JPS6249253B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for efficiently separating resorcin and hydroquinone from a mixture containing resorcin and hydroquinone, and more specifically, the present invention relates to a method for efficiently separating resorcin and hydroquinone from a mixture containing resorcin and hydroquinone. weight ratio)
Continuous rectification is carried out so that the ratio is 0.1 to 1:1, and resorcinol is separated as a distillate, while the recrystallized liquid is recrystallized with water and/or an organic solvent to separate hydroquinone, or Separating resorcin and hydroquinone from a mixture containing resorcin and hydroquinone by further redistilling the rectification liquor and recrystallizing the obtained distillate with water and/or an organic solvent to separate hydroquinone. It's a method.

In the past, resorcinol and hydroquinone were each produced independently, and there was therefore little need to industrially separate each from a mixture of the two, but in recent years, methods have been developed that allow resorcinol and hydroquinone to be co-produced. Along with this, resorcinol,
It has become necessary to separately separate resorcinol and hydroquinone from a hydroquinone mixture.

As a method for separating resorcin and hydroquinone, a recrystallization method using a specific solvent such as methanol (Japanese Patent Publication No. 12500/1983) is already known. Since resorcinol must be separated using the transfer of resorcinol, it has not always been satisfactory in terms of recovery of high-purity products and purification efficiency. On the other hand, resorcinol and hydroquinone have close boiling points and high melting points;
Furthermore, separation by rectification is considered difficult due to sublimation, etc. In fact, when a mixture of resorcin and hydroquinone is rectified, it is possible to separate resorcin in high purity as a distillate. However, it was not possible to separate hydroquinone with high purity.

For this reason, the present inventors investigated a method for efficiently separating resorcin and hydroquinone from a mixture containing resorcin and hydroquinone, and found that the mixture was continuously rectified to separate resorcin as a distillate. On the other hand, by combining recrystallization treatment and recrystallization treatment, in which hydroquinone is separated by recrystallization treatment of the rectification tank liquid,
The inventors discovered that resorcinol and hydroquinone can be separated extremely efficiently and with high purity, leading to the present invention.

That is, in the present invention, a mixture containing resorcinol and hydroquinone is prepared such that the ratio of resorcinol to hydroquinone (weight ratio, hereinafter the same) in the rectification tank liquid is 0.1 to 0.1.
Continuous rectification with a ratio of 1:1 is performed to separate resorcinol as a distillate, while the recrystallized liquid is recrystallized with water and/or an organic solvent to separate hydroquinone, or A method for separating resorcinol and hydroquinone from a mixture containing resorcinol and hydroquinone, which comprises further redistilling the rectifier liquid and recrystallizing the obtained distillate with water and/or an organic solvent to separate hydroquinone. It is.

In the present invention, the mixture containing resorcinol and hydroquinone (hereinafter referred to as RH mixture) supplied to the rectification system as a method to be purified is a mixture containing mainly resorcinol and hydroquinone, with a small amount of impurities coexisting. I can't help it.

However, impurities having a boiling point lower than that of resorcin in the rectification system are preferably removed in advance, since these impurities will be distilled out together with resorcin during rectification, making it impossible to separate and recover high purity resorcin.

In the present invention, the resorcin/hydroquinone (hereinafter referred to as R/H) ratio of the rectifier liquid is 0.1 to
Continuous rectification to achieve a concentration of 1 is an important requirement. This is because the rectification of the RH mixture is carried out at a relatively high temperature due to the high boiling points of resorcinol and hydroquinone, and as a result, thermal deterioration of resorcinol and hydroquinone progresses. , R/ of the rectifier liquid
This is based on the discovery that by maintaining the H ratio between 0.1 and 1, thermal deterioration of resorcinol and hydroquinone can be suppressed to a considerably low level.

If the R/H ratio is less than 0.1, thermal deterioration becomes significant, resulting in a significant decrease in the retention rate of resorcinol and hydroquinone, and the content of deterioration products in the rectification tank liquor becomes high. Even if the liquid is recrystallized, it is difficult to easily obtain high-purity hydroquinone, and handling of the rectification liquor is also difficult due to the sublimability of the liquor.

On the other hand, if the R/H ratio of the rectifier liquor exceeds 1, the efficiency of the recrystallization treatment for separating hydroquinone from the rectifier liquor becomes extremely poor, making it difficult to efficiently separate hydroquinone.

By continuously performing rectification under the above conditions, resorcinol is separated and recovered in high purity as a distillate.

Hydroquinone can be separated and recovered from the rectifier liquid by recrystallizing the rectifier liquid as it is, or by further distilling the rectifier liquid and recrystallizing the obtained distillate. However, the latter method is particularly effective in preventing coloration of hydroquinone, and is effective for separating and recovering hydroquinone with little coloration. In this case, it is particularly effective for the above purpose to perform redistillation in the presence of water vapor, condense the evaporated hydroquinone vapor together with the water vapor, and recrystallize it.

