Method for preparing isopropanol

Abstract

A process for producing isopropanol is provided and in the process for producing isopropanol, propylene monomer is reacted with water in a reactor to produce a reaction product comprising isopropanol, all or part of the reaction product stream is heat-exchanged with a side stream of a gas purification column and cooled, and supplying the cooled reaction product to the absorber to reduce energy usage.

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. 10-2024-0147862, 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 separating isopropyl alcohol with high purity from a reaction product of an isopropyl alcohol production process and reducing energy costs by using waste heat. Background Art

[0004] Isopropyl alcohol (IPA) is used for various purposes, including as a cleaning agent in the electronics industry, such as in the manufacture of semiconductors or liquid crystal displays (LCDs).

[0005] Isopropyl alcohol is usually prepared by the reaction of propylene monomer and water, and after the reaction, the reaction product comprises isopropyl alcohol, unreacted propylene monomer and unreacted water. Here, 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.

[0006] Furthermore, when the reaction product is discharged from the reactor into the gas phase, the gaseous reaction product must be liquefied for subsequent processes such as purification of isopropyl alcohol or recovery of unreacted propylene, and a large amount of waste heat is discarded in this process. Therefore, it is desirable to develop a method for producing isopropyl alcohol that can reduce process energy by recovering and utilizing the discarded waste heat. 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 effectively separating isopropyl alcohol and unreacted propylene monomer from the reaction product of an isopropyl alcohol production process and reducing the energy cost used in the process.

[0009] Technical Solution

[0010] In one general aspect, a method for producing isopropyl alcohol comprises: reacting propylene monomer with water to produce a reaction product comprising propylene and isopropyl alcohol; cooling the reaction product; supplying the cooled reaction product to an absorption column; introducing a lower effluent stream of the absorption column comprising isopropyl alcohol from the absorption column to an isopropyl alcohol purification section, and supplying a portion of an upper effluent stream of the absorption column comprising propylene to a gas purification column; separating the upper effluent stream of the gas purification column comprising propylene and the lower effluent stream of the gas purification column comprising isopropyl alcohol by distillation in the gas purification column, and then introducing the lower effluent stream of the gas purification column to the isopropyl alcohol purification section; and obtaining isopropyl alcohol in the isopropyl alcohol purification section, wherein cooling of the reaction product is performed by a first cooling comprising heat exchange between all or a portion of the reaction product stream and a side stream of the gas purification column, and a second cooling comprising heat exchange between the first cooled reaction product and a refrigerant.

[0011] Beneficial effects

[0012] According to the method for producing isopropyl alcohol of the present invention, the reaction product generated by the reaction of propylene monomer and water is cooled by heat exchange with a side stream of a gas purification tower before being supplied to an absorption tower, thereby effectively utilizing the thermal energy of the reaction product. Simultaneously, the purity of the produced isopropyl alcohol can be improved.

[0013] Specifically, considering the water absorption efficiency in the absorption tower, the high-temperature and gaseous reaction products should be cooled and liquefied in whole or in part, and also cooled to an appropriate temperature before being introduced into the absorption tower and then supplied to the absorption tower. At the same time, since heat energy is required to separate the components by distillation in the gas purification tower, the heat energy of the high-temperature reaction products is supplied to the gas purification tower, thereby improving the overall energy utilization efficiency.

[0014] In particular, because there is a significant difference in temperature distribution between the lower and lower middle portions of a gas purification tower, it is necessary to achieve a moderate temperature distribution between the lower and middle portions of the tower by increasing the temperature of the lower middle portion. In the present invention, the heat energy of the high-temperature reaction product is supplied to the side portions of the gas purification tower, thereby achieving an overall moderate temperature distribution across the upper and lower portions of the gas purification tower and improving separation performance within the gas purification tower. This can improve the purity of the isopropyl alcohol obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a process flow chart of a method for preparing isopropyl alcohol according to an exemplary embodiment of the present invention.

[0016] Figure 2 1 is a process flow chart of a method for preparing isopropyl alcohol according to a comparative example.

[0017] Figure 3 A temperature profile in a column of a conventional gas purification column is shown.

[0018] Figure 4 A temperature profile in a column of a gas purification column according to an exemplary embodiment of the present application is shown. DETAILED DESCRIPTION

[0019] Based on the principle that the inventors can appropriately define the concept of terms in order to describe their own invention in the best way, the terms and words used in the specification and claims of the present application should not be interpreted as having common meanings or dictionary meanings, but interpreted as having meanings and concepts meeting the technical idea of the present application.

