Method for purifying isopropanol

Abstract

The present invention provides a method for preparing isopropanol, the method comprising: cooling a reaction product and supplying the cooled reaction product to an absorption tower; a lower discharge stream of the absorption tower containing isopropanol is supplied from the absorption tower to an isopropanol purification section including first to fourth columns, and an upper discharge stream of the absorption tower containing propylene is supplied to a gas purification section including fifth and sixth columns, all or part of the reaction product is cooled by heat exchange with one or more of the lower discharge stream of the fourth column and the side discharge stream of the fifth column, and the upper discharge stream of the second column is heat exchanged with the lower discharge stream of the sixth column, and the upper discharge stream of the third column exchanges heat with one or more of the lower discharge stream of the first column and the lower discharge stream of the second column.

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. 10-2024-0147824, filed on October 25, 2024, which are hereby incorporated by reference into this specification in their entirety.

[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 of 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 various 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, require an improved design that 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 preparing isopropyl alcohol includes: reacting propylene monomer with water to prepare a reaction product including propylene and isopropyl alcohol; cooling the reaction product and supplying the cooled reaction product to an absorption tower; and supplying a lower effluent stream of the absorption tower containing isopropyl alcohol from the absorption tower to an isopropyl alcohol purification section including first to fourth towers, and supplying an upper effluent stream of the absorption tower containing propylene to a gas purification section including fifth and sixth towers, wherein the isopropyl alcohol contained in the lower effluent stream of the absorption tower supplied to the isopropyl alcohol purification section is purified by sequentially passing through the lower effluent stream of the first tower, the first side effluent stream of the second tower, the third tower, and the like. The reaction product is obtained by passing through the lower discharge stream of the first region of the absorption tower and the upper discharge stream of the fourth tower, the propylene contained in the upper discharge stream of the absorption tower supplied to the gas purification section is obtained by sequentially passing through the upper discharge stream of the fifth tower and the side discharge stream of the sixth tower, all or a part of the reaction product is cooled by heat exchange with one or more of the lower discharge stream of the fourth tower and the side discharge stream of the fifth tower, the upper discharge stream of the second tower is heat exchanged with the lower discharge stream of the sixth tower, and the upper discharge stream of the third tower is heat exchanged with one or more of the lower discharge stream of the first tower and the lower discharge stream of the second tower.

[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 is a reaction product of propylene and water, is effectively purified, so that high-purity isopropyl alcohol can be ultimately obtained. In addition, unreacted propylene contained in the reaction product can be recovered at high purity and then reused in the reaction for producing isopropyl alcohol.

[0014] Since the processes performed by at least two distillation columns in the isopropyl alcohol purification section are performed in one distillation column, the reboiler load required for operating at least two distillation columns in the prior art can be saved (energy saving), and the facility cost and operating cost of the apparatus can be reduced by reducing the number of distillation columns.

[0015] Furthermore, in the entire process for producing isopropyl alcohol, which includes an isopropyl alcohol purification section for recovering isopropyl alcohol produced after the reaction of propylene and water and a gas purification section for recovering unreacted propylene, heat exchange between the distillation columns can be used to reduce the heat energy consumption required for operating the distillation columns in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 FIG1 is a flow chart of the entire process of a method for preparing isopropyl alcohol according to one embodiment of the present invention.

[0017] Figure 2is a flow chart showing a process between a reactor and an absorption column in a process of a method for preparing isopropyl alcohol according to one embodiment of the present invention.

[0018] Figure 3 is a flow chart showing a process of an isopropyl alcohol purification section in a process of a method for preparing isopropyl alcohol according to one embodiment of the present invention.

[0019] Figure 4 is a flow chart showing a process of a gas purification section in a process of a method for preparing isopropyl alcohol according to one embodiment of the present invention.

[0020] Figure 5 is a process flow chart of a method for purifying isopropyl alcohol according to a comparative example. DETAILED DESCRIPTION

[0021] 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.

[0022] With regard to the description of the drawings, like reference numerals may be used to designate like or related components.

[0023] Unless the relevant context clearly indicates otherwise, a singular form of a noun corresponding to an item may include one or more items.

[0024] 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.

[0025] The term "and / or" includes a combination of a plurality of related components or any one of the plurality of related components.

[0026] Terms such as “first” and “second” or “1st” and “2nd” may be used to simply distinguish a corresponding component from another component, and do not limit the corresponding components in other aspects (for example, importance or order).

[0027] 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.

[0028] 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.

[0029] When a component is referred to as being “connected,” “coupled,” “supported,” or “in contact with” another component, this includes not only a case where the components are directly connected, coupled, supported, or in contact, but also a case where the components are indirectly connected, coupled, supported, or in contact via a third component.

[0030] 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 another component exists between the two components.

[0031] 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.

[0032] 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).

[0033] Furthermore, the term "pressure" mentioned in this application refers to a gauge pressure measured under atmospheric pressure conditions.

[0034] 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.

[0035] 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.

[0036] Figure 1 FIG1 is a flow chart of the entire process of a method for preparing isopropyl alcohol according to one embodiment of the present invention. Figure 2 is a detailed flow chart showing a process between a reactor and an absorption column in a process of a method for preparing isopropyl alcohol according to one embodiment of the present invention.

[0037] Reference Figure 1 and Figure 2, the reaction product comprising isopropyl alcohol can be prepared by the reaction of propylene and water carried out in a reactor. The feed comprising propylene and water can be supplied to the reactor, and the reaction product produced in the reactor can comprise isopropyl alcohol, unreacted propylene, unreacted water and various by-products. In this case, isopropyl alcohol should be separated and recovered from the reaction product, and unreacted propylene monomer needs to be reclaimed and reused in the isopropyl alcohol preparation process.

[0038] Specifically, the reactor can be operated under optimal conditions under which isopropyl alcohol can be efficiently produced by the gas phase reaction of propylene monomer and water. For example, the operating pressure of the reactor can be 10 kg / cm 2 g to 50kg / cm 2 g, 25kg / cm 2 g to 50kg / cm 2 g, or 35kg / cm 2 g to 45kg / cm 2 g, the operating temperature of the reactor may be 150° C. to 220° C., 165° C. to 220° C., or 180° C. to 215° C. When the reactor is operated at a pressure and temperature within the above ranges, isopropyl alcohol can be efficiently produced by using a gas phase reaction of propylene monomer and water.

[0039] The reaction product prepared under the operating conditions of the reactor can be a high-temperature gaseous reaction product. Meanwhile, it is necessary to preheat the feed comprising propylene and water as the reactant required for the reaction to the temperature range suitable for being supplied to the reactor, and then supply to the reactor. Therefore, according to one embodiment of the present invention, the feed can first be supplied to a heat exchanger 90, and mainly preheated by heat exchange with the reaction product. When the reaction product discharged from the reactor is heat exchanged with the feed, the high-temperature reaction product discharged from the reactor can be cooled to a level suitable for being supplied to an absorption tower 10, and the feed can be preheated to a level suitable for being supplied to the reactor. Thus, the thermal energy for heating the feed can be saved.

[0040] The feed preheated in the heat exchanger 90 may be further heated as needed and then supplied to the reactor.

[0041] Meanwhile, propylene contained in the feed may include propylene newly supplied for the reaction, propylene supplied from the upper portion of the absorption tower 10, and propylene recovered with high purity from the gas purification section described below.

[0042] The propylene that reclaims and is supplied to reactor is used as the raw material of gas phase reaction again in this technique, and reacted propylene also needs to reclaim with high purity to prepare high-purity isopropyl alcohol.Particularly, preferably as the propylene (C3H6) of raw material supply to reactor have high purity as above;But, comprise other unsaturated hydrocarbons such as ethene, butylene and amylene and impurity such as ethane, propane and carbonic acid gas at raw material propylene, during the reaction between propylene and water, may produce the by product (such as ethanol) that boiling point is similar to isopropyl alcohol.Therefore, preferably comprise relative to its gross weight for more than 97 % by weight as reactant to the propylene supplied to reactor, the propylene of such as 97 % by weight to 99.8 % by weight amount, the content of impurity is less than 3 % by weight.

