JPS6125403B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating solid components from coexisting solid and liquid under high pressure with high purity.

The present inventors have been conducting research on methods for separating substances under high pressure for some time, and have found that solid-liquid coexistence states obtained through crystallization operations under high pressure can be used to effectively separate solids with high purity. I learned that there are several problems with the method of separating and purifying this.

For example, Figure 1 is a solid-liquid phase diagram of a two-component simple eutectic mixture, where line 1 shows the solid-liquid transformation of pure component x ₁ , and line 2 shows the solid-liquid transformation of the eutectic components x ₁ and x ₂ . show. And each point A, A′, A″ is a solid phase of specific component x ₁ ,
This is the coexistence point of the mixed mother liquor consisting of components x ₁ and x ₂ , and the location of the problem will be clarified below based on this figure.

Suppose now that the crystallization operation is completed at or near point A', and the solid-liquid is completely primary separated at point A'. The separated solid must eventually be taken out to atmospheric pressure, but by the initial pressure reduction it reaches point B' on the transformation line 1 of pure component x ₁ . In this process, the solid expands, and although there is some cooling due to the heat of expansion, there is no particularly significant effect, so the explanation will be omitted for the sake of convenience. As the pressure continues to decrease, the transformation line 1
As the pressure decreases along the direction toward point E, the crystals begin to melt one after another. At this stage, the temperature drops rapidly due to latent heat due to melting of the crystal and increase in internal energy due to expansion of the molten liquid phase. When the entire amount melts at point E, the temperature gradually decreases only due to the expansion of the liquid. Note that Tm is the melting point of pure component x ₁ under atmospheric pressure.

On the other hand, when solid-liquid separation is performed at point A or A'', even if this solid phase is released into atmospheric pressure, the entire amount will not melt.For example, if pressure reduction is started from point A, Melting begins when it reaches point B, and the pressure and temperature decrease as it melts as before, but the melting point Tm is quickly reached, so the progress of melting stops.If solid-liquid separation at point A is insufficient Then, as the pressure decreases, part of the crystal melts, which appears as latent heat, and the amount of temperature decrease increases, reaching point C, and the pressure and temperature decrease further, but due to the inclusion of impurities, the temperature becomes lower than the melting point Tm. When the solid-liquid separation at point A is insufficient, the solid-liquid transformation line ₁ of pure component Melting stops when reaching point D. In this way, when starting from point A, it is not possible to melt all of the solid phase, and the purity of the product is extremely low. Also, when starting from point A'' It is self-evident that there is no need for special explanation that this tendency becomes even more pronounced.

In general, the temperature drop that accompanies depressurization can take various forms, but the amount of temperature drop when depressurizing adiabatically is extremely large, and is similar to that when many organic substances are melted from solid to liquid. The amount of temperature drop is
The temperature ranges from 70 to 150℃. Therefore, in the above explanation,
In order to melt the entire amount of high-purity specific component crystals only by reducing pressure, for example, the temperature between point B' and point E must be 70 to 150℃.
It must be the case that there is a temperature difference of
Also, the temperature dependence of transformation pressure (slope of line 1) in many organic materials is 30 to 60 kg/cm, so if the temperature difference between point B' and point E is 100°C, point B' -The pressure difference between points E must be between 3000 and 6000 Kg/ ^cm2 . Moreover, the pressure when actually performing solid-liquid separation is often several hundred to several thousand atmospheres higher than this, and in the end, in order to melt the entire amount of solid only by depressurizing operation, it is necessary to reach point A′. The pressure must be extremely high.

However, in order to perform such high pressure operation,
This requires a special high-pressure device, which poses a problem in terms of versatility. Therefore, it may be possible to heat and melt the material in a high-pressure container during depressurization without performing such a high-pressure operation. However, this requires a heat exchanger placed inside the high-pressure vessel or a heating device for the high-pressure vessel, but in the former case, solid-liquid separation, such as compression separation, becomes difficult, and the latter is especially difficult. In this case, a thick steel container must be heated, resulting in poor thermal efficiency and time efficiency. In either case, equipment costs increase, and the high-pressure vessel must be re-cooled after discharging the melt before the next operation, making it even more inefficient. In addition, it is not impossible to consider a method in which the same substance as the specific component or a suitable solvent is heated and injected into a high-pressure container to promote melting or melting of the solid. However, the thermal loss is quite large, so it is difficult to call this a fundamental solution.

