Metal catalyst and method for hydrogenolysis of cyclic compound using same

Abstract

[Problem] To perform selective hydrogenolysis of a cyclic compound that has a five-membered ring structure and is included in a saturated cyclic compound used as a hydrogen carrier. [Solution] This metal catalyst, which is used in the hydrogenolysis of a cyclic compound that has a five-membered ring structure and is included in a saturated cyclic compound used as a hydrogen carrier, includes a silica-based carrier serving as a catalyst carrier, and cobalt serving as a metal supported on the catalyst carrier.

Description

Metal catalyst and method for hydrogenolysis of cyclic compounds using the same

[0001] The present invention relates to a metal catalyst used in the hydrogenolysis of a cyclic compound having a five-membered ring structure, and a method for hydrogenolysis of a cyclic compound using the same.

[0002] Conventionally, the organic chemical hydride method has been known as a method for storing and transporting hydrogen (see Non-Patent Documents 1 and 2). The organic chemical hydride method involves a hydrogenation reaction (i.e., a hydrogen storage reaction) in which an aromatic compound such as toluene is reacted with hydrogen, and a dehydrogenation reaction (i.e., a hydrogen generation reaction) in which hydrogen is generated from a saturated cyclic compound such as methylcyclohexane (i.e., a hydrogenated aromatic compound) to recover the aromatic compound such as toluene. According to the organic chemical hydride method, the saturated cyclic compound that has absorbed hydrogen can be stored and transported in a liquid state at room temperature and pressure, and the required amount of hydrogen can be extracted at the hydrogen utilization site by a dehydrogenation reaction of the saturated cyclic compound. Saturated cyclic compounds such as methylcyclohexane and aromatic compounds such as toluene that are produced after hydrogen extraction from the saturated cyclic compound can be repeatedly used as hydrogen containers (i.e., hydrogen carriers).

[0003] It is known that the hydrogenation reaction or dehydrogenation reaction in the organic chemical hydride method can produce various by-products (impurities) in addition to the target product (see Patent Document 1).

[0004] Japanese Patent Application Laid-Open No. 2007-269522

[0005] Yoshimi Okada, Energy and Resources, Vol. 33, No. 3, 168 (2018) Yoshimi Okada, Tokyo High Pressure Gas Association Newsletter, August and September 2019 issues; Yuh-hsi Choi, Mika Ishii, Tetsuya Namba, Taku Tsujimura, Takaaki Taniguchi, 46th Petroleum and Petrochemical Symposium, Lecture Proceedings, 2A03 (2016) JP 2007-269522 A

[0006] In the organic chemical hydride method, the proportion of impurities mixed in the hydrogen carrier may gradually increase due to repeated hydrogenation and dehydrogenation reactions. Therefore, it is conceivable to remove (separate) such impurities from the hydrogen carrier by, for example, distilling the hydrogen carrier containing impurities.

[0007] In particular, impurities that may be present in hydrogen carriers include cyclic compounds having a five-membered ring structure, such as cyclopentanes, which are produced in dehydrogenation reactions (hereinafter referred to as five-membered ring compounds) (see Non-Patent Document 3). Because the boiling points of such five-membered ring compounds are relatively close to the boiling point of the hydrogen carrier, it is not easy to separate these five-membered ring compounds from the hydrogen carrier by distillation.

[0008] Therefore, after extensive research, the inventors of the present application have developed a metal catalyst that can selectively hydrocracking five-membered ring compounds mixed in a hydrogen carrier, and have found that as a result, the five-membered ring compounds can be converted into hydrocracking light hydrocarbons from the hydrogen carrier and easily separated.

[0009] In view of the above background, an object of the present invention is to provide a metal catalyst capable of selectively hydrogenolyzing cyclic compounds having a five-membered ring structure contained in saturated cyclic compounds used as hydrogen carriers, and a method for hydrogenolysis of cyclic compounds using the same.

[0010] In order to solve the above-mentioned problems, one aspect of the present invention is a metal catalyst used for the hydrogenolysis of a cyclic compound having a five-membered ring structure contained in a saturated cyclic compound used as a hydrogen carrier, the metal catalyst comprising a silica-based carrier as a catalyst support and cobalt as a metal supported on the catalyst support.

[0011] According to this embodiment, it is possible to selectively hydrolyze a cyclic compound having a five-membered ring structure contained in a saturated cyclic compound used as a hydrogen carrier. In other words, even when a cyclic compound having a five-membered ring structure is hydrolyzed while being mixed with a hydrogen carrier, it is possible to appropriately hydrolyze the compound while suppressing loss of the hydrogen carrier (i.e., unintended chemical reactions).

[0012] In the above embodiment, the metal may contain 1 to 50 wt % cobalt.

[0013] According to this embodiment, an appropriate amount of cobalt is supported on the catalyst support, so that the hydrogenolysis of cyclic compounds having a five-membered ring structure can be carried out stably.

[0014] In the above aspect, the metal may contain 5 wt % or more of cobalt.

[0015] According to this aspect, lighter hydrocarbons with fewer carbon atoms (e.g., C １ -C ５ This effectively increases the selectivity to alkane.

[0016] In the above aspect, the silica-based carrier may contain amorphous silica.

[0017] According to this aspect, lighter hydrocarbons with fewer carbon atoms (e.g., C １ -C ５ This effectively increases the selectivity to alkane.

