JP4340892B2 - Hydrocarbon cracking catalyst and method for producing the same, and method for producing hydrogen using the hydrocarbon cracking catalyst - Google Patents

Description

  The present invention is a hydrocarbon cracking catalyst for producing hydrogen by steam reforming a lower hydrocarbon gas mainly composed of methane, and is excellent in coking resistance (coking: a phenomenon in which carbon is precipitated) even under low steam, An object of the present invention is to provide a hydrocarbon cracking catalyst having excellent durability.

  Furthermore, in the steam reforming in which the lower hydrocarbon mainly composed of methane and water vapor are mixed and reacted, the present invention provides particles in which the metal nickel fine particles and the metal ruthenium fine particles, which are catalytically active components, constitute a hydrocarbon decomposition catalyst. The object of the present invention is to provide a hydrocarbon cracking catalyst having excellent catalytic activity even in a reaction at low temperature by being highly dispersed and supported either near the surface of the catalyst or near the surface of the catalyst molded body obtained by granulating the particles And

  In recent years, new energy technologies have been demanded due to environmental problems, and fixed-bed fuel cells that use hydrogen as a raw fuel, which is one of these technologies, can be used as a distributed power source that can produce electric energy efficiently and cleanly for household and industrial use. Are being studied for automobiles and automobiles.

  Steam reforming (SR), partial oxidation (POX), steam reforming (SR) are techniques for obtaining reformed gas mainly composed of hydrogen by reforming raw gas such as lower hydrocarbons mainly composed of methane. ) And partial oxidation (POX) in combination (autothermal reforming). Among such reforming techniques, steam reforming (SR) is a reaction method that can obtain hydrogen with the highest efficiency.

Steam reforming (SR) is performed according to the following reaction formula.
CH ₄ + H ₂ O → 3H ₂ + CO
In general, this reaction is carried out at around 600 ° C. to 800 ° C., and the S / C (water vapor / carbon ratio: Steam / Carbon ratio) is carried out at around 2.5 to 3.5. This reaction is an endothermic reaction, and the higher the temperature, the more the reaction can be promoted.

  Currently, nickel, iron, cobalt, and the like are used as active metal elements in hydrocarbon decomposition catalysts, and platinum, rhodium, ruthenium, iridium, palladium, and the like are used in noble metal systems. Among these, the catalyst which carry | supported the metallic element of nickel and ruthenium is mainly marketed from the high catalyst activity. Since base metal elements are relatively easy to cause carbon deposition, it is necessary to use them under a condition where the water vapor / carbon ratio is higher than that of the theoretical composition. In addition, noble metal elements are less likely to cause carbon deposition even under a low water vapor / carbon ratio. However, since the catalyst is expensive, the price of the fuel cell system using the catalyst becomes very expensive. This may be a factor that hinders the further spread of battery systems.

  As a commercially available catalyst, it is manufactured by spraying a solution containing nickel, which is an inexpensive base metal element, or ruthenium, which is an expensive noble metal element, on a bead-shaped carrier mainly composed of alumina or the like. There is something that is.

  In general, the catalytic properties during hydrogen production are more excellent as the supported active metal is finer, and the nickel-based catalyst obtained by the production method has several metal nickel particle sizes. It is as large as 10 nm, its catalytic activity at low temperature is low, its coking resistance is poor, and it is not possible to use the deterioration of catalyst characteristics with time. Further, the ruthenium-based catalyst obtained by the above-described production method has a high degree of coking resistance because the active metal element is ruthenium, but the size of the supported metal ruthenium particles is as large as several tens of nm. Further, the catalyst activity at low temperature is low and the deterioration of the catalyst characteristics with time due to sintering is remarkable, so that it cannot be used.

  From these facts, it is cheaper as a hydrocarbon cracking catalyst, and in terms of function, it exhibits excellent catalytic activity even at low temperatures, and carbon deposition (coking) is suppressed even at a low steam / carbon ratio, while being highly active. In addition, there is a strong demand for a highly durable catalyst.

  Conventionally, platinum, palladium, rhodium, ruthenium, nickel and the like are supported as catalytically active metals on a carrier such as α-alumina, magnesium oxide, and titanium oxide, and are reported as hydrocarbon decomposition catalysts (Patent Documents 1 to 5). ).

Japanese Patent Laid-Open No. 50-4001 JP 2000-503624 A Japanese Patent Laid-Open No. 2003-225566 Japanese Patent Laid-Open No. 11-276893 JP 2003-265963 A

  Patent Documents 1 to 3 describe a catalyst containing magnesium, aluminum, and nickel. However, since nickel is uniformly present in the entire particles constituting the catalyst, it contains a large amount of nickel. is there.

  Further, the technique described in Patent Document 4 has been proposed as the catalyst nickel loading is preferably 0.1 to 10 wt%, but the methane conversion rate is particularly high when the nickel loading is small. It's hard to say.

  The technique of Patent Document 5 carries two components of nickel and ruthenium as catalytic active metals, but is carried by a normal impregnation method, spray method, coating method, etc. It is considered that the particle diameter becomes large and the catalytic activity at low temperature is lowered.

  In view of this, the present invention has a catalytic activity that has excellent catalytic activity even in a reaction at a low temperature by supporting metallic nickel and metallic ruthenium, which are catalytic active components, in fine particles, and extremely excellent carbonization resistance even under low steam. It aims at providing the catalyst for hydrogenolysis.

  The technical problem can be achieved by the present invention as follows.

  That is, the present invention is a hydrocarbon decomposition catalyst containing magnesium, aluminum, nickel and ruthenium as constituent elements, wherein the metal ruthenium fine particles have an average particle diameter of 1 to 10 nm, and the metal ruthenium content is hydrocarbon. It is 0.025 to 5.0 wt% with respect to the catalyst for decomposition, and the content of metal ruthenium is 0.0001 to 0.025 with respect to the total number of moles of magnesium, aluminum, nickel and ruthenium. (Invention 1).

  Further, in the present invention, the average particle diameter of the metallic nickel fine particles is 1 to 10 nm, the content of metallic nickel is 0.1 to 40 wt% with respect to the hydrocarbon decomposition catalyst, and the content of metallic nickel Is a catalyst for cracking hydrocarbons according to the present invention, wherein the catalyst is 0.0007 to 0.342 with respect to the total number of moles of magnesium, aluminum, ruthenium and nickel (Invention 2).

  Further, the present invention is the hydrocarbon decomposition catalyst according to the first or second aspect of the present invention, wherein the number of moles of metal ruthenium with respect to the metallic nickel is 0.0004 to 30 (invention 3).

  The present invention also provides a layered double hydroxide core particle comprising magnesium and aluminum, and a layered double hydroxide layer comprising magnesium, aluminum, nickel and ruthenium on the surface of the layered double hydroxide core particle. The formed layered double hydroxide type particle powder is heated and fired to obtain oxide particle powder, and then the oxide particle powder is heated and reduced to convert nickel and ruthenium in the oxide particle powder into metal nickel fine particles and metal This is a method for producing a hydrocarbon cracking catalyst obtained by forming ruthenium fine particles (Invention 4).

  Further, in the present invention, an alkaline aqueous solution containing an anion, a magnesium raw material, and an aluminum salt aqueous solution are mixed to obtain a mixed solution having a pH value in the range of 7.0 to 13.0. Aged in the temperature range of ° C. to produce layered double hydroxide core particles composed of magnesium and aluminum, and then into an aqueous suspension containing the layered double hydroxide core particles at the time of the production of the core particles Magnesium raw material, magnesium salt aqueous solution, nickel salt aqueous solution containing magnesium, aluminum, nickel and ruthenium at a ratio of 0.05 to 0.5 with respect to the total number of moles of magnesium and aluminum added And an aqueous ruthenium salt solution, and then ripened at a pH value of 9.0 to 13.0 and a temperature of 40 ° C to 300 ° C. After carrying out the growth reaction for forming a layered double hydroxide layer on the surface of the recording core particles, it is filtered and washed with water, and the resulting layered double hydroxide particle powder is heated in the temperature range of 400 ° C to 1600 ° C. It is a method for producing a catalyst for cracking hydrocarbons, characterized in that oxide particle powder is obtained by heating and firing, and then the oxide particle powder is heated and reduced in a reducing atmosphere in a temperature range of 700 ° C. to 1100 ° C. ( Invention 5).

