RU2421460C2 - Method of producing di-(2-ethylhexyl) phosphoric acid and neodymium salt thereof - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing di-(2-ethylhexyl) phosphoric acid, which is used in extraction processes, ion exchangers, and neodymium salt thereof, which is used during catalysis. Disclosed is a method of producing di-(2-ethylhexyl) phosphoric acid and a solution of its neodymium salt in an aliphatic or acyclic solvent by reacting phosphorus trichloride with 2-ethylhexanol, followed by chlorination of the formed di-(2-ethylhexyl)phosphate and hydrolysis of di-(2-ethylhexyl) chlorophospate, wherein in order to obtain di-(2-ethylhexyl) phosphoric acid and its high-purity neodymium salt, hydrolysis is carried out through successive treatment of chlorophophate with jet steam at temperature 95-100°C and then with 20% aqueous solution of sodium hydroxide at temperature 105 -115°C, followed by treatment with hydrochloric acid in an organic solvent to obtain di-(2-ethylhexyl) phosphoric acid or with aqueous solution of neodymium chloride to obtain a solution of neodymium tris-[di-(2-ethylhexyl)] phosphate.

EFFECT: novel method of producing a high-purity compound and its neodymium salt.

9 cl, 7 ex

Description

1. The technical field to which the invention relates.

The invention relates to the field of organophosphorus compounds having practical application.

Di- (2-ethylhexyl) phosphoric acid (abbreviated names - D2EGFK, DAP, DENRA) is one of the most widely used liquid ion exchangers in extraction processes, its main industrial purpose is the extraction of rare-earth and transuranic elements from acid solutions.

Recently, it has received a new application - the neodymium salt D2EGFK is part of the catalytic butadiene polymerization system, which provides rubber with high polydispersity, viscosity and 1,4-cis fragments.

2. The level of technology

Of the known methods for producing D2EHPA, the most modern and economical is the method of obtaining it from phosphorus trichloride and 2-ethylhexanol. It includes three main stages:

- obtaining di- (2-ethylhexyl) phosphite;

- chlorinating it to di- (2-ethylhexyl) chlorophosphate;

- hydrolysis of the latter to di- (2-ethylhexyl) phosphoric acid.

A description of this process is set forth in the American patent [4. US patent 4288392] and Japanese application [5. Japanese Application 59-048493].

As a prototype, we have determined the method described in US Pat. No. 4,288,392. The indicated method for producing D2EHPA does not provide purification from neutral phosphorus-containing impurities. First of all, from tri- (2-ethylhexyl) phosphate, the formation of which is possible as a result of oxidation of the intermediate tri- (2-ethylhexyl) phosphite formed in the first stage, as well as at the stage of chlorination of di- (2-ethylhexyl) phosphite in the presence of the mass of unreacted 2-ethylhexanol. The second neutral impurity, the decomposition of which does not provide this method, is tetra- (2-ethylhexyl) pyrophosphate, for the full conversion of which into D2EHPA more stringent hydrolysis conditions are required.

The neodymium salt of di- (2-ethylhexyl) phosphoric acid, a method for the preparation of which is described in Japanese patents 60-023406 A, US 7056998, RF 2301811 C2, is a derivative of di- (2-ethylhexyl) phosphoric acid, and is obtained by the interaction of high-purity acids with neodymium chloride.

As a prototype of the second part of the application (synthesis of neodymium salt), we determined the patent of the Russian Federation 2301811 C2.

3. Disclosure of invention

We propose a method for producing D2EHPA from phosphorus trichloride and 2-ethylhexanol to obtain the target product with a basic substance content of 98-99%.

At the first stage, in contrast to the prototype, where a strict observance of the molar ratio of alcohol: phosphorus trichloride as 2.95-3.0: 1 is required, we proposed to partially replace alcohol with water and use the following alcohol: water: phosphorus trichloride ratios of 2.5 -2.3: 0.5-0.7: 1. This reduces the likelihood of the formation of trialkylphosphite, therefore, trialkylphosphate, and also reduces the consumption of 2-ethylhexanol and the yield of a by-product - 2-ethylhexyl chloride.

In a second step, a reaction mixture containing dialkyl phosphite, 2-ethylhexyl chloride and residual hydrogen chloride is chlorinated with chlorine to di- (2-ethylhexyl) chlorophosphate. US Pat. No. 4,288,392 teaches that in the presence of unreacted 2-ethylhexanol, a neutral impurity, tri- (2-ethylhexyl) phosphate, may be formed. In our case, with a reduced ratio of alcohol to phosphorus trichloride, the probability of the formation of trialkyl phosphate decreases. Hydrogen chloride released is removed by flushing with an inert gas, followed by evacuation.

The most critical step in the production of D2EHPA is the hydrolysis of the corresponding chlorophosphate.

