JPH05208133A - Steam reforming catalyst - Google Patents

Abstract

PURPOSE:To obtain a steam reforming catalyst reduced in cost while keeping good catalytic activity by supporting a catalytically active component such as rhodium, ruthenium or palladium on a carrier composed of a naturally occurring zirconia type material. CONSTITUTION:A naturally occurring zirconia type material such as zircon from Australia or baddeleyite from South Africa is used as a carrier. A catalytically active component selected from rhodium, ruthenium, palladium and platinum is supported on this carrier. The steam reforming catalyst thus obtained has the same high activity as a catalyst using a yttria-containing stabilized zirconia carrier and is low in cost and practical.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel steam reforming catalyst. More specifically, the present invention is
The present invention relates to a practical steam reforming catalyst in which the carrier made of stabilized zirconia containing yttria is replaced with a carrier made of a naturally-occurring zirconia-based material while maintaining a good catalytic activity to reduce the cost. This steam reforming catalyst is particularly useful as a reforming catalyst for fuel cells.

[0002]

2. Description of the Related Art Steam reforming is a method for producing a gas consisting of hydrogen and carbon oxides by reacting, for example, hydrocarbons and steam at high temperature in the presence of a catalyst, and is well known as a method for producing hydrogen.

As a typical conventional steam reforming catalyst,
A heat-resistant inorganic oxide such as alumina, silica, magnesia, or zirconia supported with a transition metal such as Ni, Co, or Fe as a catalyst species, or a cocatalyst such as an alkali metal or an alkaline earth metal added thereto. The catalysts are well known, and the Ni-supported alumina-based catalysts are widely used industrially. However, such a Ni-based catalyst easily produces carbon by the reforming reaction, and this carbon is deposited on the catalyst surface. It deposits and causes a decrease in activity and blockage. In order to avoid this, there is a disadvantage that the amount of steam must be increased with respect to the reforming raw material.

Therefore, the present inventors previously found that they are highly active,
We proposed a noble metal-supported zirconia-based catalyst such as Rh, Ru, Pt, or Pd, which has a high effect of suppressing the generation of carbon and is particularly useful as a reforming catalyst for a raw material for fuel cells (JP-A-3-8
0937). However, since this improved catalyst uses expensive yttria-containing stabilized zirconia obtained by chemical synthesis as a carrier, it also has a drawback that the cost of the catalyst is too high in combination with the fact that the catalytically active component is also an expensive precious metal type. .

[0005]

DISCLOSURE OF THE INVENTION The present invention overcomes the drawbacks of the conventional steam reforming catalysts, and is a practical steam reforming catalyst capable of achieving cost reduction while maintaining good catalytic activity. It is made for the purpose of providing.

[0006]

The inventors of the present invention have conducted various studies to develop a steam reforming catalyst having the above-mentioned preferable characteristics, and as a result, by using a naturally occurring zirconia-based material as a carrier material, It has been found that the object can be achieved, and the present invention has been completed based on this finding.

That is, the present invention provides at least one selected from rhodium, ruthenium, palladium and platinum.
The present invention provides a steam reforming catalyst in which various catalytically active components are supported on a carrier made of a naturally occurring zirconia-based material.

In the catalyst of the present invention, it is necessary to use, as the carrier, one composed of a naturally-produced zirconia-based material. Examples of the naturally occurring zirconia-based material include zircon from Australia and baddelite from South Africa.

Further, the carrier may be made of a mixed material obtained by adding a small amount of a carrier material usually used for a steam reforming catalyst to such a zirconia-based material. Examples of such carrier materials include alumina-based substances, silica, magnesia, and other zirconia-based substances, and their proportion in the carrier component is preferably 30% by weight or less, more preferably 20% by weight or less.

As the alumina-based substance, alumina or a mixture of alumina and at least one selected from oxides of metal elements or semi-metal elements is used. Examples of the metal element include alkali metals such as Li and K, and M
g, Ca, Ba and other alkaline earth metals, other Ti,
Cr, Mn, Fe and the like can be mentioned, and Si, B, P and the like can be mentioned as the semi-metal element. Alumina cement, which contains alumina and calcium oxide as main components, and also contains silicon oxide and a small amount of iron oxide, is one of the preferable substances.

Rhodium, ruthenium, palladium and platinum are used as a noble metal (hereinafter referred to as a catalyst metal) as a catalytically active component supported on a carrier, and rhodium and ruthenium are particularly preferable. The ratio of the catalyst metal is not particularly limited, but is usually 0.01 to 10% by weight, preferably 0.1% to the total amount of the catalyst, that is, the total amount of the catalyst metal and the carrier.
It is selected in the range of 1 to 3% by weight. If this proportion is too small, the catalytic activity will be low and the reforming effect will not be sufficient. If it is too large, the reforming effect commensurate with the amount used will not be obtained, which is uneconomical.

The catalyst of the present invention may contain a nickel-based metal, an alkali metal or an alkaline earth metal. The ratio of components other than these precious metals is preferably 30.
It is not more than 20% by weight, more preferably not more than 20% by weight.

To prepare the catalyst of the present invention, a conventional method of supporting a catalyst metal on a carrier is used, but an impregnation method is usually used. The use form of the carrier is not particularly limited, and may be a three-dimensional structure such as a columnar shape, a ring shape, a particle shape, a fibrous shape, or a honeycomb shape, or a composite structure with another carrier. When the catalyst of the present invention is used as a fuel cell reforming catalyst,
Granular carriers with a small particle size are preferred.

