Method for preparing isopropanol

Abstract

The present invention provides a process for preparing isopropanol (IPA), the process comprising (S1) reacting propylene with water in a reaction unit to obtain a reaction product comprising isopropanol (IPA); (S2) feeding the reaction product to a gas purification unit and separating a gas component comprising unreacted propylene; and (S3) feeding the reaction product from which the gas component has been separated to an IPA purification unit and obtaining purified isopropanol wherein the raw material propylene may be additionally fed to the gas purification unit and the raw material propylene and the unreacted propylene may be purified.

Description

Technical Field

[0001] Cross-reference to Related Applications

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0119564, filed on September 8, 2023, and Korean Patent Application No. 10-2024-0085390, filed on June 28, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0004] The present invention relates to a method for preparing isopropyl alcohol, and more particularly, to a method for preparing high-purity isopropyl alcohol by purifying propylene used as a raw material together with unreacted propylene. Background Art

[0005] Isopropyl alcohol (IPA) is used for various purposes in the manufacturing of the electronics industry such as 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 (C 3 H 6 ) with water. Generally, for isopropyl alcohol, referring to Figure 1 , propylene monomer reacts with water in reaction unit 100 to obtain a reaction product containing unreacted propylene monomer, unreacted water, and by-products such as n-propanol (NPA) and organic materials as well as IPA. The reaction product is transferred to gas purification unit 200 to separate the gas containing low-boiling components, which contains unreacted propylene monomer. Then, the reaction product from which the gas components have been separated is fed to an IPA purification unit 300 including a plurality of distillation columns to remove organic materials, NPA, and water, thereby obtaining a crude isopropyl alcohol product.

[0007] Preferably, the propylene (C 3 H 6 ) fed as a raw material to the reaction unit has high purity. In the case where impurities such as unsaturated hydrocarbons (e.g., ethylene, butene, pentene, etc.) are contained in propylene, by-products (e.g., ethanol) having boiling points similar to IPA may be generated during the reaction of propylene with water. In addition, impurities having boiling points similar to IPA, such as ethanol and n-propanol (NPA), may already be present in the raw material propylene.

[0008] Therefore, it is necessary to purify the raw material propylene to obtain high-purity IPA. As shown in Figure 2 , in the existing IPA preparation process, a raw material purification unit 10 including two towers is installed upstream of the reaction unit to remove impurities contained in the raw material propylene.

[0009] However, when operating an IPA preparation system equipped with a raw material purification unit to control the quality of raw material propylene, the energy consumption increases due to the use of steam, and the equipment cost and operating cost also increase due to the addition of the tower. Summary of the Invention

[0010] Technical Problem

[0011] To solve the problems mentioned in the background art, the present invention relates to a method for preparing high-purity isopropyl alcohol by purifying propylene used as a raw material together with unreacted propylene.

[0012] Technical Solution

[0013] In one general aspect, a method for preparing isopropyl alcohol includes:

[0014] (S1) Reacting propylene with water in a reaction unit to obtain a reaction product containing isopropyl alcohol (IPA);

[0015] (S2) Feeding the reaction product to a gas purification unit and separating a gas component including unreacted propylene; and

[0016] (S3) Feeding the reaction product from which the gas component has been separated to an IPA purification unit to obtain purified isopropyl alcohol,

[0017] wherein raw material propylene is additionally fed to the gas purification unit, and the raw material propylene and the unreacted propylene are purified.

[0018] In the present invention, in the gas purification tower, the raw material propylene may be fed at a position higher than that of the unreacted propylene.

[0019] Beneficial Effects

[0020] According to the present invention, since the propylene used as a raw material and the unreacted propylene are simultaneously purified in the gas purification step of the isopropyl alcohol preparation process, there is no need to add a separate tower for purifying the raw material propylene.

[0021] In addition, since in the gas purification tower, the raw material propylene is fed at a position higher than that of the unreacted propylene, the purification of the unreacted propylene with a high propane content and other impurities and the purification of the raw material propylene can be effectively carried out simultaneously while minimizing the energy consumption.

[0022] As described above, since the purification of the raw material propylene and the purification of the unreacted propylene are integrated, compared with the existing isopropyl alcohol preparation methods, not only the equipment cost and operating cost related to the addition of a separate tower can be reduced, but also the energy consumption can be reduced. Brief Description of the Drawings

[0023] Figure 1 Schematically shows a typical isopropanol preparation method.

