JPH0656743A - Production of pyruvic ester - Google Patents

Abstract

PURPOSE:To produce a pyruvic ester by oxidizing a lactic ester with oxygen in the presence of a catalyst. CONSTITUTION:A pyruvic ester is provided by oxidizing a lactic ester with molecular oxygen in the presence of a tin-molybdenum double oxide. The pyruvic ester can be produced from the lactic ester in a high selectivity on a practical industrial scale at a low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a pyruvate ester, which comprises oxidizing a lactate ester with oxygen in the presence of a catalyst. Pyruvate obtained by hydrolyzing a pyruvate ester is a substance that plays an important role in metabolic pathways in vivo, especially glycolysis and alcohol fermentation, and serves as a precursor of L-amino acid production by the presence of an enzyme. Pyruvate ester is important because it is highly safe as a solvent for electronic materials (photoresist) and the like, and the development of an economical new manufacturing process by utilizing the pyruvate ester catalyst technology. Is desired.

[0002]

2. Description of the Related Art The following methods are conventionally known as methods for producing pyruvic acid esters.

(1) An iron-molybdenum-based composite oxide (Japanese Patent Publication No. 38-3662) or a vanadium-molybdenum-based composite oxide (Japanese Patent Publication 56-1985).
No. 4) in the gas phase in the presence of the above. (2) A method of oxidizing a lactate ester in the liquid phase in the presence of a noble metal catalyst such as platinum or palladium (JP-A-54-138)
514). (3) A method of oxygen-oxidizing a lactate ester in a liquid phase in the presence of titanium, zirconium or niobium oxide (Japanese Patent Laid-Open No. 63-132859) or tungsten oxide (Japanese Patent Publication No. 64-11011).

However, in these conventionally known methods, in the vapor phase method, the equipment is expensive, and the production scale is difficult to control because of the fixed bed continuous flow system,
If it is not a mass-produced item, there is a difficulty in economic efficiency. On the other hand, the liquid phase method has many advantages such as low facility cost, excellent operational stability, adaptability to any production scale, and easy replacement and replenishment even when the catalyst deteriorates. However, even in the liquid phase, since the precious metal catalyst system is expensive, even a slight deterioration in activity adversely affects the product price. In addition, (3)
Oxide system has excellent properties such as catalyst price, stability, and selectivity of pyruvate ester, but its activity is low,
From the viewpoint of industrial practicability, it has not necessarily reached a satisfactory level.

[0005]

DISCLOSURE OF THE INVENTION When the present inventors oxidize a lactate ester to produce a pyruvate ester, the present invention uses a complex oxide as a method for producing a pyruvate ester excellent in industrial practicality. We have studied and studied the oxygen oxidation method. This complex oxide has a surface area of
It is customary to show completely different properties from the simple oxides of the constituents such as acid properties, and there is flexibility in the combination for exhibiting new functions, but it is generally used for gas phase oxidation. In many cases, there are no cases of liquid phase oxidation. As a result of detailed comparison and examination of lactate oxidation activity and pyruvate selectivity with respect to many simple oxides including the oxides of the above (3) and binary oxides including combinations thereof, The present invention has been completed by finding that a specific complex oxide which has never been used for liquid phase oxidation can produce pyruvic acid ester with excellent selectivity.

[0006]

The present invention is a method for producing a pyruvate ester, which comprises oxidizing a lactate ester with molecular oxygen in the presence of a tin-molybdenum complex oxide.

Examples of the lactate ester used as the starting material of the present invention include methyl lactate, ethyl lactate, n-propyl lactate, i-propyl lactate and n-butyl lactate.

The catalyst used in the present invention is a tin-molybdenum-based composite oxide, specifically tin oxide-molybdenum oxide (SnO ₂ —MoO ₃ ), which can be prepared by the method described below. it can.

Stannous chloride dihydrate SnCl ₂ · 2H ₂ O 13
6.6 g (720 mmol) was placed in a 1-liter Erlenmeyer flask and dissolved in 120 ml of deionized water. While stirring magnetically, 240 ml of 6N-ammonia water was slowly added to precipitate the hydroxide of tin. After standing overnight and aging, suction filtration and repeated washing with deionized water gave a white paste.

Next, ammonium paramolybdate (NH ₄ ) ₆ M
_{o 7 O 24 · 4H 2 O} 14.13g a (11.4mmol) 20
Dissolve in ml of deionized water and add to the tin hydroxide paste to turn a mud color. After thoroughly kneading for 1 hour with a crusher / mixer, spread on a glass plate and air dry, then 100 ° C.
And dried for 7 hours (101.3 g yield). A part of this dried material was filled in a quartz tube, calcined at 300 ° C. or 500 ° C. for 5 hours while passing air, and used as a catalyst. The surface area due to nitrogen adsorption is 51.9 m ² / g and 4 respectively.
It was 6.7 m ² / g. This catalyst has Sn / Mo = 9/1 (atomic ratio).

The tin oxide-molybdenum oxide (SnO ₂
MoO ₃₎ of Sn / Mo (atomic ratio) is 9.5 to 5 / 0.5 to 5
Used in a range of percentages. The amount of the catalyst used is not particularly limited, but is usually 0.05 to 1 g per 50 ml of the reaction solution.
Is preferable, and there is no great difference in the rate of change depending on the amount of catalyst.

