JP2007203129A - Method for manufacturing particulate catalyst, particulate catalyst and reformer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a particulate catalyst, by which the particulate catalyst having high activity and a long service life can be manufactured at a low cost and to provide a reformer to be operated at low temperature. <P>SOLUTION: The particulate catalyst having ≤10 μm average particle size is manufactured by forming a liquid droplet having ≤30 μm diameter from a catalytically-active component-containing aqueous solution and introducing the formed liquid droplet into a plasma flame under atmospheric pressure by using an argon carrier gas having ≤5% oxygen content. Since water-soluble salts are used as raw materials of a catalytically-active component and mixed homogeneously with one another at molecular levels to prepare the catalytically-active component and the prepared catalytically-active component is pyrolyzed instantaneously in the plasma flame, the particulate catalyst having uniform and fixed particle size can be obtained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a steam reforming suitable for a process comprising a steam reforming reaction-shift reaction-CO selective reaction for converting hydrocarbon fuel such as alcohol, methane, kerosene, etc. into hydrogen for a fuel cell by steam reforming reaction. The present invention relates to a fine particle catalyst, a fine particle catalyst for shift reaction, a method for producing a fine particle catalyst for selective oxidation of carbon monoxide, a fine particle catalyst, and a reformer provided with the same.

  Hydrogen has been produced in large quantities in large chemical plants so far. For example, when methane is used as a raw material, 4 moles of hydrogen gas is produced from 1 mole of methane by a reaction with water vapor through a two-stage chemical reaction represented by the following formula.

Steam reforming reaction: CH ₄ + H ₂ O = 3H ₂ + CO
Shift reaction: CO + H ₂ O = CO ₂ + H ₂

  Hydrogen production equipment used for polymer electrolyte fuel cells (PEFC) used in households, automobiles, etc. is technically established for the steam reforming reaction-shift reaction used in large plants. It is considered to use this. However, hydrogen production equipment for PEFC is required to be small, light, low cost, durable, and portable. In particular, reforming catalysts and shift catalysts are desired to have higher performance, improved durability, and improved mechanical strength.

  Further, the hydrogen obtained by the reforming-shift reaction contains about 1% of carbon monoxide (CO). If it is used for PEFC as it is, there is a problem that the electrode is deteriorated and the performance is lowered. Therefore, it is necessary to newly develop a carbon monoxide removal catalyst for oxidizing with oxygen as shown by the following formula to remove the carbon monoxide concentration to 10 ppm or less.

CO removal reaction: CO + 1 / 2O ₂ = CO ₂

  In this case, what is important is to selectively oxidize and remove carbon monoxide in a large excess of hydrogen, and high CO selective oxidation activity is essential.

  FIG. 1 shows a conceptual diagram of a fuel cell hydrogen production apparatus comprising the above 1) steam reforming reaction, 2) shift reaction, and 3) CO removal reaction process.

  As a conventional method for producing a catalyst, a method of liquid-phase precipitation of a catalyst component from a raw material solution, or a method of impregnating an active ingredient in an alumina carrier or the like and drying-calcining is general. In the case of the liquid phase precipitation method, since the pH of the substance to be precipitated is different for each component, the composition of the produced catalyst is not always the intended composition. Further, there is a problem that if the stirring is not performed sufficiently, the composition becomes nonuniform, or sufficient catalytic activity is not obtained by the pH adjuster. Furthermore, since a large amount of water is used, there is a problem of water treatment, and it is inevitable that the cost is increased.

  On the other hand, the impregnation method is a method of supporting the catalytically active component by utilizing the water absorption of a porous material such as alumina. In this case, the water absorption is not always constant, and the distribution of the catalytically active component becomes non-uniform. The catalyst performance is not stable, and there is a problem in the quality of the generated hydrogen gas and the durability of the catalyst itself.

  In addition, since the active ingredient is supported on the surface of the carrier, there is a problem that the active ingredient is likely to be scattered due to wear and it is difficult to maintain the activity for a long period of time.

  In view of the drawbacks of the liquid phase precipitation method and impregnation method described above, in recent years, catalyst production by a dry method rather than a wet method has been attempted. For example, in Japanese Patent Application Laid-Open No. 9-239274, a solution containing a component of a noble metal-containing composite oxide is sprayed into a plasma flame together with a carrier gas containing oxygen to generate composite oxide fine particles, which are in a fluidized state as a catalyst support. A technique for adsorbing to a liquid is disclosed.

