Method for preparing isopropanol

Abstract

Provided is a method for producing isopropanol, comprising: supplying a feed comprising isopropanol, water, and by-products to a divided wall distillation column; discharging a lower discharge stream of the first zone comprising isopropanol and by-products from a lower portion of the first zone; a lower discharge flow that discharges the second region containing water from the lower part of the second region; supplying the upper discharge stream to the layer separator, returning the oil phase stream to the upper region, and returning the water phase stream to the second region; and obtaining isopropanol from the lower discharge stream of the first zone.

Description

Technical Field

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority of Korean Patent Application No. 10-2023-0158482, filed on November 15, 2023, and Korean Patent Application No. 10-2024-0147789, filed on October 25, 2024, which are hereby incorporated by reference in their entirety as a part of this specification. Technical Field

[0003] The present invention relates to a method for preparing isopropyl alcohol, and more particularly, to a method for reducing energy usage and process costs in purifying isopropyl alcohol from a reaction product of an isopropyl alcohol production process. Background Art

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

[0005] In the process of producing isopropyl alcohol, for example, propylene and water are used as raw material components. Here, propylene and water react to produce isopropyl alcohol. The reaction product of the process of producing isopropyl alcohol contains water and by-products as well as isopropyl alcohol. Therefore, in order to obtain isopropyl alcohol from the reaction product, a method of purifying isopropyl alcohol is mainly involved.

[0006] To purify isopropyl alcohol, multiple distillation columns are used, and the distillation columns require a large amount of energy to evaporate the components to be separated. Therefore, high efficiency of the purification process of isopropyl alcohol is required, and at the same time, improved designs are required in terms of economic feasibility to reduce energy usage and also reduce operating costs and equipment 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 preparing isopropyl alcohol, which can prepare high-purity isopropyl alcohol while reducing energy usage and improving operating costs / equipment costs.

[0009] However, the objects to be solved in the present application are not limited to the above objects, and those skilled in the art can clearly understand other objects not mentioned from the following description.

[0010] Technical Solution

[0011] In one general aspect, a method for producing isopropyl alcohol comprises: supplying a feed comprising isopropyl alcohol, water, and by-products to a first region of a dividing wall distillation column divided by a dividing wall into a first region, a second region, and an upper region, and performing azeotropic distillation in the presence of an entrainer; discharging a lower effluent stream of the first region comprising isopropyl alcohol and by-products from a lower portion of the first region; discharging a lower effluent stream of the second region comprising water from a lower portion of the second region; supplying the upper effluent stream comprising water and the entrainer, discharged from an upper portion of the upper region, to a layer separator, separating the streams into an aqueous phase stream comprising water and an oil phase stream comprising the entrainer, recirculating the oil phase stream to the upper region, and recirculating the aqueous phase stream to the second region; and obtaining isopropyl alcohol from the lower effluent stream of the first region.

[0012] Beneficial effects

[0013] According to the method for producing isopropyl alcohol of the present invention, by using a dividing wall distillation column in separating isopropyl alcohol from a feed containing isopropyl alcohol, water, and by-products, a production method is provided that enables high-purity isopropyl alcohol to be obtained using fewer columns than previously required.

[0014] That is, according to the present invention, by reducing the number of distillation columns, by operating a smaller number of distillation columns than previously required, reboiler energy is reduced (energy saving), and reductions in installation cost and operating cost of the apparatus can be achieved.

[0015] Furthermore, the separated components are discharged to the first and second zones located in the lower portion of the region separated by the dividing wall in the dividing wall distillation column, and the entire stream discharged from the upper zone is circulated to the dividing wall distillation column through a layer separator. This allows the conventional functions of an azeotropic distillation column for separating water and isopropyl alcohol, and a conventional function of an entrainer recovery column for separating an entrainer from water, to be performed in a single column. This allows isopropyl alcohol having a desired purity to be separated into the lower discharge stream of the first zone of the dividing wall distillation column, and pure water to be separated into the lower discharge stream of the second zone of the dividing wall distillation column. Furthermore, the oil phase stream from the layer separator is refluxed to the upper zone of the dividing wall distillation column and simultaneously purified, thereby reducing the energy typically used independently in two or more columns and thus reducing overall energy usage. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic diagram of a dividing wall distillation column applied to a method for preparing isopropyl alcohol according to an exemplary embodiment of the present invention.

