JPH10272339A - Catalyst supporting filter for purifying exhaust gas and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas purifying catalyst supporting filter low in pressure loss and not generating the waste of a catalyst, and to provide a method for producing the exhaust gas purifying catalyst supporting filter having an advantage capable of easily controlling the amt. of a catalyst supported on the metal fiber filter and capable of efficiently supporting the catalyst only on the surface of the filter within a short time. SOLUTION: A catalyst-containing slurry is sprayed on the surface of a metal fiber filter to obtain a catalyst supporting filter having a constitution such that the catalyst is supported only on the surface of the metal fiber filter. When this catalyst supporting filter is produced, the catalyst-containing slurry (a solvent and the catalyst are mixed) is sprayed on the metal fiber filter 9 by a spray device using a spray nozzle 3 and the metal fiber filter 9 after the spraying of the slurry is dried and baked to support the catalyst only on the surface of the metal fiber filter 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to processing of carbon-based fine particles and unburned hydrocarbons in exhaust gas discharged from a combustion device such as an internal combustion engine or a boiler, or exhaust gas discharged from a combustor such as a fan heater or a stove. The present invention relates to an exhaust gas purifying catalyst-carrying filter used for removing odor components and the like in a gas and a method for manufacturing the same.

[0002]

2. Description of the Related Art In manufacturing such a type of exhaust gas purifying catalyst-carrying filter, a wash coat method, a sol-gel method and the like are known as methods for supporting a catalyst on a metal fiber filter (hereinafter simply referred to as a filter). The wash coat method is a method in which a carrier layer is formed on a filter by immersing the filter in a catalyst slurry, drying and firing.

The sol-gel method hydrolyzes an organic salt (eg, alkoxide) of a metal forming a carrier layer ceramic, coats the obtained sol on a filter, and forms a film of colloidal particles by contact with water vapor or the like. After being produced, it is dried and calcined to form a catalyst carrier layer on the filter. In addition, an impregnation method for impregnating a filter with a catalyst is also known.

[0004]

However, in all of the above-mentioned wash coat method, sol-gel method and impregnation method, the amount of catalyst carried on the filter cannot be finely controlled, and it is difficult to carry the catalyst only on the surface of the filter. is there.
In addition, since each method includes a dipping step, an extra catalyst is carried in the pores of the filter.

As a result, the pressure loss of the filter increases, and the catalyst is wasted. Furthermore, in the wash coat method, it is necessary to go through several immersion steps before reaching a predetermined catalyst loading amount,
The sol-gel method requires a minimum of several hours for the hydrolysis reaction, and the conventional catalyst-supporting method has a problem that it takes a long time to manufacture a catalyst-supporting filter, resulting in poor productivity.

The present invention has been made to solve the above-mentioned conventional problems, and is a catalyst-carrying filter for purifying exhaust gas which has a small pressure loss and carries a catalyst on a metal fiber filter. An object of the present invention is to provide an exhaust gas purifying catalyst-carrying filter that does not waste catalyst. In addition, the present invention provides an exhaust gas purifying catalyst-carrying filter having the advantages that the amount of the catalyst carried on the metal fiber filter can be easily controlled, and that the catalyst can be efficiently carried on the surface of the filter only in a short time. It is intended to provide a manufacturing method.

[0007]

In order to achieve the above object, the invention according to claim 1 is directed to an exhaust gas purifying catalyst-carrying filter in which a catalyst is carried on a metal fiber filter. The structure is characterized in that the catalyst is supported only on the surface of the metal fiber filter by spraying toward.

The invention according to claim 2 includes a step of spraying a slurry containing a catalyst on the metal fiber filter, and a drying and firing step of drying and firing the metal fiber filter after spraying the slurry. The catalyst is supported only on the surface of the metal fiber filter.

