JP2008273778A - Supported catalyst for hydrogenation / dehydrogenation reaction, production method thereof, and hydrogen storage / supply method using the catalyst - Google Patents

Abstract

To increase the reaction rate of hydrogenation or dehydrogenation and use a catalyst for a long time.
SOLUTION: Using a supported catalyst in which platinum and molybdenum carbide or tungsten carbide cover part or all of the surface of a support, a hydrogenation reaction to an aromatic compound or a dehydration of a hydrogenated derivative of the aromatic compound is performed. A hydrogen storage / supply method for performing an elementary reaction is employed.
[Selection figure] None

Description

  The present invention uses a supported catalyst for hydrogenation / dehydrogenation reaction that exhibits catalytic activity in a hydrogenation reaction to an aromatic compound or a dehydrogenation reaction of a hydrogen derivative of an aromatic compound, its production method, and its catalyst. The present invention relates to a hydrogen storage / supply method.

  In recent years, global warming has been regarded as a problem, and fuel cell systems have attracted attention as a clean energy source to replace fossil fuels. Hydrogen fuel is attracting attention as one of the fuels for fuel cell systems. This is because in a fuel cell system using hydrogen fuel as fuel, only water is discharged when power is generated, and therefore, it is attracting attention as an energy source with the smallest environmental load. However, since hydrogen is a gas and a flammable substance at room temperature, there is a problem that it is difficult to store and transport.

  Therefore, a hydrogen storage / supply system that can safely store hydrogen and supply hydrogen with good response as necessary is currently being studied. B. Method of injecting hydrogen into a cylinder and delivering it to each home. A method for obtaining hydrogen from a city gas or propane gas, which is an existing infrastructure, by a method such as steam reforming; A method for obtaining hydrogen by electrolyzing water by night electricity; A method for obtaining hydrogen by electrolyzing water with electric energy obtained from a solar cell or the like; A method for obtaining hydrogen directly from light energy and water by photocatalytic reaction; Methods for obtaining hydrogen using photosynthetic bacteria, anaerobic hydrogen-producing bacteria, and the like have been studied.

  Among these, A. Although it can be easily realized as a hydrogen supply system, since hydrogen gas is flammable, there is a problem in safety and practicality is considered to be low. B. However, there is a problem that the responsiveness of the reformer is not sufficient, although it is realistic in that a gas pipe that has already been provided with a supply pipe can be used. In addition, C.I. ~ F. However, since there is a time lag between the supply side and the demand side, there is a problem in that it cannot follow the load fluctuation caused by fluctuations in power demand.

Therefore, the above-mentioned B. ~ F. In order to realize this method, a hydrogen storage / supply system that temporarily stores the generated hydrogen and supplies the hydrogen to the fuel cell system with good response as necessary has been studied. As specific examples of such a system, a system using a hydrogen storage alloy or a system using a carbon material such as carbon nanotube or carbon nanofiber is disclosed. (For example, see Patent Document 1 and Patent Document 2.)
JP 7-192746 A Japanese Patent Laid-Open No. 5-270801

  However, in the system using the hydrogen storage alloy described above, a simple system that can control the introduction and removal of hydrogen by heat can be constructed, but the hydrogen storage amount per unit weight of the alloy is low, and even in the case of a typical LaNi alloy, The amount of occlusion remains at about 3% by weight. Further, since an alloy is used, there are disadvantages that the weight is large and the price is high.

  In addition, in the system using carbon materials, materials capable of high hydrogen storage are being developed, but they are not yet sufficient, and these materials are difficult to synthesize on an industrial scale, and there are problems with price, None of them has been put to practical use because of the quality of the carbon material obtained.

  Under such circumstances, the present inventors focused on benzene / cyclohexane-based and naphthalene / decalin-tetralin-based hydrocarbons as low-cost, hydrogen storage / supply systems with excellent safety, transportability, and storage capacity, Hydrogen that stores and / or supplies hydrogen using at least one of a hydrogenation reaction of a hydrogen storage body made of an aromatic compound and a dehydrogenation reaction of a hydrogen supply body made of a hydrogenated derivative of the aromatic compound A storage and supply system was proposed. The catalyst used here is platinum, palladium, or the like, but it is necessary to further improve the reaction rate as compared with a system using these metal catalysts.

