KR20110011276A - Steam reforming catalyst and hydrogen production apparatus using the same - Google Patents

Abstract

The present invention relates to α-alumina having a pore volume of 50 nm or more of pore diameter of 0.3 to 0.6 ml / g, a BET specific surface area of 3 to 30 m ² / g, and a crush strength of 20 to 25 kgf. A catalyst for steam reforming comprising carrying 0.3 to 5 parts by weight of ruthenium as an active metal on a carrier obtained by supporting 2 to 25 parts by weight of rare earth element oxides and 0.1 to 15 parts by weight of alkaline earth element oxides per alumina. It is about.

By performing steam reforming using the steam reforming catalyst of the present invention, it is possible to achieve long-term reforming performance and mechanical strength improvement, and thereby to stably produce a mixed gas containing hydrogen and carbon monoxide for a long time. This can be used as fuel for fuel cells or raw materials thereof.

Description

Catalyst for steam reforming and hydrogen production apparatus using the same {Catalyst for Steam Reformation and Hydrogen Production Apparatus Using Thereof}

The present invention relates to a catalyst for steam reforming and a hydrogen production apparatus using the same.

Occupying the most important position in the hydrogen production process is a so-called steam reforming technique of hydrocarbon compounds, in which hydrocarbon compounds and steam are reacted to obtain hydrogen, carbon monoxide, carbon dioxide, methane and the like. The reason why steam reforming is widely used is that equipment is inexpensive compared to partial oxidation.

Conventional steam reforming catalysts are mostly nickel-based, as disclosed in Japanese Patent Laid-Open No. Hei 4-363140. However, these catalysts are prone to carbon precipitation, and have the disadvantage that activity decreases in a short time. For this reason, it is often operated at relatively high pressure (2 MPa or more) and high water vapor / carbon ratio (3.0 or more). However, in the case of fuel cell systems, the reaction pressure is preferably lower in terms of ease of handling of the device, and in terms of power generation efficiency, steam is preferable. It is preferable that the / carbon ratio is low.

In addition, kerosene is preferable as a raw material hydrocarbon of a fuel cell from the viewpoint of energy density, economical efficiency, and ease of handling. However, since the precipitation of carbon easily occurs in the nickel-based catalyst, the raw material hydrocarbon is limited to naphtha derived from natural gas.

In addition, γ-alumina is generally used as a catalyst carrier. However, since the mechanical strength is not so strong, the catalyst is differentiated during DSS (Daily Start and Shutdown) operation of a fuel cell having a large heat load, and the pressure difference of the apparatus is increased. There is a problem such as rising.

On the other hand, representative catalyst carriers having high mechanical strength include α-alumina as disclosed in Japanese Patent Application Laid-Open No. 4-59048. However, in the conventional steam reforming catalyst using α-alumina, the raw material hydrocarbon is about naphtha, and the effect of inhibiting carbon precipitation is Insufficient

The present invention provides a reforming catalyst using alumina having increased crush strength as a carrier to provide a catalyst for reforming carbon at low pressure, low steam / carbon ratio, and having a long service life and strong mechanical strength. There is a problem to be solved in manufacturing.

The present invention is derived to solve the above problems,

To α-alumina having a pore volume of at least 50 nm of pore diameter of 0.3 to 0.6 ml / g, BET surface area of 3 to 30 m ² / g, and crush strength of 20 to 25 kgf, For reforming steam containing 0.3 to 5 parts by weight of ruthenium as an active metal on a carrier obtained by supporting 2 to 25 parts by weight of rare earth element oxides and 0.1 to 15 parts by weight of alkaline earth element oxides per α alumina There is a problem solving means in providing a catalyst.

In particular, the inventors of the present invention intensively studied how to achieve carbonaceous precipitation suppression and mechanical strength improvement in the steam reforming reaction of hydrocarbons, to prepare a catalyst for steam reforming using alumina having a specific strength as a carrier By using it, the inventors have found that both are achieved, thus completing the present invention.

In addition, the present invention provides a hydrogen producing apparatus comprising using a catalyst for steam reforming described above to obtain a reforming gas containing hydrogen as a main component from hydrocarbon compounds by steam reforming reaction. There is this.

