Process for producing 3-hydroxysulfolane and process for producing ester

Abstract

To provide a method for producing 3-hydroxy sulfolane that can remove a neutralized salt and water from a neutralized liquid while ensuring a fluid volume in a reactor.SOLUTION: A method for producing 3-hydroxy sulfolane includes the steps of: treating sulfolane represented by formula 1 with an aqueous alkali solution to obtain an aqueous solution containing 3-hydroxy sulfolane represented by formula 2; neutralizing the aqueous solution with acid to obtain a neutralized liquid; and using an organic solvent that dissolves the 3-hydroxy sulfolane and forms an azeotrope with water to azeotropic-substitute the solvent in the neutralized liquid.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing 3-hydroxysulfolane and a method for producing a carboxylic acid ester of 3-hydroxysulfolane.

Background Art

[0002] Unsaturated carboxylic acid esters of 3-hydroxysulfolane are used as sulfur-containing monomers in the polymerization of various polymers. Patent Document 1 describes an example of producing a methacrylic acid ester of 3-hydroxysulfolane through a transesterification step between 3-hydroxysulfolane and methyl methacrylate. Further, as a method for producing 3-hydroxysulfolane, sulfolene is treated with an aqueous alkali solution, neutralized to obtain a neutralized solution containing 3-hydroxysulfolane, most of the water is distilled off from the neutralized solution, acetone is added to dissolve and extract 3-hydroxysulfolane, and the neutralization salt is precipitated and filtered off.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] According to the findings of the present inventors, when attempting to industrially produce 3-hydroxysulfolane by the method described in Patent Document 1, when most of the water is distilled off from the neutralized solution to obtain a concentrate in a reactor equipped with a stirring blade, there are inconveniences such as difficulty in stirring the concentrate with the stirring blade or the possibility of damage to the inner surface of the reactor by the neutralization salt contained in the concentrate. The present invention has been made in view of such circumstances, and provides a method for producing 3-hydroxy sulfolane capable of removing a neutralized salt and water from a neutralized solution while ensuring the amount of liquid in the reactor, and a method for producing a carboxylic acid ester of 3-hydroxy sulfolane using the same.

Means for Solving the Problems

[0005] The present invention has the following aspects. [1] Treating sulfolene represented by the following formula ( 1 (Hereinafter, also referred to as "Formula 1") with an aqueous alkali solution to obtain an aqueous solution containing 3-hydroxy sulfolane represented by the following formula ( 2 (Hereinafter, also referred to as "Formula 2") ; a step of neutralizing the aqueous solution with an acid to obtain a neutralized solution; and a step of azeotropically replacing the solvent of the neutralized solution using an organic solvent that dissolves 3-hydroxy sulfolane and azeotropes with water. A method for producing 3-hydroxy sulfolane. A step of neutralizing the aqueous solution with an acid to obtain a neutralized solution, and A process for producing 3-hydroxy sulfolane, comprising a step of azeotropically replacing the solvent of the neutralized solution using an organic solvent that dissolves 3-hydroxy sulfolane and azeotropes with water.

[0006]

Chemical formula

[0007] [2] Producing 3-hydroxy sulfolane using the method of [1], The obtained 3-hydroxy sulfolane and the following formula ( 3 (Hereinafter, also referred to as "Formula 3") are subjected to a transesterification reaction with a carboxylic acid ester represented by to obtain a carboxylic acid ester of 3-hydroxy sulfolane represented by the following formula ( 4 (Hereinafter, also referred to as "Formula 4") An ester production method for obtaining a carboxylic acid ester of 3-hydroxy sulfolane represented by.

[0008]

Chemical formula

[0009] [In Formulas 3 and 4, R 1 represents a hydrogen atom, or a linear or branched alkyl group having 1 to 10 carbon atoms, and R 2represents a linear or branched alkyl group having 1 to 10 carbon atoms. [3] The method for producing an ester according to [2], wherein the boiling point of the organic solvent at standard atmospheric pressure is 100 ° C or lower.

