Method for producing alkenyl diacetate

Abstract

To provide a method for producing alkenyl diacetate that allows for stable manufacturing of a target substance with high selectivity under high temperature and high pressure conditions, while preventing corrosion of a reaction vessel.SOLUTION: A method for producing alkenyl diacetate includes reacting acetic acid (A), an alkene (B) with 3 to 8 carbon atoms, and oxygen (C) in a liquid phase in which an alkyl ester of acetic acid (D) represented by formula (I) is present, under the presence of a transition metal-containing catalyst, in a reaction vessel. In formula (I), R1 represents a straight-chain, cyclic, or branched aliphatic hydrocarbon group having 1 to 8 carbon atoms.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing alkenyl diacetates. [Background technology]

[0002] Alkenyl diacetates, which contain an alkenyl group and two acyl groups, can be used as raw materials for a variety of chemical products. Among them, 2-methylene-1,3-propane diacetate (hereinafter sometimes abbreviated as "MPDAc") has, in the same molecule, a 2,2-substituted carbon-carbon unsaturated bond that can be used in radical addition reactions, hydrosilylation reactions, or hydroformylation reactions, and two acyl groups that can be used in saponification reactions and transesterification reactions. Due to its reactivity, it can be used as a raw material for the production of a variety of chemical products.

[0003] A known method for producing MPDAc is to use isobutylene, acetic acid, and oxygen as raw materials and subject the raw material to an oxidative acetoxylation reaction in a gas phase (see, for example, Patent Documents 1 and 2).

[0004] In a gas-phase reaction, it is difficult to increase productivity because MPDAc adsorbs onto the catalyst and inhibits the reaction, and liquid-phase conditions are preferable from the viewpoint of production efficiency, as described in Patent Document 3. Patent Document 3 also reports that MPDAc can be produced by a liquid-phase reaction with high production efficiency and high cost performance without generating inorganic products in amounts equimolar to the product. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] German Patent No. 1909964 [Patent Document 2] Special Publication No. 47-28965 [Patent Document 3] International Publication No. 2020 / 022364 Summary of the Invention [Problem to be solved by the invention]

[0006] Under the liquid-phase reaction conditions described in Patent Document 3, an excess amount of acetic acid, the reaction substrate, is typically used to carry out the reaction under liquid-phase conditions. However, water produced in the reaction causes the hydrolysis of MPDAc to proceed in the acetic acid solution, resulting in a problem of a decrease in the yield of the target MPDAc. Furthermore, the acetic acid solution is prone to by-production of hydrolyzed products that are difficult to separate from MPDAc (e.g., 2-methylene-1,3-propanediol, 2-methylene-1,3-propanediol monoacetate). Therefore, when attempting to obtain MPDAc with high purity, very inefficient distillation conditions must be applied, resulting in a problem of being unable to increase productivity.

[0007] Furthermore, when a highly concentrated acetic acid solution is applied to industrial reaction conditions under high temperature and pressure, corrosion of the stainless steel or other metal reaction vessel occurs, and the eluted metal can deactivate the catalyst, or pinholes can form in the reaction vessel, causing the liquid inside the reaction vessel to leak into the heat transfer jacket. This poses the problem of not being able to stably produce the target substance, MPDAc, with high selectivity over a long period of time under high temperature and pressure conditions.

[0008] In view of the above circumstances, an object of the present invention is to provide a method for producing alkenyl diacetate, which can stably produce the target substance with high selectivity even under high-temperature and high-pressure conditions while suppressing corrosion of the reaction vessel. [Means for solving the problem]

[0009] As a result of intensive research conducted by the present inventors to solve the above problems, they discovered that by adding alkyl acetate esters to the raw materials and reacting them, alkenyl diacetates can be produced stably and with high selectivity even under high-temperature and high-pressure conditions while suppressing corrosion of the reaction vessel. Based on this finding, they conducted further research and completed the present invention.

[0010] That is, the present invention is as follows. [1] A method for producing alkenyl diacetate, comprising reacting acetic acid (A), an alkene (B) having 3 to 8 carbon atoms, and oxygen (C) in a liquid phase in the presence of an alkyl acetate (D) represented by formula (I) in a reaction vessel in the presence of a catalyst containing a transition metal. [ka] [In formula (I), R 1 represents a linear, cyclic, or branched aliphatic hydrocarbon group having 1 to 8 carbon atoms.] [2] The method for producing an alkenyl diacetate according to the above [1], wherein the alkene (B) having 3 to 8 carbon atoms is isobutylene, and the alkenyl diacetate is 2-methylene-1,3-propane diacetate. [3] The method for producing alkenyl diacetate according to the above [1] or [2], further using nitrogen (E) in an amount of 15 molar equivalents or more relative to oxygen (C). [4] The method for producing an alkenyl diacetate according to any one of the above [1] to [3], further using ethanol (F) in an amount of 0.001 to 50,000 ppm by mass relative to the mass of the alkyl acetate (D). [5] In the formula (I), R 1 represents a linear or branched aliphatic hydrocarbon group having 1 to 4 carbon atoms. [6] The method for producing an alkenyl diacetate according to any one of the above [1] to [5], wherein the boiling point of the alkyl acetate (D) is lower than 117°C. [7] The method for producing an alkenyl diacetate according to any one of the above [1] to [6], wherein the alkyl acetate (D) is ethyl acetate. [8] The method for producing alkenyl diacetate according to any one of [1] to [7] above, wherein the oxygen concentration in the gas phase in the reaction vessel is equal to or less than the explosion limit oxygen concentration of the vapor in the liquid phase as measured according to the ASTM E2079-19 standard. [9] The method for producing an alkenyl diacetate according to any one of the above [1] to [8], wherein the ratio MD / MB of the mass MD of the alkyl acetate ester (D) to the mass MB of the alkene (B) having 3 to 8 carbon atoms is 2 or more and 50 or less.

