JP2005230776A - Production method and production apparatus of catalyst carrying filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a production method and a production apparatus of a catalyst carrying filter producing the catalyst carrying filter with low pressure drop using catalyst slurry relatively easily prepared, at a low cost. <P>SOLUTION: In this production method for a porous honeycomb filter of a flow-through type carrying a catalyst for cleaning exhaust gas, after water is absorbed in the filter carrier, the filter carrier is dipped in catalyst slurry, water absorbed in the filter carrier is substituted for the catalyst slurry in the dipping liquid, or, in place of dipping the filter carrier in the catalyst slurry, the catalyst slurry is made to pass through the filter carrier, drained, for drying and baking. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method and an apparatus for manufacturing a catalyst-carrying filter suitable for removing particulate matter (PM) contained in exhaust gas discharged from an internal combustion engine such as a diesel engine.

  As a technique for removing PM contained in diesel exhaust gas, a diesel particulate filter (DPF) in which one of the gas inflow portion and the discharge portion of a porous cordierite honeycomb is alternately sealed by adjacent cells is widely known. Yes. For example, Patent Document 1 proposes a technique for carrying out continuous regeneration by supporting an oxidation catalyst on a DPF and oxidizing and burning the collected PM. In general, the catalyst is supported on the DPF by using a sol or aqueous solution containing the catalyst, so that the catalyst can be relatively easily supported up to the inside of the pores. There is also. On the other hand, a method of supporting a catalyst prepared in advance in a slurry has been studied.

However, in a general catalyst slurry loading method, the moisture in the catalyst slurry is first absorbed by the porous carrier, so that the solid content concentration in the catalyst slurry increases, and the catalyst component is contained inside the cell or cell wall. There was a problem that it was easy to solidify on the surface. In particular, a porous carrier such as DPF has a large effect because the amount of water absorption increases, and it is solidified inside the cell or does not enter the inside of the pore and is supported only on the surface of the cell wall, and the pressure loss of the filter is large. There were problems such as becoming. For this reason, a method of repeatedly supporting using a low-concentration catalyst slurry, a method using a catalyst slurry comprising fine particles of 1 μm or less and a dispersing agent (Patent Document 2), etc. have been proposed. There were problems such as an increase in cost and difficulty in preparing a catalyst slurry.
JP-A-60-235620 JP 2003-170055 A

  The object of the present invention is to solve the above-mentioned problems of the prior art and to produce a catalyst-carrying filter with a low pressure loss at a low cost by using a catalyst slurry that can be prepared relatively easily. And providing a manufacturing apparatus.

As a result of intensive studies on the above problems, the present inventors have been able to prevent an increase in the solid content concentration of the catalyst slurry by replacing the moisture with the catalyst slurry by using a carrier that has absorbed moisture in advance. The inventors have found that the catalyst can be supported uniformly and have reached the present invention.
That is, the invention claimed in the present application in order to achieve the above-described problems is as follows.

(1) A method for producing a flow-through type porous honeycomb filter carrying a catalyst for purifying exhaust gas, wherein water is absorbed in the filter carrier, and then the filter carrier is immersed in a catalyst slurry, A method for producing a catalyst-carrying filter, characterized by substituting moisture and catalyst slurry absorbed in a filter carrier therein, then draining, drying and firing.
(2) The method for producing a catalyst-carrying filter according to (1), wherein the catalyst slurry is passed through the filter carrier instead of immersing the filter carrier in the catalyst slurry.
(3) A container for immersing the honeycomb filter for exhaust gas purification in water, a drain pipe connected to the bottom of the container, a valve provided in the middle of the drain pipe, and a slurry tank for storing a catalyst slurry And a telescopic connecting pipe that connects the bottom of the slurry tank and the drain pipe via the valve, the valve draining water from the container, supplying slurry to the container, and draining the slurry And the telescopic connecting pipe is long enough to adjust the slurry liquid level of the slurry tank to be higher than the upper end of the honeycomb filter and lower than the lower end of the honeycomb filter. An apparatus for producing a catalyst-carrying filter characterized by having a thickness.