Effects of the Invention

[0010] The method for producing 3 - hydroxy - sulfolane and the method for producing an ester of the present invention can remove the neutralized salt and water from the neutralized solution while ensuring the liquid volume in the reactor when producing 3 - hydroxy - sulfolane, so that the production efficiency can be improved.

Embodiments for Carrying Out the Invention

[0011] The following definitions apply throughout this specification and the claims. The "~" indicating a numerical range means including the numerical values described before and after it as the lower limit value and the upper limit value. Room temperature means 20 to 30 ° C unless otherwise specified. pH is the value at room temperature unless otherwise specified. The water content is a value obtained by sending a sample to a Karl Fischer reagent and measuring the water content by Karl Fischer coulometric titration.

[0012] ≪Method for Producing 3 - Hydroxy - Sulfolane≫ The method for producing 3 - hydroxy - sulfolane according to this embodiment includes a step of treating sulfolene represented by the following formula 1 with an aqueous alkali solution to obtain an aqueous solution containing 3 - hydroxy - sulfolane represented by the following formula 2 (hydration step), a step of neutralizing the aqueous solution with an acid to obtain a neutralized solution (neutralization step), and a step of azeotropically replacing the solvent of the neutralized solution using an organic solvent that dissolves 3 - hydroxy - sulfolane and azeotropes with water (solvent replacement step).

[0013] Stirred tanks are generally used for industrial synthesis. A stirred tank comprises a cylindrical bottomed hollow container (reactor), a stirring blade having the central axis of the container as the rotation axis, and a motor connected to the axis of the stirring blade. A baffle may be provided to improve the stirring efficiency. In a multi-purpose stirred tank, due to the capacity of the motor and the presence of the baffle, the content to be stirred is preferably of low viscosity. The distance from the bottom of the container to the stirring blade is often set to about 1 / 3 of the container height, and there is a lower limit to the amount of content that can be stirred.

[0014]

Chemical

[0015] <Hydration step> In the hydration step, the raw material sulfolene is treated with an aqueous alkali solution, and 3-hydroxysulfolane is produced by a hydration reaction. Thereby, an aqueous solution containing 3-hydroxysulfolane is obtained. Specifically, sulfolene is dissolved in the aqueous alkali solution, and the hydration reaction is carried out by stirring at a temperature within the range of room temperature to 80 °C for 1 to 100 hours.

[0016] Examples of the alkali include sodium hydroxide, potassium hydroxide, calcium hydroxide, etc. From the viewpoints of cost, practicality, and reaction efficiency, sodium hydroxide is preferred. The concentration of the aqueous alkali solution is preferably 1 to 10 N. From the viewpoints of handleability, suppression of side reactions, suppression of coloring, etc., 1 to 8 N is more preferable, and 1 to 4 N is even more preferable.

[0017] The amount of the alkali used is preferably in the range of 0.5 to 10 times the molar amount relative to sulfolene. From the viewpoints of reaction efficiency and cost, the range of 1 to 5 times the molar amount relative to sulfolene is more preferable. From the viewpoints of suppression of side reactions and shortening of the reaction time, the range of 1 to 3 times the molar amount is even more preferable.

[0018] When the reaction temperature of the hydration reaction is above room temperature, a good reaction rate is easily obtained. When it is 80°C or below, the decomposition of raw materials hardly occurs, and the generation of by-products is easily suppressed. Specifically, when sulfolene decomposes into butadiene and sulfur dioxide gas, by-products such as oligomers or polymers of butadiene are generated, which promotes polymerization, so it is not preferable. A more practical reaction temperature is preferably in the range of room temperature to 60°C, and from the viewpoint of easily suppressing coloring by the reaction, the range of room temperature to 40°C is more preferable.