[10] The method for producing alkenyl diacetate according to any one of [1] to [9] above, wherein the catalyst is palladium supported on at least one carrier selected from the group consisting of silicon dioxide, activated carbon, and alumina.

[11] The method for producing alkenyl diacetate according to any one of the above [1] to

[10] , wherein the catalyst is a carrier having a maximum length of 2 mm or more and less than 20 mm, on which palladium is supported.

[12] The method for producing an alkenyl diacetate according to any one of the above [1] to

[11] , wherein the mass of the acetic acid (A) is more than 0 parts by mass and not more than 20 parts by mass per 100 parts by mass of the total mass of the acetic acid (A), the alkene (B) having 3 to 8 carbon atoms, and the alkyl acetate ester (D).

[13] The method for producing an alkenyl diacetate according to any one of the above [1] to

[12] , wherein the ratio MA / MB of the mass MA of the acetic acid (A) to the mass MB of the alkene (B) having 3 to 8 carbon atoms is 3 or less.

[14] The method for producing an alkenyl diacetate according to any one of the above [1] to

[13] , wherein the ratio MD / (MA+MB) of the mass MD of the alkyl acetate (D) to the sum of the mass MA of the acetic acid (A) and the mass MB of the alkene (B) having 3 to 8 carbon atoms is 1 or more and 50 or less. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a method for producing alkenyl diacetate, which can stably produce a target substance with high selectivity even under high-temperature and high-pressure conditions while suppressing corrosion of a reaction vessel. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below. In addition, while showing the preferred embodiments of the present invention together with the description of the invention-specific matters of the present invention, a combination of two or more of the individual preferred embodiments of the present invention is also a preferred embodiment of the present invention. Also, regarding the matters indicated by numerical ranges, when there are several numerical ranges, the lower limit values and upper limit values thereof can be selectively combined to form a preferred embodiment.

[0013] [Process for producing alkenyl diacetate (P)] In the process for producing alkenyl diacetate (P) according to an embodiment of the present invention, acetic acid (A), an alkene (B) having 3 to 8 carbon atoms, and oxygen (C) are reacted in a liquid phase in which an alkyl acetate (D) represented by formula (I) is present in a reaction vessel in the presence of a catalyst containing a transition metal to obtain alkenyl diacetate (P).

[0014] [Chemical formula] In formula (I), R 1 represents an aliphatic hydrocarbon group having 1 to 8 carbon atoms, which is linear, cyclic, or branched.

[0015] In the above reaction, formally, 1 equivalent of an alkene (B) having 3 to 8 carbon atoms and 2 equivalents of acetic acid (A) are oxidatively dehydrated and condensed to generate water together with alkenyl diacetate (P). As an example, when the alkene (B) having 3 to 8 carbon atoms is isobutylene, the reaction formula is as follows.

[0016] [Chemical formula]

[0017] In the method for producing alkenyl diacetate (P) according to an embodiment of the present invention, the reaction is carried out under liquid-phase conditions, thereby reducing both equipment and energy costs. Furthermore, under gas-phase conditions, the high boiling point of the product alkenyl diacetate (P) can adsorb onto the catalyst, inhibiting the reaction, and the high temperatures required to maintain the product in a gaseous state can deactivate the catalyst, making it difficult to increase productivity. Therefore, liquid-phase conditions are advantageous from the standpoint of production efficiency.

[0018] In addition, by using acetic acid (A), an alkene having 3 to 8 carbon atoms (B), and oxygen (C) as raw materials and an alkyl acetate (D) as a solvent, the following effects (1) to (5) can be further obtained. These effects are more pronounced when the alkene having 3 to 8 carbon atoms (B) is isobutylene. (1) The acid concentration derived from acetic acid (A) in the liquid phase in the reaction vessel is reduced, and corrosion of the reaction vessel is suppressed. (2) Alkyl acetate (D) is a non-polar solvent in which oxygen dissolves easily, and therefore has high oxygen solubility, resulting in a fast reaction rate. (3) The limiting oxygen concentration (LOC) of alkyl acetate (D) generally tends to be higher at higher pressures. Therefore, when oxygen is dissolved in the liquid phase at high pressure, taking into account that oxygen supply is the rate-limiting factor of the reaction, conditions with a high oxygen concentration can be safely applied even at high pressures because the main component of the liquid phase is alkyl acetate (D). (4) It prevents the water produced in the reaction from hydrolyzing the target product, alkenyl diacetate (P), and reducing the selectivity. In other words, the hydrolysis rate of alkyl acetate (D) is generally faster than that of alkenyl diacetate (P) or the intermediate alkenyl acetate, so it reacts with water first to produce acetic acid and ethanol, thereby suppressing the hydrolysis of alkenyl diacetate (P). The acetic acid produced is then consumed in the reaction. Furthermore, the presence of ethanol further reduces the hydrolysis rate of alkenyl diacetate (P) by water. (5) The inclusion of an alkyl acetate (D) in the liquid phase suppresses the formation of the alkenyl diacetate (P) isomers, and as a result, the selectivity of the alkenyl diacetate (P) is improved.

[0019] Hereinafter, in the method for producing alkenyl diacetate (P) according to the present embodiment, acetic acid (A), an alkene (B) having 3 to 8 carbon atoms, and oxygen (C) used as raw materials, an alkyl acetate (D) used as a solvent, and other components that can be used in the reaction will be described.

