Xylylenediamine production method

Abstract

The present invention provides a xylylenediamine production method that has an excellent balance between a reduction in energy for removing a solvent and a reduction in loss of generated xylylenediamine. The xylylenediamine production method comprises: a hydrogenation step for hydrogenating dicyanobenzene in the presence of a catalyst and liquid ammonia, thereby obtaining a reaction solution containing xylylenediamine; and a solvent recovery step for recovering, by distillation, the liquid ammonia from the reaction solution, wherein the solvent recovery step is executed a plurality of times.

Description

Method for Producing Xylylenediamine

[0001] The present invention relates to a method for producing xylylenediamine.

[0002] Xylylenediamine is a compound useful as a raw material for polyamide resins, a raw material for curing agents, an intermediate raw material for isocyanate resins, and the like. Xylylenediamine can be obtained, for example, by hydrogenating dicyanobenzene.

[0003] Patent Document 1 discloses that in a process for producing xylylenediamine by performing a two-stage hydrogenation reaction using dicyanobenzene as a raw material, high-purity xylylenediamine can be stably obtained over a long period of time by incorporating a solid-liquid separation step.

[0004] Japanese Patent No. 6806290

[0005] In the production process of xylylenediamine, an ammonia solvent is used from the viewpoint of improving the solubility of dicyanobenzene and reaction performance in the hydrogenation reaction of dicyanobenzene. The ammonia solvent after the hydrogenation reaction can be separated / recovered from the product and reused, however, as the amount of the ammonia solvent used increases, the energy for removing the solvent tends to increase. In addition, loss of the produced xylylenediamine may occur along with the removal of the ammonia solvent. From the viewpoint of production cost, reduction of energy for solvent removal and reduction of loss of produced xylylenediamine are required.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing xylylenediamine that is excellent in the balance between reducing energy for solvent removal and reducing loss of produced xylylenediamine.

[0007] As a result of intensive studies, the present inventors have found that in a method for producing xylylenediamine including: a hydrogenation step of hydrogenating dicyanobenzene in the presence of a catalyst and liquid ammonia to obtain a reaction solution containing xylylenediamine; and a solvent recovery step of recovering liquid ammonia from the reaction solution by distillation, the above problems can be solved by performing the solvent recovery step a plurality of times, and thus completed the present invention.

[0008] In other words, the present invention encompasses the following embodiments: <1> A method for producing xylylenediamine, comprising: a hydrogenation step of hydrogenating dicyanobenzene in the presence of a catalyst and liquid ammonia to obtain a reaction solution containing xylylenediamine; and a solvent recovery step of recovering the liquid ammonia from the reaction solution by distillation, wherein the solvent recovery step is performed multiple times. <2> The method for producing xylylenediamine according to <1>, wherein the solvent recovery step is performed two to four times. <3> The method for producing xylylenediamine according to <1> or <2>, wherein the distillation is flash distillation. <4> The method for producing xylylenediamine according to <3>, wherein in the solvent recovery step, the operating pressure is 0.1 to 3.0 MPa and the operating temperature is 50 to 200°C. <5> The method for producing xylylenediamine according to any one of <1> to <4>, wherein the operating temperature in the first solvent recovery step is lower than the operating temperature in the second solvent recovery step. <6> A method for producing xylylenediamine according to any one of <1> to <5>, wherein the operating pressure in the first solvent recovery step is higher than the operating pressure in the last solvent recovery step. <7> A method for producing xylylenediamine according to any one of <1> to <6>, wherein the ammonia concentration in the reaction solution obtained in the last solvent recovery step is 1.0% by mass or less. <8> A method for producing xylylenediamine according to any one of <1> to <7>, further comprising a rectification step. <9> A method for producing xylylenediamine according to any one of <1> to <8>, wherein the hydrogenation step is carried out in a fixed-bed reactor. <10> A method for producing xylylenediamine according to any one of <1> to <9>, wherein the dicyanobenzene contains isophthalonitrile and the xylylenediamine contains metaxylylenediamine.

[0009] According to the present invention, it is possible to provide a method for producing xylylenediamine that offers an excellent balance between reducing energy consumption for solvent removal and reducing the loss of the generated xylylenediamine.

[0010] This is a flowchart showing an example of a method for producing xylylenediamine according to this embodiment.

[0011] The following describes in detail embodiments for carrying out the present invention (hereinafter referred to as "this embodiment"). This embodiment is illustrative for explaining the present invention and is not intended to limit the present invention to the following content. The present invention can be implemented by modifying it as appropriate within the scope of its gist.

[0012] [Method for Producing Xylylenediamine] The method for producing xylylenediamine according to this embodiment (hereinafter sometimes simply referred to as the "method") includes a hydrogenation step of hydrogenating dicyanobenzene in the presence of a catalyst and liquid ammonia to obtain a reaction solution containing xylylenediamine, and a solvent recovery step of recovering the liquid ammonia from the reaction solution by distillation, wherein the solvent recovery step is performed multiple times.

