JP2022126075A - Method for producing 3-hydroxy sulfolane, and ester production method - Google Patents

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

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

Unsaturated carboxylic acid esters of 3-hydroxysulfolane are used as sulfur-containing monomers for 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. Also, as a method for producing 3-hydroxysulfolane, sulfolene is treated with an alkaline aqueous solution and neutralized to obtain a neutralized liquid containing 3-hydroxysulfolane, and most of the water is distilled off from the neutralized liquid. , acetone is added to dissolve and extract 3-hydroxysulfolane, and a neutralized salt is precipitated and filtered.

JP 2007-153763 A

According to the findings of the present inventors, when attempting to industrially produce 3-hydroxysulfolane by the method described in Patent Document 1, most of the water is removed from the neutralized liquid in a reactor equipped with a stirring blade. When distilling off to obtain a concentrate, there are problems such as difficulty in stirring the concentrate with a stirring blade, and the possibility that the inner surface of the reactor may be damaged by the neutralized salt contained in the concentrate.
The present invention has been made in view of such circumstances, and a method for producing 3-hydroxysulfolane, which can remove neutralized salts and water from the neutralized solution while ensuring the liquid volume in the reactor, and a method for producing 3-hydroxysulfolane using the same A method for producing a carboxylic acid ester of 3-hydroxysulfolane is provided.

The present invention has the following aspects.
[1] A step of treating sulfolene represented by the following formula 1 with an alkaline aqueous 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 dissolving the 3-hydroxysulfolane and subjecting the solvent of the neutralized solution to azeotropic substitution using an organic solvent that is azeotropic with water. A method for producing 3-hydroxysulfolane, comprising steps.

[2] Producing 3-hydroxysulfolane using the method of [1] above,
A method for producing an ester, wherein the obtained 3-hydroxysulfolane and a carboxylic acid ester represented by the following formula 3 are transesterified to obtain a 3-hydroxysulfolane carboxylic acid ester represented by the following formula 4.

[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 ² represents a linear or branched alkyl group having 1 to 10 carbon atoms. indicates a group. ]
[3] The method for producing an ester according to [2], wherein the organic solvent has a boiling point of 100°C or less at standard atmospheric pressure.

The method for producing 3-hydroxysulfolane and the method for producing ester of the present invention can remove neutralized salt and water from the neutralized solution while ensuring the liquid volume in the reactor when producing 3-hydroxysulfolane. Therefore, manufacturing efficiency can be improved.

The following definitions apply throughout the specification and claims.
"-" indicating a numerical range means that the numerical values before and after it are included as lower and upper limits.
Room temperature means 20-30° C. unless otherwise specified.
pH values are 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.

<<Method for producing 3-hydroxysulfolane>>
The method for producing 3-hydroxysulfolane of the present embodiment includes the step of treating sulfolene represented by the following formula 1 with an alkaline aqueous solution to obtain an aqueous solution containing 3-hydroxysulfolane represented by the following formula 2 (hydration step), the step of neutralizing the aqueous solution with an acid to obtain a neutralized solution (neutralization step), and the neutralization using an organic solvent that dissolves the 3-hydroxysulfolane and is azeotropic with water A step of azeotropically replacing the solvent of the liquid (solvent replacement step) is included.

Stirred tanks are generally used for industrial syntheses. The stirring tank includes a hollow cylindrical container (reactor) with a bottom, stirring blades having a central axis of the container as a rotation axis, and a motor connected to the shaft of the stirring blades. A baffle may be provided to improve stirring efficiency. In multi-purpose agitation tanks, it is preferable that the contents to be agitated have a low viscosity due to the capacity of the motor and the presence of baffles. The distance from the bottom of the container to the stirring blades is often set to about 1/3 of the height of the container, and there is a lower limit to the amount of content that can be stirred.

<Hydration process>
In the hydration step, the raw material sulfolene is treated with an alkaline aqueous solution to produce 3-hydroxysulfolane through a hydration reaction. This gives an aqueous solution containing 3-hydroxysulfolane.
Specifically, sulfolene is dissolved in an alkaline aqueous solution, and the mixture is stirred at a temperature within the range of room temperature to 80° C. for 1 to 100 hours to carry out a hydration reaction.