[0018] In order to solve the above-mentioned problems, one aspect of the present invention is a method for hydrogenolysis of a cyclic compound having a five-membered ring structure contained in a saturated cyclic compound used as a hydrogen carrier, using the above-mentioned metal catalyst, which is configured to produce an aromatic compound and a cyclic compound having a five-membered ring structure as an impurity by a dehydrogenation reaction of the saturated cyclic compound, perform a hydrogenation reaction of the aromatic compound containing the impurity, and perform hydrogenolysis using the metal catalyst on a mixture of the saturated cyclic compound and the impurity produced by the hydrogenation reaction of the aromatic compound.

[0019] According to this aspect, in a system based on an organic chemical hydride method, it becomes possible to selectively hydrogenolyze a cyclic compound having a five-membered ring structure contained in a saturated cyclic compound used as a hydrogen carrier.

[0020] In the above aspect, the hydrogenolysis may be carried out by supplying the mixture of the saturated cyclic compound and the impurities together with 50 to 99.8 mol % of hydrogen to the metal catalyst, the temperature of which is maintained at 150°C to 300°C.

[0021] According to this aspect, by subjecting the mixture of saturated cyclic compounds and impurities to hydrogenolysis together with 50 to 99.8 mol% of hydrogen at an appropriate catalytic temperature, it becomes possible to stably hydrogenolyze cyclic compounds having five-membered ring structures.

[0022] According to the above embodiment, it becomes possible to selectively hydrogenolyze a cyclic compound having a five-membered ring structure contained in a saturated cyclic compound used as a hydrogen carrier.

[0023] Block diagram showing the schematic configuration of a hydrogen storage and transportation system according to an embodiment. Explanatory diagram showing the relationship between by-products in the dehydrogenation reaction of methylcyclohexane and their boiling points. Explanatory diagram of the hydrogenolysis of methylcyclopentane. Explanatory diagram showing the distribution of reaction products in the hydrogenolysis of MCP. Explanatory diagram showing the distribution of reaction products in the hydrogenolysis of MCH. Explanatory diagram showing the distribution of reaction products in the hydrogenolysis of a mixed raw material of MCP and MCH.

[0024] Hereinafter, a metal catalyst according to an embodiment and a method for hydrogenolysis of a cyclic compound having a five-membered ring structure (hereinafter referred to as a five-membered ring compound) using the same will be described with reference to the drawings. Here, an example will be described in which the metal catalyst and the hydrogenolysis method using the same are applied to a hydrogen storage and transportation system 1 based on an organic chemical hydride method, as shown in FIG.

[0025] The hydrogen storage and transportation system 1 includes a hydrogenation plant 2 that generates saturated cyclic compounds as organic hydrides by adding hydrogen to aromatic compounds, and a dehydrogenation plant 3 that generates hydrogen and aromatic compounds by dehydrogenating the saturated cyclic compounds. Here, an example will be described in which methylcyclohexane (abbreviated as "MCH" as necessary) is used as the saturated cyclic compound and toluene (abbreviated as "TOL" as necessary) is used as the aromatic compound.

[0026] The hydrogenation plant 2 converts toluene into hydrogen (H ２ The hydrogenation plant 2 has a hydrogenation reactor 11 that produces methylcyclohexane by carrying out a hydrogenation reaction to add methylcyclohexane (MCH). The hydrogenation plant 2 is equipped with a storage facility 4. The storage facility 4 has an MCH storage tank 12 that stores the methylcyclohexane produced by the hydrogenation reactor 11. The storage facility 4 also has a TOL storage tank 13 that stores toluene transported from the dehydrogenation plant 3 side (i.e., storage facility 5).

[0027] The dehydrogenation plant 3 has a dehydrogenation reactor 21 that produces hydrogen and toluene by dehydrogenating methylcyclohexane based on a known method. The dehydrogenation plant 3 is equipped with a storage facility 5. The storage facility 5 has a TOL storage tank 22 that stores the toluene produced by the dehydrogenation reactor 21. The storage facility 5 also has an MCH storage tank 23 that stores methylcyclohexane transported from the hydrogenation plant 2 side (storage facility 4).

[0028] In the hydrogen storage and transportation system 1, the methylcyclohexane stored in the MCH storage tank 12 is transported to the dehydrogenation plant 3 using known transportation means (such as a ship, vehicle, or pipeline) and stored in the MCH storage tank 23. The methylcyclohexane stored in the MCH storage tank 23 is used in the dehydrogenation reaction in the dehydrogenation reaction apparatus 21. Meanwhile, the toluene stored in the TOL storage tank 22 is transported to the hydrogenation plant 2 using known transportation means and stored in the TOL storage tank 13. The toluene stored in the TOL storage tank 13 is used in the hydrogenation reaction in the hydrogenation reaction apparatus 11. In this way, methylcyclohexane and toluene are repeatedly used as hydrogen containers (hydrogen carriers).

[0029] As shown in Figure 2(A), the dehydrogenation reaction in the dehydrogenation reactor 21 produces by-products including five-membered ring compounds in addition to hydrogen and toluene. Such five-membered ring compounds include dimethylcyclopentanes (e.g., 1,1-dimethylcyclopentane, 1,3-cis-dimethylcyclopentane, 1,3-trans-dimethylcyclopentane, and 1,2-trans-dimethylcyclopentane) and ethylcyclopentane. However, as shown in Figure 2(B), the boiling points of the five-membered ring compounds are relatively close to the boiling points of the hydrogen carriers methylcyclohexane and toluene, making it difficult to separate them from the hydrogen carrier by distillation.

