JP2013017913A - Steam-reforming catalyst and hydrogen production process using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steam-reforming catalyst which is non-precious metal and has a long durability against poisoning by sulfur compounds contained in fuel hydrocarbon compounds and changes in catalyst components or carbon deposition due to changes in temperature or environment caused by repeated on/offs of a fuel cell systems and a hydrogen production process using the catalyst.SOLUTION: The steam-reforming catalyst produces hydrogen by reforming hydrocarbon compounds, and is obtained by applying a catalyst composition in which nickel is dispersed and supported on cerium oxide onto a honeycomb carrier. The content of alumina oxide in the catalyst composition is less than 20 mass%.

Description

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

Hydrogen-containing gas is widely used as a reducing gas in addition to hydrogen gas production, and also as a raw material for various chemical products. Recently, practical research has been conducted as a fuel for fuel cells. 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 steam reforming catalysts in which nickel is supported as an active component on an inorganic porous carrier such as aluminum oxide or magnesium oxide have been used industrially for a long time. For example, Patent Document 1 discloses a steam reforming catalyst in which α-alumina having a specific pore volume is supported and impregnated with 3 to 20% by mass of nickel. However, α-alumina easily reacts with nickel under high-temperature use conditions to form an inactive nickel aluminate, resulting in a decrease in activity.

  Therefore, Patent Document 2 proposes a hydrogen production catalyst in which nickel aluminate or the like is used as a carrier and nickel or iron is supported as an active ingredient. The purpose is to prevent the active ingredient from being taken in by the above-mentioned solid-phase reaction by using a carrier having a spinel structure or a velovskite structure, but these carriers have a specific surface area similar to α-alumina. Small and high temperature use conditions cause nickel particle growth, and durability is not sufficient. Further, Patent Document 3 discloses a steam reforming catalyst in which nickel is formed into a solid solution with an alkaline earth metal oxide such as magnesium oxide and carbon deposition is small even under reaction conditions having a low S / C ratio (steam / carbon molar ratio). ing. However, the oxidation resistance and carbon deposition properties were not satisfactory after long-term use. In order to suppress the carbon deposition of the nickel-based steam reforming catalyst, it is said that a method of making nickel fine particles is effective. For example, Patent Document 4 proposes a steam reforming catalyst obtained by firing a hydrotalcite compound containing magnesium, aluminum, and nickel, and having an average particle diameter of nickel metal particles of 10 nm or less. However, the production of hydrotalcite required complicated production processes such as coprecipitation, ripening, water washing, filtration, drying, and firing, and wastewater treatment equipment, and there were problems with the catalyst production method.

  Further, Patent Document 5 describes that as a performance recovery method when the performance of the nickel-based steam reforming catalyst deteriorates due to use, hydrocarbon fuel and steam are stopped, air is introduced, and precipitated carbon is removed. Yes. However, since nickel is oxidized and becomes inactive by these regeneration treatments, it is necessary to carry out a reduction treatment before reuse.

JP-A-2-43952 JP 2004-89812 A JP-A-9-77501 JP 2003-135967 A JP 2007-284322 A

  The domestic fuel cell system is repeatedly shut down daily with a balance between power and heat demand, and is required to be operated with the S / C ratio as low as possible from the viewpoint of energy saving. Due to such an operation method, an excellent ruthenium-based steam reforming catalyst is required for home fuel cells, which requires excellent oxidation resistance and carbon deposition suppression.

  The present invention has been made in view of the above circumstances, and its purpose is due to poisoning due to sulfur-containing compounds contained in hydrocarbon-based compounds as fuel, and changes in temperature and atmosphere due to repeated shutdown of the fuel cell system. The object is to provide a non-noble metal-based steam reforming catalyst having long-term durability against catalyst component alteration and carbon deposition, and a hydrogen production method using the catalyst.

  As a result of detailed studies on the steam reforming reaction, the present inventors have found a steam reforming catalyst formed by coating a honeycomb carrier with a catalyst composition in which nickel is dispersed and supported on cerium oxide, and completed the present invention. . The catalyst is excellent in oxidation resistance, and has a reforming performance with respect to various hydrocarbon compounds that is comparable to a ruthenium-based steam reforming catalyst conventionally used.

