Method for preparing isopropyl alcohol

Abstract

The present invention provides a method for preparing isopropyl alcohol, the method comprising the following steps: 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 so as to separate the first light by-product; and supplying a bottom discharge stream of the first column to a second column so as to separate into a second column top discharge stream comprising the second light by-product, a first side discharge stream of the second column, comprising a mixture of the isopropyl alcohol and water, a second side discharge stream of the second column, comprising the heavy by-product, and a second column bottom discharge stream comprising the water.

Description

Method for producing isopropyl alcohol

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0158482, filed November 15, 2023, and Korean Patent Application No. 10-2024-0147806, filed October 25, 2024, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a method for purifying isopropyl alcohol, and more particularly, to a method for reducing energy consumption and process costs in purifying isopropyl alcohol from a reaction product of an isopropyl alcohol manufacturing process.

[0005] Isopropyl alcohol (IPA) is recognized as an excellent solvent in a variety of industries and applications due to its ability to dissolve a wide range of substances, rapid vaporization, and relatively low toxicity. Isopropyl alcohol is essential for a variety of manufacturing, healthcare, and consumer applications.

[0006] The process for manufacturing isopropyl alcohol uses, for example, propylene and water as raw materials. The propylene and water react to produce isopropyl alcohol. The reaction product of the isopropyl alcohol manufacturing process includes isopropyl alcohol, unreacted propylene monomer, unreacted water, and various impurities or byproducts, such as diisopropyl ether (DIPE), acetone, n-propyl alcohol (NPA), and hexanol.

[0007] Obtaining isopropyl alcohol from the above reaction product essentially involves a purification process. Therefore, to obtain high-purity isopropyl alcohol, the purification process must be highly efficient. Simultaneously, an improved design is required from an economic perspective, one that not only reduces energy consumption but also reduces operating and facility costs.

[0008] The problem to be solved in the present invention is to provide a method for producing isopropyl alcohol that can obtain high-purity isopropyl alcohol while simultaneously reducing energy consumption and improving operating costs / equipment costs, in order to solve the problem mentioned in the technology that forms the background of the above invention.

[0009] However, the problems that the present invention seeks to solve are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

[0010] According to one embodiment of the present invention for solving the above problem, the present invention provides a process for producing a feedstock comprising: 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 a top discharge stream of the first column; supplying a bottom discharge stream of the first column comprising 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 top discharge stream of the second column comprising the second light by-product, a first side discharge stream of the second column comprising a mixture of the isopropyl alcohol and water, a second side discharge stream of the second column comprising the heavy by-product, and a bottom discharge stream of the second column comprising the water; and providing the first side discharge stream of the second column comprising the mixture of the isopropyl alcohol and water to a first zone, a second zone, and an upper zone, the first zone being partitioned by a dividing wall and having a layer separator provided at the top. The present invention provides a method for producing isopropyl alcohol, comprising the steps of supplying the isopropyl alcohol to a third column, performing azeotropic distillation in the presence of an azeotropic agent, and obtaining isopropyl alcohol from a first zone bottom discharge stream of the third column, 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 through at least one of the first reboiler and the second reboiler.

[0011] According to the method for producing isopropyl alcohol of the present invention, a method is provided for producing high-purity isopropyl alcohol using at least two dividing wall distillation columns to separate isopropyl alcohol from a feed containing isopropyl alcohol, water, and by-products, thereby obtaining high-purity isopropyl alcohol with a smaller number of columns than previously required.

[0012] That is, according to the present invention, by operating a smaller number of distillation columns than previously required, reboiler energy can be saved (energy saving), and the equipment cost and operating cost of the device can be saved by reducing the number of distillation columns.

[0013] Furthermore, by utilizing a high-temperature, high-pressure stream as a top discharge stream of a dividing wall distillation column as a reboiler heat source of another distillation column before introducing it into a condenser or a layer separator provided at the top of the dividing wall distillation column, a method for producing isopropyl alcohol with improved energy efficiency of the overall process can be provided.

[0014] Figure 1 is a process flow diagram of a method for producing isopropyl alcohol according to one embodiment of the present invention.

[0015] Figure 2 is a process flow diagram of a method for manufacturing isopropyl alcohol according to a comparative example.

[0016] The terms or words used in the description and claims of the present invention should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0017] In connection with the description of the drawings, similar reference numerals may be used for similar or related components.

[0018] The singular form of a noun corresponding to an item may include one or more of said items, unless the relevant context clearly indicates otherwise.

[0019] In this disclosure, each of the phrases "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" may include any one of the items listed together in the corresponding phrase, or all possible combinations thereof.

[0020] The term "and / or" includes any combination of a plurality of related described elements or any one of a plurality of related described elements.

[0021] Terms such as "first," "second," or "first" or "second" may be used simply to distinguish one component from another and do not qualify the components in any other respect (e.g., importance or order).

[0022] In addition, terms such as 'front', 'rear', 'top', 'bottom', 'side', 'left', 'right', 'upper', and 'lower' used in this application are defined based on the drawings, and the shape and position of each component are not limited by these terms.

[0023] Terms such as "include" or "have" are intended to specify the presence of a feature, number, step, operation, component, part or combination thereof described in the present disclosure, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0024] 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 through a third component.

[0025] When we say that a component is "on" another component, this includes not only cases where the component is in contact with the other component, but also cases where there is another component between the two components.

[0026] The term "stream" as used herein may refer to the flow of fluid within a process, or may refer to the fluid itself flowing within a pipe. Specifically, the stream may refer to both the fluid itself flowing within the pipe connecting each device and the flow of the fluid. Furthermore, the fluid may include one or more components of gas, liquid, and solid.

[0027] The term "upper" as used herein, unless otherwise specified, refers to a point 0% to 10% in height downward from the top of the device, and may specifically refer to the top (top). In addition, the term "lower" refers to a point 90% to 100% in height downward from the top of the device, and may specifically refer to the bottom (bottom).

[0028] Additionally, the “pressure” referred to herein means gauge pressure measured under atmospheric pressure conditions.

[0029] Meanwhile, unless otherwise specified herein, the operating pressure of the column means the pressure at the top of the column, and the operating temperature of the column means the temperature at the bottom of the column.

[0030] 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.

[0031] Figure 1 is a process flow diagram of a method for producing isopropyl alcohol according to one embodiment of the present invention.

[0032] A method for producing isopropyl alcohol according to the present invention includes a step of supplying a feed (10) comprising isopropyl alcohol, water, a first light by-product, a second light by-product, and a heavy by-product to a first column (100).

