JP2005034777A - Monolithic catalyst - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a monolithic catalyst which has an excellent activity per amount of noble element used in the catalyst and is vehicle-mountable. <P>SOLUTION: The monolithic catalyst has a cover layer formed by covering a monolithic carrier with catalyst active powder having at least noble metal element and carrier. Therein, when the concentration of noble metal element in the catalyst active powder is x wt.% and the cover amount of the catalyst active powder per monolithic carrier 1L is y g/L, x/y is >0 and ≤0.05. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a monolith catalyst, and more particularly to a shift catalyst having an activity of promoting a shift reaction for generating hydrogen and carbon dioxide from carbon monoxide and water vapor, and a fuel cell system equipped with the catalyst.

  Hydrogen-oxygen fuel cells are classified into various types depending on the type of electrolyte, the type of electrode, etc., and representative types include alkaline type, phosphoric acid type, molten carbonate type, solid electrolyte type, and solid polymer type. is there. Among them, a polymer electrolyte fuel cell that can operate at a low temperature (usually 100 ° C. or less) attracts attention, and in recent years, development and practical application as a low-pollution power source for automobiles has been advanced.

  In the polymer electrolyte fuel cell, it is most preferable in terms of energy efficiency to use pure hydrogen as a fuel source. However, at the present stage, in consideration of safety and infrastructure, etc., a method of using methanol, natural gas, gasoline, etc. as a fuel source and using these as hydrogen-rich reformed gas in the reformer is being sought. . However, for example, when methanol is used as a raw material, a methanol reforming reaction represented by the following formula (2)

Carbon monoxide is generated by this, and this CO acts as a catalyst poison for the platinum-based catalyst of the electrode of the fuel cell. For this reason, it is necessary to convert this CO into CO ₂ which is harmless to the platinum electrode catalyst, and the shift reaction represented by the following formula (1)

Is used to reduce the CO concentration contained in the reformed gas to about 1% by volume.

  Conventionally, Cu catalysts such as a Cu / Zn-based catalyst, a Cu / Zn / Al-based catalyst, and a Cu / Cr-based catalyst have been used as the shift catalyst for promoting the shift reaction. Here, for example, when the amount of hydrogen-rich gas supplied to the shift reaction increases rapidly, the amount of water vapor required to reduce the increased CO in the hydrogen-rich gas by the shift reaction also increases at the same time. In some cases, the necessary water vapor could not be sufficiently supplied, and the shift reaction did not proceed sufficiently.

  In order to solve this problem, for example, Patent Document 1 discloses a shift reaction catalyst comprising a catalytic metal having an activity for promoting a shift reaction and a water vapor adsorbing substance capable of adsorbing water vapor. Yes. According to the catalyst of Reference 1, when the water vapor partial pressure around the water vapor adsorbing material is low compared to the equilibrium state, the water vapor adsorbing material releases water vapor, and this water vapor is used to perform a shift reaction. It is said that the shift reaction activity can be maintained sufficiently high even when the amount of water vapor used for the shift reaction is insufficient. In Reference 1, zeolite is exemplified as the water vapor adsorbing substance.

  However, in general, the Cu catalyst has a problem that if the catalyst is not placed in a reducing atmosphere when the operation is stopped, the catalyst itself is oxidized and its activity is lowered. In addition, the CO reduction rate may suddenly decrease as the space velocity SV (Space Velocity) increases.

In order to solve these problems, noble metal catalysts such as Pt / Al ₂ O ₃ have been developed as shift catalysts other than the Cu catalyst. This noble metal-based catalyst has characteristics that heat resistance is higher than that of the Cu catalyst, and a decrease in shift activity when the space velocity SV increases is relatively small. However, the noble metal catalyst has a problem of high cost and low absolute shift activity compared to the Cu catalyst.