[0043] Meanwhile, only a part is supplied to the propylene of reactor for reaction.Therefore, except the isopropyl alcohol produced by the reaction of propylene monomer and water, reaction product can also include unreacted propylene and unreacted water.For example, reaction product can include propylene monomer of 65 % by weight to 85 % by weight, isopropyl alcohol of 4 % by weight to 8 % by weight and the water of 5 % by weight to 30 % by weight.In addition, reaction product can include light by-products and heavy by-products of at least two or more types as by-products.Particularly, reaction product can include diisopropyl ether (DIPE) as the first light by-product, acetone as the second light by-product and n-propyl alcohol (NPA) and hexanol as heavy by-products.Therefore, need to separate unreacted propylene and the technology of purifying isopropyl alcohol from various by-products from reaction product.

[0044] Meanwhile, there are various methods of recovering propylene from the reaction product, and in particular, a method of recovering high-purity propylene and recycling the recovered high-purity propylene to a reaction in which a gas-phase reaction is performed is proposed as an example.

[0045] According to one embodiment of the present invention, the recovery of propylene in the reaction product can be carried out through a gas purification section including an absorption tower, a flash tank, and at least a fifth tower and a sixth tower. Simultaneously, the purification of isopropyl alcohol in the reaction product can be carried out through an isopropyl alcohol purification section including an absorption tower, a flash tank, and at least a first tower to a fourth tower.

[0046] The method of preparing isopropyl alcohol according to one embodiment of the present invention may include cooling the reaction product and supplying the cooled reaction product to the absorption tower 10 .

[0047] Some components in the gaseous reaction product can be condensed and liquefied by cooling, and other components may exist in the reaction product in a gaseous phase and may be supplied to the absorption tower 10. For example, preferably, the isopropyl alcohol discharged through the lower effluent stream of the absorption tower 10 exists in a liquid phase, and the propylene and gas components discharged through the upper effluent stream of the absorption tower 10 exist in a gaseous phase. That is, the efficiency of component separation in the absorption tower can be improved by the phase change of some components due to cooling.

[0048] Specifically, when isopropyl alcohol is discharged through the top of the absorption tower and then reintroduced into the reactor, this has a negative impact on the isopropyl alcohol formation reaction carried out in the reactor. Therefore, it is preferred to reclaim isopropyl alcohol as much as possible through the bottom of the absorption tower. In addition, when propylene and gaseous components are discharged through the bottom of the absorption tower, an additional gas purification tower is needed to reclaim the unreacted propylene or gaseous components discharged through the bottom, which increases energy consumption. Therefore, it is preferred to reclaim these unreacted propylene and gaseous components as much as possible through the top of the absorption tower.

[0049] In addition, as the water introduced through the upper portion of the absorption tower flows downward along the absorption tower, the absorption tower absorbs isopropyl alcohol, and the temperature can be controlled to a temperature range where the absorption efficiency of water for isopropyl alcohol is optimal by cooling, and then the reaction product can be supplied to the absorption tower 10. That is, the cooling of the reaction product of the present invention can achieve the effect of improving the absorption efficiency of isopropyl alcohol in the absorption tower 10 by phase change of some components of the reaction product and temperature control of the reaction product.

[0050] From this perspective, the temperature of the cooled reaction product introduced into the absorption tower 10 may be 90° C. to 99° C., specifically, 90° C. to 95° C. In this case, the absorption efficiency of isopropyl alcohol by water in the absorption tower 100 may be further improved, and propylene discharged through the lower portion of the absorption tower may be minimized.

[0051] Meanwhile, all or a portion of the reaction product passing through the heat exchanger 90 may be cooled by heat exchanging with one or more of the lower discharge stream of the fourth tower 400 and the side discharge stream of the fifth tower 500 .

[0052] Reference Figures 2 to 4 According to one embodiment of the present invention, the reaction product is heat-exchanged with one or more of the first reboiler 410 of the fourth tower provided below the fourth tower 400 of the isopropyl alcohol purification section and the first reboiler (side reboiler, 510) of the fifth tower provided on one side of the fifth tower 500 of the gas purification section, so that energy can be used efficiently.

[0053] Specifically, first, by supplying the heat energy of the high-temperature reaction products to one or more of the fourth tower 400 and the fifth tower 500, the heat energy required to operate these towers can be reduced. That is, a large portion of the heat energy required to operate one or more of the fourth tower 400 and the fifth tower 500 can be replaced by utilizing waste heat. Second, the amount of refrigerant required to cool the reaction products in the prior art can be reduced. Third, in order to improve the purification efficiency in the fifth tower 500 of the gas purification section, a gentle temperature distribution must be achieved throughout the tower. When the heat energy of the reaction products is supplied to the lower and middle portions of the fifth tower 500, a gentle temperature distribution can be achieved in the lower and middle portions of the fifth tower.

[0054] Meanwhile, according to one embodiment of the present invention, the cooling of the reaction product may be performed by including first cooling and second cooling, wherein the first cooling is performed by heat exchange between all or a portion of the reaction product stream and one or more of the lower discharge stream of the fourth tower 400 and the side discharge stream of the fifth tower 500, and the second cooling is performed by heat exchange between a stream including the reaction product that has undergone the first cooling (high-temperature medium) and a refrigerant (low-temperature medium).

[0055] Specifically, refer to Figure 2 , the reaction product stream may be branched into a first branch stream 50, a second branch stream 60, and a third branch stream 70. Here, the first branch stream 50 may be a stream that exchanges heat with the lower exhaust stream of the fourth tower, and the second branch stream 60 may be a stream that exchanges heat with the side exhaust stream of the fifth tower. Meanwhile, the third branch stream 70 may not exchange heat with the fourth tower and the fifth tower.

[0056] Specifically, the first branch stream 50 may be a stream heat-exchanged with the lower exhaust stream of the fourth tower 400 in the first reboiler 410 of the fourth tower. Figure 2 and Figure 3 , Figure 2 The heat exchanger A is the first reboiler 410 of the fourth tower. Meanwhile, the second branch stream 60 may be a stream heat-exchanged with the side discharge stream of the fifth tower 500 in the first reboiler 510 of the fifth tower. That is, referring to Figure 2 and Figure 4 , Figure 2 The heat exchanger B is the first reboiler 510 of the fifth tower.

[0057] In this case, the first cooling may be cooling performed by heat exchange between the first branch stream 50 and the lower exhaust stream of the fourth tower and heat exchange between the second branch stream 60 and the side exhaust stream of the fifth tower.

[0058] The first and second branch streams 50 and 60 that have undergone the first cooling are combined with the third branch stream 70 that has not undergone the first cooling to form a combined stream, which can be further subjected to a second cooling by a refrigerant in a heat exchanger 80. Here, the refrigerant can be cooling water (CW).

[0059] Furthermore, the ratio of the mass flow rates of the first branch stream to the third branch stream, i.e., the mass flow rate of the first branch stream 50: the mass flow rate of the second branch stream 60: the mass flow rate of the third branch stream 70, can be 1:0.2 to 0.4:0.4 to 0.7. When this ratio is within the above range, maximum heat can be supplied relative to the sizes of the first reboiler 410 of the fourth tower and the first reboiler 510 of the fifth tower, and the sizes of the auxiliary reboiler 415 disposed below the fourth tower 400 and the second reboiler 520 disposed below the fifth tower 500 can be minimized. The reaction product cooled by the first and second cooling processes can then be supplied to the absorption tower 10. Here, the cooled reaction product can be supplied to the absorption tower 10 as a gas-liquid mixed phase. In the absorption tower 10, the lower effluent stream of the absorption tower containing isopropyl alcohol and the upper effluent stream of the absorption tower containing propylene can be separated.

[0060] The reaction product may be supplied to the lower portion of the absorption tower 10, and water may be supplied to the upper portion of the absorption tower 10. Using the water supplied to the upper portion, isopropyl alcohol contained in the reaction product is dissolved and then separated by the lower portion of the absorption tower 10, and a stream containing propylene may be separated by the upper portion of the adsorption tower 10.

[0061] The water supplied to the upper portion of the absorption tower 10 may be a stream 230 branched and supplied from a lower exhaust stream of the second tower 200 of the isopropyl alcohol purification section.

[0062] The lower discharge stream of the absorption tower 10 can be supplied to the flash tank 20, and propylene and gas components that may be present in the lower discharge stream of the absorption tower 10 can be separated by the upper part of the flash tank 20 and resupplied to the absorption tower 10. Thus, the propylene and gas components in the lower discharge stream 30 of the flash tank 20 can be removed or minimized. The lower discharge stream 30 of the flash tank 20 can be introduced into the isopropyl alcohol purification section.

