Isolation of low molecular weight aliphatic acids from aqueous solutions containing formic acid

 

(57) Abstract:

The invention relates to chemical technology of obtaining low molecular weight aliphatic acids, which are valuable raw materials for the chemical, petrochemical and forestry industry. Aqueous solutions of a mixture of lower aliphatic acids containing formic acid, treated with amines and then carry out thermal decomposition of the salts formed with simultaneous distillation of the acids. For binding of formic acid in the mixture to take 0.5 to about 0.53 mol primary or from 1.0 to 1.03 mol of the secondary amine of General formula R1R2NH, where R1- aliphatic hydrocarbon radical containing 6-25 carbon atoms; R2- H or an aliphatic hydrocarbon radical containing 1-25 carbon atoms; and from 1.0 to 1.03 mol of formaldehyde per 1 mol of formic acid and the treatment is carried out at a temperature of 50-80oC. In case of lack of tertiary amines formed in the reaction, for salt formation with all the contained in the solution acid WITH2-C5in addition enter the estimated number ready tertiary amines. The technical result - the simplification of the separation of mixtures of low-molecular Ki the th aliphatic acids, which are valuable raw materials for the chemical, petrochemical and forestry industry.

The aqueous mixture containing formic acid and other low molecular weight aliphatic acid, formed when carrying out a large number of technically important chemical processes. The aqueous acid mixture containing formic acid, are formed, for example, when wood pyrolysis, oxidation of aldehydes [Lebedev N. N. "Chemistry and technology of basic organic and petrochemical synthesis", 4th ed., M.: Chemistry, 1988, S. 392-393], the oxidation gas gasoline [Lebedev N. N. "Chemistry and technology of basic organic and petrochemical synthesis", 4th ed., M.: Chemistry, 1988, S. 398]. Another process, which are formed of a mixture of lower aliphatic acids, is the process of catalytic oxidation of paraffin hydrocarbons in the synthetic fatty acids. The composition of the resulting acid is the following: C1-C4= 5-10%, C5-C6=3-5%, WITH7-C9=8-10%, C10-C16=25-28%, C17-C20=15-20%, WITH more20=20-25% [Lebedev N. N. "Chemistry and technology of basic organic and petrochemical synthesis", 4th ed., M.: Chemistry, 1988, S. 369-372]; [Surfactant: a Handbook/AbIe acid, including and formic acid are acidic wastewater production of synthetic fatty acids. The amount of these acids is 6-7% from recycled wax at a ratio of: formic acid 47%, acetic acid 33%, propionic acid 11%, butyric acid 9% [Mankovsky N. K. "Synthetic fatty acids. Production, properties, application." M.: Chemistry, 1965, S. 160].

By themselves, these aqueous mixtures of acids are of limited use. It is therefore necessary to prioritize the allocation of low molecular weight aliphatic acids from aqueous solutions, and then splitting the individual acids. Individual lower aliphatic acids (acetic, propionic, butyric, valeric and others) are used in various industries and are scarce products. So, for example, acetic acid is used to obtain vinyl acetate, cellulose acetate, solvents, etc., propionic acid for preservation of fodder in agriculture and other

There are various methods of extraction of low molecular weight aliphatic acids from dilute aqueous solutions, for example of products of wood pyrolysis, oxidation products natural gasoline or from secularly acid of high purity from aqueous solutions containing also formic acid, due to the proximity of the boiling points of water (100oC), formic acid (100,7oC) binary azeotrope water - formic acid (107,5oC) and triple azeotrope, for example water - formic acid - acetic acid (107,05oC) etc. [OGO, S. K., Lesteva T. M., Kogan Century B. "Azeotropic mixture", Directory. L.: Chemistry, 1971, 848 S.].

Separation of mixtures of acetic, propionic, butyric and valerianic acids from formic acid is complicated, and sometimes becomes almost impossible, if the mixture contains up to 80% of water (in liquid products of pyrolysis of wood or wastewater production of synthetic fatty acids).

The known method of separation of the lower aliphatic acids from the treated sour water production of synthetic fatty acids, which consists in the following.

In the azeotropic distillation column with entrepreneur - isoamylamine - held drying an aqueous solution of acid to the water content of 35-40%. The resulting concentrate in other azeotrope column using diisopropyl ether dehydrated to a moisture content of 0.5 to 1.0%. In the third distillation column from dehydrated is ü acids WITH2-C4after removal of formic acid, separated by the method of ordinary rectification ["a Collection of articles on the development and improvement of the production of synthetic fatty acids, alcohols and various products on their basis". Shebekino, 1973, S. 126-129].

