RU2458913C1 - Method for ammonolysis of chlorohydrocarbons and method of purifying ammonium chloride separated from amine synthesis products - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to an improved method for ammonolysis of chlorohydrocarbons by reacting chlorohydrocarbons and ammonia to obtain a solution of aminochlorohydrates and ammonium chloride, neutralising that solution and separating amines. Before the neutralisation step, the solution of aminochlorohydrates and ammonium chloride undergoes at least four-step cooling: at the first step to temperature 20-25°C and holding at that temperature for about 30 minutes, followed by slow cooling at a rate of 4-5°C/h to temperature 10°C at the second step and holding at that temperature for 2 hours while stirring, further cooling at a rate of 10°C/h to temperature minus 10°C at the third step and holding for 1 hour and cooling at the fourth step to temperature minus 25°C and holding for 1 hour. Further, the solution of aminochlorohydrates is separated from the crystallised ammonium chloride by filtration and taken to the neutralisation step, and ammonium chloride is purified. At the purification step, ammonium chloride is washed with hydrochloric acid with weight ratio of HCl of 20-36% and weight ratio of ammonium chloride to acid equal to 1:2, followed by holding the mixture until formation of layers, separating ammonium chloride from hydrochloric acid and drying until all moisture is removed.

EFFECT: method reduces the amount of sodium chloride formed at the step for neutralising products of ammonolysis of chlorohydrocarbons, reduces the amount of waste water, increases energy efficiency of the process, and also increases output of amines and enables to obtain an additional commercial product in form of ammonium chloride.

6 cl, 5 ex

Description

The invention relates to organochlorine chemistry, in particular to the technology of ammonolysis of chlorohydrocarbons to produce acyclic, cyclic and polycyclic amines, which are widely used in various fields of the chemical industry.

Known methods for the ammonolysis of chlorohydrocarbons to produce ethylene diamine (EDA) and polyethylene polyamines (PEPA) by reacting dichloroethane (DCE) with a 77-78% aqueous ammonia solution at a pressure of 9 MPa at 110-130 ° C [Italian Patent No. 617348, 1961; No. 631883, RU No. 614092].

A known method of ammonolysis of chlorohydrocarbons with the formation of EDA and PEPA by the interaction of DCE with a 20-70% aqueous solution of ammonia at a molar ratio of DCE and ammonia equal to 1.0: 2.0-6.4 at a temperature of 130-180 ° C, pressure 0 , 7-7.0 MPa and with vigorous stirring [RF Patent No. 2226189, 2002].

A known method of ammonolysis of chlorohydrocarbons with the production of diaminopropanes (DAP) based on 1,2- or 1,3-dichloropropanes (DHP) and 20-60% aqueous ammonia solution with a molar ratio of DCP and ammonia equal to 1: 1.6-3 , 8 at a temperature of 130-155 ° C, a pressure of 0.8-2.5 MPa and with vigorous stirring [RF Patent No. 2226191, 2002].

A known method of ammonolysis of chlorohydrocarbons with the production of di- and polyamines by the interaction of DCE or DC with 25-55% aqueous ammonia at a molar ratio of DCE (DC) and ammonia equal to 1.0: 1.8-6.0 at a temperature of 105- 125 ° C, a pressure of 0.5-1.4 MPa and with vigorous stirring [RF Patent No. 2226188, 2002].

A known method of ammonolysis of chlorohydrocarbons to produce polypropylene polyamines (PPA) based on 1,2- or 1,3-dichloropropanes (DCP) and a 20-30% aqueous ammonia solution with a molar ratio of DCP and ammonia equal to 1.0: 2.5 -4.5 at a temperature of 140-180 ° C, a pressure of 0.6-3.0 MPa and with vigorous stirring [RF Patent No. 2226199, 2002].

A known method of ammonolysis of chlorohydrocarbons with the production of propylene diamines based on waste glycerol production under pressure and at a temperature of 50-200 ° C [AS No. 509578].

The prior art according to the claimed invention is not limited to the above technical solutions, but at the same time none of them, including those not mentioned above, solve the problem of eliminating their general disadvantage.

Ammonolysis of chlorohydrocarbons includes: direct synthesis of the initial chlorohydrocarbon with ammonia; the stage of neutralization of the reaction products; centrifugation with separation of the crystalline salt, separation of the organic layer and the aqueous phase, evaporation of amines from the aqueous phase, vacuum distillation (distillation) of amines and, if necessary, rectification of amines into individual components.

