JP2633554B2 - Method for producing high temperature combustion catalyst - Google Patents

Description

Description of the Invention (Object of the Invention) (Field of Industrial Application) The present invention relates to a method for producing a high-temperature combustion catalyst, and more specifically, has a high activity in a temperature range of about 800 to 1500 ° C, and has a long life. And a method for producing a high temperature combustion catalyst having a long temperature.

(Prior Art) In recent years, with the depletion of petroleum resources and the like, in order to use energy resources efficiently, for example, in a gas turbine or the like, it is desired to burn fuel at as high a temperature as possible.

However, conventionally, since a mixture of fuel and air is ignited and burned using a spark plug or the like, a high temperature portion exceeding 2000 ° C. partially exists in the combustor. It is known that a large amount of nitrogen oxide (NOx) is generated in this high-temperature portion, which causes problems such as environmental pollution.

In order to solve such a problem, a catalytic combustion system in which a mixture of fuel and air is burned using a catalyst has been proposed. According to this combustion method, uniform combustion is possible, and the combustion temperature can be raised to about 1500 ° C., which is the upper limit temperature at which NOx is not generated.

At present, a platinum (Pt) -based noble metal catalyst is known as a catalyst used in the catalytic combustion system. In such a noble metal-based combustion catalyst, for example, γ-alumina (γ-Al ₂ O ₃ ) is applied as an active carrier on a carrier having a certain mechanical strength, and further, the noble metal is supported by a dipping method. It is manufactured by the method.

However, the noble metal-based combustion catalyst obtained by applying the above production method is said to have a heat-resistant temperature of usually 600 ° C., and the catalyst activity rapidly decreases in a temperature range higher than 600 ° C.
There is a problem that it cannot be used.

The cause of the rapid decrease in the catalytic activity at a temperature of 600 ° C. or higher can be considered as follows. First, first
In addition, since the noble metal particles on the surface of the carrier are aggregated by heat transfer and coarsened, the catalyst surface area is reduced, and the combustion performance is reduced. Secondly, since γ-Al ₂ O ₃ undergoes a phase transition to α-Al ₂ O ₃ at a temperature of about 1000 ° C. or higher, the γ-Al ₂ O ₃ may be in the Al ₂ O ₃ layer or between the Al ₂ O ₃ and the carrier. This is considered to be caused by cracking, and the Al ₂ O ₃ layer was separated and dropped together with the catalyst metal.

Therefore, in order to improve the heat resistance of the noble metal-based combustion catalyst, the γ-Al ₂ O ₃ layer was improved, and the Pt particles on the γ-Al ₂ O ₃ layer were removed.
Attempts have been made to strongly adsorb to Al ₂ O ₃ to prevent agglomeration due to heat transfer and to prevent the γ-Al ₂ O ₃ layer from becoming α to prevent cracks.

As a result, a material in which a metal is added to the γ-Al ₂ O ₃ layer has been developed.
It has been confirmed that it can be used up to around 800 ° C.
However, even with such a catalyst, the heat resistance at the above-mentioned temperatures is not sufficient, and there is still room for improvement.

(Problems to be Solved by the Invention) As described above, in the conventional method for producing a combustion catalyst, the obtained combustion catalyst does not have sufficient heat resistance at high temperatures, for example, 800 ° C. or higher, and maintains high activity. There was a problem that you can not.

The present invention solves such a conventional problem, and is approximately 800 to 1500 ° C.
It is an object of the present invention to provide a method capable of producing a high-temperature combustion catalyst having high activity even in the above temperature range and having a long life.

[Constitution of the Invention] (Means and Actions for Solving the Problems) As a result of intensive studies to achieve the above object, the present inventors have found that when precious metal elements are mixed with alumina, both are coprecipitated. And found that a catalyst having very excellent performance in heat resistance can be obtained, and completed the present invention.

