JPH04118049A - Manufacture of honeycomb catalyst - Google Patents

Abstract

PURPOSE:To obtain a catalyst having high activity at the initial time and good heat resistance and durability by calcining at a high temp. after applying and supporting a support component, a heat resistance improving component, a catalyst component and an assist catalyst component uniformly mixed on a honeycomb substrate at the same time. CONSTITUTION:The support component of active alumina, silica, etc., to be heat-resistant metal oxide after calcining, the heat resistance improving component to be metal oxide of lanthanum and/or barium after calcining and the assist catalyst component of iron, cobalt, etc., forming base metal oxide after calcining, are added into a solution containing noble metal element of platinum, palladium, etc., to be the catalyst active component. Then, in this mixed liquid, the honeycomb substrate is dipped and each component is supported, and successively, the calcination is executed at high temp. By this method, the catalyst having table heat resistance at high temp. and high catalyst performance, is easily manufactured.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for manufacturing a honeycomb catalyst, and more specifically, to a honeycomb catalyst that has extremely excellent oxidative decomposition performance and heat resistance when converting harmful substances in exhaust gas into harmless substances. The present invention relates to a method for producing a honeycomb catalyst having the following.

[Conventional technology]

A honeycomb catalyst has a honeycomb base having an integral structure, and
A carrier component made of a heat-resistant metal oxide such as alumina, silica, silica/alumina, titania, and zirconia, a catalyst component made of a platinum group metal such as platinum, palladium, rhodium, and ruthenium, and used in combination as necessary. Supports promoter components and/or heat resistance improving components such as transition metal elements such as nickel, cobalt, iron, and copper, alkaline earth elements such as barium, calcium, and strontium, and rare earth elements such as lanthanum and cerium. be. This honeycomb catalyst is used to purify carbon monoxide, hydrocarbons, nitrogen oxides, etc. in the exhaust gas of internal combustion engines such as automobiles, as well as for deodorizing off gas, catalytic combustion for heat recovery, home heating equipment, and cooking. It is widely used for general industrial purposes such as deodorizing equipment.

As a method for manufacturing a honeycomb catalyst having an integral structure, (
1) A method in which a honeycomb substrate is coated with a slurry of a heat-resistant metal oxide such as soluble alumina or activated alumina and fired, and then a catalyst component and a co-catalyst component are impregnated and supported, and further fired, (2) Heat-resistant metal oxide After mixing the heat resistance improving component into the slurry of the product and firing it, it is crushed and made into a slurry again.The honeycomb substrate is coated with this slurry and fired to impregnate and support the catalyst component and co-catalyst component, and then fired. Methods are known.

However, these methods are cumbersome and require multiple steps such as supporting treatment and firing treatment.
Manufacturing costs increase. Furthermore, since the catalyst components cannot be uniformly dispersed and supported, there are drawbacks such as the inability to stabilize the catalyst performance and to fully exhibit its performance. In addition, when impregnating and supporting a soluble heat resistance improving component on a powdered heat resistant metal oxide, the subsequent drying,
Handling such as dust scattering during firing, crushing, etc. 1
Various problems arise.

[Problem to be solved by the invention]

The applicant previously proposed a high-temperature durable combustion catalyst in which palladium or platinum is dispersed and supported on a heat-resistant carrier such as lanthanum-doped alumina or barium-doped alumina, and a method for producing the same (Japanese Patent Application No. 01-184269). , Japanese Unexamined Patent Publication No. 61-28453).

However, with the above combustion catalyst, when supporting the noble metal component, some of the lanthanum compound or barium compound elutes or moves through the carrier, making it impossible to optimally control the supported distribution of the noble metal component. , it was found that stable catalyst performance could not be maintained.

An object of the present invention is to solve the above-mentioned technical problems and to provide a method for producing a honeycomb catalyst that can produce a catalyst having stable high temperature heat resistance and high catalytic performance through a simple process.

[Means to solve the problem]

As a result of intensive studies in view of the above-mentioned problems, the present inventors have found that by coexisting lanthanum and/or barium, which are heat resistance improving components, during calcination, thermal deterioration of the catalyst component and promoter component at high temperatures can be prevented. As a result, a uniformly mixed carrier component, heat resistance improving component, catalyst component, and promoter component can be coated and supported on a honeycomb substrate at the same time and fired at high temperatures, and the initial activity and heat resistance durability of the catalyst are further improved. We have discovered that it is possible to do this, and have arrived at the present invention.

