How is isopropyl alcohol produced?

Abstract

The present invention relates to a method for producing isopropyl alcohol, which comprises reacting propylene monomer and water in a reactor to produce a reaction product containing isopropyl alcohol, cooling all or a portion of the reaction product stream by heat exchange with a side stream of a gas purification column, and supplying the cooled reaction product to an absorption tower. This method reduces energy consumption.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0158482 filed November 15, 2023 and Korean Patent Application No. 10-2024-0147862 filed October 25, 2024, and all contents disclosed in the documents of the relevant Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a method for producing isopropyl alcohol, and more particularly to a method for separating isopropyl alcohol with high purity from a reaction product in the production process of isopropyl alcohol and utilizing waste heat to reduce energy costs. [Background technology]

[0003] Isopropyl alcohol (IPA) is used in a variety of applications in the electronics industry, including as a cleaning agent, in the manufacture of semiconductors and liquid crystal displays (LCDs).

[0004] Isopropyl alcohol is generally produced by the reaction of propylene monomer and water, and the reaction product after the reaction contains isopropyl alcohol, unreacted propylene monomer, and unreacted water. In this case, isopropyl alcohol is separated and recovered from the reaction product of the isopropyl alcohol production process, and the unreacted propylene monomer is recovered and reused in the isopropyl alcohol production process.

[0005] On the other hand, when the reaction product is discharged from the reactor in a gas phase, the gas phase reaction product must be liquefied in order to carry out subsequent processes such as isopropyl alcohol purification and recovery of unreacted propylene, but a large amount of waste heat is wasted in the process. Therefore, there is a need to develop a method for producing isopropyl alcohol that can recover and utilize the wasted waste heat and reduce process energy. Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved by the present invention is to solve the problems mentioned in the background art of the invention above by efficiently separating isopropyl alcohol and unreacted propylene monomer from the reaction product of the isopropyl alcohol production process. It is to provide a method for reducing the energy cost used in the process. [Means for solving the problem]

[0007] According to one embodiment of the present invention for solving the above-mentioned problems, the present invention provides a method for producing isopropyl alcohol, comprising the steps of: reacting propylene monomer and water to prepare a reaction product containing propylene and isopropyl alcohol; cooling the reaction product; supplying the cooled reaction product to an absorption tower; introducing a bottom discharge stream from the absorption tower containing isopropyl alcohol from the absorption tower into an isopropyl alcohol purification section and supplying a portion of the top discharge stream from the absorption tower containing propylene to a gas purification column; separating the top discharge stream from the gas purification column containing propylene and the bottom discharge stream from the gas purification column containing isopropyl alcohol by distillation in the gas purification column, and then introducing the bottom discharge stream from the gas purification column into the isopropyl alcohol purification section; and obtaining isopropyl alcohol from the isopropyl alcohol purification section, wherein the cooling of the reaction product includes a first cooling step performed by heat exchange between all or a portion of the reaction product stream and a side stream from the gas purification column, and a second cooling step performed by heat exchange between the first cooled reaction product and a refrigerant. [Effects of the Invention]

[0008] According to the method for producing isopropyl alcohol of the present invention, the reaction product produced by the reaction of propylene monomer and water is cooled by heat exchange with a side stream of the gas purification column before being supplied to the absorption tower. This makes it possible to efficiently utilize the thermal energy of the reaction product and improve the purity of the isopropyl alcohol produced.

[0009] Specifically, in consideration of the efficiency of absorption by water in the absorption tower, the high-temperature, gaseous reaction product should be cooled to liquefy all or part of it, and then cooled to a temperature suitable for introduction into the absorption tower before being supplied to the absorption tower. Meanwhile, since the gas purification column requires thermal energy to separate components by distillation, the thermal energy of the high-temperature reaction product can be supplied to the gas purification column to increase the overall efficiency of energy use.