  Further, the present inventor used a supported catalyst carrying an alloy composed of at least two kinds of metal elements as a catalyst suitable for a hydrogen storage / supply system. Although this supported catalyst makes use of the characteristics of the metal constituting the alloy rather than using a catalyst composed of only one kind of metal, the adhesion of the alloy catalyst is low due to the adverse effects of the crystal structure due to alloying. Alternatively, there is a problem that the alloy catalyst is inactivated and cannot be used for a long time.

  In view of the above, an object of the present invention is to increase the reaction rate of hydrogenation or dehydrogenation and to use the catalyst for a long time in order to solve the above-mentioned problems.

  In order to achieve such an object, the present invention provides a hydrogenation reaction to an aromatic compound or an aromatic compound using a supported catalyst in which platinum and molybdenum carbide or tungsten carbide cover part or all of the surface of a support. This is a hydrogen storage / supply method for performing a dehydrogenation reaction of a hydrogenated derivative of a compound.

  When such a hydrogen storage / supply method is used, hydrogen storage / supply can be performed stably at a high speed for a long time. This is because, in the catalyst containing platinum and molybdenum carbide or tungsten carbide used in this hydrogen storage / supply method, the active sites of molybdenum carbide or tungsten carbide enhance the hydrogenation and dehydrogenation reactions. It is. In addition, platinum supporting force is increased by supporting platinum on molybdenum carbide or tungsten carbide. Therefore, platinum can be highly dispersed. Furthermore, since an alloy is not used as a catalyst, crystal structure instability and inactivation which are problematic when an alloy containing two or more metal elements is used as a catalyst do not occur. Therefore, highly active hydrogenation and dehydrogenation reactions and stable driving for a long time can be realized.

  In another invention, a part or all of the surface of the support is a supported catalyst for hydrogenation / dehydrogenation reaction covered with platinum and molybdenum carbide or tungsten carbide.

  When such a supported catalyst for hydrogenation / dehydrogenation reaction is used, hydrogen storage / supply can be performed stably for a long time and at a high speed for the reasons described above.

  In another invention, the carrier is a supported catalyst for hydrogenation / dehydrogenation reaction, which is a porous body having fine pores.

  When such a supported catalyst for hydrogenation / dehydrogenation reaction is used, higher catalytic ability can be exhibited. This is because the porous body as a support has a high specific surface area, so that an area capable of supporting a catalyst containing platinum and molybdenum carbide or tungsten carbide is increased.

  In another invention, the porous body is a supported catalyst for a hydrogenation / dehydrogenation reaction which is activated carbon, mesoporous silicate, alumina, or alumite.

  When such a supported catalyst for hydrogenation / dehydrogenation reaction is used, higher catalytic ability can be exhibited. Since activated carbon, mesoporous silicate, and porous alumina have a high specific surface area and a unique micro-space structure, the area capable of supporting a catalyst containing platinum and molybdenum carbide or tungsten carbide is increased, and the inside of the micropores is increased. This is because it is difficult to lose the catalyst.

  In another invention, the carrier has alumina having fine pores on the reaction surface, and aluminum, an aluminum alloy, an iron alloy containing aluminum, or aluminum is closely bonded to the surface opposite to the reaction surface. Any one of the above heat-resistant alloys is used as a supported catalyst for hydrogenation / dehydrogenation reaction in which the alumina is closely held.

  When such a supported catalyst for hydrogenation / dehydrogenation reaction is used, the durability of the catalyst at high temperature can be improved. It is durable at high temperature by bonding aluminum, aluminum alloy, aluminum alloy containing aluminum, or heat-resistant alloy with aluminum closely bonded to the surface opposite to the reaction surface. It is for improving.

  In another invention, a supporting step of supporting molybdenum carbide or tungsten carbide on the surface of the support, a platinum precursor supporting step of supporting the platinum precursor on the support by impregnating the support with a platinum salt, and platinum And a reduction step of reducing the support on which the precursor is supported with a reducing agent, and a method for producing a supported catalyst for hydrogenation / dehydrogenation reaction.

  When such a method for producing a hydrogenation / dehydrogenation catalyst is employed, a supported catalyst for hydrogenation / dehydrogenation reaction having high catalytic ability can be produced.

