JPH02222730A - Method for supporting catalytic metal on catalyst carrier - Google Patents

Abstract

PURPOSE:To uniformly support a catalytic metal on catalyst carriers in a short time by immersing the carriers in a soln. contg. the metal for a certain time, pulling up the carriers, making the concn. of the soln. uniform by bubbling and repeating these operations. CONSTITUTION:Carriers 3 are put in a support frame 1 and this frame 1 is immersed in a soln. 4 contg. a catalytic metal in a soln. vessel 2. After the lapse of a certain time, the frame 1 is taken out of the soln. 4 and solenoid valves 7 are opened to introduce air from ducts 6. The soln. 4 is bubbled by the air and the concn. distribution of the soln. 4 is made uniform. The valves 7 are then closed and the frame 1 is lowered to immerse the carriers 3 in the soln. 4. These operations are repeated. The catalytic metal is uniformly supported in a short time.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is directed to a catalyst carrier, which is a step in the manufacturing process of a catalyst that purifies harmful components such as hydrocarbons, carbon oxides, and nitrogen oxides discharged from internal combustion engines. The present invention relates to a method of supporting a catalytic metal on a metal.

[Prior Art] As a conventional method for supporting a catalyst metal on a catalyst carrier, an inorganic porous support layer such as activated aluminum is formed on a honeycomb carrier base material or a three-dimensional network carrier base material to form a catalyst carrier. Then, the catalyst metal is supported on the support layer by pouring the catalyst metal-containing solution from above the catalyst carrier or by immersing the catalyst carrier in the catalyst metal-containing solution. At this time, the support layer easily adsorbs and supports the substance dissolved in the solution, so if the concentration distribution of the solution is non-uniform, the support layer will non-uniformly support the substance. In particular, since negative metal catalysts are dilute solutions, they tend to vary.

At this time, in order to uniformly support the catalytic metal on the supporting layer of the carrier, the catalytic metal-containing solution is stirred with a stirrer or circulated to maintain a uniform concentration. For example, Tokko Showa 60-'! Publication No. 5383 discloses a method for supporting a catalytic metal on the supporting layer of a carrier by circulating and contacting a solution containing a catalytic metal in an amount of 8 to 20 times the water absorption amount of the carrier along the pores of the carrier. has been done.

[Problems to be Solved by the Invention] In the above-mentioned circulation method or stirring method using a stirrer, the distribution of the amount of catalyst metal supported on the support layer is controlled by the flow rate when the catalyst metal-containing solution contacts the support, and the catalyst metal-containing solution is formed in a honeycomb shape. In the case of the catalyst carrier, a particularly large amount of the catalytic metal-containing solution is supported near the inlet of the pores.

Furthermore, since the concentration distribution of the catalytic metal-containing solution differs even within the same tank, there is a large variation in the amount supported between each carrier.

Further, due to the structure of the circulating support device, the circulation of the catalytic metal-containing solution tends to be uneven, and variations in the concentration of the catalytic metal-containing solution occur even within the same tank.

This causes variations in the amount of catalyst metal supported on the carrier, making it difficult to obtain catalysts with the same performance. Further, in the method of stirring using a stirrer, it is difficult to achieve uniform mixing due to restrictions on the mounting location of the stirrer. Moreover, there are problems such as the capacity of the carrier to be accommodated in the dipping container is limited.

The present invention was made in order to improve the above-mentioned problems, and an object of the present invention is to uniformly support a catalytic metal.

[Means for Solving the Problems] The method of supporting a catalyst metal on a catalyst carrier of the present invention includes a dipping step of immersing a catalyst carrier having a porous support layer in a catalyst metal-containing solution; It is characterized by alternately repeating a stirring process in which the solution is lifted from a metal-containing solution, and a gas is blown into the solution containing the catalyst base and stirred by bubbling.

The catalyst carrier has a honeycomb-like or three-dimensional network structure, and for example, a monolithic carrier such as cordierite, mullite, spinel, etc. is used. Furthermore, it can also be applied to metal honeycomb carriers. A porous support layer made of alumina or the like is formed in advance on this catalyst carrier, and the catalyst metal is supported on this support layer.

The catalytic metal-containing solution is a solution in which a water-soluble compound of a platinum group element that is commonly used as a catalyst is dissolved. for example,
It is an aqueous solution of nitrates of platinum, palladium, rhodium, etc.

