The method of obtaining isophthalic acid

 

(57) Abstract:

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 improves the efficiency of removal of the reaction water and to improve the quality of isophthalic acid by use of a catalyst, optionally containing salts of zinc, Nickel or a mixture of these metal salts [MT] when the ratio of [Co+Mn] : [MT] =1 : 0.01 to 0.2 and the water content in the zone of oxidation regulate through a three-stage cooling gas mixture leaving the reactor in co-current gas and the condensed vapors CH3COOH - H2O on the first and third stages and countercurrent to the second stage in combination with the process of rectification followed by a return dehydrated stream of liquid acetic acid in total with the first and second cooling stages in the oxidation zone, the output from the process watered acetic acid from the third stage cooling in a ratio that provides the water concentration in the reaction zone 4 - 10%. Processing isophthalic acid after additional oxidation PR is 1 tab.

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

There is a method for continuous preparation of aromatic carboxylic acids by liquid phase oxidation of the corresponding xylene with oxygen in the medium of acetic acid containing a small amount of water in the presence of a cobalt-manganese-bromides catalyst at elevated temperature and pressure (USA N 4792621).

The improvement consists in the method of regulating the concentration of water in the zone of oxidation reaction in the desired range, which includes:

- separation of vapors in parallel to the condensate having a relatively small weight ratio of water : solvent and vapour phase having a relatively high weight ratio of water : solvent;

- returning part of the condensate directly into the oxidation reactor in the form of direct flow phlegmy;

- removing the vapor phase from the circuit phlegmy in the form of a stream of gas-vapor mixtures;

- cooling the obtained gas-vapor stream enriched in paraoka watered acetic acid in the ratio of H2O : CH3COOH greater than the ratio in the direct flow phlegmy;

the combination of pre-determined (calculated) parts flow phlegmy with indirect recirculating flow phlegmy so that the weight ratio of water recycled to the oxidation reactor in indirect re-circulating flow and direct flow phlegmy, soak in the range from 0.01 to 0.15, preferably 0,02-0,06.

The disadvantages of this method are:

- need to install node condensation of a relatively large number of heat exchangers - condensers to provide fractional (speed) condensing a mixture of CH3COOH - H2O from the gas mixture leaving the reactor, which increases the cost of the control unit H2O in the reaction zone;

even with the 4-speed cooling gas mixture, the efficiency of water removal from the reaction zone is relatively low and the residual content in the liquid phase in the oxidation reactor remains high (12-14%), which necessitates the use of high pressure (1.5 to 1.6 MPa) and temperature (198-200oC).

Also known is a method of obtaining terephthalic acid by oxidation of m-xylene in an acetic acid medium for 30-40 min at the rate: 1, and the molar ratio of m-xylene : water : total concentration of Co and Mn acetates supplied in the reaction mixture is maintained within the interval 1,0-1,75 : 1,0-2,5 : 1,0-1,2102. The water content in the reaction zone adjust by changing the content in the original reaction mixture (IRS) or the concentration of m-xylene in the recommended interval ratios. Get isophthalic acid following qualities:

m-KBA = 0,005-0,22%

Chromaticity 19-20oH

The disadvantage of this method is the relatively low concentration of m-xylene and IRS (1,5-1,75 mol/l), which necessitates higher costs of recycling and regeneration of the solvent (CH3COOH). In addition, inadequate quality of IFC to obtain high-quality polyester and other polymeric materials (requires [m-KBA] 0,0025%, chromaticity 10oH) requires the use of complex and expensive treatment methods, for example, by hydrogenation of impurities in the aqueous medium at a temperature of 280-290oC in the presence of a catalyst Pd/C. Selected parameters of oxidation of m-xylene (T = 190-200oC and a pressure of 1.9 to 2.7 MPa) does not provide for the diversion of water directly from the reaction zone, for example, by the method of fractional condensation of CH3COOH - H2oC recycle mother liquor.

In the first stage of oxidation are O2gas at 180-210oC when the content of m-xylene in led in the process of the initial reaction mixture in 1-15 times the amount of solvent to achieve the content of m-KBA in oxidation products 500-10000 ppm and the total concentration of terephthalic acid in the reaction mass 10-35%.