  In addition, in the hydrogen production method using the catalyst, carbon deposition is caused even at a low S / C ratio by stopping the supply of the hydrocarbon compound at 600 ° C. or higher when the fuel cell system is stopped and performing the steam purge. In addition, the inventors have found that hydrogen can be produced under an energy-saving operating condition while maintaining high activity of the catalyst, and the present invention has been completed.

  The steam reforming catalyst of the present invention can perform a steam reforming reaction at a low temperature using various hydrocarbon compounds as fuel without using expensive noble metals, and is excellent in oxidation resistance and carbon precipitation suppression. . Also, the hydrogen production method using the catalyst has excellent oxidation resistance, and carbon deposition is suppressed even at a low S / C ratio. Therefore, the hydrogen production method of the present invention stably and efficiently produces hydrogen over a long period of time. Can be manufactured. Therefore, it is suitable for a fuel cell system for home use, for example, suitable for incorporation into a polymer electrolyte fuel cell or a solid oxide fuel cell.

The steam reforming catalyst of the present invention comprises a honeycomb carrier coated with a catalyst composition in which nickel is dispersed and supported on cerium oxide, and the aluminum oxide content in the catalyst composition is less than 20% by mass. It is a steam reforming catalyst. In the steam reforming catalyst of the present invention, the content of aluminum oxide such as activated alumina or α-alumina typified by γ-alumina is less than 20% by mass in the catalyst composition. The content of aluminum oxide is preferably less than 15% by mass, more preferably less than 10% by mass and less than 5% by mass, and particularly preferably less than 1% by mass of aluminum oxide.
When the content of aluminum oxide in the catalyst composition is 20% by mass or more, nickel, which is an active component, reacts with alumina to form nickel aluminate under high temperature use conditions, thereby reducing steam reforming performance and carbon deposition. Is not preferred because it tends to occur. By limiting the content of activated alumina in the catalyst composition, stable processing performance can be maintained. Further, since nickel is dispersedly supported on cerium oxide, carbon deposition hardly occurs, and hydrogen can be generated from various hydrocarbon compounds by a steam reforming reaction. Details of the present invention will be described below.

(Steam reforming catalyst)
Cerium oxide carrying the nickel in the steam reforming catalyst of the present invention, ^{10 m} 2 / g or more, preferably has a specific surface area of 50 to 250 m ² / g. This is because if it is less than 10 m ² / g, nickel cannot be supported in a highly dispersed state, and particles are likely to be aggregated, resulting in performance deterioration under use conditions at high temperatures.

  It is usually possible to use a catalyst preparation method to disperse and carry nickel on the cerium oxide, and preferably to use an impregnation method. For example, it is obtained by impregnating a cerium oxide powder with a nickel salt solution and baking.

  In the catalyst composition of the steam reforming catalyst of the present invention, cerium oxide can be coated at 80 to 300 g / L, preferably 120 to 200 g / L (per liter of honeycomb carrier). When the content of cerium oxide is less than 80 g / L, the dispersibility of nickel is lowered and sufficient oxidation resistance cannot be obtained. In order to increase the contact efficiency with the reaction gas, it is necessary to form a coat layer having a sufficient thickness on the honeycomb carrier, and it is particularly preferable to coat cerium oxide with 120 g / L or more per unit volume.

  Next, nickel is preferably contained in the catalyst composition as nickel oxide in an amount of 5 to 150 g / L, preferably 10 to 100 g / L per unit volume of the honeycomb carrier. There are few active ingredients whose nickel oxide content is less than 5 g / L, and long-term durability is difficult to obtain. Further, when the content of nickel oxide exceeds 150 g / L, the dispersibility is lowered, and it tends to aggregate under high temperature reaction conditions, which is not preferable.

In the catalyst composition of the present invention, nickel is dispersed and supported on cerium oxide, and the molar ratio of NiO / CeO ₂ is 0.05 to 2.0, more preferably 0.1 to 1.0. preferable. When the molar ratio of NiO / CeO ₂ is less than 0.05, the nickel oxide content decreases and it is difficult to obtain sufficient reforming performance. There is a possibility of degrading. Particularly preferably, the molar ratio of NiO / CeO ₂ is 0.2 to 0.5, and the crystal peak is mainly located at a position similar to the cerium dioxide fluorite structure in the powder X-ray diffraction measurement of the catalyst composition. It is preferable that the crystal peak derived from nickel oxide is not detected, or even if detected, the main peak has a peak intensity less than 1/10 of the main peak of the cerium dioxide. By setting the molar ratio in a specific range as described above, nickel is supported on fine particles in high dispersion on cerium oxide, and the effects of the present invention are maximized. The measurement conditions of X-ray diffraction in the example of the present invention are a CuKα ray source, a voltage of 45 KV, a current of 40 mA, a scanning range of 10 to 90 °, and a scanning speed of 0.198 ° / min.