[0013] Figure 1 shows a flow chart illustrating an example of the method for producing xylylenediamine according to this embodiment. As shown in Figure 1, in this embodiment, dicyanobenzene, liquid ammonia, and hydrogen are supplied to a hydrogenation reactor 10, and when these come into contact with a catalyst (not shown) installed in the hydrogenation reactor 10, a hydrogenation reaction is initiated, and a reaction solution (A) containing xylylenediamine and liquid ammonia is obtained. Next, the reaction solution (A) is supplied to a first distillation apparatus 20a, where some of the liquid ammonia in the reaction solution (A) is separated by distillation, and the liquid ammonia is recovered from the top of the first distillation apparatus 20a. The reaction solution (B) discharged from the first distillation apparatus 20a is the reaction solution from which some of the liquid ammonia in the reaction solution (A) has been separated. Next, the reaction solution (B) is supplied to a second distillation apparatus 20b, where some or all of the liquid ammonia in the reaction solution (B) is separated by distillation, and the liquid ammonia is recovered from the top of the second distillation apparatus 20b. The reaction solution (C) discharged from the second distillation apparatus 20b is the reaction solution from which some or all of the liquid ammonia in reaction solution (B) has been separated. Next, reaction solution (C) is supplied to the third distillation apparatus 20c, where some or all of the liquid ammonia in reaction solution (C) is separated by distillation, and the liquid ammonia is recovered from the top of the third distillation apparatus 20c. The reaction solution (D) discharged from the third distillation apparatus 20c is the reaction solution from which some or all of the liquid ammonia in reaction solution (C) has been separated. The state of the ammonia when recovered from the top of the distillation apparatus may be liquid or gaseous.

[0014] The manufacturing method of this embodiment, by including the above-mentioned steps, offers an excellent balance between reducing energy required for solvent removal and reducing the loss of the generated xylylenediamine. The reason for this is not entirely clear, and this is not intended to limit the reasons, but it can be inferred as follows. Conventionally, in the hydrogenation step of the production method for xylylenediamine, liquid ammonia is often used as a solvent from the viewpoint of the solubility of the raw material dicyanobenzene and the reaction performance. However, while increasing the amount of liquid ammonia used improves the reaction performance, it also increases the energy required to separate the liquid ammonia. In the conventional method of performing the solvent recovery step by distillation only once, the energy required to separate the liquid ammonia from the xylylenediamine to a level that does not pose a quality problem tends to increase. Distillation under such conditions can also affect the loss of the product xylylenediamine. Specifically, the loss of xylylenediamine can increase due to losses due to thermal denaturation of xylylenediamine itself, and losses due to removal along with liquid ammonia by vapor partial pressure. On the other hand, if one tries to minimize the loss of xylylenediamine and the energy required for liquid ammonia removal, the removal of liquid ammonia may be insufficient, potentially compromising the quality of the xylylenediamine. In this embodiment, since the solvent recovery process is performed multiple times, liquid ammonia can be separated and recovered in stages, thereby reducing the loss of xylylenediamine and further reducing the energy used.

[0015] (1) Hydrogenation Step The manufacturing method of this embodiment includes a hydrogenation step in which dicyanobenzene is hydrogenated in the presence of a catalyst and liquid ammonia to obtain a reaction solution containing xylylenediamine. In this step, dicyanobenzene is dissolved in liquid ammonia, and then hydrogenated in the liquid phase in the presence of a catalyst to obtain a reaction solution containing xylylenediamine and liquid ammonia. In the manufacturing method of this embodiment, the hydrogenation step may be performed multiple times.

[0016] (Dicyanobenzene) The dicyanobenzene used in this process may be obtained by any method, but it is industrially preferable to obtain it by the ammoxidation reaction of xylene. The ammoxidation reaction can be carried out by known methods, by supplying a reaction material mixture of a catalyst, xylene, oxygen, and ammonia, and allowing the reaction to proceed. The ammoxidation reaction can be carried out in either a fluidized bed or a fixed bed. A known catalyst can be used as the catalyst for the ammoxidation, but it is preferable to contain vanadium or chromium, and more preferably to contain both vanadium and chromium.

[0017] The amount of ammonia is preferably 2 to 20 moles, and more preferably 6 to 15 moles, per mole of xylene. When the amount of ammonia is within the above range, the yield of dicyanobenzene is good, and the space-time yield is also high. Oxygen can also be used as an oxygen-containing gas by diluting it with nitrogen, carbon dioxide, etc.

[0018] Air is preferably used as the oxygen-containing gas. The amount of oxygen is preferably 3 moles or more, and more preferably 4 to 100 moles, per mole of xylene. When the amount of oxygen is within the above range, the yield of dicyanobenzene is good, and the space-time yield is also high. The reaction temperature is preferably 300 to 500°C, and more preferably 330 to 470°C. When the temperature is within the above range, the conversion rate of xylene is good, by-products are suppressed, and dicyanobenzene can be produced in good yield. The pressure is preferably normal pressure (atmospheric pressure) to 300 kPa, and the space velocity (Gas Hourly Space Velocity = GHSV) of the reaction raw materials is 500 to 5000 h -1 It is preferable.

