JPH03249942A - Production of catalyst for steam-reforming hydrocarbon - Google Patents

Abstract

PURPOSE:To obtain the catalyst for steam-reforming hydrocarbons having large surface area and pore volume and capable of improving reforming activity by using a zirconia powder contg. 0.5-12mol% yttrium and having a specified crystal structure and an org. binder as the raw material, molding the mixture, calcining and sintering the formed body. CONSTITUTION:The zirconia powder contg. 0.5-12mol% yttrium and having essentially a tetragonal or tetragonal and cubic crystal structure and an org. binder (water-soluble binder is preferable, and carboxymethyl cellulose is exemplified) are mixed, and the mixture is molded. The molded body is then calcined appropriately at 800-1400 deg.C in a nitrogen atmosphere, and then sintered preferably at 500-800 deg.C in the air to prepare a catalyst carrier. The catalytic metal components are deposited on the carrier to obtain the desired catalyst for steam- reforming hydrocarbons.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for producing a hydrocarbon reforming catalyst, particularly a steam reforming catalyst for oil refineries and a steam reforming catalyst for fuel cells. By increasing the surface area and pore volume, it is possible to improve the reforming characteristics and the thermal stability of the catalyst. For example, when used in fuel cells for internal reforming fuel, high temperature stability can be improved. The present invention relates to a method for producing a hydrocarbon steam reforming catalyst.

[Prior Art] Steam reforming of hydrocarbons is a method of producing a gas consisting of hydrogen and carbon oxides by bringing hydrocarbons and steam into contact with a catalyst. Typical conventional catalysts for steam reforming are catalysts such as nickel, iron, cobalt, platinum, rhodium, ruthenium, palladium, etc. on an alumina support containing an alkali metal oxide, alkaline earth metal oxide, or silica. are well known (Japanese Patent Application Laid-open Nos. 50-126005 and 61-280554).

It has also been reported that catalysts of this type, in which nickel, cobalt, or ruthenium is supported on a zirconia support, also have excellent performance (Japanese Patent Publication No. 43
Publication No. -12410; Satoshi Igarashi, "Steam reforming reaction of n-butane over Rh/Zr○," 58th Catalyst Symposium (A), 4 series B12, pp. 176-177; et al.) Recently, it has been reported that catalysts in which rhodium is supported on a zirconia support and catalysts in which rhodium is supported on a zirconia support containing yttria also have excellent performance in steam reforming reactions of hydrocarbons ( Ken Otaka et al., “n-butane-steam reaction over Rh/Z r Ox catalyst with addition of third component,” 62nd Catalyst Symposium, 3.
B305.118-119).

It is also known that noble metal catalysts are supported on the surface of catalyst carriers such as alumina, silica, and silcony (JP-A-5
3-78735, JP-A-48-53980).

[Problems to be Solved by the Invention] Conventional zirconia carriers are made by kneading, for example, zirconia powder with an organic binder, then molding, and then heating it in air for 1000 m
It is manufactured by a method such as calcination for 3 hours under the conditions of ℃, but while studying the catalyst in which the catalyst metal is supported on this zirconia support, the present inventors found that in order to give a certain strength to the catalyst support, However, due to the shrinkage of the catalyst carrier due to high-temperature calcination, its surface area and pore volume become smaller. The problem is that the catalyst carrier cannot be given sufficient strength due to the catalyst carrier, which deteriorates the stability of the carrier under high-temperature conditions, and also reduces the resistance to molten salt toxicity when used as a catalyst for internal reforming fuel cells. It turns out that there is.

The present invention relates to a hydrocarbon steam reforming catalyst that has excellent mechanical strength, high surface area, and high pore volume, and can thereby improve reforming activity. HM provides a manufacturing method for.

[Means for Solving the Problems] The present invention involves molding a mixture of zirconia powder containing 15 to 12 mol% of ittria and having a crystal structure mainly of tetragonal or tetragonal and cubic crystals and an organic binder. After that, a catalyst carrier is prepared by pre-calcining in a nitrogen atmosphere and then post-calcining in air, and a catalytic metal component is supported on the catalyst carrier to produce a hydrocarbon steam reforming catalyst.

First, a method for manufacturing a catalyst carrier according to the present invention will be explained.

The zirconia powder used in the production of catalyst carriers is
A method for hydrolyzing a mixture of yttrium alkoxide and zirconium alkoxide, and a method for hydrolyzing a mixture of yttrium alkoxide (YCI) and zirconium oxychloride (Zr).
0C1a) It is produced by a method of thermally decomposing a mixture, and further, for example, a method of adding ammonia water to a mixed aqueous solution of yttrium chloride and a zirconium salt and co-precipitating it, etc. Among these methods, zirconia powder obtained by a coprecipitation method is It has a uniform composition and good particle properties, and is suitable for preparing the zirconia powder of the present invention.