In any of the above cases, the recrystallization treatment is carried out using water and/or an organic solvent as a recrystallization solvent. Organic solvents include alcohols such as methanol, ethanol, and propanol, acetone,
One or a mixture of two or more of ketones such as methyl ethyl ketone, methyl isopropyl ketone, and methyl isobutyl ketone, ethers such as isopropyl ether and tetrahydrofuran, and esters of ethyl acetate and butyl acetate can be used. Water may be used alone or as a mixture with an organic solvent.
Also, contamination with salts is acceptable as long as it is a small amount.
Recrystallization may be carried out once or multiple times, in batches or in a continuous process.

Through this recrystallization treatment, hydroquinone is separated and recovered as precipitated crystals in actual purity, and a solution containing resorcinol and hydroquinone is obtained as a liquid. By circulating all or part of this liquid to the RH mixture rectification system, resorcinol and hydroquinone can be separated and recovered in good yield. In this case, recycling is performed by removing the recrystallization solvent and accumulative impurities in the liquid by distillation or extraction, and then supplying the liquid to a rectification system. In addition, this recycling is not only directly recycled to the rectification process of the present invention, but also in the process leading up to the rectification process of the present invention, such as the manufacturing process of resorcinol and hydroquinone. If there is a process that uses a recrystallization solvent or a method that removes the recrystallization solvent and impurities, it is also possible to recycle the above liquid to that process.

Thus, according to the present invention, highly purified resorcinol and hydroquinone can be efficiently separated and recovered from the RH mixture. For example, resorcinol 70
When a mixture containing 30 parts of hydroquinone and 30 parts of hydroquinone is separated according to the present invention, it is possible to recover about 55 parts of resorcinol as a high-purity product in a process without recycling (Example 1 below). On the other hand, in the method disclosed in Japanese Patent Publication No. 12500/1983, only 36 parts of resorcin can be recovered by two recrystallizations. If the recrystallization liquid is circulated, this difference will become even more remarkable.

As described above, the present invention combines the separation and rectification of resorcinol and hydroquinone under specific conditions and the recrystallization treatment of the rectification liquor (or redistilled distillate of the rectification liquor). As a result, it has become possible to efficiently separate high-purity resorcinol and hydroquinone, and its industrial significance is extremely large.

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

In the examples, % and parts indicate weight units.

Example 1 Content ratio of resorcinol and hydroquinone (weight ratio)
A mixture of resorcinol and hydroquinone with a ratio of 7:3 is continuously fed to a rectification column with 40 theoretical plates at a rate of 100 parts per hour, and the reflux ratio and heating of the bottom liquid are adjusted to carry out the rectification. Rectification was carried out so that the resorcin content/hydroquinone content (R/H) of the can liquid was 0.5 and the hydroquinone content in the distillate was 0.3% or less. The distillate was liquefied and flaked to obtain 55 parts per hour of highly pure resorcinol with a purity of 99.8% (hydroquinone content 0.2%) as a flaky solid. On the other hand, as a rectifier liquid, 45 per hour
The resorcin content and hydroquinone content of this rectification tank liquid were 32.9% and 65.1%, respectively.
%, and the degradation products of resorcinol and hydroquinone were 2.0%. The retention rates of resorcinol and hydroquinone in this separation and rectification were each 99.6.
%, 98.0%. Add 102 parts of water to 100 parts of the above rectification tank liquid, heat and dissolve to make an aqueous solution, and then
It was gradually cooled down to. The precipitated crystals were filtered with a centrifuge and the resulting crystals were dried until the water content was 0.1% or less, and the hydroquinone purity was 97.5.
%, 43.8 parts of purified hydroquinone with a resorcin content of 2.4% were obtained. Furthermore, when the crystals were recrystallized again using water as a solvent and dried, high purity hydroquinone with a hydroquinone purity of 99.7% or less and a resorcin content of 0.2% or less was obtained.

Example 2 A resorcinol/hydroquinone mixture containing 75% resorcinol and 23% hydroquinone was continuously fed into the same rectification column as used in Example 1 at a rate of 100 parts per hour, and the reflux ratio and bottom liquid were Rectification was carried out by adjusting the heating and other conditions so that the R/H of the rectifier liquid was approximately 0.25 and the hydroquinone content in the distillate was 0.5% or less.

The distillate is liquefied and flaked to form a flaky solid with a purity of 99.4% (hydroquinone content
69.2 parts of high purity resorcinol (0.4%) was obtained per hour. On the other hand, 30.8 parts of the rectification tank liquid was extracted per hour, and the resorcin content and hydroquinone content were 18.8% and 71.8%, respectively, and the content of deterioration products of resorcinol and hydroquinone was 3.2%. The retention rates of resorcinol and hydroquinone in this separation and rectification were 99.5% and 97.4%, respectively. This rectifier liquid was further continuously subjected to simple distillation, and the distillate was collected with water and gradually cooled to 30° C. for crystallization. In simple distillation of this rectified bottom liquid, 27.9 parts per hour were distilled out, and 2.9 parts per hour remained as bottom liquid.

