Method for purifying isopropanol

Abstract

The present invention provides a process for purifying isopropanol, the process comprising: supplying a feed comprising isopropanol, 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 the lower discharge stream of the first column to a second column, and separating the lower discharge stream of the first column into an upper discharge stream of the second column comprising a second light byproduct, a first side discharge stream of the second column comprising a mixture of isopropanol and water, a second side discharge stream of the second column comprising a heavy byproduct, and a lower discharge stream of the second column comprising water, respectively.

Description

Technical Field

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0158482, filed on November 15, 2023, and Korean Patent Application No. 10-2024-0147844, filed on October 25, 2024, which are hereby incorporated by reference into this specification in their entirety. Technical Field

[0003] The present invention relates to a method for purifying isopropyl alcohol, in particular to a method for purifying isopropyl alcohol from a reaction product in an isopropyl alcohol preparation process, which can reduce energy consumption and process costs. Background Art

[0004] Isopropyl alcohol (IPA) is considered an excellent solvent in a variety of industries and applications due to its ability to dissolve a wide range of substances, rapid evaporation, and relatively low toxicity. Isopropyl alcohol is an essential substance in various manufacturing, healthcare, and direct consumer applications.

[0005] In the isopropyl alcohol preparation method, for example, propylene and water are used as raw material components. In this case, propylene and water react to produce isopropyl alcohol. Except isopropyl alcohol, unreacted propylene monomer and unreacted water, the reaction product of the isopropyl alcohol preparation method also comprises various types of impurities and by-products, such as diisopropyl ether (DIPE), acetone, n-propyl alcohol (NPA) and hexanol.

[0006] In order to obtain isopropyl alcohol from the reaction product, an isopropyl alcohol purification process is required. Therefore, in order to obtain high-purity isopropyl alcohol, the isopropyl alcohol purification process needs to be efficient and, from an economic point of view, an improved design is required, which can not only reduce energy consumption but also reduce operating costs and facility costs. Summary of the Invention

[0007] Technical issues

[0008] In order to solve the problems mentioned in the background art, an object of the present invention is to provide a method for purifying isopropyl alcohol, which can obtain high-purity isopropyl alcohol while reducing energy consumption and improving operating costs and facility costs.

[0009] However, the problems to be solved by the present application are not limited to the above-mentioned objects, and other problems not described will be clearly understood by those skilled in the art from the following description.

[0010] Technical Solution

[0011] In one general aspect, a method for purifying isopropyl alcohol includes: 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 tower; separating the first light by-product through an upper effluent stream of the first tower; supplying a lower effluent stream of the first tower comprising isopropyl alcohol, water, the second light by-product, and the heavy by-product to a second tower, and separating the lower effluent stream of the first tower into an upper effluent stream of the second tower comprising the second light by-product, a first side effluent stream of the second tower comprising a mixture of isopropyl alcohol and water, a second side effluent stream of the second tower comprising the heavy by-product, and a lower effluent stream of the second tower comprising water; and introducing the mixture of isopropyl alcohol and water into an isopropyl alcohol recovery process and separating the isopropyl alcohol and water.

[0012] Beneficial effects

[0013] According to the method for purifying isopropyl alcohol of the present invention, a feed containing isopropyl alcohol, water, and various by-products, which are reaction products of propylene and water, is effectively purified, thereby obtaining a mixture (azeotrope) of isopropyl alcohol and water with a minimized by-product content. The isopropyl alcohol and water mixture with a minimized by-product content is then subjected to a subsequent isopropyl alcohol recovery process, thereby ultimately obtaining highly pure isopropyl alcohol.

[0014] Furthermore, the process of obtaining a mixture of isopropyl alcohol and water is performed in a single distillation column, which is conventionally performed using at least two distillation columns. This allows for energy efficiency to be achieved throughout the entire isopropyl alcohol production process. Specifically, the present invention reduces the reboiler load required for operating at least two distillation columns in conventional processes (saving energy), and reduces the number of distillation columns, thereby reducing facility and operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a process flow diagram of a method for purifying isopropyl alcohol according to one embodiment of the present invention.

[0016] Figure 2 is a process flow chart of a method for purifying isopropyl alcohol according to a comparative example. DETAILED DESCRIPTION

[0017] Based on the principle that inventors are able to appropriately define the concepts of terms in order to describe their own inventions in the best way, the terms and words used in the description and claims of the present invention should not be restrictively interpreted as having common meanings or dictionary meanings, but should be interpreted as having meanings and concepts that satisfy the technical concept of the present invention.

[0018] With regard to the description of the drawings, like reference numerals may be used to designate like or related components.

[0019] Unless the relevant context clearly indicates otherwise, a singular form of a noun corresponding to an item may include one or more items.

