JP2528701B2 - Method for producing thermally conductive catalyst body - Google Patents

Description

The present invention relates to a method for producing a catalyst body having thermal conductivity,
In particular, the present invention relates to a method for producing a heat conductive catalyst body suitable for effectively utilizing reaction heat by exchanging heat through the catalyst body.

<< Prior Art >> Since the catalytic activity depends on the surface area of the catalyst, it has been conventionally practiced to make the catalyst ultrafine particles or to increase the surface area of the catalyst carrier. From this perspective,
Usually, the shape of the catalyst is powdery or granular, but with the recent proposal of a heat conduction type catalyst body (Japanese Patent Laid-Open No. 4738785), it is proposed to use the wall of the reactor as the catalyst surface (actually). Wish sho 59-17
No. 0459, Shokai No. 63-16835), and attempts have been made to effectively utilize the heat of reaction as much as possible ("Raney-type catalytic reaction element" surface, Vol. 24, 143-153 (19).
(86 years))).

<< Problems to be Solved by the Invention >> However, in order for the heat conduction type catalyst to exert its function of heat conduction, the catalyst is supported on the plane of a heat conductive carrier having a plane shape capable of forming a reaction wall. Therefore, the surface area as a catalyst becomes remarkably smaller than that of powdery or granular ones, which is inevitable as a catalyst.

As a catalyst body for solving such a drawback, we have formed a porous alumina layer on the surface of a metal having an aluminum layer, and then bound fine particles having a catalyst supporting activity to the surface of the porous alumina layer. A catalyst has been developed in which the catalytic activity itself is remarkably enhanced by supporting the catalyst (JP-A-62-137947).

The present inventors, while proceeding with further research on the above catalyst body, when the surface of the porous alumina layer is treated with hot water,
Not only can the BET surface area of the catalyst body be increased, but the step of binding fine particles having a catalyst supporting activity can be omitted by this treatment, and the catalyst can be supported on the surface of the alumina layer simultaneously with the hot water treatment. The inventors have found that the catalytic activity itself is improved when it is allowed to reach the present invention.

Therefore, the first object of the present invention is to provide a simple method for increasing the BET surface area of a catalyst body having a heat conduction function.

A second object of the present invention is to provide a novel method for improving the catalytic activity of a catalyst body having a heat transfer function per weight unit of the catalyst.

<< Means for Solving the Problems >> The above objects of the present invention are to form a porous alumina layer on the aluminum surface of a heat conductive carrier having an aluminum layer of at least 10 μm, and then heat at 50 ° C. to 350 ° C. This is achieved by a method for producing a heat conductive catalyst body, which comprises carrying a metal having catalytic activity on the alumina layer after the water treatment or while performing the hot water treatment.

The heat conductive catalyst body obtained by the method of the present invention comprises a heat conductive carrier on which the catalyst is carried. In this case, the surface on which the catalyst is supported needs to be an alumina surface, but the alumina layer may be at least 5 μm on the surface.

Therefore, as the material of the heat conductive carrier, for example, magnesium, chromium, molybdenum, tungsten, manganese, iron, cobalt, nickel, titanium, zirconium,
By a known method on the surface of a single metal or alloy plate made of vanadium, copper, silver, zinc, bismuth, tin, lead and antimony, a metal plywood obtained by polymerizing a plurality of metal plates or a spongy metal plate It is possible to use an aluminum plate provided with an aluminum layer of 10 μm or more, or an aluminum plate. In particular, iron, copper, or a stainless steel alloy coated with an aluminum layer or aluminum is preferable from the viewpoint of economical efficiency, etc. And a stainless alloy coated with an aluminum layer is preferred.

The method of forming the aluminum layer on the surface of the metal or plywood can be appropriately selected and used from known methods such as non-water plating, pressure bonding (aluminum clad), vapor deposition, and dusting.

As a method for forming a porous alumina layer on the aluminum surface of the thermally conductive carrier, ball roughening, roughening the aluminum surface by a mechanical method such as graining or a chemical method such as etching, and then using a burner or the like. The method may be appropriately selected from known methods such as a method of oxidizing treatment, a method of applying alumina, or an electrochemical method such as anodizing, and the method of anodizing is particularly preferable from the viewpoint of increasing the surface area. Alternatively, a method of anodic oxidation in addition to other methods is preferable.