[0033] The above feed (10) may be derived from a reaction product comprising isopropyl alcohol generated through the reaction of propylene monomer and water performed in the reaction section. Specifically, the feed (10) may be a residue recovered by separating and recovering a gas component comprising (unreacted) propylene and an inert gas contained in the reaction product.

[0034] Only a portion of the propylene supplied to the above reaction unit is used in the reaction. Therefore, the reaction product may include unreacted propylene and unreacted water in addition to isopropyl alcohol produced by the reaction of propylene monomer and water. For example, the reaction product may include 65 to 85 wt% of unreacted propylene monomer, 4 to 8 wt% of isopropyl alcohol, and 5 to 30 wt% of water. In addition, the reaction product may include at least two types of light byproducts and heavy byproducts as byproducts. Specifically, light byproducts may include diisopropyl ether (DIPE) and acetone, and heavy byproducts may include n-propyl alcohol (NPA) and hexanol. Therefore, a process for separating unreacted raw materials from the reaction product and purifying isopropyl alcohol from various byproducts is required.

[0035] There are various methods for recovering (unreacted) propylene from the reaction product to prepare the feed (10) of the present invention. Below, among the various methods for recovering (unreacted) propylene from the reaction product, a method for recovering high-purity (unreacted) propylene and circulating it to the reaction section where the gas phase reaction is performed is presented as an example.

[0036] According to one embodiment of the present invention, recovery of propylene among the reaction products can be performed by a gas purification unit equipped with two or more of an absorption tower, a flash drum, and a gas purification tower.

[0037] Specifically, the reaction product is supplied to the bottom of the absorption tower, and water is introduced into the top of the absorption tower to separate propylene. At this time, the water may be supplied from the bottom discharge stream of the second column described below. In the absorption tower, the gaseous isopropyl alcohol contained in the reaction product is absorbed into the water and obtained as 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 unit.

[0038] Meanwhile, the lower liquid stream of the absorption tower may contain, in addition to isopropyl alcohol and water, a small amount of low-boiling-point gas components such as propylene and inert gases that were not separated in the absorption tower. Therefore, the liquid stream containing isopropyl alcohol separated in the absorption tower may be supplied to a flash drum to additionally recover propylene. For example, the liquid stream may be supplied to one or more flash drums operated under reduced pressure to recover low-boiling-point gas components including propylene contained in the liquid stream as gas, and then supplied to a gas purification tower to additionally recover propylene that may remain in the liquid stream containing isopropyl alcohol.

[0039] Through this process, a gaseous top stream containing propylene and a liquid bottom stream containing isopropyl alcohol and water can be separated from the absorption tower, flash drum and gas purification tower.

[0040] Meanwhile, the liquid bottom stream separated from the absorption tower, flash drum, and gas purification tower may include, 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. In this way, the liquid bottom stream separated from at least one of the absorption tower, flash drum, and gas purification tower for recovery of propylene may be the feed (10) of the present invention supplied to the first column (100).

[0041] The above feed (10) can be introduced at a height point of 30 to 50% downward from the top of the first column (100).

[0042] According to one embodiment of the present invention, the first hard byproduct included in the feed (10) can be first separated and removed by the first column (100) and the separator (120) connected to the upper portion of the first column (100).

[0043] Specifically, a top discharge stream (160) of the first column (100) containing isopropyl alcohol, water, a first light by-product, and optionally a second light by-product, and a bottom discharge stream (150) of the second column containing isopropyl alcohol, water, a second light by-product, and a heavy by-product can be discharged from the top and bottom of the first column (100), respectively, by distillation.

[0044] The top discharge stream (160) of the first column may be supplied to a condenser (110) to be cooled and liquefied after being discharged from the first column (100). The liquefied top discharge stream of the first column may be supplied to a separator (120) to be subjected to liquid-liquid separation. Through the liquid-liquid separation, an aqueous stream including isopropyl alcohol, water, and optionally a second light by-product may be refluxed to the first column, and an oil phase stream (170) including 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 wt% or more, 99 wt% or more, specifically 100 wt%, when the content of the first light by-product included in the feed (10) is 100 wt%.

[0045] 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 separator (120) provided on the upper portion of the first column, at least the first light by-product must be an oily component that does not dissolve in water. That is, the first column (100) is operated under operating conditions in which the heavy by-product is not vaporized, and the separator (120) substantially separates water and isopropyl alcohol dissolved in water from the first light by-product, thereby enabling efficient separation of the first light by-product.

[0046] 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. Since the boiling point of acetone is lower than that of diisopropyl ether, the top discharge stream (160) of the first column may include water, isopropyl alcohol, acetone, and diisopropyl ether (DIPE). The isopropyl alcohol included in the top discharge stream (160) of the first column is separated from the first light by-product (oil phase) by liquid-liquid separation performed in the layer separator (120), and the water, isopropyl alcohol, and acetone included in the water phase are refluxed back to the first column (100). Therefore, the amount of isopropyl alcohol lost from the top of the first column (100) can be minimized by the layer separator (120) provided at the top of the first column (100).

[0047] Meanwhile, almost all of the first light byproduct contained in the feed (10) can be discharged outside the system. To this end, the operating conditions of the first column (100) must be controlled so that almost all of the first light byproduct contained in the feed (10) can be included in the upper discharge stream (160) of the first column (100).

[0048] Specifically, the operating temperature of the first column (100) may be 75°C or higher, 80°C or higher, and 95°C or lower, 90°C or lower. 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) may be 1 kg / cm 2 ·g or less, 0.5 kg / cm 2·g or less. The above operating pressure may refer to the pressure at the top of the first column (100). When the first column (100) is operated at the operating temperature and operating pressure as described above, the first light by-product can be separated as much as possible into the top discharge stream (160) of the first column, and thus the first light by-product can be prevented from flowing out into the bottom discharge stream (150) of the first column and remaining as an impurity in the isopropyl alcohol produced as a result. 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 described below.

[0049] Meanwhile, in order to effectively recover the isopropyl alcohol contained in the upper discharge stream (160) of the first column by the liquid-liquid separation performed in the separator (120) and reflux it back to the first column, water must be supplied to the upper portion of the first column. The water supplied to the upper portion 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 portion of the first column may be water contained in the stream (20) in which a portion of the lower discharge stream (250) of the second column containing water is branched off and circulated, as described below.

[0050] 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 recycled to the top of the first column needs to be controlled in view of the loss of isopropyl alcohol in the separator (120) and the energy usage 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 may be 0.4 to 1.2, 0.4 to 1.0, or 0.5 to 0.8 relative to the mass flow rate of the feed (10) supplied to the first column (100). When the flow rate of water supplied to the top of the first column is greater than 1.2, there is a problem that the energy usage required in the first column excessively increases. On the other hand, if the flow rate of water supplied to the upper portion of the first column is less than 0.4, it becomes difficult to supply sufficient water to the layer separator (120), and thus isopropyl alcohol may be lost as an oil phase or the amount lost may increase excessively.