[0020] In the present 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" may include any one or all possible combinations of the items listed together in one of the corresponding phrases.

[0021] The term "and / or" includes a combination of a plurality of related components or any one of the plurality of related components.

[0022] Terms such as “1st” and “2nd” or “first” and “second” may be used to simply distinguish corresponding components from other components and do not limit the corresponding components in other aspects (for example, importance or order).

[0023] In addition, terms such as "front surface", "rear surface", "upper surface", "lower surface", "side surface", "left side", "right side", "upper part" and "lower part" used in this application are defined based on the drawings, and the shape and position of each component are not limited by the terms.

[0024] The terms “including” or “having” specify the presence of features, numbers, steps, operations, components, parts or combinations 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.

[0025] When a component is referred to as being “connected,” “coupled,” “supported,” or “in contact with” another component, this includes not only the case where the components are directly connected, coupled, supported, or in contact, but also the case where the components are indirectly connected, coupled, supported, or in contact via a third component.

[0026] When a component is referred to as being 'on' another component, this includes not only a case where the component is in contact with the other component but also a case where the other component exists between the two components.

[0027] The term "flow" as used herein may refer to the flow of a fluid in a process, and may also refer to the fluid itself flowing through a pipeline. Specifically, flow may refer to both the fluid itself flowing through a pipeline connecting respective devices to each other and the flow of the fluid. In addition, a fluid may include any one or more components of a gas, a liquid, and a solid.

[0028] Unless otherwise specified, the term "upper" as used in this application refers to a point at a height of 0% to 10% downward from the uppermost portion of the device, specifically, the uppermost portion (top). In addition, the term "lower" refers to a point at a height of 90% to 100% downward from the uppermost portion of the device, specifically, the lowermost portion (bottom).

[0029] Furthermore, the term "pressure" mentioned in this application refers to a gauge pressure measured under atmospheric pressure conditions.

[0030] Meanwhile, unless otherwise specified in this specification, the operating pressure of a tower refers to the pressure at the upper portion of the tower, and the operating temperature of a tower refers to the temperature at the lower portion of the tower.

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

[0032] Figure 1 is a process flow diagram of a method for purifying isopropyl alcohol according to one embodiment of the present invention.

[0033] The method of purifying isopropyl alcohol according to the present invention includes supplying a feed 10 including isopropyl alcohol, water, a first light by-product, a second light by-product, and a heavy by-product to a first column 100 .

[0034] First, the feed 10 may be a residue obtained by separating a gaseous component containing unreacted propylene from a reaction product by a gas phase reaction of propylene monomer and water in a reaction section.

[0035] There are various methods for recovering (unreacted) propylene from the reaction product to prepare the feed 10 of the present invention. Hereinafter, among the various methods for recovering propylene from the reaction product, a method for recovering propylene with high purity and recycling the recovered propylene to the reaction section where the gas phase reaction is carried out is exemplified.

[0036] Owing to propylene being recycled to conversion zone and being used as the raw material of gas phase reaction again, therefore for the preparation of high-purity isopropyl alcohol, need with high-purity recovery reaction back unreacted propylene.Particularly, as mentioned above, preferably as the propylene (C3H6) of raw material supply to conversion zone ) have high purity.In raw material propylene, comprise impurity such as: other unsaturated hydrocarbons for example ethene, butylene, amylene etc., ethane, propane, and under the situation of carbonic acid gas, may produce the by product (for example ethanol) that boiling point is similar to isopropyl alcohol during the reaction between propylene and water.Therefore, preferably comprise with respect to its gross weight more than 97 % by weight as reactant supply to the propylene of conversion zone, for example 97 % by weight to 99.8 % by weight propylene, the content of impurity is less than 3 % by weight.

[0037] Meanwhile, only a part is supplied to the propylene of conversion zone for reaction.Therefore, except the isopropyl alcohol produced by the reaction of propylene monomer and water, reaction product can also comprise unreacted propylene and unreacted water.For example, reaction product can comprise 65 % by weight to 85 % by weight of propylene monomer, 4 % by weight to 8 % by weight of isopropyl alcohol and 5 % by weight to 30 % by weight of water.In addition, reaction product can comprise light by-products and heavy by-products of at least two or more types as by-products.Particularly, light by-products can comprise diisopropyl ether (DIPE) and acetone, and heavy by-products can comprise n-propyl alcohol (NPA) and hexanol.Therefore, need to separate unreacted raw materials from reaction product and the technology of purifying isopropyl alcohol from various by-products.

[0038] According to one embodiment of the present invention, the recovery of propylene in the reaction product may be performed through a gas purification section provided with two or more of an absorption tower, a flash tank, and a gas purification tower.

