JPH1176828A - Manufacture of exhaust gas cleaning catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacture of an exhaust gas cleaning catalyst which is excellent in durability under an atmosphere containing steam at a high temperature. SOLUTION: The manufacture of a catalyst is equipped with the following processes. In the first process, a porous inorganic support and copper ion dispersed solution are mixed by stirring under coexistence of a reducing agent, ammonia and a innert gas to obtain slurry. In the second process, the obtained slurry is dried under reduced pressure or an innert gas atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a catalyst for purifying exhaust gas discharged from various internal combustion engines, and more particularly to a method for producing an exhaust gas purifying catalyst having excellent durability. is there.

[0002]

2. Description of the Related Art Various studies have been made on catalysts for purifying unburned carbon monoxide, hydrocarbons, and nitrogen oxides in exhaust gas discharged from various internal combustion engines.
In particular, in recent years, in order to reduce the fuel consumption of internal combustion engines, in order to purify exhaust gas from lean-burn engines, nitrogen oxides are selectively removed by reducing components such as unburned carbon monoxide and hydrocarbons even under an excess of oxygen. As a reducible catalyst, a catalyst in which a base metal is contained in zeolite or the like has been proposed (Japanese Patent Application Laid-Open No. Sho 63).
-100919).

[0003] However, these catalysts have high activity, but have a problem in durability, and the deterioration of the activity cannot be suppressed. In particular, when these catalysts were exposed to an atmosphere containing water vapor at a high temperature for a long period of time, the activity was significantly deteriorated. In addition, attempts have been made to improve the durability of the catalyst by adding another metal to the catalyst containing copper, but the effect of the addition is not sufficient.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional problem, and it is intended to purify oxygen-excessive exhaust gas discharged from an internal combustion engine or the like, and to carry out steam treatment at a high temperature. It is an object of the present invention to provide a method for producing an exhaust gas purifying catalyst having excellent durability in an atmosphere containing nitrogen.

[0005]

The method for manufacturing an exhaust gas purifying catalyst provided by the present invention comprises the following steps (1) and (2).

(1) A step of stirring and mixing a porous inorganic carrier and a copper ion dispersion in the presence of a reducing agent, ammonia and an inert gas to obtain a slurry.

(2) A step of drying the obtained slurry under reduced pressure or an inert gas atmosphere.

That is, according to the present invention, a slurry in which a solution in which copper ions are dispersed and a porous inorganic carrier are mixed in the coexistence of a reducing agent, ammonia and an inert gas is formed, and then the slurry is depressurized or inert gas. An object of the present invention is to provide a method for producing an exhaust gas purifying catalyst having excellent durability in an atmosphere containing steam at a high temperature, characterized by drying under an atmosphere. According to this production method, a catalyst in which copper is contained in a porous inorganic carrier can be obtained.

The porous inorganic carrier used in the present invention is not particularly limited as long as it is a carrier having excellent heat resistance. However, when zeolite is used as the porous carrier, SiO ₂ / Al
Unless it is ₂ O ₃ = 10 or more, the heat resistance of the carrier is not sufficient, and the performance cannot be sufficiently exhibited.

As a porous inorganic carrier other than zeolite, a porous inorganic carrier such as silica, alumina, metallosilicate and aluminophosphate can be used. Although the catalyst obtained by the present invention contains copper, the copper compound used for the copper ion dispersion is not particularly limited as long as it is soluble in the catalyst. In addition, complex salts such as ammine complex salts can be used.

The content of copper is preferably 3 to 20% by weight including the carrier. The reducing agent used in the present invention is not particularly limited as long as it can reduce copper and can be added to a solvent. There is no particular limitation on the gas used when causing the reducing agent to act, as long as it is an inert gas.

When drying under reduced pressure when drying the slurry, it is desirable that the degree of vacuum be -50 KPa or more. It is desirable to dry at a temperature of 150 ° C. or higher. The inert gas used for drying is not particularly limited, but nitrogen, He, Ar, or the like can be used.

The exhaust gas purifying catalyst obtained by the present invention can be used by mixing with a binder such as clay mineral and molding. In addition, the inorganic porous carrier is molded in advance,
Thereafter, Cu can be contained as described above. The binder used for molding the inorganic porous carrier is not particularly limited, but clay minerals, SiO ₂ , Al ₂ O _{3 and the} like can be used. These can be wash-coated on a refractory carrier before use.

