JP2923064B2 - Manufacturing method of exhaust gas purification catalyst - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a nitrogen oxide (hereinafter referred to as NO
x), carbon monoxide (CO), and a catalyst for purifying exhaust gas containing hydrocarbons.

[0002]

2. Description of the Related Art In the treatment of exhaust gas from automobiles and the like, hydrocarbons and CO in exhaust gas are purified using a catalyst (composition: Pt, Rh / Al ₂ O ₃ ) commonly called a three-way catalyst. However, NOx is purified only in a very narrow range near the stoichiometric air-fuel ratio. In recent years, with the increasing global environmental issues, there is a strong demand for lower fuel consumption of automobiles.
Lean-burn engines that burn at or above the stoichiometric air-fuel ratio have attracted attention as a key technology. Recently, a crystalline silicate catalyst obtained by ion-exchange of copper as a catalyst capable of purifying NOx in a lean region has been spotlighted as a catalyst having high performance.

[0003] However, a catalyst in which copper is supported on crystalline silicate by a conventional ion exchange method has a problem that the initial activity is sufficient but the durability is poor.

[0004]

The exhaust gas temperature of a normal lean-burn engine exhaust gas ranges as high as 300 to 700 ° C., and sometimes reaches a high temperature of about 750 ° C. instantaneously. And
It may be transformed into copper oxide or metallic copper. or,
The crystalline silicate also has a demetallization phenomenon to some extent, and the crystal may be somewhat disintegrated.

[0005] In view of the above technical level, the present invention does not have the disadvantages of conventional catalysts, is used for purifying exhaust gas, and has heat resistance.
An object of the present invention is to provide a method for producing a catalyst having a high steam resistance.

[0006]

The automobile exhaust gas contains a large amount of water vapor, and is further exposed to a high-temperature atmosphere at around 700 ° C. Therefore, it is an issue to manufacture a catalyst having high heat resistance and steam resistance. The present inventors have conducted intensive studies and, as a result, have found a method for producing a catalyst having high heat resistance and steam resistance.

That is, according to the present invention, in producing a catalyst for purifying an exhaust gas containing nitrogen oxides, carbon monoxide and hydrocarbons, copper as a main active metal is impregnated with a copper halide solution by the following method. And the X-ray diffraction pattern is
A method for producing an exhaust gas purifying catalyst characterized by being supported on a crystalline silicate carrier having the characteristics shown in Table 1 above.

The copper halide used in the present invention includes cupric chloride, cuprous chloride, cupric bromide, cuprous bromide, copper iodide and the like. It is used as a complex solution and further as an alcohol solution.

[0009]

In the catalyst production method of the present invention, it is not clear why the steam resistance and heat resistance of the catalyst are improved by supporting copper on the crystalline silicate by the impregnation method using a copper halide solution. However, it is expected that copper is supported in a state where aggregation is suppressed by the electron absorption action of halogen, and further, demetalization from crystalline silicate is also suppressed.
It has been confirmed that the durability of the catalyst is improved even after the impregnated catalyst is sufficiently purged with halogen in the pretreatment.

The catalyst produced according to the present invention preferably has a honeycomb shape from the viewpoint of reducing pressure loss, but can be used in a pellet state. In addition, it has been confirmed that a binder such as silica sol and alumina sol used in molding the catalyst has almost no adverse effect on the catalyst performance.

[0011] The molar ratios of oxides in the crystalline silicate carrier is dehydrated form used in the catalyst is _{(1.0 ± 0.8) R 2 O} · _{[a · M 2 O 3 · bAl} 2 O ₃ ] · ySiO ₂ (wherein, R is an ion of an alkali metal ion and / or an organic nitrogen-containing compound or a hydrogen ion, M is a group VIII element, a rare earth element, titanium, vanadium, chromium, niobium, gallium , bismuth, Ions of one or more elements of the group consisting of tantalum and antimony, a + b = 1, a ≧ 0,
b> 0, y> 11), and the X-ray diffraction pattern is particularly shown in Table 1.

[Table 1] VS: Very strong S: Strong M: Intermediate W: Weak

[0012]

【Example】

 Example 1 A catalyst was prepared as follows. (A) Preparation of slurry 3 parts of alumina sol and 55 parts of silica sol as binder
Parts, 100 parts of crystalline silicate powder and 300 parts of water
And thoroughly agitate to make washcoat slurry.
Was. Note that the crystalline silicate composition is N
a_TwoO ・ 0.5Al _TwoO_Three・ 0.5Fe_TwoO_Three・ 25S
iO_TwoWhich is converted to H-type by protonation treatment.
Was used.

