JP5378148B2 - Reforming catalyst, reformer, and hydrogen production device - Google Patents

Description

  The present invention relates to a reforming catalyst, a reforming apparatus, and a hydrogen production apparatus for reforming hydrocarbons to generate hydrogen.

In recent years, in order to reduce the burden on the environment, the spread of fuel cell systems has been promoted, and household fuel cell systems have also been developed.
In a household fuel cell system, hydrogen is produced from reforming and shift reactions from raw materials for hydrogen production such as city gas containing hydrocarbons and petroleum-based fuels, and electricity is generated by the fuel cell using the hydrogen. (For example, refer to Patent Documents 1 and 2). Usually, in the reforming reaction, a reforming catalyst using nickel, ruthenium, platinum or the like as an active metal is used (see Patent Documents 1 to 3).

JP 2002-362902 A International Publication WO2008 / 001632 JP-A-4-363140

By the way, an odorant made of a sulfur compound such as mercaptan is added to city gas supplied to households in order to facilitate detection of gas leakage. Petroleum fuel contains a sulfur compound in the production process.
However, all of the reforming catalysts of Patent Documents 1 to 3 have low sulfur resistance and are easily deactivated by sulfur compounds. Therefore, when city gas or petroleum-based fuel is used as a raw material for hydrogen production, it has a desulfurization step with an adsorbent before the reforming step, but in the removal of sulfur compounds with the adsorbent, Alternatively, the adsorbent had to be replaced just before breakthrough, and maintenance had to be performed with high frequency.
For this reason, in order to omit the desulfurization step before the reforming step, a reforming catalyst having excellent sulfur resistance has been demanded.
Therefore, an object of the present invention is to provide a reforming catalyst excellent in sulfur resistance, a reformer using the catalyst, and a hydrogen production apparatus.

[1] One or more kinds of activities selected from the group consisting of rhodium, platinum and palladium on an alumina-containing support containing alumina having a pore diameter of 50 nm or more and a volume of 0.2 to 1.0 ml / g. A reforming catalyst, wherein the metal is supported at a ratio of 0.3% by mass or more and 5% by mass or less with respect to 100% by mass of the alumina-containing support.
[2] The reforming material according to [1], wherein the alumina-containing carrier is a carrier on which 2% by mass to 25% by mass of a rare earth element oxide is supported with respect to 100% by mass of alumina. catalyst.
[3] In the above [1], the alumina-containing carrier is a carrier on which 0.1 to 15% by mass of an alkaline earth metal element oxide is supported with respect to 100% by mass of alumina. The catalyst for reforming as described.
[4] The alumina-containing support carries 2% by mass to 25% by mass of a rare earth element oxide and 0.1% by mass to 15% by mass of an alkaline earth metal element oxide with respect to 100% by mass of alumina. The reforming catalyst according to [1], which is a supported carrier.
[5] The reforming catalyst according to any one of [1] to [4], wherein the alumina is α-alumina.
[6] A reformer comprising the reforming catalyst according to any one of [1] to [5].
[7] A hydrogen production apparatus comprising the reforming apparatus according to [6].

  The reforming catalyst of the present invention is excellent in sulfur resistance.

(Reforming catalyst)
The reforming catalyst of the present invention is one in which an active metal is supported on an alumina-containing support.
[Active metal]
The active metal in the present invention is one or more metals selected from the group consisting of rhodium, platinum and palladium. Among these, rhodium is preferable because of its superior reforming activity and sulfur resistance.

  The content of the active metal in the reforming catalyst of the present invention is 0.3 mass% or more and 5 mass% or less, preferably 0.4 mass% or more and 4 mass% or less when the alumina-containing support is 100 mass%. More preferably, it is 0.5 mass% or more and 3 mass% or less. When the content of the active metal is 0.3% by mass or more, sufficient catalytic activity can be obtained, and the amount of the reforming catalyst used can be reduced. The amount of active metal exposed to the surface can be increased.

