JPH04166227A - Oxidation catalyst - Google Patents

Abstract

PURPOSE:To obtain an oxidation catalyst excellent in heat resistance even at high temp. by depositing one or more kinds of specified metal or its oxide on a carrier comprising a multiple oxide of aluminum and titanium. CONSTITUTION:This oxidation catalyst is prepared by depositing one or more kinds of metal elements of groups Ib, Va, VIa, VIIa and VIII or their oxides on a carrier comprising a multiple oxide of aluminum and titanium. This carrier is obtained by adding a basic precipitant such as ammonia water or aq. soln. of sodium carbonate to an aq. soln. of titanium compd. and aluminum compd. to produce precipitate, and then washing, drying and calcining the precipitate at specified temp. To deposit an oxide of the above-mentioned elements, the carrier is dipped in a nitrate soln. of respective elements before calcination. To deposit metal of the above-mentioned elements, the carrier is dipped in an aq. soln. of compd. of respective elements and then reduced with hydrogen. The obtd. catalyst has excellent activity and durability against oxidization reaction of gas such as hydrogen, carbon monoxide and hydrocarbon gas.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an oxidation catalyst, for example, an oxidation catalyst for burning gases such as hydrogen, carbon oxide, hydrocarbons, etc. Methane, which is difficult to oxidize, is processed at low temperatures.
The present invention relates to an oxidation catalyst that can perform oxidation with high efficiency under conditions of a high gas flow rate/catalyst volume ratio and has excellent heat resistance even at high temperatures of 1000° C. or higher.

[Conventional technology]

The catalytic combustion method, in which combustible gases such as carbon monoxide, hydrogen, or hydrocarbons are burned in the presence of an oxidation catalyst, has been studied primarily for the purpose of purifying automobile exhaust gas, and many oxidation catalysts have been developed.

The main active ingredients are oxides of noble metals such as platinum or base metals such as copper and iron, and each active ingredient is formed into granules or honeycomb shapes, or directly supported on a carrier such as alumina or titania. This is what I did.

On the other hand, recently, as part of the development of low-NOx combustion methods, research has been carried out on oxidation catalysts for burning propane, low-calorie gases, oil, etc. This catalyst uses honeycomb-shaped ceramics such as cordierite or mullite as a base material, and this base material is coated with a carrier such as T-A1203 (comma alumina), zirconia, magnesia, α-A1203 (alpha alumina), etc. Pt as an active ingredient, Pt
, +Pd, Pd, Pt+Rh, etc., or base metal oxides such as cobalt, nickel, and manganese.

Although the conventional oxidation catalysts mentioned above show high activity against carbon oxide and propane, they have poor performance against methane, which is more stable, and their oxidation performance against methane is currently limited. Many problems remain.

Recently, as a catalyst that is heat resistant even at around 1000 degrees Celsius, a catalyst in which a catalytically active component is supported on a carrier mainly composed of a composite oxide of aluminum and lanthanum (Japanese Unexamined Patent Application Publication No. 1989-1999-1) has been developed.
No. 12132), or a catalyst whose main component is a composite oxide of an alkaline earth metal element and aluminum (Japanese Unexamined Patent Publication No. 12132)
-153158) and the like have been proposed.

[Problems to be solved by Rib 1-] When conventional catalysts are used at temperatures above 1000°C, the carrier sinters due to heat and the specific surface area rapidly decreases, so that they cannot be used practically.

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

[A means to solve problems]

The present invention is characterized in that (1) a composite oxide of luminium and titanium is used as a carrier to support one or more metals of group Il), group Va, group VIa, group VIIa, and group VIII or their oxides. oxidation catalyst.

(2) The above-mentioned item (1), which is formed by molding a composite oxide of aluminum and titanium into a honeycomb shape.
) oxidation catalyst.

(3) Cordierite, mullite or MgO, 81
, 03, an oxidation catalyst comprising a honeycomb-shaped heat-resistant base material selected from crystalline composite oxides consisting of TiO2 and coated with the catalyst of item (1) above.

It is.

[Effect]

The composite oxide of aluminum and titanium according to the present invention has a weight ratio of Al2O3:TlO2 of 5:95 to 9.
It is amorphous (some parts are crystallized, but the whole is amorphous) with a composition of 5:5, and is produced by the following method.

■ A basic precipitant such as aqueous ammonia or aqueous sodium carbonate solution is added to an aqueous solution of a titanium compound and an aluminum compound, and the precipitate formed is washed and then dried.
Fire at 500°C or higher.

(2) After mixing titanium hydroxide or oxide with an aqueous solution of an aluminum compound, a precipitant is added and the resulting precipitate is washed, dried, and fired at 500°C or higher.

(2) After mixing aluminum hydroxide or oxide with an aqueous solution of a titanium compound, a precipitant is added and the resulting precipitate is washed, dried, and fired at 500°C or higher.

The composite oxide of aluminum and titanium prepared by the above method may be formed into a honeycomb shape by adding a binder, or the composite oxide slurry 1 may be mixed with cordierite,
Mullite or MgO.

A honeycomb-shaped heat-resistant base material selected from crystalline composite oxides consisting of Al2O3 and TlO2 is immersed, wash-coated, and baked at 500° C. or higher to form a honeycomb-shaped support.

