JP3365657B2 - Catalyst for steam reforming of hydrocarbons - Google Patents

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, and more specifically, it has excellent properties such as high catalytic activity, low cost, high mechanical strength, and long catalyst life. For example, the present invention relates to a hydrocarbon steam reforming catalyst that can be suitably used in a small hydrogen production plant, a hydrogen production plant for fuel cells, and the like.

[0002]

2. Description of the Related Art A reaction for reforming hydrocarbon with steam is industrially carried out on a large scale as a reaction for producing synthesis gas or hydrogen. Nickel-based catalysts are generally used in this reaction, but when reforming higher hydrocarbons with steam, there is a problem that carbon precipitation easily occurs and the catalyst life is short. Also, nickel-based catalysts tend to cause more and more carbon precipitation when the steam / carbon ratio is reduced to save energy.
There is also a drawback that a high steam / carbon ratio (molar ratio) of up to 6.0 is required, and its improvement has been attempted.

On the other hand, noble metal catalysts are unlikely to cause carbon deposition.
Is said to be an alternative to nickel-based catalysts.
Development is being attempted. Zirconia is used as a catalyst carrier.
Then H₂ A catalyst for steam reforming, which has the effect of activating O
It is said that it has the ability to suppress carbon precipitation when used for
Zirconia as a carrier and rhodium or ruthenium as a carrier.
Various kinds of catalysts have been proposed. For example, JP-A-3-
No. 109942 discloses ruthenium as an active ingredient,
A catalyst using cobalt as a co-catalyst has excellent performance
It is described that However, these
Noble metal catalyst requires steam / carbon ratio for operation
Is as small as 1.5 to 3.0 and is energy saving,
Zirconia, which is the body, is expensive, and has good formability and mechanical strength.
Has a problem of low cost and is a cheap carrier like alumina
It has excellent mechanical strength and its properties as zirconia.
It is desirable to develop a carrier with excellent activity without loss of quality.
Was there.

[0004]

DISCLOSURE OF THE INVENTION The present invention is inexpensive and can be suitably used in hydrogen production plants for fuel cells, has long life, high activity, high strength, and low steam /
An object of the present invention is to provide a catalyst for steam reforming of hydrocarbons which can be operated at a carbon ratio.

[0005]

Means for Solving the Problems As a result of intensive studies for achieving the above-mentioned object, the present inventors have found that when alumina carrying zirconia having a zirconia sol as a precursor is used as a carrier, an alumina carrier and zirconia are used. A low-cost carrier with excellent mechanical properties that has the advantages of a carrier is obtained, and a catalyst that supports a specific co-catalyst and contains a specific active component is a hydrocarbon steam reforming reaction. It was found that the present invention has excellent catalytic performance, and based on this finding, the present invention has been completed.

That is, according to the present invention, a steam reforming of a hydrocarbon comprising lanthanum oxide and cobalt as a co-catalyst and ruthenium as an active ingredient is carried on an alumina carrier carrying zirconia whose precursor is zirconia sol. A catalyst for use is provided.

The zirconia supported on the alumina carrier used in the present invention uses zirconia sol as a precursor. A catalyst other than zirconia itself or a precursor other than zirconia sol, for example, an alumina carrier supporting zirconia using nitrate zirconia is not only low in activity for a hydrocarbon steam reforming reaction, but also at a reaction temperature. On the contrary, raising it lowers the activity. A catalyst that uses an alumina carrier that supports zirconia, which uses zirconia sol as a precursor, has catalytic activity comparable to that of a catalyst that uses zirconia itself as a carrier, as well as excellent mechanical strength, and durability of activity against thermal influence. A catalyst with excellent properties.

The amount of zirconia supported on the catalyst is usually 0.2 to 20 wt%, preferably 1.0 to 5.0 w.
t%. If the supported amount is less than 0.2 wt%, the effect of zirconia as a cocatalyst may be insufficient,
If it exceeds wt%, not only the co-catalyst effect corresponding to the amount cannot be expected, but also the carrier becomes expensive, which is disadvantageous in terms of cost. On the other hand, if it exceeds 20 wt%, peeling of the carried zirconia is likely to occur.

Zirconia is preferably present on the catalyst surface, and expensive zirconia can be effectively used by selectively attaching it to the surface. Therefore, in supporting zirconia on an alumina carrier, a method of kneading alumina or an alumina precursor powder and a zirconia sol is also applicable, but the alumina carrier is immersed in the zirconia sol, or the zirconia sol is sprayed on the alumina carrier. It is preferable to support them.

