JP4088193B2 - Hydrocarbon partial oxidation catalyst, method for producing the catalyst, and method for producing hydrogen-containing gas using the catalyst - Google Patents

Description

【００９０】
触媒調製例３及び触媒調製例５〜８の加速耐久試験前後におけるメタン転化率の低下は、触媒調製例２の場合のそれと比較して同程度であり、耐久性が良好であると判断できた。触媒調製例１４の触媒においては初期評価におけるメタン転化率は上記触媒調製例の場合とはあまり遜色はないが、加速耐久試験後のメタン転化率の低下が大きく実用触媒としては耐久性に乏しいと判断できた。また触媒調製例４および触媒調製例９〜１３の触媒については触媒調製例２と比較すると若干耐久性に劣るが、触媒調製例１４の触媒と比較すると耐久性は大幅に改善されていた。
【００９１】
本発明の部分酸化用触媒は、従来の部分酸化用触媒と比べて炭化水素原料の高負荷条件下においても長期間に亘って高レベルの水素選択率と、触媒活性を持続した。
【００９２】
【発明の効果】
以上の様に、本発明の部分酸化用触媒は、高温下でも触媒活性の劣化を抑止し、且つ炭素の析出を抑制しつつ、耐被毒性にも優れ、高活性で、しかも長期耐久性を有する。本発明の部分酸化用触媒は、燃料電池、例えば固体酸化物型燃料電池あるいは固体高分子型燃料電池に組み込まれて好適に使用される。本発明の部分酸化用触媒を用いた燃料電池は、自家用あるいは業務用コージェネレーションタイプの自家発電装置、火力発電所代替あるいは分散型発電所、電気自動車等に適用され、これらは高いエネルギー効率を発揮する。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a catalyst used when producing a hydrogen-containing gas from a hydrocarbon, and a technique related to a method for producing a hydrogen-containing gas using the catalyst. Specifically, a catalyst for partial oxidation of hydrocarbons for producing a hydrogen-containing gas from a mixed gas containing a hydrocarbon-containing gas and oxygen gas (or oxygen-containing gas), a method for producing the same, and carbonization using the catalyst This is a technique related to a method for producing a hydrogen-containing gas from hydrogen.
[0002]
[Prior art]
A hydrogen-containing gas mainly composed of hydrogen and carbon monoxide (hereinafter sometimes referred to as a source gas) is widely used as a reducing gas in addition to hydrogen gas production, and further as a raw material for various chemical products. Recently, research on practical application as fuel for fuel cells and the like has been advanced. As a method for producing a hydrogen-containing gas by reforming hydrocarbons, a hydrocarbon partial oxidation method, a steam reforming method, or an autothermal catalytic steam reforming method that combines partial oxidation and steam reforming (automatic) Thermal reforming method) is known.
[0003]
Partial oxidation methods that partially oxidize hydrocarbons to produce hydrogen-containing gases (eg, partial oxidation of methane is CH _Four + 1 / 2O ₂ → CO + 2H ₂ It is represented by ), For example, the following catalysts are used. For example, in Patent Document 1, as a partial oxidation catalyst, a coating layer is formed on an active alumina containing an oxide such as lanthanum or cerium as a stabilizer on a monolith support, and platinum and palladium are contained as catalyst components. Proposed partial oxidation catalysts have been proposed. Patent Document 2 proposes a partial oxidation catalyst in which a noble metal, Ni, Cr, Co, Ce, or La is supported as a catalyst component on a honeycomb carrier. Patent Document 3 proposes a partial oxidation catalyst in which rhodium is supported on a composite oxide composed of ceria and zirconia. However, since the technique disclosed in the Japanese Patent Publication is a technique using a pellet catalyst, and is a catalyst premised on use under conditions where water vapor is added to the reaction gas, a condition where no water vapor is added, for example, a portion of methane and air. In the oxidation reaction, the conversion rate of methane remains at a low level of about 45%. Patent Document 4 proposes a reforming method of a lower hydrocarbon fuel in which a mixed gas obtained by adding oxygen (or air) and, if necessary, water vapor to a raw material gas is partially oxidized. This publication discloses a catalyst in which about 100 μ of alumina is coated on a honeycomb support and a platinum group element is supported thereon as a catalyst, but 5 to 20 g of platinum group element per 1 L of honeycomb support. A loading amount is required. Patent Document 5 proposes a self-thermal catalytic steam reforming method of a mixed gas composed of hydrocarbon, oxygen and water or steam. In this publication, as a catalyst, a catalyst component containing at least one platinum group element in an oxide carrier material selected from the group consisting of aluminum oxide, silicon dioxide, titanium dioxide or a mixed oxide thereof, and zeolite, A catalyst coated on a support such as a ceramic honeycomb is disclosed.
[0004]
[Patent Document 1]
JP 59-97501
[Patent Document 2]
Japanese Patent Laid-Open No. 01-145301
[Patent Document 3]
Special table 2002-507535
[Patent Document 4]
JP-A-7-187605
[Patent Document 5]
JP 2002-12408
[0005]
[Problems to be solved by the invention]
As a result of intensive studies on catalysts for producing a hydrogen-containing gas by partially oxidizing a hydrocarbon gas, the present inventors have found that the prior art has the following problems.
[0006]
For example, when methane or natural gas, which is widely used as a hydrocarbon gas, is used, it is desirable to perform a partial oxidation reaction at a high temperature of 800 ° C. or higher in order to obtain a high methane conversion rate. However, since the catalyst layer is subjected to a significant thermal load due to the reaction heat during partial oxidation, there arises a problem that the catalyst activity decreases with time. In addition, a carbon generation reaction (side reaction) occurs with the partial oxidation reaction, and the precipitated carbon generated by the reaction causes the catalyst activity to deteriorate. In order to prevent such carbon deposition, it is necessary to add water vapor to the raw material gas, but no merit associated with an increase in production cost can be found.
[0007]
In addition, a catalyst poison such as a sulfur content inevitably contained in natural gas causes a problem that the catalyst is poisoned and the catalyst activity decreases with time. Natural gas is treated in advance with a desulfurizer, etc. to remove catalyst poison components and then used for partial oxidation reaction. However, if a catalyst poison removal device such as a desulfurization device is provided, there are problems such as a complicated configuration of the entire partial oxidation reaction system and a maintenance cost.
[0008]
The present invention has been made in view of the above circumstances, and its purpose is to suppress deterioration of catalytic activity even at high temperatures and to suppress carbon deposition, while being excellent in poisoning resistance and high activity, And it is providing the catalyst for partial oxidation which has long-term durability, and its manufacturing method. Another object of the present invention is to provide a method for producing a hydrogen-containing gas (or hydrogen gas) using the partial oxidation catalyst, and a method for using the gas.
[0009]
[Means for Solving the Problems]
The hydrocarbon partial oxidation catalyst of the present invention comprises a monolith support on which a catalyst component is supported. The catalyst component includes a heat-resistant inorganic oxide (a) on which a platinum group element is supported and a heat-resistant inorganic oxide. Including oxide (b) The catalyst component in the catalyst is 35 to 400 g per liter of monolith support, and the catalyst component contains 1 to 30 g of the heat-resistant inorganic oxide (a) supporting the platinum group element. In particular.
[0010]
In the catalyst, the amount of platinum group element supported on the heat-resistant inorganic oxide (a) is preferably 0.4 to 40% by mass.
[0011]
Moreover, it is preferable that the average particle diameter (measured with Electron Probe Micro Analyzer) of the heat-resistant inorganic oxide (a) carrying the platinum group element is 0.5 to 20 μm.
[0012]
In the present invention, it is recommended that 50% by mass or more of the platinum group element is platinum.
[0013]
The heat-resistant inorganic oxide (a) supporting the platinum group element is preferably at least one selected from the group consisting of activated alumina, cerium oxide, and zirconium oxide.
[0014]
As an embodiment of the present invention, the heat-resistant inorganic oxide (a) supporting a platinum group element contains activated alumina, and the heat-resistant inorganic compound (b) is cerium oxide, zirconium oxide, cerium-zirconium composite oxidation. It is also preferable that it contains at least two selected from the group consisting of products.