[0039] Specifically, propylene is separated by supplying the reaction product to the lower portion of an absorption tower and introducing water into the upper portion of the absorption tower. In this case, the water can be the water supplied from the lower discharge stream of the second tower described below. In the absorption tower, the gaseous isopropyl alcohol contained in the reaction product can be absorbed in the water and obtained by the liquid phase lower stream, and the gaseous phase stream containing propylene can be separated by the upper portion of the absorption tower. The propylene contained in the gaseous phase stream can be recycled to the reaction section.

[0040] At the same time, in addition to isopropyl alcohol and water, the liquid phase lower stream of the absorption tower may contain a small amount of low-boiling gas components comprising propylene that have not yet been separated in the absorption tower. Therefore, the liquid phase stream comprising isopropyl alcohol separated from the absorption tower can be supplied to a flash tank to additionally recover propylene. For example, the liquid phase stream can be supplied to one or more flash tanks operated under reduced pressure to recover the low-boiling gas components comprising propylene contained in the liquid phase stream as a gas, and then the liquid phase stream can be supplied to a gas purification tower to additionally recover propylene that may remain in the liquid phase stream comprising isopropyl alcohol.

[0041] Through such a process, a gas-phase upper stream containing propylene and a liquid-phase lower stream containing isopropyl alcohol and water can be separated from the absorption tower, the flash tank, and the gas purification tower.

[0042] At the same time, in addition to isopropyl alcohol and water, the liquid phase lower stream separated from the absorption tower, the flash tank, and the gas purification tower may contain 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. As described above, the liquid phase lower stream separated from one or more of the absorption tower, the flash tank, and the gas purification tower for recovering propylene may be the feed 10 of the present invention supplied to the first tower 100.

[0043] Feed 10 may be introduced to a point at a height of 30% to 550% downward from the top of first column 100 .

[0044] According to one embodiment of the present invention, the first light by-product included in the feed 10 may be first separated and removed through the layer separator 120 connected to the first tower 100 and the upper portion of the first tower 100 .

[0045] Specifically, the upper discharge stream 160 of the first column including isopropyl alcohol, water, the first light by-product, and optionally the second light by-product, and the lower discharge stream 150 of the first column including isopropyl alcohol, water, the second light by-product, and the heavy by-product can be discharged from the upper portion and the lower portion of the first column 100, respectively, by distillation in the first column 100.

[0046] The upper discharge stream 160 of the first tower can be supplied to the condenser 110 after being discharged from the first tower 100, and cooled and liquefied. The liquefied upper discharge stream of the first tower can be supplied to the layer separator 120 and subjected to liquid-liquid separation. Through liquid-liquid separation, the aqueous phase stream containing isopropyl alcohol, water and an optional second light by-product can be refluxed to the first tower, and the oil phase stream 170 containing the first light by-product can be discharged to the outside of the system. When the content of the first light by-product contained in the feed 10 is 100 weight%, the amount of the first light by-product discharged to the outside of the system can be 97 weight% or more, 99 weight% or more, and specifically 100 weight%.

[0047] In order to easily separate the first light by-product by distillation in the first tower 100 and liquid-liquid separation in the layer separator 120 provided above the first tower, at least the first light by-product should be an oily component that is insoluble in water. That is, the first tower 100 is operated under an operating condition in which the heavy by-product is not evaporated, and the first light by-product is substantially separated from water and isopropyl alcohol dissolved in water in the layer separator 120, so that the first light by-product can be effectively separated.

[0048] According to one embodiment of the present invention, the first light by-product can be water-insoluble diisopropyl ether (DIPE), and the second light by-product can be water-soluble acetone. Because the boiling point of acetone is lower than that of diisopropyl ether, the upper discharge stream 160 of the first tower can include water, isopropyl alcohol, acetone and diisopropyl ether (DIPE). The isopropyl alcohol included in the upper discharge stream 160 of the first tower is separated from the first light by-product (oil phase) by the liquid-liquid separation carried out in the layer separator 120, and the water, isopropyl alcohol and acetone included in the aqueous phase are refluxed back to the first tower 100. Therefore, the isopropyl alcohol loss at the top of the first tower 100 can be minimized by the layer separator 120 above the first tower 100.

[0049] At the same time, almost all of the first light by-products contained in the feed 10 can be discharged from the system. To this end, the operating conditions of the first tower 100 should be controlled so that almost all of the first light by-products contained in the feed 10 can be contained in the upper discharge stream 160 of the first tower 100.

[0050] Specifically, the operating temperature of the first tower 100 may be 75° C. or 80° C. or more, and 95° C. or 90° C. or less. The operating temperature may refer to the temperature at the lower portion of the first tower 100. Meanwhile, the operating pressure of the first tower 100 may be 1 kg / cm 2 ·g or less or 0.5g / cm 2 g or less. The operating pressure may refer to the pressure at the upper portion of the first tower 100. When the first tower 100 is operated at the operating temperature and the operating pressure as described above, the first light by-products can be separated as much as possible through the upper effluent stream 160 of the first tower, and thus, the first light by-products can be prevented from flowing out through the lower effluent stream 150 of the first tower and remaining as impurities in the isopropyl alcohol produced thereby.

