Method of separating mixture of naphthenic acids

FIELD: chemistry.

SUBSTANCE: invention relates to an improved method of separating a mixture of naphthenic acids. The method is characterised by that, an aqueous solution a mixture of sodium salts of naphthenic acids - naphthenic soap, with concentration of 3 to 5 M is treated with 3 to 5 M sulphuric acid with control of the pH of the medium. For each unit change of pH value, the precipitated complex of naphthenic acid and its sodium salt is separated from the reaction mass, after which each fraction of the product is dissolved in a fivefold amount of water to decompose the formed complex, and then treated with 3 to 5 M sulphuric acid to pH 1-2 and naphthenic acids are separated from the aqueous solution to obtain fractions of naphthenic acids with dissociation constant pKa=8±1.

EFFECT: formation of complexes of naphthenic acids with their sodium salts for separation of a mixture of naphthenic acids with similar chemical and physicochemical properties.

1 ex

 

The invention relates to the production of petroleum products, namely, naphthenic acids and their salts, are used as solvents, concrete additives, additives for fuel, as growth substances.

The composition of these products is complex and is not constant as it depends on the location of the oil and its fractions distillation. Remove naphthenic acids by treatment with an alkaline solution of oil and products of its distillation in the form of complex mixtures of sodium salts (malonate). Based malonate receive a mixture of naphthenic acids (Asida). Separation of naphthenic acids into fractions practiced by means of distillation, extraction, translation esters (Nametkin NS, Egorova G.M., Khamaev V.H. Naphthenic acids and the products of their chemical processing. M.: Chemistry. 1983. P.51.; Goriaev AM, Kotowaza V.N., Gaidarova S.A. A.S. 481594. 25.08.75. BE).

The disadvantage of these methods is that acidol because of its consistency fractionized, and only partially cleared from the unsaponifiable substances, phenols, resins.

The applicant and the authors are unknown methods of separation of naphthenic acids, based on the acid deposition in the form of complexes with their sodium salts.

The technical result of the proposed method lies in the fact that due to the formation of complexes of naphthenic acids and their sodium salts may divide the mixture nafte the OIC acids with similar chemical and physical properties to fractions of naphthenic acids with values of dissociation constant pKa=8±1, can only be achieved if the implementation of all essential features of the method below. To achieve the technical result of the method is confirmed by only using as a source mixture of malonate (product of complex and variable composition, containing not only the sodium salts of naphthenic acids, and other optional components); when processing fractions of the product with sulfuric acid only up to a certain interval of values of pH (1-2) and using stages of separation of naphthenic acids from an aqueous solution of each fraction of the product.

The technical result is achieved in that in the method of separating a mixture of naphthenic acid aqueous solution of a mixture of sodium salts of naphthenic acids concentrations of 3-5 M is treated with sulfuric acid at concentrations of 3-5 M with pH control environment, and at each change of pH per unit of the reaction mass is separated by precipitating the complex naphthenic acid and its sodium salt, and then each fraction is dissolved in five times the amount of water for the decomposition of the formed complex is then treated 3-5 M sulfuric acid to obtain fractions of naphthenic acids with values of dissociation constant pKa=8±1.

Experimentally it was found that in conditions of high concentration of the mixture of sodium salts of n is fanovich acids 3-5 M in the processing of sulfuric acid with a concentration of 3-5 M are formed complexes of carboxylic acids and their sodium salts, precipitated at pH 8-9. In the present case, the sequence of the sediment is determined by the dissociation constants of acids: the first fall of the weak acid dissociation constants pKa 8-9 in complex with their salts. So, naphthenic acid with a pKa of 9 forms a complex with its sodium salt as the most strong base (as a result of dissociation on the basis of weak acids form salts, which are strong conjugate base pKa+RCO=14). During the processing of the reaction mixture with sulfuric acid is separated by a narrow fraction of the product with pH values of 9.0; 8,0; 7,0; 6,0. The fraction of precipitation is dissolved in five times the amount of water, and then treated with 3-5 M sulfuric acid to pH 1-2 to extract naphthenic acids. Thus obtained naphthenic acids are a mixture thereof, close by the values of the dissociation constant.