The operation of the present invention will be described. In the invention according to the first aspect, the configuration in which the catalyst is supported only on the surface of the filter can reduce the pressure loss of the filter to a small value, and does not waste the catalyst. In the invention according to claim 2, since the slurry containing the catalyst is sprayed on the metal fiber filter, and then the metal fiber filter is dried and fired, the wash coat method, the sol-gel method,
Compared with the impregnation method, it is easier to control the amount of the catalyst carried on the filter, and the catalyst can be carried only on the filter surface in a short time.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. The present inventors have conducted intensive studies on a method of supporting a catalyst on a metal fiber filter in order to solve the above-mentioned conventional problems, and as a result, a catalyst slurry obtained by uniformly mixing a catalyst with a solvent is used for a filter using a nozzle or the like. Spraying, after this spraying step, if the catalyst can be supported through the steps of drying and baking, the catalyst can be supported only on the surface of the metal fiber filter, and the increase in pressure loss of the metal fiber filter can be prevented. The present inventors have found out the present invention based on this finding.

That is, the exhaust gas purifying catalyst-carrying filter 1 of the present invention is constituted, for example, as shown in FIG. 1, and comprises, for example, a slurry containing a catalyst carrying a catalyst, for example, a metal fiber 2 described later. By spraying toward the surface of the fiber filter, the catalyst is supported only on the surface of the metal fiber filter. In addition, in the method for manufacturing a catalyst-carrying filter for purifying exhaust gas of the present invention, a slurry containing a catalyst (mixed of a solvent and a catalyst) in a metal fiber filter 9 is sprayed onto a spray nozzle 3 as shown in FIG.
Etc., and a drying and firing step of drying and firing the metal fiber filter 9 after spraying the slurry, so that the catalyst is supported only on the surface of the metal fiber filter 9. It is characterized by having.

[0012] The above spraying device, as shown in FIG.
The catalyst slurry 4 is supplied from a container 5 in which the catalyst slurry 4 is stored to a spray nozzle 3 provided to face the metal fiber filter 9 from a catalyst slurry supply passage 7 provided with a pump 6 and not shown. The structure is such that the pressurized air guided from a pressurized air supply source such as a compressor is supplied from the pressurized air supply passage 8 and the catalyst slurry is sprayed from the spray nozzle 3 onto the metal fiber filter 9.

Next, the configuration of the present invention will be specifically described. First, the metal fibers constituting the metal fiber filter serving as the base material of the exhaust gas purifying material will be described. The raw material of the metal fibers is a high temperature heat-resistant metal. As the high-temperature heat-resistant metal, it is desirable to use a material having a resistance to heat generation when energized, for example, a Fe-Cr-Al-REM stainless steel. Specifically, Cr is 15 to
23%, Al is 2.5 to 6%, and REM is La,
One or more of Y and Ce are used, and the amount of addition is 0.1.
02 to 1%. Also, Cr 15-21%, Ni 57-
It is also possible to use a nickel chromium material having a residual Fe of 77%. In addition, an unavoidable component may be included as another composition.

[0014] The high-temperature heat-resistant metal having such heat generation is formed into a high-temperature heat-resistant metal fiber by a processing method such as a drawing method, a melt spinning method, a coil material cutting method, a wire cutting method, a chatter vibration cutting method, a coating method, and a whisker method. It is manufactured, but it is not particularly limited to these manufacturing methods, and any manufacturing method may be used. The average diameter of the high temperature heat resistant metal fiber is 5
５００500 μm, more preferably 10-100 μm.

The high temperature heat-resistant metal fiber is formed into a filter. In order to maintain the shape, the formed filter is sintered, placed in a formed body such as a metal, or mechanically entangled with a fiber by a needle punch or the like. The sintering is performed by heating in a vacuum or a non-oxidizing atmosphere at 800 to 1300 ° C. for 10 minutes to 10 hours. It is also preferable to apply a load during this sintering.

[0016] Thereafter, the substrate is placed in an oxidizing atmosphere such as air.
Heat-treated at 0 to 1100 ° C for 1 to 20 hours,
A metal fiber filter having an alumina coating formed on the fiber surface is obtained. The term “filter surface” refers to a thickness range of 0 to 300 μm in the vertical direction from the outer surface of the filter.
１５０150 μm, more preferably 0 to 50 μm.

Solvents required for preparing the slurry include water and all organic solvents such as methanol, ethanol, toluene and hexane, but are not particularly limited thereto, and any liquid may be used. You may. The catalyst carrier is not particularly limited, but may be alumina, silica, zirconia, titania, ZSM-5, USY, S
APO, Y-type zeolite, zeolites such as MOR, silica-alumina, alumina-zirconia, alumina-titania, silica-titania, silica-zirconia, titania-zirconia is preferably used at least one kind, among which titania, Zirconia and the like are preferably used.

