JP2011183346A - Catalyst for producing hydrogen, method for producing the catalyst and method for producing hydrogen - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst for producing hydrogen, which exhibits long-term durability to the poisoning by a sulfur compound contained in a hydrocarbon-based compound being a raw material and to the deterioration or coking of a catalyst component due to a temperature change or an atmospheric change because that the operation of a fuel cell system is stopped repeatedly. <P>SOLUTION: The catalyst for producing hydrogen by reforming the hydrocarbon-based compound contains a tightly mixed titanium-based oxide as a catalyst A component, an oxide of at least one element selected from the group comprising Na, K, Mg, Ca, Sr, Ba, Y, La, Pr, Nd, Ce, Cu and Zn as a catalyst B component, and at least one element selected from the group comprising Ni, Pt, Pd, Rh, Ru and Ir as a catalyst C component. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a hydrogen production catalyst for producing a hydrogen-containing gas by reforming a hydrocarbon compound, a production method for the catalyst, and a hydrogen production method using the catalyst.

Hydrogen-containing gas (syngas) mainly composed of hydrogen and carbon monoxide is widely used as a reducing gas in addition to hydrogen gas production, and as a raw material for various chemical products. Recently, it is used for fuel cells. Research into practical use is also in progress as a fuel. It is known that such a hydrogen-containing gas can be obtained by steam reforming of a hydrocarbon compound. The steam reforming reaction when methane, the main component of natural gas, is used as a raw material is shown in the following equation.
CH ₄ + H ₂ O → CO + 3H ₂
Nickel-based catalysts are mainly used as hydrogen production catalysts for industrially producing hydrogen by steam reforming of natural gas. However, in a domestic fuel cell system, the system is frequently shut down in response to the situation of power and heat demand. At this time, if the system is stopped while water and unreformed fuel are present inside the reformer, it may cause deterioration of the catalyst, deterioration of restartability, fuel leakage, and the like. Therefore, when the fuel cell system is stopped, a method is adopted in which the fuel is stopped, only water vapor is circulated, and the interior of the reformer is purged with an inert gas and then stopped. Nickel-based catalysts that have an industrial track record as a catalyst for hydrogen production are known to be oxidized and deactivated by oxidation of nickel in a high-temperature steam atmosphere. As a catalyst for hydrogen production in home fuel cell systems A ruthenium-based catalyst which is a platinum group is generally used. As the purge gas, nitrogen and air can be considered in addition to water vapor, and air is particularly preferable. However, ruthenium-based catalysts are known to have high sublimation properties in a high-temperature oxidizing atmosphere, and development of a catalyst with excellent oxidation resistance is desired. ing.

  Hydrocarbon compounds that can be used as raw materials for reforming reactions include methanol, LP gas, natural gas, gasoline, light oil, and kerosene. It is preferred to use gas, LP gas and kerosene. However, sulfur compounds such as mercaptans contained in city gas and LP gas as odorants and sulfur compounds remaining in kerosene are present in trace amounts, so that the catalyst coverage of the steam reforming catalyst and the CO conversion catalyst in the subsequent stage is small. It is known that it becomes a toxic substance, and it is desired to improve the sulfur poisoning resistance of the catalyst. Therefore, as a means of avoiding deterioration of the catalyst for hydrogen production due to sulfur compounds contained in the raw material, a pretreatment desulfurization device is installed in front of the reformer to remove the sulfur content from the raw material gas before reforming. Preventive measures such as use for reaction have been proposed. However, when these preventive measures are taken, a new problem arises in that the cost of hydrogen production rises because of the expense of installing and maintaining the pretreatment desulfurization apparatus.

  On the other hand, a catalyst containing platinum and rhodium has been proposed as a catalyst that suppresses catalyst deterioration due to sulfur poisoning in a reforming reaction of a raw material containing a sulfur compound (Patent Document 1). This document discloses that rhodium is particularly effective in improving sulfur poisoning resistance. Similarly, a steam reforming catalyst containing rhodium in addition to ruthenium has been proposed as a means for ensuring long-term catalyst stability even when a sulfur compound is contained in a raw material of hydrocarbon compounds above a certain concentration. (Patent Document 2). The rhodium-containing catalyst is excellent in sulfur poisoning resistance and oxidation resistance. However, rhodium is a very expensive noble metal among platinum group metals, which may cause a significant increase in the unit cost of the catalyst.

  In addition, in order to suppress catalyst deterioration due to sulfur poisoning, a carrier containing at least one element selected from the group consisting of Al, Ti, Ca and the like and a complex oxide with Zr is supported by at least platinum. A quality catalyst is disclosed (Patent Document 3). Further, a reforming catalyst carrier containing zirconia / titania solid solution powder and alumina or rare earth elements has been proposed (Patent Document 4). These zirconia-based carriers are inferior in heat resistance as compared with alumina-based materials generally used for platinum group metal carriers, and platinum group metal sintering and platinum group metal elements and zirconia under high temperature use conditions. There was a problem that the performance was liable to deteriorate due to the solid solution.

