Method for preparing isopropanol

Abstract

The present invention provides a process for preparing isopropanol (IPA), which may include: (S1) feeding a reaction product of propylene monomer and water to a gas purification unit and separating a gas component comprising unreacted propylene monomer; (S2) feeding the reaction product from which the gas component is separated to a first organic material removal column, discharging an upper stream comprising organic by-products and isopropanol and a lower stream comprising isopropanol, n-propanol (NPA) by-products and water; (S3) feeding the upper discharge stream of the first organic material removal column to a second organic material removal column, introducing process circulating water, and discharging an upper stream comprising organic by-products and a lower stream comprising isopropanol and process circulating water; and (S4) feeding the lower effluent stream of the first organic material removal column to an isopropanol (IPA) purification unit comprising a plurality of distillation columns and separating isopropanol.

Description

Technical Field

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority of Korean Patent Application No. 10-2023-0119554, filed on September 8, 2023, the entire contents of which are incorporated into this specification by reference. Technical Field

[0004] The present invention relates to a method for preparing isopropyl alcohol, and more particularly, to a method for reducing energy usage and minimizing losses in isopropyl alcohol. Background Art

[0005] Isopropyl alcohol (IPA) is used for various purposes in the electronics industry such as the manufacture of semiconductors, liquid crystal displays (LCDs), etc., including solvents for cleaners, raw materials for industrial paints or reagents, paints, inks, etc.

[0006] This isopropyl alcohol can be prepared by reacting propylene with water. For example, in a reaction unit, propylene monomer is reacted with water in a gas phase to obtain a reaction product comprising isopropyl alcohol, unreacted propylene monomer, unreacted water and byproducts such as organic materials, and the gas phase reaction product is passed through a downstream process tower to separate the propylene monomer, water and byproducts, and purify the isopropyl alcohol.

[0007] According to Figure 1 In the IPA preparation process shown, a feed 1 comprising propylene monomer and water is fed into a reactor 100, a reaction is carried out to obtain a gas phase reaction product 101, unreacted propylene gas 201a and a low boiling point gas component 202a are removed from the reaction product 101 in a gas purification unit comprising an absorption tower 201 and a gas purification tower 202, a stream 202b comprising IPA, water and by-products (the gaseous components are removed from the stream) is fed to an organic material removal tower 301 to remove organic materials, an upper stream 302a comprising IPA, a lower stream 302b comprising water and a side stream 302c comprising NPA are separated in a water removal tower 302, and the upper stream 302a is fed to an IPA recovery tower 303, thereby obtaining IPA, wherein water is separated therefrom by a solvent. The stream 303 a including the solvent and water separated from the IPA recovery tower 303 is separated into an upper stream 304 a of the solvent and a lower stream 304 b of water in the solvent recovery tower 304 .

[0008] In the IPA purification process, a portion of the water 302b recovered through the lower portion of the water removal tower 302 may be recovered and used as process circulating water. Conventionally, eight times more circulating water than the amount of IPA produced is used, about 40% of the used circulating water is introduced into the absorption tower 201 so that the gas phase IPA can be absorbed into the water and then separated in the liquid phase, and the remaining portion (about 60% of the original amount) is introduced into the organic material removal tower 301 and used to remove organic byproducts such as diisopropyl ether (DIPE) and hexene using liquid-liquid phase equilibrium.

[0009] In this case, since the liquid phase stream 202b containing IPA, water and by-products from which gas components have been removed in the upstream gas purification unit is introduced into the organic material removal tower 301 together with a large amount of circulating water, the feed flow rate of the dehydration tower 302 disposed downstream of the organic material removal tower 301 may be excessively increased, resulting in an increase in steam demand.

[0010] Therefore, a method is needed to achieve energy savings by reducing steam demand throughout the IPA preparation process. Summary of the invention

[0011] Technical issues

[0012] In order to solve the problems mentioned in the background art, an object of the present invention is to provide a method for minimizing the increase of energy consumption and cost by reducing the amount of circulating water used in the isopropyl alcohol production process.

