JP4960005B2 - Process for producing α, β-unsaturated carboxylic acid - Google Patents

Description

  The present invention relates to a method for producing an α, β-unsaturated carboxylic acid. Specifically, the present invention relates to a method for producing an α, β-unsaturated carboxylic acid by hydrolyzing an α, β-unsaturated carboxylic acid anhydride at the bottom of the distillation column.

Patent Document 1 discloses α, β for producing an α, β-unsaturated carboxylic acid by oxidizing an olefin or α, β-unsaturated aldehyde with molecular oxygen in a liquid phase (referred to as liquid phase oxidation). -Unsaturated carboxylic acid production catalysts and methods for their production are disclosed.
International Publication No. 02/083299 Pamphlet

  However, for example, when (meth) acrylic acid is produced by liquid-phase oxidation of propylene or isobutylene with molecular oxygen to produce (meth) acrylic acid, it becomes clear from the study by the present inventors. I came. The oxidation reaction of propylene or isobutylene is a sequential reaction in which olefin is oxidized in the first stage reaction to produce (meth) acrolein, and (meth) acrolein is oxidized in the second stage reaction to produce (meth) acrylic acid. . It is not possible to determine the route by which (meth) acrylic anhydride is synthesized in the reaction process, but the oxidation reaction of olefin proceeds to some extent, and the amount of (meth) acrolein and (meth) acrylic acid increases. From the fact that the presence of anhydrous (meth) acrylic acid is confirmed, it is presumed that it is produced by the reaction of (meth) acrolein, (meth) acrylic acid, and oxygen.

  Patent Document 1 describes the analysis result of the reaction solution, but does not mention that anhydrous (meth) acrylic acid is generated. Moreover, although it describes describing performing distillation as a purification method of (meth) acrylic acid, detailed conditions are not touched. As described above, when α, β-unsaturated carboxylic acid is produced from olefin or α, β-unsaturated aldehyde by liquid phase oxidation, no measures have been taken for α, β-unsaturated carboxylic acid anhydride. There was still room for improvement in the production of α, β-unsaturated carboxylic acids.

  The object of the present invention is to produce an α, β-unsaturated carboxylic acid in high yield.

  In order to solve the above-mentioned problems, the present inventors have intensively studied a method for economically converting an α, β-unsaturated carboxylic acid anhydride to an α, β-unsaturated carboxylic acid on an industrial scale. , Β-unsaturated carboxylic acid anhydride, α, β-unsaturated carboxylic acid, and a mixture containing water can be economically treated by treating the mixture under certain conditions. The present inventors have found that it can be converted to α, β-unsaturated carboxylic acid and have completed the present invention.

  That is, the present invention contains an α, β-unsaturated carboxylic acid, an α, β-unsaturated carboxylic acid anhydride, and water, with respect to 1 mol of the α, β-unsaturated carboxylic acid anhydride. A mixture of 5 moles or more of water and 2 moles or more of the α, β-unsaturated carboxylic acid is heated to 30 ° C. or more to hydrolyze at least a part of the α, β-unsaturated carboxylic acid anhydride. A process for producing an α, β-unsaturated carboxylic acid.

  The heating temperature of the mixture is preferably 60 ° C. or higher and 150 ° C. or lower. The heating time of the mixture is preferably 0.05 hours or more.

Further, even when the mixture further contains a low-boiler having a lower boiling point than any of the α, β-unsaturated carboxylic acid, the α, β-unsaturated carboxylic acid anhydride, and the water, By performing the hydrolysis in a distillation column, at least a part of the low-boiling substances can be removed from the top of the distillation column. In particular, the mixture is a reaction solution obtained by oxidizing an olefin or an α, β-unsaturated aldehyde in a liquid phase containing water in the presence of a palladium metal-containing catalyst , or prepared from the reaction solution. It is suitable in some cases. As a more specific embodiment,
Obtaining a reaction solution obtained by oxidizing an olefin or an α, β-unsaturated aldehyde in a liquid phase containing water in the presence of a palladium metal-containing catalyst ;
The reaction solution contains an α, β-unsaturated carboxylic acid, an α, β-unsaturated carboxylic acid anhydride, water, and a low-boiler having a boiling point lower than any of these, the α, β A step of obtaining a mixture in which the water is 5 mol or more and the α, β-unsaturated carboxylic acid is 2 mol or more with respect to 1 mol of the unsaturated carboxylic acid anhydride;
The mixture is supplied to a distillation column, and the mixture is heated to 30 ° C. or higher by a heating unit at the bottom of the distillation column to remove at least a part of the low-boiling substances from the top of the distillation column. Hydrolyzing at least part of the α, β-unsaturated carboxylic acid anhydride,
It is a manufacturing method of (alpha), (beta)-unsaturated carboxylic acid characterized by having.

  According to the method of the present invention, the target substance, α, β-unsaturated carboxylic acid, can be produced with high yield.

  In the present invention, α, β-unsaturated carboxylic acid is produced by hydrolyzing α, β-unsaturated carboxylic acid anhydride with water. At this time, α, β-unsaturated carboxylic acid is used as a catalyst, and the composition of the mixture containing these three components is adjusted to a specific range. Examples of the α, β-unsaturated carboxylic acid anhydride include methacrylic acid anhydride, acrylic acid anhydride, crotonic acid anhydride (β-methylacrylic acid anhydride), cinnamic acid anhydride (β-phenylacrylic acid). Acid anhydride) and the like.

  The α, β-unsaturated carboxylic acid anhydride becomes α, β-unsaturated carboxylic acid by hydrolysis. Therefore, in principle, α, β-unsaturated carboxylic acid anhydride can be hydrolyzed by the presence of water in the mixture, but 5 mol of water per mole of α, β-unsaturated carboxylic acid anhydride. If it is less than a mole, the hydrolysis rate becomes extremely slow, which is insufficient for industrial implementation. Therefore, in the present invention, the amount of water relative to 1 mol of the α, β-unsaturated carboxylic acid anhydride is 5 mol or more. The amount of water relative to 1 mol of the α, β-unsaturated carboxylic acid anhydride is preferably 7 mol or more, more preferably 10 mol or more, and further preferably 15 mol or more. Even if the amount of water is large, there is no problem in the progress of the hydrolysis reaction. More preferred is 5000 moles or less.