[0030] The five-membered ring compound produced in the dehydrogenation reaction apparatus 21 is stored in a mixed state with toluene in the TOL storage tank 22, and then sent to the hydrogenation plant 2 via the TOL storage tank 13. Therefore, the methylcyclohexane produced in the hydrogenation plant 2 may contain the five-membered ring compound derived from the above-mentioned dehydrogenation reaction as an impurity. This five-membered ring compound is sent back to the dehydrogenation plant 3 in a mixed state with methylcyclohexane, and circulates within the hydrogen storage and transportation system 1. It should be noted that the five-membered ring compound can be produced not only by the dehydrogenation reaction in the dehydrogenation reaction apparatus 21, but also by the hydrogenation reaction in the hydrogenation reaction apparatus 11.

[0031] Therefore, the hydrogen storage and transportation system 1 is equipped with a hydrogen cracking device 6 that performs a hydrogen cracking reaction of the five-membered ring compounds mixed in the hydrogen carrier. The hydrogen cracking device 6 uses a metal catalyst (hereinafter referred to as the "hydrogen cracking catalyst") to selectively hydrogen crack the five-membered ring compounds mixed in methylcyclohexane as impurities, converting them into light chain hydrocarbons.

[0032] The hydrocracker 6 can, for example, extract at least a portion of the hydrogenation reaction product (mainly methylcyclohexane, e.g., 98 wt % or more) produced by the hydrogenation plant 2 as a treatment target before being stored in the storage facility 4, and perform a hydrocracking reaction. In the hydrocracker 6, five-membered ring compounds in the hydrogenation reaction product are decomposed into lighter hydrocarbons (e.g., pentane, hexane, heptane, etc.). In particular, by appropriately selecting the metal used in the hydrocracking catalyst, the five-membered ring compounds can be decomposed into lighter hydrocarbons with fewer carbon atoms (e.g., C １ -C ５ The methylcyclohexane can be decomposed into hydrocarbons (alkanes) which can be removed (i.e., separated) from the methylcyclohexane by distillation or other known processes. The methylcyclohexane, with the five-membered ring compounds removed (or reduced), is recombined with the product of hydrogenation plant 2.

[0033] The target of treatment by the hydrocracker 6 may be methylcyclohexane (containing five-membered ring compounds as impurities) extracted from the MCH storage tank 12 of the storage facility 4. In this case, the methylcyclohexane from which the five-membered ring compounds have been removed by the hydrocracker 6 is returned to the MCH storage tank 12. The hydrocracker 6 may also be connected to a feed line (not shown) for the raw material to the dehydrogenation reactor 21, and may constitute part of the dehydrogenation plant 3.

[0034] Alternatively, the target of treatment by the hydrocracker 6 may be methylcyclohexane (containing five-membered ring compounds as impurities) extracted from the MCH storage tank 23 of the storage facility 5. In this case, the methylcyclohexane from which the five-membered ring compounds have been removed by the hydrocracker 6 is returned to the MCH storage tank 23. The hydrocracker 6 may also be connected to a discharge line (not shown) for the product of the hydrogenation reactor 11, and may constitute a part of the hydrogenation plant 2.

[0035] The hydrocracking apparatus 6 may be, for example, a fixed-bed flow reactor. The hydrocracking apparatus 6 is equipped with a temperature regulator (e.g., an electric heater or a heat exchanger using a heat medium). During the hydrocracking reaction in the hydrocracking apparatus 6, the temperature regulator preferably maintains the temperature of the catalyst layer made of the hydrocracking catalyst within a range of, for example, 150°C to 300°C. The metal catalyst according to this embodiment exhibits good catalytic performance even when the temperature of the catalyst layer is 200°C or lower. The reaction raw materials used in the hydrocracking reaction may contain, for example, a mixture of methylcyclohexane and a five-membered ring compound together with 50 to 99.8 mol% hydrogen.

[0036] The hydrocracking catalyst used in the hydrocracking unit 6 may be, for example, a hydrocracking catalyst containing silica as a catalyst support and cobalt as a metal supported on the catalyst support. The hydrocracking catalyst may contain 1 to 50 wt% (weight %) of cobalt. More preferably, the hydrocracking catalyst may contain 5 wt% or more of cobalt. Amorphous silica may be used as the silica-based catalyst support. However, the silica-based support is not limited to amorphous silica. For example, pure silica zeolites such as silicalite-1, zeolite beta, and high-silica USY (ultra-stable Y) may also be used, as well as ordered mesoporous silicas such as FSM-16, MCM-41, MCM-48, and SBA-15.

[0037] The organic hydride used in the hydrogen storage and transportation system 1 is not limited to the above-mentioned methylcyclohexane, as long as it is an organic compound that reversibly releases hydrogen at least by a catalytic reaction. In the hydrogen storage and transportation system 1, monocyclic hydrogenated aromatic compounds such as methylcyclohexane and cyclohexane, bicyclic hydrogenated aromatic compounds such as tetralin, decalin, and methyldecalin, and tricyclic hydrogenated aromatic compounds such as tetradecahydroanthracene can be used alone or as a mixture of two or more. Regarding toluene obtained by the dehydrogenation reaction of methylcyclohexane, if the organic hydride is changed, a corresponding other aromatic compound can be used.

[0038] Hereinafter, preferred embodiments of the hydrogenolysis catalyst and the method for hydrogenolysis of five-membered ring compounds using the catalyst according to the present invention will be specifically described based on Examples 1 to 4 and Comparative Example 1.