[0063] Meanwhile, the upper exhaust stream of the absorption tower 10 may contain propylene and gas components. The upper exhaust stream of the absorption tower 10 may be compressed by a compressor, and then a portion of the stream 40 may be supplied to the gas purification section described below, and the remaining stream may be mixed with newly supplied propylene and water, introduced into the heat exchanger 90 as described above, and then recycled to the reactor.

[0064] According to one embodiment of the present disclosure, the isopropyl alcohol purification section may include the first to fourth towers. The lower discharge stream of the absorption tower, preferably the isopropyl alcohol contained in the lower discharge stream 30 of the flash tank 20, can be obtained by sequentially passing through the lower discharge stream of the first tower, the first side discharge stream of the second tower, the first region lower discharge stream of the third tower, and the upper discharge stream of the fourth tower. Hereinafter, reference will be made to Figure 3 The purification process carried out in the isopropyl alcohol purification section is described.

[0065] According to one embodiment of the present invention, at least one or more of the lower effluent stream of the absorption tower 10, the lower effluent stream of the flash tank 20, and the lower effluent streams of the fifth tower and the sixth tower of the gas purification section can be supplied to the first tower as the feed of the isopropyl alcohol purification section. Specifically, the feed stream supplied to the first tower can be the lower effluent stream 30 of the flash tank 20. The feed stream supplied to the first tower can include isopropyl alcohol, water, a first light by-product, a second light by-product, and a heavy by-product.

[0066] The feed stream 30 supplied to the first column may be introduced to a point at a height of 30% to 50% downward from the top of the first column 100 .

[0067] According to one embodiment of the present invention, the first light by-product included in the feed 30 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 .

[0068] Specifically, the upper discharge stream of the first column including isopropyl alcohol, water, a first light by-product (first light impurity), and optionally a second light by-product, and the lower discharge stream of the second column including isopropyl alcohol, water, a second light by-product, and a heavy by-product can be discharged through the upper and lower parts of the first column 100, respectively, by distillation in the first column 100.

[0069] The upper discharge stream of the first tower can be supplied to a condenser and is cooled and liquefied after being discharged from the first tower 100. The liquefied upper discharge stream of the first tower can be supplied to a layer separator 120 and subjected to liquid-liquid separation. By liquid-liquid separation, an aqueous phase stream comprising isopropyl alcohol, water, and an optional second light by-product can be refluxed to the first tower, and an oil phase stream comprising the first light by-product can be discharged to the outside of the system. When the content of the first light by-product included in the feed stream 30 supplied to the first tower is 100 wt %, the amount of the first light by-product discharged to the outside of the system can be more than 97 wt %, more than 99 wt %, and specifically 100 wt %.

[0070] 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.

[0071] According to one embodiment of the present invention, the first light by-product can be diisopropyl ether (DIPE) that is insoluble in water, and the second light by-product can be acetone that is soluble in water. Because the boiling point of acetone is lower than the boiling point of diisopropyl ether, the upper discharge flow of the first tower can comprise water, isopropyl alcohol, acetone and diisopropyl ether (DIPE). The isopropyl alcohol comprised in the upper discharge flow 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 comprised in the aqueous phase are refluxed back to the first tower 100. Therefore, the loss of the isopropyl alcohol on the top of the first tower 100 can be minimized by the layer separator 120 above the first tower 100.

[0072] At the same time, almost all of the first light by-products contained in the feed stream 30 supplied to the first tower can be discharged to the outside of 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 30 can be contained in the upper discharge stream of the first tower 100.

[0073] 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 of 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 0.5kg / cm 2 g or less. The operating pressure may refer to the pressure at the top of first tower 100. When first tower 100 is operated at the operating temperature and pressure described above, the first light by-product can be separated as much as possible through the upper exhaust stream of the first tower, thereby preventing the first light by-product from flowing out through the lower exhaust stream of the first tower and remaining as an impurity in the isopropyl alcohol produced thereby. Furthermore, the operating temperature and operating pressure of first tower 100 are as described above, and efficient energy utilization can be achieved through heat exchange with the upper exhaust stream of the third tower described below.

[0074] Meanwhile, in order to efficiently recover isopropyl alcohol contained in the upper discharge stream of the first column and reflux the recovered isopropyl alcohol to the first column by liquid-liquid separation performed in the layer separator 120, water should 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 stream 30 supplied to the first column. The water supplied to the upper portion of the first column may be water contained in the stream 220 branched from a portion of the lower discharge stream 250 of the second column containing water and recycled, as described below.

[0075] Specifically, the stream discharged through the lower portion of the second tower 200 may be branched into a reflux stream supplied to the first reboiler 210 of the second tower 200, and the remaining stream may be branched into a stream 230 supplied to the upper portion of the absorption tower 10, a stream 240 containing water discharged to the outside of the system, and a stream 220 recycled to the upper portion of the first tower. That is, the branch stream 220 branched from a portion of the stream discharged from the lower portion of the second tower 200 containing water may be a branch stream branched from a portion of the stream 250 immediately after the stream discharged through the lower portion of the second tower 200 is branched to flow back to the first reboiler 210 of the second tower 200.

[0076] 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 220 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 220 of the lower discharge stream 250 of the second tower relative to the mass flow rate of the feed stream 30 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.

[0077] 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.

[0078] According to one embodiment of the present invention, the water introduced into the first tower 100 may be the water contained in the feed stream 30 supplied to the first tower and the water contained in the stream 220 branched from a part 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 to maintain the sum of the mass flow rate of the water contained in the feed stream 30 and the mass flow rate of the water contained in the stream 220 branched from a part of the lower discharge stream 250 of the second tower and recycled at 12 to 15 times the mass flow rate of the isopropyl alcohol contained in the feed stream 30 (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.

[0079] That is, when the ratio of the mass flow rates of isopropyl alcohol and water 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.

[0080] In addition, the ratio of the mass flow rates of isopropyl alcohol and water 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.

[0081] 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 220 recycled after being branched 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 stream 30.

[0082] Meanwhile, a first reboiler 110 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 of the first tower may be introduced into the first reboiler 110 of the first tower, 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 first reboiler 110 of the first tower.

[0083] According to one embodiment of the present invention, the heat source of the first reboiler 110 of the first tower, that is, the heat source for heat exchange with the reflux flow of the lower exhaust stream of the first tower, can be the upper exhaust stream 330 of the third tower 300, as described below. Specifically, all or a portion of the upper exhaust stream 330 of the third tower can be heat exchanged with the reflux flow of the lower exhaust stream of the first tower in the first reboiler 110 of the first tower, and then introduced into the condenser 380 or the layer separator 340 provided above the third tower 300. In this way, the heat energy of the upper exhaust stream 330 of the third tower 300 can be supplied to the first tower 100.

[0084] Meanwhile, according to one embodiment of the present invention, when the thermal energy of the upper exhaust stream 330 of the third tower 300 alone cannot completely replace the reboiler duty required for the operation of the first tower 100, an auxiliary reboiler 115 may be provided below the first tower 100 separately from the first reboiler 110 of the first tower.

[0085] According to an exemplary embodiment of the present invention, the lower exhaust stream 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.

[0086] Specifically, the following steps may be performed: supplying the lower discharge stream of the first tower containing isopropyl alcohol, water, the second light by-products, and the heavy by-products to the second tower 200, and separating the lower discharge stream of the first tower into an upper discharge stream of the second tower containing the second light by-products (second light impurities), a first side discharge stream 290 of the second tower containing a mixture of isopropyl alcohol and water, a second side discharge stream 280 of the second tower containing the heavy by-products, and a lower discharge stream 250 of the second tower containing water.

[0087] The second light by-product is a by-product having a relatively low boiling point compared to other separated components. The second light by-product can be a compound having a boiling point of 50°C to 70°C, specifically, acetone. Acetone can be a by-product produced during the gas phase reaction for preparing isopropyl alcohol, and can be a by-product produced by the oxidation of isopropyl alcohol in a subsequent process after the gas phase reaction. The upper effluent stream of the second tower can comprise more than 60% by weight, more than 70% by weight, or more than 90% by weight, and less than 100% by weight of the second light by-product, and can comprise a residual mixture of isopropyl alcohol and water. After the upper effluent stream of the second tower is discharged from the second tower, a portion of the upper effluent stream of the second tower can be refluxed back to the second tower after passing through a condenser, and the remainder can be discharged to the outside of the system.