This method is complex, requires a large number of distillation equipment, which due to the high corrosiveness of the environment quickly breaks down. Distillation of an aqueous solution containing 80-85% water and 15-20% of the amount of low molecular weight acids (formic, acetic, propionic, butyric, valerianic) causes such severe corrosion that equipment stainless steel fails in a month [Mankovsky N. To. "Synthetic fatty acids. Production, properties, applications". M.: Chemistry, 1965, S. 69]. When similar technological scheme (the same complex and require a large amount of equipment) with the help of entrepreneur - amyl - or Solidaritate - get four commercial product, such obtained according to the previous technology:

1) technical formic acid, containing about 20% acetic acid and 1-2% more high molecular weight acids;

2) technical acetic acid, coderresult, containing 94-98% of the target product

[Mankovsky N. K. "Synthetic fatty acids. Production, properties, applications". M.: Chemistry, 1965, S. 160].

As can be seen from data on the composition of the first product (technical formic acid), the latter two methods using entrepreneurs do not provide a good separation of low molecular weight aliphatic acids, as obtained technical formic acid contains about 20% acetic acid and 1-2% more high molecular weight acids. In addition, these methods require a large number of distillation equipment. Corrosive environment is extremely high.

Known methods for isolating low molecular weight fatty acids from aqueous solutions, such as waste from the production of synthetic fatty acids by transfer of low molecular weight acids in the dry sodium salt with subsequent decomposition of salts concentrated sulfuric or other acids. In this way, this series is way low molecular weight fatty acid interaction with caustic soda or soda transferred to the sodium salt, which is then dehydrated. The dry sodium salt of low molecular weight acids diluted with ice UB>-C4that distilled from sodium formate. The remaining sodium formate further decompose 100% sulfuric acid at 55-60oIn the environment of formic acid and receive formic acid [A. S. 213799 the USSR "isolation of low molecular weight fatty acids, CL. 12 ° 11, IPC 11 D. Authors: Akhmedzhanov, I. S., Tikunova Century. And. and other bull. Fig. 1968, 11].

This way, in spite of its high efficiency and simplicity, has a number of disadvantages, which doesn't allow us to play in a production environment. The main drawback is the use of formic acid to displace low-molecular-weight fatty acids. This forms a mixture of low molecular weight aliphatic acids containing formic acid and residual amounts of water, although it is anticipated that during the processing of dry sodium salts of low molecular weight aliphatic acids formic acid is only the displacement of the free acids WITH2-C4and the formation of sodium formate, in real conditions in the reaction mixture remains part of the sodium salts of the acids and unreacted formic acid. Thus, in a mixture of free low molecular weight acids contains murawinski mixture of formic acid and for example, acetic acid for any ratio of these acids in the mixture has a value of about 1.2 to 1.5, it is almost impossible satisfactorily to separate mixtures of lower aliphatic acids from formic acid by direct distillation. The application of this method results in low molecular weight aliphatic acids, contaminated with impurities of formic acid. In addition, the implementation of the discussed method requires the use of specially prepared glacial acetic acid, anhydrous formic acid and 100% sulfuric acid. In addition, treatment of the mixture of dry sodium formate and anhydrous formic acid concentrated sulfuric acid (especially when heated) leads to the irreversible loss of formic acid because of its carbonyliron emitting carbon monoxide and water

< / BR>
[Fisher L., Fisher M. "Organic chemistry. An advanced course", TRANS. from English. 2nd supplementary ed., so 1. M.: Chemistry, 1960, S. 431; Chichibabin A. E. "Basic principles of organic chemistry" 7th ed., so 1, M: Gostick., 1961, S. 295.].

The use of highly concentrated acids, particularly glacial acetic, anhydrous formic, 100% sulfuric leads to the high corrosiveness of the reaction is and then, is when obtaining the formic acid treatment of sodium formate with sulfuric acid is formed and takes requiring further costly purification of the sodium sulfate. Without such treatment the resulting sodium sulfate has no application.

There is a method of allocating a lower aliphatic acids from aqueous solutions by extraction trioctylamine at a temperature of 20-30oC, a pressure of 1 ATM and a molar ratio of acid and amine 1:1,2, separation of the liquid salts from water and subsequent thermal decomposition of the salts with trioctylamine with simultaneous distillation of the acid [A. S. 168674 the USSR, "the Method of selection of the lower aliphatic acids, CL. 12°, 11, IPC SS. Authors: Yakushkin M. I.; Bull. Fig. 1965. 5]. This method is taken as a prototype.

However, the way the prototype is not very effective for the case of allocation of a mixture of lower aliphatic acids from aqueous solutions containing formic acid, with subsequent separation of mixtures of these acids, as formic acid forms water and other aliphatic acids triple azeotropy that it is not possible to separate the mixture of these acids conventional rectification and requires special techniques.