[0051] At the same time, in order to efficiently recover the isopropyl alcohol contained in the upper discharge stream 160 of the first tower and reflux the recovered isopropyl alcohol back to the first tower through liquid-liquid separation performed in the layer separator 120, water should be supplied to the upper portion of the first tower. Since a large amount of water is discharged through the lower discharge stream 150 of the first tower, it is preferable to supply water to the first tower 100 so that the isopropyl alcohol is sufficiently dissolved in the layer separator 120 to form an aqueous phase. The water supplied to the upper portion of the first tower is supplied to the first tower separately from the feed 10. The water supplied to the upper portion of the first tower may be water contained in stream 20, which is branched from a portion of the lower discharge stream 250 of the second tower containing water and recycled, as described below.

[0052] As described above, since the water recycled from the second tower 200 to the first tower 100 contains almost no heavy by-products due to the excellent separation capability in the second tower, especially the capability of effectively separating heavy by-products, the lower exhaust stream 250 of the second tower may be recycled back to the first tower.

[0053] The water supplied to the first tower 100 is preferably supplied to the upper portion of the first tower 100. This is because the water supplied to the upper portion can dissolve isopropyl alcohol, which is highly soluble in water, as it moves from the upper portion to the lower portion, and can be discharged through the lower discharge stream 150 of the first tower. If the second light by-product is also soluble in water, the isopropyl alcohol and the second light by-product can be dissolved in the water and discharged through the lower discharge stream 150 of the first tower.

[0054] At the same time, according to one embodiment of the present invention, from the perspective of the loss of isopropyl alcohol in the layer separator 120 and the energy consumption in the first tower 100, it is necessary to control the mass flow rate of the branch stream 20 of the lower discharge stream 250 of the second tower recycled to the upper part of the first tower. Specifically, the mass flow rate of the branch stream 20 of the lower discharge stream 250 of the second tower relative to the mass flow rate of the feed 10 supplied to the first tower 100 can be 0.4 to 1.2, 0.4 to 1.0, or 0.5 to 0.8. When the flow rate of water supplied to the upper part of the first tower is greater than 1.2, the energy consumption required in the first tower is excessively increased. On the other hand, when the flow rate of water supplied to the upper part of the first tower is less than 0.4, it is difficult to supply enough water to the layer separator 120, and therefore, the loss of isopropyl alcohol in the oil phase may occur or may be excessively increased.

[0055] Meanwhile, in the layer separator 120 provided above the first tower 100, isopropyl alcohol should be contained in the aqueous phase and refluxed together with water to the first tower 100. When isopropyl alcohol is contained in the oil phase, loss of isopropyl alcohol occurs in the layer separator 120. To prevent the 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 tower 100.

[0056] According to an exemplary embodiment of the present invention, the water introduced into the first tower 100 may be the water contained in the feed 10 and the water contained in the stream 20 branched from a portion of the lower discharge stream 250 of the second tower and recycled. In order to minimize the loss of isopropyl alcohol in the layer separator 120, it is preferred 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 the stream 20 branched from a portion of the lower discharge stream 250 of the second tower and recycled is maintained at 12 to 15 times the mass flow rate of the isopropyl alcohol contained in the feed 10 (the ratio of the mass flow rates of isopropyl alcohol and water). In this case, a sufficient amount of water can be supplied to the layer separator 120, the loss of isopropyl alcohol in the oil phase in the layer separator 120 can be prevented, and the energy consumption required for the operation of the first tower 100 can be optimized.

[0057] Specifically, the branch stream 20 branched from a portion of the lower discharge stream of the second tower containing water may be a branch stream branched from a portion of the stream refluxed to the reboiler 230 from the stream immediately after being discharged to the lower portion of the second tower.

[0058] That is, when the ratio of the mass flow rates of water and isopropyl alcohol supplied to the first column is less than 12, it is difficult to ensure a sufficient amount of water in the layer separator 120, resulting in loss of isopropyl alcohol in the oil phase and difficulty in achieving a desired recovery rate of isopropyl alcohol. In addition, in this case, a portion of the first light by-product that should have been removed when contained in the oil phase in the layer separator 120 is contained in the water phase and introduced into the second column 200. In addition, when the first light by-product is introduced into the second column 200, the first light by-product is also contained in the first side discharge stream of the second column containing a mixture of isopropyl alcohol and water, thereby reducing the purity of the isopropyl alcohol recovered in the second column.