The present invention has been made based on such considerations, and it is an object of the present invention to provide a method for efficiently extracting solids with high purity from a solid-liquid mixture existing under high pressure. That is, the structure of the present invention is such that when crystals of at least one or more specific components and a mixed mother liquor of the specific component and other components are in a solid-liquid coexistence state under high pressure, this specific component is This is a method of separating and purifying the solid as it is. First, by squeezing the solid-liquid coexistence that exists under high pressure, only the liquid is released outside the high-pressure container, and then by lowering the pressure inside the high-pressure container. A part of the crystalline specific component left in the high-pressure container is melted to form a solid-liquid coexistence state, and by squeezing the solid-liquid coexistence, only the liquid is released outside the high-pressure container, and the remaining The idea is to remove the solids from the system by opening the high-pressure container.

First, there is a method for forming a solid-liquid coexistence state under high pressure, but this method does not limit the present invention. However, in general, it is preferable to use a mixture obtained by pressurizing a mixture of two or more components, which are entirely in liquid phase or mostly in liquid phase, at an appropriate temperature under normal pressure. Further, temperature control during this pressurization is also optional, and the method of the present invention can be applied to any method as long as the mixture exhibits a solid-liquid coexistence state under high pressure.

The first step of the present invention is carried out by first separating solid-liquid from the solid-liquid mixture. This one
Of course, the next separation is a high-pressure vessel (including high-pressure piping, etc.)
The same applies hereinafter), and specific examples include filtration, compression, sedimentation, and the like. In this step, it is not necessary to completely separate the solid-liquid, and rough separation by any means is acceptable, but as can be understood from the above discussion, the more complete the solid-liquid separation is, the more
It is recommended to perform as much solid-liquid separation as possible by the squeezing method, as this makes it easier to develop the subsequent steps theoretically. However, since there are limits to the compression method, even in the case of the present invention, Fig. 1A
It is natural that the pressure and temperature decrease proceed as shown in -C and A-D. FIG. 2 shows an example of the apparatus used to carry out the present invention, and the inner surface of the high-pressure container 3 is
A heat insulating layer 5 is formed as required, and hydraulically driven pistons 1 and 2 are mounted on the upper and lower sides. 6,
Reference numerals 7 and 8 are pipes for extracting compressed liquid, and check valves 6a, 7a, and 8a are provided respectively. Note that the piston 2 may be replaced with a lower plug fixed to the high pressure container 3. Further, 4 is a solid-liquid coexistence substance,
Of course, it is held under high pressure. Therefore, when performing the compression in this step, the piston 1 and/or
or 2 is operated to compress the solid-liquid coexistence material 4, and the separated liquid is discharged to the outside of the system through pipes 6, 7, and 8.

Next, as the second step of the present invention, the pressure inside the high-pressure container is reduced. As can be easily understood from the explanation of FIG. 1, the ultimate pressure at this time is below the solid-liquid equilibrium pressure indicated by 1, and the lower limit reaches the atmosphere. As a result, the crystals of the specific component are partially melted, and the liquid impurities that have adhered to the solid surface or are caught in the gaps between the crystals are washed away by the melt, and
The remaining solid is covered with its own melt and is protected from contamination, resulting in a highly pure solid.

