JPS62176544A - Catalyst for purifying exhaust gas - Google Patents

Abstract

PURPOSE:To improve exhaust gas purifying capacity, by supporting a base metal element by the pores of an inorg. porous carrier and providing a noble metal-containing alumina layer comprising Pd, Pd and Cr, Pt and Rh or Pd, Rh and Pt thereon. CONSTITUTION:A base metal element selected from Mo, Co, Fe, Ni, Cu, Ce, La, Zn and V is supported by pores of an inorg. porous carrier. Subsequently, an alumina layer containing a noble metal selected from a group consisting of Pd, Pd and Rh, Pt and Rh and Pd, Rh and Pt is provided to the surface of said carrier to form a catalyst for purifying exhaust gas. In a conventional catalyst wherein a base metal and a noble metal are allowed to coexist in a mixed state, the mixed crystal of both of them is easy to form and catalytic activity is lowered but, if both them are supported separately as mentioned above, only the positive effects of noble metal catalytic capacity and base metal catalytic capacity are taken out to achieve marked enhancement in capacity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an exhaust gas purifying catalyst having excellent catalytic performance.

Platinum group metals such as palladium, rhodium, and platinum are known to have extremely high activity as catalyst materials for exhaust gas purification.

In particular, recently, radium, rhodium, platinum, etc. have been used as mixed catalysts with platinum group elements such as platinum, palladium, or rhodium, respectively, for the purpose of purifying automobile exhaust gas and general industrial exhaust gas. It is used because of.

[Conventional technology]

Conventionally, by oxidizing unburned hydrocarbons and carbon oxides and reducing nitrogen oxides contained in exhaust gas from internal combustion engines such as automobiles, it has been converted into non-polluting water, carbon dioxide, nitrogen, etc. As a catalyst etc. used in this case,
Platinum, palladium and rhodium supported catalysts have been used.

However, since noble metals such as palladium, platinum, and rhodium are expensive and scarce in terms of resources, it is necessary to keep the amount used in the catalyst as small as possible.

Efforts are being made to simultaneously add base metals such as cobalt, nickel, copper, etc. and noble metals, and to utilize the catalytic action of these base metals to reduce the amount of precious metals used.

[Problem that the invention seeks to solve]

As mentioned above, attempts have been made to obtain inexpensive and high-performance catalysts by supporting base metal catalyst components on noble metal catalysts such as radium and platinum.

However, when the present inventors prepared a catalyst in which a noble metal and a base metal catalyst component were mixed in aluminum like conventional catalysts and investigated the performance, good performance was not obtained.

This is because noble metals (particularly radium) form a mixed crystal with the base metal catalyst components since they support a mixture of noble metals and base metal catalyst components.

Therefore, in order to improve the catalytic performance by combining a base metal catalyst component and a noble metal, it is necessary to devise ways to support the base metal catalyst component.

[Failure to solve the problem]

The present inventors presumed that the presence of noble metals such as platinum and palladium mixed with base metals was the reason why good performance as a catalyst could not be obtained, and attempted a method of separating the noble metals and base metals.

That is, a structure in which a base metal is supported in the pores of a monolithic inorganic porous carrier, and an alumina layer containing ceradium, platinum, rhodium, etc. is provided on top of it (base metal oxide and noble metal are completely separated). By supporting it, we were able to solve the conventional problems and significantly improve the performance of exhaust gas purification catalysts.

Therefore, the exhaust gas purifying catalyst of the present invention has a base metal element supported on an inorganic porous carrier, and a base metal element selected from the group consisting of palladium, palladium and rhodium, platinum and rhodium, and ranium, rhodium, and platinum. It is provided with an alumina layer containing a selected noble metal.

Here, as the base metal element, one of molybdenum, cobalt, iron, nickel, copper, cerium, rankan, zinc, and vanadium is used. Furthermore, three or more of the above elements can also be used as a composite system or a mixed system.

[Effect]

Palladium and platinum form alloys with many metals. In particular, it mixes with cobalt, nickel, and copper in any proportion to form mixed crystals.

Therefore, it is thought that if base metals such as cobalt, nickel, copper, and zinc are mixed with platinum and i4' radium, as has been the case in the past, mixed crystals will be formed with these metals, which will actually have negative effects such as a decline in performance. It will be done.

Therefore, when they are separated and supported as in the present invention, the above-mentioned negative effects can be removed, and only the positive effects of noble metal catalyst performance and base metal catalyst performance can be brought out, resulting in a significant performance improvement. is obtained.