[0059] In addition, the ratio of the mass flow rates of water and isopropyl alcohol supplied to the first tower is greater than 15, which can prevent the loss of isopropyl alcohol in the layer separator 120, but the amount of water recycled through the first tower 100 and the second tower 200 is too large, which may increase energy consumption in the two towers.

[0060] Furthermore, from the viewpoint of minimizing the loss of isopropyl alcohol in the layer separator 120 and reducing energy consumption in the first and second towers, the mass flow rate of water contained in the stream 20 recycled after branching from a part of the lower discharge stream 250 of the second tower may be 58% to 90% based on the mass flow rate of water contained in the feed 10.

[0061] Meanwhile, a reboiler 130 for supplying heat energy required for the operation of the first tower is provided below the first tower 100. A reflux stream of the lower exhaust stream 150 of the first tower may be reintroduced into the reboiler 130, heat-exchanged with a high-temperature heat source, and then reintroduced into the lower portion of the first tower 100. The heat energy required for the operation of the first tower 100 may be supplied to the first tower 100 through the reboiler 130.

[0062] According to an exemplary embodiment of the present invention, the lower exhaust stream 150 of the first column is introduced into the second column 200, and the second light by-product, the mixture of isopropyl alcohol and water, the heavy by-product, and water may be separated according to boiling points.

[0063] Specifically, the following steps may be performed: supplying a lower effluent stream 150 of the first column containing isopropyl alcohol, water, a second light by-product, and a heavy by-product, and separating the lower effluent stream of the first column into an upper effluent stream 260 of the second column containing the second light by-product, a first side effluent stream 290 of the second column containing a mixture of isopropyl alcohol and water, a second side effluent stream 280 of the second column containing heavy by-products, and a lower effluent stream 250 of the second column containing water.

[0064] The second light by-product is a by-product having a relatively lowest boiling point compared to the other separated components. The second light by-product may be a compound having a boiling point of 50° C. to 70° C., specifically, acetone. Acetone may be a by-product produced during a gas-phase reaction for producing isopropyl alcohol, or may be a by-product produced by oxidation of isopropyl alcohol in a subsequent process after the gas-phase reaction.

[0065] The upper effluent stream 260 of the second tower may contain 60% by weight or more, 70% by weight or more, or 90% by weight or more, and 100% by weight or less of the second light by-product, and may contain a mixture of isopropyl alcohol and water as the remainder. After the upper effluent stream 260 of the second tower is discharged from the second tower, a portion of the upper effluent stream of the second tower may be refluxed back to the second tower after passing through a condenser, and the remaining portion may be discharged to the outside of the system 270.

[0066] Meanwhile, the mixture of isopropyl alcohol and water may be an azeotrope of isopropyl alcohol and water. That is, water having a boiling point of about 100° C. and isopropyl alcohol having a boiling point of about 82.3° C. may 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 and lower than the boiling point of the heavy by-product.

[0067] Therefore, a portion of the water introduced into the second column forms an azeotrope with the isopropyl alcohol and is discharged through the first side discharge stream 290 of the second column, and the remaining water is discharged through the lower discharge stream 250 of the second column.

[0068] A reboiler 230 for supplying heat energy required for the operation of the second tower is provided below the second tower 200. A reflux stream of the lower exhaust stream of the second tower may be introduced into the reboiler 230, heat-exchanged with a high-temperature heat source, and then reintroduced into the lower portion of the second tower 200. The heat energy required for the operation of the second tower 200 may be supplied to the second tower 200 through the reboiler 230.

[0069] At the same time, the branch stream 20 branched from a portion of the lower discharge stream 250 of the second tower containing water can be recycled to the upper part of the first tower. The water recycled from the second tower 200 can be used to supplement a sufficient amount of water so that the phase separation between the water phase and the oil phase can be smoothly performed in the layer separator 120 provided above the first tower 100.

[0070] Meanwhile, heavy by-products may include n-propyl alcohol (NPA) and hexanol, and these heavy by-products may be discharged through the second side discharge stream 280 of the second column.

[0071] As described above, according to one embodiment of the present invention, the second tower 200 includes a partition wall spaced apart from the bottom and provided in the longitudinal direction of the tower, and the second tower may be a distillation tower partitioned into the top region 201, the bottom region 202, the supply region 203, and the discharge region 204 by the partition wall.

[0072] Reference Figure 1 The interior of the second tower 200 is divided by a partition wall and an imaginary dotted line. Specifically, the top region 201 is located above the upper end of the partition wall and is the region from which the upper exhaust stream 260 of the second tower is discharged. The bottom region 202 is located below the lower end of the partition wall and is the region from which the lower exhaust stream 250 of the second tower is discharged. At the same time, the lower exhaust stream 150 of the first tower can be supplied to the supply region 203.