The particle size of the carrier particles is 0.01 μm
To 20 μm, more preferably 0.1 to 10 μm. The reason is that the particle size of the catalyst support is 0.0
If it is less than 1 μm, it is extremely difficult to manufacture, and if it is more than 20 μm, the pores of the filter are likely to be closed or peeled off from the filter.

The catalytically active component supported on the catalyst carrier is P
t, Pd, Cu, K, Rb, Cs, Mo, Cr, Mn,
Rh, Ag, Ba, Ba, Ca, Zr, Co, Fe, L
at least one selected from a and Ce is particularly preferably Pt, Pd, Rh, Cu, K, Mo, Mn, F
e and Ce are used, and more preferably Cu, K and Mo are used.

The loading amount of these metals or metal oxides on the catalyst carrier is preferably from 0.01 g to 2 g per 1 g of the carrier in terms of each metal component, and more preferably 0.05 g / g.
It is preferable to change the amount from g to 1.0 g. The reason is as follows.
If the amount is less than 01 g, most of the activity of the catalyst is not realized, and if the amount exceeds 2 g, the catalyst particles aggregate at the stage of supporting the catalyst, which may become large and may cause clogging of the tip of the spray nozzle. .

The amount of the catalyst particles carried on the metal fiber filter is preferably 150 mg or less, more preferably 80 mg or less, per 1 g of the metal fiber filter. The reason is 15
If it exceeds 0 mg, the pores of the filter will be closed. The concentration of the catalyst in the catalyst slurry is preferably 0.1 wt% to 50 wt% with respect to the entire slurry, and 1 wt%.
To 30 wt% is more preferable. If the amount is less than 0.1 wt%, the amount of slurry sprayed on the filter becomes large, the filter surface is covered with the solvent, and it becomes difficult for the catalyst to adhere. or,
If it exceeds 50% by weight, the viscosity increases and the tip of the nozzle becomes clogged.

The catalyst slurry is prepared by adjusting the concentration of the catalyst with respect to the solvent within the above range, placing the catalyst in a ball mill pot, and stirring and pulverizing, for example, for 24 to 48 hours. The spray nozzle for spray-coating the catalyst on the metal fiber filter may be either a one-fluid nozzle or a two-fluid nozzle, but preferably a two-fluid nozzle is used, and the diameter of the nozzle is preferably 2 mm or less, more preferably 0.5 mm or less. Is more preferable.

If the nozzle diameter exceeds 2 mm, the spray particle diameter becomes too large and the filter is closed. The injection pressure is preferably in the range of 1 kg / cm ² to 30 kg / cm ² . If it is less than 1 kg / cm ² , the spray particle diameter becomes too large. If it exceeds 30 kg / cm ² , the kinetic energy of the sprayed particles is large, and it is difficult to carry the particles even when they collide with the filter. .

Under the above conditions, the catalyst is supported on the metal fiber filter, dried at a temperature between 100 ° C. and 200 ° C., and then dried at a temperature between 300 ° C. and 1000 ° C.
By firing at a temperature between C, a catalyst-carrying filter can be made. FIG. 3 shows the above-described metal fiber 2
FIG. 1 is a schematic view of a cross section of a catalyst-carrying filter 1 configured by supporting a catalyst 10 on a metal fiber filter made of a metal fiber filter, and the like.
(Preferably in the range of 0 to 150 μm, more preferably in the range of 0 to 50 μm), the catalyst 10 is supported.

FIG. 4 is a diagram showing the relationship between the depth direction of the catalyst-carrying filter and the amount of catalyst carried, that is, the distribution of the amount of catalyst carried in the depth direction of the catalyst-carrying filter. This indicates that the supported amount of catalyst becomes smaller as the filter becomes deeper and the filter becomes deeper. According to the exhaust gas purifying catalyst-carrying filter described above, since the catalyst is supported only on the surface of the filter, the pressure loss of the filter can be reduced, and
It is economical with no waste of catalyst.

