Method of extracting acrylic acid

FIELD: chemistry.

SUBSTANCE: invention relates to the technology of producing acrylic acid via gas-phase catalytic oxidation of propylene and/or acrolein, and specially to a step for extracting acrylic acid from aqueous solution formed during absorption of gaseous oxidation products with water. The method of extracting acrylic acid involves using a solvent to extract acrylic acid from its aqueous solution which contains acetic acid, formaldehyde, high-boiling impurities, distillation of the extract which contains acrylic acid, solvent, water and acetic acid, while feeding the solvent in form of condensate at low pressure with azeotropic distillation of water and solvent and extraction of the residue which contains acrylic acid and acetic acid, followed by distillation of the extracted residue which contains acrylic and acetic acid, while feeding condensate at low pressure in the presence of a polymerisation inhibitor with extraction of the desired acrylic acid and distillation of the distillate which contains acetic acid and acrylic acid, where distillation of the extract, which contains acrylic acid, solvent, water and acetic acid, is carried out while additionally feeding water to the step for distillation of the extracted residue which contains acrylic and acetic acid. The polymerisation inhibitor used is in form of an aqueous and the distilled distillate containing acetic acid and acrylic acid undergoes distillation at low pressure in the presence of a polymerisation inhibitor with extraction of acrylic acid and returning it to the step for distillation of the extracted residue containing acrylic and acetic acid.

EFFECT: high purity of the extracted acrylic acid and prevention of polymerisation of acrylic acid in equipment.

3 ex, 1 dwg

 

The invention relates to a technology for production of acrylic acid gas-phase catalytic oxidation of propylene and/or acrolein, namely the stage of selection of acrylic acid from aqueous solution formed by water absorption of the gaseous products of oxidation.

Such aqueous solutions, in addition to acrylic acid, contain a number of water-soluble by-products, the main part of which is acetic acid (up 8.0%), small amounts of formaldehyde and high-boiling impurities. In the process of selection of acrylic acid by-products cause undesirable polymerization of acrylic acid in the process equipment, and fall into the target product as impurities. To clean the target of acrylic acid with high demands, especially when receiving polymer products, therefore, an urgent task is to develop a method of selection of acrylic acid with a high degree of purity in the absence of polymerization of the acid in the process equipment.

A known method of separation of acrylic acid, including extraction of acrylic acid solvent from its aqueous solution containing these impurities, the distillation of the extract with the filing of the solvent in the form of phlegmy under reduced pressure azeotropic distillation of water and solvent and allocating CBM is fluid, containing acrylic acid and acetic acid, the subsequent distillation allocated a bottom liquid containing acrylic acid and acetic acid, with the filing of phlegmy at reduced pressure distillation of the distillate containing acetic and acrylic acid, and the target allocation of acrylic acid (Making Acrylic Acid Via Air Oxidation of Propylene, Chemical Engineering, vol.76, No.15, July 14, 1969, pp.78-80).

The disadvantage of this method is that for selection of acrylic acid with the desired degree of purity at the stage distillation allocated a bottom liquid containing acrylic acid and acetic acid, the distillation column should contain a large number of plates. It promotes polymerization of the acid in the column, which hinders continuous process and leads to reduction of the yield of acrylic acid. So, in the description of the patent (US 3798264, SS 57/04, 1974, page 2, lines 60-67) indicated that the allocation of acrylic acid as described above was experimentally found that when the concentration of acrylic acid in warded off the distillate containing acetic and acrylic acid reaches 5%acrylic acid begins to dry out in the upper part of the column. This leads to the need to stop every 4-5 days.

The closest in technical essence to the proposed method is a known method for separating acrylic is howling acid, including extraction of acrylic acid solvent from its aqueous solution containing acetic acid, formaldehyde and high-boiling impurities distillation of the extract containing acrylic acid, solvent, water and acetic acid, with a flow of solvent in the form of phlegmy under reduced pressure azeotropic distillation of water and solvent and the provision of a bottom liquid containing acrylic acid and acetic acid, the subsequent distillation allocated a bottom liquid containing acrylic acid and acetic acid, with the filing of phlegmy under reduced pressure in the presence of a polymerization inhibitor such as hydroquinone, and the polymerization inhibitor is used in solid form, with a target allocation of acrylic acid and distillation distillate containing acetic acid and 10-70% of acrylic acid, which is recycled to the stage of extraction and condensation of the reaction gases (US 3798264, SS 57/04, 1974).

