Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/42—Separation; Purification; Stabilisation; Use of additives
  • C07C51/48—Separation; Purification; Stabilisation; Use of additives by liquid-liquid treatment
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C67/00—Preparation of carboxylic acid esters
  • C07C67/08—Preparation of carboxylic acid esters by reacting carboxylic acids or symmetrical anhydrides with the hydroxy or O-metal group of organic compounds
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C67/00—Preparation of carboxylic acid esters
  • C07C67/48—Separation; Purification; Stabilisation; Use of additives

Definitions

• the present invention relates to a method for producing acrylate mainly for the recovery and reuse of acrylic acid produced by reaction in the production of acrylate, preferably high-boiling acrylate, and a method for producing and using acrylic acid. Belongs to the technical field and the technical field using acrylic acid.
• An acrylate is often produced by an esterification reaction of acrylic acid and alcohol in the presence of an acid catalyst.
• the reaction solution is distilled and purified.
• the esterification reaction solution containing the reaction solvent is neutralized to remove the acid catalyst and unreacted acrylic acid, and the organic phase and the aqueous phase are separated into two layers. It is produced by separating the layers and further removing the reaction solvent in the organic layer.
• a method is generally used in which the raw alcohol is reacted as much as possible using an excess of acrylic acid so that no alcohol remains in the reaction solution. It has been adopted.
• excessive use of acrylic acid necessitates neutralization and water washing to remove unreacted acrylic acid, resulting in not only loss of acrylic acid but also high chemical oxygen demand (COD) values. Includes the problem of producing wastewater.
• Patent Documents 1 and 2 a method has been proposed in which an esterification reaction liquid is neutralized, an aqueous liquid containing acrylic acid or an alkali metal salt thereof is acidified, and acrylic acid is extracted and recovered with an organic solvent.
• Patent Documents 1 and 2 since these methods extract and recover with an organic solvent, equipment for performing extraction and equipment for recovering the organic solvent are required, and the acrylic acid concentration in the recovered liquid is as low as 30% by weight or less.
• the recovered acrylic acid it is necessary to purify it by distillation or the like.
• JP 2006-213647 A Japanese Patent Laid-Open No. 61-243046
• An object of the present invention is that an acrylic acid extraction step using an organic solvent is not required, the concentration of acrylic acid in the recovered liquid is high, and the method for producing acrylates excellent in acrylic acid recovery efficiency, and the recovery of acrylic acid Is to provide a method.
• An acrylate production method in which the following first to fifth steps are sequentially performed.
• First step A step of stirring and mixing acrylic acid and alcohol in the presence of an acid catalyst to obtain a reaction solution containing acrylate by esterification reaction.
• Second step An alkaline aqueous solution is added to the reaction solution obtained in the first step. After neutralization by addition, the organic phase and the aqueous phase are separated into two phases, the organic phase is separated, and the acrylate is recovered.
• Step 4 The liquid obtained in the third step is divided into two phases, a phase containing a large amount of acrylic acid and / or its alkali metal salt (upper layer) and a phase containing a large amount of alkali metal sulfate (lower layer).
• Step 5 of separating The liquid obtained in the fourth step Step of separating the phase (lower layer) containing a large amount of acid alkali metal salt and recovering the remaining acrylic acid and / or the phase (upper layer) containing a large amount of the alkali metal salt
• the following 3 ′ step to 5 ′ step are sequentially performed A method for recovering acrylic acid to be carried out.
• 3 'process It contains acrylic acid and / or its alkali metal salt, alkali metal sulfate, and water, pH is 4.0 or less, and the content rate of acrylic acid and / or its alkali metal salt is Step of preparing a liquid that is 18% by weight or more in terms of acrylic acid 4 ′ step:
• the liquid obtained in the 3 ′ step is a phase (upper layer) containing a large amount of acrylic acid and / or its alkali metal salt, and sulfuric acid.
• Step of separating into two phases of a phase (lower layer) rich in alkali metal salt 5 ′ step The phase (lower layer) rich in alkali metal sulfate of the liquid obtained in step 4 ′ was separated and remained A step of recovering a phase (upper layer) rich in acrylic acid and / or its alkali metal salt
• an extraction step of acrylic acid with an organic solvent is unnecessary, and acrylic acid can be easily recovered by a simple method of removing the lower layer liquid separated into two phases.