Alkali include sodium hydroxide, potassium hydroxide, calcium hydroxide and the like. Sodium hydroxide is preferred from the viewpoint of cost, practicality and reaction efficiency.
The concentration of the alkaline aqueous solution is preferably 1 to 10N. 1 to 8 normality is more preferable, and 1 to 4 normality is even more preferable from the viewpoints of handleability, suppression of side reactions, suppression of coloration, and the like.

The amount of alkali to be used is preferably in the range of 0.5 to 10 times the molar amount of sulfolene. From the viewpoint of reaction efficiency and cost, it is more preferably in the range of 1 to 5 times the molar amount of sulfolene. From the viewpoint of suppressing side reactions and shortening the reaction time, it is more preferably in the range of 1 to 3 molar times.

When the reaction temperature of the hydration reaction is room temperature or higher, a favorable reaction rate is likely to be obtained, and when it is 80° C. or lower, decomposition of the starting material is difficult to occur, and formation of by-products is easily suppressed. Specifically, when sulfolene decomposes into butadiene and sulfurous acid gas, by-products such as butadiene oligomers or polymers are produced, which promotes polymerization, which is not preferable. A more practical reaction temperature is preferably in the range of room temperature to 60°C, and more preferably in the range of room temperature to 40°C from the viewpoint of easily suppressing coloration due to the reaction.

The reaction time of the hydration reaction is preferably 1 to 100 hours, more preferably 5 to 72 hours in terms of reaction efficiency and economy, and still more preferably 8 to 24 hours, but from the viewpoint of suppression of coloration and purity. , preferably over 24 hours.

If the hydration reaction has progressed completely, there is no need to consider removing the raw material sulfolane, but if unreacted raw materials remain after the hydration reaction, thermal decomposition, silica gel chromatography, Removal by a method such as distillation is preferred. From the point of view of low cost, it is preferable to thermally decompose while reducing the pressure at a temperature of 80 to 100° C. at which the raw material sulfolene is decomposed. Although there is no restriction on the timing of the thermal decomposition of the starting material sulfolene, it is preferable to thermally decompose the sulfolene while reducing the pressure during the water concentration step, which will be described later, because the possibility of polymerizing the butadiene produced by the thermal decomposition is low.

<Neutralization process>
In the neutralization step, the aqueous solution containing 3-hydroxysulfolane obtained in the hydration step is neutralized by adding an acid to obtain a neutralized solution.
Acids include hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, nitric acid and the like. Hydrochloric acid and sulfuric acid are preferred from the standpoints of separability between the target 3-hydroxysulfolane and the neutralized salt, workability, and the like.
The neutralized liquid obtained in the neutralization step contains 3-hydroxysulfolane, water and neutralized salt.

The end point of neutralization is preferably pH 5-8, more preferably pH 6-7. If the pH is 8 or less, coloring of the neutralized solution is unlikely to occur. When the pH is 5 or higher, the dehydration reaction of 3-hydroxysulfolane is less likely to occur. A dehydration reaction of 3-hydroxysulfolane is not preferable because 2-sulfolene, which is an isomer of sulfolene, is produced as a by-product.

<Solvent replacement step>
In the solvent replacement step, the solvent of the neutralization liquid is azeotropically replaced using an organic solvent that is azeotropic with water (hereinafter also referred to as an azeotropic solvent). An azeotropic solvent that dissolves 3-hydroxysulfolane is used.
Azeotropic substitution is preferably carried out by multistage azeotropy. Specifically, an azeotropic solvent is added to the neutralization liquid, a mixture containing the azeotropic solvent and water (hereinafter referred to as an azeotropic mixture) is distilled off, the azeotropic solvent is added again, and the azeotropic mixture is By repeating the operation of distilling off, the water in the neutralized liquid is replaced with the azeotropic solvent. The multistage azeotrope will be described later.
Azeotropic substitution results in a solution containing 3-hydroxysulfolane, neutralizing salt, and azeotropic solvent with water removed. The resulting solution is filtered to remove neutralizing salts.
The solution from which the neutralization salt has been removed (hereinafter, also referred to as an SFOH solution) can be used as it is or after removing the azeotropic solvent for the transesterification reaction described below.

Examples of azeotropic solvents are listed in Table 1. The table shows the boiling point of each solvent at standard atmospheric pressure (101.3 kPa), the azeotropic point of the two-component mixture of each solvent and water, and the content (azeotropic composition) of each solvent at the time of azeotropy.

