Preparing aromatic carboxylic acid ammonium salts

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention relates to the improved method for preparing aromatic carboxylic acid ammonium salts by reaction of aromatic carboxylic acid with ammonia in aprotonic solvent medium. Method involves carrying out the reaction in the closed vessel by continuous addition of aromatic carboxylic acid in aprotonic solvent medium and passing gaseous ammonia under condition providing maintenance of ammonia partial pressure in the range from 0.1 to 3 bars and elimination of ammonium salt suspension in aprotonic solvent. Method allows preparing ammonium salts as crystals of a definite size that exhibit narrow distribution by size.

EFFECT: improved preparing method.

9 cl, 1 dwg, 6 ex

 

The present invention relates to a method of producing ammonium salts of aromatic carboxylic acids, in particular benzoic acid.

It is known that ammonium salts of aromatic carboxylic acids can be obtained by introducing gaseous ammonia into a solution of an aromatic carboxylic acid in an aprotic solvent. DE 1115729 describes the way in which the solvent is dimethylformamide. US 2220692 describes a method of obtaining indalecio ammonium, which includes the processing dispersion almond acid in anhydrous benzene ammonia. DE 2005514 describes the method of obtaining thiosulfinates by oxidation of epislides using organic nagkalat, in particular perbenzoic acid deposition acid obtained as a by-product, by introducing dry ammonia in the form of ammonium salts. Deposition requires low temperature from -50 to -30°C.

Zh. Prikl. Khim. Volume 63, No. 6, pp. 1425-1428 describes a method of obtaining isobutyrate ammonium reaction somaclonal acid with ammonia in isopentane. The influence of pressure of ammonia was investigated, but only relative to the initial rate of formation of isobutyrate ammonium.

Although these methods produce crystalline salts of ammonium, the distribution of crystal size is wide, and the size of the crystals - neupro the act. Achieved outputs are unsatisfactory.

The purpose of this invention is the provision of a method of obtaining ammonium salts of aromatic carboxylic acids, in which case the use of stoichiometric quantities of the components of the reaction results, mainly with quantitative yield, crystals of a certain size, which have a narrow size distribution.

We found that the objective is achieved by way of obtaining ammonium salts of aromatic carboxylic acids by the reaction of aromatic carboxylic acids with ammonia in an aprotic solvent, which comprises carrying out the reaction in a closed vessel by continuously introducing a solution of an aromatic carboxylic acid in an aprotic solvent and passing ammonia gas so that the gas space of the vessel was maintained partial pressure of ammonia in the range from 0.1 to 3 bar, and removal of suspension of ammonium salt in an aprotic solvent.

Suitable aromatic carboxylic acids include those that have at least one benzene ring and the carboxyl group attached to the benzene ring directly or through a1-C4-alkalinous chain. Benzene ring and Allenova chain can be unsubstituted or substituted by one is time substituents, selected from the group which includes1-C4-alkyl, hydroxyl, C1-C4-alkoxy, halogen and nitro. Examples of suitable aromatic carboxylic acids include 2-frankenboob acid, 3-frankenboob acid, 2-pyridylcarbonyl acid, 3-pyridylcarbinol acid and 4-pyridylcarbinol acid. The method according to the present invention is particularly suitable for the conversion of benzoic acid.

The solvent used according to the present invention, is aprotic (i.e., it has no acidic hydrogen atoms). Suitable aprotic solvents include aliphatic hydrocarbons such as pentane, hexane, heptane, cyclohexane, methylcyclohexane or commercially available mixtures of aliphatic hydrocarbons, such as certain fractions of oil; aromatic hydrocarbons such as benzene, toluene, xylene or commercially available mixtures of aromatic hydrocarbons, e.g. Solvesso®150; halogenated aliphatic hydrocarbons, such as dichloromethane, trichloromethane, 1,2-dichloroethane, 1,2-dichloropropane, 1,1,2-trichloroethane, trichloroethylene; halogenated aromatic hydrocarbons such as chlorobenzene; ethers, such as diethyl ether, dimethyl ether of ethylene glycol, dimethyl ether of diethylene glycol, diisopropyl ether, Tetra drofuran, dioxane; ketones, such as acetone, methyl-tert-butylketone, methyl isobutyl ketone or methyl ethyl ketone; dimethylformamide, dimethylsulfoxide, sulfolan and aliphatic or aromatic NITRILES, such as acetonitrile or benzonitrile. These solvents can be used alone or in the form of mixtures. Preference is given to 1,2-dichloroethane and 1,2-dichloropropane, and particular preference is given to 1,2-dichloroethane.