According to the above-described method for manufacturing a catalyst-carrying filter for purifying exhaust gas, a slurry containing a catalyst is sprayed on a metal fiber filter, and then the metal fiber filter is dried and fired. Compared with the coating method, the sol-gel method, and the impregnation method, it becomes easier to control the amount of the catalyst carried on the filter, and it is possible to carry the catalyst only on the filter surface in a short time.

As a result, no extra catalyst is carried in the holes of the filter, so that the pressure loss of the filter can be reduced and the waste of the catalyst can be eliminated.
Further, the production time of the catalyst-carrying filter can be reduced, and the productivity can be improved. In particular, a metal fiber filter formed by molding, sintering, and heat-treating a metal fiber has a large surface area and can be diversified in shape, and an alumina coating is formed on the surface of the metal fiber. There is an advantage that it is difficult.

Here, a specific example of the catalyst-carrying filter of the present invention (invention product), a specific example of the conventional catalyst-carrying filter (comparative product), and an example of a comparison result between the two will be described. (Invention 1) Cr: 20.02%, Al: 4.9%, La: 0.
The cross section made from stainless steel consisting of 08%, balance Fe and unavoidable impurities by coil material cutting method is 50 × 10μm
Is cut to a length of 70 mm and the basis weight is 12
A metal fiber filter was produced by integrating the filter so as to have a concentration of 00 g / m ² .

An aqueous solution containing 3.8 g of copper nitrate trihydrate, an aqueous solution containing 2.6 g of potassium nitrate, and an aqueous solution containing 1.8 g of ammonium molybdate tetrahydrate are sequentially impregnated and supported on 7 g of commercially available titania particles. After drying at C for 1 hour, the mixture is calcined at 500 ° C. for 2 hours, dried and calcined, and 10 g of the resulting catalyst is mixed with 90 ml of 99% pure ethanol solution. The mixed solution was pulverized and mixed with a ball mill for 24 hours to prepare a catalyst slurry. This slurry was sprayed using a two-fluid nozzle with a nozzle diameter of 0.4 mm.
The metal fiber filter prepared previously was cut into a 3 cm square at a distance of 15 cm at an air pressure of 3 kg / cm ² .
The filter was sprayed for 20 seconds. Thereafter, the filter was dried at 110 ° C. for 1 hour, and then fired at 500 ° C. for 2 hours to produce an exhaust gas purifying catalyst-carrying filter (sample A). (Comparative product 1) An aqueous solution containing 3.8 g of copper nitrate trihydrate, an aqueous solution containing 2.6 g of potassium nitrate, and an aqueous solution containing 1.8 g of ammonium molybdate tetrahydrate are sequentially impregnated and supported on 7 g of commercially available titania particles, After drying at 110 ° C. for 1 hour, the mixture is calcined at 500 ° C. for 2 hours, dried and calcined, and 10 g of the resulting catalyst is mixed with 90 ml of 99% pure ethanol solution. The mixed solution was pulverized and mixed with a ball mill for 24 hours to prepare a catalyst slurry. This slurry was sprayed using a two-fluid nozzle with a nozzle diameter of 0.4 mm.
Wash coat a 5 cm square metal fiber filter similar to that used in the invention 1 from a distance of 15 cm at an air pressure of 3 kg / cm ² , dry at 110 ° C for 1 hour, and bake at 500 ° C for 2 hours Is repeated until 70 mg of catalyst particles are supported per 1 g of the metal fiber filter, and the exhaust gas purifying catalyst-carrying filter (sample B)
Was manufactured.

A diesel engine having a displacement of 265 cc was prepared by using the sample A of the catalyst-carrying filter of the present invention, the sample B of the conventional catalyst-carrying filter, and the sample C of the metal fiber filter not supporting the catalyst. An evaluation test of the catalyst-carrying filter was performed. Engine speed 1
The initial pressure loss of the filter was measured under the conditions of 500 rpm and an engine load of 75%. Further, the collection rate of carbon fine particles in exhaust gas was measured by Bosch (Smoke meter).