When the 3-hydroxysulfolane obtained in the present embodiment is used for a transesterification reaction with a carboxylic acid ester, which will be described later, the boiling point of the azeotropic solvent is lower than the boiling point of the carboxylic acid ester used in the transesterification reaction. , 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 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 alcohol, it is preferable to remove the azeotropic solvent from the SFOH solution before the transesterification reaction, because side reactions tend to occur in the transesterification reaction described below.
The azeotropic solvent is more preferably acetonitrile or ethyl methyl ketone, since the SFOH solution obtained in the solvent replacement step can be used as it is for the transesterification reaction.

Table 2 is an example for explaining multi-stage azeotropy, and shows the theoretical values when performing multi-stage azeotropy using acetonitrile (referred to as "ATN" in the table) as an azeotropic solvent. is. "Part" in the table indicates "mass part".
In the example of Table 2, the amount of the neutralization liquid is 100 parts by mass, and consists of 21.1 parts by mass of solute containing 3-hydroxysulfolane and neutralized salt and 78.9 parts by mass of water as a solvent. .
First, part of the water (50 parts by mass) is distilled off from the neutralized liquid (water concentration step) to obtain a concentrated liquid (liquid volume: 50 parts by mass) with a water content of 58% by mass.
Next, 31.8 parts by mass of acetonitrile is added (addition 1), acetonitrile and water are azeotroped, and 31.8 parts by mass of the azeotropic mixture is distilled off (distillation 1). Assuming that the content of acetonitrile in the azeotrope to be distilled off is 84.2% by weight, 31.8 parts by weight of the azeotrope consists of 5 parts by weight of water and 26.8 parts by weight of acetonitrile. As a result, a solution (liquid volume: 50.0 parts by mass) with a reduced water content of 48% by mass is obtained.
Then, 31.8 parts by mass of acetonitrile is added (addition 2), acetonitrile and water are azeotroped, and 31.8 parts by mass of the azeotropic mixture is distilled off (distillation 2). As a result, a solution (liquid volume: 50.0 parts by mass) with a reduced water content of 38% by mass is obtained.
Thus, 31.8 parts by mass of acetonitrile are added (additions 3 to 6), and acetonitrile and water are azeotroped to distill off 31.8 parts by mass of the azeotrope (distillation 3 to 6). By repeating this process, the water content gradually decreases, and 50.0 parts by weight of a solution consisting of 21.1 parts by weight of solute, -1.2 parts by weight of water, and 30.1 parts by weight of acetonitrile is obtained. The resulting solution is filtered to remove neutralizing salts to obtain an SFOH solution.

Thus, by azeotropically replacing the solvent of the neutralized liquid with the azeotropic solvent, water can be removed from the neutralized liquid while ensuring the liquid volume in the reactor.
In the solvent replacement step, azeotropic replacement is preferably performed until a solution having a water content of 1% by mass or less, preferably 0.1% by mass or less is obtained.

In the solvent replacement step, water distillation (water concentration step) before adding the azeotropic solvent first is not essential, but prior to the azeotropic replacement, part of the water contained in the neutralization solution should be distilled off. , the water contained in the neutralization solution can be efficiently removed. As a result, the number of times (the number of stages) of repeating the operation of adding the azeotropic solvent and distilling off the azeotropic mixture can be reduced.
When only water is distilled off (condensed) before adding the azeotropic solvent, if too much water is distilled off, it becomes difficult to stir the liquid in the reactor with the stirring blades. Set the distillation volume.
The number of stages in the multistage azeotrope is not particularly limited, but is preferably 1 to 10 stages, and more preferably 1 to 4 stages from the viewpoint of cost and thermal polymerization suppression.

In multistage azeotropy, the amount of the azeotropic solvent added and the amount distilled off immediately after that may be the same or different. The amount of the azeotropic solvent added in each stage may be the same or different. Also, the distillation amount in each stage may be the same or different.
The amount of liquid in the solvent replacement step may be increased or decreased as long as it is not more than the amount of liquid that can be accommodated in the reactor and is not less than the amount of liquid that can be stirred with a stirring blade. Assuming that the amount of the neutralized liquid to be subjected to the solvent replacement step is 100% by mass, the amount of the liquid after distillation is preferably 50% by mass or more, and 30% by mass or more is efficient, depending on the structure of the reactor. more preferable in terms of

Azeotropic substitution may be performed under reduced pressure. Since the azeotropic point is lowered when the pressure is reduced, the heating temperature for distilling off the azeotropic mixture can be lowered, which is preferable.
In the solvent replacement step, the treatment temperature is preferably from room temperature to 80°C, more preferably from 40°C to 60°C, when the internal temperature is the treatment temperature.
In the solvent replacement step, the treatment pressure is preferably 30 hPa to 500 hPa, more preferably 30 hPa to 400 hPa, and even more preferably 30 hPa to 300 hPa, when the internal pressure is the treatment pressure.
In the one-time (one-stage) distillation step, the treatment temperature and the treatment pressure may be constant or may change over time.

