JPH0520145B2 - - Google Patents

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. Particularly recently, palladium, rhodium, platinum, etc. have been used as mixed catalysts with other platinum group elements such as platinum, palladium, or rhodium, respectively, for the purification of automobile exhaust gas and general industrial exhaust gas, due to their high activity. It is used. [Prior art] Conventionally, for example, by oxidizing unburned hydrocarbons and carbon monoxide and reducing nitrogen oxides contained in exhaust gas from internal combustion engines such as automobiles, it has been possible to eliminate pollution and reduce water and carbon dioxide. , platinum, palladium, and rhodium supported catalysts are used as catalysts for converting nitrogen into nitrogen and the like. 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. To this end, various attempts have been made to simultaneously add base metals such as cobalt, nickel, and copper and noble metals, and to utilize the catalytic action of these base metals to reduce the amount of noble metals used. [Problems to be Solved by the Invention] As described above, attempts have been made to obtain an inexpensive and high-performance catalyst by supporting a base metal catalyst component on a noble metal catalyst such as palladium or platinum. However, when the present inventors prepared a catalyst in which noble metal and base metal catalyst components were mixed in alumina like conventional catalysts and investigated its performance, good performance could not be obtained. This is because the noble metal (particularly palladium) forms a mixed crystal with the base metal catalyst component since the noble metal and the base metal catalyst component are supported in a mixed manner. 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. [Means for solving the problem] The present inventors presume that the reason why good performance as a catalyst cannot be obtained is that noble metals such as platinum and palladium are mixed with base metals, and have developed a method for separating noble metals and base metals. I thought about it. That is, base metals are supported in the pores of a monolithic inorganic porous carrier, and palladium, platinum,
By creating a structure with an alumina layer containing rhodium, etc., and supporting base metal oxides and precious metals separately, we were able to solve the conventional problems and significantly improve the performance of exhaust gas purification catalysts. . However, the exhaust gas purifying catalyst of this invention is
A base metal element is supported on an inorganic porous carrier, and an alumina layer containing a noble metal selected from the group consisting of palladium, palladium and rhodium, platinum and rhodium, and palladium, rhodium, and platinum is provided on top of the base metal element. be. Base metal elements include molybdenum, cobalt, iron, nickel, copper, cerium, lanthanum,
One of the elements zinc and vanadium is used. Furthermore, two or more of the above elements can also be used as a composite system or a mixed system. [Operation] Palladium and platinum form alloys with many metals. In particular, it mixes with cobalt, nickel, and copper in various proportions to form mixed crystals. Therefore, as in the past, cobalt, nickel,
It is thought that when base metals such as copper and zinc are mixed with platinum and palladium, mixed crystals are likely to be formed with these metals, resulting in negative effects such as a decrease in performance. 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 remarkable performance. Improvement can be obtained. [Example] Example 1 Commercially available lanthanum nitrate 0.175 mol and cobalt nitrate
Add water to 0.175 mol of crystals to make 100 ml, and add 1.75 mol of lanthanum nitrate/1.75 mol of cobalt nitrate/
A 100 ml solution was prepared containing: A monolithic test piece (diameter 30 mm, length
50 mm, number of cells: 300 cells/in ₂ ) was impregnated for 10 minutes. After 10 minutes, remove the excess solution, blow off the excess solution using an air gun, dry with hot air at 80℃, and heat to 800℃.
It was baked in an electric furnace for 2 hours. The amount of lanthanum oxide and cobalt oxide supported was 0.9 g/test piece. An alumina coating in an amount of 3.5 g/test piece was formed on the thus obtained monolithic test piece of a monolithic support supporting lanthanum oxide and cobalt oxide in its pores. Furthermore, using a palladium nitrate solution and a rhodium nitrate solution, palladium was added to the monolithic test piece on which the alumina coating was formed at 17.5 mg/kg.
