JPH06304476A - Oxidation catalyst - Google Patents

Abstract

PURPOSE:To obtain an oxidation catalyst for burning a gas such as hydrogen, carbon monoxide and hydrocarbons. CONSTITUTION:An oxidation catalyst (1) is obtd. by making a composite oxide of zirconium and titanium as a carrier carry at least one of metals of Ib, Va, VIa, VIIa and VIIIa groups or their oxides, an oxide of rare earth elements, and an oxide of alkali earth elements. An oxidation catalyst (2) is obtd. by molding the composite oxide of zirconium and titanium into a honeycomb shape. An oxidation catalyst (3) is prepd. by coating a honeycomb-like heat resistant base selected from among cordierite, mullite and a crystalline composite oxide consisting of MgO, Al2O3 and TiO2 with the catalyst (1).

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 A catalytic combustion method in which a combustible gas such as carbon monoxide, hydrogen or hydrocarbon is burned in the presence of an oxidation catalyst has been studied mainly for the purpose of purifying automobile exhaust gas.
Many oxidation catalysts have been developed. 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, as part of the 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
Ceramics such as cordierite and mullite are used as base materials
And γ-Al on this substrate₂O ₃(Gamma alumina), di
Luconia, magnesia, α-Al₂O₃(Alpha Al
Mina) and other carriers are wash-coated to make it the active ingredient.
Precious metals such as Pt, Pt + Pd, Pd, Pt + Rh,
Or base metals such as cobalt, nickel and manganese
An oxide is supported.

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

Further, recently, as a catalyst having heat resistance even at around 1000 ° C., a catalyst having a catalytically active component supported on a carrier having 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 decrease sharply, so that it cannot be used in practice.

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 Group Ib, Group Va, Group VIa, Group VIIa and Group VIII or oxides thereof, using a complex oxide of zirconium and titanium as a carrier. An oxidation catalyst comprising an oxide of a rare earth element and an oxide of an alkaline earth element supported thereon. (2) The above-mentioned (1), wherein the composite oxide of zirconium and titanium is formed into a honeycomb shape.
Oxidation catalyst. (3) Cordierite, mullite or MgO, Al ₂
An oxidation catalyst comprising a honeycomb heat-resistant base material selected from crystalline composite oxides of O ₃ and TiO ₂ coated with the catalyst of the above item (1). Is.

[0009]

The composite oxide of zirconium and titanium referred to in the present invention means that the weight ratio of ZrO ₂ and TiO ₂ is 5: 9.
Amorphous having a composition of 5 to 95: 5 (partly crystallized but generally amorphous) is manufactured by the following method. A basic precipitant such as aqueous ammonia or an aqueous solution of sodium carbonate is added to an aqueous solution of a zirconium compound and a titanium compound, and the resulting precipitate is washed, dried, and calcined at 500 ° C. or higher. After mixing zirconium hydroxide or oxide with an aqueous solution of a titanium compound, a precipitant is added to wash the formed precipitate, which is dried and calcined at 500 ° C. or higher. A titanium hydroxide or oxide is mixed with an aqueous solution of a zirconium compound, and a precipitate is added to wash the precipitate, which is then dried and calcined at 500 ° C. or higher.

The zirconium-titanium composite oxide prepared by the above method is molded into a honeycomb by adding a binder, or a slurry of the composite oxide is made of cordierite, mullite, MgO, Al ₂ O ₃ , T.
A honeycomb heat-resistant base material selected from among crystalline composite oxides of iO ₂ is dipped and wash-coated,
A honeycomb-shaped carrier can be obtained by baking at 500 ° C. or higher.

The above MgO, Al ₂ O ₃ , and TiO
_The crystalline composite oxide consisting of ₂ is a magnesium compound such as magnesium, magnesium carbonate, magnesium hydroxide,
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-type titanium oxide at 1300 to 1700 ° C. .

Next, the thus obtained composite oxide of zirconium and titanium 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 an oxide of the above element, it may be calcined after immersing the carrier in an aqueous nitrate solution of each element, and in the case of supporting a metal of the above element. It can be prepared by immersing the carrier in an aqueous solution of a compound of each element and then reducing with hydrogen. Further, in the case of supporting an oxide of a rare earth element or an oxide of an alkaline earth element, the carrier may be immersed in an aqueous solution of a nitrate of a rare earth element or an alkaline earth element and then baked. As a method for supporting the metal of the group Ib, the group Va, the group VIa, the group VIIa, or the group VIII and the oxide thereof and the oxide of the rare earth element or the oxide of the alkaline earth element, any one of the above methods is preliminarily predicted. Therefore, a method of carrying another oxide after carrying it, or a method of carrying by carrying out baking after immersing the carrier in an aqueous solution of a compound of both components is used.

Examples of alkaline earth element oxides include MgO, CaO, and BaO, and examples of rare earth element oxides include La ₂ O ₃ , CeO ₂ , and Nd ₂ O.
_{3 and the} like, and the supported amount is preferably in the range of 1 to 30 parts by weight per 100 parts by weight of the zirconium and titanium composite oxide.