[0013] Technical Solution

[0014] In one general aspect, a method for preparing isopropanol comprises:

[0015] (S1) feeding a reaction product of propylene monomer and water to a gas purification unit, and separating a gas component including unreacted propylene monomer;

[0016] (S2) feeding the reaction product from which the gaseous components are separated to a first organic material removal tower, discharging an upper stream comprising organic by-products and isopropyl alcohol and a lower stream comprising isopropyl alcohol (IPA), normal propanol (NPA) by-products and water;

[0017] (S3) feeding the upper discharge stream of the first organic material removal tower to a second organic material removal tower, introducing process circulating water, and discharging an upper stream containing organic by-products and a lower stream containing isopropyl alcohol and process circulating water;

[0018] (S4) Feeding the lower exhaust stream of the first organic material removal tower to an isopropyl alcohol (IPA) purification unit including a plurality of distillation towers and separating isopropyl alcohol.

[0019] Beneficial Effects

[0020] According to the present invention, two organic material removal towers are used, in the first organic material removal tower, an upper stream containing organic by-products and a portion of isopropyl alcohol is separated without feeding process circulating water, and in the second organic material removal tower, the separated upper stream is contacted with a small amount of process circulating water to dissolve IPA, thereby separating the organic by-products and isopropyl alcohol, so that the feed flow rate of the downstream IPA purification unit is reduced, thereby reducing the amount of steam used.

[0021] Reduction in the amount of steam used in the IPA purification unit can achieve energy savings in the overall process and can reduce the size of the distillation column used for IPA purification, thereby minimizing cost increases. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The conventional IPA preparation process is shown.

[0023] Figure 2 A method for preparing IPA according to one embodiment of the present invention is shown. DETAILED DESCRIPTION

[0024] Based on the principle that inventors are able to appropriately define the concepts of terms in order to describe their own inventions in the best manner, the terms and words used in the description and claims of the present invention are not limited to being understood as having general meanings or dictionary meanings, but are understood as having meanings and concepts that satisfy the technical concept of the present invention.

[0025] The meaning of “include” or “comprising” used in this application specifies specific performance, regions, integers, steps, operations, elements and / or components, but does not exclude the addition of other specific performance, regions, integers, steps, operations, elements and / or components.

[0026] The term "stream" used in this application may refer to the flow of a fluid in a process, and may also refer to the fluid itself flowing through a pipeline. Specifically, stream may refer to the fluid itself and the flow of a fluid flowing through a pipeline connecting various devices to each other. In addition, a fluid may include any one or more components of a gas, a liquid, and a solid.

[0027] Unless otherwise specified, the term "upper" used in this application refers to a point at a height of 0 to 20% from the uppermost part to the lower part of the device, specifically, it may refer to the top (of the tower). In addition, the term "lower" refers to a point at a height of 80% to 100% from the uppermost part to the lower part of the device, specifically, it may refer to the bottom (of the tower).

[0028] The term "side stream" used in the present application may refer to a stream discharged at a height of 25% to 80% or 40% to 70% from the uppermost part to the lower part of the device.

[0029] In addition, the "pressure" mentioned in this application refers to the gauge pressure measured based on the atmospheric pressure.

[0030] Meanwhile, unless otherwise stated, 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 temperature of the upper or lower portion of the device. In addition, unless otherwise stated, the operating pressure of the device may refer to the pressure of the upper portion of the device.

[0031] One embodiment of the present invention relates to a method for preparing isopropyl alcohol (IPA). Hereinafter, the method for preparing IPA of the present invention will be described in detail with reference to the accompanying drawings.

[0032] Figure 2 A method for preparing isopropyl alcohol according to one embodiment of the present invention is shown. Isopropyl alcohol can be prepared using a system comprising: a reactor 100; a gas purification unit including an absorption tower 201 and a gas purification tower 202; a first organic material removal tower 301′ and a second organic material removal tower 302″; and an IPA purification unit including a water removal tower 302, an IPA recovery tower 303, a solvent recovery tower 304, and a high-boiling-point material removal tower 305. In addition, the system can be used by additionally installing a reboiler for transferring heat to a feed stream of each tower and heating the feed stream, a condenser for converting an upper stream generated by heating from a gas phase to a liquid phase, a decanter for liquid-liquid separation of a condensed stream, a valve for controlling the flow of the stream, a pump, and the like.