Acrylic acid, isolated as described above, contains a sufficiently large amount of acetic acid (0.1%), which does not allow to use it to produce esters and polymeric products without additional purification.

Use on stage distillation allocated a bottom liquid containing acrylic acid and acetic acid, reception distillation distillate containing acetic acid and 10-70% acrylic KIS is the notes, allows you to slow the polymerization of acrylic acid in the distillation column, which gives the opportunity to continue the process of selection of acrylic acid after one month of continuous operation of the column distillation. At the same time to eliminate the loss of acrylic acid distilled water containing acetic acid and 10-70% of acrylic acid, must be recycled to the stage of extraction and condensation of the reaction gases. Therefore, to completely eliminate the polymerization of acrylic acid in the distillation column is impossible, since in the loop constantly return distillate containing impurities that cause the polymerization of acrylic acid. Great return of acrylic acid in the beginning of the process of selection of acrylic acid reduces productivity and increases energy consumption. In the patent indicated that extracting acrylic acid from distilled distillate containing acetic and acrylic acid, by further distillation under reduced pressure and the return of acrylic acid cycle failed due to the polymerization of acrylic acid in the distillation column (US 3798264, page 2, lines 70-73, and page 3, lines 1-4).

The technical result that can be obtained from the use of the invention is to increase the purity of the selected acrylic acid and removing the polymerization of acrylic is islote in the process equipment.

To achieve a technical result of the proposed method of selection of acrylic acid, including extraction of acrylic acid solvent from its aqueous solution containing acetic acid, formaldehyde and high-boiling impurities distillation of the extract containing acrylic acid, solvent, water and acetic acid, with a flow of solvent in the form of phlegmy under reduced pressure azeotropic distillation of water and solvent and the provision of a bottom liquid containing acrylic acid and acetic acid, the subsequent distillation allocated a bottom liquid containing acrylic acid and acetic acid, with the filing of phlegmy under reduced pressure in the presence of a polymerization inhibitor with the target allocation of acrylic acid and distillation of the distillate, containing acetic and acrylic acid, characterized in that the distillation of the extract containing acrylic acid, solvent, water and acetic acid, provide additional water supply, on-stage distillation allocated a bottom liquid containing acrylic acid and acetic acid, the polymerization inhibitor used in the form of an aqueous solution, and distilled, the distillate containing acetic and acrylic acid, is subjected to distillation under reduced pressure in the presence of an inhibitor to polymerization with the release of acrylic acid and return it the and stage distillation allocated a bottom liquid, containing acrylic acid and acetic acid.

In the proposed method uses a new set of techniques - conducting distillation of the extract containing acrylic acid, solvent, water and acetic acid, with the additional water supply and use at the stage distillation allocated a bottom liquid containing acrylic acid and acetic acid, an inhibitor of polymerization in aqueous solution, which allows selection of acrylic acid with an effective removal of water, solvent, acetic acid and impurities that cause polymerization of acrylic acid in the distillation columns, and to obtain acrylic acid with a high degree of purity (amount of acetic acid together with low-boiling impurities is less than 0.02%). Such acid can be used to produce polymeric products and ethers. In addition, in the proposed method almost completely eliminates the polymerization of acrylic acid in the distillation columns. This gives the opportunity for a long time to carry out the selection of acrylic acid without stopping the process (after six months of their columns internal examination showed the absence of polymer), and also to carry out the extraction of acrylic acid removed from the distillate containing acetic and acrylic acid, by additional distillation below the nom pressure and the return of acrylic acid in the cycle. The yield of acrylic acid is increased to 99.6%.

Example 3 (for comparison) shows that the implementation of the method of separation of acrylic acid without additional water supply at the stage of distillation of the extract of acrylic acid and using anhydrous polymerization inhibitor at the stage distillation allocated a bottom liquid containing acrylic acid and acetic acid, yields a target of acrylic acid, containing large amounts of impurities, and the emergence of the polymer in the distillation column after 1.5 months of operation of the column.

