Method for producing purified isopropyl alcohol and production apparatus

Abstract

A method for producing purified isopropyl alcohol by dehydrating crude isopropyl alcohol containing water as an impurity, comprising: storing a mixture of the crude isopropyl alcohol and an azeotropic agent in a phase separation tank, and subjecting the mixture to phase separation into an upper phase liquid containing the azeotropic agent, water and isopropyl alcohol and a lower phase liquid containing water; azeotropically distilling the upper phase liquid in an azeotropic distillation column to extract a distillate containing an azeotropic mixture of the azeotropic agent and water and a bottoms liquid containing isopropyl alcohol; and supplying the distillate to the phase separation tank. A method for producing purified isopropyl alcohol is provided.

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for producing purified isopropyl alcohol by dehydrating crude isopropyl alcohol containing water as an impurity.

Background Art

[0002] Isopropyl alcohol (hereinafter also abbreviated as "IPA") has the property of dissolving both water and organic solvents, and is widely used as a solvent for paints, a solvent for inks, and various synthetic raw materials. Furthermore, high-purity IPA is used in large amounts in the rinsing part of semiconductor substrates in semiconductor manufacturing equipment, and the usage amount is expected to increase in the future.

[0003] As a method for synthesizing IPA, for example, a direct hydration method of propylene is known. The crude product of IPA synthesized in this way is usually purified by a distillation method, but in order to obtain high-purity IPA, it is necessary to combine a plurality of distillation steps. Specifically, considering the boiling points of the organic impurities contained in the crude product of IPA, after performing a low-boiling distillation step of removing low-boiling impurities having a lower boiling point than IPA from the top of the distillation column, a high-boiling distillation step of removing high-boiling impurities having a higher boiling point than IPA from the bottom of the distillation column is performed. This method is known as a method with high purification effect. Furthermore, in the high-boiling distillation step, since the distillate withdrawn from the top of the distillation column contains an azeotropic mixture of IPA and water, an azeotropic distillation step of mixing an azeotropic agent such as benzene and performing azeotropic distillation is carried out (for example, see Patent Document 1).

[0004] In addition, since high-purity IPA has a high production cost, when used in semiconductor manufacturing, it contributes to an increase in the semiconductor manufacturing cost. The IPA waste liquid recovered from the semiconductor manufacturing equipment is generally subjected to combustion treatment, but at that time, carbon dioxide, which is a cause of global warming, is emitted. Therefore, from the viewpoint of environmental protection, it has been desired to reduce the amount of IPA waste liquid discarded.

[0005] For this reason, the demand for purifying and reusing IPA waste liquid is increasing. As a method for purifying IPA waste liquid, a method combining a plurality of distillation steps is also applied (see, for example, Patent Document 2). Also in this case, it is strongly desired to obtain high-purity IPA at as low a production cost as possible.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] From the above, it is desired to efficiently carry out the purification of the crude product of IPA and IPA waste liquid by distillation at a low production cost. Among them, the azeotropic distillation process consumes a large amount of heat. Therefore, it would be very meaningful if purified IPA could be efficiently produced from crude IPA containing water as an impurity with a small amount of heat.

Means for Solving the Problems

[0008] The present inventors have continued intensive studies in view of the above problems. As a result, instead of directly subjecting crude IPA containing water as an impurity to azeotropic distillation, the upper-phase liquid containing an azeotropic agent, water, and isopropyl alcohol obtained by phase separation in the presence of an azeotropic agent is subjected to azeotropic distillation, and it has been found that the above problems can be solved, leading to the completion of the present invention.

[0009] That is, one aspect of the present invention is a method for producing purified isopropyl alcohol by dehydrating crude isopropyl alcohol containing water as an impurity, comprising: accommodating a mixed solution of the crude isopropyl alcohol and an azeotropic agent in a phase separation tank, and performing phase separation into an upper phase liquid containing the azeotropic agent, water, and isopropyl alcohol, and a lower phase liquid containing water; and subjecting the upper phase liquid to azeotropic distillation in an azeotropic distillation column to extract a distillate containing an azeotropic mixture of the azeotropic agent and water, and a bottoms liquid containing isopropyl alcohol, wherein the distillate is supplied to the phase separation tank.