[0019] The dicyanobenzene obtained from the above reaction can be collected and used as a raw material in the hydrogenation process. For the collection of dicyanobenzene, the gaseous ammoxidation reaction product may be cooled to the temperature at which dicyanobenzene precipitates before collection, or the gaseous ammoxidation reaction product may be collected with water or a suitable organic solvent. The organic solvent used for collection is preferably one or more organic solvents that have high solubility for dicyanobenzene and are inert to dicyanobenzene, with tolunitrile being even more preferable. The dicyanobenzene collection solution may be used directly in the hydrogenation process, but it is preferable to separate some or all of the components having a lower boiling point than dicyanobenzene (low-boiling point components) containing the organic solvent by distillation before using it in the hydrogenation process. By separating the low-boiling point components by distillation in this way, dicyanobenzene can be obtained, and the recovered organic solvent can be reused to collect the reaction product. In addition, some or all of the components having a higher boiling point than dicyanobenzene (high-boiling point components) may also be separated by distillation or extraction.

[0020] Dicyanobenzene has three isomers: the ortho isomer, phthalonitrile (1,2-dicyanobenzene); the meta isomer, isophthalonitrile (1,3-dicyanobenzene); and the para isomer, terephthalonitrile (1,4-dicyanobenzene). Any of these can be used as a raw material, either individually or in mixtures. In the manufacturing method of this embodiment, it is preferable that the dicyanobenzene contains isophthalonitrile, and it is preferable that the xylylenediamine contains metaxylylenediamine.

[0021] (Catalyst) As catalysts used in this process, known supported metal catalysts, unsupported metal catalysts, Raney catalysts, sponge catalysts, precious metal catalysts, etc., can be used. Examples of catalyst components include Ru, Rh, Ni, Pd, and Co, and these can be used individually or in combination of two or more. It is particularly preferable to use a catalyst containing Ni and / or Co. The amount of catalyst used should be the same as the amount used in known liquid-phase hydrogenation of dicyanobenzene.

[0022] (Liquid Ammonia) In this process, the liquid ammonia may contain, for example, aromatic hydrocarbons. Examples of liquid ammonia include liquid ammonia alone, or a mixture of liquid ammonia and aromatic hydrocarbons, and any of these is preferred. One or more aromatic hydrocarbons may be used.

[0023] From the viewpoint of improving the reaction performance of the hydrogenation reaction, a higher concentration of liquid ammonia is preferable, specifically 60% by mass or more, and even more preferably 100% by mass. In the hydrogenation step of this embodiment, the amount of liquid ammonia is preferably 1 to 99 parts by mass, more preferably 3 to 66 parts by mass, and even more preferably 5 to 49 parts by mass, per 1 part by mass of dicyanobenzene. By having the amount of liquid ammonia within the above range, the energy required for solvent removal can be reduced, and the selectivity of xylylenediamine in the hydrogenation reaction also tends to improve.

[0024] The means of dissolving dicyanobenzene in liquid ammonia are not particularly limited, but in addition to using a mixer such as a static mixer, it is preferable to mix and dissolve the dicyanobenzene and liquid ammonia in the dissolution tank beforehand, from the viewpoint of preventing precipitated insoluble components from adhering to the mixer, etc. In this case, it is preferable to supply molten dicyanobenzene and liquid ammonia into the dissolution tank and dissolve them, and stirring means may be used if necessary.

[0025] When dissolving dicyanobenzene in liquid ammonia, it is preferable to adjust the pressure and temperature in the dissolution tank so that the solution remains in the liquid phase. For example, the pressure in the dissolution tank is preferably 0.5 to 15 MPa, more preferably 0.7 to 10 MPa, and even more preferably 1 to 8 MPa. The solution temperature in the dissolution tank is preferably 3 to 140°C, more preferably 5 to 120°C, and even more preferably 10 to 100°C.

[0026] (Reactor) The reactor in which the hydrogenation step of this embodiment is carried out is not particularly limited, but examples include fixed-bed reactors, and it is preferable that this step be carried out in a fixed-bed reactor. Fixed-bed reactors include batch type and continuous type fixed-bed reactors, and the continuous type is preferred. When using a continuous type, a circulation method may be used in which a portion of the hydrogenation reaction liquid obtained from the outlet of the hydrogenation reactor is continuously returned to the hydrogenation reactor, or a combination of the circulation method and the one-pass method may be used as described in Japanese Patent Application Publication No. 2008-31155. When using a continuous type, the space velocity of the reaction raw materials (Liquid Hourly Space Velocity = LHSV) is 0.1 to 10 h -1 This is preferable. When carried out in a batch manner, the hydrogenation reaction time is preferably 0.5 to 8 hours.

