Dehydrogenation system

Abstract

Provided is a dehydrogenation system which can be suitably achieved even in a facility in which a multitubular heat exchange type reactor is not installed.　The present invention provides a dehydrogenation system for generating hydrogen from a hydrogenated aromatic compound. The dehydrogenation system has adiabatic reactors in a plurality of stages, each of the adiabatic reactors in the plurality of stages being filled with a dehydrogenation catalyst and configured so as to generate hydrogen from a hydrogenated aromatic compound by a dehydrogenation reaction, and the inlet temperature of the hydrogenated aromatic compound in each stage of the adiabatic reactors in the plurality of stages being 500°C or less.

Description

Dehydrogenation System

[0001] The present invention relates to a dehydrogenation system for producing hydrogen from hydrogenated aromatic compounds.

[0002] The dehydrogenation reaction for desorbing hydrogen from a hydrogenated aromatic compound (organic hydride) requires heat, so it is preferable that heat is supplied from an external source during the dehydrogenation reaction.

[0003] Patent Document 1 discloses a technology for carrying out a dehydrogenation reaction in which hydrogen is desorbed from a hydrogenated aromatic compound while heat exchange is being carried out by using a multi-tubular heat exchange reactor as a dehydrogenation reactor.

[0004] Japanese Patent Application Laid-Open No. 2012-206909

[0005] Although dedicated facilities for performing dehydrogenation reactions are often equipped with multi-tubular heat exchanger reactors, such reactors are not always available. Considering the convenience of performing dehydrogenation reactions using various facilities, it is preferable to be able to perform the dehydrogenation reaction suitably without using a multi-tubular heat exchanger reactor.

[0006] The present invention has been made in view of the above circumstances, and provides a dehydrogenation system that can be suitably implemented even in a facility in which a multi-tubular heat exchanger reactor is not installed.

[0007] According to the present invention, the following inventions are provided: [1] A dehydrogenation system for producing hydrogen from a hydrogenated aromatic compound, comprising a multi-stage adiabatic reactor, each of which is filled with a dehydrogenation catalyst and is configured to produce hydrogen from the hydrogenated aromatic compound by a dehydrogenation reaction, and the inlet temperature of the hydrogenated aromatic compound in each stage of the multi-stage adiabatic reactor is 500°C or less. [2] The dehydrogenation system according to [1], further comprising a separation unit, a compressor, and a first circulation unit, wherein the separation unit is configured to separate the product of the multi-stage adiabatic reactor into hydrogen and aromatic compounds by gas-liquid separation, the compressor is configured to compress the hydrogen separated in the separation unit, the first circulation unit is configured to circulate a portion of the hydrogen from the downstream side of the compressor to the upstream side of the multi-stage adiabatic reactor, and the molar flow rate of the hydrogen circulated by the first circulation unit is adjusted to 1 to 10 times the molar flow rate of the hydrogenated aromatic compounds supplied to the multi-stage adiabatic reactor. [3] The dehydrogenation system according to [2], further comprising a distillation apparatus and a second circulation unit, wherein the distillation apparatus is configured to separate unreacted hydrogenated aromatic compounds from the aromatic compounds separated in the separation unit by distillation, and the second circulation unit is configured to circulate the hydrogenated aromatic compounds separated by distillation in the distillation apparatus to the upstream side of the multi-stage adiabatic reactor. [4] The dehydrogenation system according to [2] or [3], wherein the inlet temperature of the hydrogenated aromatic compound in each stage of the multi-stage adiabatic reactor is 470°C or less, the pressure is 0.1 MPaG to 1.0 MPaG, and the molar flow rate of the hydrogen circulated by the first circulation part is adjusted to 3 to 10 times the molar flow rate of the hydrogenated aromatic compound supplied to the multi-stage adiabatic reactor.

[0008] In the dehydrogenation system of the present invention, by arranging multiple adiabatic reactors, it is possible to set a low temperature of the hydrogenated aromatic compound at the inlet of each stage. Adiabatic reactors tend to have a low outlet temperature and a low conversion rate of the hydrogenated aromatic compound because no external heat is supplied during the endothermic reaction. However, by arranging multiple adiabatic reactors, it is easier to prevent the outlet temperature of the final stage from dropping excessively compared to when a single adiabatic reactor is used. Therefore, it is not necessary to set the inlet temperature of the hydrogenated aromatic compound at a high temperature exceeding 500°C in each stage of the multiple adiabatic reactors. As a result, the dehydrogenation system can be suitably implemented even in facilities (e.g., existing oil refineries) that do not have a multi-tubular heat exchanger reactor installed.