[0020] <Acetic acid (A) and an alkene (B) having 3 to 8 carbon atoms> The alkene having 3 to 8 carbon atoms according to the present embodiment is a linear, branched or cyclic alkene having one or more double bonds at the internal or terminal position. Specifically, propylene, 1-butene, butadiene, isobutylene, cyclobutene, 1-pentene, 1,3-pentadiene, cyclopentene, cyclopentadiene, 1-hexene, 1,3-hexadiene, 1,3,5-hexatriene, cyclohexene, 1,3-cyclohexadiene, cyclohexatriene, 1-heptene, 1,3-heptadiene, 1,3,5-heptatriene, cycloheptene, 1,3-cycloheptadiene, 1,3,5-cycloheptatriene, 1-octene, 1,3-octadiene, 1,3,5-octatriene, 1,3,5,7-octatetraene, cyclooctene, 1,3-cyclooctadiene, 1,3,5-cyclooctatriene, cyclooctatetraene or their structural isomers can be mentioned. From the viewpoint of improving the yield of alkenyl diacetate (P), isobutylene and butadiene are preferable, and isobutylene is particularly preferable from the viewpoint of low catalyst deterioration.

[0021] In the method for producing alkenyl diacetate (P) according to this embodiment, the mass of acetic acid (A) used is, from the viewpoint of ensuring the required amount of alkenyl diacetate (P) and making it easier to suppress corrosion of the reaction vessel, preferably more than 0 parts by mass and not more than 75 parts by mass, more preferably more than 0 parts by mass and not more than 45 parts by mass, even more preferably more than 0 parts by mass and not more than 20 parts by mass, still more preferably 0.5 parts by mass or more and 15 parts by mass or less, and particularly preferably 0.7 parts by mass or more and not more than 10 parts by mass, relative to 100 parts by mass of the total mass of acetic acid (A), the alkene (B) having 3 to 8 carbon atoms, and the alkyl acetate ester (D).

[0022] The ratio MA / MB of the mass MA of the acetic acid (A) used to the mass MB of the alkene (B) having 3 to 8 carbon atoms used is preferably 85 or less, more preferably 55 or less, even more preferably 20 or less, still more preferably 10 or less, still more preferably 5 or less, still more preferably 3 or less, still more preferably 2.5 or less, and particularly preferably 2.3 or less, from the viewpoint of easily suppressing corrosion of the reaction vessel, shortening the recovery step of excess acetic acid (A) to make it an economically advantageous production method, and suppressing a decrease in yield due to side reactions. Furthermore, the above ratio MA / MB is preferably 1 or more, more preferably 1.5 or more, and even more preferably 2 or more, from the viewpoint of ensuring the required amount of alkenyl diacetate (P) and improving production efficiency. When acetic acid (A) and alkene (B) having 3 to 8 carbon atoms are added to the reaction system in multiple batches, the ratio MA / MB is the ratio of the total amount of component (A) added to the total amount of component (B) added. Furthermore, the above ratio MA / MB may be any ratio between the amount of components at the start of the reaction and the total amount of components at the time of addition to the reaction vessel, as long as it is within the above numerical range. However, if the reaction is continued to obtain a larger amount of the target substance, it is preferable that the ratio of the amount of each component be maintained within the above range during the reaction.

[0023] The ratio MD / MB of the mass MD of the alkyl acetate (D) to the mass MB of the alkene (B) having 3 to 8 carbon atoms is preferably 2 or more and 180 or less, preferably 2 or more and 160 or less, more preferably 2 or more and 100 or less, even more preferably 2 or more and 50 or less, even more preferably 5 or more and 50 or less, particularly preferably 10 or more and 40 or less, from the viewpoints of suppressing corrosion of the reaction vessel and enhancing safety.

[0024] <Oxygen (C) and nitrogen (E)> As the oxygen (C) used in the method for producing the alkenyldiacetate (P) according to the present embodiment, at least one of atomic oxygen and molecular oxygen can be used, and molecular oxygen is preferred. When using molecular oxygen, it is preferably used as a mixed gas with an inert gas such as nitrogen (E), argon, helium, and carbon dioxide, and more preferably used as a mixed gas with nitrogen (E). From the viewpoint of safety, the oxygen concentration in the gas phase part in the reaction vessel is preferably below the lower explosive limit oxygen concentration (LOC) of the vapor of the liquid phase measured according to the ASTM E2079-19 standard. Also, from the viewpoint of enhancing safety, it is preferable to further use nitrogen (E) in an amount of 9 molar equivalents or more with respect to acetic acid (C), and more preferably to further use nitrogen (E) in an amount of 15 molar equivalents or more with respect to oxygen (C).

[0025] Examples of the method for supplying molecular oxygen or a mixed gas containing molecular oxygen to the reaction system include a method of supplying it to the liquid phase part in the reaction system, a method of supplying it to the gas phase part, and a method of supplying it to both the liquid phase part and the gas phase part. When supplying molecular oxygen or a mixed gas containing molecular oxygen to the reaction system, the oxygen partial pressure is preferably supplied so as to be in the range of 0.01 to 200 atmospheres (gauge pressure), more preferably 0.1 to 100 atmospheres (gauge pressure).

[0026] <Alkyl acetate (D)> In the method for producing alkenyldiacetate (P) according to this embodiment, the reaction in the liquid phase of acetic acid (A), an alkene (B) having 3 to 8 carbon atoms, and oxygen (C) in the presence of a catalyst is carried out using an alkyl acetate (D) as a solvent. As the alkyl acetate (D), one kind of the compound represented by the above formula (I) may be used alone, or a plurality of kinds of the compounds represented by the above formula (I) may be used.