[0027] (Reaction conditions for the hydrogenation process) The hydrogen used in the hydrogenation process may contain impurities that do not participate in the reaction, such as methane and nitrogen. However, if the impurity concentration is high, it becomes necessary to increase the total reaction pressure in order to secure the required partial pressure of hydrogen, which is industrially disadvantageous. For this reason, a hydrogen concentration of 50 mol% or more is preferred, and 80 mol% or more is more preferred.

[0028] In the hydrogenation step of this embodiment, in order to efficiently produce xylylenediamine, it is essential to increase the rate of hydrogenation of nitrile groups to aminomethyl groups, and it is preferable to select reaction conditions that keep the concentrations of dicyanobenzene and cyanobenzylamine in the reaction solution obtained after the hydrogenation reaction at a low level. Specifically, it is preferable to keep the content of cyanobenzylamine relative to xylylenediamine in the reaction solution obtained after the hydrogenation reaction at 5.0% by mass or less, more preferably at 1.0% by mass or less, and even more preferably at 0.2% by mass or less. Furthermore, the conversion rate of dicyanobenzene is preferably 99.50% or higher, more preferably at 99.90% or higher, and even more preferably at 99.95% or higher.

[0029] The pressure and temperature of the hydrogenation reaction are preferably adjusted so that the solution remains in the liquid phase. The temperature of the hydrogenation reaction is preferably 20 to 200°C, more preferably 30 to 150°C, and even more preferably 40 to 120°C. The hydrogen pressure is preferably 1 to 30 MPa, more preferably 2 to 25 MPa, and even more preferably 3 to 20 MPa.

[0030] (2) Solvent recovery step The manufacturing method of this embodiment includes a solvent recovery step in which liquid ammonia is recovered from the reaction solution by distillation, and the solvent recovery step is performed multiple times. In this step, liquid ammonia is separated from the reaction solution containing xylylenediamine and liquid ammonia by distillation, and the separated liquid ammonia is recovered. The state of the ammonia when recovered may be liquid or gaseous.

[0031] (Distillation) In the solvent recovery step of this embodiment, known distillation methods such as simple distillation, pressurized distillation, fractional distillation, steam distillation, and flash distillation can be used. However, from the viewpoint of finding an excellent balance between reducing energy consumption for solvent removal and reducing the loss of the generated xylylenediamine, flash distillation is preferred among these methods.

[0032] Any distillation apparatus suitable for the above distillation method may be used for the above distillation. Examples of known distillation apparatuses include packed columns, tray columns, and flash drums. However, from the viewpoint of finding an excellent balance between reducing energy consumption for solvent removal and reducing the loss of the generated xylylenediamine, a flash drum is preferred among these.

[0033] The operating pressure and operating temperature conditions in the above distillation are not particularly limited and may be carried out under conditions suitable for the above distillation method. The operating pressure and operating temperature are, for example, preferably 0.1 to 3.0 MPa and 50 to 200°C, more preferably 0.3 to 2.5 MPa and 60 to 180°C, even more preferably 0.4 to 2.2 MPa and 65 to 170°C, and even more preferably 0.5 to 2.0 MPa and 70 to 160°C.

[0034] When distillation is flash distillation, the operating pressure and operating temperature are preferably 0.1 to 3.0 MPa and 50 to 200°C, more preferably 0.3 to 2.5 MPa and 60 to 180°C, even more preferably 0.4 to 2.2 MPa and 65 to 170°C, and even more preferably 0.5 to 2.0 MPa and 70 to 160°C, from the viewpoint of finding an excellent balance between energy reduction for solvent removal and reduction of loss of the generated xylylenediamine.

[0035] The solvent recovery step in this embodiment is performed multiple times. Here, "multiple times" means at least two times, and there is no particular upper limit. That is, this step is performed at least twice: the first solvent recovery step and the final solvent recovery step. By performing the solvent recovery step multiple times, liquid ammonia can be separated and recovered in stages, thereby reducing the loss of xylylenediamine and further reducing the energy used. As a result, there is an excellent balance between energy reduction for solvent removal and reduction of loss of generated xylylenediamine. From the above viewpoint, it is preferable to perform the step 2 to 8 times, more preferably 2 to 6 times, even more preferably 2 to 5 times, and even more preferably 2 to 4 times.

[0036] The above-mentioned effects obtained by performing the solvent recovery step multiple times are more effectively exhibited when the distillation is flash distillation. When the distillation is flash distillation, the solvent recovery step is preferably performed 2 to 8 times, more preferably 2 to 6 times, even more preferably 2 to 5 times, and even more preferably 2 to 4 times.

[0037] In this process, the ammonia separated and recovered can be reused as liquid ammonia used in the hydrogenation process described above, and from the viewpoint of production costs, reuse is preferable.