  The inventors' study has revealed that α, β-unsaturated carboxylic acid has a catalytic action in the hydrolysis reaction. As the acid catalyst, sulfuric acid, acidic ion exchange resin and the like are generally known, but in the method of the present invention, α, β-unsaturated carboxylic acid which is a hydrolysis product is converted into α, β-unsaturated. The catalyst effect is expressed by making it exist 2 mol or more with respect to carboxylic anhydride. This eliminates the need for a special apparatus for hydrolyzing the α, β-unsaturated carboxylic acid anhydride or a special operation such as separation of the catalyst, which is extremely advantageous economically. When the amount of α, β-unsaturated carboxylic acid relative to 1 mol of α, β-unsaturated carboxylic acid anhydride is less than 2 mol, sufficient catalytic effect cannot be obtained, which is insufficient for industrial implementation. It is. Examples of the α, β-unsaturated carboxylic acid include methacrylic acid, acrylic acid, crotonic acid (β-methylacrylic acid), cinnamic acid (β-phenylacrylic acid), and the like. The α, β-unsaturated carboxylic acid selected here may be the same as or different from the α, β-unsaturated carboxylic acid produced by hydrolysis of the α, β-unsaturated carboxylic acid anhydride. . The amount of the α, β-unsaturated carboxylic acid relative to 1 mol of the α, β-unsaturated carboxylic acid anhydride is preferably 2 mol or more, more preferably 3 mol or more, and further preferably 4 mol or more. Even if the amount of α, β-unsaturated carboxylic acid is large, there is no problem in the catalytic effect, but from the viewpoint of reducing the purification load, 1000 mol or less is preferable, 200 mol or less is more preferable, and 150 mol or less is more preferable. .

  In the present invention, at least a part of the α, β-unsaturated carboxylic acid anhydride is hydrolyzed by heating the mixture satisfying the above conditions to 30 ° C. or higher. When the temperature is lower than 30 ° C., the rate of hydrolysis of the α, β-unsaturated carboxylic acid anhydride becomes extremely low, which is insufficient for industrial implementation. The higher the temperature is, the more easily the hydrolysis reaction of the α, β-unsaturated carboxylic acid anhydride proceeds, but the α, β-unsaturated carboxylic acid and the α, β-unsaturated carboxylic acid anhydride are easily polymerized. 60-150 degreeC is preferable, as for the temperature of a mixture, 65-130 degreeC is more preferable, and 70-120 degreeC is further more preferable.

  The heating time of the mixture can be appropriately set to a time during which the hydrolysis reaction of the α, β-unsaturated carboxylic anhydride proceeds sufficiently, but is preferably 0.05 hours or more. When the heating time is long, the hydrolysis reaction of α, β-unsaturated carboxylic acid anhydride proceeds more, but α, β-unsaturated carboxylic acid and α, β-unsaturated carboxylic acid anhydride are easily polymerized. . The heating time of the mixture is more preferably 0.05 to 10 hours, and further preferably 0.08 to 5 hours.

In order to prevent polymerization of α, β-unsaturated carboxylic acid or α, β-unsaturated carboxylic acid anhydride, a polymerization inhibitor can be appropriately added. The polymerization inhibitor is not particularly limited. For example, phenolic compounds such as hydroquinone and p-methoxyphenol; amine compounds such as p-phenylenediamine, NN′-diphenyl-p-phenylenediamine and diphenylamine; 4-hydroxy- 2,2,6,6-tetramethylpiperidine-N-oxyl, 4- [H- (OCH ₂ CH ₂ ) _n —O] -2,2,6,6-tetramethylpiperidine-N-oxyl (where n = 1-18) N-oxyl compounds; p-nitrosophenol, nitroso compounds such as N-nitrosophenylhydroxyamine; phenothiazines such as phenothiazine, bis- (α-methylbenzyl) phenothiazine, 3,7-dioctylphenothiazine Compound; and the like. These may be used singly or in combination of two or more at any ratio.

  The mixture containing α, β-unsaturated carboxylic acid, α, β-unsaturated carboxylic acid anhydride, and water as described above is not particularly limited, but for example, olefin or α, β-unsaturated aldehyde Can be used in the gas phase or in the liquid phase (hereinafter referred to as the gas phase oxidation reaction or liquid phase oxidation reaction). In addition, when the reaction solution obtained by gas phase oxidation reaction or liquid phase oxidation reaction of olefin or α, β-unsaturated aldehyde does not satisfy the above conditions, water and / or α, β-unsaturation from the outside. Carboxylic acid can be added as appropriate. The water and / or the α, β-unsaturated carboxylic acid may be recycled by recycling the one separated in the subsequent step. In particular, it is suitable when using a reaction liquid obtained by oxidizing an olefin or an α, β-unsaturated aldehyde in a liquid phase, or a reaction liquid prepared from the reaction liquid.

  The mixture may contain an α, β-unsaturated carboxylic acid, an α, β-unsaturated carboxylic acid anhydride, and a low-boiler having a lower boiling point than water. For example, an unreacted olefin or α, β-unsaturated aldehyde, alcohols, ketones, organic acids may be used for a reaction solution obtained by gas phase oxidation reaction or liquid phase oxidation reaction of olefin or α, β-unsaturated aldehyde. , Organic acid esters, hydrocarbons, and the like may be contained, of which α, β-unsaturated carboxylic acids and α, β-unsaturated carboxylic anhydrides have lower boiling points.

  At this time, it is preferable to perform hydrolysis in a distillation column. By doing so, at least a part of the low-boiling substances and water can be removed from the top of the distillation column, and at least a part of the α, β-unsaturated carboxylic acid anhydride can be hydrolyzed. Specifically, the mixture is supplied to the distillation column, and the mixture is heated to 30 ° C. or higher in the heating section at the bottom of the distillation column, so that at least a part of low-boiling substances and water are fed from the top of the distillation column. While removing, at least a part of the α, β-unsaturated carboxylic acid anhydride can be hydrolyzed. Distillation tower type is not particularly limited, and bubble bell tray, perforated plate tray, bubble tray, jet tray, etc. that contact gas and liquid in cross flow; turbo grid tray that contacts gas and liquid in counter current, ripple Trays, dual-flow trays, kittel trays, etc .; baffle trays that are otherwise in contact with gas and liquid, disk donut trays, etc .; shelf towers, eg, Raschig rings, pole rings, interlock saddles, Dixon packing A generally used distillation column such as a packed column packed with an irregular packing material such as McMahon packing and a regular packing material typified by a throughr packing can be used. The distillation may be continuous or batchwise. The distillation may be performed under atmospheric pressure, reduced pressure, or increased pressure.