[0010] In particular, since the temperature profile of the gas purification column has a large difference between the lower and middle / lower sections, it is necessary to increase the temperature in the middle / lower section of the column to form a gentle temperature profile between the lower and middle sections of the column. In the present invention, by supplying the thermal energy of the high-temperature reaction product to the side of the gas purification column, an overall gentle temperature profile can be achieved across the upper and lower sections of the gas purification column, thereby improving the separation performance of the gas purification column. This improves the purity of the resulting isopropyl alcohol. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a process flow diagram of a method for producing isopropyl alcohol according to one embodiment of the present invention. [Figure 2] FIG. 1 is a process flow diagram of a method for producing isopropyl alcohol according to a comparative example. [Figure 3] 1 shows the temperature profile within a conventional gas purification column. [Figure 4] 3 shows a temperature profile within a gas purification column according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] The terms and words used in the description of the present invention and the claims should not be interpreted in a limited way to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, based on the principle that the inventors can appropriately define the concepts of terms in order to best describe their invention.

[0013] In connection with the description of the drawings, like reference numerals may be used for like or related components.

[0014] The singular form of a noun referring to an item can include one or more of said items unless the relevant context clearly dictates otherwise.

[0015] In this disclosure, each phrase such as "A or B," "at least one of A and B," "at least one of A or B," "A, B, or C," "at least one of A, B, and C," and "at least one of A, B, or C" can include any one or all possible combinations of the items listed in the corresponding phrase.

[0016] The term "and / or" includes combinations of the associated listed elements or any elements of the associated listed elements.

[0017] Terms such as "first," "second," or "first" or "second" may be used merely to distinguish a component from other components and do not limit the component in other respects (e.g., importance or order).

[0018] Furthermore, terms such as "front," "rear," "top," "bottom," "side," "left side," "right side," "upper," and "lower" used in this application are defined based on the drawings, and do not limit the shape or position of each component.

[0019] Terms such as "comprise" or "have" specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in this disclosure, but do not preclude the presence or possible addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0020] When a component is said to be "connected," "coupled," "supported," or "in contact with" another component, this includes not only cases where the components are directly connected, coupled, supported, or in contact, but also cases where the components are indirectly connected, coupled, supported, or in contact via a third component.

[0021] When a component is said to be located "on" another component, this includes not only the case where the component is in contact with the other component, but also the case where there is another component between the two components.

[0022] The term "stream" as used herein refers to the flow of fluid within a process, and may also refer to the fluid itself flowing through a pipe. Specifically, the term "stream" may refer to both the fluid itself and the flow of fluid flowing through a pipe connecting each device. The fluid may contain one or more components of gas, liquid, and solid.

[0023] Unless otherwise specified, the term "upper portion" used in this application means a point 0% to 10% below the top of the apparatus, specifically the top (top of the column), and the term "lower portion" means a point 90% to 100% below the top of the apparatus, specifically the bottom (bottom of the column).

[0024] Furthermore, "pressure" referred to in this application means gauge pressure measured under atmospheric pressure conditions.

[0025] On the other hand, unless otherwise specified in this application, the operating pressure of a column means the pressure at the top of the column, and the operating temperature of a column means the temperature at the bottom of the column.

[0026] The present invention relates to a method for producing isopropyl alcohol (IPA), and the method for producing isopropyl alcohol of the present invention will be described in detail below with reference to the drawings.

[0027] FIG. 1 is a process flow diagram of a method for purifying isopropyl alcohol according to one embodiment of the present invention.

[0028] A method for producing isopropyl alcohol according to the present invention includes reacting propylene monomer and water to provide a reaction product comprising propylene and isopropyl alcohol.

[0029] The isopropyl alcohol can be produced by a vapor phase reaction of propylene monomer and water. Specifically, a feedstream containing propylene monomer and water is supplied to a reactor, and the reaction product produced in the reactor may contain isopropyl alcohol, unreacted propylene monomer, and unreacted water. In this case, the isopropyl alcohol is separated and recovered from the reaction product, and the unreacted propylene monomer is recovered and reused in the isopropyl alcohol production process.

[0030] Specifically, the reactor may be operated under optimal conditions for efficiently producing isopropyl alcohol through the gas phase reaction of propylene monomer and water. For example, the operating pressure of the reactor may be 10 kg / cm. 2 g~50kg / cm 2 g, 25 kg / cm 2g~50kg / cm 2 g, or 35 kg / cm 2 g~45kg / cm 2 The operating temperature can be 150°C to 220°C, 165°C to 220°C, or 180°C to 215°C. By operating the reactor at pressures and temperatures within the above ranges, isopropyl alcohol can be effectively produced by a gas-phase reaction of propylene monomer and water.