By performing steam reforming using the steam reforming catalyst of the present invention, it is possible to achieve long-term reforming performance and mechanical strength improvement, and thereby to stably produce a mixed gas containing hydrogen and carbon monoxide for a long time. This can be used as fuel for fuel cells or raw materials thereof.

In one aspect, the present invention has a pore volume of 0.3 nm to 0.6 ml / g with a pore diameter of 50 nm or more, a BET surface area of 3 to 30 m ² / g, and a crush strength. 0.3 to 5 parts by weight of ruthenium as an active metal on a carrier obtained by supporting 2 to 25 parts by weight of rare earth element oxides and 0.1 to 15 parts by weight of alkaline earth element oxides in α alumina of 20 to 25 kgf. Provided is a catalyst for steam reforming comprising supported.

In another aspect, the present invention provides a hydrogen production apparatus characterized by obtaining a reforming gas containing hydrogen as a main component from hydrocarbon compounds by a steam reforming reaction using a steam reforming catalyst.

As the catalyst carrier component according to the present invention, α alumina having a pore diameter of 50 nm or more is used. The pore volume of 50 nm or more in pore size is 0.3-0.6 ml / g. If the pore volume is less than 0.3 ml / g, the catalytic activity is insufficient, which is not preferable. On the other hand, when the pore volume is larger than 0.6 ml / g, the catalyst strength is insufficient, which is not preferable.

Moreover, it is preferable that the BET specific surface area of the said alumina is 3-30 m <2> / g. If the BET specific surface area is smaller than 3 m 2 / g, the catalytic activity is insufficient, which is not preferable. If the BET specific surface area is larger than 30 m 2 / g, the catalyst strength is insufficient, which is not preferable.

As the rare earth element according to the present invention, it is preferable to use one or two or more rare earth elements selected from scandium, yttrium, lanthanum and cerium, and more preferably lanthanum and cerium.

The rare earth element content in the catalyst carrier is a rare earth element oxide, and is 2 to 25 parts by weight, preferably 5 to 20 parts by weight, more preferably, based on the external alumina (α alumina weight) relative to α alumina. It is good that it is 10-15 weight part. When the content of the rare earth element oxide is 25 parts by weight or more, it is not preferable because the aggregation increases and the ratio of the metal to the surface is extremely reduced, and when it is less than 2 parts by weight, the effect of inhibiting carbon precipitation of the rare earth elements is insufficient. Not.

As the alkaline earth element according to the present invention, it is preferable to use one or two or more alkaline earth metals selected from magnesium, calcium, strontium and barium, and magnesium and strontium are more preferable.

The content of the alkaline earth element in the catalyst carrier according to the present invention is an alkaline earth element oxide, and is 0.1 to 15 parts by weight, preferably 0.5 to 12 parts by weight, more preferably, based on the external alumina (α alumina weight) relative to the alumina. Is 1 to 10 parts by weight. If the content of the alkaline earth element oxide is 15 parts by weight or more, it is not preferable because the aggregation increases and the proportion of the active metal on the surface is extremely reduced. If the content is less than 0.1 part by weight, the effect of inhibiting carbon precipitation of the alkaline earth element and The activity improving effect is insufficient, which is undesirable.

The ruthenium content in the catalyst of the present invention is 0.3 to 5 parts by weight, preferably 1 to 4, as ruthenium atoms, in terms of the outer ratio (carrier weight) relative to the carrier obtained by supporting rare earth element oxide and alkaline earth element oxide on α alumina. Parts by weight, more preferably 2 to 3 parts by weight. When the content of ruthenium is 5 parts by weight or more, it is not preferable because the aggregation of the active metal increases and the proportion of the active metal that has emerged to the surface is extremely reduced, while when it is less than 0.3 parts by weight, sufficient activity cannot be exhibited. As a result, a large amount of supported catalyst is required, resulting in a problem that the reactor needs to be made larger than necessary.

The catalyst strength of the steam reforming catalyst of the present invention preferably has a catalyst crush strength of 20 to 25 kgf per catalyst particle by a wooden measurement method. If the catalyst crush strength is less than 25 kgf, it is not preferable because the catalyst ruptures and differentiates during operation of the fuel cell.

