JP2019019086A - Olefin purification method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for purifying an olefin gas capable of increasing the purity of the purified gas while maintaining a recovery rate commensurate with the actual profit by increasing the ionic strength in the absorbing liquid. A method for purifying an olefin from a raw material gas containing an olefin, wherein the raw material gas containing the olefin is used under the conditions of the following steps: a temperature of 10 to 100 ° C. and a pressure of 0.1 to 1.0 MPaG. Contact with the absorbent 1 containing an ion-binding salt consisting of a valent or divalent cation and at least one anion selected from the group consisting of nitrate ion, fluoride ion, tetrafluoroborate ion and sulfate ion. The first step of preparing the absorption liquid 2 containing the olefin; subsequently, the absorption liquid 2 is treated under the conditions of a temperature of 10 to 100 ° C. and a pressure of −0.09 MPaG or more and 0.3 MPaG or less to obtain the olefin. A method for purifying an olefin, which comprises a second step of recovering. [Selection diagram] None

Description

  The present invention relates to a method for concentrating and purifying olefins from a raw material mainly containing olefins.

Propylene, which is an example of a lower olefin, is known as a raw material for synthetic resin products such as polypropylene and acrylonitrile and synthetic rubber products, but may also be used in the field of electronic materials such as semiconductors. For such applications, propylene is required to be of higher purity.
A raw material gas mainly composed of olefin such as propylene used as a highly purified raw material contains paraffin such as propane as impurities. As a method for purifying an olefin such as propylene from the raw material gas, for example, distillation, membrane separation, adsorption separation, or chemical absorption is known.
It has been conventionally known that olefins having double bonds form complexes with silver ions and copper ions, but paraffins do not form complexes with silver ions. Due to this chemical property, it is also known that under certain conditions, the solubility of olefins in an absorbing solution containing silver ions (for example, an aqueous silver nitrate solution) is considerably greater than the solubility of paraffin in the absorbing solution. Documents relating to chemical absorption utilizing this property are disclosed (Patent Documents 1 and 2).
In the field of electronic materials, it is required to further increase the purity of propylene for the purpose of improving the yield of the manufacturing process. Therefore, for the purpose of further increasing the purity of the purified olefin gas, it has been studied to increase the concentration of silver nitrate or the like in the absorbing solution.

  As described in detail in Non-Patent Document 1, the solubility of propylene in the aqueous silver nitrate solution can be estimated to increase the solubility of the olefin in the aqueous silver nitrate solution as the concentration of silver nitrate is increased. Therefore, it can be expected that the purity of the purified olefin gas can be increased. However, there is a trade-off relationship between the purity of the purified olefin gas and the recovery rate that the recovery rate decreases as the silver nitrate concentration increases, and it is said that there is a limit from the viewpoint of practical benefits. In addition, when the silver nitrate concentration is increased, acetylenes contained in the raw material gas are easily precipitated in the refining apparatus. Therefore, it is presumed that the concentration cannot be increased from the viewpoint of safety.

Japanese Patent No. 5546447 Japanese Patent No. 1539267

Solubility of Propylene in Aqueous Silver Nitrate, Cho, I. et al. H. Cho, D .; L. Yasuda, H .; K. Marrero, T .; R. , J .; Chem. Eng. Data 1995, 40, 102.

  Thus, the problem in the present invention is to produce high-purity olefin gas, but in order to obtain high-purity olefin by chemical absorption, it is necessary to lower the solubility of the non-absorbing gas in the absorbing liquid. It becomes. In order to reduce the amount of solute dissolved in water, for example, a technique of increasing the ionic strength of the aqueous solution can be taken. That is, by increasing the ionic strength in the absorbing liquid, the solubility of the non-absorbing gas in the absorbing liquid may be lowered.

