JPS6164337A - Production of monolithic catalyst - Google Patents

Abstract

PURPOSE:To obtain a monolithic catalyst excellent in the purification efficiency of exhaust gas and durability, by forming a catalyst support layer partially different in the adhesion amount of a catalyst support components and supporting a catalytic component by said catalyst support layer. CONSTITUTION:A monolithic catalyst base material 1 comprising cordierite with the number of pores of 300/in<2> is immersed in distilled water to be sufficiently impregnated with water and drawn up to be dried in an air stream. A air feed pipe 2 consists of a straight pipe part 2a with a diameter of 6.5cm and a cone part of which the max. diameter is same as the diameter of 10.7cm of the monolithic catalyst base material 1. Therefore, the flow velocity distribution of an air stream is fastest at the central part thereof and becomes slower toward the peripheral part thereof. An alumina sol is penetrated into the base material under pressure and the whole is baked to obtain a monolithic carrier which is, in turn, immersed in an aqueous solution of platinum dinitrodiamine and, after drying, the impregnated carrier is further immersed in an aqueous rhodium chloride solution before drying.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a monolithic catalyst, and more specifically, to a method for producing a monolithic catalyst, and more specifically to a method for manufacturing a monolithic catalyst. : Therefore, the attachment Wffi of the catalyst supporting component
The present invention relates to a method for producing monolithic catalysts in which the amounts of catalyst components supported differ depending on the amount of catalyst components supported.

[Prior Art] Conventionally, when manufacturing a monolithic catalyst, a monolithic catalyst substrate is immersed in a slurry containing a catalyst-supporting component, pulled up, dried, and fired to support the catalyst on the inner surface of the pores of the substrate. It formed a layer. The catalyst component, such as a noble metal, can be supported by immersing the support layer in a solution containing the catalyst component after forming the support layer, or by incorporating the catalyst component into the slurry in advance and then forming the support layer. It was carried out by forming it integrally with the

[Problems to be Solved by the Invention] Monolithic catalysts produced by conventional production methods have substantially uniform loading density of catalyst components over the entire area of the monolithic catalyst. However, when we consider the case where a monolith catalyst is actually used by installing it in an automobile exhaust system, exhaust gas does not pass through the monolith catalyst at a uniform speed and pressure, and generally passes around the axial center of the monolith catalyst. More gas passes through. Therefore, considering the exhaust gas purification efficiency of the monolith catalyst and the durability of the catalyst,
It is better to support more catalyst components near the axial center of the monolithic catalyst. In addition, if the catalyst 11E supporting layer is made thicker near the shaft center and thinner at the outer circumference, the pressure loss near the shaft center will be higher than that at the outer circumference, the flow velocity distribution inside the catalyst will become smaller, and the catalyst performance will decrease. improves. However, a method of varying the catalyst support layer locally within the catalyst in order to form a catalyst component support distribution that corresponds to the flow velocity distribution of exhaust gas has not been provided in the past.

The present invention has been devised in view of the above circumstances, and is a novel method for producing a monolithic catalyst in which the adhesion m of the catalyst supporting component and the supporting Rm of the catalyst component are partially different depending on the usage situation of the monolithic catalyst. The purpose is to provide a method.

[Means for Solving the Problems 1] The method for producing a monolithic catalyst of the present invention involves impregnating a columnar monolithic catalyst base material with a large number of pores extending in the axial direction with water so that at least a portion of the base material is A water-containing step in which the moisture content is different from that of other parts, and a slurry containing at least a catalyst-supporting component is brought into contact with the wall surface forming the pores of the base material, and then dried and calcined to remove the catalyst-supporting component. The method is characterized by comprising a support layer forming step in which catalyst support layers with partially different adhesion m are formed, and a catalyst support step in which a catalyst component is supported on the catalyst support layer.

The base material of the monolith catalyst defines the outer shape of the monolith catalyst and serves as its skeleton. The base material has a large number of pores (100 to 600 per square inch) extending in the flow direction of the exhaust gas.
It is an integrally molded structure with a honeycomb structure or a three-dimensional network structure, and its outer shape is columnar (a shape that matches the internal shape of the exhaust system in which the monolithic catalyst is installed, such as a cylinder or a square column).
to accomplish.

Cordierite is generally used as the material for the base material, but other materials such as mullite and spinel can also be used. As for the base material itself, the same base material as the conventional base material can be used.

A feature of the production method of the present invention is that it includes a water impregnation step in which the above monolithic catalyst base material is impregnated with water so that at least a portion of the base material has a different water content than the other portion.

