Method of (meth)acrylic acid purification

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

 

The technical field to which the invention relates

The present invention relates to a method of purification of (meth)acrylic acid, in particular to a method of purification by distillation (meth)acrylic acid obtained by the method of gas-phase catalytic oxidation.

The level of technology

A method of obtaining a (meth)acrylic acid may include hydrolysis of the corresponding nitrile derivative, however, at present, a method of obtaining a (meth)acrylic acid mainly includes gas-phase catalytic oxidation of the corresponding hydrocarbon, in particular propylene or isobutylene. Has also recently been studied by the method of gas-phase catalytic oxidation using, instead of the olefin, the corresponding alkane, in which the feedstock is much cheaper.

In the production of (meth)acrylic acid according to the method of gas-phase catalytic oxidation obtained after the reaction gas containing the obtained (meth)acrylic acid is introduced into contact with the absorbing solvent, such as water, to extract gas (meth)acrylic acid in the form of a solution (meth)acrylic acid. The solution, in addition to (meth)acrylic acid, contains various impurities formed as by-products in the gas-phase catalytic oxidation in the process of production is odstv acrylic acid, and includes carboxylic acids such as formic acid, acetic acid, maleic acid and maleic anhydride; aldehydes, such as acrolein, furfural, and benzaldehyde; and acetone.

It was suggested many ways of extracting the purified (meth)acrylic acid from the solution of (meth)acrylic acid, and mainly used the method includes: removing the absorbing solvent and part of the impurities from the solution of (meth)acrylic acid at the stage of pre-treatment with the aim of obtaining raw (meth)acrylic acid, consisting mainly of a (meth)acrylic acid, its dimer and other heavy components; and cleaning of the raw (meth)acrylic acid at the stage of purification to obtain the desired product quality.

Demand for acrylic acid recently increased significantly, for example, in connection with its use as a raw material for polymer superabsorbents, which are used as disposable napkins, etc. and in the food industry. For these applications requires an acrylic acid of high purity. Using the raw (meth)acrylic acid as a raw material for polymers of acrylic acid used in the production of polymer superabsorbents, etc. can cause problems, including slow down the polymerization reaction, to reduce the level of the floor is merisalo and coating of the polymeric product.

For this reason, in industry (meth)acrylic acid is purified by distillation. The method of distillation is usually used as a method of purification of crude (meth)acrylic acid obtained gas-phase catalytic oxidation. However, (meth)acrylic acid is easily oxidized and manipulate it to cause problems.

Obtaining acrylic acid of high purity, for example, by distillation is usually associated with the problem of polymerization in the distillation column operating at high temperature. In this regard, have been proposed various improvements, such as:

1) the application of a specific inhibitor of polymerization;

2) use a certain concentration and the method of introduction of the polymerization inhibitor; and

3) set the mode of operation of distillation columns.

The method of obtaining acrylic acid of high purity by separation and removal of impurities from the crude acrylic acid obtained by the method of gas-phase catalytic oxidation, which is known as a convenient way of obtaining acrylic acid includes distillation in the presence of, for example, hydrazines (see, for example, JP 49-030312 A and JP 58-037290 B). In addition, another method involves distillation in the presence of hydrazine and ammonia (see, for example, JP 07-330659 A). This method presumably effective for deleted what I maleic acid. There is a method of continuous receipt of acrylic acid of high purity by preventing the formation of sludge in the distillation column includes the use of crude acrylic acid, the concentration of maleic acid in which is 2000 ppm (ppm) or less as a raw material for acrylic acid of high purity (see, for example, JP 2001-A).

In addition, when the acrylic acid of high purity distilled by a specified method, the acrylic acid has a tendency to polymerization, which runs the easier it is, the higher the purity of acrylic acid, and, therefore, the industrial method of obtaining acrylic acid of high purity. As such method, there is a method of preventing polymerization inside the distillation column includes, for example, suppressing polymerization of the easily polymerizable compound by adding dithiocarbamate copper (see, for example, JP 07-228548). In addition, another known method involves the supply of air (oxygen) to a distillation column under distillation to prevent polymerization of compounds containing the vinyl group, such as acrylic acid and the like (see, for example, JP 2001-122909).

In the end, the polymerization of (meth)acrylic acid in the distillation column is suppressed, however, in which the process operation of distillation columns are experiencing other problems, associated with polymerization. These problems in the cleaning process (meth)acrylic acid as follows. (Meth)acrylic acid of high purity is supplied to the tank for collecting phlegmy where the condensate (meth)acrylic acid, and here, despite the low temperature, which is maintained in the reservoir for collection of phlegmy distillation columns, the formation of the product of polymerization of (meth)acrylic acid, which is capable of polymerization product may result in stopping of the pump attached to the reservoir for collection of phlegmy. The pump stops, inevitably leads to the production stop, so you need a way of suppressing the formation of the polymeric product.

Description of the invention

The object of the present invention is an effective method of obtaining a (meth)acrylic acid of high purity by preventing the formation of the product of polymerization of (meth)acrylic acid in the condensate obtained in the production of (meth)acrylic acid to a high degree by distillation.

In this regard, the authors of the present invention conducted intensive studies with a view to resolving common issues encountered in the process of continuous production of acrylic acid of high purity, and these studies revealed the following.

(1) Oxygen (obyknovenoj), supplied to a distillation column for the purpose of preventing polymerization of acrylic acid is consumed inside the column and has no inhibitory effect on the liquid acrylic acid in the tank for collecting phlegmy.

(2) was Therefore investigated ways of increasing the supply of oxygen (usually air)supplied to the column. However, the distillation column operates at a high temperature. Thus, if a large amount of air fed into the distillation column, the distillation column can be formed is liable to detonate the gas. Thus the oxygen supply cannot be increased.

(3) in Addition, to reduce the temperature within the distillation column to prevent polymerization of the distillation column for acrylic acid is normally run a vacuum distillation column. Therefore, simply increasing the amount of air leads to an increase of the gas stream in the distillation column to an existing distillation columns leads to a decrease in production efficiency due to exceeding the limit of the efficiency of the plates of the column and to increase the flow of inert gas (i.e. air)which enters into the refrigerator, located in the upper part of the column; and reduce the cost of a new distillation columns due the helicene diameter distillation column and increase the area of heat transfer surface in the refrigerator, located in the upper part of the column.

In addition, the authors of the present invention found easily implemented in industry and effective way, which is as follows.

(4) a New version of oxygen (usually air) in the liquid acrylic acid in the tank for collecting phlegmy can prevent the formation of the product of polymerization and provides for long time stable operation of the pump attached to the reservoir for collection of phlegmy.

Thus, the present invention relates to a method of purification of (meth)acrylic acid, which comprises the following stages: distillation of the liquid containing the raw (meth)acrylic acid, which is an acrylic acid or methacrylic acid, to obtain a condensate (meth)acrylic acid, (meth)acrylic acid with a purity of 90% or more; and the supply of oxygen-containing gas, which, in particular, represents the oxygen in the condensate (meth)acrylic acid in the tank for collecting phlegmy, which receives the condensate (meth)acrylic acid.

In the present invention (meth)acrylic acid means acrylic acid or methacrylic acid.

Brief description of drawings

Figure 1 shows the vertical section, showing the example of the tank for collecting phlegmy used the first variant of the construction according to the present invention.

Figure 2 shows the vertical section showing another example of a tank for collecting phlegmy used in the design of the present invention.

Figure 3 shows the vertical section showing another example of a reservoir for collection of phlegmy used in the design of the present invention.

Figure 4 shows the vertical section showing another example of a reservoir for collection of phlegmy used in the design of the present invention.

Figure 5 schematically a flow diagram showing an example of a distilling apparatus for acrylic acid, which can be used as an option for implementation of the present invention.