  Therefore, as a shift catalyst with improved shift activity, for example, Patent Document 2 discloses that an oxide porous body composed of at least one of titanium oxide, aluminum oxide, zirconium oxide, magnesium oxide, and cerium oxide, platinum, There is disclosed a shift catalyst comprising a predetermined substance having a function of weakening the bonding force between platinum and carbon monoxide by coexisting with the platinum. In the literature 1, the catalyst performance is improved by adding a predetermined substance to change the electronic state of platinum and lowering the electron density, thereby weakening the bonding force between platinum and carbon monoxide. It is presumed that this is partly due. As the predetermined substance, at least one of molybdenum, rhenium, and niobium is exemplified.

Here, in general, in a shift catalyst incorporated and used in a polymer electrolyte fuel cell system or the like for in-vehicle use, the gas flow rate to be processed is large with respect to the catalyst volume, so that the space velocity (GHSV) is at least 10. It is desired to be sufficiently practical under conditions of about 1,000,000 ⁻¹ or more.

  In general, shift catalysts are known in the form of a pellet catalyst in which pellets carrying the catalyst are filled in a predetermined container, and a monolith catalyst in which a catalyst composition containing the catalyst is coated on a monolith support such as a honeycomb. It has been. In view of the above space velocity conditions, it is known that pellet catalysts generally exhibit superior performance compared to monolith catalysts.

On the other hand, for example, in the case of an on-vehicle shift catalyst, the risk of abrasion and crushing during vibration is great in the form of pellet catalyst, whereas in the form of monolith catalyst, these risks are low. Can be eliminated. Further, by adopting a monolithic catalyst form, the catalyst filling part of the shift reactor can be easily filled with the catalyst, and the hydrogen-rich gas permeability can be ensured by its structure. In addition, when the hydrogen-rich gas is supplied, the catalyst can be prevented from being heated and calcined, and the catalyst life and catalyst activity can be improved. Therefore, in consideration of conditions when the vehicle is mounted, a monolithic catalyst is preferable as the shift catalyst.
JP 2002-66326 A JP 2002-273227 A

Here, for example, in the shift catalyst of honeycomb form according to the literature 2, is superior to the CO reduction performance at very low space velocity conditions as 3,600H ^-1, high space velocities, e.g. 10,000 h ^-1 or more The CO reduction performance under the conditions is not described and is not clear.

As described above, a noble metal-based shift catalyst supported on a monolith support that can be used under a high space velocity condition of, for example, 10,000 h ⁻¹ or more is desired, but has not yet been developed. It is.

  Therefore, the present invention has been made in view of the above points, and an object thereof is to provide a monolith catalyst excellent in activity per noble metal element amount used in the catalyst, particularly a monolith-supported noble metal shift catalyst that can be mounted on a vehicle. It is what.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have obtained a catalytically active powder having a lower noble metal element concentration than before when coating the catalytically active powder on a monolith support. It has been found that the catalytic activity per the amount of noble metal element used is increased by thick coating. Furthermore, even if it was such a structure, it discovered that it could be used on high space velocity conditions of 10,000 h < ^-1 > or more, and a vehicle-mounted was possible, and completed this invention.

  That is, the present invention has a coating layer obtained by coating a monolithic carrier with a catalytically active powder containing at least a noble metal element and a carrier, the noble metal element concentration in the catalytically active powder is x mass%, and the monolithic carrier 1L The present invention provides a monolith catalyst having a value of x / y of more than 0 and not more than 0.05 when the coating amount of the catalytically active powder per unit is yg / L.

  The present invention also provides a shift catalyst using the monolith catalyst described above, a shift reactor in which the catalyst is disposed, a fuel reforming hydrogen generation system, a fuel cell system or a fuel equipped with the catalyst or the reactor. A reforming fuel cell moving body is provided.