Group Ib, Group Va, Group VIa, Group VIIa, VIII
As an example of the metal of the group element or its oxide, CuO,
V ₂ O ₅ , Cr ₂ O ₃ , MnO ₂ , Fe ₂ O ₃ , Ni
O, CoO, PdO, Pt, Pd, Rh, Ru and the like are included, and the supported amount thereof is preferably in the range of 0.1 to 100 parts by weight per 100 parts by weight of the zirconium and titanium composite oxide. The catalyst obtained as described above, for the oxidation reaction of gas such as hydrogen, carbon monoxide and hydrocarbon gas,
It exhibited excellent activity and durability. Hereinafter, the present invention will be specifically described with reference to examples.

[0015]

【Example】

 (Example 1) Zirconium oxynitrate and titanium chloride
The precipitation obtained by adding an aqueous solution of sodium carbonate to the mixed aqueous solution of
The carrier 1 (Z
rO ₂: TiO₂50:50) was obtained.

ZrO (OH) powder was added to water, aqueous ammonia was added to a solution prepared by adding an aqueous solution of titanium chloride, and the resulting precipitate was filtered, washed with water, dried and dried at 1000 ° C.
After firing in a carrier 2 (ZrO ₂ : TiO ₂ ratio different).
O ₂ : TiO ₂ weight ratio 90:10), carrier 3 (ZrO 2
₂ : TiO ₂ weight ratio 20:80) and carrier 4 (ZrO 2
₂ : TiO ₂ weight ratio 10:90) was obtained.

The carriers 1 to 4 are molded into pellets having a particle size of 2 to 4 mm, then immersed in an aqueous solution of lanthanum nitrate and magnesium nitrate and baked at 500 ° C. to form La ₂ O _3.
Pellets carrying 5% by weight of MgO and 5% by weight of MgO (per 100 parts by weight of carrier) were each immersed in an aqueous solution of palladium nitrate, dried and calcined at 500 ° C. to prepare catalysts 1 to 4, respectively.

Further, after the carrier 1 is molded into pellets having a particle size of 2 to 4 mm, it is immersed in an aqueous solution of lanthanum nitrate and magnesium nitrate and baked at 500 ° C. to La ₂ O.
Pellets carrying 5% by weight each of ₃ and MgO (per 100 parts by weight of carrier) 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 prepare catalysts 5-7. did.

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.

[0020]

[Table 1]

[0021]

[Table 2]

Example 2 Using the pellets of the carrier 3 prepared in Example 1, each aqueous solution of copper nitrate, vanadium nitrate, manganese nitrate, iron nitrate, nickel nitrate, cobalt nitrate and an aqueous solution of lanthanum nitrate or barium nitrate or The catalysts 8 to 13 were prepared by immersing in an aqueous solution of cerium nitrate, calcium nitrate or a mixed aqueous solution of neodymium nitrate and strontium nitrate, drying and firing at 500 ° C. for 5 hours.

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.

[0024]

[Table 3]

(Example 3) Catalyst 8 prepared in Example 2
13 was 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). The results are shown in Table 4. Table 4 also shows the results after the 1000-hour activity evaluation test.

[0027]

[Table 4]

(Embodiment 4) Diameter 1 inch, 1 square in
Hani with 200 openings per cell (200 cells)
Cam-shaped cordierite (2MgO / 2Al₂O₃・ 5
SiO₂) Base material or MgO, Al₂O₃, ZrO₂Yo
Crystalline compound oxide (MgO.4Al ₂O₃・ 6T
iO₂) Using a base material, Al of the carrier 3₂O₃: ZrO
₂(20:80) Washcoat powder on the above substrate
Then, it was baked at 1000 ° C. to obtain honeycomb carriers A and B.
ZrO₂: TiO₂The coating amount is 100 weight of honeycomb carrier
It was 40 parts by weight per part.

Each of the carriers A and B was dipped in an aqueous solution of lanthanum nitrate or magnesium nitrate, dried, and baked at 500 ° C.
Further, the catalyst was immersed in an aqueous solution of palladium nitrate, dried, and calcined at 500 ° C. to obtain catalysts 20 and 21.

These catalysts and additionally 1 at 1100 ° C.
The catalyst calcined for 000 hours was subjected to activity evaluation using a gas containing 3% of methane (remainder 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 the results shown in Table 5 were obtained.

[0031]

[Table 5]

[0032]

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 code Internal reference number FI Technical display location B01J 23/64 M 8017-4G 23/78 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 complex oxide of zirconium and titanium as a carrier.
An oxidation catalyst comprising at least one metal of Group VIII element or oxide thereof, an oxide of rare earth element, and an oxide of alkaline earth element. 2. The oxidation catalyst according to claim 1, which is formed by molding a composite oxide of zirconium and titanium into a honeycomb shape. 3. Cordierite, mullite or Mg
An oxidation catalyst comprising a honeycomb heat-resistant base material selected from the crystalline composite oxides of O, Al ₂ O ₃ and TiO ₂ coated with the catalyst of claim 1.