JPH0268101A - Pressure crystallization process - Google Patents

Abstract

PURPOSE:To improve the purity of solid products in comparison with the conventional pressure crystallization processes by imparting shock wave energy to crystal grain group while they are being compressed, enabling thereby the interior of solid products to be highly purified. CONSTITUTION:A mixture composed of more than one kind of component including specific compositions (e.g., 8% of p-cresol, the balance is m-cresol) is supplied into a high pressure vessel 1, where pressure is applied to said mixture to effect crystallization thereof, while the liquid phase thereof is continuously discharged to the outside of the vessel 1 under pressure for solid-liquid separation so that the crystal grains therein are further compressed to form solid products having specific compositions (e.g., p-cresol) in the vessel 1, which products are taken out therefrom. When pressure is applied to the mixture as described above, shock wave energy is imparted to the crystal grains in the vessel. As a result, even the interior of the solid products can be purified, causing thereby the purity of solid products to be greatly improved in comparison with conventional pressure crystallization processes.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a pressure crystallization method, and more particularly to a pressure crystallization method for increasing the purity of a solid product obtained.

(Conventional technology) Pressure crystallization has great potential for application to raw material systems that are difficult to separate using conventional distillation or cooling crystallization, is easy to obtain high-purity products, and has high Due to its easy yield and low energy consumption, it is a separation and purification technology that has been attracting a lot of attention as the chemical industry has become increasingly refined in recent years.

An overview of this pressure crystallization method can be found, for example, in Kagaku Kogyo Volume 50 (
(1986), p. 331, "Outline of pressure crystallization method and apparatus". To explain this using FIG. 1 (a diagram showing the process flow and the concept of the device), the pressure vessel (11
is provided with a lid (23) at the bottom, and a piston (5) is provided so as to move up and down within the container (1) due to the operation of the hydraulic unit (3). (
5) and the lower lid (2) form a crystallization chamber (4) within the pressure vessel (1). This crystallization chamber (4) and the drain tank (
6) means the pipe (
9). Further, the crystallization chamber (4) and the pre-crystallizer (7) are connected via a raw material supply pump (8) and a pipe 03) through a valve 0.

In this device, the raw material is fed from the raw material tank +141 to the pre-crystallizer (force), where it is cooled to produce seed crystals for pressure crystallization. When subjected to crystallization, in pressure crystallization, the supersaturation pressure is generally relatively high, several hundred atmospheres or more (this is because high pressure may be required for initial crystal formation,
Supplying liquid in the form of a slurry containing seed crystals has the advantage that there is no need to worry about such supersaturation pressure, and crystal growth can be expected without nucleation due to pressurization.

Next, the raw material is transferred from the pipe 0 to the crystallization chamber (4) via the valve 021.
). When the crystallization chamber (4) is filled with the raw material, the liquid begins to flow out through the overflow pipes having openings at the tip of the piston.This is detected and the valve Q21,0 is activated.
ω is closed and pressurization by the piston (5) is started. When the raw material liquid is pressurized, crystallization of specific substances in the raw material progresses,
The inside of the crystallization chamber (4) is in a solid-liquid equilibrium state under high pressure. The solid produced at this time is generally a substance of extremely high purity. Note that the temperature inside the crystallization chamber (4) rises due to the latent heat of solidification generated as solidification progresses, but in the pressure crystallization method, cooling is generally not performed to prevent this temperature rise, and heating is performed adiabatically. A pressure method is adopted. The temperature reached after the temperature rise, that is, the temperature at which solid-liquid separation starts, affects the purity and yield of the product, so this is adjusted by the liquid supply temperature, taking into consideration the specific heat, latent heat of solidification, etc. of the raw material mixture.

Next, when the pressure is increased to a predetermined pressure, the predetermined solid-liquid ratio (saturation state) is immediately reached. ), the pressure inside the crystallization chamber (4) remains constant and the liquid phase flows from the crystallization chamber (4) to the drain tank (6).
) is discharged. Further, as the piston (5) continues to descend, the crystal grains in the crystallization chamber (4) are compressed and the remaining liquid between the crystal grains is discharged into the drain tank (6) through the so-called "squeezing action". be done.

As the piston (5) continues to descend further, the grains are formed into a large lumpy solid product following the shape of the crystallization chamber (4), thus almost completely discharging the liquid from the solid. At the stage of separation, the liquid phase pressure in the crystallization chamber (4), which is connected to the drain tank (6) under atmospheric pressure, gradually decreases, so that the crystal surface partially melts, resulting in so-called A "sweat wash" is performed and the bulk solid product is purified.

When the pressure of the waste liquid discharged from the crystallization chamber (4) decreases to a predetermined pressure, the piston (5) stops descending, and at the same time the piston begins to rise, the high pressure container (1) also rises. , the solid product is removed from the container (1) while being placed on the lower lid (2). This is the product removal device (
(not shown), lower the high-pressure container (1) and attach it to the lower lid (2), and then return to the raw material injection process.
The same process will be repeated. Prior to the injection of raw materials, the residual liquid in the overflow pipe (5) mentioned above is purged with a gas inert to the product, such as nitrogen gas, in preparation for detecting full liquid at the time of injection in the next process. Keep it.