  In order to form the complex oxide, it is necessary to increase the oxygen concentration in the plasma flame, and it is considered that the stability of the plasma in a high frequency region is impaired. Furthermore, since the produced fine particles are separately supported on a carrier, the fine particles are not uniformly highly dispersed on the carrier, so that the performance can be lowered.

JP-A-9-239274

  Accordingly, an object of the present invention is to provide a method capable of obtaining a highly active and long-life catalyst and producing the catalyst at low cost. Another object of the present invention is to provide a catalyst suitable for reducing the size and weight for a hydrogen production apparatus for fuel cells. It is another object of the present invention to provide a reforming catalyst device that can be operated at a low temperature.

(1) The fine particle catalyst of the present invention is an aqueous solution containing a catalytically active component as droplets having a diameter of 30 μm or less, and is introduced into a plasma flame under an atmospheric pressure with an argon carrier gas having an oxygen content of 5% or less. A fine particle catalyst having a particle size of 10 μm or less is produced. According to this production method, since water-soluble salts are used as raw materials, the catalyst components uniformly mixed at the molecular level are instantly pyrolyzed with a plasma flame, so that the entire particles are uniform and have a constant particle size. A fine particulate catalyst is obtained.

(2) The particulate catalyst is preferably hollow. It was found that the synthesis in the plasma flame has a feature that some of the catalyst particles are hollow. That is, as a result of examining the particles with a transmission electron microscope (FIG. 1), it was found that the inside of the particles was hollow without containing a catalyst component. This is because, when plasma-decomposing fine droplets containing catalyst components, the droplets instantaneously become high temperature, so the outer part of the droplets decomposes into solids at the time of decomposition, but rapidly cools, so It is presumed that some water vapor is trapped in the particles and becomes hollow. It can be seen that the hollowness is advantageous as a catalyst considering that the catalytic reaction occurs near the surface of the catalyst. That is, there are advantages that the activity is improved because a uniform active component exists only on the surface used for the reaction, and that the weight per catalyst unit volume is reduced, so that the entire catalyst device is reduced in weight.

(3) The fine particle catalyst is preferably used for a steam reforming reaction, a shift reaction, or an oxidation reaction of carbon monoxide. The conventional shift catalyst has a problem in that its catalytic component is oxidized and its activity is lowered and heat resistance is deteriorated. In contrast, the catalyst of the present invention is instantaneously combined in a high-temperature atmospheric pressure plasma flame, and becomes a metastable product in a non-equilibrium state by rapid cooling. As a result, the reactivity with respect to oxygen is reduced, oxidation is difficult, and the activity is maintained. Furthermore, carbon deposition is suppressed by controlling the acidity, and a long life can be achieved.

(4) The catalytically active component used in the production of the steam reforming reaction catalyst is at least one selected from Fe, Co, Ni, Ru, Rh, Pd, Ir, and Pt, and Mg, Al, Si, It is preferable to contain at least one carrier component selected from Ti, Zr, Ba, and La.

(5) The catalytically active component used in the production of the shift reaction catalyst is at least one selected from Cr, Mn, Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Ir, and Pt, It is preferable to contain at least one carrier component selected from Mg, Al, Si, Ti, Zr, Ba, and La.

(6) The catalytically active component used in the production of the carbon monoxide oxidation reaction catalyst is selected from at least one selected from Ru, Rh, Pd, Ir, and Pt, and Al, Si, Ti, and Zr. It is preferable to contain at least one carrier component.

(7) The present invention is a fine particle catalyst for hydrogen production produced by any one of the methods (1) to (6).

(8) It is preferable to coat the fine particle catalyst on a support having a honeycomb shape, a granular shape or a cylindrical shape.

(9) The present invention is a reformer provided with the hydrogen production catalyst according to (7) or (8).

  According to the present invention, a catalyst having a uniform, high activity and fine shape can be produced very easily. In addition, since the catalyst component is uniformly and highly dispersed on the carrier, it is possible to produce a catalyst having high activity and stability as a catalyst and suitable for producing hydrogen for household fuel cells from a portable type.