[0033] Reference Figure 2 , a feed 1 including propylene monomer and water may be fed into a reactor 100 , and a reaction product 101 including isopropyl alcohol may be obtained through a gas phase reaction process.

[0034] Owing to only use a part of propylene monomer that is fed to reactor 100 in this reaction, therefore except the isopropanol produced by the reaction of propylene monomer and water, this reaction product can also include unreacted propylene monomer and unreacted water.For example, reaction product 101 can include the unreacted propylene monomer of 65 % by weight to 85 % by weight, the isopropanol of 4 % by weight to 8 % by weight and the water of 5 % by weight to 30 % by weight.In addition, reaction product can include organic material such as diisopropyl ether (DIPE), hexene, hexanol and acetone, and n-propyl alcohol (NPA) etc. as by product.Therefore, need to carry out the method for separating unreacted raw material from reaction product and purifying isopropanol from various by products.

[0035] First, a reaction product 101 obtained by a gas phase reaction of propylene monomer and water is fed to a gas purification unit, and a gas component including unreacted propylene monomer is separated (S1).

[0036] Specifically, the reaction product 101 is fed through the lower part of the absorption tower 201, the process circulating water is introduced through the upper part of the absorption tower 201, and the unreacted propylene monomer is separated. In this case, as the process circulating water, the water recovered in the distillation tower, that is, the dewatering tower 302 included in the downstream IPA purification unit can be used. In the absorption tower 201, the gas phase isopropyl alcohol contained in the reaction product can be absorbed into the process circulating water, and then obtained through the lower liquid phase stream 201b, and the gas phase stream 201a containing the unreacted propylene monomer can be separated through the upper part. The unreacted propylene monomer contained in the gas phase stream 201a is recovered to the reactor 100 and reused as a raw material for preparing isopropyl alcohol.

[0037] In one embodiment of the present invention, the flow rate of the process circulating water fed to the absorption tower 201 may be 15 wt % to 40 wt % or 15 wt % to 35 wt % 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 the isopropyl alcohol contained in the reaction product can be increased, and at the same time, the recovery energy cost of the process circulating water in the downstream can be prevented from being excessively increased.

[0038] The absorption tower 201 can be operated at a temperature of 90°C to 100°C or 90°C to 95°C and a temperature of 25 kg / cm 2 g to 40kg / cm 2 g or 25kg / cm 2 g to 35kg / cm 2 When the above operating conditions are met, the upper discharge stream containing unreacted propylene monomer and the lower discharge stream containing isopropyl alcohol can be effectively separated.

[0039] Meanwhile, in addition to isopropanol and unreacted water, the lower liquid phase stream of the absorption tower 201 may also contain a small amount of unseparated low-boiling gas components containing unreacted propylene monomers. For example, the content of the low-boiling gas components containing unreacted propylene monomers contained in the lower liquid phase stream of the absorption tower 201 may be 5 wt% or less or 2 wt% to 5 wt%.

[0040] Therefore, the liquid phase stream 201b containing isopropyl alcohol separated from the absorption tower 201 may be fed to one or more gas purification towers 202, and may be separated into an upper stream 202a containing low boiling point components and a lower stream 202b containing isopropyl alcohol, water, and by-products.

[0041] If necessary, the lower liquid phase stream of the absorption tower 201 may be fed to the gas purification tower 202 after passing through one or more flash tanks. That is, first, in the flash tank, low boiling point components may be preliminarily separated and then fed to the gas purification tower 202 again, unreacted propylene monomer and low boiling point components of inert gas may be separated through the upper part of the gas purification tower 202, and trace amounts of high boiling point components may be separated through the lower part of the gas purification tower 202.

[0042] The upper stream 202a containing low boiling point components separated from the gas purification tower 202 may contain unreacted propylene monomer and inert gas (e.g., ethane or propane). The unreacted propylene monomer contained in the upper stream of the gas purification tower 202 may be recycled to the reactor 100, and the inert gas may be diverted for exhaust.