The distillate slurry collected with water and crystallized was filtered in a centrifuge and dried until the water content was 0.2%, resulting in purified hydroquinone with a hydroquinone purity of 98.1% and a resorcin content of 1.4%. 1
15.9 copies per hour were obtained. When this crystal was recrystallized again using water as a solvent and dried, the purity
High purity hydroquinone with a resorcin content of 99.6% or more and a resorcin content of 0.3% or less was obtained.

In addition, when performing simple distillation of rectifier liquid, while supplying steam at 200℃ to the simple distiller liquid part, the temperature of the distiller liquid part is kept constant.
Distillation is carried out by heating and controlling the amount of steam supplied to maintain the temperature at 220°C, and the distillate is cooled and condensed together with water. A distillate having almost the same composition as the separated slurry was obtained.

When this was treated in the same manner, high purity hydroquinone was obtained.

Comparative Example 1 The same resorcinol and hydroquinone mixture used in Example 1 was passed through a rectification column with 40 theoretical plates per hour.
Continuously feed at a rate of 100 parts, adjust the reflux ratio, heating of the bottom liquid, etc. until the R/H of the rectified bottom liquid is from 0.05.
It was rectified so that the hydroquinone content of the distillate was 0.1% and the hydroquinone content of the distillate was 0.3% or less. The distillate was liquefied and flaked to obtain 66.6 parts per hour of high purity resorcinol with a purity of 99.8% (hydroquinone content 0.2%) as a flaky solid.

On the other hand, 33.4 parts per hour are extracted as rectification tank liquid, and the resorcin content and hydroquinone content of this rectification tank liquid are 4.2% and 70.1%, respectively, and the deterioration products of resorcin and hydroquinone are 25.7%.
It was %. Resorcinol in this separation rectification,
The retention rate of hydroquinone is 97.0% and 78.3%, respectively.
It was hot.

138 parts of water was added to 100 parts of the above-mentioned rectification tank liquid, and the solution was heated and dissolved to form an aqueous solution, and then slowly cooled to 30°C to crystallize. The slurry was passed through a centrifuge, and the resulting crystals were dried until the water content was 0.1%. The purity of hydroquinone was 92.6%, the content of resorcinol was 1.8%, and the degradation products of resorcinol and hydroquinone were 5.5%. % of hydroquinone was obtained. Furthermore, the crystals were recrystallized again using water as a solvent and dried, but the degradation products were 0.9
% remaining, and the hydroquinone purity was 98.8%.

Example 3 A resorcinol/hydroquinone mixture containing 65% resorcinol and 34% hydroquinone was continuously supplied to a rectification column with 40 theoretical plates at a rate of 100 parts per hour, and the reflux ratio, heating of the bottom liquid, etc. Rectification was carried out so that the R/H of the rectifier liquid was approximately 0.15 to 0.2 and the hydroquinone content in the distillate was 0.3% or less.

The distillate is liquefied and flaked to produce high-purity resorcinol with a purity of 99.7% (hydroquinone content 0.3%) as a flaky solid per hour.
58.6 copies were obtained. On the other hand, per hour as rectifier liquid
41.4 parts were extracted, and the resorcin content and hydroquinone content of this rectification tank liquid were 14.3% and 14.3%, respectively.
78.5%, and the degradation products of resorcinol and hydroquinone were 4.8%. The retention rates of resorcinol and hydroquinone in this separation rectification are
They were 99.1% and 95.9%.

100 parts of the above rectification liquor was dissolved in 113 parts of methyl isobutyl ketone (MIBK) and gradually cooled to 30°C to crystallize. The slurry was filtered through a centrifuge, and the resulting crystals were dried to remove MIBK, yielding 56.7 parts of purified hydroquinone with a hydroquinone purity of 98.3% and a resorcin content of 1.1%. When this crystal was recrystallized again using water as a solvent and dried, even higher purity hydroquinone with a purity of 99.7% or more and a resorcin content of 0.2% or less was obtained. In addition, after recrystallizing MIBK as described above, the crystals passed through a centrifuge were washed with water on a centrifuge, and then dried, yielding high-purity hydroquinone with a purity of 99.3% and a resorcin content of 0.4%. Obtained.

Claims (1)

[Scope of Claims] 1. A mixture containing resorcin and hydroquinone is continuously rectified so that the ratio (weight ratio) of resorcin and hydroquinone in the rectifier liquid is 0.1 to 1:1, and resorcin is distilled. 1. A method for separating resorcin and hydroquinone from a mixture containing resorcin and hydroquinone, which comprises separating hydroquinone as an effluent, and recrystallizing the rectification liquor with water and/or an organic solvent to separate hydroquinone. 2. Continuously rectify a mixture containing resorcin and hydroquinone so that the ratio (weight ratio) of resorcin and hydroquinone in the rectification tank liquid is 0.1 to 1:1 to separate resorcin as a distillate, On the other hand, the rectified liquor is further redistilled and the resulting distillate is recrystallized with water and/or an organic solvent to separate hydroquinone. Resorcinol and hydroquinone from a mixture containing resorcinol and hydroquinone separation method. 3. The method according to claim 2, wherein the redistillation is carried out in the presence of water vapor.