How is isopropyl alcohol produced?

Abstract

The present invention provides a method for producing isopropyl alcohol, the method comprising: supplying a feed containing isopropyl alcohol, water, a first light by-product, a second light by-product, and a heavy by-product to a first column and separating the first light by-product; and supplying a bottom draw stream from the first column to a second column and separating the bottom draw stream from the first column into an top draw stream from the second column containing the second light by-product, a first side draw stream from the second column containing a mixture of isopropyl alcohol and water, a second side draw stream from the second column containing the heavy by-product, and a bottom draw stream from the second column containing the water.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0158482 filed November 15, 2023 and Korean Patent Application No. 10-2024-0147806 filed October 25, 2024, and all contents disclosed in the documents of the relevant Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a method for purifying isopropyl alcohol, and more particularly to a method that can reduce energy consumption and process costs when purifying isopropyl alcohol from a reaction product in the production process of isopropyl alcohol. [Background technology]

[0003] Isopropyl alcohol (IPA) is recognized as an excellent solvent in various industries and applications due to its ability to dissolve a wide range of substances, fast evaporation, and relatively low toxicity. Isopropyl alcohol is an essential substance in a variety of manufacturing, healthcare, and consumer applications.

[0004] In the process of producing isopropyl alcohol, for example, propylene and water are used as raw materials. At this time, the propylene and water react to produce isopropyl alcohol. In addition to isopropyl alcohol, unreacted propylene monomer, and unreacted water, the reaction products in the process of producing isopropyl alcohol contain various impurities or by-products such as diisopropyl ether (DIPE), acetone, n-propyl alcohol (NPA), and hexanol.

[0005] In order to obtain isopropyl alcohol from the reaction product, a purification process of isopropyl alcohol is necessarily required. Therefore, in order to obtain high-purity isopropyl alcohol, the purification process of isopropyl alcohol needs to be highly efficient, and an improved design is required from the economic point of view of reducing energy consumption, operating costs, and equipment costs. Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved by the present invention is to provide a method for producing isopropyl alcohol that can obtain high-purity isopropyl alcohol and reduce energy consumption and improve operating costs / equipment costs in order to solve the problems mentioned in the background art of the invention described above. An object of the present invention is to provide a method for producing isopropyl alcohol that can reduce energy consumption and improve operating costs / equipment costs.

[0007] However, the problems to be solved by the present application are not limited to those mentioned above, and other problems not mentioned can be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0008] According to one embodiment of the present invention for solving the above problems, the present invention provides a method for producing a feed containing isopropyl alcohol, water, a first light by-product, a second light by-product, and a heavy by-product, the method comprising the steps of: supplying a feed containing isopropyl alcohol, water, a first light by-product, a second light by-product, and a heavy by-product to a first column equipped with a first reboiler; separating the first light by-product from an upper outlet stream of the first column; supplying the lower outlet stream of the first column containing the isopropyl alcohol, water, the second light by-product, and a heavy by-product to a second column equipped with a second reboiler; and separating an upper outlet stream of the second column containing the second light by-product, a first side outlet stream of the second column containing a mixture of isopropyl alcohol and water, a second side outlet stream of the second column containing the heavy by-product, and and a bottom outlet stream from the second column containing the mixture of isopropyl alcohol and water; supplying the first side outlet stream from the second column containing the mixture of isopropyl alcohol and water to a third column divided into a first region, a second region, and an upper region by a dividing wall and equipped with a layer separator at its upper portion, to perform azeotropic distillation in the presence of an azeotropic agent; and obtaining isopropyl alcohol from the bottom outlet stream from the first region of the third column, wherein the top outlet stream from the third column is heat exchanged with one or more of the bottom outlet stream from the first column and the bottom outlet stream from the second column by one or more of the first reboiler and the second reboiler. [Effects of the Invention]

[0009] According to the method for producing isopropyl alcohol of the present invention, when separating isopropyl alcohol from a feed containing isopropyl alcohol, water, and by-products, at least two dividing wall distillation columns are used. This method makes it possible to obtain high-purity isopropyl alcohol using fewer columns than the number of columns conventionally required.

[0010] That is, according to the present invention, by operating fewer distillation columns than conventionally required, it is possible to reduce the energy consumption of the reboiler (energy saving), and by reducing the number of distillation columns, it is possible to achieve a reduction in the capital costs and operating costs of the equipment.

[0011] Furthermore, the high-temperature, high-pressure stream discharged from the top of the dividing wall distillation column can be used as a heat source for the reboiler of another distillation column before being introduced into a condenser or layer separator at the top of the dividing wall distillation column. This provides a method for producing isopropyl alcohol with improved energy efficiency throughout the entire process. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a process flow diagram of a method for producing isopropyl alcohol according to one embodiment of the present invention. [Figure 2] FIG. 1 is a process flow diagram of a method for producing isopropyl alcohol according to a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0013] The terms and words used in the description of the present invention and the claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, based on the principle that the inventors can appropriately define the concepts of terms in order to best describe their invention.

[0014] In connection with the description of the drawings, like reference numerals may be used for like or related components.

[0015] The singular form of a noun referring to an item can include one or more of said items unless the relevant context clearly dictates otherwise.

[0016] In this disclosure, each phrase such as "A or B," "at least one of A and B," "at least one of A or B," "A, B, or C," "at least one of A, B, and C," and "at least one of A, B, or C" can include any one or all possible combinations of the items listed in the corresponding phrase.

[0017] The term "and / or" includes combinations of the associated listed elements or any elements of the associated listed elements.

[0018] Terms such as "first," "second," or "first" or "second" may be used merely to distinguish a component from other components and do not limit the component in other respects (e.g., importance or order).

[0019] Furthermore, terms such as "front," "rear," "top," "bottom," "side," "left side," "right side," "upper," and "lower" used in this application are defined based on the drawings, and do not limit the shape or position of each component.

[0020] Terms such as "comprise" or "have" specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in this disclosure, but do not preclude the presence or possible addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0021] When a component is said to be "connected," "coupled," "supported," or "in contact with" another component, this includes not only cases where the components are directly connected, coupled, supported, or in contact, but also cases where the components are indirectly connected, coupled, supported, or in contact via a third component.

[0022] When a component is said to be located "on" another component, this includes not only the case where the component is in contact with the other component, but also the case where there is another component between the two components.

[0023] The term "stream" as used herein refers to the flow of fluid within a process, and may also refer to the fluid itself flowing through a pipe. Specifically, the term "stream" may refer to both the fluid itself and the flow of fluid flowing through a pipe connecting each device. The fluid may contain one or more components of gas, liquid, and solid.

[0024] Unless otherwise specified, the term "upper portion" used in this application means a point 0% to 10% below the top of the apparatus, specifically the top (top of the column), and the term "lower portion" means a point 90% to 100% below the top of the apparatus, specifically the bottom (bottom of the column).

[0025] Furthermore, "pressure" referred to in this application means gauge pressure measured under atmospheric pressure conditions.

[0026] On the other hand, unless otherwise specified in this application, the operating pressure of a column means the pressure at the top of the column, and the operating temperature of a column means the temperature at the bottom of the column.