  In another invention, the supporting step includes a precursor supporting step for supporting a molybdenum or tungsten precursor on a support by an impregnation supporting method, and a support on which the precursor is supported on a hydrocarbon or hydrocarbon and hydrogen. The method for producing a supported catalyst for hydrogenation / dehydrogenation reaction, including a carbide step for carbideizing the precursor by heat treatment in a mixed gas atmosphere.

  When such a method for producing a hydrogenation / dehydrogenation catalyst is employed, a supported catalyst for hydrogenation / dehydrogenation reaction having high catalytic ability can be produced at low cost without requiring large facilities.

  In another aspect of the invention, the platinum precursor supporting step is performed simultaneously with the supporting step, or a method for producing a supported catalyst for hydrogenation / dehydrogenation reaction performed after the supporting step.

  When such a method for producing a hydrogenation / dehydrogenation catalyst is employed, a hydrogenation / dehydrogenation catalyst having higher catalytic ability can be produced. This is because the molybdenum precursor, tungsten precursor, molybdenum carbide, or tungsten carbide covers the support surface or supports platinum after that step, so that the platinum is deposited on the molybdenum precursor, tungsten precursor, molybdenum carbide, or tungsten carbide. It can be supported. Further, by supporting platinum on molybdenum carbide or tungsten carbide rather than directly supporting platinum on the carrier, the supporting ability of platinum can be improved and platinum can be highly dispersed.

  According to the present invention, the reaction rate of hydrogenation or dehydrogenation can be increased and the catalyst can be used for a long time.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a supported catalyst for hydrogenation / dehydrogenation reaction, a production method thereof, and a hydrogen storage / supply method using the catalyst according to the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments.

  FIG. 1 is a schematic configuration diagram of a hydrogen storage / hydrogen supply system using a supported catalyst for hydrogenation / dehydrogenation reaction according to an embodiment of the present invention.

  A hydrogen storage / hydrogen supply system 1 shown in FIG. 1 adds hydrogen from the outside to an aromatic compound to store hydrogen as an organic hydride that is a hydrogenated derivative, and dehydrogenates the organic hydride. It is an apparatus that can be decomposed into hydrogen to generate hydrogen and supply it to the outside.

  As the aromatic compound used in the hydrogen storage / hydrogen supply system 1, for example, benzene or toluene is preferably used. Moreover, as an organic hydride which is a hydrogenated derivative, for example, cyclohexane and methylcyclohexane are preferably used.

  A hydrogen storage / hydrogen supply system 1 includes a reactor 2, a tank 3 containing an aromatic compound, a tank 4 containing an organic hydride, and a tank 5 for storing a reaction product generated in the reactor 2. And mainly.

  The reactor 2 includes a heating means (for example, a heater) 6 and a supported catalyst for hydrogenation / dehydrogenation reaction (hereinafter simply referred to as “platinum supported catalyst”) 7 heated by the heating means 6. ing. Above the reactor 2, a pipe 8 for supplying the liquid raw material is disposed so as to penetrate therethrough. A spray nozzle 9 is provided at the tip of the pipe 8 inside the reactor 2, and a valve 10 is provided in the middle of the pipe 8 outside the reactor 2. A three-way valve 12 is provided on the side of the pipe 8 opposite to the spray nozzle 9.

  A pipe 11 connects between the three-way valve 12 and the bottom of the tank 3, and a liquid feed pump 13 is connected in the middle of the pipe 11. The three-way valve 12 and the bottom of the tank 4 are connected by a pipe 14, and a liquid feed pump 15 is connected in the middle of the pipe 14. The three-way valve 12 opens only between the tank 3 and the reactor 2, opens only between the tank 4 and the reactor 2, or closes between the reactor 2 and the tanks 3 and 4. It is a switchable valve.

  A piping 16 for supplying hydrogen passes through the reactor 2. A valve 17 is connected in the middle of the pipe 16. A hydrogen supply means (not shown) is connected to the tip of the pipe 16 outside the reactor 2. The vicinity of the bottom of the reactor 2 and the upper part of the tank 5 are connected by a pipe 18. In the middle of the pipe 18, a pump 19 and a cooler 20 are connected. A pipe 21 for exhausting a gas such as hydrogen is connected above the tank 5.