The test piece and rhodium were supported in an amount of 1.75 mg/test piece. In this way, a monolithic catalyst containing lanthanum, cobalt, palladium and rhodium (catalyst A) 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 3.5 mol of copper nitrate/0.175 mol of cobalt nitrate was added.
and 100ml containing 1.75 moles/cobalt nitrate
A solution was prepared. An integral structure carrier made of cordierite was impregnated with this solution, and copper and cobalt were supported in the same manner as in Example 1. The supported amount of copper oxide and cobalt oxide is 0.8
g/test piece. Obtained in this way. An alumina coating in an amount of 3.5 g/test piece was formed on a monolithic test piece of an integral structure carrier supporting copper oxide and cobalt oxide in its pores. Furthermore, palladium was supported on the monolithic test piece on which the alumina coating was formed using a palladium nitrate solution in an amount of 17.5 mg/test piece. In this way, a monolithic catalyst (catalyst B) containing copper, cobalt and palladium was obtained. Example 3 Water was added to commercially available crystals of ferric nitrate containing 0.53 mol.
A solution having a volume of 100 ml and containing 5.3 mol/ferric nitrate was prepared. A monolithic support made of cordierite was impregnated with this solution, and iron was supported in the same manner as in Example 1. The amount of iron oxide supported was 0.8 g/test piece. An alumina coating in an amount of 3.5 g/test piece was formed on the thus obtained monolithic test piece of the monolithic carrier supporting iron oxide in its pores. Furthermore, using a palladium nitrate solution, a platinum nitrate solution, and a rhodium nitrate solution on this monolithic test piece with an alumina coating formed, palladium was added to 8.8 mg/test piece, platinum was added to 8.8 mg/test piece, and rhodium was added to 17.5 mg/test piece. It was supported in the amount of the piece. In this way, a monolithic catalyst (catalyst C) containing iron, palladium, platinum and rhodium was obtained. Example 4 Water was added to commercially available crystals of 0.35 mol of nickel nitrate.
A solution containing 3.5 moles of nickel nitrate was prepared in a volume of 100 ml. A monolithic structure carrier made of cordierite was impregnated into this solution, and nickel was supported in the same manner as in Example 1. The amount of nickel oxide supported is 0.8
g/test piece. An alumina coating was formed in an amount of 3.5 g/test piece on the thus obtained monolithic test piece of the monolithic structure carrier in which the nickel acid value was supported in the pores. Furthermore, using a platinum nitrate solution and a rhodium nitrate solution, 17.5 mg of platinum/test piece was added to the monolithic test piece on which the alumina coating was formed.
Rhodium was supported in an amount of 1.75 mg/test piece. In this way, a monolithic catalyst containing nickel, platinum, and rhodium (catalyst D) was obtained. Example 5 Commercially available cerous nitrate 0.21 mol and zinc nitrate
Water was added to 0.12 mol of crystals to make 100 ml to prepare 100 ml of a solution containing 2.1 mol of cerium nitrate and 1.2 mol of zinc nitrate. An integral structure carrier made of cordierite was impregnated into this solution, and cerium and zinc were supported in the same manner as in Example 1. The amount of cerium oxide supported is
1.1g/test piece The amount of zinc oxide supported is 0.3
g/test piece. An alumina coating in an amount of 3.5 g/test piece was formed on the thus obtained monolithic test piece of the monolithic carrier supporting cerium oxide and zinc oxide in the pores. Furthermore, palladium was added at 17.5 mg/kg using a palladium nitrate solution and a rhodium nitrate solution to the monolithic test piece on which the alumina coating was formed.