[0015]
Further, in the present invention, the mass ratio of activated alumina and cerium oxide contained in the catalyst component is 100: 15 to 100: 60, and the mass ratio of cerium oxide and zirconium oxide is 100: 2 to 100: 60. preferable.
[0016]
The method for producing the partial oxidation catalyst of the present invention comprises a monolith support in a slurry of a heat-resistant inorganic oxide (a) supporting a platinum group element and a catalyst component containing the heat-resistant inorganic oxide (b). It has a gist in firing after contacting.
[0017]
The gist of the present invention is that a mixed gas containing a hydrocarbon-containing gas and an oxygen-containing gas is brought into contact with the hydrocarbon partial oxidation catalyst, and the hydrocarbon is partially oxidized to produce a hydrogen-containing gas. A method for producing a hydrogen-containing gas is provided.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
As a catalyst main active component supported on a catalyst for partial oxidation of hydrocarbons, platinum group compositions such as platinum, palladium, rhodium and iridium are more heat resistant than base metal compositions such as nickel, iron or cobalt. It is known that it has excellent characteristics of resistance to poisoning.
[0020]
However, since platinum group elements are expensive, the amount of platinum group elements used must be limited (5% by mass or less in the catalyst) in order to provide a practical catalyst because of cost and effect. Therefore, in order to make the best use of platinum group elements, we manufactured a partial oxidation catalyst with platinum group elements supported in as high a dispersion as possible on heat-resistant inorganic oxides with a high surface area such as activated alumina, and investigated their performance. It was. As a result, if it continues to be used at a high temperature, platinum group element particles grow or react with the support material, or the platinum group element undergoes a chemical change and becomes inactive, or the S content in the source gas, etc. It has been found that the catalyst has a problem that its catalytic performance such as catalytic activity deteriorates with the passage of time.
[0021]
Therefore, as a result of further studies by the present inventors to solve the above problems, a monolith using a heat-resistant inorganic oxide (a) on which a platinum group element is previously supported and a heat-resistant inorganic oxide (b) as catalyst components. The present inventors have found that the above-described various performances required as a catalyst for partial oxidation of hydrocarbons can be achieved at a high level if supported on a carrier, and have led to the present invention.
[0022]
In the present invention, a monolithic carrier is used as the carrier. Monolithic carriers are recommended because they are superior in low-pressure loss resistance and dust resistance and easier to handle than other shaped carriers such as pellets, spherical carriers, powdery carriers, and granular carriers. Further, in order to maintain the shape of the carrier at a high temperature during the partial oxidation reaction, it is desirable to use a material excellent in heat resistance strength, dust resistance, etc. as the material of the carrier, for example, cordierite, mullite, α- Preferable examples include oxides such as alumina, zirconia, titania, alumina silicate, magnesium silicate, heat-resistant alloys such as silicate, stainless steel, and Fe—Cr—Al alloy. These can be used alone or in combination to form a monolithic carrier. Among these, a carrier mainly composed of cordierite (50% by mass or more) which has high heat resistance and excellent thermal shock resistance is most preferable. The monolithic carrier has many holes (cells) penetrating in the parallel direction, but the shape of the holes may be circular or any shape such as a polygon such as a triangle, quadrilateral, hexagon, etc. The size is not particularly limited.
[0023]
The cell density of the support is not particularly limited, but in order to increase the contact efficiency with the reaction gas, it is preferably 150 to 600 cells / in 2, more preferably 250 to 600 cells / in 2. If the cell density (number of cells / square inch) is too large, individual cells may become small and clogging may occur. On the other hand, if the cell density is too small, the contact area decreases, and sufficient catalyst efficiency may not be obtained.
[0024]
In the present invention, a catalyst component is supported on the monolith support. The catalyst component is a composition containing a heat-resistant inorganic oxide (a) carrying a platinum group element and a heat-resistant inorganic oxide (b). In order to achieve the above object of the present invention, a catalyst component containing a heat-resistant inorganic oxide (a) and a heat-resistant inorganic oxide (b) substantially carrying a platinum group element may be used. The catalyst component containing the heat-resistant inorganic oxide (a) and the heat-resistant inorganic oxide (b) is, for example, a catalyst comprising the heat-resistant inorganic oxide (a), the heat-resistant inorganic oxide (b) and inevitable impurities. There may be. Alternatively, in addition to the heat-resistant inorganic oxide (a) and the heat-resistant inorganic oxide (b), any heat-resistant inorganic oxide [for example, a heat-resistant inorganic oxide (a) not carrying a platinum group element] is included. What is necessary is just to use a catalyst component, and according to the objective, you may contain a promoter etc. in the range which does not inhibit the effect of this invention.
[0025]
In the present invention, the heat-resistant inorganic oxide (a) for supporting the platinum group element and the heat-resistant inorganic oxide used for the heat-resistant inorganic oxide (b) are stable in shape at high temperatures (for example, 300 to 1000 ° C.). Any inorganic oxide can be used as long as it does not deteriorate its properties and performance. In particular, at least one selected from the group consisting of alumina (particularly activated alumina), zirconium oxide, and cerium oxide is preferable. Of course, arbitrary heat-resistant inorganic oxides (including mixtures and composite oxides) may be used together with these preferable heat-resistant inorganic oxides. Examples thereof include lanthanum oxide, titanium oxide, silica, magnesium oxide, and mixtures and composite oxides thereof. Examples of the composite oxide include alumina-ceria, alumina-lanthanum oxide, alumina-magnesia, alumina-silica, alumina-zirconia, stabilized zirconia, zirconia-ceria, zirconia-lanthanum oxide, and the like.
[0026]
As the heat-resistant inorganic oxide (a), at least one selected from the group consisting of activated alumina, cerium oxide, and zirconium oxide is recommended. These heat-resistant inorganic oxides are desirable because they are excellent in high-temperature heat resistance and excellent in carrying ability of platinum group elements. Of the above heat-resistant inorganic oxides, it is particularly preferable to use activated alumina. Activated alumina is desirable because it has a large specific surface area and a large contact area with the reaction gas, so that partial oxidation efficiency can be improved and high temperature heat resistance is also excellent. In addition, it is desirable to support a platinum group element on the activated alumina [corresponding to the heat-resistant inorganic oxide (a)] as described later, because the characteristics of the platinum group element can be maintained for a long period of time.
[0027]
Examples of the activated alumina include α-alumina, γ-alumina, δ-alumina, θ-alumina, and η-alumina. The properties of the activated alumina are not particularly limited, but the specific surface area is 25 to 250 m. ² / G activated alumina is preferred.
[0028]
The supported amount of the platinum group element supported on the heat resistant inorganic oxide (a) of the present invention is 0.4 to 40% by mass (ratio to the total amount of the heat resistant inorganic oxide (a) and the platinum group element). It is preferable that it is, More preferably, it is 1-30 mass%, More preferably, it is 5-25 mass%. When the supported amount of the platinum group element is 0.4% by mass or more, the heat resistance is improved and deterioration of the catalyst activity can be suppressed. On the other hand, if it exceeds 40% by mass, the effective active sites of platinum group elements contributing to the reaction are decreased, and the reaction efficiency during the partial oxidation reaction may be decreased.
[0029]
Examples of platinum group elements include platinum, rhodium, palladium, ruthenium and iridium. Among these, it is particularly preferable to use at least one selected from the group consisting of platinum, rhodium, and iridium in order to obtain a more excellent effect. Of course, these platinum group elements may be used in combination in any combination. In this case, it is preferable to support platinum on the heat-resistant inorganic oxide (a) as an essential component because the partial oxidation activity to hydrocarbons is further improved. In order to obtain a more excellent partial oxidation activity effect, platinum is preferably contained in an amount of 50% by mass or more (ratio to the platinum group element), more preferably 60% by mass or more, and further preferably 70% by mass or more ( The balance is any platinum group element). As a preferable combination when a plurality of platinum group elements are used in combination, a combination of platinum-rhodium, platinum-iridium and platinum-rhodium-iridium is preferable, and a combination of platinum-rhodium is most preferable.