[0039] The above-described hydrocracking unit 6 is premised on the use of a hydrocracking catalyst to hydrocracking five-membered ring compounds that have been mixed as impurities in the product of the hydrogenation reaction in the hydrogenation plant 2 (or that have been produced as by-products of the reaction). The reaction feedstock in the hydrocracking unit 6 (i.e., the target of the hydrocracking reaction) is a mixture of methylcyclohexane, which is produced by the hydrogenation reaction of toluene, and the five-membered ring compounds. In Examples 1-3 and Comparative Example 1, methylcyclopentane (abbreviated as "MCP" as necessary) was used as a model compound for the five-membered ring compounds contained in (i.e., mixed into) the reaction feedstock. In Example 4, a mixed feedstock of MCP and MCH (hereinafter sometimes referred to as "MCP+MCH") was used to more closely resemble reality.

[0040] For example, as shown in Figure 3, in the hydrogenolysis of methylcyclopentane (MCP), the ring of MCP is cleaved at positions (1)-(3), and chain compounds (hexane, 2-methylpentane, 3-methylpentane, etc.) can be produced depending on the position of the cleavage. In addition, these chain compounds can be further decomposed to produce C １ -C ５ Alkanes may be produced. Unlike the five-membered ring compounds, these hydrogenolysis products can be easily separated from methylcyclohexane by distillation or other known processes. Similarly, the hydrogenolysis products of ethylcyclopentane and other five-membered ring compounds can be easily separated from methylcyclohexane.

[0041] Table 1 shows a list of the catalyst samples used in Examples 1 to 4 and Comparative Example 1. As will be described in detail later, Examples 1 to 4 use catalysts in which different amounts of cobalt (Co) are supported on amorphous silica as a catalyst support. In addition, Comparative Example 1 uses a catalyst sample in which platinum (Pt) is supported on a commercially available support described later.

[0042]

[0043] Table 2 shows the reaction materials used in Examples 1-4 and Comparative Example 1.

[0044]

[0045] In Examples 1-3 and Comparative Example 1, the performance of each catalyst sample was evaluated when the reaction raw materials, methylcyclopentane (MCP) as a five-membered ring compound and methylcyclohexane (MCH) as a hydrogen carrier, were each supplied to a reactor together with hydrogen. As shown in Table 2, in Examples 1-3 and Comparative Example 1, when MCP was used as the reaction raw material, the hydrogen / MCP ratio (mol / mol) in the reaction raw material was 28. When MCH was used as the reaction raw material, the hydrogen / MCH ratio (mol / mol) in the reaction raw material was also 28.

[0046] In Example 4, assuming the actual feedstock in the hydrocracking unit 6, a mixed feedstock of 10 mol % methylcyclopentane as a five-membered ring compound and 90 mol % methylcyclohexane as a hydrogen carrier was prepared and fed to the reactor together with hydrogen to evaluate the performance of each catalyst sample. As shown in Table 2, in Example 4, the hydrogen / (MCP+MCH) ratio (mol / mol) in the reaction feedstock was 28.

[0047] In Examples 1-4, cobalt (Co) was used as the active species, which selectively promotes the hydrogenolysis reaction, which cleaves the carbon-carbon bond of a five-membered ring compound in the presence of hydrogen, on the assumption that the hydrogenolysis reaction would be carried out in a mild temperature range, with the catalyst layer temperature at about 200°C. Furthermore, a silica-based material was used as the catalyst support, which does not exhibit solid acidity that could cause side reactions such as isomerization.

[0048] Example 1 Preparation Method of 3.0 wt%-Co / SiO2 Catalyst 0.2294 g of cobalt nitrate hexahydrate (Co(NO3)2·6H2O) and 75 mL of pure water were added to a 300 mL recovery flask and thoroughly dissolved by ultrasonic irradiation. Then, amorphous silica powder (AEROSIL® 380, Nippon Aerosil Co., Ltd., BET specific surface area 380 m) was added as a carrier. 2The catalyst was impregnated onto silica to a Co metal loading of 3.0 wt%. After evaporation to dryness at 40 °C, the recovered product was transferred to an oven and dried overnight at 80 °C. The powder was then pressurized, crushed, and sieved to a particle size of 500–600 μm. For the catalyst reduction, 1.2001 g of the sized catalyst was loaded into a fixed-bed flow system and heated to 400 °C over 30 minutes under nitrogen flow (30 mL / min). The system was then switched to hydrogen flow (30 mL / min) for 1 hour, after which the catalyst was cooled to room temperature while maintaining the hydrogen flow, yielding a 3.0 wt% Co / SiO catalyst.

[0049] Test Method for Performance Evaluation of 3.0 wt%-Co / SiO2 Catalyst [Methylcyclopentane (MCP) Hydrogenolysis Reaction (See Table 2)] The performance evaluation test of the 3.0 wt%-Co / SiO2 catalyst prepared as described above was carried out as follows. Catalyst pretreatment consisted of loading 206.0 mg of 3.0 wt%-Co / SiO2 catalyst into a fixed-bed flow reactor and heating to 400 °C over 30 minutes under nitrogen flow (30 mL / min). The catalyst was then reduced under hydrogen flow (40 mL / min) for 1 hour. After reduction, the MCP hydrogenolysis reaction was carried out under the following conditions: hydrogen flow rate of 40 mL / min, H2 / MCP = 28 mol / mol, W / F (ratio of catalyst mass to MCP flow rate) = 58.81 g-cat.h / mol, reaction temperature of 200 °C, and total pressure of 0.1 MPa. The product was sampled 5 minutes after the start of the hydrogenolysis reaction, and analyzed by FID-GC (flame ionization detector-gas chromatograph) to determine the MCP conversion (%) and the selectivity (C-%) of the reaction product, which were used as indicators of catalyst performance (see Table 3 and Figure 4 below for the results of the performance evaluation test).