≪Ester manufacturing method≫
In the ester production method of the present embodiment, 3-hydroxysulfolane is produced using the method of the above embodiment, and the resulting 3-hydroxysulfolane and a carboxylic acid ester represented by the following formula 3 (hereinafter referred to as a raw material ester ) is subjected to an ester exchange reaction (ester exchange step) to obtain a carboxylic acid ester of 3-hydroxysulfolane represented by the following formula 4 (hereinafter also referred to as a product ester).

In formulas 3 and 4, R ¹ represents a hydrogen atom or a linear C 1-10 or branched C 3-10 alkyl group, and R ² represents a linear C 1-10 or branched represents an alkyl group having 3 to 10 carbon atoms.
Examples of the alkyl group for R ¹ or R ² include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, pentyl group, isopentyl group, hexyl group, octyl group, nonyl group, and decyl group. can. R ¹ is preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms from the viewpoint of high practicality. R ² is preferably an alkyl group having 1 to 4 carbon atoms. From the standpoint of separability, both R ¹ and R ² are more preferably methyl groups.

The method for producing an ester of the present embodiment preferably has, for example, aspect 1 or aspect 2 below.
(Mode 1) A mode in which the SFOH solution obtained in the solvent replacement step is directly used in the transesterification step. In this aspect, the azeotropic solvent contained in the SFOH solution preferably does not contain alcohol. In this aspect, the boiling point (standard atmospheric pressure) of the azeotropic solvent contained in the SFOH solution is preferably 100° C. or lower.
(Aspect 2) An aspect 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 below, and refluxed until the alcohol is removed using a Dean-Stark apparatus.

<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 the mixture is heated to carry out a transesterification reaction.
In mode 2, after the azeotropic solvent is removed from the SFOH solution, the SFOH solution is dissolved in the raw material ester, a transesterification catalyst is added, and the mixture is heated to carry out a transesterification reaction.
The transesterification reaction can be carried out using a known method described, for example, in JP-A-2007-153763.

In aspects 1 and 2, as the transesterification reaction progresses, an alcohol derived from the raw material ester is by-produced, and it is preferable to proceed with the transesterification reaction while removing the by-product alcohol. When the reaction rate reaches a predetermined value, the reaction solution is cooled to stop the reaction. Thereafter, unreacted 3-hydroxysulfolane is removed and the transesterification catalyst is removed/inactivated, and the raw material ester is distilled off from the reaction solution and concentrated to obtain the desired product ester.
In the case of mode 1, when the raw material ester is distilled off from the reaction solution of the transesterification reaction and concentrated, it is preferable to simultaneously distill off the azeotropic solvent derived from the SFOH solution.

Raw material esters 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; α-ethyl acrylates such as ethyl ethyl acrylate and α-ethyl propyl acrylate;

As for the amount of the raw material ester used, if the by-product alcohol can be easily removed without azeotropy, the transesterification reaction will proceed sufficiently even if the amount of the raw material ester is small. When the by-product alcohol is removed by azeotropy with the raw material ester, such as methyl methacrylate and methanol, if the amount of the raw material ester is too small, the by-product alcohol cannot be sufficiently removed, resulting in a decrease in reaction rate. Cheap.
On the other hand, if the amount of the raw material ester is too large, the tank efficiency of the transesterification reaction will deteriorate, which is not preferable in terms of cost.
The amount of raw material ester used is preferably within a range that does not cause these problems. For example, it is preferably in the range of 2-fold to 20-fold mol, more preferably in the range of 3-fold to 10-fold mol, relative to 3-hydroxysulfolane.