Suitable reaction vessels for the method according to the present invention include conventional reactors, preferably with a back-mixing, such as stirring reactors, circulation reactors, the reaction apparatus with stirrer, etc. of the Reaction vessel is preferably equipped with a mixing element, preferably one that provides a good distribution of gas in a liquid, for example a disk stirrer or sameaspiration stirrer. The reaction vessel is filled with a solution of an aromatic carboxylic acid in an aprotic solvent. This solution may lie below or above the surface of the liquid reaction mixture in the vessel.

Gaseous ammonia is served in the reaction vessel so that the gas space of the vessel was maintained partial pressure of ammonia in the range from 0.1 to 3 bar, preferably from 0.1 to 1 bar. The partial pressure of ammonia is usually predelay as the difference between the total pressure in the reaction vessel minus the pressure system, which is mainly determined by the vapor pressure of the solvent at the reaction temperature. The system pressure can be precisely defined by introducing the selected solvent in the reaction vessel, heating the reaction vessel to the reaction temperature and determine the pressure in the reaction vessel, which corresponds to the system pressure. If ammonia is introduced into the reaction vessel, the pressure increase relative to the pressure of the system corresponds to the partial pressure of ammonia. If method according to the invention is carried out at a constant temperature, a certain partial pressure of ammonia can be maintained by controlling the total pressure in the reaction vessel and adding ammonia so that the total pressure remains constant. Pressure measurement and control introduction ammonia is preferably automated. Total pressure (absolute pressure) is preferably from 1 to 7 bar, in particular from 1.1 to 6 bar.

The ammonia is preferably introduced into the vessel below the liquid surface. Preference is given to continuous withdrawal of gas from the gas space of the vessel, mixing it with fresh ammonia and feed it back into the vessel. This procedure provides the optimum conversion of ammonia.

A suspension of ammonium salt is removed from the reaction vessel, prefer the LNA from the base. The conclusion of the suspension is preferably performed continuously and preferably so that the liquid level or quantity of liquid in the vessel remained constant. Bred suspension can be served directly or after passing through the heat exchanger at the following stages of the reaction. The residual content of aromatic carboxylic acids, which may be determined, for example, by high performance liquid chromatography (HPLC), is usually less than 1000 ppm, generally less than 200 ppm. If necessary, ammonium salt may be selected from conventional solvent partitioning methods, for example by filtration or centrifugation. Remote solvent can be returned to the reaction process.

In the method according to the invention basically there's a low concentration of ammonia and aromatic carboxylic acids in the liquid phase and, accordingly, the rate of nucleation centers of crystallization is low. This is the reason that an aromatic carboxylic acid and ammonia react in the presence of pre-formed crystals of ammonium salts, which serve as seed crystals. Therefore, the method according to the invention in contrast to methods of the prior art, is not based on spontaneous crystallizes and, which usually leads to a very broad distribution of crystal sizes.

The temperature in the reaction vessel is preferably constant support. The optimum reaction temperature is a function of the solubility of the ammonium salt in the solvent used. High temperatures increase the solubility of the ammonium salts and so contribute to the growth of crystals, and also lead to the formation of more solid agglomerate and for cooling the deposition of crystalline material. At low temperatures the solubility of the ammonium salt is too low, so that creates a high saturation, and respectively formed only a very small crystals. Preference is given to selecting the temperature at which the solubility of the aromatic carboxylic acid in the solution is greater than 10 g/100 ml, in particular more than 35 g/100 ml and the solubility of the ammonium salts is preferably less than 2 g/100 ml, in particular less than 1 g/100 ml Temperature in the range from 70 to 110°C, preferably from 80 to 95°With, for example, is suitable as the solvent used 1,2-dichloroethane.