[0088] Meanwhile, according to one embodiment of the present invention, the upper exhaust stream of the second tower 200 may be heat exchanged with the lower exhaust stream of the sixth tower. Figure 3and Figure 4 , the upper exhaust stream of the second tower 200 may be heat-exchanged with the lower exhaust stream of the sixth tower 600 in the first reboiler 610 of the sixth tower provided below the sixth tower 600, and then introduced into the condenser 280 provided above the second tower 200. In this case, the heat exchanger D provided above the second tower 200 may be the first reboiler 610 of the sixth tower. Thus, the heat energy of the upper exhaust stream of the second tower 200 may be supplied to the sixth tower 600. The upper exhaust stream of the second tower 200, which has been heat-exchanged with the lower exhaust stream of the sixth tower 600, may be further refluxed to the second tower 200, or discharged to the outside of the system after passing through the condenser 280 provided above the second tower 200.

[0089] 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.

[0090] 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.

[0091] A first reboiler 210 of the second tower is provided below the second tower 200 to supply heat energy required for the operation of the second tower. A reflux stream of the lower exhaust stream of the second tower may be introduced into the first reboiler 210 of the second tower, 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 first reboiler 210 of the second tower.

[0092] According to one embodiment of the present invention, the heat source of the first reboiler 210 of the second tower, that is, the heat source for heat exchange with the reflux flow of the lower exhaust stream of the second tower, can be the upper exhaust stream 330 of the third tower 300, as described below. Specifically, all or a portion of the upper exhaust stream 330 of the third tower can be heat exchanged with the reflux flow of the lower exhaust stream of the second tower in the second reboiler 230, and then introduced into the condenser 380 or the layer separator 340 provided above the third tower 300. In this way, the heat energy of the upper exhaust stream of the third tower 300 can be supplied to the second tower 200.

[0093] According to one embodiment of the present invention, when the thermal energy of the upper exhaust stream 330 of the third tower 300 alone cannot completely replace the reboiler duty required for the operation of the second tower 200, an auxiliary reboiler 215 can be provided below the second tower 200 separately from the first reboiler 210 of the second tower.

[0094] At the same time, the lower discharge stream 250 of the second tower containing water, specifically, the branch stream 220 branched from a portion of the stream 250 discharged from the lower portion of the second tower 200 that is not supplied to the reboiler 210, can be recycled to the upper portion 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.

[0095] 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.

[0096] 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 a top region, a bottom region, a supply region, and a discharge region by the partition wall.

[0097] Reference Figure 3 The top region is a region above the upper end of the dividing wall from which the upper exhaust stream of the second column is discharged, and the bottom region is a region below the lower end of the dividing wall from which the lower exhaust stream 250 of the second column is discharged. Meanwhile, the lower exhaust stream of the first column may be supplied to the supply region.

[0098] The first side exhaust stream 290 of the second tower and the second side exhaust stream 280 of the second tower can be discharged from the exhaust area in the area separated by the partition wall. Specifically, the first side exhaust stream 290 can be discharged from the exhaust area at a higher position than the second side exhaust stream 280.

[0099] 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.

[0100] Specifically, refer to Figure 5 , in which a distillation column without a dividing wall is used as the C2 column, although it is not impossible to pass Figure 5 The separated materials are discharged from the upper, lower, first and second sides of the C2 column in the present invention. However, in particular, the side discharge stream 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 side discharge stream to increase the yield of isopropyl alcohol. That is, it is necessary to perform a process of introducing the side discharge stream into the C3 column, further recovering the stream containing isopropyl alcohol to the upper part, and resupplying the recovered stream to the C2 column. That is, referring to Figure 5, the same role performed by the conventional C2 tower and C3 tower can be performed by one distillation tower provided with a dividing wall, so that the number of towers can be reduced, and the energy consumption required for the tower operation (for example, steam consumption) can be reduced, and since the second tower provided with a dividing wall is used, preliminary separation is performed in the supply region and final purification is performed in the discharge region, energy consumption can be reduced more than simply combining two towers.

[0101] Meanwhile, the upper end of the partition wall may be located at a height of 3% to 30% downward from the top of second tower 200 , and the lower end of the partition wall may be located at a height of 70% to 95% downward from the top of second tower 200 .

[0102] 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.

[0103] 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.

[0104] From the viewpoint 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 in the top and bottom regions of second column 200.

[0105] Specifically, the operating temperature of the top region of the second tower 200 may be 90° C. or lower, 85° C. or lower, or 80° C. or lower, and the operating pressure of the top region may be 2 kg / cm 2 ·g or less, 1kg / cm 2 ·g or less or 0.05kg / cm 2 ·g or less. Meanwhile, the operating temperature of the bottom region of the second tower 200 may be 85°C or more or 88°C or more and 105°C or less or 103°C or less. Meanwhile, the operating pressure of the bottom region may be 1.0 kg / cm 2 ·g or less or 0.5kg / cm 2 ·g or less.

[0106] When the operating temperature and the operating pressure of the second tower 200 are as described above, effective energy can be utilized by heat exchange between the lower exhaust stream of the second tower and the upper exhaust stream of the third tower performed in the first reboiler 210 of the second tower, and at the same time, effective energy can be utilized by heat exchange between the lower exhaust stream of the sixth tower and the upper exhaust stream of the second tower performed in the first reboiler 610 of the sixth tower.

[0107] The method for preparing isopropyl alcohol according to one embodiment of the present invention may include supplying the first side discharge stream 290 of the second column including a mixture of isopropyl alcohol and water to the third column 300 and performing azeotropic distillation in the presence of an entrainer.

[0108] The third column 300 may be a dividing wall distillation column including a dividing wall connected to the bottom and extending in the longitudinal direction of the column. The dividing wall may be divided into a first region, a second region facing the first region, and an upper region located above the upper end of the dividing wall. Specifically, the dividing wall may be connected (bonded) to the bottom of the third distillation column 300 and may be arranged to extend upward in the longitudinal direction of the third distillation column 300. In this case, the first region and the second region are regions facing each other with the dividing wall therebetween, and the second region is a region facing the first region. Meanwhile, the upper region is a region located above the upper end of the dividing wall.

[0109] Specifically, first side effluent stream 290 of second column 200 may comprise a mixture of isopropyl alcohol and water, specifically, an azeotrope of isopropyl alcohol and water. More specifically, first side effluent stream 290 of second column 200 may comprise 80 wt% to 90 wt% isopropyl alcohol and 10 wt% to 20 wt% water.

[0110] Meanwhile, azeotropic distillation can be performed in the presence of an entrainer in third distillation column 300. A portion of the isopropyl alcohol and a portion of the water contained in first side effluent stream 290 of second column 200 can form an azeotrope. Since the azeotrope cannot be completely separated into these components by conventional distillation, a conventional entrainer can be used to remove the azeotropic relationship between the isopropyl alcohol and water, allowing the isopropyl alcohol and water to be separated at high purity. The entrainer of the present invention performing these functions can be one or more selected from cyclohexane, benzene, toluene, and isopropyl acetate.

[0111] The entrainer is a substance added separately from the feed components for azeotropic distillation, but in the case of isopropyl alcohol or the like, the entrainer is an impurity and therefore, the entrainer should be separated by a separate distillation column or the like, and from an economical point of view, the separated entrainer should be recyclable.

[0112] That is, referring to the prior art Figure 5In the prior art, to separate isopropyl alcohol and water from a feed containing an azeotrope of isopropyl alcohol and water and byproducts, azeotropic distillation is performed in the presence of an entrainer in a conventional azeotropic distillation column C4 without a dividing wall. The upper discharge stream, containing water and the entrainer, is then phase-separated in a layer separator, and the oil phase containing the entrainer is then refluxed back into the azeotropic distillation column C4. However, the aqueous phase contains a large amount of entrainer in addition to water. Therefore, the aqueous phase is introduced into an entrainer recovery column C5 to separate the entrainer and water by distillation. The recovered entrainer is reintroduced into the azeotropic distillation column C4, and the water is discharged to the outside of the system. Here, to separate the entrainer and water by distillation in the entrainer recovery column C5, a large amount of energy must be supplied by a reboiler located below the entrainer recovery column C5.

[0113] At the same time, according to the conventional art, heat energy required for the operation of azeotropic distillation column C4 is supplied to azeotropic distillation column C4 via a reboiler provided below azeotropic distillation column C4. When the upper discharge stream of azeotropic distillation column C4 contains water and an entrainer, the lower discharge stream of azeotropic distillation column C4 contains isopropyl alcohol and by-products. The lower discharge stream of azeotropic distillation column C4 is supplied to isopropyl alcohol recovery column C6 to obtain isopropyl alcohol at the upper portion of isopropyl alcohol recovery column C6, and the by-products are separated at the lower portion of isopropyl alcohol recovery column C6.