[0073] The first side effluent stream 290 of the second tower and the second side effluent stream 280 of the second tower can be discharged from the discharge area 204 in the area separated by the dividing wall. Specifically, the first side effluent stream 290 can be discharged from the discharge area at a higher position than the second side effluent stream 280.

[0074] 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 lower discharge stream of the first column) is separated and discharged through the upper portion, the first side, the second side, and the lower portion of one column (the second column) provided with a dividing wall, making it possible to reduce the number of distillation columns previously required for separating these components.

[0075] Specifically, refer to Figure 2 In the case of a distillation column without a dividing wall as the second column 200, although it is not possible to discharge the separated materials through the upper part, the lower part, and the first and second sides of the second column 200, in particular, the second side discharge stream 280 through which the heavy by-products are separated contains a large amount of isopropyl alcohol and water; therefore, it is necessary to further purify the second side discharge stream 280 to increase the yield of isopropyl alcohol. That is, it is necessary to perform a process of introducing the second side discharge stream 280 into the third column 300, further recovering the stream 370 containing isopropyl alcohol to the upper part, and supplying the recovered stream to the second column 200 again. That is, referring to Figure 2 According to the present invention, the same role performed by the conventional second tower 200 and the third tower 300 can be performed by one tower including a dividing wall, so that the number of towers can be reduced and energy consumption (e.g., steam consumption) required for the operation of the towers can be reduced.

[0076] Meanwhile, according to the method for purifying isopropyl alcohol of the present invention, the yield of isopropyl alcohol may refer to the ratio of the mass flow rate of isopropyl alcohol contained in the first side effluent stream (discharging the azeotrope of isopropyl alcohol and water) of the second column to the mass flow rate (e.g., tons / hour) of isopropyl alcohol contained in the feed 10, and the yield of isopropyl alcohol may be 95% by weight or more or 97% by weight or more and 99.9% by weight or less or 99.5% by weight or less. Therefore, in the case of the present invention, an excellent yield of isopropyl alcohol can be achieved using only the second column without additionally purifying the second side effluent stream (containing heavy by-products).

[0077] Therefore, according to the present invention, since a separate column for additionally purifying the second side effluent stream containing heavy by-products is not required, Figure 2 Compared to the related art shown in FIG. 1 , the number of towers for purifying isopropyl alcohol can be reduced. That is, as the number of towers performing the same function is reduced, the energy consumption required in the reboiler in each tower can be reduced. At the same time, when using second tower 200 including a dividing wall, preliminary separation occurs in supply region 203 and final purification is performed in discharge region 204, making it possible to achieve energy savings rather than simply operating two combined towers.

[0078] Meanwhile, the upper end of the partition wall may be located at a height of 3% to 30% downward from the top of the second tower, and the lower end of the partition wall may be located at a height of 70% to 95% downward from the top of the second tower.

[0079] Furthermore, first side bleed stream 290 may be discharged at a height of 5% to 33% down from the top of the second tower, and second side bleed stream 280 may be discharged at a height of 40% to 80% down from the top of the second tower.

[0080] By the location of the dividing wall and the discharge points of the first and second side effluent streams, energy consumption can be reduced compared to when two conventional columns are used, while at the same time, four streams discharged from the second column can be obtained at the desired purity.

[0081] From the perspective of the purity of separated components such as isopropyl alcohol and the energy required to separate these components, it is also necessary to control the respective operating temperatures and operating pressures of the top region 201 and the bottom region 202 of the second column 200.

[0082] Specifically, the operating temperature of the top region 201 of the second tower 200 may be below 90° C., below 85° C., or below 80° C., and the operating pressure of the top region 201 may be 2 kg / cm 2 ·g or less, 1kg / cm 2 ·g or less or 0.05kg / cm 2 ·g or less.

[0083] Meanwhile, the operating temperature of the bottom region 202 of the second tower 200 may be 85° C. or 88° C. or more and 105° C. or 103° C. or less. Meanwhile, the operating pressure of the bottom region 202 may be 1.0 kg / cm 2 ·g or less or 0.5kg / cm 2 ·g or less.

[0084] A method of purifying isopropyl alcohol according to one embodiment of the present invention may include introducing the first side discharge stream 290 of the second column including a mixture of isopropyl alcohol and water into an isopropyl alcohol recovery process, and separating isopropyl alcohol and water.

[0085] As described above, the first side effluent stream 290 of the second column may comprise a mixture of isopropyl alcohol and water, specifically, an azeotrope of isopropyl alcohol and water. More specifically, the first side effluent stream 290 of the second column may comprise 80 wt% to 90 wt% of isopropyl alcohol and 10 wt% to 20 wt% of water.