[0019] The reaction time of the hydration reaction is preferably 1 to 100 hours, more preferably 5 to 72 hours from the viewpoints of reaction efficiency and economy, and even more preferably 8 to 24 hours. However, from the viewpoints of suppressing coloring and purity, it is preferable to carry out the reaction over 24 hours.

[0020] When the hydration reaction has proceeded completely, there is no need to consider the removal of the raw material sulfolane. However, when unreacted raw materials remain in the hydration reaction, it is preferable to remove the raw material sulfolane by methods such as thermal decomposition, silica gel chromatography, or distillation. From the viewpoint of low cost, it is preferable to carry out thermal decomposition while reducing the pressure at a temperature of 80 to 100°C at which the raw material sulfolene decomposes. There is no limitation on the timing of performing the thermal decomposition of the raw material sulfolene, but from the viewpoint of low possibility of polymerization of the butadiene generated by thermal decomposition, it is preferable to carry out thermal decomposition while reducing the pressure during the subsequent water concentration step.

[0021] <Neutralization step> In the neutralization step, an acid is added to the aqueous solution containing 3-hydroxysulfolane obtained in the hydration step to neutralize it and obtain a neutralized solution. Examples of the acid include hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, nitric acid, etc. From the viewpoints of the separability between the target 3-hydroxysulfolane and the neutralization salt, workability, etc., hydrochloric acid and sulfuric acid are preferable. The neutralized solution obtained in the neutralization step contains 3-hydroxysulfolane, water, and a neutralization salt.

[0022] The end point of neutralization is preferably pH 5 - 8, more preferably pH 6 - 7. When the pH is 8 or less, coloring of the neutralized solution hardly occurs. When the pH is 5 or more, the dehydration reaction of 3 - hydroxy sulforane hardly occurs. The occurrence of the dehydration reaction of 3 - hydroxy sulforane is not preferable because 2 - sulfolene, an isomer of sulfolene, is by - produced.

[0023] <Solvent replacement step> In the solvent replacement step, the solvent of the neutralized solution is azeotropically replaced using an organic solvent that forms an azeotrope with water (hereinafter also referred to as an azeotropic solvent). As the azeotropic solvent, one that dissolves 3 - hydroxy sulforane is used. The azeotropic replacement is preferably carried out by multi - stage azeotropy. Specifically, an azeotropic solvent is added to the neutralized solution, and a mixture containing the azeotropic solvent and water (hereinafter referred to as an azeotropic mixture) is distilled off. Then, the azeotropic solvent is added again, and the azeotropic mixture is distilled off. By repeating this operation, the water in the neutralized solution is replaced with the azeotropic solvent. Multi - stage azeotropy will be described later. By azeotropic replacement, a solution containing 3 - hydroxy sulforane, neutralization salt, and an azeotropic solvent, from which water has been removed, is obtained. The obtained solution is filtered to remove the neutralization salt. The solution from which the neutralization salt has been removed (hereinafter also referred to as the SFOH solution) can be used as it is or after removing the azeotropic solvent for the subsequent transesterification reaction.

[0024] Examples of azeotropic solvents are listed in Table 1. The table shows the boiling points of each solvent, the azeotropic points of mixtures composed of each solvent and water, and the content of each solvent (azeotropic composition) at azeotropy under standard atmospheric pressure (101.3 kPa).

[0025]

Table 1

[0026] When using the 3-hydroxy sulforane obtained in this embodiment in a transesterification reaction with a carboxylic acid ester described later, if the boiling point of the azeotropic solvent is lower than the boiling point of the carboxylic acid ester used in the transesterification reaction, it is preferable in that the azeotropic solvent can be easily distilled off after mixing the SFOH solution and the carboxylic acid ester. For example, the boiling point of the azeotropic solvent at standard atmospheric pressure is preferably 100 °C or lower, and more preferably 90 °C or lower from the viewpoint of separation efficiency. When the azeotropic solvent is an alcohol, side reactions are likely to occur in the transesterification reaction described later. Therefore, it is preferable to remove the azeotropic solvent in the SFOH solution before the transesterification reaction. In terms of being easily used directly in the transesterification reaction, the azeotropic solvent is more preferably acetonitrile or ethyl methyl ketone, for the SFOH solution obtained in the solvent replacement step.