〔Example〕

Example 1 0.175 mol of commercially available lanthanum nitrate and 0.175 mol of copal nitrate.
Water was added to 175 mol of crystals to make 100-, and lanthanum nitrate was 1.75 mol/l and cobalt nitrate was 1.75 mol/l.
A 100-solution containing 1 was prepared.

A monolithic test piece of an integral structure carrier made of cordierite (diameter 30++m, length 50Iw) was placed in this solution.
l111 Number of cells: 300 cells/in) f Impregnated for 10 minutes. After 10 minutes, the excess solution was blown off using an air gun, and after drying with hot air at 80°C,
It was fired in an electric furnace at ℃ for 2 hours.

The supported amounts of lanthanum oxide and cobalt oxide are 0.
9&/ was a test piece. The monolith test piece was coated with an alumina coating in an amount of 3.5 x test piece.

Furthermore, palladium was added to the integral structure test piece on which the Albas film was formed using a palladium nitrate solution and a rhodium nitrate solution. smq/test piece and rhodium with a loading of 1.75 In9/test piece.
) was obtained.

Example 2 Water was added to commercially available crystals of 0.35 mol of copper nitrate and 0.175 mol of cobalt nitrate to make 100 ml, and 100 ml containing 3.5 mol/l of steel nitrate and 1.75 mol/l of cobalt nitrate was prepared.
A solution of - was prepared.

An integral structure carrier made of cordierite was impregnated in this solution, and copper and cobalt were supported in the same manner as in Example 1.

The amount of copper oxide and cobalt oxide supported is 0.8Fl
/ It was a test piece. An alumina film in an amount of 3.5117 test pieces was formed on the thus obtained monolithic test piece of an integral structure carrier in which copper oxide and cobalt oxide were supported in the pores.

Furthermore, palladium was supported on the monolithic test piece on which the alumina film was formed using a nitric acid/Nranium solution in an amount of 17.5 m9/test piece.

In this way, a monolithic catalyst (catalyst B) containing copper, cobalt, and 2 lazoum was obtained.
A solution containing 5.3 mol/l of ferric nitrate was prepared as WLt.

A monolithic support made of cordierite was impregnated into this solution, and iron was supported in the same manner as in Example 1.

The amount of iron oxide supported was 0.8 fl/test piece.

The thus obtained monolithic test piece of the monolithic carrier supporting iron oxide in its pores was coated with 3.5g/
An alumina coating was formed in the amount of the test piece.

Furthermore, palladium was added to the monolithic test piece on which the alumina film was formed using a palladium nitrate solution, a platinum nitrate solution, and a rhodium nitrate solution.
The test piece was loaded with platinum at a loading of 8.8 μg/test piece and rhodium @t at a loading of 75 mg/test piece.

In this way, a monolithic catalyst (catalyst C) containing iron, palladium, platinum and rhodium was obtained.

Example 4 Water was added to 0.35 mol of commercially available nickel nitrate crystals and 10
0-, and a solution containing 3.5 mol/l of nickel nitrate was prepared.

A monolithic support made of cordierite was impregnated in this solution, and nickel was supported in the same manner as in Example 1.

The amount of nickel oxide supported was 0.8 g/test piece.

3.5 g was applied to the monolithic test piece of the monolithic structure carrier in which nickel oxide was supported in the pores obtained in this way.
/test piece of alumina film was formed.

Furthermore, using a platinum nitrate solution and a rhodium nitrate solution, the monolithic test piece on which the aluminum coating was formed was coated with platinum at 17.5 cm/test piece and rhodium at 1.7 cm/test piece.
The amount of support was 5 m9/test piece.

In this way, a monolithic catalyst (catalyst D) containing nickel, platinum and rhodium was obtained.

Example 5 Commercially available cerium nitrate 0.21 mol and zinc nitrate 0.1
Add water to 2 moles of crystals, bind to 100%, and add 2 moles of cerium nitrate.
．． 1 mol/l and zinc nitrate 1.2 mol/l
A solution of 0 mj was prepared.

An integral structure carrier made of co-silite was impregnated into this solution to support cerium and zinc in the same manner as in Example 1. The amount of cerium oxide supported is 1.11! The amount of zinc oxide supported per test piece was 0.397 test beads.

An alumina film in an amount of 3.51// test piece was formed on the thus obtained monolithic test piece of the monolithic carrier in which cerium oxide and zinc oxide were fully supported in the pores.

Furthermore, 17.5 mq/test piece of radium was added to the monolithic test piece on which the alumina coating was formed using a nitric acid/ceradium solution and a rhodium nitrate solution, and rhodium-q3. The amount of support was that of smy/test piece.