Thus, the steam reforming catalyst of the present invention is obtained by coating a honeycomb carrier with a catalyst composition in which nickel is dispersed and supported on cerium oxide. As the honeycomb carrier used in the present invention, a ceramic honeycomb carrier such as cordierite or mullite having a cell number of 100 to 600 cells / inch ² (number of cells per square inch), a metal honeycomb made of stainless steel, or the like. Can be used. When the number of cells of the honeycomb carrier is 100 cells / inch ² or less, the contact area with the gas per unit volume is small, so that it is difficult to obtain a sufficient reaction rate. When the number of cells exceeds 600 cells / inch ² , the catalyst composition It is not preferable because clogging is likely to occur when a product is loaded. The steam reforming reaction is an endothermic reaction, and it is necessary to raise the catalyst temperature to 500 ° C or higher by external heating, but the fuel cell system can be started in a short time by using a lightweight and good heat transfer metal honeycomb carrier Is possible. In particular, it is preferable to use a metal honeycomb carrier in which flat plates and corrugated plates made of a ferritic stainless steel (Fe—Cr—Al) thin steel sheet containing aluminum are alternately stacked and stacked in a spiral shape. The number of cells of the metal honeycomb carrier is 100 to 600 cells / inch ² (number of cells per square inch), and the foil thickness of the stainless steel sheet is preferably 10 to 50 μm. More preferably, the number of cells is 200 to 400 cells / inch ² , and the foil thickness of the stainless steel sheet is 20 to 30 μm. Further, when the foil thickness of the stainless steel sheet is less than 10 μm, the mechanical strength of the honeycomb may be lowered, and when it exceeds 50 μm, the catalyst weight becomes heavy, which is not preferable.

  Examples of the method for producing the steam reforming catalyst of the present invention include the following methods (1) to (3). (1) The catalyst composition obtained after impregnating a cerium oxide powder with a nickel salt solution in advance and firing is wet-ground, coated on a honeycomb carrier, and fired. (2) First, wet pulverization of cerium oxide, coating on a honeycomb carrier and firing, followed by impregnation with a nickel salt solution, firing and supporting. (3) Wet-grind cerium oxide in an aqueous nickel salt solution, and simultaneously coat and fire the honeycomb carrier. In particular, the method (3) is preferable because the production equipment is simple, the number of firings is small, and the dispersibility of nickel can be improved.

  In addition, it is preferable to implement all the said baking in the air, and it bakes at the temperature of 300-900 degreeC for 0.5 to 10 hours. Although nickel is supported as nickel oxide by the above treatment, nickel metal fine particles can be obtained by reduction treatment before the start of use.

  As a nickel raw material, water-soluble nickel salt compounds such as nickel chloride, nickel sulfate, nickel ammonium sulfate, nickel nitrate, nickel acetate, nickel oxalate, nickel citrate and the like can be used.

  In addition, as described above, nickel is dispersed and supported on cerium oxide, not only by simply dispersing and supporting a nickel salt solution on cerium oxide, but also by various catalyst preparation methods using the following raw materials.

For example, as the cerium source, in addition to cerium oxide, a compound other than cerium oxide can be used by a catalyst preparation method. For example, in the production methods (1) to (3), a precursor of cerium oxide instead of cerium oxide. It is also possible to use cerium carbonate, cerium hydroxide, and the like as the body. Similarly, various cerium-based composite oxides (including solid solutions) such as Ce—Zr, Ce—Zr—La, Ce—Zr—Y, and Ce—Zr—La—Nd can be used instead of cerium oxide. . The specific surface area of the cerium-based composite oxide is 50 to 250 m ² / g, and the cerium oxide content in the composite oxide is preferably 50% or more, preferably 60% or more.