  When hydrogen is stored in the form of organic hydride, the operation is performed in the following procedure. First, the platinum-supported catalyst 7 is heated using the heating means 6. Next, the valve 17 is opened, and hydrogen is introduced into the reactor 2 via the pipe 16. At this time, it is preferable that the pump 19 is turned on and hydrogen is allowed to flow from the reactor 2 to the outside through the pipe 21. Next, the three-way valve 12 is adjusted to open only the path between the tank 3 and the reactor 2, the liquid feed pump 13 is turned on, and the aromatic compound in the tank 3 is directed to the reactor 2. send. The valve 10 is opened at regular intervals, and the aromatic compound is sprayed from the spray nozzle 9 at regular intervals. Then, a hydrogenation reaction between the sprayed aromatic compound and hydrogen occurs on the surface of the platinum-supported catalyst 7, and organic hydride is generated. The organic hydride enters the tank 5 through the pump 19. The gaseous product passing through the pipe 18 is cooled by the cooler 20 and stored in the tank 5 as a liquid. Since hydrogen is not liquefied even if it is cooled by the cooler 20, it is exhausted to the outside through the pipe 21.

  On the other hand, when hydrogen is generated by dehydrogenation reaction of organic hydride, the operation is performed in the following procedure. First, the platinum-supported catalyst 7 is heated using the heating means 6. Next, the pump 19 is turned on. Only the path between the tank 4 and the reactor 2 is opened through the three-way valve 12, the liquid feed pump 15 is turned on, and the organic hydride in the tank 4 is sent toward the reactor 2. The valve 10 is opened at regular intervals, and the organic hydride is sprayed from the spray nozzle 9 at regular intervals. Hydrogen and an aromatic compound are produced by the dehydrogenation reaction of the sprayed organic hydride on the surface of the platinum-supported catalyst 7. The aromatic compound enters the tank 5 through the pump 19. The gaseous aromatic compound passing through the pipe 18 is cooled by the cooler 20 and stored in the tank 5 as a liquid. Hydrogen is discharged to the outside through the pipe 21.

  As the catalyst carrier used in the platinum-supported catalyst 7 according to the present embodiment, for example, a known carrier such as activated carbon, molecular sieve, zeolite, porous silica, or alumina can be suitably used. Among these, a porous material is preferably used because of its large surface area.

  Examples of porous materials include activated carbon, porous silica, and aluminum oxide (alumina support), as well as alumite support and aluminum made porous by oxidizing the surface of aluminum. A coated dissimilar metal such as a clad material with iron or stainless steel is preferably used.

  Hereinafter, a supported catalyst for supporting platinum and molybdenum carbide or tungsten carbide is used as an example of an alumite support made of aluminum whose surface is coated with porous alumina (hereinafter, including a clad material of a dissimilar metal coated with aluminum). A manufacturing method will be described.

  In the present embodiment, a porous alumina layer is formed on the surface of an aluminum plate by the following steps. First, an anodic oxidation treatment is performed on an aluminum plate to form an anodic oxide film on the surface (anodic oxidation process). Next, the anodic oxide film is immersed in an acidic or alkaline aqueous solution to expand the micropores of the film (a hole expansion step). Next, the acid solution adhering to the porous alumina layer is washed with water (cleaning step) and finally fired (firing step).

  In the anodizing step of the aluminum plate, an oxide film is formed on the surface portion of the aluminum plate. An aluminum plate is used for the anode. A known material can be suitably used for the cathode as long as it is an electrode made of a material that does not dissolve in the electrolyte and has an excellent electron transfer capability. For example, examples of the material for the cathode include carbon and platinum. Further, in order to enhance the electron transfer capability, the electrode shape is coiled or meshed. Then, the anode and the cathode are installed so as to face each other in parallel. A voltage such as AC, DC, AC / DC, pulse high voltage, low voltage, voltage with a different duty ratio, or ramp voltage can be applied to each electrode. Moreover, the voltage value applies the voltage of 1-150V according to ambient temperature or a desired pore diameter.