In the prototype, the hydrolysis of di- (2-ethylhexyl) chlorophosphate is carried out in water in two stages. At the first stage, in order to reduce the further hydrolysis of the resulting D2EHPA to mono (2-ethylhexyl) phosphoric acid under the action of hydrogen chloride released, the amount of water is calculated to obtain hydrochloric acid with a concentration of hydrogen chloride of about 11% and the hydrolysis temperature does not rise above 80 ° С . After separation of hydrochloric acid, hydrolysis is continued with a new portion of water, raising the temperature to 95-100 ° C. This technique allows, after removal of volatile impurities in a vacuum, to obtain D2EHPA with a basic substance content of 95-96% and mono- (2 ethylhexyl) phosphoric acid - 2.0-2.2%.

We propose the hydrolysis of di- (2-ethylhexyl) chlorophosphate to be conducted with direct steam at a temperature of 95-100 ° C. In this case, hydrogen chloride released is removed from the reaction zone and, at the same time, light impurities, mainly 2-ethylhexyl chloride, are distilled off. The resulting D2EHPA contains 5–7% of monoester (2-ethylhexyl phosphate), 8–10% of neutral phosphorus-containing impurities, and 0.5–1.0% of hydrogen chloride as impurities.

Further processing of the reaction mass is carried out with a 20% sodium hydroxide solution taken with a 20% molar excess based on the total acidity, and heated to a temperature of 105-110 ° C with simultaneous distillation of the evolving volatile impurities and water and a gradual increase in temperature to 110 -115 ° C. Heating is stopped with the termination of the allocation of the organic layer in the condensate. The total heating time is 5-6 hours.

The concentrated solution of the sodium salt of D2EGFK is diluted with water, extracted with an organic solvent (nefras, hexane, cyclohexane), and then washed with water until neutral. For better division of layers, a 1.5-2% sodium chloride solution is used for washing. Water leaching is carried out at a temperature of 50-55 ° C. A solution of the sodium salt of D2EHPA in an organic solvent with a monoester content of about 0.1% is obtained.

This solution can be used both to isolate D2EHPA and to obtain a solution of neodymium salt.

To isolate D2EHPA, the sodium salt solution is treated with 30% hydrochloric acid, followed by aqueous washing and distilling off the solvent. The isolated D2EGPA contains 99.0-99.5% of the basic substance and 0.3-0.5% of mono- (2-ethylhexyl) phosphoric acid.

We have proposed a purified solution of the sodium salt of D2EHPA in an organic solvent to obtain a solution of neodymium salt.

In the prototype of the Russian Federation 2301811 C2, the synthesis of neodymium salt - tris- [di- (2-ethylhexyl) phosphate] neodymium, is carried out in an aqueous acetone solution using an aqueous solution of neodymium chloride and an acetone solution of the sodium salt of D2EGFK. The resulting neodymium salt is insoluble in this medium and is isolated in solid form. To prepare a catalytic system for the polymerization of butadiene, neodymphosphate is dissolved in an organic solvent - hexane, cyclohexane, methylcyclohexane. The solutions are gel-like viscous liquids. Thus, the company Rhodia offers under the brand name NdEHP-20 a solution of the neodymium salt D2EHPA in methylcyclohexane with a concentration of 18-20% and a neodymium content of 2.3-2.4%.

Given these features of neodymphosphate, it is proposed that an exchange reaction with an aqueous solution of neodymium chloride be carried out using a solution of the sodium salt D2EGFK obtained in an organic solvent. The reaction is carried out at a temperature of 50-60 ° C with vigorous stirring of two layers - water and organic for 2.5-3 hours. In this case, a small (about 5% molar) excess of neodymium chloride is used. The resulting solution of neodymphosphate is subjected to azeotropic drying.

As solvents were used: nephras 65/75, hexane, cyclohexane.

The proposed method allows to obtain gel-like solutions of tris- [di- (2-ethylhexyl) phosphate] neodymium with a concentration of 7-16%, containing 0.1-0.2% of free D2EHPA and 0.01-0.001% of water. Laboratory tests of neodymphosphate in the process of producing polybutadiene made it possible to obtain polybutadiene rubber with high physicomechanical characteristics that significantly exceeded the performance of polybutadiene obtained in the presence of a neodymium carboxylate catalyst.

Thus, the proposed method for producing D2EHPA, including the stage of purification of its sodium salt, allows to achieve a new level of acid quality, which allows it to be used in various fields of chemistry, where there are high requirements for its quality. In particular, we have proposed a method for producing a non-phosphate catalyst on its basis in an aliphatic or acyclic solvent directly from sodium salt, which greatly simplifies the technology for producing and using it in the polybutadiene catalyst system.