[0009] 1 is a diagram showing a schematic configuration of a dehydrogenation system 1. FIG. 2 is a diagram showing a schematic configuration of a dehydrogenation reaction section 2A as a modified example.

[0010] The following describes embodiments of the present invention. The various features shown in the following embodiments can be combined with each other. Furthermore, each feature can be an independent invention.

[0011] <Dehydrogenation Reaction Section 2> As shown in FIG. 1 , a dehydrogenation system 1 according to an embodiment of the present invention includes a dehydrogenation reaction section 2, a gas-liquid separation section 3, and a distillation separation section 4. The dehydrogenation reaction section 2 is configured to produce hydrogen from a hydrogenated aromatic compound (methylcyclohexane in this embodiment). An evaporator (not shown), a superheater (not shown), and the like are disposed upstream of the dehydrogenation reaction section 2. Methylcyclohexane is vaporized in the evaporator and then superheated in the superheater, and then introduced into the dehydrogenation reaction section 2. The dehydrogenation reaction section 2 includes multiple stages (three stages in this embodiment) of adiabatic reactors 21A-21C. Each of the adiabatic reactors 21A-21C is filled with a dehydrogenation catalyst. A known configuration in which a dehydrogenation catalyst is filled in a catalytic reaction vessel lined with thermal insulation can be employed as the adiabatic reactor.

[0012] The dehydrogenation catalyst used in the adiabatic reactors 21A to 21C may be a catalyst in which at least one active metal selected from nickel (Ni), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), and ruthenium (Ru) is supported on a carrier selected from alumina, silica alumina, and silica. More specifically, a catalyst in which at least one active metal selected from nickel (Ni), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), and ruthenium (Ru) is supported on a carrier selected from alumina, silica alumina, and silica (for example, a carrier having a surface area of ​​150 m ２ / g or more, pore volume 0.40 cm ３ The catalyst comprises a porous γ-alumina carrier having a carbon content of 1000 kJ / g or more, an average pore diameter of 40 Å to 300 Å, and pores having an average pore diameter of ±30 Å accounting for 60% or more of the total pore volume, and at least one active metal selected from nickel (Ni), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), and ruthenium (Ru). However, the type of catalyst is not limited to these, and any known catalyst used in the dehydrogenation reaction of organic hydrides can be used.

[0013] The dehydrogenation reaction section 2 includes heating sections 22A to 22C and a heating furnace 23. The heating sections 22A to 22C are configured to heat the methylcyclohexane introduced into the adiabatic reactors 21A to 21C, respectively. The temperature (inlet temperature) of the methylcyclohexane introduced into the adiabatic reactors 21A to 21C is preferably set to 500°C or lower. Specific examples of the inlet temperature of the methylcyclohexane are 400, 410, 420, 430, 440, 450, 460, 470, 480, 490, and 500°C, and may be within a range between any two of the values ​​exemplified here.

[0014] These inlet temperatures are relatively low for introducing methylcyclohexane into an adiabatic reactor. However, because the adiabatic reactor is configured with multiple stages and a dehydrogenation catalyst that functions favorably at relatively low temperatures is utilized, the dehydrogenation reaction of methylcyclohexane can be favorably carried out within this temperature range. Furthermore, since it becomes easier to avoid using the dehydrogenation catalyst at temperatures exceeding its heat resistance temperature, the risk of catalyst performance degradation due to sintering or the like can be easily avoided. Considering the prevention of degradation of the dehydrogenation catalyst, the inlet temperature of the hydrogenated aromatic compound in each of the adiabatic reactors 21A to 21C is preferably 470°C or less. In particular, a range of 430°C to 470°C is even more preferable as the inlet temperature range that simultaneously prevents degradation of the dehydrogenation catalyst and improves the conversion rate of methylcyclohexane. The LHSV (liquid hourly space velocity) is 8 to 48 h －１ The degree is preferable.

[0015] The pressure at the outlet of the adiabatic reactor 21C, which is the final stage, is 0.1 to 1.0 MPaG. Specifically, the pressure at the outlet of the final stage is, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0 MPaG, and may be within a range between any two of the numerical values ​​exemplified here.