That is, the method for producing a high-temperature combustion catalyst of the present invention adjusts a solution containing at least an aluminum salt and a noble metal, coprecipitates a precipitate containing aluminum and the noble metal from the solution, and removes the noble metal from the precipitate. It is characterized in that alumina to be contained is produced, and thereafter, the produced alumina is adhered to a carrier substrate.

Here, the first step of the present invention is a step of preparing a solution containing aluminum and a noble metal. Examples of the noble metal include platinum and palladium, and palladium is preferable.

The high-temperature combustion catalyst according to the present invention preferably further contains a metal oxide and a rare-earth oxide in addition to the noble metal. Therefore, the case where the metal oxide and the rare earth oxide are contained will be described below.

This metal oxide includes nickel, magnesium,
Oxides of iron and manganese [etc.] are mentioned, and oxides of nickel and magnesium are preferred. Examples of the rare earth metal include lanthanum, cerium, prasedium, neodymium [and the like], and lanthanum is preferable.
The content of aluminum, noble metal, etc. in the solution is per carrier volume of the carrier substrate when attached to the carrier substrate,
Alumina is preferably 50 to 200 g /, noble metal is 20 to 200 g /, metal oxide is 20 to 200 g /, and rare earth oxide is 10 to 50 g /.

Thus, when actually adjusting the mixed solution, first, an aqueous solution containing an aluminum salt was prepared by using alcoholate as an alumina raw material, and then, the raw material of the palladium / metal oxide / rare earth oxide was added to the aqueous solution. Add to the aqueous solution with a water soluble salt.

In the second step of the present invention, aluminum and the noble metal / metal / rare earth element (hereinafter, referred to as noble metal or the like) are prepared from the prepared solution. This is a step of coprecipitating a precipitate containing In this step, the acidity (pH) of the solution is adjusted to precipitate the aluminum, noble metal and the like as a hydroxide. At this time, the noble metal or the like desirably forms a neutral hydroxide separate from aluminum, but may be in the form of ions or the like attached to the aluminum hydroxide.

The third and fourth steps of the present invention are steps of producing alumina containing noble metal or the like from the precipitate by the co-precipitation and attaching the alumina to a carrier substrate.

When producing alumina containing a noble metal or the like from the precipitate, the precipitate is dried and calcined, and then pulverized to powder.

Next, in order to adhere the powdered alumina layer to the carrier substrate, a small amount of alumina sol is added to the alumina powder to form a slurry, and the slurryed alumina is applied on the carrier substrate, and dried and fired. . Here, the carrier substrate is not particularly limited as long as it has a safe property even at a high temperature oxidizing atmosphere of about 1500 ° C., for example, cordierite, mullite, α-alumina, zirconia spinel And ceramic carriers such as titania. The shape of the support is not particularly limited as long as the shape is usually used as a catalyst body.
Pellets, honeycombs and the like can be mentioned. Examples of the method for attaching the alumina coating liquid to these carriers include a coating method, a dipping method, and a spraying method. It is preferable that the amount of application is appropriately determined depending on the shape, size, weight and the like of the carrier.

 Thus, the high-temperature combustion catalyst according to the present invention is obtained.

Next, the operation of the method for producing a high-temperature combustion catalyst according to the present invention will be described in detail.

In the step of co-precipitating the hydroxide of aluminum, a noble metal, a metal, and a rare earth element, the hydroxide precipitates in a form in which they are mixed uniformly. Therefore, when this precipitate is dried and calcined, pulverized and slurried and applied to a carrier substrate, the aluminum, noble metal, metal and rare earth element that have been formed into the hydroxide are oxidized to the respective oxides. Mutually evenly distributed within the alumina.

When the alumina film is dried and fired, the alumina itself forms a porous film having a pore diameter of, for example, about 100 to 500 °. And, since the noble metal or the like is uniformly mixed with the alumina, fine particles of several tens to 1000 ° are uniformly supported on all alumina surfaces including the internal cavities of the porous film. .