Based on the above, the present inventor has conceived and realized the present invention. That is, it has been found that the purity of the purified olefin gas can be increased while maintaining the recovery rate commensurate with the actual benefit by increasing the ionic strength rather than the silver nitrate concentration in the absorbing solution.
That is, the present invention is as follows.
[1] A method for purifying olefin from a raw material gas containing olefin,
The following steps:
A temperature of 10 ° C. to 100 ° C., a pressure of 0.1 MPaG to 1.0 MPaG,
The olefin-containing raw material gas is an ion-binding salt comprising a monovalent or divalent cation and at least one anion selected from the group consisting of nitrate ion, fluoride ion, tetrafluoroborate ion and sulfate ion. A first step in which the olefin-containing absorbent 2 is brought into contact with the absorbent 1 containing olefin;
Subsequently, the absorption liquid 2 is treated under conditions of a temperature of 10 ° C. to 100 ° C. and a pressure of −0.09 MPaG to 0.3 MPaG to recover the olefin;
A process for purifying olefins.
[2] The method for purifying an olefin according to [1], wherein the salt concentration is 0.01 mol / L or more and 10 mol / L or less.
[3] The method for purifying an olefin according to [2], wherein the concentration of the salt is 0.1 mol / L or more and 10 mol / L or less.
[4] The method for purifying an olefin according to [3], wherein the concentration of the salt is 1 mol / L or more and 10 mol / L or less.
[5] The method for purifying an olefin according to [4], wherein the concentration of the salt is 5 mol / L or more and 10 mol / L or less.
[6] The method for purifying an olefin according to any one of [1] to [5], wherein the cation of the salt contains a silver ion and / or a monovalent copper ion.
[7] The method for purifying an olefin according to any one of [1] to [6], wherein the concentration of the olefin contained in the raw material gas is 60% or more and 99.99% or less.
[8] The method for purifying an olefin according to [7], wherein the concentration of the olefin contained in the raw material gas is 80% or more and 99.99% or less.
[9] The method for purifying an olefin according to [8], wherein the concentration of the olefin contained in the raw material gas is 90% or more and 99.99% or less.
[10] The method for purifying an olefin according to [9], wherein the concentration of the olefin contained in the raw material gas is 95% or more and 99.99% or less.
[11] The method for purifying an olefin according to [10], wherein the concentration of the olefin contained in the raw material gas is 99.5% or more and 99.99% or less.
[12] The method for purifying an olefin according to any one of [1] to [11], wherein the olefin is at least one selected from the group consisting of butene, propylene, and ethylene.
[13] The method for purifying an olefin according to any one of [1] to [12], including a step of reusing the absorbent after recovering the olefin from the absorbent 2 as the absorbent 1.

  ADVANTAGE OF THE INVENTION According to this invention, the purification method which can make the purity and recovery rate of the refined olefin gas compatible is provided.

It is a figure which shows schematic structure of the refiner | purifier which concerns on one embodiment of this invention.

Hereinafter, the present invention will be described in detail with a focus on preferred forms (hereinafter sometimes referred to as “this embodiment”).
FIG. 1 is a diagram showing a schematic configuration of the purification apparatus of the present embodiment.
In the refining apparatus of the present embodiment, the raw material gas passes through the absorption tower 1 and the stripping tower 2 to provide high-purity purified olefin. The absorption tower 1 shown in FIG. 1 is a process of selectively extracting olefins in the raw material gas into the absorption liquid 1. Non-absorbed gas that has not been absorbed is discharged from the non-absorbed gas outlet 15 to the outside of the system. In the absorption tower 1, the absorption liquid 2 in which the olefin is dissolved is supplied to the diffusion tower 2. The stripping tower 2 shown in FIG. 1 is a process for stripping the olefin in the absorbing liquid 2. The released olefin gas is recovered from the olefin gas outlet 23, and the desired purified olefin gas can be obtained. The absorption liquid from which the olefin has been diffused may be returned to the absorption tower 1 from the absorption liquid outlet 24 and reused as the absorption liquid 1.

[Raw material gas]
The source gas in the present embodiment is a mixed gas of two or more kinds of gas components including olefin gas. The olefin gas is a gas having at least one C—C unsaturated bond in the molecule, and examples thereof include ethylene, propylene, 1-butene, 2-butene, isobutene, and butadiene. Since it is diverse, it is not limited to this. The raw material gas preferably contains 60% or more of olefin gas, more preferably 80% or more, more preferably 90% or more, still more preferably 95% or more, and most preferably 99.95% or more. It is preferable that the source gas is a gas derived from a metathesis reaction because the concentration of the olefin gas in the source gas can be increased. If the olefin gas concentration in the raw material gas is high, it can be expected that the amount of components other than the olefin gas dissolved in the absorbent 1 can be reduced.

[Purified olefin gas]
The purified olefin gas in the present embodiment is a gas having at least one C—C unsaturated bond in the molecule, and examples thereof include ethylene, propylene, 1-butene, 2-butene, isobutene, and butadiene. . Since there are a wide variety of olefins, the olefin is not limited thereto. The concentration of the olefin gas is preferably 99.5% or more, more preferably 99.9% or more, further preferably 99.99% or more, and most preferably 99.999% or more. High purity of the purified olefin gas is preferable because the yield of a process using the purified olefin gas such as CVD can be increased.

