JPH064135B2 - Hydrocarbon steam reforming catalyst - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a hydrocarbon steam reforming catalyst, and more specifically, it has high catalytic activity, high heat resistance and mechanical strength, and has a long catalyst life. It has excellent characteristics such as long,
For example, the present invention relates to a hydrocarbon steam reforming catalyst that can be suitably used in a hydrogen production plant for a fuel cell, a small hydrogen production plant, and the like.

[Problems to be Solved by the Related Art and Invention] By reacting a hydrocarbon with steam, hydrogen, carbon monoxide,
Previously, nickel-based catalysts were the mainstream for accelerating the steam reforming reaction that converts into methane and carbon dioxide, but recently, precious metal-based catalysts, especially rhodium and ruthenium-based catalysts, have been receiving attention. (For example,
56-91844, JP-A-57-4232, Igarashi et al., 58th catalyst debate, 4 series B12, Nagoya).

The catalyst system described in JP-A-56-91844 is a catalyst composed of rhodium and zirconium oxide.

The catalyst system described in JP-A-57-4232 has a silica content of 0.5 to 10% by weight and an alkali metal and alkaline earth metal content of 1% by weight or less in terms of oxide. It is an activated alumina on which 0.05 to 20% by weight of ruthenium is supported.

The catalyst proposed by the present inventors described above is a catalyst system in which a rhodium metal is supported on a zirconium oxide carrier, and this catalyst has a high activity and produces a large amount of carbon on the catalyst. It is a catalyst that can be suppressed and is effective for steam reforming of hydrocarbons.

As can be seen in the above examples of zirconium, zirconium oxide (zirconia) has recently been shown to be effective as a carrier.

However, when the zirconia carrier is produced by calcination, if the calcination temperature is increased, the surface area is remarkably reduced and the catalytic activity is reduced; the mechanical strength is reduced due to shrinkage and the like, and the catalyst layer is pulverized and the like. There is a problem that the pressure loss increases and the operation becomes difficult;

The object of the present invention is to eliminate the above problems, carbonization having high advantages such as high catalytic activity, excellent heat resistance and mechanical strength, and improved stability, reforming ability and catalyst life. It is to provide a catalyst for steam reforming of hydrogen.

[Means for Solving the Problems] The inventors of the present invention have conducted extensive studies to solve the problems, and as a result, use rhodium and / or ruthenium as the active metal species, and use partially stabilized zirconia as the carrier. In particular, by using a partially stabilized zirconia having a yttrium oxide component, a magnesium oxide component or a cerium oxide component as a stabilizer, high heat resistance and mechanical strength of the carrier, for example, reduction of the surface area even at a high temperature of 500 ° C. or higher. Can be effectively prevented and can be stably used, and due to its excellent properties and the like, it can sufficiently and stably exhibit the function of the active metal species as a reforming catalyst. It was discovered that a catalyst having significantly improved ability and life can be obtained, and the present invention was completed based on the findings. It came to be achieved.

That is, the present invention is a hydrocarbon steam reforming catalyst comprising a partially stabilized zirconia carrier carrying rhodium or ruthenium.

The present invention will be described in detail below.

Partially stabilized zirconia carrier It is particularly important to select a partially stabilized zirconia carrier as a carrier in the present invention.

This partially stabilized zirconia carrier has a particularly high reactivity of zirconia itself with water, aims to improve the steam reforming ability of hydrocarbons, and is originally excellent as a carrier such as suppressing carbon deposition generated on the catalyst. In addition to the above properties, it also has excellent properties as a partially stabilized zirconia produced by the addition of a stabilizer, that is, it has excellent heat resistance and mechanical strength. It can be used for.

Such a partially stabilized zirconia carrier can be obtained by modifying and stabilizing the zirconia component by adding a stabilizer.

As the zirconium source used as a raw material for preparing the zirconia component of the partially stabilized zirconia carrier, zirconium oxide or a substance that can be converted to zirconium oxide (zirconia component) during catalyst preparation or steam reforming reaction can be used. .

