JPH0389943A - Preparation of catalyst for purifying exhaust - Google Patents

Abstract

PURPOSE:To obtain a catalyst capable of efficiently purifying HC, CO and NOX in exhaust even in the atmosphere contg. excess oxygen by utilizing copper complex salt or noble metallic complex salt as a template in the case of synthesizing zeolite. CONSTITUTION:Copper complex salt or noble metallic complex salt utilized as a template is mixed with silicon compd. and aluminum compd. This mixture is calcined to synthesize zeolite. Thereafter zeolite is carried on a refractory carrier and a catalyst is produced. As the complex salt of copper or noble metal e.g. Pt, Rh, Ir and Pd, such complex salt is shown that an inorganic or organic ligand e.g. ammonia, amine, diamine, carboxylic acid, EDTA and heterocyclic compd., etc., are coordinated to the above-mentioned metal.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing an exhaust purification catalyst used in vehicles such as automobiles, and more specifically, the present invention relates to a method for manufacturing an exhaust purification catalyst used in vehicles such as automobiles, and more particularly, the present invention relates to a method for manufacturing an exhaust purification catalyst for use in vehicles such as automobiles, and more specifically, the present invention relates to a method for manufacturing an exhaust purifying catalyst for use in vehicles such as automobiles. He, CO and NOx f
The present invention relates to a method for producing a catalyst that can be purified at a high rate.

[Conventional technology]

Catalysts that simultaneously oxidize carbon oxides (CO) and hydrocarbons (HC) and reduce nitrogen oxides (NOx) are widely used as exhaust purifying catalysts for automobiles. Basically, such catalysts are prepared by coating a γ-alumina slurry on a refractory support such as cordierite, firing it, and then adding Pd, Pt,
It supports a metal such as Rh or a mixture thereof.

By the way, the purification characteristics of the catalyst described above are greatly influenced by the set air-fuel ratio of the engine, and in the lean side where the air-fuel ratio is large, the amount of oxygen (02) is large even after combustion, and the oxidation The action becomes active and the reducing action becomes inactive. On the contrary.

On the rich side where the air-fuel ratio is small, oxidation is inactive and reduction is active. The catalyst works most effectively near the stoichiometric air-fuel ratio (A/f''=14.6), where oxidation and reduction are balanced.

Therefore, in automobiles equipped with exhaust purification devices using catalysts, feedback control is performed to detect oxygen-enriched metal in the exhaust system and maintain the air-fuel mixture near the stoichiometric air-fuel ratio.

On the other hand, there is a demand for lower fuel ratios in automobiles, and it is known that in order to achieve this, it is sufficient to completely combust a mixture with as much oxygen as possible during normal driving. However, if this is done, the air-fuel ratio will be on the lean side, resulting in an oxygen-excess atmosphere, and although HC and Co among the harmful components in the exhaust can be removed by oxidation, NOx will be prevented from contacting active metals by the 02 adsorbed on the catalyst bed. Therefore, it becomes difficult to reduce and remove it.

In order to improve these drawbacks, the applicant has filed a
In No. 291,258, they proposed a catalyst for exhaust gas purification characterized by a zeolite ion-exchanged with a transition metal supported on a refractory carrier.

The above transition metals include Cu, Co, Cr, N
i.

Fe·tMn is preferable, and Cu is particularly preferable.

Zeolite 11 As is well known, it is a crystalline aluminosilicate represented by the general formula 2xM2/n -At203-ysi02, and contains M (n-valent metal), X, y
Tunnel structure (pore size) in the crystal structure due to differences in
There are many different types available on the market. Also, S
Because part of I4+ is replaced with tA43+, there is a lack of positive charge, and to compensate for this lack, it has the property of retaining cations such as Na+ and Ni+ within the gold crystal, so it has a high cation exchange ability. .

Furthermore, zeolite has pores of several A units in size, which are comparable to the size of molecules, as is also called a molecular sieve.

Therefore, HC is selectively taken into the pores, where HC
is adsorbed at acid sites. Furthermore, since active sites of transition metals introduced by ion exchange exist in the pores, NO is adsorbed there and reacts with active CO generated from 17J, C, or HC. For this reason, lean side
NOx can be removed efficiently even when

[Problem to be solved by the invention]

However, when supporting copper, for example, through ion exchange, there is a risk that copper will adhere not only to the inside of the zeonite a pores but also to the surface of the zeolite particles. It tends to aggregate, which is a major cause of decreased activity and durability.

The Kinen f3A is intended to solve the problems of the prior art described above. The first object of the present invention is to provide a complete method for manufacturing an exhaust gas purification catalyst that has a high NOx purification rate and excellent durability. In addition to the above, the second object of the present invention is to further increase the purification rate of HC and CO.
An object of the present invention is to provide a complete method for producing an exhaust purification catalyst that can be used not only as an x-catalyst but also as a three-way catalyst.

[Means for resolving issues]

That is, the method for producing an exhaust purification catalyst of the present invention involves mixing a silicon compound, an aluminum compound, and a copper complex salt or a noble metal complex salt as a template, and baking the mixture to form a zeolite.
The zeolite is then synthesized and then supported on a refractory carrier.