• the acrylic acid concentration could be increased, and an acrylate production method and an acrylic acid recovery method excellent in recovery efficiency could be provided.
• the recovered acrylic acid can be reused in the production of acrylates and polymers as it is or after purification.
• the present invention relates to a method for producing an acrylate characterized by sequentially performing the following first to fifth steps.
• First step A step of stirring and mixing acrylic acid and alcohol in the presence of an acid catalyst to obtain a reaction solution containing acrylate by esterification reaction.
• Second step An alkaline aqueous solution is added to the reaction solution obtained in the first step. After neutralization by addition, the organic phase and the aqueous phase are separated into two phases, the organic phase is separated, and the acrylate is recovered.
• Step 4 The liquid obtained in the third step is divided into two phases, a phase containing a large amount of acrylic acid and / or its alkali metal salt (upper layer) and a phase containing a large amount of alkali metal sulfate (lower layer).
• Step 5 of separating The liquid obtained in the fourth step A step of separating a phase (lower layer) containing a large amount of acid alkali metal salt and recovering a remaining phase (upper layer) containing a large amount of acrylic acid and / or its alkali metal salt.
• the present invention relates to a method for recovering acrylic acid, characterized in that the 5 ′ step is sequentially performed.
• 3 'process It contains acrylic acid and / or its alkali metal salt, alkali metal sulfate, and water, pH is 4.0 or less, and the content rate of acrylic acid and / or its alkali metal salt is Step of preparing a liquid that is 18% by weight or more in terms of acrylic acid 4 ′ step:
• the liquid obtained in the 3 ′ step is a phase (upper layer) containing a large amount of acrylic acid and / or its alkali metal salt, and sulfuric acid.
• Step of separating into two phases of a phase (lower layer) rich in alkali metal salt 5 ′ step The phase (lower layer) rich in alkali metal sulfate of the liquid obtained in step 4 ′ was separated and remained A step of recovering a phase (upper layer) rich in acrylic acid and / or its alkali metal salt
• Production method of acrylate According to the production method of acrylate of the present invention, it is possible to produce various acrylates, which can be preferably applied to the production of high-boiling acrylates, and the boiling point under a pressure of 13.3 kPa is particularly 100 ° C. It is preferably applicable to the production of acrylates.
• Examples of the acrylate having a boiling point of 100 ° C. or higher under a pressure of 13.3 kPa include: Acrylates of alkylene oxide adducts of phenols, such as acrylates of phenol alkylene oxide adducts, acrylates of nonylphenol alkylene oxide adducts and acrylates of p-cumylphenol alkylene oxide adducts; Acrylate of 2-ethylhexyl alcohol alkylene oxide adduct; Polycyclic alkyl acrylates such as acrylates of tricyclodecane dimethylol; Polycyclic alkyl diacrylates such as tricyclodecane dimethylol diacrylate; Mono- or diacrylates of alkylene glycols such as mono- or diacrylates of ethylene glycol, mono- or diacrylates of propylene glycol, mono- or diacrylates of pentanediol and mono- or diacrylates of hexanediol;
• acrylates those that are more suitable for the production of hydrophobic acrylates than hydrophilic acrylates such as mono- or diacrylates of alkylene glycol, in that the acrylate can be prevented from dissolving on the aqueous phase side in the first step described later. It is.
• the esterification reaction may be performed according to a conventional method, and examples thereof include a method of heating and stirring acrylic acid and a high-boiling alcohol in an organic solvent in the presence of an acid catalyst.
• Alkylene oxide adducts of phenols such as phenol alkylene oxide adducts, nonyl phenol alkylene oxide adducts and p-cumyl phenol alkylene oxide adducts; 2-ethylhexyl alcohol alkylene oxide adduct; Polycyclic alkyl alcohols such as tricyclodecane dimethylol; Polycyclic alkyl dialcohols such as tricyclodecane dimethylol; Alkylene glycols such as ethylene glycol, propylene glycol, pentanediol and hexanediol; Polyalkylene glycols such as diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol and polypropylene glycol; Glycerins such as glycerin and diglycerin; Alkyl
• alkylene oxide in the alkylene oxide adduct examples include ethylene oxide and propylene oxide. Further, the addition number of alkylene oxide is preferably 1 to 20. Among these alcohols, as described above, alcohols in which the resulting acrylate is hydrophobic are preferred.