The average period of stay in the reaction vessel is preferably from 10 to 300 minutes, the Lower limit of the average period of stay is determined massoobmena settled between gas and liquid, while a longer period of stay makes the method inefficient and leads to a relatively broad distribution of crystal size.

The method according to the invention provides a virtually quantitative conversion used aromatic carboxylic acid. Crystals of ammonium salts are in the form of a suspension in a solvent, which does not actually contain dissolved aromatic carboxylic acid. Suspension may be used in subsequent reactions without filtration or evaporation. The method allows to obtain crystals of a certain size, which have a narrow size distribution.

The invention is illustrated the accompanying drawing and the following examples. The crystals obtained in examples were investigated using an optical microscope; the distribution of particle sizes was determined by measuring the laser extinction using a particle counter (measuring range 2-400 μm; sensor 400 μm × 400 μm). In each case the maximum value and the range of distribution (range = (X90-X10/X50)). To determine the unreacted benzoic acid suspension was allowed to cool, was filtered ammonium benzoate and the filtrate was analyzed by high-performance liquid chromatography.

N the drawing shows the device, which is suitable for an embodiment of the method according to the invention. The reactor 1 is equipped with a mixing element 2, is charged through line 3 with a solution of an aromatic carboxylic acid in an aprotic solvent. The pipe 4 is used for ozonation ammonia gas below the liquid surface. From the base of the reactor 1 through the pipe 5 and the pump 6 pump suspension formed ammonium salts. From the gas volume of the reactor 1 extract gas through pipeline 8 and pump 9, mixed with fresh ammonia through the metering valve 10 and returned to the reactor 1 via line 4. The metering valve 10 is controlled by the pressure regulator 7.

Example 1

A 2 l reactor with a double casing, equipped with a disk stirrer and baffles, simultaneously filed below the liquid surface with a speed of 53.3 per g·min-1a solution of 720 g of benzoic acid in 3280 g 1,2-dichloroethane (EDC) and gaseous ammonia. The reaction temperature was set at 90°C, the total pressure at 1.6 bar and the partial pressure of ammonia at the level 0,38 bar. From the gas volume, speed 50 l·h-1the gas is circulated by pumping and was introduced below the liquid surface. The period of stay in the reactor was set at 45 minutes. The resulting suspension of ammonium benzoate continuously output the Lee trough bottom gate. After 8 periods analyzed sample: coarse, not agglomerated ammonium benzoate with an average particle size of about 300 μm (distribution of particle sizes could not be determined, since the particles clog the sensor particle counter); dissolved benzoic acid: <10 ppm.

Example 2

In the reactor described in example 1, were simultaneously introduced below the liquid surface with a speed of 53.3 per g·min-1a solution of 720 g of benzoic acid in 3280 g EDC and gaseous ammonia. The reaction temperature was maintained at a level of from 80 to 81°C, the total pressure at 1.3 bar and the partial pressure of ammonia at the level of 0.37 bar. Unreacted ammonia is circulated as a circulating gas by means of a pump at a speed of 60 l·h-1. The period of stay in the reactor was set at 45 minutes. The resulting suspension of ammonium benzoate continuously taken out through the bottom gate. After 8 periods analyzed sample: coarse, not agglomerated ammonium benzoate; dissolved benzoic acid: <5 ppm; the distribution of particle size: max 90 μm, the range of 0.93.

Example 3

In the reactor described in example 1, were simultaneously introduced below the liquid surface with a speed of 53.3 per g·min-1a solution of 720 g of benzoic acid in 3280 g EDC is gaseous ammonia. The reaction temperature was set at 81°C, the total pressure at 2.1 bar and the partial pressure of ammonia at the level 1,19 bar. Unreacted ammonia is circulated as a circulating gas by means of a pump at a speed of 60 l·h-1. The period of stay in the reactor was set at 45 minutes. The resulting suspension of ammonium benzoate continuously taken out through the bottom gate. After 8 periods analyzed sample: fine grained, agglomerated ammonium benzoate; dissolved benzoic acid: 5 ppm; the distribution of particle size: max 60 μm, the range of 0.92.