Japanese Patent Laid-Open No. 04-281845 Japanese Patent Publication No. 42277779 JP 2002-121006 A JP 2008-246416 A

  Since the catalyst for hydrogen production is used under high-temperature and high-humidity conditions, thermal deterioration due to sintering of catalyst components and poisoning deterioration due to sulfur compounds contained in the raw material gas occur, so that improvement in durability is desired. Further, the catalyst life depends on the reaction temperature at the time of reforming, and if the reforming reaction proceeds efficiently at a low temperature, the catalyst life can be extended.

  The present invention has been made in view of the above circumstances, and its purpose is due to changes in temperature and atmosphere due to poisoning by sulfur compounds contained in the hydrocarbon-based compounds as raw materials and repeated shutdown of the fuel cell system. It is to provide a hydrogen production catalyst having a long-term durability against catalyst component alteration and coking, a production method thereof, and a hydrogen production method using this catalyst.

  As a result of detailed investigations on the reforming reaction of hydrocarbon compounds, the present inventors have found that titanium-based homogeneous mixed oxide is used as the catalyst A component, and Na, K, Mg, Ca, Sr, Ba, Y as the catalyst B component. At least one element selected from the group consisting of La, Pr, Nd, Ce, Cu and Zn, and at least selected from the group consisting of Ni, Pt, Pd, Rh, Ru and Ir as the catalyst C component The inventors have found that the use of a catalyst containing one kind of element improves the heat and water resistance, improves the sulfur poisoning resistance, and greatly extends the catalyst life, thereby completing the present invention.

  According to the hydrogen production catalyst of the present invention, even when the raw material gas contains a sulfur compound, the reforming reaction can be performed at a low temperature, and poisoning by the sulfur compound can be suppressed. Therefore, the hydrogen production catalyst of the present invention can be used for fuel cells, and is suitable for incorporation into, for example, household polymer electrolyte fuel cells and solid oxide fuel cells.

  The catalyst for hydrogen production of the present invention comprises a titanium-based homogeneous mixed oxide as the catalyst A component, and Na, K, Mg, Ca, Sr, Ba, Y, La, Pr, Nd, Ce, Cu and Zn as the catalyst B component. It is characterized by containing at least one element selected from the group consisting of Ni, Pt, Pd, Rh, Ru, and Ir as an oxide of at least one element selected from the group consisting of the oxides. This hydrogen production catalyst can generate hydrogen from a hydrocarbon compound by a reforming reaction. The present invention is described in detail below.

  The catalyst for hydrogen production of the present invention contains a titanium-based homogeneous mixed oxide as the catalyst A component. The catalyst A component serves as a support for the catalyst B component and the catalyst C component, and the content thereof is 50 to 98% by mass with respect to the total mass of the hydrogen production catalyst, and the more preferable content of the catalyst A component The rate is 70 to 98% by mass. When the catalyst A component is less than 50% by mass, the dispersibility of the catalyst B component and the catalyst C component is lowered, and the performance is lowered during use. On the other hand, when the content exceeds 95% by mass, the contents of the catalyst B component and the C component become low and sufficient performance cannot be obtained.

  The titanium-based dense mixed oxide as the catalyst A component is not particularly limited, but is preferably a complex oxide or a solid solution, and specifically derived from a single oxide of each constituent element in X-ray diffraction measurement. It has an amorphous crystal structure that does not show an intrinsic peak or has a broader diffraction peak than the diffraction peak of a single oxide. Among these, a titanium-based dense mixed oxide in which titanium and silicon and / or tungsten are combined is preferably used. Specific examples include titanium-silicon, titanium-tungsten binary dense mixed oxides, and titanium-tungsten-silicon ternary dense mixed oxides.

  Even in the case of titanium alone, an amorphous titanium oxide having a high surface area can be obtained, but the heat resistance is poor, and the specific surface area is rapidly decreased by heat treatment, and crystal dislocation occurs when exposed to a high temperature of 800 ° C. or higher. Such a reduction in specific surface area and crystal dislocation due to heat treatment are not preferable because they cause particle growth of the catalyst B component and the catalyst C component. In contrast, the titanium-based dense mixed oxide suppresses a decrease in specific surface area and crystal dislocation due to heat treatment, and can support other catalyst components with good dispersion and maintain the long-term durability of the catalyst. it can.

  The titanium content in the titanium-based dense mixed oxide is preferably 70 to 95% by mass, more preferably 80 to 90% by mass in terms of titanium dioxide. When the content of titanium is less than 70% by mass, the sulfur poisoning resistance is lowered and the effects of the present invention are hardly obtained. On the other hand, if the content of titanium exceeds 95% by mass, the heat resistance is insufficient and it is not suitable for the use of the present invention used at a high temperature.

