JPH0615173A - Gas purifying catalyst and gas purifying method - Google Patents

Abstract

PURPOSE:To simultaneously and efficiently execute dust collection, denitrification and desulfurization by uniformly depositing active components consisting of the oxides of the metals selected from a group consisting of Co, Ni, V and Ti on the pore surfaces of granular porous bodies or planar porous bodies consisting of silica, etc., and having the foam-like pores. CONSTITUTION:The active components consisting of the oxides of the metals selected from the group consisting of Co, Ni, V and Ti are uniformly deposited at 0.2 to 30mum thickness on the pore surfaces of the granular porous bodies, planar porous bodies or hollow cylindrical porous bodies 22 consisting of at least one kind of the silica and alumina and having the foam-like pores of 1 to 50mum diameter. Consequently, the simultaneous and efficient execution of the dust collection and the denitrification or the dust collection, the denitrification and desulfurization is possible and the smooth execution of the incineration treatment of collected dust is possible as well. Further, the regeneration of the used desulfurization components is simultaneously induced by the incineration heat of the collected dust.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to dust contained in diesel engine exhaust gas, boiler exhaust gas, etc.
The present invention relates to a gas purification catalyst and a gas purification method for simultaneously removing nitrogen oxides (NOx) and, in some cases, sulfur oxides (SOx).

[0002]

2. Description of the Related Art Hitherto, as a method for removing dust from exhaust gas of a diesel engine, filtration and dust collection using a porous filter such as foam ceramic has been the mainstream. In this method, when the filter is clogged due to the dust collected in the filter and the ventilation resistance becomes higher than a certain value, the exhaust gas is switched to incinerate and remove the collected dust. Reproduce. In this method, nitrogen oxides and sulfur oxides must be treated separately.

Further, in Japanese Patent Laid-Open No. 1-159034, an ammonia gas is injected into a flue of exhaust gas of a diesel engine, and then γ-alumina or anatase-type titania powder carrying slaked lime and vanadium oxide is injected. Then, a method is described in which a ceramics filter is provided downstream of the exhaust gas to collect powder and combustion dust in the exhaust gas, and denitrate the exhaust gas so that the exhaust gas passes through the layer. . In addition, JP-A-61-1
No. 11128, 111129 discloses a special reaction aid for preventing clogging on the exhaust gas inflow side of a porous ceramic material as a combustion furnace exhaust gas treatment apparatus containing ash, hydrogen chloride, nitrogen oxides, and sulfur oxides. Through the precoat layer,
An apparatus is described in which a solid layer containing slaked lime or calcium carbonate and calcium chloride is formed, and a catalyst layer for removing nitrogen oxides is provided on the exhaust gas outflow surface side.

[0004]

As described above, as described above,
When purifying exhaust gas from a diesel engine, only dust had to be removed and nitrogen oxides and sulfur oxides had to be treated separately. Further, it is conceivable to remove nitrogen oxides at the same time as dust by utilizing the methods described in JP-A-1-159904 and JP-A-61-111128, but the slaked lime in the preceding stage is included. With the catalyst powder, the ceramic filter in the subsequent stage was easily clogged, and it was difficult to efficiently treat the exhaust gas for a long time. The present invention has been made in view of the above points, and an object thereof is to provide a gas purification catalyst and a gas purification method that can efficiently perform dust collection and denitration, or dust collection, denitration, and desulfurization at the same time. To do.

[0005]

In order to achieve the above object, the gas purification catalyst of the present invention comprises at least one of silica and alumina and has foamed pores having a diameter of 1 to 50 μm. On the surface of the pores of the granular porous body, the plate-shaped porous body or the hollow cylindrical porous body, the active ingredient composed of an oxide of a metal selected from the group consisting of cobalt, nickel, vanadium and titanium is 0.2 to 30 μm thick. It is characterized in that it is uniformly supported on the substrate. If the pore size is less than 1 μ, there is a problem that the gas diffusion resistance becomes too large and the ventilation resistance becomes excessive, or the reaction rate decreases due to gas diffusion rate control. On the other hand, if the pore size exceeds 50μ,
Even if calcination conditions and the like are devised, it becomes difficult to maintain the catalyst strength. Further, if the supporting thickness is made to be less than 0.2 μm, it becomes difficult to evenly support the entire surface of the pores, and unevenness in carrying occurs to deteriorate the catalytic performance. On the other hand, if the supported thickness is 50 to 60% or more of the pore diameter, there are disadvantages such as partial pore clogging increases, gas diffusion resistance becomes excessive, and effective reaction surface area decreases. Therefore, even when the maximum pore diameter of the present invention is 50μ, the supported thickness is 30
It is necessary to suppress to μ. Further, in the above-mentioned gas purification catalyst, it is desirable to add platinum to the active component or to add copper oxide as a desulfurizing component to the active component in order to accelerate the combustion of the collected dust.

The catalyst of the present invention can be produced by the following production method. (1) Mixing one or more powders of silica and alumina and carbon powder having a particle size of 1 to 50 μ, adding water or a binder to form a granular, plate-like or hollow cylindrical shape, and then forming The product is dried and baked in air at 900 ° C. to burn off the carbon component to form foamed pores, and the active ingredient is dip-coated or CVD on the surface of the pores.
(Chemical vapor deposition
n) and other methods are used for uniform support. (2) One or more powders of silica and alumina are mixed with carbon powder having a particle size of 1 to 50μ, and water or a binder is added to form a granular, plate-like or hollow cylindrical shape, and then this forming The material is dried and fired at 900 ° C. in air to burn off the carbon component to form foamed pores, and the surface of the pores is first coated with a thin layer of titania by a method such as dip coating or CVD. To support the active ingredient evenly.

