JPH1073227A - Manufacture of continuous catalyst body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise a reaction invert ratio sufficiently with a longer life and excellent reaction selectivity. SOLUTION: In a base body having the surface of an alumina layer formed by anodic oxidation, the base body is immersed into a solution containing a silica source and treated at least once using a sol gel method to bake. As a result, at least the surface of the alumina layer is covered with a film of SiO2 to obtain a carrier. In this process, at least in the first treatment, weak acid is made to coexist in a treating bath. Then, a catalyst is supported on the surface of the SiO3 film as carrier obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous catalyst having a continuous catalyst surface, and more particularly to a continuous catalyst which is excellent in reaction selectivity and heat recovery efficiency and is suitable for a chemical heat pipe system.

[0002]

2. Description of the Related Art In order to construct a chemical heat pipe system, efficient heat recovery is essential. Therefore, the present inventors have been developing a tube wall type reactor having an anodized film layer on the surface where a heat transfer surface and a catalyst carrier are integrated (Murata, Yamamoto, Kameyama, Chemical Engineering Transactions, vol.19,
No. 1, 41-49 (1993)). The use of an aluminum molded body having an anodized film layer as a reactor has the advantage that the catalyst metal is not limited and the carrier surface area is large, while the Al ₂ O ₃ carrier formed by anodization is used. The surface has a drawback that a dehydration reaction is caused as a side reaction in, for example, a decomposition reaction of methanol.

[0003] In response to such a drawback, the present inventors have found that when an SiO ₂ film is formed on the surface of an Al ₂ O ₃ carrier formed by anodic oxidation by a sol-gel method, the selectivity of catalytic reaction is reduced. Can be improved, and
It has been found that the selectivity of the catalytic reaction can be maintained by making the silica particles adhered to the Al ₂ O ₃ surface finer, but it is still possible to sufficiently increase the conversion of the desired reaction and to increase the selectivity. It was not satisfactory in keeping it long enough.

[0004]

Accordingly, the present inventors have further studied a long-life continuous catalyst having excellent reaction selectivity. As a result, oxalic acid was contained in the treatment bath when the sol-gel method was used. It has been found that the coexistence of a weak acid such as the above can sufficiently improve the selectivity of the catalytic reaction, the conversion and the catalyst life, and have reached the present invention. Accordingly, an object of the present invention is to provide a method for producing a continuous catalyst body which has a long life, is excellent in reaction selectivity, and can sufficiently increase the reaction conversion.

[0005]

SUMMARY OF THE INVENTION The above objects of the present invention are as follows.
A substrate having an alumina layer surface formed by anodic oxidation is immersed in a solution containing a silica source and then fired.
By treating at least once with gel method, to obtain a carrier at least the surface of the alumina layer is covered with a film of SiO _2, then the manufacturing method of the continuous catalytic body for supporting a catalyst on the SiO ₂ film surface Wherein the sol
At least in the first treatment of the gel method, the present invention has been achieved by a method for producing a continuous catalyst body, which comprises coexisting a weak acid in a treatment bath.

The continuous substrate (hereinafter referred to as the substrate) used in the present invention includes not only aluminum itself but also a substrate having an aluminum layer on its surface at least several μm. Therefore, the substrate in the present invention, for example, magnesium,
Plates of a single metal such as chromium, molybdenum, tungsten, manganese, iron, cobalt, nickel, titanium, zirconium, vanadium, copper, silver, zinc, bismuth, tin, lead and antimony, or alloys thereof, or multiple metal plates Alternatively, a spongy metal plate, a plastic sheet, or the like provided with an aluminum layer of several μm or more by a known method, or an aluminum plate is included.

[0007] In particular, from the viewpoint of economy and the like, those obtained by coating the surface of a substrate made of iron, copper, or a stainless alloy with an aluminum layer or an aluminum substrate are preferable.
It is preferable that the substrate surface of iron or stainless steel is coated with an aluminum layer. The method of forming the aluminum layer on the surface of a metal or alloy can be appropriately selected from known methods such as non-aqueous plating, pressure bonding (aluminum cladding), vapor deposition, and brazing.