[0016] The heating units 22A to 22C are, for example, configured by conduits provided within the heating furnace 23, and are configured to heat the fluid flowing through the conduits by utilizing the heat of the heating furnace 23. The heating furnace 23 can be configured to obtain the desired amount of heat by, for example, burning natural gas. However, other known configurations, such as a configuration using an electric heating wire for heating, can be used as long as the desired amount of heat can be obtained stably. Furthermore, the configuration of the heating units 22A to 22C is not limited to one that directly utilizes the heat of the heating furnace 23 to heat the fluid, and it is also possible to employ a configuration that heats the fluid via a heat medium, for example.

[0017] <Gas-Liquid Separation Section 3> The gas-liquid separation section 3 includes separators 31A to 31D, cooling sections 32A to 32D, and compressors 33A to 33D. Hydrogen, toluene, and unreacted methylcyclohexane are mainly introduced into the gas-liquid separation section 3 from the dehydrogenation reaction section 2 in a gaseous state. The cooling section 32A condenses the toluene and methylcyclohexane by cooling the product of the dehydrogenation reaction section 2. The separator 31A is configured to separate the gas-liquid two-phase fluid that has passed through the cooling section 32A into gas and liquid. Here, the gas phase is hydrogen, and the liquid phase is toluene and methylcyclohexane. The toluene and methylcyclohexane separated in the separator 31A are sent to the distillation separation section 4. Meanwhile, the hydrogen separated in the separator 31A is pressurized (compressed) by the compressor 33A. The hydrogen pressurized by the compressor 33A is sent to the downstream cooling sections 32B to 32D and separators 31B to 31D, but a portion of it is circulated from the branch point 33 to the upstream side of the dehydrogenation reaction section 2 via the first circulation path (first circulation section) 5A.

[0018] The pressure of the hydrogen that has passed through the compressor 33A may be set appropriately according to the pressure of the methylcyclohexane flowing toward the inlet of the adiabatic reactor 21A (for example, about 0.5 to 0.7 MPaG). Because the hydrogen can be pressurized appropriately by the compressor 33A, even if the fluid pressure is reduced by passing through the multiple stages of the adiabatic reactors 21A to 21C, the hydrogen can be circulated without any problems and merged with the fluid upstream of the adiabatic reactor 21A.

[0019] In this manner, the first circulation path 5A is configured to merge a portion of the hydrogen pressurized by the compressor 33A with the methylcyclohexane flowing upstream of the adiabatic reactors 21A-21C. In this case, the molar flow rate of the hydrogen circulated through the first circulation path 5A is preferably adjusted to 1 to 10 times the molar flow rate of the methylcyclohexane supplied to the adiabatic reactor 21A. Specifically, for example, the molar flow rate of hydrogen may be 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 times the molar flow rate of the methylcyclohexane, or may be within a range between any two of the values ​​exemplified here. Increasing the molar flow rate of hydrogen makes it possible to bring the heat contained in the hydrogen into the adiabatic reactors 21A-21C, thereby accelerating the dehydrogenation reaction. Furthermore, circulating a larger amount of hydrogen can be expected to suppress a decrease in the activity of the dehydrogenation catalyst packed in the adiabatic reactors 21A-21C. However, circulating more hydrogen than necessary results in wasted power, so it is preferable to appropriately set an upper limit. In order to prevent deterioration of the dehydrogenation catalyst and improve the conversion rate of methylcyclohexane at the same time, the molar flow rate of hydrogen circulated through the first circulation line 5A is preferably adjusted to 3 to 10 times, and more preferably 5 to 7 times, the molar flow rate of the hydrogenated aromatic compound supplied to the adiabatic reactors 21A to 21C.

[0020] The cooling units 32B to 32D downstream of the compressor 33A are each configured to cool hydrogen whose temperature has increased due to pressurization. The cooling units 32A and 32B to 32D described above may be configured, for example, as water-cooled or air-cooled. However, this is not a limitation, and known temperature control devices, heat transfer devices, and heat dissipation devices may be appropriately employed as long as they are capable of substantially performing the required cooling of the product. For example, a heat exchange system that recovers and uses cold energy available near the dehydrogenation system 1 may be used. The fluids cooled in the cooling units 32B to 32D are separated into gas and liquid in the separators 31B to 31D, respectively. The toluene and methylcyclohexane separated in the separators 31B to 31D are sent to the distillation separation unit 4, along with the toluene and methylcyclohexane separated in the separator 31A.

[0021] Compressors 33B to 33D are configured to compress hydrogen in multiple stages. In this embodiment, the hydrogen that passes through compressor 33D is pressurized to the desired pressure (approximately 3 MPaG in this embodiment). The hydrogen at the desired pressure is then recovered, for example, in a pressure vessel. The number of compressor stages can be set appropriately depending on the number of compressors available in the facility being used. Furthermore, if it is necessary to pressurize the product hydrogen even more, the number of compressor stages can be increased as appropriate in addition to the compressors available in the existing facility. Even in this case, capital investment costs can be reduced compared to installing all new compressors.

