JPH08108070A - Production of oxidation catalyst - Google Patents

Abstract

PURPOSE: To produce an oxidation catalyst having superior heat resistance even at a high temp. CONSTITUTION: Oxide of an alkaline earth metal is carried on one or more kinds of oxides selected from among alumina, silica, titania and zirconia, oxide of an alkaline earth metal is carried on palladium oxide and they are mixed with a binder to prepare a slurry. A heat resistant honeycomb substrate is coated with the slurry to produce the objective oxidation catalyst.

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, is highly efficient at 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 a ceramic such as honeycomb type cordierite or mullite 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, followed by a palladium nitrate solution. Many are obtained by immersing in or chloroplatinic acid solution, drying and firing. However, such a conventional oxidation catalyst has a problem that the initial oxidation activity is high, but the heat resistance is poor and the activity is greatly reduced.

[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 technical level, the present invention intends to provide a method for producing an oxidation catalyst having excellent heat resistance even at high temperatures.

[0004]

The present invention relates to alumina, silica, titania, which carries an oxide of an alkaline earth element,
Manufacture of an oxidation catalyst characterized by coating a honeycomb heat-resistant substrate with a slurry in which at least one oxide of zirconia and palladium oxide and a binder, which also carry an oxide of an alkaline earth element, are mixed. Is the way.

In the present invention, the amount of the alkaline earth oxide supported on at least one oxide of alumina, silica and zirconia is 100 parts by weight of at least one oxide of alumina, silica, titania and zirconia. 0.5 to 20 parts by weight (hereinafter, 0.5 to 20 wt
%) Is preferable. Further, the amount of the alkaline earth element oxide supported on the palladium oxide is also 0.5 to 2
The range of 0 wt% is preferable, and examples of oxides of alkaline earth elements include MgO, CaO, BaO 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): Palladium oxide (PdO) supporting an oxide of an alkaline earth element The mixing ratio of 5:95 to 95: 5 (weight ratio) is preferable, and [carrier + (oxide of alkaline earth element / PdO)]: binder is preferably 100: 5 to 50 by weight ratio. .

[0007] 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 these honeycomb heat-resistant substrates is generally 30 to 300 g per liter of the honeycomb heat-resistant substrate. Ranges are preferred.

[0008]

[Function] 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 an alkaline earth element are used. By adding a binder and wet pulverizing and mixing, the palladium oxide carrying the carrier and the oxide of the alkaline earth element is made into fine particles and a uniformly dispersed slurry 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 an alkaline earth element, and Since the oxides of the earth elements are uniformly dispersed on the carrier that has been given heat resistance, the oxides of the alkaline earth elements and the carriers that carry the oxides of the alkaline earth elements cause sintering of palladium oxide. It acts as a barrier to prevent, and the activity does not decrease much even when used at high temperature for a long time.

[0009]

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 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 of the oxides shown in Table 1 was immersed in any one of a magnesium nitrate aqueous solution, a calcium nitrate aqueous solution, and a barium nitrate aqueous solution, evaporated to dryness with stirring, and then baked at 1000 ° C. to remove alkaline earth elements. A carrier carrying 1, 5 and 10 wt% of oxide was obtained. 20 g of the above-mentioned palladium oxide carrying magnesium nitrate, 19 g of silica sol (binder), and 350 ml of ion-exchanged water were pulverized and mixed in 80 g of each of the carriers in a ball mill for 3 hours, and the obtained slurries were 400 Individual openings (400 cells)
A honeycomb-type cordierite base material having a honeycomb structure is wash-coated and baked at 500 ° C. to form a honeycomb-type oxidation catalyst 1.
~ 6 was obtained. The wash coat amount was 5 PdO per 1 liter of the honeycomb substrate.
It was coated to give 0 g. These catalysts and the catalyst calcined at 1100 ° C. for 1000 hours were treated with 3% methane.
(Remainder air) Using gas containing, gas space velocity 300,0
The activity was evaluated under the conditions of 00 h ⁻¹ and catalyst layer inlet gas temperature of 400 ° C., and the results shown in Table 2 below were obtained.

(Example 2) Palladium oxide was immersed in an aqueous solution of calcium nitrate, and each oxide shown in Table 1 was immersed in any of an aqueous solution of magnesium nitrate, an aqueous solution of calcium nitrate and an aqueous solution of barium nitrate, and the same preparation method as in Example 1 was used. Oxidation catalysts 7 to 12 were prepared, and the same activity evaluation as in Example 1 was performed, and the results shown in Table 3 below were obtained.

(Example 3) Palladium oxide was immersed in an aqueous barium nitrate solution, and each oxide shown in Table 1 was immersed in any of an aqueous magnesium nitrate solution, an aqueous calcium nitrate solution and an aqueous barium nitrate solution, and the same preparation method as in Example 1 was used. Oxidation catalyst 1
3 to 18 were prepared and the same activity evaluation as in Example 1 was performed, and the results shown in Table 4 below were obtained.

(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 calcined at 500 ° C., PdO supported on PdO 20 wt% (support weight). / Al ₂ O ₃ was prepared, and the slurry obtained by mixing silica sol and ion-exchanged water was wash-coated on the cordierite substrate in the same manner as in Example 1. In addition, PdO is 50 g per liter of the honeycomb substrate.
It was coated so that As a result of carrying out an activity evaluation on this catalyst in the same manner as in Example 1, the methane conversion rate was 1100.
It was 100% before calcination at 65 ° C, but 65 after calcination at 1100 ° C.
%Met.

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

[Table 3]

[0017]

[Table 4]

[0018]

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. At least one oxide of alumina, silica, titania, and zirconia supporting an oxide of an alkaline earth element, and palladium oxide and a binder similarly supporting an oxide of an alkaline earth element. A method for producing an oxidation catalyst, which comprises coating a honeycomb-shaped heat-resistant substrate with the mixed slurry.