[0024] Figure 2 Schematically shows a conventional isopropanol preparation method in which the purification of the raw material propylene is carried out separately.

[0025] Figure 3 Schematically shows an isopropanol preparation method that integrates the purification of raw material propylene and the purification of unreacted propylene according to an embodiment of the present invention.

[0026] Figure 4 Shows in more detail Figure 3 the process of Detailed implementation mode

[0027] Based on the principle that the inventors can appropriately define the concept of terms in order to describe their own inventions in the best way, the terms and words used in the description and claims of the present invention are not limited to being understood as having a general meaning or the meaning in a dictionary, but are understood as having meanings and concepts that meet the technical concept of the present invention.

[0028] The meaning of "comprising" or "including" used in this application specifically defines specific properties, regions, integers, steps, operations, elements and / or components, but does not exclude the addition of other specific properties, regions, integers, steps, operations, elements and / or components.

[0029] The term "material flow" used in this application can refer to the flow of fluid in a process and can also refer to the fluid itself flowing through a pipeline. Specifically, the material flow can refer to the fluid itself and the flow of the fluid flowing through the pipeline connecting each device. In addition, the fluid can include any one or more components of gas, liquid and solid.

[0030] Unless otherwise specified, the term "upper part" used in this application refers to the point at 0 to 20% of the height from the upper end to the lower end of the device, specifically, it can refer to the (tower) top. In addition, the term "lower part" refers to the point at 80% to 100% of the height from the upper end to the lower end of the device, specifically, it can refer to the (tower) bottom.

[0031] Unless otherwise specified, the term "side stream" used in this application can refer to the stream discharged at a height of 10% to 80% or 10% to 70% from the upper end to the lower end of the device.

[0032] In addition, the "pressure" mentioned in this application refers to the gauge pressure measured based on the atmospheric pressure.

[0033] Meanwhile, unless otherwise specified, in the present invention, in apparatuses such as absorption towers, purification towers, removal towers, and recovery towers, the operating temperature of the apparatus may refer to the temperature at the upper or lower part of the apparatus. Further, unless otherwise specified, the operating pressure of the apparatus may refer to the pressure at the upper part of the apparatus.

[0034] 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.

[0035] Figure 3 Schematically shown is a method for preparing isopropyl alcohol that integrates the purification of raw material propylene and the purification of unreacted propylene according to one embodiment of the present invention.

[0036] Referring to Figure 3 , the method for preparing isopropyl alcohol according to the present invention includes: a reaction step (S1) of reacting propylene with water in a reaction unit 100; a purification step (S2) of purifying unreacted propylene in a gas purification unit 200; and a step (S3) of obtaining high-purity IPA in an IPA purification unit 300, wherein the raw material propylene is fed to the gas purification unit and purified together with the unreacted propylene, and then fed to the reaction step.

[0037] Figure 4 More specifically shown is a method for preparing isopropyl alcohol according to one embodiment of the present invention. Isopropyl alcohol can be prepared using a system that includes: a reaction unit 100; a gas purification unit including an absorption tower 201, a flash tank, a gas separation tower 202, and a gas purification tower 203; and an IPA purification unit including an organic material removal tower 301, a water removal tower 302, an IPA recovery tower 303, a solvent recovery tower 304, and an NPA removal tower 305. Further, the system can be used by additionally installing a reboiler for transferring heat to the feed stream of each tower and heating the feed stream, a condenser for converting the upper feed stream generated by heating from the gas phase to the liquid phase, a decanter for liquid-liquid separation of the condensed feed stream, valves for controlling the flow of the feed stream, pumps, and the like.

[0038] First, in the reaction unit 100, a reaction product 101 containing isopropyl alcohol can be obtained through a gas-phase reaction of propylene monomer with water.

[0039] Propylene (C 3 H 6 ) preferably fed as a raw material to the reaction unit 100 has high purity. In the case where impurities such as other unsaturated hydrocarbons (e.g., ethylene, butene, pentene, etc.), ethane, propane, and carbon dioxide are contained in propylene, by-products (e.g., ethanol) having boiling points similar to IPA may be generated during the reaction of propylene with water.

