JP2002037769A - Method for producing 2-hydroxy-4-methylthiobutanoic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing 2-hydroxy-4-methylthiobutanoic acid and enabling easy separation of the 2-hydrdoxy-4-methylthiobutanoic acid in high operationality. SOLUTION: The method for the production of 2-hdyroxy-4-methylthiobutanoic acid contains (A) a step to obtain a reaction liquid containing 2-hydroxy-4- methylthiobutanamide by the hydration reaction of 2-hydroxy-4- methylthiobutanonitrile in the presence of sulfuric acid, (B) a step to obtain a reaction liquid containing 2-hydroxy-4-methylthiobutanoic acid by the hydrolysis of 2-hydroxy-4-methylthiobutanamide in the reaction liquid obtained by the step A and (C) a step to separate the reaction liquid obtained by the step B into an oil layer containing 2-hydroxy-4-methylthiobutanoic acid and an aqueous layer. A part of the aqueous layer separated in the step C is circulated to the steps B and/or C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing 2-hydroxy-4-methylthiobutanoic acid which is useful as a feed additive or the like. Specifically, 2-hydroxy-4-
The present invention relates to a method for producing 2-hydroxy-4-methylthiobutanoic acid by hydrating and hydrolyzing methylthiobutanenitrile in the presence of sulfuric acid.

[0002]

2. Description of the Related Art Conventionally, as a method for producing 2-hydroxy-4-methylthiobutanoic acid, a method of hydrolyzing 2-hydroxy-4-methylthiobutanenitrile in the presence of sulfuric acid is known. From this sulfuric acid hydrolysis reaction solution, 2
As a method for extracting -hydroxy-4-methylthiobutanoic acid, for example, Japanese Patent Publication No. 5-1787 describes a method of extracting with an organic solvent such as isobutyl methyl ketone. However, in this method, the use of an organic solvent causes an increase in variable costs and a decrease in volumetric efficiency, and equipment and operations for recovering and purifying the organic solvent and removing the organic solvent from products and wastewater are required. Required. U.S. Pat. No. 4,912,257 describes a method in which ammonium bisulfate in a reaction solution is neutralized with ammonia to form ammonium sulfate, and oil-water separation is performed by a salting-out effect. Although this method does not require the use of an organic solvent, it is not sufficient in terms of oil water separation and extraction efficiency.

[0003]

DISCLOSURE OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide 2-hydroxy-4-methylthiobutane which can efficiently extract 2-hydroxy-4-methylthiobutanoic acid with good operability. An object of the present invention is to provide a method for producing an acid.

[0004]

Means for Solving the Problems As a result of diligent studies, the present inventors have found that when 2-hydroxy-4-methylthiobutanoic acid is produced by sulfuric acid hydrolysis of 2-hydroxy-4-methylthiobutanenitrile, a specific product is produced. It has been found that the above object can be achieved by constructing a circulatory system, and the present invention has been completed. That is, the present invention
(A): 2-hydroxy-4-methylthiobutanenitrile is hydrated in the presence of sulfuric acid to give 2-hydroxy-4-
Obtaining a reaction solution containing methylthiobutanamide,
(B): a step of hydrolyzing 2-hydroxy-4-methylthiobutanamide contained in the reaction solution obtained in (A) to obtain a reaction solution containing 2-hydroxy-4-methylthiobutanoic acid, and (C): including a step of separating the reaction solution obtained in (B) into an oil layer containing 2-hydroxy-4-methylthiobutanoic acid and an aqueous layer, and a part of the aqueous layer separated in (C). 2 circulating in (B) and / or (C)
The present invention relates to a method for producing -hydroxy-4-methylthiobutanoic acid.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
In the present invention, 2-hydroxy-4-methylthiobutanenitrile is used as a raw material.
A reaction solution containing methylthiobutanamide can be obtained [Step (A)]. The starting material, 2-hydroxy-4-methylthiobutanenitrile, can be prepared, for example, by reacting acrolein with methylmercaptan to obtain 3-methylthiopropionaldehyde and reacting it with hydrogen cyanide.

The amount of sulfuric acid used in the hydration reaction is based on 1 mole of 2-hydroxy-4-methylthiobutanenitrile.
From the viewpoint of reaction rate, it is usually at least 0.5 mol, preferably at least 0.6 mol, and from the viewpoint of liquid separation of oily water after hydrolysis, usually at most 1 mol, preferably at most 0.9 mol. It is.

The amount of water used in the hydration reaction is usually at least 15 parts by weight, preferably at least 25 parts by weight, from the viewpoint of reaction rate, based on 100 parts by weight of 2-hydroxy-4-methylthiobutanenitrile. Further, it is usually 70 parts by weight or less, preferably 50 parts by weight or less.