[0027] From the viewpoint of lowering the viscosity of the liquid in the reaction vessel at the reaction temperature (in other words, increasing the diffusion efficiency of the raw materials in the liquid) and facilitating ensuring a good reaction rate, in the above formula (I), R 1 preferably represents a linear or branched aliphatic hydrocarbon group having 1 to 4 carbon atoms.

[0028] From the viewpoint of improving the separability in the distillation purification process, the boiling point of the alkyl acetate (D) is preferably less than 117 °C, more preferably 110 °C or lower, still more preferably 100 °C or lower, even more preferably 90 °C or lower, and particularly preferably 80 °C or lower. There is no particular limitation on the lower limit value of the boiling point of the alkyl acetate (D), and for example, it is 55 °C or higher, and preferably 60 °C or higher.

[0029] Examples of the alkyl acetate (D) include methyl acetate, ethyl acetate, normal propyl acetate, isopropyl acetate, butyl acetate, pentyl acetate, hexyl acetate, and the like. From the viewpoint of enhancing the efficiency of the reaction, the alkyl acetate (D) is preferably ethyl acetate or isopropyl acetate, and more preferably ethyl acetate. Ethyl acetate has the property that the limiting oxygen concentration (LOC) for explosion increases as the pressure increases. Therefore, the pressure during the reaction can be increased while maintaining safety, and the reaction can proceed efficiently.

[0030] The ratio MD / (MA + MB) of the mass MD of the alkyl acetate (D) to the sum of the mass MA of acetic acid (A) and the mass MB of the alkene (B) having 3 to 8 carbon atoms is preferably 0.3 or more and 60 or less, more preferably 0.5 or more and 55 or less, still more preferably 1 or more and 50 or less, even more preferably 2 or more and 50 or less, still more preferably 5 or more and 50 or less, from the viewpoints of facilitating the suppression of corrosion of the reaction vessel and enhancing safety.

[0031] <ethanol (F)> From the viewpoint of facilitating the suppression of the hydrolysis rate of water under high temperature and high pressure, it is preferable to add ethanol (F) to the liquid phase as a solvent other than the alkyl acetate (D). In this case, it is preferably further used in an amount of 0.001 to 50,000 mass ppm, more preferably 0.01 to 50,000 mass ppm, still more preferably 0.1 to 50,000 mass ppm, even more preferably 1 to 50,000 mass ppm, even more preferably 10 to 50,000 mass ppm, even more preferably 100 to 50,000 mass ppm, even more preferably 200 to 50,000 mass ppm, particularly preferably 300 to 48,000 mass ppm of ethanol (F) based on the mass of the alkyl acetate (D). When ethanol (F) is present in the liquid phase, the hydrolysis rate of alkenyl diacetate (P) by water decreases, and as a result, the amounts of acetic acid (A) and the alkene (B) having 3 to 8 carbon atoms used can be reduced. Further, by the amount of ethanol (F) being within the above range, it is possible to avoid the explosion limit oxygen concentration becoming too low and maintain safety. Ethanol (F) may be produced by the reaction of ethyl acetate and water in the reaction vessel together with acetic acid. It is preferable that the total of the ethanol produced in the reaction vessel and the ethanol added to the reaction vessel as a raw material is within the range of the preferred amount of use of ethanol (F) described above.

[0032] <other solvents> In the method for producing alkenyl diacetate (P) according to this embodiment, a solvent other than alkyl acetate (D) and ethanol (F) (hereinafter sometimes simply referred to as "other solvent") may or may not be further used. From the viewpoints of safety and suppression of hydrolysis, it is preferable not to use a solvent other than alkyl acetate (D) and ethanol (F). Examples of the other solvent include hydrocarbons excluding alkenes (B) having 3 to 8 carbon atoms such as hexane, heptane, methylcyclohexane, and benzene (aliphatic hydrocarbons, aromatic hydrocarbons, etc.); heterocyclic compounds such as pyridine and quinoline; ethers such as diethyl ether, tetrahydrofuran, methyl tert-butyl ether, and cyclopentyl methyl ether; ketones such as acetone, methyl ethyl ketone, and isobutyl methyl ketone; carbonic acid esters such as diethyl carbonate and propylene carbonate; amides such as dimethylformamide and dimethylacetamide; nitriles such as acetonitrile and benzonitrile; and alcohols such as methanol, isopropyl alcohol, and phenol. These may be used alone or in combination of two or more. The amount of the other solvent used is not particularly limited as long as it does not adversely affect the reaction. For example, it is more than 0 part by mass and 5 parts by mass or less, more than 0 part by mass and 3 parts by mass or less, or more than 0 part by mass and 1 part by mass or less with respect to 100 parts by mass of alkyl acetate (D).

[0033] <Catalyst> The catalyst used in the method for producing alkenyl diacetate (P) according to this embodiment is a catalyst containing a transition metal, preferably a catalyst containing palladium, more preferably at least palladium supported on a carrier, and still more preferably a carrier supporting palladium and a transition metal of Group 11 of the periodic table. A commercially available catalyst may be used, or a catalyst synthesized by a known method may be used.

[0034] As the carrier, for example, a porous material can be used. Examples of the carrier include inorganic carriers such as silica, alumina, silica-alumina, diatomaceous earth, montmorillonite, zeolite, titania, zirconia, activated carbon; and polymer compounds such as polystyrene, polyethylene, polyamide, and cellulose. These may be used alone or in combination of two or more. Among these, inorganic carriers are preferred, silica and alumina are more preferred, and silica is even more preferred. Note that the silica may contain impurities other than SiO2.

[0035] From the viewpoints of durability, high surface area, and easy availability, etc., it is preferable that the catalyst is one in which at least palladium is supported on at least one carrier selected from the group consisting of silicon dioxide (silica), activated carbon, and alumina, and it is more preferable that at least palladium is supported on a carrier of silicon dioxide or alumina.