[0027] One embodiment of the present invention relates to a method for producing isopropyl alcohol (IPA). Hereinafter, the method for producing isopropyl alcohol of the present invention will be described in detail with reference to the drawings.

[0028] FIG. 1 is a process flow diagram of a method for producing isopropyl alcohol according to one embodiment of the present invention.

[0029] The method for producing isopropyl alcohol according to the present invention includes providing a feed 10 containing isopropyl alcohol, water, a first light by-product, a second light by-product, and a heavy by-product to a first column 100.

[0030] The feed 10 may be derived from a reaction product containing isopropyl alcohol produced by the reaction of propylene monomer and water in the reaction section. Specifically, the feed 10 may be a residue obtained by separating and recovering gas components, including (unreacted) propylene and inert gases, contained in the reaction product.

[0031] Only a portion of the propylene supplied to the reaction section is used in the reaction. Therefore, the reaction product may contain unreacted propylene and unreacted water in addition to the isopropyl alcohol produced by the reaction of propylene monomer and water. For example, the reaction product may contain 65 to 85 wt% unreacted propylene monomer, 4 to 8 wt% isopropyl alcohol, and 5 to 30 wt% water. The reaction product may also contain at least two or more light and heavy by-products as by-products. Specifically, the light by-products may include diisopropyl ether (DIPE) and acetone, and the heavy by-products may include n-propyl alcohol (NPA) and hexanol. Therefore, a process is required to separate unreacted raw materials from the reaction product and purify isopropyl alcohol from the various by-products.

[0032] There are various methods for recovering (unreacted) propylene from the reaction product to prepare the feed 10 of the present invention. Among the various methods for recovering (unreacted) propylene from the reaction product, a method for recovering (unreacted) propylene at high purity and circulating it to the reaction section where the gas-phase reaction is performed will be exemplified below.

[0033] According to one embodiment of the present invention, propylene in the reaction product can be recovered by a gas purification unit equipped with two or more of an absorption tower, a flash drum, and a gas purification tower.

[0034] Specifically, the reaction product is supplied to the bottom of an absorption tower, and water is introduced into the top of the absorption tower to separate propylene. In this case, the water may be supplied from the bottom discharge stream of the second column described below. In the absorption tower, gaseous isopropyl alcohol contained in the reaction product is absorbed by the water to obtain a bottom liquid stream, and a gaseous stream containing propylene may be separated from the top of the absorption tower. The propylene contained in the gaseous stream may be recycled to the reaction section.

[0035] Meanwhile, in addition to isopropyl alcohol and water, the lower liquid stream from the absorption tower may also contain small amounts of low-boiling gas components, such as inert gases including propylene, that were not completely separated in the absorption tower. Therefore, the liquid stream containing isopropyl alcohol separated in the absorption tower can be supplied to a flash drum to recover additional propylene. For example, the liquid stream can be supplied to one or more flash drums operated under reduced pressure to recover low-boiling gas components, including propylene, contained in the liquid stream as a gas, which can then be supplied to a gas purification tower to recover additional propylene that may remain in the liquid stream containing isopropyl alcohol.

[0036] Such a process can separate an upper stream of vapor phase containing propylene and a lower stream of liquid phase containing isopropyl alcohol, water, etc. in an absorber, flash drum, and gas purification column.

[0037] Meanwhile, the liquid phase bottom stream separated in the absorption tower, flash drum, and gas purification tower may contain, in addition to isopropyl alcohol and water, a first light by-product including diisopropyl ether (DIPE), a second light by-product including acetone, and a heavy by-product including n-propyl alcohol (NPA) and hexanol. Thus, the liquid phase bottom stream separated in one or more of the absorption tower, flash drum, and gas purification tower for recovering propylene may be the feed 10 of the present invention supplied to the first column 100.

[0038] The feed 10 may be introduced into the first column 100 at a height 30 to 50% below the top of the column.

[0039] According to one embodiment of the present invention, the first light by-product contained in the feed 10 may be first separated and removed by the first column 100 and the layer separator 120 connected to the upper portion of the first column 100.

[0040] Specifically, as a result of distillation in the first column 100, a first column upper discharge stream 160 containing isopropyl alcohol, water, a first light by-product, and optionally a second light by-product, and a first column lower discharge stream 150 containing isopropyl alcohol, water, a second light by-product, and a heavy by-product, may be discharged from the top and bottom of the first column 100, respectively.

[0041] After being discharged from the first column 100, the top discharge stream 160 from the first column may be supplied to a condenser 110, where it is cooled and liquefied. The liquefied top discharge stream from the first column may be supplied to a phase separator 120 and subjected to liquid-liquid separation. Through the liquid-liquid separation, an aqueous phase stream containing isopropyl alcohol, water, and optionally a second light by-product may be refluxed to the first column, and an oil phase stream 170 containing the first light by-product may be discharged to the outside of the system. The amount of the first light by-product discharged to the outside of the system may be 97% by weight or more, 99% by weight or more, specifically 100% by weight, when the content of the first light by-product in the feed 10 is 100% by weight.

[0042] In order for the first light by-product to be easily separated by distillation in the first column 100 and liquid-liquid separation in the phase separator 120 installed at the top of the first column, at least the first light by-product should be an oily component that is not dissolved in water. That is, the first column 100 is operated under operating conditions that do not vaporize the heavy by-product, and the phase separator 120 separates the first light by-product from essentially water and isopropyl alcohol dissolved in water, thereby enabling efficient separation of the first light by-product.

[0043] According to one embodiment of the present invention, the first light by-product may be diisopropyl ether (DIPE), which is insoluble in water, and the second light by-product may be acetone, which is soluble in water. Because the boiling point of acetone is lower than that of diisopropyl ether, the top discharge stream 160 from the first column may contain water, isopropyl alcohol, acetone, and diisopropyl ether (DIPE). The isopropyl alcohol contained in the top discharge stream 160 from the first column is separated from the first light by-product (oil phase) by liquid-liquid separation performed in the phase separator 120, and the water, isopropyl alcohol, and acetone contained in the aqueous phase are returned to the first column 100. Therefore, the phase separator 120 installed at the top of the first column 100 minimizes the amount of isopropyl alcohol lost at the top of the first column 100.

[0044] On the other hand, the first light by-product contained in the feed 10 can be almost entirely discharged to the outside of the system. To achieve this, the operating conditions of the first column 100 should be controlled so that almost entirely the first light by-product contained in the feed 10 is discharged into the top discharge stream 160 of the first column 100.

[0045] Specifically, the operating temperature of the first column 100 may be 75°C or more, 80°C or more, and 95°C or less, 90°C or less. The operating temperature may refer to the temperature at the bottom of the first column 100. Meanwhile, the operating pressure of the first column 100 is 1 kg / cm. 2 ·g or less, 0.5 kg / cm 2 The operating pressure may be 0.1 MPa or less. The operating pressure may refer to the pressure at the top of the first column 100. When the first column 100 is operated at the above-described operating temperature and operating pressure, the first light by-product can be separated as much as possible into the top discharge stream 160 of the first column. This prevents the first light by-product from flowing into the bottom discharge stream 150 of the first column and consequently remaining as an impurity in the isopropyl alcohol produced. Furthermore, when the operating temperature and operating pressure of the first column 100 are as described above, efficient energy utilization is possible through heat exchange with the top discharge stream of the third column, which will be described later.