The specific surface area of the titanium-based dense mixed oxide is preferably 50 to 250 m ² / g, more preferably 70 to ²⁰⁰ m ² / g, and still more preferably 80 to 160 m ² / g. In addition, the titanium-based dense mixed oxide has good moldability and can be easily formed into pellets or honeycomb structures of various shapes by an extrusion method or the like.

  In the titanium-based dense mixed oxide, the titanium-silicon dense mixed oxide, the titanium-tungsten dense mixed oxide, and the titanium-tungsten-silicon dense mixed oxide have a high specific surface area, It is also excellent in heat resistance and is preferably used as the catalyst A component. In particular, when the catalyst shape is a honeycomb structure by extrusion molding, good mechanical strength can be obtained by using a titanium-silicon homogeneous mixed oxide or a titanium-tungsten-silicon homogeneous mixed oxide as the catalyst A component. It is possible to produce a catalyst having

  The catalyst A component can be prepared by a common coprecipitation method using a titanium source and a silicon source and / or a tungsten source constituting a titanium-based dense mixed oxide. Examples of the titanium source include inorganic titanium compounds such as titanium chloride and titanium sulfate, and organic titanium compounds such as titanium oxalate and tetraisopropyl titanate. Examples of the silicon source include inorganic silicon compounds such as colloidal silica, water glass, and silicon tetrachloride, and organic silicon compounds such as tetraethyl silicate. Examples of the tungsten source include ammonium metatungstate, ammonium paratungstate, and tungstic acid.

For example, as a method for preparing a titanium-silicon binary mixed oxide, the following methods (1) to (3) may be mentioned.
(1) A method in which titanium tetrachloride is mixed with silica sol, ammonia is added to form a precipitate, the precipitate is washed, dried and then fired.
(2) A method in which a sodium silicate aqueous solution (water glass) is added to titanium tetrachloride to form a precipitate (coprecipitate), which is washed and dried and then fired.
(3) A method in which tetraethyl silicate is added to a water-alcohol solution of titanium tetrachloride to form a precipitate by hydrolysis, which is washed and dried and then fired.

In each of the above methods, a titanium-silicon binary mixed oxide can be easily obtained by firing the coprecipitate at 300 to 950 ° C. for 1 to 10 hours. Similarly, by adjusting the mixing ratio of the titanium source, silicon source or tungsten source as appropriate, binary or ternary titanium-based dense mixed oxides can be produced.
As a method other than coprecipitation, an amorphous oxide of titanium, titania sol, a solid titanium compound such as titanium hydroxide or titanium oxide hydrate such as metatitanic acid or orthotitanic acid, and the silicon source and tungsten source are used. It is possible to obtain a titanium-based dense mixed oxide by mixing and drying and baking, or by heating and refluxing or hydrothermal synthesis, and then heating and drying and baking.

  The hydrogen production catalyst of the present invention catalyzes an oxide of at least one element selected from the group consisting of Na, K, Mg, Ca, Sr, Ba, Y, La, Pr, Nd, Ce, Cu and Zn Contains as component B. The role of the catalyst B component includes improving the heat resistance of the catalyst A component, improving the dispersibility of the catalyst C component, and imparting basicity to the catalyst. The content of the catalyst B component is preferably 2 to 30% by mass, more preferably 5 to 20% by mass with respect to the total mass of the catalyst for hydrogen production. The titanium-based homogeneous mixed oxide of the catalyst A component has strong solid acidity, but when the content of the catalyst B component is less than 2% by mass, the solid acid point derived from the catalyst A component is expressed by the above formula. It has been confirmed that it is generated together with hydrogen and becomes an adsorption point for carbon monoxide, which is a basic gas, and the progress of the reaction is inhibited, and the reaction rate of hydrogen production is remarkably slowed. Moreover, when the content rate of a catalyst B component exceeds 30 mass%, sulfur poisoning resistance and heat resistance fall and it becomes difficult to obtain the long-term durability of a catalyst. The solid acid point is known to cause coking in the reforming reaction, and if the content of the catalyst B component is outside the optimum range, it becomes difficult to use the catalyst for a long time.

  The catalyst B component is preferably an alkaline earth metal or rare earth oxide, and contains an oxide of at least one element selected from Mg, Ca, Sr, Ba, Y, La, Ce, Pr and Nd. Is preferred. Particularly preferably, the catalyst B component is preferably contained by selecting and combining at least one of an alkaline earth metal and a rare earth element. Use of Sr—La, Sr—Ce, Sr—Pr, Sr—Nd, Ba—La, Ba—Ce, Ba—Pr and Ba—Nd as a combination of two oxides of particularly preferred catalyst B component Thus, sulfur poisoning resistance and coking are suppressed, and the target catalyst of the present invention can be used for a long time. The blending ratio of the two or more kinds of catalyst B components is not particularly limited, and it is sufficient that the total content is within the above range.

