JPS6161642A - Monolithic catalyst for purifying exhaust gas - Google Patents

Abstract

PURPOSE:To keep the high activity of a monolithic catalyst and to enhance the durability by providing the part carrying rich catalytic components on the upstream side of exhaust gas as long as the catalyst is not poisoned by lead, etc. CONSTITUTION:As for the monolithic catalyst, an appropriate position 1/10-1/3 of the total length of the monolithic catalyst distant from the end surface on the inlet side of exhaust gas is used as a cardinal point, and the part carrying rich catalytic components is formed in the range 1/5-1/3 of the total length of the catalyst from said cardinal point to the outlet side of exhaust gas. Consequently, the part carrying rich catalytic components keeps high activity without being poisoned, and has excellent activity even at low temps., because the catalyst is preignited at low temps. Besides, catalytic reaction is carried out with comparative easiness on the downstream side of the part carrying rich catalytic components as a consequence of the reaction heat of the catalytic reaction by the catalytic components of the part carrying rich catalytic components.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to the treatment of hydrocarbons (HC), -carbon oxides (CO), and nitrogen oxides (NOx) contained in the exhaust gas of private IJs vehicles, etc.
This invention relates to a monolithic catalyst for exhaust gas purification to remove harmful substances such as.

(Prior art) A monolithic catalyst is a monolithic carrier with an integrally molded structure in which a large number of cells (pores) are provided along the flow direction of exhaust gas.
After coating with activated alumina, an active component with catalytic action (usually Kikai B) is supported. This monolithic catalyst has the advantage of having a smaller heat capacity than a granular catalyst, excellent warm-up performance, and low back pressure, and is therefore widely used as a monolithic catalyst for purifying automobile exhaust gas.

By the way, in general, monolith catalysts have a slow reaction rate at low temperatures, so a large amount of catalyst components are required to maintain high activity, but as the temperature rises, the reaction rate increases and the catalyst components decrease. Even if it is less, high activity can be maintained. Further, the catalytic reaction is an exothermic reaction, and when the catalytic reaction starts, the exhaust gas temperature increases due to the reaction heat. Therefore, if a large amount of catalyst component is supported only near the inlet side of the exhaust gas of a monolithic catalyst, ignition will occur at a low temperature, and due to the reaction heat, the latter half of the monolithic catalyst will be able to maintain high activity with a low amount of catalyst supported. It seems possible.

[Problem that the invention seeks to solve]

However, as mentioned above, if a large number of catalyst components are supported near the artificial side of the monolith catalyst, although high activity can be maintained initially, it is highly susceptible to poisoning by phosphorus (P), lead (Pb), etc. , there is a problem of poor durability.

The present invention has been made to solve the problems of the prior art described above, and the technical problem of the present invention is to utilize the reaction heat of the catalyst components while avoiding deterioration due to poisoning as much as possible. The goal is to maintain high activity and improve durability of monolithic catalysts.

[Failure to solve the problem]

The above problem is solved by the following monolithic catalyst for exhaust gas purification.

That is, the monolithic catalyst for exhaust gas purification of the present invention has a columnar shape, and a large number of cells are provided inside from the exhaust gas inlet side to the outlet side, and an alumina layer is supported on the inner wall surface of the cells. This is a monolithic catalyst for exhaust gas purification in which a catalyst component is supported on the alumina layer. As a base point, a range of 115 to 1/3 of the total length of the monolith catalyst from this base point toward the exhaust gas outlet side is characterized in that more catalyst components are supported than other parts.

[Effect]

According to the monolithic catalyst for exhaust gas purification of the present invention, the highly loaded portion of the catalyst component is provided as far upstream of the exhaust gas as possible without being affected by poisoning by lead, etc. The highly loaded area continues to maintain high activity without being affected by poisoning, and at low temperatures, the catalyst components in this highly loaded area ignite early, resulting in good low-temperature activity. The catalytic reaction occurs comparatively easily with the reaction heat generated by the catalytic reaction of the catalytic component of the supporting part.

〔Effect of the invention〕

From the above, the monolithic catalyst for exhaust gas purification of the present invention has excellent effects such as improved durability and ability to maintain a highly active state for a long period of time due to less influence of poisoning in areas with high catalyst component loading. play.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

Add 150 g of a 40% aluminum nitrate aqueous solution to 00 g of alumina silica with an alumina content of 10% by weight (all percentages indicate weight%), and then add 450 ml of distilled water and stir to mix! ! ! ! A cloudy liquid was obtained. Alumina powder tooog was added thereto and stirred to prepare a slurry. A cordierite monolith carrier with a length of 100 mm and 400 cells per square inch was added to this slurry for 1 minute. ,%? The slurry in the cells (pores) was blown away by air flow. Thereafter, 110 g of
An activated alumina layer (wash coat) was formed.