Declare the parameters of the concentrations of the reagents contained in the formula are defined so that in solutions with different concentrations of reagents complexes naphthenic acids and their sodium salts are not formed.

Example. 100 g of malonate stirred with 100 ml of water, resulting in a water solution of the sodium salt of naphthenic acid concentration of 3-5 M, and potentiometric control pH of the medium is poured 3 M sulfuric acid. After each change of value of R is to 1.0 prelivanje sulfuric acid suspended and precipitated precipitated product is separated from the reaction mixture by centrifugation. The obtained fractions of precipitation are complexes of naphthenic acids and their salts of the composition 1:1. For the decomposition of the complexes precipitation is dissolved in five times the amount of water, and then to the solution add 3 M sulfuric acid to pH 1-2. When this aqueous solution is separated naphthenic acid in the form of a viscous product. The result is the fraction of naphthenic acids with pKa values of 8±1. Values of the dissociation constants determined by potentiometric titration.

The method of separating a mixture of naphthenic acids, characterized in that an aqueous solution of a mixture of sodium salts of naphthenic acids - malonate, the concentration of 3-5 M is treated with sulfuric acid at concentrations of 3-5 M with pH control environment, and at each change of pH per unit of the reaction mass is separated precipitated in the sediment complex naphthenic acid and its sodium salt, and then each fraction is dissolved in five times the amount of water for the decomposition of the formed complex is then treated 3-5 M sulfuric acid to pH 1-2 and separate the naphthenic acids from the aqueous solution to obtain fractions of naphthenic acids with values of dissociation constant pKa=8±1.



 

Same patents:

FIELD: chemistry.

SUBSTANCE: invention claims new compound, particularly (1R*2S*4R*)-4-(4-aminophenyl)-cyclohexane-1,2-dicarboxylic acid of the formula I , which can be applied in chemical industry for obtaining polyimides.

EFFECT: polyimides applied in production of liquid crystals, optical non-linear cushion layers and materials with low permittivity.

1 cl, 20 ex, 3 tbl

FIELD: chemistry.

SUBSTANCE: new cyclic carboxylic acid is obtained in reaction which includes performing connection [J] of, at least one terpen-based diene connection (conjugate diene connection), chosen from group consisting of alloocymen, ocymen, mircen, α-terpinen and α-phellandren, and [K], at least one unsaturated carboxylic acid, chosen from α,β-unsaturated carboxylic acids and monoethers of α, β-unsaturated dicarboxylic acids. Connecting agent (A) for antifouling paint is also revealed. It containes one or more substances chosen from new cyclic carboxylic acid, derivative from cyclic carboxylic acid (excluding metal salt), metal salts of cyclic carboxylic acid and metal salts of the derivative of cyclic carboxylic acid, as well as composition of antifouling paint, which contains connecting agent (A) and copolymer (B) for antifouling paint of self-cleaning type, which is a polymerising copolymer based on basic metal salt of unsaturated carboxylic acid or polymerising unsaturated copolymer based on silyl ether of unsaturated carboxylic acid. From composition of antifouling paint covering film can be formed, which has only slight influence on environment, it is evenly subjected to erosion with definite rate, is able to retain excellent properties against fouling for a long period of time and can be applied to the surfaces of ships and other objects, which are used in marine territories with high risk of fouling.

EFFECT: obtaining film of antifouling paint, which has only slight influence on environment, is evenly subjected to erosion with definite rate, is able to retain excellent properties against fouling for a long period of time.

26 cl, 12 dwg, 4 tbl

FIELD: chemistry.

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26 cl, 12 dwg, 4 tbl

FIELD: chemical technology.