[0036] It is preferable that the catalyst is one in which at least palladium is supported on a carrier having a maximum length of 2 mm or more and less than 20 mm, and in some cases, a maximum length of 2 mm or more and 10 mm or less is preferable. If the maximum length of the above carrier is 2 mm or more, it becomes easy to avoid the catalyst flowing out together with the product during continuous operation and becoming unusable in the long term. Also, if the maximum length of the above carrier is less than 20 mm, it becomes easy to prevent the surface area per unit volume from decreasing too much and the catalytic activity from becoming low. Note that the maximum length of the carrier is obtained based on the planar image or cross-sectional image of the carrier.

[0037] There is no particular limitation on the shape of the carrier, and it can be appropriately selected according to the reaction form. Specific shapes include, for example, powdery, spherical, and pellet-shaped, and the spherical shape is preferred. Note that when the carrier is spherical, the maximum length of the carrier is the diameter of the carrier, and when the shape of the carrier is other than spherical, the maximum length of the carrier is the diameter in the longitudinal direction.

[0038] The transition metal contained in the catalyst may be a simple transition metal or a compound containing a transition metal. Among transition metals, metallic palladium and palladium compounds are particularly preferred. The palladium compound is not particularly limited, but examples thereof include palladium chloride, palladium acetate, palladium nitrate, palladium sulfate, sodium chloropalladate, potassium chloropalladate, and barium chloropalladate.

[0039] In addition to the palladium, the support preferably further supports a transition metal of Group 11 of the periodic table, such as copper or gold. These transition metals may be used alone or in combination of two or more. Among these, copper and gold are preferred, and gold is more preferred, from the viewpoint of improving production efficiency. There are no particular limitations on the form of the transition metal of Group 11 of the periodic table used in preparing the catalyst, and examples include compounds such as nitrates, carbonates, sulfates, organic acid salts, and halides.

[0040] When the catalyst is a carrier carrying palladium and a transition metal of Group 11 of the periodic table, the ratio of palladium to the transition metal of Group 11 of the periodic table in the catalyst is preferably 0.001 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, of the transition metal of Group 11 of the periodic table per 1 part by mass of palladium.

[0041] There are no particular limitations on the method for preparing a catalyst in which palladium and a transition metal of Group 11 of the periodic table are supported on a carrier, and the catalyst can be obtained, for example, by sequentially carrying out the following steps (1) to (4).

[0042] Process (1) A step of impregnating a support with an aqueous solution of a palladium salt and a compound containing a transition metal of Group 11 of the periodic table to obtain a catalyst precursor A. Process (2) A step of contacting the catalyst precursor A obtained in step (1) with an aqueous solution of an alkali metal salt without drying to obtain a catalyst precursor B. Process (3) A step of obtaining a catalyst precursor C by bringing the catalyst precursor B obtained in step (2) into contact with a reducing agent such as hydrazine or formalin Step (4) A step of washing and drying the catalyst precursor C obtained in step (3) with water

[0043] As the catalyst obtained by the above preparation method, those having a specific surface area of 10 to 250 m 2 / g and a pore volume of 0.1 to 1.5 mL / g are preferred

[0044] The ratio of palladium to the carrier in the catalyst is preferably 10 to 1,000 parts by mass of the carrier with respect to 1 part by mass of palladium, and more preferably 30 to 500 parts by mass. When the carrier is 10 parts by mass or more with respect to 1 part by mass of palladium, the dispersion state of palladium is improved and the reaction performance is improved. Also, when the carrier is 1,000 parts by mass or less with respect to 1 part by mass of palladium, the industrial practicality is improved

[0045] There is no particular limitation on the amount of the above catalyst used in the method for producing alkenyldiacetate (P) according to this embodiment. However, from the viewpoint of increasing production efficiency, it is preferably 10 to 1,000% by mass, more preferably 50 to 800% by mass, and even more preferably 100 to 500% by mass with respect to the total mass of acetic acid (A), alkene (B) having 3 to 8 carbon atoms, and alkyl acetate (D)

[0046] <Catalyst activator> In the method for producing alkenyl diacetate (P) according to this embodiment, a catalyst activator may be used. The catalyst activator may be used in a state in which it is supported on the catalyst in advance, or may be charged into the reaction apparatus together with the reaction mixture. Examples of catalyst activators include hydroxides, nitrates, carboxylates, or carbonates of alkali metals such as sodium, potassium, and cesium; and hydroxides, nitrates, carboxylates, or carbonates of alkaline earth metals such as magnesium, calcium, and barium. These catalyst activators may be used alone or in combination of two or more. Among these, from the viewpoints of availability and reaction activity, salts of acetic acid (A) are preferred, alkali metal salts of acetic acid (A) are more preferred, and potassium acetate is even more preferred.

[0047] There are no particular restrictions on the amount of the catalyst activator used, but the amount of the catalyst activator used is preferably 1 to 20 mass %, more preferably 3 to 15 mass %, relative to 100 mass % which is the total of the mass of the carrier and the amount of the catalyst activator used.

[0048] <Alkenyl diacetate (P)> The alkenyl diacetate (P) obtained by the production method according to this embodiment varies depending on the alkene (B) having 3 to 8 carbon atoms used in the reaction. Specifically, when the alkene (B) having 3 to 8 carbon atoms is butadiene, the alkenyl diacetate (P) is at least one of 3,4-diacetoxybutene and 1,4-diacetoxy-2-butene. When the alkene (B) having 3 to 8 carbon atoms is isobutylene, the alkenyl diacetate (P) is at least one of MPDAc and its structural isomers. Among these, MPDAc is preferred as the alkenyl diacetate (P) because it can be used as a raw material for producing various chemical products.