[0050] [Methylcyclohexane (MCH) Hydrogenolysis Reaction (See Table 2)] The performance of the 3.0 wt% Co / SiO2 catalyst prepared above was evaluated using the following procedure. Catalyst pretreatment consisted of loading 206.0 mg of the 3.0 wt% Co / SiO2 catalyst into a fixed-bed flow reactor and heating to 400 °C over 30 minutes under nitrogen flow (30 mL / min). The reactor was then switched to hydrogen flow (30 mL / min) for 1 hour for reduction. After reduction, the hydrogenolysis reaction of methylcyclohexane (MCH) was carried out for the specified time under the following conditions: hydrogen flow rate of 40 mL / min, H2 / MCH = 28 mol / mol, W / F (ratio of catalyst mass to MCH flow rate) = 58.77 g-cat.h / mol, reaction temperature of 200 °C, and total pressure of 0.1 MPa. The product was sampled 5 minutes after the start of the hydrogenolysis reaction, and the MCH conversion (%) and the selectivity (C-%) of the reaction product were determined by FID-GC analysis, which were used as indicators of catalyst performance (see Table 3 and Figure 5 below for the results of the performance evaluation test).

[0051] Example 2 Preparation of 5.0 wt%-Co / SiO2 Catalyst 0.3796 g of cobalt nitrate hexahydrate (Co(NO3)2·6H2O) and 75 mL of pure water were added to a 300 mL recovery flask and thoroughly dissolved by ultrasonic irradiation. Then, amorphous silica powder (AEROSIL® 380, Nippon Aerosil Co., Ltd., BET specific surface area 380 m) was added as a carrier. 2 The mixture was impregnated onto silica to a Co metal loading of 5.0 wt%. After evaporation to dryness at 40°C, the recovered product was transferred to an oven and dried overnight at 80°C to obtain a powder. The powder was then pressurized, crushed, and sieved to a size of 500-600 μm. For the catalyst reduction, 1.2026 g of the sized catalyst was loaded into a fixed-bed flow system and heated to 400°C over 30 minutes under nitrogen flow (30 mL / min). The system was then switched to hydrogen flow (30 mL / min) for 5 hours. The system was then cooled to room temperature while maintaining the hydrogen flow, yielding a 5.0 wt% Co / SiO catalyst.

[0052] Test Method for Performance Evaluation of 5.0 wt%-Co / SiO2 Catalyst [Methylcyclopentane (MCP) Hydrogenolysis Reaction (See Table 2)] The performance evaluation test of the 5.0 wt%-Co / SiO2 catalyst prepared as described above was carried out as follows. Catalyst pretreatment consisted of loading 210.0 mg of 5.0 wt%-Co / SiO2 catalyst into a fixed-bed flow reactor and heating to 400 °C over 30 minutes under nitrogen flow (30 mL / min). The catalyst was then reduced under hydrogen flow (40 mL / min) for 1 hour. After reduction, the MCP hydrogenolysis reaction was carried out under the following conditions: hydrogen flow rate of 40 mL / min, H2 / MCP = 28 mol / mol, W / F (ratio of catalyst mass to MCP flow rate) = 59.95 g-cat.h / mol, reaction temperature of 200 °C, and total pressure of 0.1 MPa. The product was sampled 5 minutes after the start of the hydrogenolysis reaction, and the MCP conversion (%) and the selectivity (C-%) of the reaction product were determined by FID-GC analysis, which were used as indicators of catalyst performance (see Table 3 and Figure 4 below for the results of the performance evaluation test).

[0053] [Methylcyclohexane (MCH) Hydrogenolysis Reaction (See Table 2)] The performance of the 5.0 wt% Co / SiO2 catalyst prepared above was evaluated using the following procedure. Catalyst pretreatment consisted of loading 210.0 mg of the 5.0 wt% Co / SiO2 catalyst into a fixed-bed flow reactor and heating to 400 °C over 30 minutes under nitrogen flow (30 mL / min). The reactor was then switched to hydrogen flow (40 mL / min) for 1 hour for reduction. After reduction, the hydrogenolysis reaction of methylcyclohexane (MCH) was carried out for the specified time under the following conditions: hydrogen flow rate of 40 mL / min, H2 / MCH = 28 mol / mol, W / F (ratio of catalyst mass to MCH flow rate) = 59.91 g-cat.h / mol, reaction temperature of 200 °C, and total pressure of 0.1 MPa. The product was sampled 5 minutes after the start of the hydrogenolysis reaction, and the MCH conversion (%) and the selectivity (C-%) of the reaction product were determined by FID-GC analysis, which were used as indicators of catalyst performance (see Table 3 and Figure 5 below for the results of the performance evaluation test).