[0046] Meanwhile, in order to effectively recover isopropyl alcohol contained in the upper discharge stream 160 of the first column through the liquid-liquid separation performed in the layer separator 120 and return it to the first column, water should be supplied to the upper part of the first column. The water supplied to the upper part of the first column is supplied to the first column separately from the water contained in the feed 10. The water supplied to the upper part of the first column may be water contained in stream 20, which is a circulated stream obtained by branching off a portion of the water-containing lower discharge stream 250 of the second column, as described below.

[0047] Meanwhile, according to one embodiment of the present invention, the mass flow rate of the branch stream 20 of the bottom discharge stream 250 of the second column, which is recycled to the top of the first column, needs to be controlled in consideration of the amount of isopropyl alcohol lost in the layer separator 120 and the amount of energy consumed in the first column 100. Specifically, the mass flow rate of the branch stream 20 of the bottom discharge stream 250 of the second column relative to the mass flow rate of the feed 10 supplied to the first column 100 may be 0.4 to 1.2, 0.4 to 1.0, or 0.5 to 0.8. If the flow rate of water supplied to the top of the first column is greater than 1.2, the amount of energy required in the first column may increase excessively. On the other hand, if the flow rate of water supplied to the top of the first column is less than 0.4, it may be difficult to supply sufficient water to the layer separator 120, which may result in the loss of isopropyl alcohol as an oil phase or an excessive increase in the amount of loss.

[0048] Meanwhile, in the layer separator 120 installed at the top of the first column 100, isopropyl alcohol should be contained in the aqueous phase and refluxed together with water to the first column 100. If the isopropyl alcohol is contained in the oil phase, loss of isopropyl alcohol occurs in the layer separator 120. To prevent this loss of isopropyl alcohol, a sufficient amount of water should be secured in the layer separator 120. The amount of water in the layer separator 120 is affected by the amount of water introduced into the first column 100.

[0049] According to one embodiment of the present invention, the water introduced into the first column 100 may be water contained in the feed 10 and water contained in stream 20, which is a circulating stream formed by branching off a portion of the bottom discharge stream 250 from the second column. In order to minimize the loss of isopropyl alcohol in the phase separator 120, it is preferable that the sum of the mass flow rate of the water contained in the feed 10 and the mass flow rate of the water contained in stream 20, which is a circulating stream formed by branching off a portion of the bottom discharge stream 250 from the second column, be maintained at a ratio of 12 to 15 (mass flow rate ratio of isopropyl alcohol to water) relative to the mass flow rate of the isopropyl alcohol contained in the feed 10. In this case, a sufficient amount of water can be supplied to the phase separator 120, thereby preventing the loss of isopropyl alcohol as an oil phase in the phase separator 120 and optimizing the energy consumption required to operate the first column 100.

[0050] Specifically, the branched stream 20 obtained by branching off a portion of the water-containing discharge stream from the lower portion of the second column may be a branched stream obtained by branching off a stream to be refluxed to the reboiler 230 from the stream immediately after being discharged from the lower portion of the second column.

[0051] That is, when the mass flow ratio of the isopropyl alcohol to water supplied to the first column is less than 12, it is difficult to secure a sufficient amount of water in the layer separator 120, resulting in a loss of isopropyl alcohol as an oil phase and making it difficult to achieve a desired recovery rate of isopropyl alcohol. Furthermore, in this case, a problem may occur in that a portion of the first light by-product, which should be removed as an oil phase in the layer separator 120, is included in the aqueous phase and introduced into the second column 200. If such a first light by-product is introduced into the second column 200, it will be included in the first side discharge stream of the second column containing a mixture of isopropyl alcohol and water, resulting in a decrease in the purity of the isopropyl alcohol recovered from the second column.

[0052] Furthermore, if the mass flow ratio of the isopropyl alcohol to water supplied to the first column is greater than 15, the loss of isopropyl alcohol in the layer separator 120 can be prevented, but the amount of water circulating through the first column 100 and the second column 200 becomes excessively large, which increases the energy consumption of the two columns.

[0053] Furthermore, in order to minimize the loss of isopropyl alcohol in the layer separator 120 and reduce the amount of energy used in the first and second columns, the mass flow rate of water contained in the stream 20, which is a portion of the bottom discharge stream 250 of the second column branched off and recycled, may be 58% to 90% of the mass flow rate of water contained in the feed 10.

[0054] Meanwhile, a first reboiler 130 is provided at the bottom of the first column 100 to supply heat energy required for the operation of the first column. The reflux stream of the lower discharge stream 150 of the first column is introduced into the first reboiler 130 and is heat exchanged with a high-temperature heat source, and then may be introduced back into the bottom of the first column 100. The first reboiler 130 allows the first column 100 to be supplied with heat energy required for the operation of the first column 100.

[0055] According to one embodiment of the present invention, the heat source of the first reboiler 130, i.e., the heat source that exchanges heat with the reflux stream of the lower discharge stream 150 of the first column, may be the upper discharge stream 330 of the third column 300, as described below. Specifically, all or a portion of the upper discharge stream 330 of the third column may be heat exchanged with the reflux stream of the lower discharge stream 150 of the first column in the first reboiler 130 before being introduced into a condenser 380 or a layer separator 340 provided at the top of the third column 300. In this way, the thermal energy of the upper discharge stream of the third column 300 can be supplied to the first column 100.

[0056] Meanwhile, according to one embodiment of the present invention, if the thermal energy of the upper discharge stream 330 of the third column 300 alone cannot replace all of the reboiler energy required to operate the first column 100, an auxiliary reboiler 135 may be provided at the bottom of the first column 100, in addition to the first reboiler 130.

[0057] According to one embodiment of the present invention, the bottom effluent stream 150 of the first column is introduced into a second column 200 and separated into a second light by-product, a mixture of isopropyl alcohol and water, a heavy by-product, and water according to boiling point.

[0058] Specifically, the first column bottom discharge stream 150 containing the isopropyl alcohol, water, second light by-product, and heavy by-product may be supplied to a second column 200 equipped with a second reboiler 230, and separated into a second column top discharge stream 260 containing the second light by-product, a second column first side discharge stream 290 containing a mixture of the isopropyl alcohol and water, a second column second side discharge stream 280 containing the heavy by-product, and a second column bottom discharge stream 250 containing the water.

[0059] The second light by-product is a by-product having the lowest boiling point relative to the other components to be separated. The second light by-product may be a compound having a boiling point of 50 to 70°C, specifically acetone. The acetone may be a by-product produced during the gas-phase reaction to produce isopropyl alcohol, or may be a by-product produced by oxidation of isopropyl alcohol in a subsequent process after the gas-phase reaction. The upper discharge stream 260 from the second column may contain 60 wt% or more, 70 wt% or more, 90 wt% or more, and 100 wt% or less of the second light by-product, with the remainder being a mixture of isopropyl alcohol and water. After being discharged from the second column, the upper discharge stream 260 from the second column passes through a condenser, with a portion of the stream being refluxed back to the second column and the remainder being discharged to the outside of the system (270).