The present invention includes a carrier component that forms a heat-resistant metal oxide after firing in a solution containing a noble metal element that is a catalytically active component;
After adding and mixing a heat resistance improving component that forms metal oxides of lanthanum and/or barium after firing and a promoter component that forms base metal oxides after firing, the honeycomb substrate is immersed in this mixed solution. to support each component,
The present invention relates to a method for producing a honeycomb catalyst, which is characterized in that it is then fired at a high temperature.

There are no particular restrictions on the honeycomb substrate used in the present invention, and commonly used honeycomb substrates may be used, such as heat-resistant ceramic honeycombs such as cordierite, mullite, α-alumina, aluminum titanate, zirconia, and aluminum silicate. In addition to the above, metal honeycombs made of heat-resistant metals such as stainless steel, Ni alloy, and A1 alloy can also be used.

The catalytically active component used in the present invention is a noble metal element, preferably at least one of platinum, palladium and rhodium. These elements can be used in the form of any compound that can be fixed in a heat-resistant metal oxide, such as nitrates, hydrochlorides, ammine complexes,
Examples include metal acids and chlorides. Among these, nitrates, ammine complex salts and chlorides are particularly preferred, and are used in the form of aqueous solutions or colloids.

Examples of carriers supporting noble metal elements include heat-resistant metal oxides, specifically activated alumina, silica, magnesia, titania, zirconia, silica/alumina, silica/titania, silica/zirconia, silica/magnesia, alumina/magnesia, etc. Activated alumina is particularly preferred.

Activated alumina can also be used in the form of transition alumina powder of 10 μm or less, boehmite-like hydrated aluminum as a colloidal metal oxide, alumina sol, aluminum nitrate which becomes alumina after heat treatment, and the like.

The base metal oxide, which is a promoter component, is used to improve the activity and heat resistance of the above-mentioned noble metal component and to improve the heat resistance of the heat-resistant metal oxide. Examples of the base metal elements include iron, cobalt,
Examples include nickel, titanium, strontium, etc. Among these, at least one of iron, cobalt, nickel, and titanium is preferred. These elements can be combined with a carrier, and can be used in the form of any compound as long as they can be dispersed and fixed as fine oxide particles between the carrier particles or the particles of the noble metal component. Compounds are preferred.

In the present invention, the proportions of each metal element of the catalytic active component, the carrier component, the heat resistance improving component, and the co-catalyst component in the mixed solution are in the order listed above in molar ratios (1 to 20): (50 to
250): (5-25): The range is preferably (5-25).

[Effect]

In order to improve the activity and heat resistance of honeycomb catalysts, the carrier, catalyst components, co-catalyst components, etc. are sufficiently dispersed and mixed.
It is preferable to uniformly coat and support these on a honeycomb substrate and then fire at a high temperature.However, in the past, high-temperature firing (800°C or higher) and low-temperature firing lowered the catalytic activity of the catalyst component and co-catalyst component. Firing (500-600°C
It was necessary to perform the firing separately (see below).

However, according to the present invention, for example, 8
High-temperature firing at 00 to 1200°C can prevent thermal deterioration of the catalyst component and co-catalyst component, so the carrier component, heat resistance improving component, catalyst component and co-catalyst component are mixed at the same time and uniformly coated on the honeycomb substrate. It is possible to manufacture a honeycomb catalyst by supporting the catalyst and firing it at a high temperature once. By uniformly mixing the above components simultaneously in this way, for example, Laz 03 ' I lAl2z 03 , La2
Since the lanthanum compound existing in the state of O3, La AI O3, etc. and the precious metal element can be finely and closely supported on the alumina carrier, the exhaust gas purification reaction can be carried out extremely efficiently, and the Develops heat resistance and durability.

