JPH06319995A - Oxidation catalyst - Google Patents

Abstract

PURPOSE:To obtain an oxidation catalyst for burning a gas such as hydrogen, carbon monoxide and hydrocarbons. CONSTITUTION:The oxidation catalyst is an oxidation catalyst (1) prepd. by making at least one metal or its oxide of group Ib, Va, VIa, VIIa and VIII elements, an oxide of a rear earth element, an oxide of an alkali earth element and zirconium oxide carried on a composite oxide of aluminum and titanium as a carrier, an oxidation catalyst (2) described in (1) prepd. by molding a composite oxide of aluminum and titanium into a honeycomb shape and an oxidation catalyst (3) prepd. by coating a honeycomb-like heat-resistant base material selected from cordierite, mullite or a crystalline composite oxide consisting of MgO, Al2O3 and TiO2 with a catalyst described in (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 aluminum and titanium as a carrier. An oxidation catalyst comprising an oxide of a rare earth element, an oxide of an alkaline earth element and zirconium oxide. (2) The oxidation catalyst according to item (1), which is formed by molding a composite oxide of aluminum and titanium into a honeycomb shape. (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 aluminum and titanium referred to in the present invention means that the weight ratio of Al ₂ O ₃ and TiO ₂ is 5:
Amorphous having a composition of 95 to 95: 5 (partly crystallized but generally amorphous) is manufactured by the following method. A precipitate generated by adding a basic precipitant such as ammonia water or an aqueous solution of sodium carbonate to an aqueous solution of an aluminum compound and a titanium compound is washed, dried and calcined at 500 ° C. or higher. After mixing a hydroxide or oxide of aluminum with an aqueous solution of a titanium compound, a precipitating agent is added to wash the resulting precipitate, which is then dried and calcined at 500 ° C. or higher. A titanium hydroxide or oxide is mixed with an aqueous solution of an aluminum compound, and then a precipitate is added to wash the precipitate, which is then dried and calcined at 500 ° C. or higher.

The composite oxide of aluminum and titanium 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 or T.
Honeycomb-shaped heat-resistant base material selected from among crystalline complex oxides composed of iO ₂ is dipped and wash-coated, and
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 complex oxide consisting of ₂ is a mixture of magnesia, magnesium carbonate, Mg compound such as magnesium hydroxide, alumina, Al compound such as aluminum hydroxide and Ti compound such as anatase or rutile type titanium oxide, It means a low-expansion material obtained by crystallization at 1300 to 1700 ° C.

Next, the thus-obtained composite oxide of aluminum and titanium or the honeycomb-shaped carrier is loaded with the 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. When a rare earth element oxide, an alkaline earth element oxide, or zirconium oxide is supported, the carrier may be immersed in a rare earth element nitrate aqueous solution, an alkaline earth element nitrate aqueous solution, or a zirconium oxynitrate aqueous solution and then baked. Group Ib, Group Va, Group VIa, Group VIIa, Group VIII
Group Group metals or their oxides and rare earth element oxides,
As a method for supporting the oxide of alkaline earth element, zirconium oxide, after carrying out one of the above methods in advance, a method of carrying another oxide or after immersing the carrier in an aqueous solution of the compounds of both components A method of supporting by firing is used. The amount of the rare earth element oxide, the alkaline earth element oxide, and the amount of zirconium oxide supported is preferably in the range of 1 to 30 parts by weight per 100 parts by weight of the aluminum and titanium composite oxide.

Ib group, Va group, VIa group, VIIa group, VIII group
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 composite oxide of aluminum and titanium. 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.

[0014]

【Example】

 (Example 1) Mixed aqueous solution of aluminum nitrate and titanium chloride
The precipitate obtained by adding an aqueous solution of sodium carbonate to the liquid is filtered,
After washing with water, drying, and baking at 500 ° C, carrier 1 (Al₂O₃:
TiO₂50:50) was obtained. Boehmite Al
Add O (OH) powder to water and add titanium chloride water.
Obtained by adding aqueous ammonia to the solution containing the solution
The precipitate is filtered, washed with water, dried, and baked at 1000 ° C to form Al.₂
O₃: TiO₂Carrier 2 with different ratio (Al₂O₃: TiO
₂Weight ratio of 90:10), carrier 3 (Al₂O₃: TiO
₂Weight ratio of 20:80) and carrier 4 (Al₂O₃: Ti
O₂10:90) was obtained.

