JP2008074795A - Method for production of hydroxyalkyl acrylate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydroxyacrylate production method by which the polymerization of produced hydroxyacrylate is prevented and the recycling efficiency of a catalyst used for reaction is enhanced. <P>SOLUTION: The production method for hydroxyalkyl acrylate includes the step of reacting acrylic acid with an alkylene oxide. In this case, the following conditions (1) and/or (2) are satisfied: (1) the total amount of furfural and benzaldehyde included in acrylic acid is ≥0.1 ppm but ≤300 ppm based on acrylic acid; and (2) β-acryloxypropionic acid included in acrylic acid is ≥0.005 wt.% but ≤1 wt.% based on acrylic acid. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a hydroxyalkyl acrylate by reacting acrylic acid with an alkylene oxide. More specifically, by regulating the amount of the specific component contained in the acrylic acid used as a raw material, polymerization of hydroxyl acrylate produced is prevented, and the recycling efficiency of the catalyst used in the above reaction is reduced. It relates to a process for the production of enhanced hydroxyl acrylate.

  In recent years, acrylates have been widely synthesized. Since various useful synthetic resins can be produced by polymerizing acrylates or copolymerizing with other monomers, acrylates are very useful compounds.

  Since acrylates themselves are easily polymerized, there arises a problem that a polymer is formed by an undesired polymerization reaction. As a result, there is a problem that the polymer is clogged in the piping of the manufacturing equipment, and the manufacturing equipment cannot be operated for a long time, or the manufacturing equipment fails. As a method for solving the above-mentioned problems due to polymerization, a method of producing acrylates while preventing polymerization of acrylates using a polymerization inhibitor is known (see, for example, Patent Documents 2, 3 and 4).

  By the way, when a hydroxyalkyl acrylate is produced by reacting acrylic acid with an alkylene oxide, a catalyst is usually used. For example, a homogeneous catalyst such as a chromium compound or an iron compound is preferable as the catalyst. It is considered to be. In recent years, as regulations on wastewater and exhaust gas have become stricter from the environmental and health aspects, disposal of catalysts has been regarded as a serious problem because of its hazards. Therefore, it is desired to reduce the amount of catalyst used as much as possible. Therefore, it is also conceivable to recover and reuse only the catalyst directly from the reaction solution, or to recover and reuse the catalyst by adsorbing it to the resin, but in any case, the cost is high and the economy is inferior. However, there are various problems such that the recovery rate and capture rate are not sufficient, and in the latter case, it is difficult to reuse only the catalyst. In view of such circumstances, the present inventors have developed a novel method for producing a hydroxyalkyl acrylate that can reuse a catalyst (see Patent Document 1).

Patent Documents 5 to 7 disclose by-products generated in the production process of acrylic acid and the influence of the by-products. However, Patent Documents 5 to 7 are documents relating to esterification reaction of acrylic acid and alcohol, and are clearly different from the present invention relating to the production of hydroxyalkyl acrylate by reaction of acrylic acid and alkylene oxide. Moreover, the said patent documents 5-7 do not describe at all that the superposition | polymerization at the time of manufacture of the hydroxyl acrylate manufactured is prevented and the reuse efficiency of the catalyst used in the manufacturing process is improved.
JP 2004-75559 A (published on March 11, 2004) JP 2003-267929 A (published on September 25, 2003) Japanese Patent Publication No.58-46496 (published on April 13, 1981) Japanese Patent Laid-Open No. 5-194346 (published on August 3, 1993) Japanese Patent Laid-Open No. 9-227445 (published on September 2, 1997) JP 2003-171347 A (published June 20, 2003) JP 2005-289844 A (published October 20, 2005)

  However, the method of preventing polymerization during the production of acrylates using the above polymerization inhibitor may not sufficiently prevent polymerization of acrylates. In addition, since the polymerization inhibitor becomes an impurity, the quality of the acrylates produced may be adversely affected.

  On the other hand, in the method of recycling the catalyst, there is a problem that the catalytic activity of the recovered catalyst is lowered, and it may be difficult to efficiently reuse the catalyst. In addition, although various causes can be considered about the cause of the activity fall of the said catalyst, it is not elucidated at this time.

  The present invention has been made in view of the above-described problems of the prior art, and its purpose is to prevent polymerization during the production of the hydroxyl acrylate to be produced, and to improve the recycling efficiency of the catalyst used in the reaction. It is to provide a process for producing an enhanced hydroxyl acrylate.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that acrylics having a specific component (furfural, benzaldehyde, β-acryloxypropionic acid, maleic anhydride, and maleic acid) in a predetermined concentration range. By using acid as a raw material,
(a) can effectively prevent polymerization of hydroxyl acrylate in the production process;
(b) A reduction in the catalytic activity of the catalyst to be reused is suppressed, and the catalyst recycling efficiency can be increased.
Has been discovered for the first time, and the present invention has been completed.

That is, the method for producing hydroxyl acrylate according to the present invention includes a step of reacting acrylic acid and alkylene oxide in order to solve the above-mentioned problem. In the method for producing hydroxyalkyl acrylate, the following (1) and / or It is characterized by satisfying the condition (2).
(1) The total amount of furfural and benzaldehyde contained in the acrylic acid is 0.1 to 300 ppm by weight with respect to acrylic acid.
(2) β-acryloxypropionic acid contained in the acrylic acid is 0.005 wt% or more and 1 wt% or less with respect to acrylic acid.

  In the method for producing hydroxyl acrylate according to the present invention, the total acrylic acid content of maleic anhydride and maleic acid is 0.1 ppm by weight or more and 1,000 ppm by weight or less based on acrylic acid. Is preferred.

  According to the said structure, there exists the effect of said (a) and (b). The details of the mechanism that can provide the above effect are not known at this time. However, when the production method of hydroxyl acrylate according to the present invention was carried out, the amount of decrease in the polymerization inhibitor (hydroquinone monomethyl ether) used in the production process was smaller than that of the conventional production method. The inventors presume that a decrease in the amount of the polymerization inhibitor in the production process may be a cause for obtaining the effect (a). The present inventors speculate that the decrease in aldehydes particularly contributes to the decrease in polymerization inhibitors. Also, when reusing the catalyst in the hydroxyl acrylate production method, add fresh catalyst and raw materials (acrylic acid, alkylene oxide) to the residue obtained by distilling off the target product, hydroxyl acrylate, from the final reaction solution and react again. However, if the residue contains β-acryloxypropionic acid, maleic anhydride and maleic acid at a high concentration, the activity of the catalyst is remarkably lowered. Therefore, according to the production method of the present invention, The inventors presume that the effect of the above (b) may be obtained because the stability of the catalytic activity is improved.