  The hydrogen production catalyst of the present invention further contains at least one element selected from the group consisting of Ni, Pt, Pd, Rh, Ru and Ir as the catalyst C component. It is preferable that the content rate of the catalyst C component which is an active component is 0.05-48 mass% as a metal with respect to the total mass of the catalyst for hydrogen production. Ni is preferably selected as the catalyst C component. When Ni is used, the content of the catalyst C component is 1 to 48 mass%, more preferably 5 to 30 mass%. When the Ni content is less than 1% by mass, the initial and durability performance is insufficient. When the Ni content exceeds 48% by mass, the content of the catalyst A component and the catalyst B component is reduced, and the effects of the present invention cannot be obtained. . In the case where at least one platinum group metal selected from Pt, Pd, Rh, Ru and Ir is used as the catalyst C component, the content is preferably 0.05 to 2% by mass, more preferably It is preferable that it is 0.1-1 mass%. When the content of the platinum group metal is 0.05% by mass or less, sufficient long-term durability performance cannot be obtained, and even if it exceeds 2% by mass, an effect corresponding to the increase in the amount of the expensive platinum group metal cannot be obtained.

In a more preferred embodiment, it is particularly preferable that the catalyst component C is a combination of Ni and at least one platinum group metal selected from Pt, Pd, Rh, Ru and Ir. In this case, it is preferable that Ni is 100 and the mass ratio of other platinum group metals is in the range of 0.1 to 10, more preferably 0.3 to 3. In particular, it is preferable to select Rh or Ru as the platinum group metal used in combination with Ni. By using Ni and a platinum group metal in combination as the catalyst C component, a remarkable improvement effect of sulfur poisoning resistance and coking resistance can be obtained.
<Method for producing hydrogen production catalyst>
The catalyst for hydrogen production of the present invention comprises a titanium-based dense mixed oxide as the catalyst A component, Na, K, Mg, Ca, Sr, Ba, Y, La, Pr, Nd, Ce, Cu as the catalyst B component. And an oxide of at least one element selected from the group consisting of Zn, and at least one element selected from the group consisting of Ni, Pt, Pd, Rh, Ru and Ir as the catalyst C component It can be produced by an extrusion molding method, an impregnation method, a slurry coating method, or the like. In particular, the titanium-based homogeneous mixed oxide of the catalyst A component has good moldability and is preferably produced by an extrusion molding method. The shape of the catalyst can be a pellet shape or a honeycomb shape. The hydrogen production catalyst for industrially producing hydrogen is used by filling a multi-tubular reactor in which many reaction tubes of several inches are arranged, so that the outer diameter is in the form of a pellet of about 1 to several mm. Things are commonly used. On the other hand, since the hydrogen production catalyst of the present invention is suitable for hydrogen generation in a domestic fuel cell, it is preferable to form a honeycomb-shaped catalyst by an extrusion method that requires a small amount of gas and enables a compact design.

  As a manufacturing method of the catalyst for hydrogen production of this invention, it is preferable to manufacture by the extrusion method by making content rate of a catalyst A component into 50-98 mass% with respect to the total mass of the catalyst for hydrogen production. In particular, when extrusion-molding into a honeycomb shape, it is preferable that the content of the catalyst A component is 70 to 98% by mass with respect to the total mass of the hydrogen production catalyst. When the content of the catalyst A component exceeds 70% by mass, a catalyst for hydrogen production having a remarkably high mechanical strength in a honeycomb shape can be produced. The honeycomb catalyst by the extrusion molding method has higher mechanical strength and pressure loss can be greatly reduced as compared with a pellet catalyst having a diameter of several mm or less which is used industrially.

Cell number of preferred honeycomb catalyst is 60 to 600 cells / inch ² (number of cells per square inch), more preferably 80 to 500 cells / inch ^2, more preferably is 100 to 400 cells / inch ² . When the number of cells is less than 60 cells / inch ² , the geometric surface area becomes small and the effect of forming a honeycomb cannot be sufficiently obtained, and when it exceeds 600 cells / inch ² , the mechanical strength becomes weak, which is not preferable. Moreover, the rib thickness of the honeycomb catalyst by extrusion molding is in the range of 0.05 to 0.5 mm, preferably 0.1 to 0.4 mm, and more preferably 0.15 to 0.3 mm. If the catalyst rib thickness is less than 0.05 mm, sufficient mechanical strength of the catalyst cannot be obtained, and if it exceeds 0.5 mm, the weight of the catalyst increases and the heat capacity increases, which is not suitable for this application.