SUBSTANCE: invention relates to a method for synthesis of perfluorocyclohexene 1-carboxylic acid fluoroanhydride or perfluorocyclohexane carboxylic acid fluoroanhydride. Method involves decarbonylation of perfluorohexane dicarboxylic acid 1,2-difluoroanhydride at temperature 150-450°C in the presence of catalyst, namely, aluminum trifluoride applied on aluminum oxide, or activated carbon promoted with potassium fluoride wherein the content of metal fluorides in catalyst is 10-40 weight% to form perfluorocyclohexene 1-carboxylic acid fluoroanhydride that is isolated as the end product, or subjected to further fluorination with gaseous fluorine in inert solvent medium at temperature from -20°C to 50°C and isolation of perfluorocyclohexane carboxylic acid fluoroanhydride by rectification.

EFFECT: improved method of synthesis.

2 cl, 8 ex

FIELD: chemical technology.

SUBSTANCE: invention relates to a method for synthesis of perfluorocyclohexene 1-carboxylic acid fluoroanhydride or perfluorocyclohexane carboxylic acid fluoroanhydride. Method involves decarbonylation of perfluorohexane dicarboxylic acid 1,2-difluoroanhydride at temperature 150-450°C in the presence of catalyst, namely, aluminum trifluoride applied on aluminum oxide, or activated carbon promoted with potassium fluoride wherein the content of metal fluorides in catalyst is 10-40 weight% to form perfluorocyclohexene 1-carboxylic acid fluoroanhydride that is isolated as the end product, or subjected to further fluorination with gaseous fluorine in inert solvent medium at temperature from -20°C to 50°C and isolation of perfluorocyclohexane carboxylic acid fluoroanhydride by rectification.

EFFECT: improved method of synthesis.

2 cl, 8 ex

FIELD: polymer production.

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EFFECT: expanded synthetic possibilities.

13 cl, 1 tbl, 15 ex

FIELD: chemistry of metalloorganic compounds.

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EFFECT: valuable properties of compounds.

9 cl, 6 tbl, 8 ex

FIELD: organic chemistry, chemical technology, medicine, pharmacy.

SUBSTANCE: invention relates to the improved method for synthesis of indane-1,3-dicarboxylic acid of the formula (I): wherein R1 and R2 represents hydrogen atom. Method involves hydrolysis of compound of the formula: wherein R1 and R2 represent hydrogen atom in the presence of acidic or basic catalyst. Synthesized compound represents an intermediate substance that can be used in synthesis of aryl-condensed azapolycyclic compounds used as agents in treatment of neurological and psychiatric disorders in medicine.

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9 cl, 2 sch, 3 ex

FIELD: organic chemistry.

SUBSTANCE: invention relates to improve method for production of trans-alkyl-substituted cyclohexanecarboxylic acids of general formula 1 , wherein R is C1-C10-alkyl and trans-4-(C1-C10-alkyl)cyclohexyl radical, by hydration of respective 4-alkyl-substituted benzoic acids. In aqueous-alkali solution at elevated temperature and elevated hydrogen pressure of 0.5-15 MPa in presence of catalyst followed by isomerization at 200-400°C and isolation of reaction products by mixture acidifying. As catalyst ruthenium-nickel catalyst on carbon carrier is used, wherein catalyst contains 5 mass % of metal calculated as total catalyst mass and Ni/Ru mass ratio is (0.01-1.5):(8.5-9.99). Process is carried out at 20-150°C for 0.25-1 h, and isomerization is carried out in inert gas atmosphere in several steps after mixture filtration to separate catalyst. Compounds of present invention represent value products in production of liquid crystal materials and biologically active materials.

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1 tbl, 9 ex

FIELD: organic synthesis.

SUBSTANCE: synthesis involves oxidation of substrate with chlorine dioxide in organic solvent at 40-50°C, said selected from myrtenal or myrtenol and said organic solvent from acetone, benzene, and alcohol at molar ratio of myrtenal or myrtenol to chlorine dioxide 1:(0.5-3.5). Thus formed myrtenic acid is isolated in the form of its water-soluble salt and, when alcohol is used as solvent, in the form of ester.