[0010] Another aspect of the present invention is an apparatus for producing purified isopropyl alcohol by dehydrating crude isopropyl alcohol containing water as an impurity, comprising: a phase separation tank for accommodating a mixed solution of the crude isopropyl alcohol and an azeotropic agent and performing phase separation into an upper phase liquid containing the azeotropic agent, water, and isopropyl alcohol, and a lower phase liquid containing water; and an azeotropic distillation column for performing azeotropic distillation on the upper phase liquid. A first supply pipe for supplying the crude isopropyl alcohol to the phase separation tank and a second supply pipe for supplying the upper phase liquid to a raw material supply stage of the azeotropic distillation column are connected to the phase separation tank. A third supply pipe for supplying a distillate containing an azeotropic mixture of the azeotropic agent and water to the phase separation tank is connected to the top of the azeotropic distillation column. A draw pipe for extracting a bottoms liquid containing isopropyl alcohol is connected to the bottom of the azeotropic distillation column. A fourth supply pipe for supplying the azeotropic agent is connected to any one of the first supply pipe, the phase separation tank, the second supply pipe, the azeotropic distillation column, and the third supply pipe.

Advantages of the Invention

[0011] According to the present invention, purified IPA can be efficiently produced from crude IPA containing water as an impurity with a small amount of heat.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as necessary.

[0014] 〔Crude IPA〕 The crude IPA is not particularly limited as long as it contains water as an impurity. For example, a crude product of IPA obtained by a synthesis method such as the direct hydration method of propylene, and IPA waste liquid recovered from various industrial facilities can be mentioned. Among these, IPA waste liquid recovered from a semiconductor substrate manufacturing apparatus is preferable. Specifically, IPA waste liquid recovered from the developing section and the pre-wet section of a semiconductor substrate manufacturing apparatus is applicable. Further, in a semiconductor substrate manufacturing apparatus, a rinsing section for removing moisture adhering to the surface of the substrate is provided after a cleaning section for cleaning the substrate with an aqueous cleaning agent, and a large amount of IPA is used as the rinsing liquid. In this embodiment, IPA waste liquid recovered from the rinsing section is also preferably applied.

[0015] Although the crude product of IPA and IPA waste liquid can be applied to crude IPA, it is preferable to apply water-containing IPA obtained by purifying the crude product of IPA and IPA waste liquid to crude IPA. The water content of the crude IPA is usually 1% by mass or more and 50% by mass or less, more preferably 10% by mass or more and 20% by mass or less.

[0016] As a method for purifying the crude product of IPA and IPA waste liquid, distillation is preferable. Examples of distillation include a method of removing high-boiling impurities from the bottom of a high-boiling distillation column. It is preferable to apply a distillate containing an azeotropic mixture of IPA and water (IPA 88% by mass, water 12% by mass) withdrawn from the top of the high-boiling distillation column to the crude IPA. Note that before distillation in the high-boiling distillation column, it is also possible to remove low-boiling impurities from the top of a low-boiling distillation column usually.

[0017] 〔Azeotropic agent〕 In this embodiment, an upper-phase liquid obtained by phase-separating a mixed liquid of crude IPA and an azeotropic agent is subjected to azeotropic distillation. That is, azeotropic distillation is a distillation in which an azeotropic agent is added to separate a mixture of liquids that is difficult or impossible to separate by ordinary distillation, and an azeotropic mixture is formed and separated. In this embodiment, it is used for removing water from the upper-phase liquid. As the azeotropic agent, a compound having a lower boiling point than IPA and forming an azeotropic mixture with water is used. Further, as the azeotropic agent, a compound that forms an upper phase containing the azeotropic agent, water, and IPA and a lower phase containing water when the mixed liquid of crude IPA and the azeotropic agent is phase-separated is used. Examples of the azeotropic agent include benzene, toluene, cyclohexane, and isopropyl ether. Among these, benzene is particularly preferable.

[0018] The addition amount of the azeotropic agent is preferably 50 parts by mass or more and 1000 parts by mass or less, more preferably 80 parts by mass or more and 500 parts by mass or less, based on 100 parts by mass of crude IPA.

[0019] 〔Dehydration method〕 In this embodiment, before azeotropic distillation, the crude IPA is stored in a phase separation tank in a state where the azeotropic agent is mixed. Then, the upper-phase liquid containing the azeotropic agent, water, and IPA formed in the phase separation tank is separated and subjected to azeotropic distillation. In the conventional method for purifying crude IPA, the crude IPA is directly subjected to azeotropic distillation (see, for example, Patent Document 2). However, in this case, since a large amount of crude IPA is subjected to azeotropic distillation, in addition to an increase in heat quantity, the diameter of the azeotropic distillation column also increases, and purified IPA cannot be efficiently produced.