When the hydrolysis is performed in the distillation column, the heating time of the mixture may be the residence time in the distillation column. For example, in the case of continuous distillation, the residence time of the mixture is calculated by dividing the volume (m ³ ) of the heating section at the bottom of the distillation column by the average flow rate (m ³ / Hr) of the mixture supplied to the distillation column. be able to. For example, in the case of batch distillation, it is a time of 30 ° C. or more in the period from the end of the supply of the mixture and the start of heating to the end of the heating and the extraction of the mixture.

  There may be a plurality of distillation columns for performing the separation and hydrolysis of the low boilers and water. In this case, it is preferable to adjust so that the total value of the heating part residence time in each distillation column falls within a predetermined range.

  In order to obtain a highly purified α, β-unsaturated carboxylic acid, it is preferable to sufficiently remove water. In general, water is known to azeotrope with α, β-unsaturated carboxylic acids. Therefore, it is difficult to separate water and α, β-unsaturated carboxylic acid by ordinary distillation. Therefore, it is preferable to remove water by azeotropic distillation or solvent extraction.

  In azeotropic distillation, water and an α, β-unsaturated solvent are allowed to coexist with a solvent that azeotropes with water at a temperature lower than the azeotropic temperature of water and an α, β-unsaturated carboxylic acid (hereinafter referred to as an azeotropic solvent). Saturated carboxylic acid can be efficiently separated. At that time, by using the above hydrolysis conditions, if there is a residual low-boiling product, the separation and the hydrolysis of the remaining α, β-unsaturated carboxylic acid anhydride are performed azeotropically. It can also be carried out during the distillation operation.

  The azeotropic solvent is not particularly limited as long as it is a solvent that azeotropes with water at a temperature lower than the azeotropic temperature of water and the α, β-unsaturated carboxylic acid. For example, benzene, toluene and the like can be used. As a result, only the azeotropic solvent layer can be refluxed to the azeotropic distillation column, so that the azeotropic solvent newly supplied from outside the system should be considered only for the loss to the water layer and the azeotropic distillation column bottoms. Good.

  The supply amount of the azeotropic solvent is preferably an amount calculated from the azeotropic composition with the low boiler (water) to be removed. If the amount of azeotropic solvent is small, water removal is insufficient and the α, β-unsaturated carboxylic acid is not sufficiently purified. When the amount of the azeotropic solvent is large, the excess azeotropic solvent is mixed into the α, β-unsaturated carboxylic acid and is not sufficiently purified. For example, when toluene is used as the azeotropic solvent, it is preferable to supply about 4 times as much toluene as the weight of water to be removed from the azeotropic composition (toluene: water = 80: 20).

  The temperature of the azeotropic distillation is preferably 30 ° C. or higher, more preferably 60 ° C. or higher and 150 ° C. or lower. In order to lower the distillation temperature, a decompression operation is required, and it is economically problematic to carry out distillation at an excessively low temperature. When the distillation temperature is too high, there is a problem that polymerization of α, β-unsaturated carboxylic acid is likely to occur. The distillation pressure needs to be reduced or increased as necessary to achieve the above distillation temperature.

  In order to prevent the polymerization of the α, β-unsaturated carboxylic acid during the azeotropic distillation, the polymerization inhibitor can be appropriately used. The distillation column format is not particularly limited, and those in the above format can be used.

  After the α, β-unsaturated carboxylic anhydride is hydrolyzed by the above-described method to produce the α, β-unsaturated carboxylic acid, the α, β-unsaturated carboxylic acid is further added as necessary. It may be purified. The purification method at that time is not particularly limited, and distillation, membrane separation, solvent extraction, etc. can be performed in consideration of the purity of the required α, β-unsaturated carboxylic acid and the physical properties of the impurities to be removed. . Of these, distillation and solvent extraction are preferred from an economical viewpoint.

  Distillation can be carried out by the method described above. Further, in the solvent extraction, an α, β-unsaturated carboxylic acid and water are separated by using an extraction solvent that can be separated into a layer containing α, β-unsaturated carboxylic acid and a layer containing water. It becomes possible to do. At the same time, impurities can also be separated.

  The extraction solvent is not particularly limited as long as it can be separated into a layer containing α, β-unsaturated carboxylic acid and a layer containing water. For example, aliphatic hydrocarbons such as n-hexane, n-heptane and octane; aromatic hydrocarbons such as benzene, toluene and xylene; methyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, methacrylic acid Examples include esters such as t-butyl; ketones such as methyl isobutyl ketone; alcohols such as n-butanol, i-butanol and n-amyl alcohol; ethers such as methyl tertiary butyl ether. These may be used singly or in combination of two or more. Among these, from the viewpoint of extraction efficiency of α, β-unsaturated carboxylic acid, n-heptane, benzene, toluene, methyl methacrylate, t-butyl methacrylate, methyl tertiary butyl ether, or a mixture of these is preferable. , Methyl methacrylate, t-butyl methacrylate, or a mixture thereof is more preferable, and a mixture of toluene and methyl methacrylate, and a mixture of methyl methacrylate and t-butyl methacrylate are more preferable. The mixing ratio in the case of using a mixture of two or more solvents is not particularly limited. For example, in the case of a mixture of toluene and methyl methacrylate, 40 to 90% by mass of toluene and 10 to 60% by mass of methyl methacrylate are preferable.

  The temperature of solvent extraction is not particularly limited. The extraction efficiency of α, β-unsaturated carboxylic acid decreases at a high temperature, and the extraction efficiency of α, β-unsaturated carboxylic acid increases at a low temperature. In addition, the extraction efficiency decreases at a high temperature and further energy for heating is required, and the extraction efficiency is improved at a low temperature but energy for cooling is required. A range is preferred.