In the step of expanding the micropores in the oxide film, the anodized aluminum plate is immersed in an acid solution such as oxalic acid or sulfuric acid. Then, the pore walls of the pores in the oxide film are eluted and the pore diameter is enlarged. Further, by adjusting the immersion time in the acid solution, the oxidizing power of the acid solution, the concentration of the acid solution, etc., the pores can be expanded to a predetermined pore size. The immersion time is usually 10 hours or less, and the acid solution can be subjected to pore expansion treatment while keeping an aqueous solution of 2 to 30 wt% at 5 to 35 ° C. Moreover, when a hole expansion is not required, the hole expansion process does not necessarily need to be performed. Thereafter, the acid solution was washed with sufficient water, and subjected to hydrogen reduction treatment at 350 to 500 ° C. in an atmosphere of air, argon, nitrogen or CO ₂ as necessary, thereby making it porous. An aluminum plate (alumite carrier) is obtained.

  Next, as shown in FIG. 2, the surface of the porous alumina layer is coated with molybdenum carbide or tungsten carbide (step S101). As a method for coating the surface of the porous alumina layer with molybdenum carbide or tungsten carbide, RF reactive sputtering using molybdenum or tungsten as a target is preferably used. In addition, after the precursor is supported on the support by a precursor solution containing molybdenum or tungsten, the mixture is mixed in a mixed gas atmosphere of hydrocarbon and hydrogen or in a mixed gas atmosphere of hydrocarbon, hydrogen, and carbon monoxide (hereinafter, “ It is also possible to employ a method of supporting molybdenum or tungsten carbide by heating in a gas atmosphere containing at least hydrocarbons.

  As the sputtering gas used in the RF reactive sputtering method, argon is preferable, but in addition, an inert gas such as helium, neon, or krypton can be used. In particular, when a small amount of helium gas is used in the argon gas, ionization of the gas in the plasma can be promoted. Furthermore, in the present invention, the carbon content in molybdenum carbide can be adjusted by adding a hydrocarbon compound such as methane, ethane, propane, butane, etc. to the sputtering gas.

  In addition, a precursor solution containing molybdenum or tungsten is applied or sprayed, the precursor is supported on the support, and then heated in a gas atmosphere containing at least a hydrocarbon, whereby molybdenum carbide or tungsten carbide is supported on the support. The method of carrying on is performed by the following procedure. Here, an example in which molybdenum carbide is supported on a carrier will be described. First, a solution containing a molybdate such as ammonium molybdate is applied to the surface of the porous alumina layer, and the surface of the porous alumina layer is covered with molybdenum oxide as a precursor. Thereafter, the support covered with molybdenum oxide is heated to 300 to 850 ° C. at a rate of about 0.5 to 20 ° C./min in a gas atmosphere containing at least hydrocarbon. Then, the molybdate is reduced and then carbonized to molybdenum carbide. The molybdate may be any molybdate whose counter ion is not a metal. Usually, the counter ion is an organic compound, ammonium or other ions, and highly available are preferable. In addition, other molybdenum compounds such as molybdenum oxide can be used.

  When molybdenum oxide or tungsten oxide is used, the supported catalyst supporting the metal oxide is 250 ° C. in a hydrocarbon atmosphere such as methane, ethane, propane, or butane or a mixed gas atmosphere of hydrocarbon and hydrogen gas. By raising the temperature stepwise in a temperature range of ˜500 ° C., molybdenum oxide or tungsten oxide can be converted into highly dispersed molybdenum carbide or tungsten carbide, respectively.

  Next, a platinum solution containing platinum is applied to the surface of the porous alumina layer, thereby supporting the platinum precursor on the surface of the porous alumina layer (step S102). The platinum solution used in this step includes hexachloroplatinum (IV) acid hexahydrate, dinitrodiammineplatinum (II) nitric acid solution, hexaammineplatinum (IV) chloride solution or tetraammineplatinum (II) hydrochloride solution (0 Etc.) are preferably used. The platinum solution can be applied to the surface of the porous alumina layer by a method such as dipping, dropping, coating or spraying.