[0027] Table 2 is an example for explaining multi-stage azeotropy, and shows the theoretical values when multi-stage azeotropy is performed using acetonitrile (denoted as "ATN" in the table) as the azeotropic solvent. "Parts" in the table indicates "parts by mass". In the example of Table 2, the liquid amount of the neutralized solution is 100 parts by mass, and it consists of 21.1 parts by mass of the solute containing 3-hydroxy sulforane and the neutralized salt, and 78.9 parts by mass of water as the solvent. First, a part of water (50 parts by mass) is distilled off from the neutralized solution (water concentration step) to obtain a concentrated solution (liquid amount 50 parts by mass) with a water content of 58% by mass. Next, 31.8 parts by mass of acetonitrile is added (Addition 1), and acetonitrile and water are azeotroped to distill off 31.8 parts by mass of the azeotropic mixture (Distillation 1). Assuming that the acetonitrile content in the azeotropic mixture to be distilled off is 84.2% by mass, the 31.8 parts by mass of the azeotropic mixture consists of 5 parts by mass of water and 26.8 parts by mass of acetonitrile. Thereby, a solution (liquid amount 50.0 parts by mass) with a water content reduced to 48% by mass is obtained. Next, 31.8 parts by mass of acetonitrile is added (Addition 2), and acetonitrile and water are azeotroped to distill off 31.8 parts by mass of the azeotropic mixture (Distillation 2). Thereby, a solution (liquid amount 50.0 parts by mass) with a water content reduced to 38% by mass is obtained. In this way, 31.8 parts by mass of acetonitrile is added (Addition 3 - 6), and acetonitrile and water are azeotroped to distill off 31.8 parts by mass of the azeotrope (Distillation 3 - 6). Repeating this causes the water content to gradually decrease, and 50.0 parts by mass of a solution composed of 21.1 parts by mass of the solute, -1.2 parts by mass of water, and 30.1 parts by mass of acetonitrile is obtained. The obtained solution is filtered to remove the neutralization salt to obtain an SFOH solution.

[0028]

Table 2

[0029] In this way, by azeotropically replacing the solvent of the neutralized solution using an azeotropic solvent, water can be removed from the neutralized solution while ensuring the liquid volume in the reactor. In the solvent replacement step, it is preferable to perform azeotropic replacement until a solution with a water content of 1% by mass or less, preferably 0.1% by mass or less, is obtained.

[0030] In the solvent replacement step, the water distillation (water concentration step) before initially adding the azeotropic solvent is not essential, but by distilling off a part of the water contained in the neutralized solution prior to azeotropic replacement, the water contained in the neutralized solution can be efficiently removed. As a result, the number of times (number of stages) of repeating the operation of adding the azeotropic solvent and distilling off the azeotrope can be reduced. When only water is distilled off (concentrated) before adding the azeotropic solvent, if the amount of water distilled off is too large, it becomes difficult to stir the liquid in the reactor with the stirring blade, so the distillation amount is set so that such inconvenience does not occur. The number of stages in multi-stage azeotropy is not particularly limited, but for example, 1 - 10 stages are preferable, and from the viewpoints of cost and polymerization inhibition by heat, 1 - 4 stages are more preferable.

[0031] In multi-stage azeotropy, the addition amount of the azeotropic solvent and the distillation amount immediately after that may be the same or different. The addition amounts of the azeotropic solvent in each stage may be the same or different from each other. Also, the distillation amounts in each stage may be the same or different from each other. The increase or decrease in the liquid volume in the solvent replacement step may be within the range not exceeding the liquid volume that can be accommodated in the reactor and not less than the liquid volume that can be stirred by the stirring blade. When the liquid volume of the neutralized liquid used in the solvent replacement step is taken as 100% by mass, although it depends on the structure of the reactor, the liquid volume after distillation is preferably, for example, 50% by mass or more, and more preferably 30% by mass or more from the viewpoint of efficiency.