[0086] Thereafter, the first side discharge stream 290 of the second column can be supplied to an IPA recovery column and can be separated into a stream containing water and the entrainer and a stream containing isopropyl alcohol in the presence of an azeotropic agent (e.g., cyclohexane, benzene, etc.). That is, the azeotrope of isopropyl alcohol and water can be removed by the azeotropic agent in the IPA recovery column to obtain isopropyl alcohol purified to a high purity.

[0087] The stream containing water and the entrainer separated from the IPA recovery column can be separated into water and the entrainer, respectively, in a separate distillation column (e.g., a solvent recovery column), and the separated entrainer can be supplied back to the IPA recovery column and reused for separating isopropyl alcohol and water. [Specific implementation method]

[0089] Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following Examples are provided for illustration of the present invention. It will be apparent to those skilled in the art that various modifications and variations may be made without departing from the scope and concept of the present invention, and the scope of the present invention is not limited thereto.

[0090] In the following Examples and Comparative Examples, the process according to the present invention was simulated using the commercial process simulation program Aspen Plus V12.1.

[0091] Reality Example 1

[0092] according to Figure 1 The process diagram of the process for purifying isopropyl alcohol is shown in FIG.

[0093] Specifically, water and propylene are supplied to a reaction section and subjected to a gas phase reaction to produce a reaction product comprising isopropyl alcohol, water, and propylene. Propylene is separated and recovered from the reaction product, and a feed 10 is prepared from the remaining residue. Feed 10 contains 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.

[0094] The feed 10 was supplied to the first tower, and the water 20 recycled in the second tower was supplied to the upper portion of the first tower. At this time, a portion of the lower discharge stream of the second tower 200 was branched and introduced into the upper portion of the first tower 100, and the mass flow rate of the branch stream 20 branched from the portion of the lower discharge stream of the second tower 200 was 0.6 relative to the mass flow rate of the feed 10 supplied to the first tower 100.

[0095] Meanwhile, heat required for the operation of the first column is supplied through the reboiler 130 .

[0096] A stream 160 containing isopropyl alcohol, water, diisopropyl ether (DIPE), and acetone is discharged through the upper portion of the first column 10 and supplied to the condenser 110 and the layer separator 120, the aqueous phase containing isopropyl alcohol, water, and acetone is refluxed back to the first column 100, and the oil phase containing diisopropyl ether is discharged from the system.

[0097] The lower effluent stream of the first column is introduced into a supply region 203 of the second column including a dividing wall and is separated by distillation into four effluent streams: an upper effluent stream 260 of the second column containing acetone, a first side effluent stream 290 of the second column containing an azeotrope of isopropyl alcohol and water, a second side effluent stream 280 of the second column containing n-propyl alcohol (NPA) and hexanol, and a lower effluent stream 250 of the second column containing water. Heat required for the operation of the second column is supplied by a reboiler 230.

[0098] The upper end and the lower end of the dividing wall provided in the second column were located at heights of 17% and 83% downward from the top of the second column, respectively.

[0099] In addition, the first side bleed stream and the second side bleed stream were withdrawn at heights of 22% and 45% downward from the top of the second column, respectively.

[0100] At this time, the ratio (yield) of the mass flow rate of isopropyl alcohol contained in the first side bleed stream of the second column to the mass flow rate of isopropyl alcohol contained in the feed 10 was 99.3%, and therefore, there was no need to additionally distill the second side bleed stream of the second column to increase the yield of isopropyl alcohol.

[0101] The first side draw stream comprising the azeotrope of isopropyl alcohol and water is supplied to an IPA recovery column to ultimately obtain isopropyl alcohol in the presence of an entrainer.

[0102] In this case, the reboiler duty of each column is shown in Table 1.

[0103] Comparative Example 1

[0104] according to Figure 2 The process diagram of the process for purifying isopropyl alcohol is shown in FIG.

[0105] The lower effluent stream 150 of the first column having the same composition as in Example 1 was obtained from the same feed 10 as in Example 1 and then introduced into the second column 200 .

[0106] Second tower 200 of Comparative Example 1 is a tower not provided with a dividing wall, and as in Example 1, the stream is separated into four discharge streams by distillation of second tower 200: an upper discharge stream 260 of the second tower containing acetone, a first side discharge stream 290 of the second tower containing an azeotrope of isopropyl alcohol and water, a second side discharge stream 280 of the second tower containing n-propyl alcohol (NPA) and hexanol, and a lower discharge stream 250 of the second tower containing water.

[0107] Energy required for the operations of the first to third columns is supplied through a reboiler provided below the first to third columns.

[0108] In this case, since a large amount of isopropyl alcohol is contained in the second side bleed stream 280 of the second column and is discharged without effectively separating heavy by-products and water, it is impossible to achieve a 99% yield of isopropyl alcohol contained in the first side bleed stream 290 of the second column by operating only the second column 200, and therefore, the third column 300 is required to further purify the isopropyl alcohol in the second side bleed stream 280 of the second column and separate the heavy by-products and water.