For example, in the catalyst of the present invention obtained by simultaneously and uniformly supporting palladium, lanthanum, titanium, and alumina on a honeycomb substrate, the production of lanthanum and alumina compounds and lanthanum and palladium compounds is increased, and palladium particles are extremely It is supported in a fine and highly dispersed manner. This state was confirmed by X-ray diffraction and electron microscopy. Further, a part of lanthanum is present as an oxide between the alumina particles and between the palladium particles and suppresses the growth of these particles at high temperatures. Furthermore, the titanium oxide is interposed between the palladium particles and between the lanthanum alumina particles and inhibits the growth of these particles at high temperatures.

Since the palladium crystal particles and the lanthanum compound and/or titanium compound are dispersed and supported in extremely fine and uniform proximity, the contact area with the exhaust gas is greatly increased, and the number of active sites is increased. catalytic activity is greatly improved. In addition, particles of lanthanum oxide and titanium oxide are interposed between alumina particles and palladium particles, which improves palladium dispersion and prevents particle growth at high temperatures.
Furthermore, since titanium oxide prevents sintering of the lanthanum-alumina carrier, heat resistance and durability at high temperatures are improved.

〔Example〕

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples.

Example 1 Polyvinyl chloride square container (200mm x 200mm x 1
00), boehmite slurry (AI!, 203 no 30)
Sol obtained by adding 10 wt % HNO3 to wt % suspension), 20 wt % palladium nitrate solution (An!20
The amount of Pd relative to 3 is 6 mol%), lanthanum nitrate (Alt
Lag for os is 4 mol% as Laz03) and Til for titania sol CA12O, Tie,
A cordierite honeycomb substrate (300 cells/inch, 2150 mm x 150 mm x 50 mm) was placed in the mixed solution with the openings facing up and down, and was wash coated. The coating amount was 60 g/l per substrate volume. After coating the puffer fish, it was dried at 120°C for 3 hours, then fired at 900°C for 3 hours, and the honeycomb capacity was 030g/! ! ,,
Pd 2g/l, Lago3 Bg/l and Ti
A honeycomb catalyst on which O□ 2 g/1 was supported was obtained.

Example 2 A catalyst was produced in the same manner as in Example 1, except that an equimolar amount of a solution of chloroplatinic acid was used instead of palladium nitrate.
30 g/l, pt 2g/ILa! 's 8
A honeycomb catalyst was obtained in which T i Oz 2 g/l and T i Oz 2 g/1 were supported.

Example 3 A catalyst was produced in the same manner as in Example 1, except that a barium hydroxide solution (Af, Bag for 01 was 7 mol% as BaO) was used instead of lanthanum nitrate. And honeycomb capacity light Af, 03s
o g/i,,Pd Ig/j! Lag()+
8g/II! A honeycomb catalyst on which 2 g/l of TiOz was supported was obtained.

Example 4 A catalyst was produced in the same manner as in Example 3, except that an equimolar amount of a solution of chloroplatinic acid was used in place of palladium nitrate, and honeycomb volumetric light and Adz O:
l 30 g/l, P L 2 g/! , Ba
A honeycomb catalyst was obtained in which 8 g/l of O6 and 2 g/p of TiOz were supported.

Example 5 A catalyst was produced in the same manner as in Example 1, except that 3000 g of a 20% by weight aqueous solution of aluminum nitrate was used instead of the boehmite slurry, and the honeycomb capacity was 30 g/l of Alzos and 2 g of Pd. /
l, L a2 oi 8 g/l and TiO2
A honeycomb catalyst loaded with 2 g/l was obtained.

Example 6 In Example 5, a solution of barium hydroxide (Bai with respect to Altos is 7 mol% as BaO) was used instead of lanthanum nitrate, and an aqueous solution of nickel nitrate (Nil with respect to Al, 0. as NiO) was used instead of titania sol. A catalyst was produced in the same manner as in Example 5, except that mol %) was used, and the honeycomb capacity light and AI! ,z C)+
10 g/f, P d2 g/f! ,,BaO6,
A honeycomb catalyst was obtained in which 8 g/l, Ni01, and Bg/l were supported.

Example 7 A catalyst was produced in the same manner as in Example 5, except that an aqueous solution of ferric nitrate (the amount of Fe relative to AfzOx was 4 mol% as Fe, O,) was used instead of titania sol. Honeycomb capacitance light or Ant O+
20g/l, Pd 2g/I! ,,LazO+
A honeycomb catalyst was obtained in which 8 g/l and Fe, 0°3.9 g/l were supported.