A commercially available product can be used as the zirconium oxide.

Further, as a substance which is converted into zirconium oxide during catalyst preparation or steam reforming reaction, for example, zirconium hydroxide, zirconium halide, zirconium nitrate,
Examples thereof include zirconium nitrate, zirconium acetate, zirconium oxalate, zirconium tetramethoxide, zirconium tetraethoxide, zirconium alkoxides such as tetraisopropoxide, zirconium oxychloride, and organic zirconium compounds.

Among these, zirconium alkoxide and the like can be preferably used.

The sparingly soluble compound can also be used after being solubilized by appropriately adding alcohol or acid.

The various zirconium compounds may be used alone or in combination of two or more.

The stabilizer used as a component of the partially stabilized zirconia carrier is not particularly limited as long as it is a known various oxide used as a stabilizing component of so-called stabilized zirconia known in various material fields. There is no yttrium oxide component, magnesium oxide component and cerium oxide component.

Among these, the yttrium oxide component, the magnesium oxide component and the cerium oxide component can be particularly preferably used.

The yttrium oxide component, the magnesium oxide component, and the cerium oxide component can be formally expressed as Y ₂ O ₃ , MgO, and CeO ₂ , respectively.

As the yttrium source used as a raw material for preparing the yttrium oxide component, yttrium oxide or a substance that can be converted into yttrium oxide (yttrium oxide component) during catalyst preparation or steam reforming reaction can be used.

As the substance converted to the yttrium oxide component, for example, yttrium hydroxide, yttrium halide,
Yttrium oxyhalide, yttrium nitrate, yttrium carbonate, yttrium acetate, yttrium oxalate, yttrium trimethoxide, yttrium triethoxide, yttrium tripropoxide, yttrium triisopropoxide, yttrium alkoxide such as yttrium tributoxide You can

Among these, particularly yttrium alkoxide can be preferably used.

As the magnesium source used as a raw material for preparing the magnesium oxide component, magnesium oxide or a substance that can be converted into magnesium oxide (magnesium oxide component) during catalyst preparation or steam reforming reaction can be used.

As a substance that is converted to the magnesium oxide component, for example, magnesium hydroxide, magnesium halide,
Examples thereof include magnesium oxyhalide, magnesium nitrate, magnesium carbonate, magnesium acetate, magnesium oxalate, magnesium methoxide, magnesium ethoxide, magnesium propoxide, magnesium isopropoxide, magnesium alkoxide such as magnesium butoxide, and the like.

Among these, magnesium alkoxide and the like can be preferably used.

As the cerium source used as a raw material for preparing the cerium oxide component, cerium oxide or a substance that can be converted to cerium oxide (cerium oxide component) during catalyst preparation or steam reforming reaction can be used. As a substance that is converted into the cerium oxide component, for example, cerium hydroxide, cerium halide, cerium oxyhalide, cerium nitrate, cerium carbonate, cerium acetate, cerium oxalate, cerium methoxide, cerium ethoxide, cerium propoxide, Examples thereof include cerium alkoxides such as cerium isopropoxide and cerium butoxide.

Among these, cerium alkoxide and the like can be preferably used.

These yttrium compounds, magnesium compounds and cerium compounds can be used alone or in combination of two or more.

The sparingly soluble compound can also be used after being solubilized by appropriately adding alcohol or acid.

In the present invention, the partially-stabilized zirconia carrier can be used as a mixture or a composition with another carrier as long as it does not impair the object of the present invention.

Examples of such other carriers include zirconia, silica, alumina and zeolite.

The shape of the partially stabilized zirconia carrier is not particularly limited, and for example, fine powder, beads, pellets,
Any shape such as a plate shape, a film shape, and a monolith shape can be used.