Comparative Example 1

In the reactor described in example 1, were simultaneously introduced below the liquid surface with a speed of 53.3 per g·min-1a solution of 720 g of benzoic acid in 3280 g EDC and speed 83,0 g·min-1gaseous ammonia. The reaction temperature was set at 80°C, the total pressure at 1.0 bar and the partial pressure of ammonia at the level of 0.07 bar. Unreacted ammonia is circulated as a circulating gas at a pump speed of 50 l·h-1. The period of stay in the reactor was set at 45 minutes. The resulting suspension of ammonium benzoate continuously taken out through the bottom gate. After 8 periods analyzed sample: millcrest lichecki, silnoagressivnyh ammonium benzoate; dissolved benzoic acid: 1800 ppm; the distribution of particle size: max 290 μm, the range of 2.2.

Comparative Example 2

2 l extending to the base of the reactor equipped with reflux condenser, stirrer and baffles, at the same time was introduced below the liquid surface with a speed of 53.3 per g·min-1a solution of 720 g of benzoic acid in 3280 g of 1,2-dichloroethane and with a speed of 1.4 g·min-1gaseous ammonia. The reaction was conducted at atmospheric pressure. The temperature in the reactor ranged from 80 to 82°C. Unreacted ammonia can evaporate through the reflux condenser. The resulting suspension of ammonium benzoate continuously taken out through the bottom gate. The period of stay in the reactor was set at 45 minutes. After 6 periods were sampled and analyzed: a mixture of crystalline, selenagomezvevo benzoate ammonium with larger crystals; dissolved benzoic acid: 7200 ppm; the distribution of particle size: max 67 μm, the range of 1.24.

Comparative Example 3

The reactor described in comparative example 2, first filled with 600 g of 1,2-dichloroethane and heated to form phlegmy (about 84°). Then the solution 558,2 g of benzoic acid in 2400 g of 1,2-dichloroethane and 85.6 g of gaseous NH3at the same time, e.g. the or within 45 minutes. The reaction temperature ranged from 81 to 82°C. the Reaction was conducted at atmospheric pressure. Unreacted NH3flowed through the reflux condenser. After completed addition, from the reactor was sampled and analyzed: a mixture of crystalline, selenagomezvevo benzoate ammonium (particle size of <15 μm) and larger crystals approximately 50 μm in size; dissolved benzoic acid: 50 ppm; the distribution of particle sizes: 20 μm, the range of 1.53 (bimodal distribution).

1. The method of obtaining ammonium salts of aromatic carboxylic acids by the reaction of aromatic carboxylic acids with ammonia in an aprotic solvent, which comprises carrying out the reaction in a closed vessel by continuously introducing a solution of an aromatic carboxylic acid in an aprotic solvent and passing ammonia gas so that the gas space of the vessel was maintained partial pressure of ammonia in the range from 0.1 to 3 bar, and removal of suspension of ammonium salt in an aprotic solvent.

2. The method according to claim 1, characterized in that the ammonia is introduced into the vessel below the liquid surface of the reaction mixture.

3. The method according to claim 2, characterized in that the gas is continuously removed from the gas space of the vessel, mixed with fresh ammonia is m, and return back to the vessel.

4. The method according to any of the preceding paragraphs, characterized in that the aprotic solvent selected from aliphatic hydrocarbons, aromatic hydrocarbons, halogenated aliphatic hydrocarbons, halogenated aromatic hydrocarbons, ethers, ketones, dimethylformamide, dimethyl sulfoxide, sulfolane, aliphatic or aromatic NITRILES, and mixtures thereof.

5. The method according to claim 4, characterized in that the aprotic solvent is a 1,2-dichloroethane or 1,2-dichloropropan.

6. The method according to claim 1, characterized in that the vessel keep the temperature from 70 to 110°C.

7. The method according to claim 1, characterized in that the support vessel, the total pressure from 1 bar to 7 bar.

8. The method according to claim 1, characterized in that the average period of stay in the vessel is from 10 to 300 minutes

9. The method according to claim 1, characterized in that the aromatic carboxylic acid is a benzoic acid.



 

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