JP2003320251A - Alicyclic compound dehydrogenation catalyst - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst with a high activity capable of promoting dehydrogenation reaction of an alicyclic compound in a low temperature range. <P>SOLUTION: The alicyclic compound dehydrogenation catalyst contains a fibrous activated carbon and at least one kind metal selected from a group consisting of platinum, palladium, rhodium, iridium, ruthenium, nickel, cobalt, iron, copper, silver, and gold. The fibrous activated carbon to be used here has a specific surface area of at least 600 m<SP>2</SP>/g, an entire fine pore volume of at least 0.2 cm<SP>3</SP>/g, and an average fine pore diameter of 10-70 Å. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a dehydrogenation catalyst, and more particularly to an alicyclic compound dehydrogenation catalyst.

[0002]

2. Description of the Related Art Fuel cells, which have been attracting attention as power sources for automobiles and distributed power sources for home use, are fuel cells that use hydrogen as a fuel. In this regard, the development of hydrogen storage materials that enable efficient transport and storage of hydrogen is essential.
As a hydrogen storage material used in a fuel cell, development has been mainly conducted so far mainly on an inorganic metal material such as a hydrogen storage alloy. However, while the inorganic metal material has a large hydrogen storage capacity per volume, the hydrogen storage capacity per weight is not satisfactory.

For this reason, recently, alicyclic compounds have been attracting attention as hydrogen-absorbing substances to replace inorganic metal materials.
For example, tetralin, which is one of alicyclic compounds, becomes naphthalene by dehydrogenation (that is, release of hydrogen) as shown in the following reaction formula, and naphthalene is hydrogenated (that is, hydrogen absorption). ) To return to tetralin.

[0004]

[Chemical 1]

The alicyclic compound has a larger hydrogen storage amount per volume and weight than the inorganic metal material and is advantageous in safety and handling property, but has a problem in energy efficiency in dehydrogenation reaction. . That is, the dehydrogenation reaction of an alicyclic compound proceeds smoothly in a high temperature range, but the dehydrogenation reaction at 200 ° C. required for practical use in a fuel cell
It is difficult to proceed in the low temperature region nearby. Therefore, in order to utilize the alicyclic compound as a hydrogen storage substance, a highly active catalyst that can accelerate the dehydrogenation reaction of the alicyclic compound in a low temperature region is required.

An object of the present invention is to realize a highly active catalyst which can accelerate the dehydrogenation reaction of an alicyclic compound in a low temperature region.

[0007]

The alicyclic compound dehydrogenation catalyst according to the present invention comprises a fibrous activated carbon and platinum, palladium, rhodium, iridium, ruthenium, nickel, cobalt supported on the fibrous activated carbon. , At least one metal selected from the group consisting of iron, copper, silver and gold. The fibrous activated carbon used here has, for example, a specific surface area of at least 600 m ² / g, a total pore volume of at least 0.2 cm ³ / g and an average pore diameter of 1
It is from 0 to 70 angstroms. Further, in this dehydrogenation catalyst, usually, 0.5 to 10 g of the above metal is supported per 100 g of fibrous activated carbon.

Further, the alicyclic compound dehydrogenation catalyst according to another aspect of the present invention has a specific surface area of at least 600 m ² /
g, a total pore volume of at least 0.2 cm ³ / g and an average pore diameter of 10 to 70 angstrom, and platinum, palladium, rhodium, iridium, ruthenium, nickel, cobalt, iron supported on the carrier. ,copper,
And at least one metal selected from the group consisting of silver and gold.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The alicyclic compound dehydrogenation catalyst according to the present invention comprises a carrier on which a metal functioning as a catalyst component is supported in a dispersed state. The carrier used here has a large specific surface area, can support a metal in a highly dispersed state, and has a pore diameter set to a size capable of adsorbing an alicyclic compound.