[0060] Meanwhile, the mixture of isopropyl alcohol and water may be an azeotrope of isopropyl alcohol and water. That is, water, which has a boiling point of about 100° C., and isopropyl alcohol, which has a boiling point of about 82.3° C., form an azeotrope at an azeotropic temperature of about 81° C. The boiling point of the azeotrope of isopropyl alcohol and water is higher than the boiling point of the second light by-product but lower than the boiling point of the heavy by-product.

[0061] Thus, a portion of the water introduced into the second column forms an azeotrope with the isopropyl alcohol and is discharged into the first side draw stream 290 of the second column, and the remaining water is discharged into the bottom draw stream 250 of the second column.

[0062] A second reboiler 230 is provided at the bottom of the second column 200 to supply heat energy required for the operation of the second column. The reflux stream, which is a discharge stream from the bottom of the second column, is introduced into the second reboiler 230 and heat-exchanged with a high-temperature heat source, and then may be introduced back into the bottom of the second column 200. The second reboiler 230 allows the second column 200 to be supplied with heat energy required for the operation of the second column.

[0063] According to one embodiment of the present invention, the heat source of the second reboiler 230, i.e., the heat source that exchanges heat with the reflux stream of the lower discharge stream of the second column, may be the upper discharge stream 330 of the third column 300, as described below. Specifically, all or a portion of the upper discharge stream 330 of the third column may be heat exchanged with the reflux stream of the lower discharge stream 250 of the second column in the second reboiler 230 before being introduced into the condenser 380 or layer separator 340 provided at the top of the third column 300. In this way, the thermal energy of the upper discharge stream of the third column 300 can be supplied to the first column 100.

[0064] According to one embodiment of the present invention, if the thermal energy of the upper discharge stream 330 of the third column 300 alone cannot replace all of the reboiler energy required to operate the second column 200, an auxiliary reboiler 235 may be provided at the bottom of the second column 200, in addition to the second reboiler 230.

[0065] Meanwhile, the water-containing bottom discharge stream 250 from the second column, specifically, a branch stream 20 formed by branching off a portion of the stream 250 discharged from the bottom of the second column 200 that is not supplied to the reboiler 230, may be recycled to the top of the first column. The water recycled from the second column 200 may be used to replenish a sufficient amount of water to facilitate the phase separation of the aqueous phase and the oil phase in the phase separator 120 provided at the top of the first column 100.

[0066] Meanwhile, the heavy by-products may include n-propyl alcohol (NPA) and hexanol, and such heavy by-products may be discharged into the second side draw stream 280 of the second column.

[0067] In one embodiment of the present invention, second column 200 includes a dividing wall spaced apart from the bottom of the column and arranged along the column length, and the second column can be a distillation column divided by the dividing wall into a top region 201, a bottom region 202, a supply region 203, and a discharge region 204.

[0068] 1, the interior of second column 200 is divided by the partition wall and the imaginary dotted line. Specifically, top region 201 is a region located above the upper end of the partition wall and is a region where upper discharge stream 260 of the second column is discharged, and bottom region 202 is a region located below the lower end of the partition wall and is a region where lower discharge stream 250 of the second column is discharged. Meanwhile, lower discharge stream 150 of the first column can be supplied to supply region 203.

[0069] The first side discharge stream 290 of the second column and the second side discharge stream 280 of the second column may be discharged from a discharge region 204 within the region partitioned by the partition wall. Specifically, the first side discharge stream 290 may be discharged from a discharge region above the second side discharge stream 280.

[0070] That is, according to one embodiment of the present invention, a composition containing at least four components, such as isopropyl alcohol, water, a second light by-product, and a heavy by-product (the bottom discharge stream of the first column) is separated and discharged into an upper section, a first side section, a second side section, and a lower section by a single column (the second column) equipped with a separating wall, thereby reducing the number of distillation columns conventionally required for separating these components.

[0071] Specifically, referring to FIG. 2, in which a distillation column without a dividing wall is used as the second column C2, although it is not impossible to discharge the separated product through the top, bottom, first, and second sides of the second column C2, in particular, because the side draw stream from which heavy by-products are separated contains a large amount of isopropyl alcohol and water, additional purification of the side draw stream is required to increase the isopropyl alcohol yield. That is, a process was previously required in which the side draw stream 280 was introduced into the third column C3, and an additional stream containing isopropyl alcohol was recovered from the top and then fed back to the second column C2. That is, referring to FIG. 2, according to the present invention, the same functions as those performed by the conventional second column C2 and third column C3 can be performed by a single distillation column equipped with a dividing wall, thereby reducing the number of columns and the energy consumption (e.g., steam consumption) required to operate the columns. Furthermore, by using a second column equipped with a separation wall, separation is first performed in the feed region 203 and final purification is performed in the discharge region 204, thereby achieving a reduction in energy consumption that is greater than simply operating two columns together.

[0072] Meanwhile, the upper end of the separation wall may be located at a height of 3% to 30% below the top of the second column, and the lower end of the separation wall may be located at a height of 70% to 95% below the top of the second column.

[0073] Furthermore, the first side draw stream 290 may be discharged from a point 5 to 33% below the top of the second column, and the second side draw stream 280 may be discharged from a point 40 to 80% below the top of the second column.

[0074] The location of the separator wall and the discharge points of the first and second side streams described above allow for reduced energy consumption compared to a conventional two-column system while providing four streams of desired purity from the second column.

[0075] The operating temperature and pressure of the top region 201 and bottom region 202 of the second column 200 must also be controlled in view of the purity of the components separated along with the isopropyl alcohol and the energy required to separate these components.

[0076] Specifically, the operating temperature of the top region 201 of the second column 200 may be 90°C or less, 85°C or less, or 80°C or less, and the operating pressure of the top region 201 may be 2 kg / cm 2 ·g or less, 1kg / cm 2 ·g or less, 0.05kg / cm 2 The operating temperature of the bottom region 202 of the second column 200 may be 85°C or higher, or 88°C or higher, and 105°C or lower, or 103°C or lower. The operating pressure of the bottom region 202 may be 1.0 kg / cm or lower. 2 ·g or less, 0.5kg / cm 2 ·g or less.

[0077] When the operating temperature and pressure of the second column 200 are as described above, efficient energy utilization is possible through heat exchange with the upper discharge stream of the third column described below.

[0078] A method for producing isopropyl alcohol according to one embodiment of the present invention may include feeding a first side draw stream 290 from the second column, comprising the mixture of isopropyl alcohol and water, to a third column 300, which is divided into a first region 301, a second region 302, and an upper region 303 by a separating wall 305 and is equipped with a layer separator 340 at its top, and performing azeotropic distillation in the presence of an azeotroping agent.

[0079] Specifically, the first side draw stream 290 of the second column 200 can include a mixture of isopropyl alcohol and water, specifically an azeotropic mixture of isopropyl alcohol and water. More specifically, the first side draw stream 290 of the second column can include 80-90 wt% isopropyl alcohol and 10-20 wt% water.

