JP4560621B2 - Method for producing fine particle catalyst, alloy fine particle catalyst or composite oxide fine particle catalyst, apparatus therefor, and method for using the same - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a production method and production apparatus of a fine particle catalyst, an alloy fine particle catalyst or a composite oxide fine particle catalyst, and a steam reforming method and a carbon monoxide conversion method which are used therefor, in particular, alcohol, methane, kerosene. Of reforming catalyst used for producing hydrogen by steam reforming hydrocarbon fuel such as carbon monoxide, and carbon monoxide conversion catalyst used for converting carbon monoxide by reacting carbon monoxide with steam The present invention relates to a method, a manufacturing apparatus, and a method of using the method.

  Conventionally, a catalyst is produced by a precipitation method, a liquid phase precipitation method represented by a coprecipitation method, an impregnation method in which an active ingredient is impregnated into an alumina carrier, or a cordierite honeycomb or ceramic plate-like base material such as alumina. A method of coating an active ingredient by coating a porous material is generally used.

  In the case of the liquid phase precipitation method, a precipitate is usually obtained by adjusting the pH at the time of precipitation, but there is a problem that a large amount of washing water is used for the performance deterioration due to the mixing of the pH adjusting agent or this removal. Moreover, in order to produce two or more types of catalytically active components (also referred to as multi-component systems), there is a problem that the composition of the produced catalyst does not necessarily become the intended composition because the precipitation pH differs for each component. Furthermore, in the case of mass production, there is a problem that if the agitation is not performed sufficiently, the composition becomes non-uniform and sufficient catalytic activity cannot be obtained.

  On the other hand, in the coating method, as described above, the substrate is coated with a porous material such as alumina and then immersed in a solution of the catalytically active component, and the catalytically active component is supported using the water absorption of the porous material. However, in this case, since the water absorption rate is not always constant, there is a problem that the distribution of the catalyst active component becomes non-uniform and the catalyst performance varies among lots to be manufactured. Further, in industrial mass production, there are problems that the precipitation method and impregnation method have many steps, and therefore there are many kinds of apparatuses, and since it is usually a batch type, continuous production is difficult.

  In view of the drawbacks of the liquid phase precipitation method and the coating method described above, in recent years, an attempt has been made to produce a catalyst by a dry method rather than a wet method. For example, Japanese Patent Application Laid-Open No. 10-80636 discloses a technique for producing a fine particle catalyst by evaporating an alloy having a constant composition by arc discharge in an inert gas containing oxygen under reduced pressure.

  Japanese Patent Laid-Open No. 10-80637 discloses that two kinds of metals are arc-dissolved in an inert gas atmosphere containing an oxidizing gas, and the evaporated metal is reacted with the oxidizing gas to produce oxide fine particles of each component. The technology is disclosed.

Furthermore, Japanese Patent Laid-Open No. 2-172801 discloses a technique in which a metal powder is supplied to a plasma spraying machine to a powder supply tube and plasma sprayed into a SUS plate to form a catalyst.
JP 10-80636 A JP-A-10-80637 JP-A-2-172801

However, these methods need to evaporate the metal that is the catalyst component, and thus it is necessary to raise the temperature to the boiling point of the metal. However, since the boiling point of the metal differs from metal to metal,
There is a problem that it is not easy to control the composition ratio of the alloy catalyst to the target composition ratio.

  In addition, all of the above-described techniques produce a catalyst by batch processing, and there is a problem that the catalyst cannot be produced continuously. Furthermore, it is necessary to raise the temperature to the boiling point of the metal, and there is a problem that the device material is restricted and the cost is increased.

  In addition, when producing an alloy catalyst or a composite oxide catalyst, it is not always easy to obtain a metal that is a catalytically active component, but it is expensive even if it is available, and the types of alloys and composite oxide catalysts are limited. There is. In addition, the particle size of the catalyst produced by the conventional catalyst production apparatus is about 10 μm, and there is a problem that sufficient catalyst performance is not always exhibited.

In order to solve the above problems, the present invention provides:
(1) A fine particle catalyst is produced by introducing and reacting fine aqueous solution droplets of a catalyst component containing a catalytically active component and / or a carrier component with an inert carrier gas into an atmospheric pressure plasma space formed by microwaves of the order of gigahertz. It is characterized by that.