[0054] Example 3 Preparation of 10 wt%-Co / SiO2 Catalyst 1.4944 g of cobalt nitrate hexahydrate (Co(NO3)2·6H2O) and 150 mL of pure water were added to a 500 mL recovery flask and thoroughly dissolved by ultrasonic irradiation. Then, amorphous silica powder (AEROSIL® 380, Nippon Aerosil Co., Ltd., BET specific surface area 380 m) was added as a carrier. 2 The mixture was impregnated onto silica to achieve a 10 wt% Co metal loading. After evaporation to dryness at 40 °C, the recovered product was transferred to an oven and dried overnight at 80 °C to obtain a powder. The powder was then pressurized, crushed, and sieved to a 500-600 μm particle size. For the catalyst reduction, 1.2753 g of the sized catalyst was loaded into a fixed-bed flow system and heated to 400 °C over 30 minutes under nitrogen flow (30 mL / min). The system was then switched to hydrogen flow (40 mL / min) for 5 hours. The system was then cooled to room temperature while maintaining the hydrogen flow, yielding a 10 wt% Co / SiO catalyst.

[0055] Test Method for Performance Evaluation of 10 wt%-Co / SiO2 Catalyst [Methylcyclopentane (MCP) Hydrogenolysis Reaction (See Table 2)] The performance evaluation test of the 10 wt%-Co / SiO2 catalyst prepared as described above was carried out as follows. Catalyst pretreatment consisted of loading 220.0 mg of 10 wt%-Co / SiO2 catalyst into a fixed-bed flow reactor and heating to 400 °C over 30 minutes under nitrogen flow (30 mL / min). The catalyst was then reduced under hydrogen flow (30 mL / min) for 1 hour. After reduction, the hydrogenolysis reaction of methylcyclopentane (MCP) was carried out for the specified time under the following conditions: hydrogen flow rate of 40 mL / min, H2 / MCP = 28 mol / mol, W / F (ratio of catalyst mass to MCP flow rate) = 62.80 g-cat.h / mol, reaction temperature of 200 °C, and total pressure of 0.1 MPa. The product was sampled 5 minutes after the start of the hydrogenolysis reaction, and the MCP conversion (%) and the selectivity (C-%) of the reaction product were determined by FID-GC analysis, which were used as indicators of catalyst performance (see Table 3 and Figure 4 below for the results of the performance evaluation test).

[0056] [Methylcyclohexane (MCH) Hydrogenolysis Reaction (See Table 2)] The performance of the 10 wt% Co / SiO2 catalyst prepared above was evaluated using the following procedure. Catalyst pretreatment consisted of loading 220.0 mg of the 10 wt% Co / SiO2 catalyst into a fixed-bed flow reactor and heating it to 400 °C over 30 minutes under nitrogen flow (30 mL / min). The reactor was then switched to hydrogen flow (40 mL / min) for 1 hour for reduction. After reduction, the hydrogenolysis reaction of methylcyclohexane (MCH) was carried out for the specified time under the following conditions: hydrogen flow rate of 40 mL / min, H2 / MCH = 28 mol / mol, W / F (ratio of catalyst amount to MCH flow rate) = 62.76 g-cat.h / mol, reaction temperature of 200 °C, and total pressure of 0.1 MPa. The product was sampled 5 minutes after the start of the hydrogenolysis reaction, and the MCH conversion (%) and the selectivity (C-%) of the reaction product were determined by FID-GC analysis, which were used as indicators of catalyst performance (see Table 3 and Figure 5 below for the results of the performance evaluation test).

[0057] Example 4 Preparation of 10 wt%-Co / SiO2 catalyst A 10 wt%-Co / SiO2 catalyst was obtained in the same manner as in Example 3.

[0058] Test method for evaluating the performance of the 10 wt%-Co / SiO2 catalyst [Hydrogenolysis reaction of a mixed feedstock of methylcyclopentane (MCP) and methylcyclohexane (MCH) (see Table 2)] The performance of the 10 wt%-Co / SiO2 catalyst prepared as described above was evaluated using the following procedure. The catalyst was pretreated by loading 220.0 mg of the 10 wt%-Co / SiO2 catalyst into a fixed-bed flow reactor and heating it to 400 °C over 30 minutes under a nitrogen flow (30 mL / min). The flow was then switched to hydrogen flow (40 mL / min) and the reduction treatment was carried out for 1 hour. After the reduction treatment, the hydrogenolysis reaction of a mixture of methylcyclopentane (MCP) and methylcyclohexane (MCH) was carried out for a specified time under the following conditions: hydrogen flow rate of 40 mL / min, H2 / (MCP + MCH) = 28 mol / mol (H2:MCP:MCH = 28:0.1:0.9), W / F (ratio of catalyst amount to (MCP + MCH) flow rate) = 67.95 g-cat.h / mol, reaction temperature of 200°C, and total pressure of 0.1 MPa. Five minutes after the start of the hydrogenolysis reaction, the product was sampled and analyzed by FID-GC to determine the MCP and MCH conversions (%) and the selectivity (C-%) of the reaction products, which were used as indicators of catalyst performance (see Table 4 and Figure 6 below for the results of the performance evaluation test).

[0059] Comparative Example 1 Preparation of 1.0 wt%-Pt / SiO2 Catalyst A commercially available silica-supported platinum catalyst (1.0 wt%-Pt / SiO2) (Sigma-Aldrich, 520691-25G) was used as a catalyst sample (see Table 1).