  The pressure for performing solvent extraction is not particularly limited. Although it is possible to carry out any of atmospheric pressure, pressurization and reduced pressure, it is preferred to carry out at atmospheric pressure since the apparatus and operation are simple.

  The apparatus for performing the solvent extraction is not particularly limited as long as the extraction operation can be performed. A mixer-settler type extraction device, a rotating disk extraction tower, a perforated plate extraction tower, or the like can be used. In the case where a solid matter is precipitated by contact between the α, β-unsaturated carboxylic acid and the extraction solvent, the α, β-unsaturated carboxylic acid and the extraction solvent are contacted in advance, and the precipitated solid matter is filtered and separated. Preferably only the components are introduced into the extraction device.

  By separating the extraction solvent from the organic layer separated by solvent extraction, a highly pure α, β-unsaturated carboxylic acid can be obtained. The separation method of the extraction solvent is not particularly limited, but distillation separation is preferred as a method that is economical and simple to carry out. When carrying out the distillation, it is preferable to adopt the distillation operation conditions described above.

  The α, β-unsaturated carboxylic acid from which water has been removed by the above operation may contain impurities having a boiling point higher than that of the α, β-unsaturated carboxylic acid. In such a case, it is preferable to further perform distillation or thin film evaporation. When carrying out distillation, the distillation operation conditions can be employed. Thin film evaporation is performed by a thin film evaporator that can form a thin liquid film and instantaneously heat and evaporate a sample. Purification of a readily polymerizable substance such as an α, β-unsaturated carboxylic acid is performed. Suitable for

  Although it does not specifically limit as a thin film evaporator, A pot still type molecular distiller, a thin film descent | fall type | formula concentrator, a Smith type thin film evaporator, a louver type thin film evaporator, a Hickman type centrifugal molecular distillation apparatus, an Othmer type centrifugal molecular distillation apparatus The rotor tray type centrifugal molecular distillation apparatus is preferable, and the Smith type thin film evaporator, the Lewer type thin film evaporator, and the Hickman type centrifugal molecular distillation apparatus are more preferable.

  The conditions for thin film evaporation may be in a range that does not impair the quality of the target α, β-unsaturated carboxylic acid. The temperature for thin film evaporation is preferably 30 ° C. or higher, more preferably 60 ° C. or higher. If the evaporation temperature is too low, a sufficient evaporation rate cannot be obtained, and the recovery of the α, β-unsaturated carboxylic acid becomes insufficient. The upper limit of the evaporation temperature is preferably 150 ° C. or lower, and more preferably 120 ° C. or lower. If the evaporation temperature is too high, there is a risk of degradation of the quality of α, β-unsaturated carboxylic acid and polymerization. The pressure for performing thin film evaporation is preferably −0.101224 MPa (0.01 torr-absolute pressure) or more, and more preferably −0.101312 MPa (0.1 torr-absolute pressure) or more. If the evaporation pressure is too low, a special vacuum generator is required, which is economically problematic. The evaporation pressure is preferably −0.074661 MPa (200 torr−absolute pressure) or less, more preferably −0.094659 MPa (50 torr−absolute pressure) or less, and further preferably −0.098659 MPa (20 torr−absolute pressure) or less. If the evaporation pressure is too high, a sufficient evaporation rate cannot be obtained and the recovery of the α, β-unsaturated carboxylic acid becomes insufficient. In addition, the polymerization inhibitor can be appropriately used in order to prevent polymerization during operation. The pressure notation is a gauge pressure notation unless otherwise specified.

  The α, β-unsaturated carboxylic acid purified by the above operation may be recycled and reused to promote the decomposition of the α, β-unsaturated carboxylic acid anhydride.

  As described above, the present invention is suitable for the case of using a mixture that is a reaction liquid obtained by oxidizing an olefin or an α, β-unsaturated aldehyde in a liquid phase, or a reaction liquid prepared from the reaction liquid. is there. That is, after the reaction of oxidizing the olefin or α, β-unsaturated aldehyde in the liquid phase, the yield of the target product α, β-unsaturated carboxylic acid is remarkably increased by carrying out the method of the present invention. be able to. Hereinafter, an example of a method for oxidizing an olefin or an α, β-unsaturated aldehyde in a liquid phase will be described.

  Olefin or α, β-unsaturated aldehyde is used as a raw material for liquid phase oxidation. Examples of the olefin used as the raw material include propylene, isobutylene and 2-butene. Examples of the α, β-unsaturated aldehyde used as a raw material include acrolein, methacrolein, crotonaldehyde (β-methylacrolein), cinnamaldehyde (β-phenylacrolein), and the like. Suitable for liquid phase oxidation using propylene or isobutylene as olefin, and acrolein or methacrolein as α, β-unsaturated aldehyde as raw materials. The olefin or α, β-unsaturated aldehyde used as a raw material may contain some saturated hydrocarbons and / or lower saturated aldehydes as impurities.

  The α, β-unsaturated carboxylic acid produced is an α, β-unsaturated carboxylic acid having the same carbon skeleton as the olefin when the raw material is an olefin, and when the raw material is an α, β-unsaturated aldehyde, An α, β-unsaturated carboxylic acid in which an aldehyde group of an α, β-unsaturated aldehyde is changed to a carboxyl group. Specifically, acrylic acid is obtained when the raw material is propylene or acrolein, and methacrylic acid is obtained when the raw material is isobutylene or methacrolein.

  The reaction solvent used for the liquid phase oxidation reaction is not particularly limited, and water, alcohols, ketones, organic acids, organic acid esters, hydrocarbons, and the like can be used. Examples of alcohols include tertiary butanol and cyclohexanol. Examples of ketones include acetone, methyl ethyl ketone, and methyl isobutyl ketone. Examples of the organic acids include acetic acid, propionic acid, n-butyric acid, iso-butyric acid, n-valeric acid, iso-valeric acid and the like. Examples of the organic acid esters include ethyl acetate and methyl propionate. Examples of hydrocarbons include hexane, cyclohexane, and toluene. Among these, organic acids having 2 to 6 carbon atoms, ketones having 3 to 6 carbon atoms, and tertiary butanol are preferable. A solvent may be individual or 2 or more types of mixed solvents may be sufficient as it. Further, when at least one compound selected from the group consisting of alcohols, ketones, organic acids and organic acid esters is used as a solvent, it is preferable to use a mixed solvent of this compound and water. The amount of water in the mixed solvent is not particularly limited, but is preferably 2% by mass or more and more preferably 5% by mass or more with respect to the mass of the mixed solvent. Moreover, 70 mass% or less is preferable, and 50 mass% or less is more preferable. The mixed solvent is desirably uniform, but may be used in a non-uniform state.