In the second stage of the reaction mass is treated additionally O2gas to achieve a residual concentration of m-KBA 0,01-0,08%.

Obtained in the second stage of the IFC is mixed with acetic acid, maintained at a temperature of 150oC and purified to achieve residual m-KBA IFC 0,0027-0,0044% and metric chroma 20oH.

Significant disadvantages of this method.

1). Not an effective way of regulating the water content in the reaction zone by changing its concentration in the initial reaction mixture in the preferred limits of 5-12%. Given the inherent about the water too high, the activity of the oxidation reaction decreases, the quality of IFC deteriorating. In fact, this is confirmed by examples in which quality indicators IFC on the content of m-KBA (0,0027-0,0044%) and the metric chroma ( 20oH) do not reach the values required to clean IFC ([m-KBA] 0,0025%, chromaticity 10oH).

2). Use as a cleaning method of processing IFC acetic acid at a temperature of 150oC is not effective and does not reach the set goal: the content of m-KBA decreases from 0.01 to 0.08 to 0,0027-0,0044% (must 0,0025%).

3). The duration of the oxidation reaction in the first and second steps ( 80 min) indicates a relatively low productivity of the process.

The aim of the invention is to increase the efficiency of removal of the reaction water from the reaction zone and improving the quality of isophthalic acid.

This goal is achieved by liquid-phase oxidation of m-xylene oxygen-containing gas in an acetic acid medium at elevated temperature and pressure in the presence of catalysts consisting of salts of cobalt, manganese and bromidic compounds, regulation of water content in the zone of oxidation, followed by additional oxidation of impurities and processing acetic Ki II-th stage. Moreover, the catalyst further comprises a salt of zinc, Nickel or a mixture of these metal salts [MT] when the ratio of [Co + Mn] : [MT] = 1 : 0.01 to 0.2 and the water content in the zone of oxidation regulate through a three-stage cooling gas mixture leaving the reactor in co-current gas and the condensed vapors CH3COOH - H2O on the first and third stages and countercurrent to the second stage in combination with the process of rectification followed by a return dehydrated stream of liquid acetic acid in total with the first and second cooling stages in the oxidation zone, the output from the process watered acetic acid from the third stage cooling in a ratio that provides the water concentration in the reaction zone 4-10%. Processing isophthalic acid after additional oxidation of the impurities is carried out with acetic acid or acetic acid and water at a temperature of preferably 170-230oC.

A new method of obtaining isophthalic acid is the fact that the catalyst additionally contains a salt of zinc, Nickel or a mixture of these metal salts in the ratio of [Co + Mn] : [MT] = 1 : 0.01 to 0.2 and the water content in the zone of oxidation regulate through a three-stage cooling gas mixture leaving react and counter current to the second stage in combination with the process of rectification followed by a return dehydrated stream of liquid acetic acid in total with the first and second cooling stages in the oxidation zone, the output from the process watered acetic acid from the third stage cooling in a ratio that provides the water concentration in the reaction zone 4-10%. Processing isophthalic acid after additional oxidation of the impurities is carried out with acetic acid or acetic acid and water at a temperature of preferably 170-230oC.

Circuit description installation of oxidation of m-xylene.

The process diagram shown in the drawing.

Source reagents: m-xylene, metal - brainy catalyst, modified additives of salts of Zn and Ni, and acetic acid is continuously fed into the oxidation reactor 1, equipped with a double turbine agitator. In the lower part of the reactor serves the air. The process is conducted at a temperature 185-195oC and at high pressure. The heat of reaction decrease due to evaporation of the solvent (CH3COOH) and the reaction water.

The mixture of vapors and exhaust gases (PGS) are sent to the first stage cooling pipe in the space of once-through condenser 2, in which the temperature of the calibration gas is reduced by 20-50oC due to the evaporation of water in the annular space.

The condensed vapors of acetic acid and water from the bottom of the separation part of the refrigerator-condens - top box under the bottom plate.