Compared with the impregnation method, which is a conventional method for producing a high-temperature combustion catalyst, in the conventional impregnation method, an alumina slurry containing a rare earth oxide or the like is applied to the surface of a carrier substrate, and then dried and fired. , As a catalyst carrier. Then, this catalyst carrier is immersed in a solution in which a noble metal element or the like is dissolved to support the noble metal element or the like, and then calcined to obtain a desired high-temperature fired catalyst. Therefore, in the conventional high-temperature calcination catalyst, the impregnated noble metal element penetrates only about several microns from the surface of the porous alumina film into the internal cavity of the porous alumina film, and is not carried to the inside of the alumina porous film. Was. For this reason, the noble metal element carried on the alumina porous membrane is limited to a relatively small amount.

That is, in the conventional impregnation method, the noble metal element is supported only on the surface of the porous alumina film. On the other hand, in the coprecipitation method of the present invention, it is supported not only on the surface but also in the internal cavity. Therefore, according to the coprecipitation method of the present invention, a large amount of noble metal particles can be supported on the alumina film while being separated from each other by an appropriate distance.

Further, when a metal oxide is supported simultaneously with a noble metal element, it is difficult to uniformly support both (noble metal and metal oxide) on a catalyst carrier containing a rare earth oxide or the like by the impregnation method. This is because the two components to be supported interfere with each other and the catalyst surface required for the reaction becomes insufficient.

Therefore, when the high temperature combustion catalyst according to the present invention is used for gas combustion, a wide active surface area is secured, and the combustion reaction proceeds with high efficiency. In addition, since the metal fine particles are supported by being separated by an appropriate distance, the combustion efficiency does not decrease even when used at a high temperature for a long time.

Next, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to this.

(Example) Example 1 (1) Production of combustion catalyst An alumina coating composition having the following composition was prepared.

Aluminum nitrate 430 g Lanthanum nitrate 65 g Nickel nitrate 180 g Palladium nitrate 230 g Add an appropriate amount of ammonia water to the aqueous solution of the above composition,
The pH was adjusted to 6.5 to 7.0, and the metal salt was simultaneously precipitated with aluminum hydroxide as a nucleus. This coprecipitated composition was passed through a washing port, dried at 150 ° C. × 50 H, and then fired at 900 ° C. × 2 H.

Next, after the above composition was pulverized, 10 g of alumina sol (solid content: 80%) was added to 100 g of the composition to prepare a slurry to prepare an alumina coating liquid.

2 g of this coating solution was applied to a carrier substrate (25 mmφ × 25 mm, 200 cells) made of cordierite, dried at 120 ° C. × 2H, and fired in air at 1100 ° C. × 4H.

The resulting combustion catalyst has palladium per carrier substrate 11
It contained 100 g, 60 g of nickel as an oxide, 50 g of lanthanum as an oxide, and 200 g of alumina.

(2) Evaluation of Combustion Catalyst The combustion characteristics of the combustion catalyst were evaluated using a simulated apparatus for a catalytic combustion type gas turbine combustor.

The combustion conditions were as follows: gas flow rate 30m / s, combustion concentration methane 3%,
The combustion characteristics (catalyst temperature and combustion efficiency) of methane after a combustion time of 100 hours with a catalyst amount of 30 cc were measured.

 The results are shown in Table 1.

Examples 2 to 4 and Comparative Examples 1 to 3. In Example 1, Al, La, Pd, and Ni were co-precipitated. Of these, two or three metals including Al and Pd were co-precipitated. After settling, the same processing as in Example 1 was performed, and Examples 2 to 4 were performed.
Was obtained. The combustion characteristics of this catalyst body were evaluated in the same manner as in the above example. The results are also shown in Table 1.

As a comparative example, a catalyst body containing Al, La, Pd, and Ni and impregnating and holding at least Pd was manufactured, and the same evaluation test as in (2) was performed using the catalyst body. This result is also shown in Table 1 as a comparative example.