[0030]
The average particle diameter of the heat-resistant inorganic oxide (a) supporting the platinum group element (particle diameter after being supported on the finished catalyst) is preferably 0.5 to 20 μm, more preferably 1 It is desirable that it is ˜15 μm. When the heat-resistant inorganic oxide (a) having such an average particle size is supported on a carrier, it exhibits excellent durability even at high temperatures while maintaining catalytic activity such as activity as a partial oxidation catalyst, and has a long service life. The partial oxidation catalyst can be obtained. The particle size of the heat-resistant inorganic oxide (a) in the finished catalyst can be measured, for example, by taking a photo of the distribution of platinum group elements using Electron Probe Micro Analyzer (EPMA) on the catalyst coating layer (surface layer). That's fine.
[0031]
In order to further enhance the above-described effect of the platinum group element during the partial oxidation reaction, the supported amount of the platinum group element in the finished catalyst is preferably 0.1 to 5 g per liter of the finished catalyst, more preferably 0.8. 3 to 3 g. Even if the platinum group element is contained in excess of 5 g per liter of the finished catalyst, the effect on the cost increase due to the use of the platinum group element cannot be sufficiently obtained. On the other hand, if it is less than 0.1 g, sufficient catalytic activity may not be obtained.
[0032]
In order to further enhance the catalytic performance improvement effect of the heat-resistant inorganic compound (a) carrying the platinum group element, the catalyst component in the finished catalyst is preferably carried by 35 to 400 g per liter of monolith support. At the same time, the catalyst component preferably contains 1 to 30 g, more preferably 1 to 20 g of the heat-resistant inorganic oxide (a) supporting a platinum group element. When the supported amount of the catalyst component is 35 g or more per liter of the monolith support, the effect of the catalyst activity is further increased. On the other hand, if it is carried over 400 g, it may cause clogging or increased pressure loss.
[0033]
As the heat-resistant inorganic oxide (b) of the present invention, any of the heat-resistant inorganic oxides described above can be used, but no platinum group element is supported.
[0034]
As a result of studies conducted by the present inventors to maximize the effect of the platinum group element in the partial oxidation catalyst, the platinum group element is supported together with the heat-resistant inorganic oxide (a) supporting the platinum group element. By adding the non-heat-resistant inorganic oxide (b), the above-mentioned problem occurring in the catalyst in which only the heat-resistant inorganic oxide (a) carrying the platinum group element is carried on the carrier can be solved. That is, by including the heat-resistant inorganic oxide (a) supporting the platinum group element and the heat-resistant inorganic oxide (b) not supporting the platinum group element, the catalytic activity is deteriorated in the partial oxidation reaction. It has been found that the heat resistance is improved, and the catalyst activity is maintained stably over time for a long time even if the sulfur component is accompanied by the raw material gas.
[0035]
In order to further enhance such effects, cerium oxide is preferably used as the heat-resistant inorganic oxide (b), and cerium oxide and zirconium oxide are more preferably used. Particularly preferably, it is recommended that at least a part of cerium oxide and zirconium oxide is contained as a cerium-zirconium composite oxide. Of course, these heat-resistant inorganic oxides (b) can be used in combination of a plurality of types. For example, at least two types selected from the group consisting of cerium oxide, zirconium oxide, and cerium-zirconium composite oxide can be used. Further, combinations with other heat-resistant inorganic oxides such as activated alumina are also preferred. Further, in order to exert a more excellent effect, when the heat-resistant inorganic oxide (a) essentially contains activated alumina, the heat-resistant inorganic oxide (b) includes cerium oxide, zirconium oxide, cerium-zirconium composite oxidation. It is most preferable to combine at least two selected from the group consisting of products.
[0036]
In order to further improve the durability of the catalyst of the present invention (that is, the feature that the catalyst activity deterioration under high temperature is suppressed, the heat resistance is excellent, and the catalyst activity that is stable over time is maintained), the finished catalyst It is desirable to add a relatively high concentration of cerium oxide to the activated alumina contained in the catalyst component and to determine the amount of zirconium oxide relative to cerium oxide. Specifically, the mass ratio of activated alumina: cerium oxide in the catalyst component is preferably 100: 15-100: 60, more preferably 100: 20-100: 40, and the mass ratio of cerium oxide: zirconium oxide is Preferably it is 100: 2 to 100: 60, more preferably 100: 4 to 100: 40.
[0037]
When the mass ratio of activated alumina: cerium oxide is less than 100: 15, the effect of adding cerium oxide may be insufficient. On the other hand, even if it adds excessively exceeding 100: 60, the said effect will be saturated and it will become uneconomical.
[0038]
In the present invention, it is also desirable to use one or more base metals as promoters. Base metals include Na, K, Cs, Ni, Co, Fe, Cr, Cu, V, Pr, Mg, Mo, W, belonging to the periodic table I, II, IIIB, IV, V, VIB, VIIB, VIII. Examples include metals such as Mn, Zn, Ga, Y, Ti, Ba, Re, Bi, Nb, Ta, La, Ag, and Au. In particular, when these base metals are present in the catalyst component as solid solutions with metals, metal oxides, or platinum group elements, the catalytic action of the platinum group elements is promoted, contributes to stabilization, etc., or the hydrogen selectivity is increased. This is desirable because it can enhance the effect. These base metal elements may be supported on the catalyst component.
[0039]
The catalyst of the present invention as described above can be produced by the following method, for example, but can be appropriately changed depending on the material, composition and the like. Therefore, unless otherwise specified, the following production method can be modified as appropriate.
[0040]
The monolithic carrier used in the present invention can be produced by known methods such as casting, press molding, extrusion molding, and sheet processing using the materials as described above. Moreover, the manufacturing method of a support | carrier should just be suitably changed according to the material which comprises, a hole diameter, a hole shape, etc., and is not specifically limited.
[0041]
Various compounds (platinum element source) can be used as the platinum group element supported on the heat-resistant inorganic oxide (a) of the present invention. Platinum compounds include PtCl _Four , H ₂ PtCl ₆ , Pt (NH _Three ) _Four Cl ₂ , (NH _Four ) ₂ PtCl ₂ , H ₂ PtBr ₆ , NH _Four [Pt (C ₂ H _Four ) Cl _Three ], Pt (NH _Three ) _Four (OH) ₂ , Pt (NH _Three ) ₂ (NO ₂ ) ₂ Etc. are exemplified. As the rhodium compound, (NH _Four ) ₂ RhCl ₆ , Rh (NH) _Five Cl _Three , RhCl _Three , Rh (NO _Three ) _Three Etc. are exemplified. As the palladium compound, (NH _Four ) ₂ PdCl _Four , Pd (NH _Three ) _Four Cl ₂ , PdCl ₂ , Pd (NO _Three ) ₂ Etc. are exemplified. Ruthenium compounds include RuCl _Three , Ru (NO _Three ) _Three , Ru ₂ (OH) ₂ Cl _Four ・ 7NH _Three Etc. are exemplified. Examples of iridium compounds include (NH _Four ) ₂ IrCl ₆ , IrCl _Three , H ₂ IrCl ₆ Etc. are exemplified.
[0042]
Moreover, what is necessary is just to use a well-known heat resistant inorganic oxide as a heat resistant inorganic oxide (a) which carry | supports the said platinum group element. For example, a general-purpose product may be used as the activated alumina powder. The activated alumina powder has a specific surface area of 25 to 250 m as described above. ² / G, and boehmite that becomes active alumina by firing after loading, alumina hydrate in a pseudo boehmite state, aluminum hydroxide, or the like may be used as a raw material. Further, for example, activated alumina obtained by adding an alkali to an aqueous solution of an aluminum salt such as aluminum nitrate to form a precipitate of hydroxide and then drying and firing the precipitate may be used. Alternatively, it may be activated alumina obtained by sol-gel method in which alkoxide such as aluminum isopropoxide is hydrolyzed to prepare alumina gel and dried and calcined, and the production method is not particularly limited, but the heat resistant inorganic having the above characteristics It is desirable to use an oxide.