[0020] With regard to the drawings, like reference numerals can be used to refer to like or similar components throughout the specification.

[0021] The singular form of a noun corresponding to an item can include one or more of the items, unless explicitly stated otherwise in the relevant context.

[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" can include any one of the items listed in the corresponding phrase or all possible combinations thereof.

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

[0024] The terms such as "first (1st)" or "second (2nd)", or "first (first)" or "second (second)" can simply be used to distinguish the corresponding constituent element from other corresponding constituent elements, and the corresponding constituent element is not limited in other aspects (for example, importance or order).

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

[0026] The term "include" or "have" is intended to designate the existence of the stated features, steps, operations, constituent elements, components, or combinations thereof, but does not exclude the existence or addition of one or more other features, numbers, steps, operations, constituent elements, components, or combinations thereof.

[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 the other constituent element but also a case where the other 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] 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 process flow diagram of a method for purifying isopropyl alcohol according to an exemplary embodiment of the present invention.

[0035] The method for preparing isopropyl alcohol according to the present invention includes reacting propylene monomer with water to prepare a reaction product comprising propylene and isopropyl alcohol.

[0036] Isopropyl alcohol can be produced by reacting propylene monomer with water in the gas phase. Specifically, a feed stream comprising propylene monomer and water is supplied to a reactor, and the reaction product produced in the reactor may comprise isopropyl alcohol, unreacted propylene monomer, and unreacted water. Here, 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.

[0037] Specifically, the reactor can be operated under optimal conditions to efficiently produce isopropyl alcohol by the gaseous reaction of propylene monomer with 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 may be 150° C. to 220° C., 165° C. to 220° C., or 180° C. to 215° C. By operating the reactor within this pressure and temperature range, isopropyl alcohol can be efficiently produced through a gaseous reaction using propylene monomer and water.

[0038] The reaction product produced under the operating conditions of the reactor can be a high temperature and gaseous reaction product comprising isopropyl alcohol, unreacted propylene monomer, unreacted water and an inert gas. Relative to the gross mass of the reaction product, the reaction product can comprise 78 wt % to 88 wt % of (unreacted) propylene and an inert gas.

[0039] According to an exemplary embodiment of the present invention, in order to supply the gaseous reaction product to the absorption tower 100 , first, the reaction product may be cooled.

[0040] Some components of the gaseous reaction product are condensed and liquefied by cooling, and other components exist in the reaction product as a gas phase and can be supplied to the absorption tower 100. For example, isopropyl alcohol, which should preferably be discharged as the lower exhaust stream of the absorption tower 100, exists in a liquid phase, and unreacted propylene, inert gas, etc., which should preferably be discharged as the upper exhaust stream of the absorption tower 100, exist in a gas phase. That is, the efficiency of component separation in the absorption tower can be improved by the phase change of some components caused by cooling.

[0041] Specifically, when isopropyl alcohol is discharged to the upper portion of the absorption tower and fed back into the reactor, it may adversely affect the isopropyl alcohol production reaction in the reactor. Therefore, it is preferred to recover as much isopropyl alcohol as possible to the lower portion of the absorption tower. In addition, when unreacted propylene and inert gas are discharged to the lower portion of the absorption tower, an additional gas purification tower is required to recover the unreacted propylene or inert gas discharged to the lower portion, thereby increasing energy consumption. Therefore, it is preferred to recover as much unreacted propylene and inert gas as possible to the upper portion of the absorption tower.

[0042] In addition, the absorption water (water) introduced into the upper portion of the absorption tower flows downward along the absorption tower while the absorption tower absorbs isopropyl alcohol, and the absorption efficiency of the water in the absorption tower 100 for isopropyl alcohol is adjusted to an optimal temperature range by cooling, and the reaction product can be supplied to the absorption tower 100. 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 phase change of some components of the reaction product and temperature control of the reaction product.

[0043] Reference to conventional technology Figure 2 The reaction product is cooled by exchanging heat with a refrigerant in at least one or more heat exchangers 20 placed in the front stage of the absorption tower. In this case, the waste heat of the high-temperature reaction product may not be used, and a large amount of refrigerant is required for heat exchange, making it difficult to use energy efficiently in many ways.

