JPS61197043A - Monolithic catalyst for purifying exhaust gas - Google Patents

Abstract

PURPOSE:To utilize effectively a catalytic metal and to obtain the titled catalyst having the excellent purifying performance and durability by making the length of the following part long in a cell of a central part and short in a peripheral part which is a part undeposited with a catalytic metal in a part adjacent to an inflow side of an exhaust gas flow path of the monolithic catalyst. CONSTITUTION:In a monolithic catalyst for purifying an exhaust gas, a monolithic catalyst carrier 1 preliminarily performed with the coating of activated alumina is immersed into an aq. soln. of a photosetting resin to coat the photosetting resin on the cell wall surface in about 1/5 of the whole length (l) of the carrier in an end part 1a side of an inflow side of an exhaust gas flow path in the carrier 1 and thereafter dried. Then the carrier 1 is fitted to a holding jig 2 and the parallel irradiating light 6 is irradiated from a bias part while rotating it in the axial direction. Thereafter it is washed to flow the nonsetting resin and immersed in a deposition liquid of a catalytic metal. Thereby the nondeposited part of the catalytic metal is precisely controlled in the prescribed length.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a monolithic catalyst for exhaust gas purification. Co and H contained in engine exhaust gas
Gasoline in a monolith catalyst for exhaust gas purification that purifies harmful components such as C and NOx.

The present invention relates to a monolithic catalyst for exhaust gas purification that aims to reduce deterioration in purification performance of the catalyst due to catalyst poisonous substances such as Pb and P that are mixed in from engine oil and simultaneously contained in exhaust gas.

[Conventional technology]

Monolith catalysts for exhaust gas purification used in internal combustion engines for automobiles, etc., use a catalyst support layer such as activated alumina particles as a carrier that holds fine particles of catalyst metal on the surface of the catalyst base material and has the effect of improving catalytic activity. Cu, Ni, Fe, Mn, Co, Pd are added to the surface of the catalyst support layer.
A catalyst supported with a catalytic metal such as , Pt or Rh is usually employed.

Generally, the surface of the catalyst support layer has countless pores, and the catalytic metal is supported within the pores existing in the catalyst support layer, forming active points that become the starting point of catalytic action. .

In particular, in catalysts for purifying automobile exhaust gas,
Extremely high levels of catalyst performance such as purification performance and durability are required.

Therefore, platinum (Pt), palladium (Pd), rhodium (Rh), etc. are effective catalyst metals for removing harmful components such as Co, HC, and NOx contained in conventional automobile exhaust gas. Catalysts supported with platinum group metals, singly or in combination, have been adopted as having excellent purification performance.

Co, HC in automobile exhaust systems as mentioned above.

It is a well-known fact that in exhaust gas purifying catalysts that purify harmful components such as NOx, deterioration of purification performance is caused by catalyst poisonous substances such as Pb and P contained in the exhaust gas.

Pb contained in such exhaust gas.

Poisoning deterioration of catalysts caused by catalyst poisoning substances such as P is particularly important among the deterioration factors of automotive catalysts.

As a measure to prevent the catalyst from being poisoned by catalyst poisoning substances such as Pb and P, a large amount of catalyst poisoning substances such as Pb and P adhere to the vicinity of the inlet end of the exhaust gas flow path in the monolithic catalyst. Focusing on this, we created a monolithic catalyst for exhaust gas purification in which a catalyst metal-free region was provided in the vicinity of the inlet end of the exhaust gas flow path, and the exhaust gas was used as a trap for catalyst poisonous substances such as Pb and P. Monolithic catalysts for purification have already been proposed (for example, JP-A-58-3626).

However, in the conventional monolithic catalyst for exhaust gas purification as described above, after the monolithic catalyst carrier is coated with activated alumina, a part of it is immersed in a catalytic metal supporting solution. However, it was difficult to accurately control the length of the region where the catalyst metal was not supported due to vibrations or capillary phenomena of the catalyst metal-supporting solution.

Therefore, in a monolithic catalyst for exhaust gas purification for internal combustion engines, the inventors created a state in which the parts of the monolithic catalyst that were to be free of catalyst support were masked with a photocurable resin that was cured by light irradiation. By immersing the monolithic catalyst carrier in a catalytic metal supporting solution, the catalytic metal-free portion of the monolithic catalyst can be precisely controlled and provided at a predetermined length. A supporting method has already been proposed as a separate invention.

