JPH05168924A - Steam reforming catalyst - Google Patents

Abstract

PURPOSE:To enhance the catalytic activity and life of a steam reforming catalyst by supporting a catalytically active component selected from rhodium, ruthenium, palladium, platinum or an alloy of them on a carrier wherein an alumina substance is compounded with a zirconium carrier component. CONSTITUTION:For example, a mixture of a tetragonal zirconia powder containing 3mol% of yttria and an alumina cement powder is baked to form a carrier which is, in turn, impregnated with a ruthenium chloride solution and the impregnated carrier is dried to form a steam reforming catalyst. As mentioned above, partially stabilized or stabilized zirconia is used as a zirconla carrier component. Yttrium-containing zirconia is produced by a method for baking a powder mixture of yttria and zirconia, a coprecipitation method using a yttrium compound and a zirconium compound, a hydrolysis method or an alkoxylation method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrocarbon steam reforming catalyst. More specifically, the present invention provides a high-strength, low-cost steam reformer in which a zirconia-based carrier is replaced with a carrier in which an alumina-based substance is mixed with the carrier component while maintaining good catalytic activity and long catalyst life. Quality catalyst. This steam reforming catalyst is particularly useful as a reforming catalyst for fuel cells.

[0002]

2. Description of the Related Art Hydrocarbon reforming of hydrocarbons is a method for producing a gas consisting of hydrogen and carbon oxides by reacting hydrocarbons and steam at high temperature in the presence of a catalyst, which is well known as a method for producing hydrogen. is there. Typical conventional steam reforming catalysts include nickel, iron, cobalt, platinum, rhodium, ruthenium, palladium, etc. on an alumina-based carrier that may contain alkali metal oxides, alkaline earth metal oxides, silica, etc. It is well known that the above catalyst is supported. Further, it has been reported that a cobalt catalyst (Japanese Patent Publication No. 43-12410) and a rhodium catalyst (Japanese Patent Publication No. 56-91844) supported on a zirconia carrier have excellent performance in a steam reforming reaction of hydrocarbons. There is.

Further, the present inventors previously supported rhodium, ruthenium, palladium, and platinum on a zirconia carrier containing yttria, thereby having a high reforming activity and a catalyst excellent in long-term stability with less carbon formation. A system was proposed (JP-A-2-2878).

[0004]

However, since this improved catalyst requires an expensive zirconia-based carrier as a carrier, the catalyst cost is also high because the catalytically active component is also an expensive noble metal-based one. It has the drawback of taking too much.

The present invention provides a steam reforming catalyst which can overcome the drawbacks of the conventional steam reforming catalyst and can reduce the cost while maintaining good catalytic activity and long catalyst life. It was made for that purpose.

[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, in a catalyst in which a specific noble metal is supported on the zirconia-based carrier. It was found that the purpose can be achieved by replacing the expensive zirconia-based carrier with a carrier prepared by blending an inexpensive alumina-based substance in the carrier component,
Furthermore, an unexpected effect that the mechanical strength of the catalyst is significantly improved by blending the alumina-based substance was found, and the present invention has been completed based on these findings.

That is, according to the present invention, at least one catalytically active component selected from rhodium, ruthenium, palladium, platinum and alloys thereof is supported on a carrier prepared by mixing an alumina-based substance with a zirconia-based carrier component. And a steam reforming catalyst for hydrocarbons.

In the catalyst of the present invention, it is necessary to use, as a carrier, a zirconia-based carrier component mixed with an alumina-based substance. Examples of the zirconia-based carrier component include partially stabilized zirconia and stabilized zirconia. Particularly, zirconia containing yttria is advantageously used. In the yttria-containing zirconia, the yttria content is selected in the range of 0.5 to 20 mol%, preferably 1.5 to 10 mol%. If this proportion is less than 0.5 mol%, the effect of inclusion is not sufficient, and if it exceeds 20 mol%, the stabilization of the crystal system becomes insufficient.

To produce zirconia containing yttria, for example, a method of firing a powder mixture of yttria and zirconia in a predetermined ratio, a coprecipitation method using a yttrium compound and a zirconium compound, a hydrolysis method or an alkoxide method is used. Done by. Among them, the coprecipitation method is preferable, and particularly yttrium halide such as YCl ₃ and Zr are used.
A coprecipitation method using zirconium oxyhalide such as OCl ₂ is used.

As the alumina-based substance, alumina or a mixture of alumina and at least one selected from oxides of metal or metalloid elements is used. Examples of the metal element include alkali metals such as Li and K, Mg and C
Alkaline earth metals such as a and Ba, other Ti, Cr,
Mn, Fe, etc. may be mentioned, and as the metalloid element, S
i, B, P and the like can be mentioned. 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.

