JPS6335301B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a catalyst for producing hydrogen, and particularly to a catalyst used when producing hydrogen by reducing the catalyst with a reducing gas and then causing a catalytic reaction between the catalyst and steam. Hydrogen is one of the important synthetic raw materials in the petrochemical industry, but in recent years, it has been used in hydrogen desulfurization of heavy oil, liquefaction of coal,
The development of hydrogen-intensive processes, such as coal gasification, has significantly increased the demand for cheap, high-purity hydrogen. Conventionally, hydrogen has been synthesized by steam reforming reactions of hydrocarbons such as hexane and heptane, but with this method, the reaction products include carbon dioxide or methane in addition to hydrogen. For,
An operation is required to separate hydrogen from these. A so-called steam-iron reaction is known as a method for obtaining relatively high-purity hydrogen without requiring such a separation operation. This method uses triiron tetroxide (Fe ₃ O ₄ ) as a catalyst, first reduces the catalyst with a reducing gas such as carbon monoxide as shown in equation (1), and then brings it into contact with water vapor. Hydrogen is obtained by the reaction of formula (2). Fe ₃ O ₄ +4CO→3Fe+4CO ₂ ………(1) 3Fe＋4H ₂ O→Fe ₃ O ₄ +4H ₂ ………(2) According to the above method, the obtained hydrogen is composed of almost all other gases except water vapor. It has the advantage that high purity hydrogen can be easily obtained by condensing and removing water vapor without containing any components. However, the steam-iron reaction
A high temperature of 800 to 900°C is required, which necessitates the use of expensive equipment materials such as heat-resistant steel.In addition, both reactions (1) and (2) are slow and require a large amount of catalyst. There are some problems. Therefore, it has been desired to develop a hydrogen synthesis method that can be operated at relatively low temperatures and does not require a hydrogen separation operation like the steam-iron reaction. An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide a catalyst that can produce high-purity hydrogen from reducing gas and steam at relatively low temperatures. The present inventors investigated a method of synthesizing hydrogen by reaction with reducing gas and water vapor using various oxides as catalysts in the temperature range of 300°C to 500°C, and found that molybdenum (Mo) , oxides of at least one metal selected from tungsten (W), vanadium (V), uranium (U), iron (Fe), and nickel (Ni) with rhodium (Rh) added have high activity. I discovered that. That is, in the present invention, rhodium is added to the above-mentioned metal oxide so that an oxidation-reduction reaction similar to the steam-iron reaction can proceed at a low temperature of 300 to 500°C. The catalyst of the present invention is easily reduced by carbon monoxide (CO) or a hydrocarbon such as hexane at the above temperature, and when the catalyst thus reduced comes into contact with water vapor, it quickly reacts to produce hydrogen. However, it itself becomes oxidized. The oxide raw material used in the catalyst of the present invention may be any oxide of the above-mentioned metals, such as MoO ₃ , WO ₃ , V ₂ O ₅ , U ₃ O ₈ , Fe ₂ O ₃
Alternatively, NiO can be given. Rhodium raw materials include rhodium nitrates, chlorides,
Carbonyl, organic acid salts, etc. can be used. The amount of rhodium added to the above oxide is 0.05
~5% by weight is desirable. Further, the above oxide and rhodium may be supported on a carrier such as alumina, silica, titania, or silica carbide. Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 50 g of molybdenum trioxide (MoO ₃ ) was mixed with rhodium nitrate (Rh) having a rhodium content of 1 g.
(NO ₃ ) ₃ ) Mix with 500 ml of aqueous solution, evaporate to dryness, and then calcinate in air at 500°C for 2 hours. The obtained powder was formed into a size of 10 mm diameter x 5 mm length using a hydraulic press, and then crushed into a size of 10 to 20 meshes.
Reduction was performed in hydrogen at 450°C for 1 hour. The resulting catalyst is called A. In this case, the rhodium content is 1% by weight. Examples 2 to 6 Molybdenum trioxide (MoO ₃ ) in Example 1
The same procedure was carried out using tungsten trioxide (WO ₃ ), vanadium pentoxide (V ₂ O ₅ ), uranium octoxide (U ₃ O ₈ ), iron oxide (Fe ₂ O ₃ ), and nickel oxide (NiO) instead of The catalyst was prepared by the method described in . The resulting catalysts are designated B, C, D, E and F. Examples 7 to 9 In Example 1, 500 ml of rhodium nitrate aqueous solution
Catalysts were prepared in the same manner using 25 ml, 250 ml and 2800 ml of the aqueous solution instead. The resulting catalysts are designated G, H and I. The respective rhodium contents are 0.05, 0.5 and 5% by weight. Comparative Examples 1 to 6 Catalysts were prepared in the same manner as in Examples 1 to 6, using pure water instead of the rhodium aqueous solution. The obtained catalyst was classified into J, K, L, M, N and O.
It is called. Experimental Example 1 Using 50 g of the catalysts A to O, they were brought into contact with 20 mmol of carbon monoxide at 400° C. for 1 second, the amount of CO ₂ produced was measured, and the amount of CO reacted was determined. The catalyst was then brought into contact with 100 mmol of water vapor for 1 second, and the amount of hydrogen generated was measured. The obtained results are shown in the first section below.
Shown in the table.

[Table] From the results in Table 1, catalyst A with rhodium added
It can be seen that ~I has higher activity than those J~O to which rhodium is not added. Also, from the results of catalysts A and G to I, the rhodium content is
It can be seen that 0.5% by weight or more and 5% by weight or less is desirable. Experimental Example 2 A similar test was conducted using Catalyst A, except that the reaction temperature of Experimental Example 1, 400°C, was changed to 300°C and 500°C, respectively. The results are shown in Table 2 together with the results of Experimental Example 1. From Table 2, it can be seen that catalyst A containing rhodium exhibits high activity even at a reaction temperature of 300°C.

[Table] As described above, according to the present invention, even at low temperatures of 300°C to 500°C, CO or hydrocarbon and water vapor can be separated by a reaction similar to the steam-iron reaction.
High purity hydrogen can be produced.

Claims (1)

[Claims] 1. A catalyst for hydrogen production in which the catalyst is reduced with a reducing gas and then subjected to a catalytic reaction with water vapor to produce hydrogen, the catalyst comprising molybdenum, tungsten, vanadium, uranium, iron, and nickel. A catalyst for hydrogen production, characterized in that it is made by adding rhodium to an oxide of at least one metal selected from the group consisting of: 2. The catalyst for hydrogen production according to claim 1, wherein the reducing gas is carbon monoxide or hydrocarbons. 3. The catalyst for hydrogen production according to claim 1 or 2, wherein the catalyst material is supported on a carrier such as aluminum, silica, titania, or the like. 4 In claim 1 or 2, the amount of rhodium added to the metal oxide is
A catalyst for hydrogen production characterized in that the content is 0.05 to 5% by weight.