(2) In the above (1), the inert carrier gas is one or more selected from argon gas, helium gas, and nitrogen gas. The gas contributes to the generation of plasma and plays a role as a carrier gas for fine droplets.

(3) In (1) and (2), the inert carrier gas includes an oxidizing gas or a reducing gas. When oxidizing the produced fine particle catalyst, air, O ₂ , and N ₂ O are mixed with an inert gas as an oxidizing gas. In the case of reduction, it is preferable to mix, for example, H ₂ , H ₂ S, NH ₃ , or CH ₄ as a reducing gas with an inert gas.

(4) In (1) to (3), the particulate catalyst, which is a reaction product obtained by passing through the atmospheric pressure plasma space, is precipitated and collected in an aqueous solution.

(5) The present invention provides a fine aqueous solution droplet forming means for making an aqueous solution of a catalyst component containing a catalytically active component and / or a carrier component into fine droplets, a means for forming atmospheric pressure plasma by a gigahertz order microwave, An apparatus for producing a fine particle catalyst, comprising: means for introducing the droplets into the atmospheric pressure plasma space with an inert gas; and fine particle catalyst collecting means for collecting the produced reaction product in an aqueous solution .

  As mentioned above, according to this invention, the fine particle catalyst excellent in the catalyst performance can be manufactured compared with the conventional catalyst manufacturing method.

  Further, as a result of being able to produce the fine particle catalyst continuously and easily, the catalyst can be produced at low cost. Furthermore, an alloy catalyst or a composite oxide catalyst having a constant composition ratio can be produced without variation among production lots.

  FIG. 1 shows an ultrasonic atomizer as an apparatus for making fine droplets of a solution in which a catalytically active component is dissolved in the present invention, an atmospheric pressure plasma apparatus as a thermal decomposition apparatus, and a particulate catalyst precipitation apparatus as a collection apparatus for thermally decomposed particulate catalysts. 1 shows an example of the configuration of a production apparatus for a fine particle catalyst when using a catalyst. Note that the present invention is not limited to this.

  In general, the primary particles of the smallest unit aggregate to form secondary particles. In the present invention, the fine particle catalyst refers to the secondary particles, and the particle diameter can be measured with an electron microscope. Further, the particle diameter of the primary particles can be obtained with an X-ray diffractometer (hereinafter, this primary particle diameter is referred to as a crystallite diameter).

  An inert gas, for example, an argon gas capable of generating plasma at atmospheric pressure is introduced from the gas introduction pipe 1, adjusted to a predetermined flow rate by the flow meter 3, and introduced into the raw material solution container 16. If necessary, an oxidizing gas such as oxygen or a reducing gas such as hydrogen is introduced from the gas introduction pipe 2 and adjusted to a predetermined flow rate by the flow meter 4, and then the inert gas and After mixing, the raw material solution container 16 may be introduced.

  The raw material solution 6 filled in the raw material solution container 16 in which the catalyst component is dissolved becomes mist-like fine droplets 8 by the ultrasonic atomizer 7 installed in the water tank and is accompanied by the inert gas. To the plasma generator 14.

  The fine droplets 8 sent to the plasma generation unit 14 are pyrolyzed here to become the fine particle catalyst 18, and settle and collect in the fine particle trap container 22 filled with water. It is preferable that water be circulated in the particulate trap container 22 by the circulation pump 15. Further, by making the circulating water outlet 19 a shower type, the contact efficiency between the circulating water and the fine particle catalyst is increased, whereby the dust collection efficiency of the fine particle catalyst 18 can be increased. In addition, although the gaseous product is generated in addition to the fine particle catalyst by the decomposition of the fine droplets 8 by the plasma, the gaseous product is absorbed in water and is not released into the atmosphere. The fine particle catalyst 18 is recovered by opening the valve 17 and, after recovery, washing with water and drying.

When continuously producing a fine particle catalyst using this apparatus, as shown in FIG.
The catalyst raw material tank 23 filled with the raw material solution 6 in 16 is continuously fed by the pump 24, and further from the circulating water tank 25 filled with circulating water with the valve 17 of the particulate trap container 22 opened. Circulating water is replenished by the pump 26. Continuous production is possible by the above apparatus and operation method.