• the proportion of acrylic acid used may be appropriately set according to the target acrylate, and is preferably 1.0 to 2.0 mol, more preferably 1.1 to 1 mol, based on 1 mol of all hydroxyl groups of the high boiling alcohol. .5 moles.
• the acid catalyst examples include mineral acids such as sulfuric acid, and sulfonic acids such as p-toluenesulfonic acid, methanesulfonic acid, and trifluoromethanesulfonic acid.
• the use ratio of the acid catalyst is preferably 0.1 to 10% by weight based on the weight of the reaction solution containing the organic solvent.
• the esterification reaction may be carried out according to a conventional method.
• the reaction temperature may be appropriately set according to the raw materials to be used and the purpose, but is preferably 65 to 140 ° C., more preferably 75 to 120 ° C. from the viewpoint of shortening the reaction time and preventing polymerization.
• the reaction temperature 65 ° C. or higher the esterification reaction can be carried out quickly and the yield can be prevented from decreasing.
• the reaction temperature 140 ° C. or lower the thermal polymerization of acrylic acid or the produced acrylate Can be prevented.
• the pressure in the reaction may be normal pressure or reduced pressure. As described later, for the purpose of preventing thermal polymerization of acrylic acid or the generated acrylate, it is preferable to carry out under reduced pressure.
• organic solvents include aromatic hydrocarbons such as toluene, benzene and xylene, aliphatic hydrocarbons such as hexane and heptane, and alicyclic hydrocarbons such as cyclohexane.
• the amount of the organic solvent used is preferably 10 to 75% by weight, more preferably 15 to 55% by weight, based on the total amount of the alcohol and acrylic acid.
• the esterification reaction is preferably performed at 75 to 120 ° C. for the purpose of preventing thermal polymerization of acrylic acid or the produced acrylate.
• the esterification reaction is preferably performed in the presence of oxygen.
• the polymerization inhibitor include organic compounds and metal salts.
• organic compounds examples include benzoquinone, hydroquinone, catechol, diphenylbenzoquinone, hydroquinone monomethyl ether, naphthoquinone, t-butylcatechol, t-butylphenol, dimethyl-t-butylphenol, t-butylcresol, dibutylhydroxytoluene and phenothiazine. It is done.
• the metal salt include metal copper compounds such as cupric chloride and copper sulfate, and metal iron compounds such as ferrous sulfate.
• the addition amount of the polymerization inhibitor is preferably 10 to 50,000 ppm by weight and more preferably 100 to 10,000 ppm by weight with respect to the amount of acrylic acid used as a raw material.
• the polymerization preventing effect can be made sufficient, and by making it 10,000 ppm or less, coloring can be prevented or the curability of the product can be prevented from being lowered.
• the degree of progress of the esterification reaction is monitored by monitoring the amount of water produced by the esterification reaction, that is, the amount of dehydration, analyzing the acid concentration in the reaction solution, and analyzing the composition of the product acrylate. Judgment is made by confirming the composition.
• reaction in the presence of oxygen there are a method of reacting in an atmosphere of an oxygen-containing gas or a reaction while introducing an oxygen-containing gas into a reaction solution.
• a typical oxygen-containing gas is air, but industrially, a gas having an oxygen concentration reduced to 3 to 15% by volume in view of the danger of flammable explosion is preferably used.
• the oxygen-containing gas can be prepared by mixing oxygen or air and an inert gas. Nitrogen or argon is commonly used as the inert gas.
• Second step In the second step, an aqueous alkali solution is added to the reaction solution obtained in the first step for neutralization, and then the organic phase is separated into two phases, an organic phase and an aqueous phase, and an acrylate is obtained. Is a step of recovering.
• an alkaline aqueous solution By adding an alkaline aqueous solution to the reaction liquid obtained in the first step, it is possible to separate and remove acids such as acrylic acid and an acid catalyst from the reaction liquid with an alkaline aqueous solution.
• alkali component examples include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkali metal salts such as sodium carbonate, and alkaline earth metals such as calcium hydroxide. It is done. Among these, alkali metal hydroxides are preferable because of high neutralization effect.