Preparation of partially stabilized zirconia carrier As a method for preparing a partially stabilized zirconia carrier used as a carrier in the hydrocarbon steam reforming catalyst of the present invention,
The method is not particularly limited and, for example, a coprecipitation method, a wet kneading method, a dry kneading method, a combination thereof, or the like can be appropriately used. Examples of suitable preparation methods are as follows.

That is, as the preparation raw material, the zirconium source,
An yttrium source, a magnesium source, a cerium source, for example, an alkoxy compound thereof is used, and these are usually
In the field of catalyst preparation, a complex oxide having a large surface area consisting of fine primary particles or a hydrate thereof is precipitated by an alkoxide hydrolysis method used for preparing a complex oxide, and the obtained precipitate is appropriately washed, It can be obtained by drying, and then calcining at a predetermined temperature.

Here, the firing temperature is usually 400 to 1,000 ° C., preferably 500 to 850 ° C.

Usually, air or the like can be preferably used as the firing atmosphere.

If desired, the above firing step can be omitted.

Supported metal: ruthenium As the ruthenium source supported on such a carrier, ruthenium iodide, ruthenium chloride and other halogenated ruthenium, ammonium chloride ruthenate such as ruthenate, and ruthenium chloride such as ruthenium halide. Examples thereof include acid, ruthenium hydroxide, ruthenium dioxide, ruthenium oxide such as ruthenium tetraoxide, ruthenate such as potassium ruthenate, and organic ruthenium compounds such as ruthenium carbonyl.

Such ruthenium sources can be used alone or in combination of two or more.

Preferred is ruthenium trichloride.

Supported metal; rhodium As a rhodium source for supporting the rhodium metal,
Rhodium halides such as rhodium chloride, sodium rhodium chloride, halogenated rhodates such as ammonium chloride, rhodium chloride such as rhodium chloride, rhodium (III) hydroxide, rhodium hydroxide (I
V), rhodium nitrate, rhodium oxide, organic rhodium compounds such as rhodium carbonyl, and the like.

Such rhodium sources can be used alone or in combination of two or more.

The total supported amount of ruthenium or rhodium or ruthenium and rhodium in the steam reforming catalyst of the present invention is usually 0.1 to 5% by weight, preferably 0.3 to 3% by weight, based on the zirconia carrier.

In this case, if the supported amount is excessively increased, the carrier may be coated with the supported metal, and the effect corresponding to the supported amount may not be obtained.

Catalyst Preparation The method for preparing the steam reforming catalyst of the present invention is not particularly limited and includes, for example, an impregnation method, an immersion method, a wet adsorption method, a dry adsorption method, a CVD method, a solvent evaporation method, a dry mixing method, A wet mixing method, a spray coating method, a combination thereof, or the like can be appropriately adopted, and a stationary method, a stirring method, a solution flow method, a solvent reflux method, or the like can be used as an operation method for supporting. However, the preferred catalyst preparation examples are as follows.

That is, the partially stabilized zirconia carrier obtained by the above Preparation Examples or the like is usually added to a solution or colloidal dispersion of the ruthenium compound and / or rhodium compound in an amount of 0.1
~ 10 hours, preferably 0.5 ~ 5 hours, mixing or kneading, evaporating to dryness, then 0.1 ~ at 10 ~ 200 ° C.
After drying for 24 hours, it is baked in air or nitrogen stream at a temperature of 500 to 850 ° C. for 0.1 to 20 hours. And
If necessary, for example, the steam reforming catalyst of the present invention can be obtained by performing reduction treatment after molding into a desired shape using a tableting molding method or the like.

The solvent used for the solution or colloidal dispersion of the ruthenium compound and / or the rhodium compound may be one that can dissolve the ruthenium compound and / or the rhodium compound or can be stably maintained as a uniform colloidal solution. There is no particular limitation, and an aqueous solvent, a non-aqueous solvent, or a mixed solvent thereof can be used.

In the impregnation, a solution or colloidal dispersion of the ruthenium compound and / or rhodium compound, if necessary, various acids, bases, salts, oxidizing agents, reducing agents, pH adjusting agents, control agents, and A dissolution accelerator or the like may be added.