The specific manufacturing method of the catalyst for hydrogen production of this invention is illustrated below.
<Honeycomb catalyst manufacturing method 1>
Titanium-based intimate mixed oxide that is catalyst A component prepared in advance and starting materials of catalyst B component and catalyst C component are weighed and blended so that the composition ratio of each component is obtained, and thoroughly mixed with a mixer such as a kneader To do. At this time, a molding aid such as an organic binder or glass fiber can be appropriately added. Then, the catalyst for hydrogen production of the present invention can be prepared by adjusting the moisture and kneading, extruding the kneaded material into a honeycomb shape with a honeycomb molding die, drying and firing. The firing is preferably performed in a nitrogen, air, or oxygen atmosphere at a temperature of 300 to 800 ° C. for a holding time of 0.5 to 20 hours. If necessary, an activation treatment may be performed at 300 to 700 ° C. in a hydrogen atmosphere after firing or instead of firing.
<Honeycomb catalyst production method 2>
In the honeycomb manufacturing method 1, a honeycomb is produced by drying and firing in the same manner except that the catalyst A component and the catalyst B component, which are titanium-based dense mixed oxides, are extruded. A honeycomb catalyst is manufactured by subsequently supporting the catalyst C component on the obtained honeycomb-shaped formed body by an impregnation method or the like.
<Honeycomb catalyst manufacturing method 3>
A honeycomb is prepared by drying and firing in the same manner as in the honeycomb manufacturing method 1 except that the catalyst A component and the catalyst C component, which are titanium-based dense mixed oxides, are extruded. A honeycomb catalyst is manufactured by supporting the catalyst B component on the obtained honeycomb molded body later by an impregnation method or the like.
<Honeycomb catalyst production method 4>
A honeycomb is prepared by drying and firing in the same manner as in the honeycomb manufacturing method 1 except that extrusion molding is performed only with a titanium-based dense mixed oxide. A honeycomb catalyst is manufactured by subsequently supporting the catalyst B component and the catalyst C component on the obtained honeycomb molded body by an impregnation method or the like. At this time, the catalyst B component and the catalyst C component may be supported separately or simultaneously.

  The production method of the catalyst for hydrogen production of the present invention is not limited to the above honeycomb catalyst production method. For example, in the production methods 1 to 4, only a part of the components of the catalysts A to C are added at the time of extrusion, The remaining portion may be supported by impregnation after honeycomb formation. In particular, when a platinum group metal selected from Pt, Pd, Rh, Ru, and Ir is selected as the catalyst C component, it is preferable that the catalyst C component is supported on the surface layer portion of the catalyst cell later by the impregnation method after honeycomb formation.

  In the catalyst production method, Na, K, Mg, Ca, Sr, Ba, Y, La, Pr, Nd, Ce, Cu, and Zn as the catalyst B component are preferably water-soluble metal salts of respective elements. For example, a metal salt aqueous solution in which chloride, nitrate, sulfate, acetate or the like is dissolved in water can be added to the catalyst, or supported on the honeycomb formed body by impregnation. Further, regarding the catalyst C component Ni, Pt, Pd, Rh, Ru and Ir, it is preferable to use a water-soluble metal salt of each element. Similarly, chlorides, nitrates, sulfates and acetates of each element are used. It can be added to the catalyst as an aqueous metal salt solution or impregnated and supported on the honeycomb formed body. For example, ruthenium compounds, ruthenium chloride aqueous solution, ruthenium nitrate aqueous solution, rhodium compounds, rhodium chloride aqueous solution, rhodium nitrate aqueous solution, iridium compounds iridium chloride aqueous solution, iridium nitrate aqueous solution, platinum compounds chloroplatinic acid aqueous solution, dinitrodiaminoplatinum nitric acid aqueous solution, etc. Can be used.

Further, the method for producing the hydrogen production catalyst of the present invention is not limited to the above-described extrusion molding method, and the catalyst composition comprising the catalysts A to C is formed into various shapes such as spheres, cylinders, rings, plates, honeycombs, corrugates and the like. The catalyst for hydrogen production may be produced by supporting it on the support. In this case, the support may be made of a metal material such as cordierite, mullite, ceramics such as silicon carbide, or stainless steel.
(Method for reforming hydrocarbon compounds)
A method for producing hydrogen by reforming a hydrocarbon compound using the hydrogen production catalyst of the present invention will be described. Examples of the hydrocarbon compound used as a raw material for the reforming reaction include light hydrocarbons such as methane, ethane, propane, butane, heptane, and hexane, and petroleum hydrocarbons such as gasoline, light oil, and naphtha. , LPG, city gas, kerosene, and other industrially available raw materials can be used. However, even if hydrocarbon compounds are refined such as desulfurization treatment, sulfur compounds remain in trace amounts, or sulfur compounds such as mercaptans, thiophenes, sulfides are added as odorants to general household LPG and city gas Have been. Sulfur compounds are known to be poisons for catalysts, but by using the hydrogen production catalyst of the present invention, hydrocarbon compounds containing these sulfur compounds are also used as raw materials for reforming reactions. be able to. In addition, by installing a desulfurizer to remove sulfur compounds to a few ppm or less contained in the raw material and then carrying out the reforming reaction with the hydrogen production catalyst of the present invention, it becomes possible to use the catalyst for a long time. Needless to say, system maintenance becomes easier.