The following drawing shows the allocation of acrylic acid. The proposed method is implemented as follows. An aqueous solution of acrylic acid obtained by the absorption of the reaction gases heterogeneous catalytic oxidation of propylene and containing as a by-product acetic acid, formaldehyde and high-boiling impurities, the pipe 1 is fed to the column extraction 2. In the same column on line 3 serves extracting solvent. Of the impurities in the extraction process is transferred to the aqueous layer, which is removed from the column 2 and line 4 is sent to a rectification column 5 to extract the solvent. The resulting extract containing acrylic acid, solvent, water and a number of the above impurities, what about the pipeline 6 is sent to a rectification column 7 for the separation of solvent and water in the form of an azeotrope. Azeotrope divert the pipeline 8 to the condenser (not shown), which in the form of a liquid phase is fed into the collector-separator 9, where the solvent and water are separated into two phases. Part of the solvent from the collector-separator 9 through the pipeline 10 return in the upper part of the rectification column 7 in the form of phlegmy, and the other part via line 3 is sent to the column extraction 2. In the upper part of the rectification column 7 through the pipeline 11 is additionally injected water to almost complete separation of acrylic acid from the solvent and water. Separated in the collector-separator 9 water containing all of the formaldehyde received from the extract of acrylic acid via the pipeline 12 is fed to the rectification column 5 to extract the residual solvent. Distilled in column 5, the solvent after the condensation on the pipe 13 is sent to the collector-separator 9, and the water contaminated with various impurities, through the pipeline 14 is sent to the node wastewater. Cubic liquid containing acrylic acid, acetic acid and low-boiling impurities, leaving the cube of the column 7, the pipe 15 is fed to the rectification column 16 for separating acetic acid and low-boiling impurities. In the upper part of the column 16 serves an aqueous solution of a polymerization inhibitor. Acetic acid and low-boiling impurities are almost completely delaude from acrylic acid. The distillate containing acetic and acrylic acid coming out of the column 16, the pipe 17 is sent to a rectification column 18 for separating acrylic acid. Acrylic acid from the cube column 18, line 19 return to the rectification column 16. The distillate coming from the column 18, the pipe 20 are sent to recycling. Target acrylic acid is removed from the cube columns 16 through the pipeline 21.

If necessary, the selected acrylic acid can be cleaned of high boiling impurities immediately on an additional rectification column or in the process of obtaining polymers or esters.

The following are specific examples of implementation of the proposed method.

Example 1.

The allocation of acrylic acid is carried out as shown in the diagram. 6.4 kg/h of an aqueous solution of acrylic acid obtained by the water absorption of the reaction gases heterogeneous catalytic oxidation of propylene and containing acrylic acid, acetic acid, formaldehyde and high-boiling impurities, the pipe 1 is fed to the column extraction 2. In the same column on line 3 serves 4,615 kg/h isobutylacetate as extracting agent. Carry out the extraction process and get the water layer, containing (wt.%): acrylic acid 0.4, acetic acid 0.6 isobutyl acetate is 0.5, and the extract containing (wt.%): acrylic acid is 35, the isobutyl acetate 50, the water 13, acetic acid 0.9, formaldehyde 0,02, low-boiling impurities 0,08, high-boiling impurities is 0.1. Of the impurities in the extraction process is transferred to the aqueous layer, which is removed from the column 2 and line 4 is sent to a rectification column 5 to retrieve isobutylacetate.

The extract obtained in the amount of 9.2 kg/h through the pipeline 6 is sent to a rectification column 7 for the Department of isobutylacetate and water azeotrope. The pressure in the upper part of the column is 110 mm Hg, a temperature of 42°C, the temperature in the cube 96°C. the Azeotrope of the pipeline 8 is directed to a condenser where the liquid phase is fed into the collector-separator 9, where the isobutyl acetate and water are separated into two phases. One part of isobutylacetate in the amount of 3.4 kg/h of the collector-separator 9 through the pipeline 10 return in the upper part of the rectification column 7 in the form of phlegmy, and the other part via line 3 is sent to the column extraction 2. In the phlegm on the pipe 11 serves 0.8 kg/h of water. Separated in the collector-separator 9 water containing 0.1 wt.% formaldehyde, in the amount of 2 kg/h through the pipeline 12 is directed to mixing with the aqueous layer, leaving the rectification column 2, and the mixed stream is fed to the rectification column 5 for extracting residual isobutylacetate.

From the upper part of the column 5 is stripped off the isobutyl acetate together with water and, after condensation in the pipe 13 is sent to the collector-separator 9, and from the bottom of column 5 remove the water with a small content of acrylic acid and impurities such as acetic acid and formaldehyde, and line 14 is sent to the node wastewater. The content of formaldehyde utilized in the water during the entire period of operation of the column 7 remains constant, indicating that the effective conclusion of the process of this substance.