[0040] Therefore, in order to obtain high-purity IPA, the raw material propylene needs to be purified. In the present invention, in the gas purification unit located downstream of the reaction unit 100, specifically, in the gas purification tower 203, the raw material propylene is purified to remove impurities and then fed into the reaction unit 100.

[0041] In one embodiment of the present invention, the purified propylene fed into the reaction unit 100 preferably contains more than 97% by weight, for example, 97% to 99.8% by weight of propylene and less than 3% by weight of impurities based on its total weight.

[0042] Meanwhile, only a part of the purified propylene fed into the reaction unit 100 is used for the reaction. Therefore, in addition to isopropyl alcohol produced by the reaction of propylene monomer with water, the reaction product may also contain unreacted propylene monomer and unreacted water. For example, the reaction product 101 may 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 may contain diisopropyl ether (DIPE), hexene, acetone, n-propanol (NPA), etc. as by-products. Therefore, a method for separating unreacted raw materials from the reaction product and purifying isopropyl alcohol from various by-products is required.

[0043] For this purpose, the reaction product 101 obtained by the gas-phase reaction of purified propylene with water is fed into a gas purification unit including an absorption tower 201, a flash tank and a gas separation tower 202, and a gas component (S2) containing unreacted propylene monomer is separated.

[0044] Specifically, the reaction product 101 is fed through the lower part of the absorption tower 201, process recycle water is introduced through the upper part of the absorption tower 201, and unreacted propylene monomer is separated. In this case, as the process recycle water, the water recovered in the distillation tower, i.e., the water removal tower 302, included in the downstream IPA purification unit can be used. In the absorption tower 201, the gaseous isopropyl alcohol contained in the reaction product can be absorbed into the process recycle water and then obtained through the lower liquid stream 201b, and the gaseous stream 201a containing unreacted propylene monomer can be separated through the upper part. The unreacted propylene monomer contained in the gaseous stream 201a can be recycled to the reaction unit 100.

[0045] In one embodiment of the present invention, the flow rate of the process recycle water fed into the absorption tower 201 can be 15% to 40% or 15% to 35% by weight of the flow rate of the reaction product. When the process recycle 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 improved, and at the same time, the recovery energy cost of the process recycle water in the downstream process can be prevented from increasing excessively.

[0046] The absorption tower 201 can operate at a temperature of 90°C to 100°C or 90°C to 95°C and a pressure of 25 kg / cm 2 ·g to 40 kg / cm 2 ·g or 25 kg / cm 2 ·g to 35 kg / cm 2 ·g. 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.

[0047] Meanwhile, in addition to isopropyl alcohol and unreacted water, the lower liquid-phase stream of the absorption tower 201 may also contain a small amount of gas containing low-boiling components, and the low-boiling components include unreacted propylene monomer that has not been separated. For example, the content of the gas containing low-boiling components in the lower liquid-phase stream of the absorption tower 201 can be 5 wt% or less or 2 wt% to 5 wt%, and the low-boiling components include unreacted propylene monomer.

[0048] Therefore, the liquid-phase stream 201b containing isopropyl alcohol separated from the absorption tower 201 is fed to one or more flash tanks and the gas separation tower 202. The internal pressure in the flash tank can be reduced to 0 kg / cm 2 ·g to 5 kg / cm 2 ·g, specifically, 0 kg / cm 2 ·g to 2 kg / cm 2 ·g, and the residual unreacted propylene contained in the liquid-phase stream can be recovered as a gas and fed to the gas separation tower. The gas separation tower can operate at an internal pressure of 10 kg / cm 2 ·g to 30 kg / cm 2 ·g, specifically 10 kg / cm 2 ·g to 25 kg / cm 2 ·g. In this method, the upper gas-phase stream 202a containing residual unreacted propylene and the lower liquid-phase stream 202b containing high-boiling components such as isopropyl alcohol can be discharged from the flash tank and the gas separation tower 202.

[0049] In addition to unreacted propylene, the upper stream 202a discharged from the flash tank and the gas separation tower may still contain inert gases including ethane, propane, etc. as impurities and high-boiling components. For example, based on the total weight of the stream 202a, the stream 202a can contain 90 wt% to 98 wt% of unreacted propylene and the balance of impurities.

[0050] To remove the impurities contained in the unreacted propylene, the stream 202a containing unreacted propylene discharged from the flash tank and the gas separation tower is fed to the gas purification tower 203.

