The method of purification of terephthalic acid by crystallization

 

The invention relates to an improved method for producing isophthalic acid used in copolymerization ways of producing fibers, films, plastic bottles and structures made of polyester resin, which consists in the oxidation of metaxalone in the reaction solvent to obtain a liquid dispersion. In particular, the invention relates to a method of purification of crude isophthalic acid from the liquid dispersion also containing impurities, which are selected from unreacted starting substances, solvents, products of side reactions and/or other undesirable materials, including filtering the specified variance with obtaining crude isophthalic acid in the form of a cake; the dissolution of the specified oxide in the solvent for the selective crystallization at elevated temperature, approximately in the range from 50 to 200oWith, to obtain a solution; the crystallization of purified isophthalic acid from this solution in the specified solvent for the selective crystallization by reducing the temperature or reducing the pressure to a degree sufficient for the instantaneous evaporation of the solvent from the specified isophthalic acid specified solution; the Department indicated This purified saturated or isophthalic acid solvent with the aim of ousting the mother liquor and coloring substances and re-dissolution or soaking the washed cake isophthalic acid in water at elevated temperatures. The method allows to obtain the desired product of high purity containing 3-carboxymethylthio below 40 ppm and the content of m-Truelove acid below 2 h/2 million C. and 23 C.p. f-crystals, 1 Il., table 2.

The invention relates to a method and apparatus for producing isophthalic acid (IFC) from metaxalona. It relates also to a method and device for the purification of effluent from the oxidation reactor stream containing a mixture of isophthalic acid and minor amounts of 3-carboxyanhydride (3-KBA), m-Truelove acid and other minor impurities, which allows to obtain purified isophthalic acid in an integrated way. Isophthalic acid is used in copolymerization ways of producing fibers, films, plastic bottles and designs of polyester resins, often reinforced by other materials, such as fiberglass.

Closest to the proposed method is a method of purification of terephthalic acid obtained by oxidation of metaxalone in the reaction solvent, for example, C2-C6aliphatic monocarboxylic acid, to obtain a liquid dispersion in the specified solvent, and this dispersion contains profiltrovannym from the reaction medium, - dissolving the crude isophthalic acid (KEK) in water at elevated temperatures from 100 to 300oWith subsequent crystallization and isolation of the target product. The method allows to obtain pure isophthalic acid content, such as 3-carboxymethylthio, probably not more than 5 parts per million.

The proposed method differs from the known fact that during the purification of crude isophthalic xylote provide additional stage after filtration and prior to the dissolution in water of isophthalic acid, which comprise the dissolution of the specified crude isophthalic acid in a solvent for the selective crystallization is approximately in the range from 50 to 200oC, to a solution - crystallization of purified isophthalic acid from this solution in the specified solvent for the selective crystallization by reducing the temperature or reducing the pressure to a degree sufficient for the instantaneous evaporation of the solvent from the specified isophthalic acid, - Department indicated purified by crystallization of terephthalic acid from the solution, washing the cake of purified isophthalic acid pure or saturated isophthalic acid solvent to push uterine rest the left acids from metaxalona integrated way. On the one hand, the method includes obtaining the crude terephthalic acid by oxidation of metaxalone. Stage oxidation gives not only isophthalic acid, but also, due to incomplete oxidation, gives 3-KBA, m-Truelove acid and other isomers of the acid and aldehyde in trace quantities. Obtained at the stage of the oxidation product is a liquid dispersion containing unreacted starting materials, solvents, if used, produve adverse reactions, in particular the above, and other materials which are undesirable in isophthalic acid desired degree of purity.