In the countercurrent movement of ASG and phlegmy flowing from the reverse-flow condenser 4 in the lower part of the rectifying column-top box is the concentration of CH3COOH to a residual content of H2O no more than 10%, preferably 6-8%, which is returned by gravity to the reactor in the form of dispersed along the height of the reactor flows.

In the reverse-flow the refrigerator condenser along with the cooling ASG to 125-135 mAoC the separation of water from acetic acid in the mass transfer occurring between the liquid phase flowing down in the form of a film along the vertical tubes, and the first (steam and gas) phase, rising up. Enriched with water vapor ASG after the second stage is directed to the third stage cooling once-through refrigerator-condenser 5, where the temperature is reduced to 40-50oC.

At the bottom of the separation part of the condenser is separated liquid phase consisting of water-cut of acetic acid from the gas. Acetic acid solution containing 35-50% water, is directed to a dewatering installation, and gases serves under pressure to the cleaning method of absorption. Oxidat from the first reactability.

Example 1

The original reaction mixture (IRS) prepared in the collection volume of 3 l, where upload:

m-xylene - (589 ml) 509,5 g;

CH3COOH - (1906 ml) 2011,0 g;

Co(OAc)24H2O - 2,84 g;

Mn(OAc)24H2O - 1,43 g;

Zn(OAc)2; Ni(OAc)24H2O - 0.14 g;

HBr (40%) - 0.21 g;

H2O - (170,2 ml) to 170.2 g;

Total: 2698,93,

The contents of the collector is heated to 80oC and stirred to achieve complete dissolution of the catalyst components.

After an analysis determined the following composition of the initial reaction mixture:

m-xylene% to 18.9%;

Co2+- 0,0249%; 249 ppm;

Mn2+- to 0.0117%; 117 ppm;

Zn2+- 0,018%; 18 ppm;

Ni2+- 0,018%; 18 ppm;

H2O - 6,3%;

CH3COOH - the rest.

< / BR>
Before beginning the process of oxidation in the reactor (V = 1 l) fill in 650 ml of catalyst (without m-xylene), rinsed it with an inert gas (nitrogen), then seal, trying to pressure of 1.5 MPa and heat the solution in the reactor to 180oC under continuous flow of nitrogen through the reactor in the condensation system consisting of 3 stages of cooling.

After reaching the specified temperature include the metering pump and continuously serves the IRS in the reactions which give an air of, ensure the maintenance of excess oxygen in the exhaust gas is not more than 5 volume%. Stay (oxidation) at a flow rate IRS 1000 ml/hour corresponds to 38 minutes. At a pressure of 1.5 MPa, the temperature in the reactor support 195oC thermostat.

Waste gas-vapor mixture leaving the reactor is cooled in the first capacitor to 165oC and the liquid gas mixture is sent in separate streams to the second stage of cooling, where the temperature is reduced to 130oC. All liquid flow phlegmy with I and II level in the supply line back into the reactor, and watered the steam-gas mixture is directed to the third stage of cooling, where its temperature is reduced to 40oC. water Concentration of 6.5% in the oxidation zone is set by changing the number and composition of the exhaust from the cooling unit PPP phlegmy after 3-tier cooling 5. To do this, set the temperature of the calibration gas leaving the condenser of the second stage cooling, 130oC by changing the pressure of the evaporated water in the annular space counterflow condenser 4 in the range of 1.2-1.5 MPa (i.e., changing the temperature gradient between the refrigerant - evaporating water and cooling the flow of calibration gas and thereby regulate the value of t is less than 20% open line bypass: the cavity of the hollow plates ---> cube camera condenser 5. The total concentration of H2O in the phlegm from the end of the condenser 5 support 35% by changing the number of phlegmy going along the line of the bypass (flow regulator with correction [H2O] ) and temperature change calibration gas after countercurrent condenser (temperature controller mounted on the second pair of separator 4).

