JP3219447B2 - Oxidation catalyst - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an oxidation catalyst such as hydrogen,
Oxidation catalysts for combusting gases such as carbon monoxide and hydrocarbons.Efficient oxidation of methane, which is the least oxidizable of various combustible gases, under conditions of low temperature and high gas flow rate / catalyst volume ratio. The present invention relates to an oxidation catalyst which can be used and has excellent heat resistance even at a high temperature of 1000 ° C. or more.

[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 the purpose of purifying automobile exhaust gas.
Many oxidation catalysts have been developed. Its main components are oxides of noble metals such as platinum and base metals such as copper and iron as active components, and each active component is formed into granules or honeycombs, or directly supported on a carrier such as alumina or titania. It was made.

On the other hand, recently, as a part of the development of a low NOx combustion method, an oxidation catalyst for burning propane, low calorific gas, oil and the like has been studied. This catalyst is based on ceramics such as honeycomb type cordierite and mullite,
A carrier such as γ-Al ₂ O ₃ (gamma-alumina), zirconia, magnesia, α-Al ₂ O ₃ (alpha-alumina) is wash-coated on this substrate, and P is used as an active ingredient.
It supports an oxide of a noble metal such as t, Pt + Pd, Pd, and Pt + Rh, or an oxide of a base metal such as cobalt, nickel, and manganese.

[0004] The above-mentioned conventional oxidation catalysts show high activity for carbon monoxide and propane, but have poor performance for more stable methane. There are many problems in its oxidation performance.

Recently, as a catalyst having heat resistance even at around 1000 ° C., a catalyst in which a catalytically active component is supported on a carrier mainly composed of a composite oxide of aluminum and lanthanum (JP-A-60-12132), Alternatively, a catalyst comprising 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
When used at a temperature of at least ℃, the carrier is sintered by heat and the specific surface area is rapidly reduced, so that it cannot be used practically.

The present invention has been made in view of the above-mentioned state of the art, and aims to provide an oxidation catalyst having excellent heat resistance even at a high temperature.

[0008]

According to the present invention, there is provided (1) a compound oxide of zirconium and aluminum as a carrier and at least one of metals of Group Ib, Va, VIa, VIIa and VIII or oxides thereof. And an oxide of a rare earth element and an oxide of an alkaline earth element.

(2) The oxidation catalyst according to the above (1), wherein the composite oxide of zirconium and aluminum is formed into a honeycomb shape.

(3) Cordierite, mullite or Mg
The above-mentioned (1) is applied to a honeycomb-shaped heat-resistant base material selected from crystalline composite oxides consisting of O, Al ₂ O ₃ and TiO _2.
An oxidation catalyst characterized by being coated with the catalyst according to the above item. It is.

[0011]

The composite oxide of zirconium and aluminum according to the present invention is defined as having a weight ratio of ZrO ₂ : Al ₂ O ₃ of 5:
It is an amorphous material having a composition of 95 to 95: 5 (partly crystallized, but entirely amorphous), and is manufactured by the following method.

A precipitate formed by adding a basic precipitant such as aqueous ammonia or an aqueous sodium carbonate solution to an aqueous solution of an aluminum compound and a zirconium compound is washed, dried, and fired at 500 ° C. or higher.

After a hydroxide or oxide of aluminum is mixed with an aqueous solution of a zirconium compound, a precipitate formed by adding a precipitant is washed, dried, and then dried at 500 ° C.
The above is fired.

A hydroxide or oxide of zirconium is mixed with an aqueous solution of an aluminum compound, and a precipitate formed by adding a precipitant is washed, dried, and then dried at 500 ° C.
The above is fired.

The composite oxide of zirconium and aluminum prepared by the above-described method is formed into a honeycomb shape by adding a binder, or cordierite, mullite, MgO, Al ₂ O ₃ , TiO.
A honeycomb-like heat-resistant base material selected from crystalline composite oxides consisting of ₂ is dipped and wash-coated, and 500
By baking at a temperature of not less than ° C., a honeycomb-shaped carrier can be obtained.

The above MgO, Al ₂ O ₃ , TiO
_The crystalline composite oxide consisting of ₂ , magnesia, magnesium carbonate, Mg compounds such as magnesium hydroxide,
A low expansion property obtained by baking 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. to crystallize. .

Next, the zirconium and aluminum composite oxide or the honeycomb-like carrier thus obtained is loaded with a metal of the Ib group, Va group, VIa group, VIa group, VIIa group or VIII group element or an oxide thereof. The method for performing the method may be a conventionally used method.For example, in the case of supporting the oxide of the above element, the support may be immersed in a nitrate aqueous solution of each element and then calcined, and the metal of the above element may be supported. In this case, it can be prepared by immersing the carrier in an aqueous solution of a compound of each element and then reducing the carrier with hydrogen.

In the case of carrying a rare earth element oxide or an alkaline earth element oxide, the carrier may be immersed in a rare earth element or alkaline earth element nitrate aqueous solution and then fired.

Group Ib, Group Va, Group VIa, Group VIIa, Group VIII
As a method of supporting a metal of a group element element or an oxide thereof and an oxide of a rare earth element, an oxide of an alkaline earth element, a method of preliminarily supporting any of the above methods and then supporting another oxide, Alternatively, a method is used in which the carrier is immersed in an aqueous solution of the compounds of both components and then baked to carry the carrier.

Examples of oxides of alkaline earth elements include MgO, CaO and BaO, and examples of oxides of rare earth elements include La ₂ O _3, CeO _{2 and} Nd ₂ O.
_{And the} like, and the amount of the carrier is preferably in the range of 1 to 30 parts by weight per 100 parts by weight of the composite oxide of zirconium and aluminum.