[0044] However, reference is made to the following related to an exemplary embodiment of the present invention. Figure 1 , in subsequent processes, efficient energy use is enabled by heat exchange between the high-temperature reaction product and the side reboiler 210 of the gas purification tower. Specifically, first, the heat energy required for the operation of the gas purification tower 200 can be reduced by supplying the heat energy of the high-temperature reaction product to the gas purification tower 200. That is, most of the heat energy required for the operation of the gas purification tower 200, which will be described later, can be replaced by waste heat. Second, the conventional amount of refrigerant used to cool the reaction products can be reduced. Third, in order to improve the purification efficiency in the gas purification tower 200, a gentle temperature distribution in the tower must be achieved, and a gentle temperature distribution across the lower and middle parts of the gas purification tower can be achieved by supplying the heat energy of the reaction product to the middle and lower parts of the gas purification tower.

[0045] From this point of view, the temperature of the cooled reaction product 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 at the same time, unreacted propylene discharged to the lower portion of the absorption tower may be minimized.

[0046] Meanwhile, according to an exemplary embodiment of the present invention, the reaction product can be cooled by a first cooling process including heat exchange between all or a portion of the reaction product stream and the side stream 250 of the gas purification tower, and a second cooling process including heat exchange between the first cooled reaction product stream and a refrigerant. Generally, since heat exchange with the side stream 250 of the gas purification tower alone may not be sufficient to cool the reaction product to the desired temperature, in this case, the first cooled reaction product through heat exchange with the side stream of the gas purification tower may be subjected to additional second cooling using a refrigerant in the heat exchanger 20. Here, the refrigerant may be cooling water (CW).

[0047] According to an exemplary embodiment of the present invention, the entire reaction product stream 10 can be heat exchanged with the side stream 250 of the gas purification column. In addition, according to another exemplary embodiment of the present invention, as Figure 1 As shown, partial stream 30 of reaction product stream 10 can undergo heat exchange with side stream 250 of the gas purification tower, while the remaining stream 40 of reaction product stream 10 can be combined with the stream undergoing heat exchange with side stream 250 of the gas purification tower and heat exchanged with the refrigerant in heat exchanger 20. That is, a portion of the first cooled reaction product stream is combined with the remaining portion of the reaction product stream to form a combined stream, and a second cooling can be performed by heat exchange between the combined stream and the refrigerant. As described above, heat exchange between the reaction product and side stream 250 of the gas purification tower serves as a technical means for achieving a moderate temperature distribution in gas purification tower 200. Therefore, in order to provide appropriate energy to the middle and lower portions of the gas purification tower, a portion 30 of reaction product stream 10, rather than the entirety, is branched off and used in heat exchange with side stream 250 of the gas purification tower.

[0048] From this perspective, the ratio (branch ratio) of the mass flow rate of portion 30 to the total mass flow rate of reaction product stream 10 can be 0.1 to 1, 0.1 to 0.5, and specifically 0.1 to 0.4. At this ratio (branch ratio), the optimal amount of heat required for the operation of first reboiler 210 of gas purification column 200 can be supplied. Here, the heat required for the operation of first reboiler 210 refers to the energy required to separate unreacted propylene and inert gas to the upper portion and isopropyl alcohol and water to the lower portion. Specifically, when the ratio (branch ratio) is less than 0.1, although gas purification column 200 can receive more heat through first reboiler 210, the supplied heat is insufficient, and not all the heat required for the operation of first reboiler 210 is supplied. Conversely, when the ratio (branch ratio) is too high, all the heat required for the operation of first reboiler 210 can be supplied, but this may not be preferable in terms of equipment cost because the capacity and size of the first reboiler must be larger than necessary. Specifically, when the ratio (branch ratio) is greater than 0.5, the first reboiler 210 should be larger than necessary. In particular, since the reaction product is a high-temperature gas, its volume capacity is large, and there is a problem in that the pipe 30 for receiving it should be too large. Therefore, when the ratio (branch ratio) is greater than 0.5, the amount of heat that can be transferred to the gas purification tower 200 reaches the desired value, but since the size of the pipe in which the fluid moves is unnecessarily large, it is preferable to keep the ratio (branch ratio) below 0.5.

[0049] Subsequently, the cooled reaction product may be supplied to the absorption tower 100. Here, the cooled reaction product may be supplied as a gas-liquid mixed phase to the absorption tower 100. The lower effluent stream of the absorption tower containing isopropyl alcohol and the upper effluent stream of the absorption tower containing (unreacted) propylene may be separated in the absorption tower 100.