When reached in the concentration of H2O in the liquid part of oxidate reactor 6.5% of the reaction continue in continuous mode before the establishment of the oxidation products of steady concentration of m-KBA 1504 ppm. When reaching into the products of oxidation of m-KBA not more than 0.2% IFC oxidat withdrawn from the reactor of the first stage in the reactor of the second stage, where further treated O2gas, after which oxidat subjected to a stepwise cooled in three stages up to 60oC, with the first stage of cooling is carried out in an atmosphere O2gas containing not more than 5% of O2and on the last steps in the atmosphere of inert gas (nitrogen). Isolated from chilled to 60oC oxidate IFC contained 495 ppm [m-KBA] and had the indicator color 12oH. After processing the received IFC acetic acid at 200selected product meets the quality of high-purity IFC:

[m-KBA] = 18 ppm

[m-TC] 50 ppm

Chroma - 5oH

Loss of CH3COOH due to the combustion amounted to 37.9 kg/t IFC.

Other parameters of the example shown in the table.

Example 2. The experience is conducted under the conditions of example 1, with the only difference that the temperature of the oxidation reaction was reduced from 195oC to 192oC, and the reaction time increased from 38 minutes to 45 minutes. Example results are shown in table.

The quality of IFC: [m-KBA] = 21 ppm

[m-TC] 50 ppm

Chroma - 8oH

meets the requirements of high-purity product.

Loss of CH3COOH due to the combustion of 37.7 kg/t IFC.

Example 3. The experience is conducted under the conditions of example 1, with the only difference that the concentration of m-xylene in the IRS increased from 18.9% to 20%, of the catalyst - 1,87 times, bromine - 1,125 times. The water concentration in the reaction zone increased from 6.5% to 10%.

The results:

Received IFC satisfying quality of high-purity product: [m-KBA] = 24 ppm, m-TC 50 ppm, color 9oH. loss of CH3COOH due to the combustion amounted to 43.0 kg/t IFC.

Example 4. The experience is conducted under the conditions of example 3, with the only difference that the concentration of water in the zone of oxidation decreased from 10 to 5.1%, and the ratio of IFC : CH3COOH on Cochiti IFC. Loss of CH3COOH due to the combustion increased from 43 kg/t IFC to 48.9 kg/t IFC.

Example 5. The experience is conducted under the conditions of example 4, with the only difference that the reaction temperature oxidation decreased from 198oC to 185oC, the reaction time was increased to 45 minutes, and the water concentration was reduced to 4%. Example results are shown in table.

The quality of IFC:

[m-KBA] = 22 ppm

[m-TC] 50 ppm

Chroma - 6oH

Example 6. The experience is conducted under the conditions of example 1, with the only difference that the temperature of the oxidation reaction was reduced from 195oC to 190oC, and the water concentration was reduced to 4%. Example results are shown in table.

The quality of IFC:

[m-KBA] = 19 ppm

[m-TC] 50 ppm

Chroma - 6oH

Example 7 (comparative). The experience is conducted under the conditions of example 3, with the only difference that the refrigerating gas mixture leaving the reactor, eliminate the second stage cooling (3, 4).

Result:

The concentration of H2O in the zone of oxidation increased from 10% to 15.8% due to the inability of its allotment with only 2 stages and, as a consequence, the quality of the resulting IFC has significantly deteriorated and did not meet the requirements of high-purity product:

[m-KBA] = 120 ppm

[m-Hrasnica, from the cooling unit calibration gas leaving the reactor, exclude III stage cooling.

Result:

The water content in the reaction zone increased from 10% to 15.2%. The quality of IFC does not meet the requirements of high-purity product.

[m-KBA] = 92 ppm

[m-TC] 68 ppm

Chroma - 12oH

Example 9 (comparative). The experience is conducted under the conditions of example 3, with the only difference that site eliminate condensation II and III stage cooling and retain only the first stage of cooling.

Result:

The water content in the oxidation zone of the reactor increased from 10 to 16.9%, which in turn led to a significant deterioration in the quality of IFC:

[m-KBA] = 238 ppm

[m-TC] 60 ppm

Chromaticity 15oH

Example 10. The experience is conducted under the conditions of example 1, with the only difference that the water concentration in the reaction zone of oxidation was lowered to 2.5% and for preparation of IRS used "ice" dehydrated CH3COOH.