  The use of an atmospheric pressure plasma apparatus as the thermal decomposition apparatus eliminates the need for creating a vacuum or a reduced pressure state, so that the apparatus configuration can be greatly simplified. In addition to thermal decomposition using an atmospheric pressure plasma apparatus, an electric heating furnace, a high-frequency heating furnace, and burner heating may be used.

  As a means for making the solution in which the catalytically active component is dissolved into fine droplets, the solution may be sprayed in a mist form using a spraying device other than ultrasonic waves to form fine droplets. Moreover, it can select arbitrarily, such as a pressure spray system. In addition to the water spray method, the produced fine particle catalyst can be collected by an electric dust collection method or a filter method. In this case, it is necessary to install an exhaust gas removal device in the subsequent stage.

  Examples of the catalytically active component include metals that act as catalytically active components such as noble metals, transition metals, rare earths, alkali metals, and alkaline earths. The metal salts of these metals, such as nitrates, chlorides, sulfates, carbonates, sulfates, acetates, bromides, phosphates, oxalates, organometallic complexes, etc. are used in solution. For example, in the case of nickel, nickel nitrate, nickel chloride, nickel sulfate, nickel bromide, hexaammine nickel chloride, etc. can be used.

  It is preferable to use a carrier gas as means for introducing fine droplets containing a catalytically active component into the atmospheric pressure plasma generator. An inert gas is desirable as the carrier gas. For example, argon, nitrogen, helium, etc.

When it is desired to oxidize the catalyst component during the thermal decomposition, it is preferable to use an oxidizing gas mixed in the carrier gas. For example, the oxidizing gas is air, O ₂ , N ₂ O, or the like. It is particularly effective to mix these oxidizing gases with a carrier gas in the case of catalytically active components that are not easily oxidized by water vapor alone.

When it is desired to reduce the catalyst component, for example, H ₂ , H ₂ S, NH ₃ , CH ₄ or the like may be added as a reducing gas. In this case, even if it is prevented from being oxidized by water vapor or once oxidized in the plasma, it is immediately reduced by the reducing gas.

 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 a reducing gas for the former and an oxidizing gas for the latter, and adjusts the plasma temperature (controls the plasma power supply and carrier gas). Is possible. 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, in the case of Ni solution and Al solution, when NiO and Al ₂ O ₃ are present, they combine to form a composite oxide NiAl ₂ O ₄ , or as shown in the examples, Pt and Ru Thus, metals can be bonded to form a Pt—Ru alloy.

  It is necessary to contain at least one kind of plasma gas among carrier gas, oxidizing gas, and reducing gas, and the most effective is the above-mentioned carrier gas as a plasma generating gas, and this includes oxidizing gas or reducing gas. It is better to use a mixture of gases. However, when oxidation or reduction is not required and only decomposition is performed, only the carrier gas is sufficient.

  As the carrier gas, argon gas is preferable because the plasma is stable. Further, nitrogen gas is preferable from the viewpoint of cost. The concentration when the oxidizing gas or reducing gas is mixed with the carrier gas can be selected in consideration of the concentration of the catalyst raw material, the flow rate of atomized fine droplets, and the like.

  Furthermore, instead of oxidizing gas or reducing gas, water-soluble oxidizing agent and reducing agent are added to the raw material solution container 16 containing the catalyst components shown in FIG. It may be introduced into the part. Examples of the oxidizing agent include hydrogen peroxide and oxo acid (nitric acid, chloric acid), and examples of the reducing agent include alcohol, formic acid, aqueous ammonia, and the like.

  When the present invention is compared with the conventional method of evaporating and precipitating a metal, which is a catalytically active component, by plasma, the present invention makes it possible to suppress the temperature rise because the catalytically active component is made into fine droplets, and the crystal There is a great advantage that the increase in the diameter can be suppressed. That is, when conventional metals are evaporated by plasma, the melted metals condense and the crystallite diameter of the catalytically active component becomes large, but the present invention has few such problems. Moreover, the primary and secondary particle diameters of the fine particle catalyst to be produced can be controlled by adjusting the raw material concentration in the droplets. For example, by reducing the raw material concentration, these diameters of the fine particle catalyst to be produced can be reduced.