[0038] More specifically, this will be explained using Figure 1. When the solvent recovery process is performed three times, the reaction solution (A) obtained in the hydrogenation process, which contains xylylenediamine and liquid ammonia, is supplied to the first distillation apparatus 20a. By distillation, some of the liquid ammonia in the reaction solution (A) is separated, and this liquid ammonia is recovered from the top of the first distillation apparatus 20a. The ammonia recovered at this time can be supplied again to the hydrogenation reactor 10 as liquid ammonia and reused. Next, the reaction solution (B) discharged from the first distillation apparatus 20a, from which some of the liquid ammonia in the reaction solution (A) has been separated, is supplied to the second distillation apparatus 20b. By distillation, some of the liquid ammonia in the reaction solution (B) is separated, and this liquid ammonia is recovered from the top of the second distillation apparatus 20b. The ammonia recovered at this time can be supplied again to the hydrogenation reactor 10 as liquid ammonia and reused. Next, the reaction solution (C), from which some of the liquid ammonia in the reaction solution (B) has been separated and discharged from the second distillation apparatus 20b, is supplied to the third distillation apparatus 20c. There, some or all of the liquid ammonia in the reaction solution (C) is separated by distillation, and the liquid ammonia is recovered from the top of the third distillation apparatus 20c. The recovered ammonia can be supplied back to the hydrogenation reactor 10 as liquid ammonia and reused. In this case, the solvent recovery step in the first distillation apparatus 20a, in which liquid ammonia is recovered by distillation, is the first solvent recovery step, and the solvent recovery step in the third distillation apparatus 20c, in which liquid ammonia is recovered by distillation, is the final solvent recovery step. The state of the ammonia when recovered from the top of the distillation apparatus may be liquid or gaseous.

[0039] For example, if the solvent recovery process is performed four times, the reaction solution (D) from which some of the liquid ammonia in the reaction solution (C) has been separated, which is discharged from the third distillation apparatus 20c, is supplied to the fourth distillation apparatus 20d (not shown), where some or all of the liquid ammonia in the reaction solution (D) is separated and recovered by distillation. The same operation is performed for the fifth time and beyond.

[0040] In an example where the solvent recovery process is performed four times, the operating pressure and temperature in the first solvent recovery process are not particularly limited, but are preferably 1.0 to 3.0 MPa and 50 to 100°C, more preferably 1.5 to 2.5 MPa and 55 to 95°C, even more preferably 1.7 to 2.2 MPa and 60 to 90°C, and even more preferably 1.8 to 2.0 MPa and 65 to 85°C. By having the operating pressure and temperature in the first solvent recovery process within the above range, it is possible to suppress losses due to evaporation of xylylenediamine and losses due to thermal alteration of xylylenediamine, and to efficiently distill liquid ammonia. In an example where the solvent recovery process is performed two or three times, it is also preferable that the operating pressure and temperature in the first solvent recovery process be within the above range from the above viewpoint.

[0041] In an example where the solvent recovery process is performed four times, the operating pressure and temperature in the second solvent recovery process are not particularly limited, but are preferably 1.0 to 3.0 MPa and 80 to 150°C, more preferably 1.5 to 2.5 MPa and 85 to 145°C, even more preferably 1.7 to 2.2 MPa and 90 to 140°C, and even more preferably 1.8 to 2.0 MPa and 95 to 135°C. By having the operating pressure and temperature in the second solvent recovery process within the above range, it is possible to suppress losses due to evaporation of xylylenediamine and losses due to thermal alteration of xylylenediamine, and to efficiently distill liquid ammonia. In the example where the solvent recovery process is performed three times, the operating pressure and operating temperature in the second solvent recovery process are, from the above viewpoint, preferably 1.0 to 3.0 MPa and 80 to 150°C, more preferably 1.5 to 2.5 MPa and 85 to 145°C, even more preferably 1.7 to 2.2 MPa and 90 to 140°C, and still more preferably 1.8 to 2.0 MPa and 95 to 135°C.

[0042] In an example where the solvent recovery step is performed four times, the operating pressure and operating temperature in the third solvent recovery step are not particularly limited, but are preferably 1.0 to 3.0 MPa and 80 to 150°C, more preferably 1.5 to 2.5 MPa and 85 to 145°C, still more preferably 1.7 to 2.2 MPa and 90 to 140°C, and even more preferably 1.8 to 2.0 MPa and 95 to 135°C. When the operating pressure and operating temperature in the third solvent recovery step fall within the above ranges, loss caused by evaporation of xylylenediamine and loss caused by thermal deterioration of xylylenediamine can be suppressed, and liquid ammonia tends to be efficiently distilled.

[0043] In an example where the solvent recovery step is performed four times, the operating pressure and operating temperature in the fourth solvent recovery step are not particularly limited, but are preferably 0.1 to 1.0 MPa and 140 to 200°C, more preferably 0.2 to 0.8 MPa and 145 to 180°C, still more preferably 0.3 to 0.7 MPa and 150 to 170°C, and even more preferably 0.4 to 0.6 MPa and 155 to 165°C. When the operating pressure and operating temperature in the fourth solvent recovery step fall within the above ranges, loss caused by evaporation of xylylenediamine and loss caused by thermal deterioration of xylylenediamine can be suppressed, and liquid ammonia tends to be efficiently distilled.