[0017] Figure 2 is a process flow chart of a method for preparing isopropyl alcohol according to an exemplary embodiment of the present invention.

[0018] Figure 31 is a process flow chart of a method for preparing isopropyl alcohol according to a comparative example. DETAILED DESCRIPTION

[0019] 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.

[0020] Regarding the description of the drawings, like reference numerals may be used for like or related constituent elements.

[0021] Unless otherwise clearly indicated in the relevant context, a singular form of a noun corresponding to an item may include one or more items.

[0022] In the present disclosure, each of the phrases 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 of the items listed with the corresponding phrase of the phrase or all possible combinations thereof.

[0023] The term "and / or" includes a combination of a plurality of the related constituent elements or any one of the plurality of the related constituent elements.

[0024] Terms such as “first” or “second” or “first” or “second” may be used simply to distinguish corresponding constituent elements from other corresponding constituent elements, and the corresponding constituent elements are not limited in other aspects (for example, importance or order).

[0025] In addition, terms such as "front surface", "rear surface", "upper surface", "lower surface", "side surface", "left", "right", "upper" and "lower" used in this application are defined based on the drawings, and the shape and position of each component are not limited by the terms.

[0026] The terms “including” or “having” are intended to specify the existence of stated features, steps, operations, constituent elements, parts or their combinations, but do not preclude the existence or addition of one or more other features, numbers, steps, operations, constituent elements, parts or their combinations.

[0027] When describing that constituent elements are “connected,” “combined,” “supported,” or “in contact with” other constituent elements, it includes not only the case where the constituent elements are directly connected, combined, supported, or in contact, but also the case where they are indirectly connected, combined, supported, or in contact through a third constituent element.

[0028] When a constituent element is described as being “on” another constituent element, it includes not only a case where the constituent element is in contact with another constituent element but also a case where another constituent element exists between the two constituent elements.

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

[0030] Unless otherwise specified, the term "upper portion" used in this specification refers to a point at a height of 0% to 10% from the top of the device, specifically, the top (tower top). In addition, the term "lower portion" refers to a point at a height of 90% to 100% from the top of the device, specifically, the bottom (tower bottom).

[0031] In addition, the "pressure" mentioned in this specification refers to the gauge pressure measured under atmospheric pressure conditions.

[0032] Meanwhile, unless otherwise specifically stated in this specification, the operating pressure of a column refers to the pressure in the upper portion of the column, and the operating temperature of a column refers to the temperature in the lower portion of the column.

[0033] An exemplary embodiment of the present invention relates to a method for preparing isopropyl alcohol (IPA), and hereinafter, the method for preparing isopropyl alcohol of the present invention will be described in detail with reference to the accompanying drawings.

[0034] Figure 1 is a schematic diagram of a dividing wall distillation column according to an exemplary embodiment of the present invention, Figure 2 is a process flow chart of a method for preparing isopropyl alcohol according to an exemplary embodiment of the present invention.

[0035] The method for preparing isopropyl alcohol according to the present invention includes supplying a feed 10 containing isopropyl alcohol, water, and by-products to a first region 101 of a dividing wall distillation column divided into a first region 101, a second region 102, and an upper region 103 by a dividing wall 105, and performing azeotropic distillation in the presence of an entrainer.

[0036] First, the dividing wall type distillation column 100 according to an exemplary embodiment of the present invention may include a first region 101, a second region 102, and an upper region 103 separated by a dividing wall 105. The dividing wall 105 is connected (bonded) to the bottom of the dividing wall type distillation column 100 and extends upward in the length direction of the dividing wall type distillation column 100 and is provided. Here, the first region 101 and the second region 102 are regions that are divided so that they face each other with the dividing wall 105 therebetween, and the second region 102 is a region opposite to the first region 101. Meanwhile, the upper region 103 is a region located above the upper end of the dividing wall and is located Figure 1 The area above the imaginary boundary line marked by the dotted line.