  Further, the method for producing hydroxyl acrylate according to the present invention may be a method characterized by reacting acrylic acid and alkylene oxide in the presence of a catalyst. According to the method for producing a hydroxyalkyl acrylate of the present invention, the effect (b) can be obtained. Therefore, it is particularly effective in the production method of hydroxyalkyl acrylate using a catalyst.

  Further, the method for producing hydroxyl acrylate according to the present invention is a method characterized in that the catalyst used at least once in the production of hydroxyl alkyl acrylate is used for the reaction between acrylic acid and alkylene oxide. Good. According to the method for producing a hydroxyalkyl acrylate of the present invention, the effect (b) can be obtained. Therefore, it is particularly effective in a method for producing a hydroxyalkyl acrylate that reuses a catalyst.

  Moreover, the method for producing hydroxyl acrylate according to the present invention is a method characterized by using a residual liquid obtained by recovering hydroxyalkyl acrylate from a reaction liquid of acrylic acid and alkylene oxide for the reaction of acrylic acid and alkylene oxide. There may be. Further, the method for producing hydroxyl acrylate according to the present invention may be a method characterized in that a catalyst solution obtained by mixing the above-mentioned residue solution and a fresh catalyst is used for the reaction between acrylic acid and alkylene oxide. Good. According to the method for producing a hydroxyalkyl acrylate of the present invention, the effect (b) can be obtained. Therefore, it is particularly effective in a method for producing a hydroxyalkyl acrylate that reuses a catalyst.

  Moreover, the method for producing hydroxyl acrylate according to the present invention may be a method characterized in that the acrylic acid is acrylic acid obtained by a gas phase catalytic oxidation reaction of propylene.

  As described above, the method for producing a hydroxyalkyl acrylate according to the present invention has the effect (a). Therefore, according to the method for producing a hydroxyalkyl acrylate according to the present invention, it is possible to enjoy the advantage that the hydroxyalkyl acrylate can be efficiently produced without blockage of piping in the production facility.

  The method for producing a hydroxyalkyl acrylate according to the present invention has the effect (b). Therefore, according to the method for producing a hydroxyalkyl acrylate according to the present invention, not only the cost advantage that the production cost of the hydroxyalkyl acrylate can be reduced, but also the environment in which the amount of discarded catalyst can be reduced. You can also enjoy the benefits in terms of surface.

  The embodiment of the present invention will be described as follows. Note that the present invention is not limited to this.

The production method of hydroxyalkyl acrylate according to the present invention (hereinafter referred to as “the production method of the present invention”) includes a step of reacting acrylic acid and alkylene oxide (hereinafter referred to as “reaction step”) as described above. And, it is characterized by satisfying the following conditions (1) and / or (2).
(1) The total amount of furfural and benzaldehyde contained in the acrylic acid is 0.1 to 300 ppm by weight with respect to acrylic acid.
(2) β-acryloxypropionic acid contained in the acrylic acid is 0.005 wt% or more and 1 wt% or less with respect to acrylic acid.

  In the production method of the present invention, it is preferable that the acrylic acid has a total content of maleic anhydride and maleic acid of 0.1 to 1,000 ppm by weight with respect to acrylic acid.

The present inventors use such acrylic acid as a raw material,
(a) can effectively prevent polymerization of hydroxyl acrylate in the production process;
(b) A reduction in the catalytic activity of the catalyst to be reused is suppressed, and the catalyst recycling efficiency can be increased.
Has been discovered for the first time, and the present invention has been completed. The technical idea of prescribing the content of a specific component mixed in acrylic acid in the method for producing hydroxyl acrylate has not been known so far and has been found for the first time by the present inventors. In addition, in order to obtain acrylic acid with a specified content of the specific component, a process such as distillation is separately required, which may lead to a decrease in production efficiency and an increase in production cost. It is not usually considered to use the acrylic acid in the production method. The inventors of the present invention have solved the problems that have not been solved so far by adopting such technical ideas that are not usually adopted by those skilled in the art. In particular, it has not been known at all that the above-mentioned effect (b) can be enjoyed by using acrylic acid having a specific component content as a raw material as described above. Not what you get. Therefore, it can be said that the above (b) is a particularly remarkable effect in the present invention.

  The production method of the present invention is effective for achieving the effect (a) even when a catalyst is not used in the reaction step, but when the catalyst is used in the reaction step, the above (b) It can be said that it is more preferable in order to achieve the effect of). In particular, an embodiment of reusing (reusing) the catalyst: specifically, a method characterized in that the catalyst used at least once in the production of hydroxylalkyl acrylate is used for the reaction of acrylic acid and alkylene oxide; More specifically, the production method of the present invention is preferable in an embodiment including a step of adding acrylic acid and alkylene oxide to the residue obtained by distilling off hydroxyalkyl acrylate from the reaction solution of acrylic acid and alkylene oxide. Hereinafter, although the manufacturing method of this invention is demonstrated using the aspect which uses a catalyst for a reaction process and reuses a catalyst, this invention is not limited to this.

<Acrylic acid applied to the production method of the present invention>
The furfural and benzaldehyde content in acrylic acid that can be applied to the production method of the present invention is preferably 0.1 to 300 ppm by weight, more preferably 0.1 to 300 ppm by weight based on acrylic acid. 100 weight ppm or less is more preferable, and 0.1 weight ppm or more and 30 weight ppm or less is the most preferable. When the content of furfural and benzaldehyde in acrylic acid satisfies the above preferable conditions, the effects (a) and (b) can be easily obtained. In particular, when the content of furfural and benzaldehyde in acrylic acid satisfies the above preferable conditions, the amount of decrease in the polymerization inhibitor (hydroquinone monomethyl ether) in the production process of hydroxyl acrylate is reduced compared to the conventional production method. The effect (a) can be easily obtained.

  The content of β-acryloxypropionic acid in acrylic acid that can be applied to the production method of the present invention is preferably 0.005 wt% or more and 1 wt% or less, and 0.005 wt% or more and 0.5 wt% or less. Is more preferable, and 0.005 wt% or more and 0.2 wt% or less is most preferable.