  The present invention also provides a method for producing hydrogen by steam reforming a gas mainly comprising lower hydrocarbons, the hydrocarbon cracking catalyst according to any one of the present inventions 1 to 3, the lower hydrocarbon gas and steam. It is the manufacturing method of hydrogen characterized by making it contact (this invention 6).

  The hydrocarbon cracking catalyst according to the present invention is obtained by granulating the vicinity of the surface of particles constituting the hydrocarbon cracking catalyst or particles in the form of very fine particles not only for metallic nickel but also for metallic ruthenium. Since it is supported in a highly dispersed state near the surface of the catalyst molded body, the area in contact with the lower hydrocarbon and water vapor of metallic nickel and ruthenium, which are active metal species, is increased, and is excellent even at relatively low temperatures. Have high catalytic activity.

  Also, nickel metal and ruthenium metal are highly dispersed in either the vicinity of the surface of the particles constituting the hydrocarbon cracking catalyst with very fine particles or the vicinity of the surface of the molded catalyst obtained by granulating the particles. Therefore, even if steam reforming is performed under low steam conditions, coking is difficult. Furthermore, since the porous carrier contains a large amount of magnesium, it has excellent sulfur poisoning resistance, and therefore has excellent catalytic activity in terms of durability.

  Furthermore, the hydrocarbon decomposition catalyst according to the present invention uses a lower hydrocarbon gas such as methane as a hydrocarbon decomposition catalyst such as autothermal reforming (ATR) or partial oxidation (POX), or a carbon dioxide reforming catalyst. You can also.

  The configuration of the present invention will be described in more detail as follows.

  First, the hydrocarbon cracking catalyst according to the present invention will be described.

  The average particle diameter of the metal ruthenium fine particles of the hydrocarbon cracking catalyst according to the present invention is 10 nm or less, which is optimal for hydrogen production and has excellent catalytic activity at low temperatures. Catalysts with metal ruthenium fine particles with an average particle diameter exceeding 10 nm have a lower conversion rate of lower hydrocarbons at low temperatures in steam reforming in which hydrogen is produced by mixing lower hydrocarbon gas mainly composed of methane and water vapor. Resulting in. Preferably it is 9 nm or less, More preferably, it is 8 nm or less. The lower limit of the average particle diameter is about 0.5 nm.

  The content of metal ruthenium in the hydrocarbon cracking catalyst according to the present invention is 0.025 to 5.0 wt% with respect to the catalyst. When the content of metal ruthenium is less than 0.025 wt% or 5.0 wt% or more, the conversion rate of lower hydrocarbons at low temperatures decreases. Preferably it is 0.025 to 4.8 wt%.

  The content of ruthenium metal in the hydrocarbon cracking catalyst according to the present invention is 0.0001 when expressed as a molar ratio (Ru / (Mg + Al + Ni + Ru)) to the total number of moles of magnesium, aluminum, nickel and ruthenium contained in the catalyst. ~ 0.025 is preferred. When the molar ratio exceeds 0.025, the average particle diameter of the metal ruthenium fine particles exceeds 10 nm, so that the conversion rate of lower hydrocarbons at a low temperature decreases. Preferably it is 0.0001-0.024.

  The average particle diameter of the metal nickel fine particles of the hydrocarbon cracking catalyst according to the present invention is preferably 10 nm or less, and is optimal for hydrogen production and has excellent catalytic activity at low temperatures. In a catalyst having metallic nickel fine particles having an average particle diameter exceeding 10 nm, the conversion rate of lower hydrocarbons is reduced in steam reforming in which hydrogen is produced by mixing lower hydrocarbon gas mainly composed of methane and water vapor. End up. Furthermore, in the case of a catalyst having metallic nickel fine particles exceeding 10 nm, the coking resistance of the catalyst body is significantly lowered. Preferably it is 9 nm or less, More preferably, it is 8 nm or less. The lower limit of the average particle diameter is about 0.5 nm.

  The content of metallic nickel in the hydrocarbon cracking catalyst according to the present invention is preferably 0.10 to 40 wt% with respect to the catalyst. When the content of metallic nickel is less than 0.10 wt%, the conversion of lower hydrocarbons decreases. When it exceeds 40 wt%, the particle size of the metal nickel fine particles exceeds 10 nm, and the coking resistance is lowered. Preferably it is 0.18-39.0 wt%.

  The content of metallic nickel in the hydrocarbon cracking catalyst according to the present invention is 0.0007 when expressed as a molar ratio (Ni / (Mg + Al + Ru + Ni)) to the total number of moles of magnesium, aluminum, ruthenium and nickel contained in the catalyst. ~ 0.342 is preferred. When the molar ratio exceeds 0.342, the average particle diameter of the metallic nickel fine particles exceeds 10 nm, so that the conversion rate of lower hydrocarbons at low temperatures is lowered and the coking resistance is lowered. More preferably, it is 0.001-0.34, and still more preferably 0.0015-0.34.

  The number of moles of metal ruthenium in the hydrocarbon cracking catalyst according to the present invention is preferably 0.0004 to 30 relative to the number of moles of metal nickel.

  In the hydrocarbon cracking catalyst according to the present invention, the nickel metal and the ruthenium metal are preferably present in the vicinity of the particle surface of the particles constituting the hydrocarbon cracking catalyst. Moreover, the hydrocarbon cracking catalyst according to the present invention is preferably granulated and used in the form of a molded body, and metal nickel and metal ruthenium may be present in the vicinity of the surface of the molded body.

  Although the ratio of magnesium and aluminum in the hydrocarbon cracking catalyst according to the present invention is not particularly limited, it is preferable that the amount of magnesium is larger than that of aluminum, and the molar ratio of magnesium to aluminum is Mg: Al = 4: 1 to 1. 5: 1 is preferred. When magnesium exceeds the above range, it is difficult to easily obtain a molded article having sufficient strength, and when it is less than the above range, it is difficult to obtain the characteristics as a porous carrier.

The specific surface area value of the hydrocarbon cracking catalyst according to the present invention is preferably 7 to 320 m ² / g. If it is less than 7 m ² / g, the conversion rate decreases at a high space velocity. When it exceeds 320 m ² / g, industrial production of the layered double hydroxide particle powder as the catalyst precursor becomes difficult. More preferably, it is 20-280 m < ² > / g.

  Next, a method for producing a hydrocarbon cracking catalyst according to the present invention will be described.

  The catalyst for cracking hydrocarbons according to the present invention, after producing a layered double hydroxide particle powder as a precursor, is heated and fired in a temperature range of 400 to 1600 ° C. to form a porous oxide particle powder, , And can be obtained by heat reduction in a temperature range of 700 to 1100 ° C.

The layered double hydroxide particle powder in the present invention is prepared by mixing an alkaline aqueous solution containing anions, a magnesium raw material, and an aluminum salt aqueous solution to obtain a mixed solution having a pH value in the range of 7.0 to 13.0. The mixed solution is aged in the temperature range of 50 to 300 ° C. to produce layered double hydroxide core particles,
Next, the total number of moles relative to the total number of moles of magnesium and aluminum added to the aqueous suspension containing the layered double hydroxide core particles when the layered double hydroxide core particles are formed. After adding magnesium salt aqueous solution, aluminum salt aqueous solution, nickel salt aqueous solution and ruthenium salt aqueous solution containing magnesium, aluminum, nickel and ruthenium in a ratio of 0.05 to 0.5, the pH value is 9.0 to 13 Aging in a range of 0.0 and a temperature of 40 to 300 ° C., topographically coats magnesium, aluminum, nickel and ruthenium newly added to the surface of the layered double hydroxide core particles. Obtained by performing a growth reaction.

  The salt of magnesium, aluminum, nickel, and iron is not particularly limited as long as it is water-soluble such as nitrate.

  As a magnesium raw material, magnesium oxide, magnesium hydroxide, magnesium oxalate, magnesium sulfate, magnesium sulfite, magnesium nitrate, magnesium chloride, magnesium citrate, basic magnesium carbonate, magnesium benzoate and the like can be used.

  As the aluminum raw material, aluminum oxide, aluminum hydroxide, aluminum acetate, aluminum chloride, aluminum nitrate, aluminum oxalate, basic ammonium aluminum, or the like can be used.