[0114] However, with reference to the method for preparing isopropyl alcohol according to one embodiment of the present invention, Figure 1 and Figure 3 The present invention is designed to provide a dividing wall in the third distillation column 300, where azeotropic distillation is performed, and optimize the reflux points of the aqueous and oil phases refluxing in the layer separator 340. This allows high-purity isopropyl alcohol to be produced even without the provision of an entrainer recovery column C5, which separates the entrainer from water, as in the prior art. This reduces the heat energy typically supplied to the reboiler for operation of the entrainer recovery column C5, as well as the cooling energy required for operation of the condenser above the entrainer recovery column C5. Furthermore, when comparing the third distillation column 300 of the present invention, which functions as a dividing wall distillation column, with the azeotropic distillation column C4 and the distillation column of the prior art, in addition to the energy savings achieved by not operating the entrainer recovery column C5, the energy consumption required for operation of the distillation column can also be reduced.

[0115] To this end, according to one embodiment of the present invention, a first region disposed at the lower portion of the third distillation column 300 may be provided with a reboiler 310 connected to the lower portion of the first region, and a second region may be provided with a reboiler 315 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 (uppermost portion) of the third distillation column 300. Heat energy may be supplied to the first region and the second region through the reboiler 310 and the reboiler 315, respectively, and operating conditions of the first region and the second region may be controlled by controlling the heat energy supplied to the reboiler 310 and the reboiler 315, respectively.

[0116] According to one embodiment of the present invention, the heat energy supplied by the reboiler 310 connected to the lower portion of the first section may be 1.5 to 3 times, more specifically, 1.8 to 2.5 times, the heat energy supplied by the reboiler 315 connected to the lower portion of the second section. Thus, isopropyl alcohol having a desired purity can be separated from the lower exhaust stream of the first section of the third distillation column, and pure water can be separated from the lower exhaust stream of the second section.

[0117] The temperature of the lower portion of the first region can be 135°C or 137°C or higher and 150°C or 148°C or lower. Furthermore, the temperature of the lower portion of the second region can be 155°C or 158°C or higher and 170°C or 168°C or lower. The temperatures of the lower portions of the first and second regions are the operating temperatures at a height of 90% to 100% of the height downward from the top (uppermost portion) of column 300. By controlling the temperatures of the lower portions of the first and second regions as described above, the energy required for distillation in third distillation column 300 can be reduced, isopropyl alcohol of desired purity can be obtained from the lower portion of the first region, and pure water can be separated from the lower portion of the second region.

[0118] Meanwhile, the first region lower effluent stream discharged from the first region of the third distillation column 300 may contain isopropyl alcohol and heavy by-products. Here, the heavy by-products may include n-propyl alcohol (NPA). A portion of the first region lower effluent stream may be heat-exchanged in a reboiler 310 connected to the lower portion of the first region and then refluxed back to the first region, and the remainder of the first region lower effluent stream may be supplied to the fourth column 400.

[0119] Meanwhile, the second region lower exhaust stream discharged from the second region may contain water. A portion of the second region lower exhaust stream may be heat exchanged in a reboiler 315 connected to the lower portion of the second region and then refluxed back to the second region, while the remainder of the second region lower exhaust stream may be discharged to the outside of the system.

[0120] As described above, the area above the upper end of the partition wall in the third distillation column 300 may form the upper region. The partition wall may extend from the bottom, and the upper end of the partition wall may be located at a height of 10% to 45% downward from the top of the third distillation column 300, or specifically, at a height of 15% to 30%. Thus, the separation efficiency of the third distillation column 300 can be maximized, so that isopropyl alcohol having a desired purity can be obtained from the lower portion of the first region, and pure water can be separated from the lower portion of the second region.

[0121] An upper discharge stream 330 comprising water and an azeotropic agent may be discharged from an upper portion of the upper region.

[0122] According to one embodiment of the present invention, the upper exhaust stream 330 of the third tower may be heat-exchanged with one or more of the lower exhaust stream of the first tower and the lower exhaust stream of the second tower in one or more of the first reboiler 110 of the first tower 100 and the first reboiler 210 of the second tower 200. Thus, the heat of the upper exhaust stream 330 of the third tower is supplied to one or more of the first tower and the second tower, so that the heat energy required for the operation of one or more of the first tower and the second tower can be reduced.

[0123] That is, refer to Figure 3 , the heat exchanger C provided above the third tower may be one or more of the first reboiler 110 of the first tower and the first reboiler 210 of the second tower. The upper discharge stream 330 of the third tower may be discharged from the third tower 300 and then transferred to one or more of the first reboiler 110 of the first tower and the first reboiler 210 of the second tower, and the retained heat energy may be supplied to one or more of the first tower 100 and the second tower 200. In this case, the upper discharge stream 330 of the third tower may be heat exchanged in the first reboiler 110 of the first tower or the first reboiler 210 of the second tower, or may be heat exchanged in both the first reboiler 110 of the first tower and the first reboiler 210 of the second tower. In the case where the upper discharge stream 330 of the third tower is heat exchanged in both the first reboiler 110 of the first tower and the first reboiler 210 of the second tower, the upper discharge stream 330 of the third tower may be branched into two streams, and the branched streams may be heat exchanged in the first reboiler 110 of the first tower and the first reboiler 210 of the second tower, respectively. In this case, Figure 1 The heat exchanger C in the figure may refer to the first reboiler 110 of the first tower and the first reboiler 210 of the second tower.

[0124] After the upper exhaust stream 330 of the third tower is heat-exchanged with one or more of the first reboiler 110 of the first tower and the first reboiler 210 of the second tower, the heat-exchanged upper exhaust stream 330 of the third tower may be transferred to the condenser 380 disposed above the third tower 300. In the case where the upper exhaust stream 330 of the third tower is branched and heat-exchanged with both the first reboiler 110 of the first tower and the first reboiler 210 of the second tower, the corresponding branch streams may be combined after the heat exchange and transferred to the condenser 380.

[0125] The operating pressure of the upper portion of the third tower 300 may be 4.9 bar.g to 5.1 bar.g. When the operating pressure of the upper portion of the third tower is 4.9 bar.g or higher, the temperature of the upper exhaust stream 330 of the third tower may be at least 10°C higher than the temperature of the lower portions of each of the first tower and the second tower; therefore, the temperature difference for heat exchange in the first reboiler 110 of the first tower and the first reboiler 210 of the second tower may be maintained.

[0126] In particular, when the operating pressure of the upper portion of the third tower 300 is higher than 5.1 bar.g, a high temperature of the upper exhaust stream 330 of the third tower can be achieved, and thus there is no problem in supplying heat to the first tower 100 and the second tower 200, but the separation performance performed in the third tower 300 is degraded. In this case, additional energy must be supplied to the third tower 300 to separate the components with the desired purity, which is not preferable from the perspective of reducing energy consumption. On the other hand, when the operating pressure of the upper portion of the third tower 300 is lower than 4.9 bar.g, it is difficult to maintain the temperature of the upper exhaust stream 330 of the third tower at a high temperature, and therefore it is difficult to ensure a sufficient temperature difference to achieve heat exchange between the first reboiler 110 of the first tower and the first reboiler 210 of the second tower.

[0127] Meanwhile, the operating temperature of the upper portion of the third tower 300, specifically, the operating temperature of the upper portion of the upper region of the third tower 300 may be 120° C. or higher, specifically, 122° C. or higher. In this case, since an appropriate temperature difference (e.g., a temperature difference of at least 10° C. or higher) required for heat exchange with the lower portion of the first tower 100 and the lower portion of the second tower 200 can be ensured, energy can be efficiently supplied to the first tower 100 and the second tower 200 through the upper exhaust stream 330 of the third tower.

[0128] Furthermore, when the upper discharge stream 330 of the third tower undergoes heat exchange in both the first reboiler 110 of the first tower and the first reboiler 210 of the second tower, the upper discharge stream 330 of the third tower may be branched to form a branch stream supplied to the first reboiler 110 of the first tower and a branch stream supplied to the first reboiler 210 of the second tower. In this case, the mass flow rate ratio of the branch stream supplied to the first reboiler 110 of the first tower to the mass flow rate of the branch stream supplied to the first reboiler 210 of the second tower may be 1:5 to 1:7. With this ratio, the logarithmic mean temperature difference (LMTD) between the low-temperature medium (the lower discharge stream of each of the first and second towers) and the high-temperature medium (the upper discharge stream of the third tower) undergoing heat exchange in the first reboilers 110 and 210 of the first and second towers can be maximized, enabling efficient design and operation of the first reboilers 110 and 210 of the first and second towers. Furthermore, the sizes of the auxiliary reboilers 115 and 215 of the first and second towers can be minimized.