[0043] Meanwhile, the lower stream 202b separated from the gas purification tower 202 may include isopropyl alcohol, water, and organic materials such as n-propyl alcohol (NPA), diisopropyl ether (DIPE), hexene, and acetone as by-products.

[0044] Therefore, it is necessary to remove organic by-products from the lower effluent stream 202b of the gas purification tower.

[0045] In a conventional IPA preparation process, in order to remove organic by-products from the reaction product from which the gaseous components are separated, the process circulating water recovered in the dewatering tower 302 is fed to the organic material removal tower and used to separate the organic by-products using liquid-liquid phase equilibrium. The process circulating water is fed in an amount of 70 wt % to 95 wt % or 80 wt % to 90 wt % of the flow rate of the feed stream of the organic material removal tower and is used to dissolve isopropyl alcohol. In this case, since the process circulating water used in the upstream absorption tower and the process circulating water used in the organic material removal tower are combined and introduced into the distillation tower of the downstream IPA purification unit, there is a problem of increased steam demand due to excessive flow.

[0046] In order to solve these problems, in the present invention, two organic material removal towers are used, in the first organic material removal tower, an upper stream containing organic by-products and a portion of isopropyl alcohol is separated without feeding process circulating water, and in the second organic material removal tower, the separated upper stream is contacted with a small amount of process circulating water to dissolve IPA and thus remove the organic by-products.

[0047] More specifically, first, the reaction product from which gas components are separated, ie, the lower exhaust stream 202b of the gas purification tower is fed to the first organic material removal tower 301', and components are separated according to boiling points without feeding process circulating water (S2).

[0048] The stream fed to the first organic material removal column 301' may include isopropyl alcohol, water, n-propyl alcohol (NPA) byproduct, and organic byproducts (eg, diisopropyl ether (DIPE), hexene, hexanol, acetone, or mixtures thereof).

[0049] Since process circulating water is not fed during the component separation in the first organic material removal tower 301', dissolution of isopropyl alcohol by water does not occur, and therefore, a portion of isopropyl alcohol may be included in a stream heated by heat provided in a reboiler connected to the lower portion of the first organic material removal tower 301' together with organic by-products, moved to the upper portion of the first organic material removal tower 301', passed through a condenser, and then discharged. For example, the isopropyl alcohol in the upper stream 301'a of the first organic material removal tower may be included in an amount of 5 wt% to 25 wt%, specifically 10 wt% to 20 wt%, of the total isopropyl alcohol fed to the first organic material removal tower.

[0050] Therefore, the stream fed to the first organic material removal tower 301' may be separated into an upper stream 301'a including organic byproducts and isopropyl alcohol, and a lower stream 301'b including isopropyl alcohol, normal propanol (NPA) byproduct, and water.

[0051] In order to recover isopropyl alcohol contained in the upper stream 301′a of the first organic material removal tower, the upper discharge stream 301′b of the first organic material removal tower is fed to the second organic material removal tower 301″, a small amount of process circulating water is introduced into the second organic material removal tower 301″, and the upper stream 301″a containing organic by-products and the lower stream 301″b containing isopropyl alcohol and process circulating water are separated (S3).

[0052] More specifically, the second organic material removal tower 301″ is disposed downstream of the condenser connected to the first organic material removal tower 301′, and a feed stream 301′a containing organic by-products and isopropyl alcohol is fed to the second organic material removal tower 301″. In this case, the content of isopropyl alcohol contained in the feed stream 301′a fed to the second organic material removal tower 301″ is equivalent to 10% to 20% of the content of isopropyl alcohol contained in the feed stream of the first organic material removal tower 301′. Therefore, even when a small amount of process circulating water is introduced into the second organic material removal tower 301″, the isopropyl alcohol contained in the feed stream 301′a can be effectively separated. That is, by using a small amount of process circulating water, the isopropyl alcohol contained in the feed stream is selectively dissolved by utilizing the difference in solubility and then moved to the lower part, so that the isopropyl alcohol can be separated from the organic by-products.

[0053] Isopropyl alcohol dissolved in the process circulating water is discharged through the lower stream 301″b of the second organic material removing tower and then recycled to the first organic material removing tower 301′, which can minimize the loss of isopropyl alcohol.