[0037] Meanwhile, azeotropic distillation can be performed in the presence of an entrainer in dividing wall distillation column 100. A portion of the isopropyl alcohol and a portion of the water contained in feed 10 can form an azeotrope. Water, which has a boiling point of approximately 100°C, and isopropyl alcohol, which has a boiling point of approximately 82.3°C, form an azeotrope at an azeotropic temperature of approximately 81°C. Since these components cannot be completely separated in this azeotrope by conventional distillation, the isopropyl alcohol and water can be separated at high purity after removing the azeotropic relationship between the isopropyl alcohol and water, typically using an entrainer. The entrainer of the present invention that performs this function can be one or more selected from cyclohexane, benzene, toluene, and isopropyl acetate.

[0038] The entrainer is a material that is further added separately from the feed components for azeotropic distillation, but since the entrainer is an impurity to isopropyl alcohol etc., it should be separated by a separate distillation column etc., and the separated entrainer can be recycled from the economical viewpoint.

[0039] That is, reference to the prior art Figure 3 Conventionally, in order to separate isopropyl alcohol and water from a feed 10 containing isopropyl alcohol, water, and by-products, azeotropic distillation is performed in a conventional azeotropic column 100 without a dividing wall in the presence of an entrainer, the upper discharge stream 130 containing water and the entrainer is phase-separated from the layer separator 140, and then the oil phase (150) containing the entrainer is refluxed to the azeotropic distillation column 100. However, since the aqueous phase contains a large amount of entrainer in addition to water, the aqueous phase (190) is introduced into the entrainer recovery column 200 to separate the entrainer and water by distillation, the recovered entrainer (210) is reintroduced into the azeotropic distillation column 100, and the water (220) is discharged to the outside of the system. Here, in order to separate the entrainer and water by distillation in the entrainer recovery column 200, a large amount of energy should be supplied by the reboiler 230 provided at the lower part of the entrainer recovery column 200.

[0040] Meanwhile, according to conventional technology, heat energy required for operating the azeotropic distillation column 100 is supplied to the azeotropic distillation column 100 through the reboiler 125 provided at the lower portion. When the upper discharge stream 130 of the azeotropic distillation column 100 contains water and an entrainer, the lower discharge stream of the azeotropic distillation column 100 contains isopropyl alcohol and by-products, the lower discharge stream of the azeotropic distillation column 100 is supplied to the isopropyl alcohol recovery column 300 to obtain isopropyl alcohol at the upper portion of the isopropyl alcohol recovery column 300, and the by-products (320) are separated in the lower portion of the isopropyl alcohol recovery column 300.

[0041] However, with reference to the method for preparing isopropyl alcohol according to an exemplary embodiment of the present invention Figure 2 , a dividing wall is provided in the dividing wall type distillation column 100 for azeotropic distillation, and at the same time, the reflux point of the water phase and the oil phase in the layer separator 140 is optimized to obtain high-purity isopropyl alcohol without providing a conventional entrainer recovery tower 200 for separating the entrainer and water. Therefore, the conventional supply to the reboiler ( Figure 3 The reboiler 230 in the entrainer recovery column 200 can be used to operate the heat energy of the entrainer recovery column 200, and the cooling energy required for the operation of the condenser provided in the upper portion of the entrainer recovery column 200 for operating the entrainer recovery column 200 can also be reduced. In addition, since the entrainer recovery column 200 is not operated, energy can be reduced, and even if the dividing wall distillation column ( Figure 2 The distillation tower 100 in FIG. 1 is a distillation tower having a conventional azeotropic distillation tower ( Figure 3 The energy usage required for the operation of the distillation column can also be reduced compared to the distillation column 100 in FIG.