[0031] The reaction product produced under the operating conditions of the reactor can be a high-temperature, gas-phase reaction product containing isopropyl alcohol, unreacted propylene monomer, unreacted water, and inert gases. The reaction product can contain 78 to 88 wt% of (unreacted) propylene and inert gases based on the total mass of the reaction product.

[0032] According to one embodiment of the present invention, in order to supply the gas phase reaction product to the absorption tower 100, the reaction product may be cooled first.

[0033] The cooling condenses and liquefies some components of the gas phase reaction product, while other components remain in the gas phase in the reaction product and can be supplied to the absorber 100. For example, isopropyl alcohol to be discharged to the lower discharge stream of the absorber 100 preferably exists in the liquid phase, and unreacted propylene or inert gas to be discharged to the upper discharge stream of the absorber 100 preferably exists in the gas phase. In other words, the phase change of some components due to the cooling can improve the efficiency of component separation in the absorber.

[0034] Specifically, if isopropyl alcohol is discharged to the top of the absorption tower and then re-introduced into the reactor, it will adversely affect the isopropyl alcohol production reaction taking place in the reactor, so it is preferable to recover isopropyl alcohol as close to the bottom of the absorption tower as possible. Also, if unreacted propylene and inert gas are discharged to the bottom of the absorption tower, an additional gas purification column is required to recover the unreacted propylene or inert gas discharged to the bottom, which increases energy consumption. Therefore, it is preferable to recover as much of this unreacted propylene and inert gas as possible from the top of the absorption tower.

[0035] Furthermore, in the absorption tower, absorption water introduced into the upper part of the absorption tower absorbs isopropyl alcohol as it descends downward, and the reaction product can be supplied to the absorption tower 100 by adjusting the temperature range in which the absorption efficiency of isopropyl alcohol by water in the absorption tower 100 is highest through the cooling. 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 100 by controlling the phase change of some components of the reaction product and the temperature of the reaction product.

[0036] 2 of the related art, the reaction product is cooled by heat exchange with a refrigerant in at least one heat exchanger 20 located in the upstream stage of the absorption tower. In this case, not only is it impossible to utilize the waste heat of the high-temperature reaction product, but a large amount of refrigerant is required for heat exchange, making it difficult to efficiently utilize energy in various respects.

[0037] However, referring to FIG. 1 according to one embodiment of the present invention, efficient energy use is possible by heat exchanging the high-temperature reaction product in a side reboiler 210 of a downstream gas purification column. Specifically, first, by supplying the thermal energy of the high-temperature reaction product to the gas purification column 200, the thermal energy required for operation of the gas purification column 200 can be reduced. That is, most of the thermal energy required for operation of the gas purification column 200, which will be described later, can be replaced by utilizing waste heat. Second, the amount of refrigerant used, which was previously required for cooling the reaction product, can be reduced. Third, to improve the purification efficiency of the gas purification column 200, it is essential to achieve a gentle temperature profile in the column. By supplying the thermal energy of the reaction product to the middle and lower sections of the gas purification column, a gentle temperature profile can be achieved across the lower and middle sections of the gas purification column.

[0038] From this point of view, the temperature of the cooled reaction product may be 90 to 99° C., specifically 90 to 95° C. In this case, the efficiency of absorbing isopropyl alcohol by water in the absorption tower 100 is further improved, and unreacted propylene discharged to the bottom of the absorption tower can be minimized.

[0039] Meanwhile, according to one embodiment of the present invention, the cooling of the reaction product may include a first cooling step performed by heat exchange between all or a portion of the reaction product stream and the side stream 250 of the gas purification column, and a second cooling step performed by heat exchange between the first cooled reaction product stream and a refrigerant. Generally, heat exchange with the side stream 250 of the gas purification column alone may be insufficient to cool the reaction product to the above temperature. In this case, the reaction product first cooled by heat exchange with the side stream of the gas purification column may be additionally cooled by a refrigerant in heat exchanger 20. Here, the refrigerant may be cooling water (CW).

