Method for producing isopropyl alcohol

Abstract

The present invention provides a method for producing isopropyl alcohol (IPA), the method comprising: (S1) supplying the reaction product of propylene monomer and water to a gas purification section to separate the gas component containing unreacted propylene monomer; (S2) supplying the reaction product from which the gas component has been separated to a first organic matter removal column to discharge an upper stream containing organic by-products and isopropyl alcohol, and a lower stream containing isopropyl alcohol, n-propyl alcohol (NPA) by-products and water; (S3) supplying the upper discharge stream from the first organic matter removal column to a second organic matter removal column and adding process circulating water to discharge an upper stream containing organic by-products and a lower stream containing isopropyl alcohol and process circulating water; and (S4) supplying the lower discharge stream from the first organic matter removal column to an isopropyl alcohol (IPA) purification section including a plurality of distillation columns to separate isopropyl alcohol.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0119554 filed on September 8, 2023, and all contents disclosed in the documents of the corresponding Korean patent application are incorporated as a part of the present specification.

[0002] The present invention relates to a method for producing isopropyl alcohol, and more particularly, to a method for reducing energy consumption and minimizing loss of isopropyl alcohol.

Background Art

[0003] Isopropyl alcohol (IPA) is used in various applications in the electronic industry such as the manufacture of semiconductors and LCD (Liquid Crystal Display), including cleaning agents, raw materials for industrial coatings and reagents, and solvents for paints, inks and the like.

[0004] Such isopropyl alcohol can be produced by reacting propylene with water. For example, propylene monomer and water are subjected to a gas phase reaction in a reaction section to obtain a reaction product including by-products such as isopropyl alcohol, unreacted propylene monomer, unreacted water, and organic substances, and the gas-phase reaction product is subjected to a subsequent column to separate propylene monomer, water and by-products, which is accompanied by a process of purifying isopropyl alcohol.

[0005] According to the IPA manufacturing process shown in Figure 1, a feed 1 containing propylene monomer and water is supplied to a reactor 100 and reacted to obtain a gas-phase reaction product 101. The reaction product 101 is then purified in a gas purification section including an absorption tower 201 and a gas purification tower 202 to remove unreacted propylene gas 201a and low-boiling point gas components 202a. The stream 202b containing the IPA, water, and by-products from which the gas components have been removed is supplied to an organic matter removal tower 301 to remove organic by-products. The water removal tower 302 separates the upper stream 302a containing IPA, the lower stream 302b containing water, and the side stream 302c containing NPA. The upper stream 302a is supplied to an IPA recovery tower 303 to obtain IPA from which water has been separated by a solvent. The stream 303a containing the solvent and water separated in the IPA recovery tower 303 is separated in the solvent recovery tower 304 into an upper stream 304a of solvent and a lower stream 304b of water.

[0006] A portion of the water 302b recovered from the bottom of the water removal column 302 during the IPA purification process can be recovered and used as process circulating water. Typically, more than eight times the amount of circulating water produced by the IPA is used. Approximately 40% of the circulating water used is fed into the absorption column 201, where the gaseous IPA can be absorbed into the water and separated into the liquid phase. The remaining approximately 60% is fed into the organic matter removal column 301, where organic by-products such as diisopropyl ether (DIPE) and hexene are removed using liquid-liquid equilibrium.

[0007] Here, the organic matter removal tower 301 receives both the liquid phase stream 202b containing IPA (isopropyl alcohol) from which gaseous components have been removed in the preceding gas purification section, water, and by-products, along with a large amount of circulating water. This can potentially cause an excessive increase in the flow rate supplied to the water removal tower 302, which is located downstream of the organic matter removal tower 301, resulting in a higher steam requirement.