  The total content of maleic anhydride and maleic acid in acrylic acid that can be applied to the production method of the present invention is preferably from 0.1 ppm by weight to 1,000 ppm by weight based on acrylic acid. 0.1 wt ppm or more and 500 wt ppm or less is more preferable, and 0.1 wt ppm or more and 100 wt ppm or less is most preferable. When the contents of β-acryloxypropionic acid, maleic anhydride and maleic acid in acrylic acid satisfy the above preferable conditions, the effects (a) and (b) can be further obtained. In particular, when the contents of β-acryloxypropionic acid, maleic anhydride and maleic acid satisfy the above preferable conditions, it is possible to suppress a decrease in the activity of the catalyst, and the production method according to the present invention stabilizes the catalytic activity. Therefore, the effect (b) can be easily obtained.

  The method for obtaining acrylic acid that can be preferably applied to the production method of the present invention is not particularly limited, and may be obtained by producing acrylic acid that satisfies the preferred conditions. It may be obtained by purifying unsatisfactory acrylic acid. The acrylic acid used as the ester raw material is generally acrylic acid (crude acrylic acid) that does not satisfy the above preferred conditions due to cost problems.

  Moreover, as a manufacturing method of acrylic acid which satisfies the said preferable conditions, the method of manufacturing acrylic acid by the vapor phase catalytic oxidation reaction (gas phase catalytic oxidation method) of a well-known propylene, for example and the method of refine | purifying the said acrylic acid are mentioned. A method for producing acrylic acid by propylene vapor-phase catalytic oxidation is described in, for example, “Acrylic acid and its polymer [I], author Eizo Omori, publisher Shoshodo, date of issue December 30, 1978”. It can be done accordingly. More specifically, it is as follows. In the catalytic gas phase oxidation reaction using propylene as a raw material, the reaction is usually carried out in two stages using water vapor as a diluent. At this time, two types of catalytic gas phase oxidation catalysts are used. The first stage catalyst can mainly generate acrolein by gas phase oxidation of a raw material gas containing propylene. The second-stage catalyst can mainly generate acrylic acid by vapor-phase oxidizing a source gas containing acrolein. As the first stage catalyst, for example, a composite oxide containing iron, molybdenum and bismuth can be used. As the second stage catalyst, for example, a catalyst containing vanadium as an essential component can be used.

  In order to recover the acrylic acid produced by the above method from the product gas, the acrylic acid-containing gas (product gas) may be brought into contact with water to collect the acrylic acid as an aqueous acrylic acid solution. There are several methods for separating water from this aqueous acrylic acid solution. Typical methods include, for example, extraction of acrylic acid from water using an appropriate extraction solvent, and then acrylic acid and the extraction solvent. And a method of separating them by distillation. Another example includes a method of separating water and the azeotropic agent from acrylic acid by azeotropic distillation of the aqueous acrylic acid solution using an azeotropic agent with water. At this time, water and acetic acid can be simultaneously separated by adding an azeotropic agent that azeotropes with acetic acid, which is an impurity having a lower boiling point than acrylic acid. On the other hand, when only water is separated and acetic acid is not separated at the same time, the low boiling point impurities can be substantially removed by subjecting to a distillation step in which acetic acid is a main component of low boiling point impurities.

  In addition, various methods are exemplified as a method for purifying acrylic acid produced by the above production method to obtain acrylic acid satisfying the above preferable conditions. Examples thereof include a method of purifying acrylic acid using operations such as crystallization, distillation, and evaporation, and a method of performing an aldehyde removal reaction using amines and hydrazines. In particular, it can be said that it is preferable in terms of economy to employ a one-stage flash distillation or a very simple distillation method having a low number of theoretical plates and a low reflux ratio as a purification method of acrylic acid. However, even if acrylic acid is stored in a normal storage state, the content of β-acryloxypropionic acid increases with time. Therefore, it can be said that it is preferable to use the acrylic acid as soon as possible after obtaining acrylic acid satisfying the above preferable conditions. Acrylic acid is usually stored in a tank equipped with cold insulation equipment, and suppresses an increase in impurities such as β-acryloxypropionic acid. Even if acrylic acid does not satisfy the above preferred conditions due to long-term storage or the like, acrylic acid may be purified again by distillation or the like so as to satisfy the preferred conditions.

  The content of furfural, benzaldehyde, β-acryloxypropionic acid, maleic anhydride, and maleic acid in acrylic acid can be analyzed using known methods such as HPLC (high performance liquid chromatography) and GC (gas chromatography). Good. More specifically, for analysis of furfural and β-acryloxypropionic acid in acrylic acid, for example, acrylic acid is appropriately diluted with pure water, and TSK-GEL ODS80Ts (manufactured by Tosoh Corporation) is used as a column. It can be carried out by high performance liquid chromatography analysis using a solution in which the volume ratio of 0.1% by weight phosphoric acid aqueous solution and acetonitrile is 90:10 as the eluent. For analysis of benzaldehyde and maleic acid in acrylic acid, for example, acrylic acid is appropriately diluted with pure water, Inertsil (registered trademark) ODS-3 (manufactured by GL Science Co., Ltd.) is used as a column, and eluent is 0. It can be performed by high performance liquid chromatography analysis using a solution having a volume ratio of 1% by weight phosphoric acid aqueous solution to acetonitrile of 60:40. Maleic anhydride can be analyzed as maleic acid by hydration with water. Analytical conditions such as HPLC are not particularly limited, and may be adopted after considering appropriate optimum conditions according to the analysis target, the column to be used, and the like.

<Other conditions in the production method of the present invention>
As the conditions other than acrylic acid in the production method of the present invention, known steps and conditions in the production method of hydroxyalkyl acrylate including the step of reacting acrylic acid and alkylene oxide can be appropriately applied. Other conditions that can be suitably applied to the production method of the present invention are shown below.

(1. alkylene oxide)
Here, the alkylene oxide that can be used in the production method of the present invention is not limited. For example, an alkylene oxide having 2 to 6 carbon atoms is preferable, and an alkylene oxide having 2 to 4 carbon atoms is more preferable. More specifically, ethylene oxide, propylene oxide, butylene oxide and the like can be mentioned. Among these, ethylene oxide and propylene oxide are particularly preferable because of their high versatility.

  In the production method of the present invention, the quantity relationship between the total supply amount of acrylic acid and the total supply amount of alkylene oxide in the reaction of acrylic acid and alkylene oxide is not limited. Is preferably 1 mol or more, more preferably 1.0 to 10 mol, still more preferably 1.0 to 5.0 mol, particularly preferably 1.0 to 3.0 mol, and most preferably 1.0. -2.0 mol. In the above quantitative relationship, if the alkylene oxide is less than 1.0 mole relative to 1 mole of acrylic acid, the reaction may not easily proceed, the reaction conversion rate may decrease, and the by-product may increase. On the other hand, if there is too much alkylene oxide in the above quantity relationship, especially if it exceeds 10 moles with respect to 1 mole of acrylic acid, a recovery step of the alkylene oxide is required, which may cause economic disadvantages.

