for .

Preliminary preparation of a solution of potassium in 2-ethylhexanol and increasing its temperature is carried out in a reactor of a smaller volume than the alkylation reactor, which requires less energy than maintaining a higher temperature in the alkylation reactor according to the prototype method.

The supply of the temperature of the alcoholate heated to a temperature higher than that of the prototype method in the alkylation reactor requires less energy to compensate for the heat loss from cooling this reactor with a constantly incoming and more “cold” alcoholate solution.

A lower temperature level in the alkylation reactor in the first stage contributes to less distillation of 2-ethylhexanol into the reflux condenser. In addition, the distillation of an azeotropic mixture of 2-ethylhexanol with reaction water and its return from the reflux condenser to the reactor, which also leads to cooling of the latter, requires the present invention lower additional energy consumption to restore the working temperature in the alkylator than by the prototype method.

All these factors contribute to a more rapid conduct of the first stage of alkylation at relatively high initial concentrations of reagents, despite the lower temperature than in the prototype method in the alkylation reactor. Raising the temperature at the final stage of alkylation can increase the depth of the bimolecular conversion of PADA to the target product with a low residual concentration of PADA in the reactor and reduce the total time of the alkylation operation.

After the extraction of the reaction mixture with water, separation of the organic layer, distillation of the residual water and 2-ethylhexanol from it, the obtained target product contains less residual PADA than the prototype method due to its greater conversion at the final stage of the alkylation process carried out when the temperature is raised according to the invention .

The implementation of the method for producing N-2-ethylhexyl-N'-phenyl-p-phenylenediamine in the temperature regime proposed in the present invention allows:

- reduce the total energy consumption for alkylation by 10-15%;

- reduce the minimum time of the alkylation operation from 23 to 14 hours;

- reduce the specific consumption of 2-ethylhexanol by 10-25 kg / t of the target product;

- to reduce the content of residual PADA in the target product from 0.8-1.0% by the method of the prototype to not more than 0.62%.

The proposed method is illustrated by the following examples.

Example 1

In a 2.7 m ³ jacketed industrial reactor equipped with a stirrer, reflux condenser, reflux condenser, thermometer and dispenser, 1992 kg of 2-ethylhexanol (2400 dm ³ ) and 190 kg of caustic potassium are loaded and a solution of potassium alcoholate in 2-ethylhexanol with concentration of 24.8%. The resulting solution at a temperature of 160 ° C is dosed at a speed of 191 l / h into a 5 m ³ alkylation reactor with a jacket, equipped with a stirrer, a reflux condenser, a heat exchanger, a temperature sensor and a rotameter for measuring the alcoholate supply rate.

Preliminarily, 1210 kg of technical PADA, heated and melted with stirring, were loaded into the alkylation reactor before dosing potassium alcoholate to 200 ° C. After the start of dosing of potassium alcoholate, the temperature in the alkylation reactor is maintained in the range of 200-209 ° C, the temperature of the azeotrope at the outlet of the reflux condenser in the range of 90-100 ° C.

The potassium alcoholate solution is dosed for 11.5 hours until the residual PADA content in the reactor is 5% of the initial one, calculating it from the amount of distilled water or from the determined current concentration in the selected sample of the reaction mixture, taking into account the actual volume of the latter, after which the dosage is stopped, raised the temperature in the alkylation reactor is up to 237 ° C and dosing is continued again until the potassium alcoholate solution is exhausted and the reaction mass is maintained at this temperature for 2 hours with stirring. After completion of the alkylation, the residual PADA content is 0.35 wt.%. The total alkylation operation time is 16 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 preliminarily added to the reactor. The extraction of potassium 2-ethylhexanoate is carried out at 90-100 ° C for one hour. After extraction is complete, the aqueous layer containing potassium 2-ethylhexanoate and the remaining unreacted potassium hydroxide are separated from the organic layer. The organic layer is directed to distillation of alcohol under vacuum and the selection of the target product. 1945 kg of N-2-ethylhexyl-N'-phenyl-p-phenylenediamine is obtained with a residual PADA content of 0.5%. The yield of N-2-ethylhexyl-N'-phenyl-p-phenylenediamine at 100% PADA is 99.7%. Consumption of 2-EHS - 622 kg per 1 ton of the target product.

Example 2

A solution of potassium alcoholate in 2-ethylhexanol is prepared as described in Example 1. The resulting solution is dosed at a temperature of 135 ° C at a rate of 183 l / h into a 5 m ³ alkylation reactor with a jacket, equipped with a stirrer, reflux condenser, heat exchanger, and a temperature sensor and a rotameter for measuring the potassium alcoholate feed rate.