Figure 6 schematically a flow diagram showing another example of a distilling apparatus for acrylic acid, which can be used as an option for implementation of the present invention

The best way of carrying out the invention

Further, the present invention is described in more detail.

The method of purification of (meth)acrylic acid according to the present invention includes the following stages: distillation of the liquid containing the raw (meth)acrylic acid, which is an acrylic acid or methacrylic acid with C is poured receiving condensate (meth)acrylic acid, containing (meth)acrylic acid with a purity of 90% or more (hereinafter describe this stage may be called the "stage distillation"); and the supply of oxygen-containing gas, which represents the oxygen in the condensate (meth)acrylic acid in the tank for collecting phlegmy, which receives the condensate (meth)acrylic acid (hereinafter describe this stage may be called the "stage of oxygen").

Stage distillation is not specifically limited, provided that at this stage it is possible to obtain a condensate (meth)acrylic acid with a purity of 90% or more, mostly 95% or more. For such stage distillation can be used known methods such as described in the prior art.

The liquid containing the raw (meth)acrylic acid is not specifically limited, provided that it is a liquid containing acrylic or methacrylic acid. Examples of such liquid containing (meth)acrylic acid include the (meth)acrylic acid, a solution of (meth)acrylic acid in a suitable solvent such as water and an organic solvent. The liquid containing the raw (meth)acrylic acid, from the viewpoint of productivity and the like, preferably produced by way of gas-phase catalytic oxidation. The liquid containing the raw (meth)acrylic is howling acid, can be obtained by known methods, for example, described in the section "prior art".

The method of distillation used at the stage of distillation, is not specifically limited, provided that it is a method of distillation, which allows to obtain a condensate (meth)acrylic acid with the above purity of the liquid containing (meth)acrylic acid. In the specified method of distillation may apply different methods of distillation, such as simple distillation and fractional distillation. Distillation can be distilled continuous or batch type. The liquid containing the raw (meth)acrylic acid, usually from the viewpoint of productivity and the like, preferably distilled in the distillation column. The purity of the condensate can be set depending on various conditions, such as those used distillation column, the type of nozzle, reflux, distillation temperature and the type and amount of additive that is introduced into the liquid containing the raw (meth)acrylic acid.

At the stage of distillation of the liquid containing the raw (meth)acrylic acid, mainly distilled in the presence of a known polymerization inhibitor or inhibitor of polymerization (hereinafter in the text of the description referred to simply as "polymerization inhibitor"), such as a derivative of phenol or a derivative fenotiazina, with the purpose of preventing the formation of the product of polymerization of (meth)acrylic acid and the sustainable received in a long time, (meth)acrylic acid of high purity.

The method of obtaining the raw (meth)acrylic acid of high purity by the production of crude (meth)acrylic acid may be considered on the example of acrylic acid. The method of obtaining the raw (meth)acrylic acid of high purity by the production of crude (meth)acrylic acid includes the following methods (1) through (3).

(1) the Method includes a step of oxidation with the aim of obtaining acrylic acid by gas-phase catalytic oxidation of propane, propylene and/or acrolein; selection stage for the extraction of acrylic acid in the aqueous solution of acrylic acid by contact with water gas containing acrylic acid, which was formed at the stage of oxidation; stage extraction to extraction of acrylic acid, using a suitable extracting solvent from the aqueous solution of acrylic acid obtained at the screening stage; stage separation the purpose of separation of acrylic acid and solvent from the obtained extraction liquid; a stage of removal of low-boiling components in order to remove the low-boiling components selected from acrylic acid; purification step for cleaning liquid containing acrylic acid, from which the removed low-boiling components by distillation and the like; a stage of regeneration to return in p is izvodstvo valuable connections by sending as a source of raw materials high-boiling liquids (liquids with high boiling point), which contains the Michael adducts of acrylic acid, highlighted in the above stages, and the polymerization inhibitor used at each stage in the decomposition reactor column; and the stage of recycling to return to repeat the cycle extracted valuable compounds at any stage after stage of selection.

(2) the Method comprises: a stage of oxidation with the aim of obtaining acrylic acid by gas-phase catalytic oxidation of propane, propylene and/or acrolein; selection stage for the extraction of acrylic acid in the aqueous solution of acrylic acid by contact with water gas containing acrylic acid, which was formed at the stage of oxidation; stage azeotropic separation to isolate crude acrylic acid from the bottom of the column for azeotropic separation by distillation of the aqueous solution of acrylic acid obtained at the stage of selection in the column for azeotropic separation in the presence of an azeotropic solvent; phase separation of acetic acid in order to remove acetic acid of the selected acrylic acid; purification step to remove high boiling impurities; the stage of regeneration to return to the production of valuable compounds by sending as a source of raw materials high-boiling liquid, which contains adducts Mi is aela acrylic acid, highlighted in the above stages, and the polymerization inhibitor used at each stage in the decomposition reactor column; and the stage of recycling to return to repeat the cycle extracted valuable compounds at any stage after stage of selection.

(3) the Method includes a step of oxidation with the aim of obtaining acrylic acid by gas-phase catalytic oxidation of propane, propylene and/or acrolein; stage selection/separation for the extraction of acrylic acid in the form of a solution of acrylic acid in an organic solvent by contacting with an organic solvent gas containing acrylic acid, which was formed at the stage of oxidation, while removing water, acetic acid and the like; a stage of separation of the purpose of separation of acrylic acid from a solution of acrylic acid in an organic solvent; the stage of regeneration to return to the production of valuable compounds by sending as a source of raw materials high-boiling liquid, which contains a polymerization inhibitor and an organic solvent used at each stage, and the Michael adducts of acrylic acid, selected on the above stages in the decomposition reactor column; stage recycling to return to repeat the cycle extracted valuable connection of the clusters at any stage after stage of selection; and the stage of cleaning solvent to clean parts or the entire amount of the extracted organic solvent.

Raw acrylic acid, which is used as a source of raw material for acrylic acid of high purity at the factory for the production of acrylic acid is usually a liquid, which is obtained after removal of low-boiling components. Examples of impurities include those present in a small amount of residual low-boiling impurities such as water, furfural, benzaldehyde and acetic acid; and high-boiling impurities such as dimer (meth)acrylic acid, trimer (meth)acrylic acid, maleic anhydride, β-hydroxypropionic acid and β-alkoxyamino acid. By distillation of the liquid through the distillation columns in the upper part of the column can be obtained acrylic acid with a purity of 90% or more. In addition, the condensate (meth)acrylic acid can be obtained directly by the recovery of valuable compounds at the stage of regeneration.

The method according to the present invention can be used to produce methacrylic acid, the same as and for obtaining acrylic acid. In the case where the present invention is used to produce methacrylic acid, the crude methacrylic acid get gazopa the major catalytic oxidation of isobutylene and/or tert-butyl alcohol, in raw methacrylic acid in the form of impurities are contained, for example, citraconate acids with aldehydes, ketones and maleic acid, and the crude acrylic acid.

The liquid in the upper part of the column obtained from the distillation of a liquid containing the raw (meth)acrylic acid, typically includes in the form of trace impurities carboxylic acids, such as maleic acid and acetic acid, aldehydes such as furfural and benzaldehyde, and water. Therefore, with the aim of obtaining a pure acrylic acid, preferably carry out the additional step (removal of impurities (describe below) by adding hydrazine or mercaptans).

In the case when the purified product is used as acrylic acid of high purity, for example, in order to remove impurities that cannot be removed cost-effective ways by separation by distillation, the liquid containing raw acrylic acid-type reagent capable of interacting with such impurities with the formation of compounds which can be separated by distillation; and then the liquid containing crude acrylic acid is sent to a distillation column. Removing aldehyde component by reacting (meth)acrylic acid-containing aldehyde component, by using a reagent for UDA is placed aldehyde, disclosed in JP 2001-058970A or JP 2001-213839 and the specified method can be applied in the present invention.

