JP2003093878A - Catalyst for manufacturing hydrogen and manufacturing method for hydrogen using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an improved iron based catalyst which is stable for a decomposition reaction of a hydrocarbon even in co-presence of oxidative gas and in which a catalytic activity is maintained for a long period of time; and to provide a manufacturing method for hydrogen using the catalyst. SOLUTION: In the catalyst for manufacturing hydrogen used for the decomposition reaction of the hydrocarbon, an iron-containing substance and a substance containing at least one kind of metal selected from the group IIa metals and group VIIa metals and rare earth metals in the periodic table are carried on an alumina based carrier. In the method for manufacturing hydrogen, the hydrocarbon is decomposed by using this catalyst.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a catalyst for hydrogen production used for cracking hydrocarbons and a method for producing hydrogen using the same.

[0002]

2. Description of the Related Art Hydrogen is widely used in the chemical industry as a raw material for ammonia and methanol, and in the future, it will be used in large quantities as an energy source for fuel cells and the like.
Recently, it has been reported that an iron-based catalyst is used as a catalyst for producing hydrogen by decomposing hydrocarbons (MA Ermak
ova, DYErmakov, ALChuvilin, and GGKuvshinov,
J. Catal., 201, 183-197 (2001); Michio Serizawa, So Takenaka,
Ichiro Yamanaka, Kiyoshi Otsuka, 86th Symposium on Catalysis 3I05 (2000)). This iron-based catalyst exhibits an activity comparable to that of a Ni-based catalyst in a decomposition reaction system of pure hydrocarbons in which an oxidizing gas such as oxygen does not exist. Moreover, it is presumed that metallic iron / iron carbide participates in the reaction under the reaction conditions (report by Ermakova et al., Supra).

However, in order to prolong the catalyst life in the hydrocarbon decomposition reaction, if an appropriate amount of an oxidizing gas such as CO ₂ or H ₂ O, which is expected to react with by-product carbon, is added to the reaction system, iron is added. Was further oxidized, and the activity of the iron-based catalyst decreased. Therefore, in order to utilize the iron-based catalyst not only for the decomposition reaction of hydrocarbons but also for the reforming reaction of hydrocarbons, metallic iron / iron oxide is stable even in the reaction system containing these oxidizing gases. It is important to develop an improved iron-based catalyst that exists in the US and maintains high activity.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved iron-based catalyst which is stable against a hydrocarbon decomposition reaction even in the presence of an oxidizing gas and has a long-lasting catalytic activity. And a method for producing hydrogen from hydrocarbons using the catalyst.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies as to a catalyst used in a catalytic cracking reaction of hydrocarbons in order to solve the above problems, and as a result, a catalyst composed of specific components has good characteristics. This has led to the completion of the present invention. That is, according to the present invention, an alumina-based carrier is loaded with an iron-containing substance and a substance containing at least one metal selected from Group IIa metal, Group VIIa metal and rare earth metal of the periodic table. Provided is a catalyst for hydrogen production which is used for a characteristic hydrocarbon decomposition reaction. Further, according to the present invention, a hydrocarbon is supported on an alumina-based carrier by supporting an iron-containing substance and a substance containing at least one metal selected from Group IIa metal, Group VIIa metal and rare earth metal of the periodic table. There is provided a method for producing hydrogen by a hydrocarbon decomposition reaction, which comprises contacting the catalyst with a catalyst under heating conditions to obtain hydrogen.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, in order to produce hydrogen by decomposing hydrocarbons, an iron-based catalyst carrier is selected from iron-containing substances and Group IIa metals, Group VIIa metals and rare earth metals of the periodic table. And a substance containing at least one metal as an active ingredient.

Examples of the alumina-based substance used as the catalyst carrier in the present invention include various alumina structures and their precursors which have been heretofore known as catalyst carriers, and are not limited in any way depending on their production method and raw materials. Absent.
Such alumina-based materials include α-alumina and β-
Alumina, γ-alumina, activated alumina and the like are exemplified. Further, the alumina precursor is one that becomes alumina by firing, and examples thereof include organometallic aluminum compounds such as aluminum isopropoxide, aluminum acetylacetonate, and triethylaluminum.

The iron-containing substance used as the active component of the catalyst in the present invention includes any form, but those soluble in water or an organic solvent are recommended. Specifically, iron nitrate and iron sulfate are recommended. Inorganic acid iron salts such as iron chloride, iron halides such as iron chloride and iron bromide, organic acid irons such as iron oxalate, iron stearate and iron acetate, and organic metal irons such as ferrocene and iron acetylacetonate. It is illustrated. The addition amount of these iron-containing substances is arbitrary, but 0.01% of iron is added to the alumina-based carrier.
-100% by weight, preferably 1-70% by weight.