Furthermore, a monolith catalyst for exhaust gas purification has been proposed in which catalyst metal is supported only on the rear side of the exhaust gas flow path (Japanese Patent Publication No. 59-25855).

[Problem that the invention seeks to solve]

In view of the current state of the prior art as described above, the problem to be solved by the present invention is that the inventors have already proposed that the monolithic catalyst is hardened by light irradiation on the portion of the monolithic catalyst that is to be made non-supported. By immersing the monolithic catalyst carrier in a catalytic metal supporting solution while masking it with a photocurable resin, it is possible to precisely control and provide the non-supported portion of the catalytic metal on the monolithic catalyst to a predetermined length. □In the method of supporting catalyst metal in a monolithic catalyst for exhaust gas purification, or in the monolithic catalyst for exhaust gas purification that has already been proposed (Japanese Patent Publication No. 59-25855), there is a difference in the flow rate of exhaust gas in each cell of the monolithic catalyst. It is faster in the central part of the monolithic catalyst and slower in the peripheral cells, so catalyst poisonous substances such as Pb and P adhere to the inside of the cells located in the central part of the monolithic catalyst, and the conventional monolithic In a monolithic catalyst for exhaust gas purification, which has a fixed length of catalyst metal-free portion near the inlet end of the exhaust gas flow path of the catalyst, the arrangement of the catalyst metal-free portion in the monolith catalyst is as follows: This means that the conditions were not sufficiently compatible with the distribution of the catalyst poisonous substances.

Therefore, the technical problem of the present invention is to reduce the length of the non-supported portion of the catalyst metal in the vicinity of the inlet side of the exhaust gas flow path of the monolithic catalyst in the monolithic catalyst for exhaust gas purification for internal combustion engines. The catalytic metal in the monolithic catalyst is made to be longer in the inner cells and shorter in the peripheral cells, thereby achieving an excellent match between the arrangement of the unsupported portions of the catalytic metal in the monolithic catalyst and the distribution of the adhering sites of catalyst poisonous substances. The object of the present invention is to effectively utilize the catalytic converter to ensure excellent catalytic purification performance and durability of a monolithic catalyst for purifying exhaust gas.

[Means for solving problems]

In view of these problems in the conventional technology, the present invention provides a means for solving the problems in the conventional technology by adding catalyst metal to the vicinity of the inlet end of the exhaust gas flow path in the monolithic catalyst for exhaust gas purification. This monolithic catalyst for exhaust gas purification is designed to reduce deterioration of the catalytic activity of the monolithic catalyst due to catalyst poisoning substances by providing a non-supported portion and trapping catalyst poisonous substances that cause catalyst poisoning. The monolithic catalyst carrier is made by applying a photocurable resin to the alumina-coated cell wall surface and drying it.The photocurable resin is applied to the monolithic catalyst carrier, which is made by applying a photocurable resin to the alumina-coated cell wall surface and drying it. After forming a hardened coating area of the resin, wash and remove the photocurable resin from areas other than the area covered with the photocurable resin that has been cured by light irradiation, and immerse it in a catalytic metal supporting solution. Accordingly, the monolithic catalyst for exhaust gas purification is characterized in that portions not carrying catalytic metal are arranged in correspondence with the distribution of the portions to which catalyst poisonous substances are attached in each cell.

[Effect]

Hereinafter, the effects of the present invention will be explained.

In the present invention, when using a monolithic catalyst coated with activated alumina as an exhaust gas purification catalyst, the non-supported portions of the catalyst metal are arranged in correspondence with the distribution of the adhesion sites of catalyst poisons in each cell. This is because the catalyst poisons that cause catalyst poisoning are trapped by the non-supported parts of the catalyst metal, which are arranged in accordance with the distribution of the catalyst poison adhesion sites in each cell. This is to reduce deterioration of the catalytic activity of the monolithic catalyst, and to ensure excellent catalyst purification performance and durability of the monolithic exhaust gas purifying catalyst by effectively utilizing the catalytic metal supported on the monolithic catalyst.

〔Example〕

EMBODIMENT OF THE INVENTION Hereinafter, one example of the monolithic catalyst for exhaust gas purification of the present invention will be described based on the accompanying drawings.