Order to separate the impurities in the distillation, the liquid containing the raw (meth)acrylic acid, optionally includes a derivative of hydrazine. Examples of hydrazine derivatives include hydrazine, hydrazinehydrate, phenylhydrazine, hydrazine sulfate and chloride hydrazine. A derivative of hydrazine can be used individually or as a mixture of two or more of hydrazine derivatives. The appropriate amount of added hydrazine derivative is selected depending on the number of removed impurities and allowable concentrations of impurities in the acrylic acid of high purity, obtained after distillation.

A derivative of hydrazine, preferably directly added to the liquid containing the raw (meth)acrylic acid. The number of added hydrazine derivative is usually (0,1-2)-fold molar excess, preferably about 0.5-2)-fold molar excess, more preferably (0,5-1)-fold molar excess relative to the total number of aldehydes, such as furfural and benzaldehyde, and maleic acid in a liquid containing the raw (meth)acrylic acid.

The method of introducing a derivative of hydrazine in liquid containing the raw (meth)acrylic acid, especially the e limited, provided that the derivative of hydrazine and must be removed impurities can interact with each other.

In the present invention the purification by distillation is preferably carried out after hydrazine derivative is added to the liquid containing the raw (meth)acrylic acid, before it is loaded into the distillation column; and after giving the impurities, such as maleic acid present in the liquid containing the raw (meth)acrylic acid to react with a derivative of hydrazine. The interaction between the derivative of hydrazine and impurities mainly carried out in the reactor, which is capable of providing the required temperature and time of contact. Examples of the reactor can include a reactor equipped with a stirrer, and a tubular reactor. The reaction temperature should preferably be as low as possible, and it is usually chosen in the range from the melting point of acrylic acid or higher and temperatures of 50°With or below. The reaction time is preferably 10 min or more, and the time of contacting is generally from about 30 minutes to 3 hours.

The reaction between a derivative of hydrazine and impurities can be performed in a distillation column. In this case, the preferred time of contact, continued from adding hydrazine derivative to the derived crude (meth)acrylic the second acid to the selection of the purified (meth)acrylic acid as distillate from the top of the distillation column, ranges from 10 min to 5 hours, more preferably from 20 minutes to 3 hours. Short time of contact may be insufficient for efficient reaction between a derivative of hydrazine and impurities. Too much time probing may lead to an increase of impurities due to the reaction of decomposition of the reaction product. Thus, the time of contact selected from the above range.

Want to remove impurities such as maleic acid, are removed from the crude (meth)acrylic acid using a derivative of hydrazine, which are added during the distillation process.

With the aim of separating impurities by distillation, the liquid containing the raw (meth)acrylic acid, preferably additionally includes mercaptans. Examples of mercaptans include n-butylmercaptan, n-artilleryman and n-dodecylmercaptan. According to the present invention mercaptans can be used individually or as a mixture of two or more mercaptans.

In that case, when using mercaptans derived aldehyde from the liquid containing the raw (meth)acrylic acid can be removed by passing the liquid containing the raw (meth)acrylic acid added mercaptans, through a column of resin filled with cation exchange resin based on Sultonova the acid at a temperature of 20-90° C with the value of LHSV (time volumetric liquid velocity)0.1-10 h-1. The resulting liquid is loaded into the distillation column. The liquid can pass through the column as in the form of downward and upward flow. Mercaptans as means for removing aldehydes typically used in (1-8)-fold molar excess relative to the aldehyde component.

Stage oxygen supply is not specifically limited, provided that the oxygen-containing gas can be fed to the condensate (meth)acrylic acid in the tank for collecting phlegmy designed to collect condensate (meth)acrylic acid. At this stage of oxygen you can use any method that includes contacting the gas and the liquid in the process gas in the liquid.

Oxygen-containing gas is not specifically limited, provided that the gas contains oxygen. Examples of such oxygen-containing gas include the actual oxygen or air or a mixture of the actual oxygen and one or more gases selected from the following gases(1) -(4):

(1) nitrogen

(2) the exhaust gas after the conduct of the process

(3) air (except when the air is the only gas)

(4) carbon dioxide.

The exhaust gas after the process used by the present invention represents the first gas, which is removed after carrying out the above process of obtaining acrylic acid, or gas, which is obtained from the plant for the production of acrylates, located adjacent to the enterprise for the production of acrylic acid, or the like, and it is a gas component that has no effect on the subsequent use of acrylic acid of high purity according to the present invention. The exhaust gas after the process may be a gas component containing substances or compounds that do not affect the quality of the (meth)acrylic acid of high purity obtained by the present invention, or a gas component that contains the component in a quantity not affect the quality. Specific examples of the exhaust gas after the process include "water" and "acetic acid".

The oxygen content in the oxygen-containing gas is not specifically limited, provided that the detonating gas within the tank for collecting phlegmy is not formed, but mostly it is in the range from 5 to 30% vol. The most suitable oxygen-containing gas is air.

Feeding oxygen-containing gas depends on the size of the tank for collecting phlegmy and time spent condensate (meth)acrylic acid in which eservoir to collect phlegmy. However, the ratio (nm3/t) source of oxygen in the oxygen-containing gas to the flow of condensate in the reservoir for collection of phlegmy, under normal conditions (0°C, 1 ATM) preferably satisfies the relationship indicated in the following equation:

0,004≤/≤1,0

(where a denotes oxygen (norm. m3/hour), and indicates the flow (t/h) condensate in the reservoir for collection of phlegmy). The characters "norms." b "standards. m3/h" indicates normal conditions (0°C, 1 ATM; normal conditions).

In addition, in the present invention for suppressing the formation of the polymeric product in the process of production or purification, as described above, can be used inhibitor of polymerization (polymerization inhibitor and/or an inhibitor of polymerization). As the polymerization inhibitor may be used a known inhibitor of polymerization and/or moderator of polymerization, and specific examples include magisteriate connection, such as (meth)acrylate copper or dithiocarbamate copper, a derivative of phenol and derivative fenotiazina. The polymerization inhibitor may be used individually or as mixtures of several inhibitors of polymerization. The polymerization inhibitor may be added to the liquid containing the raw (meth)acrylic acid, or in the condensate (meth)acrylic acid. And the one and the other is a convenient way to prevent the formation of the product of polymerization of (meth)acrylic acid.

Examples of the derivative of the phenol used in the present invention include hydroquinone, metochion (methoxyhydroquinone), pyragollole, pyrocatechol, resorcinol, phenol and cresol. Derived phenol can be used individually or in mixture of two or more phenol derivatives. The number of added phenol derivation is from 0 to 800 ppm, preferably from 50 to 600 ppm relative to the weight of the liquid containing the raw (meth)acrylic acid, which is loaded into the distillation column. In addition, the number of added phenol derivation is from 0 to 500 ppm, preferably from 1 to 300 ppm relative to the weight of the condensate (meth)acrylic acid entering the reservoir for collection of phlegmy. A small added amount can lead to insufficient effect of suppressing polymerization. Too much added number has no harmful effect on the suppression of the polymerization, however, it is undesirable for economic reasons.

Examples of derived fenotiazina used in the present invention, includes phenothiazines, bis-(α-methylbenzyl)phenothiazines, 3,7-dioctylphthalate and bis-(α-dimethylbenzyl)phenothiazines. Derived fenotiazina can be used individually or as a mixture of two or more fenotiazinas. The number is added in the derived fenotiazina ranges from 0 to 400 ppm, preferably from 50 to 300 ppm relative to the weight of the (meth)acrylic acid, which is loaded into the distillation column. In addition, the number of added derived fenotiazina is from 0 to 200 ppm, preferably from 1 to 100 ppm relative to the weight of the condensate (meth)acrylic acid entering the reservoir for collection of phlegmy. A small added amount can lead to insufficient effect of suppressing polymerization. Too much added number has no harmful effect on the suppression of the polymerization, but it is undesirable for economic reasons.