(B) Coating The cordierite type monolith substrate is immersed in the slurry obtained in (a), taken out, and then the excess slurry is blown off and dried at 200 ° C. The coating amount is 100 g per liter of the base material. This coated material is referred to as coated material A.

(C) Support of copper halide 23 parts of cupric chloride is dissolved in 100 parts of water to prepare an impregnation liquid. The coated material A of (b) is immersed in this and left for 1 hour. After that, the excess liquid was blown off and dried at 200 ° C., and then calcined at 500 ° C. for 10 hours in a nitrogen atmosphere to obtain catalyst A
I got The amount of Cu supported on the crystalline silicate was 0.88 mmol / g.

(Embodiment 2) (a) similar to Embodiment 1
Through the step (b), the influence of the copper halide species was examined.
13 parts of cuprous chloride are converted to 100 parts of 30% hydrochloric acid and 1 part of cuprous chloride
3 parts of 100% ammonia, 30 g of cupric bromide in 100 parts of water, 22 g of cuprous iodide in 100 parts of 30% hydrochloric acid, and the coated product A was immersed in each. , C, D and E were obtained. The supported amount of each Cu is 0.88
mmol / g.

(Comparative Example 1) The coated product A prepared in Examples 1 (a) and (b) was immersed in a 0.04 mol aqueous copper acetate solution, and the aqueous solution was continuously supplied using a circulation pump (1 at room temperature).
(00 hours), and after sufficiently supporting copper ions on the crystalline silicate by an ion exchange method, washing was carried out completely until the anions were completely removed to obtain a catalyst F. In this method, the amount of Cu supported on the crystalline silicate is 0.88.
mmol / g.

(Experimental Example) The catalysts A to F prepared in Examples 1 and 2 and Comparative Example 1 were subjected to activity evaluation tests. The activity evaluation conditions are as follows. (Gas composition) NO: 400 ppm, CO: 1000 pp
m, C ₂ H ₄ : 1000 ppm, C ₃ H ₆ : 340 pp
m, O ₂ : 8%, CO ₂ : 10%, steam: 10%,
Balance: N ₂ , GHSV: 30000 h ⁻¹ Reaction temperature: 35
Table 1 shows the denitration ratio of the fresh catalyst at 0,400,450 ° C.

Further, as a durability test of the catalyst, the catalysts A to
F was mounted on an actual vehicle, and after running 30,000 km, the activity was evaluated under the same conditions as above. The activity results are also shown in Table 1.

As shown in Table 1, the catalysts A to E in which a copper halide was supported on a crystalline silicate were fresh and 30,000 km
It was found that the catalyst had high denitration activity even after running, and was found to be a catalyst having durability. On the other hand, it has been found that the catalyst F carrying Cu ions by a normal ion exchange method has a high activity in a fresh state, but the activity is greatly reduced after traveling 30,000 km.

[Table 2]

[0020]

The crystalline silicate catalyst supporting Cu produced by the method of the present invention can be a stable catalyst with high durability, and can be used as a lean burn engine exhaust gas purifying catalyst.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Seito Suwa 4-22, Kannonshinmachi, Nishi-ku, Hiroshima-shi, Hiroshima Mitsubishi Heavy Industries, Ltd. Hiroshima Research Laboratory (56) References JP-A-63-119849 (JP, A JP-A-63-119850 (JP, A) JP-A-3-101836 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B01J 29/88 B01D 53/94

Claims (1)

(57) [Claims] In producing a catalyst for purifying an exhaust gas containing nitrogen oxides, carbon monoxide and hydrocarbons, copper as a main active metal is removed by an impregnation method with a copper halide solution.
Composition in which the molar ratio of the oxide in the form of water is represented by the following formula
A method for producing an exhaust gas purifying catalyst, characterized in that the catalyst is supported on a crystalline silicate carrier having an X-ray diffraction pattern having the characteristics shown in Table 1 below . (1.0 ± 0.8) R ₂ O · [a · M ₂ O ₃ · bAl ₂ O ₃ ] · ySiO ₂ [In the above formula, R: alkali metal ion and / or organic nitrogen
Ion or hydrogen ion of element-containing compound, M: Group VIII element
Element, rare earth element, titanium, vanadium, chromium, nio
, Gallium, bismuth, tantalum, antimony
Ions of one or more elements in the group: a + b = 1, a ≧ 0,
b ≧ 0, y> 11]