[0032] Azeotropic replacement may be carried out under reduced pressure. Reducing the pressure is preferable in that the heating temperature for distilling off the azeotropic mixture can be lowered because the azeotropic point decreases. In the solvent replacement step, when the internal temperature is taken as the treatment temperature, the treatment temperature is preferably from room temperature to 80°C, and more preferably from 40°C to 60°C. In the solvent replacement step, when the internal pressure is taken as the treatment pressure, the treatment pressure is preferably from 30 hPa to 500 hPa, more preferably from 30 hPa to 400 hPa, and even more preferably from 30 hPa to 300 hPa. In a single (one-stage) distillation step, the treatment temperature and treatment pressure may each be constant or may change over time.

[0033] ≪Ester production method≫ In the ester production method of the present embodiment, 3-hydroxy sulfolane is produced using the method of the above embodiment, and the obtained 3-hydroxy sulfolane and a carboxylic acid ester represented by the following formula 3 (hereinafter also referred to as a raw material ester) are subjected to a transesterification reaction (transesterification step) to obtain a carboxylic acid ester of 3-hydroxy sulfolane represented by the following formula 4 (hereinafter also referred to as a produced ester).

[0034]

Chemical formula

[0035] In Formula 3 and Formula 4, R 1 represents a hydrogen atom or a linear alkyl group having 1 to 10 carbon atoms or a branched alkyl group having 3 to 10 carbon atoms, and R 2 represents a linear alkyl group having 1 to 10 carbon atoms or a branched alkyl group having 3 to 10 carbon atoms. R 1 or R 2The alkyl group as described above can be exemplified by a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a pentyl group, an isopentyl group, a hexyl group, an octyl group, a nonyl group, a decyl group, etc. From the viewpoint of high practicality, R 1 is preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. R 2 is preferably an alkyl group having 1 to 4 carbon atoms. From the viewpoint of separability, it is more preferable that both R 1 and R 2 are methyl groups.

[0036] For the method for producing an ester of the present embodiment, for example, the following Mode 1 or Mode 2 is preferable. (Mode 1) A mode in which the SFOH solution obtained in the solvent replacement step is directly used in the transesterification step. In this mode, it is preferable that the azeotropic solvent contained in the SFOH solution does not contain alcohol. In this mode, the boiling point (standard atmospheric pressure) of the azeotropic solvent contained in the SFOH solution is preferably 100°C or lower. (Mode 2) A mode in which the azeotropic solvent contained in the SFOH solution obtained in the solvent replacement step is removed and used in the transesterification step. For example, when the azeotropic solvent is alcohol, it may be concentrated under reduced pressure as described later, and further refluxed using a Dean-Stark apparatus until the alcohol is removed.

[0037] <Transesterification Step> In Mode 1, the SFOH solution obtained in the solvent replacement step and the raw material ester are mixed, a transesterification catalyst is added and heated to carry out a transesterification reaction. In Mode 2, after removing the azeotropic solvent from the SFOH solution, it is dissolved in the raw material ester, a transesterification catalyst is added and heated to carry out a transesterification reaction. The transesterification reaction can be carried out using a known method described in, for example, Japanese Patent Application Laid-Open No. 2007-153763.

[0038] In Embodiment 1 and Embodiment 2, alcohol derived from the starting ester is by-produced as the transesterification reaction proceeds. However, it is preferable to carry out the transesterification reaction while removing this by-produced alcohol. When the reaction rate reaches a predetermined value, the reaction solution is cooled to stop the reaction. Thereafter, unreacted 3-hydroxy sulfolane is removed, and the transesterification catalyst is removed and deactivated. The starting ester is distilled off from the reaction solution and concentrated to obtain the target produced ester. In the case of Embodiment 1, when distilling off and concentrating the starting ester from the reaction solution of the transesterification reaction, it is preferable to simultaneously distill off the azeotropic solvent derived from the SFOH solution.