As such a carrier, it is usually preferable to use fibrous activated carbon. Available fibrous activated carbons include, for example, pitch-based fibrous activated carbon, polyacrylonitrile-based fibrous activated carbon, rayon-based fibrous activated carbon, cellulose-based fibrous activated carbon, phenol-based fibrous activated carbon and lignin-poval-based fibrous activated carbon. A fiber material obtained by melt spinning a carbon material is subjected to infusibilization treatment and activation treatment to form pores. That is, the fibrous activated carbon that can be used here has a micropore structure or mesopore structure on the surface that allows the alicyclic compound that is a reaction product to easily reach or desorb the metal-supporting portion described below. Among the above-mentioned fibrous activated carbons, the pitch-based fibrous activated carbon is preferable because it is easy to achieve various physical properties described later and is inexpensive. Further, two or more kinds of the above fibrous activated carbon may be used in combination.

The specific surface area of the fibrous activated carbon is at least 6
00 m ² / g (that is, 600 m ² / g or more) is preferable. When the specific surface area is less than 600 m ² / g, the amount of metal supported on the fibrous activated carbon becomes small, and as a result, it may be difficult to realize a highly active dehydrogenation catalyst. Incidentally, the specific surface area here is B based on the adsorption isotherm of nitrogen.
It is a value obtained according to the ET method. The specific surface area is usually most preferably in the range of 600 to 2,100 m ² / g. If it exceeds 2,100 m ² / g, the strength of the fibrous activated carbon may decrease.

The total pore volume of the fibrous activated carbon is preferably at least 0.2 cm ³ / g (that is, 0.2 cm ³ / g or more). When the total pore volume is less than 0.2 cm ³ / g, effective adsorption and desorption of the alicyclic compound in the pores are less likely to occur, and as a result, the dehydrogenation catalyst of the present invention is used. It may be difficult to accelerate the dehydrogenation reaction of the alicyclic compound while suppressing the amount. Incidentally, the total pore volume here is a value obtained by the low temperature nitrogen adsorption method.

Further, the average pore diameter of the fibrous activated carbon is
Size of alicyclic compound (for example, the maximum width of cyclohexane molecule is 5.6Å in the horizontal direction, 4.9Å in the vertical direction; the maximum width of decalin molecule is 7.4Å, 6.6Å in the horizontal direction, and the vertical direction is in the vertical direction). 5.6Å; the maximum width of the tetralin molecule is preferably 7.8Å, the transverse direction is 7.4Å, and the longitudinal direction is 5.6Å), and the size is preferably 10 to 70 angstroms. Incidentally, the average pore diameter here is a value obtained by the low temperature nitrogen adsorption method.

Physical properties such as the specific surface area, the total pore volume and the average pore diameter as described above in the fibrous activated carbon are usually
This can be achieved by appropriately adjusting the infusibilizing treatment condition and the activating treatment condition for the fiber material used for producing the above-mentioned fibrous activated carbon.

Incidentally, the fibrous activated carbon may be set in, for example, a felt shape or a honeycomb shape. Since the fibrous activated carbon formed in a felt shape or a honeycomb shape can enhance the contact efficiency with the alicyclic compound, the dehydrogenation catalyst of the present invention using such fibrous activated carbon as a carrier is The dehydrogenation reaction of the cyclic compound can be promoted more effectively.

When the fibrous activated carbon is set in a felt shape, the above-mentioned fibrous activated carbon is entangled with a plane net made of a material such as glass fiber by, for example, the needle punch method. On the other hand, when the fibrous activated carbon is set in a honeycomb shape, a mixture of the fibrous activated carbon and a binder such as an acrylic copolymer aqueous emulsion is prepared, and the mixture is formed into a sheet. Then, the sheet-like material thus obtained is formed into a honeycomb shape by a method such as cardboard forming.

The carrier used in the present invention has a physical property capable of supporting a metal described below in a highly dispersed state, for example, one having the above-described specific surface area, total pore volume and average pore diameter. As long as it is other than fibrous activated carbon, fibrous activated carbon may be used.