[0008] Therefore, there is a need for methods to reduce energy consumption by decreasing steam requirements throughout the entire IPA manufacturing process. [Overview of the project] [Problems that the invention aims to solve]

[0009] The present invention aims to solve the problems mentioned in the background art of the above invention and provides a method that can minimize energy consumption and cost increases by reducing the use of circulating water in the isopropyl alcohol production process. [Means for solving the problem]

[0010] According to one aspect of the present invention for solving the above problems, (S1) A step of supplying the reaction product of propylene monomer and water to a gas purification unit to separate the gas component containing unreacted propylene monomer, (S2) The reaction product from which the gas components have been separated is supplied to a first organic matter removal tower to discharge an upper stream containing organic by-products and isopropyl alcohol, and a lower stream containing isopropyl alcohol (IPA), n-propyl alcohol (NPA) by-products and water. (S3) The upper discharge stream of the first organic matter removal tower is supplied to the second organic matter removal tower, and process circulating water is introduced to discharge the upper stream containing organic by-products and the lower stream containing isopropyl alcohol and process circulating water. A method for producing isopropyl alcohol is provided, which includes the step of (S4) supplying the lower discharge stream of the first organic matter removal column to an isopropyl alcohol (IPA) purification section including a plurality of distillation columns to separate isopropyl alcohol. [Effects of the Invention]

[0011] According to the present invention, by applying two organic matter removal towers, the first organic matter removal tower separates the upper stream containing organic by-products and a portion of isopropyl alcohol without supplying process circulating water, and the separated upper stream is brought into contact with a small amount of process circulating water in the second organic matter removal tower to dissolve IPA, thereby separating the organic by-products and isopropyl alcohol. This reduces the supply flow rate of the subsequent IPA purification section and thus reduces the amount of steam used.

[0012] Reducing steam usage in the IPA purification process in this way leads to overall energy savings and minimizes cost increases by allowing for a reduction in the size of the distillation columns used for IPA purification. [Brief explanation of the drawing]

[0013] [Figure 1] This diagram shows the process sequence for the conventional IPA manufacturing. [Figure 2] This figure illustrates a method for manufacturing IPA according to one embodiment of the present invention. [Modes for carrying out the invention]

[0014] The terms and words used in the description and claims of this invention should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather should be interpreted in a manner consistent with the technical idea of ​​this invention, in accordance with the principle that inventors may appropriately define the concepts of terms in order to best describe their invention.

[0015] As used in this application, the meaning of “includes” or “contains” is to embody a particular characteristic, domain, constant, step, operation, element, or component, and not to exclude the addition of other particular characteristics, domain, constant, step, operation, element, or component.

[0016] As used in this application, the term "stream" may mean the flow of fluid within a process, or it may mean the fluid itself flowing through piping. Specifically, the stream may simultaneously mean the fluid itself and the flow of fluid within piping connecting each device. Furthermore, the fluid may contain one or more components of gas, liquid, and solid.

[0017] As used in this application, the term "upper part" means a point at a height of 0-20% below the top of the device, unless otherwise specified, and specifically may mean the very top (top of the tower). The term "lower part" means a point at a height of 80-100% below the top of the device, and specifically may mean the very bottom (bottom of the tower).

[0018] As used in this application, the term "side stream" may mean, unless otherwise specified, a stream discharged from the top of the device downwards at a height of 25-80% or 40-70%.

[0019] Furthermore, the term "pressure" as used in this application refers to gauge pressure measured relative to atmospheric pressure.

[0020] On the other hand, in the present invention, in devices such as absorption towers, purification towers, removal towers, and recovery towers, the operating temperature of the device may refer to the upper or lower temperature of the device unless otherwise specified. Also, the operating pressure of the device may refer to the upper pressure of the device unless otherwise specified.

[0021] One embodiment of the present invention relates to a method for producing isopropyl alcohol (IPA), and the method for producing IPA according to the present invention will be described in detail below with reference to the drawings.

[0022] Figure 2 illustrates a method for producing isopropyl alcohol according to one embodiment of the present invention. Isopropyl alcohol can be produced using a system comprising: a reactor 100; a gas purification section including an absorption tower 201 and a gas purification tower 202; a first organic matter removal tower 301' and a second organic matter removal tower 301''; and an IPA purification section including a water removal tower 302, an IPA recovery tower 303, a solvent recovery tower 304 and a high-boiling-point substance removal tower 305. In addition, the system can further be equipped with, for use, a reboiler for transferring heat to heat the feed stream of each of the towers, a condenser for converting the overhead stream generated by said heating from a gas phase to a liquid phase, a decanter for liquid-liquid separation of the condensed stream, a valve for controlling the flow of the stream, a pump, and the like.