[0039] Examples of the starting ester include acrylic acid esters such as methyl acrylate, ethyl acrylate, and butyl acrylate; methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, and butyl methacrylate; and α-ethyl acrylate esters such as methyl α-ethyl acrylate, ethyl α-ethyl acrylate, and propyl α-ethyl acrylate.

[0040] Regarding the amount of the starting ester used, if the by-produced alcohol can be easily removed without relying on azeotropy, the transesterification reaction will proceed sufficiently even with a small amount of the starting ester. However, when the by-produced alcohol is removed by azeotropy with the starting ester, such as ethyl acrylate and ethanol, or methyl methacrylate and methanol, if the amount of the starting ester is too small, the by-produced alcohol cannot be sufficiently removed, and thus the reaction rate is likely to decrease. On the other hand, if the amount of the starting ester is too large, the kettle efficiency of the transesterification reaction deteriorates, which is not preferable in terms of cost. The amount of the starting ester used is preferably in a range where these disadvantages do not occur. For example, it is preferably in the range of 2 to 20 times the molar amount of 3-hydroxy sulfolane, and more preferably in the range of 3 to 10 times the molar amount.

[0041] Examples of the catalyst for the transesterification reaction include organotin compounds such as di-n-butyltin oxide, di-n-octyltin oxide, di-n-butyltin dimethoxide, di-n-butyltin diacrylate, di-n-butyltin dimethacrylate, and di-n-butyltin dilaurate; metal alkoxides such as sodium methoxide, lithium ethoxide, titanium tetrabutoxide, titanium tetramethoxide, titanium tetraisopropoxide, titanium tetraethoxide, tetrakis(2-ethylhexyloxy)titanium, and titanium tetrastearyloxide. From the viewpoints of superiority in reaction operation and easy availability, dibutyltin oxide, titanium tetramethoxide, and titanium tetrabutoxide are preferable.

[0042] The usage amount of the catalyst is preferably 0.01 to 5 mol% based on 3-hydroxy sulfolane, and more preferably 0.1 to 2 mol% from the viewpoints of cost and ease of catalyst treatment. Considering the transesterification reaction of 3-hydroxy sulfolane having a secondary alcohol that is difficult to react, in order to complete the transesterification reaction within a practical time of 1 to 2 days, the usage amount of the catalyst is more preferably 0.5 to 3 mol%.

[0043] In order to prevent the polymerization of the raw material ester and the produced ester, it is preferable to add a polymerization inhibitor to the reaction system. The type of the polymerization inhibitor is not particularly limited. One type of the polymerization inhibitor may be used, or two or more types may be used in combination.

[0044] Examples of the polymerization inhibitor include phenolic compounds such as hydroquinone, p-methoxyphenol, 2,4-dimethyl-6-tert-butylphenol, 2,6-di-tert-butyl-4-methylphenol, tert-butylcatechol, 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate), 2-sec-butyl-4,6-dinitrophenol; amine compounds such as N,N-diisopropyl-p-phenylenediamine, N,N-di-2-naphthyl-p-phenylenediamine, N-phenyl-N-(1,3-dimethylbutyl)-p-phenylenediamine, N,N'-bis(1,4-dimethylphenyl)-p-phenylenediamine, N-(1,4-dimethylphenyl)-N'-phenyl-p-phenylenediamine; N-oxyl compounds such as 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl, bis(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) sebacate; metal compounds such as copper, copper(II) chloride, iron(III) chloride; etc.