  When the fine droplets are plasma-decomposed, the particle size of the droplets is preferably 100 microns or less, preferably about 1 micron. This is because in the case of droplets of 100 microns or more, the crystallite diameter of the fine particle catalyst produced by thermal decomposition does not become on the nanometer order.

  As a method for collecting the fine particle catalyst produced by thermal decomposition, a method of precipitating the fine particle catalyst in a solution was used. As shown in FIG. 1, the produced fine particle catalyst 18 is precipitated in the circulating water 11, and the precipitated fine particle catalyst is taken out from the valve 17. The solution is sprayed in a shower form from the circulating water outlet 19 by the circulation pump 15, collected in the particulate trap container 22, and circulated by the circulation pump 15. Instead of this method, a collection method using an electric dust collector or a filter may be used.

 As described above, the solution containing the metal salt as the catalytically active component is made into fine droplets, and these droplets are introduced together with the carrier gas into the reaction portion in the plasma state and thermally decomposed, thereby capturing the produced fine particle catalyst. From the collection, it was confirmed that the crystallite diameter of the catalytically active component can be continuously produced in nanometer order.

(How to use fine particle catalyst)
Next, a method for using the fine particle catalyst produced in the above-described embodiment will be described below. As will be described later, the crystallite diameter (particle diameter obtained from an X-ray diffractometer) of the fine particle catalyst obtained by the present invention is several tens of nm, and these aggregate to form fine particles (secondary particles) of several μm. ing. Accordingly, when used in a spouted bed reactor, it can be used in the form of a catalyst as it is.

  In the fixed bed reactor, the obtained fine particle catalyst may be used in a desired shape using a press molding machine or a tableting machine. In addition, when it is necessary to reduce pressure loss and to suppress the deposition of dust and the like, a honeycomb or plate-like substrate may be coated with a fine particle catalyst.

  In this case, as the honeycomb base material, cordierite, an oxide such as alumina, or a stainless metal honeycomb is suitable. Furthermore, it is also possible to use it by coating it on a substrate such as a three-dimensional network structure. In this case, a binder such as alumina sol and a fine particle catalyst are mixed to form a slurry, and the slurry may be dipped in a honeycomb base material or a three-dimensional network structure and coated.

[Chemical reaction using fine particle catalyst]
A chemical reaction using the fine particle catalyst having a desired structure as described above will be described below.

  In recent years, it is particularly effective as a catalyst for producing hydrogen used in fuel cells.

  That is, liquid fuel such as kerosene or methanol, or gaseous fuel such as methane or natural gas is reformed to obtain hydrogen. For example, in the case of methane, hydrogen is produced by a three-step catalytic reaction represented by the following formula.

1) Steam reforming reaction
CH ₄ + 2H ₂ O = 4H ₂ + CO ₂
CH ₄ + H ₂ O = 3H ₂ + CO
2) CO conversion reaction
CO + H ₂ O = CO ₂ + H ₂
3) CO removal reaction
CO + 1 / 2O ₂ = CO ₂
The fine particle catalyst by the spray plasma decomposition method of the present invention is effective for the reaction consisting of the above three steps. In this case, as the fine particle catalyst used in the steam reforming reaction of 1), as a catalyst active component , Ni, Co, Fe, and / or one or more kinds of noble metal elements such as Pt, Ru, Rh, Pd and the catalyst carrier It is preferable to select a support made of Al, Ti, Zr, or Si.
2) As the fine particle catalyst used for the CO conversion reaction, a catalyst containing Fe, Cr, Cu, Zn, Ce, Mn and / or one or more kinds of noble metal elements such as Pt, Ru, Rh, Pd is desirable. If necessary, a catalyst carrier containing at least one of Al, Ti, Zr, Si, Ba, Mg, and La may be used as a catalyst carrier.
3) As the fine particle catalyst used in the CO selective oxidation reaction, a catalyst containing at least one of Pt, Ru, Rh, Pd, Fe, Cu, Mn, Ag, Co, Zn, Ni and the like is desirable.

  As another example of using the fine particle catalyst of the present invention, it can be used for an oxidation reaction or a combustion reaction represented by the following formula.