Example 8 A catalyst was produced in the same manner as in Example 6, except that an aqueous solution of cobalt nitrate (Co amount relative to Ajl! 203 was 4 mol% as Coo) was used instead of nickel nitrate. Honeycomb Capacitance Hikari Alz Os
30 g/I! ,, Pd 2g/l, BaO6,
A honeycomb catalyst was obtained in which 8 g/R and Coo 1.8 g/E were supported.

Comparative Example 1 Using the components used in Example 1, lanthanum nitrate was first added to the boehmite slurry, dried at 120°C, and then heated at 900°C.
It was baked for 3 hours. Next, 40% by weight of pure water was added to this fired product, and a 20% by weight aqueous solution of palladium nitrate and titania sol were added, and the mixture was pulverized in a porcelain ball mill for 20 hours, and the resulting slurry was wash-coated on a honeycomb substrate. After drying at 120°C, it was fired at 800°C for 2 hours to obtain a honeycomb catalyst.

Comparative Example 2 Using the components used in Example 1, first add lanthanum nitrate to boehmite slurry, dry at 120°C, and then dry at 900°C for 30 minutes.
Baked for an hour. Next, this fired product was heated in a porcelain ball mill for 20 minutes.
This was pulverized in a timed manner, wash-coated onto a honeycomb substrate, dried at 120°C, and then fired at 600°C for 2 hours. Further, the obtained honeycomb coated with a lanthanum-added alumina carrier was impregnated with a mixed solution of palladium nitrate aqueous solution and titania sol, and after drying, the honeycomb was calcined at 800°C for 2 hours to obtain a honeycomb catalyst.

Comparative Example 3 A honeycomb catalyst was produced in the same manner as in Comparative Example 2, except that an aqueous barium hydroxide solution was used instead of lanthanum nitrate.

Comparative Example 4 A honeycomb catalyst was produced in the same manner as in Comparative Example 3, except that a nickel nitrate aqueous solution was used instead of Chinania sol.

<Test Example> The performance of each catalyst obtained in Examples 1 to 8 and Comparative Examples 1 to 4 was investigated as follows.

Cut each of the above honeycomb catalysts into 20MX20aX20 with a cutter.
Cut out a section of 2.0 mm in diameter, fill it in a quartz multi-tube reaction tube, and set the catalyst layer inlet temperature to 900°C and space velocity to 30.0O.
It was aged with Oh-' through air. During the aging treatment, an activity test was conducted at regular intervals to evaluate the heat resistance and durability of the catalyst, and the results are shown in Table 1. Table 2 briefly summarizes the components of the catalysts obtained in the Examples and Comparative Examples and their manufacturing methods.

In the activity test, a gas containing 1,300 ppm of propane and 17% of oxygen was passed through the catalyst layer at a space velocity of 30,00 [)h-'.
The combustion rate of propane was measured, and the temperature at the inlet of the catalyst layer at which a combustion rate of 90% was obtained was determined.

Table 1 *: Catalyst layer inlet temperature cylinder table showing propane combustion rate of 90% From Table 1, the catalyst of the example has a lower catalyst layer inlet temperature at which a combustion rate of 90% can be obtained than the catalyst of the comparative example. It was shown that the catalyst had excellent activity, initial activity and durability.

[Effects of the Invention] According to the production method of the present invention, each component is mixed simultaneously and 1
Since the catalyst can be obtained by multiple high-temperature calcinations, the operation is simple and manufacturing costs can be reduced. Moreover, since each component can be sufficiently dispersed and mixed to be uniformly coated and supported on the honeycomb substrate, a honeycomb catalyst having stable high temperature heat resistance and high catalytic performance can be obtained.

Applicant Babcock Hitachi Co., Ltd. Agent: Patent Attorney Kawakita Takecho

Claims (1)

[Claims] (1) In a solution containing a noble metal element which is a catalytically active component,
A carrier component that forms a heat-resistant metal oxide after calcination, a heat resistance improving component that forms a lanthanum and/or barium metal oxide after calcination, and a promoter component that forms a base metal oxide after calcination are added. After mixing, a honeycomb substrate is immersed in this mixed solution to support each component, and then fired at a high temperature.