Although, in the case of dehydrated mixtures of the aliphatic acids, difficulties in the separation of mixtures of formic acid with the lowest acids remain as the relative volatility of the mixture of formic acid and, for example, acetic acid for any ratio of these acids in the mixture has a value of about 1.2 to 1.5. It is therefore virtually impossible satisfactorily to separate mixtures of lower aliphatic acids from formic acid by direct distillation.

The aim of the present invention to provide an effective method of selection of the lower aliphatic acids from aqueous solutions of mixtures of these acids containing formic acid, which simplifies the process subsequent separation into individual acids.

According to the present invention this objective is achieved by the interaction of aqueous solutions of low molecular weight aliphatic acids with primary and/or secondary amines of General formula

< / BR>
where R1- aliphatic hydrocarbon radical containing 6 to 25 carbon atoms;

R2- H or an aliphatic hydrocarbon radical containing 1 to 25 carbon atoms,

and formaldehyde at a temperature of 50-80oWith binding of formic acid for the synthesis of tertiary amines and becom the/P> The number of amines and formaldehyde take based on information contained in a solution of formic acid. 1 mol of formic acid contained in an aqueous solution of a mixture of lower aliphatic acids, using 0.5-0,53 mole of a primary or from 1.0 to 1.03 mol of secondary amine and from 1.0 to 1.03 mol of formaldehyde.

During the heating of aqueous solutions of mixtures of low molecular weight aliphatic acids containing formic acid, with primary and/or secondary amines and formaldehyde is full target using formic acid as the reducing agent, according to the following equations:

< / BR>
< / BR>
The reaction occurs, the targeted use of formic acid for primary and/or secondary amines to tertiary amines. Thus, formic acid contained in an aqueous solution of a mixture of lower aliphatic acids irreversibly reacts with primary and/or secondary amines and formaldehyde and completely removed from the mixture of these acids.

The resulting tertiary amines interact with other low molecular weight aliphatic acids (acetic, propionic, butyric and valerianic) to obtain the salts of these amines with acids WITH2-C5by the equation
2-C5defined value:

AND1+ A2+ A3< TOUKS+ Cprop+ Coil+ Cshaft< / BR>
where A1the number of primary amines contained in the amines have had taken at the beginning of the reaction, the moles;

AND2- the number of secondary amines contained in the amines have had taken at the beginning of the reaction, the moles;

AND3- the number of tertiary amines contained in the amines have had taken at the beginning of the reaction, the moles;

TOUKSthe content of acetic acid, moles;

TOprop- the content of propionic acid, moles;

TOoil- the content of butyric acid, moles;

TOshaft- the content of valerianic acid, moles;

additionally impose ready tertiary amines based

< / BR>
where aDOB- the number of added tertiary amines, g;

- average molecular weight of the added tertiary amines;

With the content of the tertiary amine added in tertiary amines have had, %.

After completion of the reaction remove the water under atmospheric or reduced pressure and get dry salts of tertiary amines with aliphatic acids is UB>3C2H5WITH3H7WITH4H9,

with simultaneous distillation of a mixture of lower aliphatic acids not containing formic acid.

Since solved the issue of the withdrawal of water and formic acid, it becomes possible to divide the remaining mixture of low molecular weight aliphatic acids WITH2-C5conventional rectification and receiving individual acids of high quality (basic substance content of 98.5-99,0%).

Example 1.

In the reaction flask 1000 ml of an aqueous solution of a mixture of low molecular weight aliphatic acid composition, %:

Formic acid 1,3

Acetic acid 7,4

Propionic acid 4,8

Butyric acid 1,7

Valerianic acid 0,8

The amount of acid 16,0

which corresponds 13,0 g (0,28 mol) of formic acid, 74,0 g (1,23 mole) of acetic acid, 48,0 g (of 0.65 mol) propionic acid, 17.0 g (0,19 mole) of butyric acid and 8.0 g (0,08 mol) valerianic acid, add 39,23 g (of 0.14 mole) of 96% octadecylamine (primary amine) and small portions under stirring added to 23.4 g (0,28 mol) of 36% aqueous solution of formaldehyde at a temperature of 50-80oC.

After the reaction the presence of/SUB>+ Coil+ Cshaft< / BR>
where A1the number of primary amines contained in the amines have had taken at the beginning of the reaction, equal to 0.14 mole;

AND2- the number of secondary amines contained in the amines have had taken at the beginning of the reaction is equal to 0 moles;

AND3- the number of tertiary amines contained in the amines have had taken at the beginning of the reaction is equal to 0 moles;

TOUKSthe content of acetic acid equal to 1.23 mole;

TOprop- the content of propionic acid, 0.65 mole;

TOoil- the content of butyric acid, equal to 0.19 mol;

TOshaft- the content of valerianic acid, equal to 0.08 mole;

0,14 + 0 + 0 <1,23 + 0,65 + 0,19 + 0,08.