[0054] In one embodiment of the present invention, the first organic material removal tower 301' can be operated at a temperature of 75°C to 130°C or 80°C to 105°C and a temperature of 0 to 2 kg / cm 2 g or 0 to 0.5 kg / cm 2 When the above operating conditions are met, the organic by-products can be effectively separated from the mixed stream without feeding process circulating water.

[0055] In addition, the second organic material removal tower 301" can be operated at a temperature of 75°C to 125°C or 80°C to 105°C and a temperature of 0 to 2 kg / cm 2 g or 0 to 0.5 kg / cm 2 When the above operating conditions are met, even a small amount of process circulating water can increase the efficiency of dissolving isopropyl alcohol.

[0056] In the second organic material removal tower 301″, the flow rate of the process circulating water may be adjusted so that the process circulating water and isopropyl alcohol contact each other at a weight ratio of 2.5:1 to 5:1. Such a flow rate of the process circulating water is significantly reduced compared to the process circulating water fed in an amount of about 80% by weight or more relative to the amount of the feed stream in the existing organic material removal tower in the conventional IPA production process. This can reduce the feed flow rate of the distillation tower included in the downstream IPA purification unit, which can reduce the amount of steam used.

[0057] Meanwhile, the liquid stream 301 ′b separated through the lower portion of the first organic material removing tower 301 ′ may include 9 to 12 wt % of isopropanol, 0.1 to 1 wt % of n-propanol, and 87 to 90 wt % of water based on the total weight of the liquid stream 301 ′b.

[0058] That is, the liquid-phase stream 301′b may contain a large amount of water, which includes unreacted water discharged from the reactor 100 and process circulating water used to absorb the gas-phase isopropyl alcohol in the absorption tower 201; and n-propyl alcohol (NPA) as a reaction by-product, and therefore, in the IPA purification unit including multiple distillation towers, a large amount of water and NPA by-products are removed to separate high-purity isopropyl alcohol (S4).

[0059] Specifically, the lower discharge stream 301'b of the first organic material removal tower 301' is fed to the dewatering tower 302, and an upper stream 302a containing isopropyl alcohol, a lower stream 302b containing water, and a side stream containing n-propyl alcohol (NPA) are separated and discharged.

[0060] The upper stream 302a separated from the water removal tower 302 may include an azeotrope of isopropyl alcohol and water, for example, may include 85 to 90 wt% of isopropyl alcohol and 10 to 15 wt% of water.

[0061] The water separated by the lower stream 302b of the dewatering tower 302 can be recovered and used as process circulating water. As described above, the water separated from the dewatering tower 302 can be fed to the upstream absorption tower 201 and used to absorb gas phase isopropyl alcohol. In addition, if necessary, the water separated from the dewatering tower 302 can be used for heat exchange for preheating the water fed to the reactor 100 because it has a high temperature of more than 100°C.

[0062] The dewatering tower 302 can be operated at a temperature of 70°C to 150°C or 80°C to 140°C and a pressure of 0 to 5 kg / cm 2 g or 0 to 3 kg / cm 2 When the above operating conditions are met, the azeotrope of isopropanol and water can be effectively separated.

[0063] Thereafter, the upper discharge stream 302a of the dewatering tower 302 may be fed to the IPA recovery tower 303, an organic solvent (e.g., cyclohexane, benzene, etc.) may be added as an azeotropic agent, and the upper stream 303a containing water and the organic solvent and the lower stream containing IPA may be discharged. That is, in the IPA recovery tower 303, the azeotrope of isopropyl alcohol and water is destroyed due to the organic solvent, so that highly purified isopropyl alcohol can be obtained.

[0064] The stream 303a containing water and an organic solvent separated by the upper portion of the IPA recovery tower can be fed to the solvent recovery tower 304, and the upper stream 304a of the solvent and the lower stream 304b of water can be separated and discharged. The solvent stream 304 can be recycled to the IPA recovery tower 303.