[0014]

Embodiments of the present invention will be described below with reference to examples and comparative examples.

(Example 1) Preparation of catalyst 1 ZSM5 zeolite (SiO ₂ / Al ₂ O ₃ = 23.
8) 10 g of an aqueous Cu ammine complex solution containing Cu in the same mole as Al contained in the zeolite (pH = 10.
In addition to 5), hydrazine monohydrate was added in the same molar amount as Cu while bubbling He gas into the solution. The obtained slurry was heated at 30 ° C. for 20 hours while bubbling He gas.
Stirred for hours.

This slurry was separated by filtration, and the obtained cake was again added to the above another solution and stirred similarly.

This is filtered off again, and the obtained cake is reduced to -1.
While gradually increasing the temperature with a vacuum dryer of 00 kPa, 25
After drying at 0 ° C. for 12 hours, catalyst 1 was obtained. The composition of the obtained catalyst was analyzed using fluorescent X-rays. As a result, the copper content was Cu / Al ₂ = 1.98.

(Example 2) Preparation of catalyst 2 The same operation as in Example 1 was carried out to prepare a cake, and when the obtained cake was dried, 50 ml of He was used in a dryer.
The temperature is gradually raised while flowing through the
After drying for an hour, catalyst 2 was obtained. The composition of the obtained catalyst was analyzed using fluorescent X-rays. As a result, the copper content is C
u / Al ₂ = 1.98.

Example 3 Preparation of Catalyst 3 In Example 1, a Cu ammine complex aqueous solution (pH = 1)
0.5) is twice as much C as Al contained in the zeolite.
Catalyst 3 was obtained in the same manner as above except that the aqueous solution was changed to an aqueous solution of Cu ammine complex containing u (pH = 10.5). The composition of the obtained catalyst was analyzed using fluorescent X-rays. As a result, the copper content was Cu / Al ₂ = 2.17.

Example 4 Preparation of Catalyst 4 In Example 1, an aqueous solution of Cu ammine complex (pH = 1)
0.5) is 5 times the molar amount of C contained in the zeolite.
Catalyst 4 was obtained in the same manner as above except that the aqueous solution was changed to an aqueous solution of Cu ammine complex containing u (pH = 10.5). The composition of the obtained catalyst was analyzed using fluorescent X-rays. As a result, the copper content was Cu / Al ₂ = 2.04.

Comparative Example 1 Preparation of Comparative Catalyst 1 ZSM5 zeolite (SiO ₂ / Al ₂ O ₃ = 23.
8) 10 g of an aqueous Cu ammine complex solution containing 0.5 moles of Cu of Al contained in the zeolite (pH = 1)
0.5) Added to aqueous solution. The resulting slurry was stirred at 30 C for 20 hours.

After filtration, the obtained cake was dried in a usual dryer at 110 ° C. for 20 hours to obtain Comparative Catalyst 1. The composition of the obtained catalyst was analyzed using fluorescent X-rays. As a result, the copper content was Cu / Al ₂ = 1.03.

(Comparative Example 2) Preparation of Comparative Catalyst 2 A cake was prepared in the same manner as in Comparative Example 1, and the obtained cake was dried in a vacuum dryer at -100 kPa at 250 ° C. for 20 hours. Obtained. The composition of the obtained catalyst was analyzed using fluorescent X-rays. As a result, the copper content is Cu
/ Al ₂ = 1.03.

Comparative Example 3 Preparation of Comparative Catalyst 3 The operation of stirring the slurry in the coexistence of Cu ion, hydrazine and He in Example 1 was performed only once, and the obtained cake was dried in a usual dryer. After drying at 110 ° C. for 20 hours, Comparative Catalyst 3 was obtained. The composition of the obtained catalyst was analyzed using fluorescent X-rays. As a result, the copper content was Cu / A
l ₂ = 0.89.