[0051] In the present invention, raw propylene containing impurities is fed to the gas purification column 203 and purified together with unreacted propylene. Based on the total weight of the raw propylene, the raw propylene fed to the gas purification column may contain 95 wt% to 99.8 wt% of propylene and the balance of impurities.

[0052] The purity of the raw propylene is higher than that of the unreacted propylene. Therefore, in terms of separation performance, it is advantageous for the gas purification column 203 that the feed port of the raw propylene is located at a position higher than the feed port of the unreacted propylene containing a large amount of impurities such as propane.

[0053] In one embodiment of the present invention, the feed port of the raw propylene may be provided at a stage corresponding to a height of 25% to 60% from the upper end of the gas purification column 203, and the feed port of the stream 202a containing unreacted propylene may be provided at a stage corresponding to a height of 50% to 85% from the upper end of the gas purification column 203. When the feed positions are satisfied, the purification of the unreacted propylene containing a large amount of impurities such as propane and the purification of the raw propylene can be effectively carried out simultaneously while minimizing the energy consumption.

[0054] Furthermore, the stream containing unreacted propylene and the raw propylene may be fed to the gas purification column 203 at a flow rate ratio of 0.2:1 to 2:1, specifically 0.4:1 to 1.5:1. When the above flow rate ratio range is satisfied, the removal efficiency of impurities can be improved while minimizing the energy consumption.

[0055] The gas purification column 203 may be operated at a temperature of 40°C to 100°C, specifically 40°C to 80°C, and a pressure of 10 kg / cm 2 ·g to 30 kg / cm 2 ·g, specifically 15 kg / cm 2 ·g to 30 kg / cm 2 ·g. When the above operating conditions are satisfied, impurities can be effectively removed from the unreacted propylene and the raw propylene while minimizing the energy consumption.

[0056] Based on the total weight of the raw propylene and the unreacted propylene, the raw propylene and the unreacted propylene purified in the gas purification column 203 under the above conditions may contain 97 wt% to 99.8 wt% of propylene and less than 3 wt% of the remaining impurities, and can be recovered through the side stream 203c and then recycled to the reaction unit 100. In addition, the stream 203a containing light components (e.g., ethane and ethylene) separated from the gas purification column 203 may be discharged, and the stream 203b containing heavy components (e.g., propane and butene) may be discharged from the lower part of the gas purification column 203.

[0057] Meanwhile, the liquid-phase stream 202b containing isopropanol discharged from the flash tank of the gas purification unit and the lower part of the gas separation column 202 may contain isopropanol, water, and organic materials such as n-propanol (NPA), diisopropyl ether (DIPE), and hexanol as by-products.

[0058] Therefore, the liquid-phase stream 202b containing isopropanol needs to be purified into high-purity isopropanol by passing through an IPA purification unit including an organic material removal column 301, a water removal column 302, an IPA recovery column 303, a solvent recovery column 304, and an NPA removal column 305.

[0059] Specifically, the reaction product from which the gas components have been separated, i.e., the lower stream 202b discharged from the flash tank of the gas purification unit and the gas separation column, can be fed to the organic material removal column 301 and contacted with process recycle water, and an upper stream 301a containing organic materials and a lower stream 301b containing isopropanol can be discharged. In this case, the water recovered from the distillation column included in the downstream IPA purification unit, i.e., the water removal column 302, can be used as the process recycle water, and this process recycle water can selectively dissolve isopropanol using the difference in solubility, so that isopropanol moves to the lower part and is separated from the organic by-products.

[0060] In one embodiment of the present invention, the flow rate of the process recycle water fed to the organic material removal column 301 can be 20 wt% to 50 wt% or 25 wt% to 45 wt% of the flow rate of the reaction product. When the process recycle water is supplied at a flow rate within the above range, the dissolution rate of isopropanol contained in the reaction product can be increased, and at the same time, an excessive increase in the recovery energy cost of the process recycle water in the downstream process can be prevented.

[0061] Subsequently, the lower discharge stream 301b of the organic material removal column is fed to the water removal column 302, and an upper stream 302a containing isopropanol, a lower stream 302b containing water, and a side stream containing n-propanol (NPA) are separated and discharged.

[0062] The upper stream 302a separated from the water removal column 302 may contain an azeotrope of isopropanol and water. For example, it may contain 80 wt% to 90 wt% of isopropanol and 10 wt% to 20 wt% of water.

