JPS591254B2 - Production method of tartaric acid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The invention relates to a process for producing tartaric acid, which is characterized by the immobilization of a catalyst in tartaric acid synthesis.

As a method for synthesizing tartaric acid, it is known to produce it from maleic acid or maleic anhydride and hydrogen peroxide using a tungstate catalyst. However, with this method, meso-tartaric acid is produced as a by-product, and the process is still unresolved. This is not a preferred method as the yield is poor as a large amount of maleic acid remains. In addition, a maleic acid aqueous solution was adjusted to pH 4.0 in the presence of tungstate.
It is also known that tartaric acid can be obtained in good yield by oxidizing while maintaining the temperature at ~6.0.

However, if tartaric acid is extracted from the reaction solution as a neutral salt or acidic salt, a large amount of tungstate will be mixed into the product. Therefore, it is necessary to remove and recover the tungstate from the reaction solution, but known methods include recovering it by adsorbing it to an anion exchange resin or adding a solvent. However, I haven't found anything very effective. That is, in the former case, the adsorption efficiency of the resin is poorer than in the case of acidity, a large amount of resin is required, and a large amount of unadsorbed tungstate remains. Also resin regenerating agent,
Refining the recovered tungstate requires a large amount of cost. Even in the latter case, a large amount of solvent is required, and the equipment and
Considerable expenses such as operation and recovery losses are required. As a result of intensive research into a tartaric acid synthesis method using maleic acid, hydrogen peroxide, and tungstic acid, the present inventors discovered that tungstate can be immobilized with stannic acid and at the same time, it can be used cyclically as a catalyst. .

In other words, stannic acid has the property of adsorbing tungstic acid and also has a stabilizing effect on hydrogen peroxide, so even if stannic acid is present in the reaction solution, the reaction will not be inhibited, and on the contrary, it will increase the yield. It was found that the rate was also good.

Furthermore, in order to efficiently adsorb tungstate to stannic acid, it is sufficient to decompose excess hydrogen peroxide after the reaction is completed, and at this time, hydrolysis of the epoxy compound is avoided as much as possible.

By keeping the pH below 5 and heating for about 10 minutes,
The tungstate can be easily adsorbed, and the stannic acid that has adsorbed the tungstate can be easily separated from the reaction solution, and the stannic acid that has adsorbed the tungstate can be recycled as is for the next reaction. I found that it can be used. That is, in the present invention, stannic acid is added simultaneously with maleic acid or maleic anhydride, hydrogen peroxide, and tungstate, and after reacting at pH 4,0 to 6.0, the tungstate is adsorbed to stannic acid. This is a method for producing tartaric acid, which is characterized in that stannic acid with tungstate adsorbed thereon is recycled and used.

When carrying out the experiment, a reaction solution containing maleic acid or maleic anhydride, a tungstate salt, and stannic acid in an amount 40 to 50 times the amount of tungstic acid is heated to pH 4.0 with caustic alkali. O
After adjusting the pH to ~6.0, the reaction is carried out by maintaining the pH at ~6.0 with caustic alkali while adding hydrogen peroxide dropwise, producing tartaric acid in high yield without producing meso form as a by-product. do.

Furthermore, after the completion of the reaction, the pH was 5. After boiling and decomposing hydrogen peroxide at a temperature of 0 or less, continuing boiling for 10 to 20 minutes and cooling, the stannic acid is separated, thereby making it possible to almost completely adsorb the tungstate in the reaction liquid onto the stannic acid. The reaction solution from which the catalyst has been removed is heated to reflux after adjusting its pH to 9 to 10, or preferably by heating in an autoclave, to hydrolyze the epoxy substance to obtain tartrate.

In the present invention, the stannic acid used may be either α-type, β-type, or β-type.

Further, the tungstate salt may be either sodium tungstate or potassium tungstate. Furthermore, as the caustic alkali, caustic potash, caustic soda, or an equimolar mixture of both may be used, and after the reaction is completed, potassium tartrate, sodium tartrate, and potassium sodium tartrate (Rotucel salt) are obtained, respectively. Also, hydrogen peroxide is per mole of maleic acid,
It is important to use 1 to 1.4 moles in order to reduce the residual amount of unreacted maleic heptacid and to increase the yield. Furthermore, pH adjustment during the reaction is important, and the optimum pH is 4.
．． 0 to 6.0. Ru. That is, in this pH range, by-products such as meso-tartaric acid are not produced, and the yield of d1 mono-tartaric acid is advantageously very high. In addition, the reaction depth is 60
It is desirable to carry out at a temperature of ~70°C. Furthermore, hydrogen peroxide
Although any concentration can be used, a concentration of 35 to 50% is preferable. In the method for producing tartaric acid invented by Mochi,
A reaction time of 3 to 7 hours is sufficient, but in order to sufficiently adsorb the tungstenate to the stannic acid, it is important to decompose the remaining hydrogen peroxide and heat for about 10 minutes at a pH of 5 or less. .

That is, if stannic acid is separated with hydrogen peroxide remaining after the reaction, tungstate is difficult to adsorb to stannic acid and remains in the reaction solution. Furthermore, even when the pH is made alkaline to facilitate decomposition of hydrogen peroxide, the adsorption rate of tungstate to stannic acid also decreases. In the method of adsorption and recovery using anion exchange resin, etc., a large amount of expensive resin is required and a large amount of cost is incurred for resin regeneration. Tungstate can be used as is as a new reaction catalyst for the next reaction, and there is no risk of tungsten being mixed into the product, so it is more economical than the other method, and at the same time improves the quality of the product. High yield and high purity tartaric acid can be obtained. Next, examples will be shown.

Example 1 Maleic anhydride 989, water 1266ml, sodium tungstate 19 and stannic acid 50f! was added and the pH was brought to 60 with a portion of a 50% solution of equimolar mixture of caustic potash and caustic soda 19239, and then 35% hydrogen peroxide 1166 was added.
9 was added dropwise within 30 to 60 minutes at 65℃, and if heat generation occurred during the process, the internal temperature was adjusted while cooling, and at the same time, the pH was adjusted to 5.
．． Add caustic solution dropwise to keep the temperature at 0.

After 4 hours of reaction, the pH was 5. Heat to boil under O2 to decompose unreacted hydrogen peroxide.

Claims (1)

[Claims] 1 In a method for producing tartaric acid, stannic acid is added simultaneously with maleic acid or maleic anhydride, hydrogen peroxide, and tungstate, and after reacting at pH 4.0 to 6.0, the reaction solution is adjusted to pH 5.0 or less. 1. A method for producing tartaric acid, which comprises heating the tartaric acid to adsorb tungstate to stannic acid, separating the tartaric acid, and recycling the stannic acid with the tungstate adsorbed.