By repeating the above steps, products are produced continuously.

(Problems to be Solved by the Invention) As described above, the conventional pressure crystallization method involves crystallizing a mixture by pressurizing it in a high-pressure container, and then discharging the liquid phase under pressure to solidify the mixture. After liquid separation and further squeezing of the crystal grains in the container, a solid product of a specific component is formed in the container, and then the product is taken out.

Here, the above-mentioned squeezing process includes a process of pressurizing the crystal grain group and discharging the residual liquid between the crystal grains to form it into a lumpy solid, and a process of forming the lumpy solid surface by reducing the liquid phase pressure after the forming. The method includes a step of purifying the lumpy solid by melting the solid by utilizing natural melting (sweat washing) and discharging the melt.

The purpose of the above-mentioned compression is not only to form a solid product that is easy to take out, but also to increase the purity of the solid product by draining as much residual liquid as possible, which contains components other than specific components.

Therefore, when the squeezing process is carried out as described above, a solid product of relatively high purity is obtained by draining the residual liquid between the crystal grains, and a solid product of even higher purity is obtained by washing with perspiration.

Incidentally, a model diagram of the state of the residual liquid after the residual liquid is discharged and molded into a lumpy solid is shown in FIG. 2, and a model diagram of the state after sweating and cleaning is shown in FIG. 3. As shown in FIG. 2, even if the residual liquid discharge operation is performed, the liquid trapped inside the crystal during the process of squeezing the crystals (black portion in the figure) remains. Also, impurities on the crystal surface (shaded area in the figure) are also F! I'm staying.

After sweating and cleaning, as shown in Figure 3, due to reduced pressure, impurities on the surface of the crystal and parts of the crystal that are in contact with the liquid trapped inside are preferentially melted, expanding the volume and increasing the absolute amount of liquid. It flows out due to

As a result, the impurity concentration of the trapped liquid decreases,
Purity of bulk solids is improved.

However, the above-mentioned sweat washing has the effect of increasing the purity of the solid product in response to the absolute amount of residual mother liquor and the temperature and pressure acting on the mother liquor, and the mother liquor is more likely to remain inside the product. Pressure also tends to remain. Therefore, there is a problem that the entire solid product cannot be highly purified. That is, the conventional pressure crystallization method has a limit in achieving high purity of the product. This is an extremely serious problem in pressure crystallization methods that require extremely high product purity.

The present invention was made in view of these circumstances, and its purpose is to solve the above-mentioned problems of the conventional products, to achieve high purity even inside the solid product, and to improve the purity of the solid product. The present invention aims to provide a pressure crystallization method that can increase the purity of a solid product compared to a method using a pressure crystallization method.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a pressure crystallization method having the following configuration. That is, the present invention supplies a mixture of two or more components including a specific component to a high-pressure container, pressurizes the mixture in the container to crystallize it, and then transfers the liquid phase under pressure to the container. In a pressure crystallization method in which a solid product of a specific component is formed in the container by discharging it to the outside for solid-liquid separation, and further squeezing the crystal grain group in the container, and then taking out the product from the container. , a pressure crystallization method characterized in that shock wave energy is applied to the crystal grain group in the container during the compression.

(Function) As explained above, in the pressure crystallization method according to the present invention, shock wave energy is applied to the crystal grain group in the container during compression. Here, this shock wave energy is, for example, ultrasonic energy, and when it is applied to an object, it has the effect of causing the object to generate heat (overall heat generation). Further, if there is a structurally non-uniform portion, there is an effect of generating frictional heat at the boundary surface of the non-uniform portion, and this frictional heat is larger than uniform heat generation.

When shock wave energy having such an effect is applied to the crystal grain group in the container during squeezing, it causes the entire crystal grain group or block-like body to generate heat, and also generates frictional heat at the solid-liquid interface. Therefore, at this time, depending on the applied shock wave energy, only the solid near the solid-liquid interface can be dissolved.

In addition, crystal boundaries can be preferentially dissolved. Such dissolution can also occur inside the massive solid because shock wave energy can be applied to the interior of the massive solid.

When such dissolution occurs, a large liquid channel is created that communicates with the outside of the bulk solid. Since shock wave energy is applied during squeezing, the liquid in the massive solid is pressurized. Therefore, the liquid between the crystal grains is easily discharged to the outside of the massive solid.

Furthermore, by reducing the structural non-uniformity, the amount of remaining mother liquor itself can be reduced. Furthermore, the generation of heat also leads to a perspiration cleaning effect based on the rise in temperature.

Therefore, even the inside of the solid product can be efficiently purified, and the purity of the solid product can be increased compared to the conventional pressure crystallization method.