On the other hand, the metal constituting the dehydrogenation catalyst of the present invention functions as a catalyst component, and includes platinum, palladium, rhodium, iridium, ruthenium, nickel,
It is a simple substance of an element selected from the group of metallic elements consisting of cobalt, iron, copper, silver and gold. Two or more kinds of these metals may be used in combination. However, when using two or more kinds of metals, it is preferable to use at least one of the metals of the first group consisting of platinum, palladium, rhodium, iridium, ruthenium and nickel. That is, the metals of the second group consisting of cobalt, iron, copper, silver and gold are preferably used in combination with the metal selected from the first group, rather than used alone. When the metal included in the first group is not used, the dehydrogenation catalyst of the present invention may have insufficient activity. Note that a particularly preferable combination of the metals of the first group is a combination of palladium and rhodium because it exhibits high activity.

It is generally preferable that the above-mentioned metal is supported by being dispersed in the form of fine particles on a carrier. The above-mentioned metal is preferably carried in an amount of 0.5 to 10 g per 100 g of the carrier, more preferably 1 to 3 g. If the amount of metal supported is less than 0.5 g, the activity of the catalyst of the present invention may be extremely reduced. Conversely, 10
If it exceeds g, the cost of the catalyst increases and it is not economical. In addition, the metal may easily fall off the carrier.

The dehydrogenation catalyst of the present invention can be produced by supporting the above metal on the above carrier. As a method for supporting the metal on the carrier, various known methods, for example, a method of dispersing an organometallic complex using the above metal in an aqueous dispersion of the carrier, an impregnation method, a precipitation method, ion exchange The law etc. can be adopted. However, in order to support the above-mentioned fine-particle metal in a highly dispersed state on the carrier, it is generally preferable to adopt the impregnation method.

The dehydrogenation catalyst of the present invention is used to accelerate the dehydrogenation reaction of an alicyclic compound. The alicyclic compound to which the dehydrogenation catalyst of the present invention can be applied is not particularly limited, and examples thereof include monocyclic hydrocarbons such as cyclohexane and its methyl compound, tetralin, decalin and their methyl compounds. Mention may be made of fused bicyclic hydrocarbons as well as fused tricyclic hydrocarbons such as perhydroanthracene. When this dehydrogenation catalyst is used in a hydrogen supply source of a fuel cell, a fused polycyclic hydrocarbon having 3 or more rings has a high melting point and is not easy to handle. Therefore, the alicyclic compound is a monocyclic hydrocarbon. It is preferred to use condensed bicyclic hydrocarbons or mixtures thereof.

When the dehydrogenation reaction of the alicyclic compound is carried out using the dehydrogenation catalyst of the present invention, the alicyclic compound is heated in the presence of the dehydrogenation catalyst. At this time, the alicyclic compound is rapidly and efficiently dehydrogenated by the action of the metal supported in a dispersed state on the carrier of the dehydrogenation catalyst. In particular, when this dehydrogenation catalyst is used, compared to the case where a metal such as platinum or palladium is directly used as the dehydrogenation catalyst,
The dehydrogenation reaction of an alicyclic compound can be remarkably promoted in a low temperature range of about 200 ° C.

[0023]

Examples Examples 1 to 4 (palladium-supporting fibrous activated carbon)
Production of) In a 200 ml eggplant-shaped flask, 15 ml of 0.1N hydrochloric acid aqueous solution and 50 mg of PdCl ₂ (30 m in terms of Pd metal)
g) was added and stirred at 80 ° C. for 30 minutes to prepare a uniform solution. 25 ml of 0.1N hydrochloric acid solution
And 970 mg of fibrous activated carbon having the properties shown in Table 1 were added and stirred for 3 hours to adsorb PdCl ₂ on the fibrous activated carbon. Then, to this solution, 0.12 ml of 37% formalin solution was added and subjected to a reduction treatment for 30 minutes, further cooled to room temperature, and an aqueous sodium hydroxide solution was added for neutralization. The palladium-supported fibrous activated carbon (dehydrogenation catalyst) thus obtained was separated by suction filtration and washed several times with deionized water. The dehydrogenation catalyst obtained was 1 mmH.
It was dried at 100 ° C. for 3 hours under a reduced pressure of g. Table 1 shows the amount of palladium contained in the dehydrogenation catalyst. This amount of palladium is a value obtained by a gravimetric method.