[0042] To this end, according to an exemplary embodiment of the present invention, the first zone 101 disposed in the lower portion of the dividing wall distillation column 100 may include a first reboiler 115 connected to the lower portion of the first zone, and the second zone 102 may include a second reboiler 125 connected to the lower portion of the second zone. Here, the lower portion refers to a point at a height 90% to 100% downward from the top (top) of the dividing wall distillation column 100. Heat energy may be supplied to the first zone 101 and the second zone 102 via the first reboiler 115 or the second reboiler 125, respectively, and the heat energy supplied to the first reboiler 115 and the second reboiler 125 may be adjusted to adjust the operating conditions of the first zone 101 and the second zone 102.

[0043] According to an exemplary embodiment of the present invention, the heat energy supplied by the first reboiler 115 may be 1.5 to 3 times, more specifically 1.8 to 2.5 times, the heat energy supplied by the second reboiler 125. Therefore, isopropyl alcohol having a desired purity can be separated from the first region of the dividing wall distillation column into a lower exhaust stream, and pure water can be separated from the second region of the dividing wall distillation column into a lower exhaust stream.

[0044] As described above, by supplying heat energy to first reboiler 115 and second reboiler 125, the lower temperature of first zone 101 can be set to 80°C or higher, or 82°C or higher, and 100°C or lower, or 95°C or lower. Furthermore, the temperature in the lower portion of second zone 102 can be set to 95°C or higher, or 100°C or higher, and 130°C or lower, or 120°C or lower. Here, each temperature in the lower portion refers to the operating temperature at a point 90% to 100% of the height downward from the top (top) of column 100 in the first and second zones. By controlling the temperatures in the lower portions of the first and second zones, the energy required for distillation in dividing wall column 100 can be reduced, isopropyl alcohol of desired purity can be obtained from the lower portion of the first zone, and pure water can be separated from the lower portion of the second zone.

[0045] Meanwhile, the first zone lower effluent stream 110 discharged from the first zone 101 of the dividing wall distillation column 100 may contain isopropyl alcohol and by-products. Here, the by-products may include n-propyl alcohol (NPA). A portion of the first zone lower effluent stream 110 may be heat-exchanged in the first reboiler 115 and then refluxed to the first zone again, and the remainder of the first zone lower effluent stream 110 may be supplied to the isopropyl alcohol recovery column 300.

[0046] Meanwhile, the second region lower exhaust stream 120 discharged from the second region 102 may contain water. A portion of the second region lower exhaust stream 120 may be heat exchanged in the second reboiler 125 and then refluxed to the second region, and the remainder of the second region lower exhaust stream 120 may be discharged from the system.

[0047] As described above, the region above the upper end of the dividing wall in the dividing wall type distillation column 100 may form the upper region 103 .

[0048] The dividing wall 105 extends from the bottom of the column, but the upper end of the dividing wall may be located at a height point 10% to 45%, specifically 15% to 30%, downward from the top of the dividing wall distillation column 100. Thus, the separation efficiency of the dividing wall distillation column 100 can be maximized to obtain isopropyl alcohol having a desired purity from the lower portion of the first region and to separate pure water from the lower portion of the second region.

[0049] An upper discharge stream 130 containing water and an entrainer can be discharged from the upper portion of the upper region. The upper discharge stream 130 passes through a condenser and is partially or completely condensed into a liquid phase, and the condensed stream can be introduced into a layer separator 140. The layer separator 140 is a device for separating fluids by density difference, and can separate an aqueous phase containing water and an oil phase containing an entrainer by the layer separator 140. The oil phase stream 150 containing the entrainer can be refluxed to the upper region 103, and the aqueous phase stream 160 containing water can be refluxed to the second region 102.

[0050] That is, since the upper effluent stream 130 is separated into an oil phase and an aqueous phase by the layer separator 140 and then the separated oil phase and aqueous phase are refluxed to the dividing wall distillation column 100 again, the mass flow rate of the upper effluent stream 130 can be the same as the sum of the mass flow rates of the aqueous phase stream 160 and the oil phase stream 150 refluxed to the dividing wall distillation column 100 through the layer separator 140. That is, substantially no components are supplied to other distillation columns or discharged from the system from the upper effluent stream 130 of the dividing wall distillation column 100. That is, the upper effluent stream 130 of the dividing wall distillation column 100 passes through the layer separator 140 and then completely refluxed to the dividing wall distillation column 100.