The immersion step is a step in which the catalyst carrier is immersed in the catalytic metal-containing solution for a certain period of time, so that the inside of the catalyst carrier is sufficiently immersed in the catalytic metal-containing solution. At this time, the catalyst metal dissolved in the solution adheres to and is supported on the support layer. On this occasion,
It is preferable that the catalyst carrier is held perpendicular to the axial direction of the cells of the honeycomb so that the catalyst metal-containing solution can easily enter and fall into the cells. Further, in this immersion, it is preferable to immerse a plurality of catalyst carriers at the same time with their axial directions aligned.

Alternatively, even one cell may be held perpendicular to the axial direction of the cell and immersed.

In the stirring step, the catalyst carrier is pulled up from the catalytic metal-containing solution, and a gas is bubbled into the catalytic metal-containing solution for stirring. This bubbling agitation allows the solution concentration in the dipping tank to be made uniform in a short time. The excess liquid in the rinsing cell falls and is stirred in the immersion tank to become a liquid with a uniform concentration again. The gas used is not particularly limited, and air, nitrogen gas, etc. are typically used.

The greatest feature of the present invention is that the dipping step and the stirring step are alternately repeated.

That is, after the concentration distribution of the catalytic metal-containing solution, which has become non-uniform due to immersion, is made uniform by bubbling agitation, the step of immersing the catalyst carrier in the catalytic metal-containing solution is performed again. Therefore, in the dipping step, the catalyst carrier is constantly and repeatedly immersed in a uniform catalyst metal-containing solution, so that the catalyst metal is uniformly supported.

The catalyst metal can be supported in a relatively short time by dipping. In addition, since bubbling can make the concentration distribution uniform in a short period of time, it has become possible to repeatedly perform the stirring step and the dipping step in a short period of time. By repeating this operation for a predetermined period of time, each catalyst carrier is brought into contact with a solution of -i degree uniformly on the support layer each time the dipping step is repeated, so that the catalyst is uniformly supported and variations are reduced. Therefore, the amount of catalyst supported on the support layer can be made uniform.

Furthermore, it is possible to eliminate non-uniformity in the amount of support among a plurality of carriers.

This bubbling agitation does not require a specific location in the solution tank like a stirrer, and can uniformly stir the catalytic metal-containing solution by introducing pressurized air, for example. Also, unlike a stirrer, the volume of the solution tank can be fully utilized for support. In bubbling, the stirring conditions can be easily adjusted by adjusting the pressure of the gas, the diameter of the bubbling gas, the shape of the aperture, and the position of the aperture, and a uniform catalytic metal-containing solution can be obtained quickly. Therefore, this dipping step and stirring step can be repeated in a short period of time, and the catalyst metal can be evenly supported in a short period of time.

[Function] In the supporting method of the present invention, the catalyst carrier is immersed in a catalyst metal-containing solution for a certain period of time, then removed from the solution, and the solution is stirred by bubbling to make the concentration ratio uniform. Once the concentration distribution is uniform, the catalyst carrier is immersed again. Repeat these two steps. The catalyst carrier was always immersed in a catalyst metal-containing solution with a uniform m-degree distribution, making it possible to support the catalyst uniformly. This bubbling agitation can make the concentration distribution uniform in a short time, so the dipping and stirring processes can be repeated in a short time, and even if multiple supports are dipped at the same time, the distribution of the catalyst metal between them can be maintained. Can be done evenly.

[Example J The present invention will be specifically explained below using Examples.

FIG. 1 is a schematic plan view when the carrier 3 is placed on the support frame 1. FIG. 2 is a schematic explanatory diagram of the arrangement of the support frame 1 and the solution tank 2. FIG. 3 is a schematic explanatory diagram when the support frame 1 is immersed in the solution tank 2 of the catalyst metal-containing solution 4.

This solution tank 2 can accommodate the support frame 1, has a depth such that the solution surface is above the top surface of the carrier 3, has an opening for bubbling, and is equipped with a solenoid valve 7 for switching between introducing and stopping air. A plurality of air pipes 6 for performing this are connected to the solution tank 2, and a swing FjX5 for swinging the support frame 1 containing the carrier 3 up and down is arranged.

As shown in Fig. 3, the support frame 1 is immersed in the solution bath 2, and after being kept for a certain period of time, the support frame 1 is pulled up by the rocker 5 and taken out from the catalyst metal-containing solution 4. At the same time, the solenoid valve 7 is opened. Then, air is introduced from the air pipe 6 to bubble the catalyst metal-containing solution 4 with air.