[0051] Meanwhile, in the layer separator (120) provided on the upper portion of the first column (100), isopropyl alcohol must be included in the aqueous phase and refluxed together with water to the first column (100). If the isopropyl alcohol is included in the oil phase, loss of isopropyl alcohol occurs in the layer separator (120), and in order to prevent such loss of isopropyl alcohol, a sufficient amount of water must 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).

[0052] According to one embodiment of the present invention, the water introduced into the first column (100) may be water included in the feed (10) and water included in the stream (20) into which a portion of the bottom discharge stream (250) of the second column is branched and circulated. In order to minimize the loss of isopropyl alcohol in the separator (120), it is preferable that the sum of the mass flow rate of the water included in the feed (10) and the mass flow rate of the water included in the stream (20) into which a portion of the bottom discharge stream (250) of the second column is branched and circulated is maintained at a ratio of 12 to 15 times (mass flow rate ratio of isopropyl alcohol and water) compared to the mass flow rate of the isopropyl alcohol included in the feed (10). In this case, a sufficient amount of water can be supplied to the separator (120), thereby preventing loss of isopropyl alcohol to the oil phase in the separator (120), and at the same time, the energy consumption required for the operation of the first column (100) can be optimized.

[0053] Specifically, the branch stream (20) from which a portion of the bottom discharge stream of the second column containing the water is branched may be a branch stream from which a portion is branched from a stream that is refluxed to the reboiler (230) among the streams immediately after being discharged to the bottom of the second column.

[0054] That is, when the mass flow rate ratio of the isopropyl alcohol and 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), so that loss of isopropyl alcohol to the oil phase occurs, making it difficult to achieve the desired recovery rate of isopropyl alcohol. Furthermore, in this case, a problem may arise that some of the first light byproducts that should be removed by including them in the oil phase in the layer separator (120) are included in the water phase and introduced into the second column (200), and when these first light byproducts are introduced into the second column (200), they are included in the first side discharge stream of the second column containing a mixture of isopropyl alcohol and water, which consequently lowers the purity of the isopropyl alcohol recovered from the second column.

[0055] In addition, when the mass flow rate ratio of the isopropyl alcohol and water supplied to the first column is greater than 15, the loss of isopropyl alcohol in the layer separator (120) can be prevented, but there is a problem in that the amount of water circulating through the first column (100) and the second column (200) becomes excessively large, thereby increasing the energy consumption of the two columns.

[0056] Furthermore, from the viewpoint of minimizing the loss of isopropyl alcohol in the separator (120) and reducing the amount of energy used in the first and second columns, the mass flow rate of water included in the stream (20) in which a portion of the lower discharge stream (250) of the second column is branched and circulated may be 58% to 90% based on the mass flow rate of water included in the feed (10).

[0057] 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. A reflux stream of the bottom discharge stream (150) of the first column can be introduced into the first reboiler (130), heat-exchanged with a high-temperature heat source, and then introduced again into the bottom of the first column (100). Heat energy required for the operation of the first column (100) can be supplied to the first column (100) through the first reboiler (130).

[0058] According to one embodiment of the present invention, the heat source of the first reboiler (130), i.e., the heat source that is heat-exchanged with the reflux stream of the bottom discharge stream (150) of the first column, may be the top discharge stream (330) of the third column (300), as described below. Specifically, all or part of the top discharge stream (330) of the third column may be heat-exchanged with the reflux stream of the bottom discharge stream (150) of the first column in the first reboiler (130) before being introduced into the condenser (380) or the layer separator (340) provided at the top of the third column (300). Through this, the thermal energy of the top discharge stream of the third column (300) can be supplied to the first column (100).

[0059] Meanwhile, according to one embodiment of the present invention, in cases where the thermal energy of the upper discharge stream (330) of the third column (300) alone cannot completely replace the reboiler energy required for the operation of the first column (100), an auxiliary reboiler (135) may be provided at the bottom of the first column (100) separately from the first reboiler (130).

[0060] According to one embodiment of the present invention, the bottom discharge stream (150) of the first column is introduced into the second column (200), so that a second light by-product, a mixture of isopropyl alcohol and water, a heavy by-product, and water can be separated according to boiling point.

[0061] Specifically, a step of supplying the bottom discharge stream (150) of the first column including the isopropyl alcohol, water, second light by-product, and heavy by-product to a second column (200) equipped with a second reboiler (230) and separating the second column top discharge stream (260) including the second light by-product, the first side discharge stream (290) of the second column including a mixture of the isopropyl alcohol and water, the second side discharge stream (280) of the second column including the heavy by-product, and the second column bottom discharge stream (250) including the water may be performed.

[0062] The second light by-product is a by-product having a relatively lowest boiling point compared to other separated components, and the second light by-product may be a compound having a boiling point of 50 to 70°C, and specifically, may be acetone. The acetone may be a by-product generated during a gas phase reaction for producing isopropyl alcohol, and may be a by-product generated by oxidation of isopropyl alcohol in a subsequent process after the gas phase reaction. The second column top discharge stream (260) may include 60 wt% or more, 70 wt% or more, 90 wt% or more, and 100 wt% or less of the second light by-product, and may include a mixture of isopropyl alcohol and water in the remainder. After the second column top discharge stream (260) is discharged from the second column, it may pass through a condenser, and a portion thereof may be refluxed back to the second column, and the remainder may be discharged outside the system (270).

[0063] Meanwhile, the mixture of isopropyl alcohol and water may be an azeotrope. 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 byproduct and lower than the boiling point of the heavy byproduct.

[0064] Therefore, some of the water introduced into the second column forms an azeotropic mixture with isopropyl alcohol and is discharged as the first side discharge stream (290) of the second column, and the remaining water is discharged as the bottom discharge stream (250) of the second column.

[0065] 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. A reflux stream among the lower discharge streams of the second column may be introduced into the second reboiler (230), heat-exchanged with a high-temperature heat source, and then introduced again into the bottom of the second column (200). The heat energy required for the operation of the second column (200) may be supplied to the second column (200) through the second reboiler (230).

[0066] 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 bottom discharge stream of the second column, may be the top discharge stream (330) of the third column (300), as described below. Specifically, all or part of the top discharge stream (330) of the third column may be heat-exchanged with the reflux stream of the bottom discharge stream (250) of the second column in the second reboiler (230) before being introduced into the condenser (380) or the layer separator (340) provided at the top of the third column (300). Through this, the thermal energy of the top discharge stream of the third column (300) can be supplied to the first column (100).