  When using a coprecipitation method, hydrothermal synthesis method, spray combustion method or sol-gel method in addition to the impregnation method, a soluble cerium salt such as cerium nitrate, cerium acetate, cerium sulfate, cerium oxalate, or cerium ammonium carbonate is used as the cerium source. Can be used.

  For example, a mixed oxide, composite oxide, solid solution or mixture of cerium and nickel using a coprecipitation method, hydrothermal synthesis method, spray combustion method, sol-gel method, etc. from a solution in which soluble cerium salt and soluble nickel salt are mixed Then, the honeycomb carrier may be coated by wet pulverization.

  As a typical production method of the steam reforming catalyst of the present invention, the production method (3) will be described in detail below.

(Method for producing steam reforming catalyst)
An aqueous slurry is prepared by supplying the catalyst composition cerium oxide and a water-soluble nickel salt compound to a pulverizer such as a ball mill and adding an appropriate amount of water to wet pulverization. In addition to the catalyst composition, in order to adjust the viscosity and stability of the slurry together with water, acidic compounds such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid and oxalic acid, basic compounds such as ammonia and tetraammonium hydroxide, polyacrylic acid and A polymer compound such as polyvinyl alcohol may be added as necessary. In addition, a binder component such as silica sol can be added in order to enhance the adhesion to the carrier.

  The average particle diameter of the slurry is preferably 0.5 to 10 μm by wet pulverization. More preferably, the average particle size is 1 to 5 μm, and more preferably 2 to 4.5 μm. Even if the average particle diameter of the slurry is smaller than 0.5 μm or exceeds 10 μm, the adhesion to the honeycomb carrier is lowered, and the coated catalyst composition is easily peeled off.

  The method for coating the honeycomb carrier with the slurry is not particularly limited, and methods such as an impregnation method, a suction method, a wet adsorption method, a spray method, and a coating method can be applied. The slurry coating operation can be performed under atmospheric pressure, under pressure or under reduced pressure. The slurry temperature at the time of slurry coating is not particularly limited, and may be heated if necessary, and can be performed within a range from room temperature to 90 ° C. In the case of using a metal honeycomb carrier, the suction impregnation method is preferably used because the catalyst component can be uniformly supported when the slurry is sucked and impregnated under reduced pressure. After the slurry coating, it is preferable to remove excess slurry (for example, slurry remaining in the cells) adhering to the honeycomb carrier by a method such as air blowing and then drying under ventilation.

  There is no restriction | limiting in particular also about the drying method, As long as the conditions which can remove the water | moisture content of a slurry, all can be used. Drying may be performed by passing hot air at room temperature or 50 to 200 ° C. into the cell. After drying, the catalyst composition can be firmly fixed to the honeycomb carrier by firing at 400 to 800 ° C. in the air. For example, when a required amount of the catalyst composition cannot be supported by a single operation, the above slurry coating-drying-firing operation may be repeated.

  In addition to nickel and cerium, the steam reforming catalyst of the present invention further includes alkali metals such as sodium, potassium, rubidium and cesium, alkaline earth metals such as magnesium, calcium, strontium and barium, yttrium, lanthanum, One or more compounds including rare earth metals such as praseodymium, neodymium, and samarium and transition metal elements such as vanadium, chromium, manganese, iron, cobalt, copper, zinc, niobium, molybdenum, and silver can be added. By adding these elements, improvement in reforming performance and carbon deposition can be suppressed, and the catalytic activity can be maintained over a long period of time. As addition amount of each element, it is preferable to add 1/3 to 1/100 mol of nickel in the catalyst composition. Raw material compounds that form oxides by firing, such as nitrates, chlorides, sulfates, acetates, and oxalates of the above elements, can be used. Moreover, the addition amount of a platinum group metal can add 1/10-1/1000 mol of nickel in a catalyst composition. Water-soluble salts such as nitrates, chlorides, sulfates and ammonium complexes can also be used for the platinum group metal raw material compounds. Further, a platinum group metal such as ruthenium, rhodium, palladium, or platinum may be added.

  When the catalyst composition contains a component other than nickel and cerium, in the method for producing the steam reforming catalyst, nickel may be dispersed and supported on cerium oxide, and then other elements may be supported. You may carry simultaneously.