Coming out of the reactor stream is served in a series of crystallizers, where the opportunity for growth of crystals of terephthalic acid by evaporation of the reaction solvent, preferably acetic acid, by reducing the pressure. Suspension from the last crystallizer filtered and washed. The filtered crystals are then dried to remove solvent to content in crude crystals IFC below 0.25 per cent. The mother liquor from the filter is fed to the plant for dehydration of the solvent for the regeneration of the solvent (acetic acid) from the water and recirculated in the apparatus of DL is but dissolved in a selective solvent for crystallization and then crystallized from a solvent for the selective crystallization of one, or, preferably, in two crystallization stages. It is desirable that the temperature of dissolution was approximately between 50 and 200oC. Provides for the separation of crystallized and more purified IFC from solvent (containing or not containing a cosolvent) according to the invention. The resulting precipitate on the filter (KEK) purified IFC washed and soaked in other solvents according to the invention for removing paint and final traces of solvent for the selective crystallization of the IFC-product.

The invention also provides for recovering and recycling solvents according to the invention at each of the stages of crystallization, washing and final soaking. The stage also strictly control the discharge of any unwanted substances in the environment.

An important aspect of the present invention are obtained the results regarding solvents, which is effective for the implementation of the refining of crude IFC stages of crystallization and separation. These results can be summarized in the following several provisions.

Solvents for the selective crystallization, which can be used in this invention include Rustem IFC, at essentially any temperature within the specified temperature range, which contains IFC solvent is processed, and (b) IFC more soluble at elevated temperatures and are less soluble at minimum or low temperature. Obviously, the term "solvent for the selective crystallization" refers to solvents that are suitable for the selective crystallization of the IFC in accordance with the above and described in more detail below, and shown on the drawing.

According to the invention the main preferred solvent for the selective crystallization is N-organic (NM), for several reasons discussed below and its exceptional properties. It is not water, thermally stable, non-toxic (safe for the environment), is not corrosive and commercially available. As shown in the drawing, the curve of the dependence of solubility on temperature indicates that IFC can be dissolved in NM at elevated temperatures and precipitated or crystallized from NM at low temperatures. The main impurities such as KBA (labeled 4-KBA) and Truelove acid (designated as p-tolarova acid), have a much greater solution which emission or deposition from a solution with the formation of crystals of purified IFC.

Although NM is the preferred solvent for the selective crystallization according to this invention, it is understood that other preferred solvents for the selective crystallization for purification of crude IFC can be selected from various polar organic solvents, including, but not right restrictions, N,N-dimethylacetamide, N,N-dimethylformamide, N-formylpiperidine, N-alkyl-2-pyrrolidone (such as N-ethylpyrrolidin), N-mercapto-alkyl-2-pyrrolidone (such as N-mercaptoethyl-2-pyrrolidone), N-alkyl-2-cooperalion (such as N-methyl-2-cooperalion), N-hydroxyalkyl-2-pyrrolidone (such as N-hydroxyethyl-2-pyrrolidone), morpholines (such as morpholine and N-formylmorpholine), carbitol,1-C12-alcohols, ethers, amines, amides, esters, and mixtures thereof.

In order to remove residual solvent trapped crystals end-IFC-product crystals IFC preferably served in a high-temperature coking camera where the use of water for partial or complete dissolution of the crystals IFC. When the crystals IFC again precipitated or otherwise separated from vymachivayut water, residual solvent remains outside, in the water. In addition to water (which rastvoriteli, which include methanol, methyl ethyl ketone and acetone. Preferably soak or re-dissolving the purified cake IFC in water at temperatures from about 150 to 280oWith the removal end of the trace amounts of solvent for crystallization and to obtain the desired particle size of the IFC and the form.

The following examples illustrate the principles and features of the invention.

Example 1 Purification of crude IFC crystallization when cooled 350 g NM (solvent), 207,9 g isophthalic acid (IFC), 2.1 g of 3-KBA and 0.21 g m-Truelove acid is added to the crystallizer equipped with a heating jacket, a thermocouple, condenser and overhead stirrer. The mixture is heated to 125oWith under stirring until complete dissolution of the solids, and the solution is maintained at 125oWith ~1 hour before start cooling. The solution is slowly cooled to 40oC for 2-4 hours, giving rise to crystals IFC. Then, the suspension is removed from the crystallizer and filter at 45-50oC. the Precipitate on the filter (210 g) was washed with 630 g of the solution NM saturated IFC (solution containing 25 g of IFC 100 g NM), removal of the cake captured the mother liquor. For washing can be used pure NM, but predpochtite the washed cake is washed again at room temperature, an equal amount of saturated solution of NMP (11 g IFC 100 g N). In addition to pure or saturated NMP for washing can be used other solvents, including p-xylene, methanol, acetone and methyl ethyl ketone.