Examples of compounds based on copper include copper compounds such as copper chloride, copper acetate, copper carbonate, (meth)acrylate, copper, copper dimethyldithiocarbamate, copper diethyldithiocarbamate or dibutyldithiocarbamate copper. The polymerization inhibitor may be used individually or as a mixture of two or more polymerization inhibitors. The number of added polymerization inhibitor is not specifically limited, but preferably ranges from approximately 1 to 1000 h/million

Examples of dithiocarbamate copper include dialkyldithiocarbamate copper, such as copper dimethyldithiocarbamate, copper diethyldithiocarbamate, dipropylthiocarbamate copper and dibutyldithiocarbamate copper; cycloalkylcarbonyl IU the and, such as atlantajournal copper, tetramethylthiuram copper, pentametilenditiokarbamata copper and hexamethylenediisocyanate copper; and collectiveintelligence copper, such as occipitocervical copper. The specified dithiocarbamate copper can be used individually or as a mixture of two or more dithiocarbamate copper.

The number of added dithiocarbamate copper is from 1 to 100 ppm, preferably from 10 to 80 ppm relative to the weight of the liquid containing (meth)acrylic acid, which is loaded into the distillation column. In addition, the number of the added dithiocarbamate copper ranges from 0 to 50 ppm, preferably from 1 to 20 ppm relative to the weight of the condensate (meth)acrylic acid entering the reservoir for collection of phlegmy. A small added amount can lead to insufficient effect of suppressing polymerization. Great to add a number of undesirable due to corrosion of the equipment in the lower part of the distillation column. In the distillation system according to the present invention dithiocarbamate copper supposedly has a stronger effect on the suppression of polymerization in the liquid in the lower part of the column, compared with the downward flow of liquid within the distillation column. Therefore, dithiocarbamate copper suppose the equipment added to the liquid, contains the raw (meth)acrylic acid, which is used as raw material or the fluid in the lower part of the distillation column.

(Meth)acrylate copper, which is used in the present invention plays the role of an inhibitor of polymerization of (meth)acrylic acid is similar to dithiocarbamato copper. The combination of (meth)acrylate copper and dithiocarbamate copper provides a significant effect of preventing polymerization.

(Meth)acrylate copper can be obtained by dissolving the carbonate copper chloride copper or copper salts of organic acids, a hydroxide of copper or copper powder in the (meth)acrylic acid. Chloride of copper is undesirable because the column for the distillation of (meth)acrylic acid is usually made of stainless steel, and under the influence of chloride of copper can occur stress corrosion cracking. Specific examples of the substances dissolved in the (meth)acrylic acid, with the purpose of obtaining a (meth)acrylate copper, which is used in the present invention include divalent carbonate copper carbonate; copper formate, copper acetate or copper salicylate as a copper salt of an organic acid; and a monovalent hydroxide or copper hydroxide of divalent copper hydroxide. In addition, the copper powder can be directly dissolved in the (meth)acrylic acid. Specified (meth)acrylate copper can be used individually or in mixture of two or more these salts of copper.

(Meth)acrylate copper can also be obtained by dissolving in a solvent containing (meth)acrylic acid. The solvent used in this case, is primarily a solvent having a boiling point which is higher than the boiling point of (meth)acrylic acid, in order to prevent contamination of the solvent (meth)acrylic acid of high purity, which is obtained in the upper part of the distillation column. Specific examples of the solvent include diphenyl ether, o-phthalates, oleates, adipate, hydrocarbons obtained by the distillation of oil from the middle and used as heat transfer oil with a boiling point 170°C and above. The solvent may be an individual or can be a mixture of two or more of these solvents.

In the case where the liquid containing the raw (meth)acrylic acid, which is used as a raw material for distillation, contains water, the water can also be used as solvent, the boiling point of which is lower than the boiling point of (meth)acrylic acid. The water content can be set based on the allowable amount of (meth)acrylic acid of high purity that must be obtained, and desired to add a quantity of copper salt (meth)acre the gross acid. In that case, when the liquid containing the raw (meth)acrylic acid, there is no water, you can add appropriate amount of water. However, depending on the requirements of a purified product may need to dehydration, so water should be added cautiously.

The number of added (meth)acrylate of copper is from 1 to 100 ppm, mainly from 5 to 80 ppm relative to the weight of the liquid containing the raw (meth)acrylic acid, which is placed in a distillation column, provided that all of the dissolved copper is transformed into a (meth)acrylate copper. In addition, the number of added (meth)acrylate of copper is from 0 to 50 ppm, preferably from 1 to 20 ppm relative to the weight of the condensate (meth)acrylic acid entering the reservoir for collection of phlegmy. A small added amount can lead to insufficient effect of suppressing polymerization. Too much added amount is undesirable due to corrosion of the equipment in the lower part of the distillation column.

(Meth)acrylate, copper, unlike dithiocarbamate copper, has a much stronger effect on the downward flow of liquid in the distillation column. Therefore, the (meth)acrylate copper is preferably added to the liquid containing the raw (meth)acrylic acid, which is used as raw material or liquid (condensate) in the top part of the distillation column.

In the present invention using one or more polymerization inhibitors that perform the aforementioned various functions. In addition to the derivative of hydrazine, dithiocarbamate copper (meth)acrylate copper, a derivative of phenol, if necessary, can be used by other polymerization inhibitors.

Examples of other polymerization inhibitors are: N-oxylene derivatives such as tert-butylnitrone, 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxide, 2,2,6,6-tetramethylpiperidine-1-oxide, 2,2,6,6-tetramethylpiperidine, 4-hydroxy-2,2,6,6-tetramethylpiperidine and 4,4',4"-Tris-1-(2,2,6,6-tetramethylpiperidinyloxy)hospit; phenylendiamine, such as p-phenylenediamine; nitroso compounds such as N-nitrosodiphenylamine; urea such as urea and thiourea, such as thiourea. These other polymerization inhibitors can be used alone or as a mixture of two or more polymerization inhibitors.

The method of adding (meth)acrylate, copper, dithiocarbamate copper, a derivative of phenol and derivative fenotiazina, each of which has an inhibitory effect on the polymerization is not specifically limited. Examples of ways to add include a method involving the direct introduction connections, has inhibiting effect on the polymerization, the liquid containing raw (IU is)acrylic acid, served in the distillation column, or in the condensate liquid (meth)acrylic acid which is obtained as distillate after distillation; and a process comprising dissolving with a suitable solvent and introducing the resulting solution into a liquid containing the raw (meth)acrylic acid, or in the distillation column. The temperature at which conduct the add connection that has inhibiting effect on the polymerization, choose arbitrarily.

According to the present invention, depending on the stages may be added substance other than the above, but the type is not specifically limited, provided that the boiling point of a substance is higher than the boiling point of the condensate (meth)acrylic acid of the present invention.

In the present invention, the liquid containing the raw (meth)acrylic acid, which was added hydrazine derivative, (meth)acrylate copper and dithiocarbamate copper is subjected to a distillation treatment to remove impurities. Application of the obtained (meth)acrylic acid is not specifically limited, and the resulting (meth)acrylic acid may find numerous applications, such as source material for obtaining a (meth)acrylate, or the source material to obtain a (meth)acrylic acid of high purity for polymers the x superabsorbents and products based on (meth)acrylic acid General use.