  The present invention relates to a solution containing a catalyst component suitable for a catalytic reaction when producing hydrogen from a hydrocarbon fuel by a steam reforming reaction, a shift reaction, and a CO removal reaction. The fine droplets are introduced into a plasma flame together with a carrier gas to which oxygen of 5% or less is added, and the oxidation reaction is accelerated simultaneously with thermal decomposition or thermal decomposition to produce a fine particle catalyst of 10 μm or less. Is.

  In the case of producing a fine particle catalyst containing fine particles and containing multiple components, it is important that the catalyst components are uniformly dispersed in the carrier.

  In the method for producing a fine particle catalyst of the present invention, first, when atmospheric pressure plasma decomposition is performed, a solution containing a catalyst component is made into fine droplets. Thereby, a fine particle catalyst having a particle diameter of 30 μm or less can be produced, and as a result, the catalyst performance can be remarkably improved.

  When a fine particle catalyst is produced from a solution containing a plurality of catalytically active components, these components are not mixed, but become an alloyed fine particle catalyst.

  FIG. 2 is a schematic view of an atmospheric pressure plasma apparatus 100 which is an apparatus for producing a fine particle catalyst of the present invention. Although this apparatus uses microwave plasma, the present invention is not limited to this, and high-frequency plasma may be used.

  A gas that generates plasma, such as argon gas, is introduced from the gas introduction tube 1, adjusted to a predetermined flow rate by the flow meter 3, and then introduced into the plasma generation unit 14 in the quartz reaction tube 9. The plasma generator 20 is turned on to generate plasma. If necessary, an oxidizing gas such as oxygen is introduced from the introduction pipe 2 to a predetermined flow rate by the flow meter 4 and then mixed by the gas mixer 5.

  These gases are sent to the plasma generator 14 by the ultrasonic atomizer 7 along with the atomized droplets 16 from the raw material solution container 6 containing the raw material solution 8 of the catalyst component. The raw material solution container 6 containing the raw material solution and the ultrasonic sprayer 7 are installed in the water tank 21.

  The fine droplets 16 sent to the plasma generation unit 14 become catalyst fine particles 18 by thermal decomposition and / or thermal decomposition and oxidation reaction. The produced catalyst fine particles 18 are collected in a fine particle trap container 22 filled with water. This water is circulated in the trap by a circulation pump 15.

  In the case of a water trap, gaseous products other than fine particles, which are decomposition products of the catalyst raw material, are absorbed and removed by water and are not released into the atmosphere. The catalyst fine particles 18 finally obtained are taken out from the valve 17 and collected. After recovery, washing and drying are performed to obtain a finished catalyst.

  In the case of a reforming catalyst, the raw material solution containing the catalytically active component is at least one selected from Fe, Co, Ni, Ru, Rh, Pd, Ir, Pt and Mg, Al, Si, Ti, Zr, A mixed solution consisting of at least one of Ba and La is preferred.

  The shift catalyst is selected from at least one selected from Cr, Mn, Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Ir, and Pt, and Mg, Al, Si, Ti, Zr, Ba, and La. The mixed solution containing at least one carrier component, the CO removal catalyst is at least one selected from Ru, Rh, Pd, Ir, Pt, and at least one selected from Al, Si, Ti, Zr A mixed solution containing the above carrier components is preferred. In addition, as a raw material containing these elements, if it is a salt soluble in water, it will not be limited to these. That is, nitrates, chlorides, sulfates, carbonates, acetates, bromides, phosphates, oxalates and the like may be used as a solution. For example, in the case of nickel, nickel nitrate, nickel chloride, nickel sulfate, nickel bromide, hexaammine nickel chloride, and the like can be used.

  As a method for making the solution into mist-like fine droplets, an ultrasonic sprayer or a pressure spray method is suitable. The diameter of the droplet is preferably 30 μm or less. This is because in the case of droplets of 50 μm or more, the decomposition products do not become fine particles of 10 μm or less. Desirably, the droplet diameter is preferably 10 μm or less.

It is preferable to use a gas composed of Ar and / or Ar—O ₂ as a carrier gas for introducing fine droplets of the catalyst raw material into the atmospheric pressure plasma generator. This is because the carrier gas not only introduces the spray droplets into the plasma generating section but also functions as a plasma generating gas.