The washed crystals are dried and analyzed for composition by gas chromatography, the results are shown in table.1: In experiment 1, with the one-stage crystallization, the content of 3-KBA reduced, essentially, from 1.00% to 39 ppm, the content of m-Truelove acid decreases from 0.10% to less than 2 ppm (the limit of experimental error). In experiment 2, with the one-stage crystallization, the content of 3-KBA is reduced from 1.00% to 27 ppm and the content of m-Truelove acid decreases from 0.10% to less than 2 h/million Therefore, it is concluded that sufficient single-stage crystallization using N as a solvent to clean raw IFC (containing up to 1.00% of 3-CBA and 0.10% m-Truelove acid) before IFC-product containing 3-IAS below 40 ppm and the content of m-Truelove acid 2 h/million

It is desirable that the temperature of the solution was reduced to approximately intervals from 5 to 100oand especially preferably be reduced to intervals of approximately 10 to 45oC.

Example 2
Department IPA from 4-KBA and p-Truelove acid
Repeat experimental methodology example to ensure that small amount of other pollutants isomers in crude IFC, such as 4-KBA and p-tolarova acid, does not create any problems for a method of obtaining purified IFC according to this invention. Analysis of purified IFC by gas chromatography are shown in table.2. Again for the purification of used single-stage crystallization with N as solvent.

Again the analysis of the product showed that the content of 4-KBA (1,00%) and p-Truelove acid (0,10%) can be effectively reduced to the level of ppm by single-stage crystallization using N as solvent.


Claims

1. The method of purification of crude isophthalic acid from the liquid dispersion also containing impurities, which are selected from unreacted starting substances, solvents, products of side reactions and/or other undesirable materials, including: filtering a specified variance with obtaining crude isophthalic acid in the form of a cake; the dissolution of the specified oxide in the solvent for the selective crystallization at elevated temperature, approximately in the range from 50 to 200oWith, to obtain a solution; the crystallization of purified isophthalic acid from the specified rastia to the extent sufficient for instantaneous evaporation of the solvent from the specified isophthalic acid specified solution; separating the indicated purified by crystallization of terephthalic acid from the solution; washing the cake of purified isophthalic acid pure or saturated isophthalic acid solvent with the aim of ousting the mother liquor and coloring substances and re-dissolution or soaking the washed cake isophthalic acid in water at elevated temperatures.

2. The method according to p. 1, where the specified dispersion contains 3-carboxybenzene and m-Truelove acid.

3. The method according to p. 1, in which the crystallization of purified isophthalic acid in the specified solvent for the selective crystallization is carried out by lowering the temperature to approximately the range of 5 to 100oC.

4. The method according to p. 3, in which the crystallization of purified isophthalic acid in the specified solvent for the selective crystallization is carried out by lowering the temperature to approximately the range from 10 to 45oC.

5. The method according to p. 1, where the specified solvent for the selective crystallization is N-organic.

6. The method according to p. 1, where the specified solvent for selective crystallization, N-ethylpyrrolidin, N-mercaptoethyl-2-pyrrolidone, N-mercaptoethyl-2-pyrrolidone, N-alkyl-2-cooperalion, N-methyl-2-cooperalion, N-hydroxyalkyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, morpholine, N-formylmorpholine, carbitols, C1-C12-alcohols, ethers, amines, amides, esters and mixtures thereof.

7. The method according to p. 1, where at the stage of washing specified KEK use a wash solvent which is chosen from the group comprising N-organic, pure or saturated isophthalic acid, p-xylene, methanol, acetone and methyl ethyl ketone.