As is apparent from Table 1, the catalyst temperature (combustion efficiency) is 1000 ° C. (90%) or more in Examples 1 to 4, but is 900 ° C. (70%) or less in Comparative Examples 1 to 3. Therefore, the catalyst body of the present embodiment, in which at least Al and Pd are coprecipitated, has better characteristics than other catalyst bodies.

Comparative Example 4 A catalyst body was produced in the same manner as in Example 1 except that the aluminum sol used in Example 1 was used in place of aluminum nitrate in an equivalent amount (55 g) as aluminum. The same evaluation test as in 2) was performed. As a result, as for the combustion characteristics after 100H, the combustion temperature was 780 ° C., and the combustion efficiency was 55%. This result indicates the importance of using an aluminum salt as an alumina raw material.

Examples 5 to 15 Except for changing the type and amount of the metal oxide and the type and amount of the rare earth oxide to be contained in the alumina coating composition, the same procedure as in Example 1 was followed to produce a catalyst, and An evaluation test was performed and the results are shown in Table 2.

[Effects of the Invention] As described above, according to the present invention, high-temperature durability of a high-temperature combustion catalyst, that is, catalyst temperature and combustion efficiency after long-time use can be significantly improved. Further, the high-temperature combustion catalyst according to the present invention is capable of efficiently utilizing combustion energy and preventing generation of NOx and the like, so that it is expected to be used in a wide range of fields, and its industrial value is extremely large.

Continuing from the front page (72) Inventor Kenjiro Shizukawa 2-4-1 Nishi-Atsujigaoka, Chofu-shi Tokyo Electric Power Company R & D Laboratory (72) Inventor Terunobu Hayata 1 Kosuka Toshiba-cho, Saiwai-ku, Kawasaki Stock (72) Inventor: Tomiaki Furuya 1st, Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi Toshiba Research Institute, Inc. (72) Inventor: Yanaka 1st: Komukai Toshiba-cho, Saiyuki-ku, Kawasaki-shi Toshiba Sogo In the laboratory (72) Inventor Junji Hizuka 1 Toshiba-cho, Komukai, Koyuki-ku, Kawasaki City Examiner, Toshio Niida, Toshiba Research Institute, Inc. (56) References JP-A-61-61636 (JP, A) JP-A-54 -16389 (JP, A) JP-A-55-162344 (JP, A) JP-B-45-41301 (JP, B1)

Claims (4)

(57) [Claims] 1. A solution containing at least an aluminum salt and a noble metal is prepared, a precipitate containing aluminum and the noble metal is coprecipitated from the solution, and alumina containing the noble metal is formed from the precipitate, and thereafter, A method for producing a high-temperature combustion catalyst, comprising causing the produced alumina to adhere to a carrier substrate. 2. A solution containing, in addition to the aluminum salt and the noble metal, a metal selected from nickel, magnesium, iron and manganese and a rare earth element selected from lanthanum, cerium, prasedium and neodymium is prepared. Precipitate the metal and the rare earth element-containing precipitate together with the noble metal, and produce the noble metal, metal, and the rare earth element-containing alumina from the precipitate, and then the produced alumina on a carrier substrate. The method for producing a high-temperature combustion catalyst according to claim 1, wherein the catalyst is adhered. 3. The high-temperature combustion catalyst according to claim 2, wherein said noble metal is palladium, said metal is at least one of nickel and magnesium, and said rare earth element is lanthanum. Production method. 4. The solution preparation step, the coprecipitation step, and the alumina deposition step, in which noble metal is added in an amount of 20 to 20 parts per unit volume of the carrier substrate.
200 (g / l), 20 to 200 (g / l) using the metal as an oxide,
4. The high-temperature combustion according to claim 2, wherein the rare earth element is an oxide of 10 to 50 (g / l) and alumina of 50 to 200 (g / l). Method for producing catalyst.