CO oxidation reaction; CO + 1 / 2O ₂ = CO ₂
Hydrogen combustion reaction: H ₂ + 1 / 2O ₂ = H ₂ O
Alcohol combustion reaction: CH ₃ OH + 3 / 2O ₂ = CO ₂ + 2H ₂ O
Hydrocarbon combustion reaction: CH ₄ + 2O ₂ = CO ₂ + 2H ₂ O
For these reactions, as the fine particle catalyst of the present invention, a noble metal such as Pt and Pd or one or more active components of transition elements such as Fe, Ni, Co, and Mn, and alumina, titania, silica, or the like may be used as a support. desirable.

The catalyst of the present invention can also be applied to the reduction reaction. For example, it is effective for the reduction reaction of NO to N ₂ represented by the following formula.

2NO + 2NH ₃ + 1 / 2O ₂ ＝ N ₂ + 3H ₂ O
As a component of the fine particle catalyst for the reduction reaction, a catalyst in which polyvalent metals such as various precious metals, Mo, V, and W are supported on a carrier such as alumina, titania, and zirconia is desirable.
In addition to the above reactions, the present invention can also be applied to decomposition reactions such as decomposition reactions of environmental pollutants containing chlorine compounds such as chlorofluorocarbon and dioxin, hydrogenation reactions, dehydrogenation reactions, and methanation reactions.

The results of manufacturing the catalyst fine particles using the atmospheric pressure plasma decomposition apparatus shown in FIG. The present invention is not limited to the following examples.
(First Example)
In the first example, a steam reforming catalyst of methane ( CH ₄ ) was manufactured using atmospheric pressure plasma for thermal decomposition. After dissolving 0.47 g of nickel nitrate Ni (NO ₃ ) ₂ · 6H ₂ O and aluminum nitrate Al (NO ₃ ) ₂ · 9H ₂ O as catalyst active components in 100 cc of 1.77 g of water and mixing well, The raw material solution container 6 shown in FIG. Next, argon gas was introduced from the gas introduction pipe 1 into the system by setting the flow meter 3 at 5 liters / minute.

  The atmospheric pressure plasma apparatus was turned on (Arios atmospheric pressure plasma apparatus, microwave output of about 1 kW, 2.5 GHz) 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 ultrasonic atomizer 7 (frequency 2.4 MHz, UD-200 manufactured by Techjam Co., Ltd.) was turned on, and the solution in which the catalyst component was dissolved was made into fine droplets. Pyrolysis with atmospheric pressure plasma for 1 hour. After the completion of the decomposition, the fine particle catalyst collected in the fine particle trap container 22 was collected by opening the valve 17, filtered and dried to obtain 0.5 g of a finished catalyst composed of Ni—Al.

  An electron micrograph of the particulate catalyst thus produced is shown in FIG. The catalyst of Comparative Example 1 produced by the conventional impregnation method described later is also shown. As is clear from this result, the particle diameter (secondary particles) of the catalyst of the first example is 5 μm or less, whereas the catalyst particle diameter of Comparative Example 1 is several tens of μm.

(Second embodiment)
In the second example, a methane steam reforming catalyst was produced as in the first example. In addition to argon as a carrier gas, oxygen as an oxidizing gas was mixed therewith. Argon gas was introduced from the gas introduction pipe 1 and oxygen gas was introduced from the gas introduction pipe 2 to obtain a fine particle catalyst made of Ni—Al in the same manner as in the first example. The oxygen concentration was 10%.

(Comparative Example 1)
As a comparative example, a conventional impregnated catalyst was produced. 20 g of Ni (NO ₃ ) ₂ · 6H ₂ O was dissolved in 20 cc of water. 2.7 cc of this solution was impregnated in 3 g of sufficiently dried alumina powder, allowed to stand overnight and then dried in a dryer at 150 ° C. Next, it was calcined in an electric furnace at 700 ° C. for 2 hours to obtain a finished catalyst.

  As a representative reaction example, the performance evaluation for the steam reforming reaction of methane was performed on the fine particle catalysts prepared in the first example, the second example, and the comparative example 1. The steam reforming reaction of methane is shown by the following formula.