[0020] In contrast, in the present embodiment, the crude IPA is not directly supplied to the azeotropic distillation column, but is stored in the phase separation tank in a state where an azeotropic agent is mixed. That is, by storing the crude IPA in the phase separation tank, it is separated into an upper phase liquid containing the azeotropic agent, water, and IPA, and a lower phase liquid containing water. Therefore, if the upper phase liquid is separated and supplied to the azeotropic distillation column, the total amount and water content of the upper phase liquid to be subjected to azeotropic distillation can be reduced with respect to the crude IPA. As a result, the amount of heat consumed during azeotropic distillation can be reduced. For example, the water content of the upper phase liquid obtained from the crude IPA having a water content of 12% by mass corresponding to the azeotropic mixture of IPA and water can be reduced to 0.1% by mass or more and 10% by mass or less, more preferably 0.5% by mass or more and 4% by mass or less.

[0021] The method for producing the crude IPA of the present embodiment will be described more specifically with reference to FIG. 1.

[0022] (Phase separation tank) In FIG. 1, the first supply pipe 1 for supplying the crude IPA, which is the liquid to be treated, is connected not to the azeotropic distillation column 2 but to the phase separation tank 4. As a result, the crude IPA is once stored inside the phase separation tank 4. At this time, the injection location of the crude IPA will be described later, but the crude IPA is supplied so as to be stored in the phase separation tank 4 in a state where the crude IPA and the azeotropic agent are mixed. As a result, in the phase separation tank 4, it is phase-separated into an upper phase liquid 5 containing the azeotropic agent, water, and IPA, and a lower phase liquid 6 containing water. In the present embodiment, the upper phase liquid 5 formed by phase separation is supplied to the raw material supply stage of the azeotropic distillation column 2 via the second supply pipe 7 and subjected to azeotropic distillation.

[0023] Here, the phase separation tank 4 is not particularly limited as long as it can be phase-separated into the upper phase liquid 5 and the lower phase liquid 6 by the specific gravity difference, and a known decanter, settler, etc. may be appropriately selected and used. The phase separation tank 4 preferably has the structure shown in FIG. 2. In this case, the phase separation tank 4 a) a phase separation chamber 8 in which a mixed liquid of the crude IPA and the azeotropic agent is stored and is phase-separated into the upper phase liquid 5 and the lower phase liquid 6, b) On one side of the phase separation chamber 8, adjacent to the phase separation chamber 8 via the first partition wall 9a, there is an upper-phase liquid storage chamber 10 that overflows the first partition wall 9a and stores the upper-phase liquid 5 flowing in from the phase separation chamber 8. c) On the other side of the phase separation chamber 8, adjacent to the phase separation chamber 8 via the second partition wall 9b, there is a lower-phase liquid storage chamber 11 that stores the lower-phase liquid 6 fed from the phase separation chamber 8 via the liquid feed pipe 14. It is compartmentalized to include these. That is, when separated from the lower-phase liquid 6 by the overflow of the upper-phase liquid 5, it becomes possible to make the separability of the upper-phase liquid 5 higher, which is preferable. At this time, since the upper end of the first partition wall 9a is lower than the upper end of the second partition wall 9b, the inflow of the upper-phase liquid 5 into the lower-phase liquid storage chamber 11 is suppressed. Also, the second supply pipe 7 is connected to the lower end region of the upper-phase liquid storage chamber 10.

[0024] The liquid feed pipe 14 consists of a communication pipe with a first opening end communicating with the lower-phase liquid 6 accommodated in the phase separation chamber 8 and a second opening end communicating with the lower-phase liquid storage chamber 11. The communication pipe has the highest height at a height corresponding to the upper end region of the first partition wall 9a, and has an upward bending portion 12 including the second opening end and a branch portion 13 that branches from the upward bending portion 12 and has a third opening end communicating with the gas phase portion of the phase separation tank 4 at a position higher than the upper end of the first partition wall 9a. As a result, the lower-phase liquid 6 accommodated in the phase separation chamber 8 is sucked from the first opening end of the communication pipe, and the lower-phase liquid 6 is drained into the lower-phase liquid storage chamber 11 from the second opening end.

[0025] Here, in the liquid feed pipe 14, since the height of the upward bending portion 12 (the height of the highest part of the pipe peripheral wall) is the height corresponding to the upper end region of the first partition wall 9a, the inflow amount of the upper-phase liquid 5 and the liquid feed amount of the lower-phase liquid 6 are well balanced. The height of the upward bending portion 12 only needs to maintain a good balance between the inflow amount of the upper-phase liquid 5 and the liquid feed amount of the lower-phase liquid 6, and keep the storage capacities of the phase separation chamber 8 and the lower-phase liquid storage chamber 11 at the desired amounts respectively. The height of the upward bending portion 12 is usually a height that is separated downward by a distance of 1 / 9, preferably 1 / 10, of the length from the upper end to the lower end of the first partition wall 9a.