The list of process steps is not exhaustive or mandatory for all known methods for the ammonolysis of chlorohydrocarbons, but a common characteristic feature for the process of producing amines by the ammonolysis of organochlorine compounds is the formation of intermediate products in the synthesis stage in the form of amino chlorohydrates and ammonium chloride. A solution of aminochlorohydrates containing ammonium chloride and unreacted ammonia is neutralized with sodium hydroxide solution. As a result of the neutralization reaction, sodium chloride is formed - it becomes necessary to purify the salt of aminochlorohydrates from the solution.

OJSC “Caustic” has implemented the technology for the production of polyethylene polyamines on an industrial scale. The industrial method includes: synthesis of aminochlorohydrates (ACH) by the water-ammonia method (interaction of dichloroethane and ammonia), desorption of ammonia from the reaction mixture, absorption of ammonia; neutralization of aminochlorides with sodium hydroxide solution; separation of amines from the aqueous layer, centrifugation of sodium chloride, distillation of polyethylene polyamines, purification of gases.

The separation of amines from the aqueous layer after neutralization is carried out in a column type evaporator.

The neutralized aqueous salt solution of amines is fed to the evaporator. From the upper part of the apparatus, water vapor with an admixture of ethylene diamine is taken, which through the separator of the evaporator enters the heat exchanger, where it is cooled by circulating water and condensed. Part of the condensate is supplied to the column for reflux (on the upper plate) in the form of reflux, and part in the form of distillate is collected in collectors and returned to the AHG synthesis unit and to the ammonia desorption-absorption unit, and the rest is discharged into the sewage collector.

The amine layer from the phase boundary in the evaporator is drained into a delaminator. The amine layer is fed from the delaminator to the distillation unit of polyethylene polyamines - for distillation of aqueous ethylenediamine (azeotrope). Get polyethylenepolyamine with a concentration of 96-98%.

From the conical part of the evaporator periodically, every 0.5-1.0 hours, a concentrated sodium chloride solution is removed to the cooler and then fed to a centrifuge.

The disadvantage of the industrial method is: the formation of a large amount of sodium chloride. Salt clogs processing equipment: evaporator tubes, centrifuges, pipelines. There is a need to constantly clean equipment from accumulated salt (flush). In addition, the constant washing of centrifuges and especially the evaporator leads to the formation of a large amount of amine-containing wastewater - up to 9 tons of effluents per ton of finished product.

The above negative features of the industrial method significantly increase the energy intensity of the process and lead to relatively high losses of the finished product.

The objective of the invention is to optimize the process of ammonolysis of chlorohydrocarbons.

The technical result when using the invention is expressed in a significant reduction in the amount of sodium chloride formed at the stage of neutralization of ammonolysis products of chlorohydrocarbons and not finding qualified use. In addition, the result is a reduction in the amount of wastewater and an increase in the energy efficiency of the process, as well as the use of the invention allows to increase the yield of amines and to obtain an additional commercial product in the form of high-quality ammonium chloride.

The above technical result is achieved by the method of ammonolysis of chlorohydrocarbons by the interaction of chlorohydrocarbons and ammonia to obtain a solution of amino chlorohydrates and ammonium chloride, including the neutralization of this solution and the separation of amines, namely, its feature is that before the stage of neutralization, the solution of amino chlorohydrates and ammonium chloride is subjected to at least four-stage cooling, while in the first stage to a temperature of 20-25 ° C and with exposure at this temperature not change e 30 min, followed by slow cooling at a speed of 4-5 ° C / hour to a temperature of 10 ° C in the second stage and holding at this temperature for 2 hours with stirring, further cooling at a speed of 10 ° C / hour to a temperature minus 10 ° C in the third stage and holding for 1 hour and cooling in the fourth stage to a temperature of minus 25 ° C and holding for 1 hour, then the solution of aminochlorohydrates is separated from the crystallized ammonium chloride by filtration and sent to the stage of neutralization, and ammonium chloride under rgayut further purification. In addition, a feature of the method lies in the fact that the solution is subjected to stepwise cooling, containing,% wt .: NH ₄ Cl - 13.7-28.7; amino chlorohydrates (ACH) - 18.0-35.5; NH ₃ - 5.7-20.8; water (H ₂ O) - 32.5-45.1.