(2. Catalyst)
Examples of the catalyst that can be used in the production method of the present invention include all homogeneous catalysts that are soluble in a reaction solution containing acrylic acid and alkylene oxide, and are not limited. Specifically, chromium (Cr ) Compound, iron (Fe) compound, yttrium (Y) compound, lanthanum (La) compound, cerium (Ce) compound, tungsten (W) compound, zirconium (Zr) compound, titanium (Ti) compound, vanadium (V) compound Preferred is a homogeneous catalyst that contains at least one selected from the group consisting of a phosphorus (P) compound, an aluminum (Al) compound, and a molybdenum (Mo) compound and is soluble in the reaction solution. Among these, a homogeneous catalyst that contains a chromium (Cr) compound and / or an iron (Fe) compound and is soluble in the reaction solution is more preferable, and a homogeneous catalyst that contains a chromium (Cr) compound and is soluble in the reaction solution. More preferred is a homogeneous catalyst made of a chromium (Cr) compound and soluble in the reaction solution. When a homogeneous catalyst that contains a chromium (Cr) compound and is soluble in the reaction solution is used as the catalyst, it can be said that the effects of the present invention are remarkably obtained, which is preferable.

  The chromium (Cr) compound is not limited and includes a compound having a chromium (Cr) atom in the molecule and soluble in the reaction solution. Specific examples include chromium chloride, acetylacetone chromium, chromium formate, chromium acetate, chromium octanoate, chromium isooctanoate, chromium acrylate, chromium methacrylate, sodium dichromate, and chromium dibutyldithiocarbamate.

  Further, the iron (Fe) compound is not limited, and examples thereof include a compound having an iron (Fe) atom in the molecule and soluble in the reaction solution. Specific examples include iron powder, iron chloride, iron formate, iron acetate, iron acrylate, and iron methacrylate.

  The yttrium (Y) compound is not limited, and examples thereof include compounds having an yttrium (Y) atom in the molecule and soluble in the reaction solution. Specific examples include yttrium acetylacetone, yttrium chloride, yttrium acetate, yttrium nitrate, yttrium sulfate, yttrium acrylate, and yttrium methacrylate.

  The lanthanum (La) compound is not limited, and examples include compounds having a lanthanum (La) atom in the molecule and soluble in the reaction solution. Specific examples include lanthanum acetylacetone, lanthanum chloride, lanthanum acetate, lanthanum nitrate, lanthanum sulfate, lanthanum acrylate, and lanthanum methacrylate.

  The cerium (Ce) compound is not limited, and examples thereof include a compound having a cerium (Ce) atom in the molecule and soluble in the reaction solution. Specific examples include acetylacetone cerium, cerium chloride, cerium acetate, cerium nitrate, cerium sulfate, cerium acrylate, and cerium methacrylate.

  The tungsten (W) compound is not limited, and examples thereof include compounds having a tungsten (W) atom in the molecule and soluble in the reaction solution. Specific examples include tungsten chloride, tungsten acrylate, and tungsten methacrylate.

  The zirconium (Zr) compound is not limited, and examples thereof include compounds having a zirconium (Zr) atom in the molecule and soluble in the reaction solution. Specifically, zirconium acetylacetone, zirconium chloride, zirconium acetate, zirconium nitrate, zirconium sulfate, zirconium acrylate, zirconium methacrylate, zirconium butoxide, zirconium propoxide, zirconyl chloride, zirconyl acetate, zirconyl nitrate, zirconyl acrylate and methacrylic acid Examples include zirconyl.

  The titanium (Ti) compound is not limited, and examples include compounds having a titanium (Ti) atom in the molecule and soluble in the reaction solution. Specific examples include titanium chloride, titanium nitrate, titanium sulfate, titanium methoxide, titanium ethoxide, titanium propoxide, titanium isopropoxide, titanium acrylate, and titanium methacrylate.

  The vanadium (V) compound is not limited, and examples thereof include compounds having vanadium (V) atoms in the molecule and soluble in the reaction solution. Specific examples include vanadium acetylacetone, vanadium chloride, vanadium naphthenate, vanadium acrylate, and vanadium methacrylate.

  The phosphorus (P) compound is not limited, and examples include compounds having a phosphorus (P) atom in the molecule and soluble in the reaction solution. Specifically, quaternary phosphonium salts such as alkylphosphines and acrylates thereof such as trimethylphosphine, tributylphosphine, trioctylphosphine, triphenylphosphine, tritoluylphosphine and 1,2-bis (diphenylphosphine) ethane. Etc.

  The aluminum (Al) compound is not limited, and examples thereof include a compound having an aluminum (Al) atom in the molecule and soluble in the reaction solution. Specific examples include aluminum acetylacetone, aluminum chloride, aluminum acetate, aluminum nitrate, aluminum sulfate, aluminum ethoxide, aluminum isopropoxide, aluminum acrylate, and aluminum methacrylate.

  The molybdenum (Mo) compound is not limited, and examples thereof include a compound having a molybdenum (Mo) atom in the molecule and soluble in the reaction solution. Specific examples include molybdenum chloride, molybdenum acetate, molybdenum acrylate, and molybdenum methacrylate.

  Examples of the catalyst that can be used in the production method of the present invention include the chromium (Cr) compound, iron (Fe) compound, yttrium (Y) compound, lanthanum (La) compound, cerium (Ce) compound, and tungsten (W) compound. And at least one selected from the group consisting of a zirconium (Zr) compound, a titanium (Ti) compound, a vanadium (V) compound, a phosphorus (P) compound, an aluminum (Al) compound, and a molybdenum (Mo) compound. A catalyst containing a homogeneous homogeneous catalyst and an amine compound (amine compound combined type) is also preferred. The amine compound is not limited as long as it is a compound having an amine functional group in the molecule. Specifically, the amine compound is a uniform amine such as trialkylamines, cyclic amines such as pyridine, and quaternary salts thereof. Compounds. By using the amine compound in combination, the catalytic activity can be synergistically improved, and both the reaction conversion rate and the reaction selectivity can be increased.