  According to the method and apparatus for producing a catalyst-carrying filter of the present invention, it is possible to prevent an increase in the solid content concentration of the catalyst slurry, so that the catalyst can be uniformly carried into the pores of the porous filter carrier, and the pressure A catalyst-carrying filter with low loss can be prepared relatively easily, and the manufacturing cost can be reduced.

  In the present invention, a known diesel particulate filter (DPF) is preferably used as a filter carrier for purifying exhaust gas. Here, the DPF is a flow-through type honeycomb filter that is alternately clogged, and the gas entering from the gas flow path in the inlet portion passes through the filter wall, soot in the gas is collected and adjoins. The gas flows out from the gas flow path.

As the catalyst slurry, one prepared by dispersing catalyst powder or catalyst carrier powder in water is used. The particle diameter of the catalyst powder or catalyst carrier powder is not particularly limited as long as it is smaller than the average diameter of the pores constituting the filter, but in order to uniformly support the catalyst inside the pores of the filter, the particle diameter should be as fine as possible. Preferably there is. For example, a catalyst such as Pt-zeolite or Pd—Al ₂ O ₂ or a catalyst carrier component such as SiO ₂ or ZrO ₂ can be used for the catalyst slurry. In addition, a slurry in which catalyst powder or catalyst support powder that has been previously screened to an average particle diameter of DPF is dispersed can be used. A catalyst slurry passed through a sieve can also be used.

  The absorption of moisture into the filter carrier can be performed by a method of immersing the filter carrier in a container containing water or a method of passing water through the filter carrier. Further, the filter carrier that has absorbed moisture can be immersed in the catalyst slurry by a method of impregnating the filter carrier into a container containing the catalyst slurry or a method of passing the catalyst slurry through the filter carrier filled in the unit. At this time, in order to uniformly support the catalyst inside the pores of the filter carrier, it is necessary to sufficiently replace the water absorbed in the pores of the filter carrier and the catalyst slurry. When the filter carrier is impregnated with the catalyst slurry, sufficient replacement is possible by moving the filter carrier up and down in the catalyst slurry. Also, sufficient replacement can be achieved by adjusting the passage speed of the catalyst slurry passing through the filter carrier.

By performing such an operation, it is possible to prevent only the moisture in the catalyst slurry from moving inside the porous filter carrier such as DPF and increase the solid content concentration of the catalyst slurry, and in the inside of the carrier and the surface of the carrier wall. It is possible to prevent the catalyst slurry from condensing. Furthermore, if the particle size of the catalyst powder is pulverized below the average diameter of the pores of the filter carrier, the catalyst powder can freely pass through the pores. It becomes possible to carry on.
Furthermore, according to the method of the present invention, it is possible to use a catalyst slurry having a high concentration. By sufficiently replacing the moisture absorbed in advance with the catalyst slurry, the catalyst is supported by a single dipping operation or passing operation. The amount can be increased, and the manufacturing cost can be reduced.

FIG. 1 is an explanatory view of a method for producing a catalyst-supporting DPF showing an example of the present invention.
The apparatus used in this manufacturing method includes a container 10 for immersing a honeycomb filter (DPF) 1 for exhaust gas purification in water, a drain pipe 3 connected to the bottom of the container 10, and a middle of the drain pipe 3. Provided with a valve 2, a slurry tank 6 for storing the catalyst slurry 7, and a telescopic connection pipe 5 for connecting the bottom of the slurry tank 6 and the drain pipe 3 via the valve 2, The valve 2 has a function of switching the drainage of the water 4 from the container 10 and the supply and drainage of the catalyst slurry 7 into the container 10, and the telescopic connecting pipe 5 is connected to the catalyst slurry of the slurry tank 6. It has a length sufficient to adjust the liquid level to be higher than the upper end portion of the honeycomb filter 1 and lower than the lower end portion thereof.