The monolithic carrier on which the activated alumina layer had been formed was thoroughly soaked in distilled water to absorb water, then pulled out, the excess moisture was blown off, and the carrier was immersed in an aqueous solution containing palladium chloride, dinitrodiammine platinum, and rhodium chloride. At this time, 80% of the axial length of the monolithic carrier was immersed, and immersion and lifting were repeated at 1 minute intervals for 30 minutes, followed by drying. As a result, 80% of the monolith carrier contained 0.23 g of palladium (Pd) and platinum (Pd) per 11 monolith carriers.
0.23 g of Pt) and 0.046 g of rhodium (Rh) were supported. At this stage, the two on the population side of the monolithic carrier
In the portion 01, no catalyst component is supported.

Next, the monolithic carrier was turned upside down, that is, with the inlet side of the monolithic carrier facing down, 4Q+u was immersed in the mixed aqueous solution of palladium chloride, dinitrodiammine platinum, and rhodium chloride in the axial direction, and the 4Q+u was immersed at intervals of 1 minute. This process was repeated for 30 minutes to obtain a monolithic catalyst. As a result, 0.11 g of palladium and 0.1 g of platinum were added per monolith carrier to a portion 40 mm from the artificial side of the monolith carrier.
1 g and 0.022 g of rhodium were supported. Therefore,
As for the monolith carrier as a whole, monolith carrier 1 (11i
0.34 g of palladium, 0.34 g of platinum, and 0.068 g of rhodium were supported per unit.

In addition, as shown in Fig. 1, the supporting density of the catalyst components is 2011 from the inlet side end face to the outlet side of the monolithic catalyst.
The range of ~40 dragons (for convenience of explanation, the corresponding part is indicated with a notch) was twice as large as the other parts. That is, 0.83 g of palladium per 12 volumes of the monolithic carrier was added to the portion 20 to 40 fins from the inlet side end face of the monolithic catalyst.
0.83 g of platinum and 0.17 g of rhodium are supported,
Other parts contain 0.42 g of palladium and 0.4 g of platinum.
2 g and 0.083 g of rhodium were supported. The monolithic catalyst obtained as a result is designated as catalyst A.

(Comparative Example) An activated alumina layer was formed in the same manner as in the example using the same monolithic carrier as in the example. Next, the entire monolith carrier was immersed in an aqueous solution containing palladium chloride, dinitrodiammine platinum, and rhodium chloride for 30 minutes, taken out, excess moisture was blown off, and then dried.

The resulting monolithic catalyst was monolithic carrier 1 (0.34 g of palladium, 0.34 g of platinum, and 0.068 g of rhodium were uniformly supported on the entire monolithic carrier). shall be.

(Catalyst performance test) Regarding the monolithic catalysts obtained in the above examples and comparative examples,
The following catalyst performance test was conducted to evaluate the performance.

First, Catalyst A and Catalyst B were each housed in a metal container, attached to the engine exhaust system of a vehicle, and driven for 200 hours in a pattern simulating city driving.

After that, catalyst A and catalyst B were each installed in the exhaust system of an engine with a displacement of 2.8β, and the engine speed was 2000 rpm/380.
The exhaust gas obtained by operating under msHg conditions is adjusted to a constant temperature with a cooler and then introduced into the catalyst to produce hydrocarbons (HC),
- The purification rate of carbon oxide (Co) and nitrogen oxide (NOx) was measured. Among these, the results of the purification rate of -carbon oxide are shown in FIG.

As is clear from FIG. 2, it can be seen that catalyst A according to the example exhibits higher activity than catalyst B according to the comparative example, even though the catalyst components are supported in the same amount. . This is due to the fact that ignition occurs at a low temperature in the highly loaded part of catalyst A, and the downstream area of the catalyst uses this reaction heat to exhibit sufficient activity. This is thought to be due to the fact that it was located in an area where there is little activity, so it had high activity even after the durability test.

Although Figure 2 only shows the purification rate of carbon monoxide,
Almost the same results as in FIG. 2 were obtained for other components, namely hydrocarbons and nitrogen oxides.

Although specific embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and includes various embodiments within the scope of the claims. .

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a monolithic catalyst for exhaust gas purification according to an example of the present invention, and FIG. 2 is a schematic diagram of a monolithic catalyst for purifying exhaust gas according to an example of the present invention and a monolithic catalyst for exhaust gas purification according to a comparative example. It is a graph showing the purification rate of carbon monoxide.

Claims (1)

[Claims] (1) It has a columnar shape, and a large number of cells are provided inside from the exhaust gas inlet side to the outlet side, and an alumina layer is supported on the inner wall surface of the cell, and a catalyst component is supported on this alumina layer. A monolithic catalyst for exhaust gas purification, which is a monolithic catalyst for exhaust gas purification, with an appropriate position in the range of 1/10 to 1/3 of the total length of the monolithic catalyst from the end face of the exhaust gas inlet side of the monolithic catalyst as a base point, and an exhaust gas outlet from this base point. A monolithic catalyst for exhaust gas purification, characterized in that a larger amount of catalyst components is carried in a range of 1/5 to 1/3 of the total length of the monolithic catalyst than in other parts.