JP2003299955A - Catalyst - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for preventing the generation of trouble such that condensed water is stagnated in pores provided to the substrate of a catalyst. <P>SOLUTION: A modified catalyst is manufactured by preparing a ceramic honeycomb at first (step S100), placing the ceramic honeycomb under a vacuum environment (step S110), and charging a filler (step S120). By this method, the pores of the ceramic honeycomb are filled with the filler. Thereafter, the excess filler on the surface of the ceramic honeycomb is removed (step S130), and the filled ceramic honeycomb is dried (step S140). The processes of the steps S110-S140 are repeated several times (step S150), and the filled ceramic honeycomb is baked (step S160). A catalytically active component is supported on the ceramic honeycomb filled with the filler (step S170) to complete a modified catalyst. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a catalyst in which active species are supported on a base material having a predetermined shape.

[0002]

2. Description of the Related Art As a method for producing hydrogen from a reformed fuel such as hydrocarbons or alcohols, a reforming catalyst in which a catalytically active component containing an active species is supported on a ceramic base material having a predetermined shape. Is known (for example, Japanese Patent Laid-Open No. 6-31165). Ceramics is an excellent base material that can be relatively easily molded into an arbitrary shape, and can be used in the shape of, for example, a honeycomb monolith. By making the base material thinner, the performance of the reformer equipped with the reforming catalyst can be made smaller and lighter. Further, by improving the shape of the base material, it is possible to reduce the amount of the catalytically active component supported on the base material.

[0003]

Since ceramics is a porous body having many pores, when ceramics is used as a catalyst base material as described above, the temperature inside the reformer is increased when the reformer is started. When is low, condensed water may enter the pores. When the condensed water enters the pores, when the temperature of the catalyst is about to rise, the condensed water vaporizes to remove heat, so that the temperature rise of the catalyst is suppressed. As described above, if the temperature rise of the catalyst is suppressed, the catalyst activity cannot be sufficiently obtained, and a longer starting time (warming time) is required at the time of starting. Such a problem has been common not only to the reforming catalyst but also to a catalyst in which a catalytically active component is supported on a porous substrate such as ceramics.

The present invention has been made to solve the above-mentioned conventional problems, and provides a technique for preventing condensed water from accumulating in the pores of the base material of the catalyst and causing an inconvenience. The purpose is to

[0005]

Means for Solving the Problems and Actions / Effects Thereof In order to achieve the above object, the present invention is a catalyst for supporting active species on a substrate, wherein the substrate comprises a porous body. ,
The gist is that a predetermined filler is filled in the pores of the porous body.

According to such a catalyst of the present invention, since the pores are filled with the filler in the porous body provided in the base material supporting the active species, the pores are filled when the catalyst temperature decreases. It is possible to prevent condensed water from entering the inside. Therefore, it is possible to prevent the temperature rise of the catalyst from being hindered due to the consumption of heat due to vaporization of the condensed water staying in the pores. As described above, since the temperature rise of the catalyst is not suppressed, the catalyst activity can be sufficiently secured, and the time required for warming up the reactor equipped with the catalyst can be shortened.

In such a catalyst of the present invention, the base material may be provided with a ceramic porous body.

Further, in the catalyst of the present invention, the filler may contain a metal oxide.

At this time, the filler may contain silicon oxide.

In the catalyst of the present invention, the filler may include particles having an average particle size of 0.01 to 0.3 μm.

Alternatively, in the catalyst of the present invention, the catalyst may have an activity of promoting a reaction of producing hydrogen from a predetermined reformed fuel.

The present invention can be implemented in various forms other than those described above. For example, various catalysts such as a shift catalyst and a carbon monoxide selective oxidation catalyst, and a catalyst substrate used for producing such a catalyst. Alternatively, it can be realized in the form of a reactor including such a catalyst or a fuel cell system including a reformer.

[0013]

1 is a process diagram showing a method for producing a reforming catalyst according to an embodiment of the present invention. In the present embodiment, first, a ceramic honeycomb serving as a base material of the catalyst is prepared (step S100). This step S1
As the honeycomb carrier prepared in No. 00, for example, a ceramic monolith such as cordierite can be used.