Group Ib, Group Va, Group VIa, Group VIIa, Group VIII
Examples of metals or oxides of group III elements include CuO, V ₂
O ₅ , Cr ₂ O ₃ , MnO ₂ , Fe ₂ O ₃ , NiO, C
There are oO, PdO, Pt, Pd, Rh, Ru and the like, and the supporting amount thereof is preferably in the range of 0.1 to 30 parts by weight per 100 parts by weight of the composite oxide of zirconium and aluminum.

The catalyst obtained as described above exhibited excellent activity and durability against the oxidation reaction of gases such as hydrogen, carbon monoxide, and hydrocarbon gas. 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 nitrate and aluminum nitrate was filtered, washed with water, dried, and then calcined at 500 ° C to obtain carrier 1 (Zr
O ₂ : Al ₂ O ₃ weight ratio 50:50) was obtained.

A precipitate obtained by adding boehmite AlO (OH) ₄ powder to water and further adding aqueous ammonia to a solution to which an aqueous zirconium chloride solution has been added is filtered, washed with water, dried and calcined at 1000 ° C. to obtain ZrO ₂ : Supports ₂ having different Al ₂ O ₃ ratios (ZrO ₂ : Al ₂ O ₃ weight ratio 90: 1)
0), carrier 3 (ZrO ₂ : Al ₂ O ₃ weight ratio 20:
80) and carrier 4 (ZrO ₂ : Al ₂ O ₃ weight ratio 1)
0:90).

After the carriers 1 to 4 are formed into pellets having a particle size of 2 to 4 mm, they are immersed in an aqueous solution of lanthanum nitrate and magnesium nitrate and fired at 500 ° C. to obtain La ₂ O ₃ and M _2.
The pellets each supporting 5% by weight of gO (per 100 parts by weight of carrier) were immersed in an aqueous solution of palladium nitrate, dried, and calcined at 500 ° C. to prepare Catalysts 1 to 4, respectively. The pellets of the carrier 1 were immersed in each of an aqueous solution of chloroplatinic acid, an aqueous solution of ruthenium chloride, and an aqueous solution of rhodium chloride, and dried.
Hydrogen reduction was performed at 0 ° C. to prepare Catalysts 5 to 7.

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

[0027]

[Table 1]

[0028]

[Table 2]

(Example 2) Using pellets of the carrier 3 prepared in Example 1, aqueous solutions of copper nitrate, vanadium nitrate, manganese nitrate, iron nitrate, nickel nitrate, cobalt nitrate and lanthanum nitrate, barium nitrate or cerium nitrate, nitric acid The catalyst 8 was immersed in a mixed aqueous solution of calcium, neodymium nitrate, and strontium nitrate aqueous solution, dried and calcined at 500 ° C. for 5 hours.
~ 13 were prepared.

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

[0031]

[Table 3]

Example 3 Catalysts 8 to 13 prepared in Example 2 were immersed in an aqueous solution of palladium nitrate and calcined at 500 ° C. to prepare Catalysts 14 to 19.

The activity of these catalysts was evaluated using a gas containing 1% methane (remainder air) at a gas superficial velocity of 50,000 h ^-1 and a reaction temperature of 400 ° C. 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 Honeycomb cordierite (2MgO.2Al ₂ O ₃ .5Si) having a diameter of 1 inch and 200 openings (200 cells) per square inch
O ₂ ) substrate or crystalline composite oxide (MgO.4Al ₂ O ₃ .6Ti) composed of MgO, Al ₂ O ₃ , TiO ₂
O ₂₎ with a base, ZrO carrier _{3 2: Al 2 O 3 (} 2
0:80) The powder was wash-coated on the substrate and
It was baked at 00 ° C. to obtain honeycomb carriers A and B. ZrO ₂
· Al ₂ O ₃ coating quantity was 40 parts by weight per 100 parts by weight honeycomb carrier.

Each of the carriers A and B is immersed in an aqueous solution of lanthanum nitrate and magnesium nitrate, dried and calcined at 500 ° C.
The catalyst was further immersed in an aqueous solution of palladium nitrate, dried and calcined at 500 ° C. to obtain Catalysts 20 and 21.

These catalysts, and also 1100 ° C. at 1
The activity of the catalyst calcined for 2,000 hours was evaluated using a gas containing 3% methane (remaining air) at a gas superficial velocity of 300,000 h ^-1 and a catalyst layer inlet gas temperature of 400 ° C.
Was obtained.

[0038]

[Table 5]

[0039]

As described in detail above, 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. ⁷ Identification code FI B01J 23/78 B01J 23/56 301M 23/89 23/64 102M F23D 14/18 104M (56) References JP-A-60-12132 (JP, A) JP-A-61-54240 (JP, A) JP-A-58-219293 (JP, A) JP-A-60-202738 (JP, A) JP-A-60-202190 (JP, A) (58) Survey Field (Int. Cl. ⁷ , DB name) B01J 21/00, 38/74 F23D 14/18

Claims (3)

(57) [Claims] 1. A group Ib, Va, VIa, VIIa, or zirconium and aluminum composite oxide as a carrier.
An oxidation catalyst comprising a metal of Group VIII or an oxide thereof, and at least one oxide of a rare earth element or an alkaline earth element. 2. The oxidation catalyst according to claim 1, wherein the composite oxide of zirconium and aluminum is formed into a honeycomb shape. 3. Cordierite, mullite or MgO,
Al_TwoO_Three, TiO _TwoCrystalline composite oxide
The catalyst according to claim 1 is applied to a honeycomb-shaped heat-resistant substrate selected from the group consisting of:
An oxidation catalyst characterized by being coated.