In addition, there is no restriction | limiting in particular about the method of supporting the said rare earth element and alkaline earth element in alpha-alumina, A well-known method, such as a normal impregnation method and a pore fill method, can be employ | adopted. Usually, it is dissolved in a solvent such as water, ethanol or acetone as a metal salt or a complex and impregnated into a carrier. The supported metal salts or metal complexes are preferably chlorides, nitrates, sulfates, acetates, acetoacetates and the like.

There is no restriction | limiting in particular also about a supporting process, It can be impregnated simultaneously or sequentially.

Although water is almost removed by drying after supporting, there is no particular limitation in this drying step, and a temperature of 100 to 150 ° C or the like is preferably used under inert gas under air. After the drying step, the carrier supporting the rare earth element and the alkaline earth element is preferably baked at a temperature of 350 to 1000 ° C. If it is lower than 350 DEG C, immobilization of the bile support in the carrier is insufficient, which is not preferable. Moreover, when it is higher than 1000 degreeC, since aggregation of a supporting element arises, it is not preferable. The firing atmosphere is preferably in air, and there is no particular limitation on the gas flow rate. The firing time is preferably 2 hours or more. If it is shorter than 2 hours, immobilization of the supported element on the carrier is insufficient, which is not preferable.

After cooling the calcined carrier, carrying out of ruthenium is then carried out. There is no restriction | limiting in particular about a supporting method, Well-known methods, such as a normal impregnation method and a pore filling method, can be employ | adopted. Usually, as a metal salt or a complex, it melt | dissolves in solvents, such as water, ethanol, or acetone, and impregnates a carrier. The supported metal salts or metal complexes are preferably chlorides, nitrates, sulfates, acetates, acetoacetates and the like. There is no restriction | limiting in particular also about the number of loading, and can be impregnated once or several times. After supporting, almost no moisture is removed by drying, but there is no particular limitation on this drying step, and a temperature of 100 to 150 ° C or the like is preferably used under inert gas under air.

The supported catalyst thus obtained is activated by performing a reduction treatment or a metal immobilization treatment as necessary. There is no particular limitation on the treatment method, and gas phase reduction or liquid phase reduction is preferably used under hydrogen flow.

There is no restriction | limiting in particular about the form of the steam reforming catalyst of this invention.

For example, it is possible to use a catalyst formed by tableting, pulverizing and sintered to an appropriate range particle size, a catalyst extruded by adding a suitable binder, a powdered catalyst and the like.

In addition, the catalyst is supported by a metal, such as a carrier formed by tableting, crushing, and granulated in an appropriate range, an extruded carrier, a powder or a carrier molded into a suitable form such as spherical, ring, tablet, cylindrical or flake. Although etc. can be used, spherical catalyst is preferable from a viewpoint of mechanical strength.

In addition, a catalyst obtained by molding the catalyst itself into a monolith type, a honeycomb phase, or the like, or a catalyst coated with a monolith or honeycomb phase using a suitable material, or the like can be used.

In the form of a reactor used for the steam reforming reaction according to the present invention, a flow-through fixed bed reactor is preferably used. There is no restriction | limiting in particular about the shape of a reactor, A well-known shape can be taken according to the objective of each process, such as cylindrical shape and flat plate shape. It is also possible to use fluidized bed reactors.

In the present invention, the steam reforming reaction refers to a reaction in which hydrocarbon compounds are reacted with steam in the presence of a catalyst and converted into a reforming gas containing carbon monoxide and hydrogen. In the case of reacting with water vapor, an oxygen-containing gas (automatic heating reforming reaction) is also included.