From the obtained relations can be seen that the reaction mixture has a large excess of free acid which must be neutralized by adding ready tertiary amines. The amount added of the tertiary amine is N,N-dimethyl-N-octadecylamine is calculated by the formula

< / BR>
where is the molecular weight of the added N,N-dimethyl-N-octadecylamine equal to 297 g;

With the content of the tertiary amine to be added Amina equal 90,8%.

< / BR>
After the reaction from the reaction mass is distilled water. Dehydrated salts of tertiary whom decomposition to amine and a mixture of low molecular weight aliphatic acids. The bulk of the acid Argonauts at a temperature of 180-230oC. the Obtained mixture of lower aliphatic acids not containing formic acid, simple rectification dispersed on the individual acids.

The yield of acid is:

Acetic acid 70,10 g (99.0% purity) (93,8% of theoretical.)

Propionic acid 46,61 g (98.9 per cent purity) (96,0% of theory.

Butyric acid 16,36 g (99.0% purity) (95,3% of theoretical.)

Valerianic acid EUR 7.57 g (99.1% of purity) (93,8% of theory.

The residue after thermal decomposition weight 643,7 g represents N,N-dimethyl-N-octadecylamine composition, %:

Primary amines 0,0

Secondary amines 0,0

Tertiary amines 91,4

The amount of amines 91,4

The output of the tertiary amine to 92.1% (from theory.).

Example 2.

In the reaction flask 1000 ml of an aqueous solution of a mixture of low molecular weight aliphatic acid composition, %:

Formic acid 9,8

Acetic acid 4,4

Propionic acid 1,3

Butyric acid 0,6

Valerianic acid, and 0.5

The amount of acid 16,6

which corresponds 98,0 g (2,13 mole) of formic acid, 44,0 g (to 0.73 mol) of acetic acid, 13,0 g (0,18 mol) propionic acid, 6.0 g (of 0.07 mole) of butyric acid and 5.0 g (0.05 mole) valerianic is the so called add 177,0 g (2,12 mol) of 36% aqueous solution of formaldehyde at a temperature of 50-80oC. do Next, as in example 1. The yield of acid is:

Acetic acid 42,44 g (98,8% purity) (95,3% of theoretical.)

Propionic acid 12,32 g (98,7% purity) (93,5% of theoretical.

Butyric acid 5,74 g (98.9 per cent purity) (94,7% of theoretical.)

Valerianic acid and 4.75 g (98,7% purity) (93,8% of theory.

The residue after thermal decomposition weight 325,7 g represents N,N-dimethyl-N-octadecylamine composition,%:

Primary amines 0,0

Secondary amines 0,0

Tertiary amines 90,8

The amount of amines 90,8

The output of the tertiary amine for 93.9% of theoretical.).

Example 3.

In the reaction flask 1000 ml of an aqueous solution of a mixture of low molecular weight aliphatic acid composition, %:

Formic acid 9,8

Acetic acid 4,4

Propionic acid 1,3

Butyric acid 0,6

Valerianic acid, and 0.5

The amount of acid 16,6

which corresponds 98,0 g (2,13 mole) of formic acid, 44,0 g (to 0.73 mol) of acetic acid, 13,0 g (0,18 mol) propionic acid, 6.0 g (of 0.07 mole) of butyric acid and 5.0 g (0.05 mole) valerianic acid, add 316,6 g (1,13 mole) 96% octadecylamine (primary amine ) and small portions under stirring add 182,3 g (2,19 mol) of 36% aqueous solution of formaldehyde at the rate which the notes 42,51 g (98,7% purity) (95.8% of theory.)< / BR>
Propionic acid 12,48 g (98,8% purity) (94,6% of theory.

Butyric acid 5,86 g (99.0% purity) (94.2% of theory.)

Valerianic acid 4,88 g (98.9 per cent purity) (94,6% of theory.

The residue after thermal decomposition weight 331,2 g represents N,N-dimethyl-N-octadecylamine composition, %:

Primary amines 0,0

Secondary amines 0,0

Tertiary amines 91,2

The amount of amines 91,2

The output of the tertiary amine to 95.5% of theoretical.).

Example 4.

