JPS6116263B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing pyruvic acid, and more particularly to a method for producing pyruvic acid by reacting lactic acid with an oxygen-containing gas.

Pyruvic acid is an important intermediate in metabolic pathways in living organisms and is a useful synthetic raw material for synthesizing various physiologically active substances. It also serves as an important raw material in a method for producing L-tryptophan by an enzymatic method by using indole, pyruvic acid, and ammonia as raw materials and allowing tryptophanase to act on the raw materials. In addition, it is also important as a main raw material for synthesizing L-cysteine through the action of cysteine de-sulfhydrase on hydrogen sulfide, ammonia, and pyruvate, and similarly, it is used as a main raw material for synthesizing L-cysteine through the action of tyrosinase on phenol, ammonia, and pyruvate.
-It is also the main raw material in the synthesis of tyrosine.

Conventionally, pyruvic acid has been produced by reacting sodium cyanide and acetyl chloride to synthesize acetyl cyanide, which is then hydrolyzed, or by dry distilling tartaric acid in the presence of potassium hydrogen sulfate. There is.

However, the method using acetyl cyanide has drawbacks such as low yield, generation of large amounts of by-products, and difficulty in separation and purification. In addition, the method using tartaric acid as a raw material has drawbacks such as an expensive raw material, a low yield of 50 to 60%, and a large consumption of potassium hydrogen sulfate, which is an auxiliary raw material.

The production of pyruvic acid from lactic acid, which is easily produced from inexpensive and industrially available large quantities of raw materials such as acetaldehyde and hydrocyanic acid, has the potential to become a promising production process from an industrial perspective. . However, conventionally known methods for deriving pyruvic acid from lactic acid include (1) dehydrogenation of lactic acid by the action of lactate dehydrogenase or microorganisms or bacteria that have lactate dehydrogenase, and (2) permanganate. Known methods include oxidative dehydrogenation of lactic acid by reagent oxidation using an oxidizing agent such as potassium, and (3) dehydrogenation of lactic acid in the gas phase at high temperatures.

Therefore, method (1) described above produces α as a by-product.
- Disadvantages include the production of ketoglutaric acid as a by-product, which is difficult to separate, and a large amount of high BOD wastewater. Method (2) has drawbacks such as the yield being only 50% at most and the oxidizing agent, potassium permanganate, being expensive; method (3) has low yields, especially selectivity, and a long catalyst lifespan. However, there are also problems, such as not being suitable for small-scale production.

An object of the present invention is to provide a new method for producing pyruvic acid, which does not have the drawbacks of conventional methods.

As a result of various studies on the oxidative dehydrogenation method of lactic acid, and in particular the catalysts used for oxidative dehydrogenation, the present inventor found that it is efficient to react lactic acid with an oxygen-containing gas in the presence of a catalyst containing bismuth in platinum or/and palladium. The present invention was completed by discovering that pyruvic acid can be effectively provided. Platinum or/
When a catalyst containing only noble metals such as palladium is used, pyruvic acid is substantially not produced even when lactic acid is oxidized and dehydrogenated, or even if it is produced, it is less than when a catalyst containing bismuth is used. The amount produced is so small that it cannot be used for industrial production. However, when a catalyst containing bismuth is used together with the above-mentioned noble metal, pyruvic acid is surprisingly produced from lactic acid with efficiency and yield that was previously unimaginable.

That is, the gist of the present invention is to oxidize lactic acid with an oxygen-containing gas in the presence of a catalyst containing platinum or/and palladium and bismuth.

According to the method of the present invention, pyruvic acid can be efficiently obtained using acetaldehyde, which can be obtained industrially in large quantities at low cost, and lactic acid, which is easily derived from hydrocyanic acid, as starting materials.

Lactic acid, which is the starting material of the present invention, is usually subjected to the reaction in the form of lactate. Lactates include alkali metal salts such as sodium or potassium lactate;
Alkaline earth metal salts such as calcium or magnesium lactate, or ammonium salts are used, but sodium salts are particularly frequently used.

The method of the invention carries out the reaction in the liquid phase. The reaction is carried out in a suitable solvent that dissolves the lactate, but
It is usually advantageous to use water as reaction solvent.