[0060] Performance Evaluation Test Method for 1.0 wt%-Pt / SiO2 Catalyst [Methylcyclopentane (MCP) Hydrogenolysis Reaction (See Table 2)]. The performance evaluation test for the above-mentioned commercial product (1.0 wt%-Pt / SiO2 catalyst) was carried out as follows. 101.0 mg of 1.0 wt%-Pt / SiO2 catalyst was loaded into a fixed-bed flow reactor and heated to 400 °C over 30 minutes under nitrogen flow (30 mL / min). The catalyst was then reduced under hydrogen flow (40 mL / min) for 1 hour. After reduction, the hydrogenolysis reaction of methylcyclopentane (MCP) was carried out for the specified time under the following conditions: hydrogen flow rate of 40 mL / min, H2 / MCP = 28 mol / mol, W / F (ratio of catalyst mass to MCP flow rate) = 28.83 g-cat.h / mol, reaction temperature of 200 °C, and total pressure of 0.1 MPa. The product was sampled 5 minutes after the start of the hydrogenolysis reaction, and the MCP conversion (%) and the selectivity (C-%) of the reaction product were determined by FID-GC analysis, which were used as indicators of catalyst performance (see Table 3 and Figure 4 below for the results of the performance evaluation test).

[0061] [Methylcyclohexane (MCH) Hydrogenolysis Reaction (See Table 2)] Performance evaluation of the above-mentioned commercially available product (1.0 wt%-Pt / SiO2 catalyst) was performed using the following procedure. Catalyst pretreatment was performed by loading 101.0 mg of 1.0 wt%-Pt / SiO2 catalyst into a fixed-bed flow reactor and heating it to 400 °C over 30 minutes under nitrogen flow (30 mL / min). The reaction was then switched to hydrogen flow (40 mL / min) for 1 hour for reduction. After reduction, the hydrogenolysis reaction of methylcyclohexane (MCH) was performed for the specified time under the following conditions: hydrogen flow rate of 40 mL / min, H2 / MCH = 28 mol / mol, W / F (ratio of catalyst amount to MCH flow rate) = 28.81 g-cat.h / mol, reaction temperature of 200 °C, and total pressure of 0.1 MPa. The product was sampled 5 minutes after the start of the hydrogenolysis reaction, and the MCH conversion (%) and the selectivity (C-%) of the reaction product were determined by FID-GC analysis, which were used as indicators of catalyst performance (see Table 3 and Figure 5 below for the results of the performance evaluation test).

[0062] Table 3 shows the results of the performance evaluation tests for each catalyst in Examples 1-3 and Comparative Example 1. FIG. 4 shows the distribution of reaction products in the hydrogenolysis of MCP in the performance evaluation tests for each catalyst in Examples 1-3 and Comparative Example 1. FIG. 5, like FIG. 4, shows the distribution of reaction products in the hydrogenolysis of MCH in the performance evaluation tests for each catalyst. In the performance evaluation tests for each catalyst, hydrogenolysis reactions were carried out under the same conditions using methylcyclopentane (MCP) and methylcyclohexane (MCH) as the sole reaction raw materials.

[0063]

[0064] As shown in Table 3, in Comparative Example 1 (1.0 wt%-Pt / SiO2 catalyst), when MCP was used as the feedstock, the hydrogenolysis reaction hardly occurred, and the MCP conversion was less than 1%. When MCP was used as the feedstock, the reaction products were the direct ring-opening products n-hexane, 2-methylpentane, and 3-methylpentane, as shown in Figure 4. Also, as shown in Table 3, when MCH was used as the feedstock, the MCH conversion was less than 3%. When MCH was used as the feedstock, the reaction products were all toluene (TOL), as shown in Figure 5.

[0065] According to the results of Comparative Example 1, when platinum was used as the active species supported on silica, activity was exhibited in the dehydrogenation aromatization reaction of cyclohexanes (here, the reaction of producing TOL by dehydrogenation of MCH), but almost no activity was exhibited in the hydrogenolysis reaction of cyclopentanes (here, MCP).

[0066] In contrast, Example 1 (3.0 wt%-Co / SiO2 catalyst) showed activity in the hydrogenolysis reaction of MCP, with a conversion rate of MCP of approximately 2% (see Table 3). When MCP was used as the raw material, the reaction product was C, which is easy to separate in the subsequent process. １ -C ５The proportion of alkanes (i.e., light alkanes with 1-5 carbon atoms) was approximately 20%, and the remainder consisted of the direct ring-opening products n-hexane, 3-methylpentane, and 2-methylpentane, as well as naphthenes cyclopentane and cyclohexane (see Figure 4).When MCH was used as the feedstock, the hydrogenolysis reaction hardly occurred, the MCH conversion was less than 1% (see Table 3), and the reaction product was entirely toluene (TOL) (see Figure 5).

[0067] In Example 2 (5.0 wt% Co / SiO2 catalyst), the activity of the MCP hydrogenolysis reaction was further improved compared to Example 1, and the MCP conversion rate was 20.5% (see Table 3). １ -C ５ The proportion of alkanes accounted for 73.6%, with the remainder consisting of direct ring-opening products (i.e., n-hexane, 2-methylpentane, and 3-methylpentane) and naphthenes (i.e., cyclopentane and cyclohexane) (see Figure 4). When MCH was used as the feedstock, the hydrogenolysis reaction hardly occurred, as in Example 1, and the MCH conversion was less than 1% (see Table 3). When MCH was used as the feedstock, the reaction products were C １ -C ５ The proportion of alkanes was 39% (see Figure 5).