[0050] The reaction product may be supplied to the lower end of the absorption tower 100, the isopropyl alcohol contained in the reaction product may be dissolved and separated into the lower portion of the absorption tower 100 using the solvent supplied to the absorption tower 100, and the stream containing propylene may be separated into the upper portion. The solvent used in the absorption tower 100 may be, for example, water.

[0051] The lower effluent stream 110 of the absorption tower containing isopropyl alcohol can be introduced into the isopropyl alcohol purification section. Specifically, the lower effluent stream 110 of the absorption tower contains unreacted water and water as absorption water in addition to isopropyl alcohol, and may contain light by-products including diisopropyl ether (DIPE) and heavy by-products including n-propyl alcohol (NPA). The isopropyl alcohol in the isopropyl alcohol purification section can be separated from the light by-products, heavy by-products and water and recovered at high purity.

[0052] At the same time, the upper discharge stream of the absorption tower 100 may contain propylene. More specifically, the upper discharge stream of the absorption tower 100 may contain inert gas in addition to propylene, and further contain a small amount of isopropyl alcohol, light by-products, and heavy by-products. The upper discharge stream of the absorption tower 100 can be discharged from the upper part of the absorption tower, a portion 130 can be introduced into the gas purification tower 200, and the remaining portion 120 can be recycled to the reactor for isopropyl alcohol production. The upper discharge stream of the absorption tower 100 may contain 92% to 98% by weight of propylene and inert gas.

[0053] According to an exemplary embodiment of the present invention, the operating pressure of the absorption tower 100 may be 20 kg / cm 2 g to 40kg / cm 2 g, 25kg / cm 2 g to 40kg / cm 2 g, or 25kg / cm 2 g to 35kg / cm 2 g, and its operating temperature may be 80° C. to 110° C., 90° C. to 110° C., or 90° C. to 100° C. By operating the absorption tower 100 at a pressure and temperature within the above ranges, the stream can be effectively separated into an upper effluent stream containing unreacted propylene monomer and a lower effluent stream containing isopropyl alcohol.

[0054] Water for absorbing isopropyl alcohol in the absorption tower 100 may be supplied to the upper portion of the absorption tower 100. As described above, water is used to separate isopropyl alcohol and heavy by-products into the lower portion. From this perspective, the mass flow rate (e.g., tons / hour) of water supplied to the upper portion of the absorption tower 100 may be 15% to 30% of the total mass flow rate of the reaction product supplied to the absorption tower.

[0055] When the mass flow rate ratio of the water supplied to the upper portion of absorption tower 100 is less than 15%, it is difficult to fully absorb isopropyl alcohol in the water, and isopropyl alcohol is contained in the upper discharge stream of absorption tower 100. In this case, isopropyl alcohol is contained in the propylene recycled to the reactor and acts as a factor that inhibits the forward reaction of the isopropyl alcohol synthesis reaction carried out in the reactor. In addition, the energy consumption for separating the isopropyl alcohol in the gas purification tower increases. At the same time, when the mass flow rate ratio of the water supplied to the upper portion of absorption tower 100 is greater than 30%, even the propylene and inert gas that should be discharged as the upper discharge stream of absorption tower 100 are contained in the lower discharge stream of the absorption tower. Therefore, a separate gas purification tower is required to separate the propylene and inert gas contained in the lower discharge stream of the absorption tower, and the energy consumption is increased.

[0056] In addition, the upper discharge flow of the absorption tower 100 can contain 92 wt% to 98 wt% of propylene and inert gas, and in terms of component separation efficiency in the absorption tower, it is preferred that the mass flow rate (e.g., tons / hour) of water supplied to the upper part of the absorption tower 100 is 15% to 30% of the total mass flow rate of the reaction products supplied to the absorption tower.

[0057] The method for preparing isopropyl alcohol according to an exemplary embodiment of the present invention may include separating an upper effluent stream 270 of the gas purification tower containing propylene and a lower effluent stream 260 of the gas purification tower containing isopropyl alcohol by distillation (200) in the gas purification tower 200, and then introducing the lower effluent stream of the gas purification tower into an isopropyl alcohol purification section.