  The amount of the catalyst used in the production method of the present invention is not limited. For example, it contains at least one selected from the group consisting of the aforementioned chromium (Cr) compounds and the like, and is a homogeneous catalyst (amine compound) that is soluble in the reaction solution. In the case of using a type that does not use A), it is preferably 0.01 to 10 mol%, more preferably 0.02 to 5 mol%, still more preferably 0.04 to 3 mol based on acrylic acid. %. If the amount used is less than 0.01 mol%, the reaction rate becomes small, so the reaction time becomes longer and the production cost may increase. If it exceeds 10 mol%, the reaction selectivity of by-products increases. There is a fear.

  Moreover, when using the amine compound combined type catalyst mentioned above, it is preferable that the usage-amount of an amine compound shall be 0.01-10 mol% with respect to acrylic acid, More preferably, it is 0.02-5 mol %, More preferably 0.04 to 3 mol%. The use amount of the homogeneous catalyst that contains at least one selected from the group consisting of chromium (Cr) compounds and the like and is soluble in the reaction solution is preferably 0.01 to 5 mol%, more preferably. Is 0.02 to 5 mol%, more preferably 0.04 to 3 mol%. If the amount used is less than 0.01 mol%, a synergistic effect may not be obtained, and if it exceeds 5 mol%, the production cost may increase.

(3. Reuse of catalyst)
As described above, the production method of the present invention is effective in an embodiment in which the catalyst is reused. The reuse of the catalyst is not particularly limited as long as the catalyst used at least once in the production of hydroxylalkyl acrylate can be reused. For example, in the production method of the present invention, the residual liquid obtained by collecting hydroxyalkyl acrylate from the reaction liquid of acrylic acid and alkylene oxide is reused for the next reaction (that is, the second and subsequent reactions of acrylic acid and alkylene oxide). A method is mentioned. The recycling method may be a method including a step of adding acrylic acid and alkylene oxide (raw material) to the residue, or vice versa. The method for recovering the hydroxyalkyl acrylate (target product) from the reaction solution is not particularly limited, and examples thereof include a method of recovering the target product by distilling the reaction solution. Therefore, in the above case, “residue liquid obtained by recovering hydroxyalkyl acrylate from the reaction liquid of acrylic acid and alkylene oxide” means “residue liquid obtained by distilling hydroxyalkyl acrylate from the reaction liquid of acrylic acid and alkylene oxide”. Can do.

  The residue liquid does not need to be completely recovered and the target product may remain somewhat. The residual liquid contains the catalyst used for the reaction, but may contain other components such as by-products and residual raw material compounds, and is not particularly limited. The by-products and the remaining raw material compounds are preferably distilled off in the same manner as the hydroxyalkyl acrylate.

  In the production method of the present invention, a catalyst solution obtained by mixing the above-mentioned residue solution and a fresh catalyst (hereinafter referred to as “fresh catalyst” where appropriate) is reused in the next reaction. There may be. The catalyst solution may be obtained by adding a fresh catalyst to the above-mentioned residue solution, or may be obtained by adding a residue solution to a fresh catalyst. The method of using the catalyst solution may be a method including a step of adding acrylic acid and alkylene oxide (raw material) to the catalyst solution, or vice versa. Here, “fresh catalyst” means not only a catalyst that has never been used in the production of hydroxylalkyl acrylate (referred to as “unused catalyst” as appropriate), but 90% or more of the catalyst activity of the unused catalyst. It is also meant to include a catalyst having the following catalytic activity. As a method for measuring the catalytic activity, for example, the “simple catalytic activity measuring method” shown in the Examples can be applied.

  After starting the reaction between acrylic acid and alkylene oxide when mixing the residual liquid obtained by distilling off hydroxyalkyl acrylate from the reaction liquid of acrylic acid and alkylene oxide and reusing it in the next reaction. In what stage has passed, there is no particular limitation as to whether or not the above distillation and addition should be used for the next reaction, and the reaction should be started again. And can be arbitrarily set so that the catalyst efficiency, the yield of the purpose, and the like can be further improved.

  In addition, when the above residue liquid and fresh catalyst are mixed and reused for the next reaction, the fresh catalyst may be dissolved in the residue liquid in advance and used for the next reaction, or the next reaction may start. After that, the fresh catalyst may be dissolved in the residual liquid, or only a part of the fresh catalyst may be dissolved in the residual liquid in advance and the remaining fresh catalyst may be dissolved after the next reaction starts. Alternatively, the fresh catalyst may be dissolved in a part of the residue liquid in advance, and the remaining residue liquid may be added after the next reaction starts. The production method of the present invention is not particularly limited to these, but in particular, the entire amount of the fresh catalyst to be added is dissolved in the total amount of the residual liquid used in the next reaction, and then used in the next reaction. It is more preferable because the operation is not complicated and it is easy to handle as a catalyst used in the next reaction. The fresh catalyst is preferably the same as the catalyst that can be used in the above-described production methods of the present invention.

  In the production method of the present invention, the total amount of the residue liquid may be used for the next reaction, but only a part of it may be used, or it may be arbitrarily divided into a plurality of reactions. There is no particular limitation as long as at least a part of the catalyst once used for the reaction can be used again as the reaction catalyst.

  The amount of fresh catalyst added is preferably 0.02 to 0.8 times the amount of catalyst contained in the residual liquid used for the next reaction, more preferably 0.05 to 0. .5 times the amount, more preferably 0.1 to 0.3 times the amount. When the amount added is less than 0.02 times, the reactivity is low and the reaction time is excessively prolonged, and the amount of impurities produced may increase. May be added in an excessive amount, resulting in an economic disadvantage because no further effect can be expected. In addition, if the replenishment amount of the fresh catalyst is 0 times, that is, if the next reaction is performed only with the catalyst contained in the residual liquid, the reactivity is further reduced, and the amount of residual alkylene oxide in the reaction kettle at the end of the supply of alkylene oxide The risk of explosion may increase due to an increase, and the reaction rate may be slow and the reaction time may be extended, which may increase the amount of impurities generated.

  In the production method of the present invention, the total amount of the catalyst contained in the residual liquid used in the next reaction and the amount of the fresh catalyst to be added is the amount of the catalyst used in the reaction. It is preferable that the amount of the catalyst used in the production method of the present invention falls within the range.