8. The method according to p. 7, where the specified wash solvent is N-organic, pure or saturated isophthalic acid.

9. The method according to p. 1, further comprising after the stage of separation of the phase displacement of the specified solvent for the selective crystallization of the displacing solvent chosen from the group consisting of water, methanol, methyl ethyl ketone and acetone.

10. The method according to p. 9, where the specified displacement solvent is water.

11. The method according to p. 1, where the specified re-dissolution or soaking cake of purified isophthalic acid in water is carried out at temperatures in the range of about Odanah particle sizes isophthalic acid and forms.

12. The method of obtaining isophthalic acid, including: oxidation of metaxalone in the reaction solvent to obtain a liquid dispersion in the specified reaction solvent, and this dispersion also contains impurities, which are selected from unreacted starting materials, accidentally captured the reaction solvents, products of side reactions and/or other undesirable materials; filtering the specified variance with the formation of a hard cake isophthalic acid; dissolving the specified oxide in the solvent for the selective crystallization at elevated temperature, approximately in the range from 50 to 200oWith, to obtain a solution; the crystallization of purified isophthalic acid from this solution in the specified make the solvent by lowering the temperature or reducing the pressure to a degree sufficient for the instantaneous evaporation of the solvent from the specified isophthalic acid specified solution; separating the indicated purified by crystallization of terephthalic acid from the solution; washing the cake of purified isophthalic acid pure or saturated, isophthalic acid solvent with the aim of ousting the mother liquor and coloring videatur.

13. The method according to p. 12, where the specified solvent, which oxidizes the specified betaxolol is acetic acid.

14. The method according to p. 12, where this dispersion contains 3-carboxybenzene and m-Truelove acid.

15. The method according to p. 12, in which the crystallization of purified isophthalic acid in the specified solvent for the selective crystallization is carried out by lowering the temperature to approximately the range of 5 to 100oC.

16. The method according to p. 15, in which the crystallization of purified isophthalic acid in the specified solvent for the selective crystallization is carried out by lowering the temperature to approximately the range from 10 to 45oC.

17. The method according to p. 12, where the specified solvent for the selective crystallization is N-organic.

18. The method according to p. 12, where the specified solvent for the selective crystallization selected from the group consisting of N,N-dimethylacetamide, N,N-dimethylformamide, N-formylpiperidine, N-alkyl-2-pyrrolidone, N-ethylpyrrolidin, N-mercaptoethyl-2-pyrrolidone, N-mercaptoethyl-2-pyrrolidone, N-alkyl-2-cooperalion, N-methyl-2-cooperalion, N-hydroxyalkyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, morpholine, N-formylmorpholine, carbitol,

20. The method according to p. 19, where the specified wash solvent is N-organic, pure or saturated isophthalic acid.

21. The method according to p. 12, further comprising after the stage of separation of the phase displacement of the specified solvent for the selective crystallization of the displacing solvent chosen from the group consisting of water, methanol, methyl ethyl ketone and acetone.

22. The method according to p. 21, where the specified displacement solvent is water.

23. The method according to p. 12, where the specified re-dissolution or soaking cake of purified isophthalic acid in water is carried out at temperatures in the range of about 180 to 280oWith the removal of the final traces of solvent for crystallization and obtain the specified particle size isophthalic acid and forms.

24. The method according to p. 12, where a specified liquid dispersion receive, feeding the stream coming out of this stage of oxidation, in a series of crystallizers, where the opportunity for growth of crystals of terephthalic acid with troweling precipitate crude isophthalic acid and drying the specified KEK crude isophthalic acid to remove the reaction solvent.

25. The method according to p. 12, where the mother liquor from this stage filtration dehydrate for the regeneration of the solvent and recycling it to the specified stage of oxidation.

Priority items:
06.05.1998 - PP.1, 2, 4-14, 16-25;
13.01.1999 - PP.3 and 15.