[0063] The water separated by the lower stream 302b of the water removal column 302 can be recovered and used as process recycle water. As described above, the water separated from the water removal column 302 can be used as the process recycle water fed to the upstream absorption column 201 and the organic material removal column 301. In addition, if necessary, the water separated from the water removal column 302, because it has a high temperature of more than 100 °C, can be used for heat exchange to preheat the water fed to the reaction unit 100.

[0064] Thereafter, the upper discharge stream 302a of the water tower 302 can be fed into the IPA recovery tower 303, an organic solvent (e.g., cyclohexane, benzene, etc.) can be added as an azeotropic agent, and the upper stream 303a containing water and the organic solvent and the lower stream containing IPA can be discharged. That is, in the IPA recovery tower 303, the azeotrope of isopropanol and water is broken due to the organic solvent, and thus highly purified isopropanol can be obtained.

[0065] The stream 303a containing water and the organic solvent separated from the upper part of the IPA recovery tower can be fed into the solvent recovery tower 304, and the upper stream 304a containing the solvent and the lower stream 304b containing water can be separated and discharged. The solvent stream 304 can be recycled to the IPA recovery tower 303.

[0066] Meanwhile, the side discharge stream 302c of the water tower 302 containing n-propanol (NPA) can be fed into the NPA removal tower 305, the stream 305b containing NPA can be discharged from the lower part of the NPA removal tower 305, and the upper stream 305a can be recycled to the water tower 302.

[0067] There are no particular limitations on the operating conditions of the distillation towers included in the IPA purification unit, and they can be appropriately selected within the generally applicable range.

[0068] According to the present invention, since the raw material propylene and the unreacted propylene are purified simultaneously in the gas purification step of the isopropanol preparation process, a separate tower for purifying the raw material propylene is not required.

[0069] In addition, since in the gas purification tower, the raw material propylene is fed at a position higher than that of the unreacted propylene, the purification of the unreacted propylene with a high propane content and other impurities and the purification of the raw material propylene can be effectively carried out simultaneously while minimizing the energy consumption.

[0070] As described above, since the purification of the raw material propylene and the purification of the unreacted propylene are integrated, compared with the existing isopropanol preparation methods, not only the equipment cost and operating cost associated with adding a separate tower can be reduced, but also the energy consumption can be reduced. [Detailed Description of the Embodiment]

[0072] Hereinafter, the present invention will be described in more detail with reference to the embodiments. However, the following embodiments are provided for illustrative purposes of the present invention. It is obvious to those skilled in the art that various modifications and changes can be made without departing from the scope and concept of the present invention, and the scope of the present invention is not limited thereto.

[0073] In the following Examples and Comparative Examples, the method according to the present invention was simulated using the commercial process simulation program Aspen Plus. As the constants required for the simulation, the values stored in the program, the values described in the literature, etc. were used.

[0074] Example 1

[0075] As Figure 3 and Figure 4 shown in

[0076] (Step 1)

[0077] Water and propylene purified in the downstream gas purification column 203 are fed to the reaction unit 100, and the reaction is carried out to obtain a reaction product 101 containing isopropyl alcohol (IPA) as a product.

[0078] (Step 2)

[0079] The reaction product 101 is fed to the absorption column 201 of the gas purification unit 200. The process recycle water recovered in the downstream water removal column 302 is introduced through the upper part of the absorption column 201. The liquid stream 201b that has absorbed gaseous IPA is discharged through the lower part of the absorption column 201. The gaseous stream 201a containing unreacted propylene monomers is separated through the upper part of the absorption column 201 and recycled to the reaction unit 100. The absorption column 201 operates under the conditions of a pressure of 33 kg / cm 2 ·g and an upper / lower temperature of 95 °C. The IPA-absorbed liquid stream 201b is fed to the flash tank and the gas separation column 202. The internal pressure of the flash tank is reduced to 0.5 kg / cm 2 ·g, and the gas separation column operates at a pressure of 20 kg / cm 2 ·g, and a gaseous upper stream 202a containing residual unreacted propylene and a liquid lower stream 202b containing IPA are discharged.