In this way, a monolithic catalyst (catalyst E) containing cerium, zinc, radium and rhodium was obtained.

Example 6 28% in 0.23 mol of commercially available molybdenum oxide crystals
Add ammonia water and add 100 - Molybdenum oxide 2゜3
A solution containing mol/l was prepared.

A monolithic support made of cordierite was impregnated in this solution, and molybdenum was supported in the same manner as in Example 1. The amount of molybdenum oxide supported was 1.0 g/test piece.

The monolithic test piece of the monolithic structure support with molybdenum oxide supported in the pores obtained in this way was
An alumina film of 'J/test piece amount was formed. Furthermore, 17.5m9/test piece of radium and 1.751n9/test piece of rhodium were loaded on the monolithic test piece on which the alumina coating was formed using a nitric acid/9radium solution and a rhodium nitrate solution. It was supported by the amount.

Example 7 Anhydrous ethanol was added to 0.23 mol of commercially available vanadium (II) chloride crystals, the mixture was stirred at 100°C, and vanadium chloride 2
．． A solution fe containing 3 mol/l was prepared.

A monolithic support made of cordierite was impregnated into this solution, and vanadium was supported in the same manner as in Example 1. The amount of vanadium compound supported was 0.617 test pieces.

The monolithic test piece of the monolithic carrier supporting vanadium in the pores thus obtained was 3.5117
An alumina coating was formed in the amount of the test piece.

Furthermore, 17.5 m9 of 7-sodradium was applied to this monolithic test piece on which the alumina coating was formed using a palladium nitrate solution, a platinum nitrate solution, and a rhodium nitrate solution.
/test piece, platinum was supported in an amount of 8.75.719/test piece, and rhodium was supported in an amount of 1.75 In9/test piece.

In this way, a monolithic catalyst containing vanadium, noradium, platinum, and rhodium (catalyst G) was obtained.

Comparative Example 1 3.51! /test piece of alumina film was formed.

Lanthanum and cobalt were supported on the alumina coated test piece in the same manner as in Example 1. The supported amount of lanthanum oxide and cobalt oxide is 0.91
It was 17 test pieces. Obtained in this way,
A monolithic test piece with an integral structure supporting lanthanum oxide and cobalt oxide in an alumina coating,
Using nitric acid/ceradium solution and rhodium nitrate/'
P radium was supported in an amount of 17.5 In9/test piece and rhodium was supported in an amount of 1.75~/test piece.

In this way, a monolithic catalyst containing lanthanum, cobalt, palladium and rhodium (catalyst H) was obtained.

Comparative Example 2 An alumina coating in an amount of 3.517 test pieces was formed on a monolithic test piece (diameter 30 m, length 50 wm, number of cells 300 cells/in) of an integral structure carrier made of cordierite.

Copper and cobalt oxides were applied to the test piece on which the alumina coating was formed in the same manner as in Example 2. The amount of copper oxide and cobalt oxide supported was 0.8/i/test piece.

Palladium was applied to the thus obtained monolithic test piece of an integral structure carrier supporting copper oxide and cobalt oxide in an alumina coating using a nitric acid/radium solution at 17.5"+9/test.・Supported by the amount of pieces supported.

In this way, a monolithic catalyst (catalyst I) containing copper, cobalt and 4-radium was obtained.

Comparative Example 3 Monolith test piece of monolithic carrier made of cordierite (diameter 305 m, length 50 m).

Iron was supported in the same manner as in Example 3 on a test piece on which an alumina coating was formed in an amount of 3.511/test piece on a test piece having an alumina coating of 3.511 cells/1n2). The amount of iron oxide supported was 0.81/test piece.

8. Add palladium to the test piece using para-nitrate solution, platinum nitrate solution and platinum nitrate solution.
8 da/test piece, platinum was supported at 8.81n9/test piece, and rhodium was supported at x, 7 sw/test piece.

In this way, a monolithic catalyst (catalyst J) a-containing iron, mother porosity, platinum and rhodium was obtained.

Comparative Example 4 An alumina coating in an amount of 3.517 test pieces was formed on a monolithic test piece (diameter: 30 mm, length: 50 mm, number of cells: 300 cells/in), which was a monolithic carrier made of cordierite.

Nickel was supported on the test piece on which the alumina coating was formed in the same manner as in Example 4.

The amount of nickel oxide supported was 08 g/8 da/test piece.

Platinum was applied at 17.5 d/test piece and rhodium was applied at 1.75 mp/test piece in the same manner as in Example 4 to the monolithic test piece of the monolithic carrier in which nickel oxide was supported in the alumina film thus obtained. The amount supported was that of the test piece.