[Carrier]
The alumina-containing support in the present invention is a support containing alumina, preferably a support in which a rare earth element oxide and an alkaline earth metal element oxide are supported on alumina. Here, the alumina has pores (macropores) having a pore diameter of 50 nm or more, and the pore volume is 0.2 ml / g or more and 1.0 ml / g or less.
When the volume of pores having a pore diameter of 50 nm or more is smaller than 0.2 ml / g, the catalytic activity becomes insufficient, and when the volume of pores having a pore diameter of 50 nm or more is larger than 1.0 ml / g, the catalyst strength is insufficient. Become.
Further, it is preferable that the BET specific surface area of alumina is less than ^3m 2 / g or more ^{30 m} 2 / g. When the BET specific surface area of alumina is 3 m ² / g or more, the catalytic activity is high, and when the BET specific surface area is 30 m ² / g or less, the catalyst strength is higher.
Of the alumina, α-alumina is preferable in that the pores and the BET specific surface area can be easily obtained.

As the rare earth element, it is preferable to use one or more rare earth elements selected from scandium, yttrium, lanthanum, and cerium, and lanthanum and cerium are more preferable because the effect of suppressing carbon deposition is more excellent.
The content of the rare earth element in the alumina-containing support is preferably 2% by mass or more and 25% by mass or less, more preferably 5% by mass or more and 20% by mass or less when the mass of alumina is 100% by mass. More preferably, it is 10 mass% or more and 15 mass% or less. If the content of the rare earth element oxide is 2% by mass or more, the effect of suppressing the carbon precipitation by the rare earth element becomes higher, and if it is 25% by mass or less, the rare earth element oxide is less likely to aggregate and is exposed to the surface. The amount of active metal can be increased.

As the alkaline earth metal element, it is preferable to use one or more alkaline earth metals selected from magnesium, calcium, strontium, and barium, because the carbon precipitation suppression effect and the activity improvement effect are more excellent. More preferred are magnesium and strontium.
The content of the alkaline earth metal element in the alumina-containing support is preferably 0.1% by mass or more and 15% by mass or less, and 0.5% by mass or more and 12% by mass or less when alumina is 100% by mass. More preferably, it is more preferably 1% by mass or more and 10% by mass or less. When the content of the alkaline earth metal element oxide is 0.1% by mass or more, the carbon precipitation suppressing effect and the activity improving effect of the alkaline earth metal element are further increased. The metal group element is less likely to aggregate, and the amount of active metal exposed on the surface can be increased.

  In the reforming catalyst of the present invention, a combination of rhodium, cerium and strontium is preferable as the combination of the active metal, rare earth element and alkaline earth metal element because it is particularly excellent in catalytic activity and sulfur resistance.

[Strength]
The catalyst strength of the reforming catalyst of the present invention is preferably such that the catalyst crushing strength measured by the Kiyama method is 50 N or more per catalyst particle. If the catalyst crushing strength is 50 N or more, the catalyst is difficult to break during operation of the fuel cell system, and powdering can be prevented.

[shape]
The reforming catalyst of the present invention may be in the form of a powder or may be a molded body formed into a predetermined shape. Examples of the shape of the molded body include a spherical shape, a ring shape, a tablet shape, a cylindrical shape, and a flake shape.
Examples of a method for obtaining a molded body include a method in which a reforming catalyst is formed by tableting, pulverized and then sized, and a method in which a binder is added to the reforming catalyst and extrusion molding is performed. In addition, after compressing, molding, and sizing the alumina-containing carrier, a method of supporting the active metal, a method of adding a binder to the alumina-containing carrier, extrusion molding, and then supporting the active metal Can be applied.
Further, the reforming catalyst may be monolithic or honeycomb-shaped. Further, the reforming catalyst may be coated on a monolithic or honeycomb structure.

[Method for producing reforming catalyst]
The reforming catalyst is obtained by preparing an alumina-containing support and then supporting an active metal on the alumina-containing support.