[0051] The entrainer contained in the oil phase stream 150 is reused in the azeotropic distillation performed in the dividing wall distillation column 100. Furthermore, both the phase-separated oil phase and aqueous phase are refluxed to the dividing wall distillation column 100, but the reflux point is optimized, thereby separating the lower effluent stream 110 of the first zone and the lower effluent stream 120 of the second zone with high purity. At the same time, the entrainer 170 inevitably consumed as the process proceeds can be supplied to the layer separator 140 and replenished.

[0052] That is, the stream discharged to other distillation columns or the outside of the system through the dividing wall distillation column 100 of the present invention may include two streams: the lower discharge stream 110 of the first region containing isopropyl alcohol and by-products and the lower discharge stream 120 of the second region containing water.

[0053] At the same time, the operating pressure of the upper region 103 can be 0 kg / cm 2 g or above or 0.1kg / cm 2 g and above and 3kg / cm 2 ·g or less or 2kg / cm 2 g or less. The operating pressure may be an operating pressure at a height of 0% to 10% downward from the top of the dividing wall distillation column 100. Therefore, the energy required for distillation can be minimized, while isopropyl alcohol having a desired purity can be obtained in the lower portion of the first region and pure water can be separated in the lower portion of the second region.

[0054] The reflux point of the aqueous phase to the second region may be a point 10% to 50% from the bottom of the tower, specifically, a point 25% to 40% from the height of the dividing wall. Figure 1 When the height of the dividing wall is m and the height of the reflux point from the bottom of the column is n (m and n are expressed as the same unit of length), the reflux point of the aqueous phase to the second region may be a point at a ratio of n / m corresponding to the height m of the dividing wall from the bottom of the column. Thus, the energy required for distillation can be maximized while pure water can be separated from the lower portion of the second region.

[0055] More specifically, by setting the position of the upper end of dividing wall 105 and the position of the reflux point of the aqueous phase to the second region as described above, it is possible to simultaneously ensure sufficient operation of both the azeotropic distillation zone for separating isopropyl alcohol and water using an entrainer and the distillation zone for purifying isopropyl alcohol in dividing wall distillation column 100. Furthermore, upper region 103 in the upper dividing wall shares the first and second regions, thereby reducing the energy required in condenser 135. Furthermore, the liquid reflux flow, which branches from the bottom of upper region 103 into first and second regions 101 and 102 and flows downward, is optimized and distributed between the first and second regions, minimizing the amount of heat required in the reboiler in each region.

[0056] Meanwhile, according to an exemplary embodiment of the present invention, the lower discharge stream 110 of the first zone discharged from the first zone 101 may be supplied to the isopropyl alcohol recovery tower 300. The isopropyl alcohol recovery tower 300 is operated by a reboiler 330 provided at the lower portion, and isopropyl alcohol (310) may be obtained at the upper portion of the isopropyl alcohol recovery tower 300, and by-products (320) may be separated at the lower portion of the isopropyl alcohol recovery tower.

[0057] Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are provided to illustrate the present invention, and it will be apparent to those skilled in the art that various modifications and variations may be made without departing from the scope and spirit of the present invention, and the scope of the present invention is not limited thereto.

[0058] 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.

[0059] Example 1

[0060] According to Figure 2 The process diagram shown is a process for purifying isopropyl alcohol.

[0061] Specifically, a feed 10 was prepared containing 85.7 wt% of isopropyl alcohol, 13.57 wt% of water, and 0.73 wt% of n-propyl alcohol (NPA) as a by-product.

[0062] Feed 10 is supplied to the first region of a dividing wall distillation column 100 and subjected to azeotropic distillation in the presence of cyclohexane as an azeotropic agent. The dividing wall distillation column 100 is provided with a dividing wall whose upper end is located at the 18% point downward from the top of the column.