The technique of this anodic oxidation is well known, and it is also well known to use, for example, a chromic acid aqueous solution, a hydrobromic acid aqueous solution, a sulfuric acid aqueous solution or the like as the treatment liquid. The conditions of anodization are as follows:
The BET surface area can be appropriately set so as to be large, but in the present invention, the temperature of the anodizing treatment solution is preferably room temperature to 50 ° C, particularly 30 to 40 ° C. If the temperature is below room temperature, the surface area will be small. On the other hand, if the temperature exceeds 50 ° C, the dissolution is so severe that it becomes difficult to economically form an oxide film.

The treatment time of this anodic oxidation depends on the treatment conditions. For example, if a 2.5 wt% chromic acid aqueous solution is used as the treatment liquid, the treatment bath temperature is 30 ° C., and the current density is 19.0 A / m ² , it takes 2 hours. It is preferable that the time is at least 4 hours.

The hot water treatment applied to the surface of the heat conductive carrier on which the porous alumina layer is formed as described above is a means of treating the porous alumina surface supporting the catalyst with hot water or steam at 50 to 350 ° C. is there. In this case, if the temperature is lower than 50 ° C, the surface area of the catalyst is insufficient, and if the temperature exceeds 350 ° C, a better effect cannot be obtained, which is not economical.

Furthermore, it is preferable that the pH of the hot water be 7 or more, especially 10 to 12 because the treatment time can be shortened.

The treatment time of hot water treatment varies depending on the pH of hot water,
It is preferably 5 minutes or more, and the BET surface area can be significantly increased by treating for about 2 hours regardless of the pH value.

By the hot water treatment as described above, the BET surface area can be increased about 10 times, so by supporting a metal having catalytic activity on the alumina surface after the hot water treatment, the catalytic ability of the catalyst body can be improved by the hot water treatment. It will be about 10 times that without. Alumina surface after or before hot water treatment
In the case of binding fine particles having a catalyst-supporting activity such as silica and γ-alumina disclosed in No. 62-237947, it is possible to further increase the BET surface area by about 1.7 times as compared with the case of only hot water treatment. You can

Here, the metal having catalytic activity is not particularly limited, for example, platinum group metal, alloy of platinum group metal,
It is preferable to select from gold, gold alloy, manganese, iron, zinc, copper, nickel, nickel alloy, cobalt and cobalt alloy, particularly platinum, palladium, ruthenium,
It is preferably selected from manganese, zinc, iron, nickel, copper and cobalt. It is also possible to combine these catalyst substances.

As a method of supporting a metal having catalytic activity,
The electrodeposition method, the chemical adhesion method, the vacuum deposition method, the cathode sputtering method, the metal spray method, the metal clad method and the like can be appropriately selected and used from among known methods.

Especially when a chemical deposition method is adopted, the hot water treatment and the step of supporting a metal having catalytic activity can be carried out simultaneously, so that the treatment step is not only simplified and preferable, but the reason is not always clear. However, such simultaneous treatment is preferable because the catalyst activity per catalyst weight unit is particularly increased.

By binding the fine particles having the catalyst supporting activity before the hot water treatment, the catalytic activity is maximized. However, in this case, the catalytic activity becomes too high and the selectivity of the reaction deteriorates, which may cause side reactions. Therefore, it is necessary to pay particular attention to the catalyst to be used, the target reaction, and the like.

That is, for example, in the case of using platinum as a metal having catalytic activity, a hydrothermal treatment in an aqueous solution of chloroplatinic acid is performed after the anodization using a heat conductive carrier to which catalyst supporting active particles are bound, if necessary. Should be done. In this case, the treatment time can be shortened by increasing the concentration of chloroplatinic acid.
The pH is set to a value convenient for supporting a metal having catalytic activity, and the treatment time may be set in consideration of pH, temperature conditions, liquid concentration and the like.