(Method for producing hydrogen by steam reforming reaction)
Next, the hydrogen production method of the present invention will be described below. In the hydrogen production method of the present invention, a hydrocarbon compound as a fuel and steam are mixed, steam reforming is performed at a catalyst layer temperature of 500 to 1,000 ° C. and an inlet gas space velocity (SV) of 500 to 100,000 H ⁻¹ . Hydrogen is produced by contact with a porous catalyst. The catalyst layer temperature is preferably 600 to 900 ° C., and the inlet gas space velocity is preferably 1,000 to 30,000 H ⁻¹ . The reaction pressure is normal pressure or higher and 5 MPa or lower, preferably 3 MPa or lower.

  Examples of hydrocarbon compounds used as fuel for the steam reforming reaction include light hydrocarbons such as methane, ethane, propane, butane, heptane, and hexane, and petroleum hydrocarbons such as gasoline, light oil, and naphtha. Fuels that can be stably obtained industrially, such as gas, LPG, city gas, and kerosene, can be used. Such hydrocarbon compounds have trace amounts of sulfur-containing compounds remaining, or sulfur-containing compounds such as mercaptans, thiophenes, and sulfides are added as odorants to general household LPG and city gas. These sulfur-containing compounds are known to be poisons for the catalyst. After introducing the pretreatment desulfurizer and removing the sulfur-containing compounds contained in the fuel before introducing the fuel into the reformer. It is preferable to carry out the reforming reaction.

  The ratio of the number of moles of water vapor introduced into the reformer to the number of moles of carbon atoms contained in the hydrocarbon compound (S / C ratio) is 2 to 5, more preferably 2.5 to 4. If the S / C ratio is less than 2, carbon is likely to precipitate, and if it is greater than 5, the energy cost increases, which is not preferable.

  The hydrogen production method of the present invention can be used for a reformer of a household fuel cell that is assumed to be repeatedly started and stopped every day (DSS operation). In DSS operation, it is preferable to purge the inside of the reformer with steam and stop the fuel cell. However, since conventional nickel-based steam reforming catalysts deteriorate in a high-temperature oxidizing atmosphere, an inert gas such as nitrogen or argon is introduced. It was necessary to stop the fuel cell. The steam reforming catalyst of the present invention formed by coating a honeycomb carrier with a catalyst composition in which nickel is dispersed and supported on cerium oxide has excellent oxidation resistance, and can supply only fuel without using the inert gas. The fuel cell can be stopped by stopping and purging the interior of the reformer with water vapor. When stopping the fuel cell, it is preferable to perform the steam purge by stopping the fuel supply when the catalyst layer temperature is in the range of 500 to 1,000 ° C. When the fuel supply is stopped when the catalyst layer temperature is less than 500 ° C., carbon tends to precipitate, and when it exceeds 1,000 ° C., the catalyst tends to be thermally deteriorated, which is not preferable. It is particularly preferable that the fuel supply is stopped and the steam purge is performed when the catalyst layer temperature is 700 to 900 ° C.

  Further, in the hydrogen production method of the present invention, when the performance of the steam reforming catalyst deteriorates after long-term use, the fuel supply to the reformer is stopped and the steam purge is performed when the catalyst layer temperature is in the range of 700 to 900 ° C. The reforming performance can be recovered by carrying out the above. Degradation of the steam reforming catalyst is caused by coking or adhesion of sulfur compounds, but it is estimated that the decomposition of carbon accumulated on the catalyst and the desorption of sulfur compounds are promoted by the steam purge treatment to regenerate the catalyst. The

  Further, in the hydrogen production method of the present invention, a trace amount of oxygen may be added together with the fuel and water vapor if necessary. By adding oxygen, the hydrocarbon compound generates heat by a partial oxidation reaction, and the temperature of the catalyst can be raised to a predetermined temperature without heating from the outside. Regarding the ratio of the hydrocarbon-containing gas and the oxygen-containing gas, the ratio of the number of moles of oxygen molecules to the number of moles of carbon atoms (oxygen / carbon ratio) is preferably 0 to 0.75.

  The reformed gas obtained by the hydrogen production method of the present invention mainly contains hydrogen and carbon monoxide, and can be used as a raw material for fuel cells and chemical industries. 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 the reformed gas can be used as fuel for fuel cells. A preferred application that can be made.