That is, Ar is preferable because it is easily ionized and stably enters a plasma state. In addition, Ar is necessary to make a stable plasma state. However, when the decomposition product is made more oxidized, it is not sufficient to oxidize only with water of spray droplets, so it is necessary to introduce O _2. preferable. However, it should be noted that when the O ₂ concentration exceeds 5%, the stability of the plasma is poor and the plasma flame tends to disappear. The O ₂ concentration is preferably 5% or less. As the atmospheric pressure plasma source, high-frequency plasma and microwave plasma are suitable. The frequency is preferably 10 MHz to 50 GHz.

  The method for using the fine particle catalyst produced by the spray plasma decomposition method of the present invention will be described below. In the fixed bed reactor, as described above, the powdered catalyst can be used in a desired shape using a press molding machine or a tableting machine. Most preferably, the fine powder according to the present invention is applied to a ceramic support such as a honeycomb, granular, spherical, or cylindrical shape that has low pressure loss, excellent mechanical strength, and can suppress scattering of dust and the like. It is to be used after coating. Examples of the honeycomb support include oxide-based oxides such as cordierite and alumina, and stainless-based metal honeycombs.

In the present invention, when there are two or more types of catalyst components, whether each component is present alone or in combination depends on the production conditions for plasma decomposition. For example, an alloy catalyst in which metals are bonded together or a complex oxide in which oxides are bonded together uses only Ar as the plasma gas and Ar-O ₂ as the latter (however, the O ₂ concentration is 5% or less), and the plasma temperature is adjusted. It is possible by adjusting. Of course, it is also possible for each to exist as a single substance. It is determined from the viewpoint of catalytic activity whether it is present alone or an alloy or composite oxide.

For example, when a reforming catalyst is produced, when a mixed solution of Ni solution and Al is used and reacted by the spray plasma method of the present invention, formation of NiAl ₂ O ₄ which is a composite oxide of Ni and Al is recognized. It has been. Further, as shown in the examples, in the mixed solution of noble metals used for the CO removal catalyst, it is possible to form a Pt—Ru alloy by bonding metals like Pt and Ru. In this case, compared with the conventional precipitation method and impregnation method, since it can be made into fine particles with a uniform composition as described above, the catalytic activity is high. In the case of a reforming catalyst, Ni is usually the active site, but in the plasma synthesis of the present invention, NiAl ₂ O ₄ that has high heat resistance at the same time as Ni is produced, and high temperature heat resistance is manifested to maintain Ni in a highly dispersed state. Presumed to be.

  Furthermore, as a result of examining the catalyst according to the present invention in detail, it was found that some of the catalyst particles have a feature of being hollow. That is, as a result of examining the particles with a transmission electron microscope, it was found that the inside of the particles was free of catalyst components and consisted of bubbles. This is presumed to be because, in plasma synthesis, the temperature becomes instantaneously high, so that water vapor is confined in the particles and rapidly cooled during decomposition. It can be seen that the hollowness is advantageous as a catalyst considering that the catalytic reaction occurs near the surface of the catalyst. That is, there are advantages that the activity is improved because a uniform active component exists only on the surface used for the reaction, and that the weight per catalyst unit volume is reduced, so that the entire catalyst device is reduced in weight.

In this example, a steam reforming catalyst of methane (CH ₄ ) was produced using a microwave plasma apparatus (output: about 1 kW, 2.5 GHz) at atmospheric pressure. Nickel nitrate Ni (NO ₃ ) ₂ · 6H ₂ O and aluminum nitrate Al (NO ₃ ) ₃ · 9H ₂ O were prepared as 30% NiO-70% Al ₂ O ₃ after thermal decomposition as catalyst activation components 100 cc of the mixed solution was placed in the raw material solution container 6 shown in FIG. Subsequently, the argon gas was introduced into the system from the gas introduction pipe 1 with the flow meter 3 set to 5 L / min. The plasma apparatus was turned on to generate argon plasma. Next, the power of the circulation pump 15 was turned on, and water was dropped into the fine particle trap by a shower method. Finally, the power of the ultrasonic atomizer 7 (frequency 2.4 MHz) was turned on, and the solution in which the catalyst component was dissolved was made into fine droplets of about 3 μm. After the thermal decomposition by atmospheric pressure plasma was completed, the particulate catalyst collected in the particulate trap container 22 was collected by opening the valve 17, filtered and dried to obtain a catalyst made of Ni-alumina.