[0026] In addition, since the branch portion 13 is provided in the liquid delivery pipe 14, when the lower-phase liquid 6 is delivered, the siphon effect prevents destabilization. Here, the pressure in the gas phase portion of the phase separation tank 4 communicating with the third opening end is not particularly limited, but from the viewpoints of preventing air from mixing in and separation performance in distillation, it is preferably 900 hPa or more and 4013 hPa or less, and more preferably 1013 hPa or more and 2013 hPa or less.

[0027] From the viewpoints of preventing the release of harmful substances and preventing air from mixing in, as shown in FIG. 2, the third opening end communicates with the gas phase portion of the phase separation tank 4. The third opening end is at a position 40 cm or more higher than the upper end of the first partition wall 9a, preferably 50 cm or more higher. Note that the third opening end may communicate with the outside of the phase separation tank 4.

[0028] From the viewpoint of stably separating the upper-phase liquid 5 and the lower-phase liquid 6, it is preferable to maintain the state in which the lower-phase liquid 6 is held at a certain height in the phase separation chamber 8. For this purpose, it is preferable to previously store a certain amount of water in the phase separation chamber 8, specifically, an amount of water that can make the residence time of the mixed liquid of crude IPA and the azeotropic agent in the phase separation chamber 8 10 minutes or more and 90 minutes or less. The amount of water previously stored in the phase separation chamber 8 is generally an amount corresponding to a height of 50 cm or more and 300 cm or less from the bottom of the phase separation chamber 8.

[0029] When supplying crude IPA to the phase separation chamber 8, in order not to disturb the phase separation of the mixed liquid of crude IPA and the azeotropic agent stored in the phase separation chamber 8, it is preferable to insert the opening end of the first supply pipe 1 into the lower-phase liquid 6 at a certain depth and reduce the flow rate of the crude IPA. The flow rate of the crude IPA is preferably 0.1 m / s or more and 2 m / s or less, and more preferably 0.3 m / s or more and 1 m / s or less.

[0030] In this embodiment, since the mixture of crude IPA and the azeotropic agent is phase-separated before being subjected to azeotropic distillation, a significantly larger amount of the mixture will be supplied to the phase separation tank 4 than when phase separation occurs after azeotropic distillation. At this time, when using the phase separation tank 4 having the structure shown in FIG. 2, the separation between the upper-phase liquid 5 and the lower-phase liquid 6 is excellent, and the mixing of components of the other phase can be suppressed as much as possible, which is particularly effective.

[0031] (Azeotropic distillation column) To the raw material supply stage of the azeotropic distillation column 2, the upper-phase liquid 5 is supplied from the upper-phase liquid storage chamber 10 via the second supply pipe 7. And from the top of the azeotropic distillation column 2, the first distillate containing the azeotropic mixture of the azeotropic agent and water and IPA, which is withdrawn via the condenser 3, is supplied to the phase separation tank 4 via the third supply pipe 15. On the other hand, from the bottom of the azeotropic distillation column 2, the first bottoms liquid containing IPA is withdrawn via the first withdrawal pipe 16. At this time, the first bottoms liquid may be used as purified IPA, or as will be described later, the purified first bottoms liquid may be used as purified IPA.

[0032] Here, it is preferable that the first distillate has an azeotropic agent content of 40% by mass or more and 80% by mass or less, a water content of 1% by mass or more and 10% by mass or less, and an IPA content of 14% by mass or more and 54% by mass or less. Further, it is more preferable that the first distillate has an azeotropic agent content of 40% by mass or more and 50% by mass or less, a water content of 2% by mass or more and 8% by mass, and an IPA content of 40% by mass or more and 50% by mass or less.

[0033] The azeotropic distillation column 2 may be either a tray column or a packed column, but a tray column is preferred. The theoretical number of plates of the azeotropic distillation column 2 is preferably 10 or more and 200 or less, and more preferably 20 or more and 50 or less. Examples of the trays in the tray column include cross-flow trays and shower trays. Examples of the packings in the packed column include Raschig rings and Lessing rings. Examples of the materials for the column and the packings include iron, stainless steel, Hastelloy, borosilicate glass, quartz glass, fluororesin (e.g., polytetrafluoroethylene), etc.