As a method for supplying 2-hydroxy-4-methylthiobutanenitrile, sulfuric acid and water in the hydration reaction, it is preferable to supply 2-hydroxy-4-methylthiobutanenitrile in sulfuric acid from the viewpoint of the reaction rate. Preferably, at this time, the water may be mixed with sulfuric acid before supplying 2-hydroxy-4-methylthiobutanenitrile, or may be supplied into sulfuric acid together with 2-hydroxy-4-methylthiobutanenitrile. Alternatively, some may be mixed with sulfuric acid before supplying 2-hydroxy-4-methylthiobutanenitrile, and some may be supplied into sulfuric acid together with 2-hydroxy-4-methylthiobutanenitrile. . Water is preliminarily mixed with 2-hydroxy-4-methylthiobutanenitrile or sulfuric acid, that is, 2
You may use it in the state contained in the aqueous solution of -hydroxy-4-methylthiobutanoic acid or sulfuric acid.

[0009] The reaction temperature of the hydration reaction is usually 40 to 70 ° C.
And the reaction time is usually in the range of 1 to 3 hours. Also, the hydration reaction is usually performed at around normal pressure,
If necessary, the reaction may be performed under increased or reduced pressure.

The reaction solution containing 2-hydroxy-4-methylthiobutanoic acid can be obtained by hydrolyzing 2-hydroxy-4-methylthiobutanamide in the reaction solution obtained in step (A) [ Step (B)]. Here, by circulating a part of the aqueous layer separated in the step (C) described later in this step, the obtained reaction liquid can be separated into oil and water with good liquid separation and distribution efficiency.

The circulation amount of the aqueous layer is the sum of the amount of ammonium sulfate and ammonium bisulfate contained in the aqueous layer per mole of the sulfuric acid used for the hydration reaction and, if necessary, the sulfuric acid added to the hydrolysis reaction. , Usually in the range of 1.0 to 2.0 mol, preferably 1.2 to 1.8 mol.

In the step (B), water may be added if necessary. In this case, the amount of water to be added is determined by the sum of the amount of water and the amount of water contained in the reaction solution obtained in the step (A) and the amount of water contained in the circulating aqueous layer. 100 parts by weight to 300 parts by weight,
Preferably, it is in the range of 200 to 300 parts by weight.

In the step (B), sulfuric acid may be added as required. In this case, the amount of sulfuric acid used for the hydration reaction may be reduced as compared with the case where sulfuric acid is not added to the hydrolysis reaction.

When a part of the aqueous layer separated in the step (C) is circulated to the step (B), from the viewpoint of operability, an aqueous layer circulating the reaction solution obtained in the step (A) and After mixing with water or sulfuric acid as necessary, it is preferable to subject the resulting mixture to a hydrolysis reaction. Further, while the reaction solution obtained in the step (A) is subjected to a hydrolysis reaction, an aqueous layer circulated therein and, if necessary, water or sulfuric acid may be gradually added.

The reaction temperature of the hydrolysis reaction is usually 90 to 1
The reaction time is usually in the range of 2 to 6 hours. In addition, the hydrolysis reaction is usually performed at around normal pressure, but may be performed under increased or reduced pressure as necessary.

The reaction solution obtained in the step (B) is separated into an oil layer containing 2-hydroxy-4-methylthiobutanoic acid and an aqueous layer, so that 2-hydroxy-4-
Methylthiobutanoic acid can be obtained [Step (C)]. In the reaction solution, when ammonium bisulfate or ammonium sulfate is precipitated, oil and water may be separated as they are, but from the viewpoint of liquid separation, it is preferable to dissolve these precipitates by heating, Even when no precipitate is present, liquid separation can be improved by heating. The temperature at the time of oil-water separation is usually 30 to 110 ° C,
Preferably it is in the range of 70 to 90 ° C. In addition, operations such as concentration may be performed in order to enhance liquid separation.

A part of the aqueous layer separated in the step (C) is circulated to the step (B) as described above. For an aqueous layer that is not circulated, the aqueous layer usually contains ammonium bisulfate and ammonium bisulfate, so ammonium bisulfate may be neutralized with ammonia and then ammonium sulfate may be recovered. A trace amount of the contained 2-hydroxy-4-methylthiobutanoic acid may be recovered by an appropriate method.

In the oil layer separated in the step (C), it depends on the conditions of the steps (A) to (C), but usually, in addition to 2-hydroxy-4-methylthiobutanoic acid, water, ammonium sulfate, Ammonium sulfate and the like. The operation of obtaining a product from the oil layer varies depending on the required form and quality of the product. From the viewpoint of increasing the concentration of 2-hydroxy-4-methylthiobutanoic acid in the product, the oil layer is mixed with ammonia. After neutralizing ammonium bisulfate to ammonium sulfate [Step (D)], it is preferable to remove insolubles such as ammonium sulfate precipitated from the obtained mixed solution by filtration or decantation [Step (E)].

The amount of ammonia used in the step (D) is usually about equimolar to ammonium bisulfate contained in the oil layer separated in the step (C). Further, as a form of ammonia, ammonia gas or liquid ammonia is preferable from the viewpoint of reducing the moisture in the mixed solution,
On the other hand, from the viewpoint of operability, an aqueous ammonia solution is preferred.

In the step (E), when the insoluble matter is removed by filtration, it is preferable to heat the filter from the viewpoint of filterability, and the filtration temperature is usually in the range of 50 to 90 ° C. When removing insolubles by decantation, it is preferable that the insolubles be sufficiently settled by standing or centrifugation.