CH ₄ + 2H ₂ O = 4H ₂ + CO ₂
For this reaction, 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 constant 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 reaction apparatus was a normal fixed bed type atmospheric pressure flow reaction apparatus. FIG. 3 shows an apparatus diagram.

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. The temperature was raised to 600 ° C. while flowing nitrogen gas 30, 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 / min . Water vapor was introduced into the catalyst 36 by bubbling this gas into water 35 heated to 60 ° C. with 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.

  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. 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 the first example and the second example have a higher methane conversion rate and an equilibrium attainment rate of 1 than the catalyst of the comparative example 1. As a result, it has been clarified that the catalyst of the present invention exhibits higher activity than the conventional catalyst.
(Third embodiment)
An application example in the case of performing a carbon monoxide (CO) conversion reaction using the fine particle catalyst prepared in the second embodiment will be described below. The CO conversion reaction is a reaction in which carbon monoxide is reacted with water vapor to form hydrogen and carbon dioxide as shown by the following formula.

CO + H ₂ O = CO ₂ + H ₂
The apparatus used in the third embodiment is the same as the apparatus of FIG. 3 used in the first and second embodiments, and is basically the same except that the gas type is CO. 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 The reaction gas was bubbled into water heated to 50 ° C with a 15% carbon monoxide-nitrogen mixed gas at 70 ml / min. Steam was then introduced into the reactor. The reaction temperature was 350 ° C. and 400 ° C. As a result, the gas composition after the reaction was carbon monoxide 5.3% at 350 ° C. and 1.2% at 400 ° C., and the CO conversions were 65% and 92%, respectively. In addition, hydrogen and carbon dioxide as products were confirmed.
Thus, it was revealed that the fine particle catalyst produced by atmospheric pressure plasma shows high activity even in the CO conversion reaction.

  In general, it is known that a metal as a catalytically active component is highly dispersed as its particle size is smaller and its activity is excellent. Therefore, in order to improve the performance as a catalyst, the point is how to reduce the particle diameter of the metal which is the catalytically active component and to make it highly dispersed. From this point of view, it will be shown below whether the method for producing a fine particle catalyst according to the present invention is excellent in adjusting the fine particle catalyst.

(Fourth embodiment)
In the fourth embodiment, a fine particle catalyst was produced by thermal decomposition using atmospheric pressure plasma as shown in FIG. 1 for a platinum catalyst which is one of the noble metal catalysts often used as an oxidation catalyst or a combustion catalyst. Tetraammineplatinum dichloride ([Pt (NH ₃ ) ₄ ] Cl ₂ ) containing 5% platinum (Pt) is dissolved in a solution, and this solution is made into fine droplets, which are thermally decomposed by atmospheric pressure plasma to produce platinum fine particle catalyst. Manufactured.
The crystal structure of the platinum fine particle catalyst obtained in the fourth example was measured with a powder X-ray diffractometer. FIG. 4 shows the result. From this result, platinum was metallic, and the crystallite diameter was calculated using the Sherrer equation, and the result was 24.7 nm. From the fourth example, it was confirmed that platinum fine particles having a nano-sized crystallite diameter can be produced.

(Comparative Example 2)
The platinum catalyst was manufactured by a method of manufacturing a platinum catalyst by heating a platinum solution to a high temperature and evaporating water, which was a conventional technique, and was compared with the catalyst of the example. The tetraammineplatinum dichloride ([Pt (NH ₃ ) ₄ ] Cl ₂ ) solution used in the fourth example was evaporated to dryness in a 120 ° C. dryer and then calcined at 600 ° C. As a result of measuring this sample with an X-ray diffractometer, the crystal structure was metallic platinum, which was the same as in the fourth example , but the crystallite diameter was determined to be 43.8 nm.

When the crystallite diameters of the platinum produced in the fourth example and the comparative example 2 were compared, the platinum catalyst produced by the fourth example according to the present invention was compared with the platinum of the comparative example 2 produced by the conventional pyrolysis method. In comparison, the crystallite size was found to be extremely small.