[0034] In this embodiment, in order to perform azeotropic distillation on the upper-phase liquid 5 with a reduced water content as compared with the crude IPA, the amount of heat consumed can be greatly reduced. As a result, the azeotropic distillation column 2 can be downsized as compared with the case of performing azeotropic distillation on the crude IPA.

[0035] The number of stages from the raw material supply stage of the azeotropic distillation column 2 to the bottom of the column is usually 5 or more, more preferably 10 or more and 30 or less, as the number of theoretical plates. It is preferable to confirm the total number of theoretical plates of the azeotropic distillation column 2 by actually operating and performing composition analysis.

[0036] The gauge pressure at the top of the azeotropic distillation column 2 is not particularly limited. For example, it is 0.0 MPaG or more and 0.1 MPaG or less. At this time, the temperatures at the top and bottom of the azeotropic distillation column 2 may be appropriately set according to the gauge pressure.

[0037] The water content of the first bottoms liquid depends on the type of the azeotropic agent used and the like, but is usually 1% by mass or less, preferably 1000 ppm or more and 1 ppm or less. The purity of the first bottoms liquid (excluding the water content) is usually 99.9% by mass or more, preferably 99.99% by mass or more and 99.999999% by mass or less.

[0038] (Supply of the first distillate to the phase separation tank) In this embodiment, the first distillate is supplied to the phase separation tank 4 via the third supply pipe 15 and circulated. That is, the azeotropic agent, water, and IPA contained in the first distillate are phase-separated again into the upper-phase liquid 5 and the lower-phase liquid 6, and since the upper-phase liquid 5 is subjected to azeotropic distillation, the recovery rate of IPA is increased.

[0039] Here, although the third supply pipe 15 is provided in parallel with the first supply pipe 1, the third supply pipe 15 may be connected to the first supply pipe 1.

[0040] In order to phase-separate the crude IPA supplied to the phase separation tank 4, a fourth supply pipe 17 for supplying an azeotropic agent to the phase separation tank 4 is provided, but the fourth supply pipe 17 may be connected to any one of the first supply pipe 1, the second supply pipe 7, the azeotropic distillation column 2, and the third supply pipe 15.

[0041] (IPA Recovery Distillation Column) The lower phase liquid 6 contains water and IPA. Specifically, the content of IPA in the lower phase liquid 6 is 5% by mass or more and 50% by mass or less, preferably 10% by mass or more and 30% by mass or less. For this reason, the lower phase liquid 6 is supplied to the raw material supply stage of the IPA recovery distillation column 19 via the fifth supply pipe 18, and a side cut liquid containing an azeotropic mixture of IPA and water is withdrawn from above the side of the IPA recovery distillation column 19. Then, the side cut liquid is supplied to the phase separation tank 4 via the sixth supply pipe 20 and circulated. That is, the water and IPA contained in the side cut liquid are phase-separated again into the upper phase liquid 5 and the lower phase liquid 6, and since the upper phase liquid 5 is azeotropically distilled, the recovery rate of IPA is increased. Note that the lower phase liquid 6 may be discarded without distillation. Also, the second distillate may be withdrawn from the top of the column.

[0042] On the other hand, a second bottoms liquid containing water is withdrawn from the bottom of the IPA recovery distillation column 19 via the second withdrawal pipe 21.

[0043] Here, in the IPA recovery distillation column 19, conditions that enable efficient withdrawal of a second distillate containing an azeotropic mixture of IPA and water from the top or above the side of the column may be adopted according to the distillation conditions in the azeotropic distillation column 2, and distillation may be performed.

[0044] When the crude IPA is derived from IPA waste liquid discharged from various industrial facilities and recovered, as impurities, in addition to water, it often has a complex composition containing various organic impurities. Usually, most of the organic impurities are removed by low-boiling distillation, high-boiling distillation, etc., but it is not easy to completely remove the organic impurities. In particular, the IPA waste liquid recovered from the rinsing section of a semiconductor substrate manufacturing apparatus may contain low-boiling impurities such as methanol and ethanol. In this case, a third distillate containing low-boiling impurities is withdrawn from the top of the IPA recovery distillation column 19 via the third withdrawal pipe 22. In this case, the third distillate may be discarded.

[0045] 〔Other purification processes〕 The first bottoms may be purified by adsorption or the like. Also, the first bottoms may be purified by filter filtration to remove metal particles, inorganic particles, organic particles, etc. Further, the first bottoms may be purified by an ion exchange resin or the like to remove metal ions and the like.

[0046] The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments, and the above embodiments may be appropriately modified within the scope of the gist of the present invention.