[0045] The amount of the polymerization inhibitor used can be set as appropriate. For example, it is preferably 100 ppm or more based on the raw material ester used, and more preferably 500 ppm or more to obtain a sufficient polymerization prevention effect. On the other hand, considering the cost, the amount of the polymerization inhibitor used is preferably 10,000 ppm or less, and more preferably 5,000 ppm or less considering the coloring of the product and the convenience in the usage scenario.

[0046] Also, it is preferable to bubble an oxygen-containing gas such as air into the transesterification reaction solution to prevent polymerization. The amount of the oxygen-containing gas introduced can be set as appropriate so as to obtain a desired polymerization prevention effect. For example, when using air as the oxygen-containing gas, it is preferably bubbled at 0.5 - 3.0 mL / min per mole of the raw material ester used. It is particularly preferable to add a polymerization inhibitor to the transesterification reaction solution and carry out the reaction while introducing an oxygen-containing gas such as air into the reaction solution from the viewpoint of amplifying the polymerization prevention effect.

[0047] In the transesterification reaction, a batch reactor or a continuous reactor may be used. For example, in a batch reactor, while stirring the reaction solution containing the catalyst, in order to advance the reaction, the by-produced alcohol (R 2 OH) can be removed from the system while carrying out the transesterification reaction.

[0048] The reaction pressure during the transesterification reaction is not particularly limited, and it can be carried out under reduced pressure, normal pressure, or increased pressure. The reaction temperature during the transesterification reaction depends on the reaction pressure, but for example, the range from normal temperature to 150 °C is preferable. In order to remove the by-produced alcohol (R 2 OH) and obtain a higher reaction rate, 60 to 150 °C is more preferable. The reaction time of the transesterification is preferably 1 to 50 hours, and more preferably 5 to 36 hours from the viewpoints of practicality and efficiency.

[0049] After completion of the transesterification reaction, it is preferable to deactivate the catalyst as necessary, recover the unreacted 3-hydroxythiolane, and purify the produced ester. The deactivation of the catalyst can be carried out by a known method. The produced ester is usually solid at normal temperature. The purification of the produced ester can be carried out by a known purification method such as vacuum distillation, recrystallization, etc.

Example

[0050] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0051] <Example 1> This example is an example in which water in the neutralized solution is azeotropically replaced using acetonitrile as an azeotropic solvent. (Hydration step · Neutralization step) 18 g (0.15 mol) of sulfolene was dissolved in 55 mL of 3.28 N aqueous sodium hydroxide solution and allowed to stand at 30 °C for 24 hours. Analysis by gas chromatography confirmed that almost all of the starting sulfolene had disappeared. The reaction solution was cooled with ice water, 8 g of sulfuric acid was added, and it was neutralized to about pH 6.5 to obtain a neutralized solution (100 g). The water content of the neutralized solution was 48 mass%.

[0052] (Solvent replacement step) Multi-stage azeotropy was carried out under the conditions shown in Table 3 to replace the water contained in the neutralized solution with acetonitrile as the solvent. After distilling off the azeotropic mixture, the water content of the liquid in the reactor was measured. Based on the distillation amount and the addition amount, the liquid volume in the reactor was calculated, and the content of the solute relative to the liquid volume in the reactor was calculated as the solid content. The ratio of the liquid volume to the initial liquid volume in the reactor was calculated as the still residue amount. These results are shown in a table (hereinafter the same). The solution after the multi-stage azeotropy was filtered with a pressure filter to remove the neutralization salt. Furthermore, the filtrate was heated to 80 °C and concentrated under reduced pressure to decompose and remove the remaining starting materials. Thus, an SFOH solution (41 g) in which 3-hydroxy sulfolane was dissolved in acetonitrile was obtained. In the SFOH solution, the GC purity of 3-hydroxy sulfolane was 97% and the water content was 0.13 mass%.