Hydrocarbon compounds used as a raw material are organic compounds with 1 to 40 carbon atoms, preferably 1 to 30 carbon atoms. Specifically, there are saturated aliphatic hydrocarbons, unsaturated aliphatic hydrocarbons, aromatic hydrocarbons, and the like. The saturated aliphatic hydrocarbons and unsaturated aliphatic hydrocarbons can be used regardless of chain or cyclic. Also about aromatic hydrocarbon, it can use regardless of monocyclic or polycyclic. Such hydrocarbon compounds may contain a substituent. As the substituent, any of chain and cyclic can be used, and examples thereof include an alkyl group, a cycloalkyl group, an aryl group, an alkylaryl group and an aralkyl group. In addition, these hydrocarbon compounds may be substituted by substituents containing hetero atoms, such as a hydroxyl group, an alkoxy group, a hydroxycarbonyl group, an alkoxycarbonyl group, and a formaldehyde group.

Specific examples of hydrocarbon compounds that can be used in the present invention include methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane, decane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, Saturated aliphatic hydrocarbons such as heptadecane, octadecane, nonadecane, eicosane, unsaturated aliphatic hydrocarbons such as ethylene, propylene, butene, pentene, hexene, cyclic hydrocarbons such as cyclopentane, cyclohexane, benzene, toluene, xylene, naphthalene Aromatic hydrocarbons, such as these, are mentioned. In addition, mixtures thereof are also preferably used. For example, materials which can be industrially obtained at low cost, such as natural gas, LPG, naphtha, gasoline, kerosene and diesel, are exemplified. Specific examples of hydrocarbon compounds having a substituent containing a hetero atom include methanol, ethanol, propanol, butanol, dimethyl ether, phenyl, anisole, acetaldehyde, acetic acid and the like.

Moreover, the raw material which contains hydrogen, water, a carbon dioxide, carbon monoxide, etc. in the said raw material can also be used. For example, when hydrodesulfurization is carried out as a pretreatment of a raw material, the residual content of hydrogen used in the reaction can be used as it is without particular separation.

When the sulfur concentration contained in the hydrocarbon compound used as a raw material is too high, since the reforming catalyst of the present invention may be inactivated, the concentration is the mass of sulfur atoms, preferably 10 mass ppb or less. For this reason, if necessary, desulfurization of the raw material in advance can also be preferably performed.

There is no restriction | limiting in particular in the sulfur concentration in the raw material supplied to a desulfurization process, It can use if it can convert into the said sulfur concentration in a desulfurization process.

There is no particular limitation on the desulfurization method, however, a room temperature desulfurization agent based on activated carbon is used, and there is no particular limitation on the method of carrying out the desulfurization process, and the desulfurization process may be performed immediately before the steam reforming reactor, or may be treated in an independent desulfurization process. One hydrocarbon may be used.

In the steam reforming reaction using the catalyst of the present invention, the amount of steam introduced into the reaction system is a value defined as the ratio of the number of moles of water molecules to the number of moles of carbon atoms included in the raw hydrocarbon compounds (steam / carbon ratio), Preferably it is 0.3-10, More preferably, it is 0.5-5, More preferably, it is the range of 2-3. If the value is less than 0.3, coke is easily precipitated on the catalyst, and the hydrogen fraction cannot be increased. If the value is larger than 10, the reforming reaction proceeds, but the expansion of the steam generating equipment and the steam recovery equipment is prevented. It may cause. Although the addition method does not have a restriction | limiting in particular, You may introduce into a reaction zone at the same time as a raw material hydrocarbon compound, You may introduce only a part from other positions of a reactor zone or divide into several times.

In the steam reforming reaction using the catalyst of the present invention, the spatial velocity distribution of a raw material to be introduced into the reactor, GHSV is preferably from 10 to 10,000h ^-1, more preferably from 50 to 5,000h ^-1, more preferably from 100 to 3,000 h ^-1 range. LHSV is preferably from 0.05 to 5.0h ^-1, more preferably between 0.1 and 2.0h ^-1, and more preferably from 0.2 to 1.0h ^-1 range.

Although reaction temperature is not specifically limited, 200-1000 degreeC range is preferable, 300-900 degreeC range is more preferable, 400-800 degreeC range is more preferable.

The reaction pressure is not particularly limited, but is preferably in the range of atmospheric pressure to 20 MPa, more preferably in the range of atmospheric pressure to 5 MPa, particularly preferably in the range of atmospheric pressure to 1 MPa.