When the catalyst body produced by the method of the present invention is used purely as a catalyst body, it can be used by inserting the catalyst into the reaction tube by simultaneously supporting the catalyst on the front and back sides of the carrier. However, in order to effectively exhibit the function of heat exchange utilizing the function of heat conduction, it is preferable that the catalyst body is at least one wall surface of the reaction tube. By doing so, as disclosed in Japanese Utility Model Publication No. 63-16835,
By supplying the heat generated as a result of the reaction to the raw material gas through the catalyst body, the heat can be effectively utilized for the reaction as well as in a reaction chamber having one surface of the catalyst body as at least one wall. While causing an exothermic reaction, an endothermic reaction may be performed in an adjacent reaction chamber having the other surface as at least one wall, and heat generated by the exothermic reaction may be supplied to the endothermic reaction chamber via the catalytic body. In the former case, it is not necessary to support the catalyst on the surface that comes into contact with the raw material gas, but in the latter case, the catalysts suitable for the desired exothermic reaction and endothermic reaction are respectively supported on the front and back of the catalyst carrier. Let

As described above, the catalyst body obtained according to the present invention can be used in various ways.
The shape may be ribbon, tube, honeycomb, or the like.

At this time, if a spongy metal is used as the catalyst carrier, the heat conductivity of the catalyst carrier is increased, and the catalyst having heat exchange can be made extremely excellent. As the spongy metal, for example, Al, Mo, Cu, Ni-Cu alloy, Mo-Cu-Al.
Examples thereof include alloys.

In the present invention, by selecting the kind of metal having catalytic activity according to the desired reaction, a heat conductive catalyst body that is extremely effective for oxidation reaction, hydrogenation reaction, dehydrogenation reaction, and hydrolysis reaction. Can be obtained.

Further, as shown in FIG. 5, the catalyst carrier according to the present invention has a remarkably higher thermal conductivity than alumina usually used as a catalyst carrier, and is suitable for having a heat exchange function.

<Effects of the Invention> As described in detail above, the catalyst body obtained by the present invention is not only a large BET surface area and excellent in catalytic ability, but also a good heat conductor. It is suitable for effectively utilizing the heat of reaction that was considered to be waste heat. In particular, the thermal efficiency of the chemical heat pump can be remarkably improved by applying it to the partition walls of the exothermic reaction chamber and the endothermic reaction chamber of the chemical heat pump.

<< Examples >> The present invention will be described in more detail with reference to Examples below, but the present invention is not limited thereto.

Example 1 [Demonstration of Effect of Hot Water Treatment] An aluminum plate having a thickness of 0.1 m / m was washed with 20% by weight of sodium hydroxide for 3 minutes, then with water, and then with 30% by weight of nitric acid for 1 hour. , Then washed with water. The thermally conductive carrier treated as described above is treated with a 2.5 wt% chromic acid aqueous solution at a liquid temperature of 30
° C., in the case of performing 6 hours anodic oxidation at a current density of 20A / m ² BE
The T surface area was measured. Furthermore, the heat conductive carrier is 3% by weight.
The BET surface area of the alumina sol solution, which was immersed in the alumina sol solution at room temperature and coated with alumina, which was treated with hot water at 80 ° C for 1 hour in hot water at pH = 10, and those which were performed together were also measured. FIG. 1 shows the results.

As is clear from the results shown in Fig. 1, the alumina coating treatment increased the BET surface area by about 1.4 times, and the hydrothermal treatment increased the BET surface area by about 9 times, compared with the case of only anodization. Showed that the BET surface area increased about 16 times.

Next, a stainless plate having a thickness of 0.4 m / m was non-water-plated with aluminum to a thickness of about 40 μm to obtain a heat conductive carrier. The heat conductive carrier thus obtained was washed with 5% by weight of sodium hydroxide for 5 minutes, then washed with water, then with 30% by weight of nitric acid and further washed with water. The BET of the anodized surface when the thermally conductive carrier pretreated as described above was anodized with 2.5 wt% aqueous chromic acid solution at a liquid temperature of 30 ° C. and a current density of 19.0 A / m ² for 6 hours and 18 hours. The result of measuring the surface area, expressed as BET per heat transfer area, is as shown in FIG.
Also, after anodic oxidation for 2 to 18 hours, pH is 10.8 and 82 ℃.
FIG. 2 also shows the results of measuring the BET surface area after the hot water treatment for 2 hours in hot water in relation to the treatment time of anodization. From the results in FIG. 2, it is clear that the hot water treatment increased the BET surface area by about 7 times as compared with the case where only the anodic oxidation was not performed. It was also found that under the conditions of this anodic oxidation, an anodic oxidation time of about 4 hours was sufficient. The BET surface area of the alumina layer in this case is about 225 m ² / g-
It was Al ₂ O ₃ .