(Fifth embodiment)
In Example 5, a catalytically active component containing two types of components, platinum and ruthenium (Ru), was pyrolyzed by the atmospheric pressure plasma method shown in FIG. 1 to produce a fine particle catalyst. First, a chloroplatinic acid (H ₂ PtCl ₆ ) solution containing 15% platinum and an 8.5% ruthenium chloride (RuCl ₂ ) solution were mixed at a ratio of 1: 1. In this example, hydrogen gas was used as the reducing gas and mixed with argon gas as the carrier gas.

Argon gas is introduced from the gas introduction pipe 1 shown in FIG. 1 and hydrogen gas (concentration 5%) from the gas introduction pipe 2 is introduced, and the mixed gas contains a solution in which the catalyst component is dissolved. The raw material solution container 16 was introduced.

In the same manner as in the first example, alloy fine particles of platinum and ruthenium were obtained. FIG. 5 shows the results of examining the crystal structure of the produced alloy fine particle catalyst powder with an X-ray diffractometer. None of the ruthenium or ruthenium oxide peaks were observed, confirming that the diffraction peak of platinum (III) was shifted 0.86 ° higher than the standard peak. This indicates that platinum and ruthenium are alloyed. The crystallite diameter of platinum calculated using the Sherrer equation was 29.7 nm when hydrogen was used as the reducing gas.

  As is clear from the fifth example, it was found that platinum and ruthenium formed an alloy rather than merely being mixed. Therefore, it was found that the fine particle alloy catalyst can be easily produced according to the present invention.

(Sixth embodiment)
In the sixth example, a solution in which two types of catalytically active components of platinum and ruthenium were dissolved was made into fine droplets, and this was thermally decomposed by plasma to produce a fine particle catalyst. At that time, methanol was used as a reducing agent. . Others are the same as the fourth embodiment.

  Methanol, which is a reducing agent, was previously added to a mixed solution of platinum and ruthenium, made into fine droplets by ultrasonic waves, and thermally decomposed by atmospheric pressure plasma. FIG. 6 shows the results of measurement of the produced fine particle catalyst powder with an X-ray diffractometer.

As in the fifth example, no ruthenium or ruthenium oxide peak was observed, and the peak of platinum (III) was shifted by 0.46 ° from the standard peak, indicating that it was alloyed. In addition, the crystallite diameter of platinum calculated using the Sherrer equation was 23.0 nm, and an alloy catalyst having finer particles was obtained compared to the fourth example using hydrogen as a reducing agent.

  By using the fine particle catalyst, the fine particle catalyst production method and the fine particle catalyst produced by the apparatus according to the present invention, hydrocarbon fuel such as alcohol, methane, kerosene and the like can be efficiently steam reformed to produce hydrogen. it can. Further, it can be used as a reforming catalyst for producing hydrogen by reacting carbon monoxide and water vapor.

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 a block diagram of the activity evaluation apparatus of a catalyst. FIG. 3 is an X-ray diffraction diagram of platinum catalyst powder. FIG. 3 is an X-ray diffraction diagram of a platinum-ruthenium alloy catalyst powder produced by mixing hydrogen gas as a reducing gas with argon gas. It is an X-ray diffraction pattern of the powder of the platinum-ruthenium alloy catalyst manufactured using methanol as a reducing agent.

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 (5)

A fine particle catalyst characterized by introducing fine reaction solution droplets of a catalyst component containing a catalyst active component and / or a carrier component into an atmospheric pressure plasma space formed by a microwave of gigahertz order by an inert carrier gas and reacting them. Production method. 2. The method for producing a fine particle catalyst according to claim 1, wherein the inert carrier gas is at least one selected from argon gas, helium gas, and nitrogen gas. 3. The method for producing a fine particle catalyst according to claim 1, wherein the inert carrier gas contains an oxidizing gas or a reducing gas. 4. The method for producing a fine particle catalyst according to claim 1, wherein the reaction product obtained by passing through the atmospheric pressure plasma space is collected by precipitation in an aqueous solution. A fine aqueous solution dropping means for making an aqueous solution of a catalyst component containing a catalytically active component and / or a carrier component into fine droplets;
Means for generating atmospheric pressure plasma by microwaves in the order of gigahertz;
Means for introducing the droplets into the atmospheric pressure plasma space with an inert gas;
An apparatus for producing a particulate catalyst, comprising: a particulate catalyst collecting means for collecting the produced reaction product in an aqueous solution.