[0043]
In order to support the platinum group element on the heat-resistant inorganic oxide (a), it can be preferably prepared by the following production method, but basically, the solution containing the platinum group element source was brought into contact with the heat-resistant inorganic oxide. Thereafter, it may be fired after drying by an arbitrary method.
[0044]
For example, in order to immobilize a platinum group element on activated alumina, activated alumina is brought into contact with a solution to which an appropriate amount of a platinum group element source has been added so that the desired amount of platinum group element is supported. After directly supporting the group element source, drying may be performed by any method to remove moisture, and then firing may be performed. In addition, an inorganic acid such as hydrochloric acid, sulfuric acid or nitric acid; an organic acid such as acetic acid or oxalic acid may be added to the solution according to the purpose such as improvement of solubility or pH adjustment. The supporting method in this case is not particularly limited, and methods such as an impregnation method, an immersion method, a wet adsorption method, a spray method, and a coating method can be adopted, but an impregnation method is preferable. Moreover, the conditions at the time of contact can also be changed suitably. For example, the contact operation can be performed under atmospheric pressure or reduced pressure. There is no restriction | limiting in particular also in the temperature at the time of contact, You may heat as needed, Preferably what is necessary is just to carry out in the range of about 90 degreeC from room temperature. In the present invention, it is also preferable to support two or more kinds of platinum group elements on a heat-resistant inorganic oxide. In such a case, for example, a solution containing two or more desired platinum group element sources may be prepared, and the platinum group elements may be simultaneously supported by contacting the solution with a heat-resistant inorganic oxide. Alternatively, a solution containing a platinum group element source may be prepared individually, and the solution may be sequentially contacted with a heat-resistant inorganic oxide. The firing conditions are not particularly limited, and for example, the firing may be performed in air or in a reducing atmosphere. For example, the platinum group element of the present invention is obtained by firing within a range of 300 to 600 ° C. for about 2 to 6 hours. As a result, a heat-resistant inorganic oxide (a) on which is supported is obtained.
[0045]
Incidentally, the heat-resistant inorganic oxide (a) supporting the platinum group element may be aggregated depending on the production conditions to increase the particle size. For example, the pulverization time may be reduced in the wet pulverization step during slurry preparation. By adjusting, an average particle diameter can be 0.5-20 micrometers.
[0046]
As the heat resistant inorganic oxide (b), a known one can be used as in the case of the heat resistant inorganic oxide (a). For example, general-purpose products may be used for cerium oxide, zirconium oxide, and zirconium-cerium composite oxide. For example, the cerium-zirconium composite oxide may be obtained by the following preparation method.
(1) A method of drying and firing after mixing a cerium salt aqueous solution and a zirconium salt aqueous solution
(2) A method in which an aqueous solution of cerium salt and an aqueous solution of zirconium salt are mixed, co-precipitated with an ammonium compound, etc., filtered, washed and dried and fired.
(3) Method of solid-phase reaction after mixing cerium oxide and zirconium oxide
(4) A method of immersing a zirconium salt aqueous solution in cerium oxide and drying and baking, or a method of immersing a cerium salt aqueous solution in zirconium oxide and drying and baking
(5) A method of impregnating a heat-resistant inorganic oxide such as activated alumina with a cerium salt aqueous solution and a zirconium salt aqueous solution, followed by drying and firing.
In the preparation of the cerium-zirconium composite oxide, the starting materials for cerium and zirconium are not particularly limited. For example, as the cerium compound, a commercially available cerium oxide or cerium oxide sol, or a cerium salt compound such as cerium nitrate, cerium chloride, cerium carbonate, or cerous acetate, or cerium oxide or cerium hydroxide prepared from these compounds can be used. . Further, as the zirconium compound, commercially available zirconium oxide or zirconium oxide sol may be used, various halides such as zirconium tetrachloride or partial hydrolysis products thereof, various oxyhalogens such as zirconyl chloride (zirconium oxychloride). , Various oxygenates such as zirconyl sulfate, zirconium nitrate and zirconyl nitrate, carbonates such as zirconium carbonate and zirconyl carbonate, various organic acid salts such as zirconium acetate, zirconyl acetate and zirconyl oxalate, and further alkoxides of zirconium, various Complex salts can be used. Of course, these raw materials may be used as they are or, if necessary, those prepared in zirconium oxide, zirconium hydroxide, or the like. The composite oxide (b) can be obtained by firing these materials using a known method, for example, baking in air at 300 to 800 ° C., preferably 400 to 800 ° C. for about 0.5 to 3 hours.
[0047]
Content of a heat resistant inorganic oxide (a) and a heat resistant inorganic oxide (b) can be adjusted by adjusting each addition amount suitably.
[0048]
As a method for supporting the above catalyst component on the monolith support, for example, a heat-resistant inorganic oxide (a) supporting a platinum group element and a heat-resistant inorganic oxide (b) are supplied to a pulverizer such as a ball mill and wet pulverized. The slurry may be prepared by the above, and the support may be brought into contact with the slurry. In addition, according to this method, since the heat-resistant inorganic oxide (a) and the heat-resistant inorganic oxide (b) can be supported on the carrier almost uniformly, it is preferable for obtaining the above excellent effect.
[0049]
When preparing the slurry, acids such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid and oxalic acid; basic substances such as ammonia and tetraammonium hydroxide; polyacrylic acid and the like are used to adjust the viscosity of the slurry and improve the stability of the slurry. Polymer compounds such as polyvinyl alcohol; etc. may be added as necessary. As a contact method, it is preferable to immerse the carrier in the slurry because the active ingredient can be uniformly supported. After immersion, it is recommended that excess slurry (for example, slurry remaining in the cell) adhering to the carrier is removed by a method such as air blowing and then subjected to a drying step. There is no particular limitation on the drying method, and the water content of the slurry supported by any method may be removed. The drying conditions may be either room temperature or high temperature. Further, firing after drying is desirable because the catalytically active component can be firmly fixed on the carrier. The firing method is not particularly limited, but it is desirable to dry at 400 to 800 ° C., for example, in air or in a reducing atmosphere. In addition, when a necessary carrying amount cannot be obtained by the above carrying method, the carrying amount can be adjusted by repeating the dipping operation after firing, for example.
[0050]
When using a cocatalyst, a cocatalyst such as any metal salt compound or oxide is mixed with the above slurry, or these metals are added to the heat resistant inorganic oxide (a) or the heat resistant inorganic oxide (b). You may fix and use beforehand. As a method for immobilization, the same method as in the case of supporting a platinum group element on the heat-resistant inorganic oxide (a) may be employed. Of course, a desired base metal may be further supported on the calcined catalyst by other known methods. These base metal elements may be dispersed and supported in the catalyst component.
[0051]
In order to adjust the heat-resistant inorganic oxide (a) carrying a platinum group element to aggregated particles having a relatively large average particle diameter of, for example, 0.5 to 20 μm in the finished catalyst, the above heat-resistant inorganic oxide is used. A platinum group element compound is impregnated and supported on oxide powder or pellet-like heat-resistant inorganic oxide, and this is pulverized with a mill or the like to adjust the particle size to the target. The platinum group element-supported heat-resistant inorganic oxide (a) having the particle size adjusted in this way may be supported on the monolith support by the above method together with the heat-resistant inorganic oxide (b) not containing the platinum group element. By this method, the catalyst component [heat-resistant inorganic oxide (a), (b)] can be coated (supported) almost uniformly on the support surface (the heat-resistant inorganic oxide coating layer is sometimes referred to as a coating layer). ).
[0052]
Hereinafter, a method for producing a hydrogen-containing gas by partially oxidizing hydrocarbons using the catalyst of the present invention will be described. However, the method for producing a hydrogen-containing gas using the catalyst of the present invention is not limited to the following examples. And can be changed as appropriate.
[0053]
In the present invention, a hydrocarbon-containing gas and an oxygen-containing gas (or oxygen gas) mixed gas (which may be added with water vapor if necessary) is brought into contact with the catalyst of the present invention, thereby producing a hydrocarbon. Is partially oxidized to produce a hydrogen-containing gas mainly composed of hydrogen and carbon monoxide.
