JPH04200745A - Production of continuous catalyst body and oxidation of low concentration organic matter using the same - Google Patents

Abstract

PURPOSE:To obtain a highly active continuous catalyst body with good reproducibility by a method wherein a metal having A>= oxide on the surface thereof is treated with hot water and, after drying, the treated metal is baked at a specific temp. and a catalyst is subsequently supported on the baked one. CONSTITUTION:An alumina layer is formed to the surface of a continuous substrate having an AR layer of at least several mum on the surface thereof and this substrate is subsequently treated with hot water at 40-350 deg.C. After hot water treatment or simultaneously with this treatment, a metal (e.g., platinum group metal, gold, Pd or Ni) having calalytic activity is supported on the alumina layer. At this time, the treated substrate is dried after hot water treatment and subsequently baked at 400-500 deg.C. As a result, a continuous catalyst body having stable and high catalytic activity can be obtained with good reproducibility.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a continuous catalyst body, and more particularly to a method for manufacturing a continuous catalyst body in which an ultrafine particle catalyst is supported on the surface of a continuous carrier having an alumina surface, and a method for oxidizing low-concentration organic substances using the catalyst body obtained thereby. .

[Conventional technology]

Since the catalytic activity depends on the surface size of the catalyst, conventional methods have been to make the catalyst into ultrafine particles or to increase the surface area of the catalyst carrier. From this point of view, usually
The shape of the catalyst is powder or granular, but with the recent proposal of a thermally conductive catalyst (Japanese Unexamined Patent Publication No. 47-38785), a proposal was made to use the wall of the reactor as the catalyst surface (Japanese Unexamined Patent Publication No. 47-38785). 63-
16835), and attempts have been made to utilize the reaction heat as effectively as possible.
986)). However, in order to perform its heat conduction function, a thermally conductive catalyst has a catalyst supported on the surface of a thermally conductive carrier having a planar shape that can form a reaction wall. The surface area is significantly smaller than that of powder or granules, which is disadvantageous as a catalyst. These drawbacks can be solved by roughening the metal surface, binding fine particles with catalyst-supporting activity to the surface, and then supporting ultrafine catalyst particles (particularly in catalyst bodies) that have significantly increased catalytic activity. 1982-237947), and furthermore, a method of increasing the BET surface area of the catalyst by hydrothermal treatment of a metal having aluminum oxide on the surface, and a method of increasing the BET surface area of the catalyst by hydrothermal treatment of a metal having aluminum oxide on the surface; A method of improving the catalytic activity itself by supporting the catalyst on the surface of the layer has also been proposed (Japanese Patent Laid-Open No. 2-14
No. 4154). However, there is a drawback that the catalytic activity of the continuous catalyst bodies produced by the above-mentioned production method varies.

[Question B that the invention attempts to solve]

Therefore, the present inventors conducted intensive studies to obtain a highly active continuous catalyst with good reproducibility, and found that a metal having aluminum oxide on the surface was treated with hot water and then dried.
When the catalyst is supported after calcining at 550°C, a highly active continuous catalyst body can be obtained with good reproducibility, and after being subjected to hydrothermal treatment using an aqueous solution containing the catalyst component, it is dried.
It has been found that particularly good results can be obtained when the material is then fired at a temperature of 400 to 550°C, and the present invention has been achieved. Therefore, an object of the present invention is to provide a method for producing a highly active continuous catalyst body with good reproducibility.

[Means to solve the problem]