Preliminarily, 1230 kg of technical PADA, heated and melted with stirring, was loaded into the alkylation reactor before dosing potassium alcoholate to 232 ° C. After the start of dosing of the alcoholate, the temperature of the azeotrope at the outlet of the reflux condenser is maintained in the range of 90-100 ° C.

The dosage of the alcoholate solution is carried out for 12 hours until the alcoholate solution is completely consumed, after which the reaction mass is kept under stirring for 5 hours. After alkylation is completed, the residual PADA content is 0.42 wt.%. The total alkylation operation time is 17 hours.

The selection of the target product is carried out as described in example 1. Obtain 1980 kg of N-2-ethylhexyl-N'-phenyl-p-phenylenediamine with a residual PADA of 0.62%. The yield of N-2-ethylhexyl-N'-phenyl-p-phenylenediamine at 100% PADA is 99.5%. Consumption of 2-EHS - 628 kg per 1 ton of the target product.

Example 3

A solution of potassium alcoholate in 2-ethylhexanol is prepared as described in Example 1. The resulting solution at a temperature of 145 ° C is dosed at a rate of 220 l / h into a 5 m ³ alkylation reactor with a jacket, equipped with a stirrer, reflux condenser, heat exchanger, and a temperature sensor and a rotameter for measuring the rate of alcoholate delivery.

Preliminarily, 1220 kg of technical PADA, heated and melted with stirring, are loaded into the alkylation reactor before dosing of potassium alcoholate. After the start of dosing of potassium alcoholate, the temperature in the alkylation reactor is raised to 209 ° C, the temperature of the azeotrope at the outlet of the reflux condenser is maintained in the range of 90-100 ° C.

The alcoholate solution is dosed for 10 hours until the residual PADA content in the reactor is 5% of the initial one, calculated as described in Example 1, after which the temperature in the alkylation reactor is raised to 237 ° C and kept under stirring while continuing to dose the remaining potassium alcoholate for 2 hours, and after the alcoholate is exhausted, the reaction mass is stirred at this temperature for another 3 hours. After completion of the alkylation, the residual PADA content is 0.25 wt.%. The total alkylation operation time is 15 hours.

The selection of the target product is carried out as described in example 1. Get 1961 kg of N-2-ethylhexyl-N'-phenyl-p-phenylenediamine with a residual PADA of 0.45%. The yield of N-2-ethylhexyl-N'-phenyl-p-phenylenediamine at 100% PADA is 99.6%. Consumption of 2-EHS - 624 kg per 1 ton of the target product.

Example 4

A solution of potassium alcoholate in 2-ethylhexanol is prepared as described in Example 1. The resulting solution is dosed at a temperature of 135 ° C at a rate of 178.6 l / h into a 5 m ³ alkylation reactor with a jacket, equipped with a stirrer, reflux condenser, heat exchanger, and a sensor for determination of temperature and rotameter for measuring the rate of supply of alcoholate.

Preliminarily, 1215 kg of technical PADA, heated and melted with stirring, are loaded into the alkylation reactor before dosing potassium alcoholate to 231 ° C. After the alcoholate is dosed, the temperature of the azeotrope at the outlet of the reflux condenser is maintained in the range of 90-100 ° C.

The dosage of the alcoholate solution is carried out for 14 hours until the alcoholate solution is completely consumed, after which the reaction mass is kept under stirring for 4 hours. After completion of the alkylation, the residual PADA content is 0.39 wt.%. The total alkylation operation time is 18 hours.

The selection of the target product is carried out as described in example 1. Receive 1955 kg of N-2-ethylhexyl-N'-phenyl-p-phenylenediamine with a residual PADA content of 0.58%. The yield of N-2-ethylhexyl-N'-phenyl-p-phenylenediamine at 100% PADA is 99.3%. Consumption of 2-EHS - 640 kg per 1 ton of the target product.

Example 5

A solution of potassium alcoholate in 2-ethylhexanol is prepared as described in Example 1. The resulting solution is dosed at a temperature of 160 ° C at a rate of 244 l / h into a 5 m ³ alkylation reactor with a jacket, equipped with a stirrer, reflux condenser, heat exchanger, and a temperature sensor and a rotameter for measuring the rate of alcoholate delivery.