From the bottom of column (7) derive the cubic liquid containing (wt.%): acrylic acid 97,003, acetic acid 2,5, formaldehyde 0, low-boiling impurities 0,22, high-boiling impurities 0,277, isobutyl acetate and water traces. Cubic liquid through the pipeline 15 is fed to the rectification column 16 for separating acetic acid and low-boiling impurities. The pressure in the upper part of the column is 35 mm Hg, 60°C, the temperature in the cube 82°C. In the upper part of the column 16 serves aqueous solution of hydroquinone as a polymerization inhibitor. An aqueous solution of hydroquinone is prepared in a separate apparatus by dissolving solid hydroquinone in hot water. For the best transportation aqueous solution of hydroquinone on the pipeline during its injection into the column from the resulting aqueous hydroquinone solution prepared in the acrylic acid content of 5.6% of water. The resulting solution was served in the upper part of the column 16 of the calculation of 1.1 g of hydroquinone n is 1 kg of acrylic acid, contained in the supplied bottom liquid. The distillate coming from the column 16 and containing (wt.%): acrylic acid 73,12, acetic acid 25, low-boiling impurities 1,88, through the pipeline 17 is sent to a rectification column 18 for separating acrylic acid. The pressure in the upper part of the column is 35 mm Hg, temperature 38°C, the temperature in the cube 80°C. the Acrylic acid from the cube column 18 containing (wt.%): water 0,1, acetic acid 6, low-boiling impurities less than 0.1, the number 0,307 kg/h through the pipeline 19 returned to the rectification column 16. The distillate coming from the column 18 and containing (wt.%): acetic acid 80,95, acrylic acid 2,0, low-boiling impurities 7.25 and water 9,8, the pipeline 20 sent for recycling. In the upper part of the column 18 is metered solution of hydroquinone in an acrylic acid content of 5.6% of water based 1.1 g of hydroquinone per 1 kg of acrylic acid contained in the feed distillate. Target acrylic acid is removed from the cube columns 16 through the pipeline 21 in the amount of 3,228 kg/h of Acrylic acid contains (wt.%): acetic acid 0,015, low-boiling impurities 0,003, high-boiling impurities 0,285 and water traces. The yield of acrylic acid is 99,57%.

After six months of their columns internal examination showed the absence of the polymer.

Example 2.

Selection of acrylic acid is carried out on primary with the following differences. As the solvent used n-butylacetoacetate has the following composition (wt.%): acrylic acid 32, n-butyl acetate 55, water 10,8, acetic acid 1,1, formaldehyde 0,02, low-boiling impurities 0,08, high-boiling impurities is 0.1. Distillation column of 7 runs under pressure in the upper part of the column, equal to 90 mm Hg, and a temperature of 45°C, temperature in the cube 98°C. n-butyl acetate in the amount of 3.4 kg/h of the collector-separator 9 through the pipeline 10 return in the upper part of the rectification column 7 in the form of phlegmy, and the other part via line 3 is sent to the column extraction 2. In the phlegm on the pipe 11 serves 1.2 kg/h of water.

From the bottom of column (7) derive the cubic liquid containing (wt.%): acrylic acid 96,735, acetic acid, 2,8, formaldehyde 0, low-boiling impurities 0,2, high boiling impurities 0,265, n-butyl acetate and water traces. A solution of hydroquinone served in the upper part of the column 16 of the calculation of 1.3 g of hydroquinone per 1 kg of acrylic acid contained in the supplied bottom liquid. In the upper part of the column 18 is metered solution of hydroquinone in acrylic acid, not containing water, at the rate of 1.3 g of hydroquinone per 1 kg of acrylic acid contained in the feed distillate. Target acrylic acid contains (wt.%): acetic acid 0,014, low-boiling impurities 0,004, high-boiling impurities 0,285 and water traces. The yield of acrylic acid is you is 99,58%.

After six months of their columns internal examination showed the absence of the polymer.

Example 3 (for comparison).

Selection of acrylic acid is conducted according to example 1 with the following differences. Distillation column of 7 runs under pressure in the upper part of the column, equal to 110 mm Hg, and a temperature of 57°C, the temperature in the cube 92°C. Distillation of the extract of acrylic acid in column 7 carried out without additional water. In the upper part of the column 16 and 18 serves a solution of hydroquinone in acrylic acid without water content.

