JPH07241469A - Production of oxidation catalyst - Google Patents

Abstract

PURPOSE:To produce an oxidation catalyst for combustion of gases such as hydrogen, CO and hydrocarbon. CONSTITUTION:One or more kinds of oxides selected from among alumina, silica, titania and zirconia each with carried oxide of an alkaline earth metal are mixed with palladium oxide with carried oxide of a rare earth element and a binder to prepare a slurry and the objective oxidation catalyst is produced by coating a heat resistant honeycomb base material with the slurry.

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 which burns a 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 alumina, silica, titania, which carries an oxide of an alkaline earth element,
At least one or more oxides of zirconia and a slurry in which a rare earth element oxide-supported palladium oxide and a binder are mixed, and a honeycomb-shaped heat-resistant substrate is coated with a method for producing an oxidation catalyst. Is.

In the present invention, the amount of the alkaline earth element oxide supported on at least one or more oxides of alumina, silica, titania and zirconia is 100 parts by weight of at least one or more oxides of alumina, silica, titania and zirconia. 0.5 to 20 parts by weight (hereinafter, 0.
5 to 20 wt%) is preferable, and MgO, CaO, and BaO are examples of alkaline earth element oxides.
And so on. The amount of the rare earth element oxide supported on the palladium oxide is preferably in the range of 0.5 to 20 wt%, and La ₂ O is an example of the rare earth element oxide.
₃ , CeO ₂ , Nd ₂ O _{3 and the} like.

At least one of alumina, silica, titania, and zirconia supporting an oxide of an alkaline earth element (hereinafter, these are referred to as a carrier): a mixing ratio of palladium oxide (PdO) supporting an oxide of a rare earth element. Is in the range of 5:95 to 95: 5 (weight ratio), [carrier +
(Rare earth element oxide / PdO)]: The weight ratio of the binder is preferably 100: 5 to 50.

[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]

[Operation] At least one oxide (carrier) of alumina, silica, titania, or zirconia supporting an oxide of an alkaline earth element and palladium oxide powder supporting an oxide of a rare earth element are used as a binder. By adding and wet pulverizing and mixing, a carrier supporting an oxide of an alkaline earth element and a palladium oxide supporting an oxide of a rare 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 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 is alkaline. Since the oxides of the earth elements are uniformly dispersed in the heat-resistant carrier, the carriers carrying the rare earth oxides and alkaline earth oxides prevent sintering of palladium oxide. It acts as a barrier and its activity is not significantly reduced even when it is used at high temperature for a long time.

[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 of the oxides shown in Table 1 was immersed in any one of an aqueous magnesium nitrate solution, an aqueous calcium nitrate solution and an aqueous barium nitrate solution, evaporated to dryness with stirring, and then 100
It was fired at 0 ° C. to obtain a carrier carrying 1, 5 and 10 wt% of an alkaline earth element oxide. 80g of each carrier,
20 g of palladium oxide carrying the above-mentioned lanthanum oxide,
19 g silica sol (binder) and 350 ion-exchanged water
After adding milliliter to each and pulverizing and mixing in a ball mill for 3 hours, each of the resulting slurries was wash-coated on a honeycomb-shaped cordierite substrate having 400 openings (400 cells) per square inch, and 500 The honeycomb type oxidation catalysts 1 to 6 were obtained by baking at 0 ° C. The wash coat amount was such that palladium oxide (PdO) was 50 g per liter of the honeycomb substrate.

These catalysts and additionally 10 at 1100 ° C.
The catalyst that was 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.
Got the result.

[0012]

[Table 1]

[0013]

[Table 2]

Example 2 Palladium oxide was added to a cerium nitrate aqueous solution, and each oxide shown in Table 1 was added to magnesium nitrate.
The oxidation catalysts 7 to 12 were prepared by immersing in an aqueous solution of either calcium nitrate or barium nitrate, and the same preparation method as in Example 1 was used. Similarly, 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 dipped in an aqueous solution of neodymium nitrate and each oxide shown in Table 1 was dipped in an aqueous solution of magnesium nitrate, calcium nitrate or barium nitrate and oxidized by the same preparation method as in Example 1. Catalyst 13-18
Was prepared and the same activity evaluation as in Example 1 was carried out.
Got the result.

[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 an oxide of an alkaline earth element, and palladium oxide and a binder supporting an oxide of a rare earth element. A method for producing an oxidation catalyst, which comprises coating a honeycomb-shaped heat-resistant substrate with