JPH06292829A - Production of oxidizing catalyst - Google Patents

Abstract

PURPOSE:To provide a production method of an oxidizing catalyst for burning a gas such as hydrogen, carbon monoxide, a hydrocarbon, etc. CONSTITUTION:This production method of the oxidizing catalyst is to a slurry formed by mixing at least one kind of oxide such as alumina, silica, titania, and zirconia carrying the oxides of rare earth elements thereon, palladium oxide carrying the oxides of rare earth elements thereon and a binder to a heat resistant honeycomb like base material.

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 above-mentioned state of the art, the present invention is 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 similarly supporting an oxide of a rare 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 or more oxides of alumina, silica, titania, and zirconia is 10 or more oxides of at least one of alumina, silica, titania, and zirconia.
0.5 to 20 parts by weight per 0 parts by weight (hereinafter, 0.5 to 2 parts by weight)
The range of 0 wt%) is preferable. The amount of the rare earth element oxide supported on the palladium oxide is 0.5 to 2
The range of 0 wt% is preferable, and La ₂ O ₃ , CeO ₂ , Nd ₂ O _{3 and the} like can be cited as examples of oxides of rare earth elements.

At least one of alumina, silica, titania, and zirconia supporting an oxide of a rare earth element (hereinafter referred to as a carrier): Palladium oxide (PdO) supporting an oxide of a rare earth element is mixed at a mixing ratio of 5 :
In the range of 95 to 95: 5 (weight ratio), [carrier + (rare earth element oxide / PdO)]: binder is 1 by weight.
The range of 00: 5 to 50 is preferable.

[0008] As the binder of alumina sol, etc. silica sol is used, the honeycomb heat-resistant substrate of cordierite _{(2MgO · 2Al 2 O 3 ·} 5SiO 2), mullite _{(3Al 2 O 3 · 2SiO 2} ) and MgO, Al
_A crystalline composite oxide composed of ₂ O ₃ and TiO ₂ is used, and the coating amount of the slurry coated on the honeycomb heat-resistant substrate is generally in the range of 30 to 300 g per liter of the honeycomb heat-resistant substrate. preferable.

[0009]

[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 a rare earth element. By wet pulverizing and mixing, a carrier supporting an oxide of a rare earth element and a palladium oxide similarly supporting an oxide of a rare earth element are made into fine particles and a slurry uniformly dispersed can be obtained. The oxidation catalyst obtained by wash-coating this on a honeycomb heat-resistant substrate is active because the particle size of palladium oxide is small, and each particle of palladium oxide is coated with an oxide of a rare earth element, and Since the oxides of the elements are uniformly dispersed in the heat-resistant carrier, the rare earth element oxides and the carriers carrying the rare earth element oxides act as a barrier to prevent sintering of palladium oxide. Even when used at high temperature for a long time, there is little decrease in activity.

[0010]

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 palladium oxide was immersed in an aqueous lanthanum nitrate solution, evaporated to dryness with stirring, and then baked at 1000 ° C. to oxidize lanthanum oxide at 1, 5 and 10 wt%. Palladium powder was obtained. Next, each oxide shown in Table 1 was treated with a lanthanum nitrate aqueous solution,
Immerse in either cerium nitrate aqueous solution or neodymium nitrate aqueous solution, evaporate to dryness with stirring, then 1000 ° C
And oxides of rare earth elements at 1, 5 and 10 wt%
A supported carrier was obtained. To 80 g of each carrier, 20 g of the above-mentioned palladium oxide, 19 g of silica sol (binder) and 350 ml of ion-exchanged water were added, and the mixture was pulverized and mixed in a ball mill for 3 hours, and then 400 sq. To a honeycomb-shaped cordierite substrate having openings (400 cells) and baked at 500 ° C.
Got 6. The wash coat amount was 50 Pd of palladium oxide (PdO) per liter of the honeycomb substrate.
It was coated so that it would be g.

These catalysts and additionally 10 at 1100 ° C.
The catalyst calcined for 00 hours was subjected to activity evaluation using a gas containing 3% of methane (the balance of air) under the conditions of a gas space velocity of 300,000 h ⁻¹ and a catalyst layer inlet gas temperature of 400 ° C., and Table 2
Got the result.

[0012]

[Table 1]

[0013]

[Table 2]

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

[0015]

[Table 3]

Example 3 Palladium oxide was dipped in an aqueous solution of neodymium nitrate, and each oxide shown in Table 1 was dipped in an aqueous solution of lanthanum nitrate, cerium nitrate or neodymium nitrate, and oxidized by the same preparation method as in Example 1. Catalysts 13 to 18 were prepared, 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 such that PdO was 50 g per liter. The activity of this catalyst was evaluated in the same manner as in Example 1. As a result, the methane conversion was 1100 ° C. before calcination.
Although it was 00%, it was 65% after firing 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 obtained by mixing at least one oxide of alumina, silica, titania, and zirconia supporting a rare earth element oxide with palladium oxide and a binder similarly supporting a rare earth element oxide. A method for producing an oxidation catalyst, which comprises coating a honeycomb heat-resistant base material.