Ittria content in zirconia powder is 0.5~
The content is 12 mol%, preferably 1.0 to 8 mol%, more preferably 1.5 to 6 mol%, and if the itria content increases, the catalyst strength will be insufficient, and at least it will not be suitable for practical use as a catalyst. Strength is insufficient.

The particle size of the zirconia powder suitable for use in the present invention is 0.
．． 05 μm to 5 μm, preferably 0.1 μm to 1 μm
It is μm.

Next, the organic binder mixed with the zirconia powder is
Water-soluble ones are preferably used, such as carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxybutyl cellulose, polyvinyl alcohol, polyvinyl butyral, polyethylene glycol, and the like.

To produce a catalyst carrier, first, zirconia powder and an organic binder are kneaded together with a small amount of water using a stirrer such as a kneader, and then extrusion molded into a pellet, dried, and prepared for firing. .

The mixing ratio of the zirconia powder and the organic binder is preferably 100:1 to 3:1 by weight; if the zirconia powder is too large, the desired surface area and pore volume of the catalyst carrier cannot be obtained, or the catalyst carrier may be too small. catalytic strength is lost.

Next, the dried pellet-shaped catalyst carrier for firing is pre-calcined under conditions of 800°C to 1400°C in an atmosphere of an inert gas such as nitrogen.

The temperature range of this pre-firing is important; if it is below 800°C, the organic binder will not be sufficiently carbonized, and the desired surface area and
The pore volume cannot be obtained, and if the temperature is higher than 1400°C, the desired pore volume cannot be obtained due to shrinkage.

After such pre-baking, it is then heated in air at 500°C to 800°C.
It is subjected to post-calcination under the conditions of ℃. In the post-calcination, the organic binder particles are carbonized in the catalyst carrier and the remaining carbon particles are removed, and the firing temperature is 500°C.
If the temperature is below 800° C., the calcination will be insufficient, and if the temperature exceeds 800° C., the catalyst carrier will shrink, making it impossible to obtain the desired surface area and pore volume.

In this way, the surface area and pore volume of the catalyst carrier can be
It can be made larger than that obtained by conventional manufacturing methods.

Further, the catalyst carrier of the present invention contains 0.5 mol% to 12 mol% of itria in the zirconia carrier, but under the temperature conditions of catalyst calcination and reforming reaction (approximately 500°C
-1000℃), it has a mainly tetragonal crystal structure, and when the IJ content is less than the above range, the proportion of monoclinic crystals increases, and when it exceeds the above range, the proportion of monoclinic crystals increases. The proportion of crystals increases.

In the steam reforming catalyst of the present invention, if the monoclinic or cubic crystal structure increases, the catalyst strength will be lost;
Further, in the temperature range for catalyst preparation and steam reforming reaction, it is necessary that at least 35% or more of the crystal structure consisting of tetragonal and cubic crystals be tetragonal.

In the catalyst carrier of the present invention, the proportion of tetragonal crystals is 9
It ranges from 8 to 35%, more preferably from 90 to 50%, and the more tetragonal crystals it contains, the higher the mechanical strength.

Next, a catalytic metal is supported on this catalyst carrier to obtain the hydrocarbon steam reforming catalyst of the present invention.

As a supporting method, a normal supporting method can be used, but the catalyst metal may be supported only on the surface layer of the catalyst carrier. In order to adsorb the catalytic metal component only on the outer surface layer of the carrier, it is preferable to select a solvent that has an appropriately suppressed affinity for the carrier and in which the affinity of the catalytic component is smaller than that for the carrier.

The above objective is achieved by using specific organic solvents, which prevent the catalytic metal from penetrating into the support.

Suitable solvents for supporting the metal catalyst metal salt on the surface of the catalyst carrier in the present invention include ketones such as acetone, methyl ethyl ketone, and diethyl ketone, alcohols such as methanol and ethanol, and acetic acid, methyl acetate, and ethyl acetate. Acetic acid compounds, ethers such as diethyl ether,
Furthermore, a mixed solvent with other solvents such as water and hydrocarbons can be used. Water can be used up to 50% in the mixed solvent. If the amount of water is too large, the catalytic metal component will penetrate into the carrier, which is not preferable.

In addition, the catalytic metal components supported on this catalyst carrier include:
The effects of the present invention are best exhibited in the case of a noble metal catalyst consisting of rhodium, ruthenium, palladium, platinum, or a mixture thereof, and rhodium or ruthenium is particularly preferred in combination with the yttria-containing zirconia support in the present invention.