Comparative Example 1 (Production of Palladium-Supported Granular Activated Carbon
Concrete) Proceeding as in the case of, except for using the granular activated carbon of Examples 1 to 4 having properties shown in Table 1 in place of the fibrous activated carbon to produce a palladium granular activated carbon (dehydrogenation catalyst). Table 1 shows the amount of palladium contained in the dehydrogenation catalyst. This amount of palladium is a value obtained in the same manner as in Examples 1 to 4.

Evaluation 1 The dehydrogenation catalysts obtained in Examples 1 to 4 and Comparative Example 1 were individually added to 8 ml of tetralin and the mixture was heated to 2 with a mantle heater.
Heated to 20 ° C. The addition amount of the dehydrogenation catalyst was set to 0.007 to 0.015 mmol in terms of palladium.

FIG. 1 shows the results of examining changes in the integrated value of the TON value (turnover number) during heating. In addition,
The TON value is a value obtained by dividing the amount of hydrogen produced (mmol) by the amount of metal in the dehydrogenation catalyst (here, the amount of palladium) (mmol). The larger the value, the more the dehydrogenation reaction is promoted. There is. According to FIG. 1, the dehydrogenation catalysts of Examples 1 to 4 in which fibrous activated carbon was used as a carrier showed higher dehydrogenation activity for tetralin than the dehydrogenation catalyst of Comparative Example 1 in which granular activated carbon was used as a carrier. I understand. Further, comparing the results of Examples 1 to 4, it can be seen that the activity increases as the specific surface area of the fibrous activated carbon used as the carrier increases. By the way, when comparing Example 2 and Example 3 in which the specific surface areas of the fibrous activated carbons are close to each other, the initial activity is somewhat higher in Example 2, but Example 2 after 2 hours has elapsed after the start of heating. It can be seen that is more active. This is because the total pore volume and the average pore diameter of the fibrous activated carbon are greatly different between Example 2 and Example 3, and the pore distribution state of the fibrous activated carbon is different, so that the dispersion of the palladium fine particles on the fibrous activated carbon is performed. This is probably because the states are different.

Examples 5 to 7 (Production of platinum-supported fibrous activated carbon
Manufacturing) 50 ml of deionized water in a 100 ml three-necked flask, 970 mg of fibrous activated carbon having the properties shown in Table 1 and H ₂ Pt
80 mg of Cl ₆ .6H ₂ O (30 mg in terms of Pt metal) was added, and the mixture was stirred at 80 ° C. for 2 hours. After cooling this to room temperature, 163 mg of Na ₂ CO ₃ was added for neutralization. Then, the inside of the flask was once set to a nitrogen atmosphere, then set to a hydrogen atmosphere, and stirred at room temperature for 16 hours to carry out a reduction treatment. The platinum-supported fibrous activated carbon (dehydrogenation catalyst) thus obtained was separated by suction filtration and washed several times with deionized water. The obtained dehydrogenation catalyst was dried at 100 ° C. for 3 hours under a reduced pressure of 1 mmHg. Table 1 shows the amount of platinum contained in the dehydrogenation catalyst. The amount of platinum is determined by the atomic absorption method.