Next, the ceramic honeycomb is placed in a reduced pressure environment (step S110). That is, the ceramic honeycomb is housed in a predetermined container, and the inside of the container is depressurized using a vacuum pump. Then, the filler is put into the container (step S120). The filler is for filling the pores of the ceramic honeycomb.
As the filler, a sol substance having sufficiently fine particles as a solid component can be used. The particle size of the solid component may be, for example, about 10 nm to 3 μm. In particular, it is preferable to use a filler including particles having an average particle diameter of 10 to 300 nm. As the solid component included in the filler, silica (silicon oxide), zircon (zirconium orthosilicate), or metal oxide such as ferric oxide, titania, alumina, or zirconia can be used. These solid components are dispersed in a dispersion medium such as an organic solvent, water, or another hydrophilic solvent to form a sol. When such a filler is put into the container, the filler is filled in the pores of the ceramic honeycomb. As described above, the filler is a fluid that can be easily filled in the pores of the ceramic honeycomb, and obtains sufficient strength, durability and heat resistance by a predetermined treatment such as drying and firing described later. It is a thing.

When the filler is charged to fill the pores with the filler, the ceramic honeycomb is taken out from the container to remove the excess filler which is not filled and remains on the surface of the ceramic honeycomb ( Step S130). As a method of removing the surplus filler, for example, a method of blowing compressed air onto the honeycomb surface or a method of washing the honeycomb surface with water can be used. In particular, the method using compressed air is advantageous because the operation of removing the filler does not become excessive and the operation of removing the filler can be performed more easily.

After the excess filler is removed, the ceramic honeycomb filled with the filler is dried (step S140) to harden the filler. Then, step S1
The process from 10 to step S140 is repeated several times (step S150) to more sufficiently fill the pores of the ceramic honeycomb with the filler.

After the operation of filling the filling material, the ceramic honeycomb is fired (step S160). When this firing step is performed, the water content of the filler filled in the pores is
Evaporated and removed. Then, a catalytically active component is supported on the fired ceramic honeycomb (step S1).
70), the reforming catalyst is completed.

As the step of supporting the catalytically active component,
A step of forming an oxide layer containing alumina or titania on a ceramic honeycomb and a step of supporting a catalyst active material on the oxide layer may be performed. The oxide layer can be formed by preparing an oxide slurry using an oxide powder such as alumina or titania and a predetermined binder, and coating the ceramic honeycomb with the slurry. The catalyst active material is appropriately selected according to the type of reformed fuel used for the reforming reaction to generate hydrogen. When a hydrocarbon such as natural gas or gasoline is used as the reforming fuel, platinum,
A noble metal such as ruthenium, rhodium, palladium or iridium may be selected. When using methanol as the reforming fuel, a Cu-Zn catalyst can be selected. In order to support the precious metal as the catalyst active material, the ceramic honeycomb having the oxide layer formed thereon may be immersed in a solution containing the salt of the precious metal, and supported by an ion exchange method or an impregnation method. it can. In order to support the Cu-Zn catalyst as a catalyst active material,
The above ceramic honeycomb may be coated with a slurry of Cu—Zn catalyst produced by a coprecipitation method. In the treatment for supporting the catalytically active component, the reforming catalyst is completed by finally drying and calcining.

A reforming catalyst is manufactured according to the manufacturing process of FIG. 1, and this reforming catalyst is assembled in a predetermined container to complete a reformer. FIG. 2 is a schematic diagram showing how the reforming catalyst 12 manufactured according to the manufacturing process of FIG. 1 is assembled to complete the reformer 10. In FIG. 2, a state of the reformer 10 including four reforming catalysts 12 supporting catalytically active components on a ceramic honeycomb whose pores are filled with a filler is shown. As described above, the reformer 10 may include a plurality of ceramic honeycombs instead of a single ceramic honeycomb. The reformer 10 thus assembled with the reforming catalyst 12 operates as a reformer by connecting to the pipe for supplying the reformed fuel and the pipe for discharging the reformed gas obtained by the reforming reaction. It will be possible.