Then, the concentration distribution of the catalyst metal-containing solution 4 becomes uniform. Then, the electromagnetic valve 7 is closed, and the support frame 1 is lowered by the swinger 5 to immerse the catalyst carrier 3 in the catalyst metal-containing solution 4. By repeating this operation, a catalyst having a uniform amount of support can be produced.

(Example 1) A honeycomb carrier (938φX100m1400 cells/1n2) having a coating layer mainly composed of Y-alumina was
(3 rows x 3 pieces) were accommodated in the support frame 1. The catalytic metal-containing solution 4 was an aqueous chloroplatinic acid solution containing 6.1 g of platinum. O
, ff were adjusted and placed in the solution tank 2. Next, the support frame 1 was lowered and the carrier 3 was immersed in the catalyst metal-containing solution 4. 4
After 0 seconds, the support frame 1 was raised, and air was introduced into the catalyst metal-containing solution 4 from the air pipe 6 to perform air bubbling for 10 seconds. Thereafter, the support frame 1 was lowered again and the carrier 3 was immersed in the catalyst metal-containing solution 4. This operation was repeated for 60 minutes.

(Comparative Example 1) A chloroplatinic acid aqueous solution containing 6.0 g of the same platinum as in Example 1 was adjusted to 20.0 fI on the same carrier as in Example 1, and supported for 60 minutes using a forced support liquid circulation method using a conventional pump. was carried out.

The distribution ratio of the amount of platinum supported on the catalyst was investigated for each carrier of this Example and Comparative Example. The results are shown in the △ and 8- line graphs in FIG. All of the nine supports in the examples showed a distribution ratio of about 1.0 and the catalyst metal was supported uniformly, but in the case of the comparative examples, the supported amount distribution ratios of ■, ■, and ■ were higher than in the other cases. The high square mark in the center indicates that those placed in the corners are lower than those in the example and are not supported uniformly.

(Example 2) Platinum in catalyst metal-containing solution 4 of Example 1 was replaced with 1.2 rhodium.
The catalyst was supported in the same manner except that the rhodium chloride aqueous solution containing g was used instead.

(Comparative Example 2) Under the same conditions as Comparative Example 1, rhodium 1.
It was supported using an aqueous rhodium chloride solution containing 2 g.

For each of the carriers of Example 2 and Comparative Example 2, the ifi ratio was determined based on the amount of rhodium supported on the catalyst. The results are shown in the line graphs 8 and B- in FIG. The line graph of Example 8 is a straight line, but the line graph of Comparative Example B' is wavy and not uniformly supported. The supported amount distribution ratio of the carrier located at the corner of the support frame is low.

(Example 3) As shown in Fig. 4, a honeycomb carrier (93M1φ
10.0 J of a chloroplatinic acid aqueous solution containing 4.0 g of platinum was prepared, and the dipping step and stirring step were repeated in the same manner as in Example 1 to support the catalyst.

(Comparative Example 3) A chloroplatinic acid aqueous solution containing 4.0 g of platinum as in Example 3 was prepared in an amount of 20.0.11 on the same carrier as in Example 3, and supported in the same manner as in Comparative Example 1 for 60 minutes.

For each of the carriers of Example 3 and Comparative Example 3, the distribution ratio of the amount of platinum supported on the catalyst was investigated. The results are shown in C and C' in Figure 7.
This is shown in the line graph. C in Example 3 is straight and evenly supported, whereas Comparative Example 3 is higher on the right shoulder and is more supported only on the inside, and is higher than C in Example, but on the contrary, it is lower on the wall side. This indicates that uniform loading is not achieved.

(Example 4) Ceramic carrier 3 with a three-dimensional network structure having a coating layer mainly composed of Y-alumina (93 mmφ×100 mL 13
A catalyst was supported in the same manner as in Example 1 by housing nine pieces of mesh in a support frame.

(Comparative Example 4) The same carrier as in Example 4 was used in the same manner as in Comparative Example 1.
We carried out the support at

The platinum loading ratio of the catalyst was investigated for each carrier in Example 4 and Comparative Example 4. The results are shown in D and D in Figure 8.
- Shown in the line graph. D in Example 4 shows a straight line indicating that the particles are uniformly supported, whereas D' in Comparative Example shows a waveform graph indicating that the particles are not uniformly supported.