Comparative Example 4 Preparation of Comparative Catalyst 4 The aqueous Cu ammine complex solution of Comparative Example 1 (pH = 1)
0.5) of Cu ammine complex aqueous solution (pH = 10.0.5) containing 2.5 times mole of Cu of Al contained in the zeolite.
The same operation was performed except for changing to 5) to obtain Comparative Catalyst 4. The composition of the obtained catalyst was analyzed using fluorescent X-rays. As a result, the copper content was Cu / Al ₂ = 1.98.

(Comparative Example 5) Preparation of Comparative Catalyst 5 A cake was prepared in the same manner as in Comparative Example 4, and the obtained cake was passed through a dryer at a flow rate of 50 ml / min.
The temperature was gradually raised and dried at 250 ° C. for 12 hours to obtain Comparative Catalyst 5. The composition of the obtained catalyst was analyzed using fluorescent X-rays. As a result, the copper content was Cu / Al ₂ = 1.9.
It was 8.

(Evaluation of Performance) The obtained catalysts 1 to 4 and comparative catalysts 1 to 5 were molded by a tableting machine, and then pulverized to 500 μm to 1 μm.
The particles were sieved to have a size of mm and used as a catalyst for evaluation. Before performing the performance evaluation, a pretreatment of the evaluation catalyst was performed. That is, O ₂ 6%, N ₂
In an atmospheric pressure fixed bed through which a balanced gas was passed at SV = 10,000 hr ^-1 , the catalyst for evaluation was heated at 500 ° C. for 1 hour.
hr.

Thereafter, the pretreated catalyst for evaluation 0.7
5 ml was taken, and a gas having a composition shown in Table 1 (hereinafter, referred to as a reaction gas) was SV = 200,000 on a fixed bed under normal pressure flow.
hr- ¹ . NOx at catalyst bed inlet and catalyst bed outlet
The concentration was measured using a chemiluminescence NOx meter from 600 ° C. to 200 ° C. in steps of 50 ° C. when the NOx concentration reached a steady state, and the NOx purification rate (%) at each temperature was determined. Table 2 shows the results.

[0029]

[Table 1]

The NOx purification rate (%) was calculated by the following equation.

NOx purification rate (%) = (inlet NOx concentration−outlet NOx concentration) ÷ inlet NOx concentration × 100

[0032]

[Table 2]

(Evaluation of durability performance) The obtained catalysts 1 to 4 and comparative catalysts 1 to 5 were molded by a tableting machine, and then pulverized to 500 μm.
It was sized to 〜1 mm to obtain a catalyst for evaluation. Before performing the performance evaluation, a pretreatment of the evaluation catalyst was performed. That is, a gas having an O ₂ flow of 6% and a N ₂ balance at a normal pressure is SV = 10,000 h
The catalyst for evaluation was kept at 500 ° C. for 1 hour in a fixed bed under normal pressure flowing at r ⁻¹ .

Then, 2 ml of the pre-treated catalyst for evaluation was used.
Then, a gas having a composition shown in Table 3 (hereinafter referred to as a durable gas) was applied to a fixed pressure flowing fixed bed at 600 ° C. for 5 hours by SV.
= 10,000 hr ^-1 .

[0035]

[Table 3]

0.75 ml of the catalyst subjected to the above durability treatment
Then, the catalyst was evaluated in the same manner as in the performance evaluation described above, and the durability performance was evaluated. Table 4 shows the results.

[0037]

[Table 4]

As apparent from Tables 3 and 4, the catalyst 1
Nos. 4 to 4 are excellent in durability under durability conditions including water vapor, and particularly excellent in durability at a low temperature of 300 ° C. to 400 ° C.

[0039]

As described above, according to the present invention,
With the above configuration, it is possible to obtain an exhaust gas purifying catalyst that purifies oxygen-excessive exhaust gas discharged from an internal combustion engine or the like and has excellent durability in an atmosphere containing steam at a high temperature.

Claims (2)

[Claims] 1. A method for producing an exhaust gas purifying catalyst, comprising the following steps (1) and (2). (1) A porous inorganic carrier and a copper ion dispersion solution are mixed with a reducing agent,
A step of obtaining a slurry by stirring and mixing in the presence of ammonia and an inert gas. (2) A step of drying the obtained slurry under reduced pressure or an inert gas atmosphere. 2. The method for producing an exhaust gas purifying catalyst according to claim 1, wherein the porous inorganic carrier is zeolite.