As Comparative Example 1, a conventional impregnated catalyst was produced. A solution prepared by calcination of Ni (NO ₃ ) ₂ · 6H ₂ O to become 30% NiO-70% Al ₂ O ₃ water was impregnated in a well-dried alumina powder and left overnight. Next, it was dried in a dryer at 150 ° C. and calcined in an electric furnace at 700 ° C. for 2 hours to obtain a finished catalyst.

About the catalyst of Example 1 manufactured as mentioned above and the comparative example 1, the result observed by the electron micrograph is shown in FIG. The average particle size of the catalyst of Example 1 is 5 μm or less. On the other hand, the catalyst particle diameter of Comparative Example 1 is several tens of micrometers which is the particle diameter of the alumina used.
FIG. 4 shows an electron micrograph when the spherical particles shown in FIG. 3 are ground in a mortar. It turns out that it is a hollow particle which consists of a wall about 100 nm thick. In addition, it can be seen that Ni-like particles are dispersed on the outer side of the wall, and Ni particles are not present on the inner wall of the sphere. Thus, it was confirmed that the catalyst particles synthesized in the plasma flame are hollow spherical catalysts.

  In this example, a steam reforming catalyst for methane was produced in the same manner as in Example 1. However, in addition to argon as a carrier gas, oxygen as an oxidizing gas was mixed therein. The oxygen concentration was 4.5%. Argon gas was introduced from the gas introduction tube 1 and oxygen gas was introduced from the gas introduction tube 2 to obtain a fine particle catalyst made of Ni-alumina in the same manner as in Example 1.

  In this example, a Ni-alumina catalyst was obtained in the same manner as in Example 3 except that the oxygen concentration was 2%.

  This embodiment is exactly the same as the first embodiment except that a high-frequency plasma apparatus (output: about 1 Kw, frequency: 13.6 MHz) is used as the atmospheric pressure plasma source.

  The obtained catalyst powder was granulated to 1.2 to 2 mm with a press machine, and the steam reforming performance of methane was measured under the same conditions using the activity evaluation apparatus shown in FIG. 4 as described in Examples 1 and 2. .

  About the fine particle catalyst prepared in Examples 1-4 and Comparative Example 1, the performance evaluation with respect to the steam reforming reaction of methane was performed. FIG. 5 shows a fixed bed type atmospheric pressure flow apparatus used for performance evaluation. Using this apparatus, the conversion rate of methane at a constant temperature was determined and used as an index of catalyst activity. The conversion rate was determined by measuring the methane concentration at the inlet and outlet of the reaction tube at a predetermined temperature and calculating the conversion rate from the following equation.

Conversion rate = (reaction tube inlet CH ₄ amount−reaction tube outlet CH ₄ amount) / reaction tube inlet CH ₄ amount

  The measuring method is shown below. First, 70 mg of the fine particle catalyst of the present invention or the impregnated catalyst of Comparative Example 1 was filled in a quartz reaction tube 40 having a diameter of 6 mm, and a thermocouple 37 was fixed to the outer wall of the reaction tube and set in an electric furnace 39. While flowing nitrogen gas 30, the temperature was raised to 500 ° C. and 600 ° C., and then hydrogen gas 29 was introduced for 1 hour to reduce the catalyst. After the reduction, the methane cylinder 27 and the nitrogen cylinder 28, which are reaction gases, are adjusted to have a methane concentration of 10% and a flow rate of 70 ml / mi. Steam was introduced into the catalyst 36 by bubbling this gas into water 35 heated by a mantle heater 34. After removing the water from the gas after the reaction with a water trap 41, the gas is analyzed with a gas chromatography 42, and the methane conversion rate is determined from the amount of hydrogen and carbon monoxide produced and the amount of methane at the inlet and outlet to determine the catalytic activity. Evaluation was performed. Incidentally, water vapor / carbon = 2.5.