[0044] The operating pressure and operating temperature in the final solvent recovery step are not particularly limited, but are preferably 0.1 to 1.0 MPa and 140 to 200°C, more preferably 0.2 to 0.8 MPa and 145 to 180°C, still more preferably 0.3 to 0.7 MPa and 150 to 170°C, and even more preferably 0.4 to 0.6 MPa and 155 to 165°C. When the operating pressure and operating temperature in the final solvent recovery step fall within the above ranges, the ammonia concentration in the reaction solution tends to be sufficiently reduced while reducing the loss of the produced xylylenediamine. The term "final solvent recovery step" refers to the solvent recovery step that is performed last among multiple solvent recovery steps. For example, when the solvent recovery step is performed twice, it corresponds to the second solvent recovery step, and when the solvent recovery step is performed three times, it corresponds to the third solvent recovery step.

[0045] From the viewpoint of achieving an excellent balance between reduction of energy for solvent removal and reduction of loss of the produced xylylenediamine, it is preferable that the operating pressure in the first solvent recovery step is higher than the operating pressure in the final solvent recovery step.

[0046] From the above viewpoint, when the solvent recovery step is performed twice, it is preferable that the operating pressure in the first solvent recovery step is higher than the operating pressure in the second solvent recovery step. When the solvent recovery step is performed three times, it is preferable that the operating pressure in the first solvent recovery step and the operating pressure in the second solvent recovery step are higher than the operating pressure in the third solvent recovery step. When the solvent recovery step is performed four times, it is preferable that the operating pressure in the first solvent recovery step, the operating pressure in the second solvent recovery step, and the operating pressure in the third solvent recovery step are higher than the operating pressure in the fourth solvent recovery step.

[0047] From the viewpoint of achieving an excellent balance between reduction of energy for solvent removal and reduction of loss of the produced xylylenediamine, it is preferable that the operating temperature in the first solvent recovery step is lower than the operating temperature in the second solvent recovery step.

[0048] From the above viewpoint, when the solvent recovery process is performed twice, it is preferable that the operating temperature in the first solvent recovery process is lower than the operating temperature in the second solvent recovery process. When the solvent recovery process is performed three times, it is preferable that the operating temperature in the first solvent recovery process is lower than the operating temperature in the second solvent recovery process, and that the operating temperature in the second solvent recovery process is lower than the operating temperature in the third solvent recovery process. When the solvent recovery process is performed four times, it is preferable that the operating temperature in the first solvent recovery process is lower than the operating temperature in the second solvent recovery process, and that the operating temperature in the second solvent recovery process is lower than the operating temperature in the third solvent recovery process, and that the operating temperature in the third solvent recovery process is lower than the operating temperature in the fourth solvent recovery process.

[0049] In the solvent recovery step of this embodiment, the ammonia concentration in the reaction solution obtained in the final solvent recovery step is preferably 1.0% by mass or less, and more preferably 0.8% by mass or less, from the viewpoint of achieving an excellent balance between reducing energy for solvent removal and reducing the loss of the generated xylylenediamine. The ammonia concentration in the reaction solution obtained in the final solvent recovery step can be adjusted by the operating pressure and / or operating temperature of the distillation in the solvent recovery step of this embodiment. The ammonia concentration in the reaction solution can be measured by any method such as ion chromatography or capillary electrophoresis.

[0050] (3) Rectification step The manufacturing method of this embodiment may further include a rectification step. The rectification step of this embodiment is a step of rectifying the reaction solution obtained after the final solvent recovery step. That is, it is a step of rectifying the reaction solution containing xylylenediamine obtained after the solvent recovery step, in which the liquid ammonia concentration in the reaction solution is 1.0% by mass or less, in order to obtain xylylenediamine of higher purity. From the viewpoint of obtaining xylylenediamine of higher purity, it is preferable that the manufacturing method of this embodiment includes a rectification step.

[0051] In this embodiment, the rectification process is preferably carried out by distillation, preferably using a distillation column with 2 or more theoretical stages, and more preferably using a distillation column with 5 or more theoretical stages. The operating pressure of the distillation column is preferably 1 to 30 kPa (abs), more preferably 1 to 10 kPa (abs). The temperature at the bottom of the distillation apparatus is preferably 80 to 195°C, more preferably 100 to 185°C.