[0129] The upper exhaust stream 330 of the third tower 300 may be heat-exchanged with one or more of the lower exhaust streams of the first tower and the lower exhaust streams of the second tower in one or more of the first reboiler 110 of the first tower and the first reboiler 210 of the second tower, and then all or part of it may be condensed into a liquid phase while being cooled. The condensed upper exhaust stream 330 of the third tower 300 may be introduced into a condenser 380 provided above the third tower and further condensed to a desired condensation condition.

[0130] The additionally condensed stream discharged from the condenser 380 may be introduced into the layer separator 340 provided above the third column. The layer separator 340 is a device for separating fluids by density difference, and the fluid may be separated into an aqueous phase containing water and an oil phase containing an azeotropic agent by the layer separator 340. The oil phase containing the azeotropic agent may be refluxed to the upper region, and the aqueous phase containing water may be refluxed to the second region.

[0131] That is, after the upper discharge stream 330 is separated into the oil phase and the water phase by the layer separator 340, the separated oil phase and water phase are refluxed back to the third distillation column 300; therefore, 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 water phase stream and the oil phase stream refluxed back to the third distillation column 300 through the layer separator 340. That is, the upper discharge stream 330 of the third distillation column 300 is discharged from the third column 300, supplied to one or more of the first reboiler 110 of the first column and the first reboiler 210 of the second column, supplied to the condenser 380, passed through the layer separator 340, and then all refluxed back to the third distillation column 300.

[0132] The entrainer contained in the oil phase stream is reused for the azeotropic distillation performed in the third distillation column 300. In addition, when the separated oil phase and water phase are all refluxed to the third distillation column 300 and the reflux point is optimized, the first zone lower effluent stream and the second zone lower effluent stream can be separated with high purity.

[0133] The reflux point of the aqueous phase to the second region may be a point corresponding to 10% to 50%, specifically 25% to 40%, of the height of the partition wall from the bottom. Thus, the energy required for distillation can be minimized while separating pure water from the lower portion of the second region.

[0134] More specifically, by setting the position of the upper end of the dividing wall and the reflux point of the aqueous phase to the second region as described above, it is possible to simultaneously ensure sufficient azeotropic distillation for separating isopropyl alcohol and water using an entrainer and a distillation region for purifying isopropyl alcohol within third distillation column 300. Furthermore, since the first and second regions share the upper region of the dividing wall, energy consumption required in condenser 380 can be reduced, and since the liquid phase reflux flow branching from the lowest portion of the upper region into the first and second regions and flowing downward is optimized and distributed, the amount of heat required in the reboiler in each region can be minimized.

[0135] Meanwhile, according to one embodiment of the present invention, the first region lower effluent stream discharged from the first region can be supplied to the fourth tower 400 to recover isopropyl alcohol. The first region lower effluent stream can contain isopropyl alcohol and a small amount of heavy by-products. Isopropyl alcohol can be ultimately obtained from the upper portion of the fourth tower 400, and the heavy by-products can be separated by the lower portion of the fourth tower.

[0136] The fourth tower 400 may include a first reboiler 410 of the fourth tower located below, and as described above, the lower exhaust stream of the fourth tower may be heat-exchanged with the reaction product stream before being introduced into the absorption tower in the first reboiler 410 of the fourth tower. Figure 2 and Figure 3 , the first branch stream 50 of the branch stream of the reaction product stream can be in the first reboiler (410) of the fourth tower, Figure 2 Heat exchanger A) in the fourth column is used for heat exchange with the lower exhaust stream of the fourth column.

[0137] Meanwhile, when the heat energy of the first branch stream 50 alone cannot completely replace the reboiler duty required for the operation of the fourth tower 400 , an auxiliary reboiler 415 may be provided below the fourth tower 400 separately from the first reboiler 410 of the fourth tower.

[0138] Meanwhile, as described above, the upper exhaust stream of the absorption tower 10 may contain propylene and gas components, and after the upper exhaust stream of the absorption tower 10 is compressed by a compressor, a portion of the stream 40 may be supplied to the gas purification section described below. Figure 1 and Figure 4 Describe the recovery process performed in the gas purification section.

[0139] The stream supplied to the gas purification section can be specifically supplied as feed stream 40 to the fifth column 500 of the gas purification section. Feed stream 40 to fifth column 500 contains propylene and gaseous components, the gaseous components including light gaseous components with a lower boiling point than propylene and heavy gaseous components with a higher boiling point than propylene. Furthermore, feed stream 40 to fifth column 500 may contain isopropyl alcohol, water, light byproducts such as diisopropyl ether, and heavy byproducts such as n-propyl alcohol, although in small amounts, which have not yet been separated by passing through the lower portion of absorption column 100. Propylene recycled to the reactor via fifth column 500 can be recovered at a higher purity, while isopropyl alcohol that may have been lost through the upper portion of fifth column 500 can be fully recovered in the lower portion.

[0140] As described above, the side stream of the fifth tower 500 may be heat-exchanged with all or a portion of the reaction product supplied to the absorption tower 10. To this end, the fifth tower 500 may include a first reboiler 510 of the fifth tower 500 connected to the side of the fifth tower 500. That is, the heat exchange between the reaction product and the side stream of the fifth tower 500 may be performed in the first reboiler 510 of the fifth tower 500. Specifically, referring to Figure 2 and Figure 4 , the second branch stream 60 in the branch stream of the reaction product stream can be in the first reboiler (510) of the fifth tower, Figure 2 Heat exchanger B) in the fifth tower 500 is used for heat exchange with the side discharge stream of the fifth tower 500.

[0141] More specifically, the side bleed stream of fifth tower 500 can be discharged at a height of 55% to 85% from the top of fifth tower 500 and heat exchanged with the reaction products. For example, if the side bleed stream is discharged at a height of less than 55%, there is a problem of shortening the length of the contact zone where a specific component is evaporated and contacts the refluxed liquid phase component, i.e., the distillation zone where actual distillation and purification are performed. Meanwhile, if the side bleed stream is discharged at a height exceeding 85%, the temperature of the side bleed stream is too high, making it difficult to perform heat exchange with the reaction products or to achieve the heat exchange effect (cooling the reaction products and heating the side stream).

[0142] Meanwhile, the side discharge stream of the fifth tower 500 heat-exchanged with the reaction product in the first reboiler 510 of the fifth tower may be re-supplied to a stage including a height of the fifth tower 500 from which the side stream is discharged.

[0143] In addition, the temperature of the side bleed stream discharged from the fifth tower 500 may be 40° C. to 80° C. or 40° C. to 60° C., and the temperature of the side bleed stream supplied to the fifth tower 500 again after heat exchange may be 80° C. to 100° C. or 85° C. to 95° C. Thus, the temperature distribution according to the height of the fifth tower 500 can be appropriately controlled. Therefore, the heat energy required in the fifth tower 500, which is supplied only by the second reboiler 520 in the related art, can be replaced to the greatest extent, more specifically, more than half can be replaced.

[0144] Meanwhile, according to one embodiment of the present invention, the operating pressure of the upper portion of the fifth tower 500 may be 15 kg / cm 2 g to 20kg / cm 2 g or 16kg / cm 2 g to 19 kg / cm 2 g high pressure. Furthermore, the operating temperature of the lower portion of fifth tower 500 may be 140° C. to 180° C. or 150° C. to 180° C. Within the above ranges of the operating temperature and pressure of fifth tower 500, the separation efficiency of fifth tower 500 is improved, allowing isopropyl alcohol, water, and by-products to be completely recovered to the lower portion of fifth tower 500. Furthermore, inexpensive cooling water can be used as a cooling heat source in the condenser disposed above fifth tower 500.