 

Same patents:

The invention relates to an improved method for producing isophthalic acid, which is an important monomer and intermediate in polymer chemistry for the production of chemical fibers, polyester films, varnishes, dyes, plastics

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

The invention relates to a method of purification by crystallization or recrystallization in water adipic acid, which is one of the main substances used to obtain polyamide 6-6, which contains traces of catalyst, with a minimum purity specified adipic acid is at least 95%, and the specified crystallization or recrystallization is carried out in the presence of a strong proton acid and/or in the presence of carbon monoxide

The invention relates to a method of purification of adipic acid, which is used to obtain polyamide

The invention relates to a technology for technical formate sodium from aqueous solution technical Chlorella, which is a waste product of chloroform
The invention relates to a method of catalytic hydroxycarbonylmethyl pentenoic acid to adipic acid
The invention relates to chemical technology, namely the production of monochloracetic acid - intermediate to obtain carboxymethyl cellulose, herbicides, ethylenediaminetetraacetic acid, pharmaceuticals

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

FIELD: chemistry.

SUBSTANCE: invention relates to an improved method, by which the carboxylic acid/diol mixture, that is suitable as the initial substance for the manufacture of polyester, obtained from the decolourised solution of carboxylic acid without actually isolating the solid dry carboxylic acid. More specifically, the invention relates to the method of manufacturing a mixture of carboxylic acid/diol, where the said method includes the addition of diol to the decolourised solution of carboxylic acid, which includes carboxylic acid and water, in the zone of the reactor etherification, where diol is located at a temperature sufficient for evaporating part of the water in order to become the basic suspending liquid with the formation of the specified carboxylic acid/diol mixture; where the said carboxylic acid and diol enter into a reaction in the zone of etherification with the formation of a flow of a complex hydroxyalkyl ether. The invention also relates to the following variants of the method: the method of manufacture of the carboxylic acid/diol mixture, where the said method includes the following stages: (a) mixing of the powder of damp carboxylic acid with water in the zone for mixing with the formation of the solution of damp carboxylic acid; where the said carboxylic acid is selected from the group, which includes terephthalic acid, isophthatic acid, naphthalenedicarboxylic acid and their mixtures; (b) discolourisation of aforesaid solution of damp carboxylic acid in the zone for reaction obtaining the decolourised solution of carboxylic acid; (c) not necessarily, instantaneous evaporation of the said decolourised solution of carboxylic acid in the zone of instantaneous evaporation for the removal of part of the water from the decolourised solution of carboxylic acid; and (d) addition of diol to the decolourised solution of carboxylic acid in the zone of the reactor of the etherification, where the said diol is located at a temperature, sufficient for the evaporation of part of the water in order to become the basic suspending liquid with the formation of the carboxylic acid/diol mixture; where the aforesaid carboxylic acid and diol then enter the zone of etherification with the formation of the flow of complex hydroxyalkyl ether; and relates to the method of manufacture of carboxylic acid/diol, where the said method includes the following stages: (a) the mixing of the powder of damp carboxylic acid with water in the zone for mixing with the formation of the solution of carboxylic acid; (b) discolourisation of the said solution of damp carboxylic acid in the reactor core with the formation of the decolourised solution of carboxylic acid; (c) crystallisation of the said decolourised solution of carboxylic acid in the zone of crystallisation with the formation of an aqueous suspension; and (d) removal of part of the contaminated water in the aforesaid aqueous solution and addition of diol into the zone of the removal of liquid with the obtaining of the said carboxylic acid/diol mixture, where diol is located at a temperature sufficient for evaporating part of the contaminated water from the said aqueous suspension in order to become the basic suspending liquid.

EFFECT: obtaining mixture of carboxylic acid/diol.

29 cl, 4 dwg

FIELD: chemistry.