• the amount of the alkali component in the aqueous alkali solution is preferably 1 or more, and more preferably 1.0 to 1.6 times in terms of molar ratio to the acid content of the reaction solution. When the amount is within the above range, the acid content is sufficiently neutralized.
• the concentration of the aqueous alkaline solution is preferably 1 to 25% by weight, more preferably 3 to 25% by weight, and particularly preferably 10 to 25% by weight. When the concentration is 1% by weight or more, it is possible to prevent an increase in the amount of waste water after the neutralization treatment, and when it is 25% by weight or less, the acrylate can prevent polymerization.
• the neutralization treatment in the second step is performed by supplying the reaction solution and the alkaline aqueous solution to a tank apparatus and stirring them, or using a static mixer or the like.
• an organic solvent can be added to the reaction solution before neutralization.
• the reaction solution obtained in the first step is neutralized by adding an alkaline aqueous solution, and then separated into two phases, an organic phase and an aqueous phase.
• the neutralization treatment can be performed in a plurality of times.
• the reaction solution can be washed with water for various purposes.
• the copper polymerization inhibitor when used in the esterification reaction, the copper polymerization inhibitor can be efficiently removed, which is preferable.
• a method for the water washing treatment a conventional method may be followed. Specifically, a method of adding water to the reaction solution obtained by the esterification reaction, stirring and mixing, and the like may be mentioned. As water, it is preferable to use pure water.
• the organic phase and the aqueous phase are separated into two phases, the organic phase is separated, and the acrylate is recovered.
• the lower aqueous phase may be extracted.
• the extracted aqueous phase is subjected to a third step which will be described later.
• the organic solvent can be removed to make the acrylate of the final product, if necessary.
• the solvent removal treatment may be carried out in accordance with a conventional method, for example, a method in which the solvent removal tank is decompressed and the organic solvent is removed.
• the degree of vacuum in the solvent removal tank may be appropriately set according to the raw material to be used and the purpose, and is preferably 0.5 to 50 kPa, and a method of gradually increasing the degree of vacuum depending on the degree of solvent removal is preferable.
• this solvent removal treatment is performed under reduced pressure while supplying oxygen or adding a polymerization inhibitor and maintaining the temperature at, for example, 20 ° C. or more and 80 ° C. or less. Is preferred.
• the organic solvent is removed from the organic phase in the solvent removal process in the solvent removal tank, a filter aid is supplied to the solvent removal tank, and the vertical horizontal filter type filter connected to the solvent removal tank is used.
• the reaction product can also be filtered by depositing a filter aid.
• the organic layer can be washed with water before the solvent removal treatment as necessary.
• the third step fractionates the aqueous phase obtained in the second step [hereinafter referred to as the aqueous phase (2). ]
• a sulfuric acid aqueous solution having a sulfuric acid concentration of 70% by weight or more was added thereto, the pH was adjusted to 4.0 or lower, and the acrylic acid and / or its alkali metal salt content in the liquid was 18% in terms of acrylic acid. % Or more.
• the sulfuric acid concentration of the sulfuric acid aqueous solution used in the third step is 70% by weight or more. When less than 70% by weight is used, two-phase separation in the fourth step becomes difficult, and the recovery rate of acrylic acid (salt) decreases.
• the sulfuric acid concentration of the aqueous sulfuric acid solution is preferably 75% by weight or more, preferably 100% by weight or less, and more preferably 99% by weight or less.
• an aqueous sulfuric acid solution is added to the aqueous phase (2) to adjust the pH to 4.0 or less.
• the pH of the preferred aqueous phase is in the range of 0 to 4.0, more preferably in the range of 1 to 3.5.
• the amount of the sulfuric acid aqueous solution added to the aqueous phase (2) is arbitrary as long as the pH of the aqueous phase is 4.0 or less.
• the temperature is preferably 25 ° C. or more, more preferably 25 to 40 ° C., and particularly preferably 30 to 40 ° C. By setting this temperature to 25 ° C. or higher, it is possible to prevent the sulfate from being precipitated in the third step.
• acrylic acid and / or an alkali metal salt thereof in the liquid [hereinafter referred to as “acrylic acid (salt)”].
• acrylic acid (salt) Is 18% by weight or more and preferably 60% by weight or less in terms of acrylic acid.
