JPS5934692B2 - Production method of trimethylolacetic acid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for producing trimethyloleacetic acid by oxidizing pentaerythritol (hereinafter abbreviated as pentol) with an oxygen-containing gas.

For a method of producing trimethylol acetic acid by oxidizing pentol with an oxygen-containing gas, please refer to "NewerMeth".
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3) is known.

Therefore, the method described in this document uses platinum as a catalyst, and the reaction solution is kept at a temperature of 6 to 7 in an aqueous solution containing sodium bicarbonate, and the reaction temperature is kept at a low temperature of around 35°C. This is a method of causing a reaction. According to the above-mentioned literature, the time required for the reaction is as long as 8 hours for the conversion of pentol to reach 65%, and the selectivity to trimethyloleacetic acid is as low as 50%. Further, as described in the above-mentioned literature, the reaction rate becomes extremely slow at a pentol conversion rate of about 65%, and the reaction substantially stops at this point. That is, the above-mentioned method has disadvantages in that the reaction time is long, the yield is low, and the reaction temperature must also be kept low.
The object of the present invention is to provide a process for the production of trimethylolacetic acid from pentol, which does not have the above-mentioned drawbacks. As a result of various studies on the oxidation reaction of pentol, the present inventor used palladium as a catalyst and
The present inventors have discovered that trimethylol acetic acid can be produced very advantageously by keeping the H range between 7 and 10, and have completed the present invention.

That is, in the method of the present invention, pentol is dissolved in an aqueous solution, and the pH of the reaction solution is adjusted to 7 to 7 in the presence of a palladium catalyst.
This is a method for producing trimethylolacetic acid by carrying out an oxidation reaction with an oxygen-containing gas while maintaining the molecular weight within the range of 10.

According to the above-mentioned method of the present invention, there are no drawbacks seen in the above-mentioned known methods, the reaction proceeds rapidly, and the conversion rate of pentol reaches almost 100%, and unlike the above-mentioned known method, pentol The conversion rate is 65% and the reaction does not substantially stop.

In addition, as described in the comparative example below, when a platinum catalyst was used, it was necessary to maintain the reaction temperature at a low temperature of about 35°C in order to maintain the selectivity; When used, the selection rate does not decrease much even if the reaction temperature is raised to about 60°C. The oxidation reaction of pentol is a considerably exothermic reaction (heat of reaction 130-140 cal/mo
In order to maintain the reaction temperature at around 35° C., a large heat exchanger and a refrigerator are required when using an industrial scale reactor. However, when a palladium catalyst is used according to the method of the present invention, there is a slight decrease in selectivity even when the reaction temperature rises to about 60°C, so trimethylolacetic acid can be advantageously produced without the need for a large heat exchanger. You can. In the case of the method of the present invention, the conversion rate of pentol is 66, as in the known method using a platinum catalyst.
The conversion rate reaches 100% in a short time without substantially stopping at 5%.

In addition, the selectivity to trimethylol acetic acid by the method of the present invention is 65% when the reaction is carried out using a conventionally known platinum catalyst and kept at a low temperature even under reaction conditions that show a 100% conversion of pentol. A value of 50-60% is obtained, which is equivalent to the selectivity in the case of %. In the method of the present invention, the pentol used as a raw material is usually intercalated with water, which is a solvent, and the pentol concentration in the aqueous solution is adjusted to 2 to 2.
When the concentration of pentol is increased to 10 wt% or more, a portion of pentol will be dissolved in water, and the remaining portion will be suspended as a solid in the aqueous solution. In order to maintain the pH of the reaction solution in the range of 7 to 10, the pH value decreases as the reaction progresses, so alkaline substances must be added sequentially in synchronization with the reaction. It is necessary to add

The alkaline substances used at this time are usually
Alkali metal hydroxides, carbonates, bicarbonates, and alkaline earth hydroxides are frequently used. There is no difference whether these alkaline substances are added in a solid state or in an aqueous solution state. The pH range of the reaction solution is 7 to 1 as described above.
If it is outside the range of 0, the reaction product will decrease.