In addition, the above-mentioned crystalline composite oxide consisting of MgO, Al2O3, and TiOz includes magnesia, magnesium carbonate,
A mixture of Mg compounds such as magnesium hydroxide, alumina, ^l compounds such as aluminum hydroxide, and T1 compounds such as anatase or rutile titanium oxide,
It means a low-expansion product obtained by crystallizing by firing at 1300 to 1700°C.

Next, the aluminum and titanium composite oxide or honeycomb-shaped support obtained in this way was coated with Ib group, Va.
The method for supporting metals of Groups VIa, Group VIIa, and Group VIII or their oxides may be any conventional method. For example, when supporting oxides of elements in -1-, each The carrier may be immersed in an aqueous solution of the nitrate of the element and then fired, and in the case of supporting the metal of the above element, the carrier can be prepared by immersing the carrier in an aqueous solution of a compound of each element and then reducing the carrier with hydrogen.

Examples of metals or oxides of group Ib, Va, VIa, VIIa, and VIII elements include CuO, V2O5
゜[:r, L, Mn口, , Fea03
, NiO, CoO, Pt, Pd.

Rh, Ru, etc. are supported in an amount of 0.000 parts per 100 parts by weight of aluminum and titanium composite oxide.
A range of 1 to 30 parts by weight is preferred.

The catalyst obtained as described above has excellent activity and
It showed durability.

Hereinafter, the present invention will be specifically explained with reference to Examples.

[Example 1] A precipitate obtained by adding a sodium carbonate aqueous solution to a mixed aqueous solution of aluminum nitrate and titanium chloride was filtered, washed with water, dried, and then calcined at 500°C to obtain carrier 1 (Tie, : A).
A weight ratio of 12O3 of 50:5 (1) was obtained.

The precipitate obtained by adding boehmite Al0(OH) powder to water and adding ammonia water to a solution containing an aqueous titanium chloride solution is filtered, washed with water, dried, and then calcined at 1000°C to produce TlO2:1203 with different ratios. Carrier 2 (
Tin□: Al2O3 weight ratio 90:10), carrier 3 (T102: Al2O3 weight ratio 20:80)
and carrier 4 (T102: weight ratio of Al2O3
10:90) was obtained.

After forming carriers 1 to 4 into pellets with a particle size of 2 to 4 mm, they were immersed in an aqueous palladium chloride solution, dried, and then subjected to hydrogen reduction at 400°C to prepare catalysts 1 to 4, respectively. The pellet of carrier 1 was immersed in a chloroplatinic acid aqueous solution, a ruthenium chloride aqueous solution, and a rhodium chloride aqueous solution, dried, and then subjected to hydrogen reduction at 400° C. to prepare catalysts 5 to 7.

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

Table 1 [Example 2] Using the pellet of carrier 2 prepared in Example 1, copper nitrate,
Vanadium nitrate, chromium nitrate, manganese nitrate, iron nitrate,
Catalysts 8 to 13 were prepared by immersing them in aqueous solutions of nickel nitrate and cobalt nitrate, drying them, and then calcining them at 500°C for 5 hours.

These catalysts were prepared using air containing propane or methanol as a raw material at a reaction temperature of 500°C and a superficial gas velocity of 10.
An activity evaluation test was conducted under the conditions of 000h-, and the results are shown in Table 3.

Table 3 [Example 3] Catalysts 8 to 13 prepared in Example 2 were immersed in an aqueous platinum nitrate solution and subjected to hydrogen reduction at 400°C to prepare catalysts 14 to 19.

These catalysts were prepared using a gas containing 1% methane (the balance being air) at a superficial gas velocity of 50,000 h-' and a reaction temperature of 800°C.
The activity was evaluated under the following conditions, and the results are shown in Table 4. Table 4
The results after the 1000-hour activity evaluation test are also listed.

[Example 4] Honeycomb-shaped cordierite with a diameter of 1 inch and 200 openings (200 cells) per square inch
(2Mg0・2A1203・5S102) Base material or Mg
O, ^1.03. Using a crystalline composite oxide (MgO.4A)20.6TiO-based material consisting of TiO2, wash coat the TiO2.^1.03 (20:80) powder of carrier 3 on the substrate and heat at 1000°C. The honeycomb carriers A and B were obtained by baking.The coating amount of TlO2.Al2O3 was 20 parts by weight per 100 parts by weight of the honeycomb carrier.

Each of carriers A and B was immersed in a mixed aqueous solution of palladium chloride and platinum chloride, dried, and then subjected to hydrogen reduction at 400°C to obtain catalyst 20.21.

These catalysts and the catalysts calcined for 1000 hours at 1200°C were evaluated for their activity using a gas containing 3% methane (remaining air) at a superficial gas velocity of 300,000 h-1 and a gas temperature at the inlet of the catalyst layer of 400°C. The results shown in Table 5 were obtained.

〔Effect of the invention〕

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

Claims (3)

[Claims] (1) An oxidation catalyst comprising a composite oxide of aluminum and titanium supporting one or more metals of group Ib, group Va, group VIa, group VIIa, group VIII or their oxides. (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 MgO, Al_2
A honeycomb-shaped heat-resistant base material selected from crystalline composite oxides consisting of O_3 and TiO_2 is
An oxidation catalyst characterized by being coated with the catalyst of item 1).