(4. Reaction between acrylic acid and alkylene oxide)
The reaction between acrylic acid and alkylene oxide in the production method of the present invention may be a so-called batch reaction (batch reaction) or a continuous reaction (continuous reaction). In addition, the batch reaction can be completed easily, and in that case, it can be said that it is preferable because it does not require equipment for recovering unreacted acrylic acid or alkylene oxide, and the continuous reaction is preferable in the batch reaction. Since there is no occupation time of the reactor such as raw material charging, temperature rise, cooling, extraction and standby as in the case of carrying out the reaction, it can be said that it is preferable in terms of productivity.

  In the production method of the present invention, for example, when the reaction is carried out batchwise, it is carried out by introducing (adding) a liquid alkylene oxide into acrylic acid. The alkylene oxide may be introduced (added) after the acrylic acid is dissolved in the solvent. At this time, the alkylene oxide may be added all at once, continuously or intermittently. When continuously or intermittently added, as is often done in this type of reaction, the reaction can be continued even after introduction of the alkylene oxide, so-called aging can be performed to complete the reaction. Acrylic acid does not necessarily need to be charged at once in the initial stage, and can be divided into several parts. Further, alkylene oxide and acrylic acid may be added simultaneously or intermittently.

  In addition, when reacting by a batch type, it is preferable to include a catalyst beforehand in acrylic acid, a hydroxyalkyl acrylate, a solvent, or those liquid mixture, and to introduce | transduce alkylene oxide after that. In addition, when acrylic acid is dividedly charged, a part of the catalyst may be included in the acrylic acid to be dividedly charged and may be charged together with the acrylic acid.

  When the reaction is carried out continuously, acrylic acid and liquid alkylene oxide are continuously charged into a tube-type or tank-type reactor, and the reaction solution is continuously withdrawn from the reactor. . At this time, the catalyst may be continuously supplied together with the raw material and continuously extracted together with the reaction solution, or a part of the reaction solution may be circulated.

  In the case of carrying out the reaction in a continuous manner, the catalyst is preferably preliminarily included in acrylic acid, hydroxyalkyl acrylate, a solvent or a mixture thereof and then charged into the reactor.

  The raw acrylic acid and the raw material alkylene oxide may be charged into the reactor from different charging lines, or mixed in advance by piping, a line mixer, a mixing tank or the like before being charged into the reactor. Then, you may throw it in. Further, when the reactor outlet liquid is circulated to the reactor inlet, this liquid may be mixed with the raw material acrylic acid and the raw material alkylene oxide and then charged into the reactor. However, when acrylic acid and alkylene oxide are charged into the reaction liquid from separate charging lines, the molar ratio in the reaction liquid becomes excessive in the vicinity of the acrylic acid charging port. Before starting, it is preferable to add the respective raw materials after mixing them in advance by piping or the like.

  The reaction temperature is usually preferably in the range of 40 to 130 ° C, more preferably in the range of 50 to 100 ° C. If the reaction temperature is lower than 40 ° C, the progress of the reaction slows and deviates from the practical level. On the other hand, if the reaction temperature is higher than 130 ° C, the amount of by-products increases, acrylic acid as a raw material, There is a risk of polymerization of the hydroxyalkyl acrylate product.

  In this reaction, the reaction may be performed in a solvent for the purpose of allowing the reaction to proceed gently. Common solvents such as toluene, xylene, heptane, and octane can be used as the solvent. The internal pressure during the reaction depends on the type of raw materials used and the mixing ratio, but is generally carried out under pressure.

  Moreover, the polymerization inhibitor generally used can be used in the case of reaction. Examples of the polymerization inhibitor include hydroquinone, methyl hydroquinone, tert-butyl hydroquinone, 2,6-di-tert-butyl hydroquinone, 2,5-di-tert-butyl hydroquinone, 2,4-dimethyl-6-tert- Phenol compounds such as butylphenol and hydroquinone monomethyl ether; N-isopropyl-N′-phenyl-para-phenylenediamine, N- (1,3-dimethylbutyl) -N′-phenyl-para-phenylenediamine, N- (1- Paraphenylenediamines such as methylheptyl) -N′-phenyl-para-phenylenediamine, N, N′-diphenyl-para-phenylenediamine, N, N′-di-2-naphthyl-para-phenylenediamine; thiodiphenylamine , Phenothiazine, etc. Dialkyldithiocarbamate copper salts such as copper dibutyldithiocarbamate, copper diethyldithiocarbamate, copper dimethyldithiocarbamate; nitrosodiphenylamine, isoamyl nitrite, N-nitroso-cyclohexylhydroxylamine, N-nitroso-N-phenyl-N- Nitroso compounds such as hydroxylamine or salts thereof; 2,2,4,4-tetramethylazetidine-1-oxyl, 2,2-dimethyl-4,4-dipropylazetidine-1-oxyl, 2,2, 5,5-tetramethylpyrrolidine-1-oxyl, 2,2,5,5-tetramethyl-3-oxopyrrolidine-1-oxyl, 2,2,6,6-tetramethylpiperidine-1-oxyl, 4- Hydroxy-2,2,6,6-tetramethylpiperidine-1-oxy 6-aza-7,7-dimethyl-spiro (4,5) decane-6-oxyl, 2,2,6,6-tetramethyl-4-acetoxypiperidine-1-oxyl, 2,2,6 Examples thereof include N-oxyl compounds such as 6-tetramethyl-4-benzoyloxypiperidine-1-oxyl. The addition amount of the polymerization inhibitor is preferably 0.0001 to 1% by weight, more preferably 0.001 to 0.5% by weight, based on the carboxylic acid.

  In the production method of the present invention, the obtained hydroxyalkyl acrylate may be further purified as necessary. Although it does not specifically limit as a purification method, For example, the refinement | purification by distillation is mentioned. More specifically, for example, distillation using a rectification column such as a general-purpose distillation column, a packed column, a bubble bell column, and a perforated plate column can be mentioned, but it is not particularly limited thereto. Further, other purification means may be used in combination with distillation purification. Moreover, the above-mentioned polymerization inhibitor can be used as appropriate during purification.

  Examples will be shown below, and the embodiments of the present invention will be described in more detail. Of course, the present invention is not limited to the following examples, and it goes without saying that various aspects are possible in detail. Further, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims, and the present invention is also applied to the embodiments obtained by appropriately combining the disclosed technical means. It is included in the technical scope of the invention.

  Moreover, all the academic literatures and patent literatures described in this specification are incorporated herein by reference.

[Preparation of purified acrylic acid]
A gas containing acrylic acid obtained by catalytic vapor phase oxidation of propylene was collected with water. The resulting acrylic acid aqueous solution was subjected to azeotropic dehydration using toluene to separate water and acetic acid produced as a by-product. Thereafter, high boiling point substances were separated by distillation to extract crude acrylic acid.