From the bottom of column (7) derive the cubic liquid containing (wt.%): acrylic acid 93,74, acetic acid 2,6, formaldehyde 0,08, low-boiling impurities 0,2, high-boiling impurities 0,28, isobutyl acetate 3 and the water of 0.1. Target acrylic acid contains (wt.%): acetic acid 0,11, low-boiling impurities 0,08, high-boiling impurities 0.28 and water traces. The yield of acrylic acid is 99.1%.

Separated in the collector-separator 9 water during the whole time of the column 7 contains not more than 0.05% formaldehyde, indicating that accumulation in column 7. In the first month of the column 7 in its Central part there is a temperature change, the content of isobutylacetate in acrylic acid coming out of the bottom of the column, gradually increases up to 10%, indicating that deterioration divide the nutrient capacity of the column. After work columns over 1.5 months the temperature in the bottom part of column rises above 98°C, after which the column stop for cleaning from the polymer.

The method of selection of acrylic acid, including extraction of acrylic acid solvent from its aqueous solution containing acetic acid, formaldehyde and high-boiling impurities distillation of the extract containing acrylic acid, solvent, water and acetic acid, with a flow of solvent in the form of phlegmy under reduced pressure azeotropic distillation of water and solvent and the provision of a bottom liquid containing acrylic acid and acetic acid, the subsequent distillation allocated a bottom liquid containing acrylic acid and acetic acid, with the filing of phlegmy under reduced pressure in the presence of a polymerization inhibitor with the target allocation of acrylic acid and distillation of the distillate containing acetic and acrylic acid, characterized in that the distillation of the extract containing acrylic acid, solvent, water and acetic acid, provide additional water supply, on-stage distillation allocated a bottom liquid containing acrylic acid and acetic acid, the polymerization inhibitor used in the form of an aqueous solution, and distilled, the distillate containing acetic and acrylic acid, is subjected to distillation at pony is hinnon pressure in the presence of an inhibitor to polymerization with the release of acrylic acid and return it to the stage distillation allocated a bottom liquid, containing acrylic acid and acetic acid.



 

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23 cl, 3 ex

FIELD: chemistry.

SUBSTANCE: invention relates to an improved method of producing butylacrylate involving: reaction of acrylic acid with butanol in the presence of water and a catalyst in a reactor; where the starting material is an aqueous solution of acrylic acid which is at least one of: (1) condensed water, obtained from vapour used in a kinetic vacuum pump which transports gas after trapping fluid process medium- vapour which is blown at high speed, (2) water for hydraulic sealing in a liquid ring pump which isolates liquid-water after air is let into the housing, (3) water used for collecting acrylic acid in the device which collects acrylic acid from an acrylic acid-containing gas, and acrylic acid which is not present in the aqueous solution of acrylic acid, where the device used for collecting acrylic acid is one or more devices selected from a group comprising a packed column, a plate-type column, a spray column and a scrubber. The invention also relates to a method of producing a super-absorbing polymer based on acrylic acid, involving the following steps: polymerisation of acrylic acid, in which the aqueous phase used is an emulsified aqueous solution of an acrylic acid monomer and water, dehydration of the obtained mixture during azerotropic distillation, where the starting material is aqueous acrylic acid solution which is at least one of the following: condensed water obtained from vapour used in a kinetic vacuum pump which transports gas after trapping fluid process medium - vapour, which is blown at high speed, water for hydraulic sealing in a liquid ring pump which isolates liquid-water after air is let into the housing, water used for collecting acrylic acid in the device which collects acrylic acid from an acrylic acid-containing gas, and acrylic acid which is not present in the aqueous solution of acrylic acid, where the device used for collecting acrylic acid is one or more devices selected from a group comprising a packed column, a plate-type column, a spray column and a scrubber.

EFFECT: design of an efficient method of using aqueous solution of (meth)acrylic acid with low concentration, formed at the stage for producing/storing (meth)acrylic acid.

13 cl, 2 ex

FIELD: explosives.

