Preparation method of 2,4,6-trimethylpyridine_Industrial additives

Background technology of preparation method of 2,4,6-trimethylpyridine

As we all know, the key to purifying 2,4,6-trimethylpyridine by recrystallization is The key is to select a suitable recrystallization solvent so as to dissolve as many other impurities as possible while precipitating 2,4,6-trimethylpyridinium salt crystals. What is used in the existing preparation method is absolute ethanol as the recrystallization solvent. In the ethanol solution of 2,4,6-trimethylpyridine, 98% concentrated sulfuric acid is added to react with it to generate a sulfonate. After the cooling crystallization was filtered, the obtained crystals were recrystallized with 3 times the weight of ethanol. Use ammonia water to decompose it to Ph = 8 at room temperature, and then distill it to obtain 2,4,6-trimethylpyridine with a purity of more than 95%.

However, the solvent in the above-mentioned existing methods is anhydrous ethanol, but anhydrous ethanol is not easy to be used repeatedly, thus causing problems such as increased costs, waste of resources, and low industrial value.

Therefore, in view of the above situation, it is imperative to invent a new preparation method of 2,4,6-trimethylpyridine that can provide good purity.

Preparation method of 2,4,6-trimethylpyridine Contents of the invention

The technical problem to be solved by the present invention is the solvent in the existing method It is anhydrous ethanol, but anhydrous ethanol is not easy to use repeatedly, which causes problems such as increased costs, waste of resources, and low industrial value.

In order to solve the above technical problems, the present invention innovatively uses 95% industrial ethanol as the solvent for recrystallization, and makes corresponding inventive adjustments to the subsequent preparation process. After testing, it is found that the effect is the same as the original one. There is not much difference, the cost is lower, it can be used repeatedly, and it has huge industrial value.

That is: a preparation method of 2,4,6-trimethylpyridine, which is characterized in that it includes the following steps:

Convert 2,4,6-trimethylpyridine Add the raw materials of pyridine, industrial ethanol solvent and concentrated sulfuric acid into the reactor, and stir the reaction until crystallization appears in the reactor;

Filter or suction filtration;

After filtration, there are still The crystals containing some impurities are washed at high temperature;

The crystal lattice in which some impurities are still contained in 2,4,6-trimethylpyridine sulfate after washing is recrystallized.

It is preferable to use industrial ethanol with the same volume as the raw material as the dispersant and solvent during salt formation and crystallization, and use industrial ethanol with the same mass as the crystallization as the solvent for recrystallization.

When performing high-temperature washing, you can use industrial ethanol with twice the crystal quality, put the crystals into the industrial ethanol, and then heat it under reflux and stirring conditions to boil the industrial ethanol. Stop heating after half an hour and continue stirring. It is cooled by cooling water. When the temperature drops to normal temperature, it is released and filtered. The concentration of the obtained crystals after decomposition can reach 97%~98%.

When recrystallizing as described, water will be selected as the main recrystallization in the crystal lattice of 2,4,6-trimethylpyridine sulfate that still partially contains impurities after washing. Solvent, select industrial ethanol as the dispersant and auxiliary solvent for recrystallization; put the washed salt crystals into industrial ethanol with 1.5 times the crystal quality, and then add 30% of the crystal quality water to it. Other conditions and steps are the same as washing The conditions are the same; after recrystallization, the concentration of the obtained crystals after decomposition reaches more than 99%. After the 2,4,6-trimethylpyridine sulfonate is dissolved in water, solid sodium hydroxide tablets are added thereto under stirring, and the reaction process is controlled, and the preferred reaction temperature is controlled at 45 to 45 60 degrees Celsius; when the pH value of the material reaches 8~9, continue stirring for half an hour. After ensuring that the reaction is complete, stop stirring and let the material stand for stratification. The material can be released from the bottom of the reactor. The lower layer is sodium sulfate solution and the upper layer is It is a water-containing 2,4,6-trimethylpyridine product.

The filtrate contains part of 2,4,6-trimethylpyridine sulfate and other impurity salts. A sodium hydroxide solution with a mass fraction of 50% can be slowly added to the filtrate to decompose the filtrate. Salt, part of the salt is removed by filtration, and the remaining filtrate can be obtained by distillation to obtain industrial ethanol, water and fractions containing 2,4,6-trimethylpyridine.

The beneficial effects of the present invention are: utilizing the alkaline properties of pyridine compounds, through sulfation, crystallization in ethanol, recrystallization and alkaline hydrolysis, the crude 2,4 extracted from the primary distillation, Purify 2,4,6-trimethylpyridine from the 6-trimethylpyridine fraction and determine the experimental conditions. The concentration of refined 2,4,6-trimethylpyridine can be increased to 97%~98%, and the recovery rate is no drops too much; and can be increased to more than 99% in further recrystallization.

Specific embodiments of the preparation method of 2,4,6-trimethylpyridine

The present invention is applied to the preparation of 2,4, The method of 6-trimethylpyridine is a major improvement based on the shortcomings of the existing method of preparing 2,4,6-trimethylpyridine, and has very important practical significance.

1. Selection of raw materials

The pyridine raw material is initially distilled at 167~173°C to extract the 2,4,6-trimethylpyridine fraction, of which 2,4,6- Trimethylpyridine content is 50~70%.