EFFECT: increased yield of product to 66%, reduced expenses, and shortened reaction time.

3 cl, 1 tbl, 2 ex

The invention relates to new derivatives and analogs 3-arylpropionic acid having the General formula (I), and their stereo and optical isomers and racemates, as well as their pharmaceutically acceptable salts, wherein in the formula And is located in the meta - or para-position and represents a

where: R represents hydrogen;

-ORawhere Rarepresents hydrogen, alkyl, phenyl or alkylphenyl;

-NRaRbwhere Raand Rbare the same or different and represent hydrogen, alkyl, phenyl, alkylphenyl, cyano;

R1represents alkyl, cyano;

-ORewhere Rerepresents alkyl, phenyl or alkylphenyl;

-O-(CH2]m-ORfwhere Rfrepresents alkyl, and m is an integer of 1-2;

-SRdwhere Rdrepresents an alkyl or phenyl;

-SO2ORawhere Rarepresents alkyl, phenyl or alkylphenyl;

-COORdwhere Rdrepresents alkyl;

R2represents hydrogen or alkyl;

R3and R4

D is situated in the ortho-, meta - or para-position and represents a

-OSO2Rdwhere Rdrepresents alkyl, phenyl or alkylphenyl;

-OCONRfRawhere Rfand Rarepresent hydrogen, alkyl, phenyl or alkylphenyl;

-NRcCOORdwhere Rcrepresents hydrogen or alkyl and Rdrepresents alkyl, phenyl or alkylphenyl;

-NRcCORawhere Rcrepresents hydrogen or alkyl, and Rarepresents hydrogen, alkyl, phenyl or alkylphenyl;

-NRcRdwhere Rcand Rdrepresent hydrogen, alkyl, phenyl or alkylphenyl;

-NRcSO2Rdwhere Rcrepresents hydrogen or alkyl, and Rdrepresents alkyl, phenyl or alkylphenyl;

-NRcCONRaRkwhere Rcrepresents hydrogen, Raand Rkare the same or different and each represents hydrogen, alkyl, phenyl or alkylphenyl;

-NRcCSNRaRkwhere Rcrepresents hydrogen, Raand Rkare the same or different and each represents hydrogen, phenyl иLASS="ptx">-SRcwhere Rcrepresents alkyl, phenyl or alkylphenyl;

-SO2ORawhere Rarepresents alkyl, phenyl or alkylphenyl;

-CN;

-CONRcRawhere Rcrepresents hydrogen or alkyl, and Rarepresents hydrogen or alkyl;

D’ is located in the meta-position and represents-ORfwhere Rfrepresents alkyl; or is located in the ortho-, meta - or para-position and represents hydrogen;

D’ is located in the ortho - or para-position and represents-NO2, -ORfwhere Rfrepresents alkyl; or is located in the ortho-, meta - or para-position and represents hydrogen;

where specified, the alkyl means a straight or branched alkyl group having from 1 to 6 carbon atoms, or cyclic alkyl having from 3 to 6 carbon atoms, with the specified alkyl may be substituted by one or more than one group of alkyl, alkoxy, halogen or phenyl; where the specified phenyl may be substituted by one or more than one group of alkyl, alkoxy, nitro, thiol, or halogen; the invention also relates to a method of their production, pharmaceutical preparations containing them, the Sabbath.

FIELD: chemistry.

SUBSTANCE: crystalline calcium salt of gluconic acid or its compound with excipients is processed in grinding activator devices, or to a value of supplied specific energy of not more than 10.4 kJ/g and achieving amorphous-crystalline state, or to a value of specific energy of not less than 10.5 kJ/g and achieving amorphous state. The obtained substances are analysed using X-ray diffraction, infrared, NMR, EPR spectroscopy, mass- and chromatography-mass spectrometry and differential thermal analysis.

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13 cl, 10 dwg, 12 ex

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 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: 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: 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: 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: 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: 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: 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: 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

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