According to the present invention, in a monolith catalyst having a coating layer formed by coating a monolithic carrier with a catalytically active powder containing at least a noble metal element and a carrier, the noble metal element concentration in the catalytically active powder is x mass%, When the amount of the catalytically active powder per liter of monolith support is yg / L, the value per noble metal element used is increased by setting the value of x / y to be larger than 0 and 0.05 or less. . That is, it is possible to effectively use catalytic metal elements, particularly noble metal elements. Moreover, since the shift catalyst of the present invention can be used even under a space velocity condition as high as 10,000 to 100,000 h ^−1, it can be mounted on a vehicle, such as a solid polymer fuel cell system, a vehicle equipped with the system, etc. Can be applied to.

  The first aspect of the present invention has a coating layer formed by coating a monolithic carrier with a catalytically active powder containing at least a noble metal element and a carrier, the noble metal element concentration in the catalytically active powder is x mass%, A monolith catalyst having a value of x / y greater than 0 and 0.05 or less, where the coating amount of the catalytically active powder per liter of support is yg / L.

According to the present invention, the catalytic activity per noble metal element amount to be used is increased by coating the monolith support thickly with a catalytically active powder having a lower noble metal element concentration than in the prior art. Further, when the present invention is used for a shift catalyst, it can be used even under a high source gas space velocity condition of 10,000 h ⁻¹ or more, and is mounted on a device that requires a high space velocity condition such as a vehicle. It becomes possible to do.

  Here, the monolith catalyst of the present invention has a coating layer formed by coating a monolithic carrier with a catalytically active powder containing at least a noble metal element and a carrier, and the concentration of the noble metal element in the catalytically active powder is x mass%, It is characterized in that the value of x / y is larger than 0 and 0.05 or less when the coating amount of the catalytically active powder per liter of the monolith support is yg / L. Preferably, the value of x / y is 0.0001 to 0.01.

First, the catalytically active powder only needs to contain at least a noble metal element and a carrier, and the other components are not particularly limited. Here, the noble metal element contained in the catalytically active powder is not particularly limited, and an element conventionally used as a catalytically active metal can be used. Here, the noble metal element concentration (the “x mass%”) in the catalytically active powder is preferably 0.01 to 2 mass%, more preferably 0.1 to 2 mass%, and particularly preferably 0 in terms of metal. .25 to 2% by mass. Particularly remarkable catalytic activity can be obtained when the content of the noble metal element is 0.01% by mass or more. On the other hand, when the content is 2% by mass or less, a good balance with other components is obtained, an excellent catalytic activity is obtained, and the cost is low. Further, the surface area occupied by the noble metal element can be maintained well during the reaction, and the production of CH ₄ and the consumption of H ₂ to be obtained are prevented. In addition, when using together 2 or more types of noble metal elements, it calculates with the total amount. In addition, as the carrier contained in the catalytically active powder, those generally used as catalyst carriers can be preferably used. Preferably, the carrier is an oxide carrier, more preferably the oxide carrier is heat stable. This is because when a thermally unstable component is contained, it collapses during the catalytic reaction and is inappropriate as a catalyst. Examples of the heat-stable oxide carrier include zirconium oxide (ZrO ₂ ), cerium oxide (CeO ₂ ), uranium oxide (UO ₂ ), thorium oxide (ThO ₂ ), and aluminum oxide (Al ₂ O _3). ), Calcium oxide (CaO), magnesium oxide (MgO), beryllium oxide (BeO), silicon oxide (SiO ₂ ), niobium oxide (Nb ₂ O), iron (III) oxide (Fe ₂ O ₃ ), manganese oxide ( Examples thereof include oxides such as MnO ₂ ) diphosphorus pentoxide (P ₂ O ₅ ) and divanadium pentoxide (V ₂ O ₅ ), and nitrides and composite oxides thereof. Here, one of these may be used alone, but two or more may be used in combination. The BET specific surface area of the carrier is preferably 40 m ² / g or more, more preferably 60 m ² / g or more, and particularly preferably 80 m ² / g or more. In addition, when using 2 or more types of support | carriers together, it calculates with the total amount.