The above object of the present invention is to form an alumina layer on the surface of a continuous substrate having an aluminum layer of at least several micrometers on the surface, and then after or simultaneously with the hot water treatment at 40° C. to 350” C. A method for producing a continuous catalyst in which a metal having catalytic activity is supported on the alumina layer, the continuous catalyst comprising a step of drying after the hydrothermal treatment and firing at 400 to 550''C. This was achieved using the manufacturing method. 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 the surface of at least several micrometers. The substrate in this case may be a single metal or metals such as, for example, magnesium, chromium, molybdenum, tungsten, manganese, iron, cobalt, nickel, titanium, zirconium, vanadium, copper, silver, zinc, bismuth, tin, lead and antimony. It is possible to use an alloy plate, a plurality of metal plates, a spongy metal plate, a plastic sheet, etc., on which an aluminum layer of several μm or more is provided on the surface by a known method, or an aluminum plate. From this point of view, it is preferable to use an iron, copper, or stainless alloy substrate whose surface is coated with an aluminum layer, or an aluminum substrate.When considering strength, it is preferable to use an iron or stainless alloy substrate whose surface is coated with an aluminum layer. Methods for forming an aluminum layer on the surface of metals or alloys include non-aqueous plating, pressure bonding (aluminum cladding), vapor deposition,
The method for attaching a dowel can be appropriately selected from known methods such as the following. The aluminum surface of the substrate can be roughened by known methods such as anodic oxidation, ball polishing, etc.
Among these, it is particularly preferable to use the anodic oxidation method for medical purposes. The anodic oxidation technique is well known, and it is also common to use, for example, a chromic acid aqueous solution, an oxalic acid aqueous solution, a sulfuric acid aqueous solution, etc. as a treatment liquid. The conditions for anodizing are preferably set appropriately so that the BET surface area of aluminum is large. In the present invention, it is preferable that the arc of the anodizing solution is between room temperature and 50°C. B
ET surface area becomes smaller. On the other hand, if the temperature exceeds 50°C, the dissolution will be severe and it will be difficult to economically form an oxide film. The processing time for this anodic oxidation varies depending on the processing conditions, but for example, the processing liquid is 2.5% by weight chromic acid aqueous solution, the processing liquid temperature is 30°C, and the current density is 19.5%. OA/m'', the heating time is preferably 2 hours or more, and the heating time is preferably 4 hours or more. Or, it is treated with steam. If it is less than 40°C, the surface area of the final catalyst will be insufficient, while if it exceeds 350°C, it will not be possible to obtain better effects and it will not be economical. The pH of the hot water is preferably 7 or more, especially 10 to 12, in order to shorten the treatment time.The treatment time of the hot water treatment varies depending on the pH of the hot water, but
The treatment time is preferably at least 1 minute, and by treating for about 2 hours, the BET surface area can be significantly increased almost regardless of the pH value. In the present invention, after the above hot water treatment, the temperature is 400 to 550°C.
Fire it with By this calcination, the surface of the substrate after the hydrothermal treatment becomes a γ-alumina layer that can firmly support the ultrafine particle catalyst. If the firing temperature is below 400°C, the formation of the T-alumina layer will be insufficient, and if the firing temperature is above 550°C, the substrate will be damaged or the surface area of the alumina will decrease, which is undesirable.The firing time is 10 minutes to 5 minutes. time, preferably 1 hour to 3
It's time. In the present invention, the target highly active continuous catalyst can be obtained by supporting the catalyst on the surface of the substrate prepared as described above by a known impregnation method or electrodeposition method. In the above-mentioned hot water treatment, when hot water containing a catalyst component at 70 to 90°C, preferably 80 to 85°C is used, the catalyst can be supported on the substrate surface at the same time as the hot water treatment. Not only can the process for producing the continuous catalyst body of the present invention be simplified, but also a continuous catalyst body that is particularly excellent in catalytic activity can be obtained. Therefore, after treatment with hot water containing catalyst components, drying,
A method of subsequently firing at a temperature of 400 to 550 is a preferred embodiment of the present invention. In this case, the amount of catalyst contained in the hot water is not particularly limited, but is preferably in the range of 0.5 mmol/liter to 5 mmol/liter; too high a concentration will be uneconomical; This increases the processing time required. The catalyst used in the present invention is not particularly limited, but includes, for example, platinum group metals, alloys of platinum group metals, gold, gold alloys,
It is preferable to select from palladium, rhodium, manganese, iron, zinc, copper, nickel, nickel alloy, cobalt, cobalt alloy, ruthenium and ruthenium alloy, etc., especially platinum, palladium, rhodium, manganese, zinc, iron, nickel. and cobalt. It is also possible to combine these catalyst materials. In addition, when a catalyst component is contained in hot water during hydrothermal treatment, salts of the above metals or fine particles of the above metals can be used alone or in combination as the catalyst component, but in particular chloroplatinic acid can be used. It is preferable to use After hot water treatment, when calcined at 400 to 550°C for about 3 hours, a uniform T-alumina layer is formed on the surface of the substrate, and due to the strong binding force between Mr-alumina and the catalyst particles, the substrate of the catalyst particles It is presumed that the amount supported on the surface can be made uniform and large, thereby increasing the activity as a catalyst and improving reproducibility. In the continuous catalyst body of the present invention, for example, when platinum is used as the catalyst metal, the apparent amount of catalyst supported is about 50 times that of a commercially available plate-shaped platinum catalyst, and the reaction rate constant is about 25 times that of a commercially available plate-shaped platinum catalyst. In addition to being used as a mere catalyst, the continuous catalyst body of the present invention can also be used as a catalyst.
For example, it can be used in a variety of ways, such as by providing a heat exchange function and using it as a wall of the reaction chamber to directly extract the reaction heat to the outside. , ribbon-like, tubular-like, honeycomb-like, etc., and by selecting the type of metal with catalytic activity according to the desired reaction, oxidation reaction, hydrogenation reaction, dehydrogenation reaction, hydrolysis reaction, etc. For example, if the catalyst obtained according to the present invention is used, oxidation reactions of organic substances at low concentrations can be easily carried out as described in Examples below.