The mixed gas containing carbon monoxide and hydrogen obtained by the steam reforming reaction using the catalyst of the present invention can be used as a fuel for a fuel cell as it is in the case of a solid oxide fuel cell. In addition, when carbon monoxide removal is required, such as a phosphoric acid fuel cell or a solid polymer fuel cell, it can be used suitably as a raw material of hydrogen for fuel cells by using a carbon monoxide removal process together.

Hereinafter, the present invention will be described in detail through examples. However, the following examples are only for illustrating the present invention in detail and are not intended to limit the scope of the present invention by these examples.

<Examples>

(1) α-alumina having a pore volume of 0.4 ml / g, surface area of 5 m 2 / g, and crush strength of 21 kgf is used as the catalyst carrier A.

(2) Cerium nitrate and magnesium nitrate were impregnated and supported on the catalyst carrier A, with the amount of supported cerium oxide being 13 parts by weight at an external rate, and the amount of the supported magnesium oxide being 5% by weight at an external rate, and dried at 150 ° C. for 8 hours or more. After that, air firing was carried out at 800 ° C. for 8 hours. This is called catalyst carrier B.

(3) Ruthenium chloride is impregnated and impregnated in the catalyst carrier B in an amount such that the amount of supported ruthenium is 3 parts by weight at an external rate, dried at 120 ° C for at least 12 hours, and hydrogen reduced at 500 ° C for 1 hour.

Comparative Example

The same method as in Example 1 was carried out, except that α alumina having a pore volume of 0.4 ml / g, surface area of 5 m 2 / g, and crush strength of 21 kgf was used instead of the catalyst carrier, with pore volume of 0.4 ml / g, surface area. Α alumina with 2 m 2 / g and crush strength of 18 kgf was used as catalyst carrier.

<Experiment>

Modified catalyst evaluation experiments of the catalysts prepared according to the Examples and Comparative Examples were carried out according to the following procedure.

-Prepare 12 ml of steam reforming catalyst (size = 3mm) after supporting active material and firing.

Place the prepared catalyst inside the reactor and flow a certain level of flow to meet the following conditions.

Total flow = 1,029ml / min, SV = 5,145hr ^-1 , S / C ratio = 2.5

=> H2O = 0.59ml / min, CH4 = 295ml / min

-CH ₄ conversion by temperature was measured by adjusting the temperature of the catalyst layer to 600 ~ 750 ℃, and durability evaluation was performed for a long time at the operating temperature.

-The gas analysis after reforming was measured using gas chromatograph (GC / TCD, Model DS6200, Donam Instrument), and the analysis gas items are H ₂ , N ₂ , CH ₄ , CO, CO ₂ .

The result is shown in FIG.

As described above, those skilled in the art will understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential features. Therefore, it should be understood that the embodiments described above are all illustrative and not restrictive. The scope of the present invention should be construed as being included in the scope of the present invention all changes or modifications derived from the meaning and scope of the claims to be described later rather than the detailed description and equivalent concepts thereof.

1 is a view showing a reforming catalyst evaluation results according to the present invention.

Claims (4)

2 to 25 parts by weight of rare earth element oxide per α alumina in α alumina having a pore volume of 0.3 to 0.6 ml / g with a pore diameter of 50 nm or more, a BET specific surface area of 3 to 30 m ² / g, and a crush strength of 20 to 25 kgf. A catalyst for steam reforming, comprising carrying 0.3 to 5 parts by weight of ruthenium as an active metal on a carrier obtained by supporting 0.1 to 15 parts by weight of alkaline earth element oxide. The method of claim 1, The rare earth element oxide is a catalyst for steam reforming, characterized in that the oxide of one or two or more rare earth elements selected from scandium, yttrium, lanthanum and cerium. The method of claim 1, The catalyst for steam reforming, wherein the alkaline earth element oxide uses an oxide of one or two or more alkaline earth elements selected from magnesium, calcium, strontium and barium. A hydrogen production apparatus comprising obtaining a reforming gas containing hydrogen as a main component from hydrocarbon compounds by a steam reforming reaction using the steam reforming catalyst according to any one of claims 1 to 3.

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