The zirconia sol, which is a precursor of zirconia, has a spherical particle shape or a shape in which spheres are linearly connected, and any shape of the sol can be used. It is preferably a sol, and the particle size is 50 to 2,000 angstroms, preferably 100 to 1,000 angstroms,
The pH range in which the zirconia sol is stabilized may be any of acid side, neutral side or alkaline side.

As described above, the zirconia sol is preferably carried on the alumina carrier by impregnating the alumina carrier with the zirconia sol or spraying the zirconia sol onto the alumina carrier to attach the zirconia sol to the alumina carrier. Be done. For the impregnation, usually, a sol aqueous solution having a zirconia content of 20 to 30 wt% can be used as it is, but if necessary to adjust the supported amount of zirconia, dipping the carrier in the zirconia sol or spraying the zirconia sol on the carrier, It may be repeated by adding a drying operation in the middle, and when a small amount of the sol may be supported, it can be used after further diluting the zirconia sol with pure water. A predetermined amount of zirconia sol is attached to an alumina carrier and then dried, and then preferably 1 to 400 to 900 ° C.
When calcined for 3 hours, an alumina carrier supporting zirconia is obtained.

As the alumina carrier used in the present invention, alumina having any crystal structure can be used as long as it is a commonly used alumina carrier. Active α-alumina is preferred. The shape is not particularly limited, for example, fine powder, beads, pellets,
It may have any shape such as a plate shape or a monolith shape.

Support of lanthanum oxide and cobalt as a promoter on the zirconia-supported alumina carrier is carried out as follows.

The lanthanum oxide as a cocatalyst is supported on the alumina carrier by a method of immersing the alumina carrier in an aqueous solution of lanthanum salt or a method of spraying the aqueous solution on the carrier. The salt that can be used as a raw material is water-soluble, and any salt can be used as long as it does not leave a component that becomes a catalyst poison after thermal decomposition on the alumina carrier, and is easy to thermally decompose or economical. From the viewpoint, it is preferable to use nitrates or halides. Particularly preferably, lanthanum nitrate is used. These lanthanum oxide sources may be used alone or in combination of two or more.

After the lanthanum salt is attached to the alumina carrier, the alumina carrier is calcined at 400 to 900 ° C., so that the lanthanum oxide is supported on the alumina carrier. The supported amount of lanthanum oxide is usually 0.1 to 10 wt% and preferably 0.5 to 5.0 wt% with respect to the catalyst. Carrying amount is 0.1wt
If it is less than 10%, the catalytic activity may decrease, and it may be 10wt%.
If it exceeds, the cocatalyst effect corresponding to the amount cannot be expected.

The loading of cobalt as the cocatalyst on the alumina carrier is carried out in the same manner as the loading of lanthanum oxide on the alumina carrier. As the cobalt source, oxalates, nitrates, carbonates, acetates, hydroxides, oxides, halides, basic salts, alkoxides, other organic compounds, etc. are used.
Particularly preferably, cobalt nitrate is used. These cobalt sources may be used alone or in combination of two or more. The supported amount of cobalt is usually 0.1 to 10 wt% with respect to the catalyst, preferably 0.5 to 5.0 w.
t%. If the supported amount is less than 0.1 wt%, the catalytic activity may decrease, and if it exceeds 10 wt%, the co-catalyst effect corresponding to the amount cannot be expected.

The combined use of lanthanum oxide and cobalt as a co-catalyst significantly improves the conversion rate of hydrocarbons.

The ruthenium contained as an active ingredient in the catalyst of the present invention is loaded on the alumina carrier in the same manner as the lanthanum oxide is loaded on the carrier. As the ruthenium source, ruthenium iodide, ruthenium halide such as ruthenium chloride, halogenated ruthenium salt such as ammonium chloride ruthenate, ruthenium halide such as ruthenium chloride, ruthenium hydroxide, ruthenium dioxide,
Ruthenium oxide such as ruthenium tetraoxide, ruthenate such as potassium ruthenate, and organic ruthenium compound such as ruthenium carbonyl are used. Such ruthenium sources can be used alone or in combination of two or more. Particularly preferred is ruthenium chloride. The amount of ruthenium supported on the catalyst is usually 0.02 to 5.0 wt%, preferably 0.1 to 3.0 wt%. Carrying amount 0.0
If it is less than 2 wt%, the catalytic activity may decrease, and 10
If it exceeds wt%, the co-catalyst effect corresponding to the amount cannot be expected. Ruthenium is also loaded on the carrier in the same manner as lanthanum oxide and cobalt.

The loading of lanthanum oxide, cobalt and ruthenium may be carried out separately or simultaneously. Preferably, ruthenium and cobalt are loaded after the lanthanum oxide is loaded.