[0040] According to one embodiment of the present invention, the entire reaction product stream 10 may be heat exchanged with the side stream 250 of the gas purification column. According to another embodiment of the present invention, as shown in FIG. 1 , a portion 30 of the reaction product stream 10 may be heat exchanged with the side stream 250 of the gas purification column, and the remaining stream 40 of the reaction product stream 10 may be combined with the stream heat exchanged with the side stream 250 of the gas purification column and heat exchanged with a refrigerant in heat exchanger 20. That is, the first cooled portion of the reaction product stream may be combined with the remaining reaction product stream to form a combined stream, and the second cooling may be performed by heat exchange between the combined stream and a refrigerant. As described above, heat exchange between the reaction product and the side stream 250 of the gas purification column also serves as a technical means for achieving a gradual temperature profile within the gas purification column 200. Therefore, in order to provide adequate energy to the lower and middle side of the gas purification column, a portion 30 of the reaction product stream 10, but not all of it, can be branched off and participate in heat exchange with a side stream 250 of the gas purification column.

[0041] In this regard, the ratio (branching ratio) of the mass flow rate of the partial stream 30 to the total mass flow rate of the reaction product stream 10 can be 0.1 to 1, 0.1 to 0.5, or specifically 0.1 to 0.4. This ratio (branching ratio) can provide an optimal amount of heat required to operate the first reboiler 210 of the gas purification column 200. Here, the amount of heat required to operate the first reboiler 210 refers to the energy required to separate unreacted propylene and inert gases into the upper portion and isopropyl alcohol and water into the lower portion. Specifically, when the ratio (branching ratio) is less than 0.1, the first reboiler 210 supplies insufficient heat compared to the amount of heat that the gas purification column 200 can receive, and the first reboiler 210 is unable to receive all of the heat required to operate. Conversely, if the ratio (branching ratio) is too large, although it is possible to supply all of the heat required to operate the first reboiler 210, the capacity and size of the first reboiler will be unnecessarily large, which is undesirable from the standpoint of equipment costs. Specifically, if the ratio (branching ratio) exceeds 0.5, there is a problem that the first reboiler 210 will be unnecessarily large. In particular, since the reaction product is a high-temperature gas, the volumetric flow rate is high and the piping 30 required to accommodate it will be excessively large, which is an equipment problem. Therefore, if the ratio (branching ratio) exceeds 0.5, even though the amount of heat that can be transferred to the gas purification column 200 reaches the required value, the size of the piping through which the fluid moves will be unnecessarily large. Therefore, it is preferable to maintain the ratio (branching ratio) at 0.5 or less.

[0042] The cooled reaction product may then be supplied to the absorber 100. Here, the cooled reaction product may be supplied to the absorber 100 as a gas-liquid mixed phase. In the absorber 100, a bottom discharge stream from the absorber containing isopropyl alcohol and an top discharge stream from the absorber containing (unreacted) propylene may be separated.

[0043] The reaction product may be supplied to the lower end of the absorber 100, and isopropyl alcohol contained in the reaction product may be dissolved using a solvent supplied to the absorber 100 and separated in the lower part of the absorber 100, while a stream containing propylene may be separated in the upper part. The solvent used in the absorber 100 may be, for example, water.

[0044] The bottom discharge stream 110 from the absorber containing isopropyl alcohol can be introduced into an isopropyl alcohol purification section. Specifically, the bottom discharge stream 110 from the absorber can contain, in addition to isopropyl alcohol, unreacted water and water as absorption water, as well as light by-products including diisopropyl ether (DIPE) and heavy by-products including n-propyl alcohol (NPA). In the isopropyl alcohol purification section, the isopropyl alcohol can be separated from the light by-products, heavy by-products, and water and recovered at a high purity.

[0045] Meanwhile, the top discharge stream of the absorber 100 contains propylene. More specifically, the top discharge stream of the absorber 100 may contain inert gases in addition to propylene, and may further contain small amounts of isopropyl alcohol, the light by-products, and the heavy by-products. The top discharge stream of the absorber 100 is branched after being discharged from the top of the absorber, and a portion 130 may be introduced into the gas purification column 200, and the remaining portion 120 may be recycled to the reactor for producing isopropyl alcohol. The top discharge stream of the absorber 100 may contain 92 to 98 wt% of propylene and inert gases.