  In addition, the reformed gas can be reduced in carbon monoxide concentration by CO modification reaction, or impurities can be removed by cryogenic separation method, PAS method, hydrogen storage alloy or palladium membrane diffusion method, etc. It can be gas. 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
Preparation of slurry: 40 g of activated alumina (γ-alumina) having a specific surface area of 155 m ² / g, 160 g of cerium oxide having a specific surface area of 237 m ² / g, water and nitric acid are supplied to a ball mill and wet pulverized to obtain an aqueous slurry. Prepared. When the obtained slurry was observed with a particle size distribution analyzer (laser diffraction scattering type), the average particle size was 3.1 μm.

Metal honeycomb carrier: Fe-Cr-Al heat-resistant stainless steel plate having a foil thickness of 30 μm as a honeycomb carrier, 400 cells per square inch of cross-sectional area, an outer diameter of 20 mm, and a length of 66 mm (Geometric surface area of about 3000 m ² / m ³ ) was used.

  Catalyst production: The lower part of the metal honeycomb carrier is immersed in the slurry, sucked from the upper part under reduced pressure, the slurry is filled into the cell, the carrier is taken out, and then the compressed air is blown to leave the excess slurry remaining in the cell. Was removed. The metal honeycomb carrier thus coated with the slurry was dried at 150 ° C. and then fired in air at 500 ° C. for 2 hours. Next, nickel nitrate hexahydrate was impregnated in an aqueous solution dissolved in water, dried and then calcined in air at 500 ° C. for 2 hours to obtain a finished catalyst (A). The composition ratio and supported amount of the catalyst composition of the finished catalyst (A) are shown in Table 1.

(Examples 2-4, Comparative Examples 1-2)
Production of catalyst: The catalysts of Examples 2 to 4 and Comparative Examples 1 and 2 were prepared in the same manner as in Example 1 except that the charging ratio of activated alumina and cerium oxide was changed during slurry preparation in Example 1. Table 1 shows the composition ratios and supported amounts of the catalyst compositions of the finished catalysts (B) to (D) and the comparative catalysts (a) to (b).

（実施例５）
スラリーの調製：比表面積１５３ｍ^２／ｇの酸化セリウム１８０ｇと硝酸ニッケル６水和物７８ｇと水及び硝酸をボールミルにて湿式粉砕して水性スラリーを調製した。得られたスラリーの平均粒子径は３．０μｍであった。

(Example 5)
Preparation of slurry: 180 g of cerium oxide having a specific surface area of 153 m ² / g, 78 g of nickel nitrate hexahydrate, water and nitric acid were wet-ground in a ball mill to prepare an aqueous slurry. The average particle diameter of the obtained slurry was 3.0 μm.

  Production of catalyst: The obtained slurry was coated on the same metal honeycomb carrier as in Example 1, dried at 150 ° C, and then calcined in air at 500 ° C for 2 hours to obtain a finished catalyst (E). Table 2 shows the composition ratio and supported amount of the catalyst composition of the finished catalyst (E).

(Examples 6 to 7)
Completed catalysts (F) and (G) were obtained in the same manner as in Example 5 except that the addition ratio of cerium oxide and nickel nitrate hexahydrate was changed in the slurry preparation of Example 5. Table 2 shows the composition ratios and supported amounts of the catalyst compositions of the finished catalysts (F) and (G).

(Example 8)
Implementation was performed except that in the slurry preparation of Example 5, a commercially available cerium-based composite oxide (specific surface area 162 m ² / g, CeO ₂ / ZrO ₂ / La ₂ O ₃ = 65/27/8) was used instead of cerium oxide. In the same manner as in Example 5, a finished catalyst (H) was obtained. The composition ratio and supported amount of the catalyst composition of the finished catalyst (H) are shown in Table 2.