Examples

[0047] Hereinafter, examples of the present invention will be described, but the present invention is not limited to the examples. In the present examples, % and ppm are based on mass unless otherwise specified. In the following examples and comparative examples, the content of components in the sample was measured by the following method.

[0048] (Method for measuring the water content in the sample) Equipment: Karl Fischer moisture meter CA-200 (manufactured by Mitsubishi Chemical Analytic) When it is assumed that the water content in the sample exceeds 1%, the sample was diluted with IPA, and then the water content in the diluted sample was measured. The water content in the IPA used for dilution was measured in advance and confirmed to be 100 ppm or less. When it is assumed that the water content in the sample is 1% or less, the water content in the sample was measured without dilution. Note that when the water content in the sample is higher than assumed, it only takes more time for the measurement and does not affect the measured value. Also, when the water content in the sample is 100 ppm or less, more than 5 g of the sample was collected with a Terumo syringe in a glove box with a dew point of -60°C or lower, and the water content in the sample was measured. This analytical method was able to quantify if the water content in the sample was 1 ppm or more.

[0049] (Method for Measuring the Contents of Benzene and IPA in the Sample) The contents of benzene and IPA in the sample were measured by gas chromatography analysis. Apparatus: Gas chromatography analyzer GC-8A (manufactured by Shimadzu Corporation) Detector: TCD Carrier: Hydrogen Column: Porapak T Column temperature: 130°C Inlet temperature: 150°C Injection volume: 5 μL

[0050] <Example 1> The crude IPA derived from the IPA-containing waste liquid recovered from a semiconductor manufacturing apparatus equipped with a rinse section of a semiconductor substrate was purified by an apparatus obtained by partially modifying the apparatus for producing purified IPA shown in FIGS. 1 and 2 to obtain purified IPA. As the crude IPA, an azeotropic mixture (88% by mass of IPA, 12% by mass of water) obtained by subjecting the IPA waste liquid to low-boiling distillation to remove low-boiling impurities from the top of the column and then high-boiling distillation to remove high-boiling impurities from the bottom of the column was used.

[0051] Here, the capacity of the phase separation chamber 8 was 24 L, the capacity of the upper-phase liquid storage chamber 10 was 15 L, and the capacity of the lower-phase liquid storage chamber 11 was 15 L. Also, the height of the upper end of the first partition wall 9a was 30 cm lower than the height of the second partition wall 9b, and it was at a height separated by an interval of 1 / 5 of the length from the upper end to the lower end of the second partition wall 9b.

[0052] Furthermore, one open end of the liquid delivery pipe 14 was connected to the bottom of the phase separation chamber 8 and communicated with the lower-phase liquid 6, and the other open end of the liquid delivery pipe 14 communicated with the lower-phase liquid storage chamber 11. Also, the height of the upward bending portion 12 of the liquid delivery pipe 14 (the height of the highest part of the pipe peripheral wall) was at a height separated downward by an interval of 1 / 10 of the length from the upper end to the lower end of the first partition wall 9a. Furthermore, the open end of the branch portion 13 was at a position 50 cm higher than the upper end of the first partition wall 9a and communicated with the gas phase portion of the phase separation tank 4.

[0053] After accommodating an amount of water such that the height from the bottom of the phase separation chamber 8 became 120 cm, crude IPA was supplied to the phase separation chamber 8 via the first supply pipe at a flow rate of 0.3 m / s. Here, the residence time of the mixed liquid of crude IPA and the azeotropic agent in the phase separation chamber 8 was 25 minutes.

[0054] Also, benzene as an azeotropic agent was supplied to the phase separation chamber 8 via the fourth supply pipe 17 in an amount such that it became 90 parts by mass with respect to 100 parts by mass of the crude IPA supplied to the phase separation chamber 8, and it was phase-separated into an upper-phase liquid 5 containing the azeotropic agent, water, and IPA, and a lower-phase liquid 6 containing water and IPA.

[0055] The upper-phase liquid 5 formed in the phase separation chamber 8 overflowed the upper end of the first partition wall 9a and flowed into the upper-phase liquid storage chamber 10. On the other hand, the lower-phase liquid 6 formed in the phase separation chamber 8 was sent to the lower-phase liquid storage chamber 11 via the liquid delivery pipe 14.

[0056] The upper-phase liquid 5 that flowed into the upper-phase liquid storage chamber 10 had a composition of 26% by mass of IPA and 1% by mass of water, and the water content was significantly reduced with respect to the crude IPA. The upper-phase liquid 5 was supplied to the raw material supply stage of the azeotropic distillation column 2 via the second supply pipe at a flow rate of 59 L / h and subjected to azeotropic distillation.