[0145] At the same time, according to one embodiment of the present invention, when the reaction product and the side discharge stream of the fifth tower 500 are heat exchanged by the first reboiler 510 of the fifth tower, a gentle temperature distribution according to the height of the fifth tower 500 can be achieved, and the effect of increasing the section in which the temperature changes according to the height of the fifth tower 500, that is, the distillation zone in which distillation and purification can be performed can be obtained. That is, the stream introduced into the fifth tower 500 contains not only light components such as propylene and inert gases, but also heavy components such as isopropyl alcohol and water. That is, since the stream introduced into the fifth tower 500 contains components with large boiling point differences, the temperature distribution in the fifth tower 500 usually changes rapidly in a specific section. In this case, there is a region where the temperature change according to the height of the tower is small and component separation is difficult (the so-called dead zone). However, through the heat exchange of the first heat exchanger 510 of the fifth tower of the present invention, a gentle temperature distribution is achieved in the fifth tower 500, that is, an appropriate temperature gradient according to the height of the tower is achieved, so that the region in which component separation is difficult can be converted into a region in which component separation can be performed by stripping, thereby improving the component separation efficiency of the fifth tower 500.

[0146] In addition, according to the prior art Figure 5In the case where the fifth tower 500 is operated with only one lower reboiler as shown, a high-grade heat source (e.g., steam) of high temperature (e.g., 160° C. or higher) is required for the lower reboiler. However, as in one embodiment of the present invention, when the first reboiler 510 of the fifth tower 500 is provided in the fifth tower 500, the first reboiler 510 of the fifth tower 500 can be operated by utilizing low-grade waste heat of approximately 120° C., and at the same time, the amount of high-grade heat source required for the second reboiler 520 of the fifth tower 500 can be reduced compared to the prior art, thereby reducing the amount of thermal energy used.

[0147] Meanwhile, the fifth tower 500 may further include a second reboiler 520 connected to a lower portion of the fifth tower 500 in addition to the first reboiler 510. The heat energy supplied to the fifth tower by the first reboiler 510 of the fifth tower may be 50% to 90% of the total heat energy supplied to the fifth tower 500 by the first reboiler 510 of the fifth tower and the second reboiler 520 of the fifth tower.

[0148] The upper exhaust stream of the fifth tower 500 may include propylene, a light gas component, and a heavy gas component, and the upper exhaust stream of the fifth tower 500 may be supplied to the sixth tower 600 after passing through a condenser.

[0149] In the sixth tower 600, a portion of the side discharge stream of the sixth tower containing propylene can be recycled to the reactor, and the remaining portion can be purged and discharged outside the system. The gas phase component containing inert gas in the upper discharge stream of the sixth tower 600 is purged to separate and remove a portion or all of the inert gas, thereby reducing the inert gas content in the stream flowing back to the reactor, thereby preventing the accumulation of inert gas in the process.

[0150] Meanwhile, as described above, the lower exhaust stream of the sixth tower 600 may be discharged to the first reboiler (610; Figure 3 The heat exchanger D) in the second tower 200 exchanges heat with the upper exhaust stream of the second tower 200. Thus, the heat energy of the upper exhaust stream of the second tower 200 can be supplied to the sixth tower 600. Furthermore, if the heat energy of the upper exhaust stream of the second tower 200 alone cannot completely replace the reboiler duty required for the operation of the sixth tower 600, an auxiliary reboiler 615 can be provided below the sixth tower 600, separately from the first reboiler 610 of the sixth tower.

[0151] 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.

[0152] 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.

[0153] Example 1

[0154] according to Figure 1 and Figures 2 to 4 The process of preparing isopropyl alcohol is carried out according to the process flow.

[0155] Specifically, water and propylene are supplied to the reactor and reacted in a gas phase to produce a reaction product comprising isopropyl alcohol, water, and propylene. The reaction product is passed through a heat exchanger 90 and branched into a first branch stream to a third branch stream. The mass flow ratio of these first branch streams to the third branch stream is 1:0.33:0.57. The first branch stream 50 is heat exchanged with the lower exhaust stream of the fourth tower 400 in the first reboiler 410 of the fourth tower, and the second branch stream 60 is heat exchanged with the side exhaust stream of the fifth tower 500 in the first reboiler 510 of the fifth tower. Each heat-exchanged branch stream is combined with the third branch stream 70 and supplied to the upper part of the absorption tower 10.

[0156] At this time, the heat energy required for the operation of the fourth column is completely replaced by the heat energy supplied from the first branch stream, and thus, there is no need to supply a separate heat source to the auxiliary reboiler 415 to operate the fourth column.

[0157] Meanwhile, after the lower exhaust stream of the absorption tower 10 is supplied to the flash tank 20, the lower exhaust stream of the flash tank 20 is supplied to the first tower 100 in the isopropyl alcohol purification section including the first to fourth towers. The upper exhaust stream of the absorption tower 10 is compressed by a compressor, and then a portion thereof is supplied to the fifth tower 500 in the gas purification section including the fifth and sixth towers.

[0158] The feed stream 30 supplied to the first column 100 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.

[0159] Isopropyl alcohol is obtained by sequentially passing through the lower effluent stream of the first tower 100, the first side effluent stream of the second tower 200, the lower effluent stream of the first region of the third tower 300, and the upper effluent stream of the fourth tower 400. Diisopropyl ether (DIPE) is removed from the upper portion of the first tower 100, and acetone is removed from the upper portion of the second tower 200. Simultaneously, water is removed from the lower effluent stream of the second tower 200 and the lower portion of the second region of the third tower 300, respectively. Heavy by-products are removed from the second side effluent stream of the second tower 200 and the lower effluent stream of the fourth tower 400, respectively.

[0160] Meanwhile, propylene and a gas component are contained in the stream 40 supplied to the fifth tower 500. Propylene is recovered by sequentially passing through the upper discharge stream of the fifth tower 500 and the side discharge stream of the sixth tower 600.

[0161] Here, the upper exhaust stream of the second tower 200 is heat-exchanged with the lower exhaust stream of the sixth tower 600 in the first reboiler 610 of the sixth tower. The heat-exchanged upper exhaust stream of the second tower passes through the condenser 280 provided above the second tower 200 and is then branched into a stream that refluxes to the second tower 200 and a stream that is discharged to the outside of the system.

[0162] At this time, the heat energy required for the operation of the sixth column is completely replaced by the heat energy supplied from the upper exhaust stream of the second column, and therefore, there is no need to supply a separate heat source to the auxiliary reboiler 615 to operate the sixth column.

[0163] At the same time, the upper exhaust stream 330 of the third tower 300 was branched into streams at a mass flow ratio of 1:6. The branched streams were supplied to the first reboiler 110 of the first tower and the first reboiler 210 of the second tower, respectively, to supply heat energy to the lower portions of the first and second towers. At this time, the operating pressure in the upper region of the third tower 300 was 5.0 bar·g, and the temperature of the upper exhaust stream 330 of the third tower 300 was 122°C. Simultaneously, the temperature of the lower exhaust stream of the first tower was 85°C, and the temperature of the lower exhaust stream of the second tower was 95°C. The temperature difference between the low-temperature medium and the high-temperature medium supplied to the first reboiler 110 of the first tower and the first reboiler 210 of the second tower was suitable, thereby achieving efficient heat exchange.

[0164] At this time, the operating conditions of the first tower and the second tower cannot reach the desired levels by relying solely on the heat energy of the upper exhaust stream 330 of the third tower, so additional heat energy is supplied to the first tower and the second tower through the auxiliary reboiler 115 and the auxiliary reboiler 215 provided below the first tower and the second tower, respectively.

[0165] Meanwhile, the first region lower discharge stream of the third tower 300 containing isopropyl alcohol and n-propyl alcohol was supplied to the fourth tower 400, isopropyl alcohol was obtained from the upper portion of the fourth tower 400, and the isopropyl alcohol content in the upper discharge stream of the fourth tower was confirmed to be 99.8 wt%.

[0166] In this case, the reboiler duties of each tower are shown in Table 1. Specifically, since the heat energy supplied to the first reboiler 110 of the first tower and the first reboiler 210 of the second tower is supplied from the upper portion of the third tower, the heat energy supplied by the auxiliary reboiler 115 and the auxiliary reboiler 215 provided below the first tower and the second tower, respectively, is shown in Table 1 as the reboiler duties of each of the first tower and the second tower. At the same time, the heat energy supplied by the reboiler 310 connected to the lower portion of the first region of the third tower and the heat energy supplied by the reboiler 315 connected to the lower portion of the second region of the third tower are also shown in Table 1.

[0167] Comparative Example 1

[0168] according to Figure 5 The process for producing isopropyl alcohol was carried out according to the process diagram. The flow rate and composition of the stream introduced into the C1 column of the isopropyl alcohol purification stage were the same as those introduced into the first column of Example 1, and the flow rate and composition of the stream introduced into the C7 column of the gas purification stage were the same as those introduced into the fifth column of Example 1. Isopropyl alcohol for Comparative Example 1 was obtained from the upper portion of the C6 column. As in Example 1, the heat energy required for operating each column to achieve an isopropyl alcohol content of 99.8 wt% in the upper effluent stream of the C6 column was measured, and the results are shown in Table 1.