  Table 1 shows the results. The reaction temperatures are 500 ° C. and 600 ° C. Table 1 shows that the higher the methane conversion, the better the catalytic activity. Equilibrium attainment rate indicates the ratio of the experimental value to the value obtained by theoretically obtaining the methane conversion rate from thermodynamic data, and if this is 1, it indicates that the theoretical value has been reached.

  As shown in Table 1, it can be seen that the catalysts of Examples 1 to 4 according to the present invention have a higher methane conversion rate and an equilibrium attainment rate of 1 than the catalyst of Comparative Example 1. When the amount of oxygen added to the argon gas in the preliminary experiment is more than 5%, the methane conversion rate of the obtained catalyst is higher than that of Comparative Example 1 in terms of performance, but the plasma stability is poor. It often turns out that the plasma flame disappears and is not practical. Accordingly, the oxygen concentration is set to 5% or less.

  As a result, it has been clarified that the catalyst of the present invention exhibits higher activity than the conventional catalyst.

In this example, the powder catalyst produced in Example 1 was coated on a honeycomb carrier, and its steam reforming performance was examined. The alumina sol and the catalyst powder of Example 1 were mixed with water to form a slurry, which was coated on a honeycomb support of 400 cells / (inch) ² and fired at 600 ° C. to obtain a honeycomb catalyst. The coating amount of the catalyst powder is 100 g / L-honeycomb. The honeycomb catalyst was examined for steam reforming performance of methane in the same manner as in Example 1 using the apparatus shown in FIG. As a result, the reaction temperature was 40% at 500 ° C and 75% at 600 ° C. The honeycomb catalyst has a lower external surface area, that is, the active point because the catalyst has a smaller external surface area, that is, the activity is lower, but the performance is still higher than the comparative catalyst. From this result, it was revealed that the catalyst of the present invention has sufficient performance even when used as a honeycomb catalyst.

In this example, the effect of changing the droplet size of the spray droplets on the activity was investigated. The droplet size was 3, 30, and 50 μm, and a catalyst made of Ni-alumina was obtained in the same manner as in Example 1. . As a result of observing these catalysts with an electron micrograph, the particle size was 2-4 μm when the droplet size was 3 μm, 7-10 μm when the droplet size was 20 μm, and 13-15 μm when the droplet size was 30 μm. Using these fixed catalysts and the normal pressure flow apparatus shown in FIG. 4, the conversion of methane at a constant reaction temperature was determined in the same manner as in Example 1, and the catalytic activity was examined. Table 2 shows the results.

  As can be seen from this table, when the catalyst particle size is 10 μm or more, the conversion rate of methane rapidly decreases. This is because as the particle size increases, the active points decrease as the geometric outer surface area decreases. From this result, it was found that by making the droplet diameter 30 μm or less, the catalyst particles can be 10 μm or less and the performance is high.

  In this example, the effect of suppressing carbon deposition by controlling solid acidity (in this case, weakening solid acidity) was added to the Ni-alumina catalyst of Example 1 by adding alkali metal Mg and rare earth element La, respectively. .

Aluminum nitrate _{Al (NO 3) 3 · 9H} 2 O and 8.8 g, and a nickel nitrate _{Ni (NO 3) 2 · 6H} 2 O and 4.7 g, magnesium nitrate Mg (NO ₃₎ the ₂ · 6H ₂ O 6.0g Water Dissolve in 100cc and mix well. Using this solution, a Ni-Mg-alumina catalyst was produced in the same manner as in Example 3.

Similarly, aluminum nitrate Al (NO ₃ ) _{3 ·} 9H ₂ O 17.6g, nickel nitrate Ni (NO ₃ ) ₂ · 6H ₂ O 4.7g, lanthanum nitrate La (NO ₃ ) ₃ · 6H ₂ O 0.7g Is dissolved in 100 cc of water and mixed well. Using this solution, a Ni-La-alumina catalyst was produced in the same manner as in Example 3.

  In the carbon deposition experiment, the methane conversion was measured by the method shown in Example 4. In Example 4, water vapor / carbon was 2.5, but in this experiment, the water vapor / carbon ratio was changed to 2.0, 1.8, 1.6, and 1.4. As a result, when the Ni-alumina catalyst of Example 1 is 1.8, the Ni-La-alumina catalyst of this example is 1.6, and the Ni-Mg-alumina catalyst is 1.4, a decrease in activity is observed and the pressure of the catalyst layer increases. The reaction gas stopped flowing. This is because carbon was deposited on the catalyst surface. From this experimental result, it was clarified that when Mg and La were added to Ni, the steam reforming reaction proceeded even with a smaller amount of steam, and carbon deposition was suppressed.