The carriers 1 to 4 are molded into pellets having a particle size of 2 to 4 mm, immersed in an aqueous solution of lanthanum nitrate, magnesium nitrate and zirconium oxynitrate and baked at 500 ° C. to give lanthanum oxide, magnesium oxide and zirconium oxide. Pellets each carrying 5% by weight (per 100 parts by weight of the carrier) were immersed in an aqueous palladium nitrate solution, dried, and then calcined at 500 ° C. to prepare catalysts 1 to 4, respectively. Further, after the carrier 1 was molded into pellets having a particle size of 2 to 4 mm, lanthanum nitrate, magnesium nitrate and zirconium oxide were each contained at 5% by weight (per 100 parts by weight of the carrier).
The supported pellets are dipped in an aqueous solution of chloroplatinic acid, an aqueous solution of ruthenium chloride, and an aqueous solution of rhodium chloride, respectively, and dried.
Hydrogen reduction was carried out at 0 ° C. to prepare catalysts 5 to 7. The activity of these catalysts was evaluated under the conditions of Table 1 (flammable gas was diluted with air), and the results are shown in Table 2.

[0016]

[Table 1]

[0017]

[Table 2]

(Example 2) Using the pellets of the carrier 3 prepared in Example 1, aqueous solutions of copper nitrate, vanadium nitrate, manganese nitrate, iron nitrate, nickel nitrate, and cobalt nitrate, an aqueous solution of zirconium oxynitrate, and lanthanum nitrate and nitric acid were used. It was immersed in a mixed solution of barium, an aqueous solution of cerium nitrate and calcium nitrate or an aqueous solution of neodymium nitrate and strontium nitrate, dried, and then calcined at 500 ° C. for 5 hours to prepare catalysts 8 to 13. Air containing propane or methanol is used as a raw material for these catalysts at a reaction temperature of 500.
An activity evaluation test was carried out under the conditions of ℃ and gas space velocity of 10,000 h ⁻¹ , and the results are shown in Table 3.

[0019]

[Table 3]

(Example 3) 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. 1% methane for these catalysts
(Remainder air) Using gas containing, gas space velocity of 50,00
The activity was evaluated under conditions of ⁰ h ⁻¹ and a reaction temperature of 400 ° C., and the results are shown in Table 4. Table 4 also shows the results after the 1000-hour activity evaluation test.

[0021]

[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, Al of the carrier 3₂O₃: TiO₂(2
0:80) La to powder₂O₃With 5% by weight of
Wash coat the above substrate and bake at 1000 ° C
Honeycomb carriers A and B were obtained. La₂O₃Supported Al
₂O₃: TiO₂The coating amount is 100 parts by weight of the honeycomb carrier.
It was 40 parts by weight. Carriers A and B are nitric acid
After immersing in an aqueous palladium solution, drying and baking at 500 ° C,
Rani magnesium nitrate, zirconium oxynitrate aqueous solution
And then dried and calcined at 500 ° C to obtain catalysts 20 and 21.
It was These catalysts and further 1000 hours at 1100 ° C
The catalyst that was calcined during
Use, gas space velocity 300,000h^-1, Catalyst layer inlet
The activity was evaluated under the condition of a temperature of 400 ° C, and the results of Table 5 are shown.
Obtained.

[0023]

[Table 5]

[0024]

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 Va, group VIa, group VIIa, or VI using a complex oxide of aluminum and titanium as a carrier.
An oxidation catalyst comprising at least one metal of Group II element or oxide thereof, oxide of rare earth element, oxide of alkaline earth element and zirconium oxide. 2. The oxidation catalyst according to claim 1, which is formed by molding a composite oxide of aluminum 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.