Various embodiments of this process can be considered, and the one described in the claims is just one example, but a typical method is to gradually reduce the pressure continuously or stepwise and remove the resulting melt. This is a method of sequential separation. Therefore, the pressure drop in the high-pressure container does not occur instantaneously, and the molten liquid is removed from the solid-liquid coexistence system each time, so that the temperature-lowering effect due to the heat of expansion of the molten liquid is small. Moreover, since this melt is removed each time along with the impurity liquid, the effect of removing the impurity liquid is extremely high, and the melting point drop due to impurities in the specific component crystals is also small. Because of this, it is recommended to perform compression at least once at any stage of sequential pressure reduction to sufficiently perform solid-liquid separation. When the liquid phase is sufficiently removed by this compression, the polycrystalline fine particles of the specific substance are compressed, as in the case of powder compaction of metals, ceramics, etc. (mechanical press, rubber press, etc.), and huge block-shaped solid crystals are obtained. It will be done.

In general, the higher the pressure range is used for such compression, the higher the recovery efficiency of the solid phase, and the lower the pressure range, the higher the purity of the solid phase, and the stronger the solid phase block when released to atmospheric pressure. Therefore, it is desirable to perform many compressions in the process of stepwise or continuous pressure reduction, and more desirable effects can be obtained if compression is performed each time stepwise or in conjunction with continuous pressure reduction.

The degree of squeezing referred to here should be expressed as the difference between the average pressure in the solid-liquid coexistence phase and the pressure in the discharged liquid phase, and in most cases the pressure is tens to hundreds of atmospheres, sometimes over 1000 atmospheres. Therefore, good results can be obtained.

The block-shaped solid obtained as described above is finally depressurized to atmospheric pressure or a pressure close to it, and
After that, the high-pressure container is opened and taken out, but the purity can be further improved by squeezing again just before taking out to separate the solid and liquid, or by pressing and separating the natural melt after taking out or after partially melting by active heating. can be obtained as a solid. In particular, during compression after decompression to atmospheric pressure, the pressure of the mother liquor in the stagnation area compressed at the back of the insulation layer, the gap between the piston and the container, etc. is released, so the liquid phase remaining in this stagnation area is separated and removed. It is effective in doing so. However, this squeezing is not necessarily an essential step, since this impure liquid phase can also be forced out as a gas before the solid is removed from the high-pressure vessel. This kind of separation by gas is
At the time when the solid has already become a block by compression, it is effective to separate the mother liquor remaining in the stagnation portion and to remove the molten mother liquor on the surface of the block.
Furthermore, by squeezing the block solid phase at this time, the amount of melting due to reduced pressure can be minimized. It is preferable that the gas is one that does not react with the components of the mixture. Usually, a gas of several atmospheres, sometimes 10 atmospheres or more, is flowed from above or replaced with the remaining mother liquor. There is nothing special about replacing the remaining mother liquor in a vacuum.

Further, the above solid-liquid separation or solid removal operation by reducing pressure or squeezing can be made more effective by performing the treatment in a state where heat exchange between the high-pressure container and the internal object to be treated is cut off. In other words, when the temperature of the internal processed material decreases due to depressurization, a temperature difference occurs between it and the high-pressure container, but as a result, when heat flows in from the high-pressure container side, the high-purity solid phase becomes more concentrated than necessary. It will melt, and the temperature of the high-pressure vessel itself may drop, adversely affecting the next cycle. On the other hand, if a heat insulating layer is formed, the melting of the solid phase will be blocked from the influence of external conditions, making it possible to virtually control the operation only by pressure management, and ensuring uniformity within the high-pressure vessel. The advantages of pressure manipulation such as uniformity and uniformity of condition propagation can be meaningfully enjoyed. As such a heat insulating layer, a synthetic resin such as phenolic resin is recommended as a material with a low heat capacity, but the presence or absence of the heat insulating layer and the material thereof are not intended to limit the present invention.

If one were to heat and melt the entire amount of the remaining solid phase, the solid phase would be, for example, 50 kg of benzene.
In this case, the latent heat is 30 cal/g, so the total
1500Kcal/50Kg is required, and even if heated with a 2KW heater, it would theoretically have to be heated for 75 minutes, and if heat conduction due to the heat outflow temperature gradient is taken into account, a longer heating time will be required. On the other hand, if the solid is to be discharged as it is, only about one minute is sufficient, and the impact on productivity is significant.