[0054]
As the hydrocarbon-containing gas (raw material gas), light hydrocarbons such as methane, propane, butane, pentane, and hexane; petroleum hydrocarbons such as gasoline, kerosene, and naphtha can be used, and there is no particular limitation. For example, natural gas or liquefied natural gas mainly composed of methane, city gas mainly composed of liquefied natural gas, and LPG (liquefied petroleum gas) mainly composed of propane and butane are also abundant in resources. It is preferable because it is readily available. In addition, various synthetic liquid fuels such as methanol or dimethyl ether starting from natural gas, and biogas mainly containing methane are also preferable from the viewpoint of effective use of resources.
[0055]
In addition, when using the catalyst of this invention, even if sulfur content is contained in raw material (hydrocarbon) gas, it is not necessary to remove this sulfur content. For example, natural gas contains sulfur as an impurity in addition to hydrocarbons such as methane, ethane, and propane (for example, 5 to 30 mg / Nm as total sulfur). ^Three Degree). In the case of using such hydrocarbon gas containing sulfur, conventionally, the hydrocarbon gas must be desulfurized to remove catalyst poison components such as sulfur and then contacted with the catalyst. However, since the catalyst of the present invention has excellent durability against a catalyst poison component such as sulfur, it is possible to prevent the catalyst performance from being deteriorated by the catalyst poison component even when used for a long time. That is, when the catalyst of the present invention is used, it is not necessary to provide a catalyst poison component removing device such as a desulfurization device, which is desirable from the viewpoint of cost and maintenance. Moreover, since inexpensive natural gas can be used as it is as a carbon-containing gas, the production cost can be reduced.
[0056]
The oxygen-containing gas used in the present invention is not particularly limited, and any known oxygen-containing gas can be used. From an economic viewpoint, it is preferable to use air.
[0057]
In the present invention, the continuous flow method (a method in which the raw material gas is continuously brought into contact with the catalyst) is preferable as the reaction method. In the present invention, a mixed gas of a hydrocarbon-containing gas and an oxygen-containing gas (or oxygen gas) is brought into contact with the catalyst under substantially adiabatic conditions (meaning that external heating is not performed). The mixing ratio of the mixed gas at this time In order to perform an efficient partial oxidation reaction, it is preferable to adjust (oxygen molecule / carbon atom ratio) to be in the range of 0.45 to 0.65. More preferably, it is adjusted to be 0.48 to 0.6.
[0058]
The pressure during the partial oxidation reaction is preferably normal pressure or higher, preferably 5 MPa · G or lower, more preferably 3 MPa · G or lower. Further, SV (gas space velocity) during the reaction can be arbitrarily selected, but preferably 5,000 to 500,000H. ^-1 , More preferably 10,000-300,000H ^-1 It is. In addition, in order to promote efficient partial oxidation reaction while preventing thermal deterioration of the catalyst, the reaction conditions are changed as appropriate, such as adjusting the amount of gas mixture so that the catalyst layer temperature is in the range of 600 ° C to 1000 ° C. It is desirable to do.
[0059]
In addition, in the conventional partial oxidation reaction, it is necessary to add water vapor in order to prevent carbon deposition. However, when using the catalyst of the present invention, carbon deposition does not substantially occur even if water vapor is not added. (Zero or trace amount that does not affect the catalyst). Therefore, it is not necessary to add water vapor in the present invention. In the case of the catalyst of the present invention, the effect of increasing the hydrogen generation ratio during the partial oxidation reaction can be obtained by adding steam. The cost increases when steam is added, but in the case of the present invention, the hydrogen production ratio is improved by the addition of steam, so that an effect commensurate with the cost increase due to the addition of steam is obtained. When steam is added, an exothermic reaction (hydrocarbon oxidation reaction) and an endothermic reaction (hydrocarbon-steam reaction) occur, so that the amount of heat generated can be suppressed as compared with the case where steam is not added.
[0060]
The oxygen-containing gas (or oxygen gas) or water vapor may be introduced into the catalyst layer after being added to the hydrocarbon-containing gas, or may be introduced into the catalyst layer separately from the hydrocarbon-containing gas.
[0061]
In the present invention, as an example of efficiently starting the partial oxidation of hydrocarbon, it is desirable to preheat the raw material gas and then introduce it into the catalyst layer. The preheating temperature varies depending on the type of hydrocarbon, the composition of the raw material gas, the reaction conditions, and the like, but it is preferably preheated to 200 to 700 ° C, more preferably 300 to 600 ° C. In addition, after the reaction in the catalyst layer is started, the catalyst temperature rises due to the reaction heat, and the reaction becomes self-supporting. Therefore, it is not necessary to preheat the raw material gas. Of course, the raw material gas may be preheated if necessary in consideration of the heat balance of the entire reaction system. Besides the method of preheating the raw material gas, for example, prior to the introduction of the raw material gas, the catalyst is preferably heated to 200 to 700 ° C., more preferably 300 to 600 ° C., and the heating is stopped after the reaction starts. May be. The method for heating the catalyst is not particularly limited. For example, (1) a method of introducing heated air or nitrogen into the catalyst layer, (2) a method of heating the catalyst layer from the outside with a heater, or (3) methanol. Examples thereof include a method of introducing a gas containing a substance that can be oxidized more easily than the raw material hydrocarbon of the present invention, such as hydrogen and dimethyl ether, into the catalyst layer and heating the catalyst with the reaction heat.
[0062]
The hydrogen-containing gas mainly composed of hydrogen and carbon monoxide obtained in the present invention can be used as a fuel for fuel cells and a raw material for the chemical industry as it is. In particular, among fuel cells, molten carbonate fuel cells and solid oxide fuel cells, which are classified as high-temperature operation types, can use carbon monoxide and hydrocarbons as fuels in addition to hydrogen. It is also desirable to use the catalyst of the present invention or a hydrogen-containing gas obtained by the catalytic reaction.
[0063]
In principle, a high-temperature-operated fuel cell is capable of performing a partial oxidation reaction of hydrocarbons in the cell (internal reforming) by the catalytic action of an electrode. However, in reality, problems such as carbon precipitation occur depending on the type of hydrocarbon and impurities contained in the hydrocarbon, and therefore the total amount of hydrocarbon may not be internally reformed. Therefore, it is necessary to pre-treat the hydrocarbon before introducing the hydrocarbon into the fuel cell. However, the pre-reforming can be suitably performed using the catalyst of the present invention.
[0064]
In addition, the hydrogen-containing gas obtained by the partial oxidation reaction using the catalyst of the present invention can be further reduced in carbon monoxide concentration by CO modification reaction, cryogenic separation method, PAS method, hydrogen storage alloy or palladium membrane diffusion method, etc. Thus, impurities can be removed and high-purity hydrogen gas can be obtained. For example, in order to reduce the carbon monoxide contained in the hydrogen-containing gas, water vapor is added (or not added) to the hydrogen-containing gas obtained by the partial oxidation reaction, and the carbon monoxide modifier is used to reduce CO. A modification reaction may be performed to oxidize carbon monoxide to carbon dioxide. As the catalyst used for the CO modification reaction, for example, a known catalyst mainly composed of copper or iron may be used. Moreover, although the carbon monoxide concentration can be reduced to about 1% by the CO modification reaction, the carbon monoxide poisons the catalytic action of the electrode used in the low temperature operation type solid polymer fuel cell. Therefore, in order to avoid such poisoning of the catalyst, it is desirable that the carbon monoxide concentration be 100 ppm or less. In order to reduce the carbon monoxide concentration to 100 ppm or less, for example, a small amount of oxygen may be added to the gas after the CO modification reaction to selectively oxidize and remove carbon monoxide.
[0065]
【Example】
Catalyst preparation example 1
Carrier: A cordierite honeycomb carrier (manufactured by Nippon Choshi Co., Ltd.) having 400 cells per square inch of cross-sectional area was cut into an outer diameter of 25.4 mmφ and a length of 77 mm (carrier volume of 39.0 ml) to obtain a carrier of this example. .