[0067] According to one embodiment of the present invention, in cases where the thermal energy of the upper discharge stream (330) of the third column (300) alone cannot completely replace the reboiler energy required for the operation of the second column (200), an auxiliary reboiler (235) may be provided at the bottom of the second column (200) separately from the second reboiler (230).

[0068] Meanwhile, the bottom discharge stream (250) of the second column containing water, specifically, a branch stream (20) that is a portion of the stream (250) discharged to the bottom of the second column (200) and 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 supplement a sufficient amount of water so that the phase separation of the water phase and the oil phase performed in the separator (120) provided at the top of the first column (100) may be smoothly performed.

[0069] Meanwhile, the heavy byproducts may include n-propyl alcohol (NPA) and hexanol, and these heavy byproducts may be discharged as a second side discharge stream (280) of the second column.

[0070] According to one embodiment of the present invention, a second column (200) includes a dividing wall provided along the length of the column and spaced apart from the bottom of the column, and the second column may be a distillation column divided into a top region (201), a bottom region (202), a supply region (203), and a discharge region (204) by the dividing wall.

[0071] Referring to Fig. 1, the interior of the second column (200) is divided by the dividing wall and an imaginary dotted line. Specifically, the top region (201) is a region located above the upper end of the dividing wall and is a region where the upper discharge stream (260) of the second column is discharged, and the bottom region (202) is a region located below the lower end of the dividing wall and is a region where the lower discharge stream (250) of the second column is discharged. Meanwhile, the lower discharge stream (150) of the first column can be supplied to the supply region (203).

[0072] The first side discharge stream (290) of the second column and the second side discharge stream (280) of the second column can be discharged from the discharge area (204) among the areas partitioned by the separation wall. Specifically, the first side discharge stream (290) can be discharged from the discharge area above the second side discharge stream (280).

[0073] That is, according to one embodiment of the present invention, by separating and discharging a composition (bottom discharge stream of the first column) including at least four components, such as isopropyl alcohol, water, a second light by-product, and a heavy by-product, into an upper portion, a first side portion, a second side portion, and a lower portion through one column (the second column) having a dividing wall, the number of distillation columns previously required for separation of these components can be reduced.

[0074] Specifically, referring to FIG. 2, which uses a distillation column without a dividing wall as the second column (C2), it is not impossible to discharge the separated product through the upper part, lower part, first part, and second part of the second column (C2) in FIG. 2, but especially since the side discharge stream from which heavy by-products are separated contains a large amount of isopropyl alcohol and water, additional purification of the side discharge stream is required in order to increase the yield of isopropyl alcohol. That is, a process was required to introduce the side discharge stream (280) into the third column (C3), additionally recover a stream containing isopropyl alcohol from the upper part, and supply it again to the second column (C2). That is, referring to FIG. 2, according to the present invention, since the same role performed by the conventional second column (C2) and third column (C3) can be performed by a single distillation column having a dividing wall, the number of columns can be reduced, and the amount of energy required for column operation (e.g., amount of steam) can be reduced. In addition, since the second column having a dividing wall is used, preliminary separation occurs in the supply area (203) and final purification is performed in the discharge area (204), an energy consumption reduction effect greater than that obtained by simply combining two columns can be obtained.

[0075] Meanwhile, the upper end of the separating wall may be located at a height point of 3% to 30% downward from the top of the second column, and the lower end of the separating wall may be located at a height point of 70 to 95% downward from the top of the second column.

[0076] Furthermore, the first side discharge stream (290) may be discharged at a height point of 5 to 33% downward from the top of the second column, and the second side discharge stream (280) may be discharged at a height point of 40 to 80% downward from the top of the second column.

[0077] Through the location of the above-mentioned separation wall and the discharge points of the first and second side discharge streams, energy consumption can be reduced compared to when using two existing columns, while at the same time obtaining four streams discharged from the second column with the desired purity.

[0078] The operating temperature and operating pressure of the top region (201) and the bottom region (202) of the second column (200) also need to be controlled from the viewpoint of the purity of the separated components, such as isopropyl alcohol, and the energy required to separate these components.

[0079] 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, 1 kg / cm 2 ·g or less, 0.05 kg / cm 2 ·g or less. Meanwhile, the operating temperature of the bottom region (202) of the second column (200) may be 85°C or higher, 88°C or higher, and 105°C or lower, 103°C or lower. Meanwhile, the operating pressure of the bottom region (202) may be 1.0 kg / cm 2 ·g or less, 0.5 kg / cm 2 ·g may be less.

[0080] When the operating temperature and operating 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.

[0081] A method for producing isopropyl alcohol according to one embodiment of the present invention may include a step of supplying a first side discharge stream (290) of a second column containing a mixture of isopropyl alcohol and water to a third column (300) which is partitioned into a first region (301), a second region (302), and an upper region (303) by a dividing wall (305) and is equipped with a layer separator (340) at the upper portion, thereby performing azeotropic distillation in the presence of an azeotropic agent.

[0082] Specifically, the first side discharge stream (290) of the second column (200) may comprise a mixture of isopropyl alcohol and water, specifically an azeotropic mixture of isopropyl alcohol and water. More specifically, the first side discharge stream (290) of the second column may comprise 80 to 90 wt% of isopropyl alcohol and 10 to 20 wt% of water.

[0083] Meanwhile, the third distillation column (300) according to one embodiment of the present invention is a dividing wall distillation column, and may include a first region (301), a second region (302), and an upper region (303) partitioned by a dividing wall (305). The dividing wall (305) may be connected (joined) to the bottom of the third distillation column (300) and may be provided to extend upward in the longitudinal direction of the third distillation column (300). At this time, the first region (301) and the second region (302) are regions partitioned to face each other with the dividing wall (305) interposed therebetween, and the second region (302) is a region facing the first region (301). Meanwhile, the upper region (303) is a region located above the upper end of the dividing wall, and is a region located above an imaginary boundary line indicated by a dotted line in the third column (300) in FIG. 1.

[0084] Meanwhile, azeotropic distillation may be performed in the presence of an azeotropic agent in the third distillation column (300). A portion of the isopropyl alcohol and a portion of the water included in the first side discharge stream (290) of the second column (200) may 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 azeotropic mixture thus formed cannot be completely separated into these components by general distillation, a general azeotropic agent is used to remove the azeotropic relationship between the 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 may be at least one selected from the group consisting of cyclohexane, benzene, toluene, and isopropyl acetate.