With rapid cooling of the solution, the substance crystallizes and precipitates without the formation of large crystals. Rapid cooling does not allow a high degree of release of the substance from the solution. Due to the slow (gradual) cooling of the solution, it becomes possible to regulate the movement of particles in the solution, which allows them to naturally group, forming initially tiny crystals, which then grow into larger crystals. Slowly cooling the solution, first a saturated and then supersaturated solution is obtained, and in a supersaturated solution, the growth and precipitation of crystals in time is ensured.

The next object from the claimed group of inventions is a method of purification of ammonium chloride isolated from a solution of intermediate products of the synthesis of amines. The cleaning method consists in washing the initial ammonium chloride with hydrochloric acid with a mass fraction of Hcl of 20-36% with a weight ratio of the starting product: acid equal to 1: 2, followed by maintaining the mixture until the layers are separated, separating ammonium chloride from hydrochloric acid and drying it until it is absent moisture. In addition, a product containing: NH ₄ Cl - 76.3-96.7; ACH - 0.1-7.5; NH ₃ - 0.9-12.0; H ₂ O - 0.1-14.7, washing with hydrochloric acid is carried out at least two times with the possibility of using abhase hydrochloric acid with an HCl concentration of at least 20%.

The starting ammonium chloride, isolated as a by-product of the process of ammonolysis of chlorohydrocarbons, contains amino chlorides, ammonia and water as impurities. The peculiarity of the method for purification of ammonium chloride is due to the need to purify precisely these impurities, and this method is applicable only for purification of ammonium chloride isolated from the products of the ammonolysis of chlorohydrocarbons, and this method can be used along with the method of separation of ammonium chloride in the group of inventions aimed at obtaining a single technical result.

As a result of purification of ammonium chloride, a white crystalline product of the composition is obtained,% wt .: NH ₄ Cl - 99.5-99.9; ACH - 0.0-0.3; H ₂ O - 0.0-0.1.

The analysis of the scientific and technical level did not allow us to find a known method that matches the entire set of essential features with the solution stated for the first object; accordingly, the prior art did not reveal a similar technical solution for the purification of ammonium chloride isolated from the products of the synthesis of amines by the method of ammonolysis of chlorohydrocarbons. This allows us to assert that the claimed technical solutions comply with such a patentability condition as novelty.

The essence of the method is disclosed in the following description.

The synthesized products of ammonolysis of chlorohydrocarbons in the form of a solution of the composition,% wt .: NH ₄ Cl - 13.7-28.7; amino chlorohydrates (ACH) - 18.0-35.5; NH ₃ - 5.7-20.8; water (H ₂ O) - 32.5-45.1 - is cooled first stepwise to a temperature of 20-25 ° C. This temperature corresponds to the onset of saturation in the first cooling stage. Extract is made for the time (about 30 min) necessary to stop the precipitation of crystals of ammonium chloride. Then the solution is gradually cooled until the next saturation of the solution - to a temperature of 10 ° C. Cooling is carried out slowly (gradually), namely at a speed of 4-5 ° C / h and with the stirrer working, to eliminate local areas of supercooling at the walls of the apparatus. Maintain at this temperature for 2 hours - until the termination of the process of precipitation of crystals of ammonium chloride. Then it is cooled to a temperature of minus 10 ° С (with a working stirrer and at a cooling rate of about 10 ° С / h) and maintained for 1 h. The next cooling stage: lower the temperature of the solution to minus 25 ° С. Stand for 1 hour.

Crystals released during step cooling are separated by filtration through microfiber filter materials. The filtrate is a solution of the composition,% wt .: NH ₄ Cl - 0.0-2.0; ACH - 23.2-40.8; NH ₃ - 6.4-29.3; H ₂ O - 45.7-51.5, which is neutralized with a sodium hydroxide solution and then polyamines are isolated. As a result of neutralization of the filtrate with a solution of sodium hydroxide, its separation occurs: the upper layer is amine; medium - water-salt; lower - salt. The amine layer from the phase boundary is poured into a distillation cube, in which water with ethylene diamine (azeotrope) is distilled off, and commercial polyethylene polyamines are obtained in the cube. The yield of amines is 94-98%.