[0080] Meanwhile, third distillation column 300 according to one embodiment of the present invention is a dividing wall distillation column and may include first region 301, second region 302, and upper region 303, which are separated by dividing wall 305. Dividing wall 305 may be connected to the bottom of third distillation column 300 and extend upward in the longitudinal direction of third distillation column 300. In this case, first region 301 and second region 302 are separated regions that face each other across dividing wall 305, and second region 302 is a region facing first region 301. Meanwhile, upper region 303 is a region located above the upper end of the dividing wall, and is a region located above the imaginary boundary line indicated by the dotted line in third column 300 in FIG. 1.

[0081] Meanwhile, azeotropic distillation can be performed in the third distillation column 300 in the presence of an azeotropic agent. A portion of the isopropyl alcohol and a portion of the water contained in the first side discharge stream 290 of the second column 200 can form an azeotrope. Water, which has a boiling point of about 100°C, and isopropyl alcohol, which has a boiling point of about 82.3°C, form an azeotrope at an azeotropic temperature of about 81°C. Since the components of the azeotropic mixture formed in this manner cannot be completely separated by conventional distillation, an azeotropic agent is typically used to remove the azeotropic relationship between isopropyl alcohol and water, and then the isopropyl alcohol and water can be separated with high purity. The azeotropic agent of the present invention that performs this function can be one or more selected from the group consisting of cyclohexane, benzene, toluene, and isopropyl acetate.

[0082] The azeotropic agent is a substance that is added separately from the feed components for azeotropic distillation. However, since the azeotropic agent is an impurity in terms of isopropyl alcohol, etc., the azeotropic agent should be separated using a separate distillation column or the like, and from an economical point of view, the separated azeotropic agent should be recycled.

[0083] 2, a conventional method for separating isopropyl alcohol and water from a feed containing an isopropyl alcohol-water azeotrope and by-products involves azeotropic distillation using a conventional azeotropic distillation column C4 without a separating wall in the presence of an azeotropic agent. The top discharge stream containing water and azeotropic agent is then phase-separated in a layer separator, and the oil phase containing the azeotropic agent is then refluxed back to the azeotropic distillation column C4. However, because the aqueous phase still contains a large amount of azeotropic agent in addition to water, the aqueous phase is introduced into the azeotropic agent recovery column C5, where the azeotropic agent and water are separated by distillation. The recovered azeotropic agent is then introduced back into the azeotropic distillation column C4, while the water is discharged outside the system. Separating the azeotropic agent and water by distillation in the azeotropic agent recovery column C5 requires the supply of a large amount of energy via a reboiler installed at the bottom of the azeotropic agent recovery column C5.

[0084] Meanwhile, in the prior art, the azeotropic distillation column C4 receives heat energy required for its operation from a reboiler installed at the bottom. When the top discharge stream of the azeotropic distillation column C4 contains water and an azeotropic agent, the bottom discharge stream of the azeotropic distillation column C4 contains isopropyl alcohol and by-products. The bottom discharge stream of the azeotropic distillation column C4 is supplied to an isopropyl alcohol recovery column C6, and isopropyl alcohol is obtained from the top of the isopropyl alcohol recovery column C6, and by-products are separated from the bottom of the isopropyl alcohol recovery column C6.

[0085] However, referring to FIG. 1 , which illustrates a method for producing isopropyl alcohol according to one embodiment of the present invention, the present invention provides a dividing wall in the third distillation column 300 where azeotropic distillation is performed, and optimally designs the reflux point of the aqueous and oil phases refluxed from the layer separator 340. This allows for the production of high-purity isopropyl alcohol without the need for an azeotropic agent recovery column C5, which separates the azeotropic agent from the water. This not only reduces the thermal energy required to operate the conventional azeotropic agent recovery column C5 via a reboiler, but also reduces the cooling energy required to operate the condenser installed above the azeotropic agent recovery column C5. Furthermore, in addition to the energy savings achieved by not using the azeotropic agent recovery column C5, the energy consumption required to operate the distillation column can also be reduced when comparing the third distillation column 300 of the present invention, which is a dividing wall distillation column, with the conventional azeotropic distillation column C4.

[0086] To this end, according to one embodiment of the present invention, the first region 301 provided at the bottom of the third distillation column 300 may be provided with a reboiler 315 connected to the bottom of the first region, and the second region 302 may be provided with a reboiler 325 connected to the bottom of the second region. Here, the term "bottom" refers to a point 90% to 100% below the top (highest part) of the third distillation column 300. The first and second regions 301 and 302 may receive thermal energy from the reboilers 315 and 325, respectively, and the operating conditions of the first and second regions 301 and 302 may be adjusted by adjusting the thermal energy supplied by the reboilers 315 and 325, respectively.

[0087] According to one embodiment of the present invention, the thermal energy supplied by the reboiler 315 connected to the lower part of the first zone may be 1.5 to 3 times, more specifically 1.8 to 2.5 times, the thermal energy supplied by the reboiler 325 connected to the lower part of the second zone. As a result, isopropyl alcohol of a desired purity can be separated into a lower discharge stream from the first zone of the third distillation column, and pure water can be separated into a lower discharge stream from the second zone.

[0088] The temperature at the bottom of the first zone 301 can be 135°C or higher, 137°C or higher, and 150°C or lower, 148°C or lower. The temperature at the bottom of the second zone 302 can be 155°C or higher, 158°C or higher, and 170°C or lower, 168°C or lower. Here, each temperature at the bottom is the operating temperature at a point 90% to 100% below the top (highest part) of the column 100 in the first and second zones. By controlling the temperatures at the bottom of the first and second zones in this manner, it is possible to reduce the energy required for distillation in the third distillation column 300, as well as to obtain isopropyl alcohol of a desired purity from the bottom of the first zone and separate pure water from the bottom of the second zone.

[0089] Meanwhile, the first zone lower effluent stream 310 discharged from the first zone 301 of the third distillation column 300 may include isopropyl alcohol and heavy by-products. Here, the heavy by-products may include n-propyl alcohol (NPA). A portion of the first zone lower effluent stream 310 may be heat exchanged in a reboiler 315 connected to the bottom of the first zone and then returned to the first zone, and the remainder of the first zone lower effluent stream 310 may be supplied to the fourth column 400.

[0090] Meanwhile, the second zone lower discharge stream 320 discharged from the second zone 302 may contain water. A portion of the second zone lower discharge stream 320 may be heat exchanged in a reboiler 325 connected to the lower part of the second zone and then returned to the second zone, and the remainder of the second zone lower discharge stream 320 may be discharged to the outside of the system.

[0091] As described above, in the third distillation column 300, the region located above the upper end of the separation wall may form the upper region 303.

[0092] The separation wall 305 extends from the bottom of the column, and the upper end of the separation wall may be located at a height of 10 to 45%, or more specifically, 15 to 30%, below the top of the third distillation column 300. This maximizes the separation efficiency of the third distillation column 300, allowing isopropyl alcohol of a desired purity to be obtained from the bottom of the first zone and pure water to be separated from the bottom of the second zone.

[0093] From the top of the upper region, a top effluent stream 330 comprising water and entrainer can be discharged.

