JPS58189036A - Catalyst for purifying exhaust gas - Google Patents

Abstract

PURPOSE:To obtain an extremely inexpensive catalyst usable as a three-component catalyst for purifying exhaust gas, by supporting palladium, iron and zirconium on a ceramic carrier. CONSTITUTION:As the exhaust gas purifying catalyst of an automobile, palladium, iron and zirconium are supported as catalytic metals by a ceramic carrier. Because thus obtained catalyst has high CO and HC purifying efficiency in a side rich in CO and H2 and shows high purifying efficiency with respect to three components of CO/HC/NOX, it is sufficiently usable as a three-component catalyst and is extremely inexpensive.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a catalyst used for purifying exhaust gas from automobiles.

In recent years, due to the demand for improved drivability and fuel costs,
The number of automobiles equipped with electronically controlled fuel supply systems is increasing. This next car is commonly used for gas purification.
The original catalyst is used.

Such a catalyst has an air-fuel ratio [air/fuel (mu/1)=14
7] Because high purification performance of Co/HC/NOx is required by wiping the nearby VC, conventionally! Latitudinium-based materials or Gratener-radium-rhodium materials are used. However, since they are composed of precious metals with high catalytic value, they have the disadvantage of increasing the additional cost of automobiles.

In contrast, the present inventors have conducted various studies on catalyst components that should replace the conventional three-way catalyst mentioned above, and have found that the main difference between the three-way catalyst and the oxidation catalyst is that the fuel is higher than the stoichiometric air-fuel ratio. (hereinafter referred to as rich side) CO purification rate,
It was determined that this was the difference in HC purification rate.

As a result of intensive research based on the above findings, the inventors of the present invention found that by combining iron and norconium with yaradium in the ceramic carrier as a medium, the CO purification rate and HC purification rate on the rich side could be improved. We have discovered an extremely inexpensive exhaust gas purification catalyst that has a remarkable improvement, shows high purification rates for the three components Co/HC/NOx, and can be fully used as a three-way catalyst, just like the conventional three-way catalyst.

That is, the exhaust gas purification catalyst of the present invention is applied to a ceramic carrier.
It supports radium, iron, and zirconium as catalyst metals.

Next, the present invention will be explained in detail.

Example: Nitric acid/mother porosity solution (paNo, ts&/1
The ceramic carrier having a honeycomb structure was wash-coated with activated alumina in 0.00 t) and then immersed for 5 hours, and the ceramic carrier was impregnated with palladium nitrate. Subsequently, this ceramic carrier was dried at 130° C. for 3 hours and then fired at 500° C. for 3 hours to prepare a radium-coated ceramic carrier.

Next, the palladium-coated ceramic was added to the ferric nitrate solution (0,1+no4/z) and the carrier was heated to 5:1'&!
Soak 11 TeI4111g diiron f: 19 sa-v, 13
Dry at 0℃ for 31 minutes, then bake at 500℃ for 3 hours! A lanoum/iron coating carrier was prepared.

Next, the above-mentioned zirconium/iron coated ceramic carrier was immersed in the zirconium oxynitrate solution for 15 hours to form a zirconium oxynitrate solution, dried at 130°C for 3 hours, and then fired at 500°C for 3 hours. /
An iron/zirconium coated exhaust gas cleaning contact TS1 was manufactured.

Comparative Example 1 Similar to the above example, a ceramic carrier was immersed in a nitric acid/radium solution for a long time to impregnate a sufficient amount of nitric acid/9ranium, thoroughly dried at 130°C, and then fired at 500°C for 3 hours. 90 Comparative Example 2 An exhaust gas catalyst coated with Norconium oxynitrate (0.1 mot/z) was prepared by the same method as in the previous example. After soaking for hours to impregnate zolconium oxynitrate, drying at 130°C for 3 hours, and baking at 500°C for 3 hours. Exhaust gas purification catalyst II coated with radium/zirconium! did.

Comparative Example 3 A ceramic carrier coated with cylindrical porcelain was prepared in the same manner as in the above example.
1 mO'/z) for 3 hours to impregnate it with nitric acid, dried at 130°C for 3 hours, and then fired at 500°C for 3 hours to obtain a palladium/iron coated exhaust gas purifying catalyst. Manufactured.

The activity tests of the purification catalyst of this example and the purification catalysts of Specific IIR Examples 1 to 3 were conducted as shown in FIG.
Do this using m 7'j.

That is, the heater 1 is wound around the upper part, and each of the catalysts 4 is filled in advance in the O-touch filling 11!3 in the nine tail tube 2. Continuing,
co/H21 combined gas pump.