Furthermore, if the surface of the solid taken out in the form of a block is wet with a liquid containing a large amount of impurities,
Drop separation can be easily achieved by simply melting the block-shaped solid surface with hot air or the like. The above explanation mainly focused on the example of a two-component simple eutectic mixture for convenience.
This method may be a multi-component eutectic system or a mixture of solid solution systems. Further, the specific component is not limited to one specific substance, but may be a eutectic or an intermolecular compound of two substances. In short, it can be applied to all mixtures in which components other than specific components are concentrated or diluted in the liquid phase as they solidify or melt under high pressure.

Examples of the present invention will be described below.

Example 1 A stock solution containing about 10% pseudocumene (mp-43.9°C) mixed with mesitylene (mp-44.8°C) was pressurized to obtain a solid-liquid coexistence state. The mother liquor was separated by pressing at -13°C and 1500 atm, and after the pressure was lowered to 1000 atm, the mother liquor was further separated by pressing. The pressure was then returned to atmospheric pressure, and solid mesitylene was collected after about 30 seconds. This amount was about 50% of the solid amount when separated under 1000 atmospheres, but its purity exceeded 99.9%, and the mesitylene liquid separated and removed under atmospheric pressure had a purity of 99.5%. Ta.

Example 2 A mixed solution of m-cresol and p-cresol (mixing ratio 20:80) was heated to 2000 atm at 40°C to create a solid-liquid coexistence state. This was squeezed to separate solid and liquid, and when the remaining solid was returned to atmospheric pressure, it became a solid-liquid coexistence at 30°C.
When this is immediately compressed and separated and the remaining solid (p-cresol) is taken out of the high-pressure container, the pressure is 2000 atm.
The yield was 80% of the theoretical yield by compression at 40°C, and the purity achieved was 99.5%.

Since the present invention is configured as described above, it has become possible to extract a solid substance with high purity and good yield from a solid-liquid coexistence material existing under high pressure.

[Brief explanation of the drawing]

FIG. 1 is a solid-liquid transformation diagram for explaining the separation of solid-liquid coexisting substances, and FIG. 2 is a cross-sectional view conceptually showing a high-pressure vessel used for carrying out the present invention. 1, 2... Piston, 3... High pressure vessel, 5...
insulation layer.

Claims (1)

[Claims] 1. When crystals of at least one or more specific components and a mixed mother liquor of the specific component and other components are in a solid-liquid coexistence state under high pressure, A method of separating and purifying,
First, by squeezing the solid-liquid coexistence material existing under high pressure, only the liquid is released outside the high-pressure container, and by lowering the pressure inside the high-pressure container, the crystals remaining in the high-pressure container are isolated. A part of the components is melted to form a solid-liquid coexistence state, and only the liquid is released outside the high-pressure container by squeezing the solid-liquid coexistence, and the remaining solid is released by opening the high-pressure container. A solid-liquid separation method characterized by extraction from the system. 2. After the initial discharge of liquid outside the high-pressure container, the pressure within the high-pressure container is gradually reduced in a continuous or stepwise manner to melt a portion of the solid and successively separate the melted liquid. The method described in item 1. 3. The method according to claim 2, wherein in separating the molten liquid, compression is performed at least once at any stage to separate the liquid phase. 4. The method according to any one of claims 1 to 3, wherein at least the steps after the first discharge of liquid to the outside of the high-pressure container are performed in a container provided with a heat insulating layer. 5. The method according to any one of claims 1 to 4, wherein the solid taken out from the high-pressure container is heated and partially melted and removed. 6. When separating the molten liquid, the solid phase after the liquid phase has been separated by compression at least once is lowered to a pressure lower than the processing pressure before the compression, and a gaseous body is caused to flow on the surface of the solid phase. The method according to any one of claims 1 to 5, wherein the liquid phase is separated by. 7. When separating the melt, the solid phase is compressed at least once to separate the liquid phase, and then the pressure is lowered to lower than the processing pressure before the compression, and then the solid phase is compressed again. Claims 1 to 5, in which the liquid phase is separated by flowing a gaseous body over the surface of the liquid phase.
The method described in any of the paragraphs.