  After the platinum precursor is supported on the carrier, a method of firing at 350 ° C. to 500 ° C., a method of gradually raising the temperature in a temperature range of 100 ° C. to 400 ° C. in a hydrogen gas atmosphere, or hydrazine or boron hydride, etc. The platinum precursor is reduced by a method of reacting with a hydride solution (step S103). In this way, a supported catalyst in which platinum and molybdenum carbide or tungsten carbide are supported on a support can be prepared.

  Although the embodiment of the present invention has been described above, the present invention is not limited to the embodiment and can be implemented with various modifications.

  For example, in the above embodiment, the platinum-supported catalyst for the hydrogenation reaction of the aromatic hydrocarbon / dehydrogenation reaction of the hydrogenated derivative is employed, but it is used to perform only the hydrogenation reaction of the aromatic hydrocarbon. Conversely, it may be used to perform only the dehydrogenation reaction of the hydrogenated derivative (organic hydride).

  Furthermore, in the present embodiment, molybdenum carbide or tungsten carbide completely covers the surface of the carrier, but only a part of the surface of the carrier may be covered with molybdenum carbide or tungsten carbide. Furthermore, each particle of molybdenum carbide or tungsten carbide may be dispersed on the surface of the carrier.

  Further, the method used for coating molybdenum carbide is not limited to the RF reactive sputtering method and the method using a precursor solution. For example, a method in which the temperature is raised stepwise in a temperature range of 250 ° C. to 500 ° C. in a gas atmosphere containing at least a hydrocarbon, a chemical vapor deposition method (CVD), a reactive ion plating method, a reactive vapor deposition method, and a reaction A laser ablation method can also be used.

  Furthermore, in the anodizing process of the aluminum plate, an example of a method for producing an oxide film on the surface of the aluminum plate has been described, but any method may be used as long as it is a method for producing an oxide film.

  In the present embodiment, first, the carrier is loaded with molybdenum carbide or tungsten carbide, and then platinum is loaded. However, platinum may be loaded first, and then molybdenum carbide or tungsten carbide may be loaded. . However, in order to efficiently combine platinum and molybdenum carbide or tungsten carbide, it is preferable to support platinum after supporting molybdenum carbide or tungsten carbide on the carrier. This is because fine molybdenum carbide or the like contributes to the dispersion of platinum, and thus platinum is further dispersed by applying a platinum precursor on the molybdenum carbide or the like. Since platinum is highly dispersed and the supporting force with molybdenum carbide or the like is increased, the catalytic activity is improved and the catalyst life is extended.

  Examples of the present invention will be described below. However, the present invention is not limited to the respective examples.

Test Method In the hydrogenation and dehydrogenation reaction apparatus shown in FIG. 1, cyclohexane or methylcyclohexane was dehydrogenated using the samples of Examples and Comparative Examples described later. The reaction conditions include a set temperature of 320 ° C., a reaction pressure of 0.1 MPaG, a catalyst layer volume of 4.3 ml, a raw material charging rate of 0.15 ml / min, a liquid space velocity of 2.0 h ⁻¹ , and a hydrogen addition amount of 10 ml / min (hydrogen / Oil ratio 0.3 mol / 1 mol). The hydrogen generation rate and the conversion rate of cyclohexane were determined by analysis by gas chromatography. Table 1 shows the hydrogen generation rate, the cyclohexane conversion rate, and the benzene selectivity when the cyclohexane dehydrogenation reaction was performed. Table 2 shows the hydrogen generation rate, the methylcyclohexane conversion rate, and the toluene selectivity when the methylcyclohexane dehydrogenation reaction was performed. Further, Table 3 shows changes in the reaction rate with time when the cyclohexane dehydrogenation reaction was performed.

In addition, the cyclohexane (methylcyclohexane) conversion rate, the benzene (toluene) selectivity, and the hydrogen production rate used in Examples and Comparative Examples were defined as follows.
Cyclohexane (methylcyclohexane) conversion (%) = (number of moles of benzene (toluene) produced / number of moles of raw material cyclohexane (methylcyclohexane)) × 100
Benzene (toluene) selectivity (%) = (number of moles of benzene (toluene) produced / number of moles of raw material cyclohexane (methylcyclohexane)) × 100
Hydrogen production rate (mL / min) = capacity of hydrogen produced per minute Hydrogen production activity (mL / min / g) = capacity of hydrogen produced per minute per 1 g of platinum

Example 1
An aqueous solution of chloroplatinic acid H ₂ PtCl ₆ containing 18 mg of platinum was sprayed onto molybdenum carbide, followed by firing at 350 ° C. for 3 hours in a nitrogen gas atmosphere. Thereafter, the temperature was gradually increased from room temperature to 350 ° C. in a 10% hydrogen atmosphere diluted with nitrogen gas to prepare a 0.5% platinum-supported molybdenum carbide (Pt / Mo ₂ C) catalyst.