In the reaction flask 1000 ml of an aqueous solution of a mixture of low molecular weight aliphatic acid composition, %:

Formic acid 9,8

Acetic acid 4,4

Propionic acid 1,3

Butyric acid 0,6

Valerianic acid, and 0.5

The amount of acid 16,6

which corresponds 98,0 g (2,13 mole) of formic acid, 44,0 g (to 0.73 mol), 13,0 g (0,18 mol) propionic acid, 6.0 g (of 0.07 mole) of butyric acid and 5.0 g (0.05 mole) valerianic acid, add 546,7 g dioctylamine (secondary amine) composition, %:

Primary amines 0,0

Secondary amines 93,9

Tertiary amines 0,0

The amount of amines 93,9

which corresponds to 513 g (2,13 mole) of dioctylamine, heated to 50-80oWith small portions add 177,5 g (2,12 mol) of 36% aqueous solution formaldehyde) (95,0% of theory.)

Propionic acid 12,71 g (99.0% purity) (94.5% of theoretical.

Butyric acid 5,69 g (98,7% purity) (93,7% of theoretical.)

Valerianic acid 4,79 g (99.0% purity) (94.8% of theory.

The residue after thermal decomposition weight 556,3 g is trioctylamine composition, %:

Primary amines 0,0

Secondary amines 0,0

Tertiary amines 92,6

The amount of amines 92,6

The output of the tertiary amine of 94.8% (from theory.).

Example 5.

In the reaction flask 1000 ml of an aqueous solution of a mixture of low molecular weight aliphatic acid composition, %:

Formic acid 9,8

Acetic acid 4,4

Propionic acid 1,3

Butyric acid 0,6

Valerianic acid, and 0.5

The amount of acid 16,6

which corresponds 98,0 g (2,13 mole) of formic acid, 44,0 g (to 0.73 mol), 13,0 g (0,18 mol) propionic acid, 6.0 g (of 0.07 mole) of butyric acid and 5.0 g (0.05 mole) valerianic acid, add 563,1 g dioctylamine (secondary amine) composition, %:

Primary amines 0,0

Secondary amines 93,9

Tertiary amines 0,0

The amount of amines 93,9

which corresponds 528,75 g (2,20 mole) of dioctylamine, heated to 50-80oWith small portions add 184,0 g (2,20 mol) of 36% aqueous formaldehyde solution. Next t theory.)

Propionic acid 12,90 g (98,8% purity) (95,7% of theory.

Butyric acid of 5.84 g (99.1% of purity) (94,0% of theory.)

Valerianic acid 4,89 g (99.3% of purity) (95.2% of theoretical.

The residue after thermal decomposition weight 556,3 g is trioctylamine composition, %:

Primary amines 0,0

Secondary amines 0,0

Tertiary amines 93,4

The amount of amines 93,4

The output of the tertiary amine 97,0% (from theory.).

Example 6.

In the reaction flask 1000 ml of an aqueous solution of a mixture of low molecular weight aliphatic acid composition, %:

Formic acid 8,3

Acetic acid - 10,0%

Propionic acid 2,0

Butyric acid 0,75

Valerianic acid 0,6

The amount of acid 21,65

which corresponds 83,0 g (1,80 mole) of formic acid, 100.0 g (1,67 mole) of acetic acid, 20,0 g (of 0.27 mole) of propionic acid and 6.0 g (0,06 mol) valerianic acid, add 666,7 g of aliphatic amines C8composition, %:

Primary amines a 3.87

Secondary amines 50,80

Tertiary amines 38,83

The amount of amines 93,50

which corresponds 25,80 g (of 0.20 mole) of a primary amine, 338,7 g (1,41 mol) of the secondary amine and 258,9 g (to 0.73 mol) of tertiary amine is heated to 50-80oWith small portions Prov is:

Acetic acid 93,59 g (98.9 per cent purity) (92,6% of theoretical.)

Propionic acid 18,66 g (98.9 per cent purity) (92,3% of theory.

Butyric acid of 6.96 g (99.0% purity) (91,9% of theoretical.)

Valerianic acid 5,65 g (99.0% purity) (93,2% of theory.

The residue after thermal decomposition weight 665,4 g is an amine composition, %:

Primary amines 0,0

Secondary amines 0,0

Tertiary amines to 91.1

The amount of amines to 91.1

The output of the tertiary amine to 93.5% of theoretical.).

The novelty of the proposed method of allocation of low molecular weight aliphatic acids is that for the first time, aqueous solutions of a mixture of lower aliphatic acids containing formic acid, in contrast to the known methods, the process is not ready tertiary amines, and heated with primary and/or secondary amines and formaldehyde. This known reaction of Escalera - Clark (variant of Lacerta - Vallaha) obtaining tertiary amines by reductive alkylation of primary and/or secondary amines using formic acid as the reducing agent used in the method, proposed by us, with a new purpose - for the complete and irreversible removal of formic acid from aqueous solutions of a mixture of low molecular weight alifaticheskih groups in the newly synthesized tertiary amines have had. Further the interaction of the formed tertiary amines with all other aliphatic acids WITH2-C5and the removal of water leads to the production of dry salts of acids WITH2-C5with tertiary amines. Thermal decomposition of these salts leads to the distillation of a mixture of aliphatic acids, free from formic acid to allow subsequent separation of this mixture on an individual acid by simple rectification.

