JPS5936893B2 - Method for producing lactate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a lactate, and more particularly, a method for producing a lactic acid salt, and more specifically, a method for producing a lactic acid salt, in which a lactic acid amide obtained by contact hydration of lactic acid nitrile in the presence of manganese or a manganese compound is hydrated in the presence of an alkaline substance. The present invention relates to a method for producing lactate by hydrolysis.

Lactate is an extremely useful compound as a plasticizer such as casein, an antifreeze agent, a moisture absorbent, a corrosion inhibitor for alcoholic antifreeze, and a raw material for pyruvate.

Conventionally, to produce this lactate, lactic acid nitrile is hydrolyzed using sulfuric acid, this is converted into methyl ester and separated, and then hydrolyzed to produce free lactic acid, which is then neutralized with caustic alkali etc. This process was necessary.

In this conventional method, not only are there many and complicated processes, but
It had many drawbacks, such as producing a large amount of ammonium sulfate as a by-product.

As a result of various researches aimed at providing a method for producing lactate without the many complicated steps and by-product of ammonium sulfate as in conventional methods, the present inventor discovered that lactate can be produced by contact hydration of lactate nitrile. The inventors discovered that lactate can be obtained in good yield by adding an alkali to an aqueous lactic acid amide solution and hydrolyzing it, leading to the completion of the present invention.

That is, the method of the present invention involves adding an alkaline substance to an aqueous lactic acid amide solution obtained by contact hydration of lactic acid nitrile in the presence of manganese or a manganese compound, and heating the mixture at 30 to 200°C.
This is a method for producing lactate by hydrolyzing it with

According to the method of the present invention, lactate can be industrially advantageously produced without the complicated steps and by-product of ammonium sulfate that are required in conventional methods.

That is, it is well known that ordinary nitriles, such as acetonitrile, can easily give carboxylic acid salts when hydrolyzed in a basic aqueous solution. However,
In the case of lactic acid nitrile, it decomposes into acetaldehyde and hydrocyanic acid in a basic aqueous solution, making it impossible to obtain a carboxylic acid salt. Therefore, the hydrolysis of lactic acid nitrile is
Because acid, usually sulfuric acid, is used, the process is complicated and a large amount of ammonium sulfate is produced as a by-product. In the method of the present invention, lactate can be obtained in high yield by adding an alkaline substance to an aqueous lactic acid amide solution obtained by catalytic hydration of lactic acid nitrile and hydrolyzing it, and there is no by-product of ammonium sulfate. It is a non-polluting process with no waste water that needs to be treated. In the method of the present invention, first, lactic acid nitrile as a raw material is catalytically hydrated in the presence of manganese or a manganese compound to obtain lactic acid amide.

The catalyst used for this catalytic hydration is manganese or a manganese compound.

That is, metallic manganese or manganese dioxide (Mn
O2), trioxide] Manganese (Mn04), manganese sesquioxide (Mn2O3), manganous oxide (MnO)
or a compound such as manganous hydroxide (Mn(OH)2). These materials can be used alone or as a mixture of two or more.

Although these compounds or metals can be prepared from various starting materials of manganese, they exhibit substantially the same activity regardless of differences in starting materials or manufacturing methods. For example, manganese dioxide can be produced by thermal decomposition of manganese nitrate or the like, or commercially available manganese dioxide can be used as is. The catalyst is in the form of powder, granules or tablets,
When used in a suspended bed reactor, powder is used, and when used in a fixed bed reactor, granular or chained 1 is used. A carrier in which manganese dioxide is supported can also be used. Although there is no particular restriction on the amount of catalyst used, a larger amount of catalyst is used than in the case of other catalytic reactions. The aqueous solution of nitrile lactate used in the method of the present invention has a concentration of nitrile lactate of 1 to 5.
0wt%, preferably 5-30wt0! ) is within the range.

The reaction temperature at which the lactic acid nitrile aqueous solution and the catalyst manganese dioxide are brought into contact is 30 to 200°C, preferably 50 to 200°C.
The temperature range is 130°C. If the reaction temperature is lower than the above range, the reaction rate is slow and not substantial, and if the reaction temperature is higher than the above range, the decomposition of lactic acid nitrile and the oxidation reaction of alcohol groups occur simultaneously, resulting in a decrease in yield, which is not preferable. After the reaction is completed, the catalyst is separated from the reaction solution to obtain an aqueous lactic acid amide solution. If the reaction is carried out in a fixed bed,
For example, a 10% aqueous solution of lactic acid nitrile is passed through a reactor filled with a manganese dioxide tablet shaping catalyst at 70° C., and the effluent is cooled and collected.

The collection liquid is used as it is or by ion exchange treatment or activated carbon treatment to form an aqueous lactic acid amide solution in the production of lactate, which is the method of the present invention. The lactic acid amide concentration of the lactic acid amide aqueous solution is usually in the range of 5 to 30 wt%. In the method of the present invention, an alkaline substance is then added to the lactic acid amide aqueous solution obtained by the above method to perform hydrolysis.

The alkaline substances used include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkali metal carbonates or bicarbonates such as sodium carbonate, potassium carbonate, sodium bicarbonate, and potassium bicarbonate, calcium hydroxide,
Refers to alkaline earth metal hydroxides such as barium hydroxide. Among the above alkaline substances, sodium hydroxide is usually used frequently. The amount of the alkaline substance used is equivalent to the lactic acid amide used, or slightly in excess of the equivalent.

If the amount used is less than the equivalent amount, the conversion rate of lactic acid amide will not reach 100%, which is not preferable. In the case of a batch reaction, the alkaline substance may be added in its entirety at the beginning of the reaction, or may be added sequentially in synchronization with the progress of the reaction. In the method of the present invention, the reaction temperature when hydrolyzing lactic acid amide is 3
A temperature range of 0 to 200°C, usually 5Q to 100°C, is frequently used.

The time required for the reaction depends on the reaction temperature, but
In the temperature range of 0 to 100°C, in the case of batch reaction,
It is in the range of 1 to 5 hours.

After the hydrolysis reaction, the reaction solution may be concentrated as is or treated with activated carbon to obtain a concentrated aqueous solution or solid of lactate.

Free lactic acid can also be obtained by performing ion exchange using a conventional method. Examples are shown below. Example * Filled with 9 mt of granular manganese dioxide with a particle size of 2 m/m, inner diameter 12 m/m, packed bed height 10C1! 4g/Hr of 10% lactic acid nitrile aqueous solution from the bottom of the fixed powder reactor
and hydrated at a reaction temperature of 70°C to obtain an aqueous lactic acid amide solution.

To 509 prepared by concentrating this lactic acid amide aqueous solution to 10 wt %, 2.39 g of sodium hydroxide (solid) was added, and the mixture was reacted at 65° C. for 3 hours with stirring.

After the reaction was completed, the reaction solution was analyzed by high performance liquid chromatography, and the conversion rate of lactic acid amide was 98%, and the selectivity to sodium lactate was 93%.

Claims (1)

[Claims] 1. A method for producing lactate, which comprises adding an alkaline substance to an aqueous lactic acid amide solution obtained by contact hydration of lactic acid nitrile in the presence of manganese or a manganese compound and hydrolyzing it at 30 to 200°C.