  In this example, application examples when a shift reaction is performed on the catalyst of the present invention are shown below. First, the performance of the catalyst made of Ni-alumina produced in Example 1 was examined. The apparatus used for the performance evaluation is the same as that shown in FIG. 5 and is basically the same except that the gas type is CO instead of methane. The performance evaluation is shown by CO conversion. That is, the conversion rate of CO at a constant temperature was obtained and used as an index of catalyst activity. The conversion rate was determined by measuring the CO amount at the inlet and outlet of the reaction tube at a constant temperature, and calculating the conversion rate from the following equation.

  Conversion rate = (reaction tube inlet CO amount-reaction tube outlet CO amount) / reaction tube inlet CO amount

  As the reaction gas, 15% carbon monoxide-nitrogen mixed gas was bubbled into water heated to 50 ° C. at 70 ml / min, and water vapor was introduced into the reactor. The reaction temperature was 350 and 400 ° C.

8.3g of copper nitrate Cu (NO ₃ ) ₂ · 3H ₂ O and zinc nitrate Zn (NO ₃ ) ₂ · 6H ₂ O are dissolved in 100cc of 9.5g of water, and the microwave plasma apparatus shown in Fig. 2 is used. Then, a Cu—Zn catalyst was produced in the same manner as in Example 1. The shift reaction of this catalyst was measured in the same manner as in Example 8.

Dissolve 7.8 g of nickel nitrate Ni (NO ₃ ) ₂ · 6H ₂ O and 9.6 g of ferric nitrate Fe (NO ₃ ) ₃ · 9H ₂ O in 100 cc of water, and use the microwave plasma device shown in FIG. The Ni—Fe catalyst was produced in the same manner as in Example 1. The shift reaction activity of this catalyst was measured in the same manner as in Example 8.

Nickel nitrate Ni (NO ₃ ) ₂ · 6H ₂ O 5.3g, ferric nitrate Fe (NO ₃ ) ₃ · 9H ₂ O 6.9g,
10 g of aluminum nitrate Al (NO ₃ ) _{3 ·} 9H ₂ O is dissolved in 100 cc of water, and a Ni-Fe-alumina catalyst is produced in the same manner as in Example 1 using the microwave plasma apparatus shown in FIG. did. The shift reaction activity of this catalyst was measured in the same manner as in Example 8.

  The shift reaction activities of the catalysts of Examples 8 to 11 are summarized in Table 3 above.

  As can be seen from Table 3, the CO conversion rate of all the catalysts was high, and the catalyst of the present invention was found to be effective for the shift reaction. In particular, when Example 8 is compared with Examples 10 and 11, when Fe is added to Ni, the activity is improved and the effect of compounding is recognized, and when alumina is further added, Ni and Fe are highly dispersed and the highest activity is obtained. showed that.

In this example, a fine particle catalyst was produced using a microwave plasma apparatus shown in FIG. 2 for a platinum catalyst which is one of the noble metal catalysts. Aluminum nitrate is mixed with a tetraammineplatinum dichloride ([Pt (NH ₃ ) ₄ ] Cl ₂ ) solution containing 5% platinum (Pt), and this is thermally decomposed by microwave plasma to produce a platinum-alumina fine particle catalyst. did. The platinum content was 4 wt% with respect to alumina.

In this example, a fine particle catalyst was produced by thermally decomposing a solution containing a catalytically active component containing two kinds of components of platinum and ruthenium (Ru) and aluminum nitrate using a microwave plasma apparatus shown in FIG. Mix chloroplatinic acid (H ₂ PtCl ₆ ) solution containing 15% platinum and 8.5% ruthenium chloride (RuCl ₂ ) solution, mix aluminum nitrate with this solution, and use argon gas-hydrogen (5%) as the carrier gas. Then, a catalyst made of Pt-Ru / alumina was produced using a plasma apparatus. Platinum and ruthenium were both 2 wt% with respect to alumina.

