JPH05329367A - Manufacture of oxidation catalyst - Google Patents

Abstract

PURPOSE:To provide a manufacturing method of an oxidation catalyst which is for carrying out combustion of a gas such as hydrogen, carbon monoxide, a hydrocarbon, etc. CONSTITUTION:An oxidation catalyst is manufactured by a method which involves coating a honeycomb-like heat-resistance substrate with a slurry prepared by mixing at least one kind of oxides among alumina, silica, titania, and zirconia with palladium oxide on which an oxide of rare earth metals is carried, and a binder.

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, in particular, 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 oxidized 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 a honeycomb-type cordierite or mullite ceramics as a base material, and a carrier containing alumina, silica, titania, zirconia, etc. as a main component is wash-coated on the base material and baked, and then a palladium nitrate solution is used. Most of them 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 of poor heat resistance and a large decrease in activity.

[0003]

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

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

[0005]

Means for Solving the Problems The present invention provides a honeycomb-shaped heat-resistant slurry prepared by mixing palladium oxide carrying at least one oxide of alumina, silica, titania and zirconia and a rare earth element oxide and a binder. A method for producing an oxidation catalyst, which comprises coating a base material.

In the present invention, the mixing ratio of at least one of alumina, silica, titania, and zirconia (hereinafter, these are referred to as a carrier): palladium oxide (PdO) carrying an oxide of a rare earth element is 5:95 to 95. : 5 (weight ratio), and the mixing ratio of (carrier + oxide of rare earth element supported): binder is 100: 5.
The range of 50 (weight ratio) is preferable. The amount of the rare earth element oxide supported on palladium oxide was 10
0.5 to 20 parts by weight per 0 parts by weight (hereinafter, 0.5 to 20 parts by weight)
Wt%), and examples of oxides of rare earth elements include La ₂ O ₃ , CeO ₂ , Nd ₂ O ₃ and the like. Alumina sol, silica sol, etc. are used as the binder, and cordierite (2MgO.2Al ₂ O ₃ .5SiO ₂ ) is used as the honeycomb heat-resistant base material,
Mullite _{(3Al 2 O 3 · 2SiO 2} ) and MgO, A
A crystalline composite oxide composed of 1 ₂ O ₃ and TiO ₂ is used, and the coating amount of the slurry coated on these honeycomb heat-resistant base materials is generally 1
A range of 30 to 300 g per liter is preferable.

[0007]

[Operation] At least one or more oxides (supports) of alumina, silica, titania, and zirconia, and palladium oxide powder on which oxides of rare earth elements are previously supported are added by a binder and wet pulverized and mixed. The palladium oxide carrying the carrier and the oxide of the rare earth element is finely divided and a uniformly dispersed slurry is obtained. The oxidation catalyst obtained by washcoating this on a honeycomb heat-resistant substrate is active because the particle size of palladium oxide is small,
Further, since each particle of palladium oxide is coated with the oxide of the rare earth element and is uniformly dispersed in the carrier, the oxide of the rare earth element and the carrier act as a barrier to prevent sintering of the palladium oxide, and the long-time at high temperature. The decrease in activity is small even when used for a long time.

[0008]

EXAMPLES The present invention will be specifically described 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 1,5 and 10 wt% of lanthanum oxide. Palladium powder was obtained. 20g of this powder and 19g of silica sol (binder)
And 350 ml of ion-exchanged water, each carrier 80 shown in Table 1.
g and mixed with a ball mill for 3 hours, and then each of the resulting slurries was made into a honeycomb cordierite (2MgO.2Al ₂ O ₃ .5SiO ₂ ) having 400 openings (400 cells) per square inch. The base material was wash-coated and baked at 500 ° C. to obtain honeycomb-type oxidation catalysts 1 to 6. The amount of wash coat 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 of 300,000 h ⁻¹ and catalyst layer inlet gas temperature of 400 ° C. using a gas containing 3% of methane (remaining air).
Got the result.

[0010]

[Table 1]

[0011]

[Table 2]

(Example 2) Example 1 using cerium nitrate
Oxidation catalysts 7 to 12 were adjusted by the same adjustment method as described above, and the same activity evaluation as in Example 1 was performed, and the results in Table 3 were obtained.

[0013]

[Table 3]

(Example 3) Oxidation catalysts 13 to 18 were prepared by using neodymium nitrate in the same manner as in Example 1, and the same activity evaluation as in Example 1 was carried out to obtain the results shown in Table 4.

[0015]

[Table 4]

(Comparative Example) Pd loaded with 20 wt% of PdO (based on the weight of the carrier) was immersed in an aqueous solution of palladium nitrate in the Al ₂ O ₃ carrier shown in Table 1, dried and baked at 500 ° C.
O / Al ₂ O ₃ was prepared, and silica sol,
A cordierite substrate was wash-coated with a slurry mixed with ion-exchanged water. The coating was performed such that PdO was 50 g per liter of the honeycomb substrate. As a result of carrying out an activity evaluation on this catalyst in the same manner as in Example 1, the methane conversion was 100% before calcination at 1100 ° C., but 11
It was 65% after firing at 00 ° C.

[0017]

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 honeycomb heat-resistant substrate is coated with a slurry obtained by mixing palladium oxide carrying at least one oxide of alumina, silica, titania, and zirconia and a rare earth element oxide and a binder. A method for producing a characteristic oxidation catalyst.