The proportion of the alumina-based substance is preferably 10 to 80% by weight, more preferably 20 to 80% by weight based on the total amount of the carrier.
It is selected in the range of 70% by weight. If this proportion exceeds 80% by weight, the reforming characteristics and coking suppression effect of the zirconia-based carrier catalyst will deteriorate, and if it is less than 10% by weight, the effect of improving the strength and reducing the catalyst price will not be sufficient.

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

A conventional method is used for supporting the catalyst metal on the carrier, 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 an internal reforming catalyst for a fuel cell, a granular carrier having a small particle size is preferable.

The steam reforming reaction using the catalyst of the present invention is usually carried out at 300 to 1000 ° C., but the catalyst of the present invention is 7
Since coking hardly occurs even at a temperature of 00 ° C. or lower, it is particularly suitable as a reforming catalyst for 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 and carbon in the source gas (hereinafter,
S / C) is preferably small because it is economically advantageous not to use excess steam as much as possible for the reaction, but on the other hand, if S / C is too small, coking tends to occur, so S / C is less than that of coking. 1.2 or above without problems,
It is preferably 1.4 or more.

The steam reforming reaction in which the catalyst of the present invention is effectively used is not particularly limited. For example, light hydrocarbon-containing gas such as LNG and LPG, petroleum fraction such as naphtha and kerosene, coal liquefied oil, etc. Examples include a reaction in which hydrogen, carbon monoxide, carbon dioxide, or methane is produced by catalytically cracking a raw material mainly composed of a hydrocarbon, particularly a hydrocarbon having a not so large molecular weight (about C _{1 to} C ₃₀ ). ..

The raw material is preferably composed of only hydrocarbons, but may contain a small amount of different components. The raw materials advantageously have a specific gravity of 0.80 or less, preferably 0.75 or less and a C / H weight ratio of 6.5 or less, preferably 6.0 or less.

When the different component is a sulfur compound, the content of the compound is 0.5 ppm or less when the raw material is naphtha, and kerosene usually contains about 50 ppm of the sulfur compound.
When using this as a raw material, it is desirable to use it after removing it to 0.5 ppm or less. As the removing means, hydrodesulfurization or the like is adopted.

[0019]

EFFECTS OF THE INVENTION The steam reforming catalyst of the present invention has excellent reaction efficiency, high hydrogen production efficiency, low S / C and suppressed carbon production even at a high temperature up to 1000 ° C., for example 600 to 700 ° C. In addition, there is a remarkable effect that the cost can be reduced and the strength can be increased while maintaining the good catalytic activity and the long life of the catalyst.

[0020]

EXAMPLES Next, the present invention will be described in more detail by way of examples.

Examples and Comparative Examples Tetragonal zirconia (hereinafter referred to as 3YSZ) powder containing 3 mol% yttria and alumina cement powder (alumina 92.5% by weight, calcium oxide 7.5% by weight).
Were mixed in the composition ratio shown in Table 1, and this mixture was mixed for 5 mm.
A tablet was formed into a cylindrical shape having a diameter of 5 mm. Next, after firing the pellets at 1000 ° C. for 3 hours, the surface area was measured by the BET method and the strength was measured by a Kiya type hardness meter. The results of these measurements are shown in Table 1.

[Table 1] From this, it was found that any of the carrier samples showed higher strength than the conventional zirconia-based carrier.

Sample No. thus obtained The second carrier was impregnated with a ruthenium chloride solution so that 0.37% of ruthenium was supported and dried at 100 ° C. for 3 hours to obtain a steam reforming catalyst. After 1.2 cc of this catalyst was packed in a reaction tube and subjected to reduction treatment, desulfurized light naphtha (specific gravity 0.70, C / H weight ratio 5.52,
Sulfur content of 50 wppb) as a hydrocarbon raw material at 650 ° C
(Reaction tube outlet temperature) S under the condition of 0.2 kg / cm ² G
/ C about 3.0 and material supply space velocity (GHSV) about 8
The reaction was carried out at 000 h ⁻¹ . For comparison, the results are shown in Table 2 together with the case where the catalyst was prepared in the same manner as in the above-mentioned Example except that the carrier was changed to the conventional zirconia carrier and the reaction was carried out in the same manner as in the Example.

[0023]

[Table 2] From this, it can be seen that even a catalyst using a carrier to which 50% of inexpensive alumina cement is added exhibits almost the same high activity as a catalyst using a conventional zirconia carrier.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Satoshi Sakurada 1-3-1, Nishitsurugaoka, Oi-cho, Iruma-gun, Saitama Prefecture Tonen Corporation Research Institute

Claims (1)

[Claims] 1. A hydrocarbon obtained by supporting at least one catalytically active component selected from rhodium, ruthenium, palladium, platinum and alloys thereof on a carrier in which an alumina-based substance is mixed with a zirconia-based carrier component. Steam reforming catalyst.