The catalyst obtained as described above needs to be reduced before it is subjected to the reaction, but it may be reduced in either liquid phase or gas phase. In the case of liquid phase reduction, potassium formate, formalin, hydrazine, An aqueous solution such as sodium borohydride can be used for reduction under heating at 40 to 80 ° C., and in the case of gas phase reduction, the catalyst is 100 to 600.
It can be reduced while maintaining the temperature at 0 ° C. while flowing hydrogen gas.

The steam reforming catalyst of the present invention is used for promoting the steam reforming reaction of hydrocarbons. The hydrocarbon is not particularly limited, and examples thereof include linear or branched saturated aliphatic groups having 1 to 10 carbon atoms such as methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane, and decane. Examples include hydrocarbons, saturated alicyclic hydrocarbons such as cyclohexane, methylcyclohexane, and cyclooctane.

The hydrocarbon may be one kind among the above-mentioned various kinds, or a mixture of two or more kinds, and may be various refined petroleum fractions. There is no particular limitation on the steam that reacts with the hydrocarbon.

When the reaction is carried out using the catalyst of the present invention, the steam / carbon ratio is usually 2 to 12, preferably 2 to
It is preferable to determine the amount of hydrocarbons and the amount of water vapor so as to be 8.

The reaction temperature is usually 500 to 850 ° C, preferably 650 to 850 ° C. The reaction pressure is
Usually 0 to 50 kg / cm ² G, preferably 0 to 20 k
It is g / cm ² G.

The reaction system may be either a continuous flow system or a batch system, but a continuous flow system is preferred. When the continuous flow system is adopted as the reaction system, the gas space velocity (GHSV) of the mixed gas of hydrocarbon and water vapor
Is usually 1,000 to 40,000 h ^-1 , preferably 2,000 to 20,000 h ^-1 . The reaction system is not particularly limited and may be a fixed bed system, a moving bed system, a fluidized bed system, or the like. The form of the reactor is not particularly limited, and for example, a tubular reactor can be adopted.

[0026]

EXAMPLES The present invention will now be described in detail based on examples, but the present invention is not limited thereto.

Example 1 (Production of catalyst) 20 g of pure water was added to 500 g of aluminum hydroxide, kneaded in a kneader and dried, and then 15 g of graphite was added to a pulverized product of 10 mesh pass, After mixing 3/16 in x 3/16 in
Tablet to size and then press the tablet in an electric furnace
100 ° C. × 4 hrs. A catalyst carrier precursor (designated as carrier A) was prepared by calcining, and separately from this, 30 wt% zirconia sol 150c stabilized on the acidic side.
c is weighed in a 300 cc beaker and the carrier A60
g in this zirconia sol for 1.5 hrs. Soak,
Then, after taking out, 110 ° C. × 20 hrs. Dry and then in an electric furnace at 500 ° C x 1 hr. It was calcined to prepare a catalyst carrier (designated as carrier B).

Next, 1.6 g of lanthanum nitrate was added to 8 cc of pure water.
The lanthanum nitrate aqueous solution prepared for dissolution in was added to 60 g of the carrier B by a spray method, and the temperature was 110 ° C for 20 hours.
s. After drying, 450 ° C. × 1 hr. A catalyst carrier (designated as carrier C) was prepared by firing.

Finally, ruthenium and cobalt are supported on an alumina carrier supporting zirconia and lanthanum oxide to form a catalyst, and the ruthenium and cobalt are supported on the alumina carrier as a ruthenium metal prepared in advance.
Mixed aqueous solution containing 75 wt% ruthenium chloride and 3.75 wt% cobalt nitrate as cobalt metal 1
It was carried out by spraying 0 cc on the carrier C, but the spraying operation was carried out in two steps. That is, first, 5 cc of the mixed aqueous solution is sprayed on 38 g of the carrier C, and then 1
10 ° C. × 20 hrs. Dry, and further 500 ° C. × 1 hr.
The first spraying is completed by firing, and then the remaining mixed aqueous solution of 5 cc is again spray-supported on the carrier C, and further 110 ° C. is also used during the first spraying operation.
× 20 hrs. After drying, 500 ° C x 1 hr. A catalyst was obtained by firing. Part of the alumina in this catalyst is X
It was linearly converted to α-alumina.

This catalyst has the following composition after hydrogen reduction:
The hexane steam reforming performance evaluation and mechanical strength are shown in Table 1.
It was the street.