Example 8 (Production of platinum-supporting fibrous activated carbon) In a 100 ml three-necked flask, 50 ml of deionized water, 970 mg of fibrous activated carbon having the properties shown in Table 1 and H ₂ Pt.
80 mg of Cl ₆ .6H ₂ O (30 mg in terms of Pt metal) was added, and the mixture was stirred at 80 ° C. for 2 hours. After cooling this to room temperature, 163 mg of Na ₂ CO ₃ was added for neutralization, 77 mg of hydrazine monohydrate was further added, and the mixture was stirred at 50 ° C. for 2 hours. After cooling the contents of the flask to room temperature, the obtained platinum-supported fibrous activated carbon (dehydrogenation catalyst) was separated by suction filtration and washed several times with deionized water. The obtained dehydrogenation catalyst was dried at 100 ° C. for 3 hours under a reduced pressure of 1 mmHg. Table 1 shows the amount of platinum contained in the dehydrogenation catalyst. This platinum amount was examined in the same manner as in Examples 5-7.

Evaluation 2 The dehydrogenation catalysts obtained in Examples 5 to 8 were individually added to 8 ml of tetralin and heated to 220 ° C. with a mantle heater. The amount of dehydrogenation catalyst added was 0.00 in terms of platinum.
It was set to 7 to 0.015 mmol.

FIG. 2 shows the result of examining the change in the integrated value of the TON value (turnover number) during heating. In FIG. 2, comparing Example 7 and Example 8 using the fibrous activated carbon having the same properties, the T of Example 8 is higher than that of Example 7.
It can be seen that the ON value is decreasing. From this, in the production process of the dehydrogenation catalyst of the present invention, the reduction activation method under hydrogen atmosphere (Example 7) is more active than the reduction activation method using hydrazine (Example 8). It can be seen that a high dehydrogenation catalyst can be produced.

Example 9 Using the fibrous activated carbon having the properties shown in Table 1, a palladium-supported fibrous activated carbon (dehydrogenation catalyst) was obtained in the same manner as in Examples 1 to 4. Table 1 shows the amount of palladium contained in this dehydrogenation catalyst. The amount of palladium is obtained in the same manner as in Examples 1 to 4.

Evaluation 3 A flow reactor as shown in FIG. 3 was produced. In the figure, a flow reactor 1 comprises a glass tube flow fixed bed reactor 2 having an inner diameter of 9.5 mm. This flow type fixed bed reactor 2 is filled with 0.004 mmol of the dehydrogenation catalyst obtained in Example 9 in terms of palladium,
One end of a gas supply path 4 having a gas flow rate controller 3 is connected to one end. A nitrogen gas supply device 5 such as a nitrogen gas cylinder is connected to the other end of the gas supply path 4. Further, one end of a sample supply path 7 equipped with a metering pump 6 is connected to the same end of the flow type fixed bed reactor 2. The sample supply path 7 is for supplying tetralin to be dehydrogenated to the flow type fixed bed reactor 2. From the other end of the flow type fixed bed reactor 2 is extended an analytical sample supply passage 9 connected to a gas chromatography 8 equipped with an FID as a detector. The analytical sample supply path 9 is provided with a cooling trap 10, and the cooling trap 10 has a gas meter 11.

Dehydrogenation treatment of tetralin was carried out using the flow reactor 1 described above. Here, tetralin is supplied to the flow type fixed bed reactor 2 at a rate of 2.0 ml / hour, and nitrogen gas is supplied to the flow type fixed bed reactor 2 from the nitrogen gas supply device 5 at a rate of 10 ml / min. It was supplied as a carrier gas. The dehydrogenation reaction conditions in the flow type fixed bed reactor 2 were set to normal pressure and 300 ° C. Further, the analysis sample containing tetralin and naphthalene from the flow type fixed bed reactor 2 cooled in the cooling trap 10 is supplied to the gas chromatography 8 through the analysis sample supply passage 9 for quantitative analysis, and by the gas meter 11. The flow rates of nitrogen gas and hydrogen gas were measured. Then, based on these results, the relationship between the reaction time and the integrated value of the TON value (turnover number) was examined.