  In the hydrogen production method of the present invention, the hydrocarbon compound serving as the raw material gas can be used by mixing with water vapor. The ratio of the number of moles of water vapor to the number of moles of carbon atoms contained in the hydrocarbon compound (S / C ratio) is 1 to 5, preferably 2 to 4, more preferably 2.5 to 3.5. . When the steam / carbon ratio is smaller than 1, coke is likely to precipitate, and when it is larger than 5, the equipment becomes larger, which is not preferable.

The pressure is normal pressure or more and 5 MPa or less, preferably 3 MPa or less. Gas space velocity (SV) is 500~100,000H ^-1, and it is preferably a 1,000~30,000H ^-1. In order to perform an efficient reforming reaction, the reaction temperature should be such that the catalyst layer temperature is in the range of 500 to 1,000 ° C., preferably 600 to 900 ° C.

  The catalyst for producing hydrogen of the present invention has excellent oxidation resistance, and a trace amount of oxygen may be added if necessary. With respect to the ratio of the hydrocarbon-containing gas to the oxygen-containing gas, the hydrocarbon compound generates heat due to the partial oxidation reaction due to the addition of oxygen, and the temperature of the catalyst can be raised to a predetermined temperature without heating from the outside. The ratio of the number of moles of oxygen molecules to the number of moles of atoms (oxygen / carbon ratio) can be 0 to 0.75.

  The reformed gas obtained by the hydrogen production catalyst of the present invention mainly contains hydrogen and carbon monoxide and can be used as a fuel for fuel cells and a raw material for the chemical industry. For example, molten carbonate fuel cells and solid oxide fuel cells, which are classified as high-temperature operation fuel cells, can use carbon monoxide and hydrocarbons as fuel, so that the reformed gas can be used as fuel for fuel cells. This is a preferred application that can be used.

  The reformed gas is a high-purity hydrogen gas by further reducing the carbon monoxide concentration by CO modification reaction or removing impurities by a cryogenic separation method, PAS method, hydrogen storage alloy or palladium membrane diffusion method, etc. It can be. For example, the CO modification reaction is a reaction in which carbon monoxide and water are converted into hydrogen and carbon dioxide, and the carbon monoxide concentration can be reduced to about 1%. As the catalyst used for the CO modification reaction, for example, a known catalyst mainly composed of copper or iron may be used. When it is necessary to further reduce the carbon monoxide concentration, such as the fuel of a low-temperature operation type solid polymer fuel cell, it is oxidized to carbon dioxide by a CO selective oxidation catalyst installed at the subsequent stage of the CO modification catalyst, or CO selective methane It is desirable that the carbon monoxide concentration be 10 ppm or less by converting it to methane using a catalyst.

  Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to the examples without departing from the spirit of the present invention.

Example 1
First, a titanium-silicon dense mixed oxide was prepared as follows. A titanium-containing aqueous solution was obtained by diluting 180 liters of a sulfuric acid aqueous solution of titanyl sulfate (TiO ₂ concentration 250 g / liter, total sulfuric acid concentration 1100 g / liter) with 250 kg of water. Next, 300 kg of ammonia water (concentration 25%) and 400 kg of water are added to 16.7 kg of silica sol (Snowtex-30 manufactured by Nissan Chemical Co., Ltd.) to prepare an aqueous solution, and the titanyl sulfate diluted aqueous solution is gradually added dropwise with stirring. Thus, a coprecipitated gel was produced. The mixture was allowed to stand for 15 hours and then filtered to obtain a coprecipitated gel, which was thoroughly washed with water and dried at 150 ° C. for 10 hours. After drying, it was fired at 650 ° C. for 5 hours, and the fired product was pulverized with a hammer mill to prepare a titanium-silicon dense mixed oxide. This titanium-silicon dense mixed oxide had a TiO ₂ / SiO ₂ mass ratio of 90/10 and a BET specific surface area of 105 m ² / g. Further, no clear intrinsic peak of SiO ₂ was observed in the X-ray diffraction measurement chart, and the crystal had a broad anatase TiO ₂ crystal structure.

After adding 400 g of starch as a molding aid to 20 kg of the above-mentioned titanium-silicon dense mixed oxide, mixing, adding an appropriate amount of water and kneading with a kneader, the outer shape is 80 mm square and the aperture is 2. It was formed into a honeycomb shape having a thickness of 1 mm, a wall thickness of 0.4 mm, and a length of 100 mm. Next, after drying at 80 ° C., firing was performed at 550 ° C. in an air atmosphere for 5 hours to obtain a honeycomb formed body made of the catalyst component A having 146 cells / inch ² cells. Next, it was impregnated with an aqueous barium acetate solution by an impregnation method, dried and calcined at 500 ° C. for 2 hours to carry the catalyst B component. Next, it was impregnated with an aqueous nickel nitrate solution, dried, and calcined in the air at 500 ° C. to carry the catalyst C component to obtain a finished catalyst. When the composition of the obtained catalyst was analyzed, it was Ti—Si dense mixed oxide: BaO: Ni = 90: 5: 5 (mass ratio). The catalyst composition was analyzed quantitatively using a fluorescent X-ray apparatus.