For the implementation of the reaction of Escalera - Clark (variant of Lacerta-Vallaha) (in the case of using it to obtain the N-methylamines) the permissible use of an excess of formic acid and formaldehyde (usually applied ["Organikum. Workshop on organic chemistry." TRANS. with it. M.: Mir, so 2, 1979, S. 186-187]), and unreacted formic acid and formaldehyde do not interfere with the selection of the target product (N-methylated amines).

In the case of the present invention, it is necessary to impose severe restrictions on fluctuations in the ratios of reagents. This is caused by the specificity of the purpose for which it is the reaction of Escalera-Clark:

a) an increase in the amount of formic acid is more than 1.0 mole on from 0.50 to 0.53 mol of primary amine, or from 1.0 to 1.03 mol allows you to satisfactorily divide mixture of lower aliphatic acids by simple azeotropic distillation. Thus, the purpose of the invention in this case can not be reached;

b) increase the number of primary amine more from 0.50 to 0.53 mol or secondary amine more from 1.0 to 1.03 mol per 1 mol of formic acid, due to the fact that the reaction mixture consists of more aliphatic acid, results in the conditions necessary for the implementation process (i.e. during heat treatment salts of amines) to the flow following schema transformations:

< / BR>
In this case, due to the formation as by-products of monosubstituted and disubstituted amides irreversibly use some of the acids that it was necessary to allocate. Naturally, the output acids WITH2-C5as a result, significantly reduced;

C) increasing the amount of formaldehyde over from 1.0 to 1.03 mol per 1 mol of formic acid and from 0.50 to 0.53 mol of primary amine, or from 1.0 to 1.03 mol of the secondary amine is also unacceptable due to possible contamination with excess formaldehyde target lower aliphatic acids WITH2-C5when the distillation of products from thermal decomposition of the reaction mixture;

g) in addition, you must balance the number of tertiary amines and aliphatic acids WITH2-C5. The molar ratio is. the ri content of the tertiary amine is less than 1.0 mol per 1.0 mol of the acid WITH2-C5some of these acids remains free, unreacted salt formation from tertiary amines. This leads to the fact that the free acid is lost at the stage of dehydration, as aliphatic acid WITH2-C5due to the fact that the boiling point of the acids or their water azeotrope close to the boiling point of water, therefore, in case of lack synthesized tertiary amines for the neutralization of the aliphatic acids WITH2-C5add the calculated amount of the tertiary amine.

Thus, the use of the proposed method of selection of the lower aliphatic acids compared with the existing methods has the following advantages:

a) while under the prototype is allocated the entire amount of the lower aliphatic acids, including formic acid, the presence of formic acid is not possible to satisfactorily divide this mixture by straight distillation of the individual acids, according to the present invention is the selection of a mixture of lower aliphatic acids, free from formic acid, which allows subsequent is emy our method allows the removal of formic acid from a mixture of acids as a result of irreversible its interaction with primary and/or secondary amines or mixtures of these amines and formaldehyde, while receiving valuable to the national economy tertiary amines. They will be able to find a use for the synthesis of various Quaternary ammonium compounds which are bactericides, extractants non-ferrous and precious metals, flotation agents of metallic and non-metallic ores and other

1. Isolation of low molecular weight aliphatic acids from aqueous solutions containing formic acid, by their interaction with amines and subsequent thermal decomposition of the salts formed with simultaneous distillation of the acids, wherein the binding of formic acid, the acid is treated with from 0.5 to 0.53 mol primary or from 1.0 to 1.03 mol of the secondary amine of General formula:

R1R2NH,

where R1- aliphatic hydrocarbon radical containing 6-25 carbon atoms;

R2- H, or an aliphatic hydrocarbon radical containing 1-25 carbon atoms;

and from 1.0 to 1.03 mol of formaldehyde for each mol of formic acid at a temperature of 50-80oC.

2. The method according to p. 1, characterized in that in case of lack of tertiary amines formed in the reaction, for salt formation with all the contained in the solution acid WITH2-C5THEshaft,

where A1the number of primary amines contained in the amines have had taken at the beginning of the reaction, the mol;

AND2- the number of secondary amines contained in the amines have had taken at the beginning of the reaction, the mol;

AND3- the number of tertiary amines contained in the amines have had taken at the beginning of the reaction, the mol;

TOUKSthe content of acetic acid, mol;

TOprop- the content of propionic acid, mol;

TOoil- the content of butyric acid, mol;

TOshaft- the content of valerianic acid, mol;

additionally impose ready tertiary amines based

< / BR>
where a3.EXT- the number of added tertiary amines, g;

MA3.EXT- average molecular weight of the added tertiary amines;

With a content of tertiary amines, adding tertiary amines have had, %.