In the present invention, when a lactate ester is oxidized with oxygen to produce a pyruvate ester, tin-catalyst is used as a catalyst.
The method is performed in the presence of a molybdenum-based composite oxide, and this method can be industrially advantageously carried out not only in the liquid phase but also in the gas phase.

When carried out in the liquid phase, it is usually 90 to 17
It is carried out at a temperature of 0 ° C, preferably 100-150 ° C.

When it is carried out in the gas phase, it is usually 18
It is carried out at a temperature of 0 to 350 ° C, preferably 200 to 300 ° C. In this case, for example, a fixed bed flow type continuous vapor phase operation is preferably used.

The reaction time in the liquid phase is not particularly limited,
It is carried out for 10 hours or less, preferably 5 hours or less. The reaction pressure is generally 1 to 10 atm.

As the molecular oxygen used for oxygen oxidation in the present invention, oxygen gas or a mixed gas of oxygen and nitrogen in an arbitrary ratio (for example, air) is generally used.

Further, as a method of supplying oxygen, a method of stirring the reaction mixture and flowing it into a gas phase part, a method of blowing it into a liquid, and a pressure regulator in an autoclave in the pressurization system are used. A possible method is to keep the partial pressure constant.

The pyruvic acid ester produced in the present invention is highly reactive, and since it is a reaction at a relatively high temperature, it is preferable that the starting concentration of the lactate ester is low. For this purpose, it is preferable to use a reaction solvent. The solvent used is an ester-based solvent, and a solvent having a higher boiling point than that of pyruvic acid ester is preferable in order to simplify the purification, and examples thereof include dimethyl succinate, diethyl succinate, and acetophenone.

The desired method for purifying pyruvic acid ester is carried out by separating the catalyst by filtration or decantation after the reaction, and then performing distillation under reduced pressure or the like.

[0020]

Industrial Applicability According to the method of the present invention, the desired pyruvate ester can be produced from lactate ester with high selectivity, industrially and practically.

[0021]

EXAMPLES Next, the method of the present invention will be described more specifically and in detail by way of examples, but the present invention is not limited to the examples.

Example 1 In a flat-bottomed three-necked flask equipped with a reflux condenser, a gas inlet and a liquid outlet, 50 ml of a dimethyl succinate dilute solution containing 240 mmol of ethyl lactate and a catalyst SnO ₂ -MoO ₃ (calcined at 300 ° C.) were added. 0.1 g of powder of 100 mesh or less was added, heated to an oil bath temperature of 130 ° C., and oxygen gas was blown at 6 liters / hour from a Teflon capillary while stirring electromagnetically at 1000 rpm. After 3 hours, the reaction solution was sampled, the catalyst was separated with a small centrifuge, and analyzed by gas chromatography. As a result, the conversion rate of ethyl lactate was 38.4% and the selectivity of ethyl pyruvate was 98.9%.

Example 2 The same procedure as in Example 1 was carried out except that the catalyst SnO ₂ —MoO ₃ was used for 5 hours at 500 ° C. and the reaction was carried out for 5 hours. The conversion rate of ethyl lactate was 36.4%. The ethyl pyruvate selectivity was 94.2%.

Example 3 A glass reaction tube having an inner diameter of 8 mm was charged with the catalyst SnO ₂ -MoO ₃ (500
2 cm ³ of 10-14 mesh passing crushed pieces (calcined at 0 ° C.) were charged, and a mixed gas containing 5% ethyl lactate and 10% oxygen was aerated so that the space velocity was 3600 / hour. 250 ° C
After 3 hours of passing through the column, the effluent gas was absorbed in ice-cold n-propanol and analyzed by gas chromatography. The conversion rate of ethyl lactate was 54.0% and the selectivity of ethyl pyruvate was 81.8%. Met.

Comparative Example 1 The same procedure as in Example 1 was carried out except that molybdenum oxide (MoO ₃ ) simple oxide was used in place of the catalyst SnO ₂ —MoO ₃ (calcined at 300 ° C.) in Example 1. However, the change rate of ethyl lactate was 37% and the selectivity of ethyl pyruvate was 66%.

Comparative Example 2 The same procedure as in Example 1 was repeated except that tin oxide (SnO ₂ ) (calcined at 500 ° C.) was used instead of the catalyst SnO ₂ —MoO ₃ (calcined at 300 ° C.) in Example 1. However, the change rate of ethyl lactate was 16% and the selectivity of ethyl pyruvate was 88%. Comparative Example 3 The same procedure as in Example 1 was carried out except that iron oxide-molybdenum oxide (Fe ₂ O ₃ —MoO ₃ ) was used instead of the catalyst SnO ₂ —MoO ₃ (calcined at 300 ° C.) in Example 1. However, the change rate of ethyl lactate was 3% and the selectivity of ethyl pyruvate was 14%.

Claims (5)

[Claims] 1. A method for producing a pyruvate ester, which comprises oxidizing a lactate ester with molecular oxygen in the presence of a tin-molybdenum-based composite oxide. 2. The method for producing a pyruvic acid ester according to claim 1, which comprises oxidizing in a liquid phase. 3. The method for producing a pyruvic acid ester according to claim 2, which is carried out at a temperature of 90 to 170 ° C. 4. The method for producing a pyruvic acid ester according to claim 1, which comprises oxidizing in a gas phase. 5. The method according to claim 4, wherein the temperature is 180 to 350 ° C.
The method for producing a pyruvic acid ester according to 1.