(Example 5) The catalyst obtained in Example 1 was designated as A1, and as shown in FIG. 9, the amount of platinum supported was measured by dividing it into three parts, top, middle, and bottom (a, b, and c). The results are shown in FIG.

(Comparative Example 5) The catalyst obtained in Comparative Example 1 was designated as A'1, and was divided into three parts a, b, and c, upper, middle, and lower, as in Example 5, and the amount of platinum supported at each position was measured. is shown in Figure 1O.

In the case of A1 of the example, there is no change depending on the location within the carrier, and the support is uniform, but in the case of A-1 of the comparative example, there is more C in the lower part and less a in the upper part, and the support is not uniform.

(Concentration difference depending on the position of the catalyst metal-containing solution) When the catalyst metal-containing solution was supported by the method of Example 1 and Comparative Example 1, the solution tank was as shown in FIG. Figure 12 shows the concentration change of the catalytic metal in the catalytic metal-containing solution, which decreases with the passage of time for supporting the catalytic metal (the concentration of the catalytic metal-containing solution was sampled with a whole pipette in 1.3.5).
．． Samples were taken and measured at 10 minutes and every 10 minutes thereafter.

). In the case of Example 1, the density changes are the same at all positions, but in the case of Comparative Example 1, differences are observed in the density changes at the three locations. Therefore, it is assumed that the amount of catalyst metal supported on the carrier also varies.

(Performance evaluation of catalyst) In addition, the catalysts obtained in Example 1 and Comparative Example 1 were
The product was installed in the exhaust system of an engine, and was subjected to a conventional durability test to examine the purification efficiency of hydrocarbons, carbon oxides, and nitrogen oxides. The results are shown in line graphs in Figures 13, 14, and 15.

In the case of A1 of the example, the reduction in purification rate due to an increase in durability time is smaller than in the case of A''1 of the comparative example. In other words, this shows that the catalyst performance is excellent.

[Effects] According to the method of the present invention, by bubbling in the stirring step, the concentration distribution of the catalyst metal-containing solution in the solution tank in the dipping step can be made uniform. Therefore, by repeating the dipping step and the stirring step alternately, it is possible to eliminate variations in the amount of catalyst metal supported between and within the catalyst carriers. Moreover, a large number of catalysts can be supported at the same time, and catalysts of the same quality can be obtained.

In addition, the catalyst obtained by this method has superior durability and performance compared to conventional catalysts because the catalytic metal is uniformly supported.

[Brief explanation of the drawing]

FIG. 1 to FIG. 4 are schematic diagrams for explaining this process, and FIG. 1 is a plan view when the carrier base material is loaded on the support frame;
Figure 2 is a schematic diagram of the process of immersing the support frame in Figure 1 in a catalyst metal-containing solution, Figure 3 is a schematic diagram of the process of immersion, and Figure 4 is a schematic diagram of the process of immersing the support frame in Figure 1.
The figure shows the arrangement when the number of loaded carrier base materials is 6, FIG. 5 is a graph showing the supported foot distribution ratio of Example 1 and Comparative Example 1, and FIG. 6 is a graph showing the carrier foot distribution ratio of Example 2 and Comparative Example 2 FIG. 7 is a graph showing the supported amount distribution ratio of Example 3 and Comparative Example 3, and FIG. 8 is a graph showing the supported amount distribution ratio of Example 4 and Comparative Example 4. 4h ratio, FIG. 9 is a schematic diagram showing the portions of the catalyst carrier supporting valve 11 to be compared, and FIG. 10 is a graph showing the supported amount distribution ratio of Example 5 and Comparative Example 5. FIG. 11 is a plan view showing the part of the support frame for examining the concentration change of the catalyst metal-containing solution;
FIG. 12 is a graph showing the 6% a change depending on the supporting time of the catalytic metal-containing solution in the portions shown in FIG. 11, 13.14.
FIG. 15 is a graph showing the purification rate after durability of the example and the comparative example. FIG. 13 shows the HC purification rate, FIG. 14 shows the CO purification rate, and FIG. 15 shows the NOX purification rate. 1... Support frame 3... Carrier 6... Air piping

Claims (1)

[Claims] An immersion step in which a catalyst carrier having a porous support layer is immersed in a catalytic metal-containing solution; and a stirring step in which the catalyst carrier is lifted from the catalytic metal-containing solution and gas is blown into the catalytic metal-containing solution to stir it by bubbling. A method for supporting a catalytic metal on a catalyst carrier, characterized in that the method is carried out alternately and repeatedly.