 

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The invention relates to a method of purification of d,l-malic acid used in the food industry

FIELD: crystal growing.

SUBSTANCE: invention relates to adipic acid crystals and treatment thereof to achieve minimum crystal caking. Crystals are prepared by crystallization of adipic acid from aqueous medium or between treating it with aqueous solution. Crystals are then subjected to ripening stage, that is crystals are held at temperature between 10 and 80°C until content of exchangeable water in crystals falls below 100 ppm, while using an appropriate means to maintain ambient absolute humidity at a level of 20 g/m3. Renewal of ambient medium is accomplished by flushing crystal mass with dry air flow having required absolute humidity. Means to maintain or to lower absolute humidity contains moisture-absorption device placed in a chamber. Content of exchangeable water in crystals is measured for 300 g of adipic acid crystals, which are enclosed in tightly sealed container preliminarily flushed with dry air and containing 2 g of moisture absorbing substance. In chamber, temperature between 5 and 25°C is maintained for 24 h. Content of water will be the same as amount of water absorbed by absorbing substance per 1 g crystals. Total content of water exceeds content of exchangeable water by at least 20 ppm.

EFFECT: minimized caking of crystals and improved flowability.

13 cl, 5 ex

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention relates to the improved method for isolating crystalline terephthalic acid comprising less 150 mas. p. p. per million (ppm) of p-toluic acid with respect to weight of terephthalic acid. Method involves the following steps: (1) preparing a solution containing from 10 to 35 wt.-% of dissolved terephthalic acid wherein from 150 to 1100 ppm of p-toluic acid is dissolved with respect to mass of terephthalic acid at temperature from 260°C to 320°C and under pressure providing maintaining the solution in liquid phase; (2) charge of solution from step (1) to crystallization zone comprising multitude amount of associated crystallizers wherein the solution is subjected for cooling at evaporation at the controlled rate by the moderate pressure and temperature reducing resulting to crystallization of terephthalic acid and wherein the solution pressure at the end of crystallization zone is equal to atmosphere pressure or lower; (3) condensation of solvent evaporated from crystallizers and recovering the condensed solution to the crystallization zone to place of descending flow from crystallizer wherein solvent is removed by evaporation, and (4) isolation of solid crystalline terephthalic acid comprising less 150 ppm of p-toluic acid with respect to the terephthalic acid mass by separation of the phase liquid-solid substance under atmosphere pressure. The advantage of method is preparing the end product in improved crystalline form and carrying out the process under atmosphere pressure or pressure near to atmosphere pressure.

EFFECT: improved method of crystallization.

3 cl, 1 dwg, 1 tbl, 2 ex

FIELD: chemical industry; methods of production of the purified crystalline terephthalic acid.