According to the present invention stage oxygen supply carried out when the concentration of (meth)acrylic acid in the condensate is 90% or more. However, depending on the situation stage oxygen is preferably carried out in the case when the concentration of (meth)acrylic acid in the condensate is less than 90%. Examples of such situations include the case when the temperature of the condensate in the tank for collecting phlegmy relatively high (for example, 40°C and above); and the case when the condensate contains a substance which easily causes the occurrence of an exothermic reaction with (meth)acrylic acid, or when the condensate in the reservoir for collection of phlegmy contains an easily polymerizable substance (e.g., acrolein). Using an oxygen-containing gas in the condensate in terms of, when, as indicated above, it is easy course of polymerization of the (meth)acrylic acid can be stably for a long period of time to obtain a (meth)acrylic acid of high purity.

The method of purification of (meth)acrylic acid of the present invention can be implemented using a conventional apparatus or device which is used for production or purification of (meth)acrylic acid as such or using a partially modified apparatus or device is.

At a chemical enterprise is usually used distillation column. In particular, the example of the distillation column includes a column / tube sheet plates, bubble cap column, a column with a nozzle, or combinations thereof (for example, the combination of a casing / tube sheet plates and columns with a nozzle). The presence or absence of the overflow fitting or bottom of the descent is irrelevant for the present invention. In the present invention can be used either option.

Specific examples of dishes include nozzle plates, each of which is equipped with overflow pipe / tube sheet plates, cap plates, plates SUPERFRAC, plates MAX-FRAC and plates with dual flow without overflow fittings.

Examples of nozzles, which are mainly used for the present invention include commonly used nozzles, such as columnar nozzle, a cylindrical nozzle, saddle-shaped nozzle, a spherical cap, cubic nozzle and pyramidal nozzle; and structured packing and disordered attachments, having a special form of high-efficiency nozzles, commercial production of which was established recently.

Examples of commercially available structured packings include mesh structured packing, such as SULZER PACKING (available from Sulzer Brothers Ltd.), SUMITOMO SULZER PACKING (available from KOMPAN and Sumitomo Heavy Industries, Ltd.) and TECHNOPACK (available from Mitsui & Co., Ltd.); lamellar structured packing, such as MELLAPAK (available from Sumitomo Heavy Industries, Ltd.), TECHNOPACK (available from Mitsui & Co., Ltd.) and MC PACK (available from Mitsubishi Chemical Engineering Corporation); lattice structured packing, such as FLEXI-GRID (available from Koch-Glitsch); and other structured packing, such as GEM-PAK (available from Koch-Glitsch); MONTZ-PAK (available from the company Julius Montz GmbH), GOOD ROLL PACKING (available from Tokyo Tokushu Kanaami K.K.), HONEYCOMB PACK (available from the company NGK Insulators, Ltd.) and IMPULSE PACKING (available from the company Nagaoka International Corporation).

Examples of commercially available disordered attachments include ring process, the nozzle PALL RINGS (available from BASF Aktiengesellschaft); CASCADE MINI-RING (available from the company Mass Transfer Ltd.); IMTP (available from Saint-Gobain NorPro); INTALOX SADDLES (available from Saint-Gobain NorPro); TELLERETT (available from Nittetsu Chemical Engineering Ltd.); and FLEXI RINGS (available from the company JGC Corporation).

The nozzle may be used alone, or use a combination of two or more nozzles. In addition, the nozzle can be used in combination with commonly used plates.

The specific conditions in the distillation column, you can usually choose from a temperature in the lower part of the column constituting from 60 to 100°and the pressure in the upper part of the column, are is it from 1.33 to 26.7 kPa.

In the present invention a heat exchanger located in the upper part of the distillation column and is used for cooling the gas at the top of the column, can be used as a refrigerator for condensing vapor (meth)acrylic acid obtained by distillation. The heat exchanger is usually divided into a heat exchanger located inside the column, and a heat exchanger located outside the column. The heat exchanger, in addition to actually use as a refrigerator, can be used to condense the exhaust gas or as a heater to heat the fluid in the lower part of the column, and the number of installed heat exchangers is not specifically limited. The type of heat exchanger is not specifically limited, and specific examples of heat exchangers include vertical lattice heat exchanger fixed tube horizontal heat exchanger fixed tube heat exchanger with U-shaped tubes, heat exchanger, heat exchanger pipe, spiral type heat exchanger, the heat exchanger in the form of a square block and the heat exchanger of plate type.

A reservoir for collecting phlegmy not specifically limited, provided that the tank receives a portion or substantially all of the resultant condensate. The temperature of the liquid in the collection tank FLEG is s, depending on the industrial used in refrigerator water typically ranges from 15 to 40°C. the Temperature of the liquid in the tank to collect phlegmy preferably low, as in the tank for collecting phlegmy collect (meth)acrylic acid which is a substance that can easily dry out. The average residence time of liquid in the tank to collect phlegmy (is the quotient of the speed of the fluid volume in the reservoir fluid) is usually from 2 to 30 min, but the present invention is not specifically limited.

According to the present invention, the type and amount of the above polymerization inhibitor or retarder polymerization in the condensate, which is in the tank for collecting phlegmy may be limited depending on the application of (meth)acrylic acid obtained in accordance with the present invention. The type and amount of the above polymerization inhibitor or inhibitor of polymerization is not specifically limited in the case when (meth)acrylic acid obtained according to the present invention, used as starting material to obtain acrylates or as raw materials for the production of acrylates high purity polymer superabsorbents.

In that case, when (meth)acrylic acid obtained according to the present invention, use, for example, as a product of acrylic acid of General application or the product of acrylic acid of high purity, as the polymerization inhibitor used methoxyhydroquinone, usually with a concentration in the range from 180 to 220 ppm (default value is 200 ppm). Then usually spend the execution of the order. In addition, in the case where the (meth)acrylic acid obtained according to the present invention, used as an intermediate product, the concentration of the polymerization inhibitor is usually in the range from 10 to 200 ppm for the derived phenol in the range of from 5 to 100 ppm for the derived fenotiazina, although the concentration varies depending on conditions such as the influence of the following reactions.

The device, which are used for feeding oxygen-containing gas is not specifically limited, however, the oxygen-containing gas mainly thoroughly dispersed in the condensate (meth)acrylic acid. For this reason, the oxygen-containing gas supplied into the fluid, mainly thoroughly mix through the use of, for example, a liquid injection device for injection of a liquid in the form of small bubbles, such as a bubbler in the form of a tube having on the surface of the hole injection into the liquid, through which the injected oxygen-containing the first gas, or having a porous body made of sintered metal carbide; and a feed pipe for introducing an oxygen-containing gas in the device for injection in a liquid.

Materials for various devices, such as various nozzles, building columns, heater, refrigerator, refrigerator for exhaust gases, a tank for collecting phlegmy, pipelines and pump, attached as attachments for each column used in accordance with the present invention, is chosen depending on the easily polymerizable compound and temperature. As such materials often use stainless steel, but the material in the present invention is not limited to stainless steels. Examples of these materials include SUS 304, SUS 304L, SUS 316, SUS 316L, SUS 317, SUS 317L, SUS 327 and Hastelloy. The materials chosen depending on the physical properties of each fluid with regard to corrosion resistance.

Next, a variant of implementation of the present invention is described with reference to the drawings. Figure 5 shows an example of distilling apparatus for acrylic acid, which can be accomplished the present invention.

As shown in Figure 5, distillation apparatus for acrylic acid consists of a body column (distillation column) 1 for the distillation of crude acrylic acid refrigerator 20 for cooling the vapor, contains acrylic acid for the purpose of condensation; a tank for collecting phlegmy 21, where collecting the condensate formed in the fridge 20; refrigerator for exhaust gases 25 for further cooling of the gas that has been cooled in the refrigerator for 20 to extract valuable compounds; and vacuum equipment 26 to create a reduced pressure within the distillation system.

In the lower part of the body column 1 posted discharge port 2 to remove liquid from the bottom of the column. To the exhaust pipe 2 is attached boot pipe 3, through which comes the part removed from the bottom of the column of fluid and the pipe 11.