SUBSTANCE: method of separating multi-atom alcohols, for instance, neopentylglycol and sodium formiate, includes evaporation and cooling of reaction mixture, addition of organic solvent, crystallisation of sodium formiate, separation of sodium formiate from saturated solution of multi-atom alcohol, for instance, by filtration, and crystallisation of multi-atom alcohol. Reaction mixture is evaporated until two liquid layers are formed, which are separated into light phase - water-multi-atom alcohol and heavy phase -water-salt, separated water-salt fraction of solution is cooled until sodium formiate contained in it in form of cryslallohydrate is crystallised, sodium formiate crystals are separated, and remaining mother-solution is returned to process head, to evaporation stage, then separated light phase - water-multi-atom alcohol is additionally evaporated until 70% of contained in it sodium formiate is crystallised, then cooled to 25-30°C and subjected to processing with organic solvent from line of single-atom saturated alcohols, for instance, methane, for removal of remaining admixtures, with further crystallisation of multi-atom alcohol from remaining mother-solution.

EFFECT: reduction of amount of used organic solvent, elimination of high-temperature stage of extraction, preservation of yield of pure target products.

2 cl, 2 dwg, 1 ex

FIELD: chemistry.

SUBSTANCE: method of obtaining product - purified carboxylic acid, includes: (a) oxidation of aromatic initial materials in primary oxidation zone with formation of raw carboxylic acid suspension; where raw carboxylic acid suspension contains terephthalic acid; where said oxidation is carried out at temperature within the range from 120°C to 200°C; (b) withdrawal of admixtures from raw suspension of carboxylic acid, removed at temperature from 140°C to 170°C from stage of oxidation of paraxylol in primary oxidation zone and containing terephthalic acid, catalyst, acetic acid and admixtures, realised in zone of solid products and liquid separation with formation of mother liquid flow and product in form of suspension; where part of said catalyst in said suspension of raw carboxylic acid is removed in said mother liquid flow; and where into said zone of solid products and liquid separation optionally additional solvent is added; (c) oxidation of said product in form of suspension in zone of further oxidation with formation of product of further oxidation; where said oxidation is carried out at temperature within the range from 190°C to 280°C; and where said oxidation takes place in said zone of further oxidation at temperature higher than in said primary oxidation zone; (d) crystallisation of said product of further oxidation in crystallisation zone with formation of crystallised product in form of suspension; (e) cooling of said crystallised product in form of suspension in cooling zone with formation of cooled suspension of purified carboxylic acid; and (i) filtration and optionally drying of said cooled suspension of purified carboxylic acid in filtration and drying zone in order to remove part of solvent from said cooled suspension of carboxylic acid with obtaining of said product - purified carboxylic acid.

EFFECT: purified carboxylic acid with nice colour and low level of admixtures, without using stages of purification like hydration.

8 cl, 1 tbl, 1 dwg, 1 ex

FIELD: chemistry.

SUBSTANCE: proposal is given of a method of removing impurities from a water mixture or purified water mixture through extraction of the water mixture or purified water mixture using an extractive solvent in the extraction zone with formation of a stream of extract and a stream of raffinate and, optionally, separation of the extract stream and the solvent rich stream in the separation zone with formation of a stream of organic impurities with high boiling point and a stream of extractive solvent.

EFFECT: provision for extracting metallic catalyst in active form, reusable at the paraxylene recycling stage.

29 cl, 2 dwg, 1 tbl

FIELD: chemistry.

SUBSTANCE: invention relates to a thermal separation method using fractional condensation of a product-gas mixture, obtained through heterogeneous catalysed partial oxidation of propene and/or propane in gaseous phase to acrylic acid, for separating at least one mass flow, concentrated with acrylic acid, from a product-gas mixture containing acrylic acid, which involves continuous static operation of at least one device for thermal separation, containing at least one effective separation chamber with a fractionation column which has mass-transfer trays as built-in separating elements, in which the product-gas mixture is loaded, containing acrylic acid as at least one mass flow, and from which at least one mass flow containing acrylic acid is unloaded under the condition that, the overall mass flow loaded into the effective separation chamber and obtained from combining separate mass flows loaded into the separating chamber, contains X wt % components distinct from acrylic acid, the mass flow which is unloaded from the effective separation chamber with the largest content of acrylic acid, contains Y wt % components distinct from acrylic acid, ratio X:Y is ≥5, effective separation chamber, except the loading and unloading place, is bordered by a solid phase and contains, besides the mass-exchange trays as built-in separating elements in the fractionation column, at least one circulating heat exchanger, and total volume of the chamber, filled with liquid phase, is ≥1 m3, wherein temperature of the liquid phase is at least partially ≥80°C, when the effective separation chamber is divided into n separate volume elements, wherein the highest and lowest temperature of liquid phase in a separate volume element differ by not more than 2°C, and the volume element in the effective separation chamber is solid, total dwell time ttotal.

