JPH05301044A - Oxidation catalyst - Google Patents

Abstract

PURPOSE:To provide an oxidation catalyst having heat resistance even at high temp. with which methane can be efficiently oxidized under conditions of low temp. and high ratio of gas flow rate/catalyst volume. CONSTITUTION:This oxidation catalyst consists of a composite oxide of zirconium and aluminum as a carrier on which zirconium oxide and one or more kinds of metal elements in Ib group, Va group, VIa group, VIIa group or VIII group or oxides of these are carried. Or, the catalyst is carried on a honeycomb heat-resistant base body consisting of cordierite, mullite or crystalline composite oxide such as MgO, Al2O3 and TiO2.

Description

Detailed Description of the Invention

[0001]

This invention relates to oxidation catalysts such as hydrogen,
Regarding an oxidation catalyst for burning gases such as carbon monoxide and hydrocarbons, methane, which is the most difficult to oxidize among various combustible gases, is highly efficiently oxidized under conditions of low temperature and high gas flow rate / catalyst volume ratio The present invention relates to an oxidation catalyst that can be processed and has excellent heat resistance even at a high temperature of 1000 ° C. or higher.

[0002]

2. Description of the Related Art The catalytic combustion method of burning a combustible gas such as carbon monoxide, hydrogen, or hydrocarbon in the presence of an oxidation catalyst has been studied mainly for purifying automobile exhaust gas, and many oxidation catalysts have been developed. Has been done. The main ones are oxides of noble metals such as platinum and base metals such as copper and iron as active ingredients, and each active ingredient is formed into granules or honeycombs, or directly loaded on a carrier such as alumina or titania. It was made.

On the other hand, recently, a part of development of low NOx combustion method
Burning propane, low calorific value gas, oil, etc.
Oxidation catalysts are being studied. This catalyst is of honeycomb type
Using ceramics such as cordierite and mullite as the base material
And γ-Al on this substrate₂O ₃(Gamma alumina), di
Luconia, magnesia, α-Al₂O₃(Alpha Al
As a active ingredient, wash coat a carrier such as Mina)
Precious metals such as Pt, Pt + Pd, Pd, Pt + Rh,
Rubic acid of base metals such as cobalt, nickel and manganese
The compound is supported.

Although the above-mentioned conventional oxidation catalysts show high activity with respect to carbon monoxide and propane, they are inferior in performance to more stable methane, and at present, to methane. Many problems remain in its oxidation performance.

Further, recently, as a catalyst having a heat resistance around 1000 ° C., a catalyst having a catalytically active component supported on a carrier containing a composite oxide of aluminum and lanthanum as a main component (JP-A-60-12132), Alternatively, a catalyst containing a composite oxide of an alkaline earth metal element and aluminum as a main component (JP-A-62-153158) has been proposed.

[0006]

The conventional catalyst is 1000
If it is used at a temperature of ℃ or above, the carrier will be sintered by heat and the specific surface area will be drastically reduced.

In view of the above-mentioned state of the art, the present invention aims to provide an oxidation catalyst having excellent heat resistance even at high temperatures.

[0008]

The present invention provides (1) one or more metals of Ib group, Va group, VIa group, VIIa group, VIII group element or its oxide with a complex oxide of zirconium and aluminum as a carrier. And an oxidation catalyst carrying zirconium oxide.

(2) The oxidation catalyst according to item (1), which is formed by molding a composite oxide of zirconium and aluminum into a honeycomb shape.

(3) Cordierite, mullite or M
An oxidation catalyst comprising a honeycomb heat-resistant base material selected from crystalline complex oxides composed of gO, Al ₂ O ₃ and TiO ₂ and coated with the catalyst according to the above item (1). Is.

[0011]

The composite oxide of zirconium and aluminum referred to in the present invention means a weight ratio of ZrO ₂ : Al ₂ O ₃ of 5:
Amorphous having a composition of 95 to 95: 5 (partly crystallized but generally amorphous) is manufactured by the following method.