The concentration of lactate when carrying out the reaction is 3-
30 wt%, usually in the range of 5 to 20 wt%. When the lactate concentration is lower than 5wt%, the energy consumption used for product isolation increases and 20wt%
If it is higher than %, the reaction rate decreases and side reactions increase, which is not preferable.

The catalyst used in the method of the present invention is a catalyst containing platinum or/and palladium and bismuth, and is usually supported on a suitable carrier and subjected to the reaction. As a carrier, activated carbon, alumina,
Alternatively, magnesia is often used. The amount of catalyst components supported on the carrier is 0.5 to 10 wt% of precious metal,
Preferably 1-5wt%, bismuth 0.5-10wt
%, preferably in the range of 1 to 5 wt%.

Here, bismuth is a single bismuth or a bismuth compound, and oxides, hydroxides, etc. are used as the bismuth compound.

The supported catalyst is prepared, for example, by adding bismuth trichloride to a dilute hydrochloric acid aqueous solution of chloroplatinic acid, immersing activated carbon, making it basic with sodium carbonate, reducing it with formalin, and washing with water. It can also be prepared by immersing a commercially available noble metal catalyst supported on activated carbon in an aqueous solution in which a bismuth compound is dissolved. As the water-soluble bismuth compound, bismuth trichloride, bismuth oxychloride, etc. are used, and a method of dissolving the compound in an aqueous solution of dilute hydrochloric acid and immersing it in a carrier is often used.

The amount of catalyst to be used is not particularly limited, but is usually in the range of 5 to 50 g per 1 reaction solution. After the reaction, the catalyst is separated and heated for a long time.
Can be used repeatedly.

The oxidizing agent used in the method of the present invention is an oxygen-containing gas such as oxygen or air, and air is preferably used.

The reaction temperature for carrying out the method of the present invention ranges from room temperature to
The temperature is 100°C, preferably from 35 to 75°C, and the reaction pressure is from normal pressure to 5 kg/cm ² . The time required for the reaction is determined by the amount of catalyst used and the reaction temperature, but in the case of a batch reaction, usually
It is in the range of 0.5 to 5 hours.

The present invention will be explained below with reference to Examples.

Example 1 A stainless steel cylindrical container according to Content 1 equipped with a baffle plate, a turbine blade type stirrer, and an air blowing pipe was used as a reactor. sodium lactate
240g of an aqueous solution of 24.0g dissolved in distilled water and 2wt
% Pt and 5 wt% Bi(OH) ₃ were charged into the above reactor and heated from the outside in a hot water bath to maintain the reaction temperature at 64°C.

Air was blown in from the air blowing tube at a rate of 250 ml/min, and the reaction was carried out while stirring at 700 revolutions/min.

Two hours and 30 minutes after the start of the reaction, high performance liquid chromatography analysis revealed that more than 90% of the sodium lactate had disappeared, so at this point the reaction was stopped and the catalyst was separated from the reaction solution. The reaction solution was clear and colorless, and no coloration was observed. When the reaction solution was quantified by high-performance liquid chromatography, 20 g of sodium pyruvate (yield 85%) was produced, 1 g of a condensate of pyruvic acid, and 2 grams of unreacted sodium lactate.
g remained, and the production of sodium acetate was 0.2 g. The reaction solution was concentrated to half its volume, and the NMR spectrum was measured, and the production of pyruvate was confirmed from the absorption of methyl protons of pyruvic acid.

Example 2 A reaction was carried out using the same apparatus and reaction conditions as in Example 1, except that the catalyst used was 2 wt% Pd and 2 wt% Bi(OH) ₃ activated carbon powder. When the reaction solution was quantified using high performance liquid chromatography, sodium pyruvate was found to be
14g (yield: 60%) It was confirmed that 6g of unreacted sodium lactate and 2g of a condensate of pyruvic acid were produced.

Comparative Example A reaction was carried out using the same reaction method and reaction conditions as in Example 1, except that the catalyst used was a commercially available platinum powder (manufactured by Engelhard) supporting 5 wt% Pt. A sample was collected 4 hours after the start of the reaction and fractionated using high performance liquid chromatography, and the conversion rate of sodium lactate was 20%, and only a trace amount of pyruvic acid was produced.

Claims (1)

[Claims] 1. A method for producing pyruvic acid, which comprises reacting in the presence of a catalyst containing platinum or/and palladium and bismuth when producing pyruvic acid by oxidizing lactic acid with an oxygen-containing gas.