[0023] Referring to Figure 2, a feed 1 containing propylene monomer and water is supplied to a reactor 100, and a reaction product 101 containing isopropyl alcohol can be obtained through a gas phase reaction process.

[0024] Since only a part of the propylene monomer supplied to the reactor 100 is used in the reaction, the reaction product can contain unreacted propylene monomer and unreacted water in addition to the isopropyl alcohol produced by the reaction of propylene monomer and water. For example, the reaction product 101 can contain 65 to 85% by weight of unreacted propylene monomer, 4 to 8% by weight of isopropyl alcohol, and 5 to 30% by weight of water. In addition, the reaction product can contain, as by-products, organic substances such as diisopropyl ether (DIPE), hexene, hexanol, acetone, n-propyl alcohol (NPA), and the like. Therefore, a step of separating unreacted raw materials from the reaction product and purifying isopropyl alcohol from various by-products is required.

[0025] First, the reaction product 101 obtained by the gas phase reaction of propylene monomer and water is supplied to a gas purification section to separate gas components including unreacted propylene monomer (S1).

[0026] Specifically, the reaction product 101 is supplied to the lower stage of the absorption tower 201, and process circulating water is introduced to the upper stage of the absorption tower 201 to separate the unreacted propylene monomer. Here, the process circulating water can be water recovered from the distillation tower, i.e., the water removal tower 302, which is included in the subsequent IPA purification section. In the absorption tower 201, the gaseous isopropyl alcohol contained in the reaction product is absorbed by the process circulating water and obtained as the lower liquid phase stream 201b, and in the upper stage, the gaseous stream 201a containing the unreacted propylene monomer can be separated. The unreacted propylene monomer contained in the gaseous stream 201a is recovered in the reactor 100 and reused as a raw material for the production of isopropyl alcohol.

[0027] In one embodiment of the present invention, the flow rate of the process circulating water supplied to the absorption tower 201 can be 15 to 40% by weight or 15 to 35% by weight of the flow rate of the reaction product. When the process circulating water is supplied at a flow rate within the above range, the absorption capacity of isopropyl alcohol contained in the reaction product can be improved, and the energy costs for recovering the process circulating water in the subsequent stages can be prevented from increasing excessively.

[0028] The absorption tower 201 can be operated at a temperature of 90-100°C or 90-95°C and a pressure of 25-40 kg / cm²·g (2.45-3.92 MPa·g) or 25-35 kg / cm²·g (2.45-3.43 MPa·g). When these operating conditions are met, the upper discharge stream containing unreacted propylene monomer and the lower discharge stream containing isopropyl alcohol can be effectively separated.

[0029] On the other hand, the lower liquid phase stream of the absorption tower 201 may contain small amounts of low-boiling point gas components, including unreacted propylene monomers that have not yet been separated, in addition to isopropyl alcohol and unreacted water. For example, the content of unreacted propylene monomers and other low-boiling point gas components in the lower liquid phase stream of the absorption tower 201 may be 5% by weight or less, or in the range of 2 to 5% by weight.

[0030] Therefore, the liquid phase stream 201b containing isopropyl alcohol separated in the absorption tower 201 can be supplied to one or more gas purification towers 202 to separate it into an upper stream 202a containing low-boiling point components and a lower stream 202b containing isopropyl alcohol, water, and by-products.

[0031] If necessary, the lower liquid phase stream of the absorption tower 201 can be supplied to the gas purification tower 202 after passing through one or more flash drums. That is, first, the low-boiling point components are separated in the flash drums, and this is then supplied again to the gas purification tower 202 to separate the unreacted propylene monomer and inert gas low-boiling point components in the upper part from trace amounts of high-boiling point components in the lower part.

[0032] The upper stream 202a, which contains low-boiling point components separated in the gas purification tower 202, may contain unreacted propylene monomers and inert gases (e.g., ethane, propane). Unreacted propylene monomers contained in the upper stream of the gas purification tower 202 can be recovered in reactor 100, and the inert gases can be branched off for exhaust.