[0085] The above azeotropic agent is a substance that is additionally added separately from the feed component for azeotropic distillation, but since the azeotropic agent becomes an impurity in terms of isopropyl alcohol, etc., the azeotropic agent must be separated through a separate distillation column, etc., and from an economical point of view, the separated azeotropic agent must be recyclable.

[0086] That is, referring to FIG. 2 regarding the prior art, in the past, in order to separate isopropyl alcohol and water from a feed containing an azeotropic mixture of isopropyl alcohol and water and by-products, azeotropic distillation was performed in a conventional azeotropic distillation column (C4) without a dividing wall in the presence of an azeotropic agent, and the top discharge stream containing water and the azeotropic agent was phase-separated in a layer separator, and then the oil phase containing the azeotropic agent was refluxed back to the azeotropic distillation column (C4). However, since the aqueous phase still contained a large amount of azeotropic agent in addition to water, the aqueous phase was introduced into an azeotropic agent recovery column (C5), the azeotropic agent and water were separated by distillation, the recovered azeotropic agent was introduced back into the azeotropic distillation column (C4), and the water was discharged to the outside of the system. Here, in order to separate the azeotropic agent and water by distillation in the azeotropic agent recovery column (C5), a large amount of energy had to be supplied through a reboiler provided at the bottom of the azeotropic agent recovery column (C5).

[0087] Meanwhile, according to the prior art, the azeotropic distillation column (C4) received heat energy required for the operation of the azeotropic distillation column (C4) by a reboiler provided 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, and the bottom discharge stream of the azeotropic distillation column (C4) is supplied to an isopropyl alcohol recovery column (C6), so that 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).

[0088] However, referring to FIG. 1 regarding a method for producing isopropyl alcohol according to one embodiment of the present invention, the present invention provides a dividing wall in a third distillation column (300) in which azeotropic distillation is performed, and by optimally designing the reflux points of the water phase and the oil phase refluxed in the layer separator (340), high-purity isopropyl alcohol can be obtained even without an azeotropic agent recovery column (C5) for separating the azeotropic agent and water in the past. Through this, not only can the heat energy supplied to the reboiler for the operation of the azeotropic agent recovery column (C5) in the past be saved, but also the cooling energy required for the operation of the condenser provided on the upper portion of the azeotropic agent recovery column (C5) for the operation of the azeotropic agent recovery column (C5) can be saved. Furthermore, in addition to energy savings due to non-operation of the azeotropic recovery column (C5), the energy consumption required for operation of the distillation column can be reduced even when comparing the third distillation column (300) of the present invention, which is a dividing wall distillation column, with a conventional azeotropic distillation column (C4) and distillation columns.

[0089] To this end, according to one embodiment of the present invention, a first region (301) provided at the lower portion of the third distillation column (300) may be provided with a reboiler (315) connected to the lower portion of the first region, and a second region (302) may be provided with a reboiler (325) connected to the lower portion of the second region. Here, the lower portion refers to a point at a height of 90% to 100% downward from the top (upper portion) of the third distillation column (300). The first and second regions (301, 302) may be supplied with thermal energy through reboilers (315, 325), respectively, and the operating conditions of the first and second regions (301, 302) may be controlled by controlling the thermal energy supplied to each of the reboilers (315, 325).

[0090] According to one embodiment of the present invention, the heat energy supplied through the reboiler (315) connected to the lower part of the first region may be 1.5 to 3 times the heat energy supplied through the reboiler (325) connected to the lower part of the second region, and more specifically, may be 1.8 to 2.5 times. Through this, isopropyl alcohol of a desired purity can be separated as a lower discharge stream of the first region of the third distillation column, and pure water can be separated as a lower discharge stream of the second region.

[0091] The bottom temperature of the first zone (301) may be 135°C or higher, 137°C or higher, and 150°C or lower, 148°C or lower. In addition, the bottom temperature of the second zone (302) may be 155°C or higher, 158°C or higher, and 170°C or lower, 168°C or lower. Here, each bottom temperature is an operating temperature at a point of 90% to 100% of the height downward from the top (uppermost part) of the column (100) among the first and second zones. By controlling the bottom temperatures of the first and second zones as described above, it is possible to reduce the energy required for distillation of the third distillation column (300), and isopropyl alcohol of a desired purity can be obtained from the bottom of the first zone, and pure water can be separated from the bottom of the second zone.

[0092] Meanwhile, the first zone bottom discharge stream (310) discharged from the first zone (301) of the third distillation column (300) may include isopropyl alcohol and heavy byproducts. Here, the heavy byproducts may include n-propyl alcohol (NPA). A portion of the first zone bottom discharge stream (310) may be heat-exchanged in a reboiler (315) connected to the lower portion of the first zone and then refluxed back to the first zone, and the remainder of the first zone bottom discharge stream (310) may be supplied to the fourth column (400).

[0093] Meanwhile, the second zone bottom discharge stream (320) discharged from the second zone (302) may contain water. A portion of the second zone bottom discharge stream (320) may be heat-exchanged in a reboiler (325) connected to the lower portion of the second zone and then refluxed back to the second zone, and the remainder of the second zone bottom discharge stream (320) may be discharged outside the system.

[0094] As described above, the region located above the top of the dividing wall in the third distillation column (300) may form an upper region (303).

[0095] The above separation wall (305) extends from the bottom of the column, and the upper end of the separation wall may be positioned at a height point of 10 to 45% downward from the top of the third distillation column (300), or specifically at a height point of 15 to 30%. Through this, the separation efficiency of the third distillation column (300) can be maximized, so that isopropyl alcohol of a desired purity can be obtained from the bottom of the first region, and pure water can be separated from the bottom of the second region.

[0096] An upper discharge stream (330) containing water and azeotropic agent can be discharged from the upper portion of the upper region.

[0097] According to one embodiment of the present invention, the top discharge stream (330) of the third column can be heat-exchanged with at least one of the bottom discharge stream of the first column and the bottom discharge stream of the second column in at least one of the first reboiler (130) of the first column (100) and the second reboiler (230) of the second column (200). By doing so, by supplying the heat of the top discharge stream (330) of the third column to at least one of the first column and the second column, the heat energy required for the operation of at least one of the first column and the second column can be reduced.