• the content is preferably 20% by weight or more, particularly preferably 20 to 60% by weight. If this proportion is lower than 18% by weight, two-phase separation cannot be performed in the fourth step.
• Examples of the method for setting the content ratio of acrylic acid (salt) in the liquid to 18% by weight or more in terms of acrylic acid include a method of adjusting the concentration of the aqueous alkali solution used in the second step and the amount of the aqueous alkali solution used. .
• the content rate of acrylic acid (salt) in a liquid is less than 18 weight%, water is distilled off or acrylic acid (salt) is added, and the content rate of acrylic acid (salt) is the said. It can also be a percentage.
• the ratio of acrylic acid (salt) in the liquid can be measured by methods such as liquid chromatography, gas chromatography, and ion chromatography. In this case, a calibration curve is prepared in advance using acrylic acid (salt), and the ratio can be determined by correcting the measured value by the absolute calibration curve method. When measured as an acrylate, it is converted to acrylic acid by calculation.
• Patent Document 1 Japanese Patent Laid-Open No. 2006-213647
• Patent Document 2 Japanese Patent Laid-Open No. 61-243046
• the acrylic acid concentration in the aqueous phase described in Example 3 was 15.5 wt%, and none of them was separated into two phases.
• the inventors of the present invention have not disclosed or disclosed in the above-mentioned known literature at all by setting the acrylic acid (salt) concentration in the liquid to a specific value, which is not disclosed in the above-mentioned known literature. It has been found that two-phase separation can be achieved.
• the liquid obtained in the third step is separated into two phases: a phase containing a large amount of acrylic acid (salt) (upper layer) and a phase containing a large amount of alkali metal sulfate (lower layer). It is a process to do.
• the temperature is preferably 25 to 40 ° C, more preferably 30 to 40 ° C. By maintaining in this temperature range, precipitation of sulfate can be prevented.
• the method of separating into two phases of a phase (upper layer) rich in acrylic acid (salt) and a phase (lower layer) rich in alkali metal sulfate is not particularly limited, but the specific gravity difference Are preferably used, and examples thereof include a stationary separation method and a centrifugation method.
• the liquid obtained in the third step may be allowed to stand at the above-mentioned preferable temperature for a certain period of time.
• Fifth step is to separate a phase (lower layer) containing a large amount of alkali metal sulfate of the liquid obtained in the fourth step, and a remaining phase (upper layer) containing a large amount of acrylic acid (salt). It is a process to collect.
• phase By a 4th process, it is made to isolate
• the ratio of acrylic acid (salt) in the recovered phase varies depending on the raw materials and conditions used, but an aqueous solution containing 25 to 60% by weight of acrylic acid (salt) is preferably obtained.
• the recovered aqueous solution of acrylic acid (salt) varies depending on the processing conditions, but is obtained as an aqueous solution containing acrylic acid as a main component and slightly containing an alkali metal salt of acrylic acid.
• the recovered aqueous solution of acrylic acid (salt) can be used as it is, or it can be purified and used, and acrylic acid can be separated and used.
• the recovered aqueous solution of acrylic acid (salt) can be suitably used for the production of polyacrylic acid or polyacrylate by polymerizing as it is without purification depending on the intended use.
• the obtained polyacrylic acid and polyacrylic acid salt (preferably sodium salt) can be suitably used for applications such as a dispersant, a thickener and a flocculant.
• the acrylic acid (salt) aqueous solution can be purified prior to the polymerization, and the purified acrylic acid (salt) aqueous solution can be used for the polymerization.
• acrylic acid When separating and using acrylic acid from the recovered aqueous solution of acrylic acid (salt), an organic solvent such as toluene is added to the recovered aqueous solution of acrylic acid (salt) and heated to distill off water azeotropically. A method is mentioned.
• the obtained acrylic acid can be used as a raw material for producing polymers and acrylates. It can also be used as a raw material acrylic acid in the first step.
• the treatment method for the phase containing a large amount of alkali metal sulfate extracted from the treatment tank as the lower layer is not particularly limited, but can be subjected to combustion treatment as it is.
• the solution can be cooled to separate the alkali metal sulfate as crystals. It is also possible to recover the aqueous solution of acrylic acid (salt) by distilling off the water and then separating the precipitated sulfate.