[Non-absorbing gas]
The non-absorbing gas in the present embodiment is a gas that has not been absorbed by the absorbent 1 in the absorption tower. The non-absorbing gas may contain olefin gas, but the concentration of the olefin gas is preferably low from the viewpoint of increasing the purification yield. Preferably, the concentration of the olefin gas is 60% or less, more preferably 40% or less, and still more preferably 20% or less.

[Absorbent]
The absorbing liquid 1 in the present embodiment is a liquid containing a salt having an affinity for the olefin gas, and due to its high ionic strength, the solubility of the non-absorbing gas in the absorbing liquid can be lowered.
The salt contained in the absorption liquid 1 is composed of a cation and an anion. First, since the cation has a high affinity with an olefin, a monovalent silver ion, a monovalent copper ion, and these A mixture is preferred. The concentration of the cation in the absorbing liquid 1 is preferably higher from the viewpoint of increasing the solubility of the olefin gas in the absorbing liquid. The concentration of the cation is preferably from 0.01 mol / L to 10 mol / L, more preferably from 0.1 mol / L to 10 mol / L, still more preferably from 1 mol / L to 10 mol / L, and more preferably from 5 mol / L to 10 mol / L. L or less is most preferable. When the cation concentration is 0.01 mol / L or more and 10 mol / L or less, it is preferable from the viewpoint of yield, and it is also excellent in terms of profit.
In the present embodiment, not only the above silver ions and monovalent copper ions but also monovalent or divalent cations are added as cations to increase the cation concentration, thereby making the effects of the present invention more prominent. This is preferable. The monovalent or divalent cation species is not particularly limited, and for example, Na ⁺ or K ⁺ can be used. The inclusion of monovalent or divalent cations is preferred because the balance between the purity of the purified gas and the recovery rate is good even at high concentrations.

As anions, from the viewpoint of compatibility with monovalent silver ions and monovalent copper ions, F ⁻ , Cl ⁻ , Br ⁻ , I ⁻ , CN ⁻ , NO ₃ ⁻ , SCN ⁻ , ClO ₄ ⁻ , CF ₃ SO ₃ ⁻ , BF ₄ ⁻ , and PF ₆ ⁻ , and mixtures thereof are preferable. From the viewpoint of lowering the solubility of gas components other than the olefin gas in the absorbing liquid, the anion concentration in the absorbing liquid 1 is preferably higher. The anion concentration is preferably 0.01 mol / L or more and 10 mol / L or less, more preferably 0.1 mol / L or more and 10 mol / L or less, further preferably 1 mol / L or more and 10 mol / L or less, and 5 mol / L or more and 10 mol / L or less. L or less is most preferable. When the anion concentration is 0.01 mol / L or more and 10 mol / L or less, it is preferable from the viewpoint of yield, and it is also excellent in practical benefits. In order to increase the concentration of anions, salts other than silver ions and copper ions, which are F ⁻ , Cl ⁻ , Br ⁻ , I ⁻ , CN ⁻ , NO ₃ ⁻ , SCN ⁻ , ClO ₄ ⁻ , CF ₃ SO ₃ ^-, BF ₄ ^-, and PF ₆ ^- may be added to salt absorbing liquid 1 containing.
Examples of the solvent of the absorbing liquid 1 include water, alcohols such as polyethylene glycol, ionic liquids such as imidazolium compounds and pyridinium compounds. From the viewpoint of salt solubility, it is preferable to include water.

[Absorption tower]
The absorption tower 1 has an absorption tower body 11, a raw material gas inlet 12, an absorbing liquid outlet 13, an absorbing liquid inlet 14, and a non-absorbing gas outlet 15, and brings the raw material gas into contact with the absorbing liquid 1. . The absorption tower main body 11 is a sealed container, and a predetermined amount of the absorption liquid 1 is received therein.
The end of the raw material gas inlet 12 is opened in the absorbing liquid, for example, inside the absorption tower main body 11, and introduces the supplied raw material gas into the absorption tower main body 11. The open end of the raw material gas inlet 12 may be provided with, for example, a single opening or may be provided with a plurality of openings for aeration.
The end of the absorption liquid outlet 13 is open inside the absorption tower body 11, and the absorption liquid 2 in the absorption tower 1 is led out of the tower. The derived absorbing liquid 2 is sent to the stripping tower 2.
The end of the absorption liquid inlet 14 is open inside the absorption tower body 11, and the absorption liquid is introduced into the absorption tower body 11 into the tower.
The non-absorbing gas outlet 15 is connected to the upper portion of the absorption tower body 11 and guides the gas (non-absorbing gas) that has not been absorbed by the absorbing liquid 1 to the outside of the tower.

