JPH0731881A - Production of oxidation catalyst - Google Patents

Abstract

PURPOSE:To provide a method for producing an oxidation catalyst which is used for burning gas such as hydrogen, carbon monoxide and hydrocarbon. CONSTITUTION:This oxidation catalyst is produced by mixing at least one kind of oxide selected from among alumina, silica, titania and zirconia which are carried with oxide of rare earth elements, palladium oxide carried with oxide of alkaline earth elements and a binder, and coating a honeycomb heat resistant base material with slurry of the obtained mixture.

Description

Detailed Description of the Invention

[0001]

This invention relates to oxidation catalysts such as hydrogen,
A method for producing an oxidation catalyst for burning gases such as carbon monoxide and hydrocarbons. Particularly, methane, which is the most difficult to oxidize among various combustible gases, has high efficiency under the conditions of low temperature and high gas flow rate / catalyst volume ratio. Can be oxidised with
The present invention relates to a method for producing an oxidation catalyst having excellent heat resistance even at a high temperature of 000 ° C or higher.

[0002]

2. Description of the Related Art Recently, as an oxidation catalyst, as part of the development of a low NOx combustion method, an oxidation catalyst that burns low calorific gas, oil, propane, methane, etc. has been studied. This type of catalyst uses ceramics such as honeycomb-type cordierite and mullite as a base material, and a carrier whose main component is alumina, silica, titania, zirconia, etc. is wash-coated on this base material and baked, followed by a palladium nitrate solution. Many are obtained by immersing in or chloroplatinic acid solution, drying and firing. However, although such a conventional oxidation catalyst has a high initial oxidation activity, it has a problem that it has poor heat resistance and a large decrease in activity.

[0003]

The conventional catalyst is 1000
When used at a temperature of ℃ or higher, the noble metal which is the active component is sintered by heat and the active sites are reduced, so that it cannot be used practically.

In view of the conventional state of the art, the present invention intends to provide a method for producing an oxidation catalyst having excellent heat resistance even at high temperatures.

[0005]

The present invention relates to at least one oxide of alumina, silica, titania, and zirconia supporting an oxide of a rare earth element and palladium oxide supporting an oxide of an alkaline earth element. A method for producing an oxidation catalyst, comprising coating a honeycomb heat-resistant base material with a slurry mixed with a binder.

In the present invention, the amount of the rare earth element oxide supported on at least one oxide of alumina, silica, titania, and zirconia is alumina, silica,
At least one oxide of titania and zirconia 1
0.5 to 20 parts by weight per 00 parts by weight (hereinafter, 0.5 to
20 wt%) is preferable, and La ₂ O ₃ , CeO ₂ , Nd ₂ O ₃ is used as an example of the oxide of the rare earth element.
And so on. The amount of the alkaline earth element oxide supported on palladium oxide is preferably in the range of 0.5 to 20 wt%, and examples of the alkaline earth element oxide include MgO, CaO, BaO and the like. next,
At least one kind of alumina, silica, titania, and zirconia supporting an oxide of a rare earth element (hereinafter, these are referred to as a carrier): a mixing ratio of palladium oxide (PdO) supporting an oxide of an alkaline earth element is 5: 95-9
The ratio is 5: 5 (weight ratio), and [carrier + (oxide of alkaline earth element / PdO)]: binder is 10 by weight.
The range of 0: 5 to 50 is preferable. Alumina sol, silica sol, etc. are used as the binder, and cordierite (2MgO.2Al ₂ O ₃ is used as the honeycomb heat-resistant base material.
・ 5SiO ₂ ), mullite (3Al ₂ O ₃ .2Si)
O ₂ ) and a crystalline complex oxide composed of MgO, Al ₂ O ₃ and TiO ₂ are used, and the coating amount of the slurry coated on these honeycomb heat-resistant substrates is generally 1 liter of the honeycomb heat-resistant substrate. The range of 30 to 300 g is preferable.