Result:

Loss of CH3COOH due to the combustion increased from 37.9 kg/t IFC to 58,0 kg/t IFC.

The quality of IFC:

[m-KBA] = 16 ppm

[m-TC] 50 ppm

Chroma - 12oH

In terms of color does not reach significance ( 10oH) requirements for high-purity IFC.

oC in the ratio of IFC : CH3COOH = 1 : 4. The quality of the product has deteriorated in all respects, and did not meet the requirements of high-purity product:

[m-KBA] = 27 ppm

[m-TC] 50 ppm

Chroma - 12oH

Example 12. The experience is conducted under the conditions of example 2, with the only difference that the processing of the received IFC conducted acetic acid at 170oC. the results of the example shown in the table.

The quality of IFC: [m-KBA] = 18 ppm

[m-TC] 50 ppm

Chroma - 8oH

meets the requirements of high-purity product.

Example 13. The experience is conducted under the conditions of example 3, with the only difference that the processing of the received IFC spend acetic acid at 230oC in the ratio of IFC : CH3COOH = 1 : 4 and subsequent cooling acetic acid solution IFC to 60oC. the isolated product were satisfied with the quality of high-purity IFC: [m-KBA] = 9 ppm

[m-TC] 50 ppm

Chroma - 4oH

Example 14. The experience is conducted under the conditions of example 4, with the only difference that is reprocessed IFC water at a temperature of 230oC. the results of the example shown in the table.

The quality of IFC: [m-KBA] = 19 ppm

[m-TC] 50 ppm

Chroma - 6oH

udovletworyaet the itsey, that is reprocessed IFC water at a temperature of 170oC. the results of the example shown in the table.

The quality of IFC: [m-KBA] = 20 ppm

[m-TC] 50 ppm

Chroma - 7oH

Example 16. The experience is conducted under the conditions of example 1, with the only difference that zinc salts substituted Nickel salt in the same amount.

< / BR>
Example results are shown in table.

The quality of IFC: [m-KBA] = 18 ppm

[m-TC] 50 ppm

Chroma - 5oH

Example 17. The experience is conducted under the conditions of example 1, with the only difference that the salt of Nickel is replaced with a zinc salt in the same amount.

< / BR>
Example results are shown in table.

The quality of IFC: [m-KBA] = 20 ppm

[m-TC] 50 ppm

Chroma - 7oH

Example 18. The experience is conducted under the conditions of example 1, with the only difference that the addition of salts of zinc and Nickel is not performed. The quality of the product has deteriorated in all respects, and did not meet the requirements of high-purity product:

[m-KBA] = 30 ppm

[m-TC] 50 ppm

Chroma - 13oH

Example 19. The experience is conducted under the conditions of example 1, with the only difference that the addition of salts of Nickel and zinc is very low.

< / BR>
The results of example PR is changed in the conditions of example 1, the only difference that the addition of zinc salts and Nickel increased significantly.

< / BR>
Example results are shown in table.

[m-KBA] = 25 ppm

[m-TC] 50 ppm

Chroma - 8oH

Example 21. The experience is conducted under the conditions of example 1, with the only difference that, as the additives used zinc salts in the ratio of

< / BR>
Example results are shown in table.

[m-KBA] = 24 ppm

[m-TC] 50 ppm

Chromaticity 10oH

Example 22. The experience is conducted under the conditions of example 1, with the only difference that, as the additives used zinc salts in the ratio of

< / BR>
The results are shown in the table.

[m-KBA] = 25 ppm

[m-TC] 50 ppm

Chromaticity 10oH

Example 23. The experience is conducted under the conditions of example 1, with the only difference that, as the additives used Nickel salts in proportions

< / BR>
The results are shown in the table.

[m-KBA] = 24 ppm

[m-TC] 50 ppm

Chromaticity 10oH

Example 24. The experience is conducted under the conditions of example 1, with the only difference that, as the additives used Nickel salts in proportions

< / BR>
The results are shown in the table.

[m-KBA] = 25 ppm

[m-TC] 50 ppm

Chromaticity 10oH

Example 25. OPV ratios

< / BR>
The product does not match the quality of high-purity product.