  The amount of olefin or α, β-unsaturated aldehyde in the reaction solution for performing the liquid phase oxidation reaction is preferably 0.1% by mass or more, and 0.5% by mass or more with respect to the reaction solvent present in the reactor. More preferred. Moreover, 50 mass% or less is preferable and 30 mass parts or less are more preferable.

  In carrying out the liquid phase oxidation reaction, it is preferable to use a catalyst. Although it does not specifically limit as a catalyst seed | species, It is suitable to use a noble metal containing catalyst. A noble metal refers to palladium, platinum, rhodium, ruthenium, iridium, gold, silver, rhenium, or osmium. Of these, palladium, platinum, rhodium, ruthenium, iridium and gold are preferable, and palladium is particularly preferable.

  The catalyst may be a supported catalyst in which a noble metal is supported on a carrier, or may be a non-supported catalyst. Examples of the carrier used as a supported catalyst include activated carbon, carbon black, silica, alumina, magnesia, calcia, titania and zirconia, among which activated carbon, silica and alumina are preferably used. Further, the loading ratio of the noble metal is preferably 0.1% by mass or more, more preferably 1% by mass or more, further preferably 2% by mass or more, and particularly preferably 4% by mass or more based on the mass of the carrier before loading. Moreover, 40 mass% or less is preferable, 30 mass% or less is more preferable, 20 mass% or less is further more preferable, and 15 mass% or less is especially preferable.

  The noble metal-containing catalyst can be prepared by dissolving a noble metal compound in a solvent and reducing it using a reducing agent. The target noble metal-containing catalyst is precipitated by this reduction. The reduction can be performed in the gas phase, but is preferably performed in the liquid phase. Hereinafter, a liquid phase reduction method for reducing a noble metal compound in a liquid phase will be described.

  First, a noble metal compound is dissolved in a solvent to obtain a noble metal compound solution. Although the noble metal compound is not particularly limited, for example, a noble metal chloride, oxide, acetate, nitrate, sulfate, tetraammine complex, acetylacetonate complex, etc. are preferable, and noble metal chloride, oxide, acetate, Nitrate and sulfate are more preferred, and noble metal chlorides, acetates and nitrates are particularly preferred. As the solvent, one or more solvents selected from the group consisting of water, alcohols, ketones, organic acids and hydrocarbons can be used. The concentration of the noble metal compound in the noble metal compound solution is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and particularly preferably 0.5% by mass or more. Moreover, 20 mass% or less is preferable, 10 mass% or less is more preferable, and 7 mass% or less is especially preferable.

  When preparing a supported catalyst, the noble metal compound in the noble metal compound solution may be supported on a carrier. Examples of the supporting method include a method of adding a support in a noble metal compound solution, and a method of impregnating a noble metal compound solution in a support.

  Next, a noble metal-containing catalyst can be obtained by adding a reducing agent to the noble metal compound solution to reduce the noble metal compound. The reducing agent to be used is not particularly limited, and examples thereof include hydrazine, formaldehyde, sodium borohydride, hydrogen, formic acid, formic acid salt, ethylene, propylene, and isobutylene. When the reducing agent is a gas, it is preferably carried out in a pressurizing apparatus such as an autoclave in order to increase the solubility in the solution. In that case, it is preferable to pressurize the inside of a pressurization apparatus with a reducing agent. The pressure is preferably 0.1 to 1 MPa. When the reducing agent is a liquid, there is no limitation on the apparatus for reducing the noble metal, and the reduction can be performed by adding the reducing agent to the noble metal compound solution. Although the usage-amount of a reducing agent at this time is not specifically limited, About 1-100 mol is preferable with respect to 1 mol of noble metal compounds. The temperature and reduction time of the system at the time of reduction vary depending on the reduction method, the noble metal compound used, the solvent, the reducing agent, etc., but cannot be generally stated, but in the case of the liquid phase reduction method, the reduction temperature is 0 to 100 ° C. 0.5-24 hours are preferred.

  The noble metal-containing catalyst is preferably used in a state of being suspended in a reaction solution for performing liquid phase oxidation, but may be used in a fixed bed. The amount of the noble metal-containing catalyst in the reaction solution is preferably 0.01 parts by mass or more as a catalyst present in the reactor with respect to 100 parts by mass of the solution present in the reactor performing liquid phase oxidation. 2 parts by mass or more is more preferable. Moreover, 50 mass parts or less are preferable, and 30 mass parts or less are more preferable.

  The liquid phase oxidation reaction is preferably carried out using a gas containing molecular oxygen as an oxidizing agent. As the gas containing molecular oxygen, air is preferable from its oxygen concentration and economy, but if necessary, such as when producing at a higher oxygen concentration, pure oxygen or pure oxygen and air, nitrogen, A mixed gas with carbon dioxide, water vapor or the like can also be used. The amount of molecular oxygen is preferably 0.1 mol or more, more preferably 0.3 mol or more, and even more preferably 0.5 mol or more with respect to 1 mol of the olefin or α, β-unsaturated aldehyde. Moreover, 30 mol or less is preferable, 25 mol or less is more preferable, and 20 mol or less is further more preferable.

  The gas containing molecular oxygen is preferably supplied in the form of fine bubbles in the liquid phase using a gas disperser. Examples of the gas distributor include a perforated plate, a nozzle, and a porous plate. The superficial velocity of the gas containing molecular oxygen is preferably 0.2 cm / s or more, and more preferably 0.5 cm / s or more. Moreover, 30 cm / s or less is preferable and 25 cm / s or less is more preferable.