To boot the pipe 3 is attached to the pipe 4 for supplying liquid from the bottom of the column supplied through the pipe 3 and the pipe 4 is attached to the heater 5 to heat the fluid from the lower portion of the column, coming through the pipeline 4. The heater 5 is attached to the pipe 6 for supplying heated fluid from the lower part of the column and the pipe 6 is connected to the pipe 7 for supplying liquid from the lower part of the column from the pipeline 6 in the case of the column 1.

The pipe 11 is attached to the pump 12 for supplying the liquid from the bottom of the column through line 11, and 12 are attached to the pump tubing 13.

On the other hand, to the upper part of the case is column 1 of the attached pipe 19 for the delivery of gas, contains acrylic acid. The pipe 19 is attached to the refrigerator 20 and the refrigerator 20 is connected with a reservoir for collecting phlegmy 21. With a reservoir for collecting phlegmy 21 is connected fridge for flue gas 25 and the pump 22 to deliver the condensate collected in reservoir for collecting phlegmy 21. Fridge for flue gas 25 is connected to the vacuum equipment 26.

To the pump 22 is attached to the pipe 23 for returning part of the condensate in the case of the column 1. From line 23 branches pipeline 24 for the selection of the condensate in the form of purified acrylic acid and a pipe 27 for directing part of the condensate in the refrigerator 20 and fridge for exhaust gases 25.

The pipe 27 is attached to the pipe 30 for supplying the polymerization inhibitor to a part of the condensate. The pipe 27 is divided into the first pipe 28 for supplying the polymerization inhibitor, which provides the fridge 20 condensate with the added polymerization inhibitor, and the second pipe 29 for supplying the polymerization inhibitor, which provides the fridge for exhaust gases 25 condensate with the added polymerization inhibitor. In addition, the refrigerator 20 and fridge for exhaust gases 25 each provided with a nozzle for spraying inhibitor of polymerization through the first 28 and second 29 pipelines to feed the inhibitor of polymerization in each of the refrigerators.

As shown in figure 1, a reservoir for collecting phlegmy 21 consists of a body vessel 41; inlet pipe 42 for supplying condensate from the refrigerator 20 inside of the tank 41; of the outlet pipe 43 for discharging condensate into the body of the tank 41, with the help of the pump 22; outlet fitting for removal of gaseous components from the chassis of the tank 41 in the fridge for exhaust gases 25; and bubbler (perforated pipe) 46, placed in the lower part inside the tank 41.

Bubbler 46 is a tubular design, which is nearly horizontal and contains many holes 47, which are located on the surface of the top of the bubbler 46; and a hole 48 for removal of the liquid, which is located on the bottom surface of the bubbler 46. To the bottom of the bubbler 46 attached nozzle 45 for supplying oxygen-containing gas, through which oxygen-containing gas from the outside enters the bubbler 46 and the body of the tank 41.

The liquid containing crude acrylic acid is fed into the casing columns for distillation, and part of the liquid in the lower part of the column is circulated as follows: the discharge pipe 2, the loading pipe 3, the pipe 4, the reboiler 5, pipe 6 and the pipe 7. Another part of the liquid in the lower part of the column is withdrawn as residue through wygraj the second pipe 2, the pipeline 11, a pump 12 and line 13.

The distillate from the top of the column enters the refrigerator 20 to the pipe 19 for condensation in the refrigerator 20, thereby forming a condensate of acrylic acid. On the other hand, the mixed liquid consisting of a condensate of acrylic acid from a reservoir to collect phlegmy 21 and inhibitor of polymerization supplied through the supply pipe inhibitor of polymerization of 30, is injected into the refrigerator 20 through the nozzle. The condensate of acrylic acid condenses in the refrigerator 20 and is introduced into the housing 41 of the tank for collecting phlegmy 21 together with the polymerization inhibitor from the refrigerator 20 through the inlet 42.

Part of the condensate of acrylic acid in the tank for collecting phlegmy 21 is returned to the upper part of the column through the pump 22 and line 23. Another part of the condensate of acrylic acid is supplied to the nozzles located inside the refrigerator 20 and cooler for exhaust gases 25, on the first pipe 28 for supplying the polymerization inhibitor and the second pipe 29 for the supply of the polymerization inhibitor, which is connected with the pipe 30 for supplying the polymerization inhibitor through pipe 27. The remainder of the condensate of acrylic acid is given in the form of purified acrylic acid through line 24.

Inside reservoir oxygen-containing gas (for example, air) is supplied to the bubbler 46 through pipe 45 for supplying oxygen-containing gas. Oxygen-containing gas injected through the holes 47 and the hole for removing fluid 48 in the form of bubbles, each of which has a small size. The condensate of acrylic acid inside the tank 41 interacts type gas-liquid oxygen-containing gas, thereby preventing the condensation polymerization of acrylic acid. Thus, polymerization of acrylic acid in the condensate in the tank for collecting phlegmy 21 and departing from it flows is prevented and thereby preventing the formation of polymeric products in pipelines or pumps in the tank for collecting phlegmy 21 and departing from it flows.

The gas from the shell of the tank 41 is supplied through the outlet 44 in the fridge for exhaust gases 25 and is cooled. Condensed while acrylic acid is returned to the reservoir for collection of phlegmy 21 in the form of condensate, and gas components are discharged into the exhaust system using vacuum equipment 26.

In the process of purification of acrylic acid in the distillation apparatus shown in Figure 5, the temperature in the lower part of the column is preferably from 60 to 120°S, more preferably from 70 to 100°C. the Pressure in the upper part of the column preferably the composition is AET from 1 to 50 kPa, more preferably from 2 to 20 kPa.

In the present invention the design variant for supplying oxygen-containing gas in the condensate in the tank for collecting phlegmy 21 is not limited to the variant shown in figure 1.

According to the present invention a reservoir for collecting phlegmy may, as shown, for example, in figure 2, to include instead of the bubbler inlet pipe 56, representing a tubular structure, which is almost horizontally in the lower part of the body of the tank 41; and many nozzles 47, which are located above suction inlet 56 for injection of gas into the inlet 56 in the form of small bubbles. In the present invention a reservoir for collecting phlegmy 21 may, as shown, for example, in Fig. 3, to include instead of the nozzles 57 a lot of nozzles made of metal 67, which are a porous material for dispersion of the gas in the inlet pipe 56 in the form of small bubbles.

Different design alternatives are shown in figure 2 and 3, can prevent the polymerization of acrylic acid in the condensate in the reservoir for collection of phlegmy 21 or outgoing flows, and thereby prevent the formation of polymeric products in pipelines or pumps in the tank for collecting phlegmy 21 and departing from it flows the same version of the design shown in figure 1.

D is more, part of the preferred design of the present invention, is shown in Figure 4, with the goal of effectively shielding the condensate of acrylic acid and an oxygen-containing gas may additionally include a baffle 50, located inside the tank 41 above the bubbler 46, in order to suppress the emission of the gas injected through the holes 47. Such construction provides longer contact between the condensate of acrylic acid within the tank 41 and the oxygen-containing gas, which will ensure more effective prevention of polymerization of acrylic acid under the action of the oxygen-containing gas.

Further, another part of the preferred design of the present invention, shown in Fig.6, with the goal of effectively shielding the condensate of acrylic acid and an oxygen-containing gas may additionally include a pipe for circulating 31, which departs from the pipe 23 and is connected with a reservoir for collecting phlegmy 21 for forced movement (circulation) condensate of acrylic acid with a pump 22. This design increases the concentration of oxygen-containing gas in the condensate of acrylic acid, even more efficiently enhances the inhibitory activity of the oxygen-containing gas to Polimeri is the situation of acrylic acid.