[0109] Specifically, the second side discharge stream 280 of the second tower is introduced into the third tower 300, a stream containing isopropyl alcohol is separated by the upper portion of the third tower and supplied to the second tower again, water is separated by the lower portion of the third tower, and heavy by-products (n-propyl alcohol and hexanol) are separated from one side of the third tower.

[0110] In this case, the reboiler duty of each column is shown in Table 1.

[0111] [Table 1]

[0112]

[0113] In Table 1, the total energy consumption in Example 1 represents the relative energy consumption when the total energy consumption in Comparative Example 1 is set to 100, and the energy consumption in the reboiler in each tower in Example 1 represents the value obtained by allocating the relative energy consumption in proportion to the actual energy consumption.

[0114] Referring to Table 1, Example 1 saves about 36% of energy compared to Comparative Example 1. In Example 1, unlike Comparative Example 1 in which three towers were operated, only two towers were used to obtain the same amount of isopropyl alcohol while saving total energy consumption.

[0115] [Detailed description of main components]

[0116] 10: Feed

[0117] 100: First Tower 200: Second Tower

[0118] 300: Third Tower 110: Condenser

[0119] 120: Layer separator 130, 230: Reboiler

[0120] 150: Lower discharge stream of the first tower 160: Upper discharge stream of the first tower

[0121] 250: Lower discharge flow of the second tower

[0122] 260: Upper discharge flow of the second tower

[0123] 280: Second side discharge stream of the second tower

[0124] 290: First side discharge stream of the second tower

[0125] 201: Top area 202: Bottom area

[0126] 203: Supply area 204: Discharge area

Claims

1. A method for purifying isopropyl alcohol, the method 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; separating the first light by-product from the upper effluent stream of the first column; supplying a lower effluent stream of the first column containing isopropyl alcohol, water, a second light by-product, and a heavy by-product to a second column, and separating the lower effluent stream of the first column into an upper effluent stream of the second column containing the second light by-product, a first side effluent stream of the second column containing a mixture of isopropyl alcohol and water, a second side effluent stream of the second column containing heavy by-products, and a lower effluent stream of the second column containing water; and The mixture of isopropyl alcohol and water is introduced into an isopropyl alcohol recovery process and the isopropyl alcohol and water are separated.

2. The method according to claim 1, wherein The upper discharge stream of the first column contains isopropyl alcohol, water, and a first light by-product and a second light by-product.

3. The method according to claim 2, wherein: The first light by-product is separated by the following steps: supplying the upper exhaust stream of the first column to a condenser and liquefying the upper exhaust stream of the first column, and The liquefied upper discharge stream of the first column is supplied to a layer separator to perform liquid-liquid separation on the upper discharge stream of the first column, an aqueous phase stream containing isopropyl alcohol, water, and a second light by-product is refluxed to the first column, and an oil phase stream containing the first light by-product is removed.

4. The method according to claim 1, wherein The first light by-product includes diisopropyl ether (DIPE).

5. The method according to claim 1, wherein The second tower includes a partition wall spaced apart from the bottom and provided in the longitudinal direction of the tower, 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 bleed stream and the second side bleed stream of the second column are discharged from the discharge zone, and The first side exhaust stream is discharged from the exhaust region at a higher position than the second side exhaust stream.

6. The method according to claim 5, wherein: The upper end of the dividing wall is located at a height of 3% to 30% downward from the top of the second column, and The lower end of the dividing wall is located at a height of 70% to 95% downward from the top of the second column.

7. The method according to claim 5, wherein: The first side bleed stream is discharged at a height of 5% to 33% below the top of the second column, and The second side bleed stream is withdrawn at a height of 40% to 80% down from the top of the second column.

8. The method according to claim 1, wherein A branched stream branched from a portion of the lower discharge stream of the second column containing water is recycled to the upper portion of the first column.

9. The method according to claim 8, wherein The mass flow rate of the branch stream recycled to the upper portion of the first column is 0.4 to 1.2 relative to the mass flow rate of the feed supplied to the first column.

10. The method according to claim 1, wherein The second light by-product has a boiling point of 50°C to 70°C.

11. The method according to claim 10, wherein: The second light by-product includes acetone.

12. The method according to claim 1, wherein The upper discharge stream of the second column contains 50 to 100 wt % of the second light by-product and the remainder is a mixture of isopropyl alcohol and water.

13. The method according to claim 1, wherein The heavy by-product has a boiling point of 85°C to 99°C.

14. The method according to claim 13, wherein The heavy by-products include n-propanol (NPA) and hexanol.

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