4. The implementation of the invention

I. Preparation of di- (2-ethylhexyl) phosphite.

Example 1

In a four-necked flask equipped with a stirrer, reflux condenser, thermometer and dropping funnel, a mixture of 142.2 g of 2-ethylhexanol and 4 ml of water is placed. With vigorous stirring and cooling, 60 g of phosphorus trichloride are added over 1 hour, maintaining the temperature in the reactor 10-15 ° C. The molar ratio of phosphorus trichloride: 2-ethylhexanol: water is 1: 2.5: 0.5. Upon completion of the addition of phosphorus trichloride, the temperature is raised to 20-25 ° C and with stirring a weak stream of nitrogen is applied to remove the released hydrogen chloride and kept at this temperature for 2 hours, then the temperature is raised to 40-45 ° C and kept for another 2.5 hours hydrogen chloride blowing. As a result, crude di- (2-ethylhexyl) phosphite is obtained with a basic substance content of 76.40% and a residual hydrogen chloride content of 4.7%. The yield of phosphite was 170.3 g.

Example 2

Similarly to the description in example 1, the production of phosphite is carried out at a molar ratio of phosphorus trichloride: 2-ethylhexanol: water, equal to 1: 2.3: 0.7. The yield of crude phosphite was 158 g with a basic substance content of 82.6% and a residual hydrogen chloride content of 4.5%.

II. Preparation of di- (2-ethylhexyl) chlorophosphate.

Example 3

In a four-necked flask equipped with a stirrer, reflux condenser, thermometer and bubbler, the raw di- (2-ethylhexyl) phosphite described in examples 1 and 2 is placed. The reaction mass is cooled to a temperature of 10 ° C and chlorine gas is passed with stirring. Chlorination is carried out at a temperature below 20 ° C until a yellow-green liquid stains. Chlorination time is 1-1.5 hours. The consumption of chlorine is 30-35 g. The temperature of the reaction mixture is raised to 40-45 ° C and hydrogen chloride is blown off with a stream of nitrogen with stirring to a content of less than 1%. In this case, 165-180 g of crude di- (2-ethylhexyl) chlorophosphate are obtained with a basic substance content of 80-90%, determined by bound chlorine.

III. Hydrolysis of di- (2-ethylhexyl) chlorophosphate.

Example 4

In a flask equipped with a gas bubbler, a thermometer, a refrigerator with a receiver connected to a vacuum pump, 165 g of crude di- (2-ethylhexyl) chlorophosphate with a basic substance content of 80.0% obtained in the previous stage are placed, heated to a temperature of 95 -100 ° C and at a residual pressure of 150-160 mm Hg and serve hot steam. About 19.5 g of 2-ethylhexyl chloride are distilled off. The steaming is terminated when the formation of the organic phase in the receiver ceases. Stripping duration 2.5-3 hours. In this case, hydrogen chloride released as a result of hydrolysis is absorbed by water to obtain dilute hydrochloric acid. 145 g of crude di- (2-ethylhexyl) phosphoric acid are obtained with a basic substance content of 83.3% and 6.5% mono (2-ethylhexyl) phosphoric acid.

IV. Obtaining the sodium salt of di- (2-ethylhexyl) phosphoric acid.

Example 5

To 145 g of crude di- (2-ethylhexyl) phosphoric acid containing 83.3% of the basic substance, 6.5% of mono- (2-ethylhexyl) phosphoric acid, 10.2% of neutral impurities, 131 g of 20% are added with stirring aqueous solution of caustic soda.

The reaction mass is heated with simultaneous distillation of water to a temperature of 103-105 ° C. As water is distilled off, the temperature in the reactor rises to 110-115 ° C. In order to avoid thickening, water is added to the reaction mass, maintaining this temperature. The process continues until the formation of the organic layer in the distillation ceases. The total heating and distillation time is 6 hours. The residue is diluted by adding 350 ml of water, cooled to 60-65 ° C, poured 220 ml of hexane and stirred for 15-20 minutes. After settling, the aqueous layer is separated, and the organic layer is washed with a 1.5-2% solution of sodium chloride (3-4 times 350-380 ml) at a temperature of 50-55 ° C until the pH of the aqueous phase is neutral. This gives 488 g of a solution of the sodium salt of di- (2-ethylhexyl) phosphoric acid in hexane with a basic substance content of 20% and the sodium salt of mono (2-ethylhexyl) phosphoric acid 0.1%. The yield is 84.3% (for phosphorus trichloride).