EXAMPLES

Further, the present invention is described in more detail using examples, but the following examples do not limit the essence of the present invention. Acrylic acid as starting materials and impurities analyzed by gas chromatograph (GC14A from Shimadzu Corporation). Maleic acid in process chromatography converted into maleic anhydride, and the content of maleic acid and the content of maleic anhydride cannot be determined separately. Therefore, the total content of maleic acid and maleic anhydride in the description below, indicated by the content of maleic acid.

<Example 1>

Distillation of the liquid containing crude acrylic acid is carried out in a distillation apparatus shown in Figure 5, using a distillation column made of stainless steel SUS 316, inner diameter which is 1100 mm, length 20000 mm, and in the case of the column 1 are 21 / tube sheet plates (plates with double thread). In the middle of the pipeline 4 is a pump for feeding liquid from the bottom of the column to the reboiler 5. The reboiler is located a vertical tubular heat exchanger, and the liquid from the bottom of the column flows through tubes of reboiler 5.

The mixture (downloadable liquid)containing 98.5% of wt. acrylic to the slots, to 0.3% wt. maleic acid and 0.3% wt. dimer of acrylic acid in the form of a liquid containing crude acrylic acid, served inside of the column 1 with a temperature of 90°in the amount of 1300 kg/h. In addition, downloadable fluid is not shown in the diagram of tank polymerization inhibitor injected liquid obtained by dissolving 8 wt.%. methanone and 1% wt. fenotiazina in acrylic acid, in the amount of 60 kg/hour.

The process is carried out at a pressure in the upper part of the column of 2.8 kPa, at a temperature in the lower part of the column 75°and with a reflux ratio of 1, and the temperature of the condensate in the tank for collecting phlegmy 21 is 27°With, and receive in the upper part of the column highly pure acrylic acid, purity is 99.8 per cent or more. The number obtained from the upper part of the column of acrylic acid is 97% of the amount loaded into the column 1 of the liquid.

A liquid prepared by dissolving 8% methanone in acrylic acid, serves in the number is 3.08 kg/h from another not shown in the diagram tank inhibitor of polymerization using a pipe 30 for supplying the polymerization inhibitor.

The internal diameter of the tank for collecting phlegmy 21 is 820 mm, its length is 3200 mm, and the inside of the tank in its lower part there is a bubbler 46 (length 2500 mm, bore diameter 2 mm, 25 hole is Tille), as shown in Fig. 1. Air as the oxygen-containing gas is served in the bubbler 46 in the amount of 1.5 nm3/hour.

A continuous process is carried out for 6 months. During the whole process ensures continuous operation of the pump 22, is attached to the tank for collecting phlegmy 21.

<Example 2>

The operation is performed in the same conditions as described in Example 1, except that the supply pipe instead of the bubbler 46 is supplied to the nozzle (1/8MJJRP015PTFE from company H. Ikeuchi & Co., Ltd.) in five positions, as shown in Fig. 2. A continuous process is carried out for 6 months. During the process ensures continuous operation of the pump 22.

<Example 3>

The operation is performed in the same conditions as described in Example 2, except that instead of injectors use cermets (FUJIPLATE from Fuji Filter MGF Co., Ltd.) with a pore size of 5 μm, as shown in Figure 3. A continuous process is carried out for 6 months. During the process ensures continuous operation of the pump 22.

<Comparative examples 1-3>

The flow of oxygen-containing gas in the tank for collecting phlegmy 21 in Examples 1-3 cease. 3 days after cessation of oxygen-containing gas pump 22 is stopped due to overload. Inspection of pump 22 confirms the formation of polymeric products which act between the shaft and mechanical seal.

<4>

The raw material for distillation serves in the amount of 1300 kg/h to a distillation column made of stainless steel (SUS 316) with an inner diameter of 1100 mm, length 20000 mm, which inside contains 8 m unordered nozzle (IMTP from Saint-Gobain NorPro) and 9 / tube sheet plates (plates with double thread), located in the lower part of the body of the column 1. Raw acrylic monomer as a raw material for distillation is a mixture containing 98.5% of wt. acrylic acid, and 0.3% wt. maleic acid, 0,276% wt. dimer of acrylic acid, 0.02% of wt. furfural and 0,004% wt. benzaldehyde.

Before applying the mixture to a distillation column in it add 1650 ppm of hydrazine monohydrate, 40 h/million dibutyldithiocarbamate copper, 40 ppm of copper acrylate and 300 ppm of hydroquinone by weight of the mixture. Used copper acrylate obtained by dissolution of the carbonate of the divalent copper acrylic acid, and the formation of compounds and mixing carried out for 30 min at a temperature of 20°C.

The process is carried out at a pressure in the upper part of the column of 10.1 kPa, at a temperature in the lower part of the column 95°and with a reflux ratio of 1, and the temperature of the condensate in the tank for collecting phlegmy 21 is 27°With, and receive in the upper part of the column highly pure acrylic acid, the purity of which 99.5% or more and which function is 1 ppm or less of furfural and benzaldehyde in relation to the weight of the product. The number obtained from the upper part of the column of acrylic acid is 95% of the amount of the mixture supplied to the column 1.

A reservoir for collecting phlegmy 21 and bubbler 46 are the same as in Example 1, and the air as the oxygen-containing gas is served in the bubbler 46 2 nm3/hour. In addition, the supply line of an inhibitor of polymerization of 30 continuously add metochion so that the concentration of metochion in liquid acrylic acid, present in the tank for collecting phlegmy 21, was in the range of from 180 to 220 h/million

A continuous process is carried out for 6 months. During the process ensures continuous operation of the pump 22.

<Example 5>

The operation is performed in the same conditions as described in Example 4, except that the supply pipe, instead of the bubbler, is supplied to the nozzles in five positions, as shown in figure 2. A continuous process is carried out for 6 months. During the process ensures continuous operation of the pump 22.

<Example 6>

The operation is performed in the same conditions as described in Example 5, except that instead of the injectors, use a metal with a pore size of 3 μm, as shown in Figure 3. A continuous process is carried out for 6 months. During the critical us the sa 22.

<Comparative examples 4-6>

The flow of oxygen-containing gas in the tank for collecting phlegmy 21 in Examples 4-6 stop. A few days after cessation of oxygen-containing gas pump 22 is stopped due to overload. Inspection of pump 22 confirms the formation of a polymer product between the shaft and mechanical seal.

<Example 7>

The process is carried out in the same conditions as described in Example 4, except that instead of hydrazine monohydrate, which is used in Example 4, the mixture was added 2200 ppm (relative to the weight of the mixture) n-dodecylmercaptan as a reagent for removing aldehydes, and in the distillation column Example 4 download liquid containing crude acrylic acid which is obtained by passing the mixture through a column of cation exchange resin based on sulfonic acid (DIAION PK-216H, a trademark of Mitsubishi Chemical Corporation).

A continuous process is carried out for 6 months. During the process ensures continuous operation of the pump 22.

Industrial applicability

The method of purification of (meth)acrylic acid of the present invention is able to prevent the formation of polymeric products obtained in the condensate (meth)acrylic acid of high purity and to prevent contamination of the production line, as well as the allows you to avoid abnormal operation of the apparatus of the synthesis or purification, caused by the formation of polymeric products, and thereby enables stable production of (meth)acrylic acid of high purity in a long time.

In addition, the present invention solves the problem of overloading of the pump, which is connected to the reservoir for collection of phlegmy distillation columns, due to the formation of polymeric products and allows you to avoid difficulties with extended operation for a long period of time in the case, when you get the (meth)acrylic acid with a purity of 90% or more by distillation of the crude (meth)acrylic acid obtained by catalytic oxidation in the gas phase; the present invention also enables the stable production of (meth)acrylic acid of high purity in a long time, even if in the future you will need to get even more pure product. Thus, the present invention has a high value to the industry.