[0065] At the same time, the side discharge stream 302c of the dewatering tower 302 containing normal propanol (NPA) can be fed to the high boiling point material removal tower 305, the stream 305b containing NPA can be discharged through the lower part of the high boiling point material removal tower 305, and the upper stream 305a can be recycled to the dewatering tower 302.

[0066] As described above, according to the present invention, two organic material removal towers are used, and in the first organic material removal tower, an upper stream containing organic by-products and a portion of isopropyl alcohol is separated without feeding process circulating water, and in the second organic material removal tower, the separated upper stream is contacted with a small amount of process circulating water to dissolve IPA, thereby separating the organic by-products and isopropyl alcohol, so that the feed flow rate of the downstream IPA purification unit is reduced, thereby reducing the amount of steam used.

[0067] Reduction in the amount of steam used in the IPA purification unit can achieve energy savings in the overall process and can reduce the size of the distillation column used for IPA purification, thereby minimizing cost increases. [Specific implementation method]

[0069] Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following Examples are provided to illustrate the present invention. It will be apparent to those skilled in the art that various modifications and variations may be made without departing from the scope and concept of the present invention, and the scope of the present invention is not limited thereto.

[0070] In the following examples and comparative examples, the method according to the present invention was simulated using the commercial method simulation program Aspen Plus. As constants required for the simulation, values ​​stored in the program, values ​​described in literature, etc. were used.

[0071] Example 1

[0072] like Figure 2 As shown in , isopropyl alcohol is prepared using a system, which includes: a reactor 100; a gas purification unit, including an absorption tower 201 and a gas purification tower 202; a first organic material removal tower 301′ and a second organic material removal tower 302″; and an IPA purification unit, including a water removal tower 302, an IPA recovery tower 303, a solvent recovery tower 304 and a high boiling point material removal tower 305.

[0073] (Step 1) Gas Separation in Gas Purification

[0074] In the reactor 100, a feed 1 containing water at 100°C and a propylene monomer is fed and subjected to a gas phase reaction, the obtained reaction product 101 is fed through the lower part of the absorption tower 201, and 40% of the process circulating water recovered in the dehydration tower 302 of the IPA purification unit is introduced through the upper part of the absorption tower 201.

[0075] In the absorption tower 201 , a liquid phase stream 201 b absorbing gaseous isopropyl alcohol is discharged through a lower portion, and a gas phase stream 201 a containing unreacted propylene monomer is separated through an upper portion and then circulated to the reactor 100 .

[0076] The liquid phase stream 201b absorbing isopropyl alcohol passes through a gas purification tower 202 and is then separated into a low-boiling point upper stream 202a and a lower stream 202b containing isopropyl alcohol, water, and by-products.

[0077] (Step 2) Separating organic byproducts in a first organic material removal tower without feeding process circulating water

[0078] The lower stream 202b of the gas purification tower is fed to the first organic material removal tower 301', and the components are separated according to the boiling point without feeding process circulating water, so that the lower stream 202b is separated into an upper stream 301'a containing organic by-products and a portion of isopropyl alcohol (about 10% of the total isopropyl alcohol) and a lower stream 301'b containing isopropyl alcohol, normal propanol (NPA) by-product and water.

[0079] (Step 3) Introducing process circulating water into the second organic material removal tower and recovering part of the IPA

[0080] The upper discharge stream 301′b of the first organic material removal tower 301′ is fed to the second organic material removal tower 301″, and part of the process circulating water recovered in the dewatering tower 302 of the IPA purification unit is fed to the second organic material removal tower 301″, and the upper stream 301″a containing organic by-products and the lower stream 301″b containing isopropyl alcohol and process circulating water are separated. The lower stream 301″b is recovered and recycled to the first organic material removal tower 301′. At this time, the feed flow rate of the process circulating water is controlled so that the process circulating water and isopropyl alcohol contact each other at a flow ratio of 3:1 in the second organic material removal tower 301″. As a result, the process circulating water is fed in an amount of 6 weight % of the flow rate of the stream 202b fed to the first organic material removal tower 301′.