The filter cake is a product in the form of white crystals and yellowing when exposed to air. The composition of the obtained product,% wt .: NH ₄ Cl - 76.3-96.7; ACH - 0.1-7.5; NH ₃ - 0.9-12.0; H ₂ O - 0.1-14.7.

The precipitate of the composition,% wt .: NH ₄ Cl - 76.3-96.7; ACH - 0.1-7.5; NH ₃ - 0.9-12.0; H ₂ O - 0.1-14.7 - placed in a reactor with a capacity of 1 dm ³ equipped with a mixing device and a drain fitting. At room temperature, the precipitate is washed with hydrochloric acid with a mass fraction of Hcl of 20-36% and at a weight ratio of precipitate: acid equal to 1: 2 for 30 minutes. Then the resulting pulp is filtered. Get filtrate No. 1, which is a solution of hydrochloric acid, composition% wt .: hydrogen chloride (Hcl) - 20-36; NH ₄ Cl - 2.8-3.4; ACH - 0.6-1.1.

The residue obtained after the first washing is poured with a fresh portion of a hydrochloric acid solution with the same concentration of HCl and, with a weight ratio of residue: acid equal to 1: 2, is stirred for 10-15 minutes. The resulting pulp is filtered. Get the filtrate No. 2, which is a solution of hydrochloric acid composition% wt .: hydrogen chloride (Hcl) - 19-36; NH ₄ Cl - 0.0-2.8; ACH - 0.0-0.6.

The residue obtained after the second washing is dried with air with a temperature of 30-50 ° C in a vibroaeric boiling layer or at a temperature of 80-90 ° C until there is no moisture. Get a crystalline product of a white color composition,% wt .: NH ₄ Cl - 99.5-99.9; ACH - 0.0-0.3; H ₂ O - 0.0-0.2.

Double washing is enough to obtain NH ₄ Cl with a purity of 99.5-99.9%.

To prove the conformity of the claimed solution to such a patentability condition as industrial applicability, and to better understand the essence of the invention, we give examples of its specific implementation, which cannot exhaust the essence of the technical solution.

Example 1. In a reactor (V - 1 dm ³ ) equipped with a stirrer, a thermocouple (or a thermometer), a heat exchange jacket, the amine synthesis product is loaded by ammonolysis of chlorocarbons - a solution of ACH and ammonium chloride (with a temperature of 140 ° C) in an amount of 500 g, composition,% wt .: NH ₄ Cl - 28.7; AHG - 18; NH ₃ - 20.8; H ₂ O - 32.5. With stirring, cool the solution to 25 ° C, incubate for 30 minutes until the cessation of crystals. Cooling is carried out with brine supplied to the heat transfer jacket. Then the solution is cooled to a temperature of 10 ° C at a speed of 4-5 ° C / h with a working stirrer. Maintain at this temperature for 2 hours. Next, the solution is cooled to a temperature of minus 10 ° C (with a working stirrer and a cooling rate of about 10 ° C / h). Stand for 1 h. Then the solution is cooled to minus 25 ° C. Stand for 1 h. Separated crystals are separated by filtration. Filtration is carried out through a polypropylene filter. Get 324 g of a solution of the composition,% wt .: NH ₄ Cl - exc .; ACH - 23.2; NH ₃ 29.3; H ₂ O - 47.5, neutralize and isolate the polyamines by known methods and a precipitate in the amount of 176 g of the composition,% wt .: NH ₄ Cl - 76.7; ACH - 7.5; NH ₃ 5.2; H ₂ O — 10.6.

324 g of the ACH solution are neutralized with 241 g of a 40% aqueous NaOH solution, the reaction mass is defended, the upper amine layer is drained and polyamines are isolated by distillation. The yield is 98%.