  As the nickel salt raw material, nickel oxide, nickel hydroxide, nickel sulfate, nickel carbonate, nickel nitrate, nickel chloride, nickel benzoate, basic nickel carbonate, nickel formate, nickel citrate, nickel diammonium sulfate, etc. may be used. it can.

  As the ruthenium salt raw material, ruthenium nitrate, ruthenium chloride or the like can be used.

  When the number of moles of the growth reaction with respect to the core particles is less than 0.05, the conversion rate of the lower hydrocarbon is lowered and the effect of the present invention cannot be obtained. When it exceeds 0.5, the average particle diameter of the metallic nickel fine particles and the metallic ruthenium fine particles becomes large, the conversion rate of lower hydrocarbons at low temperatures is lowered, and further the coking resistance is lowered. Preferably it is 0.10-0.45, More preferably, it is 0.12-0.4.

  When the pH value in the growth reaction is less than 9.0, magnesium, aluminum, nickel, and ruthenium added at the time of the growth reaction are separated and mixed without forming a coating layer. Cannot be obtained. When the pH value exceeds 13.0, there is too much elution of aluminum, making it difficult to obtain the target composition. Preferably it is 9.0-12.5, More preferably, it is 9.5-12.0.

  When the reaction temperature in the growth reaction is less than 40 ° C., the magnesium, aluminum, nickel, and ruthenium added during the growth reaction are separated and mixed without forming a coating layer, and the target catalyst of the present invention I can't get it. When the temperature exceeds 300 ° C., large aluminum hydroxide particles and aluminum hydroxide oxide particles are mixed in addition to the layered double hydroxide particles, and the sintering of the catalytically active metal fine particles is promoted to have desired characteristics. No catalyst body can be obtained. Preferably it is 60-250 degreeC.

  The aging time in the growth reaction is not particularly limited, but is 1 to 80 hours, preferably 3 to 24 hours, and more preferably 5 to 18 hours. If it is less than 1 hour, magnesium, aluminum, nickel and ruthenium added during the growth reaction do not form a sufficient coating layer on the surface of the layered double hydroxide core particles. Growth reactions over 80 hours are not industrial.

  There is no problem even if cobalt as an impurity contained in a trace amount in the nickel raw material is contained in the catalyst according to the present invention.

  The average plate surface diameter of the layered double hydroxide particle powder that is a precursor of the hydrocarbon decomposition catalyst in the present invention is preferably 0.05 to 0.4 μm. When the average plate surface diameter is less than 0.05 μm, it is difficult to filter and wash and industrial production is difficult. When it exceeds 0.4 μm, it is difficult to produce a catalyst molded body. .

  The crystallite size D006 of the layered double hydroxide particle powder in the present invention is preferably 0.001 to 0.08 μm. When the crystallite size D006 is less than 0.001 μm, the viscosity of the aqueous suspension is very high and industrial production is difficult, and when it exceeds 0.08 μm, it is difficult to produce a catalyst compact. is there. More preferably, it is 0.002-0.07 micrometer.

The specific surface area value of the layered double hydroxide particle powder in the present invention is preferably 3.0 to 300 m ² / g. When the specific surface area value is less than 3.0 m ² / g, it is difficult to produce a catalyst molded body. When the specific surface area value exceeds 300 m ² / g, the viscosity of the aqueous suspension is very high. It is difficult to filter and wash, making it difficult to produce industrially. More preferably, it is 5.0-250 m < ² > / g.

  The nickel content of the layered double hydroxide particle powder in the present invention is preferably 0.0057 to 26.463 wt%, more preferably 0.01 to 20 wt% with respect to the entire layered double hydroxide particle powder. is there. The number of moles of nickel in the layered double hydroxide particle powder is such that the ratio Ni / (Mg + Al + Ni + Ru) to the total number of moles of magnesium, aluminum, nickel and ruthenium contained in the layered double hydroxide particle powder is 0. 001 to 0.32 is preferable, and 0.0015 to 0.3 is more preferable.

  In the present invention, the ruthenium content of the layered double hydroxide particle powder is preferably 0.0013 to 3.328 wt%, more preferably 0.002 to 2.00 wt% with respect to the entire layered double hydroxide particle powder. %. The number of moles of ruthenium content of the layered double hydroxide particle powder is such that the ratio Ru / (Mg + Al + Ni + Ru) to the total number of moles of magnesium, aluminum, nickel and ruthenium contained in the layered double hydroxide particle powder is 0. 0015 to 0.022 are preferable, and 0.0002 to 0.02 are more preferable.

  The number of moles of ruthenium in the layered double hydroxide particle powder in the present invention is preferably 0.0004 to 30 with respect to the number of moles of nickel.

  The ratio of magnesium to aluminum in the layered double hydroxide particle powder in the present invention is not particularly limited, but the molar ratio of magnesium to aluminum is more preferably Mg: Al = 4: 1 to 1.5: 1.

  The oxide particle powder in the present invention is obtained by firing the layered double hydroxide particle powder at 400 ° C to 1600 ° C. When the firing temperature of the layered double hydroxide particle powder is less than 400 ° C., porous oxide particles cannot be obtained. When the temperature exceeds 1600 ° C., the properties as a porous body carrier deteriorate. Preferably it is 450-1500 degreeC, More preferably, it is 500-1400 degreeC. The firing atmosphere may be oxygen, air, or an inert gas such as nitrogen or argon.

  The firing time of the oxide particle powder in the present invention is not particularly limited, but is preferably 0.5 to 24 hours. If it exceeds 24 hours, it is hard to say that it is industrial. Preferably it is 1 to 10 hours.

  The ruthenium content of the oxide particle powder obtained after firing the layered double hydroxide particle powder in the present invention is preferably 0.025 to 5.0 wt%, more preferably 0.005%, based on the whole oxide particle powder. It is 05-4.0 wt%. Further, the number of moles of ruthenium content of the oxide particle powder and the ratio to the total metal ions are approximately the same as the number of moles and the ratio of the layered double hydroxide particle powder.

  The nickel content of the oxide particle powder obtained after firing the layered double hydroxide particle powder in the present invention is preferably 0.10 to 40 wt%, more preferably 0.18 to the entire oxide particle powder. 35 wt%. Further, the number of moles of nickel content of the oxide particle powder and the ratio to the total metal ions are approximately the same as the number of moles and the mole ratio of the layered double hydroxide particle powder.

The oxide particle powder in the present invention is a porous body, the average plate surface diameter is preferably 0.05 to 0.4 μm, and the specific surface area value is preferably 7.0 to 320 m ² / g.

  The hydrocarbon cracking catalyst according to the present invention can be obtained by reducing the oxide particle powder in the range of 700 ° C to 1100 ° C. When the reduction temperature of the oxide particle powder is lower than 700 ° C., nickel is not metallized, so that the target catalytic activity of the present invention cannot be obtained. When the temperature exceeds 1100 ° C., the sintering of nickel and ruthenium proceeds and the particle size of the metal nickel fine particles and metal ruthenium fine particles increases, so that the conversion rate of lower hydrocarbons at low temperatures is lowered, and further the coking resistance is lowered. Preferably it is 700-950 degreeC. The atmosphere during the reduction is not particularly limited as long as it is a reducing atmosphere such as a gas containing hydrogen. The heat treatment time is not particularly limited, but is preferably 0.5 to 24 hours. If it exceeds 24 hours, no industrial merit can be found. Preferably, it is 1 to 10 hours.

  The powdered catalyst obtained as described above may be molded according to each application to be used. The shape and size are not particularly limited, but may be, for example, a spherical shape, a cylindrical shape, a tubular shape, or a shape applied to a honeycomb body. In general, the size of a catalyst body having a spherical, cylindrical, or tubular shape is preferably about 0.1 to 30 mm. Depending on conditions, the strength and pore distribution density of the molded body may be adjusted by adding various binders such as organic substances and inorganic substances. In the present invention, granulation and molding may be performed before the heat treatment.

  Also known is a method of firing layered double hydroxide particle powder to obtain a composite oxide, and then hydrating the composite oxide with an aqueous solution containing anions to obtain layered double hydroxide particle powder. In the present invention, nickel and ruthenium may be supported by the following production method. The layered double hydroxide particle powder supporting nickel and ruthenium may be heat-reduced after being heated and fired as necessary in the same manner as described above.