The alumina-containing support is obtained by supporting rare earth elements and alkaline earth metal elements on alumina, drying, firing, and cooling.
As a method for supporting the rare earth element and the alkaline earth metal element on alumina, for example, a normal impregnation method or a pore fill method can be employed. The rare earth element and the alkaline earth metal element may be supported simultaneously or sequentially.
In the impregnation method or the pore fill method for supporting a rare earth element and an alkaline earth metal element on alumina, a solution in which a compound of a rare earth element or an alkaline earth metal element is dissolved in a solvent such as water, ethanol, or acetone is used. As the rare earth element or alkaline earth metal element compound, chloride, nitrate, sulfate, acetate, acetoacetate, or the like is used.
In the drying process after supporting the rare earth element and the alkaline earth, heat drying or vacuum drying is applied. As an example, a method of drying at a temperature of 100 ° C. or higher and 150 ° C. or lower in an air atmosphere or an inert gas atmosphere such as nitrogen or argon can be given.
In the firing step after drying, it is preferable to fire the alumina supporting the rare earth element and the alkaline earth metal element at a temperature of 350 ° C. or higher and 1000 ° C. or lower. If the firing temperature is 350 ° C. or higher, the rare earth element oxide and alkaline earth metal element oxide can be sufficiently immobilized on alumina, and if it is 1000 ° C. or lower, the rare earth element oxide and alkaline earth metal element oxide are oxidized. Aggregation of objects can be suppressed. The firing atmosphere is preferably an air atmosphere, and the air flow rate is not particularly limited. The firing time is preferably 2 hours or more in order to sufficiently fix the rare earth element oxide and the alkaline earth metal element oxide to the alumina.

An active metal is supported on the alumina-containing support obtained as described above, dried, and subjected to reduction treatment or metal immobilization treatment as necessary to obtain a reforming catalyst.
As the supporting method, for example, a normal impregnation method or a pore fill method can be employed.
In an impregnation method or a pore fill method when an active metal is supported on an alumina-containing support, a solution in which an active metal compound is dissolved in a solvent such as water, ethanol, or acetone is used. As the active metal compound, chloride, nitrate, sulfate, acetate, acetoacetate and the like are used. The number of times of carrying may be one time or two or more times.
In the drying step after supporting the active metal, heat drying or vacuum drying is applied. As an example, a method of drying at a temperature of 100 ° C. or higher and 150 ° C. or lower in an air atmosphere or an inert gas atmosphere such as nitrogen or argon can be given.
Examples of the reduction treatment method include gas phase reduction and liquid phase reduction under a hydrogen atmosphere.

(Hydrogen production method)
The hydrogen production method of the present invention is a method for reforming hydrocarbons using a reforming catalyst. Specifically, it is a method of obtaining a reformed gas containing carbon monoxide and hydrogen by reacting a raw material for hydrogen production containing hydrocarbons with steam in the presence of the reforming catalyst. When reacting with steam, an oxygen-containing gas may be accompanied (autothermal reforming reaction).

  In the reforming reaction using the reforming catalyst, a flow type fixed bed reactor, a fluidized bed reactor or the like is used as a reactor. The shape of the reactor may be appropriately selected according to the purpose of the reforming reaction, and for example, a cylindrical shape, a flat plate shape, or the like is applied.

Hydrocarbons used for the reaction are organic compounds having 1 to 40 carbon atoms, preferably 1 to 30 carbon atoms. Specific examples include saturated aliphatic hydrocarbons, unsaturated aliphatic hydrocarbons, and aromatic hydrocarbons. In addition, saturated aliphatic hydrocarbons and unsaturated aliphatic hydrocarbons can be used regardless of chain or cyclic. Aromatic hydrocarbons can be used regardless of whether they are monocyclic or polycyclic.
The hydrocarbons may have a substituent. The substituent may be either a chain or a ring, and examples thereof include an alkyl group, a cycloalkyl group, an aryl group, an alkylaryl group, and an aralkyl group. Further, it may be substituted with a substituent containing a hetero atom such as a hydroxy group, an alkoxy group, a hydroxycarbonyl group, an alkoxycarbonyl group, or a formyl group.

Specific examples of hydrocarbons include saturated aliphatics such as methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane, decane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, nonadecane, and eicosane. Examples thereof include hydrocarbons, unsaturated aliphatic hydrocarbons such as ethylene, propylene, butene, pentene and hexene, cyclic hydrocarbons such as cyclopentane and cyclohexane, and aromatic hydrocarbons such as benzene, toluene, xylene and naphthalene.
Specific examples of hydrocarbons having a substituent containing a hetero atom include oxygen-containing compounds such as methanol, ethanol, propanol, butanol, dimethyl ether, phenol, anisole, acetaldehyde, and acetic acid.
Also, a mixture of these hydrocarbons can be used preferably. For example, natural gas, petroleum-based fuel (for example, LP gas, naphtha, gasoline, kerosene, light oil, etc.) such as gas and oil that can be obtained industrially at low cost can be used.