[0033] On the other hand, the lower stream 202b separated in the gas purification column 202 may contain isopropyl alcohol, water, and, as by-products, organic substances such as n-propyl alcohol (NPA), diisopropyl ether (DIPE), hexene, and acetone.

[0034] Therefore, it is necessary to remove organic by-products from the lower discharge stream 202b of the gas purification tower.

[0035] In conventional IPA manufacturing processes, process circulating water recovered from the water removal column 302 is supplied to the organic matter removal column to remove organic by-products from the reaction product from which the gaseous components have been separated. This water is then used to separate the organic by-products using liquid-liquid phase equilibrium. The process circulating water is supplied to the organic matter removal column at a rate of 70-95% by weight or 80-90% by weight of the supply stream flow rate to dissolve isopropyl alcohol. In such cases, the process circulating water used in the preceding absorption column and the process circulating water used in the organic matter removal column are combined and flow into the distillation column of the subsequent IPA purification section, resulting in a problem of increased steam demand due to excessive flow rates.

[0036] To solve these problems, the present invention employs two organic matter removal towers. In the first organic matter removal tower, the upper stream containing organic by-products and a portion of isopropyl alcohol is separated without the supply of process circulating water. In the second organic matter removal tower, the separated upper stream is brought into contact with a small amount of process circulating water to dissolve IPA and remove the organic by-products.

[0037] To explain in more detail, first, the reaction product from which the gas components have been separated, i.e., the lower discharge stream 202b of the gas purification tower, is supplied to the first organic matter removal tower 301', and the components are separated by boiling point without the supply of process circulating water (S2).

[0038] The stream supplied to the first organic matter removal tower 301' may contain isopropyl alcohol, water, n-propyl alcohol (NPA) by-products, and organic by-products (e.g., diisopropyl ether (DIPE), hexene, hexanol, acetone, or mixtures thereof).

[0039] In the first organic matter removal tower 301', since process circulating water is not supplied during component separation, isopropyl alcohol is not dissolved by water. Therefore, the stream, which is heated by the heat provided by the reboiler connected to the lower part of the first organic matter removal tower 301', moves to the upper part, and is then discharged through the condenser, may contain some isopropyl alcohol along with organic by-products. For example, the upper stream 301'a of the first organic matter removal tower may contain 5-25% by weight, more specifically 10-20% by weight, of the total isopropyl alcohol supplied to the first organic matter removal tower.

[0040] As a result, the stream supplied to the first organic matter removal tower 301' can be separated into an upper stream 301'a containing organic by-products and isopropyl alcohol, and a lower stream 301'b containing isopropyl alcohol, n-propyl alcohol (NPA) by-products and water.

[0041] To recover the isopropyl alcohol contained in the upper stream 301'a of the first organic matter removal tower, the upper discharge stream 301'a of the first organic matter removal tower is supplied to the second organic matter removal tower 301'', and a small amount of process circulating water is added to separate it into the upper stream 301''a containing organic by-products and the lower stream 301''b containing isopropyl alcohol and process circulating water (S3).

[0042] More specifically, a second organic matter removal tower 301'' is placed downstream of the condenser connected to the first organic matter removal tower 301', and a stream 301'a containing organic by-products and isopropyl alcohol is supplied to the second organic matter removal tower 301''. In this case, the isopropyl alcohol content in the stream 301'a supplied to the second organic matter removal tower 301'' is at a level corresponding to 10% to 20% of the isopropyl alcohol content in the supply stream of the first organic matter removal tower 301'. Therefore, even if a small amount of process circulating water is introduced into the second organic matter removal tower 301'', the isopropyl alcohol contained in the supply stream 301'a can be effectively separated. That is, a small amount of process circulating water selectively dissolves the isopropyl alcohol contained in the supply stream using the difference in solubility and moves to the lower section, thereby separating it from the organic by-products.

[0043] The isopropyl alcohol dissolved in the circulating water of the process is discharged into the lower stream 301''b of the second organic matter removal tower, and then recirculated to the first organic matter removal tower 301', thereby minimizing the loss of isopropyl alcohol.