In this way, a monolithic catalyst (catalyst K) containing nickel, platinum and rhodium was obtained.

Comparative Example 5 3.51! /test piece amount of alumina film was formed.

Cerium and zinc were supported on the test piece on which the alumina coating was formed in the same manner as in Example 5. The amount of cerium oxide supported was 1.111/test piece, and the amount of zinc oxide supported was 0.3117/test piece.

Example 5 was used as a monolithic test piece of an integrated structure carrier in which cerium oxide and zinc oxide were supported in the alumina coating thus obtained.

In this way, a monolithic catalyst (catalyst L) containing cerium, zinc, palladium and rhodium was obtained.

Comparative Example 6 Monolithic test piece of monolithic carrier made of co-silite (diameter 30 m, length 50 m).

An alumina coating was formed in an amount of 3.5 da/test piece on a cell of 300 cells/1n2.

Molybdenum was supported on the test piece on which the alumina coating was formed in the same manner as in Example 6.

The amount of molybdenum oxide supported was 1.011/test piece.

In the same manner as in Example 6, one arm of radium was applied at 17.5III to the monolithic test piece of the monolithic carrier in which molybdenum oxide was supported in the alumina film thus obtained.
9/test piece, rhodium was supported in an amount of 1.75 In9/test piece. In this way, a monolithic catalyst containing molybdenum, palladium and rhodium (catalyst M) was obtained.

Comparative Example 7 A monolith test piece of an integral structure carrier made of cordierite (diameter 30 m, length 50 m).

An alumina coating was formed in an amount of 3.511/test piece on a cell (300 cells/1n2).

Vanadium was supported on the test piece on which the alumina coating was formed in the same manner as in Example 7.

The amount of vanadium compound supported is 0.61! / It was a test piece.

A monolithic test piece of an integrally structured carrier in which a vanadium compound is supported in the alumina film thus obtained is treated in the same manner as in Example 7 with 17.5 ml of SOUM:
'19/test piece, platinum was supported at 8.75 m9/f stop piece, and rhodium was supported at an amount of 1.75 m9/f strike piece.

In this way, a monolithic catalyst (catalyst N) containing vanadium, palladium, platinum and rhodium was obtained.

Catalyst activity evaluation test The catalysts (catalysts A to N) obtained in Examples 1 to 7 and Comparative Examples 1 to 7 were subjected to accelerated deterioration tests as described below, and the catalyst formulas and catalysts before and after durability were evaluated. The activity was evaluated by measuring the N gas purification rate, and the results are shown in the table below.

The accelerated deterioration test (durability test) was conducted by connecting a multiconverter V-tube filled with a test catalyst to the concentric circle of the exhaust system of an 8-cylinder engine (electronic fuel injection control), and at a stoichiometric air-fuel ratio of 10
A 0 hour durability test was conducted.

Catalytic gas temperature was 700-720°C. As a fuel, commercially available unleaded gasoline has a lead content of 0.01.9/
A blended fuel with leaded gasoline and 2/gin oil added to give a US gallon and a phosphorus content of 0.03.9/US gallons was used.

In addition, measurement of the gas purification rate for evaluating the activity of the catalyst type or catalyst N before and after durability is carried out using 18
A 00cc 4-cylinder Ennon was operated at an air-fuel ratio (A/F) of 14.5, and the gas composition was HC2450ppmc, CO.
This was carried out by passing a gas containing NOx, 56%, and 2340 ppm of NOx through the catalyst before and after durability testing, and determining the purification rate of each component gas.

At this time, the temperature of the gas entering the catalyst bed was measured at 360°C.

Note) HC is hydrocarbon, CO is carbon monoxide, and N
Ox represents nitrogen oxide.

〔Effect of the invention〕

As is clear from a comparison of the results obtained in Examples 1 to 7 and Comparative Examples 1 to 7 in Table 1, the catalysts prepared by the method of the present invention are significantly superior to the catalysts prepared by the conventional method. It shows excellent catalytic performance.

Claims (2)

[Claims] (1) A base metal element is supported in the pores of an inorganic porous carrier, and a noble metal selected from the group consisting of palladium, palladium and rhodium, platinum and rhodium, and palladium, rhodium, and platinum is contained thereon. Exhaust gas purification catalyst with an alumina layer. (2) The catalyst for exhaust gas purification according to claim 1, wherein the base metal element is at least one selected from the group consisting of molybdenum, cobalt, iron, nickel, copper, cerium, lanthanum, zinc, and vanadium. .