  Furthermore, the coating amount of the catalytically active powder per liter of monolith support (the “yg / L”) is preferably 40 to 500 g / L. When the coating amount is 40 g / L or more, the catalyst activity is excellent. On the other hand, when the coating amount is 500 g / L or less, the ventilation resistance in the catalyst is kept low, clogging on the honeycomb carrier is suppressed, and the production is easy.

  Here, the catalytically active powder may contain various other metal elements in addition to the noble metal element. However, the catalytically active powder may be a cerium element and / or a group 4 or group in the periodic table. It preferably contains an element belonging to Group 5 (also referred to as “Group 4 or Group 5 element” in this specification). More preferably, the catalytically active powder contains both a cerium element and a Group 4 or Group 5 element in addition to a noble metal element. As will be described later, the inclusion of these elements results in excellent catalytic performance when the monolith catalyst of the present invention is used as a shift catalyst. Furthermore, in the present invention, the noble metal element contained in the catalytically active powder is preferably one or more elements selected from the group consisting of platinum, rhodium, palladium, ruthenium, iridium and osmium elements. Examples of the Group 4 or Group 5 element include titanium, zirconium, vanadium, niobium and tantalum elements. Among these elements, one kind may be used alone, or two or more kinds may be used in combination. Here, the noble metal element is particularly preferably a platinum element, and the Group 4 or Group 5 element is preferably a niobium element. By containing these elements, the monolith catalyst of the present invention is particularly excellent in catalytic activity when used as a shift catalyst.

  The monolith carrier is not particularly limited and conventionally known ones can be used. Examples thereof include metal honeycombs, ceramic honeycombs, metal foams, ceramic foams, and the like.

  Here, the present invention forms a coating layer by coating a catalytically active powder having a low noble metal element concentration compared to the conventional one thicker than the conventional one, regardless of the amount of noble metal element used at the same level as before. It is characterized in that high shift activity can be obtained. Therefore, the thickness of the thinnest portion of the coating layer of the catalytically active powder is preferably 0.1 to 0.5 mm.

  In the monolith catalyst of the present invention, the coating layer is not limited to only one layer, and may have two or more layers. Here, for example, when the monolith catalyst of the present invention has n coating layers, it is referred to as the first layer to the n-th layer from the side closer to the monolith support surface, and the first layer is the bottom layer. . Further, in this case, adjacent layers having the same composition are counted as one layer. At this time, each coating layer is not particularly limited as long as it has the same characteristics as the above-described coating layer, for example, the concentration of the noble metal element in the coating layer. About the noble metal element density | concentration in each said coating layer, it is preferable that this density | concentration is always increasing or it is always decreasing as it goes from a lower layer to an upper layer. Here, in the adjacent coating layers, when the composition other than the noble metal element concentration is different but the noble metal element concentration is equal, it is included in the “increase” or “decrease”.

That is, according to one preferable aspect of the present invention, the monolith catalyst of the present invention has n coating layers (n ≧ 2), and the noble metal element concentration in the kth layer is C _k mass%. Always when

It is preferable that Thus, there are the following advantages when the concentration of the noble metal element in the coating layer is constantly increasing from the lower layer to the upper layer. That is, in general, in a monolith catalyst, the catalytically active powder is easily thickly coated on the corner portion of the monolith support during coating, and a catalytic metal element, particularly a noble metal element, existing deep in the coating layer of the corner portion is effective. There is a problem that the catalytic activity per amount of noble metal element used is lowered and the cost is increased. However, according to the above aspect, the above problem can be solved by reducing the amount of the noble metal element contained in the lower layer.