[PH dependence of hot water treatment]

Next, in order to see the effect of pH in hot water treatment, hot water treatment at 82 ° C. for 1 hour (marked with ●) at various pH values was performed using a thermally conductive carrier anodized under the above conditions for 6 hours. The BET surface area was measured after 2 hours (circle). The result is the third
As shown in the figure, it is clear from this result that particularly good results can be obtained when the pH is 7 or more.
The dependence of the BET surface area on the hot water treatment time at 82 ° C. is as shown in FIG. 4, and it was found that the hot water treatment time of 1 hour is sufficient if the pH is 7 or more.

[Preparation of heat conductive catalyst]

After the above anodic oxidation for 6 hours, the thermally conductive carrier treated with hot water at pH 10 and 82 ° C. for 1 hour was treated with 0.5% by weight of chloroplatinic acid of pH 10.
It was immersed in the aqueous solution at room temperature for 1 hour. The characteristics of the obtained catalyst body were as follows.

The reaction rate constant is the oxidation reaction of acetone (200 ° C,
This is the value obtained for the initial concentration of acetone: 600 ppm).

Comparative Example 1. In exactly the same manner as in Example 1 except that hot water treatment was not performed,
A thermally conductive catalyst body was obtained. The various characteristics of the obtained catalyst body are as follows, and it was confirmed that neither the catalyst weight standard rate constant nor the platinum weight standard rate constant was inferior to the case of the present invention of Example 1.

Example 2 A catalyst body was obtained in exactly the same manner as in Example 1 except that the treatment bath of chloroplatinic acid was changed to 82 ° C. The properties of the obtained catalyst body are as follows, and it was found that the performance was improved as compared with the case of Example 1.

Example 3 The performance of the catalyst body obtained in exactly the same manner as in Example 2 except that the hydrothermal treatment was not performed is as shown in the following table.
Even better results were obtained than in the case of. Since immersion in a chloroplatinic acid aqueous solution having a pH of 10 at 82 ° C. is substantially equivalent to hydrothermal treatment, the results of this example show that the catalyst has the highest activity by supporting the catalyst simultaneously with hydrothermal treatment. It demonstrates that a catalyst body can be produced. Although the amount of platinum supported on the catalyst body of this example was substantially the same as that of Examples 1 and 2, since the platinum weight-based rate constant was large, the catalyst was supported simultaneously with the hot water treatment. As a result, it is estimated that the activity of the catalyst situation also increased.

[Brief description of drawings]

FIG. 1 shows anodizing treatment, alumina coating treatment,
It is shown that the BET surface area is increased by the hot water treatment and the combination thereof. Figure 2 shows the BET surface area of the anodized surface and p after the anodization.
It is a graph showing the anodic oxidation time dependence of the BET surface area after H2 hot water treatment at 82 ° C for 2 hours. In the figure, ○ indicates that hot water treatment was performed, and □ indicates that hot water treatment was not performed. FIG. 3 is a graph showing the pH dependence of the BET surface area during hot water treatment. In the figure, ● indicates the case of hot water treatment for 1 hour, and ○ indicates the case of 2 hours. FIG. 4 is a graph showing the dependency of BET surface area on hot water treatment time. FIG. 5 is a graph comparing the thermal conductivity of alumina, aluminum, anodized aluminum, and various carriers obtained by further coating γ-alumina on anodized aluminum.

Claims (3)

(57) [Claims] 1. A porous alumina layer is formed on the aluminum surface of a heat conductive carrier having an aluminum layer of at least 10 μm and then subjected to hot water treatment at 50 ° C. to 350 ° C., or while performing hot water treatment. A method for producing a heat conductive catalyst body, which comprises supporting a metal having catalytic activity on the alumina layer. 2. The method for producing a heat conductive catalyst body according to claim 1, wherein the catalyst-supporting active fine particles are bound on the surface of the porous alumina layer before or after the hot water treatment. 3. The binding of the catalyst-supporting active fine particles is performed on the surface of the porous alumina layer before the hot water treatment.
The method for producing the heat conductive catalyst body described in 1.