【Effect of the invention] As detailed above, according to the method for producing a continuous catalyst of the present invention, the catalytic activity of the continuous catalyst obtained is stable, the reproducibility is good, and a highly active continuous catalyst can be obtained. In addition, since it is a continuous catalyst, it has a heat exchange function and can effectively utilize the reaction heat that was conventionally treated as waste heat.It is especially applicable to the partition between the exothermic reaction chamber and endothermic reaction chamber of chemical heat pumps. By doing so, the thermal efficiency of chemical heat pumps can be significantly improved. 【Example】

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited thereto. Reference Example 1゜An aluminum plate substrate with a thickness of 0.1 mm was washed with 20% by weight sodium hydroxide for 3 minutes, then washed with water, and then washed with 30% sodium hydroxide.
It was washed with nitric acid (wt%) and then with water. The substrate pretreated as described above was anodized using a 2.5% by weight aqueous chromic acid solution at a liquid temperature of 30°C and a current density of 19.0A/m'' for 12 hours.The resulting anodized alumina surface A substrate having a temperature of 85°C
Items that were not fired after being immersed in hot water for 2 hours,
X-ray measurements were performed on the surfaces of those fired at 300°C, 1400°C, and 1550°C, respectively, and as shown in Figure 1, the surfaces of those that were not fired and those fired at 300°C were Al0 ( OH), whereas
The surface of those fired at 400℃ and 550℃ is γ-A+
. It was confirmed that 0. Example 1゜ Containing 2.25 g/liter of platinum at 85°C, pH 11.4
Two substrates having anodized alumina surfaces prepared in Reference Example 1 were immersed in a chloroplatinic acid solution of 300 ml for 2 hours.
℃ and 400℃ to catalyze. A reaction tube was filled with 0.6 g of each of the obtained continuous catalysts, and the pressure was set at 1 atm.
A low concentration of 600 ppm of acetone vaporized and entrained in the air was sent under conditions of ℃ and combusted. This reaction tube was used as an integral reactor to collect and analyze gas, and the reaction rate constant per surface area of each continuous catalyst, the amount of platinum supported, and the reaction rate constant per platinum were determined from the changes in concentration.The results are shown in Table 1. Met. The results in Table 1 confirm that calcination at 400° C. after hydrothermal treatment is important in obtaining a highly active continuous catalyst body. In addition, when X-ray measurements were performed on the substrate surface of each continuous catalyst body in the same manner as in Reference Example 1, it was found that the substrate surface of the continuous catalyst body calcined at 300°C was Al0(OH), whereas 4
The substrate surface of the continuous catalyst body calcined at 00℃ is 7A1z○3
It was confirmed that Example 2゜A catalyst was supported in the same manner as in Example 1 except that a chloroplatinic acid solution containing 1.0 g/'J liter of platinum was used, and then hydrogen reduction was performed at 200°C for 2 hours to obtain a catalyst body. Ta. The amount of platinum supported per substrate surface area of this catalyst was 83 g-pt.
/m2. The combustion activity of the obtained continuous catalyst body was determined under the same conditions as in Example 1, and the reaction rate per substrate surface area was 2.
．． It was 60×10-'mff/(m2-secC). Example 3 A continuous catalyst body was obtained in the same manner as in Example 2, except that a chloroplatinic acid solution containing 0.25 g/liter of platinum was used. The amount of platinum supported per substrate surface area of the obtained continuous catalyst body was 0.3 Lg pt/m. Also, Example 2
When the combustion activity was investigated under the same conditions as above, the reaction rate per substrate surface area was 0.84X10-3 m"/(m
Reference Example 2 When the amount of catalyst supported on a commercially available plate-shaped catalyst was measured, the amount of platinum supported was 0.036 g-pt per substrate surface area.
/m2. The reaction rate constant per surface area of the catalyst, determined in the same manner as in Example 2, was 0.10XI O-”m
3/(m''-sec).

[Brief explanation of the drawing]

FIG. 1 is an X-ray diffraction diagram obtained by measuring the surface of a substrate having an anodized alumina surface after the surface was subjected to hydrothermal treatment. however,
The temperature and time in the figure represent firing conditions.

Claims (1)

[Claims] 1) An alumina layer is formed on the surface of a continuous substrate having an aluminum layer of at least several micrometers on the surface, and then heated at 40°C.
After or simultaneously with hot water treatment at ~350°C,
A method for manufacturing a continuous catalyst body in which a metal having catalytic activity is supported on the alumina layer, the continuous catalyst body comprising a step of drying after the hot water treatment and firing at 400 to 550°C. Production method. 2) The method for producing a continuous catalyst body according to claim 1, further comprising the firing step between the hydrothermal treatment step and the catalyst supporting step. 3) The method for producing a continuous catalyst body according to claim 1, wherein the hydrothermal treatment is carried out in an aqueous solution containing catalyst components. 4) Metals with catalytic activity include platinum metals, platinum metal alloys, gold, gold alloys, palladium, rhodium, manganese, iron, zinc, copper, nickel, nickel alloys, cobalt, cobalt alloys, ruthenium and ruthenium alloys. 3. The method for producing a continuous catalyst body according to claim 2, wherein at least one metal selected from the group consisting of: 5) As a catalyst component, at least one member selected from the group consisting of platinum metal, gold, palladium, rhodium, manganese, iron, zinc, copper, nickel, nickel alloy, cobalt, cobalt alloy, ruthenium, and ruthenium alloy. 4. The method for producing a continuous catalyst body according to claim 3, wherein the metal or metal salt is used. 6) A method for oxidizing a low concentration organic substance, which comprises oxidizing a low concentration organic substance using a continuous catalyst produced by the method according to any one of claims 1 to 5.