• Acrylic acid recovery method The acrylic acid recovery method of the present invention is characterized by sequentially performing the following third to fifth steps.
• 3 'process It contains acrylic acid and / or its alkali metal salt, alkali metal sulfate, and water, pH is 4.0 or less, and the content rate of acrylic acid and / or its alkali metal salt is Step of preparing a liquid that is 18% by weight or more in terms of acrylic acid 4 ′ step:
• the liquid obtained in the 3 ′ step is a phase (upper layer) containing a large amount of acrylic acid and / or its alkali metal salt, and sulfuric acid.
• Step of separating into two phases of a phase (lower layer) rich in alkali metal salt 5 ′ step The phase (lower layer) rich in alkali metal sulfate of the liquid obtained in step 4 ′ was separated and remained A step of recovering a phase (upper layer) rich in acrylic acid and / or its alkali metal salt
• Step 3 ′ contains acrylic acid and / or its alkali metal salt, alkali metal sulfate salt, and water, has a pH of 4.0 or less, and acrylic acid and / or its This is a step of preparing a liquid having an alkali metal salt content of 18% by weight or more in terms of acrylic acid.
• the pH of the liquid obtained in the third 3 ′ step is in the range of 4.0 or less, preferably in the range of 0 to 4.0, and more preferably in the range of 1 to 3.5.
• the content ratio of acrylic acid and / or its alkali metal salt in the liquid obtained in the third step is 18% by weight or more and preferably 60% by weight or less in terms of acrylic acid.
• the content is preferably 20% by weight or more, particularly preferably 20 to 60% by weight. If the content is less than 18% by weight, two-phase separation cannot be performed in the 4 ′ step.
• the alkali metal salt of acrylic acid and the alkali metal sulfate alkali metal salt are not particularly limited, but sodium salt and potassium salt are preferably mentioned, and the sodium salt is More preferably.
• the liquid obtained by a 3 'process is a liquid obtained through the 3rd process from the 1st process in the manufacturing method of the acrylate of the said invention.
• the temperature of the liquid in the 3 ′ step is preferably 25 ° C. or higher, more preferably 25 to 40 ° C., and particularly preferably 30 to 40 ° C. By setting the temperature of the liquid to 25 ° C. or higher, it is possible to prevent the sulfate from being precipitated in the third ′ step.
• Step 4 'Step 4' step is a step in which the liquid obtained in step 3 'is a phase (upper layer) containing a large amount of acrylic acid and / or an alkali metal salt thereof and a phase containing a large amount of an alkali metal sulfate ( It is a step of separating into two phases of the lower layer.
• 4th process is synonymous with 4th process except using the liquid obtained at 3 'process instead of the liquid obtained at 3rd process, and its preferable aspect is also the same.
• Step 5 'Step 5' step is to separate a phase (lower layer) containing a large amount of alkali metal sulfate in the liquid obtained in step 4 ', and to leave the remaining acrylic acid and / or alkali metal salt thereof.
• This is a step of recovering a phase (upper layer) containing a large amount.
• 5th process is synonymous with 5th process except using the liquid obtained at 4 'process instead of the liquid obtained at 4th process, and its preferable aspect is also the same.
• the acrylic acid (salt) aqueous solution recovered by the acrylic acid recovery method of the present invention varies depending on the processing conditions, but is obtained as an aqueous solution containing acrylic acid as a main component and slightly containing an alkali metal salt of acrylic acid.
• the recovered aqueous solution of acrylic acid (salt) can be used as it is, or it can be purified and used, and acrylic acid can be separated and used.
• acrylic acid and / or an alkali metal salt thereof may be isolated and / or purified from an aqueous solution of acrylic acid (salt) recovered by the acrylic acid recovery method of the present invention by a known method.
• the recovered aqueous solution of acrylic acid (salt) is polymerized as it is without purification depending on the intended use, so that polyacrylic acid or polyacrylic acid can be obtained. It can be suitably used for the production of acrylates.
• % means% by weight.
• Example 1 3,000 g of acrylic acid, 1,470 g of dipentaerythritol (hereinafter referred to as “DPET”), 70 g of 78% sulfuric acid, 10 g of hydroquinone (hereinafter referred to as “HQ”) and 2,450 g of toluene were charged into a 10 L reaction kettle. It heated in the oil bath set to 100 degreeC under the pressure of 53 kPa, and it was made to react for 10 hours, removing condensed water as azeotropic water with toluene. The reaction liquid weight at this time was 6,250 g. After completion of the reaction, 3,500 g of toluene was added.