SUBSTANCE: method is described for reducing amount and/or removing permanganate-reducing compounds for methanol carbonylation process to produce acetic acid, where the method involves a stage for separating the said carbonylation product, resulting in a volatile fraction containing acetic acid, organic iodide, water and at least one permanganate-reducing compound, and a less volatile fraction; distillation of the said volatile fraction, resulting in a purified acetic acid product and a first overhead fraction containing organic iodide, water, acetic acid and at least one permanganate-reducing compound; distillation of at least part of the first overhead fraction in a first distillation apparatus to form a second overhead fraction rich in permanganate-reducing compound; addition of dimethyl ether to the second overhead fraction, extraction of the second overhead fraction with water to form a second overhead extraction stream and a water stream containing at least one permanganate-reducing compound and separation from the water stream, containing at least one permanganate-reducing compound; and returning at least the first part of the extracted second overhead fraction to the said distillation apparatus, method of producing acetic acid and method of separating a mixture obtained during carbonylation of methanol.

EFFECT: more efficient removal of permanganate-reducing compound from a system by returning part of the stream of purified product, reduced loss during waste removal.

34 cl, 2 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to an improved method of reducing and/or removing reducing permanganate compounds (RPC), carboxylic acids C3-8 and C2-12 of alkyl iodide compounds, formed during carbonylation of a carbonylation-capable reagent, chosen from a group consisting of methanol, methylacetate, methyl formate, dimethyl ether and their mixture, into commercial-grade acetic acid, in which products of the said carbonylation include a volatile phase, which is distilled thereby obtaining purified commercial-grade acetic acid and the first distillate, containing methyl iodide, water and at least one reducing permanganate compound, where improvement includes stages: (a) separation of the obtained first distillate into a light and a heavy phase, with subsequent distillation of at least part of the light phase for obtaining a second distillate, containing methyl iodide, dimethyl ether and at least said one reducing permanganate compound, which is taken to the next distillation stage, where a stream is formed as distillate, containing reducing permanganate compound; (b) addition of dimethyl ether into supply of said stream containing reducing permanganate compound, and extraction of this stream with water to form the first raffinate and first aqueous extraction stream, containing at least said one reducing permanganate compound; and (c) extraction of the first raffinate with water to form the second raffinate and second aqueous extraction stream, containing at least said one reducing permanganate compound. Invention also relates to a method of separating a mixture, containing water, acetic acid, methyl iodide, methyl acetate, methanol and at least one reducing permanganate compound (RPC), obtained by separating the liquid-vapour phase of the output stream of the methaol carbonylation reactor to form a vapour phase and a liquid phase, distillation of the vapour phase to form a liquid product which contains acetic acid, and first distillate, condensation of at least part of the first distillate thereby obtaining a liquid composition which contains methyl acetate, methyl iodide, water, methanol and at least one reducing permanganate compound (RPC), separation of the obtained liquid composition into a light and a heavy phase, which includes methyl iodide, where the light phase is the said mixture, where the said method involves stages: (a) distillation of the mixture to obtain a second distillate which contains at least one reducing permanganate compound (RPC), which is taken for the next distillation stage, where a stream is formed as distillate, containing reducing permanganate compound and dimethyl ether; and (b) extraction of concentrated reducing permanganate compound with water, where stage (b) includes at least two consecutive extraction stages, where each extraction stage involves bringing concentrated reducing permanganate compound into contact with water and separation of the aqueous stream, containing at least said one reducing permanganate compound, where dimethyl ether is added to the said distillate stream concentrated with reducing permanganate compound before extraction of the concentrated reducing permanganate compound with water.

EFFECT: process is described for removing reducing permanganate compounds from a stream from carbonylation of methanol.

28 cl, 2 dwg

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: proposed method involves the following stages: (a) reaction of carbon monoxide with at least one reagent chosen from a group, consisting of methanol, methyl acetate, methyl formate and dimethyl ether and their mixture in a reaction medium, containing water, methyl iodide and catalyst for obtaining the reaction product, containing acetic acid; (b) gas-liquid separation of the said reaction product to obtain a volatile phase, containing acetic acid, water and methyl iodide and a less volatile phase, containing the said catalyst; (c) distillation of the above mentioned volatile phase to obtain a purified product of acetic acid and a first overhead fraction, containing water, methylacetate and methyl iodide; (d) phase separation of the above mentioned first overhead fraction to obtain the first liquid phase, containing water, and second liquid phase, containing methyl iodide and methyl acetate; and (e) feeding dimethyl ether directly or indirectly into a decantation tank of light fractions for phase separation of the said first overhead fraction in a quantity, sufficient for increasing separation of the first overhead fraction to form the first and second liquid phases.

EFFECT: improvement of the method of producing acetic acid.

8 cl, 1 dwg

FIELD: chemistry.