(Comparative Example 1)
A comparative catalyst was obtained in the same manner as in Example 1 except that the catalyst B component was not supported in Example 1. When the composition of the obtained catalyst was analyzed, it was Ti—Si homogeneous mixed oxide: Ni = 95: 5 (mass ratio).

(Examples 2 to 7)
Example 1 is the same as Example 1 except that the types and mass ratios of the catalyst component B and the catalyst component C supported by the impregnation method on the honeycomb formed body of the intimate mixed oxide of titanium and silicon are changed as shown in Table 1. Thus, a finished catalyst was obtained.

(Example 8)
A close-mixed oxide of titanium-tungsten-silicon was prepared as follows. To 168 liters of sulfuric acid aqueous solution of titanyl sulfate (250 g / L in terms of TiO ₂ ), 80 kg of water and 8 kg of ammonium metatungstate aqueous solution (containing 50 wt% as WO ₃ manufactured by Nippon Inorganic Chemical Industry Co., Ltd.) were added to obtain a titanium-tungsten containing aqueous solution. Created. Next, to 13.3 kg of silica sol (Nissan Chemical Snowtex-30), 280 kg of ammonia water (concentration 25%) and 400 kg of water were added to prepare an aqueous solution, and the above-mentioned dilute aqueous solution of titanyl sulfate was gradually added dropwise with stirring. A coprecipitated gel was formed. While this aqueous solution was kept at a temperature of about 30 ° C. and stirred, aqueous ammonia was further added until the pH reached 6, and the mixture was left to stand for aging for 2 hours. The coprecipitated gel thus obtained was washed thoroughly with water, dried at 150 ° C. for 10 hours, and then fired at 650 ° C. for 5 hours to obtain a titanium-tungsten-silicon homogeneous mixed oxide. This titanium-tungsten-silicon dense mixed oxide had a mass ratio of TiO ₂ / WO ₃ / SiO ₂ of 84/8/8 and a BET specific surface area of 85 m ² / g. Further, no clear intrinsic peaks of WO ₃ and SiO ₂ were observed in the X-ray diffraction measurement chart, and a broad anatase TiO ₂ crystal structure was exhibited.

  After adding and mixing 400 kg of starch as a forming aid, an aqueous solution in which 19 kg of the above-mentioned titanium-tungsten-silicon mixed oxide and 1.0 kg of barium acetate are dissolved, and kneading with a kneader. In the same manner as in Example 1, the following was molded by an extrusion molding machine, dried and fired, and a honeycomb molded body containing the catalyst A component and the catalyst B component was obtained. Next, it was impregnated with an aqueous ruthenium nitrate solution by an impregnation method, dried and calcined in nitrogen at 500 ° C. for 2 hours to carry a catalyst C component to obtain a finished catalyst. When the composition of the obtained catalyst was analyzed, it was Ti—W—Si dense mixed oxide: BaO: Ru = 95: 3: 2 (mass ratio).

(Examples 9 to 10)
In the same manner as in Example 8, a honeycomb formed body containing an intimate mixed oxide of titanium-tungsten-silicon and a catalyst B component (BaO) was obtained. The resulting honeycomb formed body was further loaded with catalyst component B and then with catalyst component C so as to have the composition shown in Table 1 to obtain a finished catalyst. Table 1 shows the mass ratio of each catalyst component determined by composition analysis of the finished catalyst.

(Example 11)
In Example 8, a commercially available titanium-tungsten powder (DT52 manufactured by Millennium Inorganic Chemicals, specific surface area 90 m ² / g, WO ₃ content 10 mass%) was used in place of the titanium-tungsten-silicon dense mixed oxide. A honeycomb formed body containing a catalyst A component and a catalyst B component (BaO) was obtained in the same manner as in Example 8 except that. When the above-mentioned titanium-tungsten powder was measured by X-ray diffraction, no clear WO ₃ peak was observed, and it was confirmed that this was a titanium-tungsten homogeneous mixed oxide having a broad anatase TiO ₂ crystal structure. did. Next, the molded body is impregnated with an aqueous solution of lanthanum nitrate, dried and then calcined in air at 500 ° C. for 2 hours to support the catalyst B component (La ₂ O ₃ ), cooled, and impregnated with ruthenium nitrate. Then, it was dried and calcined in nitrogen at 500 ° C. for 2 hours to carry a catalyst C component to obtain a finished catalyst. When the composition of the obtained catalyst was analyzed, it was Ti—W dense mixed oxide: BaO: La ₂ O ₃ : Ru = 93: 3: 3: 1 (mass ratio).

(Example 12)
In Example 11, a finished catalyst was obtained in the same manner as in Example 11 except that the types and ratios of the catalyst B component and the catalyst C component supported after honeycomb formation were changed to the compositions shown in Table 1.