The active component of the other catalyst used in combination with the iron-containing substance is a metal of Group IIa or VI of the periodic table.
A substance containing at least one metal selected from Group Ia metals and rare earth metals (hereinafter, also referred to as “specific metal-containing substance”) is used. These are not limited as long as they are metals having no hydrocarbon decomposing activity, but magnesium is preferable as the Group IIa metal,
The Group VIIa metal is preferably manganese or rhenium, and the rare earth metal is preferably lanthanum, cerium, europium or the like. Substances containing these metals are
Examples are inorganic salts such as nitrates and sulfates, halides such as chlorides and bromides, organic acid salts such as oxalates and acetates, and organometallic compounds such as cyclopentadienyl metal and acetylacetonate metal. To be done. The amount of these elements added is arbitrary, but 0.01% of metal element is added to the alumina-based carrier.
It is -80% by weight, preferably 1-20% by weight.

The method for preparing the catalyst of the present invention includes (1)
A method of impregnating an alumina-based material as a carrier with an iron compound and a specific metal-containing material, (2) a method of precipitating iron and a specific metal-containing material on an alumina-based carrier, (3) iron and a specific metal-containing material on an alumina-based carrier Examples thereof include a method of dropping a solution of a metal-containing substance (incipient wetness method), (4) a method of kneading an alumina-based carrier, an iron compound and a specific metal-containing substance. In the case of the above (2), it is usually preferable to combine an inorganic acid salt of iron and a salt of a specific metal-containing substance with a basic precipitant, and as the precipitant, aqueous ammonia, potassium carbonate, sodium carbonate or the like should be used. Is preferred.

The hydrocarbon used as a raw material for producing hydrogen in the present invention is usually a gas or liquid hydrocarbon at room temperature, specifically, an aliphatic hydrocarbon such as methane, ethane, ethylene or propane; Alicyclic hydrocarbons such as cyclohexane and cyclopentane; aromatic hydrocarbons such as benzene, toluene and xylene are preferable, but hydrocarbons that are solid at room temperature such as paraffin wax can also be used.
These hydrocarbons may be used alone or in combination of two or more.

The hydrocarbon can be used as it is as a pure product, or can be diluted with an inert gas such as argon, nitrogen or helium for thermodynamically and efficiently and efficiently decomposed it. . The dilution rate at this time is arbitrary. The reaction temperature is 200 to 1,200 ° C., preferably 50
The contact time between the catalyst surface and the hydrocarbon gas is 0.01 to 1000 seconds, preferably 0.1 to 800 ° C.
50 seconds is preferable. Further, oxygen, water or carbon dioxide can be allowed to coexist in the reaction system, and carbon partially attached to the catalyst or carbon produced during the reaction is partially removed by these. The reaction formula in this case is as follows. Supply of _{C + H 2 O → CO +} H 2 C + CO 2 → 2CO C + O 2 → CO H 2 O for ₂ reaction system, _{O 2} and CO ₂ may be carried out continuously or intermittently. Further, the addition amount thereof is arbitrary, but in each case, carbon 1 contained in the raw material hydrocarbon is
0.001 to 100 mol, preferably 0.0
It is a ratio of 1 to 10 mol.

The thermal decomposition method of the present invention may employ either a batch system or a distribution system, but the distribution system is preferred. When using the distribution method, the fixed bed method,
A moving bed system, a circulating fluidized bed system (Ueyama et al., "Chemical Engineering" P. 27, December 1994 issue), etc. can be appropriately adopted. When the method of the present invention is carried out in a fixed bed system, it is preferable that the catalyst is packed in a tubular reactor to provide a catalyst packed bed. At this time, it is desirable to fix the catalyst layer by laminating a filter layer having pores smaller than the particle size of the carbonaceous material on the upper and lower ends of the catalyst packed layer.

Since the catalyst of the present invention contains a specific metal-containing substance in addition to the iron-containing substance, it is closely related to the catalytically active species even if an oxidizing gas such as water coexists in the reaction system. Stable presence of metallic iron / iron carbide (the presence of which is confirmed by powder X-ray diffraction after the reaction in the catalyst system of the present invention), which has excellent catalytic activity and catalyst life. is there. This suggests that this catalyst is not only useful for producing hydrogen by decomposing hydrocarbons, but that it can be used for reforming reactions in the future.

[0015]

EXAMPLES Next, the present invention will be described more specifically by way of examples. Example 1 3.62 g of iron nitrate (support ratio of iron to alumina: 10 wt%)
And 5.27 g of magnesium nitrate (10 wt% in the same amount) are dissolved in 50 g of distilled water, and then 5 g of commercially available activated alumina is suspended in the aqueous solution to support the metal component on the alumina.
Next, distilled water was evaporated to dryness, left at 100 ° C. overnight, and then calcined at 700 ° C. for 3 hours to obtain iron / Mg /
6.30 g of catalyst consisting of alumina was obtained. 1 g of the catalyst thus obtained was mixed well with 5 g of quartz sand having a particle size of 100 to 1000 μm, and this was filled in the center of a quartz reaction tube having an inner diameter of 12 mm to form a catalyst layer. In this case, both ends of the catalyst layer were filled with quartz wool so that the catalyst did not move during the reaction. This reaction tube was loaded into an electric furnace, and the reduction treatment of the catalyst was performed at 600 ° C. for 2 hours while flowing hydrogen into the electric furnace.