[0063] The first zone 101 of the dividing wall distillation column 100 is supplied with heat energy by the first reboiler 115 and operates at a lower temperature of 84.3°C, and the second zone 102 is supplied with heat energy by the second reboiler 125 and operates at a lower temperature of 103°C.

[0064] The upper discharge stream 130 discharged to the upper region 103 of the dividing wall distillation column 100 is supplied to the condenser 135 and condensed, and the condensed stream is then supplied to the layer separator 140. The stream is separated into an aqueous phase and an oily phase in the layer separator 140, and then the oily phase stream 150 containing cyclohexane is refluxed to the upper region, and the aqueous phase stream 160 containing water is refluxed to the second region. Here, the reflux point of the aqueous phase stream to the second region is a point at a height of 30% from the bottom of the column at the dividing wall.

[0065] Meanwhile, the lower exhaust stream of the first zone containing isopropyl alcohol and n-propyl alcohol is supplied to the isopropyl alcohol recovery tower 300, and the lower exhaust stream of the second zone containing water is discharged from the system.

[0066] The content of isopropyl alcohol obtained in the upper portion of the isopropyl alcohol recovery column 300 was confirmed to be 99.8 wt %. In addition, based on the energy used in the comparative example, the energy (cooling energy) used in the condenser 135 and the energy (heat energy) used in the first reboiler 115 and the second reboiler 125 are shown in Table 1.

[0067] Comparative Example 1

[0068] According to Figure 3 The process diagram shown is a process for purifying isopropyl alcohol.

[0069] From the same feed 10 as that used in Example 1, isopropyl alcohol was recovered from the upper portion of the isopropyl alcohol recovery column 300 using a conventional azeotropic distillation column 100 having no dividing wall, an entrainer recovery column 200, and an isopropyl alcohol recovery column 300. Each of the three columns had a condenser at the upper portion and reboilers 125, 230, and 330 at the lower portion.

[0070] Specifically, feed 10 is supplied to a conventional azeotropic distillation column 100 to undergo azeotropic distillation in the presence of cyclohexane. Upper effluent stream 130 containing water and an entrainer is phase-separated in a layer separator 140, and the oil phase containing the entrainer is refluxed to the distillation column 100 again, and the aqueous phase containing water is supplied to an entrainer recovery column 200. The lower effluent stream of the azeotropic distillation column 100, containing isopropyl alcohol and by-products, is supplied to an isopropyl alcohol recovery column 300 to recover isopropyl alcohol from the upper portion.

[0071] Meanwhile, in Comparative Example 1, the composition and flow rate of the lower effluent stream of the azeotropic distillation column 100 introduced into the isopropyl alcohol recovery column 300 were the same as those in Example 1, and the operating conditions and energy usage of the isopropyl alcohol recovery column 300 in Comparative Example 1 were also the same as those in Example 1. As a result, it was confirmed that the isopropyl alcohol content obtained in Comparative Example 1 was 99.8% by weight, the same as in Example 1.

[0072] At this time, the energy (cooling energy) used in the condensers of the azeotropic distillation column 100 and the entrainer recovery column 200, and the energy (heat energy) used in the reboilers 125 and 230 of the azeotropic distillation column 100 and the entrainer recovery column 200, respectively, are shown in Table 1.

[0073] [Table 1]

[0074]

[0075] For the same feed 10, Example 1 is an example in which isopropyl alcohol and by-products were separated using a dividing wall distillation column, and the isopropyl alcohol was introduced into an isopropyl alcohol recovery column to obtain isopropyl alcohol having a purity of 99.8% by weight, while Comparative Example 1 is an example in which a conventional azeotropic distillation column and an entrainer recovery column for entrainer recovery were used, but isopropyl alcohol and by-products were separated from the conventional distillation column and the isopropyl alcohol was introduced into the isopropyl alcohol recovery column as in Example 1 to obtain isopropyl alcohol having a purity of 99.8% by weight.

[0076] The "condenser load" of the azeotropic distillation column and the entrainer recovery column is a value distributed based on the ratio of energy actually used in the condensers of each column, when the total energy usage of the condensers of each column is 100 kW. In this case, the amount of energy used in the condenser provided above the dividing wall distillation column of Example 1 was 42.7 kW, and it was confirmed that the amount of energy used in the condenser was reduced.