The precipitate obtained as a result of step cooling (crystallization) is transferred to a 1 dm ³ reactor equipped with a mixing device and a drain fitting. At room temperature, the precipitate is washed with hydrochloric acid with a mass fraction of Hcl 36%. The weight ratio of precipitate: acid is 1: 2. When the stirrer is working, stirring is carried out for 30 minutes. Stop stirring. Filtered. Get 270 g of filtrate No. 1, which is a solution of hydrochloric acid composition,% wt .: hydrogen chloride (Hcl) - 35.6; NH ₄ Cl - 2.8; ACH - 0.6. The residue obtained after the first washing with acid is poured with a fresh portion of the acid solution at a weight ratio of precipitate: acid equal to 1: 2, and stirred for 15 minutes, then filtered. Get filtrate No. 2 in an amount of 430 g, which is a solution of hydrochloric acid composition,% wt .: Hcl - 36; NH ₄ Cl - exc .; AChG - s.c., and the precipitate in the amount of 262 g is dried with air at a temperature of 30-50 ° C in a vibroaeric boiling layer until there is no moisture.

After drying, a product is obtained in an amount of 128 g, which is a white crystalline powder composition,% wt .: NH ₄ Cl - 99.9; AHG - from .; H ₂ O - 0.1.

Example 2. In the conditions of example 1,500 g of the synthesis products of amines obtained by the method of ammonolysis of chlorohydrocarbons, a solution of ACH and ammonium chloride composition,% wt .: NH ₄ Cl - 13.7; ACG - 35.5; NH ₃ - 5.7; H ₂ O - 45.1 is subjected to stepwise cooling with stirring. Get 438 g of a solution of the composition,% wt .: NH ₄ Cl - 2.0; ACH - 39.9; NH ₃ 6.4; H ₂ O — 51.7 and 62 g of a precipitate of the composition,% wt .: NH ₄ Cl — 96.7; ACH - 0.1; NH ₃ 0.9; H ₂ O - 2.3.

438 g of the ACH solution are neutralized with 311 g of a 40% aqueous NaOH solution, the reaction mass is defended, the upper amine layer is drained and polyamines are isolated by distillation. The yield is 94%.

The precipitate is washed with hydrochloric acid under the conditions of example 1. Use a solution of hydrochloric acid with a mass fraction of Hcl 20%. Allocate 110 g of filtrate No. 1, which is a solution of hydrochloric acid composition,% wt .: Hcl - 19.8; NH ₄ Cl - 3.4; ACH - 1.1, and 122 g of filtrate No. 2, which is a solution of hydrochloric acid composition,% wt .: Hcl - 19.9; NH ₄ Cl - 2.8; ACH - 0.6. The washing product (filter cake) after drying at a temperature of 80 ° C, obtained in an amount of 53 g, is a crystalline white powder composition,% wt .: NH ₄ Cl - 99.5; ACH - 0.3; H ₂ O - 0.2.

Example 3. In the conditions of example 1,500 g of the solution obtained by synthesis of amines by the method of ammonolysis of chlorohydrocarbons of the composition,% wt .: NH ₄ Cl - 22.5; ACH - 31.2; NH ₃ - 10; H ₂ O - 36.3, subjected to stepwise cooling with stirring - get 358 g of a solution of ACH composition,% wt .: NH ₄ Cl - 1.2; ACH - 40.8; NH ₃ - 12.29; H ₂ O - 45.7 and 142 g of sediment composition,% wt .: NH ₄ Cl - 76.3; ACH - 4.8; NH ₃ - 4.2; H ₂ O, 14.7.

358 g of the ACH solution neutralize 274 g of a 40% aqueous NaOH solution, the reaction mass is defended, the upper amine layer is drained and polyamines are isolated by distillation. The yield is 95%.

In the conditions of example 1, the resulting precipitate is washed with a solution of hydrochloric acid with a mass fraction of Hcl 34%. Allocate 350 g of filtrate No. 1, which is a solution of hydrochloric acid composition,% wt .: Hcl - 33.5; NH ₄ Cl - 3.4; ACH - 0.8, and 268 g of filtrate No. 2, which is a solution of hydrochloric acid composition,% wt .: Hcl - 33.9; NH ₄ Cl - 1.4; ACH - 0.2, and the filter cake, which after drying at a temperature of 90 ° C is a crystalline powder (in the amount of 92 g) of a white composition,% wt .: NH ₄ Cl - 99.9; AHG - from .; H ₂ O - 0.1.