[0022] <Distillation Separation Section 4> The distillation separation section 4 includes a distillation column 41 (distillation apparatus). The distillation column 41 is configured to separate unreacted methylcyclohexane by distillation from the toluene separated in the gas-liquid separation section 3. The methylcyclohexane separated by distillation in the distillation column 41 is circulated upstream of the dehydrogenation reaction section 2 via a second circulation path (second circulation section) 5B. The purity of the methylcyclohexane introduced from the distillation column 41 into the second circulation path 5B is preferably about 95% (e.g., 80 to 99 mol%). Since the distillation column 41 allows for the distillation separation of toluene and methylcyclohexane to be performed, and the methylcyclohexane can be recycled, waste of raw materials and the like is unlikely to occur even when a relatively large amount of unreacted methylcyclohexane is generated in the adiabatic reactors 21A to 21C.

[0023] Generally, in a dehydrogenation reaction using an adiabatic reactor, heat cannot be supplied by heat exchange during the reaction, and therefore the purity of the product toluene tends to be lower than when a multi-tubular heat exchange reactor is used. However, in this embodiment, by utilizing the distillation column 41, the purity of the product toluene can be increased as needed. Furthermore, in the distillation column 41, by-products of the dehydrogenation reaction (heavy components, etc.) can also be separated and removed. The separated product toluene can be sent to a storage device or the like and stored, and then circulated to the hydrogenation system by, for example, known transportation means (pipeline, vehicle, ship, etc.). Furthermore, the separated product toluene can be used for other purposes, such as blending with gasoline.

[0024] As described above, in this embodiment, by devising the dehydrogenation reaction conditions, the dehydrogenation system 1 is constructed using relatively general-purpose equipment such as a multi-stage adiabatic reactor, a compressor, and a distillation column. Therefore, for example, it is possible to construct the dehydrogenation system 1 by suitably utilizing devices present in an existing oil refinery facility. Furthermore, it is possible to perform the dehydrogenation reaction by effectively utilizing various existing facilities other than facilities dedicated to performing the dehydrogenation reaction.

[0025] <Modification: Dehydrogenation Reaction Section 2A> In the above-described dehydrogenation reaction section 2, three-stage adiabatic reactors 21A to 21C are used, but the number of stages can be further increased. For example, five-stage adiabatic reactors 21A to 21E are used in the dehydrogenation reaction section 2A. Increasing the number of reactor stages alleviates the disadvantage of adiabatic reactors, namely, the inability to supply heat by heat exchange during the dehydrogenation reaction.

[0026] The number of stages in the adiabatic reactor is preferably 3 or more. Specifically, for example, it may be 3, 4, 5, 6, 7, 8, 9, or 10 stages, or may be within a range between any two of the values ​​exemplified here (e.g., 3 to 10 stages, 4 to 9 stages, etc.). The number of reactor stages can be determined appropriately, taking into consideration the number of adiabatic reactors available in the facility to be utilized.

[0027] Other Embodiments The organic hydride that is the reactant of the dehydrogenation reaction in the dehydrogenation system 1 is not limited to methylcyclohexane, but may be a monocyclic hydrogenated aromatic compound such as cyclohexane, a bicyclic hydrogenated aromatic compound such as tetralin, decalin, or methyldecalin, or a tricyclic hydrogenated aromatic compound such as tetradecahydroanthracene, either singly or as a mixture of two or more of them. Taking into consideration the convenience of storage and transportation, it is preferable to select an organic hydride that can be handled as a stable liquid at room temperature and normal pressure.

[0028] Furthermore, the aromatic compounds generated together with hydrogen in the dehydrogenation reaction of the dehydrogenation system 1 are not limited to toluene, and depending on the type of organic hydride mentioned above, for example, monocyclic aromatic compounds such as benzene and xylene, bicyclic aromatic compounds such as naphthalene, tetralin and methylnaphthalene, and tricyclic aromatic compounds such as anthracene can be used alone or as a mixture of two or more types.