Examples of noble metal compounds include ruthenium chloride (RuC).
15.3HJ), Ruthenium Red (Ruz(OH)
-C14.'INHs.38.0) etc., and these compounds are preferably dissolved in the above solvent at 0.05% to 5%, preferably 0.1% to 2%.

Note that the catalyst metal component in the present invention is not limited to a noble metal catalyst, and of course may be a normal catalyst metal such as nickel, iron, cobalt, etc. that has been conventionally used as a steam reforming catalyst.

In order to adsorb the catalytic metal salt onto the catalyst carrier using the metal salt solution prepared in this manner, it is preferable to introduce the catalytic carrier into the metal solution and immerse it in the adsorbent. The amount of solution to be used and the amount of carrier to be used are in a weight ratio of 1=1 to 50:
L is preferably 3:1 to 10:1. The immersion time is preferably 1 minute to 24 hours.

In order to adsorb the catalyst metal salt only on the surface layer of the catalyst carrier, the concentration of the solution, the amount of solution used, the immersion time, etc. affect the adsorption, but by combining them appropriately, it is possible to make it adsorb only on the surface layer, and this can be confirmed using the XL Micro Analyzer. This can be easily done by

The catalyst of the present invention can be obtained by immersing the catalyst carrier in the metal salt solution and then drying it.

In addition, when using it for a reforming reaction, it is subjected to hydrogen reduction treatment and then used.

Further, the shape of the catalyst used in the present invention is generally cylindrical, ring-shaped, or particulate, but is not necessarily limited thereto. It may be a fibrous or three-dimensional structure.

The steam reforming reaction of hydrocarbons is represented by the following reaction formula.

CmHn4+mH,0-+mCO+(+m　)T.

However, m = about 1 to 20 n=about 4-42 Taking the methane reforming reaction as an example, CH4+H20→CO+3Hz CO+H, O→COz+H2 is shown.

The reaction temperature is generally 300 to 1000°C, but 700°C
The catalyst of the present invention is suitable as a steam reforming catalyst because coking hardly occurs even at temperatures below .degree.

The reaction pressure is approximately 0.01kg/cm”G~50kg/
ca+'G.

Particularly preferably about 0.1 kg/cm'G ~30k
g/co+'G.

From the perspective of productivity, steam/carbon (S/C
) is preferably smaller, but in order to avoid the problem of coking, it is preferably 1.2 or more, preferably 1°4 or more.

The raw materials used in the steam reforming reaction include gases containing light hydrocarbons such as LNG and LPG, petroleum fractions such as naphtha and kerosene, and liquefied coal oil. (about C+~C3°)
etc. can be used. The raw material gas preferably consists of only hydrocarbons, but may contain trace amounts of other components. The content of sulfur compounds as foreign components is preferably 0.5 ppm or less when the raw material is naphtha. Also, kerosene is usually 50pp.
However, if this is used as a raw material, it is desirable to use it after removing it to 0.5 ppm or less. Hydrodesulfurization or the like is employed as a removal means.

Further, the specific gravity of the hydrocarbons as raw materials is 0.80 or less, preferably 0.75 or less, and the C/H weight ratio is 6.5 or less.
Preferably, hydrocarbons of 6.0 or less are used.

The reforming catalyst of the present invention has a high surface area and a high pore volume, so the reforming (conversion) efficiency is high, and the calcination temperature can be increased compared to conventional production methods, so the catalyst carrier Since it can improve thermal stability and has an excellent effect of suppressing carbon adhesion (coking), it is suitable for use as a steam reforming catalyst for fuel cells using hydrocarbons as raw materials. For example, in a molten carbonate fuel cell, it has been pointed out that the molten carbonate of the electrolyte scatters and adheres to the catalyst surface, resulting in a decrease in activity due to the elution of catalyst components. The catalyst is carbonate stable and is particularly useful for internal reforming fuel cell applications. As for the method of applying the catalyst layer in the internal reforming fuel cell, it is usually preferable to arrange the catalyst layer in the fuel gas flow path on the anode side of the cell or between the stacked cells.

[Action and effect of invention]

Conventional ittria-containing zirconia catalyst supports are prepared by molding a kneaded mixture of zirconia powder and an organic binder and then firing it in air, but this method not only removes the organic binder in the support but also reduces the shrinkage effect of the support. occurs at the same time, making it impossible to achieve a high surface and high pore volume. However, as in the present invention, itria
After molding a mixture of zirconia powder containing mol% to 12 mol% and having a crystal structure mainly consisting of tetragonal or tetragonal and cubic crystals and an organic binder, the organic pine powder is first formed by pre-calcining in a nitrogen atmosphere. can be carbonized in the molded body, thereby reducing the degree of shrinkage of the molded body, and by removing carbon by subsequent post-calcination in air, high surface area and high pore volume can be achieved. It can be used as a catalyst carrier.