  That is, a layered double hydroxide particle powder made only of magnesium and aluminum is formed, and after being fired, a porous oxide formed body is formed, and then impregnated with a solution containing nickel and ruthenium to form a porous oxide powder or formed You may carry | support using the method of reproducing | regenerating the layered double hydroxide particle phase containing nickel and ruthenium near the surface of the body.

  In addition, a layered double hydroxide particle powder in which nickel is present on the particle surface is obtained in accordance with the above production method, molded and fired to form a porous oxide molded body, and impregnated with a solution containing ruthenium, The oxide powder or the powder may be supported by a method of regenerating a layered double hydroxide particle phase containing nickel near the surface of the compact and ruthenium near the surface of the compact.

  Further, a layered double hydroxide particle powder in which ruthenium is present on the particle surface is obtained according to the above production method, molded and fired to form a porous oxide molded body, and impregnated with a solution containing nickel, It may be supported by a method of regenerating a layered double hydroxide particle phase containing ruthenium near the surface of the oxide powder or the molded body and nickel near the surface of the molded body.

  Also, a layered double hydroxide particle powder in which nickel and ruthenium are present on the particle surface is obtained according to the above production method, molded and fired to form a porous oxide molded body, and further impregnated with a solution containing nickel and ruthenium. Thus, nickel or ruthenium can be supported in the vicinity of the surface of the porous oxide powder or molded body, and the layered double hydroxide particle phase containing nickel and ruthenium can be supported in the vicinity of the surface of the molded body. good.

  Next, a hydrogen production method using the hydrocarbon cracking catalyst according to the present invention will be described.

In the method for producing hydrogen using the hydrocarbon decomposition catalyst according to the present invention, the reaction temperature is 400 to 900 ° C., and the molar ratio (S / C) of water vapor to lower hydrocarbon is 1.2 to 6.0. The lower hydrocarbon gas mainly composed of methane and water vapor are brought into contact with the hydrocarbon decomposition catalyst according to the present invention under the condition that the space velocity (GHSV) is 500 to 600,000 h ⁻¹ .

  When the reaction temperature is less than 400 ° C., the conversion rate of lower hydrocarbons is low, and when the reaction is carried out for a long time, coking is likely to occur, and the catalytic properties may be deactivated at the end. When it exceeds 900 ° C., lower hydrocarbons such as methane are decomposed. Preferably it is 450-900 degreeC, More preferably, it is 500-850 degreeC.

  When the molar ratio S / C of water vapor to lower hydrocarbon is less than 1.2, the coking resistance is lowered. On the other hand, when S / C exceeds 6.0, a large amount of water vapor is required for hydrogen production, which is expensive and unrealistic. Preferably it is 1.5-6.0, More preferably, it is 1.8-5.0.

Incidentally, the space velocity (GHSV) is preferably 800～300,000H ^-1, more preferably 1,000~200,000h ^-1.

  The lower hydrocarbon gas used for hydrogen production is preferably a hydrocarbon having 1 to 6, preferably 1 to 4 carbon atoms. Such things include, for example, ethane, propane, butane in addition to methane.

  The hydrocarbon cracking catalyst according to the present invention has sufficient catalytic activity, durability and resistance even when it is switched to steam reforming after being started by autothermal reforming reaction, or even when steam reforming is performed for a long time. It is an optimum catalyst in a fuel cell system that can exhibit caulking properties and sulfur poisoning resistance and introduces DSS (Daily start-up shut-down).

<Action>
The reason why the hydrocarbon decomposition catalyst according to the present invention has excellent catalytic activity at low temperatures is not yet clear, but the present inventor presumes as follows.

  The hydrocarbon cracking catalyst according to the present invention is derived from the above production method, and is formed near the surface of the particles constituting the catalyst with particles as fine as 1 to 10 nm, which are finer than metal nickel and metal ruthenium, or granulated. Since it is supported on the surface of the resulting catalyst molded body, it has an excellent catalytic activity because it can efficiently contact the lower hydrocarbon gas with nickel and ruthenium in the hydrocarbon decomposition reaction. Have high catalytic activity.

  In addition, as described above, the hydrocarbon cracking catalyst according to the present invention has high catalytic activity and is excellent in coking resistance even under low steam and can exhibit high catalytic activity.

  A typical embodiment of the present invention is as follows.

  The plate surface diameter of the layered double hydroxide particle powder is the average value of the measured values using “electron micrograph TEM1200EX (manufactured by JEOL Ltd.)” (acceleration voltage: 100 kV).

  D006 (particle thickness) of the layered double hydroxide particle powder is “X-ray diffractometer RINT-2500 (manufactured by Rigaku Corporation)” (tube: Cu, tube voltage: 40 kV, tube current: 300 mA, Layered double water using a goniometer: wide angle goniometer, sampling width: 0.020 °, scanning speed: 2 ° / min, diverging slit: 1 °, scattering slit: 1 °, light receiving slit: 0.50 mm) This is a value calculated using the Scherrer equation from the diffraction peak curve of the D006 crystal plane of the oxide particle powder.

  Identification of the layered double hydroxide particle powder was performed by X-ray diffraction measurement. X-ray diffraction measurement was performed using the X-ray diffractometer at a diffraction angle 2θ of 3 to 80 °.

  The size of the particles of metallic nickel and metallic ruthenium is indicated by the average value of the numerical values measured from the electron micrograph. The size of the metal fine particles exceeding 10 nm is “X-ray diffractometer RINT-2500 (manufactured by Rigaku Corporation)” (tube: Cu, tube voltage: 40 kV, tube current: 300 mA, goniometer: wide angle goniometer. , Sampling width: 0.020 °, scanning speed: 2 ° / min, diverging slit: 1 °, scattering slit: 1 °, light receiving slit: 0.50 mm), and the size of the fine particles using Scherrer's equation Was calculated. The particle sizes of metallic nickel and metallic ruthenium obtained from this X-ray diffractometer were the same as those obtained from the electron micrograph.

  The contents of magnesium, aluminum, nickel, and ruthenium constituting the catalyst were determined by dissolving the catalyst with an acid and measuring it with a “plasma emission spectrometer SPS4000 (Seiko Electronics Co., Ltd.)”.

  The BET specific surface area value is the B.B. E. T.A. Measured by the method.

  The amount of carbon deposited during the steam reforming reaction was determined by measuring the amount of carbon in the catalyst body before and after the catalytic reaction with a carbon sulfur measuring device.

  A typical embodiment of the present invention is as follows.

Example 1 <Preparation of hydrocarbon catalyst>
MgSO ₄ · 7H ₂ O 110.9 g and Al ₂ (SO ₄ ) ₃ · 8H ₂ O 36.47 g were dissolved in water to make 1000 ml. Separately, a 1000 ml solution in which 12.54 g of NaCO ₃ was dissolved was added to 220.2 ml of NaOH (14 mol / L concentration) to prepare a total amount of 2000 ml of an alkali mixed solution. The mixed solution of the magnesium salt and the aluminum salt was added to the alkali mixed solution and aged at 98 ° C. for 20 hours to obtain layered double hydroxide core particles. The pH of the reaction solution at this time was 10.1.
Next, 14.08 g of MgSO ₄ .7H ₂ O, 30.04 g of NiSO ₄ .6H ₂ O, 4.630 g of Al ₂ (SO ₄ ) ₃ .8H ₂ O and 1.976 g of RuCl _{3 were} added to this alkaline suspension. 500 ml of a mixed solution of magnesium salt, nickel salt, aluminum salt, and ruthenium salt dissolved in water was added to adjust the pH of the reaction solution to 11.8, and further aged at 254 ° C. for 8 hours, to form the layered double hydroxide core. It was made topotactically grow on the particle surface to obtain layered double hydroxide particles. The total number of moles of magnesium, aluminum, nickel, and ruthenium added during the growth reaction was 0.250 with respect to the total number of moles of magnesium and aluminum added during the formation of the core particles. The average plate surface diameter of the layered double hydroxide particles obtained here was 0.251 μm, the crystallite size D006 was 0.051 μm, and the BET was 18.9 m ² / g.