[0046] According to one embodiment of the present invention, the operating pressure of the absorber 100 is 20 kg / cm 2 g~40kg / cm 2 g, 25 kg / cm 2 g~40kg / cm 2 g, or 25 kg / cm 2 g~35kg / cm 2The pressure and temperature of the absorber 100 can be 80° C. to 110° C., 90° C. to 110° C., or 90° C. to 100° C. By operating the absorber 100 at pressures and temperatures within the above ranges, an upper effluent stream containing unreacted propylene monomer and a lower effluent stream containing isopropyl alcohol can be effectively separated.

[0047] Water used to absorb isopropyl alcohol in the absorber 100 may be supplied to the upper part of the absorber 100. As described above, the water serves to separate isopropyl alcohol and heavy by-products to the lower part. In this regard, the mass flow rate (e.g., ton / hr) of water supplied to the upper part of the absorber 100 may be 15 to 30% of the total mass flow rate of the reaction product supplied to the absorber.

[0048] If the mass flow ratio of water supplied to the top of the absorber 100 is less than 15%, isopropyl alcohol is not sufficiently absorbed by water, resulting in isopropyl alcohol being contained in the top discharge stream of the absorber 100. In this case, isopropyl alcohol is contained in the propylene recycled to the reactor, which acts as a factor inhibiting the forward reaction of isopropyl alcohol synthesis occurring in the reactor. Furthermore, the energy consumption for separating isopropyl alcohol in the gas purification column increases. On the other hand, if the mass flow ratio of water supplied to the top of the absorber 100 is greater than 30%, propylene and inert gases that should be discharged to the top discharge stream of the absorber 100 are also contained in the bottom discharge stream of the absorber. This requires an additional gas purification column to separate the propylene and inert gases contained in the bottom discharge stream of the absorber, thereby increasing energy consumption.

[0049] Furthermore, the top discharge stream from the absorber 100 may contain propylene and inert gases at 92 to 98 wt %, but from the viewpoint of the efficiency of component separation in the absorber, the mass flow rate (e.g., ton / hr) of water supplied to the top of the absorber 100 is preferably 15 to 30% of the total mass flow rate of the reaction products supplied to the absorber.

[0050] The method for producing isopropyl alcohol according to one embodiment of the present invention includes separating an upper discharge stream 270 of the gas purification column containing propylene and a lower discharge stream 260 of the gas purification column containing isopropyl alcohol by distillation in the gas purification column 200, and then introducing the lower discharge stream of the gas purification column into the isopropyl alcohol purification section.

[0051] Specifically, the top discharge stream 130 from the absorber 100 introduced into the gas purification column 200 contains inert gases in addition to propylene, and may contain small amounts of isopropyl alcohol, water, and light by-product diisopropyl ether, as well as heavy by-product n-propyl alcohol, which were not completely separated in the bottom of the absorber 100. The gas purification column 200 allows for the recovery of propylene to be recycled to the reactor with higher purity, and also allows for the complete recovery of isopropyl alcohol from the bottom, which would otherwise be lost to the top of the gas purification column 200.

[0052] As described above, the side stream 250 of the gas purification column 200 may be heat exchanged with all or a portion of the reaction product 10 supplied to the absorption tower 100. To this end, the gas purification column 200 may include a first reboiler 210 connected to the side of the gas purification column 200. That is, the first reboiler may be a side reboiler of the gas purification column 200. That is, heat exchange between the reaction product 10 and the side stream 250 of the gas purification column may be performed in the first reboiler 210.

[0053] More specifically, the side stream 250 from the gas purification column is discharged from a point 55 to 85% below the top of the gas purification column 200 and can be heat exchanged with the reaction product. For example, if the side stream 250 is discharged from a point below the 55% height, there is a problem that the contact zone where certain components are vaporized and simultaneously contacted with the refluxed liquid phase components, i.e., the distillation zone where actual distillation and purification occur, is shortened. On the other hand, if the side stream is discharged from a point above the 85% height, the temperature of the side stream is too high, making it difficult to exchange heat with the reaction product or resulting in no heat exchange effect (cooling the reaction product and heating the side stream).

[0054] Meanwhile, the side stream of the gas purification column that has been heat exchanged with the reaction product in the first reboiler 210 can be re-supplied to the stage to which the height point of the gas purification column from which the side stream was discharged belongs.