  The crude acrylic acid (1 L) obtained above was crystallized in a 7 ° C. refrigerator. Thereafter, the mixture was gradually melted at room temperature, and when the half amount (0.5 L) was melted, the melt was extracted. This melt (molten acrylic acid) was crystallized again in a refrigerator at 7 ° C. Thereafter, the mixture was gradually melted at room temperature, and when the half amount (0.25 L) was melted, the melt was extracted. Purified acrylic acid was prepared by measuring the amount of hydridoquinone monomethyl ether (hereinafter referred to as “MQ” where appropriate) in this melt and adjusting the MQ to 200 ppm by weight.

  The contents of furfural, benzaldehyde, β-acryloxypropionic acid, maleic anhydride, and maleic acid in crude acrylic acid and purified acrylic acid were measured as follows. For analysis of furfural and β-acryloxypropionic acid in acrylic acid, acrylic acid was appropriately diluted with pure water, TSK-GEL ODS80Ts (manufactured by Tosoh Corporation) was used as a column, and 0.1 wt% as an eluent. It was carried out by high performance liquid chromatography analysis using a solution having a volume ratio of aqueous phosphoric acid to acetonitrile of 90:10. The analysis of benzaldehyde and maleic acid in acrylic acid was performed by appropriately diluting acrylic acid with pure water, using Inertsil (registered trademark) ODS-3 (manufactured by GL Sciences Inc.) as a column, and 0.1 eluent as eluent. It was carried out by high performance liquid chromatography analysis using a solution having a volume ratio of 60% by weight of a phosphoric acid aqueous solution and acetonitrile. Maleic anhydride was analyzed as maleic acid by hydration with water. The measured contents of furfural, benzaldehyde, β-acryloxypropionic acid, maleic anhydride, and maleic acid in crude acrylic acid and purified acrylic acid are shown in Table 1 or 2.

In Examples and Comparative Examples shown below and Tables 1 and 2,
Acrylic acid is represented as “AA”, furfural as “FF”, benzaldehyde as “BzCHO”, β-acryloxypropionic acid as “APA”, and maleic anhydride and maleic acid as “A”. May be referred to as “MA”.

[Example 1]
140 g out of 420 g of total supply of purified acrylic acid, 2.52 g (0.010 mol) of chromium acetate (monohydrate) as a catalyst, 0.42 g of phenothiazine as a polymerization inhibitor and hydroquinone monomethyl ether An amount of 0.63 g was charged into a 1 L SUS316 autoclave with a stirrer and the inside thereof was replaced with nitrogen, then the temperature was raised to 85 ° C., and the internal pressure was set to 0.05 MPa (G).

  Ethylene oxide was supplied at 136 g / h for 0.7 hours (94 g), then acrylic acid (280 g) was supplied at 215 g / h, and ethylene oxide (178 g) was supplied at 136 g / h for 1.3 hours. The reaction was carried out while maintaining the temperature.

  The reaction temperature after the supply of acrylic acid and ethylene oxide was kept constant at 85 ° C., and the reaction was continued until the concentration of the acid component as acrylic acid (measured by neutralization titration) reached 0.10% by weight. However, since the concentration of the acid component at the time when the reaction was continued for 1.0 hour became 0.10% by weight, the reaction solution was cooled to 30 ° C. or less over 10 minutes (the reaction duration was finally 1). 2 hours). The acid component of the obtained reaction solution was 0.05% by weight.

  Subsequently, the glass round bottom flask with a volume of 1 L set in the vacuum distillation apparatus was depressurized to a vacuum degree of 4 hPa, and the obtained reaction solution was transferred from the autoclave to the flask by pumping. While bubbling the reaction liquid by introducing air at a rate of 3 ml / min, the reaction temperature was kept at 40-50 ° C. for 30 minutes to dissipate unreacted ethylene oxide. The acid component of the obtained reaction solution was 0.05% by weight.

  Thereafter, the reaction solution was purified by distillation at a flask internal temperature of 50 to 90 ° C. for 3 hours to obtain 69.5 g of a reaction solution in which hydroxyethyl acrylate was distilled off. The acid component of the obtained reaction solution was 0.05% by weight.

[Example 2]
Furfural and benzaldehyde were added to purified acrylic acid, and the contents were adjusted to 100 ppm by weight and 50 ppm by weight, respectively. The procedure was the same as Example 1 except that the acrylic acid obtained above was used.

Example 3
Furfural and benzaldehyde were added to purified acrylic acid, and the contents were adjusted to 250 ppm by weight and 50 ppm by weight, respectively. The procedure was the same as Example 1 except that the acrylic acid obtained above was used.

[Comparative Example 1]
Furfural and benzaldehyde were added to purified acrylic acid to adjust the respective contents to 400 ppm by weight and 100 ppm by weight. The procedure was the same as Example 1 except that the acrylic acid obtained above was used.

[Comparative Example 2]
Same as Example 1 except that crude acrylic acid was used.

[Comparative Example 3]
To the crude acrylic acid, β-acryloxypropionic acid, maleic acid and maleic anhydride were added, and the respective contents were adjusted to 1.81 wt% and 1580 wt ppm. The procedure was the same as Example 1 except that the acrylic acid obtained above was used.

Example 4
Of 380 g of the total amount of purified acrylic acid, 127 g, chromium acetate (monohydrate) 2.28 g (0.009 mol) as a catalyst, and quinone monomethyl ether 0.57 g as a polymerization inhibitor The mixture was charged into a 1 L capacity SUS316 autoclave equipped with a stirrer, and the inside thereof was replaced with nitrogen. Then, the temperature was raised to 85 ° C., and the internal pressure was set to 0.05 MPa (G).

  Propylene oxide was fed at 158 g / h for 0.7 hours (113 g), then acrylic acid (235 g) was fed at 196 g / h, and propylene oxide (202 g) was fed at 158 g / h for 1.3 hours, during which 85 The reaction was carried out while maintaining the temperature.

  The reaction temperature after completion of the supply of acrylic acid and propylene oxide was kept constant at 85 ° C., and the reaction was continued until the concentration of the acid component as acrylic acid (measured by neutralization titration) reached 0.10% by weight. However, since the concentration of the acid component at the time when the reaction was continued for 1.5 hours became 0.10% by weight, the reaction solution was cooled to 30 ° C. or less over 10 minutes (the reaction duration was finally 1). .7 hours). The acid component of the obtained reaction liquid was 0.04% by weight.