Although various methods can be considered for manufacturing the monolithic catalyst for exhaust gas purification according to the present invention, a method using a photocurable resin will be described here.

FIG. 1 shows the formation of a hardened photocurable resin masking near the inlet end 1a of the exhaust gas flow path of the monolithic catalyst carrier 1 in order to manufacture the monolithic catalyst for exhaust gas purification of this example. FIG.

First, a monolithic catalyst carrier 1 made of cordierite coated with activated alumina is immersed in an aqueous solution of a photocurable resin, and the monolithic catalyst carrier 1 on the inflow side end 1a side of the exhaust gas flow path in the monolithic catalyst carrier 1 is immersed in an aqueous solution of a photocurable resin. Approximately 1 of total length l
A photocurable resin was applied to the cell wall of No. 15 and then dried.

Next, a light shielding plate 3 as shown in FIG. Holding plate member 4. The monolithic catalyst carrier 1 is attached to a monolithic catalyst carrier holding jig 2 made of a holding bar 5, and while the monolithic catalyst carrier 1 is rotated with the axial direction of the monolithic catalyst carrier 1 as the rotation axis, the inflow side of the exhaust gas flow path coated with the photocuring resin is Parallel light 6 from a high-pressure mercury lamp was irradiated from the direction of the end 1a.

At the same time, while gradually enlarging the opening of the light shielding plate 3, the monolithic catalyst carrier holding jig 2 was tilted so that the parallel irradiation light 6 was gradually irradiated obliquely with respect to the axial direction of the monolithic catalyst carrier 1.

In this way, as the irradiation angle of the parallel irradiation light 6 becomes oblique, the reaching length of the parallel irradiation light 6 within the monolithic catalyst carrier 1 becomes shorter.By adopting the light irradiation method as described above, the monolithic catalyst carrier 1 The curing area of the photocurable resin in the central part can be shortened (the length of the monolithic catalyst carrier is approximately 1159 of the total length of the monolithic catalyst carrier at the periphery as shown in Figure 2). Monolithic catalyst carrier 1 coated with a cured photocurable resin on about 1/10 of the area of the monolithic catalyst carrier 1
was able to mask the cell walls.

Thereafter, after washing to wash away the uncured photocurable resin, it is immersed in a catalytic metal supporting solution consisting of a mixed solution of dinitrodiammine platinum and rhodium chloride, and the mixed solution is stirred to form PT as a catalytic metal.

A monolithic catalyst of the present invention (product A of the present invention) was produced by supporting Rh.

In addition, in FIG. 2, 1a is the inflow side end of the exhaust gas flow path, and lb is a portion where no catalyst metal is supported.

In addition, as a comparative amount, about 175 mm of the total length l of the monolithic catalyst carrier 1 was added to the monolithic catalyst carrier 1 coated with activated alumina in the same manner as in the above-mentioned example in the vicinity of the inlet end 1a of the exhaust gas flow path (comparative product B). , about 1/10 (comparison amount C
A monolithic catalyst was prepared in the same manner by immersing the cell wall surface of the cell in a solution of a cured resin (for example, polyvinyl alcohol, etc., which is easily cured by heating) and then masking it by drying and heating.

These monolithic catalyst carriers 1 (invention product A, comparative product B
, Comparative product C) and unmasked monolithic catalyst carrier L (comparative amount D) were immersed in a catalyst metal support solution in the same manner as the monolithic catalyst of the present invention (present invention product A) described above, and comparative amount B was prepared. (The length of the unsupported part is about 115 of the total length l of the monolithic catalyst carrier), comparative amount C (the length of the unsupported part is about 1/10 of the total length l of the monolithic catalyst carrier), comparative amount D (no unsupported part)
Monolithic catalysts were manufactured for each of the following.

The four types of monolith catalysts A, B, and
C, D, displacement; 2.87! 2 in a driving pattern modeled after city driving by connecting to the exhaust system of the engine.
After running for 00 hours, the purification rate as a monolith catalyst was comparatively evaluated by changing the large gas temperature of the catalyst bed.

The comparative evaluation test results are shown in Table 1.

Table 1 Note 1) Temperature indicates the gas temperature ("C) entering the catalyst bed.

Note 2) Product A of the present invention has an unsupported portion length of approximately 115 mm in the central portion and approximately 1710 mm in the peripheral portion relative to the total length β of the monolithic catalyst carrier.

