JPS631934B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses pyruvate ester as a raw material,
The present invention relates to a method for producing high-purity pyruvic acid in high yield.

Pyruvic acid is a substance that has attracted attention as a synthetic intermediate for various organic compounds, and has recently been used in pharmaceuticals,
Its use in fields such as cosmetics is increasing.

Various methods are known for producing pyruvic acid, such as fermentation using hydrocarbons as raw materials and oxidation of propylene glycol, but all of these methods produce highly purified pyruvic acid. It has been difficult to produce with high yield.

Pyruvic acid can be obtained directly by hydrolysis of pyruvic acid ester, but since pyruvic acid and pyruvic acid ester are easily changed, side reactants are mixed in, making it difficult to obtain high purity pyruvic acid in high yield. I couldn't do it.

As a result of intensive research, the present inventors discovered that when producing pyruvic acid using pyruvic acid ester as a raw material,
50% hydrolysis and distillation purification of pyruvate ester
The present inventors have discovered that extremely high purity (99% or higher) pyruvic acid can be produced at a high yield of 97% or higher if the process is carried out at a temperature of ~80°C, leading to the completion of the present invention.

If pyruvic acid is produced under the above conditions according to the method of the present invention, it is not necessary to treat it under a nitrogen atmosphere, and it is possible to prevent contamination of acetic acid and the like, which are commonly found as by-products.

The amount of water added during hydrolysis of the pyruvate ester is preferably 4 to 10 times the mole of the pyruvate. When there is little water, hydrolysis is slow and by-products are likely to be produced. When a large amount of water is used, hydrolysis is easily carried out, but it is necessary to treat a large amount of water in the purification process, which is uneconomical.

In the hydrolysis of organic acid esters, sulfuric acid or the like is generally used as a catalyst because the organic acids produced are stable. However, in the case of pyruvic acid esters, the pyruvic acid produced is It is not preferable to use these as catalysts because it leads to deterioration of pyruvic acid and a decrease in yield during the hydrolysis and distillation purification steps. On the other hand, H-type ion exchange resins such as cation exchange resins (for example, "Amberlite 200C" manufactured by Organo Co., Ltd.) do not have the same adverse effects as sulfuric acid, so they cannot be used as catalysts in the present invention. Can be done. However, the hydrolysis of pyruvate esters proceeds even without a catalyst.
It is not always necessary to use a catalyst; rather, hydrolysis without a catalyst is preferred in order to prevent deterioration of the pyruvic acid produced.

The fact that pyruvic acid with a purity of 99% or more can be produced in high yield as in the method of the present invention is extremely revolutionary. Since the pyruvic acid produced by the method of the present invention has high purity, there is little deterioration that is normally observed in pyruvic acid, and it is convenient to store and handle.

As the pyruvate ester, methyl pyruvate and ethyl pyruvate are mainly used.

The present invention will be specifically explained below using Examples and Comparative Examples.

Example 1 510 g of methyl pyruvate and water were added to the reaction vessel of 2.
450 g was charged, and hydrolysis was carried out at 75 to 80° C. under reduced pressure for 7 hours while distilling the generated methanol out of the system. Next, the produced pyruvic acid aqueous solution is rectified at 76 to 80°C under reduced pressure to improve its purity.
99.5% pyruvate was obtained in 97% yield.

Example 2 Using the same apparatus as in Example 1, 510 g of methyl pyruvate and 900 g of water were charged. 74-80℃ under reduced pressure while distilling the generated methanol out of the system.
Hydrolysis was carried out for 6 hours. Next, the produced pyruvic acid aqueous solution was rectified at 75 to 80°C under reduced pressure to obtain pyruvic acid with an accuracy of 99.2% and a yield of 97.1%.

Example 3 Using the same apparatus as in Example 1, 510 g of methyl pyruvate and 360 g of water were charged. 50 to 55℃ under reduced pressure while distilling the generated methethanol out of the system.
Hydrolysis was carried out for 12 hours. Next, the produced pyruvic acid aqueous solution was rectified at 75 to 80°C under reduced pressure to obtain pyruvic acid with a purity of 99% in a yield of 97%.

Comparative Example 510g of methyl pyruvate and water were added to the reaction vessels of 1 and 2.
450 g was charged and hydrolysis was carried out at 95 to 100° C. for 7 hours under reduced pressure while removing the generated methanol from the system. Next, the purified aqueous pyruvic acid solution was rectified at 75 to 80°C under reduced pressure to obtain pyruvic acid with a purity of 96.0% in a yield of 65%.

Comparative Example 2 510g of methyl pyruvate and water were added to the reaction pot of 2.
450 g was charged, and hydrolysis was carried out at 75 to 80°C under reduced pressure for 7 hours while removing the generated methanol from the system. Next, the produced pyruvic acid aqueous solution was rectified at 95 to 100°C under reduced pressure to obtain pyruvic acid with a purity of 95% in a yield of 70%.

Claims (1)

[Claims] 1. A method for producing pyruvic acid, which comprises performing hydrolysis and distillation purification at a temperature of 50 to 80°C when producing pyruvic acid by hydrolyzing a pyruvic acid ester.