[0029] A dehydrogenation reaction simulation was performed under the following conditions to investigate the conversion rate and outlet temperature of methylcyclohexane in the adiabatic reactors 21A to 21C. The catalyst assumed to be used was a homogeneous alkali-added sulfur-platinum supported alumina catalyst. The alumina support had a surface area of ​​150 m. ２ / g or more, pore volume is 0.40 cm ３ The porous γ-alumina support satisfies the requirements of a pore volume of 1.0 wt % or more, an average pore diameter of 40 Å to 300 Å, and a ratio of pores with an average pore diameter of ±30 Å to the total pore volume of 60% or more. This catalyst contains, for example, 1.0 wt % sulfur, 1.0 wt % platinum dispersed and supported, and 0.4 wt % sodium as an alkali metal in terms of elemental sodium. Regarding the method for producing a homogeneous alkali-added sulfur-platinum-supported alumina catalyst, for example, the method described in paragraphs 0060, 0063, and 0067 of International Publication No. 2021-214954 is applicable, and therefore a detailed description thereof will be omitted here. Using this catalyst, the molar flow rate of hydrogen circulated through the first circulation path 5A is adjusted to six times the molar flow rate of methylcyclohexane supplied to the adiabatic reactor 21A, and the LHSV (liquid hourly space velocity) is adjusted to 48 h －１The conversion rates of methylcyclohexane and the outlet temperatures of the adiabatic reactors 21A to 21C were calculated when a dehydrogenation reaction was carried out under conditions of a pressure of 0.35 MPaG and inlet temperatures of 430°C, 440°C, 450°C, 460°C, and 470°C, respectively.

[0030] This simulation revealed that in the three-stage adiabatic reactors 21A to 21C, the conversion rate of methylcyclohexane increases toward the downstream side, and that a conversion rate of 70% to 90% is expected to be achieved in the third-stage adiabatic reactor 21C.

[0031] It was also found that when three adiabatic reactors 21A to 21C are used instead of one, the outlet temperatures of the adiabatic reactors 21A to 21C do not drop significantly.

[0032] 1: Dehydrogenation system, 2: Dehydrogenation reaction section, 2A: Dehydrogenation reaction section, 3: Gas-liquid separation section, 4: Distillation separation section, 5A: First circulation path, 5B: Second circulation path, 21A: Adiabatic reactor, 21B: Adiabatic reactor, 21C: Adiabatic reactor, 21D: Adiabatic reactor, 21E: Adiabatic reactor, 22A: Heating section, 22B: Heating section, 22C: Heating section, 22D: Heating section, 22E: Heating section, 23: Heating furnace, 31A: Separator, 31B: Separator, 31C: Separator, 31D: Separator, 32A: Cooling section, 32B: Cooling section, 32C: Cooling section, 32D: Cooling section, 33: Branch point, 33A: Compressor, 33B: Compressor, 33C: Compressor, 33D: Compressor, 41: Distillation column

Claims

1. A dehydrogenation system for producing hydrogen from hydrogenated aromatic compounds, comprising a multi-stage adiabatic reactor, each of which is filled with a dehydrogenation catalyst and is configured to produce hydrogen from hydrogenated aromatic compounds by a dehydrogenation reaction, wherein the inlet temperature of the hydrogenated aromatic compounds in each stage of the multi-stage adiabatic reactor is 500°C or less.

2. A dehydrogenation system according to claim 1, further comprising a separation unit, a compressor, and a first circulation unit, wherein the separation unit is configured to separate the product of the multi-stage adiabatic reactor into hydrogen and aromatic compounds by gas-liquid separation, the compressor is configured to compress the hydrogen separated in the separation unit, the first circulation unit is configured to circulate a portion of the hydrogen from the downstream side of the compressor to the upstream side of the multi-stage adiabatic reactor, and the molar flow rate of the hydrogen circulated by the first circulation unit is adjusted to 1 to 10 times the molar flow rate of the hydrogenated aromatic compounds supplied to the multi-stage adiabatic reactor.

3. A dehydrogenation system according to claim 2, further comprising a distillation apparatus and a second circulation section, wherein the distillation apparatus is configured to separate by distillation unreacted hydrogenated aromatic compounds from the aromatic compounds separated in the separation section, and the second circulation section is configured to circulate the hydrogenated aromatic compounds separated by distillation in the distillation apparatus to the upstream side of the multiple-stage adiabatic reactor.

4. A dehydrogenation system according to claim 2 or 3, wherein the inlet temperature of the hydrogenated aromatic compound in each stage of the multi-stage adiabatic reactor is 470°C or less, the pressure is 0.1 MPaG to 1.0 MPaG, and the molar flow rate of the hydrogen circulated by the first circulation section is adjusted to 3 to 10 times the molar flow rate of the hydrogenated aromatic compound supplied to the multi-stage adiabatic reactor.

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