[0081] (Step 4) IPA Separation in IPA Purification Unit

[0082] The material stream 301′b discharged through the lower part of the first organic material removal tower 301′ is fed to the dewatering tower 302, and the upper material stream 302a containing isopropyl alcohol, the lower material stream 302b containing water, and the side stream containing normal propanol (NPA) are separated and discharged. Water is recovered through the lower material stream 302b, and then part of the lower material stream 302b is fed to the upstream absorption tower 201 and the second organic material removal tower 301″.

[0083] The upper discharge stream 302a of the dewatering tower 302 is fed to the IPA recovery tower 303, cyclohexane is added as an azeotropic agent, an upper stream 303a containing water and cyclohexane is discharged, and IPA is separated through the lower part.

[0084] At the same time, the side discharge stream 302c of the dewatering tower 302 containing n-propanol (NPA) is fed to the high boiling point material removal tower 305, the stream 305b containing NPA is discharged through the lower part of the high boiling point material removal tower 305, and the upper stream 305a is recycled to the dewatering tower 302.

[0085] Comparative Example 1

[0086] like Figure 1 As shown in , isopropyl alcohol is prepared using a system comprising: a reactor 100; a gas purification unit comprising an absorption tower 201 and a gas purification tower 202; an organic material removal tower 301; and an IPA purification unit comprising a water removal tower 302, an IPA recovery tower 303, a solvent recovery tower 304, and a high boiling point material removal tower 305.

[0087] (Step 1) Gas Separation in Gas Purification

[0088] The same method as step 1 of Example 1 was carried out.

[0089] (Step 2) Feeding process recycle water into an organic material removal tower and separating organic by-products

[0090] The lower stream 202b of the gas purification tower is fed to the organic material removal tower 301, and the process circulating water recovered in the dehydration tower 302 of the IPA purification unit is fed in an amount of 88 wt% of the flow rate of the stream 202b fed to the organic material removal tower 301, and the liquid phase 301a containing the organic by-product and the liquid phase 301b containing isopropyl alcohol and water are separated. As the process circulating water, the water separated and recovered in the downstream dehydration tower 302 is used.

[0091] (Step 3) IPA Separation in IPA Purification Unit

[0092] The material stream 301b discharged from the lower part of the organic material removal tower 301 is fed to the dewatering tower 302, and the upper material stream 302a containing isopropyl alcohol, the lower material stream 302b containing water and the side stream containing normal propanol (NPA) are separated and discharged. Water is recovered through the lower material stream 302b, and then the lower material stream 302b is fed to the upstream absorption tower 201 and the organic material removal tower 301.

[0093] The upper discharge stream 302a of the dewatering tower 302 is fed to the IPA recovery tower 303, cyclohexane is added as an azeotropic agent, an upper stream 303a containing water and cyclohexane is discharged, and IPA is separated through the lower part.

[0094] At the same time, the side discharge stream 302c of the dewatering tower 302 containing n-propanol (NPA) is fed to the high boiling point material removal tower 305, the stream 305b containing NPA is discharged through the lower part of the high boiling point material removal tower 305, and the upper stream 305a is recycled to the dewatering tower 302.

[0095] Comparative Example 2

[0096] The same process as in Comparative Example 1 was performed except that process circulating water recovered in the water removal tower 302 of the IPA purification unit was fed in an amount of 6 weight % of the flow rate of the feed stream 202 b in the organic material removal tower 301 .

[0097] Table 1 shows comparison of IPA purification processes and results according to Examples and Comparative Examples.

[0098] [Table 1]

[0099]

[0100] As can be seen from Table 1, in Example 1, in the first organic material removal tower, without feeding process circulating water, the upper stream containing organic by-products and a portion of IPA was separated, and a small amount of process circulating water (6% of the flow rate of the feed stream of the first organic material removal tower) was supplied to the second organic material removal tower to dissolve the IPA contained in the upper stream of the first organic material removal tower, separate the organic by-products and isopropyl alcohol, and reduce the feed flow rate of the water removal tower in the IPA purification unit. As a result, the amount of steam used was reduced, and a high IPA recovery rate was maintained.

[0101] On the other hand, in Comparative Example 1, when process circulating water corresponding to 88% of the flow rate of the feed stream was introduced into one organic material removal tower, the flow rate of the feed stream of the water removal tower increased excessively, resulting in an increase in the amount of steam used.