Ru 0.21 wt% ZrO ₂ 3.20 wt% Co 1.00 wt% La ₂ O ₃ 1.04 wt% Al ₂ O ₃ BALANCE

Comparative Example 1 (Production of catalyst) 20 g of pure water was added to 500 g of aluminum hydroxide, kneaded in a kneader and dried, and then 15 g of graphite was added to a pulverized product of 10 mesh pass, After mixing 3/16 in x 3/16 in
Tablet to size and then press the tablet in an electric furnace
100 ° C. × 4 hrs. A catalyst carrier precursor (designated as carrier A) was prepared by calcining, and separately from this, 30 wt% zirconia sol 150c stabilized on the acidic side.
c is weighed in a 300 cc beaker and the carrier A60
g in this zirconia sol for 1.5 hrs. Soak,
Then, after taking out, 110 ° C. × 20 hrs. Dry and then in an electric furnace at 500 ° C x 1 hr. It was calcined to prepare a catalyst carrier (designated as carrier B).

Then, ruthenium and cobalt are finally supported on the alumina carrier supporting zirconia to form a catalyst. The ruthenium and cobalt are supported on the alumina carrier in an amount of 0.75 wt% as a ruthenium metal prepared in advance.
Ruthenium chloride and cobalt metal of 3.75wt%
% Cobalt nitrate mixed aqueous solution 10 cc Carrier B 38 g
In the same manner as in Example 1 by spraying twice, and after the spraying operation, 110 ° C. × 20 hrs. Dry and then in an electric furnace at 500 ° C x 1 hr. A catalyst was obtained by firing. Part of the alumina in this catalyst is α
-It was aluminized.

This catalyst has the following composition after hydrogen reduction:
The hexane steam reforming performance evaluation and mechanical strength are shown in Table 1.
It was the street.

Ru 0.21 wt% Co 1.00 wt% ZrO ₂ 3.20 wt% Al ₂ O ₃ BALANCE

Comparative Example 2 Commercially available zirconia was mixed with ruthenium chloride (ruthenium metal was 0.5 wt% relative to zirconia) and cobalt nitrate (cobalt metal was 1.0 wt relative to zirconia).
%) Was impregnated, dried at 120 ° C. for 6 hours, and then calcined at 500 ° C. for 1 hour to prepare a catalyst.

This catalyst has the following composition after hydrogen reduction:
The methane steam reforming performance evaluation results and mechanical strength are shown in Table 1.

Ru 0.5 wt% Co 1.0 wt% ZrO ₂ BALANCE (Steam reforming reaction) The performance evaluation of the catalysts of Examples and Comparative Examples was carried out under the following conditions. n-Hexane steam reforming reactivity evaluation condition Catalyst usage amount 25 cc Catalyst size 3/16 in x 3/16 in (tablet product) Outlet total gas space velocity 5,000 hr ^-1 steam / carbon 2.5 (molar ratio) Pressure Normal Pressure Reaction temperature 750 ° C. Reaction time 7 days The hexane conversion rate (%) showing the performance of the catalyst was calculated by the following formula. Hydrocarbon compounds were detected in addition to methane and hexane in the n-hexane steam reforming reactivity evaluation, but they were ignored because the produced amount was very small.

[0039]

[Equation 1] Here, CO _out : CO concentration (%) at the catalyst layer outlet side CO _{2 out} : CO ₂ concentration (%) at the catalyst layer outlet side Hexane _out : Hexane concentration (%) at the catalyst layer outlet side CH _{4 out} : Catalyst layer CH ₄ concentration at exit (%)

[0040]

[Table 1]

[0041]

INDUSTRIAL APPLICABILITY According to the present invention, a hydrocarbon which can be suitably used in a hydrogen production plant for a fuel cell, has a performance such as a long life, high activity and high strength and can be operated at a low steam / carbon ratio. The steam reforming catalyst of was obtained.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadakuni Kitamura 5-16-16 Tsujido Motomachi, Fujisawa-shi, Kanagawa 31 (72) Inventor Atsushi Furuya 1-18-18 Higashi, Satte-shi, Saitama 611 Skate Heights 611 (56) Reference Documents JP-A-5-221602 (JP, A) JP-A-5-261286 (JP, A) JP-A-5-168924 (JP, A) JP-A-2-2879 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B01J 21/00-37/36 C01B 3/34

Claims (2)

(57) [Claims] 1. A catalyst for steam reforming of hydrocarbons, which comprises lanthanum oxide and cobalt as a co-catalyst and ruthenium as an active component on an alumina carrier carrying zirconia whose precursor is zirconia sol. 2. The catalyst for steam reforming of hydrocarbon according to claim 1, wherein the amount of zirconia supported is 0.2 to 20 parts by weight with respect to 100 parts by weight of the catalyst.