FIG. 3 is an explanatory view schematically showing how the filler is filled in the pores of the ceramic honeycomb. FIG. 3A shows a ceramic honeycomb before filling,
(B) represents the ceramic honeycomb after filling.

As described above, in the reforming catalyst using the ceramic honeycomb as the base material, the pores of the ceramic honeycomb are filled with the filler in advance, so that the pores of the ceramic honeycomb are condensed in the pores when the temperature of the reformer is low. It is possible to prevent water from staying. Therefore, heat is consumed because the condensed water staying in the pores is vaporized, the temperature rise of the reforming catalyst is suppressed, and sufficient catalytic activity cannot be obtained.
Can be prevented. Further, since the temperature rise of the reforming catalyst is not suppressed in this way, the warm-up time can be shortened when starting the reformer.

For example, if the catalyst temperature temporarily or partially drops during the operation of the reformer, condensed water may be generated at a place where the temperature has dropped. Further, at the time of starting the reformer, when the reforming catalyst and the steam are sufficiently heated from the upstream side of the reformer and the reforming catalyst is not sufficiently warmed, Condensed water may form on the reforming catalyst. Even in such a case, if the pores of the catalyst base material are filled with a filler, condensed water is prevented from entering the pores of the catalyst base material, resulting in insufficient catalytic activity. It is possible to prevent the above-mentioned inconvenience that the warm-up time is required to be longer than the above.

In the method of manufacturing the reforming catalyst shown in FIG. 1, the ceramic honeycomb is placed under a reduced pressure environment in step S110, but it may be placed under a pressurized environment. If the bubbles in the pores can be removed so that the filler easily enters the pores of the ceramic honeycomb, the subsequent filling operation can be favorably performed.

Further, in the firing step of step S160 of FIG. 1, it is desirable to set the firing temperature range so that the degree of the filler becoming porous due to the firing can be allowed. The filler containing the above-mentioned oxide may cause porosity depending on the firing temperature, but such porosity is suppressed, and the effect of filling the pores with the filler is sufficiently obtained. (For example, 400 ° C. to 60 ° C.)
0 ° C.) and the firing temperature are set.

The reforming catalyst shown in the above embodiment can be used, for example, in a fuel cell system. If a reformer equipped with the reforming catalyst of the above embodiment is provided in a fuel cell system, and hydrogen produced from a predetermined reformed fuel using this reformer is subjected to an electrochemical reaction in the fuel cell, Good. At that time, if steam and air (oxygen) are supplied to the reformer together with the reformed fuel, the partial oxidation reaction can be allowed to proceed in the reformer together with the steam reforming reaction. By adjusting the amount of air supplied to the reformer, the steam reforming reaction can be promoted by using the heat generated by the partial oxidation reaction while maintaining the inside of the reformer within a desired temperature range.

In such a structure, in addition to the reformer, a carbon monoxide reducing unit is further provided to further reduce the carbon monoxide concentration in the hydrogen-rich gas obtained by the reforming reaction and supply the hydrogen-rich gas to the fuel cell. Is desirable. The carbon monoxide reducing unit may be a shift unit that proceeds a shift reaction that produces hydrogen and carbon dioxide from carbon monoxide and water. Alternatively, it may be a CO selective oxidization unit that advances a carbon monoxide selective oxidation reaction that oxidizes carbon monoxide in preference to hydrogen. Further, hydrogen may be separated from the hydrogen-rich gas obtained by the reforming reaction using a hydrogen separation membrane containing palladium or the like, and supplied to the fuel cell as hydrogen gas having high purity.

As described above, if the reforming catalyst of the embodiment is used in the fuel cell system, the rise of the reforming temperature is prevented due to the condensed water staying in the pores of the ceramic honeycomb. You can prevent it from happening,
The reforming reaction can proceed stably, and the power generation in the fuel cell can be stably performed. Further, since the warm-up time of the reformer can be shortened, the warm-up time of the entire system can be shortened when the fuel cell system is started.

Modification: The present invention is not limited to the above embodiment, but can be carried out in various modes without departing from the scope of the invention.
For example, the following modifications are possible.