(Comparative Example 2)
In Example 11, a comparative catalyst was obtained in the same manner as in Example 11 except that the catalyst B component (BaO and La ₂ O ₃ ) was not added at the time of forming the honeycomb and after forming the honeycomb. When the composition of the obtained catalyst was analyzed, it was Ti—W dense mixed oxide: Ru = 99: 1 (mass ratio).

  The compositions of the catalysts of Examples 1 to 12 and Comparative Examples 1 and 2 are shown in Table 1.

（比較例３）
比較用ペレット触媒を以下のようにして調製した。外径３ｍｍ活性アルミナペレット担体（比表面積１１５ｍ^２／ｇ）に硝酸ニッケル水溶液に浸漬し、８０℃の空気を通風しながらロータリーエバポレーターで十分に乾燥した後に５００℃で空気中で焼成して比較触媒を得た。得られた触媒の組成はＡｌ_２Ｏ_３：Ｎｉ＝９０／１０であった。

(Comparative Example 3)
A comparative pellet catalyst was prepared as follows. A comparative catalyst which is immersed in an aqueous nickel nitrate solution on an activated alumina pellet carrier with an outer diameter of 3 mm (specific surface area 115 m ² / g), sufficiently dried by a rotary evaporator while ventilating air at 80 ° C., and calcined in air at 500 ° C. Got. The composition of the obtained catalyst was Al ₂ O ₃ : Ni = 90/10.

(Initial performance test)
The initial performance of the hydrogen production catalyst was measured under the following test conditions using a laboratory activity test apparatus. First, each catalyst sample was reduced in a hydrogen stream at 500 ° C. for 2 hours, and then the city gas 13A was used as a raw material gas without being desulfurized, and the catalyst inlet temperature was 700 ° C., GHSV = 20,000 H ^{− The} reforming reaction was carried out under the condition of ¹ steam / carbon (S / C) molar ratio = 3.0. Each concentration of the product gas was measured using gas chromatography (Shimadzu Corporation: gas chromatograph GC-8A), and the raw material conversion after 3 hours from the start of the reaction was calculated by the following formula (1).

なお、上記式において、ＣＯ濃度、ＣＯ_２濃度およびＣＨ_４濃度は、それぞれ生成ガス（触媒出口）における一酸化炭素、二酸化炭素およびメタンのガス濃度を表す。実施例１〜実施例１２及び比較例１〜３の水素製造用触媒の性能試験結果を表２に示す。

In the above formula, the CO concentration, the CO ₂ concentration, and the CH ₄ concentration represent the gas concentrations of carbon monoxide, carbon dioxide, and methane in the product gas (catalyst outlet), respectively. Table 2 shows the performance test results of the hydrogen production catalysts of Examples 1 to 12 and Comparative Examples 1 to 3.

(Durability test)
In order to confirm the durability, a tube furnace was used to pass a gas containing 10% of water in a nitrogen stream through the catalyst sample, and hydrothermal accelerated aging was performed at 800 ° C. for 100 hours. The reforming reaction was carried out under the same conditions after aging, and the measured values of the raw material conversion rate 12 hours after the start of the reaction are shown in Table 2 as the durability performance. Although the performance difference is small in the initial performance, the durability of the catalyst of the present invention is better than that of the comparative catalyst. This durability performance test is a performance test for complex factors such as heat resistance, water resistance, sulfur poisoning resistance and coking resistance of the catalyst.

  The catalyst for hydrogen production according to the present invention has little deterioration in performance when hydrogen is produced by reforming a raw material gas comprising a hydrocarbon compound, and can be used stably over a long period of time, particularly a raw material gas containing a sulfur compound It can be suitably applied to.

Claims (6)

  A catalyst for hydrogen production that generates hydrogen by a reforming reaction, wherein the catalyst A component is a titanium-based dense mixed oxide, and the catalyst B component is Na, K, Mg, Ca, Sr, Ba, Y, La, Pr, An oxide of at least one element selected from the group consisting of Nd, Ce, Cu and Zn, and at least one element selected from the group consisting of Ni, Pt, Pd, Rh, Ru and Ir as the catalyst C component A catalyst for producing hydrogen, comprising:   The catalyst for hydrogen production according to claim 1, wherein the catalyst A component is a titanium-based dense mixed oxide comprising titanium and silicon and / or tungsten.   The catalyst for hydrogen production according to claim 1 or 2, wherein the content of the titanium-based dense mixed oxide as the catalyst A component is 50 to 98 mass% with respect to the total mass of the catalyst for hydrogen production.   A method for producing a catalyst for hydrogen production, wherein the catalyst for hydrogen production according to any one of claims 1 to 3 is produced by an extrusion molding method.   5. The hydrogen production catalyst according to claim 4, wherein in forming into a honeycomb shape, the content of the titanium-based dense mixed oxide as the catalyst A component is 70 to 98 mass% with respect to the total mass of the hydrogen production catalyst. Production method.   A hydrogen production method comprising producing hydrogen from a hydrocarbon compound by a reforming reaction using the hydrogen production catalyst according to any one of claims 1 to 3.