A basic precipitant such as ammonia water or an aqueous solution of sodium carbonate is added to an aqueous solution of an aluminum compound and a zirconium compound to wash the resulting precipitate, which is dried and calcined at 500 ° C. or higher.

After mixing aluminum hydroxide or oxide with an aqueous solution of a zirconium compound, a precipitating agent is added to wash the resulting precipitate, which is then dried at 500 ° C.
The above is fired.

After mixing a hydroxide or oxide of zirconium with an aqueous solution of an aluminum compound, a precipitating agent is added to wash the resulting precipitate, which is then dried at 500 ° C.
The above is fired.

The composite oxide of zirconium and aluminum prepared by the above method is molded into a honeycomb form by adding a binder, or cordierite, mullite or MgO, Al ₂ O ₃ , T is added to a slurry of the composite oxide.
A honeycomb-shaped heat-resistant base material selected from among crystalline composite oxides of iO ₂ is dipped and wash-coated, and 5
A honeycomb-shaped carrier can be obtained by baking at a temperature of 00 ° C. or higher.

The above MgO, Al ₂ O ₃ and TiO
_The crystalline composite oxide consisting of ₂ means a magnesium compound such as magnesia, magnesium carbonate, magnesium hydroxide,
A low-expansion product obtained by crystallization of a mixture of an Al compound such as alumina and aluminum hydroxide and a Ti compound such as anatase or rutile titanium oxide at 1300 to 1700 ° C. .

Next, the thus-obtained composite oxide of zirconium and aluminum or a honeycomb-shaped carrier is loaded with a metal of the Ib group, Va group, VIa group, VIIa group, or VIII group element or its oxide. The method may be a conventionally used method, for example, in the case of supporting the oxides of the above elements, it may be carried out by immersing the carrier in a nitrate aqueous solution of each element and then firing, and in the case of supporting the metal of the above elements. Can be prepared by immersing the carrier in an aqueous solution of a compound of each element and then reducing with hydrogen.

When supporting zirconium oxide, the carrier may be immersed in an aqueous solution of zirconium oxynitrate and then baked.

Group Ib, Group Va, Group VIa, Group VIIa, Group VIII
As a method for supporting the metal of the group element or its oxide and zirconium oxide, after supporting one of the above-mentioned methods in advance, a method of supporting another oxide, or immersing the carrier in an aqueous solution of a compound of both components A method of supporting by firing is used.

The amount of zirconium oxide supported is 1 to 100 parts by weight of the composite oxide of zirconium and aluminum.
A range of 30 parts by weight is preferred.

Ib group, Va group, VIa group, VIIa group, VIII
Examples of the metal or oxide of the group element include CuO, V
₂ O ₅ , Cr ₂ O ₃ , MnO ₂ , Fe ₂ O ₃ , NiO,
There are CoO, PdO, Pt, Pd, Rh, Ru, etc.,
The supported amount is preferably in the range of 0.1 to 100 parts by weight per 100 parts by weight of the zirconium-aluminum composite oxide.

The catalyst obtained as described above is suitable for the oxidation reaction of gases such as hydrogen, carbon monoxide and hydrocarbon gas.
It showed excellent activity and durability. Hereinafter, the present invention will be specifically described with reference to examples.

[0023]

【Example】

Example 1 A precipitate obtained by adding an aqueous solution of sodium carbonate to a mixed aqueous solution of zirconium oxynitrate and aluminum nitrate was filtered, washed with water, dried and then baked at 500 ° C. to obtain a carrier 1 (Zr
A weight ratio of O ₂ : Al ₂ O ₃ 50:50) was obtained.

Boehmite AlO (OH) Powder was added to water, and further calcining the precipitate obtained by adding ammonia water to the solution was added aqueous solution of zirconium oxychloride filtered at 1000 ° C. After washing with water and dried ZrO _2: Al ₂ O ₃
Supports 2 (ZrO ₂ : Al ₂ O _{3 in} different weight ratios)
0:10), carrier 3 (ZrO ₂ : Al ₂ O ₃ weight ratio 2
0:80) and Carrier 4 (ZrO ₂ : Al ₂ O ₃ weight ratio 10:90) were obtained.