In the supporting layer forming step following the above-mentioned water-containing step, water permeation into the slurry containing the catalyst-supporting component is reduced in areas of the monolithic catalyst base material with a high water content, and in extreme cases water is absorbed. Water may also reduce the viscosity of the slurry. Furthermore, in areas where the water content of the monolithic catalyst base is low, water in the slurry permeates into the monolithic catalyst base, increasing the viscosity of the slurry. For this reason, there are differences in the amount of slurry deposited. That is, areas with a high water content have a low slurry adhesion rate, and areas with a low water content have a large amount of slurry adhesion, making it possible to partially vary the adhesion of the catalyst-carrying component.

In the water impregnation step, water is sufficiently absorbed into the monolithic catalyst base material by, for example, a dipping method or an injection method, and then a portion of the base material is selectively dried to have different water contents. Here, the part of the base material that is selectively dried includes, for example, the shaft center part. In other words, it is desirable to selectively dry the portions through which exhaust gas passes through when used as a monolithic catalyst, and the moisture content has a distribution in the direction perpendicular to the axial direction.
It is desirable that the moisture content of the axial center portion be lower than that of the peripheral portion.

As a method for removing (drying) more water impregnated into a monolithic catalyst solid phase from a 1 q portion than from other portions, there is, for example, a method of blowing air at different flow rates from one end surface of the base material. That is, a high-velocity air stream is selectively blown onto the areas that need to be dried, and the air stream is used to partially dry and remove moisture.

A preferred method is to blow an air flow having a temperature distribution from one end surface of the substrate. In this case, the air flow that blows selectively onto the areas to be dried is heated to a high temperature. It is also preferable to blow an air flow having both a flow rate of 15 and a temperature distribution.

In other words, the airflow that is blown onto the areas to be selectively dried can be made at a high temperature and at a high flow rate.

Another similar method is to conversely apply suction drying from one end surface of the substrate under low pressure. In this case, the parts to be selectively dried are suction dried at a low pressure.

Another method is to treat the base material in advance to vary the amount of water absorption. For example, when molding the base material, it is preferable to change the amount of water absorption by giving a roughness distribution to the inner surface of the pores of the base material. You can also change the amount of water absorbed.

In the catalyst supporting step, a slurry containing at least a catalyst supporting component is brought into contact with the pore surface of the monolithic KM material using a dipping method, press-in method, suction method, etc., with the monolithic KM material having partially different water contents. Here, more slurry adheres to areas with low moisture content, and less slurry adheres to areas with high moisture content. Thereafter, it is dried and fired to form a catalyst supporting layer.

Here, alumina is mainly used as a supporting component in the slurry, but it is not limited to alumina.

Further, a catalyst component may be mixed into this slurry for use.

The catalyst supporting step is performed in the same manner as conventionally. In other words, the conventionally known catalyst components are platinum (Pt), palladium (Pd), iridium (Ir), and ruthenium (RL, I).
), rhodium (Rh), osmium (O6>, etc.), or base metals such as chromium (Cr), nickel (Ni), vanadium (V), vA (Cu), etc. can be used. The monolithic catalyst carrier on which the catalyst supporting layer has been formed is immersed in a solution containing the catalyst to support the catalyst components on the catalyst supporting layer.The monolithic catalyst is then dried and calcined to obtain a monolithic catalyst.

Incidentally, in the case where a plurality of types of catalyst components are supported by a plurality of solutions each containing a separate catalyst component, the above-mentioned supporting step is sequentially repeated for each solution.

[Example] Hereinafter, the present invention will be explained based on examples.

(First example) Diameter 10.7 cm, length 15 cm, number of pores 300/
A monolithic catalyst substrate consisting of square inches of cordierite was immersed in distilled water to fully saturate it with water. Thereafter, it was lifted up and an air stream was sent through it in the manner shown in FIG. 1 to dry the moisture. In other words, the blow pipe 2 has a straight pipe part 2a with a diameter of 6.5 cm.
and the maximum diameter is 10.7c, which is the same as the diameter of the monolith catalyst base material.
It consists of a cone portion 2b of m. Therefore, the flow velocity distribution of the airflow is fastest in the central part (the part with the same diameter as the straight pipe part) and slowest in the peripheral part. Therefore, as for the dehydration m of the monolithic base material 1, as schematically shown in FIG. 2, the axial center part is dehydrated more than the peripheral part. In the case of this embodiment, dry air of 30"C is fed into the straight pipe section 2a at a rate of f of 10m3/sec.
The moisture was dried by spraying with f1ffi for 1 minute. Next, alumina silua 00g (alumina included tijffi1c
lffi%), aluminum nitrate aqueous solution (aluminum nitrate 40%), distilled water 45Qml, alumina 100
A slurry consisting of 0 g was injected into the base material to adhere to the inner surface of the pores. Then, it was dried at 200°C for 1 hour and roughly calcined at 700°C for 2 hours to obtain a monolithic catalyst carrier with a catalyst support layer formed on the surface.

The monolithic catalyst carrier was immersed in distilled water to absorb sufficient water, then pulled out and the excess water was blown off.