[0044] In one embodiment of the present invention, the first organic matter removal tower 301' can be operated at a temperature of 75 to 130°C or 80 to 105°C and a pressure of 0 to 2 kg / cm²·g (0 to 0.20 MPa·g) or 0 to 0.5 kg / cm²·g (0 to 0.049 MPa·g). When these operating conditions are met, organic by-products can be effectively separated from the mixing stream even without the supply of process circulating water.

[0045] Furthermore, the second organic matter removal tower 301'' can be operated at a temperature of 75-125°C or 80-105°C and a pressure of 0-2 kg / cm²·g (0-0.20 MPa·g) or 0-0.5 kg / cm²·g (0-0.049 MPa·g). When these operating conditions are met, the efficiency of dissolving isopropyl alcohol can be increased even by adding a small amount of process circulating water.

[0046] In the second organic matter removal column 301'', the flow rate of the process circulating water can be adjusted so that it comes into contact with isopropyl alcohol in a weight ratio of 2.5:1 to 5:1. This flow rate of process circulating water is significantly lower than the amount of process circulating water supplied to the feedstream in the existing organic matter removal column in the conventional IPA manufacturing process, which was approximately 80% by weight or more. This reduces the supply flow rate to the distillation column included in the subsequent IPA purification section, thereby reducing steam usage.

[0047] On the other hand, the liquid phase stream 301'b separated at the bottom of the first organic matter removal tower 301' may contain 9-12% by weight of isopropyl alcohol, 0.1-1% by weight of n-propyl alcohol, and 87-90% by weight of water, based on its total weight.

[0048] In other words, the liquid phase stream 301'b may contain a large amount of water, including unreacted water discharged from the reactor 100 and process circulating water used to absorb gaseous isopropyl alcohol in the absorption tower 201, as well as n-propyl alcohol (NPA), a reaction by-product. Therefore, a large amount of water and NPA by-products are removed in an IPA purification section, which includes multiple distillation towers, to separate high-purity isopropyl alcohol (S4).

[0049] Specifically, the lower discharge stream 301'b of the first organic matter removal tower 301' is supplied to the water removal tower 302, separating and discharging the upper stream 302a containing isopropyl alcohol, the lower stream 302b containing water, and the side stream containing n-propyl alcohol (NPA).

[0050] The upper stream 302a separated in the water removal tower 302 contains an azeotropic mixture of isopropyl alcohol and water, and may include, for example, 85-90% by weight of isopropyl alcohol and 10-15% by weight of water.

[0051] The water separated as the lower stream 302b of the water removal tower 302 can be recovered and used as process circulating water. As described above, the water separated in the water removal tower 302 can be supplied to the preceding absorption tower 201 and used to absorb isopropyl alcohol in the gas phase. Also, since the water separated in the water removal tower 302 is at a high temperature of over 100°C, it can be used for heat exchange to preheat the water supplied to the reactor 100, if necessary.

[0052] The water removal tower 302 can be operated at a temperature of 70-150°C or 80-140°C and a pressure of 0-5 kg / cm²·g (0-0.49 MPa·g) or 0-3 kg / cm²·g (0-0.29 MPa·g). When these operating conditions are met, the azeotropic mixture of isopropyl alcohol and water can be effectively separated.

[0053] Subsequently, the upper discharge stream 302a of the water removal tower 302 is supplied to the IPA recovery tower 303, and an organic solvent (e.g., cyclohexane, benzene, etc.) is added as an azeotrope to discharge the upper stream 303a containing water and organic solvent, and the lower stream containing IPA. That is, in the IPA recovery tower 303, the azeotrope of isopropyl alcohol and water is broken by the organic solvent, making it possible to obtain highly purified isopropyl alcohol.

[0054] The water and organic solvent separated at the top of the IPA recovery tower are supplied to the solvent recovery tower 304 via stream 303a, where they are separated into an upper stream 304a of solvent and a lower stream 304b of water, which can then be discharged. The solvent stream 304 can be recycled back to the IPA recovery tower 303.

[0055] On the other hand, the side discharge stream 302c of the water removal tower 302, which contains n-propyl alcohol (NPA), is supplied to the high-boiling-point substance removal tower 305, which discharges the NPA-containing stream 305b to the bottom, and the upper stream 305a can also be recirculated back to the water removal tower 302.