  Further, the raw materials for producing hydrocarbons from hydrogen may include hydrogen, water, carbon dioxide, carbon monoxide, nitrogen, oxygen, and the like. For example, when hydrodesulfurization treatment is performed before the reforming reaction, unreacted hydrogen may remain in the raw material for hydrogen production. Can be used.

In the reforming reaction, as a method of supplying steam to the raw material for hydrogen production, for example, a method of supplying steam simultaneously with the raw material for hydrogen production in the reaction zone, a separate position in the reactor zone or several times For example, a method of supplying steam part by part.
The amount of steam to be supplied is a value defined as the ratio of the number of moles of water molecule to the number of moles of carbon atoms contained in the hydrocarbons (hereinafter referred to as “steam / carbon ratio”), preferably 2.0 or more and 10 In the following, it is preferable that the amount be in the range of 2.5 to 5 inclusive. If the steam / carbon ratio is 2.0 or more, it is difficult for carbon to precipitate on the reforming catalyst surface, and the hydrogen fraction can be easily increased. On the other hand, when the steam / carbon ratio is 10 or less, it is possible to avoid an increase in the size of the steam generating equipment and the steam collecting equipment.

In the reforming reaction, the space velocity of the hydrogen-producing feedstock introduced into the reactor at GHSV, preferably ^{10h -1} over 10,000 h ^-1 or less, more preferably ^{50h -1} over 5,000H ^-1 or less, More preferably, it is the range of 100h- ¹ or more and 3,000h- ¹ or less. In LHSV, preferably 0.05 h ^-1 or 5.0 h ^-1 or less, more preferably 0.1 h ^-1 or 2.0 h ^-1 or less, more preferably 0.2 h ^-1 or 1.0 h ^-1 or less of It is a range.
The reaction temperature is preferably in the range of 300 ° C. to 900 ° C., more preferably 400 ° C. to 800 ° C.
The reaction pressure is preferably greater than atmospheric pressure

  The above-described hydrogen production method is particularly preferably applied to, for example, production of hydrogen to be supplied to a fuel cell.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.

[Example 1]
Α-alumina having a pore volume of 50 nm or more and a volume of 0.4 ml / g and a surface area of 5 m ² / g was impregnated with cerium nitrate and strontium nitrate. At that time, the supported amount of cerium oxide (CeO ₂ ) was 13% by mass when the mass of α-alumina was 100% by mass, and the supported amount of strontium oxide (SrO) was 100% by mass of α-alumina. The cerium nitrate and strontium nitrate were impregnated so as to be 5% by mass.
Subsequently, after drying at 150 degreeC for 8 hours or more, it baked at 800 degreeC in the air atmosphere for 8 hours, and obtained the alumina containing support | carrier.
The alumina-containing support is impregnated with rhodium chloride so that the amount of rhodium supported is 2% by mass when the mass of the alumina-containing support is 100% by mass, dried at 120 ° C. for 12 hours or more, A reforming catalyst was obtained by hydrogen reduction for a period of time.

[Example 2]
In Example 1, a reforming catalyst was obtained in the same manner as in Example 1 except that rhodium chloride was impregnated so that the supported amount of rhodium was 0.5% by mass.
[Example 3]
In Example 1, rhodium chloride and platinum chloride were used for the alumina-containing support, and the platinum support was 0.5% so that the rhodium support was 1.5% by mass when the mass of the alumina-containing support was 100% by mass. A reforming catalyst was obtained in the same manner as in Example 1 except that the impregnation was carried out so that the content of the catalyst was 1%.

[Example 4]
In Example 1, a reforming catalyst was obtained in the same manner as in Example 1 except that lanthanum nitrate was impregnated instead of cerium nitrate.

[Example 5]
In Example 1, a reforming catalyst was obtained in the same manner as in Example 1 except that calcium nitrate was supported by impregnation with calcium nitrate instead of strontium nitrate.