  The layered double hydroxide particle powder thus obtained was molded into spherical beads having a diameter of 3 mm. After calcination in air at 810 ° C. for 22 hours to obtain oxide particle powder, reduction treatment is carried out at 820 ° C. in a gas stream with a hydrogen / argon volume ratio of 20/80 for 3 hours, and a hydrocarbon decomposition catalyst Got. The content of nickel in the obtained catalyst was 18.26 wt% (Ni / (Mg + Al + Ni + Ru) = 0.143 (molar ratio)), and the size of the metal nickel fine particles was 7 nm. The ruthenium content in the obtained catalyst was 2.621 wt% (Ru / (Mg + Al + Ni + Ru) = 0.012 (molar ratio)), and the size of the metal ruthenium fine particles was 6 nm. The metal nickel particles and metal ruthenium are presumed to exist only near the particle surface.

<Hydrogen production reaction using hydrocarbon catalyst>
Evaluation of the catalyst for hydrocarbon was made by filling a catalyst tube with 20 to 50 g in a stainless steel reaction tube having a diameter of 20 mm.
Through this catalyst tube (reactor), city gas 13A and water vapor were circulated as a raw material gas at a reaction pressure of 0.5 MPa, a reaction temperature of 400 ° C. to 1000 ° C., and a space velocity of 50000 h ⁻¹ . The water vapor / carbon ratio (S / C) at this time is 1.5 or 3.0.

The methane conversion shown in the table is calculated from the following formula.
Methane conversion rate (%) = (1-outlet methane concentration / inlet methane concentration) × 100

The reaction results are shown in Tables 1 to 3.
Table 1 shows the relationship between the reaction temperature (400 ° C. to 1000 ° C.) and the methane conversion rate when GHSV is 50000 h ⁻¹ , water vapor / carbon (S / C) is 3.0 and the reaction is performed for 24 hours.
Table 2 shows the relationship between the reaction time and the methane conversion rate when GHSV is 50000 h ⁻¹ , the reaction temperature is 700 ° C., and the water vapor / carbon (S / C) is 1.5 and 3.0.
Table 3 shows the relationship between the reaction time at GHSV of 50000 h ⁻¹ , the reaction temperature of 700 ° C., and the water vapor / carbon (S / C) of 1.5, and the amount of deposited carbon before and after the measurement of the catalytic activity.

<Example 2>
92.94 g of MgCl ₂ .6H ₂ O and 22.07 g of AlCl ₃ .6H ₂ O were dissolved in water to make 1000 ml. Separately, a 1000 ml solution in which 16.53 g of NaCO ₃ was dissolved was added to 93.08 ml of NaOH (14 mol / L concentration) to prepare an alkaline mixed solution of 2000 ml in total. The mixed solution of the magnesium salt and the aluminum salt was added to the alkali mixed solution and aged at 60 ° C. for 3 hours to obtain layered double hydroxide core particles. The pH of the reaction solution at this time was 7.5.
Next, 500 ml of MgCl ₂ · 6H ₂ O 20.25 g, NiCl ₂ · 6H ₂ O 4.636 g, AlCl ₃ · 6H ₂ O 4.811 g and RuCl ₃ 0.124 g were dissolved in this alkaline suspension. A mixed solution of magnesium salt, nickel salt, aluminum salt and ruthenium salt is added, the pH of the reaction solution is adjusted to 9.5, and further aged for 14 hours at 55 ° C., and the top surface of the layered double hydroxide core particles is topographed. Growing ticks, layered double hydroxide particles were obtained. The total number of moles of magnesium, aluminum, nickel, and ruthenium added during the growth reaction was 0.200 with respect to the total number of moles of the magnesium and aluminum added during the formation of the core particles. The layered double hydroxide particles obtained here had an average plate surface diameter of 0.062 μm, a crystallite size D006 of 0.005 μm, and a BET of 276.8 m ² / g.

  The layered double hydroxide particle powder thus obtained was molded into spherical beads having a diameter of 3 mm. After calcining in air at 1380 ° C. for 7 hours to form oxide particles, reduction treatment is performed at 790 ° C. in a gas stream with a hydrogen / argon volume ratio of 20/80 for 9 hours, and a hydrocarbon decomposition catalyst Got. The content of nickel in the obtained catalyst was 3.339 wt% (Ni / (Mg + Al + Ni + Ru) = 0.052 (molar ratio)), and the size of the metal nickel fine particles was 2 nm. The ruthenium content in the obtained catalyst was 0.172 wt% (Ru / (Mg + Al + Ni + Ru) = 0.0008 (molar ratio)), and the size of the metal ruthenium fine particles was 1 nm. The metal nickel particles and metal ruthenium are presumed to exist only near the particle surface.

<Example 3>
138.29 g of MgCl ₂ .6H ₂ O and 32.85 g of AlCl ₃ .6H ₂ O were dissolved in water to make 1000 ml. Separately, a 1000 ml solution in which 23.99 g of NaCO ₃ was dissolved was added to 237.6 ml of NaOH (14 mol / L concentration) to prepare a total amount of 2000 ml of an alkali mixed solution. A mixed solution of the magnesium salt and aluminum salt was added to the alkali mixed solution, and aging was performed at 84 ° C. for 12 hours to obtain layered double hydroxide core particles. The pH of the reaction solution at this time was 9.4.
Next, 26.08 g of MgCl ₂ .6H ₂ O, 26.27 g of NiCl ₂ .6H ₂ O, 6.194 g of AlCl ₃ .6H ₂ O and 1.476 g of Ru (NO ₃ ) _{3 were} added to this alkaline suspension. 500 ml of a mixed solution of magnesium salt, nickel salt, aluminum salt and ruthenium salt is added to adjust the pH of the reaction solution to 10.6, and further aged at 142 ° C. for 11 hours. The layered double hydroxide core particles It was grown topotactically on the surface to obtain layered double hydroxide particles. The total number of moles of magnesium, aluminum, nickel, and ruthenium added during the growth reaction was 0.238 with respect to the total number of moles of magnesium and aluminum added during the formation of the core particles. The average plate surface diameter of the layered double hydroxide particles obtained here was 0.278 μm, the crystallite size D006 was 0.034 μm, and the BET was 54.7 m ² / g.

  The layered double hydroxide particle powder thus obtained was molded into spherical beads having a diameter of 3 mm. After calcination in air at 720 ° C. for 3 hours to obtain oxide particle powder, reduction treatment is carried out at 720 ° C. in a gas stream having a hydrogen / argon volume ratio of 20/80 for 12 hours, and a hydrocarbon decomposition catalyst Got. The content of nickel in the obtained catalyst was 11.78 wt% (Ni / (Mg + Al + Ni + Ru) = 0.090 (molar ratio)), and the size of the metal nickel fine particles was 3 nm. The ruthenium content in the obtained catalyst was 0.922 wt% (Ru / (Mg + Al + Ni + Ru) = 0.004 (molar ratio)), and the size of the metal ruthenium fine particles was 2 nm. The metal nickel particles and metal ruthenium are presumed to exist only near the particle surface.

<Example 4>
40.65 g of MgSO ₄ .7H ₂ O and 14.86 g of Al ₂ (SO ₄ ) ₃ .8H ₂ O were dissolved in water to make 1000 ml. Separately, a 1000 ml solution in which 6.178 g of NaCO ₃ was dissolved was added to 202.1 ml of NaOH (concentration of 14 mol / L) to prepare an alkaline mixed solution of 2000 ml in total. A mixed solution of the magnesium salt and aluminum salt was added to the alkali mixed solution, and the mixture was aged at 85 ° C. for 7 hours to obtain layered double hydroxide core particles. The pH of the reaction solution at this time was 8.9.
Next, 14.74 g of MgSO ₄ .7H ₂ O, 23.29 g of NiSO ₄ .6H ₂ O, 5.386 g of Al ₂ (SO ₄ ) ₃ .8H ₂ O and Ru (NO ₃ ) _{3 were} added to this alkaline suspension. 500 ml of a mixed solution of magnesium salt, nickel salt, aluminum salt and ruthenium salt dissolved in 0.956 g was added to adjust the pH of the reaction solution to 9.1, and further aged at 91 ° C. for 18 hours, and the layered double water It was made topotactically grow on the surface of the hydroxide core particles to obtain layered double hydroxide particles. The total number of moles of magnesium, aluminum, nickel and ruthenium added during the growth reaction was 0.435 with respect to the total number of moles of magnesium and aluminum added during the formation of the core particles. The average plate surface diameter of the layered double hydroxide particles obtained here was 0.182 μm, the crystallite size D006 was 0.014 μm, and the BET was 113.6 m ² / g.