Examples of the transesterification catalyst include organic 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. Tin compounds; metal alkoxides such as sodium methoxide, lithium ethoxide, titanium tetrabutoxide, titanium tetramethoxide, titanium tetraisopropoxide, titanium tetraethoxide, tetrakis(2-ethylhexyloxy)titanium, titanium tetrastearyl oxide; can be exemplified. Dibutyltin oxide, titanium tetramethoxide, and titanium tetrabutoxide are preferred from the viewpoint of superiority in reaction operation and availability.

The amount of the catalyst to be used is preferably 0.01 to 5 mol % relative to 3-hydroxysulfolane, and more preferably 0.1 to 2 mol % from the viewpoints of cost and ease of catalyst treatment.
Considering that it is a transesterification reaction of 3-hydroxysulfolane having a hard-to-react secondary alcohol, in order to complete the transesterification reaction in a practical time of 1 to 2 days, the amount of catalyst used is more preferably 0.5 to 3 mol %.

A polymerization inhibitor is preferably added to the reaction system in order to prevent polymerization of the raw material ester and the produced ester. The type of polymerization inhibitor is not particularly limited. One type of polymerization inhibitor may be used, or two or more types may be used in combination.

Polymerization inhibitors include hydroquinone, p-methoxyphenol, 2,4-dimethyl-6-tert-butylphenol, 2,6-di-tert-butyl-4-methylphenol, tert-butyl-catechol, 2,6- Phenolic compounds such as di-tert-butyl-4-methylphenol, pentaerythritol tetrakis (3,5-di-tert-butyl-4-hydroxyhydrocinnamate), 2-sec-butyl-4,6-dinitrophenol ; N,N-diisopropyl paraphenylenediamine, N,N-di-2-naphthyl paraphenylenediamine, N-phenylene-N-(1,3-dimethylbutyl) paraphenylenediamine, N,N'-bis(1, Amine compounds such as 4-dimethylphenyl)-paraphenylenediamine, N-(1,4-dimethylphenyl)-N'-phenyl-paraphenylenediamine; 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, etc. metal compounds such as copper, copper (II) chloride, and iron (III) chloride; and the like.

The amount of the polymerization inhibitor to be used can be appropriately set. For example, it is preferably 100 ppm or more, more preferably 500 ppm or more to obtain a sufficient polymerization inhibitory effect, relative to the raw material ester used. On the other hand, the amount of the polymerization inhibitor used is preferably 10,000 ppm or less from the viewpoint of cost, and more preferably 5,000 ppm or less in consideration of coloring of the product, convenience in use, and the like.

It is also preferable to bubble an oxygen-containing gas such as air into the transesterification reaction solution in order to prevent polymerization. The amount of the oxygen-containing gas to be introduced can be appropriately set so as to obtain the desired effect of preventing polymerization. For example, when air is used as the oxygen-containing gas, it is preferable to bubble 0.5 to 3.0 mL/min with respect to 1 mol 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 enhancing the effect of preventing polymerization.

In the transesterification reaction, a batch reactor or a continuous reactor may be used. For example, while stirring the reaction liquid containing the catalyst in a batch reactor, the transesterification reaction can be carried out while removing alcohol (R ² OH) produced as a by-product out of the system in order to advance the reaction.

The reaction pressure for the transesterification reaction is not particularly limited, and any of reduced pressure, normal pressure, and increased pressure can be used.
The reaction temperature for the transesterification reaction is preferably in the range of normal temperature to 150° C., although it depends on the reaction pressure. A temperature of 60 to 150° C. is more preferable in order to remove the by-produced alcohol (R ² OH) and obtain a higher reaction rate.
The transesterification reaction time is preferably 1 to 50 hours, more preferably 5 to 36 hours from the viewpoint of practicality and efficiency.

After completion of the transesterification reaction, it is preferable to deactivate the catalyst as necessary, recover unreacted 3-hydroxysulfolane, and purify the produced ester.
Deactivation of the catalyst can be carried out by a known method.
The product ester is generally solid at ambient temperature. The produced ester can be purified by known purification methods such as vacuum distillation and recrystallization.

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

<Example 1>
This example is an example in which acetonitrile is used as an azeotropic solvent to azeotropically replace water in the neutralized liquid.
(Hydration process/neutralization process)
18 g (0.15 mol) of sulfolene was dissolved in 55 mL of a 3.28N sodium hydroxide aqueous solution and allowed to stand at 30° C. for 24 hours. Gas chromatograph analysis confirmed that most of the raw material sulfolene had disappeared. The reaction liquid was cooled with ice water, 8 g of sulfuric acid was added, and neutralized to about pH 6.5 to obtain a neutralized liquid (100 g). The water content of the neutralization liquid was 48% by mass.