The results are shown in the table.

[m-KBA] = 30 ppm

[m-TC] 50 ppm

Chromaticity 25oH

Example 26. The experience is conducted under the conditions of example 1, with the only difference that, as the additives used salts of zinc and Nickel in the ratio

< / BR>
The product does not match the quality of high-purity product. The results are shown in the table.

[m-KBA] = 30 ppm

[m-TC] 50 ppm

Chromaticity 25oH

The proposed method of producing isophthalic acid has the following advantages compared with the prototype.

1. Provides an efficient way of regulating the composition of the reaction mass in the reaction zone on the water content and thereby promotes the transformation of m-xylene in IFC, reducing the rate of occurrence of side reactions, leading to the deterioration of the color and increases the efficiency of mass transfer of oxygen from the gas in the liquid phase due to the increased solubility in water and acetic acid, a medium containing 4-10% of water.

2. Improves the quality of IFC (the content of m-KBA 0,0025%, chromaticity 10oH) compared with prototype: m-KBA 0,0027-0,0044%, chromaticity 20oH.

1. in acetic acid medium at elevated temperature and pressure in the presence of catalysts, consisting of salts of cobalt, manganese and bromidic compounds, regulation of water content in the zone of oxidation, followed by additional oxidation of impurities and by treatment with acetic acid using recycle mother solutions after separation IFC from acetic acid solutions at stage I or II, wherein the catalyst further comprises a salt of zinc, Nickel or a mixture of these metal salts [MT] when the ratio of [Co + Mn] : [MT] = 1 : 0.01 to 0.2 and the water content in the zone of oxidation regulate through a three-stage cooling gas mixture, coming out of the reactor in terms of co-current gas and the condensed vapors CH3COOH-H2O - on the first and third stages and countercurrent to the second stage in combination with the process of rectification, followed by a return dehydrated stream of liquid acetic acid in total with the first and second cooling stages in the oxidation zone, the output from the process watered acetic acid from the third stage cooling in a ratio that provides the water concentration in the reaction zone 4 - 10%.

2. The method according to p. 1, characterized in that the processing of isophthalic acid after additional oxidation of the impurities is carried out with acetic acid or acetic acid, and water at the rate the

 

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EFFECT: improved preparing method.

2 tbl, 1 dwg, 10 ex

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention relates to the improved method for preparing dimethyl-1,5-naphthalene dicarboxylate that is used in preparing polymers based on thereof and articles made of these polymers. The economic and effective method involves the following stages: (1) dehydrogenation of 1,5-dimethyltetraline to yield 1,5-dimethylnaphthalene; (2) oxidation of 1,5-dimethylnaphthalene prepared at dehydrogenation stage to yield 1,5-naphthalene dicarboxylic acid being without accompanying isomerization stage, and (3) esterification of 1,5-naphthalene dicarboxylic acid prepared at oxidation stage in the presence of methanol to yield the final dimethyl-1,5-naphthalene dicarboxylate.

EFFECT: improved preparing method.

9 cl, 3 dwg, 5 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: method and composition for selective removal of iron solvent oxide from surface of titanium parts without damaging them.

SUBSTANCE: method comprises steps of adding to distillation tower organic acid such as alkyl mono-carboxylic acid having 2 - 6 C atoms or benzoic acid or their mixture at first temperature range 30 -125°C; passing said organic acid through distillation tower at absence of molecular oxygen; adding to organic acid of first temperature and without molecular oxygen aqueous solution of hydro-halide acid whose temperature is less that said first temperature for preparing aqueous solution of solvent composition at second temperature that is less than first temperature; providing contact of titanium part and solvent composition in distillation tower at absence of molecular oxygen.

EFFECT: possibility for selective removal of iron oxide from surface of titanium parts without damage of said parts.

18 cl, 1 dwg, 6 tbl, 14 ex

FIELD: chemical industry; petrochemical industry; methods of extraction of the unreacted xylene from the acetic acid at production of the terephthalic or isophthalic acid.