  The layered double hydroxide particle powder thus obtained was molded into spherical beads having a diameter of 3 mm. After calcining in air at 550 ° C. for 8 hours to form oxide particles, reduction treatment is performed at 900 ° C. in a gas stream with a hydrogen / argon volume ratio of 20/80 for 5 hours to obtain a hydrocarbon cracking catalyst. Got. The content of nickel in the obtained catalyst was 27.61 wt% (Ni / (Mg + Al + Ni + Ru) = 0.222 (molar ratio)), and the size of the metal nickel fine particles was 6 nm. The ruthenium content in the obtained catalyst was 1.783 wt% (Ru / (Mg + Al + Ni + Ru) = 0.008 (molar ratio)), and the size of the metal ruthenium fine particles was 4 nm. The metal nickel particles and metal ruthenium are presumed to exist only near the particle surface.

<Example 5>
109.4 g of MgSO ₄ · 7H ₂ O and 41.51 g of Al ₂ (SO ₄ ) ₃ · 8H ₂ O were dissolved in water to make 1000 ml. Separately, a 1000 ml solution in which 17.55 g of NaCO ₃ was dissolved was added to 221.7 ml of NaOH (14 mol / L concentration) to prepare a total amount of 2000 ml of an alkali mixed solution. A mixed solution of the magnesium salt and aluminum salt was added to the alkali mixed solution, and aging was performed at 74 ° C. for 11 hours to obtain layered double hydroxide core particles. The pH of the reaction solution at this time was 8.5.
Next, 42.14 g of MgSO ₄ · 7H ₂ O, 86.44 g of NiSO ₄ · 6H ₂ O, 15.99 g of Al ₂ (SO ₄ ) ₃ · 8H ₂ O and 4.093 g of RuCl _{3 were} added to the alkaline suspension. 500 ml of a mixed solution of magnesium salt, nickel salt, aluminum salt and ruthenium salt dissolved in the solution is added to adjust the pH of the reaction solution to 8.2, followed by aging at 81 ° C. for 12 hours, and the layered double hydroxide core It was made topotactically grow on the particle surface to obtain layered double hydroxide particles. The total number of moles of magnesium, aluminum, nickel, and ruthenium added during the growth reaction was 0.488 with respect to the total number of moles of magnesium and aluminum added during the formation of the core particles. The average plate surface diameter of the layered double hydroxide particles obtained here was 0.115 μm, the crystallite size D006 was 0.009 μm, and the BET was 178.3 m ² / g.

  The layered double hydroxide particle powder thus obtained was molded into spherical beads having a diameter of 3 mm. After calcining in air at 480 ° C. for 12 hours to obtain oxide particle powder, reduction treatment is carried out at 840 ° C. in a gas stream with a hydrogen / argon volume ratio of 20/80 for 16 hours to obtain a hydrocarbon cracking catalyst. Got. The content of nickel in the obtained catalyst was 33.19 wt% (Ni / (Mg + Al + Ni + Ru) = 0.274 (molar ratio)), and the size of the metal nickel fine particles was 8 nm. The ruthenium content in the obtained catalyst was 3.430 wt% (Ru / (Mg + Al + Ni + Ru) = 0.016 (molar ratio)), and the size of the metal ruthenium fine particles was 7 nm. The metal nickel particles and metal ruthenium are presumed to exist only near the particle surface.

<Example 6>
251.9 g of Mg (NO ₃ ) ₂ · 6H ₂ O and 65.81 g of Al (NO ₃ ) ₃ · 9H ₂ O were dissolved in water to make 1000 ml. Separately, a 1000 ml solution in which 28.51 g of NaCO ₃ was dissolved was added to 329.9 ml of NaOH (14 mol / L concentration) to prepare an alkaline mixed solution of 2000 ml in total. A mixed solution of the magnesium salt and aluminum salt was added to the alkali mixed solution, and aging was performed at 152 ° C. for 3 hours to obtain layered double hydroxide core particles. The pH of the reaction solution at this time was 9.6.
Next, 23.93 g of Mg (NO ₃ ) ₂ .6H ₂ O, 31.99 g of Ni (NO ₃ ) ₂ .6H ₂ O and 6.252 g of Al (NO ₃ ) ₃ .9H ₂ O were added to this alkaline suspension. And 500 ml of a mixed solution of magnesium salt, nickel salt, aluminum salt and ruthenium salt in which 8.631 g of Ru (NO ₃ ) ₃ is dissolved, the pH of the reaction solution is adjusted to 10.8, and further at 168 ° C. for 14 hours. The layer was aged and grown topotropically on the surface of the layered double hydroxide core particles to obtain layered double hydroxide particles. The total number of moles of magnesium, aluminum, nickel, and ruthenium added during the growth reaction was 0.167 with respect to the total number of moles of magnesium and aluminum added during the formation of the core particles. The average plate surface diameter of the layered double hydroxide particles obtained here was 0.324 μm, the crystallite size D006 was 0.006 μm, and the BET was 32.2 m ² / g.

  The layered double hydroxide particle powder thus obtained was molded into spherical beads having a diameter of 3 mm. After calcining in air at 1420 ° C. for 8 hours to obtain oxide particle powder, reduction treatment is carried out at 1080 ° C. in a gas stream having a hydrogen / argon volume ratio of 20/80 for 2 hours, and a hydrocarbon decomposition catalyst Got. The content of nickel in the obtained catalyst was 8.912 wt% (Ni / (Mg + Al + Ni + Ru) = 0.069 (molar ratio)), and the size of the metal nickel fine particles was 3 nm. The ruthenium content in the obtained catalyst was 4.186 wt% (Ru / (Mg + Al + Ni + Ru) = 0.199 (molar ratio)), and the size of the metal ruthenium fine particles was 2 nm. The metal nickel particles and metal ruthenium are presumed to exist only near the particle surface.

<Example 7>
Mg (NO ₃ ) ₂ · 6H ₂ O 235.0 g and Al (NO ₃ ) ₃ · 9H ₂ O 78.15 g were dissolved in water to make 1000 ml. Separately, a 1000 ml solution in which 36.84 g of NaCO ₃ was dissolved was added to 242.2 ml of NaOH (14 mol / L concentration) to prepare an alkaline mixed solution of 2000 ml in total. A mixed solution of the magnesium salt and aluminum salt was added to the alkali mixed solution, and aging was carried out at 113 ° C. for 14 hours to obtain layered double hydroxide core particles. The pH of the reaction solution at this time was 9.2.
Then, this alkaline _{suspension, Mg (NO 3) 2 ·} 6H 2 O 45.04g and _{Ni (NO 3) 2 · 6H} 2 O 116.1g and _{Al (NO 3) 3 · 9H} 2 O 14.98g And 500 ml of a mixed solution of magnesium salt, nickel salt, aluminum salt and ruthenium salt in which 2.484 g of RuCl ₃ are dissolved, the pH of the reaction solution is adjusted to 10.4, and further aged at 121 ° C. for 9 hours, The layered double hydroxide core particles were grown topographically on the surface to obtain layered double hydroxide particles. The total number of moles of magnesium, aluminum, nickel and ruthenium added during the growth reaction was 0.333 with respect to the total number of moles of magnesium and aluminum added during the formation of the core particles. The layered double hydroxide particles obtained here had an average plate surface diameter of 0.212 μm, a crystallite size D006 of 0.021 μm, and a BET of 88.1 m ² / g.

  The layered double hydroxide particle powder thus obtained was molded into spherical beads having a diameter of 3 mm. After calcination in air at 890 ° C. for 2 hours to obtain oxide particle powder, reduction treatment is carried out at 880 ° C. in a gas stream having a hydrogen / argon volume ratio of 20/80 for 4 hours to obtain a hydrocarbon decomposition catalyst Got. The content of nickel in the obtained catalyst was 24.93 wt% (Ni / (Mg + Al + Ni + Ru) = 0.200 (molar ratio)), and the size of the metal nickel fine particles was 4 nm. The ruthenium content in the obtained catalyst was 1.288 wt% (Ru / (Mg + Al + Ni + Ru) = 0.006 (molar ratio)), and the size of the metal ruthenium fine particles was 3 nm. The metal nickel particles and metal ruthenium are presumed to exist only near the particle surface.