The test piece was loaded with rhodium in an amount of 3.5 mg/test piece. In this way, a monolithic catalyst (catalyst E) containing cerium, zinc, palladium and rhodium was obtained. Example 6 0.23 mole of commercially available molybdenum oxide (28) crystals
% aqueous ammonia was added to make the volume to 100 ml, and a solution containing 2.3 mol/molybdenum oxide 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 is
It was 1.0g/test piece. An alumina coating of 3.5 g/test piece was formed on the thus obtained monolithic test piece of the monolithic carrier in which molybdenum oxide was supported in the pores. Furthermore, palladium 17.5 mg/test piece and rhodium 1.75 mg/
The amount supported was that of the test piece. In this way, a monolithic catalyst (catalyst F) containing molybdenum, palladium and rhodium was obtained. Example 7 Anhydrous ethanol was added to 0.23 mol of commercially available crystals of vanadium chloride () to make 100 ml to prepare a solution containing 2.3 mol/vanadium chloride. 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 is
It was 0.6g/test piece. An alumina coating in an amount of 3.5 g/test piece was formed on the thus obtained monolithic test piece of the monolithic carrier in which vanadium was supported in the pores. Furthermore, palladium 17.5 mg/test piece, platinum 8.75 mg/test piece, and rhodium 1.75 mg/test were added to this monolithic test piece with an alumina coating formed using a palladium nitrate solution, a platinum nitrate solution, and a rhodium nitrate solution. It was supported in the amount of the piece. In this way, a monolithic catalyst (catalyst G) containing vanadium, palladium (platinum, and rhodium) was obtained. Comparative Example 1 A monolithic test piece of a monolithic carrier made of cordierite (diameter 30 mm, length 50 mm, Number of cells
300 cells/in ² ) were coated with an alumina coating in an amount of 3.5 g/test piece. Lanthanum and cobalt were supported on the alumina coated test piece in the same manner as in Example 1. The amount of lanthanum oxide and cobalt oxide supported was 0.9 g/test piece. The thus obtained monolithic test piece, which is an integrally structured carrier in which lanthanum oxide and cobalt oxide are supported in the alumina coating, was coated with palladium at 17.5 mg/test piece and Rhodium 1.75
The loading amount was mg/test piece. In this way, a monolithic catalyst (catalyst H) containing lanthanum, cobalt, palladium and rhodium was obtained. Comparative Example 2 A monolith test piece of an integral structure carrier made of cordierite (diameter 30 mm, length 50 mm, number of cells)
An alumina coating was formed in an amount of 300 cells/in ₂ ) and 3.5 g/test piece. Copper and cobalt were supported on the test piece on which the alumina coating was formed in the same manner as in Example 2. The supported amount of copper oxide and cobalt oxide is
It was 0.8g/test piece. The thus obtained monolithic test piece with copper oxide and cobalt oxide supported in the alumina coating was coated with palladium at a loading amount of 17.5 mg/test piece using a palladium nitrate solution. carried it. In this way, a monolithic catalyst (catalyst I) containing copper, cobalt and palladium was obtained. Comparative Example 3 Monolithic test piece of monolithic carrier made of cordierite (diameter 30 mm, length 50 mm, number of cells)
300 cells/in ² ) were coated with an alumina coating in an amount of 3.5 g/test piece. Iron was supported on the test piece on which the alumina coating was formed in the same manner as in Example 3. The amount of iron oxide supported was 0.8 g/test piece. Palladium was applied to the thus obtained monolithic test piece of a monolithic carrier in which iron oxide was supported in an alumina coating using a palladium nitrate solution, a platinum nitrate solution, and a rhodium nitrate solution.
The supported amounts were 8.8 mg/test piece, platinum at 8.8 mg/test piece, and rhodium at 1.75 mg/test piece. In this way, a monolithic catalyst (catalyst J) containing iron, palladium, platinum and rhodium was obtained. Comparative Example 4 Monolithic test piece of monolithic carrier made of cordierite (diameter 30mm, length 50mm, number of cells)
300 cells/in ² ) was coated with an alumina coating in an amount of 3.5 g/test piece. 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 0.8 g/test piece. In the same manner as in Example 4, 17.5% platinum was applied to the monolist piece of the monolithic carrier in which nickel oxide was supported on the alumina film thus obtained.
