JPS58154549A - Crystallization of crystal of m-xylenesulfonic acid - Google Patents

Abstract

PURPOSE:In crystallizing continuously the titled crystal from the reaction product of stylene and sulfuric acid, to obtain crystal having large particle diameters and low sulfuric acid content with using a crystallizer with a simple structure, by repeating intermittently operations of rise in temperature and drop in temperature. CONSTITUTION:m-Xylene is reacted with sulfuric acid to give m-xylenesulfonic acid, the solution of the reaction product is cooled to 30-40 deg.C, crystal is crystallized, the temperature of the mother liquor is intermittently raised to 45-50 deg.C, fine crystal in the mother liquor is dissolved and eliminated, the mother liquor is recooled to 30-40 deg.C, the crystallizing action is continued, and the desired crystal is crystallized continuously. Preferably the sulfuric acid concentration of the mother liquor is 50-70wt% and the slurry concentration is 35-45wt%, and the intermittent rise in temperature is carried out 2-4 times per average retention time of crystallization so that crystal with particle diameters of improved efficiency is obtained. EFFECT:The enlargement and the uniformity of particle diameters of crystal are enabled by one-stage agitated crystallizer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for crystallizing dioxysilenosulfone 5It from a reaction product liquid obtained by reacting xylene and sulfur 12.

Conventionally, -sulfuric acid has been widely used as a sulfonating agent for xylene. However, since the sulfonation reaction is carried out with sulfuric acid, K has a limit value of sulfuric acid once, and this il
Below the degree of chain elevation, the reaction hardly progresses.

In the sulfonation reaction of m-xylene, the monosulfuric acid performance level is 6.
There is a Kll limit value around 8% by weight (!11 is water, the same applies hereinafter). However, in the sulfonation reaction of xylene using sulfuric acid, as the reaction progresses, isocell water is produced and sulfuric acid-jIl is reduced. For this reason, in order to increase the reaction rate of xylene, it is necessary to add a large excess of sulfuric acid to xylene, and the ratio of sulfuric acid/xylene = 1. 5-2 has been used sparingly. Therefore, the reaction product liquid contains a large amount of un-J[th sulfur.

On the other hand, the solubility of m-xylene sulfonic acid in sulfuric acid water mouth fluid varies considerably depending on the sulfuric acid concentration, and
to 70% by weight, the degree of IIS is low, and the solubility is extremely low below 50° C., which is the industrially usable crystallization temperature.

Therefore, under such conditions, m-xylene sulfonic acid can be continuously separated from the reaction product solution by crystallization.
When crystallization separation was performed in a stirred continuous crystallization tank, the slurry was transparent during batch operation, but became cloudy during continuous operation - this is likely due to the generation of a large number of extremely fine crystals. found. For example, in the batch method, the average grain size of the crystals was 1 to 1.2IIIm, but in continuous crystallization, it was 0.
．． The particles were as small as 3 to 0.5 μm, and many fine particles of 0°2 μ or less were also observed.

In addition, after continuous operation for a long period of time, the amount of crystals adhering to the vessel wall became noticeable. In this continuous crystallization operation, the crystal grain size is small, so it is difficult to shake out the pit, and the crystals contain a large amount of sulfuric acid, so in order to ensure quality, the sulfuric acid content must be kept below a certain amount. requires a large amount of rinsing, and therefore the yield of m-xylene sulfonic acid is poor and the
First, it is uneconomical.

In order to eliminate the above disadvantages, a crystallizer with a classification system is usually used for continuous crystallization, or a multi-stage crystallizer is used for a stirred tank.
ll) Countermeasures are taken, such as reducing the 1st degree of sieving by reducing the 1st degree of sieving to bring it closer to the batch operation method. However, all of these methods involve an increase in construction costs.

The inventor of the present invention has conducted intensive research on a method for increasing and making the crystal grain size uniform in a stirred continuous crystallization tank with a simple structure similar to that used in the cocoon-shielded crystallization experiment. And K11L, which undergoes continuous crystallization at tK, temporarily @
The temperature was raised to dissolve the crystals attached to IIK, and
After dissolving the deposited crystals at 1K, continuous crystallization was carried out as in the case of overcurrent, and it was discovered that the grain size of the crystals increased abnormally after the temperature was raised, and the present invention was achieved.

That is, in the present invention, m-xylene and sulfuric acid are reacted to form 'Cm-
Xylene sulfonic acid is produced and the reaction product is cooled.
- In the method of continuously crystallizing and separating crystals of xylene sulfonic acid, the mother liquor temperature at the time of crystallization is 50 to 40°C, and the mother liquor temperature is intermittently raised by 45 to 50'CK. The mold inside melted and disappeared,
This is a method in which the mother liquor is cooled again to 50 to 40°C and the crystallization operation is continued.

The crystallization conditions in the present invention are ii) acid yield of 50 to 70% by weight;
(The remainder is water) and the temperature is preferably 30 to 40°C. Here, the sulfuric acid concentration is the sulfuric acid content when the sum of sulfuric acid and water in the reaction solution is 1100% by weight. The solubility of m-xylene sulfonic acid in an aqueous sulfuric acid solution is sulfuric acid concentration of 60% by weight (the remainder is water with a small KIi value around 1, and 50 to 70% by weight)
Within this range, the difference in solubility is small and is suitable for crystallization operations.