<Example 8>
167.2 g of MgSO ₄ · 7H ₂ O and 43.41 g of Al ₂ (SO ₄ ) ₃ · 8H ₂ O were dissolved in water to make 1000 ml. Separately, a 1000 ml solution in which 14.74 g of NaCO ₃ was dissolved was added to 118.8 ml of NaOH (14 mol / L concentration) to prepare an alkaline mixed solution of 2000 ml in total. A mixed solution of the magnesium salt and aluminum salt was added to the alkali mixed solution, and aging was performed at 65 ° C. for 4 hours to obtain layered double hydroxide core particles. The pH of the reaction solution at this time was 8.1.
Next, 18.84 g of MgSO ₄ .7H ₂ O, 10.58 g of NiSO ₄ .6H ₂ O, 4.891 g of Al ₂ (SO ₄ ) ₃ .8H ₂ O and Ru (NO ₃ ) _{3 were} added to this alkaline suspension. 500 ml of a mixed solution of magnesium salt, nickel salt, aluminum salt and ruthenium salt dissolved in 1.737 g was added, the pH of the reaction solution was adjusted to 9.8, and further aged at 81 ° C. for 8 hours, the layered double water It was made topotactically grow on the surface of the hydroxide core particles to obtain layered double hydroxide particles. The total number of moles of magnesium, aluminum, nickel and ruthenium added during the growth reaction was 0.143 with respect to the total number of moles of magnesium and aluminum added during the formation of the core particles. The average plate surface diameter of the layered double hydroxide particles obtained here was 0.082 μm, the crystallite size D006 was 0.008 μm, and the BET was 214.3 m ² / g.

  The layered double hydroxide particle powder thus obtained was molded into spherical beads having a diameter of 3 mm. After calcination in air at 940 ° C. for 5 hours to obtain oxide particle powder, reduction treatment is carried out at 960 ° C. in a gas stream with a hydrogen / argon volume ratio of 20/80 for 8 hours to obtain a hydrocarbon cracking catalyst. Got. The content of nickel in the obtained catalyst was 5.425 wt% (Ni / (Mg + Al + Ni + Ru) = 0.040 (molar ratio)), and the size of the metal nickel fine particles was 2 nm. The ruthenium content in the obtained catalyst was 1.401 wt% (Ru / (Mg + Al + Ni + Ru) = 0.006 (molar ratio)), and the size of the metal ruthenium fine particles was 3 nm. The metal nickel particles and metal ruthenium are presumed to exist only near the particle surface.

<Example 9>
98.95 g of MgCl ₂ .6H ₂ O and 20.26 g of AlCl ₃ .6H ₂ O were dissolved in water to make 1000 ml. Separately, a 1000 ml solution in which 14.87 g of NaCO ₃ was dissolved was added to 315.6 ml of NaOH (14 mol / L concentration) to prepare an alkaline mixed solution of 2000 ml in total. A mixed solution of the magnesium salt and aluminum salt was added to the alkali mixed solution, and aging was performed at 95 ° C. for 18 hours to obtain layered double hydroxide core particles. The pH of the reaction solution at this time was 12.5.
Next, 500 ml of MgCl ₂ .6H ₂ O 19.19 g, NiCl ₂ .6H ₂ O 90.93 g, AlCl ₃ · 6H ₂ O 3.931 g and RuCl ₃ 5.742 g were dissolved in this alkaline suspension. A mixed solution of magnesium salt, nickel salt, aluminum salt and ruthenium salt is added to adjust the pH of the reaction solution to 12.8, and further aged for 12 hours at 284 ° C., and the top surface of the layered double hydroxide core particles is topographed. Growing ticks, layered double hydroxide particles were obtained. The total number of moles of magnesium, aluminum, nickel, and ruthenium added during the growth reaction was 0.454 with respect to the total number of moles of the magnesium and aluminum added during the formation of the core particles. The average plate surface diameter of the layered double hydroxide particles obtained here was 0.398 μm, the crystallite size D006 was 0.078 μm, and the BET was 4.1 m ² / g.

  The layered double hydroxide particle powder thus obtained was molded into spherical beads having a diameter of 3 mm. After calcining in air at 610 ° C. for 14 hours to form oxide particles, reduction treatment is performed at 760 ° C. in a gas stream having a hydrogen / argon volume ratio of 20/80 for 7 hours, and a hydrocarbon decomposition catalyst Got. The content of nickel in the obtained catalyst was 38.63 wt% (Ni / (Mg + Al + Ni + Ru) = 0.326 (molar ratio)), and the size of the metal nickel fine particles was 9 nm. The ruthenium content in the obtained catalyst was 4.712 wt% (Ru / (Mg + Al + Ni + Ru) = 0.023 (molar ratio)), and the size of the metal ruthenium fine particles was 10 nm. The metal nickel particles and metal ruthenium are presumed to exist only near the particle surface.

<Example 10>
202.6 g of MgSO ₄ · 7H ₂ O and 80.02 g of Al ₂ (SO ₄ ) ₃ · 8H ₂ O were dissolved in water to make 1000 ml. Separately, a 1000 ml solution in which 25.39 g of NaCO ₃ was dissolved was added to 228.9 ml of NaOH (14 mol / L concentration) to prepare an alkaline mixed solution of 2000 ml in total. A mixed solution of the magnesium salt and aluminum salt was added to the alkali mixed solution, and aging was carried out at 53 ° C. for 12 hours to obtain layered double hydroxide core particles. The pH of the reaction solution at this time was 7.1.
Next, 8.079 g of MgSO ₄ .7H ₂ O, 0.517 g of NiSO ₄ .6H ₂ O, 3.188 g of Al ₂ (SO ₄ ) ₃ .8H ₂ O and 0.027 g of RuCl _{3 were} added to this alkaline suspension. 500 ml of a mixed solution of magnesium salt, nickel salt, aluminum salt and ruthenium salt dissolved in the solution is added to adjust the pH of the reaction solution to 9.2, and further aged at 42 ° C. for 1 hour, to form the layered double hydroxide core. It was made topotactically grow on the particle surface to obtain layered double hydroxide particles. The total number of moles of magnesium, aluminum, nickel, and ruthenium added during the growth reaction was 0.042 with respect to the total number of moles of the magnesium and aluminum added during the formation of the core particles. The average plate surface diameter of the layered double hydroxide particles obtained here was 0.051 μm, the crystallite size D006 was 0.001 μm, and the BET was 298.2 m ² / g.

  The layered double hydroxide particle powder thus obtained was molded into spherical beads having a diameter of 3 mm. After calcining in air at 1100 ° C. for 13 hours to form oxide particle powder, reduction treatment is performed at 1010 ° C. in a gas stream with a hydrogen / argon volume ratio of 20/80 for 4 hours. Got. The content of nickel in the obtained catalyst was 0.222 wt% (Ni / (Mg + Al + Ni + Ru) = 0.002 (molar ratio)), and the size of the metal nickel fine particles was 1 nm. The ruthenium content in the obtained catalyst was 0.026 wt% (Ru / (Mg + Al + Ni + Ru) = 0.0001 (molar ratio)), and the size of the metal ruthenium fine particles was 2 nm. The metal nickel particles and metal ruthenium are presumed to exist only near the particle surface.