SUBSTANCE: the invention is pertaining to the field of production of the terephthalic or isophthalic acid by oxidation of the corresponding alkyl benzene, in particular, to the stage of separation of the reaction mixture including the acetic acid in the capacity of the dissolvent. The method is intended for extraction of the unreacted para-xylene or meta-xylene at the regeneration of the acetic acid using isobutyl acetate as the azeotropic agent for dehydration of the acetic acid. From the azeotropic distillation column at the temperature of 94-100°С separate the fraction containing the para-xylene or meta-xylene, which is fed into the run-down tank, where separate the aqueous phase from the organic phase. In the azeotropic section of the azeotropic distillation column determine the ratio of the para-xylene or meta-xylene and the isobutyl acetate in the stored fraction of the organic phase and periodically remove the accumulated part of the organic phase until the mass ratio of the concentrations of the para-xylene or meta-xylene and the azeotropic agent attains the interval from 0.5 up to 6. As the version of realization of the method route the circulation of the part of the accumulated fraction of the organic phase from the run-down tank to the azeotropic column. The technical result of the invention is upgrade of the production process of regeneration of the acetic acid and the unreacted alkylbenzene using the phase of the azeotropic distillation of xylenes from the acetic acid.

EFFECT: the invention ensures the upgrade of the production process of regeneration of the acetic acid and the unreacted alkylbenzene using the phase of the azeotropic distillation of xylenes from the acetic acid.

8 cl, 4 tbl, 5 dwg

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention relates to an improved method for synthesis of halogenphthalic acid. Method involves mixing from 3 to 7 weight parts of acetic acid with 1 weight part of halogen-ortho-xylene, with from 0.25 to 2 mole% of cobalt source as measured for above said halogen-ortho-xylene, with from 0.1 to 1 mole% of manganese source measured for above said halogen-ortho-xylene, with from 0.01 to 0.1 mole% of metal source as measured for above said halogen-ortho-xylene wherein this metal is chosen from zirconium, hafnium and their mixtures, with from 0.02 to 0.1 mole% of bromide source as measured for above said halogen-ortho-xylene wherein halogen-ortho-xylene is represented by the formula (IV): wherein X represents halogen atom. Method involves holding the reaction mixture under pressure 1600 KPa, not less. At temperature 130-2000C, addition of molecular oxygen-containing gas to the reaction mixture in consumption 0.5 normal m3 of gas/h per kg of halogen-ortho-xylene in the reaction mixture for time sufficient for 90% conversion of halogen-ortho-xylene to yield halogenphthalic acid. Also, invention relates to a method for synthesis of halogenphthalic anhydride by distillation and dehydration of halogenphthalic acid, and to a method for synthesis of polyesterimide that involves interaction of halogenphthalic anhydride with 1,3-diaminobenzene to yield bis-(halogenphthalimide) of the formula (II): wherein X means halogen atom, and interaction of bis-(halogenphthalimide) of the formula (II) with alkaline metal salts of dihydroxy-substituted aromatic hydrocarbon of the formula (IV): OH-A2-OH wherein A2 means a bivalent radical of aromatic hydrocarbon to yield polyesterimide.

EFFECT: improved method of synthesis.

20 cl, 2 tbl, 5 ex

FIELD: process for continuous production of terephthalic or isophthalic acid by liquid phase oxidation of respective aromatic dialkyl hydrocarbon.

SUBSTANCE: in order to prepare reaction solvent at least part of mother liquor separated from produced acid is used. Oxidation catalyst concentration in mother liquor is measured beforehand and then oxidation catalyst concentration is continuously corrected due to direct control (regardless of water content). Predetermined quantities of solvent and aromatic hydrocarbon as raw material are continuously supplied to oxidizing reactor for oxidizing aromatic hydrocarbon by means of molecular oxygen. Water concentration in condensate returned from reactor is measured and controlled by means of discharged quantity of returned condensate for stabilizing water concentration in reaction system in order to obtain in the result dicarboxylic acid. Oxidation temperature is sustained stable due to controlling pressure; oxygen concentration in exhaust gas is sustained stable due to controlling feed of oxygen containing gas.

EFFECT: production of stable quality acid, rational consumption of resources, power and water for performing process.

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