Further, the batch reactor using the flask and the dehydrogenation catalyst obtained in Example 9 were used to dehydrogenate tetralin. Here, 8 ml of tetralin and a dehydrogenation catalyst (0.004 in terms of palladium) were added to the batch reactor.
And 30) using a mantle heater.
Heated to 0 ° C. And heating time (reaction time) and TO
The relationship between the N value (turnover number) and the integrated value was examined.

The above results are shown in Table 2 and FIG. From this result, it can be seen that a higher TON value can be obtained when the flow type fixed bed reactor is used than when the batch type reactor is used. From this, it can be seen that the dehydrogenation reaction using the dehydrogenation catalyst of Example 9 is more likely to proceed using the flow type fixed bed reactor than using the batch type reactor. This is because desorption of the dehydrogenated reaction product from the dehydrogenation catalyst is promoted in the flow type fixed bed reactor.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

Since the dehydrogenation catalyst of the present invention has a specific metal supported on fibrous activated carbon, it can accelerate the dehydrogenation reaction of an alicyclic compound in a low temperature range.

Further, a dehydrogenation catalyst according to another aspect of the present invention is one in which a specific metal is supported on a carrier whose specific surface area, total pore volume and average pore diameter are set within predetermined ranges. Therefore, the dehydrogenation reaction of the alicyclic compound can be promoted in the low temperature region.

In particular, when a flow type fixed bed reactor is used, the dehydrogenated catalyst according to the present invention easily desorbs the dehydrogenated reaction product, so that the reaction is promoted.

[Brief description of drawings]

FIG. 1 is a graph showing a result of evaluation 1 in an example.

FIG. 2 is a graph showing the results of evaluation 2 in the examples.

FIG. 3 is a schematic diagram of a flow reactor used in Evaluation 3 of Example.

FIG. 4 is a graph showing the results of evaluation 3 in the example.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ identification code FI theme code (reference) C07C 5/387 C07C 5/387 15/24 15/24 (72) Inventor Masakatsu Nomura Kawanishi, Hyogo Prefecture Hanayashiki 1-21-18 (72) Inventor Masahiro Miura 8-chome, Makami-cho, Takatsuki-shi, Osaka 8-1-418 (72) Inventor Tetsuya Sato 37-29 Yamadahigashi, 4-chome, Suita-shi, Osaka F-Term (reference) 4G069 BA08A BA08B BB02A BB02B BC31A BC32A BC33A BC66A BC67A BC68A BC70A BC71A BC72A BC72B BC74A BC75A BC75B CB07 CB66 BA06 BA06 BA05 BA05 BA25 AC25X EC05Y EC08H CA41 CC10

Claims (4)

[Claims] 1. A fibrous activated carbon and at least one selected from the group consisting of platinum, palladium, rhodium, iridium, ruthenium, nickel, cobalt, iron, copper, silver and gold supported on the fibrous activated carbon. An alicyclic dehydrogenation catalyst containing the metal of 2. The fibrous activated carbon has a specific surface area of at least 600 m ² / g and a total pore volume of at least 0.2 cm ^3.
The catalyst for dehydrogenation of alicyclic compounds according to claim 1, wherein the dehydrogenation catalyst has an average pore diameter of / g and an average pore diameter of 10 to 70 angstroms. 3. The metal of 0.5 to 10 g is supported per 100 g of the fibrous activated carbon.
An alicyclic compound dehydrogenation catalyst according to item 1. 4. A carrier having a specific surface area of at least 600 m ² / g, a total pore volume of at least 0.2 cm ³ / g and an average pore diameter of 10 to 70 Å, and platinum and palladium supported on the carrier. ,rhodium,
Iridium, ruthenium, nickel, cobalt, iron,
An alicyclic compound dehydrogenation catalyst containing at least one metal selected from the group consisting of copper, silver and gold.