  The temperature and pressure at which the liquid phase oxidation reaction is carried out are appropriately selected depending on the reaction solvent and raw materials used. The reaction temperature is preferably 60 ° C. or higher, more preferably 70 ° C. or higher. Moreover, 200 degrees C or less is preferable and 150 degrees C or less is more preferable. The reaction pressure is preferably a pressure equal to or higher than the pressure at which the reaction liquid liquefies at the reaction temperature, specifically 0.05 MPa or higher, more preferably 0.1 MPa or higher. The higher the reaction pressure, the faster the oxidation reaction proceeds. Therefore, the reaction pressure is preferably set to a high value, but is preferably 10 MPa or less, and more preferably 8 MPa or less, from an economical viewpoint.

  In order to prevent polymerization of raw materials and products at a high temperature during the liquid phase oxidation reaction, it is preferable to use a polymerization inhibitor. As the polymerization inhibitor, for example, the polymerization inhibitors described above can be used.

  The liquid phase oxidation reaction can be carried out by either a batch system or a continuous system, but a continuous system is preferred industrially. In the case of a continuous type, there is no restriction as long as a gas-liquid solid reaction can be carried out, but for example, a packed tower reactor, a bubble tower reactor, a stirred tank reactor, a spray tower reactor, a plate tower reactor, etc. Used. Among these, when a noble metal-containing catalyst is suspended in a reaction solution and a liquid phase oxidation reaction is performed, a bubble column reactor and a stirred tank reactor are preferably used. If necessary, the reactor can be arranged in a multistage series of two or more stages, and the liquid phase oxidation reaction can be carried out so that the reaction liquid sequentially flows through each tank. The residence time of the reaction solution in the reactor can be appropriately selected depending on the amount of the noble metal-containing catalyst, the reaction temperature, the pressure, etc., but is preferably 0.1 hr or more, more preferably 0.2 hr or more, and preferably 10 hr or less, More preferably, it is 8 hr or less.

  In the liquid phase oxidation reaction, gas containing molecular oxygen that has passed through the liquid phase part in the reactor (hereinafter referred to as unreacted oxygen gas) may form explosive gas in the gas phase part. It is preferable to supply an inert gas such as nitrogen, carbon dioxide, water vapor or the like to the phase part and, in some cases, the liquid phase part, to avoid the formation of squealing air. Since the unreacted oxygen gas or the gas obtained by diluting the unreacted oxygen gas with the inert gas contains low-concentration raw materials and reaction solvents, the raw materials and reaction solvents are usually used from the viewpoint of air pollution prevention or cost. After recovery, it is dissipated into the atmosphere after being processed by an insicator or the like. Examples of the recovery method include an absorption method and an adsorption method.

  By the liquid phase oxidation reaction as described above, a reaction mixture containing α, β-unsaturated carboxylic acid and α, β-unsaturated carboxylic acid anhydride is obtained.

  The production method of the α, β-unsaturated carboxylic acid according to the present invention can increase the yield of the α, β-unsaturated carboxylic acid by carrying out the method as described above. Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these examples.

  FIG. 1 is a system diagram showing the configuration of an apparatus for producing an α, β-unsaturated carboxylic acid using an olefin or an α, β-unsaturated aldehyde as a raw material. The oxidation reactor (A) is supplied with the raw material olefin or α, β-unsaturated aldehyde and oxygen-containing gas (1), and a liquid phase oxidation reaction is performed in the presence of a noble metal-containing catalyst. A plurality of oxidation reactors (A) may be installed, in which case they may be arranged in series or in parallel.

  After completion of the liquid phase oxidation reaction, the mixture i (2), which is a reaction liquid containing a catalyst, is supplied to the catalyst separator (B), and the noble metal-containing catalyst (4) is separated. The separated noble metal-containing catalyst (4) is preferably recycled again to the oxidation reactor (A) and reused.

  The separation of the catalyst can be carried out at any pressure of reduced pressure, normal pressure or increased pressure. When an olefin is used as a raw material, particularly the olefins preferably used in the present invention, such as propylene, isobutylene, 2-butene, etc., all have a low boiling point, the above separation is preferably carried out under pressure. When α, β-unsaturated aldehyde is used as a raw material, it can be carried out at normal pressure, but it may be carried out under pressure.

  When the particle size of the catalyst is large and the specific gravity is large, sedimentation separation by gravity can be performed as the above separation, but when the particle size of the catalyst is small or the specific gravity is small, centrifugation using centrifugal force instead of gravity, It is preferable to use filtration that separates the filtrate into a filtrate and a filtrate by a partition called a filter medium using gravity, pressure, or reduced pressure.

  When centrifuging, as a centrifugal sedimentator, for example, a cylindrical centrifuge, solid discharge separator, vertical decanter, vertical multistage decanter, automatic batch horizontal decanter, continuous discharge horizontal decanter, sontrifuge As a centrifugal filter, for example, a batch centrifugal filter, an automatic batch centrifugal filter, an automatic discharge centrifugal dehydrator, a screw discharge centrifugal dehydrator, a vibration discharge centrifugal dehydrator, an extrusion plate centrifugal dehydrator, An extrusion plate type multistage centrifugal dehydrator, a screw discharge type (horizontal type) centrifugal dehydrator, or the like can be used.

  At the time of filtration, as a pressure filter, for example, a pressure Nutsche, a plate frame type filter, a concave plate type filter, an Eimco-Burwell pressure filter, a reversible pressure filter, a Kelly type filter, a Sweetland type Filter, Valez type filter, horizontal plate type pressure filter, vertical cylindrical pressure leaf filter, continuous cross flow type filter, continuous rotary cylindrical pressure filter, continuous double cylinder type Pressure filter, continuous drum belt type pressure filter, continuous rotary filter press, continuous pressure leaf filter, etc., vacuum filter is vacuum nutsche, vacuum leaf filter, continuous multi-chamber cylindrical type A vacuum filter, a continuous single-chamber cylindrical vacuum filter, a continuous vertical disk vacuum filter, a continuous horizontal vacuum filter, etc. are used, and when separating a slurry catalyst continuously, Cross flow filter is preferred It is needed.

  When a plurality of oxidation reactors (A) are installed, it is preferable to install a catalyst separator (B) at the outlet of each reactor.