The carriers 1 to 4 are molded into pellets having a particle diameter of 2 to 4 mm, and then immersed in an aqueous solution of zirconium oxynitrate to prepare 5
Pellets carrying 5% by weight of zirconium oxide (per 100 parts by weight of carrier) by calcination at 00 ° C were immersed in an aqueous palladium nitrate solution, dried, and then calcined at 500 ° C to prepare catalysts 1 to 4, respectively. Further, the pellets of the carrier 1 were immersed in an aqueous solution of chloroplatinic acid, an aqueous solution of ruthenium chloride and an aqueous solution of rhodium chloride, dried, and then reduced with hydrogen at 400 ° C. to give a catalyst 5
~ 7 was prepared.

The activity of these catalysts was evaluated under the conditions shown in Table 1 (flammable gas was diluted with air), and the results are shown in Table 2.

[0027]

[Table 1]

[0028]

[Table 2]

Example 2 Using the pellets of the carrier 3 prepared in Example 1, the pellets were immersed in a mixed aqueous solution of copper nitrate, vanadium nitrate, manganese nitrate, iron nitrate, nickel nitrate, cobalt nitrate aqueous solution and zirconium oxynitrate aqueous solution. After drying, it was calcined at 500 ° C. for 5 hours to prepare catalysts 8 to 13.

An activity evaluation test was conducted on these catalysts using air containing propane or methanol as a raw material under the conditions of a reaction temperature of 500 ° C. and a gas space velocity of 10,000 h ⁻¹ , and the results are shown in Table 3.

[0031]

[Table 3]

(Example 3) The catalysts 8 to 13 prepared in Example 2 were immersed in an aqueous palladium nitrate solution and then calcined at 500 ° C to prepare catalysts 14 to 19.

The activity of these catalysts was evaluated under the conditions of gas space velocity of 50,000 h ⁻¹ and reaction temperature of 400 ° C., using a gas containing 1% of methane (the balance of air), and the results are shown in Table 4. Table 4 also shows the results after the 1000-hour activity evaluation test.

[0034]

[Table 4]

Example 4 With a diameter of 1 inch, 1 square inch
Honeycomb having 200 openings (200 cells)
Cordierite (2MgO / 2Al)₂O₃・ 5Si
O₂) Base material or MgO, Al₂O₃, TiO₂More
Crystalline composite oxide (MgO.4Al ₂O₃・ 6TiO
₂) Using a base material, ZrO of the carrier 3₂: Al₂O₃(2
0:80) Powder was wash-coated on the above-mentioned substrate, and 10
Baking was performed at 00 ° C. to obtain honeycomb carriers A and B. Zr
O₂: Al₂O₃The coating amount is 100 parts by weight of the honeycomb carrier.
It was 40 parts by weight per unit.

Each of the carriers A and B was dipped in an aqueous solution of palladium nitrate, dried and calcined at 500 ° C., further dipped in an aqueous solution of zirconium oxynitrate, dried and calcined at 500 ° C. to obtain catalysts 20 and 21.

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

[0038]

[Table 5]

[0039]

As described above in detail, according to the present invention, an oxidation catalyst having high activity and excellent heat resistance can be provided.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location B01J 23/64 104 M 8017-4G 23/72 M 8017-4G 23/74 M 8017-4G 23 / 89 M 8017-4G

Claims (3)

[Claims] 1. A group Ib group, a Va group, a VIa group, a VIIa group using a composite oxide of zirconium and aluminum as a carrier,
An oxidation catalyst comprising one or more metals of Group VIII elements or oxides thereof and zirconium oxide supported thereon. 2. The oxidation catalyst according to claim 1, which is obtained by molding a composite oxide of zirconium and aluminum into a honeycomb shape. 3. Cordierite, mullite or Mg
An oxidation catalyst comprising a honeycomb heat-resistant base material selected from crystalline composite oxides of O, Al ₂ O ₃ and TiO ₂ coated with the catalyst of claim 1.