[0077] Similarly, the "reboiler duty" of the azeotropic distillation column and the entrainer recovery column of Comparative Example 1 is a value distributed according to the ratio of energy actually used in the reboilers of each column, when the total energy usage of the reboilers of each column is 100 kW. In this case, the amount of energy used in each of the reboilers provided in the first and second zones of the dividing wall distillation column of Example 1 is 28.3 kW and 13.7 kW, respectively. The total amount of energy used in the reboilers of the dividing wall distillation column of Example 1 is 42 kW, confirming a reduction in the amount of energy compared to Comparative Example 1.

[0078] Furthermore, even considering the amounts of energy required in the condenser and reboiler used in the dividing wall distillation column of Example 1 and the conventional azeotropic distillation column of Comparative Example 1, respectively, the dividing wall distillation column of Example 1 was able to operate well with only about half the energy used in the conventional distillation column of Comparative Example 1.

[0079] [Explanation of Reference Numerals]

[0080] 10: Feed

[0081] 100: Dividing wall distillation column

[0082] 200: Entrainer recovery tower

[0083] 300: Isopropyl alcohol recovery tower

Claims

1. A method for preparing isopropyl alcohol, comprising: supplying a feed containing isopropyl alcohol, water, and by-products to a first region of a dividing wall distillation column divided by a dividing wall into a first region, a second region, and an upper region, and performing azeotropic distillation in the presence of an entrainer; discharging a lower discharge stream of the first zone comprising isopropyl alcohol and by-products from a lower portion of the first zone; discharging a lower portion discharge stream of the second region comprising water from a lower portion of the second region; supplying an upper discharge stream discharged from an upper portion of the upper region and containing water and the entrainer to a layer separator, separating the stream into an aqueous phase stream containing water and an oil phase stream containing the entrainer, recirculating the oil phase stream to the upper region, and recirculating the aqueous phase stream to the second region; as well as Isopropyl alcohol is obtained from the lower effluent stream of the first zone.

2. The method for preparing isopropyl alcohol according to claim 1, in, The dividing wall distillation column includes a dividing wall connected to the bottom of the column and extending in the length direction of the column, and The partition wall divides the area into a first area, a second area opposite to the first area, and an upper area provided above the upper end of the partition wall.

3. The method for preparing isopropyl alcohol according to claim 1, wherein The upper end of the dividing wall is set at a height point 15% to 30% downward from the top of the dividing wall distillation column.

4. The method for preparing isopropyl alcohol according to claim 1, wherein The first zone and the second zone include a first reboiler and a second reboiler connected to respective lower portions.

5. The method for preparing isopropyl alcohol according to claim 1, wherein The temperature of the lower portion of the first zone is 85°C to 100°C.

6. The method for preparing isopropyl alcohol according to claim 1, wherein The temperature of the lower portion of the second region is 95° C. to 115° C., and is higher than the temperature of the lower portion of the first region.

7. The method for preparing isopropyl alcohol according to claim 1, wherein The reflux point of the aqueous phase to the second region is a point at a height of 20% to 50% from the bottom of the column to the dividing wall.

8. The method for preparing isopropyl alcohol according to claim 1, wherein The by-products include n-propanol (NPA).

9. The method for preparing isopropyl alcohol according to claim 1, wherein The azeotropic agent is one or more selected from cyclohexane, benzene, toluene and isopropyl acetate.

10. The method for preparing isopropyl alcohol according to claim 1, wherein The mass flow rate of the upper discharge stream is equal to the sum of the mass flow rates of the water phase stream and the oil phase stream which are refluxed to the dividing wall distillation column through the layer separator.

11. The method for preparing isopropyl alcohol according to claim 1, in, The lower discharge stream of the first zone is supplied to an isopropyl alcohol recovery tower, and Isopropyl alcohol is obtained at the upper portion of the isopropyl alcohol recovery column, and by-products are separated at the lower portion of the isopropyl alcohol recovery column.

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