[0066]
Platinum group element-supported activated alumina: a specific surface area of 155 m in a mixed solution of an aqueous solution of nitric acid of dinitrodiamine platinum containing 1.075 g of platinum and an aqueous solution of rhodium nitrate containing 0.538 g of rhodium ² / G of activated alumina (200 g) was impregnated and mixed, and then dried at 150 ° C. for 15 hours to remove moisture. After drying, the powder is calcined in air at 400 ° C. for 2 hours, whereby activated alumina carrying 0.80% by mass of platinum group elements (0.53% by mass of platinum and 0.27% by mass of rhodium) is supported. Was prepared.
[0067]
Cerium-zirconium composite oxide: Cerium carbonate powder was fired at 400 ° C. for 2 hours and then pulverized to obtain cerium oxide powder. An aqueous solution of zirconyl oxynitrate was added to the cerium oxide powder so that the mass ratio of cerium oxide: zirconium oxide was 100: 30 and mixed uniformly. The obtained mixed slurry was dried at 120 ° C. to remove moisture, and then fired in air at 500 ° C. for 1 hour to prepare a cerium-zirconium composite oxide.
[0068]
Preparation of slurry: 111.3 g of the platinum group element-supporting activated alumina, 36.0 g of the cerium-zirconium composite oxide, pure water and acetic acid were supplied to a ball mill and wet pulverized to prepare an aqueous slurry.
[0069]
Production of catalyst: The carrier is immersed in the slurry to adhere the slurry, and then taken out. Then, compressed air is blown onto the carrier to remove excess slurry remaining in the cell, followed by drying at 150 ° C. After the catalyst component was attached to the carrier, the catalyst component was firmly supported on the carrier by firing in air (500 ° C.) for 1 hour. The carrier carrying the catalyst component was further immersed in the slurry, and the same operation was repeated to carry 9.8 g of the catalyst component on the carrier to obtain a catalyst (completed catalyst). The catalyst component was supported by 252 g per liter of the carrier of the finished catalyst, and the total supported amount of platinum group elements per liter of the finished catalyst was 1.52 g (platinum: 1.01 g, rhodium: 0.51 g). The mass ratio of activated alumina: cerium oxide: zirconium oxide in the finished catalyst was 100: 25: 7.5. When the distribution layer of the Pt-Rh-supported activated alumina was randomly sampled at 3000 magnifications and analyzed with an Electron Probe Micro Analyzer (EPMA) on the coating layer of the finished catalyst, the Pt-Rh-containing activated alumina particles were average particles. It was uniformly dispersed with a diameter of 0.7 μm.
[0070]
Catalyst preparation example 2
In the same manner as in Catalyst Preparation Example 1, activated alumina carrying 12% by mass of a platinum group element (platinum: 10% by mass, rhodium: 2% by mass) was prepared. Similarly to Catalyst Preparation Example 1, a cerium / zirconium composite oxide having a mass ratio of cerium oxide: zirconium oxide of 100: 20 was prepared. 8.78 g of the platinum group element-supported activated alumina, 33.8 g of the cerium-zirconium composite oxide, and a specific surface area of 106 m ² 104.8 g / g activated alumina was placed in a ball mill, and a slurry was prepared in the same manner as in Catalyst Preparation Example 1, and then a catalyst was produced. About 9.8 g of the catalyst component was supported on the obtained catalyst support (corresponding to 252 g of the catalyst component per liter of the catalyst support). The total supported amount of platinum group elements per liter of the finished catalyst was 1.80 g (platinum: 1.50 g, rhodium: 0.30 g). The mass ratio of active alumina: cerium oxide: zirconium oxide in the catalyst component was 100: 25: 5. As in the catalyst preparation example 1, the coating layer of the finished catalyst was analyzed by taking 30 photographs of the distribution of Pt-Rh-supported activated alumina randomly at a magnification of 3000 times with EPMA. 4 μm in diameter) was uniformly dispersed.
[0071]
Catalyst preparation example 3
In the same manner as in Catalyst Preparation Example 1, activated alumina carrying 20% by mass of a platinum group element (platinum: 15% by mass, rhodium: 5% by mass) was prepared. Specific surface area 106m ² / G of activated alumina (200 g) was impregnated in an aqueous solution in which cerium nitrate and zirconium oxynitrate were mixed, dried at 120 ° C., and then fired in air (500 ° C.) for 1 hour to carry a cerium-zirconium composite oxide Activated alumina was prepared. This composite oxide had an active alumina: cerium oxide: zirconium oxide mass ratio of 100: 30: 6. 8.78 g of the platinum group-supported activated alumina, 127.5 g of the cerium-zirconium composite oxide, and a specific surface area of 106 m ² 11.7 g of activated alumina / g was put into a ball mill, and a slurry was prepared in the same manner as in Catalyst Preparation Example 1, and then a catalyst was produced. The resulting catalyst carrier was supported with 9.9 g of catalyst component (corresponding to 253 g of catalyst component per liter of carrier). The total supported amount of platinum group elements per liter of the finished catalyst is 3.0 g (platinum: 2.25 g, rhodium: 0.75 g), and the mass ratio of active alumina: cerium oxide: zirconium oxide in the catalyst component is 100: 25: 5. When the coating layer of the finished catalyst was analyzed by EPMA in the same manner as in Catalyst Preparation Example 1, activated alumina containing Pt—Rh (average particle size: 7 μm) was uniformly dispersed.
[0072]
Catalyst preparation example 4
Weighed 8.78 g of activated alumina carrying 12% by mass of the platinum group element prepared in Catalyst Preparation Example 2 (platinum: 10% by mass, rhodium 2% by mass), placed in a ball mill with pure water and acetic acid, and wetted for 12 hours. Crushed. To this aqueous slurry, 33.8 g of the cerium-zirconium composite oxide prepared in Catalyst Preparation Example 2 and a specific surface area of 106 m ² 104.8 g / g activated alumina and pure water were added, and wet grinding was further continued for 20 hours. A catalyst was produced in the same manner as in Catalyst Preparation Example 1 using the obtained aqueous slurry. The obtained finished catalyst had 9.7 g of catalyst component supported on the carrier (corresponding to 248 g of catalyst component per liter of carrier). The total supported amount of platinum group elements per liter of the finished catalyst is 1.77 g (platinum: 1.47 g, rhodium: 0.30 g), and the weight ratio of active alumina: cerium oxide: zirconium oxide in the catalyst component is 100: 25: 5. When the coating layer of the finished catalyst was analyzed by EPMA in the same manner as in Catalyst Preparation Example 1, activated alumina containing Pt—Rh of 0.5 μm or more was not detected.
[0073]
Catalyst preparation example 5
In the same manner as in Catalyst Preparation Example 1, an activated alumina carrying 10.5% by mass of platinum group elements (platinum: 9.0% by mass, rhodium: 1.5% by mass) was prepared. In the same manner as in Catalyst Preparation Example 3, a cerium-zirconium composite oxide supported on activated alumina having a weight ratio of activated alumina: cerium oxide: zirconium oxide of 100: 50: 10 was prepared.
[0074]
8.43 g of the platinum group element-supported activated alumina, 126.4 g of the cerium-zirconium composite oxide, and a specific surface area of 106 m ² A catalyst was prepared in the same manner as in Catalyst Preparation Example 1. The obtained finished catalyst had 10.0 g of catalyst component supported on the carrier (corresponding to 256 g of catalyst component per liter of carrier). This finished catalyst carries 1.54 g of platinum group elements per liter (platinum: 1.32 g, rhodium: 0.22 g), and the mass ratio of active alumina: cerium oxide: zirconium oxide in the catalyst component is 100: 40: 8. The coating layer of this finished catalyst was analyzed by EPMA in the same manner as in Catalyst Preparation Example 1. As a result, Pt—Rh-supported alumina (average particle size 3 μm) was uniformly dispersed.