Before removing the insoluble matter from the mixture obtained in the step (D), the mixture is concentrated to remove water, so that more insoluble matter can be precipitated, A product with a reduced ammonium sulfate content can be obtained. For example, when it is desired to reduce the content of ammonium sulfate in the product to 1% by weight or less, it is preferable to concentrate the water in the liquid phase portion of the mixed solution to usually 5% or less, preferably 2% or less.

The insoluble matter removed by filtration or decantation in the step (E) is usually 2-hydroxy-4
-Since methylthiobutanoic acid is attached to the surface or contained inside, at least a part of the insoluble matter is circulated to the step (D) in order to recover the 2-hydroxy-4-methylthiobutanoic acid. Is preferred. In this case, the insolubles may be washed with water to elute 2-hydroxy-4-methylthiobutanoic acid, and the obtained washing liquid may be circulated.

In the present invention, instead of circulating a part of the aqueous layer separated in the step (C) as described above to the step (B), one part of the aqueous layer separated in the step (C) is used. By circulating the part to the step (C), 2-hydroxy-4-methylthiobutanoic acid can be similarly efficiently removed with good operability. In this case, the circulating amount of the aqueous layer and other conditions may be determined according to the case of circulating in the step (B). Further, a part of the aqueous layer separated in the step (C) may be circulated to both the step (B) and the step (C).

[0024]

The present invention will now be described by way of examples, which should not be construed as limiting the invention. Example 1 The following operations (1) to (4) were repeated four times. : To 74.0 g (0.74 mol) of concentrated sulfuric acid (98%),
Under stirring, 175.4 g (1.0 mol) of a 74.8% aqueous solution of 2-hydroxy-4-methylthiobutanenitrile was added to 50
After dropping at 30 ° C over 30 minutes, the mixture was kept at 50 ° C for 90 minutes. : To the reaction solution obtained in the above, the aqueous layer obtained in the previous step and water were added in the amounts shown in Table 1 [However, at the first time, ammonium bisulfate 6 was used instead of the aqueous layer and water.
0 g (0.52 mol) and 38.2 g of ammonium sulfate
(0.29 mol) in 114 g of water was added], and the mixture was stirred at 115 ° C for 4 hours. Table 1 shows the change over time in the residual ratio of 2-hydroxy-4-methylthiobutanamide determined by liquid chromatography. : The reaction solution obtained in was allowed to stand, and separated into an oil layer and an aqueous layer. Table 1 shows the weight of the aqueous layer and the contents of ammonium bisulfate and ammonium sulfate in the aqueous layer determined by neutralization titration (NaOH). : 25% aqueous ammonia solution 6.8 in the oil layer obtained in
g (0.1 mol) and the total amount of the washing solution obtained in the previous step were added (only 6.8 g (0.1 mol) of a 25% aqueous ammonia solution was added at the first time), and the mixture was concentrated under reduced pressure. A slurry having a water content of the oil phase of 2% or less was obtained. : The slurry obtained in was filtered to obtain a filtrate. Table 1 shows the weight of the product, the sulfate ion concentration in the product determined by ion chromatography, and the moisture in the product determined by the Karl Fischer method. The residue separated by filtration was washed with 10 g of water.

[0025]

[Table 1]

[0026]

According to the method for producing 2-hydroxy-4-methylthiobutanoic acid of the present invention, the efficiency and efficiency of 2-hydroxy-4-methylthiobutanoic acid are improved.
-Hydroxy-4-methylthiobutanoic acid can be removed.

Continued on the front page (72) Inventor Takehiro Otani 5-1 Sokaicho, Niihama-shi, Ehime Sumitomo Chemical Industries, Ltd. (72) Inventor Shogo Sudo 5-1 Sokaicho, Niihama-shi, Ehime Sumitomo Chemical Industries, Ltd. F term (reference) 4H006 AA02 AC46 AC53 AC63 AD16 AD17 BC10 BD42 BD53 BE03 BE14 TA04 TB56

Claims (3)

[Claims] (A) a step of subjecting 2-hydroxy-4-methylthiobutanenitrile to a hydration reaction in the presence of sulfuric acid to obtain a reaction solution containing 2-hydroxy-4-methylthiobutanamide; (B): (B): A step of subjecting 2-hydroxy-4-methylthiobutanamide contained in the reaction liquid obtained in A) to a hydrolysis reaction to obtain a reaction liquid containing 2-hydroxy-4-methylthiobutanoic acid, and (C): ( The reaction solution obtained in B) was treated with 2-hydroxy-4
-A step of separating into an oil layer containing methylthiobutanoic acid and an aqueous layer, wherein a part of the aqueous layer separated in (C) is circulated to (B) and / or (C). A method for producing hydroxy-4-methylthiobutanoic acid. 2. The method according to claim 1, further comprising: (D): a step of mixing the oil layer separated in (C) with ammonia; and (E): a step of removing insolubles from the mixture obtained in (D). 2. The production method according to 1. 3. The production method according to claim 2, wherein at least a part of the insoluble matter removed in (E) is circulated to (D).