Preliminarily, 1235 kg of technical PADA, heated and melted with stirring, are loaded into the alkylation reactor before dosing potassium alcoholate to 201 ° C. After the start of dosing of the alcoholate, the temperature in the alkylation reactor is raised to 208-209 ° C, the azeotrope temperature at the outlet of the reflux condenser is maintained in the range of 90-100 ° C.

The alcoholate solution is dosed for 9 hours, maintaining the temperature in the alkylation reactor in the range of 200–209 ° С until the residual PADA content in the reactor is 5% of the initial one, calculated as described in Example 1, after which the temperature in the alkylation reactor is raised to 237 ° C and maintained with stirring, continuing to dose the remaining potassium alcoholate for 3 hours, and after its exhaustion, the reaction mass was stirred at this temperature for another 2 hours.

After alkylation is completed, the residual PADA content is 0.22 wt.%. The total alkylation operation time is 14 hours.

The selection of the target product is carried out as described in example 1. Receive 1989 kg of N-2-ethylhexyl-N'-phenyl-p-phenylenediamine with a residual PADA content of 0.35%. The yield of N-2-ethylhexyl-N'-phenyl-p-phenylenediamine at 100% PADA is 99.6%. Consumption of 2-EHS - 635 kg per 1 ton of the target product.

Example 6

A solution of potassium alcoholate in 2-ethylhexanol is prepared as described in Example 1. The resulting solution at a temperature of 160 ° C is dosed at a rate of 244 l / h into a 6.3 m ³ jacketed alkylation reactor equipped with a stirrer, reflux condenser, heat exchanger, and a sensor for determination of temperature and rotameter for measuring the rate of supply of alcoholate.

Preliminarily, 1235 kg of technical PADA, heated and melted with stirring, are loaded into the alkylation reactor before dosing potassium alcoholate to 201 ° C. After the start of dosing of apogolate, the temperature in the alkylation reactor is raised to 208-209 ° C, the temperature of the azeotrope at the outlet of the reflux condenser is maintained in the range of 90-100 ° C.

The alcoholate solution is dosed for 9 hours, maintaining the temperature in the alkylation reactor in the range of 200–209 ° С until the residual PADA content in the reactor is 5% of the initial one, calculated as described in Example 1, after which the temperature in the alkylation reactor is raised to 237 ° C and maintained with stirring, continuing to dose the remaining potassium alcoholate for 3 hours, and the alkylation process ends.

After completion of the alkylation, the residual PADA content is 0.15 wt.%. The total alkylation time is 12 hours.

The selection of the target product is carried out as described in example 1. Obtain 1995 kg of N-2-ethylhexyl-N'-phenyl-p-phenylenediamine with a residual PADA content of 0.22%. The yield of N-2-ethylhexyl-N'-phenyl-p-phenylenediamine at 100% PADA is 99.8%. Consumption of 2-EHS - 632 kg per 1 ton of the target product.

The conditions and results of the syntheses carried out according to Examples 1-6, as well as Examples 7-10, carried out in temperature conditions of the present invention, similarly to Examples 2-6, are presented in Table 1.

Claims (4)

1. A method of producing N-2-ethylhexyl-N'-phenyl-p-phenylenediamine, comprising alkylating p-aminodiphenylamine with a solution of potassium alcoholate in 2-ethylhexanol, in uniform portions of p-aminodiphenylamine introduced into the reaction to a heated melt, distilling the alcohol azeotrope with water and separation by aqueous extraction of the organic layer with the isolation of N-2-ethylhexyl-N'-phenyl-p-phenylenediamine from it, characterized in that the temperature of the dosed alcoholic solution of potassium alcoholate is maintained in the range of 135-160 ° C, at the initial stage of alkylation, the melt p-aminodiphenylamine is maintained at a temperature of 200-209 ° C; upon reaching a conversion of p-aminodiphenylamine equal to 95%, the temperature is raised to 231-237 ° C. 2. The method according to claim 1, characterized in that the dosing rate of an alcoholic solution of potassium alcoholate to melt p-aminodiphenylamine to its 95% conversion in industrial reactors of 5 m ³ or more is maintained in the range from 179 to 244 l / h. 3. The method according to claim 2, characterized in that after 95% conversion of p-aminodiphenylamine, the dosing of the potassium alcoholate alcohol solution is carried out until the content of p-aminodiphenylamine in the reaction mass is not higher than 0.15-0.42 wt.%. 4. The method according to claim 3, characterized in that the dosage of the alcoholic solution of potassium alcoholate is started when the temperature in the alkylation reactor reaches 231-237 ° C.