[0080] Subsequently, the gaseous stream 202a containing unreacted propylene is fed to the gas purification column 203, the raw material propylene having the composition shown in Table 1 is additionally fed to the gas purification column 203, and the unreacted propylene and the raw material propylene are purified simultaneously (operating conditions: 27 kg / cm 2· a pressure of ·g, an upper temperature of 45 °C, and a lower temperature of 65 °C). At this time, the gas-phase stream 202a containing unreacted propylene is fed at a position 85% from the upper end of the gas purification column 203, and the raw material propylene is fed at a position 25% from the upper end, which is higher than the position of the gas-phase stream 202a.

[0081] The raw material propylene and unreacted propylene purified in the gas purification column 203 are recovered through the side stream 203c and recycled to the reaction unit 100.

[0082] (Step 3)

[0083] The liquid-phase stream 202b containing isopropyl alcohol discharged from the lower part of the flash tank and the gas separation column 202 is fed to the organic material removal column 301 of the IPA purification unit 300, brought into contact with the process circulating water recovered in the downstream water removal column 302, and the upper stream 301a containing organic materials and the lower stream 301b containing isopropyl alcohol are discharged.

[0084] The discharged stream 301b from the lower part of the organic material removal column is fed to the water removal column 302. The upper stream 302a containing isopropyl alcohol, the lower stream 302b containing water, and the side stream containing n-propanol (NPA) are separated and discharged. The upper discharged stream 302a of the water removal column 302 is fed to the IPA recovery column 303, cyclohexane is added as an azeotropic agent, the upper stream 303a containing water and cyclohexane is discharged, and IPA is separated from the lower part of the IPA recovery column 303 to obtain the final IPA product.

[0085] Meanwhile, the side discharged stream 302c of the water removal column 302 containing n-propanol (NPA) is fed to the NPA removal column 305. The stream 305b containing NPA is discharged from the lower part of the NPA removal column 305, and the upper stream 305a is recycled to the water removal column 302.

[0086] [Table 1]

[0087]

[0088] Example 2

[0089] Except that in Step 2, the gas-phase stream 202a containing unreacted propylene is fed at a position 65% from the upper end of the gas purification column 203, and the raw material propylene is fed at a position 45% from the upper end, which is higher than the position of the gas-phase stream 202a, the same method as in Example 1 is carried out.

[0090] Example 3

[0091] Except in step 2 where the gas-phase stream 202a containing unreacted propylene is fed at a position 45% from the upper end of the gas purification column 203 and the raw material propylene is fed at a position 65% from the upper end, which is lower than the position of the gas-phase stream 202a, the same method as in Example 1 is carried out.

[0092] Example 4

[0093] Except in step 2 where the gas-phase stream 202a containing unreacted propylene is fed at a position 25% from the upper end of the gas purification column 203 and the raw material propylene is fed at a position 85% from the upper end, which is lower than the position of the gas-phase stream 202a, the same method as in Example 1 is carried out.

[0094] Comparative Example 1

[0095] (Step 1)

[0096] Water and raw material propylene having the composition shown in Table 1 are fed to the reaction unit 100, and the reaction is carried out to obtain a reaction product 101 containing IPA as a product.

[0097] (Step 2)

[0098] The reaction product 101 is fed to the absorption column 201 of the gas purification unit 200. The process recycle water recovered in the downstream water removal column 302 is introduced through the upper part of the absorption column 201. The liquid-phase stream 201b that has absorbed the gas-phase IPA is discharged through the lower part of the absorption column 201. The gas-phase stream 201a containing unreacted propylene monomers is separated through the upper part of the absorption column 201 and recycled to the reaction unit 100. The absorption column 201 is operated under the conditions of a pressure of 33 kg / cm 2 ·g and an upper / lower temperature of 95 °C. The liquid-phase stream 201b that has absorbed IPA is fed to a flash tank and a gas separation column 202. The internal pressure of the flash tank is reduced to 0.5 kg / cm 2 ·g, and the gas separation column is operated under a pressure of 20 kg / cm 2 ·g, and a gas-phase upper stream 202a containing residual unreacted propylene and a liquid-phase lower stream 202b containing IPA are discharged.

[0099] Subsequently, the gas-phase stream 202a containing unreacted propylene is fed to the gas purification column 203, and the unreacted propylene is purified (operating conditions: pressure 27 kg / cm 2 ·g, upper temperature 45 °C, lower temperature 65 °C). Then, a side stream 203c containing purified unreacted propylene is recovered and recycled to the reaction unit 100.