[0169] Specifically, a lower effluent stream of the C1 column having the same composition as in Example 1 was obtained and introduced into the C2 column.

[0170] The C2 column of Comparative Example 1 is a column not provided with a dividing wall, and as in Example 1, the stream was distilled to separate four discharge streams: an upper discharge stream of the C2 column containing acetone, a first side discharge stream of the C2 column containing an azeotrope of isopropyl alcohol and water, a second side discharge stream of the C2 column containing n-propyl alcohol (NPA) and hexanol, and a lower discharge stream of the C2 column containing water.

[0171] In this case, since the second side bleed stream of the C2 column contains a large amount of isopropyl alcohol and is discharged without effectively separating heavy by-products and water, the C3 column is required to additionally purify the isopropyl alcohol in the second side bleed stream of the C2 column and separate the heavy by-products and water. Specifically, the second side bleed stream of the C2 column is introduced into the C3 column, and a stream containing isopropyl alcohol is separated from the upper portion of the C3 column and supplied back to the C2 column.

[0172] The energy required for the operations of the C1 to C3 columns is supplied through a reboiler provided below the C1 to C3 columns.

[0173] Isopropyl alcohol, which is contained in the first side effluent stream of the C2 column and contains an azeotrope of isopropyl alcohol and water, is recovered from the upper portion of the C6 column using conventional C4 column (azeotropic distillation column), C5 column (entrainer recovery column), and C6 column (isopropyl alcohol recovery column) without a dividing wall. Specifically, isopropyl alcohol is obtained by sequentially passing through the lower effluent stream of the C4 column and the upper effluent stream of the C6 column. Each of the C4 to C6 columns is equipped with an upper condenser and a lower reboiler.

[0174] Meanwhile, propylene and gas components were contained in the stream supplied to the C7 column of the gas purification section of Comparative Example 1. Propylene was recovered by sequentially passing through the upper discharge stream of the C7 column and the side discharge stream of the C8 column.

[0175] As a result, it was confirmed that the content of isopropyl alcohol obtained in Comparative Example 1 was 99.8% by weight, similar to Example 1.

[0176] In this case, the energy (heat energy) (reboiler duty) used in the reboiler provided below each column (C1 to C8 columns) in Comparative Example 1 is shown in Table 1.

[0177] [Table 1]

[0178]

[0179] As can be seen from the above results, in the case of Example 1, the purity and yield of isopropyl alcohol were maintained at a high level. In particular, by using a dividing wall distillation column having a specific structure as the second and third columns and using the heat of the upper exhaust stream of the third column as the energy source required for operating the first and second columns, it can be understood that the energy efficiency of the entire process from the first to fourth columns was maximized.

[0180] Furthermore, all or a portion of the heat energy required for the operations of the fifth tower and the fourth tower is replaced by the heat energy of the reaction product before being supplied to the absorption tower, and all or a portion of the heat energy required for the operation of the sixth tower is replaced by the heat energy of the upper exhaust stream of the second tower, making it possible to effectively utilize the energy required for the entire process including reaction, purification, and recovery of unreacted substances to produce isopropyl alcohol.

[0181] [Detailed description of main components]

[0182] 100: First Tower 200: Second Tower

[0183] 300: The third tower 300: The third tower

[0184] 400: Fourth Tower 500: Fifth Tower

[0185] 600: Sixth Tower

Claims

1. A method for preparing isopropyl alcohol, comprising: reacting propylene monomer with water to produce a reaction product comprising propylene and isopropyl alcohol; cooling the reaction product and supplying the cooled reaction product to an absorption tower; and supplying the lower effluent stream of the absorption tower containing isopropyl alcohol from the absorption tower to an isopropyl alcohol purification section including first to fourth towers, and supplying the upper effluent stream of the absorption tower containing propylene to a gas purification section including fifth and sixth towers, The isopropyl alcohol contained in the lower discharge stream of the absorption tower supplied to the isopropyl alcohol purification section is obtained by sequentially passing through the lower discharge stream of the first tower, the first side discharge stream of the second tower, the first region lower discharge stream of the third tower, and the upper discharge stream of the fourth tower. Propylene contained in the upper effluent stream of the absorption tower supplied to the gas purification section is obtained by sequentially passing through the upper effluent stream of the fifth tower and the side effluent stream of the sixth tower, All or a portion of the reaction product is cooled by heat exchange with one or more of the lower discharge stream of the fourth column and the side discharge stream of the fifth column, The upper exhaust stream of the second tower is heat exchanged with the lower exhaust stream of the sixth tower, and The upper exhaust stream of the third column is heat-exchanged with one or more of the lower exhaust stream of the first column and the lower exhaust stream of the second column.

2. The method according to claim 1, wherein The lower discharge stream of the absorption tower comprises isopropyl alcohol, water, a first light by-product, a second light by-product and a heavy by-product, separating the first light by-product from the upper effluent stream of the first column, and The lower exhaust stream of the first column, which includes isopropyl alcohol, water, a second light by-product, and a heavy by-product, is supplied to the second column.

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

4. 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.

5. The method according to claim 4, wherein The first side effluent stream of the second column comprises a mixture of isopropyl alcohol and water, The second side bleed stream of the second column comprises heavy by-products, and The heavy by-products include n-propanol (NPA) and hexanol.

6. The method according to claim 1, wherein The lower effluent stream of the second column contains water, and A branched stream branched from a portion of the lower exhaust stream of the second tower is recycled to the upper portion of the first tower and the upper portion of the absorption tower.

7. The method according to claim 6, wherein: supplying the lower exhaust stream of the absorption tower to the first tower, and The mass flow rate of the stream branched from a portion of the lower exhaust stream of the second tower and recycled to the upper portion of the first tower is 0.4 to 1.2 relative to the mass flow rate of the lower exhaust stream of the absorption tower supplied to the first tower.

8. The method according to claim 1, wherein The third column includes a dividing wall connected to the bottom and extending in the longitudinal direction of the column, and The third tower is partitioned by the partition wall into a first region, a second region facing the first region, and an upper region located above an upper end of the partition wall.

9. The method according to claim 1, wherein The upper exhaust stream of the third tower is heat-exchanged with the lower exhaust stream of the first tower and the lower exhaust stream of the second tower through the first reboiler of the first tower and the first reboiler of the second tower.

10. The method according to claim 9, wherein: The upper exhaust stream of the third tower is branched to form a branch stream supplied to the first reboiler of the first tower and a branch stream supplied to the first reboiler of the second tower, and A ratio of a mass flow rate of the branch stream supplied to the first reboiler to a mass flow rate of the branch stream supplied to the second reboiler is 1:5 to 1:

7.

11. The method according to claim 1, wherein supplying the first region lower exhaust stream of the third tower to the fourth tower, isopropyl alcohol is obtained through the upper part of the fourth column, Heavy by-products are separated through the lower portion of the fourth column.

12. The method according to claim 1, wherein The cooling of the reaction product comprises a first cooling and a second cooling, wherein the first cooling is performed by exchanging heat between all or a portion of the reaction product stream and one or more of the lower discharge stream of the fourth tower and the side discharge stream of the fifth tower, and the second cooling is performed by exchanging heat between the reaction product stream having undergone the first cooling and a refrigerant.

13. The method according to claim 12, wherein: The fifth tower includes a first reboiler of the fifth tower provided beside the fifth tower and a second reboiler of the fifth tower provided below the fifth tower, and Heat exchange between all or a portion of the reaction product stream and the side draw stream of the fifth column is performed in a first reboiler of the fifth column.

14. The method according to claim 12, wherein: The reaction product stream is branched into a first branch stream, a second branch stream and a third branch stream, The first cooling is performed by heat exchange between the first branch stream and the lower exhaust stream of the fourth tower and heat exchange between the second branch stream and the side exhaust stream of the fifth tower. The first branch flow and the second branch flow that have undergone the first cooling are combined with the third branch flow that has not undergone the first cooling to form a combined flow, and The second cooling is performed by heat exchange between the combined stream and a refrigerant.

15. The method according to claim 14, wherein The mass flow rate of the first branch flow: the mass flow rate of the second branch flow: the mass flow rate of the third branch flow is 1:0.2 to 0.4:0.4 to 0.7.

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