On the other hand, according to another preferred embodiment of the present invention, the monolith catalyst of the present invention has n coating layers (n ≧ 2), and the noble metal element concentration in the k-th layer is C _k mass%. Always when

It is preferable that In this way, when the concentration of the noble metal element in the coating layer is constantly decreasing from the lower layer to the upper layer, there are the following advantages. That is, in general, when a monolith catalyst is used, heat easily dissipates from the surface of the coating layer formed on the monolith support when the raw material gas passes through the monolith, and accordingly, the temperature around the noble metal element decreases. The catalytic activity may be reduced. On the other hand, if the amount of the noble metal element contained in the upper layer is reduced as in the above embodiment, the heat radiation from the coating layer is suppressed by the upper coating layer, so that the periphery of the noble metal element is maintained at a high temperature and the catalytic activity is increased. Therefore, it is possible to prevent the decrease.

  It does not specifically limit as a method to manufacture the monolith catalyst of this invention, A conventionally well-known method can be used. For example, a composition containing a precious metal element, a carrier and other necessary additives is calcined and pulverized in advance to prepare a catalytically active powder. After adding water and necessary additives to this, stirring and pulverizing are performed to obtain catalytic activity. It can be produced by preparing a powder slurry, coating this onto a monolith carrier to form a coating layer, and drying and firing the monolith carrier.

  The second of the present invention is a shift catalyst having an activity of promoting the shift reaction represented by the following formula (1),

This is a shift catalyst using the monolith catalyst of the present invention. Hereinafter, embodiments in which the monolith catalyst of the present invention is applied to a shift catalyst will be described in detail, but the present invention is not limited to the following embodiments.

  First, the shift reaction for producing hydrogen and carbon dioxide from carbon monoxide and water vapor can be understood by being decomposed into the following formulas (i) and (ii).

Here, if the active oxygen (O) generated simultaneously when H ₂ is generated from H ₂ O by the reaction represented by the above formula (i) moves to the oxidation active point on the catalyst metal that oxidizes CO, The oxidation reaction represented by formula (ii) also proceeds efficiently. Therefore, in order in the shift catalyst of the present invention to proceed efficiently shift reaction represented by the formula (1), the active species which can be taken out of H ₂ from the H _{2 O} in the catalyst layer (A), the CO It is preferable that an active species (B) having an oxidizing ability and an active species (C) having an excellent oxygen carrying ability are present. Due to the presence of the three active species, a catalyst having excellent shift reactivity can be obtained even at low temperatures. Here, if the active species (A), (B) and (C) are present in the catalyst, H ₂ can be produced from gaseous H ₂ O, and the dispersion of these components in the catalyst It doesn't matter about sex. This is because even when the active species (A) and (B) are not adjacent to each other, the active oxygen (O) is transported through the active species (C), and a smooth reaction can be ensured. In addition, the presence of the active species (A) exhibits excellent CO conversion even at a low temperature of 300 ° C. unlike conventional catalysts, and the above mechanism promotes water and CO adsorption.

  In the present invention, the noble metal element is the active species (B). Therefore, when the monolith catalyst of the present invention is used as a shift catalyst, it is preferable that the active species (A) and (C) are further present in the coating layer in addition to the noble metal element. Here, examples of the active species of (A) include the Group 4 or Group 5 elements. Moreover, a cerium element is illustrated as an active species of (C). As described above, in the shift catalyst of the present invention, platinum element is particularly preferable as the noble metal element contained in the catalytically active powder forming the coating layer, and niobium as the Group 4 or Group 5 element. Elements are particularly preferred. This is because when these elements are present in the catalyst layer, a high CO conversion rate is obtained, and when a platinum element is present, an effect of suppressing a methane formation reaction as a side reaction is also obtained.

  In the monolith catalyst of the present invention, when the catalytically active powder contains a cerium element, the content of the cerium element in the catalytically active powder is preferably 5 to 95 mol%, more preferably 30 to 90, in terms of metal. Mol%. Sufficient catalytic activity is obtained when the content of the cerium element is 5 mol% or more. On the other hand, at 95 mol% or less, a good balance with other components and excellent catalytic activity can be obtained.