≤20 h, where A = (Ti-To)/10°C, To= 100°C, Ti = arithmetic mean value of the highest and lowest temperature of the ith volume element in the liquid phase in °C, msi = total mass of acrylic acid in the volume of the liquid phase of the ith volume element, mi = total liquid phase mass unloaded from the ith volume element, and is the sum of all volume elements i, under the condition that, volume elements i with liquid phase mass mi and as volume elements with a dead zone are also not included in the sum of all volume elements i, as well as volume elements i, which do not contain liquid phase, and total amount of liquid phase contained in volume elements with a dead zone is not more than 5 wt % of the total amount of liquid phase contained in the effective separation chamber.

EFFECT: separation of mass flow concentrated with acrylic acid.

10 cl, 12 dwg, 2 ex, 2 tbl

FIELD: chemistry.

SUBSTANCE: sodium hydroxide solution is added to a technical mixture of benzoic and cinnamylic acid, obtaining a precipitate. Water is added to obtain a homogeneous solution. The obtained technical mixture of sodium salts of benzoic and cinnamylic acid with composition ranging from 2:1 to 1:2 and overall concentration ranging from 3 to 5 M is then mixed with sulphuric acid with concentration ranging from 3 to 5 M. Addition of sulphuric acid is stopped at pH of the medium between 8 and 9, and the precipitated complex of cinnamylic acid with its sodium salt is filtered from the reaction mixture, dissolved in excess amount of water to dissolve sodium salt of cinnamylic acid. Cinnamylic acid precipitates, and is further treated with sulphuric acid with concentration ranging from 3 to 5 M to pH between 1 and 2. The precipitated crystals of cinnamylic acid are separated; the reaction mixture remaining after separation of the complex is mixed with a solution of sulphuric acid with concentration ranging from 3 to 5 M until pH between 1 and 2. As a result, crystalline benzoic acid forms.

EFFECT: formation of complexes of carboxylic acids with their sodium salts for separating components of a mixture of carboxylic acids with similar chemical and physico-chemical properties.

2 ex

FIELD: chemistry.

SUBSTANCE: invention refers to the improved method for oxidising of aromatic hydrocarbon such as para-xylol, meta-xylol, 2,6-dimethylnaphthalene or pseudocumene with forming of corresponding organic acid. The oxidation is implemented by the source of molecular oxygen in liquid phase at temperature range from 50°C to 250°C in the presence of catalyst being a) oxidation catalyst based on at least one heavy metal representing cobalt and one or more additive metals being selected from manganese, cerium, zirconium, titanium, vanadium, molybdenum, nickel and hafnium; b) bromine source; and c) unsubstituted polycyclic aromatic hydrocarbon. The invention refers also to the catalytic system for obtaining of organic acid by the liquid-phase oxidation of aromatic hydrocarbons representing: a) oxidation catalyst based on at least one heavy metal representing cobalt and one or more additive metals being selected from manganese, cerium, zirconium, titanium, vanadium, molybdenum, nickel and hafnium; b) bromine source; and c) unsubstituted polycyclic aromatic hydrocarbon.

EFFECT: activation of the aromatic hydrocarbons oxidation increasing the yield of target products and allowing to decrease the catalyst concentration and the temperature of the process.

45 cl, 4 tbl, 16 ex

Up!