2. Selection of solvents

2. 1. Selection of solvent types

The existing preparation method uses absolute ethanol as the solvent, but absolute ethanol is not easy to repeat. use. The present invention uses 95% industrial ethanol as the solvent for recrystallization. After testing, it is found that the effect is not much different from the original, the cost is lower, it can be used repeatedly, and it has industrial value.

2. 2. Selection of the amount of solvent

The key to the reaction is that ethanol can dissolve other impurities and try to crystallize 2,4,6-trimethylpyridine sulfate. Use with raw materialsA small volume of industrial ethanol is used as the dispersant and solvent during salt formation, and it is more appropriate to use industrial ethanol of the same quality as the crystallization as the solvent for recrystallization.

3. Selection of reaction conditions

3. 1 Selection of reaction temperature

The reaction between concentrated sulfuric acid and raw materials will release a large amount of heat. Since industrial ethanol is used as Dispersant, and the boiling point of industrial ethanol is 75 degrees Celsius, so the reaction temperature must be lowered. In order to prevent the dispersant from being lost during the reaction and ensure the reaction rate, the reaction temperature is positioned at 40 degrees Celsius.

3. 2 Selection of reaction time

This reaction is an acid-base reaction. The reaction speed is very fast and can be regarded as an instantaneous reaction. However, in order to ensure that the reaction is complete and the crystals are fully precipitated, After the concentrated sulfuric acid is completely added dropwise, the mixture is still stirred at 40 degrees Celsius for half an hour, then taken out and cooled to room temperature while stirring.

4. Washing

The filtered crystals still contain some impurities. Since the solubility of sulfate of 2,4,6-trimethylpyridine in ethanol is very small, purification by recrystallization is not only impossible on an industrial scale, but the loss of 2,4,6-trimethylpyridine is also very small. big. Considering that other impurity salts are highly soluble in ethanol, purifying 2,4,6-trimethylpyridine only requires high-temperature washing.

4. 1 Washing conditions

In order to ensure that the impurities in 2,4,6-trimethylpyridine sulfate are removed as much as possible, industrial ethanol with twice the crystal quality can be used. Put the crystals into ethanol, then heat under reflux and stirring conditions to boil the ethanol. Stop heating after half an hour, continue stirring and cool down with cooling water. When the temperature drops to normal temperature, release and filter. The concentration of the obtained crystals after decomposition can reach 97%~98%

5. Recrystallization

Through washing, 2,4,6-trimethylpyridine with a concentration of about 98% can be obtained Sulfate crystallization. However, there are still some impurities trapped in the crystal lattice of 2,4,6-trimethylpyridine sulfate. These impurities cannot be removed by simple washing, so such impurities must be removed by recrystallization. Since the solubility of 2,4,6-trimethylpyridine sulfate in water is relatively large, water was chosen as the main recrystallization solvent. However, because the amount of water used in recrystallization is too small, it is difficult to release and filter when the temperature is cooled to regenerate crystals, and it is easy to re-enclose impurities in the crystal lattice. Therefore, ethanol was selected as the dispersant and auxiliary solvent for recrystallization. During recrystallization, the washed salt crystals can be put into ethanol with 1.5 times the crystal quality, and then water with 30% of the crystal quality can be added to it. Other conditions and steps are the same as the washing conditions. After recrystallization, the concentration of the obtained crystals after decomposition can reach more than 99%.

6. Decomposition of sulfonate

Since the solubility of 2,4,6-trimethylpyridine sulfonate in 100g of water is about 50g, it can be dissolved in water Finally, add solid sodium hydroxide tablets to it while stirring. Since the reaction releases a large amount of heat, cooling water is required to control the reaction temperature and the reaction process. The reaction temperature is preferably controlled at 45 to 60 degrees Celsius. When the Ph value of the material reaches 8~9, it proves that the reaction is over. Continue stirring for half an hour. After ensuring that the reaction is complete, stop stirring and let the material stand for stratification. After 15 minutes, the material can be released from the bottom of the reactor. The lower layer is sulfuric acid. Sodium salt solution, the upper layer is the aqueous 2,4,6-trimethylpyridine product.

7. Treatment of filtrate

The filtrate contains some 2,4,6-trimethylpyridine sulfate and other impurity salts. Any discharge will not only pollute the environment but also be a kind of Waste, the useful ingredients need to be extracted. A sodium hydroxide solution with a mass propyl carbonate fraction of 50% can be slowly added to the filtrate to decompose the salt. The resulting sodium sulfate has low solubility in water. Part of the salt can be removed by filtration, and the remaining filtrate can be distilled. Industrial ethanol, water and fractions containing 2,4,6-trimethylpyridine were obtained.

To sum up: the present invention innovatively uses 95% industrial ethanol as the solvent for recrystallization, and makes corresponding inventive adjustments to the subsequent preparation process. After testing, it is found that the effect is different from the original one. It is not big, has lower cost, can be used repeatedly, and has huge industrial value of sodium tetraborate. Utilizing the alkaline properties of pyridine compounds, through sulfation, crystallization in ethanol, recrystallization, and alkaline hydrolysis, the crude 2,4,6-trimethylpyridine fraction extracted from the primary distillation is purified 2,4, 6-trimethylpyridine, by determining the experimental conditions, the concentration of refined 2,4,6-trimethylpyridine can be increased to 97%~98% without much decrease in recovery rate; and it can be improved in further recrystallization to more than 99%.

The above description of the preferred embodiments enables those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.