[Dispersion Tower]
The stripping tower 2 has a stripping tower main body 21, an absorbing liquid inlet 22, an absorbing liquid outlet 24, and an olefin gas outlet 23, and dissipates gas components absorbed by the absorbing liquid 1 in the absorbing tower 1. Let The stripping tower main body 21 is a sealed container, and a predetermined amount of the absorbing liquid can be received therein.
The end of the absorption liquid inlet 22 is open in the diffusion tower main body 21, and introduces the absorption liquid 2 led out from the absorption tower main body 11 into the diffusion tower main body 21.
The end of the absorption liquid outlet 24 is open in the diffusion tower main body 21, and the absorption liquid is led out from the diffusion tower main body 21. The derived absorbing liquid may be returned to the stripping tower 2.
The olefin gas outlet 23 is connected to the upper part of the stripping tower main body 21 and guides the purified olefin gas taken out from the absorbent 2 to the outside of the tower.

[Separation mechanism]
A mechanism for efficiently performing gas separation in the present embodiment will be described.
The raw material gas introduced into the absorption tower 1 and the absorption liquid 1 are in gas-liquid contact within the tower. The structure of the absorption tower may be a packed tower, a spray tower, or a wet wall tower. The contact may be either countercurrent contact or cocurrent contact. In the case of packed towers, the packing introduced into the packed tower for the purpose of increasing the gas-liquid interface includes Raschig rings, Lessing rings, Dixon packing, pole rings, saddles, McMahon packing, sulzer packing, etc. It doesn't matter. The temperature in the absorption tower main body 11 is advantageously low, since the amount of olefin absorption increases. For example, the temperature is preferably 0 ° C. or higher and 60 ° C. or lower, more preferably 0 ° C. or higher and 40 ° C. or lower. The internal pressure in the absorption tower body 11 is preferably a high pressure within a certain range because the amount of olefin absorption increases. From a practical point of view, the internal pressure in the absorption tower body 11 is preferably 0.1 MPaG (gauge pressure) or more and 1.0 MPaG or less, for example. The absorption tower body 11 can be equipped with a temperature adjusting device for maintaining the absorption liquid at a desired temperature.

  In the absorption tower 1, when the continuously supplied raw material gas comes into contact with the absorbing liquid 1, the olefin in the raw material gas is preferentially absorbed by the absorbing liquid 1, while the non-absorbing gas is discharged outside the tower. The The absorbing liquid 2 in which the olefin gas is absorbed is led out of the tower from the absorbing liquid outlet 13 and sent to the stripping tower 2.

  The absorbent 2 in which the olefin gas introduced into the stripping tower 2 is dissolved dissipates gas components in the absorbent in the tower. As the stripping tower 2 having such a structure, a structure in which the absorbing liquid 2 is dispersed is suitable, and examples thereof include a known packed tower and spray tower, and any of them may be used. Moreover, the stripping tower 2 can be equipped with a temperature adjusting device for maintaining the absorbing liquid in the stripping tower main body 21 at a desired temperature.

  From the viewpoint of efficiently dissipating the olefin gas component, it is preferable that the inside of the stripping tower is an environment that is equal to or higher than the boiling point of the olefin gas, and the internal temperature in the stripping tower body 21 is higher than that of the absorption tower body 11. The internal pressure is preferably lower than that of the absorption tower body 11. The temperature of the absorbing liquid in the strip tower main body 21 is preferably 10 ° C. or higher and 70 ° C. or lower, and more preferably 20 ° C. or higher and 70 ° C. or lower. The internal pressure in the diffusion tower main body 21 is preferably, for example, −0.09 MPaG or more and 0.3 MPaG or less, and more preferably 0 MPaG or more and 0.3 MPaG or less.

In the stripping tower 2, the high-purity olefin gas is taken out from the absorbing liquid 2 in which the olefin gas is absorbed, while the absorbing liquid from which the olefin gas has been taken out is led out of the tower from the absorbing liquid outlet 24. The derived absorption liquid may be sent to the absorption tower 1 as the absorption liquid 1.
Thus, by using the purification apparatus in the present invention, a high-purity olefin gas having an olefin concentration higher than that of the raw material gas can be obtained.