  Subsequently, the glass round bottom flask with a volume of 1 L set in the vacuum distillation apparatus was depressurized to a vacuum degree of 4 hPa, and the obtained reaction solution was transferred from the autoclave to the flask by pumping. While bubbling the reaction liquid by introducing air at a rate of 3 ml / min, the reaction temperature was kept at 40-50 ° C. for 30 minutes to dissipate unreacted ethylene oxide. The acid component of the obtained reaction liquid was 0.04% by weight.

  Thereafter, the reaction solution was purified by distillation at a flask internal temperature of 50 to 90 ° C. for 3 hours to obtain 69.5 g of a reaction solution in which hydroxypropyl acrylate was distilled off. The acid component of the obtained reaction solution was 0.05% by weight.

Example 5
Furfural and benzaldehyde were added to purified acrylic acid, and the contents were adjusted to 250 ppm by weight and 50 ppm by weight, respectively. Example 4 was repeated except that the acrylic acid obtained above was used.

[Comparative Example 4]
Furfural and benzaldehyde were added to purified acrylic acid to adjust the respective contents to 400 ppm by weight and 100 ppm by weight. Example 4 was repeated except that the acrylic acid obtained above was used.

[Comparative Example 5]
Example 4 was repeated except that crude acrylic acid was used.

[Comparative Example 6]
To the crude acrylic acid, β-acryloxypropionic acid, maleic acid and maleic anhydride were added, and the respective contents were adjusted to 1.81 wt% and 1580 wt ppm. Example 4 was repeated except that the acrylic acid obtained above was used.

[Method for evaluating catalyst activity]
(Simple catalytic activity measurement method)
A 50 mL SUS pressure vessel (with a pressure of 10 MPa) was charged with 0.20 g of chromium acetate (monohydrate) (catalyst), 5.30 g of hydroxypropyl acrylate, 10.00 g of acrylic acid and 8.05 g of propylene oxide, and sealed. did. This was immersed in an oil bath at 70 ° C. for 30 minutes. After cooling the SUS pressure vessel, the acid component concentration of the internal solution was measured by titration to determine the conversion amount of acrylic acid. The conversion amount was defined as “AA conversion amount of fresh catalyst”.

  In the above SUS pressure vessel (withstand pressure of 10 MPa), 5.50 g of residual liquid (herein referred to as “distilled bottom”) from which the target product was distilled off in each Example or each Comparative Example, 10.00 g of acrylic acid, and propylene oxide 8 .05 g was charged and sealed. This was immersed in an oil bath at 70 ° C. for 30 minutes. After cooling the SUS pressure vessel, the acid component concentration of the internal solution was measured by titration to determine the conversion amount of acrylic acid. The conversion amount was defined as “distillation bottom AA conversion amount”.

  By calculating the ratio of the AA conversion amount of the distillation bottom to the AA conversion amount of the fresh catalyst, “catalytic activity (%) of the distillation bottom” was obtained.

[Amount of hydrone quinone monomethyl ether after reaction]
The amount of hydridoquinone monomethyl ether (MQ) distilled from the reaction solution after the reaction was analyzed as follows. 1 ml of a sample and 15 ml of acetic acid (special grade reagent) were placed in a Meyer flask, 0.2 ml of a saturated sodium nitrite aqueous solution was added and mixed, and after standing for 5 minutes, the absorbance (420 nm) was measured using a spectrophotometer.

〔result〕
Table 1 shows the results of Examples 1 to 3 and Comparative Examples 1 to 3.

  The results of Examples 4 to 5 and Comparative Examples 4 to 6 are shown in Table 2.

  According to the results shown in Tables 1 and 2, those of the examples are clearly higher than the catalyst activity (%) of the distillation bottom liquid in the comparative example. It was shown that the nature increased.

  Further, the amount of MQ distilled out in the examples was clearly higher than that in the comparative examples. This indicates that the amount of decrease in the polymerization inhibitor (hydroquinone monomethyl ether) in the production process according to the example was smaller than that in the comparative example. From these results, it is speculated that according to the production method of the present invention, the polymerization of hydroxyl acrylate in the production process can be effectively prevented by the decrease in the amount of the polymerization inhibitor reduced in the production process.

  ADVANTAGE OF THE INVENTION According to this invention, the merit that a hydroxyalkyl acrylate can be efficiently manufactured without obstruction | occlusion of piping etc. in manufacturing equipment can be enjoyed. Furthermore, according to the present invention, not only the cost advantage that the production cost of hydroxyalkyl acrylate can be reduced, but also the environmental advantage that the amount of discarded catalyst can be reduced can be enjoyed.

  Therefore, the present invention can be suitably used in the industry for producing hydroxyalkyl acrylate.

Claims (7)

In a process for producing a hydroxyalkyl acrylate comprising the step of reacting acrylic acid with an alkylene oxide,
A process for producing a hydroxyalkyl acrylate characterized by satisfying the following conditions (1) and / or (2):
(1) The total amount of furfural and benzaldehyde contained in the acrylic acid is 0.1 to 300 ppm by weight with respect to acrylic acid;
(2) β-acryloxypropionic acid contained in the acrylic acid is 0.005 wt% or more and 1 wt% or less with respect to acrylic acid.   2. The hydroxy according to claim 1, wherein the acrylic acid has a total content of maleic anhydride and maleic acid of 0.1 to 1,000 ppm by weight based on acrylic acid. Method for producing alkyl acrylate.   The method for producing a hydroxyalkyl acrylate according to claim 1 or 2, wherein acrylic acid and alkylene oxide are reacted in the presence of a catalyst.   The method for producing a hydroxyalkyl acrylate according to claim 3, wherein the catalyst used at least once in the production of the hydroxyl alkyl acrylate is used for the reaction of acrylic acid and alkylene oxide.   The method for producing a hydroxyalkyl acrylate according to claim 3, wherein the residue liquid obtained by recovering the hydroxyalkyl acrylate from the reaction liquid of acrylic acid and alkylene oxide is used for the reaction of acrylic acid and alkylene oxide.   6. The method for producing a hydroxyalkyl acrylate according to claim 5, wherein a catalyst liquid obtained by mixing the residue liquid and a fresh catalyst is used for the reaction of acrylic acid and alkylene oxide.   The method for producing a hydroxyalkyl acrylate according to any one of claims 1 to 6, wherein the acrylic acid is acrylic acid obtained by a gas phase catalytic oxidation reaction of propylene.