[0098] That is, referring to FIG. 1, the heat exchanger A provided on the upper portion of the third column may be at least one of the first reboiler (130) of the first column and the second reboiler (230) of the second column. The upper discharge stream (330) of the third column is discharged from the third column (300) and then transferred to at least one of the first reboiler (130) and the second reboiler (230), and the retained heat energy may be supplied to at least one of the first column (100) and the second column (200). At this time, the upper discharge stream (330) of the third column may be heat-exchanged in the first reboiler (130) or the second reboiler (230), and 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 each of the first reboiler (130) and the second reboiler (230). 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 with at least one 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 on the upper portion of the third column (300). When the upper discharge stream (330) of the third column is branched and heat-exchanged with both the first reboiler (130) and the second reboiler (230), each branch stream can be joined after heat exchange and transferred to the condenser (380).

[0099] The operating pressure at the top of the third column (300) may be 4.9 bar.g to 5.1 bar.g. When the operating pressure at the top of the third column is 4.9 bar.g or higher, the temperature of the top discharge stream (330) of the third column may be at least 10°C higher than the temperatures at the bottoms of the first and second columns, thereby enabling the maintenance of a temperature difference for heat exchange in the first reboiler (130) of the first column (100) and the second reboiler (230) of the second column (200).

[0100] In particular, when the operating pressure at the top of the third column (300) is greater than 5.1 bar.g, it is possible to realize a high temperature of the upper discharge stream (330) of the third column, so that there is no problem in supplying heat to the first column (100) and the second column (200), but the separation performance performed in the third column (300) is deteriorated. In this case, additional energy must be supplied to the third column (300) in order to separate components with the desired purity, which is not desirable from the perspective of reducing energy usage. Conversely, when the operating pressure at the top of the third column (300) is less than 4.9 bar.g, it is difficult to maintain the temperature of the upper discharge stream (330) of the third column at a high temperature, making it difficult to secure a sufficient temperature difference to enable heat exchange in the first reboiler (130) and the second reboiler (230).

[0101] Meanwhile, the operating temperature of the upper portion of the third column (300), specifically, the operating temperature of 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, an appropriate temperature difference (for example, a temperature difference of at least 10°C or higher) required for heat exchange with the lower portions of the first column (100) and the second column (200) can be secured, thereby enabling efficient energy supply to the first column (100) and the second column (200) by the upper discharge stream (330) of the third column.

[0102] Furthermore, the top discharge stream (330) of the third column can be heat-exchanged with the bottom discharge stream of the first column and the bottom discharge stream of the second column through the first reboiler (130) and the second reboiler (230). That is, when the top discharge stream (330) of the third column is heat-exchanged in both the first reboiler (130) and the second reboiler (230), the top discharge stream (330) of the third column can be branched to form a branch stream supplied to the first reboiler (130) and a branch stream supplied to the second reboiler (230). At this time, the ratio of the mass flow rate of the branch stream supplied to the first reboiler and the mass flow rate of the branch stream supplied to the second reboiler can be 1:5 to 1:7. In the case of the above ratio, the logarithmic mean temperature difference (LMTD) between the low-temperature medium (bottom discharge stream of the first and second columns) and the high-temperature medium (top discharge stream of the third column) heat-exchanged in the first reboiler (130) and the second reboiler (230) can be maximized, so that the first reboiler (130) and the second reboiler (230) can be efficiently designed and operated. Furthermore, the sizes of the auxiliary reboilers (135, 235) of the above-mentioned first and second columns can be minimized.

[0103] The top discharge stream (330) of the third column (300) may be heat-exchanged with at least one of the bottom discharge stream of the first column and the bottom discharge stream of the second column in at least one of the first reboiler (130) of the first column (100) and the second reboiler (230) of the second column (200), and then cooled to condense all or part of it into a liquid phase. The condensed top discharge stream (330) of the third column (300) may be introduced into a condenser (380) provided at the top of the third column to undergo further condensation to a desired condensation condition.

[0104] The discharge stream of the condenser (380) that has undergone the above additional condensation can be introduced into a layer separator (340) provided at the top of the third column. The layer separator (340) is a device that separates fluids based on density differences, and the fluid can be separated into a water phase containing water and an oil phase containing an azeotropic agent by the layer separator (340). The oil phase stream (350) containing the azeotropic agent can be refluxed to the upper region (303), and the water phase stream (360) containing water can be refluxed to the second region (302).

[0105] That is, since the upper discharge stream (330) is separated into an oil phase and an aqueous phase by the layer separator (340), and the separated oil phase and aqueous phase are refluxed back to the third distillation column (300), the mass flow rate of the upper discharge stream (330) of 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) that are refluxed to the third distillation column (300) through the layer separator (340). That is, there may be substantially no component supplied to, for example, another distillation column or discharged outside the system from the upper discharge stream (330) of the third distillation column (300). That is, the upper discharge stream (330) of the third distillation column (300) is discharged from the third column (300), then supplied to at least one of the first reboiler (130) and the second reboiler (230), and then supplied to the condenser (380), and then passes through the layer separator (340) and is entirely refluxed to the third distillation column (300).

[0106] The azeotropic agent included in the above oily stream (350) is used again for azeotropic distillation performed in the third distillation column (300). In addition, by refluxing all of the phase-separated oil phase and water phase 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 that is inevitably consumed as the process progresses can be supplied (370) to the layer separator (340) and replenished.

[0107] The reflux point of the above-mentioned water into the second region may be a point at 10% to 50% of the height of the separating wall from the bottom of the tower, and specifically, a point at 25% to 40%. This allows for minimizing the energy required for distillation while simultaneously separating pure water from the lower portion of the second region.

[0108] More specifically, when the position of the upper end of the separating wall (305) and the position of the reflux point to the second zone of the water are set as described above, the azeotropic distillation zone for separating isopropyl alcohol and water using an azeotropic agent and the distillation zone for purifying isopropyl alcohol can be sufficiently secured simultaneously within the third distillation column (300). Furthermore, since the upper zone (303) above the separating wall is shared by the first and second zones, the amount of energy required for the condenser (380) can be reduced, and the liquid reflux stream that branches off from the lowermost part of the upper zone (303) to the first zone (301) and the second zone (302) and flows downward is optimally distributed to the first zone and the second zone, thereby minimizing the amount of heat required by the reboiler in each zone.

[0109] Meanwhile, according to one embodiment of the present invention, the first region bottom discharge stream (310) discharged from the first region (301) can be supplied to a fourth column (400) for recovering isopropyl alcohol. The fourth column (400) is operated by a reboiler (430) located at the bottom, and isopropyl alcohol can be obtained (410) from the top of the fourth column (400) and heavy byproducts can be separated (420) from the bottom of the fourth column.

[0110] Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are intended to illustrate the present invention, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope and technical spirit of the present invention, and the scope of the present invention is not limited to these examples alone.

[0111] The following examples and comparative examples simulate the method according to the present invention using the commercial process simulation program Aspen Plus (Aspen Plus V12.1).