  It is preferable to first separate the unreacted raw material from the mixture ii (3) after separating the catalyst as described above. When olefin is used as a raw material, it is preferable to also separate the α, β-unsaturated aldehyde which is a product that has progressed to the first stage reaction. The olefin and the α, β-unsaturated aldehyde may be separated at the same time if possible, but usually only the separation of the olefin can be carried out first because of the boiling point.

  Since the olefin which is a raw material preferably used in the present invention has a low boiling point, equilibrium flash distillation using a flash drum (C) is preferable. Equilibrium flash distillation is an operation for separating a raw material into a gas and a liquid corresponding to temperature and pressure by flushing (injecting) the raw material into a separator through a pressure reducing valve (heating as necessary). The temperature of the reaction solution before flushing is preferably set from the range of reaction temperature or reaction temperature ± 15 ° C., and the pressure is preferably set from the range of reaction pressure or reaction pressure ± reaction pressure × 0.3. It is more preferable to flush the reaction solution at the reaction temperature and reaction pressure as it is. The pressure in the column is preferably in the range of 0 MPa to reaction pressure × 0.95. By the above operation, the vapor is mainly separated into a vapor mainly composed of olefin and other liquid. Since equilibrium flash distillation is a separation operation in one stage of the separation column, the vapor usually contains α, β-unsaturated aldehyde, a solvent component, dissolved gas, etc., although they are in a small amount. When a higher degree of separation is required, a normal distillation column such as a plate column or a packed column can be used. It is preferable that the vapor of the unreacted olefin (5) is liquefied by compression or cooling operation and then recycled to the oxidation reactor (A) for reuse.

  When α, β-unsaturated aldehyde is used as a raw material, the mixture ii (3) can be directly supplied to the hydrolysis / low boiling point removal column (D), which is the next step, instead of the flash drum (C). .

  The mixture iii (6) after separating the unreacted olefin (5) by the above operation is then fed to the hydrolysis / low boiling removal tower (D), and the α, β-unsaturated carboxylic acid of the α, β-unsaturated carboxylic acid is obtained by the method of the present invention. Hydrolysis is performed. At the same time, low-boiling substances contained in the mixture iii (6) are distilled off. For example, when olefin is used as a raw material, α, β-unsaturated aldehyde, which is a product that has progressed to the first stage reaction, is contained as a low-boiling product. When α, β-unsaturated aldehyde is used as a raw material, the raw material is contained as a low-boiling substance. In addition, when a reaction solvent having a lower boiling point than that of an α, β-unsaturated carboxylic acid and a higher boiling point than that of an α, β-unsaturated aldehyde is used during the liquid phase oxidation reaction, the reaction solvent has a low boiling point. Included as a thing.

  At this time, if the molar ratio of water and α, β-unsaturated carboxylic acid to α, β-unsaturated carboxylic acid anhydride in mixture iii (6) does not satisfy the conditions of the present invention, water and / or An α, β-unsaturated carboxylic acid (7) can be added as appropriate. As a result, in the hydrolysis / low boiling removal tower (D), α, β-unsaturated carboxylic acid anhydride can be converted to α, β-unsaturated carboxylic acid, and low boiling product (8) is hydrolyzed by the heating. At the same time, it can be distilled off.

  A plurality of hydrolysis / low boiling removal towers (D) may be installed. For example, when a reaction solvent having a lower boiling point than α, β-unsaturated carboxylic acid and higher boiling point than α, β-unsaturated aldehyde is used during the liquid phase oxidation reaction, α, β-unsaturation is first used. The low boiling point, mainly aldehyde, can be separated and then the reaction solvent can be separated. When a plurality of hydrolysis / low-boiling removal towers (D) are provided, the hydrolysis of the α, β-unsaturated carboxylic acid may be carried out in at least one tower. The separated α, β-unsaturated aldehyde and the low boiling point product (8) such as a reaction solvent are preferably recycled to the oxidation reactor (A).

  The mixture iv (9) after removing the low boiler is fed to the azeotropic distillation column (E). From the top of this tower, a mixed vapor (10) of water and an azeotropic solvent is obtained, which is condensed and separated into water and an azeotropic solvent by a layer separator (not shown). The separated azeotropic solvent is preferably refluxed to the azeotropic distillation column. The separated water is preferably discarded after a solvent removal treatment (not shown) in water as necessary. Although it does not specifically limit as a solvent separation method, Distillation separation is preferable from an economical viewpoint.

  The mixture v (11) after removing the water is supplied to the purification column (F) and separated into the α, β-unsaturated carboxylic acid (12) and the other mixture vi (13). Thereafter, the mixture vi (13) is supplied to the thin film evaporator (G) to further separate the α, β-unsaturated carboxylic acid (12) and the high boiling residue (14).

  In the apparatus of FIG. 1, water is separated by azeotropic distillation, but water can also be separated by solvent extraction. FIG. 2 is a system diagram showing the configuration of an apparatus for separating water by solvent extraction. This is a preferred example of separating α, β-unsaturated carboxylic acid and water by solvent extraction. The mixture iv (9) obtained by treating in the same manner as in the apparatus of FIG. 1 was subjected to a solvent extraction column (H) with an aqueous layer (15) and an organic layer (16) containing an α, β-unsaturated carboxylic acid and an extraction solvent. ) And are separated. Since the water layer (15) may contain a slight amount of extraction solvent, it is preferably discarded after performing a solvent removal treatment (not shown) in water as necessary. Although it does not specifically limit as a solvent separation method, Distillation separation is preferable from an economical viewpoint.

  The organic layer (16) is introduced into the solvent recovery tower (I), and the extraction solvent (17) is separated. The separated solvent is preferably recycled again to the solvent extraction tower (H) and reused. The mixture vii (18), which is the liquid after separating the extraction solvent, is supplied to the purification tower (F), and is passed through the purification tower (F) and the thin film evaporator (G) as in FIG. Saturated carboxylic acid (10) is recovered.

  Hereinafter, the present invention will be described in more detail with reference to examples. Gas chromatography was used for component analysis in the examples.