[0068] In Example 3 (10 wt% Co / SiO2 catalyst), the activity of the MCP hydrogenolysis reaction was further improved compared to Examples 1 and 2, and the MCP conversion rate reached 32.7% (see Table 3). １ -C ５ The proportion of alkanes accounted for 76.8%, with the remainder consisting of direct ring-opening products (i.e., n-hexane, 2-methylpentane, and 3-methylpentane) and naphthenes (i.e., cyclopentane and cyclohexane) (see Figure 4). When MCH was used as the feedstock, the hydrogenolysis reaction hardly occurred, as in Examples 1 and 2, and the MCH conversion was less than 1% (see Table 3). When MCH was used as the feedstock, the reaction products were C １ -C ５ The proportion of alkanes was 39% (see Figure 5).

[0069] According to the results of Examples 1-3, cobalt as an active species supported on amorphous silica exhibits high cracking activity and C in the hydrogenolysis reaction of cyclopentanes. １ -C ５ While it showed high selectivity to alkanes, it was found that the activity in the hydrogenolysis of cyclohexanes was low.

[0070] In Examples 1 to 3, examples were shown in which the metal catalyst used in the hydrogenolysis reaction of cyclopentanes (i.e., the hydrogenolysis catalyst) contained 3.0 wt%, 5.0 wt%, and 10 wt% cobalt, respectively, but similar effects can be expected within the range of 1.0 wt% to 50 wt% cobalt. １ -C ５ In order to effectively increase the selectivity to alkanes, the hydrogenolysis catalyst should contain at least 5 wt % of cobalt as an active species.

[0071] In Example 4, the 10 wt%-Co / SiO2 catalyst (Example 3), which showed the best performance in Examples 1-3, was used to carry out the hydrogenolysis reaction of a mixed feedstock of MCP and MCH in order to more closely approximate reality. Table 4 shows the performance evaluation test results for each catalyst in Example 4. Figure 6 shows the distribution of reaction products in the hydrogenolysis of MCP+MCH in relation to the performance evaluation test for each catalyst in Example 4.

[0072]

[0073] As shown in Table 4, in Example 4, the conversion rate of the entire MCP+MCH mixed raw material was 16.6%, of which the conversion rate of MCP was 13.2% and the conversion rate of MCH was 3.4%.

[0074] These results confirmed that, even in a performance evaluation test using MCP+MCH, which is intended for practical application to a hydrogen storage and transportation system 1 as shown in Figure 1, the 10 wt%-Co / SiO2 catalyst suppresses the hydrogenolysis of MCH while highly selectively hydrogenolysis of MCP.

[0075] As shown in FIG. 6, the reaction product was C even when MCP+MCH was used as the raw material. １ -C５ The proportion of alkanes was 58.2%, and it was also confirmed that cracking to light alkanes proceeded with high selectivity.

[0076] As described above, from the results of Examples 1 to 4 (see Tables 3 and 4 and Figures 4 to 6), it was found that the application of a metal catalyst in which cobalt is supported on a silica-based carrier such as amorphous silica enables the highly selective hydrocracking of cyclopentanes contained in methylcyclohexane to light alkanes.

[0077] Although the description of specific embodiments has been completed above, the present invention is not limited to the above-described embodiments and modifications, and can be implemented in a wide variety of modifications. The metal catalysts and the components of the method for hydrogenolysis of cyclic compounds using the same shown in the above-described embodiments are not necessarily all essential, and at least those skilled in the art can select appropriate components without departing from the scope of the present invention.

[0078] For example, the application of the metal catalyst and the method for hydrogenolysis of cyclic compounds using the same according to the present invention is not limited to the hydrogenolysis device 6 provided in the above-described hydrogen storage and transportation system 1. They can be widely applied to hydrogenolysis of cyclic compounds having a five-membered ring structure contained in saturated cyclic compounds.

[0079] 1: Hydrogen storage and transportation system 2: Hydrogenation plant 3: Dehydrogenation plant 4: Storage facility 5: Storage facility 6: Hydrocracking unit 11: Hydrogenation reactor 12: MCH storage tank 13: TOL storage tank 21: Dehydrogenation reactor 22: TOL storage tank 23: MCH storage tank

Claims

1. A metal catalyst used for the hydrolysis of a cyclic compound having a five-membered ring structure contained in a saturated cyclic compound used as a hydrogen carrier, the metal catalyst comprising: a silica-based carrier as a catalyst carrier; and cobalt as a metal supported on the catalyst carrier.

2. The metal catalyst according to claim 1, comprising 1 to 50% by weight of cobalt as said metal.

3. The metal catalyst according to claim 2, containing 5% by weight or more of cobalt as said metal.

4. The metal catalyst according to claim 1 or 2, wherein the silica-based support contains amorphous silica.

5. A method for hydrolysis of a cyclic compound having a five-membered ring structure contained in a saturated cyclic compound used as a hydrogen carrier, using the metal catalyst described in any one of claims 1 to 3, comprising the steps of: producing an aromatic compound and a cyclic compound having a five-membered ring structure as an impurity thereof by a dehydrogenation reaction of the saturated cyclic compound; carrying out a hydrogenation reaction of the aromatic compound containing the impurity; and carrying out hydrolysis of the mixture of the saturated cyclic compound and the impurity produced by the hydrogenation reaction of the aromatic compound using the metal catalyst.

6. The hydrocracking method according to claim 5, wherein the hydrocracking is carried out by supplying the mixture of the saturated cyclic compounds and the impurities together with 50 to 99.8 mol % hydrogen to the metal catalyst, the temperature of the catalyst layer being maintained at 150°C to 300°C.

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