[0094] According to one embodiment of the present invention, the upper discharge stream 330 of the third column may be heat exchanged with one or more of the lower discharge stream of the first column and the lower discharge stream of the second column in one or more of the first reboiler 130 of the first column 100 and the second reboiler 230 of the second column 200. Thus, by supplying heat from the upper discharge stream 330 of the third column to one or more of the first column and the second column, the thermal energy required to operate one or more of the first column and the second column can be reduced.

[0095] 1, heat exchanger A provided at the top of the third column may be one or more of the first reboiler 130 of the first column and the second reboiler 230 of the second column. After being discharged from the third column 300, the top discharge stream 330 of the third column may be transferred to one or more of the first reboiler 130 and the second reboiler 230 to supply its heat energy to one or more of the first column 100 and the second column 200. In this case, the top discharge stream 330 of the third column may be heat exchanged in the first reboiler 130 or the second reboiler 230, or may be heat exchanged in both the first reboiler 130 and the second reboiler 230. When the upper discharge stream 330 of the third column is heat exchanged in both the first reboiler 130 and the second reboiler 230, the upper discharge stream 330 of the third column may be branched into two streams, and each branched stream may be heat exchanged in the first reboiler 130 and the second reboiler 230, respectively. In this case, heat exchanger A in FIG. 1 may refer to both the first reboiler 130 and the second reboiler 230. After the upper discharge stream 330 of the third column is heat exchanged in one or more of the first reboiler 130 and the second reboiler 230, the heat-exchanged upper discharge stream 330 of the third column may be transferred to a condenser 380 provided at the top of the third column 300. When the upper discharge stream 330 of the third column is branched and heat exchanged in both the first reboiler 130 and the second reboiler 230, the respective branched streams may be combined and transferred to the condenser 380 after heat exchange.

[0096] The operating pressure at the top of the third column 300 may be 4.9 barg to 5.1 barg. When the operating pressure at the top of the third column is 4.9 barg or higher, the temperature of the upper discharge stream 330 of the third column is at least 10°C higher than the temperature at the bottom of the first and second columns, making it possible to maintain a temperature difference for heat exchange between the first reboiler 130 of the first column 100 and the second reboiler 230 of the second column 200.

[0097] In particular, if the operating pressure at the top of the third column 300 is greater than 5.1 barg, a high temperature of the third column's upper discharge stream 330 can be achieved, and there is no problem with the heat supply to the first column 100 and the second column 200, but the separation performance of the third column 300 is reduced. In this case, additional energy must be supplied to the third column 300 to separate the components to the desired purity, which is undesirable from the perspective of reducing energy consumption. Conversely, if the operating pressure at the top of the third column 300 is less than 4.9 barg, it becomes difficult to maintain a high temperature of the third column's upper discharge stream 330, and it is difficult to ensure a sufficient temperature difference to enable heat exchange between the first reboiler 130 and the second reboiler 230.

[0098] Meanwhile, the operating temperature of the upper portion of the third column 300, specifically the upper portion of the upper region of the third column 300, may be 120° C. or higher, specifically 122° C. or higher. In this case, a suitable temperature difference (e.g., a temperature difference of at least 10° C.) required for heat exchange with the lower portions of the first column 100 and the second column 200 can be ensured, thereby enabling efficient energy supply to the first column 100 and the second column 200 via the upper discharge stream 330 of the third column.

[0099] Furthermore, the upper discharge stream 330 of the third column may be heat exchanged with the lower discharge stream of the first column and the lower discharge stream of the second column by the first reboiler 130 and the second reboiler 230. That is, when the upper discharge stream 330 of the third column is heat exchanged with both the first reboiler 130 and the second reboiler 230, the upper discharge stream 330 of the third column may be branched to form a branch stream supplied to the first reboiler 130 and a branch stream supplied to the second reboiler 230. In this case, the ratio of the mass flow rate of the branch stream supplied to the first reboiler to the mass flow rate of the branch stream supplied to the second reboiler may be 1:5 to 1:7. This ratio maximizes the logarithmic mean temperature difference (LMTD) between the low-temperature medium (the lower discharge streams of the first and second columns) and the high-temperature medium (the upper discharge stream of the third column) that are heat exchanged in the first reboiler 130 and the second reboiler 230, allowing for efficient design and operation of the first reboiler 130 and the second reboiler 230. Furthermore, the sizes of the auxiliary reboilers 135, 235 of the first and second columns can be minimized.

[0100] The upper discharge stream 330 of the third column 300 may be heat exchanged with one or more of the lower discharge stream of the first column 100 and the lower discharge stream of the second column in one or more of the first reboiler 130 of the first column 100 and the second reboiler 230 of the second column 200, and then cooled, and may be condensed in whole or in part into a liquid phase. The condensed upper discharge stream 330 of the third column 300 may be introduced into a condenser 380 provided at the top of the third column, and may undergo additional condensation until the desired condensation conditions are reached.

[0101] The discharge stream from condenser 380 after the additional condensation may be introduced into layer separator 340 provided at the top of the third column. Layer separator 340 is a device that separates fluids based on density differences, and can separate the fluid into an aqueous phase containing water and an oil phase containing an entrainer. An oil phase stream 350 containing an entrainer may be refluxed to upper region 303, and an aqueous phase stream 360 containing water may be refluxed to second region 302.

[0102] That is, after the top discharge stream 330 is separated into an oil phase and an aqueous phase by the layer separator 340, the separated oil phase and aqueous phase are returned to the third distillation column 300. Therefore, the mass flow rate of the top discharge stream 330 from the third distillation column may be equal to the sum of the mass flow rates of the aqueous phase stream 360 and the oil phase stream 350, which are returned to the third distillation column 300 via the layer separator 340. That is, substantially no components are supplied from the top discharge stream 330 from the third distillation column 300 to, for example, another distillation column or discharged to the outside of the system. That is, the top discharge stream 330 from the third distillation column 300 is discharged from the third column 300 and then supplied to one or more of the first reboiler 130 and the second reboiler 230, and then supplied to the condenser 380. After passing through the layer separator 340, the entire amount is returned to the third distillation column 300.

[0103] The azeotropic agent contained in the oil phase stream 350 is reused in the azeotropic distillation carried out in the third distillation column 300. By refluxing all of the separated oil and aqueous phases to the third distillation column 300 and optimizing the reflux point, the first zone bottom discharge stream 310 and the second zone bottom discharge stream 320 can be separated with high purity. Meanwhile, the azeotropic agent, which is inevitably consumed as the process progresses, can be replenished by being supplied (370) to the layer separator 340.

[0104] The reflux point of the aqueous phase to the second zone can be 10% to 50% of the height of the separation wall from the bottom of the column, specifically 25% to 40%, thereby minimizing the energy required for distillation and separating pure water from the bottom of the second zone.

[0105] More specifically, when the position of the upper end of the separation wall 305 and the position of the reflux point of the aqueous phase to the second region are set as described above, an azeotropic distillation region for separating isopropyl alcohol from water using an azeotropic agent and a distillation region for purifying isopropyl alcohol can be sufficiently secured simultaneously within the third distillation column 300. Furthermore, by sharing the upper region 303 above the separation wall between the first and second regions, the amount of energy required for the condenser 380 can be reduced. Furthermore, by optimally distributing the liquid reflux stream, which is branched from the bottom of the upper region 303 to the first and second regions 301 and 302 and flows downward, to the first and second regions, the amount of heat required for the reboiler in each region can be minimized.