Example 1
(Liquid-phase oxidation reaction of isobutylene)
As a reactor for performing the liquid phase oxidation reaction, a jacketed stainless steel stirred tank reactor having an inner diameter of 126 mm and a capacity of 4 liters was used. About 150 g of a palladium metal-containing silica-supported catalyst and a 75% by mass tertiary butanol aqueous solution were charged into the reactor in advance, and the total liquid volume was adjusted to about 3 liters. The palladium metal-containing silica-supported catalyst is prepared by dissolving palladium nitrate in water, adding a silica support to the palladium support, supporting palladium nitrate on the silica support, and then reducing with formaldehyde. used.

  Subsequently, nitrogen gas was supplied from the upper part of the reactor, and the supply was stopped when the gas phase pressure became 4.8 MPa. After the liquid phase temperature was raised to 90 ° C., liquefied isobutylene was continuously supplied to the reactor at about 237 g / hr and the solvent at about 2135 g / hr. As the solvent, a solvent prepared by containing 200 ppm of p-methoxyphenol as a polymerization inhibitor in a 75% by mass aqueous tertiary butanol solution was used. Next, the liquid phase oxidation reaction was carried out by continuously supplying air from the compressed air cylinder through the sparger at a rate of about 800 g / hr to the reactor liquid phase while maintaining the gas phase pressure.

  The reaction solution subjected to the liquid phase oxidation reaction was continuously withdrawn from the reactor, and the palladium metal-containing supported catalyst was continuously separated by filtration under pressure. The filtered reaction solution was flushed into a flash drum under atmospheric pressure to separate unreacted isobutylene.

(Hydrolysis of methacrylic anhydride)
Using the mixture obtained by the above operation, hydrolysis of methacrylic anhydride was carried out. The composition of the mixture is shown in Table 1. Specifically, this mixture was introduced into a 3 L glass flask equipped with a heating oil bath, a glass Oldershaw distillation column (inner diameter 35 mm, 20 stages) was connected, and batch distillation was performed at a pressure of 0 MPa. did. Analytical values of distillation time, mixture temperature, and the amount of methacrylic anhydride present in the mixture are shown in Table 2. The heating time in batch distillation (the time when the temperature of the distillation column bottom liquid was 30 ° C. or higher) was 4.2 hours.

(Example 2)
(Liquid-phase oxidation reaction of isobutylene)
The same procedure as in Example 1 was carried out except that the supply amounts of liquefied isobutylene, solvent and air were 1.174 times that of Example 1.

(Hydrolysis of methacrylic anhydride)
The same procedure as in Example 1 was performed except that the mixture obtained by the above operation was used and the pressure was adjusted so that the temperature in the flask was 60 ° C. or lower. The composition of the mixture is shown in Table 3. Table 4 shows the distillation time, mixture temperature, distillation pressure, and analytical values of methacrylic anhydride present in the mixture. In addition, the heating time in batch distillation (time when the temperature of the distillation column bottom liquid was 30 ° C. or higher) was 9.1 hours.

Abbreviations in Table TBA: Tertiary butyl alcohol H ₂ O: Water MAA: Methacrylic acid ANH: Methacrylic anhydride

It is a systematic diagram which shows the structure of the apparatus which manufactures (alpha), (beta)-unsaturated carboxylic acid from the olefin or the (alpha), (beta) -unsaturated aldehyde which can implement one Embodiment of this invention. It is a systematic diagram which shows the structure of the apparatus which manufactures (alpha), (beta)-unsaturated carboxylic acid from the olefin or the (alpha), (beta) -unsaturated aldehyde which can implement one Embodiment of this invention.

Explanation of symbols

1 Olefin or α, β-unsaturated aldehyde and oxygen-containing gas 2 Mixture i
3 Mixture ii
4 Precious metal-containing catalyst 5 Unreacted olefin 6 Mixture iii
7 Water and / or α, β-unsaturated carboxylic acid 8 Low boiling 9 Mixture iv
10 Mixed vapor of water and azeotropic solvent 11 Mixture v
12 α, β-unsaturated carboxylic acid 13 mixture vi
14 High boiling residue 15 Aqueous layer 16 Organic layer 17 Extraction solvent 18 Mixture vii
A oxidation reactor B catalyst separator C flash drum D hydrolysis / low boiling removal tower E azeotropic distillation tower F purification tower G thin film evaporator H solvent extraction tower I solvent recovery tower

Claims (4)

  An α, β-unsaturated carboxylic acid, an α, β-unsaturated carboxylic acid anhydride, and water are contained, and the water is 5 mol or more per 1 mol of the α, β-unsaturated carboxylic acid anhydride. In addition, the mixture in which the α, β-unsaturated carboxylic acid is 2 mol or more is heated to 30 ° C. or more to hydrolyze at least a part of the α, β-unsaturated carboxylic acid anhydride. A method for producing an α, β-unsaturated carboxylic acid.   The mixture further contains a low boiling point lower than any of the α, β-unsaturated carboxylic acid, the α, β-unsaturated carboxylic acid anhydride, and the water, and the hydrolysis is performed. The method for producing an α, β-unsaturated carboxylic acid according to claim 1, wherein at least a part of the low-boiling substances is removed from the top of the distillation column by being carried out in a distillation column. The mixture is a reaction solution obtained by oxidizing an olefin or an α, β-unsaturated aldehyde in a liquid phase containing water in the presence of a palladium metal-containing catalyst , or prepared from the reaction solution. The method for producing an α, β-unsaturated carboxylic acid according to claim 2.
Obtaining a reaction solution obtained by oxidizing an olefin or an α, β-unsaturated aldehyde in a liquid phase containing water in the presence of a palladium metal-containing catalyst ;
The reaction solution contains an α, β-unsaturated carboxylic acid, an α, β-unsaturated carboxylic acid anhydride, water, and a low-boiler having a boiling point lower than any of these, the α, β A step of obtaining a mixture in which the water is 5 mol or more and the α, β-unsaturated carboxylic acid is 2 mol or more with respect to 1 mol of the unsaturated carboxylic acid anhydride;
The mixture is supplied to a distillation column, and the mixture is heated to 30 ° C. or higher by a heating unit at the bottom of the distillation column to remove at least a part of the low-boiling substances from the top of the distillation column. Hydrolyzing at least part of the α, β-unsaturated carboxylic acid anhydride,
The method for producing an α, β-unsaturated carboxylic acid according to claim 3, wherein:

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