[0075]
Catalyst preparation example 6
A catalyst was prepared in the same manner as in Catalyst Preparation Example 2, except that the mass ratio of cerium oxide: zirconium oxide in the cerium-zirconium composite oxide was 100: 40. The obtained finished catalyst had 9.7 g of catalyst component supported on the carrier (corresponding to 249 g of catalyst component per liter of carrier). This finished catalyst carries 1.78 g of platinum group elements (platinum: 1.48 g, rhodium: 0.30 g) per liter, and the mass ratio of active alumina: cerium oxide: zirconium oxide in the catalyst component is 100: 22: 9. The coating layer of the finished catalyst was analyzed by EPMA in the same manner as in Catalyst Preparation Example 1. As a result, Pt—Rh-supported alumina (average particle size of 4 μm) was uniformly dispersed.
[0076]
Catalyst preparation example 7
In the same manner as in Catalyst Preparation Example 1, an activated alumina carrying 12% by mass of rhodium alone as a platinum group element was prepared. Further, a cerium-zirconium composite oxide having a mass ratio of cerium oxide: zirconium oxide of 100: 20 was prepared in the same manner as in Catalyst Preparation Example 2. 5.85 g of the platinum group element-supported activated alumina, 33.8 g of the cerium-zirconium composite oxide, and a specific surface area of 106 m ² 107.5 g / g activated alumina was put in a ball mill, and a slurry was prepared in the same manner as in Catalyst Preparation Example 1, and a catalyst was produced using the slurry. The obtained catalyst carrier was loaded with 9.6 g of catalyst component (corresponding to 247 g of catalyst component per liter of carrier). The amount of rhodium supported per liter of the finished catalyst was 1.18 g, and the mass ratio of active alumina: cerium oxide: zirconium oxide in the catalyst component was 100: 25: 5. When the coating layer of the finished catalyst was analyzed by EPMA in the same manner as in Catalyst Preparation Example 1, Rh-supported alumina particles (average particle size of 4 μm) were uniformly dispersed.
[0077]
Catalyst preparation example 8
In Catalyst Preparation Example 2, chloroiridic acid (H ₂ IrCl ₆ ) A catalyst was prepared in the same manner as in Catalyst Preparation Example 2, except that an aqueous solution was used and activated alumina carrying only 12% by mass of iridium as a platinum group element was prepared. The resulting finished catalyst had 9.9 g of catalyst component supported on the carrier (corresponding to 254 g of catalyst component per liter of carrier). 1.82 g of iridium was supported per liter of the finished catalyst, and the mass ratio of active alumina: cerium oxide: zirconium oxide in the catalyst component was 100: 25: 5. When the coating layer of the finished catalyst was analyzed by EPMA in the same manner as in Catalyst Preparation Example 1, Ir-supported alumina particles (average particle diameter of 4 μm) were uniformly dispersed.
[0078]
Catalyst preparation example 9
In Catalyst Preparation Example 2, the platinum group element was replaced with cerium oxide (specific surface area 80 m ² / G), a catalyst was prepared in the same manner as in Catalyst Preparation Example 2, except that the catalyst was prepared. The obtained finished catalyst had 9.8 g of catalyst component supported on the carrier (corresponding to 251 g of catalyst component per liter of carrier). A total of 1.79 g of platinum group elements (platinum: 1.49 g, rhodium: 0.30 g) is supported per liter of the finished catalyst, and the mass ratio of active alumina: cerium oxide: zirconium oxide in the catalyst component is 100: 34. : 5. When the coating layer of the finished catalyst was analyzed by EPMA in the same manner as in Catalyst Preparation Example 1, Pt—Rh-supported cerium oxide particles (average particle size: 7 μm) were uniformly dispersed.
[0079]
Catalyst preparation example 10
In catalyst preparation example 2, instead of activated alumina as a platinum group element, zirconium oxide (specific surface area of 60 m ² / G), a catalyst was prepared in the same manner as in Catalyst Preparation Example 2, except that the catalyst was prepared. The obtained finished catalyst had 9.6 g of catalyst component supported on the carrier (corresponding to 246 g of catalyst component per liter of carrier). A total of 1.76 g of platinum group elements (platinum: 1.47 g, rhodium: 0.29 g) is carried per liter of the finished catalyst, and the mass ratio of active alumina: cerium oxide: zirconium oxide in the catalyst component is 100: 27: 13. When the coating layer of the finished catalyst was analyzed by EPMA in the same manner as in Catalyst Preparation Example 1, the Pt—Rh-supported zirconium oxide particles (average particle size 7 μm) were uniformly dispersed.
[0080]
Catalyst preparation example 11
12.2 g of the cerium-zirconium composite oxide prepared in Catalyst Preparation Example 2 and a specific surface area of 106 m ² A catalyst was produced in the same manner as in Catalyst Preparation Example 2, except that 126.4 g of activated alumina / g was used. The obtained finished catalyst had 10.0 g of catalyst component supported on the carrier (corresponding to 255 g of catalyst component per liter of carrier). Further, a total of 1.82 g of platinum group elements (platinum: 1.52 g, rhodium: 0.30 g) is supported per liter of the finished catalyst, and the mass ratio of aluminum oxide: cerium oxide: zirconium oxide in the catalyst component is 100: 7. .6: 1.5. When the coating layer of the finished catalyst was analyzed in the same manner as in Catalyst Preparation Example 1, Pt—Rh-carrying alumina particles (average particle size of 4 μm) were uniformly dispersed.
[0081]
Catalyst preparation example 12
A catalyst was prepared in the same manner as in Catalyst Preparation Example 2 except that the mass ratio of cerium oxide: zirconium oxide was set to 100: 1 in Catalyst Preparation Example 2. The obtained finished catalyst had 9.8 g of catalyst component supported on the carrier (corresponding to 250 g of catalyst component per liter of carrier). Further, a total of 1.79 g of platinum group elements (platinum: 1.49 g, rhodium: 0.30 g) is supported per liter of the finished catalyst, and the mass ratio of aluminum oxide: cerium oxide: zirconium oxide in the catalyst component is 100: 30. : 0.3. When the coating layer of the finished catalyst was analyzed in the same manner as in Catalyst Preparation Example 1, Pt—Rh-carrying alumina particles (average particle size of 4 μm) were uniformly dispersed.
[0082]
Catalyst preparation example 13
In the same manner as in Catalyst Preparation Example 1, an activated alumina carrying 0.3% by mass of a platinum group element (platinum: 0.2% by mass, rhodium: 0.1% by mass) was prepared. 122.7 g of the platinum group element-supported activated alumina and 24.6 g of the cerium-zirconium composite oxide prepared in Catalyst Preparation Example 1 were placed in a ball mill, and a slurry was prepared in the same manner as in Catalyst Preparation Example 1, and then the catalyst was prepared. Manufactured. The resulting catalyst support was loaded with 9.8 g of catalyst component (corresponding to 252 g of catalyst component per liter of the catalyst support). The total supported amount of platinum group elements per liter of the finished catalyst was 0.63 g (platinum: 0.42 g, rhodium: 0.21 g). The mass ratio of active alumina: cerium oxide: zirconium oxide in the catalyst component was 100: 15: 5. When the coating layer of the finished catalyst was analyzed in the same manner as in Catalyst Preparation Example 1, Pt—Rh-containing activated alumina (average particle size: 0.5 μm) was uniformly dispersed.
[0083]
Catalyst Preparation Example 14 (Comparative Example)
Specific surface area 106m ² 134.1 g / g activated alumina and 12.2 g cerium-zirconium composite oxide prepared in Catalyst Preparation Example 2 were placed in a ball mill. Furthermore, a nitric acid aqueous solution of dinitrodiamine platinum containing 0.878 g of platinum, a rhodium nitrate aqueous solution containing 0.176 g of rhodium, pure water and acetic acid were added to the ball mill to prepare an aqueous slurry by performing wet grinding for 20 hours, Using this slurry, a catalyst was produced in the same manner as in Catalyst Preparation Example 1. The obtained finished catalyst had 9.8 g of catalyst component supported on the carrier (corresponding to 252 g of catalyst component per liter of carrier). Further, a total of 1.80 g of platinum group elements (platinum: 1.50 g, rhodium: 0.30 g) is supported per liter of the finished catalyst, and the mass ratio of active alumina: cerium oxide: zirconium oxide in the catalyst component is 100: 7. .6: 1.5.