[0056] According to the present invention as described above, by applying two organic matter removal towers, the first organic matter removal tower separates the upper stream containing organic by-products and a portion of isopropyl alcohol without supplying process circulating water, and the second organic matter removal tower separates the separated upper stream by contacting it with a small amount of process circulating water to dissolve IPA and separate the organic by-products and isopropyl alcohol, thereby reducing the supply flow rate of the subsequent IPA purification section and decreasing the amount of steam used.

[0057] Reducing steam usage in the IPA purification process in this way leads to energy savings throughout the entire process, and minimizes cost increases by allowing for a reduction in the size of the distillation columns used for IPA purification.

[0058] The present invention will be described in more detail below with reference to examples. However, the following examples are for illustrative purposes only, and it will be obvious to an ordinary person that various changes and modifications are possible within the scope of the present invention and the technical concept, and the scope of the present invention is not limited to these examples alone.

[0059] The following examples and comparative examples simulate the method according to the present invention using the commercial process simulation program AspenPlus. The constants required for the simulation were values ​​built into the program, values ​​described in the literature, etc.

[0060] Example 1 As shown in Figure 2, isopropyl alcohol was produced using a system comprising a reactor 100; a gas purification section including an absorption tower 201 and a gas purification tower 202; a first organic matter removal tower 301' and a second organic matter removal tower 301''; and an IPA purification section including a water removal tower 302, an IPA recovery tower 303, a solvent recovery tower 304, and a high-boiling-point substance removal tower 305.

[0061] (Step 1) Gas separation in the gas purification section In the reactor 100, feed 1 containing water at 100°C and propylene monomer was supplied and a gas-phase reaction was carried out. The resulting reaction product 101 was then supplied to the lower stage of the absorption tower 201, and 40% of the process circulating water recovered in the water removal tower 302 of the IPA purification section was added to the upper stage of the absorption tower 201.

[0062] In the absorption tower 201, the liquid phase stream 201b, from which the gas-phase isopropyl alcohol had been absorbed, was discharged to the bottom, and the gas-phase stream 201a containing unreacted propylene monomer was separated to the top and circulated to the reactor 100.

[0063] The liquid phase stream 201b, which absorbed the isopropyl alcohol, was passed through the gas purification column 202 and separated into a low-boiling point upper stream 202a and a lower stream 202b containing isopropyl alcohol, water, and by-products.

[0064] (Step 2) Separate organic by-products in the first organic matter removal tower without supplying process circulating water. The lower stream 202b of the gas purification tower was supplied to the first organic matter removal tower 301', and without supplying process circulating water, component separation was performed based on boiling point, separating the stream into an upper stream 301'a containing organic by-products and some isopropyl alcohol (about 10% of the total isopropyl alcohol) and a lower stream 301'b containing isopropyl alcohol, n-propyl alcohol (NPA) by-products and water.

[0065] (Step 3) Process circulating water is introduced into the second organic matter removal tower to recover some of the IPA. The upper discharge stream 301'a of the first organic matter removal tower 301' was supplied to the second organic matter removal tower 301'', and a portion of the process circulating water recovered in the water removal tower 302 of the IPA purification section was supplied to separate it into the upper stream 301''a containing organic by-products and the lower stream 301''b containing isopropyl alcohol and process circulating water. The lower stream 301''b was recovered and recycled to the first organic matter removal tower 301'. Here, the supply flow rate of the process circulating water was controlled so that the process circulating water and isopropyl alcohol came into contact in the second organic matter removal tower 301'' at a flow rate ratio of 3:1, resulting in a supply rate of 6% by weight of the flow rate of stream 202b supplied to the first organic matter removal tower 301'.

[0066] (Step 4) IPA separation in the IPA purification section The stream 301'b discharged from the lower part of the first organic matter removal tower 301' was supplied to the water removal tower 302, where the upper stream 302a containing isopropyl alcohol, the lower stream 302b containing water, and the side stream containing n-propyl alcohol (NPA) were separated and discharged. After recovering the water as the lower stream 302b, a portion of it was supplied to the upstream absorption tower 201 and the second organic matter removal tower 301''.