[0058] Specifically, the upper exhaust stream 130 of the absorption tower 100 introduced into the gas purification tower 200 may contain, in addition to propylene, an inert gas, and may also contain isopropyl alcohol, water, a light by-product of diisopropyl ether, and a heavy by-product of n-propyl alcohol, although in small amounts, which have not yet been separated to the lower part of the absorption tower 100. The propylene recycled to the reactor can be recovered at a higher purity by the gas purification tower 200, and the isopropyl alcohol that may have been lost to the upper part of the gas purification tower 200 can be completely recovered to the lower part.

[0059] As described above, the side stream 250 of the gas purification tower 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 tower 200 may include a first reboiler 210 connected to the side of the gas purification tower 200. That is, the first reboiler may be a side reboiler of the gas purification tower 200. That is, heat exchange between the reaction product 10 and the side stream 250 of the gas purification tower may be performed in the first reboiler 210.

[0060] More specifically, the side stream 250 of the gas purification column can be discharged at a height point between 55% and 85% of the height from the top of the gas purification column 200 and heat exchanged with the reaction products. For example, if the side stream 250 is discharged at a height point below 55%, the contact zone where certain components are evaporated and simultaneously contacted with the refluxed liquid components, i.e., the distillation zone where substantial distillation and purification are performed, may be shortened. Meanwhile, if the side stream is discharged at a height point above 85%, the temperature of the side stream is too high, making heat exchange with the reaction products difficult or possibly failing to achieve the desired heat exchange effect (cooling the reaction products and heating the side stream).

[0061] Meanwhile, the side stream of the gas purification tower subjected to heat exchange in the first reboiler 210 may be resupplied to the stage to which the height point of the gas purification tower from which the side stream is discharged belongs.

[0062] In addition, the temperature of the side stream discharged from the gas purification tower 200 can be 40° C. to 80° C. or 40° C. to 60° C., and the temperature of the side stream re-supplied to the gas purification tower 200 after heat exchange can be 80° C. to 100° C. or 85° C. to 95° C. Therefore, the temperature distribution of the height of the gas purification tower 200 can be appropriately controlled. Therefore, as much as possible, specifically more than half of the heat energy required in the gas purification tower, which is conventionally supplied only by the second reboiler 220, can be replaced.

[0063] Meanwhile, according to an exemplary embodiment of the present invention, the operating pressure of the upper portion of the gas purification tower 200 may be as high as 15 kg / cm 2 g to 20kg / cm 2 g or 16kg / cm 2 g to 19 kg / cm 2 g. Furthermore, the operating temperature of the lower portion of gas purification tower 200 can be 140°C to 180°C or 150°C to 180°C. Within the operating temperature and pressure ranges of gas purification tower 200, the separation efficiency of gas purification tower 200 is improved, allowing all of isopropyl alcohol, water, and byproducts to be recovered in the lower portion of gas purification tower 200. Furthermore, inexpensive cooling water can be used as a cooling heat source in the condenser provided in the upper portion of gas purification tower 200.

[0064] Specifically, Figure 3 A graph shows the temperature distribution along the height of a gas purification tower operated with a conventional reboiler located in the lower portion of the tower, without heat exchange between the reaction product and the tower's side stream. As demonstrated in the corresponding temperature distribution, since materials with higher melting points concentrate in the lower portion of the tower, only the lower portion maintains a high temperature, while the temperature rapidly decreases in the middle and lower portions, and the lowered temperature remains in the upper portion. Consequently, distillation and purification become difficult in the temperature zone where the temperature remains constant.

[0065] However, Figure 4 A diagram showing the temperature distribution at the height of the gas purification tower when the reaction product is heat-exchanged with the side stream 250 of the gas purification tower through the first reboiler 210 according to an exemplary embodiment of the present invention is shown. Therefore, it is recognized that a mild temperature distribution of the gas purification tower 200 can be achieved, and a section of the gas purification tower where the temperature changes with the height, that is, a distillation zone where distillation and purification can be performed, is increased. That is, the stream introduced into the gas purification tower 200 contains heavy components such as isopropyl alcohol and water and light components such as propylene and inert gases. That is, since the stream introduced into the gas purification tower 200 contains components with large differences in boiling points, the temperature distribution in the gas purification tower 200 is generally as follows. Figure 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 tower height. However, the temperature distribution in the gas purification tower 200 is smoothly achieved by heat exchange in the first reboiler 210 of the present invention. That is, an appropriate temperature gradient depending on the tower height is achieved, thereby converting the region where component separation is difficult to achieve into a region where component separation can be achieved by steam stripping, thereby improving the component separation efficiency of the gas purification tower 200.