[0084]
Example 1
A catalyst in which a refractory for heat insulation was applied to a reaction tube made of Inconel was filled with the catalyst of Catalyst Preparation Example 1, and a partial oxidation reaction evaluation test was performed. As a raw material hydrocarbon, city gas 13A (methane 87.3%, sulfur content 5 ppm) is used, and a mixed gas prepared using oxygen as the oxygen-containing gas so that the oxygen / carbon ratio is 0.54 is a reaction gas. Used as.
[0085]
At the start of the reaction, the reaction gas was supplied to the reactor, and when the reaction gas temperature reached 350 ° C., the reaction start in the catalyst layer was confirmed, so the heating of the reaction gas was stopped. , SV30,000H ^-1 The reaction was continued adiabatically while feeding. The catalyst layer temperature during the reaction exceeded 800 ° C. The components of the resulting product gas were analyzed using gas chromatography (Shimadzu Corporation: gas chromatograph GC-8A). As a result, the conversion of city gas 13A was 79%, the hydrogen selectivity was 89%, and the carbon monoxide selectivity was 81%.
[0086]
As a result of continuing the reaction test for 2,000 hours under the above reaction conditions, the conversion rate of natural gas during the test period was stable at 78 to 80%, and the hydrogen selectivity and carbon monoxide selectivity during this period were also stable. It was. Elemental analysis of the extracted catalyst after the reaction by fluorescent X-ray revealed no change in the content of the catalyst component due to the reaction, and no carbon deposition was observed.
[0087]
Example 2
The same reactor as in Example 1 was filled with the catalyst of Catalyst Preparation Example 2, and a partial oxidation reaction evaluation test was performed. Natural gas as raw material hydrocarbon (methane 93.5%, total sulfur content 19.3mg / Nm ^Three And a mixed gas prepared so that the oxygen / carbon ratio is 0.54 using air as the oxygen-containing gas.
[0088]
At the start of the reaction, the reaction gas was supplied to the reactor, and when the reaction gas temperature reached 370 ° C., the reaction start at the catalyst layer was confirmed, so the heating of the reaction gas was stopped. , SV20,000H ^-1 The reaction was continued adiabatically while feeding. The catalyst layer temperature during the reaction exceeded 800 ° C. When the product gas was analyzed in the same manner as in Example 1, the natural gas conversion was 75%, the hydrogen selectivity was 87%, and the carbon monoxide selectivity was 77%. The reaction was continued under the above reaction conditions, and the natural gas conversion rate at an elapsed time of 5000 hours was stably maintained at 74 to 76%, and the hydrogen selectivity and carbon monoxide selectivity during this period were also stable. Further, no increase in pressure loss was observed in the catalyst layer during this period.
Accelerated durability evaluation
Example 3
Each catalyst prepared in the above Catalyst Preparation Examples 2 to 14 was cut into a size of 7 × 7 × 10 mm and subjected to accelerated durability evaluation. The reaction apparatus was the same as in Example 1, and industrial methane (methane content 99.5% or more, sulfur content 0.7 ppm) was used as the raw material gas, and air was used as the oxygen-containing gas. As an initial evaluation of the catalyst, the oxygen / carbon ratio is 0.54 and the SV is 40,000H. ^-1 The reaction was performed under the reaction gas inlet temperature of 40 ° C. For durability evaluation, after the initial evaluation, the reaction conditions were oxygen / carbon ratio 0.54, SV 400,000H. ^-1 The reaction gas inlet temperature was 250 ° C. and the reaction was continued for 150 hours. Thereafter, the reaction was performed under initial evaluation conditions, and the catalyst was evaluated after durability. The results are shown in Table 1.
[0089]
[Table 1]

[0090]
The decrease in the methane conversion rate before and after the accelerated endurance test in Catalyst Preparation Example 3 and Catalyst Preparation Examples 5 to 8 was comparable to that in the case of Catalyst Preparation Example 2, and it was determined that the durability was good. . In the catalyst of Catalyst Preparation Example 14, the methane conversion rate in the initial evaluation is not much inferior to that in the above catalyst preparation example, but the decrease in the methane conversion rate after the accelerated durability test is large and the durability as a practical catalyst is poor. I was able to judge. Further, the catalysts of Catalyst Preparation Example 4 and Catalyst Preparation Examples 9 to 13 were slightly inferior in durability as compared with Catalyst Preparation Example 2, but the durability was greatly improved as compared with the catalyst of Catalyst Preparation Example 14.
[0091]
The partial oxidation catalyst of the present invention maintained a high level of hydrogen selectivity and catalytic activity over a long period of time even under high load conditions of the hydrocarbon raw material, compared to conventional partial oxidation catalysts.
[0092]
【The invention's effect】
As described above, the catalyst for partial oxidation of the present invention suppresses deterioration of catalytic activity even at high temperatures and suppresses carbon deposition, has excellent poisoning resistance, high activity, and long-term durability. Have. The catalyst for partial oxidation of the present invention is suitably used by being incorporated in a fuel cell, for example, a solid oxide fuel cell or a solid polymer fuel cell. The fuel cell using the partial oxidation catalyst of the present invention is applied to a private or commercial cogeneration type private power generator, a thermal power plant alternative or distributed power plant, an electric vehicle, etc., and these exhibit high energy efficiency. To do.

Claims (9)

A partial oxidation catalyst for partial oxidation of hydrocarbons in a hydrocarbon-containing gas to which steam is not added , the catalyst comprising a monolith support carrying a catalyst component, the catalyst component comprising platinum, rhodium and A heat-resistant inorganic oxide (a) supporting at least one platinum group element selected from the group consisting of iridium and a heat-resistant inorganic oxide (b) not supporting a platinum group element, Partial oxidation of hydrocarbon, characterized in that the catalyst component is 35 to 400 g per liter of monolith support, and the catalyst component contains 1 to 30 g of heat-resistant inorganic oxide (a) supporting the platinum group element. Catalyst.   The platinum group element amount supported on the heat resistant inorganic oxide (a) is 0.4 to 40% by mass with respect to the total amount of the heat resistant inorganic oxide (a) and the platinum group element. 2. The partial oxidation catalyst according to 1.   3. The catalyst for partial oxidation according to claim 1, wherein an average particle size (measured by Electron Probe MicroAnalyzer) of the heat-resistant inorganic oxide (a) supporting the platinum group element is 0.5 to 20 μm.   The partial oxidation catalyst according to claim 1, wherein 50% by mass or more of the platinum group element is platinum.   The partial oxidation according to any one of claims 1 to 4, wherein the heat-resistant inorganic oxide (a) for supporting the platinum group element is at least one selected from the group consisting of activated alumina, cerium oxide, and zirconium oxide. Catalyst.   The heat-resistant inorganic oxide (a) supporting the platinum group element contains activated alumina, and the heat-resistant inorganic compound (b) is selected from the group consisting of cerium oxide, zirconium oxide, and cerium-zirconium composite oxide. The catalyst for partial oxidation according to any one of claims 1 to 5, comprising at least two or more selected from the above.   The mass ratio of activated alumina and cerium oxide contained in the catalyst component is 100: 15 to 100: 60, and the mass ratio of cerium oxide to zirconium oxide is 100: 2 to 100: 60. Oxidation catalyst.   A method for producing a partial oxidation catalyst according to any one of claims 1 to 7, comprising at least one platinum group element selected from the group consisting of platinum, rhodium and iridium. a catalyst for partial oxidation of hydrocarbon, characterized in that a monolith support is brought into contact with a slurry of a catalyst component comprising a) and a heat-resistant inorganic oxide (b) not supporting a platinum group element, and then calcined Manufacturing method. The mixed gas and water vapor seen containing a hydrocarbon-containing gas and oxygen-containing gas is not added, is brought into contact with the partial oxidation catalyst for hydrocarbons according to claim 1, partial oxidation of the hydrocarbon And producing a hydrogen-containing gas.