[0067] The upper discharge stream 302a of the water removal tower 302 was supplied to the IPA recovery tower 303, cyclohexane was added as an azeotrope, and the water and cyclohexane were discharged into the upper stream 303a, while the IPA was separated into the lower section.

[0068] Meanwhile, the side discharge stream 302c of the water removal tower 302 containing n-propyl alcohol (NPA) was supplied to the high-boiling-point substance removal tower 305, and the stream 305b containing NPA was discharged to the bottom, while the upper stream 305a was recirculated back to the water removal tower 302.

[0069] Comparative Example 1 As shown in Figure 1, isopropyl alcohol was produced using a system comprising a reactor 100; a gas purification section including an absorption tower 201 and a gas purification tower 202; an organic matter removal tower 301; and an IPA purification section including a water removal tower 302, an IPA recovery tower 303, a solvent recovery tower 304, and a high-boiling-point substance removal tower 305.

[0070] (Step 1) Gas separation in the gas purification section The same process as in Step 1 of Example 1 was followed.

[0071] (Step 2) Organic by-products are separated by supplying process circulating water to a single organic matter removal tower. The lower stream 202b of the gas purification tower was supplied to the organic matter removal tower 301, and process circulating water recovered in the water removal tower 302 of the IPA purification section was supplied to the organic matter removal tower 301 in an amount equal to 88% by weight of the flow rate of stream 202b supplied to the organic matter removal tower 301, separating it into a liquid phase 301a containing organic by-products and a liquid phase 301b containing isopropyl alcohol and water. The process circulating water used was water separated and recovered in the downstream water removal tower 302.

[0072] (Step 3) Separate the IPA in the IPA purification section. The stream 301b discharged from the lower part of the organic matter removal tower 301 was supplied to the water removal tower 302, where the upper stream 302a containing isopropyl alcohol, the lower stream 302b containing water, and the side stream containing n-propyl alcohol (NPA) were separated and discharged. After recovering the water as the lower stream 302b, it was supplied to the upstream absorption tower 201 and the organic matter removal tower 301.

[0073] The upper discharge stream 302a of the water removal tower 302 was supplied to the IPA recovery tower 303, cyclohexane was added as an azeotrope, and the water and cyclohexane were discharged into the upper stream 303a, while the IPA was separated into the lower section.

[0074] Meanwhile, the side discharge stream 302c of the water removal tower 302 containing n-propyl alcohol (NPA) was supplied to the high-boiling-point substance removal tower 305, and the stream 305b containing NPA was discharged to the bottom, while the upper stream 305a was recirculated back to the water removal tower 302.

[0075] Comparative Example 2 The same process as in Comparative Example 1 was carried out, except that the circulating process water recovered in the water removal tower 302 of the IPA purification section was supplied to the organic matter removal tower 301 so that it amounted to 6% by weight of the flow rate of the supply stream 202b.

[0076] Table 1 below compares the purification process and results of IPA in the examples and comparative examples.

[0077] [Table 1]

[0078] As shown in Table 1 above, in Example 1, in the first organic matter removal tower, without supplying process circulating water, the upper stream containing organic by-products and a portion of the IPA was separated. Then, a small amount of process circulating water (6% of the supply stream flow rate of the first organic matter removal tower) was introduced into the second organic matter removal tower to dissolve the IPA contained in the upper stream of the first organic matter removal tower and separate the organic by-products and isopropyl alcohol. This reduced the supply flow rate of the water removal tower in the IPA purification section, decreased steam usage, and maintained a high IPA recovery rate.

[0079] In contrast, in Comparative Example 1, process circulating water equivalent to 88% of the supply stream flow rate was introduced into a single organic matter removal tower, resulting in an excessive increase in the supply stream flow rate of the water removal tower and an increase in steam usage.