  In FIG. 1, first, as shown in (A), after DPF 1 is filled and fixed in container 10, water 4 that is about twice the amount of water absorbed by DPF 1 is slowly supplied into DPF 1 from the top of unit 10. To do. The water that has not been absorbed by passing through the DPF 1 is drawn out from the extendable drainage pipe 3 provided with the valve 2 provided at the lower part of the container 10. At this time, the valve 2 prevents the catalyst slurry 7 from flowing into the drain pipe 3. Next, as shown in (B), the valve 2 is switched, and the catalyst slurry 7 stored in the slurry tank 6 enters the DPF 1 in the container 10 via the extendable connecting pipe 5 communicating with the slurry tank 6. Supply. That is, by holding the slurry tank 6 so that the slurry liquid level of the slurry tank 6 is higher than the upper end of the DPF, and then slowly raising the slurry tank 6, the catalyst slurry 7 is connected to the connecting pipe 5 and the drainage. It is led through a tube 3 to a container 10 filled with DPF1. Next, as shown in (C), by holding the slurry tank 6 so that the liquid level of the slurry tank 6 is lower than the lower end portion of the DPF 1, and then slowly lowering the slurry tank 6, the catalyst slurry 7 becomes It is returned to the original slurry tank 6. By repeating the operations (B) and (C), the water absorbed in the DPF and the catalyst slurry can be sufficiently replaced.

Hereinafter, the present invention will be described in detail using specific examples.
[Example 1]
DPF (Hitachi Metals Co., porous cordierite) was immersed in water, thoroughly After water, 22 .mu.m (625 mesh) sieve Pt-TiO ₂ catalyst dispersed catalyst slurry through the (solid concentration 25wt %) Soaked and impregnated. At this time, the DPF was moved up and down several times in the catalyst slurry, sufficiently replaced, taken out, drained by centrifugation, dried and calcined, and the increase in pressure loss due to catalyst loading was measured.

[Comparative Example 1]
In Example 1, the same operation as in Example 1 was carried out except that the catalyst slurry was directly impregnated without absorbing water into the DPF, and the increase in pressure loss was measured.
[Comparative Example 2]
In Comparative Example 1, the same operation as in Comparative Example 1 was performed except that the concentration of the catalyst slurry was changed to 10 wt%.

  Table 1 shows the catalyst loading amount and pressure loss increase ratio of the catalyst loading DPF obtained in Example 1 and Comparative Examples 1 and 2. From Table 1, it can be seen that the production method of Example 1 can ensure a sufficient amount of supported catalyst and that the increase in pressure loss is small. On the other hand, in Comparative Example 1, the supported amount was sufficient, but the increase in pressure loss was large, and in Comparative Example 2, since the supported catalyst amount was small, sufficient performance could not be expected.

  With the production method and production apparatus of the present invention, a catalyst slurry can be used to uniformly carry a catalyst into the pores of a porous DPF, and an oxidation catalyst-carrying DPF can be prepared relatively easily. Become.

Explanatory drawing of the manufacturing method of the catalyst carrying filter which shows an example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... DPF, 2 ... Valve, 3 ... Drain pipe, 4 ... Water, 5 ... Connection pipe, 6 ... Slurry tank, 7 ... Catalyst slurry, 10 ... Container.

Claims (3)

  A method for manufacturing a flow-through type porous honeycomb filter carrying a catalyst for purifying exhaust gas, wherein water is absorbed in the filter carrier, and then the filter carrier is immersed in a catalyst slurry, and the filter is immersed in the immersion liquid. A method for producing a catalyst-carrying filter, characterized by substituting moisture absorbed by a carrier and catalyst slurry, then draining, drying and calcining.   The method for producing a catalyst-carrying filter according to claim 1, wherein the catalyst slurry is passed through the filter carrier instead of immersing the filter carrier in the catalyst slurry. A container for immersing the honeycomb filter for exhaust gas purification in water, a drain pipe connected to the bottom of the container, a valve provided in the middle of the drain pipe, a slurry tank for storing catalyst slurry, A retractable connecting pipe that connects the bottom of the slurry tank and the drain pipe via the valve, the valve switches each of drainage of water from the container, supply of slurry into the container, and drainage. The telescopic connecting pipe has a length sufficient to adjust the slurry liquid level of the slurry tank to be higher than the upper end of the honeycomb filter and lower than the lower end of the honeycomb filter. An apparatus for producing a catalyst-carrying filter, wherein

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