  Furthermore, in the monolith catalyst of the present invention, when the catalytically active powder contains a Group 4 or Group 5 element, the content of the Group 4 or Group 5 element in the catalytically active powder is preferably in terms of metal. 5 to 50 mol%. Sufficient catalytic activity can be obtained when the content of the Group 4 or Group 5 element is 5 mol% or more. On the other hand, at 50 mol% or less, a good balance with other components and excellent catalytic activity can be obtained. In addition, when using together 2 or more types of elements, it calculates with the total amount.

  Here, conventionally, as the monolith-supported shift catalyst having the active species (A), (B) and (C), for example, zirconium oxide which is a raw material of the active species (A), and a raw material of the active species (C) A shift catalyst is known in which a cerium oxide is mixed to form a slurry, a monolith substrate is coated with the slurry, dried and fired, and then a platinum element as an active species (B) is supported on the coating layer. It has been. However, in the shift catalyst, the active species (A), (B) and (C) are close to each other and can act in cooperation in the vicinity of the surface of the coating layer on which platinum element is supported. Therefore, it is presumed that shift activity decreases under high space velocity conditions. On the other hand, in the shift catalyst of the present invention, the active species (A), (B) and (C) are uniformly present in the catalytically active powder forming the coating layer. For this reason, it is considered that the active species can work in cooperation not only on the surface of the coating layer but also on the entire coating layer, and a high shift activity can be maintained even under high space velocity conditions.

  When the monolith catalyst of the present invention is applied to a shift catalyst, the coating layer of the monolith catalyst can contain various components in addition to the above for the purpose of enhancing the shift activity. For example, as described in Japanese Patent Application Laid-Open No. 2002-273227, a substance having a function of weakening the bonding force between a noble metal element and carbon monoxide, such as molybdenum and a rhenium element, may be further included. By containing these metals, the shift activity can be further improved.

In the present invention, the catalytically active powder forming the coating layer contains a noble metal element such as platinum, rhodium, palladium, ruthenium, iridium and osmium elements. Examples of the raw material compound used for containing the noble metal element include dinitrodiamine platinum and platinum chloride as the raw material compound of platinum element, and dinitrodiamine platinum is particularly preferable. This is because the dispersibility in the catalytically active powder is excellent. In addition, in order to use chloride, when manufacturing a catalyst industrially on a large scale, it is necessary to consider air pollution due to the calcined exhaust gas, and chlorine corrosion of the exhaust pipe has a great adverse effect. Similarly, as a raw material compound such as rhodium, palladium, ruthenium, iridium and osmium, nitrates, ammonium salts and the like are preferably used. The cerium element material compound is preferably cerium oxide or a cerium-zirconium composite oxide. This is because these compounds are compounds having a redox ability capable of moving oxygen atoms in the crystal, so that the use of these compounds can suppress the so-called methanation reaction that consumes H ₂ generated in the shift reaction. Furthermore, as a raw material compound of Group 4 or Group 5 elements such as titanium, zirconium, vanadium, niobium and tantalum elements, cerium oxide, zirconium oxide, titanium oxide, niobium oxide and divanadium pentoxide, and nitrides thereof Examples of the compound used as a carrier in the present invention, such as complex oxides. Among them, a compound used as a carrier in the present invention is preferably used in terms of easy production, and cerium-zirconium composite oxide is particularly preferably used for the above reasons.

By storing the shift catalyst of the present invention in a reaction vessel and allowing the reformed gas to flow into the vessel, CO contained in the reformed gas can be efficiently converted to CO ₂ . That is, it can be used as a shift reactor. Moreover, it can be set as a shift reactor also by using directly the shift catalyst of this invention which is a monolith catalyst, without using such a reaction container. That is, the third of the present invention is a reactor for performing a shift reaction represented by the following formula (1),

It is the shift reactor by which the shift catalyst of this invention is arrange | positioned. As described above, since the shift catalyst of the present invention is excellent in CO conversion even when used at a space velocity of 10,000 h ⁻¹ or more, the shift reactor can be miniaturized and is particularly advantageous.