mg/test piece, rhodium was supported in a carrier amount of 1.75 mg/test piece. In this way, a monolithic catalyst (catalyst K) containing nickel, platinum and rhodium was obtained. Comparative Example 5 A monolith test piece of an integral structure carrier made of cordierite (diameter 30 mm, length 50 mm, number of cells)
An alumina coating was formed in an amount of 3.5 g/test piece on 300 cells/in ² ). 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 1.1 g/test piece, and the amount of zinc oxide supported was 0.3 g/test piece. In the same manner as in Example 5, 17.5 mg of palladium/test piece and 3.5 mg of rhodium were added to the thus obtained monolithic test piece, which is an integrally structured carrier in which cerium oxide and zinc oxide were supported in the alumina coating. The amount of support on the test piece was as follows. In this way, a monolithic catalyst containing cerium, zinc, palladium and rhodium (catalyst L)
I got it. Comparative Example 6 Monolithic test piece of monolithic carrier made of cordierite (diameter 30 mm, length 50 mm, number of cells)
An alumina coating was formed in an amount of 3.5 g/test piece on 300 cells/in ² ). 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 1.0 g/test piece. In the same manner as in Example 6, 17.5 mg of palladium was applied to the monolithic test piece of the monolithic carrier supporting the molybdenum oxide in the alumina film obtained in this way, and 1.75 mg of rhodium was applied to the test piece.
The loading amount was that of the test piece. In this way, a monolithic catalyst containing molybdenum, palladium and rhodium (catalyst M) was obtained. Comparative Example 7 Monolithic test piece of monolithic carrier made of cordierite (diameter 30 mm, length 50 mm, number of cells)
An alumina coating was formed in an amount of 3.5 g/test piece on 300 cells/in ² ). 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 was 0.6 g/test piece. In the same manner as in Example 7, 17.5 mg of palladium was applied to the monolithic test piece of the monolithic carrier having a vanadium compound supported on the alumina film obtained in this manner, 8.75 mg of platinum was applied to the test piece, and rhodium was supported at a carrier amount of 1.75 mg/test piece. In this way, a monolithic catalyst containing vanadium, palladium, platinum and rhodium (catalyst N)
I got it. 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 catalysts A to N were tested before and after durability testing. The activity was evaluated by measuring the gas purification rate and the results are shown in the table below. The accelerated deterioration test (durability test) was conducted on the concentric circles of the exhaust system of an 8-cylinder engine (electronic fuel injection control).
A multi-converter filled with a test catalyst was connected and a 100-hour durability test was conducted under the stoichiometric air-fuel ratio. The gas temperature entering the catalyst was 700 to 720°C. As a fuel, commercially available unleaded gasoline has a lead content of 0.01.
A blended fuel with leaded gasoline and engine oil added to give a phosphorus content of 0.03 g/US gallon and phosphorus content of 0.03 g/US gallon was used. Also, catalyst A to catalyst N before and after durability
To measure the gas purification rate to evaluate the activity of
F) Operate at 14.5, and the gas composition is
HC2450ppmc, CO0.56%, and _NOX 2340ppm
The gas containing the gas is passed through the catalyst before and after durability,
This was done by 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.

【table】

〔Effect of the invention〕

Examples 1 to 7 and Comparative Examples 1 to 7 in Table 1
As is clear from comparing the results obtained with the above, the catalyst prepared by the method of the present invention exhibits extremely superior catalytic performance compared to the catalyst prepared by the conventional method.

Claims (1)

[Claims] 1 At least one base metal element selected from the group consisting of molybdenum, cobalt, iron, nickel, copper, cerium, lanthanum, zinc, and vanadium is supported in the pores of the inorganic porous carrier, and palladium , palladium and rhodium, platinum and rhodium, and an alumina layer containing a noble metal selected from the group consisting of palladium, rhodium, and platinum.