Thereafter, the monolithic catalyst carrier was immersed in a dinitrodiamine platinum aqueous solution (1% by weight of platinum) for 1 hour at 200°C for 1 hour and 11 J.
Dry. After soaking in distilled water in the same manner, the platinum-supported monolithic catalyst carrier was immersed in an aqueous rhodium chloride solution (0.1fflff1% rhodium) for 1rR.
It was dried at 0°C for 1 hour. In the manner described above, the monolithic catalyst of the first example, in which platinum and rhodium were supported as catalyst components, was produced.

(Second Example) The same base material as in the first example was used except for the water-containing process before press-fitting the slurry, the slurry was applied in the same manner, and platinum and rhodium were applied in the same manner as drying and baking. A monolithic catalyst of the second example was produced by supporting the male.

In the water impregnation step, the monolithic catalyst substrate 3 was immersed in distilled water to be sufficiently impregnated with water, and then dried by sending an air flow through a rectifier 4 having a U diameter of 1Q and 7 cm as shown in FIG. The pores of the fluid regulating fluid 4 have a large diameter at the axial center and a small diameter at the periphery. Therefore, the amount of water dehydrated from the monolithic catalyst base material 3 is greater in the axial center than in the peripheral part, as schematically shown in FIG.

In this case, 30°C dry air is supplied to the inlet of the flow regulator 4 for 10 minutes.
Moisture was dried by blowing at ff1ffl at m3/sec for 1 minute.

(Conventional example) The water-containing step before press-fitting the slurry was omitted, and other than that, the same base material as in the first embodiment was used, the slurry was applied in the same way, and platinum and rhodium were applied in the same way after drying and firing. A conventional monolithic catalyst was produced by supporting the catalyst.

(Evaluation) The monolithic catalysts of the first and second embodiments and the conventional example were housed in a monolithic catalytic converter 5 with an artificial diameter of 5.5 cm shown in FIG. Next, a closed-loop system using a three-way catalyst
A durability test of 50,000 krn was conducted by installing the system on a vehicle.

After durability, the converters containing the monolithic catalysts of the first and second embodiments and the conventional example were tested on the engine bench for 30 minutes.
The calcification rate of )-IClCO%NOx at 0°C and 350°C was measured and the results are shown in the table.

From the table, the exhaust gas purification rate of the monolithic catalysts manufactured according to the first example and the second example was 300°C after the durability test of running 50,000 km compared to the monolithic catalyst manufactured according to the conventional example.
It is 1.2 to 1.4 times better than J5 at 350"C, and 1.0 to 1.1 times better than J5 at 350"C.In other words, from the table, the monoliths manufactured by the first example and the second example It is clear that the catalytic performance of the catalyst is superior compared to monolithic catalysts produced by conventional methods.

[Effects of the Invention] The production method of the present invention makes it possible to partially and arbitrarily change the level of catalyst components supported within the monolithic catalyst. Therefore, it is possible to obtain a monolithic catalyst with a loading distribution of catalyst components suitable for actual use, and
A monolithic catalyst with excellent nineization effect, durability, etc. can be obtained.

Furthermore, according to the manufacturing method of the present invention, the catalyst support layer is thick near the axial center of the monolithic catalyst base material and thinner near the periphery, so that the pressure loss near the axial center is higher than the pressure loss near the periphery. Therefore, the contact period i between the exhaust gas and the catalyst near the shaft center becomes longer, and the catalyst performance improves. Therefore, a monolithic catalyst with high exhaust gas purification efficiency and excellent durability can be obtained. It also prevents wasteful use of raw materials.

[Brief explanation of the drawing]

The fourth figure represents the relationship between the amount of dewatering and the radial position during the water-containing process.
The figure is a pictorial diagram showing the relationship between the amount of water removed during the water-containing process and the diameter. FIG. 5 is a longitudinal sectional view of the humperter assembly used in the evaluation test of the example. 1.3...Monolith catalyst base material 2...Blow pipe 4...Rectifier (Fig. 2) Fig. 4 (t)
Figure 5

Claims (3)

[Claims] (1) a water impregnation step of impregnating water into a columnar monolithic catalyst base material having a large number of pores extending in the axial direction so that at least a portion of the base material has a different water content than the other portion; A support layer forming step in which a slurry containing at least a catalyst support component is brought into contact with the wall surface forming the pores of the base material, and then dried and fired to form a catalyst support layer in which the amount of the catalyst support component deposited is partially different. A method for producing a monolithic catalyst, comprising the steps of: and a catalyst supporting step of supporting the catalyst component on the catalyst supporting layer. (2) The water impregnation step involves impregnating the base material with water and then selectively drying a portion of the base material to have different water contents. Production method. (3) The method for producing a monolithic catalyst according to claim 1, wherein the water content has a distribution in a direction perpendicular to the axial direction, and the water content in the central portion is lower than that in the peripheral portion.