Examples 2-5
Activated carbon, mesoporous silicate (FSM-16), silica and alumina were used as the carrier, respectively, and a solution containing ammonium molybdate was applied to the carrier, and then heated at 350 ° C. in an air atmosphere. Then, activated carbon loaded with molybdenum oxide, mesoporous silicate, silica and alumina are mixed in a stepwise manner at a volume ratio of 350 to 500 ° C. in a mixed gas atmosphere of methane (or butane): hydrogen = 1: 10. Molybdenum oxide was converted to molybdenum carbide by heating reaction for a period of time.

Thereafter, each supported catalyst covered with molybdenum carbide was impregnated with a chloroplatinic acid H ₂ PtCl ₆ solution containing 18 mg of platinum, and then dried. Then, each supported catalyst was prepared by performing hydrogen reduction stepwise over 3 hours at 100 to 350 ° C. in a hydrogen gas atmosphere (Examples 2 to 5).

Comparative Example 1
An aqueous solution of chloroplatinic acid H ₂ PtCl ₆ containing 18 mg of platinum was sprayed on activated carbon as a carrier, and then calcined at 350 ° C. for 3 hours under nitrogen gas. Thereafter, in a 10% hydrogen atmosphere diluted with nitrogen gas, the temperature was raised stepwise from room temperature to 350 ° C. to prepare a 0.5% platinum-supported activated carbon (Pt / AC) catalyst (Comparative Example 1).

  As a result of the dehydrogenation reaction of cyclohexane in a nitrogen atmosphere, the catalysts of Examples 1 to 5 in which molybdenum carbide is supported are 6% more than the conventional catalyst in which molybdenum carbide is not supported (Comparative Example 1). The hydrogen generation rate was higher than 12 times.

Example 6
An aluminum plate having a length of 40 mm, a width of 40 mm, and a thickness of 5 mm is used for 7 hours at a current density of 0.5 A / dm ² N using a 4 wt% oxalic acid solution as an electrolyte solution in an environment of 20 ° C. Anodization was performed to obtain an anodized film having a thickness of 50 microns. Thereafter, the substrate was immersed in a 4 wt% oxalic acid solution heated to 20 ° C. for 5 minutes to carry out a hole expansion treatment.

  After washing the acid solution, porous aluminum was obtained by heat treatment at 350 ° C. for 3 hours in an air atmosphere.

  Next, after a solution containing ammonium molybdate was applied to the porous alumina surface of the porous alumite support, it was 350 ° C. in an atmosphere of a mixed gas of butane and hydrogen (butane: hydrogen = 1: 10 by volume). The reaction was carried out for 5 hours, and the support was coated with molybdenum carbide.

Next, an aqueous solution of chloroplatinic acid H ₂ PtCl ₆ containing 18 mg of platinum was sprayed onto a porous alumite support on which molybdenum carbide was supported, and then calcined at 350 ° C. for 3 hours in a nitrogen gas atmosphere. After that, in a 10% hydrogen atmosphere diluted with nitrogen gas, the temperature is raised stepwise from room temperature to 350 ° C., whereby platinum / molybdenum carbide-supported alumite supporting 3 g of platinum per 1 m ² of the surface area of the porous alumite. A catalyst (3 g / m ² Pt / Mo ₂ C / Al ₂ O ₃ / Al) was prepared (Example 6).

Comparative Example 2
Moreover, after spraying a chloroplatinic acid H ₂ PtCl ₆ aqueous solution containing 18 mg of platinum onto the porous alumina surface of the porous alumite support, firing was performed at 350 to 500 ° C. for 3 hours in an air stream. Thereafter, in a 10% hydrogen atmosphere diluted with nitrogen, the temperature is increased stepwise from room temperature to 350 ° C., whereby a platinum supported alumite catalyst supporting 3 g of platinum per 1 m ² of the surface area of the porous alumite (3 g / m ² Pt / Al ₂ O ₃ / Al) was prepared (Comparative Example 2).