There are various types of zeolites as shown in the first section below.

Super Cage Entrance and Network Structure of Zeolite (Table 1) Preferred zeolites to be synthesized using the method of the present invention include, for example, ZSM-5 and Ferrierite.
te). For zsM-s, for example, g, tea, cocoty mouth (G.

T, Kokotailo), varnish, xle, c+
-ton (S, L.

LawLon) and Day, H. Olson (D.)
i.

01 son) “Structure of Synthesis Zeolite ZSM-5 (Structure of
5yntheticzeolite ZSM-5)”
Nature Volume 272, 197
Source: March 30, 1998, page 437. Also, regarding ferrierite, for example, Earl, Gramli Nochimeyer.

Gramlich-Meier, W. M. Meier and B. Gu. Smith (B, K.

Sm1th), ``Onfall Twin the Framework Structure of Zeolite Fuelierai) (
On faults in the fra
mework 5trucLureof zeoli
te ferrieriQ ” Zeitschrif)
7yuA/Crystalgraphy (Zei Lscb
rif Lfur Kristallo-graphi
e) 'I 69.201-210 (1984) and C, L. Kibii (C, L.

Kibby), x-, J, PeCl ivy (A, J
, Perro Lta) & 7JF, E.
-yノVsu(B", E, MassoLh).

Composition and Catal Properties of Synthesis
yticProperties of 5ynthet
ic FerrieriLe)”Journal ofcaLalysis
35.256-272 (1974).

Among the above zeolites, compared to other zeolites, ZSM-5 has a large 8i02/At203 ratio and high acid strength; it has a 10-membered oxygen ring; it has very little crystal water, is hydrophobic, and has few weak acid sites. It is most preferable to have the following characteristics.

Silicon compounds and aluminum compounds jp! :J may be one commonly used for producing the above zeolite), and may be a compound or composition containing 5102, A, or t203f, such as silica sol or sodium aluminate.

The ratio of silicon compound and aluminum is determined depending on the desired zeolite.

Complex salts of copper or noble metals such as PL, Rh, Ir, Pd as templates may be prepared by combining said metal with inorganic or organic ligands such as ammonia, amines, diamines, carboxylic acids, ethylenediaminetetraacetic acid (edta). ), complex salts coordinated with heterocyclic compounds, etc. Among these various complex salts, a suitable one is selected in consideration of zeolite synthesis conditions, ease of handling, availability, properties (solubility, etc.), etc. Further, the ratio of the tensile rate is ultimately determined depending on the amount of copper or noble metal supported on the zeolite.

Zeolite is usually synthesized by mixing each component in water, reacting in an autoclave, washing with water, drying, and then calcining at about 500°C. Mixing conditions and autoclave treatment conditions are selected as appropriate.

Examples of the refractory carrier used in the method of the present invention include ceramic carriers such as cordierite, metal carriers, and the like.

The amount of zeolite spread on the refractory carrier, the size and shape of the refractory carrier, and other properties are selected depending on the characteristics required of the catalyst.

[Effect]

When a copper complex salt or a noble metal complex salt is used as a template, the copper complex salt or noble metal complex salt becomes a nucleus in the initial stage of zeolite synthesis, and a cage of 5Si-0 is formed by a so-called template reaction. The copper or noble metal is then incorporated into available sites within the zeolite lattice or pores during the calcination step, during which the ligands disappear. At this time, the chemical bond between the copper or noble metal and the zeolite lattice is stronger than the electrostatic bond due to ion exchange, and migration of the copper or noble metal can be prevented. Furthermore,
By incorporating a large amount of copper or precious metal into effective sites within the pores of the zeolite, sintering is less likely to occur and thermal stability is improved.

〔Example〕

The present invention will be explained in more detail with reference to the following examples and comparative examples. However, the present invention is not limited to the following examples.

Examples 1 to 10 Examples in which the zeolite is ZSM-5=i are shown below.

The following ingredients: ) Silica sol (30wt%5in2) II) 7 Lumi7 acid t Thorium (1,5Na2
0/AtzOs) aqueous solution 1ii) Pure water lv) Template aqueous solution (1 mol/L) was finally 608i (J2・A/!403-1.5Na20
-1. The mixture is mixed so that the composition ratio becomes s (ten rate).550 H2O, and the mixture is stirred at room temperature for 20 to 30 minutes.

Then, in an autoclave at 190℃ for 60 to 100 minutes.
After reacting for a time, washing with water, drying, and baking at about 500°C.

50 parts of the ZSM-5 powder synthesized above, 70 parts of silica sol (10 wL% 5i02), and 20 parts of pure water are mixed and stirred to obtain a slurry. Next, this entire slurry was wash coated on a cosinilite monolith test piece with a diameter of 30 cavities and a length of 50 cavities (coating amount: 120 mm).
f/l). This was baked at 500°C for 3 hours.