Modification 1: In the above embodiment, the ceramic honeycomb is used as the catalyst substrate, but a porous body other than ceramics may be used as the substrate. When using a catalyst base material having a porous body, by filling the pores of the porous body with a filler, the same effect of preventing the inconvenience caused by the retention of condensed water in the pores is obtained. be able to.

Modification 2: The catalyst base material made of a porous material may have a shape other than a honeycomb. For example, the present invention can be applied to the case where a pellet-shaped catalyst base material is used. In such a case, a pellet-like porous body in which the pores are closed with a filler is prepared, and the surface of the pellet is coated with the slurry containing the metal oxide described above, and then the surface is coated. The catalyst active material described above may be supported.

Modified Example 3 In addition to the reforming catalyst, the present invention can be applied to general catalysts in which a catalytically active component is supported on a porous substrate. For example, in the above-described fuel cell system, a shift catalyst that promotes a shift reaction that reduces the carbon monoxide concentration in the reformed gas and a carbon monoxide selective oxidation catalyst that promotes a carbon monoxide selective oxidation reaction are similarly used. It can be manufactured. Alternatively, an exhaust gas purifying catalyst that is mounted on a vehicle to purify exhaust gas may be manufactured by the same method. If applied to the manufacturing process of a catalyst in a usage form involving temperature drop of the catalyst, such as repeating start and stop of the device equipped with the catalyst, it is possible to prevent condensed water from staying inside the catalyst base material and obtain the same effect. You can

[0032]

EXAMPLES A. Manufacturing Process: The method for manufacturing the reforming catalyst according to the embodiment of the present invention will be described below. Here, the state of the catalyst base material before filling the pores with the filler and supporting the catalytically active component was compared between the examples. As an example of the present invention, steps S100 to S16 of the manufacturing process shown in FIG.
Prepared according to 0. First, the manufacturing process of the catalyst base material of Example 1 will be described.

(A-1) Example 1: When manufacturing the catalyst substrate of Example 1, a cordierite monolith was prepared as the ceramic honeycomb used in step S100 of FIG. In step S110, the pressure inside the container accommodating the ceramic honeycomb was reduced to 15 mmHg. In step S120, a mixture of zircon and colloidal silica was used as the filler. The mixing ratio of both is such that the weight ratio of the solid components is 50 wt.
The amount is set to be%. In step S130, the excess filler was removed from the ceramic honeycomb surface using compressed air. The drying process in step S140 is performed at 200 ° C. for 3
It was performed for 0 minutes. Further, as steps corresponding to step S150, steps S110 to S140 described above are performed.
Repeated three times. The firing process of step S160 was performed at 500 ° C. for 60 minutes.

(A-2) Examples 2 to 7: The catalyst base materials of Examples 2 to 7 are the same as the catalyst base material of Example 1 except that different fillers were added in the step S120. Manufactured to. FIG. 4 is a diagram collectively showing the fillers used for producing each catalyst base material of Examples 1 to 7. As shown in FIG. 4, the catalyst base material of Example 2 used a mixture of zircon and colloidal silica as the filler, as in the catalyst base material of Example 1. At that time, the mixing amount of both was such that the weight ratio of the solid components was 75 wt% of zircon and 25 wt% of colloidal silica.

The catalyst base materials of Examples 3 and 4 used a mixture of red iron oxide (mainly ferric oxide) and colloidal silica as a filler. In Example 3, the mixing ratio of the two is such that the weight ratio of the solid components is 50 wt.
%, And colloidal silica 50 wt%. In Example 4, the weight ratio of the solid components was 75% by weight of red iron oxide,
The amount was 25 wt% of colloidal silica.

The catalyst substrates of Examples 5 and 6 used a mixture of titania and colloidal silica as the filler. In Example 5, the mixing ratio of the two is such that the weight ratio of the solid components is 50 wt% of titania and 50 wt.
The amount was set to wt%. In Example 6, the weight ratio of the solid components was such that titania was 75 wt% and colloidal silica was 25 wt.
The amount is set to be%. Further, in the catalyst base material of Example 7, only colloidal silica was used as the filler.

In the production of the catalyst base material of the above example, zircon having an average particle size of 2.8 μm, red iron oxide and titania having an average particle size of 0.35 μm, and colloidal silica having an average particle size of 0.02 μm were used. Using.