[0066] In addition, when the gas purification column 200 is operated only by the second reboiler 220, conventionally Figure 2 As shown, the second reboiler 220 requires a high-grade heat source (e.g., steam) at a high temperature (e.g., above 160° C.), but as in an exemplary embodiment of the present invention, when the first reboiler 210 is provided in the gas purification tower 220, low-level waste heat at about 120° C. can be used to operate the first reboiler 210. At the same time, the amount of high-grade heat source required for the second reboiler 220 can be reduced compared to conventional technology, thereby reducing thermal energy usage.

[0067] Meanwhile, the gas purification tower 200 may further include a second reboiler 220 connected to the lower portion of the gas purification tower in addition to the first reboiler 210. The heat energy supplied to the gas purification tower by the first reboiler may be 50% to 90% of the total heat energy supplied to the gas purification tower by the first and second reboilers.

[0068] The upper effluent stream 270 from the gas purification column contains propylene and inert gas, and can be supplied to the inert gas removal column via a condenser. In the inert gas removal column, a portion of the upper effluent stream from the inert gas removal column containing propylene can be recycled to the reactor, while the remaining portion can be purged and discharged from the system. The gas components containing inert gas in the upper effluent stream from the inert gas removal column are purged to separate and remove some or all of the inert gas, thereby reducing the inert gas content in the stream flowing back to the reactor and preventing inert gas accumulation in the process.

[0069] The inert gas may include, for example, one or more selected from hydrocarbons having 2 or 3 carbon atoms. As a specific example, the inert gas may include one or more selected from ethane and propane.

[0070] The lower effluent stream of the absorption column and the lower effluent stream of the gas purification column contain isopropyl alcohol, water, diisopropyl ether (DIPE) and n-propyl alcohol (NPA), and these can be passed through an isopropyl alcohol purification section to obtain high-purity isopropyl alcohol.

[0071] 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.

[0072] 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.

[0073] Example 1

[0074] According to Figure 1 The process diagram shown is a process for preparing isopropyl alcohol.

[0075] Specifically, water and propylene are supplied to the reaction section and react in the gas phase to produce a gaseous reaction product comprising isopropyl alcohol, water, and propylene. The temperature of the reaction product-containing stream 10 is 120°C. Before being supplied to the absorption tower 100, the reaction product stream 10 is branched, and a portion of the stream is heat-exchanged with a first reboiler 210 disposed in the side of the gas purification tower 200. Here, the ratio of the mass flow rate of the branched portion to the total mass flow rate of the reaction product stream 10 is 0.2.

[0076] Gas purification tower 200 at 15kg / cm 2The gas purification tower 200 is operated at an upper operating pressure of 1.5 g and a lower operating temperature of 160° C. Heat required for the operation of the gas purification tower 200 is supplied through a first reboiler 210 connected to a side of the gas purification tower 200 and a second reboiler 220 connected to a lower portion of the gas purification tower 200 .

[0077] The side stream of the gas purification tower 200 is discharged from a point 30% below the top of the gas purification tower and heat-exchanged with a portion of the stream branched from the reaction product stream 10. Here, the temperature of the side stream discharged from the gas purification tower 200 is 60° C., and the temperature of the stream supplied to the gas purification tower 200 again after the heat exchange is 95° C.

[0078] At the same time, a portion of the stream branched from the reaction product stream 10 was heat-exchanged with a side stream of the gas purification column, merged with the remaining stream branched from the reaction product stream 10 at a temperature of 105° C., and introduced into the heat exchanger 20. It was further cooled in the heat exchanger 20 and then supplied to the absorption tower 100, and the temperature of the reaction product when supplied to the absorption tower 100 was 95° C.

[0079] The upper exhaust stream of the absorption tower 100 contains isopropyl alcohol and water in addition to propylene, and the isopropyl alcohol and water are discharged to the lower portion of the gas purification tower 200 , and propylene is discharged to the upper portion of the gas purification tower 200 .

[0080] At this time, when the mass flow rate of the feed 130 of the gas purification tower is 100, the mass flow rate ratios between the upper exhaust stream 280 and the lower exhaust stream 260 of the gas purification tower are 97.7 and 2.3, respectively. Meanwhile, the upper exhaust stream 280 contains 0.03 wt% ethane, 98.77 wt% propylene, and 1.2 wt% propane, while the lower exhaust stream 260 does not contain ethane, propylene, and propane, and both inert gas and unreacted propylene are removed to the upper part of the gas purification tower.