The following templates a) to j): a) (Cu(edLa)) Brz edta: ethylenediaminetetraacetic acid (Cu(NH3) 4 ) Brt (Cu(en)2 ) C4 or (cu(en)s )
en: Ethylenediamine t2 d) [C-4:) 2) B...e) (Cu (imidazole) 4) Br2 f) (PL(en)2) CA2 or CPL(e
n)3) ctsg) (''(NH3)4) C
4・l(,0 or CP t (NH3)6 ) C14
h) (Rh(en)z ,) Ctz or (Rh(
en)3) C13') (Rh(NH3)6)B
All of rs D (Pd(NH4))Br2 was used to obtain catalysts I to X&. The figure is a perspective view of an exhaust purification catalyst 1 obtained by the method of the present invention.

Comparative Example 1 ZSM was prepared in the same manner as Examples 1 to 10, except that k) TPA・OH (triphosphoric acid) was used as the tensile rate.
-5 powder was synthesized, and a 0.02 mol/l acetic acid acetic acid solution 80
9 steel supported by ion exchange method for rrtl gold (2,8s
y/l) and obtained catalyst X.

Comparative Example 2 0,02 mo ], / was replaced with (10003 mo 1/l (Rh(Nl(3)6)
Rhodium was supported (Q, 3V/l) in the same manner as in Comparative Example 1 except for using the C12 aqueous solution joOm'i,
Catalyst Xll was obtained.

Comparative Example 3 Copper silicate with pentasil type zeolite structure (ZSM-
Structure containing Cu in place of At in 5) 50 parts of powder, 35 parts of silica sol (20 wL% 5i02), and 20 parts of pure water were mixed and stirred to obtain a slurry. Below, Examples 1 to 10
Catalyst X■ was obtained in the same manner as above.

Performance evaluation test〉 Test 1 Catalysts ■～■ and catalysts
-1A/F=22. Time = 3h Evaluation conditions: Inlet gas temperature 400℃, 5V = 60000
The initial activity and the activity after durability were evaluated under h-IA/F=22.

The results are shown in Table 1 below.

Table 1: Initial activity and activity after durability As shown in the first column, catalysts 1 to 2 produced by the method of the present invention use a copper complex as a tensile rate.
Copper exists in a stable state, and the activity after durability is higher than that of Catalyst X produced by an ion exchange method. In addition, with the catalyst Xl1l using copper silicate, the decrease in activity after durability is not large because the copper does not sinter, but the No purification rate decreases because the copper is contained in the silicate lattice. A1□I don't know.

Therefore, catalysts I~■ produced by the method of the present invention
Compensates for the weaknesses of copper ion exchange zeolite catalyst X and copper silicate catalyst X, respectively, and is excellent as a tri-lean NOx catalyst.

Test 2 Catalysts ■~X and Catalyst 1. The following conditions for Xl,
h-1A/F = 14.6 and 222 hours = 3h Evaluation conditions: Incoming gas temperature 400°C, 5V- = 60000h
The activity after durability was evaluated under -IA/F214.6 and 22. The results are shown in Table 2.

Table 2 Activity after durability As shown in Table 2, catalysts ① to Catalyst X.

It has high activity after durability over a wide range of air-fuel ratios compared to mowing.

Furthermore, among the catalysts produced by the method of the present invention, the activity differs depending on the type of tensile rate.

In other words, as is clear from comparing catalysts ■ to X with catalyst I, catalysts
The purification rate of C and CO is also high.

Furthermore, there is little variation in overall activity due to changes in air-fuel ratio.

Therefore, copper-zeolide catalysts I~■ cannot be used as binary catalysts, but noble metal-zeolide catalysts I~■ cannot be used as binary catalysts.
~X, there is little deterioration even in a rich atmosphere and it can be used satisfactorily as a three-way catalyst. Therefore, the noble metal-zeolide catalyst produced by the method of the present invention can be used not only as a lean NOx catalyst but also in atmospheres with a wide range of air-fuel ratios.

〔Effect of the invention〕

As mentioned above, the method for producing an exhaust purification catalyst of the present invention uses a copper complex salt or a noble metal complex salt as a template for zeolite synthesis, so that copper or noble metal gold is effectively dispersed in the zeolite pores during the zeolite synthesis process. By doing so, gold can be obtained as a catalytic species. Therefore, sintering of copper or precious metals due to thermal load during the manufacturing process or use of the catalyst does not occur, and the activity and durability of the resulting catalyst are improved.

In addition, when using precious metal complex salt purple as a template, it has a high purification rate of tt C and CO in addition to NOx, and can be used as a lean NOx catalyst, but also has high activity in a wide range of atmospheres with A/F = 13 to 25. A catalyst having the following properties can be easily obtained.

Furthermore, since the method of the present invention allows the use of various complex salts as templates, various modifications are possible, and the method can quickly respond to a wide variety of demands for exhaust purification catalysts.

[Brief explanation of drawings]

The figure is a perspective view of an example of an exhaust purification catalyst manufactured using the method of the present invention. In the diagram, 1... Exhaust purification catalyst

Claims (1)

[Claims] A catalyst for exhaust purification, characterized in that a silicon compound, an aluminum compound, and a copper complex salt or a noble metal complex salt as a template are mixed, fired to synthesize zeolite, and then the zeolite is supported on a refractory carrier. Production method.