<Reference Example 1>
199.7 g of MgSO ₄ · 7H ₂ O, 78.84 g of Al ₂ (SO ₄ ) ₃ · 8H ₂ O, 170.5 g of NiSO ₄ · 6H ₂ O and 3.364 g of RuCl ₃ were dissolved in water to make 1000 ml. Separately, a 1000 ml solution in which 24.07 g of NaCO ₃ was dissolved was added to 595.0 ml of NaOH (14 mol / L concentration) to prepare an alkaline mixed solution of 1000 ml in total.
The mixed solution of the above magnesium salt and aluminum salt was added to this alkali mixed solution and aged at 132 ° C. for 24 hours to obtain layered double hydroxide particle powder as a catalyst precursor. The plate surface diameter of the layered double hydroxide particle powder was 0.298 μm, the crystallite size D006 was 0.041 μm, and the BET was 59.3 m ² / g.
Subsequently, this powdery catalyst precursor was formed into spherical beads having a diameter of 3 mm. Calcination was performed in air at 850 ° C. for 24 hours, and reduction treatment was performed at 850 ° C. in a gas stream having a hydrogen / argon volume ratio of 20/80 for 5 hours to obtain a hydrocarbon decomposition catalyst. The content of nickel in the obtained catalyst was 42.811 wt% (Ni / (Mg + Al + Ni + Ru) = 0.360 (molar ratio)), and the size of the metal nickel fine particles was 35 nm. The ruthenium content in the obtained catalyst was 1.843 wt% (Ru / (Mg + Al + Ni + Ru) = 0.0009 (molar ratio)), and the size of the metal ruthenium fine particles was 18 nm. In addition, it is estimated that metal nickel particle and metal ruthenium exist in the whole particle | grain.

<Reference Example 2>
138.7 g of MgCl ₃ · 6H ₂ O, 28.40 g of AlCl ₃ · 6H ₂ O, 54.75 g of NiCl ₂ · 6H ₂ O and 9.761 g of RuCl ₃ were dissolved in water to make 1000 ml. Separately, a 1000 ml solution in which 17.46 g of NaCO ₃ was dissolved was added to 157.0 ml of NaOH (concentration of 14 mol / L) to prepare an alkali mixed solution having a total volume of 1000 ml.
The mixed solution of the above magnesium salt and aluminum salt was added to this alkali mixed solution and aged at 72 ° C. for 18 hours to obtain layered double hydroxide particle powder as a catalyst precursor. The plate surface diameter of the layered double hydroxide particle powder was 0.068 μm, the crystallite size D006 was 0.003 μm, and the BET was 284.5 m ² / g.
Subsequently, this powdery catalyst precursor was formed into spherical beads having a diameter of 3 mm. Firing was performed in air at 1250 ° C. for 20 hours, and reduction treatment was performed at 1000 ° C. in a gas stream having a hydrogen / argon volume ratio of 20/80 for 10 hours to obtain a hydrocarbon decomposition catalyst. The content of nickel in the obtained catalyst was 23.783 wt% (Ni / (Mg + Al + Ni + Ru) = 0.196 (molar ratio)), and the size of the metal nickel fine particles was 22 nm. The ruthenium content in the obtained catalyst was 8.191 wt% (Ru / (Mg + Al + Ni + Ru) = 0.039 (molar ratio)), and the size of the metal ruthenium fine particles was 20 nm. In addition, it is estimated that metal nickel particle and metal ruthenium exist in the whole particle | grain.

<Comparative Example 1>
The α-alumina powder was fired in air at 1150 ° C. for 10 hours as 2.5 mm spherical beads. To this, 1000 ml of a solution in which 212.2 g of Ni (NO ₃ ) ₂ · 6H ₂ O was dissolved in pure water was applied by spraying, dried, and then fired in air at 660 ° C. for 6 hours. Further, reduction treatment was performed at 800 ° C. for 9 hours in a gas stream having a hydrogen / argon volume ratio of 20/80. The content of nickel in the obtained catalyst was 10.2 wt% (Ni / (Al + Ni) = 0.256), and the size of the metal nickel fine particles was 48 nm.

<Comparative example 2>
The α-alumina powder was fired in air at 1200 ° C. for 5 hours as 2.5 mm spherical beads. To this, 1000 ml of a solution in which 212.2 g of RuCl ₃ was dissolved in pure water was applied by spraying, dried and baked in air at 580 ° C. for 5 hours. Further, reduction treatment was performed at 540 ° C. for 3 hours in a gas stream having a hydrogen / argon volume ratio of 20/80. The ruthenium content in the obtained catalyst was 9.015 wt% (Ru / α-Al ₂ O ₃ + Ru = 0.048), and the size of the metal ruthenium fine particles was 15 nm.

  As is apparent from Table 1, when the hydrocarbon cracking catalyst according to the present invention is used, the methane conversion is almost in the vicinity of chemical equilibrium at any temperature of 400 ° C to 1000 ° C.

  As is apparent from Table 2, when the hydrocarbon cracking catalyst according to the present invention is used, even when S / C is 1.5 and 3.0, the methane conversion is almost near the chemical equilibrium and high conversion. And maintains a high methane addition rate even in a long-time reaction.

  As is apparent from Table 3, when the hydrocarbon cracking catalyst according to the present invention is used, the methane conversion is as high as 84% or more, and the carbon deposition amount is 0.2% or less. It has excellent caulking properties.

The present invention constitutes a catalyst for cracking hydrocarbons in a state of fine particles that do not have metal nickel and metal ruthenium, which are catalytically active components, in steam reforming in which a lower hydrocarbon mainly composed of methane and steam are mixed and reacted. The catalyst has excellent catalytic activity even at low temperatures by being highly dispersed and supported either in the vicinity of the surface of the particles to be formed or in the vicinity of the surface of the catalyst compact obtained by granulating the particles. Moreover, it has excellent coking resistance even under low steam, and has excellent catalytic activity in terms of durability.

Claims (5)

A catalyst for hydrocarbon decomposition comprising magnesium, aluminum, nickel and ruthenium as constituent elements, the catalyst comprising layered double hydroxide core particles comprising magnesium and aluminum , and the surface of the layered double hydroxide core particles A layered double hydroxide type particle powder formed with a layered double hydroxide layer made of magnesium, aluminum, nickel and ruthenium is heated and fired to obtain an oxide particle powder, and then the oxide particle powder is heated. It is obtained by reducing nickel and ruthenium in oxide particle powder into metal nickel fine particles and metal ruthenium fine particles, the metal ruthenium fine particles have an average particle diameter of 1 to 10 nm, and the metal ruthenium content is carbonized. 0.025 to 5.0 wt% with respect to the catalyst for hydrogenolysis, and the content of metal ruthenium is magnesi Beam, aluminum, relative to the total number of moles of nickel and ruthenium, hydrocarbon cracking catalyst which is a 0.0001 to 0.025. The average particle diameter of the metal nickel fine particles is 1 to 10 nm, the metal nickel content is 0.1 to 40 wt% with respect to the hydrocarbon decomposition catalyst, and the metal nickel content is magnesium, aluminum, ruthenium. The catalyst for cracking hydrocarbons according to claim 1, which is 0.0007 to 0.342 with respect to the total number of moles of nickel and nickel. The catalyst for cracking hydrocarbons according to claim 1 or 2, wherein the number of moles of metal ruthenium with respect to metal nickel is 0.0004 to 30. An alkaline aqueous solution containing an anion, a magnesium raw material, and an aluminum salt aqueous solution are mixed to obtain a mixed solution having a pH value in the range of 7.0 to 13.0, and then the mixed solution is aged at a temperature range of 50 ° C to 300 ° C. To produce layered double hydroxide core particles composed of magnesium and aluminum, and then to the aqueous suspension containing the layered double hydroxide core particles, the magnesium added at the time of forming the core particles and the above Addition of magnesium raw material containing magnesium, aluminum, nickel and ruthenium, aluminum salt aqueous solution, nickel salt aqueous solution and ruthenium salt aqueous solution with a ratio of 0.05 to 0.5 with respect to the total number of moles of aluminum After aging, the pH value is in the range of 9.0 to 13.0 and the temperature is in the range of 40 ° C to 300 ° C. The layered double hydroxide layer is subjected to a growth reaction to form a coating, filtered, washed with water, and the resulting layered double hydroxide particle powder is heated and fired in a temperature range of 400 ° C. to 1600 ° C. A method for producing a catalyst for cracking hydrocarbons, comprising obtaining particle powder and then heat-reducing the oxide particle powder in a reducing atmosphere at a temperature range of 700 ° C to 1100 ° C. A method for producing hydrogen by steam reforming a gas mainly comprising a lower hydrocarbon, comprising contacting the hydrocarbon cracking catalyst according to any one of claims 1 to 3, the lower hydrocarbon gas, and steam. To produce hydrogen.