[0007]

[Function] A binder is added to at least one oxide (carrier) of alumina, silica, titania, or zirconia supporting an oxide of a rare earth element, and palladium oxide powder supporting an oxide of an alkaline earth element. By wet pulverizing and mixing, the carrier carrying the oxide of the rare earth element and the palladium oxide carrying the oxide of the alkaline earth element are made into fine particles and a slurry uniformly dispersed is obtained. The oxidation catalyst obtained by wash-coating this on a honeycomb substrate is active because the particle size of palladium oxide is small, and each particle of palladium oxide is coated with an oxide of an alkaline earth element and is rare earth metal. Since it is uniformly dispersed in a carrier that has been coated with an oxide of an element and has been given heat resistance, a carrier that supports an oxide of an alkaline earth element and an oxide of a rare earth element prevents the sintering of palladium oxide. As a result, the decrease in activity is small even when used at high temperature for a long time.

[0008]

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

Example 1 First, 100 to 200 mesh of palladium oxide was immersed in an aqueous magnesium nitrate solution, evaporated to dryness with stirring, and then baked at 1000 ° C. to obtain 1,5 and 10 wt% of magnesium oxide. % Supported palladium oxide powder was obtained. Next, each oxide shown in Table 1 is immersed in any one of a lanthanum nitrate aqueous solution, a cerium nitrate aqueous solution, and a neodymium nitrate aqueous solution, evaporated to dryness with stirring, and then baked at 1000 ° C. to oxide a rare earth element. To obtain a carrier carrying 1, 5 and 10 wt%.

[0010]

[Table 1]

20 g of the above-mentioned palladium oxide carrying magnesium oxide, 19 g of silica sol (binder) and 350 ml of ion-exchanged water were pulverized and mixed in 80 g of each carrier with a ball mill for 3 hours, and each obtained slurry was squared. A honeycomb-type cordierite substrate having 400 openings (400 cells) per inch was wash-coated and baked at 500 ° C. to obtain honeycomb-type oxidation catalysts 1 to 6. The amount of washcoat was palladium oxide (PdO) per liter of honeycomb substrate.
Was 50 g.

These catalysts and additionally 10 at 1100 ° C.
The activity of the catalyst calcined for 00 hours was evaluated under the conditions of gas space velocity 300,000 h ⁻¹ and catalyst inlet gas temperature 400 ° C. using a gas containing 3% of methane (remaining air), and the results in Table 2 were obtained. .

[0013]

[Table 2]

(Example 2) Palladium oxide was immersed in an aqueous solution of calcium nitrate, and each oxide shown in Table 1 was immersed in an aqueous solution of lanthanum nitrate, cerium nitrate or neodymium nitrate, and oxidized by the same preparation method as in Example 1. Catalysts 7 to 12 were prepared, and the same activity evaluation as in Example 1 was performed, and the results in Table 3 were obtained.

[0015]

[Table 3]

Example 3 Palladium oxide was immersed in an aqueous barium nitrate solution, and each oxide shown in Table 1 was immersed in an aqueous solution of lanthanum nitrate, cerium nitrate or neodymium nitrate,
The oxidation catalysts 13 to 18 were prepared by the same preparation method as in Example 1, and the same activity evaluation as in Example 1 was performed, and the results in Table 4 were obtained.

[0017]

[Table 4]

(Comparative Example) Al ₂ O ₃ shown in Table 1 was immersed in an aqueous solution of palladium nitrate, evaporated to dryness with stirring, and then baked at 500 ° C. to carry 20 wt% of PdO (based on the weight of the carrier) of PdO. / Al ₂ O ₃ was prepared and Example 1
Similarly to the above, a slurry in which silica sol and ion-exchanged water were mixed was wash-coated on a cordierite substrate. The honeycomb substrate was coated so that PdO was 50 g per liter of volume. As a result of performing the same activity evaluation on this catalyst as in Example 1, the methane conversion was 100% before the calcination at 1100 ° C, but it was 65% after the calcination at 1100 ° C.

[0019]

As described in detail above, according to the present invention, it is possible to produce an oxidation catalyst having excellent heat resistance as compared with a catalyst produced by a conventional production method.

Claims (1)

[Claims] 1. A slurry prepared by mixing at least one oxide of alumina, silica, titania, and zirconia supporting oxides of rare earth elements and palladium oxide and binder supporting oxides of alkaline earth elements. A method for producing an oxidation catalyst, which comprises coating a honeycomb heat-resistant base material.