(Solvent replacement step)
Multistage azeotropy was performed under the conditions shown in Table 3, and water contained in the neutralized liquid was replaced with acetonitrile as a solvent.
After distilling off the azeotrope, the water content of the liquid in the reactor was measured. The amount of liquid in the reactor was calculated based on the amount of distillation and the amount of addition, and the content of the solute with respect to the amount of liquid 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 residual volume of the kettle. These results are shown in the table (hereinafter the same).
After completion of the multistage azeotropic distillation, the solution was filtered through a pressure filter to remove neutralized salts.
Further, the filtrate was heated to 80° C. and concentrated under reduced pressure to decompose and remove the remaining raw materials.
An SFOH solution (41 g) of 3-hydroxysulfolane dissolved in acetonitrile was thus obtained. The GC purity of 3-hydroxysulfolane in the SFOH solution was 97%, and the water content was 0.13% by mass.

<Example 2>
In this example, methyl ethyl ketone (denoted as "MEK" in the tables) was used as an azeotropic solvent to azeotropically replace water in the neutralization solution. Table 4 shows the multistage azeotropic conditions.
(Hydration process/neutralization process)
99.6 g (0.84 mol) of sulfolene was dissolved in 0.85 liter of 1.5N sodium hydroxide aqueous solution and allowed to stand at room temperature for 72 hours. Gas chromatograph analysis confirmed that most of the raw material sulfolene had disappeared. The reaction liquid was cooled with ice water, 60 g of sulfuric acid was added, and neutralized to about pH 7.2 to obtain a neutralized liquid (1011 g). The water content of the neutralization liquid was 81% by mass.

(Solvent replacement step)
A portion (249 g) of the obtained neutralized liquid was subjected to multistage azeotropic distillation under the conditions shown in Table 4 to replace the water contained in the neutralized liquid with methyl ethyl ketone.
After completion of the multistage azeotropic distillation, the solution was filtered through a pressure filter to remove neutralized salts.
Further, the filtrate was heated to 80° C. and concentrated under reduced pressure to decompose and remove the remaining raw materials.
An SFOH solution (81 g) of 3-hydroxysulfolane dissolved in methyl ethyl ketone was thus obtained. The water content of 3-hydroxysulfolane in the SFOH solution was 0.08 wt%.

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

<Example 3>
This example is a comparative example in which water in the neutralized solution was distilled off without azeotropic substitution.
(Hydration process/neutralization process)
A neutralized liquid (1011 g) was obtained in the same manner as in Example 2. A portion (500 g) of the obtained neutralized liquid was evaporated to dryness to obtain 102 g of slurry (remaining amount in kettle: 20% by mass).

The dried slurry of Example 3 was hard and stuck to the walls. When manufacturing with an industrially used device, the viscosity is high and the stirring blades do not rotate, and the minimum remaining amount in the kettle (minimum value of the remaining amount in the kettle) is as low as 20% by mass, so the stirring blades do not rotate. Industrial production of 3-hydroxysulfolane is difficult.
On the other hand, in Examples 1 and 2, the minimum remaining amount in the pot was 36% by mass and 29% by mass, respectively. The amount of residual liquid in the reactor is secured, and the slurry is in a state of fluidity, so the stirring blades can be rotated, making it possible to produce 3-hydroxysulfolane using industrially used equipment. be.

Claims (3)

A step of treating sulfolene represented by the following formula 1 with an alkaline aqueous 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 dissolving the 3-hydroxysulfolane and subjecting the solvent of the neutralized solution to azeotropic substitution using an organic solvent that is azeotropic with water. A method for producing 3-hydroxysulfolane, comprising steps.

Producing 3-hydroxysulfolane using the method of claim 1,
A method for producing an ester, wherein the obtained 3-hydroxysulfolane and a carboxylic acid ester represented by the following formula 3 are transesterified to obtain a 3-hydroxysulfolane carboxylic acid ester represented by the following formula 4.

[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 ² represents a linear or branched alkyl group having 1 to 10 carbon atoms. indicates a group. ] 3. The method for producing an ester according to claim 2, wherein the organic solvent has a boiling point of 100[deg.] C. or less at standard atmospheric pressure.