[0049] <Reaction conditions> In the method for producing alkenyl diacetate (P) according to this embodiment, the reaction conditions such as the reaction temperature, reaction pressure, and reaction time may be appropriately set according to the amounts of acetic acid (A), alkene (B) having 3 to 8 carbon atoms, and alkyl acetate (D) used, the type of alkyl acetate (D), and the composition of the catalyst, etc., and are not particularly limited. For example, the reaction temperature is preferably in the range of 80 to 200°C. By setting the reaction temperature to 80°C or higher, the reaction rate does not become too slow, and alkenyl diacetate (P) can be efficiently produced. The reaction temperature is more preferably 90°C or higher. On the other hand, by setting the reaction temperature to 200°C or lower, side reactions including combustion are less likely to occur, alkenyl diacetate (P) can be efficiently produced, and corrosion of the reaction apparatus by carboxylic acid can also be suppressed. The reaction temperature is more preferably 180°C or lower, and even more preferably 160°C or lower. Also, the reaction time for 100 parts by mass of the catalyst to pass through 100 parts by mass of the reaction solution can be, for example, in the range of 0.1 to 30 hours. From the viewpoint of production efficiency, it may be 0.2 hours or more, and from the same viewpoint, it may be 24 hours or less, 10 hours or less, or 8 hours or less.

[0050] The reaction mode in the method for producing alkenyl diacetate (P) according to this embodiment may be either a continuous mode or a batch mode, and is not particularly limited. For example, when adopting a batch mode as the reaction mode, the catalyst may be charged into the reaction apparatus all at once together with the raw materials. Also, for example, when adopting a continuous mode as the reaction mode, the catalyst may be pre-filled into the reaction apparatus, or may be continuously charged into the reaction apparatus together with the raw materials. The catalyst may be used in any form of a fixed bed, a fluidized bed, or a suspension bed.

[0051] (Purification) In the method for producing alkenyl diacetate (P) according to this embodiment, purification may be performed after the above reaction. Specifically, the alkenyl diacetate (P) produced by the above reaction can be isolated by separating the catalyst and then purifying the reaction solution. The means for separating the catalyst is not particularly limited. In the case of a fixed-bed continuous system, the catalyst may simply be passed through a catalyst layer. In the case of a batch system, the catalyst may be separated by a conventional solid-liquid separation means, such as natural filtration, pressure filtration, reduced-pressure filtration, or centrifugal filtration. The means for purifying the reaction solution is not particularly limited, but for example, distillation, extraction, or column chromatography can be used. These methods may be performed in combination. Among these, distillation or extraction is preferred. The raw materials and solvent separated by the above purification can be reused in the reaction, and the separated catalyst can also be reused in the reaction.

[0052] In the method for producing alkenyl diacetate (P) according to the embodiment of the present invention described above, the target substance, alkenyl diacetate (P), can be produced efficiently with high conversion, high selectivity, and high yield, stably even under high temperature and high pressure conditions, while suppressing corrosion of the reaction vessel. [Example]

[0053] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these.

[0054] [Analysis conditions] The solution after the reaction (reaction mixture) was analyzed using a gas chromatograph GC2014 (Shimadzu Corporation, FID detector) and a capillary column (Agilent Technologies, DB-1, length 30 m, inner diameter 0.25 mm, film thickness 0.25 μm) under the following conditions. Column temperature: 50°C (5 min) → 10°C / min heating → 250°C (5 min) ·FID temperature: 250℃ ·Inlet temperature: 250℃ Carrier gas: Helium Make-up gas: Helium ·Injection volume: 0.2μL Column gas flow rate: 0.38 mL / min Split ratio: 20

[0055] [Composition of the product] The production amount of MPDAc after 6 hours and 24 hours of reaction was calculated from the recovered amount of the product solution and the analysis results of the above gas chromatograph. Also, the types and amounts of other components in the above product solution were calculated in the same manner.

[0056] [Fe content] One part by mass of the product solution after 24 hours of reaction was taken and placed in an eggplant flask. Under vacuum, the temperature was gradually raised from 50 °C in an oil bath and finally dried at 250 °C. After cooling the eggplant flask to room temperature, 100 parts by mass of a 1 mass% nitric acid aqueous solution was added to the eggplant flask, and the Fe content in the product solution was quantified by an ICP emission spectroscopic analyzer (Avio 500 manufactured by PerkinElmer). The detection limit of Fe for the above ICP emission spectroscopic analyzer is 0.1 mass ppm.

[0057] [Lower Explosion Limit Oxygen Concentration (LOC)] LOC means the limiting oxygen concentration at which explosiveness disappears for a three-component gas. While it has a property of decreasing in proportion to temperature, the pressure dependence depends on the property of the substance. For example, the LOC of 2-methyltetrahydrofuran at 100 °C and 1 atm is 9.4%, and the LOC at 100 °C and 20 atm is 9.1%. Therefore, it can be said that 2-methyltetrahydrofuran is a solvent that is more likely to explode when pressurized. Thus, when increasing the pressure to increase the oxygen solubility, it is necessary to lower the oxygen concentration of the supplied gas to ensure safety. On the other hand, ethyl acetate has an LOC of 9.4% at 100 °C and 1 atm, and an LOC of 9.9% at 100 °C and 20 atm. Therefore, it can be said that ethyl acetate becomes safer when pressurized.

[0058] The LOC is measured, for example, by the method described in "Experimental Limiting Oxygen Concentrations for Nine Organic Solvents at Temperatures and Pressures Relevant to Aerobic Oxidations in the Pharmaceutical Industry", Organic Process Research & Development, 2015, 19, 11, 1537-1543. The value of LOC in this specification is the value measured by the procedure described in this reference.