[0112] Example 1

[0113] The manufacturing process of isopropyl alcohol was performed according to the process diagram shown in Fig. 1.

[0114] Specifically, water and propylene were supplied to a reaction unit and subjected to a gas phase reaction to produce a reaction product including isopropyl alcohol, water, and propylene. Propylene was separated and recovered from the reaction product, and feed (10) was prepared from the remaining residue. The feed (10) contained 10.395 wt% of isopropyl alcohol, 88.9 wt% of water, 0.5 wt% of diisopropyl ether (DIPE) as a first light by-product, 0.005 wt% of acetone as a second light by-product, and 0.2 wt% of n-propyl alcohol (NPA) and hexanol as heavy by-products, respectively.

[0115] The above feed (10) was supplied to the first column, and a portion of the bottom discharge stream of the second column (200) was branched and introduced to the upper portion of the first column (100), and the mass flow rate of the branch stream (20) into which a portion of the bottom discharge stream of the second column (200) was branched was 0.6 compared to the mass flow rate of the feed (10) supplied to the first column (100).

[0116] A stream (160) containing isopropyl alcohol, water, diisopropyl ether, and acetone was discharged from the top of the first column (10), and supplied to a condenser (110) and a layer separator (120), so that the water 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.

[0117] The bottom discharge stream of the first column was introduced into the feed area (203) of the second column having a dividing wall, and separated by distillation into four discharge streams: a second column top discharge stream (260) containing acetone, a second column first side discharge stream (290) containing an azeotropic mixture of isopropyl alcohol and water, a second column second side discharge stream (280) containing n-propyl alcohol (NPA) and hexanol, and a second column bottom discharge stream (250) containing water.

[0118] 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). The 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 each branch stream was introduced into the first reboiler (130) and the second reboiler (230) at a mass flow rate ratio of 1:6, thereby supplying thermal energy to the bottoms of the first and second columns.

[0119] At this time, the operating conditions of the first and second columns did not reach the desired level with only the heat energy of the third column upper discharge stream (330), so additional heat energy was supplied to the first and second columns through auxiliary reboilers (135, 235) provided at the bottom of each of the first and second columns.

[0120] Meanwhile, the first side discharge stream (290) of the second column contained 85.78 wt% of isopropyl alcohol, 13.58 wt% of water, and 0.64 wt% of n-propyl alcohol (NPA) as a by-product. In addition, since the ratio of the mass flow rate of isopropyl alcohol contained in the first side discharge stream (290) of the second column to the mass flow rate of isopropyl alcohol contained in the feed (10) was 99.4%, there was no need to perform additional distillation on the second side discharge stream (280) of the second column for the purpose of increasing the recovery rate of isopropyl alcohol.

[0121] Next, the first side discharge stream (290) of the second column containing an azeotropic mixture of isopropyl alcohol and water was supplied to the first zone of the third column (300) to perform azeotropic distillation in the presence of cyclohexane as an azeotropic agent.

[0122] The upper discharge stream (330) discharged to the upper region (303) of the third column (300) was branched at a mass flow rate 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. At this time, the operating pressure of the upper region (303) of the third column (300) was 5.0 bar.g, and the temperature of the upper discharge stream (330) was 122°C. Meanwhile, the temperature of the lower discharge stream of the first column supplied to the first reboiler (130) was 85°C, and the temperature of the lower discharge stream of 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, so that efficient heat exchange was performed.

[0123] The upper discharge stream (330) of the third column after heat exchange in the first reboiler (130) and the second reboiler (230) was separated into an oil phase and an aqueous phase while sequentially passing through a condenser (380) and a separator (340). The oil phase stream (350) containing cyclohexane was refluxed to the upper 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 separating wall from the bottom of the tower.

[0124] Meanwhile, the first region bottom discharge stream (310) containing isopropyl alcohol and n-propyl alcohol was supplied to the fourth column (400), and isopropyl alcohol was obtained from the top of the fourth column (400), and the content of isopropyl alcohol in the top discharge stream of the fourth column was confirmed to be 99.8 wt%.

[0125] At this time, the energy consumed in the reboiler of each column is shown in Table 1. Specifically, since the heat energy supplied to the first reboiler of the first column and the second reboiler of the second column is supplied from the top of the third column, the reboiler energy consumed in the first column and the second column is the heat energy supplied through the auxiliary reboilers (135, 235) provided at the bottom of each of the first and second columns, and is shown in Table 1. Meanwhile, the heat energy supplied through the reboiler (315) connected to the bottom of the first region of the third column and the heat energy supplied through the reboiler (325) connected to the bottom of the second region of the third column are each shown in Table 1.

[0126] Comparative Example 1

[0127] The manufacturing process of isopropyl alcohol was performed according to the process diagram as shown in Fig. 2.

[0128] For the same feed (10) as in Example 1, a bottom discharge stream of the first column (C1) having the same composition as in Example 1 was obtained and introduced into the second column (C2).

[0129] The second column (C2) of Comparative Example 1 was a column without a dividing wall, and, similarly to Example 1, the second column (C2) was distilled to separate four discharge streams: a second column top discharge stream containing acetone, a first side discharge stream of the second column containing an azeotropic mixture of isopropyl alcohol and water, a second side discharge stream of the second column containing n-propyl alcohol (NPA) and hexanol, and a second column bottom discharge stream containing water.

[0130] In this case, since the second side discharge stream of the second column contained a large amount of isopropyl alcohol and was discharged without effectively separating heavy byproducts and water, it was impossible to achieve a yield of 99% of isopropyl alcohol contained in the first side discharge stream of the second column by operating only the second column (C2), and thus a third column (C3) was required to further purify isopropyl alcohol in the second side discharge stream of the second column and separate heavy byproducts and water.

[0131] Specifically, the second side discharge stream of the second column was introduced into the third column (C3), and a stream containing isopropyl alcohol was separated from the top of the third column and supplied again 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.

[0132] The energy required for operating the first to third columns was supplied through a reboiler installed at the bottom of the first to third columns.

[0133] The first side discharge stream of the second column containing an azeotropic mixture of isopropyl alcohol and water was recovered from the top of the isopropyl alcohol recovery column (C6) using a conventional azeotropic distillation column (C4) without a dividing wall, an azeotropic agent recovery column (C5), and an isopropyl alcohol recovery column (C6). Each of the three columns was equipped with a condenser at the top and a reboiler at the bottom.