[0055] In addition, the temperature of the side stream discharged from the gas purification column 200 may be 40°C to 80°C or 40°C to 60°C, and the temperature of the side stream supplied again to the gas purification column 200 after heat exchange may be 80°C to 100°C or 85°C to 95°C. This allows the temperature profile for each height of the gas purification column 200 to be appropriately controlled. This allows the thermal energy required for the gas purification column, which was previously supplied only by the second reboiler 220, to be replaced as much as possible, specifically more than half.

[0056] Meanwhile, according to one embodiment of the present invention, the operating pressure at the top of the gas purification column 200 is 15 kg / cm 2 g~20kg / cm 2 g, or 16 kg / cm 2 g~19kg / cm 2The gas purification column 200 can be operated under high-pressure conditions of 10 ...

[0057] Specifically, Figure 3 is a graph showing the temperature profile for each height of a gas purification column operated with a conventional reboiler installed at the bottom of the gas purification column without heat exchange between the reaction product and a side stream of the gas purification column. As can be seen from the temperature profile, the lower part of the column is maintained at a high temperature because substances with relatively high boiling points are concentrated in the lower part, and the temperature drops sharply in the middle and lower parts, and the lowered temperature is maintained in the upper part as well. In this section where the temperature is maintained constant at each height, distillation and purification are difficult to perform.

[0058] Meanwhile, FIG. 4 is a graph showing the temperature profile for each height of the gas purification column when the reaction product and the side stream 250 of the gas purification column are heat exchanged by the first reboiler 210 according to one embodiment of the present invention. As a result, it can be seen that a gentle temperature profile can be achieved in the gas purification column 200, and the section where the temperature changes with each height of the gas purification column, i.e., the distillation region where distillation and purification can occur, increases. That is, the stream introduced into the gas purification column 200 contains not only light components such as propylene and inert gases, but also heavy components such as isopropyl alcohol and water. That is, because the stream introduced into the gas purification column 200 contains components with large boiling point differences, the temperature profile within the gas purification column 200 generally becomes abrupt as shown in FIG. 3. In this case, there is a region (so-called dead zone) where the temperature change is small and component separation is difficult depending on the height of the column. However, by using heat exchange with the first reboiler 210 of the present invention, a gradual temperature profile can be achieved within the gas purification column 200, i.e., an appropriate temperature gradient can be achieved depending on the height of the column. This converts the region where component separation is difficult into a region where component separation by stripping is possible, thereby increasing the component separation efficiency of the gas purification column 200.

[0059] Conventionally, when the gas purification column 200 is operated using only the second reboiler 220, as shown in FIG. 2, a high-temperature (e.g., 160°C or higher) high-grade heat source (e.g., steam) is required for the second reboiler 220. However, when the first reboiler 210 is provided in the gas purification column 200, as in one embodiment of the present invention, the first reboiler 210 can be operated using low-grade waste heat of about 120°C. In addition, the amount of high-grade heat source required for the second reboiler 220 can be reduced compared to conventional methods, thereby reducing the amount of thermal energy used.

[0060] Meanwhile, the gas purification column 200 may further include a second reboiler 220 connected to a lower portion of the gas purification column in addition to the first reboiler 210. The thermal energy supplied to the gas purification column by the first reboiler may be 50% to 90% of the total thermal energy supplied to the gas purification column by the first reboiler and the second reboiler.

[0061] The top discharge stream 270 from the gas purification column contains propylene and inert gases, and can be supplied to an inert gas removal column via a condenser. In the inert gas removal column, a portion of the top discharge stream from the inert gas removal column containing propylene can be recycled to the reactor, and the remainder can be purged and discharged to the outside of the system. The gas phase components including inert gases in the top discharge stream from the inert gas removal column can be purged to separate and remove some or all of the inert gases, thereby reducing the content of inert gases in the stream returned to the reactor and preventing the accumulation of inert gases in the process.

[0062] The inert gas may include, for example, one or more selected from the group consisting of hydrocarbons having 2 to 3 carbon atoms. As a specific example, the inert gas may include one or more selected from the group consisting of ethane and propane.