[0100] (Step 3)

[0101] Perform the same process as step 3 of Example 1.

[0102] Comparative Example 2

[0103] (Step 1)

[0104] Install a raw material purification unit 10 including two towers upstream of the reaction unit 100, and feed and purify the raw material propylene having the composition shown in Table 1 (operating conditions of the first tower: pressure 22 kg / cm 2 ·g, upper temperature 45 °C, lower temperature 52 °C; operating conditions of the second tower: pressure 24 kg / cm 2 ·g, upper temperature 52 °C, lower temperature 62 °C).

[0105] Subsequently, feed water and the propylene purified in the raw material purification unit 10 to the reaction unit 100 to carry out the reaction, thereby obtaining a reaction product 101 containing IPA as the product.

[0106] (Step 2)

[0107] Feed the reaction product 101 to the absorption tower 201 of the gas purification unit 200. Introduce the process circulating water recovered in the downstream water removal tower 302 into the upper part of the absorption tower 201. Discharge the liquid stream 201b that has absorbed gaseous IPA from the lower part of the absorption tower 201. Separate the gaseous stream 201a containing unreacted propylene monomers from the upper part of the absorption tower 201 and recycle it to the reaction unit 100. The absorption tower 201 operates under the conditions of a pressure of 33 kg / cm 2 ·g and an upper / lower temperature of 95 °C. Feed the liquid stream 201b that has absorbed IPA to a flash tank and a gas separation tower 202, reduce the internal pressure of the flash tank to 0.5 kg / cm 2 ·g, and the gas separation tower operates under a pressure of 20 kg / cm 2 ·g, and discharge the upper gaseous stream 202a containing residual unreacted propylene and the lower liquid stream 202b containing IPA.

[0108] Subsequently, feed the gaseous stream 202a containing unreacted propylene to the gas purification tower 203 to purify the unreacted propylene (operating conditions: pressure 27 kg / cm 2 ·g, upper temperature 45 °C, lower temperature 65 °C), and then recover the side stream 203c containing purified unreacted propylene and recycle it to the reaction unit 100.

[0109] (Step 3)

[0110] Perform the same process as step 3 of Example 1.

[0111] Table 2 shows a comparison of the IPA preparation methods and results according to the examples and comparative examples.

[0112] [Table 2]

[0113]

[0114] In Table 2, in the IPA preparation method, in Examples 1 to 4 where the purification of the raw material propylene and the unreacted propylene were carried out simultaneously in the gas purification tower, it was confirmed that the impurity concentrations in the propylene recovered in the gas purification tower and the final IPA product obtained were reduced.

[0115] Specifically, in the gas purification tower 203, in Examples 1 and 2 where the raw material propylene was fed at a position higher than that of the unreacted propylene, i.e., a position closer to the upper end, the separation performance was favorable, and thus the energy consumption was significantly reduced. At the same time, in Examples 3 and 4, since the raw material propylene was fed at a position lower than that of the unreacted propylene, i.e., the feeding positions of the raw material propylene and the unreacted propylene in the gas purification tower were inappropriate, the energy consumption was high.

[0116] In Comparative Example 1, since the raw material propylene was introduced into the reaction unit 100 without purification, the energy consumption was low, but due to the impurities contained in the raw material propylene, the impurity concentrations in the propylene recovered in the gas purification tower 203 and the final IPA product obtained were high. Therefore, it was difficult to use the IPA product as a high-purity IPA product.

[0117] In Comparative Example 2, since the raw material propylene was purified in a separate raw material purification unit 10 and then fed into the reaction unit 100, the impurity concentrations in the propylene recovered in the gas purification tower and the final IPA product obtained were reduced, but the number of towers required for the raw material purification unit 10 and the gas purification tower 203 increased to 3. Compared with the examples where the raw material propylene and the unreacted propylene were purified simultaneously in the gas purification tower 203, the installation cost and operation cost increased. In addition, compared with Examples 1 and 2 where the feeding positions of the raw material propylene and the unreacted propylene were optimized, the energy consumption was also unfavorable.