[0052] (4) Solid-Liquid Separation Step The manufacturing method of this embodiment may further include a solid-liquid separation step. This step is a step of separating the reaction solution into solid and liquid components to remove solid components. The timing of executing the solid-liquid separation step is not particularly limited. For example, if the hydrogenation step is executed twice, the solid-liquid separation (solid-liquid separation step) may be executed between the first and second hydrogenation steps. Alternatively, the manufacturing method of this embodiment may execute the solid-liquid separation step after the solvent recovery step, and then execute the second hydrogenation step. When the solvent recovery step is executed multiple times, for example, the solid-liquid separation step may be included between the first and second solvent recovery steps, but it is preferable that the solvent recovery step be executed multiple times consecutively. When the manufacturing method of this embodiment includes a rectification step and a solid-liquid separation step, it is preferable that the solid-liquid separation step is executed after the solvent recovery step, and then the second hydrogenation step is executed, and the reaction solution obtained from the second hydrogenation step is rectified.

[0053] The solid components in this process are insoluble matter generated in the step preceding the solid-liquid separation process. The main component is thought to be catalyst powder derived from the catalyst used in the fixed-bed reactor. Specifically, the main component is thought to be fine catalyst powder with a particle size of 1 to 500 μm.

[0054] Solid-liquid separation can be carried out using known methods, but adsorption, filtration, or sedimentation separation is preferred, adsorption or filtration is more preferred, and adsorption is even more preferred.

[0055] Adsorption methods include magnetic adsorption and intermolecular force adsorption, with magnetic adsorption being preferred. By using magnetic adsorption, it is possible to efficiently remove catalyst fine particles derived from catalysts using ferromagnetic components such as nickel and cobalt used in the hydrogenation process, thereby obtaining a solution with almost no catalyst fine particles remaining. Magnetic adsorption is preferably performed using a magnetic filter. Regarding the magnetic force of the magnetic filter, it is desirable to select a magnetic force that can remove catalyst fine particles, taking into consideration the size of the magnetic filter and the flow rate of the solution. Specifically, 0.1 to 3 Tesla (T) is preferred, and 0.5 to 2 Tesla (T) is more preferred.

[0056] While there are no particular limitations on the filter used for filtration, filtration using a sintered metal filter is preferred. When using a sintered metal filter, the filter diameter is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 10 μm or less. When the filter diameter of the sintered metal filter is 100 μm or less, fine catalyst particles flowing out from the hydrogenation process can be efficiently removed.

[0057] Methods of sedimentation include static separation and centrifugation.

[0058] The embodiments will be described in more detail below with reference to examples, but the scope of these embodiments is not limited by these examples.

[0059] [Example 1] As shown in Figure 1, a reaction solution (A) with the following composition and temperature is supplied to the flash drum as the first distillation apparatus 20a, and ammonia is separated by distillation under operating temperature of 80°C and operating pressure of 1.9 MPa, and ammonia is recovered from the top of the column. Next, the reaction solution (B) obtained from the bottom of the first flash drum is supplied to the flash drum as the second distillation apparatus 20b, and ammonia is separated by distillation under operating temperature of 130°C and operating pressure of 1.9 MPa, and ammonia is recovered from the top of the column. Next, the reaction solution (C) obtained from the bottom of the second flash drum is supplied to the flash drum as the third distillation apparatus 20c, and ammonia is separated by distillation under operating temperature of 160°C and operating pressure of 0.5 MPa, and ammonia is recovered from the top of the column, and reaction solution (D) is obtained from the bottom of the third flash drum. At this time, in the calculation by the simulation below, the ammonia concentration in reaction solution (D) was set to 0.8 mass%. The loss of metaxylylenediamine escaping from the top of the column during the solvent recovery process, and the total amount of heat generated during the solvent recovery process, are calculated using AVEVA PRO / II Simulation (product name), a simulator from AVEVA Corporation. The loss of metaxylylenediamine due to thermal degradation during the solvent recovery process is calculated based on the simulation results and experimental results. Specifically, the amount of metaxylylenediamine evaporated from the flash drum is obtained through simulation, the flash drum is sized, and the residence time is determined. Then, the amount of metaxylylenediamine that degrades at that residence time and temperature is calculated from the degradation rate of metaxylylenediamine, which is determined separately through experiments. These results are shown in Table 1.

[0060] (Composition of reaction solution (A)) Ammonia: 89.1% by mass Metaxylylenediamine: 10.6% by mass Low boiling point component: 0.1% by mass High boiling point component: 0.2% by mass

[0061] (Temperature of reaction solution (A)) Temperature: 48°C

[0062] [Example 2] The distillation conditions in the second flash drum were set to an operating temperature of 160°C and an operating pressure of 0.5 MPa, and the calculation using the simulator was performed under the same conditions as in Example 1, except that distillation was not performed using the third flash drum. At this time, the ammonia concentration in the reaction solution (C) was set to 0.8% by mass during the calculation using the simulator.