[0134] Specifically, the first side discharge stream of the second column containing an azeotropic mixture of isopropyl alcohol and water was supplied to a conventional azeotropic distillation column (C4) to perform azeotropic distillation in the presence of cyclohexane. After the top discharge stream containing water and an azeotropic agent was phase-separated in a layer separator, the oil phase containing the azeotropic agent was refluxed back to the azeotropic distillation column (C4), and the water phase containing water was supplied to an azeotropic agent recovery column (C5). The bottom discharge stream of the azeotropic distillation column (C4) containing isopropyl alcohol and heavy by-products was supplied to an isopropyl alcohol recovery column (C6) to recover isopropyl alcohol from the top.

[0135] Meanwhile, the composition and flow rate of the bottom discharge stream of the azeotropic distillation column (C4) introduced into the isopropyl alcohol recovery column (C6) in Comparative Example 1 were the same as those in Example 1, and the operating conditions and energy used of the isopropyl alcohol recovery column (C6) in Comparative Example 1 were also the same as those in Example 1. As a result, the content of isopropyl alcohol obtained in Comparative Example 1 was confirmed to be 99.8 wt%, as in Example 1.

[0136] At this time, the energy (heat energy) used in the reboiler provided at the bottom of each column (C1 to C6 columns) in Comparative Example 1 is shown in Table 1.

[0137] Column Energy used in the reboiler (Reboiler duty) (kW) Total energy used in the reboiler (Total reboiler duty) (kW) Energy saving rate (Energy saving) (%) Comparative example 1 C1 10.3 1000 C2 30.2 C3 5.2 C4 30.5 C5 15.3 C6 8.6 Example 1 1st column 2.0 41.3 58.7 2nd column 5.9 3rd column (1st area) 13.2 3rd column (2nd area) 11.6 4th column 8.6 1) The total energy usage in Example 1 indicates the relative energy usage when the total energy usage in Comparative Example 1 is 100. 2) The energy usage used in each reboiler of each column in Example 1 is a value obtained by apportioning the total energy usage in Example 1 according to the ratio of the amount of energy actually used in each reboiler.

[0138] As can be seen from the above results, in the case of Example 1, it was possible to maintain a high level of purity and yield of isopropyl alcohol. In particular, when the second and third columns are dividing wall distillation columns having a specific structure and the heat of the top discharge stream of the third column is used as an energy source required for the operation of the first and second columns, it can be seen that the energy efficiency of the overall process spanning the first to fourth columns is maximized.

[0139] [Explanation of symbols]

[0140] 10: Feed

[0141] 100: Column 1 200: Column 2

[0142] 300: 3rd column 400: 4th column

Claims

1. A step of supplying a feed including isopropyl alcohol, water, a first light by-product, a second light by-product, and a heavy by-product to a first column having a first reboiler; A step of separating the first light by-product from the upper discharge stream of the first column; The step of supplying the bottom discharge stream of the first column containing the isopropyl alcohol, water, the second light by-product, and the heavy by-product to a second column equipped with a second reboiler, and separating the top discharge stream of the second column containing the second light by-product, the first side discharge stream of the second column containing a mixture of the isopropyl alcohol and water, the second side discharge stream of the second column containing the heavy by-product, and the bottom discharge stream of the second column containing the water, respectively; The step of supplying the first side discharge stream of the second column containing the mixture of isopropyl alcohol and water to a third column partitioned into a first zone, a second zone, and an upper zone by a dividing wall and equipped with a layer separator at the upper portion, thereby performing azeotropic distillation in the presence of an azeotropic agent, and Comprising a step of obtaining isopropyl alcohol from the first region bottom discharge stream of the third column, A method for producing isopropyl alcohol, 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 through at least one of the first reboiler and the second reboiler.

2. In paragraph 1, A method for producing isopropyl alcohol, wherein the upper discharge stream of the third column is heat-exchanged with at least one of the lower discharge stream of the first column and the lower discharge stream of the second column and then sequentially supplied to a condenser provided at the upper portion of the third column and the layer separator.

3. In paragraph 1, The second column is spaced apart from the top and includes a dividing wall provided along the length of the column, The second column is divided into a top region, a bottom region, a supply region, and a discharge region by the dividing wall, The first side discharge stream and the second side discharge stream of the second column are discharged from the discharge area, A method for producing isopropyl alcohol, wherein the first side discharge stream is discharged from a discharge area above the second side discharge stream.

4. In paragraph 1, The third column includes a dividing wall connected to the top and extending in the length direction of the column, A method for producing isopropyl alcohol, wherein the method comprises partitioning the first region, the second region facing the first region, and the upper region located above the upper end of the partition wall by the partition wall.

5. In paragraph 1, A method for producing isopropyl alcohol, wherein a portion of the bottom discharge stream of the second column containing the water is branched off and recycled to the top of the first column.

6. In paragraph 5, A method for producing isopropyl alcohol, 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. In paragraph 1, A method for producing isopropyl alcohol, wherein the top discharge stream of the third column is heat-exchanged with the bottom discharge stream of the first column and the bottom discharge stream of the second column through the first reboiler and the second reboiler.

8. In paragraph 1, The upper discharge stream of the third column branches to form a branch stream supplied to the first reboiler and a branch stream supplied to the second reboiler, A method for producing isopropyl alcohol, wherein the ratio of the mass flow rate of the branch stream supplied to the first reboiler and the mass flow rate of the branch stream supplied to the second reboiler is 1:5 to 1:

7.

9. In paragraph 1, A method for producing isopropyl alcohol, wherein the top discharge stream of the third column is pressurized to 4.9 bar.g to 5.1 bar.g and then heat-exchanged with at least one of the bottom discharge stream of the first column and the bottom discharge stream of the second column.

10. In paragraph 1, A method for producing isopropyl alcohol, comprising supplying an upper discharge stream containing water and an azeotropic agent discharged from the upper region of the third column to the separator, separating the upper discharge stream into an aqueous phase stream containing water and an oil phase stream containing an azeotropic agent, refluxing the oil phase stream to the upper region, and refluxing the aqueous phase stream to the second region.

11. In paragraph 10, The point of return to the second area of ​​the above award is, A method for producing isopropyl alcohol at a point of 20% to 50% of the height of the separating wall from the bottom of the tower.

12. In paragraph 10, A method for producing isopropyl alcohol, wherein the mass flow rate of the upper discharge stream is equal to the sum of the mass flow rates of the water phase stream and the oil phase stream that pass through the layer separator and are refluxed to the third distillation column.

13. In paragraph 1, The first zone bottom discharge stream of the third column is supplied to the fourth column, A method for producing isopropyl alcohol, wherein isopropyl alcohol is obtained from the upper portion of the fourth column and heavy by-products are separated from the lower portion of the fourth column.

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