As a method for preparing the catalyst, there is also used a method in which the catalyst metal and the above-mentioned carrier material are well mixed in the form of powder, which is then molded by compression molding or the like and then calcined. Although a conventional method is used for mixing in the firing method, it is usually a twin type, such as a cylinder type, an inclined cylinder type, a V type, or the like.
In addition to a container rotary type mixer such as a double cone type, a fixed type mixer that rotates a screw or a ribbon, a mortar is used on a small scale. The molding pressure during molding after mixing is usually 5
00-2000 kg / cm ² , firing treatment is usually 700-
It is preferable to perform heat treatment at 800 ° C. for 1 to 2 hours.

As a typical example of the steam reforming reaction using the catalyst of the present invention, a hydrocarbon reforming reaction for producing hydrogen, carbon monoxide, carbon dioxide, methane and the like will be described below. The steam reforming reaction is usually carried out in the temperature range of 300 to 1000 ° C., but the catalyst of the present invention hardly causes coking even at 700 ° C. or lower and has high activity. It is suitable as a reforming catalyst for carbonate fuel cells.

The reaction pressure is usually 0.01 to 50 k.
g / cm ² G, preferably 0.1 to 30 kg / cm ² G
Is. The molar ratio of water vapor to carbon in hydrocarbons (hereinafter referred to as S / C) is preferably small because it is economically advantageous not to use excess water vapor for the reaction, but it is preferable to reduce S / C. If it is too much, coking tends to occur, so the S / C does not have a problem of caulking.
Above all, it is particularly preferable to be 1.5 or more.

The hydrocarbons are not particularly limited, but hydrocarbons only are preferable, and they may contain a trace amount of different components. Examples of such hydrocarbons include LN.
Mainly gas containing light hydrocarbons such as G and LPG, petroleum fractions such as naphtha and kerosene, and hydrocarbons such as coal liquefied oil, especially hydrocarbons having a relatively low molecular weight (C _{1 to} C ₂₀ ). Things are included.

The hydrocarbons advantageously have a specific gravity of 0.80 or less, preferably 0.75 or less and a C / H weight ratio of 6.5.
The following are preferred, and those of 6.0 or less are preferred.

When the different component is a sulfur compound,
Since it causes catalyst deterioration, it is preferably 1 ppm or less, more preferably 0.5 p or less in advance due to hydrodesulfurization.
It is desirable to use after removing to pm or less.

The steam reforming catalyst of the present invention is advantageous when used as a reforming catalyst for a fuel cell because it has high reforming efficiency and can suppress carbon deposition (coking).

[0021]

EFFECTS OF THE INVENTION The steam reforming catalyst of the present invention has excellent reaction efficiency, high hydrogen production efficiency, and low S / C and carbon production even under high temperatures up to 1000 ° C. (for example, 600 to 700 ° C.). As described above, it has the advantages that good catalytic activity can be maintained and the cost can be significantly reduced, and is particularly useful as a reforming catalyst for fuel cells.

[0022]

The present invention will be described in more detail with reference to Examples.

Examples 1 and 2 and Comparative Example Australian zircon (58% by weight of ZrO ₂ , Si
O ₂ 39% by weight and other small amounts of Al, Fe and Hf oxides) and South African baddelite (ZrO ₂ 96
% By weight, and a small amount of other oxides of Si, Fe, and Hf) are formed into spherical particles of 1 mmφ, and then 100
By firing at 0 ° C. for 3 hours, desired carrier sample Nos. 1 and No. 1 Created 2.

For comparison, a partially stabilized zirconia (hereinafter referred to as 3YSZ) powder containing 3 mol% yttria was similarly shaped and fired to obtain a conventional carrier sample No. Created 3. The surface area of these carriers was measured by the BET method. The results are shown in Table 1.

[0025]

[Table 1]

From the above, it can be predicted that any of the carrier samples has the same surface area as that of the conventional zirconia-based carrier and exhibits sufficient catalyst supporting ability.

Each carrier sample thus obtained had a density of 0.
Impregnation treatment with a ruthenium chloride solution was carried out so that 5% by weight of ruthenium was supported, followed by drying at 100 ° C. for 3 hours. 1 to 2, the steam reforming catalyst and the carrier sample No. 1 as examples of the present invention. From 3 was prepared a steam reforming catalyst for comparison. After 0.25 cc of a 4-inch diameter reaction tube was filled with this catalyst and reduction treatment was performed, propane was used as a hydrocarbon raw material at 650 ° C. (reaction tube outlet temperature) at a steam / carbon ratio (S / C) under normal pressure. 3.0
And raw material supply space velocity (GHSV) of 48000 h ⁻¹
And the propane conversion was measured. The results are shown in Table 2.

[0028]

[Table 2]

As a result, even a catalyst using a carrier made of a naturally-occurring zirconia-based material exhibits substantially the same high activity as a conventional catalyst using a chemically synthesized yttria-containing stabilized zirconia carrier. I understand.

Example 3 The raw material supply space velocity under the reaction conditions of Examples 1 and 2 was 2000.
When the reaction was carried out in the same manner as in Examples 1 to 2 using the same catalysts as those in Examples 1 to 2 except that 0h ⁻¹ was used, the propane conversion was 100% in all, and particularly in practical use in fuel cells. It has been found that under normal operating conditions the catalyst of the invention can be used exactly as a conventional catalyst.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor ▲ Sai ▼ Akira Nishitsurugaoka 1-3-1 Oi-cho, Iruma-gun, Saitama Tonen Co., Ltd. Research Institute (72) Satoshi Sakurada Oi-cho, Iruma-gun, Saitama Nishitsurugaoka 1-3-1, Tonen Co., Ltd.

Claims (1)

[Claims] 1. A steam reforming catalyst comprising at least one catalytically active component selected from rhodium, ruthenium, palladium and platinum supported on a carrier made of a naturally occurring zirconia-based material.