[0063] The bottom discharge stream of the absorption tower and the bottom discharge stream of the gas purification column contain isopropyl alcohol, water, diisopropyl ether (DIPE), and n-propyl alcohol (NPA), which can be passed through an isopropyl alcohol purification section to obtain high-purity isopropyl alcohol.

[0064] The present invention will be described in more detail below with reference to examples. However, the following examples are for illustrative purposes only, and it will be apparent to those skilled in the art that various changes and modifications can be made within the scope and technical concept of the present invention, and the scope of the present invention is not limited to these examples.

[0065] In the following Examples and Comparative Examples, the method of the present invention was simulated using Aspen Plus V12.1, a commercial process replication program.

[0066] Example 1 The isopropyl alcohol production process was carried out according to the process diagram shown in Figure 1.

[0067] Specifically, water and propylene were supplied to a reaction section and reacted in a gas phase to produce a gas phase reaction product containing isopropyl alcohol, water, and propylene. The temperature of the reaction product stream 10 was 120°C. Before supplying the reaction product stream 10 to the absorption tower 100, the reaction product stream 10 was branched, and a portion of the stream was heat exchanged with a first reboiler 210 installed on the side of the gas purification column 200. The mass flow rate of the branched portion of the stream was 0.2 relative to the total mass flow rate of the reaction product stream 10.

[0068] The gas purification column 200 has an upper operating pressure of 15 kg / cm 2 The gas purification column 200 was operated at a temperature of 160° C. and a lower operating temperature of 160° C. Heat required for operation of the gas purification column 200 was supplied by a first reboiler 210 connected to the side of the gas purification column 200 and a second reboiler 220 connected to the lower part of the gas purification column 200.

[0069] The side stream from the gas purification column 200 was discharged from a point 30% below the top of the gas purification column and was heat exchanged with a partial stream branched off from the reaction product stream 10. Here, the temperature of the side stream discharged from the gas purification column 200 was 60°C, and the temperature of the stream returned to the gas purification column 200 after heat exchange was 95°C.

[0070] Meanwhile, a portion of the stream branched off from the reaction product stream 10 was heat exchanged with a side stream of the gas purification column, and then combined with the remaining branched stream of the reaction product stream 10 at a temperature of 105°C, and introduced into heat exchanger 20. The reaction product was further cooled in heat exchanger 20 and then supplied to absorber 100, and the temperature of the reaction product was 95°C when supplied to absorber 100.

[0071] The top discharge stream from the absorber 100 contains, in addition to propylene, isopropyl alcohol and water, and the isopropyl alcohol and water are discharged to the bottom of the gas purification column 200, and the propylene is discharged to the top of the gas purification column 200.

[0072] The mass flow ratio of the top discharge stream 280 to the bottom discharge stream 260 of the gas purification column was 97.7 and 2.3, respectively, when the mass flow rate of the feed 130 to the gas purification column was 100. Meanwhile, the top discharge stream 280 contained 0.03 wt% ethane, 98.77 wt% propylene, and 1.2 wt% propane, and the bottom discharge stream 260 contained no ethane, propylene, or propane. All inert gases and unreacted propylene were removed at the top of the gas purification column.

[0073] As a result, the heat energies supplied by the first reboiler and the second reboiler for operating the gas purification column 200 were 82 kW and 18 kW, respectively. On the other hand, the refrigerant energy required by the heat exchanger 20 provided in the upstream stage of the absorption tower to supply the reaction product to the absorption tower at a temperature of 95°C was 396 kW.

[0074] Comparative Example 1 The reaction product having the same composition and temperature as in Example 1 was subjected to an isopropyl alcohol production process according to the process flow diagram shown in Figure 2. Furthermore, the operating conditions were controlled so that the flow rates and compositions of the upper and lower discharge streams of the gas purification column 200 were the same as in Example 1.

[0075] That is, in Comparative Example 1, the gas purification column 200 was not equipped with a first reboiler, and the second reboiler provided at the bottom of the gas purification column 200 supplied the same amount of thermal energy (100 kW) as that supplied by the first and second reboilers in Example 1.