As the reduction treatment, it is usually preferable to bring hydrogen into contact with the catalyst precursor filled in the reaction tube while heating.

Hydrocarbon Steam Reforming Reaction The steam reforming catalyst of the present invention is used for promoting a hydrocarbon steam reforming reaction.

The hydrocarbon is not particularly limited, for example, methane,
Linear or branched saturated aliphatic hydrocarbons such as ethane, propane, butane, pentane, hexane, heptane, octane, nonane, decane, and alicyclic saturated hydrocarbons such as cyclohexane, methylcyclohexane, cyclooctane, etc. Can be mentioned.

The hydrocarbon may be one kind of the above-mentioned various kinds alone or a mixture of two or more kinds thereof, and may be various refined petroleum fractions.

There is no particular limitation on the steam that reacts with the hydrocarbon.

It is considered that the hydrocarbon reacts with water vapor according to the following reaction formula.

C _n H _m + nH ₂ O → nCO + (n + m / 2) H ₂ (I) C _n H _m + 2nH ₂ O → nCO ₂ + (2n + m / 2) H ₂ (II) [where the formula (I ) And n in the formula (II) represent a real number of 1 or more, and m represents a real number of 2 or more. ] In addition to the above, CH ₄ due to hydrocracking of hydrocarbons, etc.
The generation reaction (III), and the subsequent equilibration reaction CH ₄ + H ₂ OCO + 3H ₂ (IV) CO + H ₂ OCO ₂ + H ₂ (V) may occur simultaneously.

Therefore, theoretically, the amounts of the hydrocarbon and steam used can be determined by the stoichiometric amount so as to follow the above reaction formulas (I) to (V), but when the catalyst of the present invention is used, It is preferable to determine the amount of hydrocarbons and the amount of water vapor so that the steam / carbon ratio is 1 to 12, preferably 3 to 8.

By adopting such a steam / carbon ratio, a hydrogen-rich gas can be obtained particularly efficiently and stably.

The reaction temperature is usually 300 to 950 ° C, preferably 400 to 8
It is 50 ° C.

The catalyst of the present invention has a sufficiently high catalytic activity even at a reaction temperature of 500 ° C. or lower, and since it uses a specific partially stabilized zirconia carrier as a carrier, its high heat resistance and mechanical strength Due to its excellent properties such as
It should be noted that even at a high temperature of 0 ° C., the reduction of the surface area of the carrier and thus the catalyst itself and the destruction due to pulverization, etc. are effectively prevented, and long-time operation can be performed while stably maintaining a high catalytic activity. Deserve.

The reaction pressure is usually 0 to 50 kg / cm ² G, preferably 0 to 20
It is kg / cm ² G.

The reaction system may be either a continuous flow system or a batch system, but the 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 steam is usually
It is 1,000 to 40,000 h ^-1 , preferably 2,000 to 20,000 h ^-1 .

With the catalyst of the present invention, it should be noted that continuous operation is possible even at such high gas hourly space velocities.

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 type of reactor is not particularly limited, and for example, a tubular reactor or the like can be adopted.

In this way, when the hydrocarbon is reacted with steam in the presence of the catalyst of the present invention, the reaction usually proceeds mainly according to the reaction formula (I). Equilibrium reaction (V) in which carbon monoxide and water are reacted to form carbon dioxide and hydrogen and equilibrium reaction (IV) in which carbon monoxide and hydrogen are reacted to form methane and water Etc. are simultaneously triggered, resulting in a mixture of hydrogen, methane, carbon monoxide and carbon dioxide. However, the main product is hydrogen.

The obtained mixed gas can be directly used for various purposes, or can be separated into each gas component and provided for each purpose.

[Examples] Next, examples of the present invention will be described.