[0059] [Production Example 1: Preparation of Catalyst 1] A 250 mL (144 g) of silica carrier (5 mm φ) was immersed in an aqueous solution containing 4.00 g (13.6 mmol) of sodium tetrachloropalladate and 3.90 g (9.5 mmol) of tetrachloroauric acid tetrahydrate, and the whole amount was absorbed with water. Subsequently, 200 mL of an aqueous solution containing 16 g (131 mmol) of sodium metasilicate was added, and the mixture was allowed to stand for 20 hours. Then, 9.50 g (190 mmol) of hydrazine monohydrate was added to reduce the palladium salt and gold salt to metals. After washing the reduced catalyst with water, it was dried at 110 °C for 4 hours. Then, the carrier containing the above metal palladium was put into an aqueous solution containing 13.34 g (136 mmol) of potassium acetate, and after absorbing the whole solution, it was dried at 110 °C for 4 hours to prepare Catalyst 1.

[0060] [Production Example 2: Preparation of Catalyst 2] An aqueous solution containing 4.00 g (13.6 mmol) of sodium tetrachloropalladate and 3.90 g (9.5 mmol) of tetrachloroauric acid tetrahydrate was immersed with 250 mL (225 g) of a γ-alumina support (5 mmφ), and the entire amount was absorbed. Subsequently, 200 mL of an aqueous solution containing 16 g (131 mmol) of sodium metasilicate was added, and the mixture was allowed to stand for 20 hours. Then, 9.50 g (190 mmol) of hydrazine monohydrate was added to reduce the palladium salt and gold salt to metals. After washing the reduced catalyst with water, it was dried at 110 °C for 4 hours. Then, the carrier containing the above metal palladium was put into an aqueous solution containing 13.34 g (136 mmol) of potassium acetate, and after absorbing the whole solution, it was dried at 110 °C for 4 hours to prepare Catalyst 2.

[0061] [Example 1] A columnar SUS-316 stainless steel reaction vessel with a diameter of 15 mm and a length of 20 cm equipped with an electric heater was filled with 100 parts by mass of Catalyst 1 prepared in Production Example 1. Then, at a temperature of 100 °C and a pressure of 0.8 MPaG inside the reaction vessel, from the lower part of the reaction vessel, acetic acid (A), isobutylene which is an alkene (B) having 3 to 8 carbon atoms, a solvent, and a liquid containing other components (hereinafter also referred to as "reaction liquid"), and a gas (oxygen (C) and nitrogen (E)) were passed through using a plunger pump and a gas cylinder with flow rate controlled by a mass flow controller at a flow rate of 100 parts by mass per hour (the composition is as shown in Table 1-1), and the reaction was carried out for 24 hours. During the reaction, the set pressure of the back pressure valve installed at the tip of the outlet of the reaction vessel was set to 0.8 MPaG, and the gas-liquid two-phase flow was periodically discharged into the condenser SUS pipe cooled in a water tank at 10 °C, passed through a gas-liquid separation device, and the condensed product liquid was collected every 1 hour. The residence time of the reaction liquid in the reaction vessel (in other words, the time required for the reaction liquid to pass through the catalyst layer) was set to 1 hour. The composition of the product after 6 hours and 24 hours of the reaction, as well as the result of the amount of Fe in the product liquid after 24 hours of the reaction, are shown in Table 1-1. In Table 1, the type and amount of the catalyst used, the composition of the above reaction liquid and gas which are the feed components input into the reaction vessel, and the physical properties and characteristics of the feed components are shown together.

[0062] [Example 2] The reaction was carried out in the same manner as in Example 1, except that the compositions of the reaction liquid and gas were changed as shown in the "Feed Components" column in Table 1-1. The evaluation results are shown in Table 1-1 together with the compositions of the feed components.

[0063] [Example 3] Except for changing the gas composition as shown in Table 1-1, the reaction was carried out in the same manner as in Example 1. The evaluation results are shown in Table 1-1 together with the composition of the feed components.

[0064] [Example 4] Except for changing the reaction pressure as shown in Table 1-1, the reaction was carried out in the same manner as in Example 1. The evaluation results are shown in Table 1-1 together with the composition of the feed components.

[0065] [Examples 5 to 7, 9 to 11] The reaction was carried out in the same manner as in Example 1, except that the composition of the reaction solution was changed as shown in Tables 1-1 and 1-2. The evaluation results are shown in Tables 1-1 and 1-2 together with the composition of the feed components. Note that the exact LOC value of isopropyl acetate is unknown, and therefore is indicated as "-" in Table 1-1.

[0066] [Example 8] Except for changing the catalyst as shown in Table 1-2, the reaction was carried out in the same manner as in Example 1. The evaluation results are shown in Table 1-2 together with the compositions of the feed components.

[0067] [Comparative Example 1] The reaction was carried out in the same manner as in Example 1, except that the composition of the reaction solution was changed as shown in Table 1-2, the alkyl acetate (D) was not used, and the amount of acetic acid (A) used was increased. The evaluation results are shown in Table 1-2 together with the composition of the feed components.

[0068] [Comparative Examples 2 and 3] Except for changing the composition of the reaction solution as shown in Table 1-2 and using a solvent other than the alkyl acetate (D), the reaction was carried out in the same manner as in Example 1. The evaluation results are shown in Table 1-2.