1. The method of purification of (meth)acrylic acid, comprising the stage of:

distillation of the liquid containing the raw (meth)acrylic acid, which is an acrylic acid or methacrylic acid, in the presence of one or more polymerization inhibitors selected from the group consisting of a derivative of phenol, produced by the water fenotiazina, (meth)acrylate copper and dithiocarbamate copper, with the aim of obtaining condensate (meth)acrylic acid, (meth)acrylic acid with a purity of 90% or more;

add in the condensation polymerization inhibitor comprising a derivative of phenol; and

feeding oxygen-containing gas, which contains oxygen in the condensate (meth)acrylic acid in the tank for collecting phlegmy that collects condensate (meth)acrylic acid, where the oxygen-containing gas is fed to the condensate in the tank for collecting phlegmy using the device for injection into the liquid, in the form of bubbles, each of which has a small size, and a feed pipe for introducing an oxygen-containing gas in a device for injection into the liquid, and

the ratio (nm3/t) between the supply of oxygen in the oxygen-containing gas and the flow of condensate supplied to the reservoir for collection of phlegmy, 0°C, 1 ATM satisfies the relation shown in the following equation 0,004≤/≤1.0, where And denotes the flow About2(nm3/h)denotes the flow (t/h) condensate supplied to the reservoir for collection of phlegmy, and the symbol "h" in "nm3/h" indicates the value at normal conditions (0°C, 1 ATM: normal conditions).

2. The method of purification of (meth)acrylic acid according to claim 1, where the liquid containing the raw (meth)AK the sludge acid, get by way of gas-phase catalytic oxidation.

3. The method of purification of (meth)acrylic acid according to claim 1, where the liquid containing the raw (meth)acrylic acid during the distillation is subjected to distillation in a distillation column.

4. The method of purification of (meth)acrylic acid according to claim 1, where the condensate obtained at the stage of distillation, contains (meth)acrylic acid with a purity of 95% or more.

5. The method of purification of (meth)acrylic acid according to any one of claims 1 to 4, which further includes a step of adding a polymerization inhibitor in the condensate (meth)acrylic acid.

6. The method of purification of (meth)acrylic acid according to claim 5, where the polymerization inhibitor is one or more compounds selected from the group comprising (meth)acrylate, copper, dithiocarbamate copper and derived fenotiazina.

7. The method of purification of (meth)acrylic acid according to claim 6, where dithiocarbamate copper selected from the group including copper dimethyldithiocarbamate, copper diethyldithiocarbamate, dipropylthiocarbamate copper, dibutyldithiocarbamate copper, atlantajournal copper, tetramethylthiuram copper, pentametilenditiokarbamata copper, hexamethylenediisocyanate copper and occipitocervical copper.

8. The method of purification of (meth)acrylic acid according to claim 6, where (meth)acrylate copper is obtained by dissolving one or more compounds selected from the group VK is ycause the copper powder, the carbonate of the divalent copper, monovalent hydroxide copper hydroxide of divalent copper and copper acetate, (meth)acrylic acid.

9. The method of purification of (meth)acrylic acid according to any one of claims 1 to 4, where the liquid containing the raw (meth)acrylic acid, optionally includes a derivative of hydrazine.

10. The method of purification of (meth)acrylic acid according to claim 9, where the derivative of hydrazine selected from the group which includes hydrazine, hydrazinehydrate, phenylhydrazine, hydrazine sulfate and chloride hydrazine.

11. The method of purification of (meth)acrylic acid according to any one of claims 1 to 4, where the liquid containing the raw (meth)acrylic acid, optionally includes mercaptan.

12. The method of purification of (meth)acrylic acid according to claim 11, where the mercaptan selected from the group including n-butylmercaptan, n-artilleryman and n-dodecylmercaptan.



 

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EFFECT: improved economic characteristics of process due to reduced loss of acetic acid and additional recovery of acetic acid when performing hydrolysis of methyl acetate.

6 cl, 3 dwg, 6 tbl, 3 ex

The invention relates to an improved method of isolation and purification of adipic acid, used for the production of polyamide-6,6 or polyurethanes, which consists in treating the reaction mixture obtained by direct oxidation of cyclohexane to adipic acid by molecular oxygen in an organic solvent and in the presence of a catalyst, removing by-products from the reaction mixture and the adipic acid by crystallization, and before adipic acid from the reaction environment carry out consistently the following operations: the decantation of the two phases of the reaction medium with the formation of the upper organic the cyclohexane phase, containing mainly cyclohexane, and the lower phase, containing mainly the solvent, the resulting dicarboxylic acid, the catalyst and other reaction products and unreacted cyclohexane; distillation bottom phase to separate, on the one hand, distillate containing at least a part of the most volatile compounds, such as organic solvent, water and unreacted cyclohexane, cyclohexanone, cyclohexanol, complex cyclohexylamine esters and possibly lactones, and, with the pin acid from residue from distillation by means of crystallization and thus obtained crude adipic acid is subjected in aqueous solution purification by hydrogenation and/or oxidation with subsequent crystallization and recrystallization of the purified adipic acid in water

The invention relates to an improved method of processing the reaction mixture formed by the reaction of direct oxidation of hydrocarbons to carboxylic acids

The invention relates to the production of acetic acid

The invention relates to a method of reducing and/or removing permanganatometricly compounds, such as acetaldehyde, propionic acid and alkylidene impurities in the process of carbonylation of methanol

The invention relates to a method for producing high-purity acrylic acid (options) with a residual content of aldehydes less than 10 parts/million

The invention relates to the field of waste

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 lies in the following: concentrated solution of lithium salt is introduced into mixture of sodium salts of naphthenic acids, mixed and left for separation into layers and formation of viscous mass of lithium salt of naphthenic acid high-molecular fraction with molecular weight more than 200 in sediment, and in upper water layer - of low-molecular fraction of naphthenic acids lithium salt with molecular weight less than 200, with subsecutive separation.

EFFECT: separation of concentrated water solutions of naphthetic acids lithium salts according to their molecular weight.

2 cl, 2 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: organic chemistry.

SUBSTANCE: invention relates to method for purification of monochloroacetic acid from dichloroacetic acid impurities. Claimed method includes hydrogenolysis in presence of hydrogen in film regime at 135-145°C in cascade of sequentially bonded reactors with fixed bed of heterogeneous catalyst namely palladium on activated carbon. Preferably reactor cascade with intermediate cooling with cold flow of monochloroacetic acid as cooling agent is used.

EFFECT: simplified process; product of improved quality.

3 cl, 7 ex, 3 dwg

The invention relates to the production of acetic acid by carbonyliron of methanol with carbon monoxide, in particular to the purification method of the circulating flow boiling components at the stage of distillation of acetic acid

The invention relates to an improved method of reducing the content of 4-carboxybenzene in the production of terephthalic or 3-carboxymethylthio in the production of isophthalic acid, comprising: (a) dissolving crude terephthalic acid or crude isophthalic acid in a solvent at a temperature of from 50 to 250With obtaining a solution; (b) crystallization of the purified acid from this solution by reducing the temperature and/or pressure; (C) the Department specified crystallized terephthalic acid or isophthalic acid from the solution; (d) adding an oxidant to the reactor oxidation carboxyanhydride for oxidation specified filtered solution of stage (C), leading to the transformation of 4-carboxybenzene or 3-carboxymethylthio in terephthalic acid or isophthalic acid; (e) evaporating the solvent from this solution from step (d); (f) cooling the concentrated solution from step (e) for crystallization additional quantities of purified terephthalic acid or isophthalic acid and filtering the specified slurry and recycling the most part, the mother liquor from step (f) in the devices is
The invention relates to a new process for the preparation of fluorinated acids emulsifiers of waste water for the purpose of regeneration, namely, that first from waste water of polymerization of fluorinated monomers remove interfering components selected from finely dispersed solids and transferred to the solid component, and then connect the fluorinated acid emulsifiers on anion exchange resin and elute from it these fluorinated acid emulsifiers
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