[0057] Here, the azeotropic distillation column 2 is a packed column with a packing height of 100 cm, and it was confirmed by experiments that the number of theoretical plates is 35. In addition, a condenser 3 was provided at the top of the azeotropic distillation column 2. Considering the flow rate of the upper-phase liquid 5, the azeotropic distillation column 2 was designed to be small-sized with a diameter of 10 cm.

[0058] In the azeotropic distillation column 2, the temperature at the top of the column was set to 68°C, and the gauge pressure at the top of the column was set to 0 kPaG. Also, a first distillate containing an azeotropic mixture of benzene and water and IPA was supplied from the top of the azeotropic distillation column 2 to the phase separation tank 4 via the third supply pipe 15 and circulated, and the reflux flow rate of the first distillate was set to 59 L / h. Here, the composition of the first distillate was 68% by mass of benzene, 6% by mass of water, and 26% by mass of IPA.

[0059] Also, the lower-phase liquid 6 sent to the lower-phase liquid storage chamber 11 was supplied to the IPA recovery distillation column 19 at 4 L / h via the fifth supply pipe 18 and distilled. At this time, a second distillate containing an azeotropic mixture of IPA and water was withdrawn from the top of the IPA recovery distillation column 19 at 1.7 L / h and supplied to the phase separation tank 4 via a separately provided supply pipe. That is, in this example, the second distillate was not withdrawn from above the side of the IPA recovery distillation column 19. Also, a third distillate containing low-boiling impurities was not withdrawn from the top of the IPA recovery distillation column 19 via the third extraction pipe 22. On the other hand, a second bottoms liquid containing water was withdrawn from the bottom of the IPA recovery distillation column 19 via the second extraction pipe 21. In the IPA recovery distillation column 19, the temperature at the top of the column was set to 85°C, and the gauge pressure at the top of the column was set to 10 kPaG.

[0060] By purifying the above-mentioned crude IPA, the purified IPA withdrawn from the first extraction pipe 16 had a water content of 30 ppm, a purity (excluding the water content) of 99.99% by mass, and was of high quality as anhydrous IPA.

[0061] On the other hand, when the crude IPA was directly supplied to the feed stage of the azeotropic distillation column 2 without being supplied to the phase separation tank 4 and subjected to azeotropic distillation, the flow rate of the crude IPA was calculated to be 62 L / h, which was a value larger than the flow rate (59 L / h) of the upper-phase liquid 5 in Example 1. And the amount of heat consumed in the azeotropic distillation column 2 was calculated to be 32.8 MJ / h, which was significantly increased compared to the amount of heat (23.7 MJ / h) consumed in the azeotropic distillation column 2 in Example 1. Also, the diameter of the azeotropic distillation column 2 was calculated to require 12 cm, which was a value larger than the diameter (10 cm) of the azeotropic distillation column 2 in Example 1.

Explanation of Symbols

[0062] 1; First supply pipe 2; Azeotropic distillation column 3; Condenser 4; Phase separation tank 5; Upper-phase liquid 6; Lower-phase liquid 7; Second supply pipe 8; Phase separation chamber 9a; First partition wall 9b; Second partition wall 10; Upper-phase liquid storage chamber 11; Lower-phase liquid storage chamber 12; Upward bending part 13; Branch part 14; Liquid supply pipe 15; Third supply pipe 16; First extraction pipe 17; Fourth supply pipe 18; Fifth supply pipe 19; IPA recovery distillation column 20; Sixth supply pipe 21; Second extraction pipe 22; Third extraction pipe

Claims

1. A method for producing purified isopropyl alcohol by dehydrating crude isopropyl alcohol containing water as an impurity, comprising: A phase separation step of placing the mixture of the crude isopropyl alcohol and the azeotropic agent in a phase separation tank and separating the mixture into an upper phase liquid containing the azeotropic agent, water, and isopropyl alcohol and a lower phase liquid containing water; and an azeotropic distillation step of azeotropically distilling the upper phase liquid in an azeotropic distillation column to extract a distillate containing an azeotropic mixture of the azeotropic agent and water and a bottoms containing isopropyl alcohol, The method for producing purified isopropyl alcohol, wherein the distillate is supplied to the phase separation tank.