Note 3) Comparison amount B is the length of the unsupported portion in each cell relative to the total length l of the monolithic catalyst carrier, which is approximately 115.

Note 3) The comparative amount C is the length of the unsupported portion in each cell relative to the total length l of the monolithic catalyst carrier, which is approximately 1710.

Note 4) The comparison weighing is one in which no unsupported portion was provided over the entire length l of the monolithic catalyst carrier.

Note that the purification rates in Table 1 are based on the purification targets of HC and Co.
, NOx, and the catalyst bed temperatures were 300°C and 400°C.

As is clear from Table 1, the monolithic catalyst for exhaust gas purification of the present invention has a comparative amount B (the length of the unsupported portion in each cell relative to the total length l of the monolithic catalyst carrier is approximately 1
15), comparative amount C (monolith catalyst carrier total length l
(The length of the non-supported portion in each cell is approximately 1/10 of the total length of the unsupported portion in each cell.)

Even when compared with the comparative amount D (no non-supported portions were provided over the entire length of the monolithic catalyst carrier), the catalytic activity was superior, and moreover, the non-supported portions of the catalyst metal of the same length were provided. It is understood that the catalyst has excellent catalytic activity compared to the monolithic catalysts (comparative quantities B and C).

In addition, as the photocurable resin for masking, in addition to water-soluble colloidal resins, any photocurable resin commonly used for ordinary printing, such as polycinnamic acid, can be used. It can also be used suitably.

It should be noted that the photocurable resin coated on the monolithic catalyst carrier 1 in a cured state as described above is easily burned away by exhaust gas from the engine, so it goes without saying that it does not affect the catalytic function of the monolithic catalyst at all. Nor.

[Effects of the Invention] As is clear from the above, according to the monolithic catalyst for exhaust gas purification according to the present invention, in the monolithic catalyst for exhaust gas purification for an internal combustion engine, the portion near the inlet side of the exhaust gas flow path of the monolithic catalyst By making the length of the unsupported part of the catalyst metal longer in the central cell and shorter in the peripheral cells, the arrangement of the unsupported part of the catalyst metal in the monolithic catalyst and the distribution of the adhering parts of the catalyst poison can be improved. By making the monolithic catalyst compatible, the catalytic metal in the monolithic catalyst can be used effectively, thereby providing the advantage of ensuring excellent catalyst purification performance and durability of the monolithic catalyst for exhaust gas purification.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a situation in which a monolithic catalyst carrier coated with a photocurable resin is irradiated with parallel irradiation light for producing a monolithic catalyst for exhaust gas purification according to the present invention. FIG. 2 is a diagram illustrating the distribution of the non-supported portions of the catalyst metal in the vicinity of the #II portion on the inlet side of the exhaust gas flow path in the monolithic catalyst for exhaust gas purification of the present invention. ■・−・−Monolith catalyst carrier. 1 a--11 Inlet end of exhaust gas passage. 1 b ------Unsupported site of one catalytic metal. 2-...-Monolith catalyst carrier holding jig. 3.---One light shielding plate. 4-...-retention plate member. 5-----One holding bar. Parallel irradiation light to 6-・-. 7-・One rotation direction. 8...-111 slope direction. β~...-Full length of monolithic catalyst carrier.

Claims (1)

[Claims] 1. A catalyst metal-free region is provided in the vicinity of the inlet end of the exhaust gas flow path in a monolithic catalyst for exhaust gas purification to trap catalyst poisonous substances that cause catalyst poisoning. This is a monolithic catalyst for exhaust gas purification that aims to reduce the deterioration of the catalytic activity of the monolithic catalyst due to catalytic poisoning substances, and is a monolithic catalyst carrier in which a photocurable resin is applied to the cell wall surface coated with activated alumina and dried. On the other hand, after forming a hardened coating part of the photocurable resin in accordance with the distribution of the adhering parts of the catalyst poison substance in each cell of the monolithic catalyst for exhaust gas purification, the photocuring resin is cured by light irradiation. By cleaning and removing the photocurable resin from areas other than those covered with the catalytic resin and immersing it in a catalytic metal supporting solution, the catalytic metal is A monolithic catalyst for exhaust gas purification characterized by the arrangement of unsupported parts.