[0063] [Example 3] The distillation conditions in the first flash drum were set to an operating temperature of 70°C and an operating pressure of 1.9 MPa, the distillation conditions in the second flash drum were set to an operating temperature of 100°C and an operating pressure of 1.9 MPa, and the distillation conditions in the third flash drum were set to an operating temperature of 130°C and an operating pressure of 1.9 MPa. Furthermore, the reaction solution (D) obtained from the bottom of the third flash drum was supplied to the flash drum as a fourth distillation apparatus 20d (not shown), and ammonia was distilled and separated under conditions of an operating temperature of 160°C and an operating pressure of 0.5 MPa. The ammonia was recovered from the top of the column, and the reaction solution (E) (not shown) was obtained from the bottom of the fourth flash drum. Except for these conditions, the calculation using the simulator was performed under the same conditions as in Example 1. At this time, the ammonia concentration in the reaction solution (E) was set to 0.8% by mass during the calculation using the simulator.

[0064] [Comparative Example 1] The distillation conditions in the first flash drum were set to an operating temperature of 160°C and an operating pressure of 0.5 MPa, and the calculation using the simulator was performed under the same conditions as in Example 1, except that distillation was not performed in the second and third flash drums. At this time, the ammonia concentration in the reaction solution (B) was set to 0.8% by mass when performing the calculation using the simulator.

[0065] [Comparative Example 2] The calculation using the simulator was performed under the same conditions as in Comparative Example 1, except that a vent condenser (75°C) was installed at the top of the first flash drum.

[0066] [Comparative Example 3] The procedure was the same as in Comparative Example 1, except that distillation was performed using a distillation column (1 theoretical stage, bottom temperature 160°C, 0.5 MPa, temperature of condenser installed at top of column: 9°C) instead of the first flash drum.

[0067] (Regarding the loss of metaxylylenediamine) In Examples 1 to 3 and Comparative Examples 1 to 3, the loss of metaxylylenediamine was evaluated from the total value of the loss of metaxylylenediamine due to vapor partial pressure in the solvent recovery step (2) calculated by the above simulator, and the loss of metaxylylenediamine due to thermal deterioration. The evaluation criteria are as follows. The results are shown in Table 1. <Evaluation Criteria> A: Metaxylylenediamine loss is less than 1.1% by mass. B: Metaxylylenediamine loss is 1.1% by mass or more and 5.0% by mass or less. C: Metaxylylenediamine loss is 5.0% by mass or more.

[0068] (Regarding the total heating ratio) In Examples 1 to 3 and Comparative Examples 1 to 3, the total heating amount in the solvent recovery step (2) calculated using the above simulator was calculated as the ratio of the total heating amount in each example to the total heating amount in Example 1 (total heating ratio). The results are shown in Table 1.

[0069]

[0070] A comparison of Examples 1-3 with Comparative Examples 1-3 demonstrates that the manufacturing method of this embodiment offers an excellent balance between reducing energy consumption for solvent removal and reducing the loss of the generated xylylenediamine.

[0071] Furthermore, a comparison between Example 1 and Example 2 showed that Example 1, in which the solvent recovery process was performed three times, could reduce the loss of generated xylylenediamine more effectively than Example 2, in which the solvent recovery process was performed twice.

[0072] Furthermore, a comparison between Example 1 and Example 3 showed that Example 3, which performed the solvent recovery process four times, reduced the energy required for solvent removal and further reduced the loss of the generated xylylenediamine compared to Example 1, which performed the solvent recovery process three times.

[0073] 10: Hydrogenation reactor, 20a: First distillation apparatus, 20b: Second distillation apparatus, 20c: Third distillation apparatus.

Claims

1. A method for producing xylylenediamine, comprising: a hydrogenation step of hydrogenating dicyanobenzene in the presence of a catalyst and liquid ammonia to obtain a reaction solution containing xylylenediamine; and a solvent recovery step of recovering the liquid ammonia from the reaction solution by distillation, wherein the solvent recovery step is performed multiple times.

2. The method for producing xylylenediamine according to claim 1, wherein the solvent recovery step is performed two to four times.

3. The method for producing xylylenediamine according to claim 1, wherein the distillation is flash distillation.

4. The method for producing xylylenediamine according to claim 3, wherein in the solvent recovery step, the operating pressure is 0.1 to 3.0 MPa and the operating temperature is 50 to 200°C.

5. The method for producing xylylenediamine according to claim 1, wherein the operating temperature in the first solvent recovery step is lower than the operating temperature in the second solvent recovery step.

6. The method for producing xylylenediamine according to claim 1, wherein the operating pressure in the first solvent recovery step is higher than the operating pressure in the last solvent recovery step.

7. The method for producing xylylenediamine according to claim 1, wherein the ammonia concentration in the reaction solution obtained in the final solvent recovery step is 1.0% by mass or less.

8. A method for producing xylylenediamine according to claim 1, further comprising a rectification step.

9. The method for producing xylylenediamine according to claim 1, wherein the hydrogenation step is carried out in a fixed-bed reactor.

10. The method for producing xylylenediamine according to claim 1, wherein the dicyanobenzene contains isophthalonitrile and the xylylenediamine contains metaxylylenediamine.

Images