• DPET dipentaerythritol
• HQ hydroquinone
• the upper layer (organic phase) was further added with 1,360 g of a 20% aqueous sodium hydroxide solution, stirred, allowed to stand, and separated into an upper layer (organic phase) and a lower layer (aqueous phase).
• 400 g of pure water was added and stirred, then allowed to stand, and separated into an upper layer (organic phase) and a lower layer (aqueous phase) of 8,660 g.
• MQ hydroquinone monomethyl ether
• Example 2 To 300 g of the neutralized wastewater obtained in Example 1, 78% sulfuric acid was gradually added until the pH reached 3. The temperature of the liquid at the time of adding sulfuric acid was maintained at 25-30 ° C. The added 78% sulfuric acid was 59.0 g. Next, the solution was kept at a temperature of 30 to 35 ° C., allowed to stand, and separated into an upper layer (acrylic acid aqueous solution layer) and a lower layer (sodium sulfate aqueous solution layer). The liquid separated into two phases was transferred to a separating funnel, and the lower layer (sodium sulfate aqueous solution layer) was extracted. The obtained upper acrylic acid aqueous solution layer was 151.8 g, the acrylic acid concentration was 37.4%, and 76.7% acrylic acid was recovered with respect to the acrylic acid contained in the neutralized wastewater. did it.
• Example 3 To 300 g of the neutralized wastewater obtained in Example 1, 98% sulfuric acid was gradually added until pH 2 was reached. The temperature of the liquid at the time of adding sulfuric acid was maintained at 25-30 ° C. The added 98% sulfuric acid was 52.1 g. Next, the solution was kept at a temperature of 30 to 35 ° C., allowed to stand, and separated into an upper layer (acrylic acid aqueous solution layer) and a lower layer (sodium sulfate aqueous solution layer). The liquid separated into two phases was transferred to a separating funnel, and the lower layer (sodium sulfate aqueous solution layer) was extracted. The obtained upper acrylic acid aqueous solution layer was 128.4 g, the acrylic acid concentration was 44.6%, and 77.4% of acrylic acid was recovered with respect to the acrylic acid contained in the neutralized wastewater. It was.
• Example 2 (Comparative Example 2) The supplementary examination of Example 1 in patent document 1 was implemented. That is, 2,000 g of acrylic acid, 1,200 g of DPET, 50 g of 78% sulfuric acid, 10 g of HQ, and 2,450 g of toluene were charged into a 10 L flask, heated in an oil bath set at 120 ° C. under a pressure of 60 kPa, and condensed water was added to toluene. The mixture was reacted for 10 hours while removing as azeotropic water. The reaction liquid weight at this time was 6,900 g.
• Example 4 3,000 g of acrylic acid, 1,600 g of pentaerythritol, 70 g of 78% sulfuric acid, MQ 7 g, and 2,000 g of toluene are charged into a 10 L reaction kettle, heated in an oil bath set at 100 ° C. under a pressure of 50 kPa, and condensed water is added. The reaction was allowed to proceed for 6 hours while removing. The reaction solution weight at this time was 6,100 g. After completion of the reaction, 3,500 g of toluene was added.
• the reaction kettle was charged with 40 g of ion exchange water, heated to 80 ° C. with nitrogen sealing, and 1 g of 10% aqueous sodium persulfate solution was added. Subsequently, a monomer solution obtained by dissolving 5 g of sodium hypophosphite in 210 g of the acrylic acid aqueous solution recovered in Example 2 and 10 g of a 10% sodium persulfate aqueous solution were reacted from separate injection ports while maintaining a polymerization temperature of 80 ° C. The solution was continuously added dropwise to the vessel for 4 hours to obtain a polyacrylic acid aqueous solution.
• the acrylate production method of the present invention can be used for the production of acrylates, more preferably for the production of high-boiling acrylates.
• the separated and recovered acrylic acid can be used for the production of acrylates and polymers. Can be reused.
• the acrylic acid separated and recovered by the acrylic acid recovery method of the present invention can be reused in the production of acrylates and polymers.

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