SUBSTANCE: the invention is pertaining to the improved method of production and separation of the crystalline terephthalic acid containing less than 150 mass ppm of the p-toluene acid in terms of the mass of the terephthalic acid. The method provides for the following stages: (1) loading of (i) para- xylene, (ii) the water reactionary acetic-acidic medium containing the resolved in it components of the oxidation catalyst, and (iii) the gas containing oxygen fed under pressure in the first zone of oxidation, in which the liquid-phase exothermal oxidization of the para-xylene takes place, in which the temperature and the pressure inside the first being under pressure reactor of the oxidization are maintained at from 150°С up to 180°С and from 3.5 up to 13 absolute bars; (2) removal from the reactor upper part of the steam containing the evaporated reactionary acetic-acidic medium and the gas depleted by the oxygen including carbon dioxide, the inertial components and less than 9 volumetric percents of oxygen in terms of the non-condensable components of the steam; (3) removal from the lower part of the first reactor of the oxidized product including (i) the solid and dissolved terephthalic acid and (ii) the products of the non-complete oxidation and (ii) the water reactionary acetic-acidic medium containing the dissolved oxidation catalyst; (4) loading of (i) the oxidized product from the stage (3) and (ii) the gas containing oxygen, into the second being under pressure zone of the oxidation in which the liquid-phase exothermal oxidization of the products of the non-complete oxidization takes place; at that the temperature and the pressure in the second being under pressure reactor of the oxidization are maintained from 185°С up to 230°С and from 4.5 up to 18.3 absolute bar; (5) removal from the upper part of the second steam reactor containing the evaporated water reactionary acetic-acidic medium and gas depleted by the oxygen, including carbon dioxide, the inertial components and less, than 5 volumetric percents of oxygen in terms of the non-condensable components of the steam; (6) removal from the lower part of the second reactor of the second oxidized product including (i) the solid and dissolved terephthalic acid and the products of the non-complete oxidation and (ii) the water reactionary acetic-acidic medium containing the dissolved oxidation catalyst; (7) separation of the terephthalic acid from (ii) the water reactionary acetic-acidic medium of the stage (6) for production the terephthalic acid containing less than 900 mass ppm of 4- carboxybenzaldehyde and the p-toluene acid; (8) dissolution of the terephthalic acid gained at the stage (7) in the water for formation of the solution containing from 10 up to 35 mass % of the dissolved terephthalic acid containing less than 900 mass ppm of the 4- carboxybenzaldehyde and the p-toluene acid in respect to the mass of the present terephthalic acid at the temperature from 260°С up to 320°С and the pressure sufficient for maintaining the solution in the liquid phase and introduction of the solution in contact with hydrogen at presence of the catalytic agent of hydrogenation with production of the solution of the hydrogenated product; (9) loading of the solution of the stage (8) into the crystallization zone including the set of the connected in series crystallizers, in which the solution is subjected to the evaporating cooling with the controlled velocity using the significant drop of the temperature and the pressure for initiation of the crystallization process of the terephthalic acid, at the pressure of the solution in the end of the zone of the crystallization is atmospheric or below; (10) conduct condensation of the dissolvent evaporated from the crystallizers and guide the condensed dissolvent back into the zone of the crystallization by feeding the part of the condensed dissolvent in the line of removal of the product of the crystallizer, from which the dissolvent is removed in the form of the vapor; and (11) conduct separation of the solid crystalline terephthalic acid containing less than 150 mass ppm of the p-toluene acid in terms of the mass of the terephthalic acid by separation of the solid material from the liquid under the atmospheric pressure. The method allows to obtain the target product in the improved crystalline form.

EFFECT: the invention ensures production of the target product in the improved crystalline form.

8 cl, 3 tbl, 2 dwg, 3 ex

FIELD: chemistry.

SUBSTANCE: invention pertains to the perfection of the method of regulating quantities of dissolved iron in liquid streams during the process of obtaining aromatic carboxylic acids or in the process of cleaning technical aromatic carboxylic acids, characterised by that, to at least, part of the liquid stream for regulating the quantity of dissolved iron in it, at least one peroxide with formula R1-O-O-R2 is added. Here R1 and R2 can be the same or different. They represent hydrogen or a hydrocarbon group, in quantities sufficient for precipitation of the dissolved iron from the liquid. The invention also relates to the perfection of the method of obtaining an aromatic carboxylic acid, through the following stages: A) contacting the crude aromatic material which can be oxidised, with molecular oxygen in the presence of an oxidising catalyst, containing at least, one metal with atomic number from 21 to 82, and a solvent in the form of C2-C5 aliphatic carboxylic acid in a liquid phase reaction mixture in a reactor under conditions of oxidation with formation of a solid product. The product contains technical aromatic carboxylic acid, liquid, containing a solvent and water, and an off-gas, containing water vapour and vapour of the solvent; B) separation of the solid product, containing technical aromatic carboxylic acid from the liquid; C) distillation of at least part of the off gas in a distillation column, equipped with reflux, for separating vapour of the solvent from water vapour. A liquid then forms, containing the solvent, and in the upper distillation cut, containing water vapour; D) returning of at least, part of the liquid from stage B into the reactor; E) dissolution of at least, part of the separated solid product, containing technical aromatic carboxylic acid, in a solvent from the cleaning stage with obtaining of a liquid solution of the cleaning stage; F) contacting the solution from the cleaning stage with hydrogen in the presence of a hydrogenation catalyst and under hydrogenation conditions, sufficient for formation of a solution, containing cleaned aromatic carboxylic acid, and liquid, containing a cleaning solvent; G) separation of the cleaned aromatic carboxylic acid from the solution, containing the cleaning solvent, which is obtained from stage E, with obtaining of solid cleaned aromatic carboxylic acid and a stock solution from the cleaning stage; H) retuning of at least, part of the stock solution from the cleaning stage, to at least, one of the stages B and E; I) addition of at least, one peroxide with formula R1-O-O-R2, where R1 and R2 can be the same or different, and represent hydrogen or a hydrocarbon group, in a liquid from at least one of the other stages, or obtained as a result from at least one of these stages, to which the peroxide is added, in a quantity sufficient for precipitation of iron from the liquid.

EFFECT: controlled reduction of the formation of suspension of iron oxide during production of technical aromatic acid.

19 cl, 1 dwg, 6 ex, 4 tbl

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