That is, when the pH is more acidic than 7, the reaction rate is significantly reduced and the reaction does not substantially proceed. If the pH is more strongly alkaline than 10, side reactions will increase and the selectivity to trimethylolacetic acid will decrease. The catalyst used in the process of the invention is usually palladium on activated carbon. It is used by being supported on a carrier such as alumina.

The amount of palladium supported on the carrier is suitably in the range of 0.1 to 10 wt. The above catalyst is prepared by a conventional method,
Commercially available supported catalysts can also be used. In the case of a supported catalyst having the above-mentioned supported amount, the amount of catalyst to be used is usually in the range of 10 to 2,009 times the reaction solution 11.

The reaction temperature is usually in the range of room temperature to 80°C,
In order to prevent side reactions, the temperature is preferably in the range of room temperature to 60°C.

As the oxygen-containing gas used as the oxidizing agent, pure oxygen or air is usually used, and the latter is particularly advantageous.

The reaction pressure used is usually in the range of normal pressure to 5 atm.

A suspended bed reactor is suitable for implementing the method of the present invention, but the amount of oxygen-containing gas blown in such a method is
Usually, it is used in a range of 0.1 to 51/Min with respect to the reaction solution 11.

The stirring method usually used is a bubble column method using blown gas or a turbine blade type stirrer, but it is important to maintain good stirring conditions, that is, good contact between gas, liquid, and solid. Effective in maintaining reaction rate.
Trimethylol acetic acid obtained by the method of the present invention is an extremely useful compound used as a raw material for alkyd resins, a reagent for reacting with water-insoluble compounds to provide an aqueous solution, and other raw materials for synthesis.

Next, the present invention will be explained with reference to Examples and Comparative Examples. Example 1 A thermometer, a sintered glass air blowing tube, and a reflux condenser were attached to a 500 ml Mitsuro flask and used as a reactor.

The reactor was stirred from the bottom by a magnetic stirrer and heated or cooled by a water bath. Pentol 209
was dissolved in 200 cc of water, and 2 wt.
Using 8g of % palladium activated carbon powder supported catalyst, temperature 4
The reaction was carried out at 5° C. while blowing air at a rate of 11/min.

5.89 An aqueous solution of caustic soda dissolved in 30 ml of water was added dropwise as the reaction progressed, and...
It was kept within the range of 8.0.

The entire amount of the caustic soda aqueous solution was consumed in 3 hours, and the conversion rate of pentol reached 100%.

After removing the catalyst from the reaction solution, the furnace solution was passed through a strongly acidic ion exchange resin column to convert the sodium salt of trimethylolacetic acid into the free acid, and then evaporated to dryness in a vacuum concentrator to obtain a white solid at 12.49%. Obtained.

The melting point of the white solid obtained is 210-215°C, and I
The R spectrum matched that of the standard. Moreover, the selection rate of trimethylol acetic acid was 62%. Example 2 Using the same apparatus as in Example 1, reactions were carried out under the same reaction conditions, with only the pH of the reaction solution being varied, and the results are shown in the table below.

Example 3 Using the same apparatus as in Example 1, reactions were carried out under the same reaction conditions with only the reaction temperature being varied, and the results are shown in the table below.

Comparative Example 1 Using the same apparatus as in Example 1 and under the same reaction conditions, the catalyst used was changed to a 2wt% platinum-supported carbon powder catalyst, and the reaction was carried out at a reaction temperature of 40°C and various pH values. The results are shown in the table below. Indicated.

Comparative Example 2 Using the same apparatus as in Example 1 and using the same reaction conditions, the catalyst used was changed to a 2 wt % platinum-supported carbon powder catalyst, and the pH was 7. O
The results of the reaction at various reaction temperatures while maintaining the temperature at ~7.5 are shown in the table below.

Claims (1)

[Claims] 1. A method for producing trimethylolacetic acid, which comprises oxidizing pentaerythritol in an aqueous solution with an oxygen-containing gas in the presence of a palladium catalyst while maintaining the pH of the reaction solution in the range of 7 to 10.