  Table 2 shows the results of comparing each hydrogen generation rate, reaction activity and selectivity of the dehydrogenation reaction when the dehydrogenation reaction of methylcyclohexane was performed at 320 ° C. using Comparative Example 2 and Example 6. It was. The platinum / molybdenum carbide-supported alumite catalyst of Example 6 exhibited a hydrogen generation rate and reaction activity approximately 1.5 times higher than when the platinum-supported alumite catalyst of Comparative Example 2 was used. As products other than hydrogen, the presence of a trace amount of methane was confirmed by gas chromatography analysis of the outlet gas.

  FIG. 3 shows a cyclohexane dehydrogenation reaction at 300 ° C. using a conventional supported catalyst (without molybdenum carbide coating) and a supported catalyst according to this example (with molybdenum carbide coating) in a hydrogen atmosphere. Is a graph comparing the time change of each hydrogen generation rate.

  As shown in the graph of FIG. 3, both when the supported catalyst of Comparative Example 1 is used and when the supported catalyst of Example 1 is used, the hydrogen generation rate is stable without decreasing during the test time of 120 minutes. Was.

  The present invention can be used in industries that use hydrogen as a fuel.

1 is a schematic configuration diagram of a hydrogen storage / supply system using a supported catalyst for hydrogenation / dehydrogenation reaction according to an embodiment of the present invention. 2 is a flowchart for explaining a method for producing a supported catalyst for hydrogenation / dehydrogenation reaction shown in FIG. 1. In the Example of this invention, the dehydrogenation reaction of the cyclohexane using each catalyst of Example 1 and Comparative Example 1 is performed for a long time, and it is a graph which compares and shows the time change of each hydrogen generation rate.

Claims (9)

  Platinum and molybdenum carbide or tungsten carbide are used to carry out a hydrogenation reaction to an aromatic compound or a dehydrogenation reaction of a hydrogenated derivative of the aromatic compound using a supported catalyst that covers part or all of the surface of the support. A method for storing / supplying hydrogen, characterized in that: Part or all of the surface of the carrier
A supported catalyst for hydrogenation / dehydrogenation reaction, which is covered with platinum and molybdenum carbide or tungsten carbide.   The supported catalyst for hydrogenation / dehydrogenation reaction according to claim 2, wherein the carrier is a porous body having fine pores.   The supported catalyst for hydrogenation / dehydrogenation reaction according to claim 3, wherein the porous body is activated carbon, mesopore silicate, alumina, or alumite. The carrier has alumina having the fine pores on the reaction surface,
Any one of aluminum, an aluminum alloy, an iron alloy containing aluminum, or a heat-resistant alloy in which aluminum is closely bonded to the surface holds the alumina tightly on the surface opposite to the reaction surface. The supported catalyst for hydrogenation / dehydrogenation reaction according to claim 3, wherein   6. The supported catalyst for hydrogenation / dehydrogenation reaction according to claim 5, wherein the alumina is obtained by converting aluminum on the reaction surface side into alumina having fine pores by anodic oxidation. A supporting step of supporting molybdenum carbide or tungsten carbide on the surface of the carrier;
A platinum precursor supporting step of supporting the platinum precursor on the support by impregnating the support with a platinum salt;
And a reduction step of reducing the support on which the platinum precursor is supported with a reducing agent. A method for producing a supported catalyst for a hydrogenation / dehydrogenation reaction. The carrying step includes
A precursor supporting step of supporting a molybdenum or tungsten precursor on a support by an impregnation supporting method;
The support carrying the precursor is subjected to a heat treatment in a hydrocarbon or a mixed gas atmosphere of hydrocarbon and hydrogen, thereby comprising a carbide step for carbideizing the precursor. The method for producing a supported catalyst for hydrogenation / dehydrogenation reaction according to claim 7.   The method for producing a supported catalyst for hydrogenation / dehydrogenation reaction according to claim 7 or 8, wherein the platinum precursor supporting step is performed simultaneously with the supporting step or after the supporting step.

Images