[0053]

Table 3

[0054] <Example 2> This example is an example in which water in the neutralized solution was azeotropically replaced using methyl ethyl ketone (denoted as "MEK" in the table) as the azeotropic solvent. The conditions for multi-stage azeotropy are shown in Table 4. (Hydration step · Neutralization step) 99.6 g (0.84 mol) of sulfolene was dissolved in 0.85 liter of 1.5 N aqueous sodium hydroxide solution and allowed to stand at room temperature for 72 hours. Analysis by gas chromatography confirmed that almost all of the starting sulfolene had disappeared. The reaction solution was cooled with ice water, 60 g of sulfuric acid was added, and the solution was neutralized to about pH 7.2 to obtain a neutralized solution (1011 g). The water content of the neutralized solution was 81% by mass.

[0055] (Solvent replacement step) Using a part (249 g) of the obtained neutralized solution, multi-stage azeotropic distillation was carried out under the conditions shown in Table 4 to replace the water contained in the neutralized solution with methyl ethyl ketone as the solvent. The solution after completion of multi-stage azeotropic distillation was filtered through a pressure filter to remove the neutralized salt. Furthermore, the filtrate was heated to 80 °C and concentrated under reduced pressure to decompose and remove the remaining starting materials. Thus, an SFOH solution (81 g) in which 3-hydroxy sulfolane was dissolved in methyl ethyl ketone was obtained. The water content of 3-hydroxy sulfolane in the SFOH solution was 0.08% by mass.

[0056] The SFOH solutions obtained in Examples 1 and 2 can be used in a method for producing a carboxylic acid ester of 3-hydroxy sulfolane using a known transesterification reaction method.

[0057]

Table 4

[0058] <Example 3> This example is a comparative example in which the water in the neutralized solution was distilled off without azeotropic replacement. (Hydration step · Neutralization step) A neutralized solution (1011 g) was obtained in the same manner as in Example 2. A part (500 g) of the obtained neutralized solution was dried to dryness by evaporation to obtain a slurry of 102 g (residue in the kettle: 20% by mass).

[0059] The dried slurry of Example 3 was hard and sticking to the wall surface. When produced using an industrially used apparatus, the production of industrial 3-hydroxy sulfolane is difficult because the viscosity is high and the stirring blade does not rotate, and the minimum kettle residue (the minimum value of the kettle residue) is as low as 20% by mass, so the stirring blade does not rotate. On the other hand, in Examples 1 and 2, the minimum kettle residues were 36% by mass and 29% by mass, respectively. Since the amount of the remaining liquid in the reactor is ensured and the slurry is in a fluid state, the stirring blade can be rotated, and the production of 3-hydroxy sulfolane using an industrially used apparatus is possible.

Claims

1. A step of treating sulfolene represented by the following formula (1) with an aqueous alkali solution to obtain an aqueous solution containing 3-hydroxysulfolane represented by the following formula (2); A step of neutralizing the aqueous solution with an acid to obtain a neutralized solution; and A solvent substitution step of dissolving the 3-hydroxysulfolane and performing azeotropic substitution of the solvent of the neutralized solution using an organic solvent that is miscible with 3-hydroxysulfolane and azeotropic with water, A method for producing 3-hydroxysulfolane, wherein the liquid volume in the solvent substitution step is 29% by mass or more based on the liquid volume of the neutralized solution subjected to the solvent substitution step. 【Chemical 1】

2. 3-Hydroxysulfolane is produced using the method according to Claim 1, and an ester production method of obtaining a carboxylic acid ester of 3-hydroxysulfolane represented by the following formula (4) by subjecting the obtained 3-hydroxysulfolane and a carboxylic acid ester represented by the following formula (3) to a transesterification reaction. [[Chemical Formula 2]] [In Formula (3) and Formula (4), R １ represents a hydrogen atom, or a linear or branched alkyl group having 1 to 10 carbon atoms, and R ２ represents a linear or branched alkyl group having 1 to 10 carbon atoms.]

3. The ester production method according to Claim 2, wherein the boiling point of the organic solvent at standard atmospheric pressure is 100°C or lower.

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