（水熱加速エージング）
実施例及び比較例の各触媒試料を以下の条件で水熱加速エージングを実施した。
処理温度：８００℃
処理時間：１００時間
処理ガス：２Ｌ／ｍｉｎ １０％Ｈ_２Ｏ／Ｎ_２バランス
（メタン改質性能試験）
水熱加速エージング後の試料を水素気流中で５００℃にて１時間還元してから、ラボ活性試験装置を用いて以下の試験条件で水蒸気改質触媒のメタン改質性能試験を実施した。燃料として都市ガス１３Ａを脱硫処理せずにそのまま使用し、触媒層温度７５０℃、ＧＨＳＶ＝５，０００Ｈ^−１でスチーム／カーボン（Ｓ／Ｃ）モル比＝３．０の条件にて水蒸気改質反応を実施した。ガスクロマトグラフィー（島津製作所：ガスクロマトグラフＧＣ−８Ａ）を用いて生成ガスの各濃度を測定し、反応開始２４時間後のメタン転化率を下記数式（１）により算出した。

(Hydrothermal accelerated aging)
Hydrothermal accelerated aging was performed on the catalyst samples of Examples and Comparative Examples under the following conditions.
Processing temperature: 800 ° C
Processing time: 100 hours Processing gas: 2 L / min 10% H ₂ O / N ₂ balance (methane reforming performance test)
The sample after hydrothermal acceleration aging was reduced in a hydrogen stream at 500 ° C. for 1 hour, and then a methane reforming performance test of the steam reforming catalyst was performed using a laboratory activity test apparatus under the following test conditions. Using city gas 13A as fuel without desulfurization, steam reforming under conditions of catalyst layer temperature of 750 ° C., GHSV = 5,000H ⁻¹ and steam / carbon (S / C) molar ratio = 3.0 The reaction was carried out. Each concentration of the product gas was measured using gas chromatography (Shimadzu Corporation: Gas Chromatograph GC-8A), and the methane conversion rate 24 hours after the start of the reaction was calculated by the following mathematical formula (1).

なお、上記数式において、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。

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 3 shows the test results of the methane reforming reforming performance after hydrothermal acceleration aging for the samples of Examples 1 to 8 and Comparative Examples 1 and 2.

(Propane reforming and steam purge repeated test)
Next, after each methane reforming performance test for each catalyst sample of the example, the durability against the DSS operation was repeatedly checked by repeating the fuel supply of the lab activity test apparatus and the steam purge by stopping the fuel. A high-purity propane gas is used as the fuel, the GHSV at the time of fuel supply is 5,000 H ⁻¹ and the steam / carbon (S / C) ratio is 2.5, and the catalyst layer temperature is maintained at 750 ° C. One cycle consists of stopping the supply every hour and performing the steam purge for 1 hour. The flow rate of the catalyst outlet gas in the first cycle and the 10th cycle and the gas concentrations of carbon monoxide, carbon dioxide and methane in the outlet gas were measured, and the C1 conversion rate with respect to the number of moles of carbon of the supplied propane was obtained. It is shown in Table 3.

  The steam reforming catalyst of the present invention has excellent durability against DSS operation without using an expensive noble metal, and can be suitably applied to a reformer of a domestic fuel cell.

Claims (6)

A steam reforming catalyst obtained by coating a honeycomb carrier with a catalyst composition in which nickel is dispersed and supported on cerium oxide, wherein the content of aluminum oxide in the catalyst composition is less than 20% by mass. Quality catalyst. The steam reforming catalyst according to claim 1, wherein the cerium oxide has a specific surface area of 10 m ² / g or more and is coated with 80 to 300 g / L of cerium oxide per unit volume of the honeycomb carrier. 3. The water vapor according to claim 1, wherein the nickel is coated at 5 to 150 g / L in terms of nickel oxide per unit volume of the honeycomb carrier, and the molar ratio of Ni / Ce is 0.05 to 2.0. Reforming catalyst. A hydrogen production method for producing hydrogen by a fuel reforming reaction using the steam reforming catalyst according to any one of claims 1 to 3, wherein the catalyst layer temperature is 500 to 1,000 ° C and the inlet gas space velocity is 500 to 100,000H. ^A method for producing hydrogen in which the steam reforming catalyst is brought into contact with ^-1 . The hydrogen production method according to claim 4, wherein when hydrogen production is stopped in the DSS operation, the fuel supply is stopped at a catalyst layer temperature of 500 to 1,000 ° C., and the steam purge is performed. The method for producing hydrogen according to any one of claims 4 to 5, wherein when the performance of the steam reforming catalyst is deteriorated, steam purging is performed at a catalyst layer temperature of 700 to 900 ° C to regenerate the steam reforming catalyst.