C3H6/C1H1ll mixed gas Menbero, 02 Menbea, Co, Ganpe 8, No & Nbe 9, 1st N2 & Nbe 10 and 2nd ON, & Nbe I No respectively, the exhaust gas composition during automatic military operation. 1. Second. Third pulp JJI, 13m-1
Open 3* and open 4th. Fifth. 6th pulp 134 + I
JB, 136 is closed and the pipe gas is passed through the reaction tube 2 until the O component composition in the mixed gas from the mixer 12 becomes constant and the flow rate becomes stable. However, lIl
! The N2 gas from the N2 membrane 1 of No. 2 is supplied to the mixer 12 through a humidifying chamber 14t filled with water. mixed r
An Fi point meter 15 is interposed between i11 and the branch points of the first and fourth pulps 131e134.

Next, when the component composition in the mixed gas reaches the same level, the first. Second. Third pulp 131, 13. .

13, close, $4. Fifth. @60 Palzo J34゜JJ
Open the heater 1 to supply the mixed gas to the catalyst device of the automobile and the reaction tube 2 heated to about 100 m, and the gas that has passed through the 1s rate to the drain port, to
, opened and introduced into the analyzer 18 through the 9th 6th cable /13, recorded in the record 119, and the purification performance t of each catalyst.
I loved pi. -], we discussed the purification performance of mixed gases with different air-fuel ratios (m/r) using 6 tm of oxygen supplied from 02 Menbea. The Ic and co purification rates are shown in Figure 2, and the HC purification rates are shown in Figure 1g3. In addition,
OA in Figure 2 is book 1j! The CO purification % characteristic line by the catalyst of Example 1IA, B1 is the same characteristic -1CI by the catalyst of Comparative Example 1
is the same characteristic line due to the catalyst of Comparative Example 2, and Dl is the same characteristic line due to the catalyst of Comparative Example 3. The 3-year-old mackerel is the HC purification characteristic line by the catalyst of Honryo M Ministry, B1 is the same % characteristic line by the catalyst of Comparative Example 1, C word is the same characteristic line by the catalyst of Comparative Example 2,
DI is the same characteristic line for Comparative Example 30 catalyst.

As is clear from FIG. 2 and FIG. It can be seen that the catalyst has the highest CO purification rate, and has sufficient HC purification performance, although the rich side He purification rate is slightly inferior to the purification catalyst of Comparative Example 2 in which Dalanium/zirconium 'fr is supported. On the other hand, Comparative Example 2 in which zirconium was supported
The purification catalyst of Comparative Example 30, which supported rich acid, had a better Hc m' conversion rate, but its CO purification rate was lower than that of Comparative Example 30, which supported ・franium/iron, and the CO purification rate of Tiside was that of Comparative Example 2. Although it is relatively high, the He purification rate is extremely inferior.

Although the purification catalyst of the present invention has excellent purification performance as described above, by using iron and zirconium in combination with radium, the rich side CO purification rate is reduced due to their synergistic effect, while the He purification rate is reduced due to their synergistic effect. This is thought to be due to the complementary effect of the low purification rate of fZr. Note that the purification catalysts of the present example and comparative examples 1 to 3 had a NOx purification rate of 80 degrees or more on the rich side.

In addition, the obtained present example and comparative example IC + purification catalyst were sintered in air at a temperature of 950°C for 100 hours.
The CO purification rate, HC# conversion rate, and NOx purification rate were investigated using the following. The results are shown in Table 1 below. Furthermore, the low-temperature activity degree of each catalyst after the above-mentioned sintering was compared. The results are shown in Section 2 below.

From Table 1 and Table 2, it can be seen that the purification catalyst of this example has sufficient purification performance even in actual use.

As detailed above, according to the present invention, rich side CO
It has a high conversion rate and He purification rate, and shows high purification rates for the three components of CO, YC, and Ox, just like the conventional three-way catalyst.
As a result, it is possible to provide an extremely inexpensive exhaust gas purification catalyst that can be fully used as a three-way catalyst.

Figure 1 shows the catalyst activity test equipment used in the examples of the present invention.
FIG. 2 is a characteristic diagram showing the CO purification rate of each catalyst with respect to changes in the air-fuel ratio, and FIG. 183 is a characteristic diagram showing the He purification rate of each catalyst with respect to changes in the air-fuel ratio.

DESCRIPTION OF SYMBOLS 1... Heater, 2... Reactor, 3... Catalyst packed cylinder, 4... Catalyst, 5-11... Lumper, 1j... Mixer, 18... Analyzer, 19...Recorder.

Applicant Sub-Agent Patent Attorney Suzue Takehiko Figure 2 Nitrogen f ratio (A/F) 3i131jA ! AIF)

Claims (1)

[Claims] An exhaust gas purification catalyst made by supporting palladium, iron, and zirconium as catalytic metals on a ceramic carrier.