2. The phase separation tank comprises: a) a phase separation chamber in which the mixed liquid is accommodated and separated into the upper phase liquid and the lower phase liquid; b) an upper phase liquid storage chamber adjacent to the phase separation chamber via a first partition wall on one side of the phase separation chamber, and in which the upper phase liquid overflows the first partition wall and flows in from the phase separation chamber; c) a lower phase liquid storage chamber adjacent to the phase separation chamber via a second partition wall on the other side of the phase separation chamber, and in which the lower phase liquid sent from the phase separation chamber via a liquid sending pipe is stored; It is divided into two sections, the liquid delivery pipe is a communication pipe having a first open end communicating with the lower phase liquid contained in the phase separation chamber and a second open end communicating with the lower phase liquid containing chamber; the communicating pipe has a maximum portion at a height corresponding to an upper end region of the first partition wall, an upwardly bent portion including the second opening end, and a third opening end at a position higher than the upper end of the first partition wall, the third opening end being connected to a gas phase portion of the phase separation tank at a position higher than the upper end of the first partition wall, and a branch portion branching off from the upwardly bent portion, a supply pipe for supplying the upper phase liquid to a raw material supply stage of the azeotropic distillation column is connected to the upper phase liquid storage chamber, A discharge pipe for discharging the lower phase liquid is connected to the lower phase liquid storage chamber, 2. The method for producing purified isopropyl alcohol according to claim 1, wherein an upper end of the first partition wall is lower than an upper end of the second partition wall.

3. The method for producing purified isopropyl alcohol according to claim 1 or 2, wherein the azeotropic agent is benzene.

4. The lower phase liquid further comprises isopropyl alcohol; The method further includes a step of distilling the lower phase liquid in an isopropyl alcohol recovery distillation column and extracting a second distillate containing an azeotropic mixture of isopropyl alcohol and water, and a second bottoms containing water; The method for producing purified isopropyl alcohol according to claim 1 or 2, wherein the second distillate is supplied to the phase separation tank.

5. The second distillate is withdrawn from the upper side of the isopropyl alcohol recovery distillation column, The method for producing purified isopropyl alcohol according to claim 4, wherein low-boiling impurities are extracted from the top of the isopropyl alcohol recovery distillation column and disposed of.

6. An apparatus for producing purified isopropyl alcohol by dehydrating crude isopropyl alcohol containing water as an impurity, A phase separation tank that accommodates a mixture of the crude isopropyl alcohol and an azeotropic agent and separates the mixture into an upper phase liquid containing the azeotropic agent, water, and isopropyl alcohol and a lower phase liquid containing water; and an azeotropic distillation column for azeotropically distilling the upper phase liquid, The phase separation tank is connected to a first supply pipe for supplying the crude isopropyl alcohol to the phase separation tank, and a second supply pipe for supplying the upper phase liquid to a raw material supply stage of the azeotropic distillation column; A third supply pipe is connected to the top of the azeotropic distillation column, and supplies a distillate containing an azeotropic mixture of the entrainer and water to the phase separation tank. A withdrawal pipe for withdrawing bottoms containing isopropyl alcohol is connected to the bottom of the azeotropic distillation column, A fourth supply pipe for supplying the azeotropic agent is connected to any one of the first supply pipe, the phase separation tank, the second supply pipe, the azeotropic distillation column, and the third supply pipe.

7. The phase separation tank comprises: a) a phase separation chamber in which the mixed liquid is accommodated and separated into the upper phase liquid and the lower phase liquid; b) an upper phase liquid storage chamber adjacent to the phase separation chamber via a first partition wall on one side of the phase separation chamber, and in which the upper phase liquid overflows the first partition wall and flows in from the phase separation chamber; c) a lower phase liquid storage chamber adjacent to the phase separation chamber via a second partition wall on the other side of the phase separation chamber, and in which the lower phase liquid sent from the phase separation chamber via a liquid sending pipe is stored; It is divided into two sections, the liquid delivery pipe is a communication pipe having a first open end communicating with the lower phase liquid contained in the phase separation chamber and a second open end communicating with the lower phase liquid containing chamber; the communicating pipe has a maximum portion at a height corresponding to an upper end region of the first partition wall, an upwardly bent portion including the second opening end, and a third opening end at a position higher than the upper end of the first partition wall, the third opening end being connected to a gas phase portion of the phase separation tank at a position higher than the upper end of the first partition wall, and a branch portion branching off from the upwardly bent portion, The second supply pipe is connected to the upper phase liquid storage chamber, A discharge pipe for discharging the lower phase liquid is connected to the lower phase liquid storage chamber, The apparatus for producing purified isopropyl alcohol according to claim 6, wherein an upper end of the first partition wall is lower than an upper end of the second partition wall.

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