[0008] The technique of anodic oxidation is well known, and it is also well known to use, for example, an aqueous solution of chromic acid, an aqueous solution of oxalic acid, an aqueous solution of sulfuric acid, or the like as a processing solution. The anodizing conditions are preferably set as appropriate so that the BET surface area of aluminum is increased. In the present invention, the temperature of the anodizing treatment liquid is preferably 10 to 40 ° C. If the temperature exceeds 40 ° C., the substrate is severely dissolved, and it is difficult to form an oxide film economically. The processing time of this anodization varies depending on the processing conditions. For example, when an oxalic acid aqueous solution is used as the processing liquid, the processing liquid temperature is 20 ° C., and the current density is 50 A / m ² , the processing time is 2 hours or more, particularly 4 hours or more. It is preferable that The thickness of the anodic oxide film is preferably 25 to 150 μm. If the thickness is less than 25 μm, even if the sol-gel method is repeated, the silica cannot be coated with a sufficient thickness, so that the life of the catalyst body cannot be made sufficient.

In the present invention, the alumina surface formed as described above is further treated at 10 to 80 ° C., preferably at 20 ° C.
The hydration treatment may be carried out with water or warm water at ５０50 ° C.
Incidentally, the pH of the hydration-treated water is usually around 7. The processing time of the above processing is preferably from 5 minutes to 120 minutes from the viewpoint of production efficiency.

When the above processing is performed, 30
Bake at 0-550 ° C. By this firing, the surface of the substrate after the treatment becomes a γ-alumina layer to which the silica particles can firmly adhere. If the sintering temperature is lower than 300 ° C., the formation of the γ-alumina layer is insufficient. The firing time is 10 minutes to 5 hours, preferably 1 to 5 hours.
3 hours.

In the present invention, at least one step of immersing the substrate having the anodic oxide film, which has been subjected to the above-mentioned hydration treatment and calcination as necessary, in a solution containing a silica source, followed by drying and calcination is included. Implement once. By repeating this step, the thickness of the silica layer on the alumina layer can be increased. The silica source in this case can be appropriately selected from known ones used in the sol-gel method, such as colloidal silica.

In the present invention, in order to form a silica surface even inside the alumina layer to improve the reaction conversion rate and extend the life of the catalyst body, ethyl orthosilicate (TEOS) is used. It is also preferable to use a silica alkoxide capable of forming a film with such fine silica particles. In the case of the above TEOS, ethylene glycol (EG) is used as a dispersion medium. However, when a silica source that sufficiently disperses into fine particles as an aqueous solution is used, water can be used as a dispersion medium.

When a silica sol is used as a silica source, the pH of the treatment solution is adjusted to 1 to 4, the concentration of the silica sol is adjusted to 10 to 50% by weight,
It is preferable to perform time treatment. On the other hand, when a silica alkoxide is used as a silica source, the pH of the treatment liquid is set to 4 to 6, and the concentration of the silica alkoxide is set to 10 to 10.
The treatment is preferably performed at 10 to 40 ° C. for 6 to 72 hours. In this solution, for example, Mg
It is preferable to contain a salt of an alkali metal and / or an alkaline earth metal such as Cl ₂ in the range of 0.1 to 1% by weight.

In the present invention, in order to make the effect of the sol-gel method sufficient, at least in the first treatment bath of the sol-gel method, a weak acid such as an organic acid or carbonic acid or MgC is added.
It is contained l ₂ · 6H ₂ metal salt of O, and the like. Examples of the organic acid include oxalic acid, acetic acid, an aliphatic or aromatic carboxylic acid, and it is particularly preferable to use oxalic acid. The amount of the weak acid to be contained is preferably from 1 to 20% by weight, particularly preferably from 3 to 10% by weight.

In the present invention, the desired continuous catalyst can be obtained by supporting the catalyst on the SiO ₂ surface of the substrate carrier prepared as described above by a known impregnation method or an electrodeposition method. The catalyst concentration in the treatment liquid in the impregnation method is not particularly limited, but is preferably in the range of 0.5 mmol / L to 5 mmol / L. If the concentration is too high, it will be uneconomical, and if it is too low, the required processing time will be long.

Although the catalyst used in the present invention is not particularly limited, for example, platinum group metals, alloys of platinum group metals,
Gold, gold alloys, palladium, rhodium, rhenium, manganese, iron, zinc, copper, nickel, nickel alloys, cobalt, cobalt alloys, ruthenium and ruthenium alloys, preferably selected from tin and the like, especially platinum, palladium, It is preferred to select from rhodium, manganese, zinc, iron, nickel and cobalt. Further, these catalyst substances can be combined, and salts of the above metals,
Alternatively, the above metal fine particles can be used alone or in combination.