In addition, the type of city II wave energy to be applied and its conditions (
(strength, application time, etc.) may be selected depending on the type of mixture to be pressure-crystallized, crystallization pressure, solid-liquid separation pressure, etc.

In addition, the shock wave energy may be applied over the entire period from the start to the end of the pressing process, or may be applied only for a part of the pressing process depending on the case. It may be performed only during sweat cleaning due to the decrease in liquid phase pressure after the process, and in conjunction with the sweat cleaning.
Moreover, the shock wave energy may be applied continuously or intermittently.

(Example) An example according to the present invention will be described. The apparatus used in the example is the same as that shown in FIG. 1, with an ultrasonic energy applying means (not shown) added thereto. Others are
This is similar to that explained in FIG. 1 above.

First, a cresol mixture (p-cresol 80χ, remainder 1-cresol) is cooled to 15'C in a pre-crystallizer (7) to form a slurry, and then crystallized from pipe 0 through valve 021. The mixture was injected into the analysis chamber (4).

Next, the slurry cresol mixture in the crystallization chamber (4) is pressurized to 1200 atm to crystallize, and then the valve (11
) was opened and the liquid phase was discharged to the outside of the container while maintaining a pressure of 1200 atm to perform solid-liquid separation.

After the discharge, the crystal grains in the container were compressed while applying ultrasonic energy to the crystal grains in the crystallization chamber (4). Here, the ultrasonic energy was continuously applied during the squeezing process.

The frequency of the second ultrasonic wave was 500 KHz, the output power density was 5 W/cm'', and the ultrasonic wave was launched toward the crystal grain group in the upper crystallization chamber (4).The ultrasonic energy application time was: The duration was 5 seconds.This operation of applying ultrasonic energy was extremely simple and could be performed without requiring advanced techniques.

After squeezing, the pressure in the crystallization chamber (4) was reduced to atmospheric pressure, the high pressure container (1) was opened, and the solid product was taken out.

As a result, p-cresol with a purity of 99.55X was obtained. Product yield was 32.2x. This purity value is
High purity compared to 99.30χ when using the conventional method,
Although the difference between the two is numerically small, it is of extremely great significance industrially. The above conventional method is
This is a method in which no ultrasonic energy is applied during squeezing, and other operating conditions are the same as in Example 1.

Imperial Family 11 In Example 2, the crystallization pressure and the pressure at the time of liquid phase discharge (solid-liquid separation pressure) were set to 1500 atm. Other operating conditions are the same as in Example 1.

As a result, p-cresol with a purity of 99.65χ was obtained. Product yield was 35.2x. This purity value is
This is higher than the purity of 99.50χ obtained by the conventional method.

1 plate 1 In Example 3, the crystallization pressure and the pressure at the time of discharging the liquid phase (solid-liquid separation pressure) were set to 1800 atm. Other operating conditions are the same as in Example 1.

As a result, p-cresol with a purity of 99.80χ was obtained. Product yield was 37.2x. This purity value is
This is higher than the purity of 99.60χ obtained by the conventional method.

Pressure crystallization was carried out in the same manner as in Example 1, except for the conditions of the ultrasonic energy used to apply the scattered soil.

Ultrasonic frequency is 600KHz, output power density is 6W
The volume was 8 ml. The ultrasonic energy application time was 5 seconds as in Example 1.

As a result, ρ-cresol with a purity of 99.65χ was obtained. Product yield was 35.1x. This purity value is
This is higher than the purity of 99.301 obtained by the conventional method. Note that the purity was higher than in Example 1 because the applied ultrasonic energy was large and the perspiration cleaning effect was exhibited accordingly (effects of the invention) Pressure crystallization according to the present invention According to this method, it is possible to achieve high purity even to the inside of the solid product, which makes it possible to increase the purity of the solid product compared to the conventional pressure crystallization method.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the process flow and the concept of the apparatus related to the pressure crystallization method, Fig. 2 is a model diagram regarding the state of the residual liquid after the residual liquid is discharged and a lumpy solid is formed;
FIG. 3 is a model diagram regarding the state after sweating and cleaning. (1) --- One pressure vessel (2) --- One lower lid (3
) --- One hydraulic unit (4) --- One crystallization chamber (5)
--- Piston (6) --- Drainage tank (7
) --- Ichikobei crystallizer (8) --- One raw material supply pump <9) (13) One one piping arf) -- One pressure reduction mechanism (Ill (J'l) 06) -- Ri [ 04) ---One raw material tank 09-overflow pipe

Claims (1)

[Claims] (1) A mixture of two or more components including a specific component is supplied to a high-pressure container, the mixture is pressurized and crystallized in the container, and the liquid phase is subsequently discharged from the container under pressure. In the pressure crystallization method, a solid product of a specific component is formed in the container by solid-liquid separation, and the crystal grain group in the container is compressed, and the product is taken out from the container. A pressure crystallization method characterized by sometimes applying shock wave energy to a group of crystal grains in a container.