In Comparative Example 2, a tetraammine platinum dichloride ([Pt (NH ₃ ) ₄ ] Cl ₂ ) solution, which is a conventional technique, was impregnated into alumina powder, dried at 120 ° C., and calcined at 600 ° C. to obtain a finished catalyst. The platinum content was 4 wt% with respect to alumina.

Using the catalysts of Examples 12 and 13 and Comparative Example 2 above, the oxidation removal performance of CO was examined.
The measurement is the same as that of the fixed bed type atmospheric pressure flow apparatus shown in FIG. 5, and the gas composition is 1% CO-residual air. The reaction temperature was 150 ° C and 200 ° C. Table 4 shows the results.

  As is apparent from Table 4, it can be seen that the catalyst of this example has higher CO removal performance than the comparative example catalyst.

  By using the catalyst of the present invention and the production method thereof, hydrocarbon fuel such as alcohol, methane, and kerosene can be efficiently subjected to steam reforming reaction-shift reaction-CO removal reaction. It is extremely effective as a catalyst to be produced. CO selective oxidation catalysts are also effective in removing harmful carbon monoxide in the environment.

It is a conceptual diagram of the hydrogen manufacturing apparatus for fuel cells. It is a block diagram of the particulate catalyst manufacturing apparatus which is one embodiment of this invention. It is an electron micrograph of the fine particle catalyst which consists of this invention. It is an electron micrograph when the fine particle catalyst of FIG. 3 is ground. It is a block diagram of a catalyst activity evaluation device.

Explanation of symbols

1, 2 Gas introduction pipe
3, 4 Flow meter
5 Gas mixer
6 Raw material solution
7 Ultrasonic atomizer
8 Fine droplet
9 Quartz reaction tube
10 Gas outlet
11 Circulating water
12, 13 electrodes
14 Plasma generator
15 Circulation pump
16 Container for raw material solution
17 Valve
18 Fine particle catalyst
19 Circulating water outlet
20 Plasma generator
21 Aquarium
22 Particle trap container
23 Catalyst material tank
24, 26 pump
25 Circulating water tank
27, 28, 29, 30 Gas cylinder
31, 32, 33 Mass flow controller
34 Mantle heater
35 water
36 Catalyst
37 Thermocouple
38 Temperature controller
39 Electric furnace
40 Quartz reaction tube
41 water trap
42 Gas chromatography
43 exhaust gas

Claims (9)

  An aqueous solution containing a catalytically active component is made into droplets having a diameter of 30 μm or less, and introduced into a plasma flame under an atmospheric pressure with an argon carrier gas having an oxygen content of 5% or less to produce a fine particle catalyst having an average particle size of 10 μm or less. A method for producing a fine particle catalyst.   2. The method for producing a fine particle catalyst according to claim 1, wherein the fine particle catalyst is hollow.   The method for producing a fine particle catalyst according to claim 1 or 2, wherein the fine particle catalyst is used for a steam reforming reaction, a shift reaction, or an oxidation reaction of carbon monoxide.   The catalytic active component used in the production of the steam reforming reaction catalyst is at least one selected from Fe, Co, Ni, Ru, Rh, Pd, Ir, and Pt, and Mg, Al, Si, Ti, and Zr. The method for producing a fine particle catalyst according to any one of claims 1 to 3, further comprising at least one carrier component selected from Ba, La and La.   The catalytic active component used in the production of the shift reaction catalyst is at least one selected from Cr, Mn, Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Ir, and Pt, and Mg, Al. The method for producing a fine particle catalyst according to any one of claims 1 to 3, comprising at least one carrier component selected from Si, Ti, Zr, Ba, and La.   The catalytically active component used for producing the carbon monoxide oxidation reaction catalyst is at least one selected from Ru, Rh, Pd, Ir, and Pt, and at least selected from Al, Si, Ti, and Zr. The method for producing a fine particle catalyst according to any one of claims 1 to 3, comprising one type of carrier component.   A fine particle catalyst for hydrogen production produced by the method according to any one of claims 1 to 6.   A catalyst for hydrogen production, wherein the particulate catalyst according to claim 7 is coated on a support having a honeycomb shape, a granular shape, or a cylindrical shape.   A reformer comprising the hydrogen production catalyst according to claim 7 or 8.