In addition to using the continuous catalyst of the present invention as a mere catalyst, for example, by having a heat exchange function and using it as a wall of a reaction chamber, the reaction heat can be directly extracted to the outside. Therefore, various usage methods such as a chemical heat pipe system are possible. Also,
Depending on the method of use, the shape can be a plate, a ribbon, a tube, a honeycomb, or the like. Also, by selecting the type of metal having catalytic activity according to the desired reaction,
It is extremely effective for oxidation reaction, hydrogenation reaction, dehydrogenation reaction, hydrolysis reaction and the like. For example, when a catalyst obtained by the present invention is used, a decomposition reaction of a low-concentration organic substance can be efficiently performed as described in Examples below.

[0018]

DETAILED DESCRIPTION OF THE INVENTION The present invention uses a sol-gel method in which an alumina layer is provided on the surface of a substrate having an anodizable surface by anodic oxidation, and then immersed in a solution containing a silica source and then fired. Process at least once. In this case, a weak acid such as oxalic acid coexists in at least the first treatment bath. Thus, to obtain a carrier at least the surface of the alumina layer is covered with a film of SiO _2, then it carried out by supporting the catalyst on the SiO ₂ film surface.

[0019]

The continuous catalyst obtained according to the present invention is
Not only good reaction selectivity but also high reaction conversion and long life are suitable for use in chemical heat pipes and the like.

[0020]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto. Embodiment 1 FIG. Aluminum substrate (JISA1050: thickness 0.3
mm) was anodized (current density: 50 A / m ² ) in a 4% by weight aqueous solution of oxalic acid (20 ° C.) to give a thickness of 100 μm.
(Al ₂ O ₃ ) layer was formed.

The obtained substrate was immersed in about 300 ml of silica sol (48%) to which 12.5 g of oxalic acid was added.
The resultant was baked at 00 ° C. to obtain a substrate carrier having an alumina layer surface provided with a SiO ₂ film. Then, contains pd of 1.0 g / liter, pH is dried after being immersed for 25 hours in a solution of 25 ° C. at 11, the Pd on the SiO ₂ 0.7 g /
m ^{2 was} supported to produce a continuous catalyst A.

[0022]

Comparative Example 1 A continuous catalyst B for comparison was obtained in exactly the same manner as in Example 1 except that oxalic acid was not used in the sol-gel method.

The cut continuous catalyst A and C to the ^second corner 8mm respectively, diluted with quartz sand, 300 ° C., a partial pressure 0.1,
At a space velocity (SV) of about 1,000 h ^-1 , the results of a methanol decomposition reaction performed using each catalyst were as shown in FIG. The results in FIG. 1 proved that it is effective to add an acid during the sol-gel process.

[Brief description of the drawings]

FIG. 1 is a graph showing respective conversion rates and reaction selectivities when a methanol decomposition reaction is carried out using continuous catalysts A and B.

Claims (5)

[Claims] 1. A substrate having an alumina layer surface formed by anodic oxidation is immersed in a solution containing a silica source and then baked at least once using a sol-gel method, whereby at least the alumina layer is treated. Surface is SiO
_2. A method for producing a continuous catalyst body in which a carrier is obtained by coating with a film of No. ₂ and then a catalyst is supported on the surface of the SiO ₂ film, wherein at least the first treatment of the sol-gel method comprises the steps of: And a method for producing a continuous catalyst. 2. The method for producing a continuous catalyst according to claim 1, wherein the weak acid is oxalic acid. 3. The method for producing a continuous catalyst according to claim 1, wherein the thickness of the alumina layer formed by anodic oxidation is 25 to 150 μm. 4. The continuous catalyst according to claim 1, wherein at least one of the treatments by the sol-gel method is a treatment with ethyl orthosilicate fine particles dispersed in ethylene glycol. Production method. 5. The method according to claim 1, wherein before the treatment by the sol-gel method, the surface of the alumina layer is subjected to hydration treatment using water at room temperature to 80 ° C., and then calcined at 350 ° C. to 550 ° C. A method for producing a continuous catalyst body according to any one of the above.