[0102] Meanwhile, in Comparative Example 2 (in which different flow rates of circulating water were applied under the same conditions as the amount of steam used in Comparative Example 1), since a small amount of process circulating water was introduced while applying one organic material removal tower, the feed flow rate of the dehydration tower was reduced, but the amount of circulating water was insufficient compared to IPA in the feed stream in the organic material removal tower, and IPA was not sufficiently dissolved. As a result, it was confirmed that the IPA recovery rate was significantly reduced.

[0103] [Detailed description of main components]

[0104] 100: Reactor

[0105] 201: Absorption Tower

[0106] 202: Gas purification tower

[0107] 301, 301′, 301″: organic material removal tower

[0108] 302: Dewatering Tower

[0109] 303: IPA recovery tower

[0110] 304: Solvent recovery tower

[0111] 305: High boiling point material removal tower

Claims

1. A method for preparing isopropyl alcohol, the method comprising: (S1) feeding a reaction product of propylene monomer and water to a gas purification unit, and separating a gas component including unreacted propylene monomer; (S2) feeding the reaction product from which the gaseous components are separated to a first organic material removal tower, discharging an upper stream comprising organic by-products and isopropyl alcohol, and a lower stream comprising isopropyl alcohol (IPA), normal propanol (NPA) by-products, and water; (S3) feeding the upper discharge stream of the first organic material removal tower to a second organic material removal tower, introducing process circulating water, and discharging an upper stream containing organic by-products and a lower stream containing isopropyl alcohol and process circulating water; (S4) Feeding the lower exhaust stream of the first organic material removal tower to an isopropyl alcohol (IPA) purification unit including a plurality of distillation towers and separating isopropyl alcohol.

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

3. The method according to claim 1, wherein: The stream fed to the first organic material removal tower in step (S2) comprises isopropyl alcohol, water, n-propyl alcohol (NPA) by-product, and organic by-products.

4. The method according to claim 3, wherein: The organic by-product includes diisopropyl ether (DIPE), hexene, hexanol, acetone or a mixture thereof.

5. The method according to claim 1, wherein: In step (S2), process circulating water is not fed to the first organic material removal tower.

6. The method according to claim 1, wherein: The isopropyl alcohol in the upper discharge stream of the first organic material removal tower is contained in an amount of 5 wt % to 15 wt % of the entire isopropyl alcohol fed to the first organic material removal tower.

7. The method according to claim 1, wherein: In step (S3), the second organic material removal tower is provided downstream of the condenser connected to the first organic material removal tower.

8. The method according to claim 1, wherein: The process circulating water fed to the second organic material removing tower selectively dissolves isopropyl alcohol in a stream containing organic by-products and isopropyl alcohol to induce liquid-liquid separation.

9. The method according to claim 8, wherein: The isopropyl alcohol dissolved in the process circulating water is discharged through the lower portion of the second organic material removing tower and then recycled to the first organic material removing tower.

10. The method according to claim 1, wherein: In the second organic material-removing tower, the process circulating water is fed at a flow rate at which the process circulating water and the isopropyl alcohol contact each other in a weight ratio of 2.5:1 to 5:

1.

11. The method according to claim 1, wherein: Step (S4) comprises: Feeding the lower discharge stream of the first organic material removal tower to the water removal tower of the IPA purification unit, and discharging an upper stream comprising a mixture of isopropyl alcohol and water, a lower stream comprising water, and a side stream comprising normal propanol (NPA); Feeding the upper discharge stream of the water removal tower and the organic solvent to the IPA recovery tower of the IPA purification unit, and discharging an upper stream containing water and the organic solvent and a lower stream containing IPA; feeding an upper discharge stream of the IPA recovery tower to a solvent recovery tower of the IPA purification unit, and discharging an upper stream of solvent and a lower stream of water; and The side discharge stream of the water removal column is fed to the high boiling point material removal column of the IPA purification unit, and a stream containing NPA is discharged through the lower part of the high boiling point material removal column.

12. The method according to claim 11, wherein: Water contained in the lower discharge stream of the water removal tower is recovered in the IPA purification unit and used as process circulating water.

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