[0118] [Detailed description of main components]

[0119] 10: Raw material purification unit

[0120] 100: Reaction unit

[0121] 200: Gas purification unit

[0122] 201: Absorption tower

[0123] 202: Flash tank and gas separation tower

[0124] 203: Gas purification tower

[0125] 300: IPA purification unit

[0126] 301: Organic material removal tower

[0127] 302: Water removal tower

[0128] 303: IPA recovery tower

[0129] 304: Solvent recovery tower

[0130] 305: NPA removal tower

Claims

1. A method for preparing isopropyl alcohol, the method comprising: (S1) reacting propylene with water in a reaction unit to obtain a reaction product comprising isopropyl alcohol (IPA); (S2) feeding the reaction product to a gas purification unit and separating gas components including unreacted propylene; and (S3) feeding the reaction product from which the gaseous components are separated into an IPA purification unit to obtain purified isopropanol, Herein, raw material propylene is additionally fed to the gas purification unit, and the raw material propylene and the unreacted propylene are purified.

2. The method according to claim 1, wherein: The gas purification unit includes an absorption tower, a flash tank, a gas separation tower and a gas purification tower. contacting the reaction product fed through the lower portion of the absorption tower with process circulating water fed through the upper portion of the absorption tower, discharging a gas phase upper stream containing unreacted propylene and a liquid phase lower stream containing components absorbed into the process circulating water from the absorption tower, The lower discharge stream of the absorption tower is fed to the flash tank and the gas separation tower, and the gas phase upper stream containing residual unreacted propylene and the liquid phase lower stream containing isopropanol are discharged from the flash tank and the gas separation tower, feeding the gas phase upper stream containing unreacted propylene discharged from the flash tank and the gas separation tower and the raw material propylene to the gas purification tower, discharging a side stream containing purified propylene and a lower stream containing high boiling point components, discharging a gas containing low boiling point components through the upper part of the gas purification tower, and The purified propylene separated from the gas purification column is fed to the reaction unit.

3. The method according to claim 2, wherein: In the gas purification tower, the raw material propylene is fed at a position higher than the unreacted propylene.

4. The method according to claim 2, wherein: The feed port of the raw material propylene is fed at a stage corresponding to a height of 25% to 60% from the upper end of the gas purification tower, and A stream containing unreacted propylene is fed at a stage corresponding to a height of 50% to 85% from the upper end of the gas purification column.

5. The method according to claim 2, wherein: A stream including unreacted propylene and the raw material propylene are fed at a flow ratio of 0.2:1 to 2:

1.

6. The method according to claim 2, wherein: The gas purification tower is at a temperature of 40°C to 100°C and a pressure of 10 kg / cm 2 g to 30kg / cm 2 · Operate under pressure of g.

7. The method according to claim 2, wherein: The raw material propylene fed to the gas purification tower includes 95 wt% to 99.8 wt% of propylene based on the total weight of the raw material propylene.

8. The method according to claim 2, wherein: The raw propylene and the unreacted propylene purified in the gas purification tower include 97 wt% to 99.8 wt% of propylene based on the total weight of the raw propylene and the unreacted propylene.

9. The method according to claim 2, wherein: The gas containing low-boiling-point components discharged from the gas purification tower includes ethane, ethylene, and a mixture thereof.

10. The method according to claim 1, wherein: The IPA purification unit includes an organic material removal tower, a water removal tower, an IPA recovery tower, an n-propanol removal tower and a solvent recovery tower. The liquid phase stream discharged from the flash tank and the gas separation tower of the gas purification unit is fed to the organic material removal tower and contacted with process circulating water, and an upper stream containing organic materials and a lower stream containing isopropyl alcohol are discharged from the organic material removal tower, The lower discharge stream of the organic material removal tower is fed to the dewatering tower, and an upper stream comprising a mixture of isopropyl alcohol and water, a lower stream comprising water, and a side stream comprising normal propyl alcohol (NPA) are discharged from the dewatering tower. The upper discharge stream of the dewatering tower and the organic solvent are fed to the IPA recovery tower, and the upper stream containing water and the organic solvent and the lower stream containing IPA are discharged from the IPA recovery tower, feeding the upper discharge stream of the IPA recovery tower to the solvent recovery tower, and discharging an upper stream containing a solvent and a lower stream containing water from the solvent recovery tower, and The side discharge stream of the water removal column is fed to the n-propanol removal column, and a stream containing NPA is discharged through the lower portion of the n-propanol removal column.

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