[0069] [Table 1-1]

[0070] [Table 1-2]

[0071] As shown in Table 1-1, in Example 1, the yield of MPDAc, which is alkenyl diacetate (P), after 6 hours of reaction was 45% relative to the supplied isobutylene. Furthermore, the amount of MPDAc isomers with a boiling point close to that of MPDAc produced as a by-product was small, allowing MPDAc to be synthesized under conditions that facilitated its purification. Furthermore, the reaction results were the same both after 6 and 24 hours of reaction, confirming the long life of the catalyst. Furthermore, the Fe content was less than 0.1 ppm by mass, the analytical lower limit, and no Fe elution due to corrosion of the reaction vessel was observed.

[0072] Furthermore, as shown in Tables 1-1 and 1-2, in Examples 2 to 11, there was no corrosion of the reaction vessel, and MPDAc could be produced stably with high productivity even under high temperature and high pressure conditions.

[0073] On the other hand, as shown in Table 1-2, Comparative Example 1, in which alkyl acetate (D) was not used as a solvent, showed a significant decrease in the reaction rate (i.e., the consumption rate of isobutylene, which is the alkene (B) having 3 to 8 carbon atoms). Additionally, compared with Examples 1 to 11, in which alkyl acetate (D) was used, the amount of MPDAc produced decreased, and the amount of isomers with similar boiling points produced increased, resulting in a decrease in the MPDAc yield. Furthermore, when the reaction was carried out for a long period of time, the amount of MPDAc produced, which is the target substance, decreased, confirming that the catalytic activity decreased over time. Additionally, compared with Examples 1 to 11, in which alkyl acetate (D) was used, higher levels of Fe were detected in the reaction solution, indicating the progression of corrosion of the SUS-316 reactor.

[0074] In Comparative Example 2 where methanol was used as the solvent instead of the alkyl acetate (D), the reaction rate decreased significantly compared to Example 1. In addition, compared to Example 1, the production amount of MPDAc decreased, the production amount of isomers with boiling points close to each other increased, and the yield of MPDAc decreased. Furthermore, when the reaction was carried out for a long time, a decrease in the production amount of the target product MPDAc was observed, and it was confirmed that the catalytic activity decreased over time. Also, compared to Example 1 where Fe in the product solution was not detected, Fe was detected in the product solution, and it was found that corrosion of the reaction vessel made of SUS-316 occurred.

[0075] Furthermore, in Comparative Example 3 where N,N-dimethylformamide was used as the solvent instead of the alkyl acetate (D), the reaction rate decreased significantly compared to Example 1. Also, a large amount of the hydrolyzates (monoalcohol form, diol form) of MPDAc in the product was detected. Compared to Example 1, the production amount of MPDAc decreased, the amount of the hydrolyzate of MPDAc with a boiling point close to it increased, and the yield of MPDAc decreased. Furthermore, when the reaction was carried out for a long time, a decrease in the production amount of the target substance MPDAc was observed, and it was confirmed that the catalytic activity decreased over time.

[0076] [Example 12] MPDAc is produced by the same procedure as in Example 1 except that nitrogen gas is not used. The product thus obtained has a lower reaction rate due to a reduction in bubbles in the reaction vessel and a decrease in the diffusion rate of the reaction solution compared to Example 1, but it is possible to produce MPDAc with a high selectivity in the same manner as in Example 1.

Industrial Applicability

[0077] By the production method of the present invention, it is possible to stably produce alkenyl diacetate with a high selectivity even under high-temperature and high-pressure conditions while suppressing the corrosion of the reaction vessel. The obtained alkenyl diacetate can be used as a raw material for producing various industrially useful compounds.

Claims

1. A method for producing alkenyl diacetate, comprising reacting acetic acid (A), an alkene (B) having 3 to 8 carbon atoms, and oxygen (C) in a liquid phase in the presence of a catalyst containing a transition metal in a reaction vessel in the presence of an alkyl acetate (D) represented by the formula (I). 【Chemical 1】 [In formula (I), R １ represents an aliphatic hydrocarbon group having 1 to 8 carbon atoms, which is linear, cyclic, or branched.]

2. The method for producing alkenyl diacetate according to claim 1, wherein the alkene (B) having 3 to 8 carbon atoms is isobutylene, and the alkenyl diacetate is 2-methylene-1,3-propanediacetate.

3. The method for producing alkenyl diacetate according to claim 1 or 2, further using nitrogen (E) in an amount of 15 molar equivalents or more based on oxygen (C).

4. The method for producing alkenyl diacetate according to claim 1 or 2, further using ethanol (F) in an amount of 0.001 to 50,000 mass ppm based on the mass of the alkyl acetate (D).

5. In the formula (I), R １ represents an aliphatic hydrocarbon group having 1 to 4 carbon atoms and being linear or branched, the method for producing an alkenyl diacetate according to claim 1 or 2.

6. The method for producing alkenyl diacetate according to claim 1 or 2, wherein the boiling point of the alkyl acetate (D) is less than 117 °C.

7. The method for producing alkenyl diacetate according to claim 1 or 2, wherein the alkyl acetate (D) is ethyl acetate.

8. The method for producing alkenyl diacetate according to claim 1 or 2, wherein the oxygen concentration in the gas phase part in the reaction vessel is equal to or lower than the explosion limit oxygen concentration of the vapor of the liquid phase measured according to the ASTM E2079-19 standard.

9. [[ID= ​ ​ ​ ​ ​ ​ ​ The method for producing an alkenyldiacetate according to claim 1 or 2, wherein the ratio MA / MB of the mass MA of acetic acid (A) to the mass MB of an alkene (B) having 3 to 8 carbon atoms is 3 or less.

14. The method for producing an alkenyldiacetate according to claim 1 or 2, wherein the ratio MD / (MA + MB) of the mass MD of an alkyl acetate (D) to the total of the mass MA of acetic acid (A) and the mass MB of an alkene (B) having 3 to 8 carbon atoms is 1 or more and 50 or less.

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