[0106] Meanwhile, according to one embodiment of the present invention, the first zone lower discharge stream 310 discharged from the first zone 301 can be supplied to a fourth column 400 for recovering isopropyl alcohol. The fourth column 400 is operated with a reboiler 430 located at the bottom, and isopropyl alcohol can be obtained from the top of the fourth column 400 (410), and heavy by-products can be separated from the bottom of the fourth column (420).

[0107] 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 apparent to those skilled in the art that various changes and modifications can be made within the scope and technical concept of the present invention, and the scope of the present invention is not limited to these examples.

[0108] In the following Examples and Comparative Examples, the method of the present invention was simulated using Aspen Plus V12.1, a commercial process replication program.

[0109] Example 1 The isopropyl alcohol production process was carried out according to the process diagram shown in Figure 1.

[0110] Specifically, water and propylene were supplied to the reaction section and reacted in a gas phase to produce a reaction product containing isopropyl alcohol, water, and propylene. Propylene was separated and recovered from the reaction product, and the residue was used to prepare Feed 10. Feed 10 contained 10.395 wt% isopropyl alcohol, 88.9 wt% water, 0.5 wt% diisopropyl ether (DIPE) as a first light by-product, 0.005 wt% acetone as a second light by-product, and 0.2 wt% n-propyl alcohol (NPA) and hexanol as heavy by-products.

[0111] The feed 10 was supplied to the first column, and a portion of the bottom discharge stream of the second column 200 was branched off and introduced into the top of the first column 100. The mass flow rate of the branched stream 20, which was obtained by branching off a portion of the bottom discharge stream of the second column 200, was 0.6 relative to the mass flow rate of the feed 10 supplied to the first column 100.

[0112] A stream 160 containing isopropyl alcohol, water, diisopropyl ether, and acetone was discharged from the top of the first column 10 and fed to a condenser 110 and a layer separator 120. The aqueous phase containing isopropyl alcohol, water, and acetone was refluxed back to the first column 100, and the oil phase containing diisopropyl ether was discharged outside the system.

[0113] The bottom draw stream from the first column was introduced into a feed zone 203 of a second column equipped with a separating wall and separated by distillation into four draw streams: a top draw stream from the second column 260 containing acetone, a first side draw stream from the second column 290 containing an azeotrope of isopropyl alcohol and water, a second side draw stream from the second column 280 containing n-propyl alcohol (NPA) and hexanol, and a bottom draw stream from the second column 250 containing water.

[0114] Meanwhile, a first reboiler 130 was provided at the bottom of the first column 100, and a second reboiler 230 was provided at the bottom of the second column 200. An upper discharge stream 330 of the third column, which will be described later, was branched to form a branch stream supplied to the first reboiler 130 and a branch stream supplied to the second reboiler 230, and the respective branch streams were introduced into the first reboiler 130 and the second reboiler 230 at a mass flow ratio of 1:6, thereby supplying thermal energy to the bottoms of the first and second columns.

[0115] At this time, the thermal energy of the upper discharge stream 330 of the third column alone was not enough to maintain the desired operating conditions of the first and second columns, so additional thermal energy was supplied to the first and second columns by auxiliary reboilers 135 and 235 installed at the bottom of the first and second columns, respectively.

[0116] Meanwhile, the first side draw stream 290 from the second column contained 85.78 wt % isopropyl alcohol, 13.58 wt % water, and 0.64 wt % n-propyl alcohol (NPA) as a by-product. Also, because the ratio of the mass flow rate of isopropyl alcohol contained in the first side draw stream 290 from the second column to the mass flow rate of isopropyl alcohol contained in Feed 10 was 99.4%, there was no need to proceed with additional distillation of the second side draw stream 280 from the second column to increase the recovery rate of isopropyl alcohol.

[0117] The first side draw stream 290 from the second column, containing an azeotropic mixture of isopropyl alcohol and water, was then fed to a first zone of a third column 300 and subjected to azeotropic distillation in the presence of cyclohexane as an azeotroping agent.

[0118] The upper discharge stream 330 discharged from the upper region 303 of the third column 300 was branched at a mass flow ratio of 1:6 and supplied to the first reboiler 130 and the second reboiler 230, respectively, to supply heat energy to the lower portions of the first and second columns. The operating pressure of the upper region 303 of the third column 300 was 5.0 barg, and the temperature of the upper discharge stream 330 was 122°C. Meanwhile, the temperature of the lower discharge stream from the first column supplied to the first reboiler 130 was 85°C, and the temperature of the lower discharge stream from the second column supplied to the second reboiler 230 was 95°C. The temperature difference between the low-temperature medium and the high-temperature medium supplied to the first reboiler 130 and the second reboiler 230 was appropriate, allowing for efficient heat exchange.

[0119] After heat exchange in the first reboiler 130 and the second reboiler 230, the top discharge stream 330 of the third column was separated into an oil phase and an aqueous phase while passing through a condenser 380 and a layer separator 340 in that order. The oil phase stream 350 containing cyclohexane was refluxed to the top region, and the aqueous phase stream 360 containing water was refluxed to the second region. Here, the reflux point of the aqueous phase stream to the second region was 30% of the height of the separation wall from the bottom of the column.

[0120] Meanwhile, the first zone bottom discharge stream 310 containing isopropyl alcohol and n-propyl alcohol was fed to a fourth column 400, and isopropyl alcohol was obtained from the top of the fourth column 400. The content of isopropyl alcohol in the top discharge stream from the fourth column was confirmed to be 99.8 wt%.

[0121] The energy consumed by the reboilers of each column is shown in Table 1. Specifically, the thermal energy supplied to the first reboiler of the first column and the second reboiler of the second column is supplied from the upper part of the third column, so the reboiler energy consumed in the first and second columns is shown in Table 1 as the thermal energy supplied by auxiliary reboilers 135 and 235 installed at the lower part of the first and second columns, respectively. Meanwhile, the thermal energy supplied by reboiler 315 connected to the lower part of the first region of the third column and the thermal energy supplied by reboiler 325 connected to the lower part of the second region of the third column are shown in Table 1, respectively.

[0122] Comparative Example 1 The isopropyl alcohol production process was carried out according to the process diagram shown in Figure 2.

[0123] A bottom discharge stream from the first column C1 having the same composition as in Example 1 was obtained from the same feed 10 as in Example 1, and introduced into the second column C2.

[0124] The second column C2 in Comparative Example 1 was a column without a separating wall. The second column C2 separated the mixture into four effluent streams by distillation in the same manner as in Example 1: a top effluent stream from the second column containing acetone, a first side effluent stream from the second column containing an azeotropic mixture of isopropyl alcohol and water, a second side effluent stream from the second column containing n-propyl alcohol (NPA) and hexanol, and a bottom effluent stream from the second column containing water.