[0076] In this case, in order to cool the reaction product to 95°C, which is a temperature suitable for supplying the reaction product to the absorption tower, as in Example 1, it was necessary to supply 478 kW of refrigerant energy from the heat exchanger 20 provided in the upstream stage of the absorption tower. [Explanation of symbols]

[0077] 10 Reaction Products 100 Absorption Tower 200 Gas Purification Column 210 No. 1 reboiler 220 Second reboiler

Claims

1. reacting propylene monomer and water to provide a reaction product comprising propylene and isopropyl alcohol; cooling the reaction product; feeding the cooled reaction product to an absorber; From the absorption tower, a bottom discharge stream of the absorption tower containing isopropyl alcohol is introduced into an isopropyl alcohol purification section, and a portion of the top discharge stream of the absorption tower containing propylene is supplied to a gas purification column; In the gas purification column, an upper discharge stream of the gas purification column containing propylene and a lower discharge stream of the gas purification column containing isopropyl alcohol are separated by distillation, and then the lower discharge stream of the gas purification column is introduced into the isopropyl alcohol purification section; obtaining isopropyl alcohol from an isopropyl alcohol purification unit; 1. A method for producing isopropyl alcohol, wherein the cooling of the reaction product comprises a first cooling step performed by heat exchange of all or a portion of the reaction product stream with a side stream of the gas purification column, and a second cooling step performed by heat exchange of the first cooled reaction product stream with a refrigerant.

2. a side stream from the gas purification column being discharged at a height 55 to 85% below the top of the gas purification column and being subjected to heat exchange with the reaction product; 2. The method for producing isopropyl alcohol according to claim 1, wherein the heat-exchanged side stream of the gas purification column is re-supplied to the stage corresponding to the height point of the gas purification column from which the side stream was discharged.

3. 2. The method for producing isopropyl alcohol according to claim 1, wherein the temperature of the side stream discharged from the gas purification column is 40°C to 80°C.

4. The method for producing isopropyl alcohol according to claim 1, wherein the temperature of the cooled reaction product supplied to the absorption tower is 90 to 99 ° C.

5. The gas purification column includes a first reboiler connected to a side of the gas purification column and a second reboiler connected to a bottom of the gas purification column; 2. The method for producing isopropyl alcohol according to claim 1, wherein heat exchange between all or a portion of the reaction product stream and a side stream of the gas purification column occurs in the first reboiler.

6. The thermal energy supplied to the gas purification column by the first reboiler is 50% to 90% of the total thermal energy supplied to the gas purification column by the first reboiler and the second reboiler. The method for producing isopropyl alcohol according to claim 5.

7. the first cooling is performed by heat exchange between a portion of the reaction product stream and a side stream of the gas purification column; a portion of the first cooled reaction product stream is combined with a remaining portion of the reaction product stream to form a combined stream; 2. The method for producing isopropyl alcohol according to claim 1, wherein the second cooling is performed by heat exchange between the combined stream and a refrigerant.

8. 8. The method for producing isopropyl alcohol according to claim 7, wherein the ratio of the mass flow rate of the partial stream to the total mass flow rate of the reaction product stream is 0.1 to 0.

5.

9. The top of the gas purification column is 15 kg / cm ２ ・G or more, 20kg / cm ２ 2. The method for producing isopropyl alcohol according to claim 1, wherein the method is operated at a pressure of 0.5 g or less.

10. 2. The method for producing isopropyl alcohol according to claim 1, wherein the lower part of the gas purification column is operated at a temperature of 140°C or higher and 180°C or lower.

11. the top effluent stream of the gas purification column comprises propylene and an inert gas; 2. The method for producing isopropyl alcohol according to claim 1, wherein the top effluent stream of the gas purification column is fed to an inert gas removal column, and a portion of the top effluent stream of the inert gas removal column containing propylene is recycled to the reactor, and the remainder is purged.

12. 2. The method for producing isopropyl alcohol according to claim 1, wherein the bottom discharge stream of the absorption tower and the bottom discharge stream of the gas purification column comprise isopropyl alcohol, water, diisopropyl ether (DIPE), and n-propyl alcohol (NPA).

13. Water is supplied to the top of the absorption tower, The method for producing isopropyl alcohol according to claim 1, wherein the mass flow rate of water supplied to the upper part of the absorption tower is 15 to 30% of the total mass flow rate of the reaction product supplied to the absorption tower.

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