Example 6

Obtaining highly pure di- (2-ethylhexyl) phosphoric acid. 200 g of a hexane solution of the sodium salt of di- (2-ethylhexyl) phosphoric acid obtained under the conditions of Example 5 are treated with 48 ml of 30% hydrochloric acid at a temperature of 40-50 ° C, stirring for 15-20 minutes and after separation of the aqueous layer, it is washed twice with warm water, 100 ml each. Then hexane is distilled off at atmospheric pressure and kept in a vacuum of 30-50 mm Hg. at a temperature of 90-100 ° C. 48.7 g (yield 99.4%) of di- (2-ethylhexyl) phosphoric acid are obtained with a basic substance content of 99.45% and 0.3% of mono-2-ethylhexylphosphoric acid.

Example 7. Obtaining a solution of tris- [di- (2-ethylhexyl) phosphate] neodymium in hexane. To 75 g of a solution of the sodium salt of di- (2-ethylhexyl) phosphoric acid obtained under the conditions of Example 5, 600 ml of hexane are added and with vigorous stirring 114 g of an aqueous solution of neodymium chloride with a pH of 5.2 and a neodymium content of 2.5 are added. % After adding 2/3 of the volume of the solution of neodymium chloride, the organic layer becomes gel-like. Upon completion of the addition, the reaction mass is heated, continuing vigorous stirring, to 50-60 ° C and maintained at this temperature for 2.5-3 hours. The mixture is then allowed to delaminate at this temperature for 1 hour. The aqueous layer was separated, and the organic was washed three times, adding 200 ml of demineralized water, stirring for 30 minutes at 50-60 ° C until there were no chlorine ions in the aqueous layer. The organic layer is subjected to azeotropic drying, driving off the hexane azeotrope with water and replenishing the volume with a new portion of hexane. Drying is carried out to a moisture content in the solution of 0.01-0.001%. 170-245 g of a lilac-colored solution are obtained with a content of 1.1-2.3% neodymium and 7.37-15.43% bound di- (2-ethylhexyl) phosphoric acid and about 0.1% free di- (2- ethylhexyl) phosphoric acid.

Similar results were obtained in the preparation of a solution of tris- [di- (2-ethylhexyl) phosphate] neodymium in nephras 65/75 and cyclohexane.

Claims (9)

1. A method of producing di- (2-ethylhexyl) phosphoric acid and a solution of its neodymium salt in an aliphatic or acyclic solvent by reacting phosphorus trichloride with 2-ethylhexanol followed by chlorination of the resulting di- (2-ethylhexyl) phosphite and hydrolysis of di- (2- ethylhexyl) chlorophosphate, characterized in that to obtain di- (2-ethylhexyl) phosphoric acid and its neodymium salt of high purity, the hydrolysis is carried out by sequential treatment of chlorophosphate with hot steam at a temperature of 95-100 ° C and then with a 20% aqueous solution of caustic sodium at a temperature of 105-115 ° C, followed by treatment in an organic solvent with hydrochloric acid to obtain di- (2-ethylhexyl) phosphoric acid or an aqueous solution of neodymium chloride to obtain a solution of neodymium tris- [di- (2-ethylhexyl)] phosphate. 2. The method according to claim 1, characterized in that, in order to reduce the consumption of 2-ethylhexanol in the synthesis of di- (2-ethylhexyl) phosphite, it is partially replaced with water at a molar ratio of phosphorus trichloride: 2-ethylhexanol: water equal to 1 : 2.3-2.5: 0.7-0.5. 3. The method according to claim 1, characterized in that, in order to reduce the loss of di- (2-ethylhexyl) phosphoric acid, hydrolysis is carried out with direct steam while distilling off the resulting solution of hydrogen chloride and volatile impurities. 4. The method according to claim 1, characterized in that the hydrolysis of neutral phosphorus-containing impurities in di- (2 ethylhexyl) phosphoric acid is carried out in an alkaline medium at a temperature of 105-115 ° C with simultaneous distillation of volatile impurities and water. 5. The method according to claim 1, characterized in that, in order to remove water-soluble impurities, the sodium salt of di- (2-ethylhexyl) phosphoric acid is dissolved in an aliphatic or acyclic solvent, washed with water, treated with hydrochloric acid and isolated di- (2- ethylhexyl) phosphoric acid. 6. The method according to claim 5, characterized in that to obtain a solution of the neodymium salt of di- (2-ethylhexyl) phosphoric acid in an aliphatic or acyclic solvent, the sodium salt of di- (2-ethylhexyl) phosphoric acid in this solvent is treated with an aqueous solution of neodymium chloride . 7. The method according to claim 5, characterized in that the solution of neodymium salt in an aliphatic or acyclic solvent is subjected to azeotropic drying. 8. The method according to claim 5, characterized in that the concentration of neodymium salt in an aliphatic or acyclic solvent is 7-16%, and the moisture content is less than 0.01%. 9. The method according to claim 5, characterized in that as the aliphatic or acyclic solvent in the preparation of the neodymium salt of di- (2-ethylhexyl) phosphoric acid, nefras 65/75, hexane, cyclohexane can be used.