[0125] In this case, the second side draw stream of the second column contained a large amount of isopropyl alcohol, and the heavy by-products and water were not effectively separated when the second side draw stream was discharged, so it was impossible to achieve a 99% yield of isopropyl alcohol contained in the first side draw stream of the second column by operating the second column C2 alone. Therefore, a third column C3 was required to further purify the isopropyl alcohol in the second side draw stream of the second column and separate the heavy by-products and water.

[0126] Specifically, the second side discharge stream of the second column was introduced into the third column C3, a stream containing isopropyl alcohol was separated from the top of the third column and fed back to the second column C3, water was separated from the bottom of the third column, and heavy by-products (n-propyl alcohol and hexanol) were separated from the side of the third column.

[0127] The energy required to operate the first to third columns was supplied by reboilers installed at the bottom of the first to third columns.

[0128] The first side draw stream from the second column, containing an azeotropic mixture of isopropyl alcohol and water, was passed through a conventional azeotropic distillation column C4 without a separating wall, an azeotropic agent recovery column C5, and an isopropyl alcohol recovery column C6, and isopropyl alcohol was recovered from the top of the isopropyl alcohol recovery column C6. Each of the three columns was equipped with a condenser at the top and a reboiler at the bottom.

[0129] Specifically, the first side draw stream from the second column, containing an azeotropic mixture of isopropyl alcohol and water, was fed to a conventional azeotropic distillation column C4, where azeotropic distillation was carried out in the presence of cyclohexane. The top draw stream, containing water and azeotropic agent, was phase-separated in a phase separator. The oil phase, containing azeotropic agent, was then refluxed back to the azeotropic distillation column C4, while the aqueous phase, containing water, was fed to the azeotropic agent recovery column C5. The bottom draw stream from the azeotropic distillation column C4, containing isopropyl alcohol and heavy by-products, was fed to the isopropyl alcohol recovery column C6, where isopropyl alcohol was recovered from the top.

[0130] Meanwhile, in Comparative Example 1, the composition and flow rate of the bottom discharge stream from azeotropic distillation column C4 introduced into isopropyl alcohol recovery column C6 were the same as in Example 1, and the operating conditions and energy used for isopropyl alcohol recovery column C6 in Comparative Example 1 were also the same as in Example 1. As a result, the content of isopropyl alcohol obtained in Comparative Example 1 was confirmed to be 99.8 wt%, the same as in Example 1.

[0131] At this time, the energy (heat energy) used in the reboilers installed at the bottom of each column (columns C1 to C6) in Comparative Example 1 is shown in Table 1.

[0132] [Table 1]

[0133] As can be seen from the above results, high levels of isopropyl alcohol purity and yield were maintained in Example 1. In particular, when dividing wall distillation columns having a specific structure were used as the second and third columns and the heat of the top discharge stream of the third column was used as the energy source required to operate the first and second columns, it was found that the energy efficiency of the entire process from the first to fourth columns was maximized. [Explanation of symbols]

[0134] 10 Feeds 100 Column 1 200 Column 2 300 Column 3 400 Column 4

Claims

1. supplying a feed comprising isopropyl alcohol, water, a first light by-product, a second light by-product, and a heavy by-product to a first column equipped with a first reboiler; separating the first light by-product from the top effluent stream of the first column; feeding the bottom draw stream from the first column, which includes the isopropyl alcohol, water, a second light by-product, and a heavy by-product, to a second column equipped with a second reboiler, and separating the bottom draw stream from the first column into a top draw stream from the second column which includes the second light by-product, a first side draw stream from the second column which includes the mixture of isopropyl alcohol and water, a second side draw stream from the second column which includes the heavy by-product, and a bottom draw stream from the second column which includes the water; feeding the first side draw stream from the second column, comprising the mixture of isopropyl alcohol and water, to a third column, the third column being divided by a dividing wall into a first region, a second region, and an upper region, the third column being equipped with a layer separator thereon, to perform azeotropic distillation in the presence of an azeotroping agent; obtaining isopropyl alcohol from the first zone bottoms effluent stream of the third column; the top effluent stream of the third column is heat exchanged with one or more of the bottom effluent stream of the first column and the bottom effluent stream of the second column by one or more of the first reboiler and the second reboiler.

2. 2. The method for producing isopropyl alcohol according to claim 1, wherein the top discharge stream of the third column is heat exchanged with at least one of the bottom discharge stream of the first column and the bottom discharge stream of the second column, and then sequentially supplied to a condenser provided at an upper portion of the third column and the layer separator.

3. the second column includes a separation wall spaced from the bottom and extending along the length of the column; the second column is divided by the separation wall into a top region, a bottom region, a supply region, and a discharge region; a first side draw stream and a second side draw stream of the second column are discharged from the discharge region; 2. The method for producing isopropyl alcohol according to claim 1, wherein the first side discharge stream is discharged from a discharge region above the second side discharge stream.

4. the third column includes a separation wall connected to the bottom and extending along the length of the column; The method for producing isopropyl alcohol according to claim 1, wherein the separation wall divides the mixture into a first region, a second region opposite the first region, and an upper region located above an upper end of the separation wall.

5. 2. The method for producing isopropyl alcohol according to claim 1, wherein a branched stream obtained by branching off a portion of the bottom discharge stream of the second column containing water is recycled to the top of the first column.

6. The method for producing isopropyl alcohol according to claim 5, wherein the mass flow rate of the branch stream recycled to the top of the first column is 0.4 to 1.2 relative to the mass flow rate of the feed supplied to the first column.

7. 2. The method for producing isopropyl alcohol of claim 1, wherein the top effluent stream of the third column is heat exchanged with the bottom effluent stream of the first column and the bottom effluent stream of the second column by the first reboiler and the second reboiler.

8. an upper outlet stream of the third column is split to form a split stream fed to the first reboiler and a split stream fed to the second reboiler; 2. The method for producing isopropyl alcohol according to claim 1, wherein the ratio of the mass flow rate of the branch stream supplied to the first reboiler to the mass flow rate of the branch stream supplied to the second reboiler is 1:5 to 1:

7.

9. 2. The method for producing isopropyl alcohol according to claim 1, wherein the top discharge stream of the third column is pressurized at 4.9 bar.g to 5.1 bar.g and then heat exchanged with one or more of the bottom discharge stream of the first column and the bottom discharge stream of the second column.

10. 2. The method for producing isopropyl alcohol according to claim 1, wherein an upper discharge stream containing water and entrainer discharged from an upper portion of the upper region of the third column is supplied to the layer separator and separated into an aqueous phase stream containing water and an oil phase stream containing entrainer, and the oil phase stream is refluxed to the upper region and the aqueous phase stream is refluxed to the second region.

11. The reflux point of the aqueous phase to the second region is The method for producing isopropyl alcohol according to claim 10, wherein the separation wall is located at a point 20% to 50% of the height from the bottom of the column.

12. 11. The method for producing isopropyl alcohol according to claim 10, wherein the mass flow rate of the top discharge stream is the same as the sum of the mass flow rates of the aqueous phase stream and the oil phase stream that are refluxed to the third distillation column through the layer separator.

13. the first zone bottom effluent stream of the third column is fed to a fourth column; 2. The method for producing isopropyl alcohol according to claim 1, wherein isopropyl alcohol is obtained from the top of the fourth column and heavy by-products are separated from the bottom of the fourth column.

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