[Example 6]
In Example 1, a reforming catalyst was obtained in the same manner as in Example 1, except that magnesium nitrate was impregnated instead of strontium nitrate to support magnesium oxide.

[Example 7]
In Example 1, a reforming catalyst was obtained in the same manner as in Example 1 except that barium nitrate was impregnated instead of strontium nitrate to support barium oxide.

[Example 8]
In Example 1, a reforming catalyst was obtained in the same manner as in Example 1 except that cerium nitrate was impregnated so that the supported amount of cerium oxide was 8% by mass.

[Example 9]
In Example 1, a reforming catalyst was obtained in the same manner as in Example 1 except that cerium nitrate was impregnated so that the amount of cerium oxide supported was 18% by mass.

[Example 10]
In Example 1, a reforming catalyst was obtained in the same manner as in Example 1 except that strontium nitrate was impregnated so that the supported amount of strontium oxide was 2% by mass.

[Example 11]
In Example 1, a reforming catalyst was obtained in the same manner as in Example 1 except that no cerium oxide was supported.

[Example 12]
In Example 1, a reforming catalyst was obtained in the same manner as in Example 1 except that no strontium oxide was supported.

[Comparative Example 1]
In Example 1, a reforming catalyst was obtained in the same manner as in Example 1 except that rhodium chloride was impregnated so that the supported amount of rhodium was 0.1% by mass.

[Comparative Example 2]
In Example 1, a reforming catalyst was obtained in the same manner as in Example 1 except that rhodium chloride was impregnated so that the supported amount of rhodium was 0.2% by mass.

[Comparative Example 3]
In Example 1, instead of α-alumina, for the reforming, the same procedure as in Example 1 was used, except that γ-alumina having a pore volume of 50 nm or more and a volume of 0 ml / g and a surface area of 150 m ² / g was used. A catalyst was obtained.

(Evaluation)
[Sulfur resistance]
The reforming catalyst was evaluated by a reforming reaction. The reaction used a fixed bed microreactor. The catalyst filling amount was 50 cm ^3, and LP gas having a sulfur content of 5 ppm was used as a raw material for hydrogen production. The reaction conditions are as follows. Microreactor inlet reaction temperature 500 ° C., microreactor outlet reaction temperature 700 ° C., reaction pressure 0.1 MPa, steam / carbon ratio 2.5 mol / mol, GHSV 300 h ⁻¹ .
The reformed gas obtained by the reaction was quantitatively analyzed by gas chromatography. Tables 1 to 3 show the conversion rates of the raw materials obtained from the reformed gas composition after 200 hours of reaction. Here, the conversion rates in Tables 1 to 3 are the ratios of the raw materials converted to CO, CH ₄ , and CO ₂ and are calculated based on carbon.

In the reforming catalysts of Examples 1 to 12 in which any one of rhodium, platinum, and palladium was supported on an alumina-containing support in the range of 0.3 mass% to 5 mass%, a hydrocarbon raw material that was not desulfurized was used. Nevertheless, the decrease in activity was suppressed.
On the other hand, in the reforming catalyst of Comparative Example 1 in which the supported amount of the active metal was out of the above range, the activity was significantly decreased in the reforming catalyst of Comparative Example 2 using ruthenium as the active metal. .
In the reforming catalyst of Comparative Example 3 using γ-alumina, which has a pore volume of 50 nm or more and the volume of pores not in the range of 0.2 ml / g or more and 1.0 ml / g or less, the crushing strength was low.

Claims (3)

In an alumina-containing support containing α-alumina having a pore volume of 50 nm or more and a pore volume of 0.2 ml / g or more and 1.0 ml / g or less, an active metal composed of rhodium is 0 % relative to 100% by mass of the alumina-containing support. .5% by mass to 2% by mass ,
The alumina-containing carrier carries 2% by mass to 25% by mass of a rare earth element oxide and 0.1% by mass to 15% by mass of an alkaline earth metal element oxide with respect to 100% by mass of the α-alumina. A reforming catalyst, characterized by being a support . A reforming apparatus comprising the reforming catalyst according to claim 1 . A hydrogen production apparatus comprising the reformer according to claim 2 .