[0080] On the other hand, Comparative Example 2 was applied under the same steam usage conditions as Comparative Example 1, but with a different circulating water flow rate. By applying one organic matter removal tower and introducing a small amount of process circulating water, the supply flow rate of the water removal tower was reduced. However, the amount of circulating water in the supply stream of the organic matter removal tower was insufficient for the IPA, and the IPA was not sufficiently dissolved, resulting in a significant decrease in the IPA recovery rate. [Explanation of Symbols]

[0081] 100 reactors 201 Absorption Tower 202 Gas purification tower 301, 301', 301'' Organic removal tower 302 Water removal tower 303 IPA Recovery Tower 304 Solvent recovery tower 305 High boiling point substance removal column

Claims

1. (S1) A step of supplying the reaction product of propylene monomer and water to a gas purification unit to separate the gas component containing unreacted propylene monomer, (S2) The reaction product from which the gas components have been separated is supplied to a first organic matter removal tower to discharge an upper stream containing organic by-products and isopropyl alcohol, and a lower stream containing isopropyl alcohol (IPA), n-propyl alcohol (NPA) by-products and water. (S3) The upper discharge stream of the first organic matter removal tower is supplied to the second organic matter removal tower, and process circulating water is introduced to discharge the upper stream containing organic by-products and the lower stream containing isopropyl alcohol and process circulating water. A method for producing isopropyl alcohol, comprising the steps of (S4) supplying the lower discharge stream of the first organic matter removal column to an isopropyl alcohol (IPA) purification section including a plurality of distillation columns to separate isopropyl alcohol.

2. The method for producing isopropyl alcohol according to claim 1, wherein step (S1) comprises contacting the reaction product of propylene monomer and water with process circulating water in an absorption tower of a gas purification unit to remove a gas phase stream containing unreacted propylene monomer, and then separating low-boiling point gas components from a liquid phase stream containing components absorbed into the process circulating water.

3. The method for producing isopropyl alcohol according to claim 1, wherein the stream supplied to the first organic matter removal tower in step (S2) comprises isopropyl alcohol, water, an n-propyl alcohol (NPA) by-product, and an organic by-product.

4. The method for producing isopropyl alcohol according to claim 3, wherein the organic by-product comprises diisopropyl ether (DIPE), hexene, hexanol, acetone, or a mixture thereof.

5. The method for producing isopropyl alcohol according to claim 1, wherein process circulating water is not supplied to the first organic matter removal tower in step (S2).

6. The method for producing isopropyl alcohol according to claim 1, wherein the upper discharge stream of the first organic matter removal tower contains 5 to 15% by weight of the total isopropyl alcohol supplied to the first organic matter removal tower.

7. The method for producing isopropyl alcohol according to claim 1, wherein in step (S3), the second organic matter removal tower is located downstream of the condenser connected to the first organic matter removal tower.

8. The method for producing isopropyl alcohol according to claim 1, wherein the process circulating water supplied to the second organic matter removal tower is a stream containing organic by-products and isopropyl alcohol, selectively dissolving the isopropyl alcohol and inducing liquid-liquid separation.

9. The method for producing isopropyl alcohol according to claim 8, wherein the isopropyl alcohol dissolved in the circulating water of the process is discharged to the lower part of the second organic matter removal tower and then recirculated to the first organic matter removal tower.

10. The method for producing isopropyl alcohol according to claim 1, wherein in the second organic matter removal tower, the process circulating water is supplied at a flow rate such that the process circulating water and isopropyl alcohol come into contact in a weight ratio of 2.5:1 to 5:

1.

11. Step (S4) involves supplying the lower discharge stream of the first organic matter removal tower to the water removal tower of the IPA purification section, discharging it into an upper stream containing a mixture of isopropyl alcohol and water, a lower stream containing water, and a side stream containing n-propyl alcohol (NPA). The upper discharge stream and organic solvent of the water removal tower are supplied to the IPA recovery tower of the IPA purification section, and the upper stream containing water and organic solvent and the lower stream containing IPA are discharged. The solvent recovery tower of the IPA purification section is supplied with the upper discharge stream of the IPA recovery tower to discharge the upper stream of solvent and the lower stream of water. A method for producing isopropyl alcohol according to any one of claims 1 to 10, comprising supplying the side discharge stream of the water removal tower to the high-boiling-point substance removal tower of the IPA purification section and discharging the stream containing NPA to the bottom.

12. The method for producing isopropyl alcohol according to claim 11, wherein in the IPA purification section, the water contained in the lower discharge stream of the water removal tower is recovered and used as process circulating water.

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