According to the present invention, since the surface area and pore volume of the catalyst carrier can be secured without causing the catalyst carrier to shrink too much, the reforming activity of the reforming reaction can be improved. Since it can be calcined, the thermal stability of the carrier can be increased.If the catalyst produced by the present invention is used as a catalyst for an internal reforming fuel cell, for example, it will be resistant to molten salts at high temperatures. It is possible to reduce toxicity.

In addition, 0.0% of ittria was used as a catalyst carrier. By using a zirconia support containing 5 to 12 mol % and having a crystal structure of at least 35% tetragonal crystals, a hydrocarbon steam reforming catalyst with high catalytic strength can be obtained.

Hereinafter, this will be explained in detail using examples.

(Example 1) (Preparation of catalyst carrier) Zirconia powder containing 3 mol% ittria (manufactured by Tosoh ■)
To 100 parts by weight of TZ-3Y), 10 parts by weight of carboxymethyl cellulose (trade name: Ceracidar 520P, manufactured by Yuken Kogyo ■) and 25 parts by weight of water were added, and the mixture was thoroughly kneaded using a Ni-gu, and then mixed to 1/16. 'It was extruded into a pellet shape and dried at 100°C for 3 hours.

Next, the dried catalyst carrier was heated for 100 min in a nitrogen atmosphere.
Two types of catalyst carriers, one pre-calcined at 0°C for 1 hour and one pre-calcined at 1200°C for 1 hour, were further heated in air for 700 min.
℃ for 3 hours to obtain the catalyst support 1 of the present invention.
2 was prepared.

On the other hand, for comparison, a kneaded product of the same zirconia powder and organic binder as above was prepared in a cylindrical shape (5 mmφ x 5 m).
A comparative carrier was obtained by forming a tablet into a tablet and firing it in air at 1000°C for 3 hours.

The surface area of the obtained catalyst carrier 1.2 in the present invention and the comparative carrier were measured by the BET method, and the pore volume was measured by mercury pressure forming.

It is shown in Table 1.

As can be seen from Table 1 below, the catalyst carrier 1, which is a product fired at 1000°C, has a higher It was found that the surface area was four times larger and the pore volume was also significantly increased, and the pore volume of the catalyst carrier, which was fired at 1200°C, was still lower than that of the comparative product fired at 1000°C. It can be seen that the catalyst carrier of the present invention can be fired at a higher temperature.

Next, each of the above three types of catalyst carriers was impregnated with an aqueous ruthenium chloride solution to support 0.37% by weight of ruthenium, and dried at 100° C. for 3 hours to obtain a hydrocarbon reforming catalyst.

After filling a reaction tube with 1.2 cc of these three types of catalysts and performing a reduction treatment in a hydrogen atmosphere, desulfurized light naphtha was used as a hydrocarbon raw material, and the temperature was 650°C (reaction tube outlet temperature). , under normal pressure, steam/carbon ratio (S/C)
and raw material supply space velocity (GH3V), respectively, 3.0.8
000h-', 3゜0.16000h-', 1.5.8
000h-1.

Figure 1(a) shows the amount of hydrogen produced, and Figure 1(b) shows the amount of methane leakage.

As can be seen from Figure 1, the 1000°C calcined catalyst of the present invention (■), the 1200°C calcined catalyst (•), and the comparative catalyst (
It can be seen that while the amount of hydrogen produced is large, the amount of methane leaked is small.

[Example 2] The catalyst of the present invention prepared in Example 1 was pulverized into 8 to 16 meshes, 5 g of which was weighed, and molten carbonate (
70 g of Li/K = 62/38).

Then, the elution amount of the catalyst component was measured after 2 days, 4 days, and 7 days.

As a result, zirconia was hardly eluted, yttrium was slightly eluted, but it was about 25 ppm on the 7th day, and ruthenium was not detected.

This shows that the catalyst of the present invention is stable against molten carbonate.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the reforming characteristics of the catalyst of the present invention and the comparative catalyst in a hydrocarbon reforming reaction.

Claims (2)

[Claims] (1) Contains 0.5 mol% to 12 mol% yttria,
After shaping a mixture of zirconia powder whose crystal structure is mainly tetragonal, or tetragonal and cubic, and an organic binder, pre-calcining in a nitrogen atmosphere and then post-calcining in air to prepare a catalyst support, A method for producing a catalyst for a hydrocarbon steam reforming catalyst, characterized in that a catalyst metal component is supported on the catalyst carrier. (2) Pre-firing in the nitrogen atmosphere at 800°C to 1400°C
The method for producing a hydrocarbon steam reforming catalyst according to claim 1, wherein the post-calcination in air is carried out at a temperature of 500 to 800°C.