  As described above, in the present invention, by increasing the ionic strength, not the silver nitrate concentration in the absorbing liquid 1, that is, by containing a specific amount of a salt composed of a specific type of anion and cation in the absorbing liquid. In the purification of olefin gas, the purity of the purified olefin gas can be increased while maintaining a recovery rate commensurate with actual benefits.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.
<Example 1>
In this example, the apparatus shown in FIG. 1 was used, and propylene was purified from the raw material gas using the propylene gas having the concentration shown in Table 1 as the raw material gas.
In this example, stainless steel cylindrical tubes (inner diameter 54.9 mm × height 500 mm: volume 1185 cm ³ ) were used as the absorption tower body 11 of the absorption tower 1 and the diffusion tower body 21 of the diffusion tower 2, respectively. As the absorption liquid 1, the mixed aqueous solution of silver nitrate and sodium nitrate described in Table 1 was received in the absorption tower body 11, and the mixed aqueous solution having the same concentration was first received in the diffusion tower body 21. The pressure and temperature of the absorption tower main body and the stripping tower main body were adjusted as shown in Table 1. The mixed aqueous solution of silver nitrate and sodium nitrate received in the absorption tower body 11 and the stripping tower body 21 was circulated between the absorption tower body 11 and the stripping tower body 21 at a flow rate of 25 cm ³ / min. The supply amount of the source gas was a flow rate of 663 cm ³ / min.
Table 1 shows the olefin concentration and recovery rate in the purified gas from the stripping tower 2 during steady operation.

<Examples 2-27 and Comparative Example 1>
Propylene gas was purified in the same manner as in Example 1 except that the absorbent, raw material gas and operating conditions listed in Table 1 were used. The results are shown in Table 1.
As described above, it has been found that by increasing the ionic strength in the absorption liquid, it is possible to achieve a recovery rate commensurate with actual benefits while increasing the purity of the purified olefin gas.

  When the olefin purification method and purification apparatus of this embodiment are used, a high-purity olefin gas can be supplied at a recovery rate commensurate with actual benefits, and the olefin purification method and apparatus are suitably used for electronic material applications such as the semiconductor field.

1 Absorption tower 1
11 Absorption tower body 12 Raw material gas inlet 13 Absorbing liquid outlet 14 Absorbing liquid inlet 15 Non-absorbing liquid outlet 2 Stripping tower 2
21 Exhaust tower body 22 Absorbent inlet 23 Olefin gas outlet 24 Absorber outlet

Claims (13)

A method for purifying olefin from a raw material gas containing olefin,
The following steps:
Under conditions of a temperature of 10 ° C. or more and 100 ° C. or less and a pressure of 0.1 MPaG or more and 1.0 MPaG or less, a raw material gas containing the olefin is converted into a monovalent or divalent cation, nitrate ion, fluoride ion, tetrafluoroborate ion. And a first step of making the absorbent 2 containing the olefin contacted with the absorbent 1 containing an ion-binding salt consisting of at least one anion selected from the group consisting of sulfate ions;
Subsequently, the absorption liquid 2 is treated under conditions of a temperature of 10 ° C. to 100 ° C. and a pressure of −0.09 MPaG to 0.3 MPaG to recover the olefin;
A process for purifying olefins.   The method for purifying an olefin according to claim 1, wherein the concentration of the salt is 0.01 mol / L or more and 10 mol / L or less.   The method for purifying an olefin according to claim 2, wherein the concentration of the salt is 0.1 mol / L or more and 10 mol / L or less.   The method for purifying an olefin according to claim 3, wherein the concentration of the salt is 1 mol / L or more and 10 mol / L or less.   The method for purifying an olefin according to claim 4, wherein the salt concentration is 5 mol / L or more and 10 mol / L or less.   The method for purifying an olefin according to any one of claims 1 to 5, wherein the cation of the salt contains silver ions and / or monovalent copper ions.   The method for purifying an olefin according to any one of claims 1 to 6, wherein the concentration of the olefin contained in the raw material gas is 60% or more and 99.99% or less.   The method for purifying an olefin according to claim 7, wherein the concentration of the olefin contained in the raw material gas is 80% or more and 99.99% or less.   The method for purifying an olefin according to claim 8, wherein the concentration of the olefin contained in the raw material gas is 90% or more and 99.99% or less.   The method for purifying an olefin according to claim 9, wherein the concentration of the olefin contained in the raw material gas is 95% or more and 99.99% or less.   The method for purifying an olefin according to claim 10, wherein the concentration of the olefin contained in the raw material gas is 99.5% or more and 99.99% or less.   The method for purifying an olefin according to any one of claims 1 to 11, wherein the olefin is at least one selected from the group consisting of butene, propylene and ethylene.   The method for purifying an olefin according to any one of claims 1 to 12, comprising a step of reusing the absorbent after recovering the olefin from the absorbent 2 as the absorbent 1.

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