It is preferable to keep the crystallization temperature as low as possible because it can prevent dissolution loss of m-xylene sulfonic acid, but in the present invention, since the temperature raising and lowering operations are repeated intermittently, energy loss during that time is taken into account. Therefore, it is desirable to crystallize at a relatively high temperature, and from the viewpoint of crystallization efficiency and economical efficiency, 5.
0 to 4Q'C is preferred. Furthermore, in relation to the crystallization temperature, the temperature at which fine crystals are dissolved and disappeared is preferably 45 to 50°C. This temperature is set at the saturation temperature at which all the crystals can be dissolved.

Slurry concentration is usually 50-50% by weight, ays5-45
i amount % gives good results.

The concentration at which fine crystals klliI are dissolved cannot be unconditionally determined due to the differences in sulfuric acid concentration, slurry concentration, stirring speed, impurity concentration, wax temperature and time required for dissolution and disappearance, etc., but in general Average SW time for continuous crystallization 2~
If the process is carried out four times, seven crystals with an efficient particle size can be obtained.

In the present invention, unreacted sulfuric acid contained in the mother liquor after crystallization and separation of m-xylene sulfonic acid in the reaction product solution is waste F.
According to the present invention, it is possible to obtain m-xylene sulfonic acid crystals with a large particle size and a low sulfuric acid content while using crystallization with a simple structure. Not only that, but compared to the conventional method,
Since it is possible to hide flies for a long time, the construction cost of the crystallization device can be significantly reduced.

Example 1 A reaction product solution consisting of all 6811% of m-xylene-4-sulfone, 26% by weight of unreacted sulfuric acid, 8% by weight of water, and 1% by weight of others and 4 il of 48° 8% by weight diluted
Acid is supplied to a glass crystallizer equipped with a stirrer and a full jacket at a rate of 190 parts by weight and 221 parts by weight per unit time, and continuous crystallization is carried out at 40° C. under atmospheric pressure. The average tW waiting time at this time was about 3 hours. Furthermore, the sulfuric acid concentration of the mother liquor at this time was 60% by weight (the rest was water), m-xylene-
The solubility of 4-sulfonic acid is 2% by weight, and the slurry concentration is 4
It was 0% by weight.

By raising and lowering the temperature of the cooling water flowing through the jacket part every hour, the crystallization temperature was raised from 40°C to 48°C in S minutes, the same temperature was maintained for 5 minutes, and then the cooling operation was performed. The temperature was lowered to 40°C in about 7 minutes.1 By repeating this operation, the fine crystals in the slurry in the inking machine disappeared, and the same transparency as in the batch operation was able to be maintained.

411 parts by weight of the slurry extracted from the overflow was centrifuged into C and K to obtain crude crystals and liquid V, 156 parts by weight and 255 parts by weight S1, respectively.

Next, 10% of the crude crystals were rinsed with 15.6 parts by weight of water, and the seed crystal and rinsing solution were each 110Ji
61.6 parts by weight and 61.6 parts by weight were obtained.

The sulfuric acid content in the crude crystals and the dry crystals was 3.3% and 0.6% by weight, respectively. Note that the flatness *a of the crystal was approximately 10.

Example 2 Crystallization and separation were carried out under the same conditions as in Example 1, except for those not subjected to the S-removal operation. That is, the crystallization temperature is 40℃ to 50℃
The procedure of raising the temperature to 40° C. over 4 minutes, maintaining the same temperature for 4 minutes, and lowering the temperature to 40° C. over 8 minutes was repeated every 2 hours.

The sulfuric acid content contained in the obtained crude crystals and seed crystals was 5.7 each.
% by weight and 0.9% by weight.

The average grain size of the crystals was 1wIA, which is the same as in Example 1.

Comparative Example 1 Under the same conditions as in Example 1, a continuous crystallization/separation experiment was conducted using a conventional method.

When continuous crystallization was continued for a long time, the crystals became finer and the slurry became cloudy.

The sulfuric acid content in the obtained crude crystals and fine crystals was 5.
．． They were 4% by weight and 2.1% by weight.

Further, the average particle size of the crystals was 0.3 to 0.5 mm and was moldy.

Patent applicant: Mitsubishi Gas Chemical Co., Ltd. Representative Kazuyoshi Nagano

Claims (1)

[Claims] In a method for producing m-xylene sulfonic acid by reacting 1-xylene and sulfuric acid, cooling the reaction product solution, and [continuously crystallizing and separating m-xylene sulfonic acid]
By setting the mother liquor temperature at 50 to 40°C during crystallization and intermittently raising the illumination liquid temperature to 45 to 50°C, the mother liquor was heated again at 30°C after the fine crystals in the mother liquor were dissolved.
Cool to ~40°C and continue crystallization operation t-si v4I
Method for crystallizing m-xylene sulfonic acid crystals as mold