SUBSTANCE: method of (meth)acrylic acid purification includes the stages as follows: distillations of the liquid containing raw (meth)acrylic acid being acrylic acid or methacrylic acid with one or more polymerisation inhibitors added as chosen from group consisting of phenol derivative, phenothiazine derivative, copper (meth)acrylate and copper dithiourethane, for the purpose to produce condensate of (meth)acrylic acid, containing (meth)acrylic acid of purity at least 90%; adding polymerisation inhibitor containing phenol derivative to condensate; and delivery of oxygen-containing gas that contains oxygen to condensate of (meth)acrylic acid in reflux tank wherein condensate of (meth)acrylic acid is collected, wherein oxygen-containing gas is delivered to condensate in reflux tank with using small-size bubble liquid injector, and pressure connection for oxygen-containing gas delivery to liquid injector whereat ratio (nm/tn) of oxygen delivery in oxygen-containing gas and condensate flow supplied to reflux tank at 0°C, 1 atm complies with ratio shown in equation 0.004≤A/B≤1.0, where A stands for O2 delivery (nm3/hour), B stands for condensate flow (tn/hour) of the condensate supplied to reflux tank, and symbol n in nm3/hour specifies the value under normal conditions (0°C, 1 atm: normal conditions).

EFFECT: effective method of high purity acid production wherein acid polymer formation in made condensate is prevented.

12 cl, 6 dwg, 7 ex

FIELD: chemistry.

SUBSTANCE: present invention pertains to improvement of the method of producing (met)acrylic acid and complex (met)acrylic esters, involving the following stages: (A) reacting propane, propylene or isobutylene and/or (met)acrolein with molecular oxygen or with a gas, containing molecular oxygen through gas-phase catalytic oxidation, obtaining crude (met)acrylic acid; (B) purification of the obtained crude (met)acrylic acid, obtaining a (met)acrylic acid product; and (C) reacting raw (met)acrylic acid with alcohol, obtaining complex (met)acrylic esters, in the event that the installation used in any of the stages (B) and (C), taking place concurrently, stops. The obtained excess crude (met)acrylic acid is temporarily stored in a tank. After restoring operation of the stopped installation, the crude (met)acrylic acid, stored in the tank, is fed into the installation, used in stage (B), and/or into the installation used in stage (C). (Met)acrylic acid output of the installation used in stage (A) should be less than total consumption of (met)acrylic acid by installations used in stages (B) and (C).

EFFECT: the method allows for processing (met)acrylic acid, temporarily stored in a tank, when stage (B) or (C) stops, without considerable change in workload in stage (A).

2 ex

FIELD: chemistry.

SUBSTANCE: invention concerns improved method for obtaining (meth)acrylic acid involving steam phase catalytic oxidation of propylene, propane or isobutylene for production of reaction mix, absorption of oxidised reaction product in water to obtain water solution containing (meth)acrylic acid, concentration of water solution in the presence of azeotropic agent and distillation of obtained (meth)acrylic acid in distillation column to obtaining purified (meth)acrylic acid. During operation of distillation column, including operation interruption and resumption, the column is washed with water, and afterwards azeotropic distillation is performed in the presence of azeotropic agent.

EFFECT: efficient and fast cleaning of distillation column with extraction of valuable substance.

5 cl, 5 dwg, 3 ex

FIELD: chemistry.

SUBSTANCE: invention relates to an improved method for synthesis of p-terphenyl-2',5'-dicarboxylic acid through akylation of p-xylene with a cyclohexanol alkylation agent in the presence of a catalyst - sulphuric acid and then dehydrogenation of the obtained 2,5-dicyclohexyl-p-xylene in liquid phase at atmospheric pressure and temperature 260-290°C on aluminium-palladium catalysts, with extraction of 2',5'-dimethyl-p-terphenyl during cooling and then its oxidation with oxygen in a solution of glacial acetic acid at high temperature in the presence of a dissolved cobalt-manganese-bromine catalyst and extraction of p-terphenyl-2',5'-dicarboxylic acid crystals from the reaction mixture after cooling, where alkylation is carried out in molar ratio of p-xylene, cyclohexanol and sulphuric acid equal to 2-5:2-5:2-4 and temperature 0-5°C while adding the first half of cyclohexanol and raising temperature to 10-20°C until the end of the alkylation process, and oxidation of 2',5'-dimethyl-p-terphenyl is carried out at 105-110°C.

EFFECT: method enables to increase output of the said product by several times.

3 ex

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