Example 4. In the conditions of example 1 from 500 g of a solution of ACH composition,% wt .: NH ₄ Cl - 17.3; ACH - 28.7; NH ₃ - 12.5; H ₂ O - 41.2, stepwise cooling with stirring to obtain 404 g of a solution of ACH composition,% wt .: NH ₄ Cl - 1.7; ACH - 34.2; NH ₃ - 12.6; H ₂ O — 51.5 and 96 g of a precipitate of the composition,% wt .: NH ₄ Cl — 83.5; ACH - 3.2; NH ₃ - 12.0; H ₂ O - 1.3.

404 g of the ACH solution are neutralized 313 g of a 40% aqueous solution of NaOH, the reaction mass is defended, the upper amine layer is drained and the polyamines are isolated by distillation. The yield is 98%.

200 g of filtrate No. 1, which is a solution of abhase hydrochloric acid of the composition,% wt .: Hcl - 19.8; NH ₄ Cl - 3.1; AChG — 0.9, and using second-time hydrochloric acid with a mass fraction of HCl of 20%, 207 g of filtrate No. 2, which is a solution of abhazic hydrochloric acid of the composition,% wt .: Hcl — 19.9; NH ₄ Cl - 0.04; ACH - 0.11. A filter cake is obtained which, after drying at a temperature of 90 ° C. in an amount of 73 g, is a white crystalline powder of the composition,% wt .: NH ₄ Cl - 99.9; ACH - 0.01; H ₂ O - 0.09.

Example 5. Take 500 g of the reaction mass of the composition,% wt .: NH ₄ Cl - 28.7; AHG - 18; NH ₃ - 20.8; H ₂ O - 32.5. Ammonia is desorbed and the reaction mass is neutralized with 640 g of a 40% aqueous NaOH solution. The neutralized aqueous saline solution of amines is transferred to the evaporator. Through the evaporator separator, water vapor with an admixture of ethylene diamine is transferred to a heat exchanger cooled by circulating water, where it is condensed. The amine layer from the phase boundary in the evaporator is poured into a delaminator and then transferred to a distillation cube, where water is distilled off and a commodity polyamine is obtained. The yield is 75%.

A concentrated solution of sodium chloride from the conical part of the evaporator is removed to a cooler and then to a centrifuge, dissolved in water and drained into a sewage collector.

Claims (6)

1. The method of ammonolysis of chlorohydrocarbons by the interaction of chlorohydrocarbons and ammonia to obtain a solution of aminochlorohydrates and ammonium chloride, the neutralization of this solution and the separation of amines, characterized in that before the stage of neutralization, the solution of aminochlorohydrates and ammonium chloride is subjected to at least a four-stage first cooling, to a temperature of 20-25 ° C and with holding at this temperature for about 30 minutes, followed by slow cooling at a speed of 4-5 ° C / h to a temperature of 10 ° C in the second stage and holding at this temperature for 2 hours with stirring, further cooling at a speed of 10 ° C / h to a temperature of minus 10 ° C in the third stage and holding for 1 h and cooling at the fourth stage to a temperature of minus 25 ° C and holding at for 1 h, then the solution of aminochlorohydrates is separated from the crystallized ammonium chloride by filtration and sent to the stage of neutralization, and ammonium chloride is subjected to purification. 2. The method according to claim 1, characterized in that stepwise cooling is subjected to a solution containing wt.%: NH ₄ Cl - 13.7-28.7; amino chlorohydrates (ACH) - 18.0-35.5; NH ₃ - 5.7-20.8; water (H ₂ O) - 32.5-45.1. 3. The method of purification of ammonium chloride containing impurities of aminochlorohydrates, ammonia and water obtained by crystallization from a solution of aminochlorohydrates and ammonium chloride during ammonolysis according to claim 1, wherein the initial ammonium chloride is washed with hydrochloric acid with a mass fraction of Hcl 20-36% at a weight ratio of ammonium chloride: acid equal to 1: 2, followed by maintaining the mixture until the layers are separated, separating ammonium chloride from hydrochloric acid and drying it until there is no moisture. 4. The method according to claim 3, characterized in that the purification of hydrochloric acid is subjected to a product containing wt.%: NH ₄ Cl - 76.3-96.7; ACH - 0.1-7.5; NH ₃ - 0.9-12.0; H ₂ O - 0.1-14.7. 5. The method according to claim 3, which consists in the fact that the washing with hydrochloric acid is carried out at least two times. 6. The method according to claim 3, which consists in the use of hydrochloric acid with a HCl concentration of at least 20% as hydrochloric acid.