The shift catalyst and shift reactor of the present invention can be mounted and used in a fuel reforming hydrogen generation system, a fuel cell system, or a fuel reforming fuel cell vehicle. FIG. 1 shows a system flow diagram of a fuel reforming hydrogen generation system mounted on a vehicle. Referring to the drawings, first, fuel such as methanol, gasoline, hydrocarbons, etc. is supplied to the fuel tank. The fuel is vaporized in the vaporizer, and if necessary, sulfur contained in the desulfurizer is removed. In the reforming section, the fuel is reformed into a hydrogen-rich reformed gas, usually by steam reforming using steam. Also, a hydrogen-rich reformed gas can be obtained by autothermal reforming in which a gas containing oxygen is simultaneously supplied in addition to water vapor and a partial oxidation reaction is also performed. Next, the reformed gas is sent to the shift unit, and CO contained in the reformed gas is converted to CO ₂ to reduce the CO concentration to about 1% by volume. The reformed gas with the CO concentration reduced to about 1% by volume is subsequently transferred to the CO selective oxidation unit, and the CO concentration is reduced to the ppm order. The reformed gas and oxidant (usually air) whose CO concentration has been reduced to the order of ppm are supplied to the fuel cell to advance the power generation reaction. Note that spent fuel and oxidant are discharged from the fuel cell. The fuel reforming hydrogen generation system preferably further includes a hydrogen extractor having a hydrogen separation membrane or the like. This is because the generated hydrogen gas can be easily separated and purified.

  The monolith catalyst of the present invention can exhibit an excellent CO conversion rate when applied to a shift catalyst as described above. By using the shift catalyst having such characteristics for CO conversion in the fuel reformed gas, it is possible to efficiently reduce the CO concentration in the fuel gas supplied to the fuel cell. In particular, since the CO concentration can be reduced to a very low concentration even when the space velocity is high, it can be used effectively even in a moving body such as an automobile in which the mounting range is limited.

  The embodiment of the monolith catalyst of the present invention has been described above by taking the shift catalyst as an example, but the monolith catalyst of the present invention is not limited to this and can be applied to various catalysts.

  Next, the present invention will be described in detail using examples.

Example 1
12. Dinitrodiamine platinum complex salt containing 8.451% by mass of platinum element in terms of metal, using cerium-zirconium composite oxide (BET specific surface area 70 m ² / g) of Ce / Zr = 68/32 (molar ratio) as a carrier. After making 2 g into an aqueous solution having a total liquid volume of 1.0 L, the carrier is added, impregnated with platinum element, sufficiently stirred, dried for one day, and then calcined at 400 ° C. for 1 hour to obtain a catalytically active powder. Got.

  A catalytically active powder slurry was prepared by adding alumina sol (equivalent to 4 g in terms of alumina) as a coating aid to 200 g of the catalytically active powder, and further adding 1.0 L of water and wet grinding. The pulverization is performed for 1 hour using a commercially available ball-type vibration mill. At this time, the average particle diameter is adjusted to 1.0 to 5.0 μm by adjusting the ball diameter, pulverization time, amplitude, and vibration frequency. did. The platinum element content in the catalytically active powder was 0.5% by mass.

  A 0.12 L cordierite honeycomb monolith support (400 cells / inch) was coated with the catalyst active powder slurry prepared above, dried at 200 ° C., and fired at 500 ° C. in air to obtain a shift catalyst. . Here, the coating amount of the catalytically active powder on the monolith support was 24 g (200 g / L), and the content of platinum element in the total volume of the shift catalyst was 1.0 g / L.