(Examples 1 to 5) Preparation Example of Partially Stabilized Zirconia Support A zirconium alkoxide was used as a zirconium source of a zirconia component (formally ZrO ₂ ), and a yttrium oxide component (formally Y ₂ O) was used as a stabilizer thereof. ₃ ), these alkoxides are used as the yttrium source, magnesium source, and cerium source corresponding to the magnesium oxide component (formally MgO) or the cerium oxide component (formally CeO ₂ ) and dissolved in isopropyl alcohol. And hydrolyze by adding water with sufficient stirring to precipitate as a complex oxide (hydrate) with a large surface area consisting of ultrafine particles with a primary particle size of 0.03 μm or less, and after washing the resulting precipitate , Dried at 120 ° C for a whole day and then calcined in air for 3 hours to obtain a carrier for the partially stabilized zirconia-supported catalyst shown in Table 1. A partially stabilized zirconia carrier having a predetermined composition was obtained.

Catalyst Preparation Example Each partially stabilized zirconia support obtained above was added with Ru.
0.5 wt% of Cl ₃ or RhCl ₃ was supported as a metal, respectively, and reduction treatment with hydrogen was carried out in the reaction tube to prepare each partially stabilized zirconia-supported steam reforming catalyst shown in Table 1.

Using each of the catalysts prepared above, an atmospheric fixed bed flow reactor was used as a reactor, n-butane was used as a reaction raw material, and a reaction temperature was set at 450.
The steam reforming reaction was carried out at a reaction temperature factor of 822.7 (g-cat · min / n-butane mole) and a steam / carbon ratio (feed ratio of steam and n-butane, converted from the molar ratio) of 12 ° C.

As a result of analysis by continuous gas chromatography, the results shown in Table 1 as the catalytic activity (total conversion rate) and the composition of the produced gas (carbon monoxide, methane, carbon dioxide and hydrogen) after 10 hours from the start of the reaction Got

(Comparative Examples 1 and 2) ZrO ₂ .xH ₂ O prepared by preparing ZrO ₂ · xH ₂ O in air at 500 ° C. for 1 hour
₂ Support, RuCl ₃ or RhCl ₃ as metal, respectively
The catalysts shown in Table 1 were Ru / ZrO ₂ and Rh / ZrO ₂ impregnated and supported so as to be 0.5% by weight.

A reaction was carried out in the same manner as in Example 1 using each of these catalysts.

The results are shown in Table 1.

(Example 6 and Comparative Example 3) As shown in Table 2, a long-term life test was conducted under the same conditions as in Example 1 using the same catalysts as those used in Example 1 and Comparative Example 1, respectively. It was

Table 2 shows the total conversion rates at the initial stage of the reaction and after 1000 hours, the pressure loss of the catalyst layer (relative value) and the change in the surface area of the catalyst by the BET method.

Tables 1 and 2 show examples of the results. From these results, the catalyst using the partially stabilized zirconia carrier of the present invention is compared with the catalyst using the conventional zirconia carrier. In addition, it has excellent catalytic activity, excellent heat resistance and mechanical strength, has a small decrease in surface area even at high temperatures, and is extremely resistant to powdering and destruction of the catalyst due to shrinkage, etc. It was confirmed that the catalyst was an excellent hydrocarbon steam reforming catalyst having an improved life.

EFFECTS OF THE INVENTION According to the present invention, since a specific carrier called a partially stabilized zirconia carrier is used as a catalyst carrier, the catalyst activity is high, the heat resistance and the mechanical strength are excellent, and the stability and the reforming ability are high. Also, it is possible to provide a catalyst for steam reforming of hydrocarbons, which has excellent advantages such as improved catalyst life.

Claims (2)

[Claims] 1. A catalyst for steam reforming of hydrocarbon, comprising rhodium or ruthenium supported on a partially stabilized zirconia carrier. 2. The steam reforming of hydrocarbon according to claim 1, wherein the partially stabilized zirconia carrier has a zirconia component and a yttrium oxide component, a magnesium oxide component or a cerium oxide component as a stabilizer thereof. catalyst.