Next, methane / carbon dioxide /
While passing a mixed gas of nitrogen / oxygen (volume ratio: 65/8/4/21) at a rate of 40 cm ³ / min, the internal temperature of the reaction tube was raised to 800 ° C at a rate of 5 ° C / min to carry out the reaction. Started. When the obtained produced gas composition was analyzed by gas chromatography after 2, 4 and 6 hours, the results shown in Table 1 were obtained for the methane addition rate and the hydrogen production rate. No organic products such as ethane, ethylene and benzene were observed. Six hours after the reaction was started, the methane conversion was 95.2% and the hydrogen production rate was 0.008233 mol / hour, and the catalyst activity was not lowered even after 6 hours.
The methane conversion rate (%) is calculated by the following formula. Methane conversion rate = [(cracked carbon) + (CO production)] x 10
0 / [(cracked carbon) + (CO production amount) + (unreacted methane)] where, cracked carbon = [(raw material methane) + (raw material CO2)]
-[(Unreacted methane) + (unreacted CO2) + (produced CO)]

Comparative Example 1 A catalyst (iron / alumina) prepared in the same manner as in Example 1 was used, except that manganese nitrate was not used. As a result, as shown in Table 1, the conversion rate of methane was 79. The hydrogen generation rate was 2% and the hydrogen generation rate was 0.0604 mol / hour, and the methane conversion rate after 6 hours was as low as 14% or more.

Examples 2 to 6 Instead of the magnesium nitrate used in Example 1,
Catalysts prepared by using nitrates of manganese, lanthanum, cerium, europium and yttrium to prepare a catalyst (iron / metal / alumina) having a supporting rate of 10% were reacted in the same manner as in Example 1, and the results are shown in Table 1. The following results were obtained. It was found that the activity of each of these catalysts was small.

Comparative Examples 2 to 4 Instead of the magnesium nitrate used in Example 1,
A catalyst prepared in the same manner as in Example 1 was used, except that chromium, vanadium, and lithium nitrates were used, respectively, and the same reaction was performed. As a result, the methane conversion rate after 6 hours was remarkably active at around 20%. It was falling.

Comparative Example 5 A catalyst supporting 10% of manganese was prepared from only manganese nitrate and alumina without using an iron compound and reacted in the same manner as in Example 1. The methane conversion was 8 even after 2 hours. %, And the activity of the catalyst containing no iron was extremely low.

[0021]

[Table 1]

[0022]

According to the present invention, in the reaction for decomposing hydrocarbons to produce hydrogen, it has a stable catalytic activity even in the presence of an oxidizing gas such as carbon dioxide, water and oxygen, and has a long life. A useful catalyst is provided that maintains the catalyst life over time.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B01J 38/06 C01B 3/26 38/12 3/40 C01B 3/26 B01J 23/74 301M // C01B 3 / 40 23/84 311M (72) Inventor Isao Takahara 1-1-1 East, Tsukuba City, Ibaraki Prefecture Independent Administrative Law Institute of Industrial Science and Technology Tsukuba Center (72) Inventor Naoki Mimura 1-1-1, East, Tsukuba City, Ibaraki Prefecture Independent Administrative Law F-Term in Tsukuba Center, National Institute of Advanced Industrial Science and Technology (Reference) 4G040 DA03 DB01 DC02 DC04 DC05 4G069 AA03 AA08 BA01A BA01B BC08A BC10A BC10B BC32A BC38A BC42B BC43B BC44B BC61A BC62B BC64A BC66A BC66B CC40 FA01 GA03 GA06 GA02 GA06 GA02 GA14 GA02

Claims (5)

[Claims] 1. An alumina-based carrier carrying an iron-containing substance and a substance containing at least one metal selected from Group IIa metals, Group VIIa metals and rare earth metals of the periodic table. A catalyst for hydrogen production used in a hydrocarbon decomposition reaction. 2. The catalyst for hydrogen production used in the hydrocarbon decomposition reaction according to claim 1, wherein the Group IIa metal is magnesium. 3. The catalyst for hydrogen production used in the hydrocarbon decomposition reaction according to claim 1, wherein the Group VIIa metal is manganese or rhenium. 4. A catalyst in which a hydrocarbon is carried on an alumina-based carrier and an iron-containing substance and a substance containing at least one metal selected from Group IIa metals, Group VIIa metals and rare earth metals of the periodic table. A method for producing hydrogen by a decomposition reaction of hydrocarbon, which comprises contacting under heating to obtain hydrogen. 5. The method for producing hydrogen according to claim 1, wherein carbon dioxide and / or oxygen and / or water are allowed to coexist during the decomposition reaction.