Examples 2 and 3
A shift catalyst was prepared by the method described in Example 1 except that the platinum element content and the catalytic active powder coating amount in the catalytically active powder were adjusted to the values shown in Table 1.

Activity test The shift activity test was done about the shift catalyst prepared in the said Examples 1-3.

First, for each 40 mL of the catalyst, a 2% hydrogen-containing nitrogen atmosphere was passed at a space velocity (GHSV) of 30,000 h ⁻¹ , and an activation treatment was performed at 400 ° C. for 1 hour. Next, the catalyst was cooled to 200 ° C. in a nitrogen atmosphere, and the outlet gas was analyzed by gas chromatography while raising the temperature. At this time, the space velocity was 30,000 h ⁻¹ . In all shift catalyst activity tests, the input gas composition was 2.5 / 24/35/15 / 23.5% by volume of CO / H ₂ O / H ₂ / CO ₂ / N ₂ and the reaction The gas flow rate was 20 L / min.

  Using the outlet CO concentration obtained by analyzing the outlet gas, the CO conversion rate was calculated by the following formula. The results are shown in FIG.

As can be seen from Table 1, the shift catalyst of the present invention has a shift activity as high as about 30% at an outlet gas temperature of 300 ° C., for example, despite a very high space velocity condition of 30,000 h ^−1. Indicated.

  As described above, according to the present invention, it is possible to obtain a monolith catalyst that is excellent in activity per amount of noble metal element used in the catalyst and can effectively use the noble metal element.

FIG. 1 is a diagram showing a system flow diagram of a fuel reforming hydrogen generation system mounted on a vehicle. It is a figure which shows the result of having performed the activity test about the shift catalyst of this invention prepared in Examples 1-3.

Claims (14)

  Having a coating layer formed by coating a monolithic carrier with a catalytically active powder containing at least a noble metal element and a carrier, wherein the catalytic activity per liter of the monolithic carrier is set to x% by mass of the noble metal element concentration in the catalytically active powder The monolith catalyst whose value of x / y when the coating amount of powder is set to yg / L is larger than 0 and 0.05 or less.   The monolith catalyst according to claim 1, wherein the value of x is 0.01 to 2.0, and the value of y is 40 to 500.   The monolith catalyst of Claim 1 or 2 whose thickness of the thinnest part among the said coating layers is 0.1-0.5 mm.   The monolith catalyst according to any one of claims 1 to 3, wherein the carrier contained in the catalytically active powder is a heat-stable oxide.   The monolithic catalyst according to claim 4, wherein the catalytically active powder contains a cerium element and a Group 4 or Group 5 element.   The monolith catalyst according to claim 5, wherein the noble metal element contained in the catalytically active powder is one or more selected from the group consisting of platinum, rhodium, palladium, ruthenium, iridium and osmium elements.   The monolith catalyst according to claim 6, wherein the noble metal element is a platinum element.   The monolith catalyst according to claim 5, wherein the Group 4 or Group 5 element is a niobium element. When the coating layer has n layers (n ≧ 2) and the noble metal element concentration in the kth layer is C _k mass%,

The monolith catalyst according to any one of claims 1 to 8, wherein When the coating layer has n layers (n ≧ 2) and the noble metal element concentration in the kth layer is C _k mass%,

The monolith catalyst according to any one of claims 1 to 8, wherein A shift catalyst having an activity of promoting a shift reaction represented by the following formula (1),

The shift catalyst using the monolith catalyst of any one of Claims 1-10. A reactor for performing a shift reaction represented by the following formula (1),

A shift reactor in which the shift catalyst according to claim 11 is arranged.   A fuel reforming type hydrogen generation system, a fuel cell system, or a fuel reforming type fuel cell moving body equipped with the shift catalyst according to claim 11 or the shift reactor according to claim 12.   The fuel reforming type hydrogen generation system, fuel cell system, or fuel reforming type fuel cell moving body according to claim 13, wherein a hydrogen extractor is mounted.

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