The collection rate of the carbon-based fine particles was obtained by converting the Bosch reflectance before and after the filter into a black smoke density and calculating the following formula (1). Carbon-based fine particle collection rate (%) = [inlet carbon fine particle concentration (mg / Nm ³ ) −outlet carbon fine particle concentration (mg / Nm ³ ) / inlet carbon fine particle concentration (mg / Nm ³ )] × 100 ... ( 1) Table 1 shows the results of the above evaluation experiments.

[0032]

[Table 1]

As can be inferred from the results shown in Table 1, by supporting the catalyst by using the spray (spray) supporting method of the present invention, compared with the catalyst supporting filter according to the conventional method, the filter is supported. The pressure loss can be reduced, and the manufacturing time of the filter can be significantly reduced. In addition, the collection rate of the carbon-based fine particles of the catalyst-carrying filter has substantially the same performance as that of the filter manufactured by the conventional method.

In addition, the inventors tested the releasability of the catalyst from the filter. A commercially available wire mesh carries a catalyst under the same conditions as the invention 1 described above, and each of this filter (sample M) and the filter of the invention 1 (sample A) is held in an electric furnace. A heat cycle test was repeated at 600 ° C. every 10 minutes. The rate of release from the filter was calculated based on the amount initially loaded.

In performing this test, a process of rapidly lowering the temperature of the filter heated to 600 ° C. to 300 ° C. occurs, which is directly applied to the filter surface by a pressurized air injection device installed in the furnace. Perform by applying compressed air. The above heat cycle test was repeated 10 times. Table 2 shows the results.

[0036]

[Table 2]

As is apparent from the above results, the metal fiber filter has a large surface area and a complicated surface shape as compared with a commercially available wire mesh, and has a heat treatment to form an alumina coating on the fiber surface. It can be seen that the catalyst is hardly peeled off for the reasons described above.

[0038]

As described above, according to the exhaust gas purifying catalyst-carrying filter of the first aspect of the present invention, pressure loss can be reduced under normal exhaust gas processing conditions.
When installing a filter for collecting particulates in a diesel engine, the back pressure of the engine can be reduced, and there is no hindrance to engine operation.

In particular, the metal fiber filter to which the present invention is applied has the advantages that the surface area is large and the surface shape is complicated, so that the catalyst can be easily carried and the catalyst is hardly peeled off. According to the method for manufacturing a catalyst-carrying filter for purifying exhaust gas of the invention according to claim 2, the time required for carrying the catalyst, which has been a problem in the conventional method, can be greatly reduced, and the filter can be manufactured industrially at low cost and easily. Can be manufactured. or,
The amount of supported catalyst can be easily controlled.

[Brief description of the drawings]

FIG. 1 is an enlarged view of a catalyst-carrying filter.

FIG. 2 is a schematic view of a manufacturing apparatus for performing the method for manufacturing a catalyst-carrying filter according to the present invention.

FIG. 3 is a sectional view of a catalyst-carrying filter according to the present invention.

FIG. 4 is a distribution diagram of a catalyst loading amount in a depth direction of the catalyst loading filter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Exhaust gas purification catalyst supporting filter 2 Metal fiber 3 Spray nozzle 4 Catalyst slurry 5 Container 6 Pump 7 Catalyst slurry supply passage 8 Pressurized air supply passage 9 Metal fiber filter 10 Catalyst

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tatsuhiko Kato 5-6-5 Midorigaoka, Shinshiro-shi, Aichi (72) Inventor Koichi Goi 3-23-26, Uechi, Okazaki-shi, Aichi (72) Inventor Yukio Aizawa 203, Kizuki-Omachi, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture (72) Inventor Yasuo Sekido 6-28-7, Yokodai, Isogo-ku, Yokohama-shi, Kanagawa Prefecture 1

Claims (2)

[Claims] 1. A catalyst-carrying filter for purifying an exhaust gas in which a catalyst is carried on a metal fiber filter, wherein the catalyst is carried only on the surface of the metal fiber filter by spraying a slurry containing the catalyst toward the metal fiber filter. An exhaust gas purifying catalyst-carrying filter having a configuration. 2. A step of spraying a slurry containing a catalyst on the metal fiber filter; and a step of drying and firing the metal fiber filter after spraying the slurry, and drying and firing the metal fiber filter. A method for producing an exhaust gas purifying catalyst-carrying filter, characterized in that the filter is carried on only the surface.