B. Performance evaluation of catalyst substrate: Examples 1 to 1 above
7 For each catalyst substrate, the state after filling the pores with the filler was evaluated. The evaluation of the state after filling was carried out by observing the cross section of each catalyst substrate with a scanning electron microscope (SEM). It was observed that the pores of the ceramic honeycomb were blocked by filling the filler with the catalyst base material. Among them, in the catalyst base material of Example 7 using only colloidal silica as the filler, the state in which the pores were closed was the best.

FIG. 5 shows an image obtained by performing SEM analysis on the cross sections of the catalyst base materials of Example 1 and Example 7 as an example of observing how the pores of the ceramic honeycomb are blocked. . FIG. 5 (A) is an image of the catalyst base material of Example 7, and FIG. 5 (B) is an image of the catalyst base material of Example 1. It was observed that the catalyst base material of Example 7 shown in FIG. 5 (A) was more fully filled with the pores of the ceramic honeycomb. Further, as shown in FIG. 5 (B), in the catalyst base material of Example 1 in which the filling property was insufficient as compared with Example 7, the excess filler not used for filling the pores was More remained on the ceramic honeycomb surface.

[Brief description of drawings]

FIG. 1 is a process chart showing a method for producing a reforming catalyst according to an embodiment of the present invention.

FIG. 2 is a reforming catalyst 12 manufactured according to the manufacturing process of FIG.
FIG. 3 is a schematic diagram showing how the reformer 10 is completed by assembling the components.

[Fig. 3] Fig. 3 is an explanatory view schematically showing how a filler is filled in the pores of a ceramic honeycomb.

FIG. 4 is a diagram collectively showing fillers used for producing each catalyst base material of Examples 1 to 7.

FIG. 5 shows the catalyst base materials of Examples 1 and 7.
It is a figure which shows the image obtained by carrying out SEM analysis of the cross section after filling a filler with the inside of a pore.

[Explanation of symbols]

10 ... Reformer 12 ... Reforming catalyst

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masayoshi Taki             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. (72) Inventor Eiji Suzuki             36, Higashiishine, Ichiriyama Town, Kariya City, Aichi Prefecture             Within Wayu Kagaku Co., Ltd. F-term (reference) 4G069 AA02 AA08 BA02A BA02B                       BA04A BA04B BA05A BA05B                       BA13A BA13B BA16A BA16B                       BB04A CC17 CC25 EA19                       FA02 FA03 FB14 FB15 FB18                       FB20

Claims (12)

[Claims] 1. A catalyst for supporting active species on a base material, wherein the base material comprises a porous body, and the pores of the porous body are filled with a predetermined filler. catalyst. 2. The catalyst according to claim 1, wherein The base material is a catalyst including a ceramic porous body. 3. The catalyst according to claim 1 or 2, wherein The filler is a catalyst containing a metal oxide. 4. The catalyst according to claim 3, wherein The filler is a catalyst containing silicon oxide. 5. The catalyst according to claim 1, wherein the filler comprises particles having an average particle size of 0.01 to 0.3 μm. 6. The catalyst according to claim 1, wherein the catalyst has an activity of promoting a reaction of producing hydrogen from a predetermined reformed fuel. 7. A method for producing a catalyst, comprising: (a) preparing a base material made of a porous body; and (b) filling a predetermined filler in the pores of the base material. And (c)
And a step of supporting a catalytic substance containing an active species on the base material filled with the filler. 8. The method for producing a catalyst according to claim 7, wherein the filler contains colloidal silica. 9. The method for producing a catalyst according to claim 7 or 8, wherein the step (b) is a method for producing a catalyst in which the filler is filled under a pressurized condition. 10. The method for producing a catalyst according to claim 7 or 8, wherein the step (b) is a method for producing a catalyst in which the filler is filled under a reduced pressure condition. 11. The method for producing a catalyst according to claim 7, wherein after the step (d), the surplus remaining on the surface of the base material before the step (c). A method for producing a catalyst, which further comprises a step of removing the filler. 12. The method for producing a catalyst according to claim 11, wherein the step (d) uses compressed air to remove the excess filler.