[0081] Therefore, the heat energy supplied by the first and second reboilers for the operation of the gas purification column 200 is 82kW and 18kW, respectively. Meanwhile, the refrigerant energy required in the heat exchanger 20 provided in the front stage of the absorption column for supplying the reaction product to the absorption column at a temperature of 95°C is 396kW.

[0082] Comparative Example 1

[0083] For the reaction product having the same components and temperature as Example 1, according to Figure 2 In addition, the operating conditions were controlled so that the flow rates and compositions of the upper and lower exhaust streams of the gas purification tower 200 were the same as those of Example 1.

[0084] That is, in Comparative Example 1, the gas purification tower 200 is not provided with the first reboiler, and the same amount of energy (100 kW) as the heat energy supplied by the first and second reboilers in Example 1 is supplied by the second reboiler provided at the lower portion of the gas purification tower 200 .

[0085] In this case, in order to cool the reaction product to 95° C. as the same as in Example 1 as a temperature suitable for supplying to the absorption tower, it is necessary to supply 478 kW of refrigerant energy through the heat exchanger 20 provided in the front stage of the absorption tower.

[0086] [Explanation of Reference Numerals]

[0087] 10: Reaction products

[0088] 100: Absorption Tower

[0089] 200: Gas purification tower

[0090] 210: First reboiler

[0091] 220: Second reboiler

Claims

1. A method for preparing isopropyl alcohol, comprising: reacting propylene monomer with water to produce a reaction product comprising propylene and isopropanol; cooling the reaction product; supplying the cooled reaction product to an absorption tower; introducing a lower effluent stream of the absorption tower containing isopropyl alcohol from the absorption tower into an isopropyl alcohol purification section, and supplying a portion of an upper effluent stream of the absorption tower containing propylene to a gas purification tower; separating an upper effluent stream of the gas purification column containing propylene and a lower effluent stream of the gas purification column containing isopropyl alcohol by distillation in the gas purification column, and then introducing the lower effluent stream of the gas purification column into the isopropyl alcohol purification section; as well as Isopropanol is obtained in the isopropanol purification section, The cooling of the reaction product is performed by a first cooling process including heat exchange between all or part of the reaction product stream and a side stream of the gas purification tower, and a second cooling process including heat exchange between the first cooled reaction product and a refrigerant.

2. The method for preparing isopropyl alcohol according to claim 1, in, The side stream of the gas purification tower is discharged at a height point of 55% to 85% downward from the top of the gas purification tower and is subjected to heat exchange with the reaction product. The heat-exchanged side stream of the gas purification column is resupplied to the stage to which the height point of the gas purification column from which the side stream was discharged belongs.

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

5. The method for preparing isopropyl alcohol according to claim 1, in, The gas purification tower includes a first reboiler connected to a side portion of the gas purification tower and a second reboiler connected to a lower portion of the gas purification tower, and Heat exchange between all or a portion of the reaction product stream and a side stream of the gas purification column is performed in the first reboiler.

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

7. The method for preparing isopropyl alcohol according to claim 1, in, 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, combining a portion of the first cooled reaction product stream with the remainder of the reaction product stream to form a combined stream, The second cooling is performed by heat exchange between the combined flow and the refrigerant.

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

5.

9. The method for preparing isopropyl alcohol according to claim 1, wherein The upper part of the gas purification tower is at 15kg / cm 2 g and above and 20kg / cm 2 Operate at pressures below g.

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

11. The method for preparing isopropyl alcohol according to claim 1, in, The upper exhaust stream of the gas purification tower contains propylene and inert gas, and An upper effluent stream of the gas purification column is supplied to an inert gas removal column, a portion of the upper effluent stream of the inert gas removal column containing propylene is recycled to a reactor, and the remaining portion is purged.

12. The method for preparing isopropyl alcohol according to claim 1, wherein The lower effluent stream of the absorption column and the lower effluent stream of the gas purification column contain isopropyl alcohol, water, diisopropyl ether (DIPE) and n-propyl alcohol (NPA).

13. The method for preparing isopropyl alcohol according to claim 1, in, Water is supplied to the upper portion of the absorption tower, and The mass flow rate of the water supplied to the upper portion of the absorption tower is 15% to 30% of the total mass flow rate of the reaction product supplied to the absorption tower.

Images