The gas purification method of the present invention uses the above-mentioned gas purification catalyst to pass the exhaust gas between the granular porous bodies, or the plate-shaped porous body or the hollow cylindrical porous body from one surface to the other surface. It is characterized by removing nitrogen oxides and dust, or nitrogen oxides, dusts and sulfur oxides in the exhaust gas by passing them. A reducing agent such as ammonia or hydrocarbon is added to the exhaust gas. Then, when the gas purification operation is continued, dust is accumulated on the gas inlet side of the porous body to increase the ventilation resistance, and the copper oxide is converted to copper sulfate to lose the desulfurization activity. A regeneration gas is flowed through the plate-shaped porous body or the hollow cylindrical porous body to burn dust and desorb sulfur dioxide. As the regeneration gas, air, dilution air, oxygen, oxygen-enriched air, etc. are used. Further, in the gas purification method of claim 6, when a packed bed or a moving bed is formed by using a granular gas purification catalyst, and the exhaust gas is passed through the bed to be purified, the bed is divided into two parts, and the gas inlet side The layer having non-reactivity is filled in the layer so that only dust in the exhaust gas is removed, and the layer on the downstream side is provided with:
It is characterized in that it is filled with the gas purification catalyst described in 2 or 3, and the exhaust gas is subjected to denitration, or denitration and desulfurization. Further, in the gas purification method of claim 7, when a packed bed or a moving bed is formed with a particulate gas purification catalyst and the exhaust gas is passed through the bed to be purified, the bed is divided into three parts, and a layer on the gas inlet side is formed. Is filled with non-reactive particles to remove only the dust in the exhaust gas, and the second layer is filled with the gas purification catalyst according to claim 3 or the gas purification catalyst supporting only copper sulfate. It is characterized in that the exhaust gas is desulfurized mainly, and the layer on the gas outlet side is filled with the gas purification catalyst according to claim 1 or 2 to denitrate the exhaust gas.

When the regenerated gas is caused to flow in the same direction as the gas to be treated, the dust accumulated on the inlet side is ignited first, and the dust is burned in the state of combustion. In order to ignite the dust, it is necessary to raise the temperature of the regenerated gas, but adding a platinum component to the catalyst or using oxygen-enriched air as the regenerated gas is effective for promoting combustion and lowering the ignition temperature. is there. However, depending on the conditions, dilution air may be used as the regeneration gas in order to prevent catalyst deterioration due to overheating. In order to return copper sulfate to copper oxide and regenerate the desulfurization activity, it is necessary to heat the catalyst until the pyrolysis of iron sulfate, but in the method of the present invention, the regenerated gas is further heated by the heat of dust combustion. Since it passes through the catalyst layer or the inside of the catalyst, it can be regenerated without external heat supply. The method according to claim 6, wherein the layer is divided into two parts, only the dust is removed in the layer on the gas inlet side, and the layer on the downstream side is filled with a gas purification catalyst to perform denitration and desulfurization. The combustion heat generated in the dust removal layer is carried to the catalyst layer by the regeneration gas and used for catalyst regeneration. However, local heat generation due to dust combustion does not occur in the catalyst layer, which is more effective in suppressing catalyst deterioration. According to claim 7, the layer divided into three, in the layer of the gas inlet side to perform only dust removal, desulfurization in the second layer, the method to perform the denitration in the third layer, SO ₂ during normal operation In addition, it is difficult for the denitration catalyst activity to decrease due to, and the combustion heat generated in the dust removal layer during regeneration is first carried to the desulfurization layer by the regeneration gas and used for catalyst regeneration, and finally passes through the denitration catalyst layer. Deterioration of the denitration catalyst due to dust combustion heat generation is further suppressed.

[0009]

EXAMPLES Examples of the present invention will be described below. Example 1 Carbon powder having an average particle diameter of 15 μm was mixed with powder carrier material 10 of 55 wt% silica and 45 wt% alumina at a ratio of 2 and granulated with a tumbling granulator while spraying water. Next, this molded product is dried and calcined in air at 900 ° C. to burn off the carbon component to form foamed pores, which is then immersed in a mixed solution of nickel nitrate and titanium nitrate and exposed to an air atmosphere of 400 The firing at 0 ° C. was repeated 4 times to uniformly support the active ingredient on the surface of the pores. Finally, a catalyst having an average pore diameter of 16μ and a titanium oxide / nickel oxide mixed layer on the surface of the pores having an average thickness of 6μ was carried almost uniformly.

Example 2 Water was added to a mixture of the same powder carrier raw material and carbon powder as in Example 1 to form a slurry, which was extracted and molded into a plate shape by a molding machine. Next, this molded product was dried and calcined in air at 900 ° C. to burn off the carbon component to form foamed pores, and the active ingredient was applied to the pore surface by the same raw material and method as in Example 1. It was carried evenly. Finally, the average pore size is 12
In μ, a catalyst was obtained in which a mixed layer of titanium oxide and nickel oxide was carried almost uniformly on the surface of pores with an average thickness of 5 μ.

Example 3 Water was added to a mixture of the same powder carrier raw material and carbon powder as in Example 1 to form a slurry, which was molded into a hollow cylinder by a rubber press. Next, the molded product is dried and dried in air to 90
Firing was performed at 0 ° C. to burn off the carbon component to form foamed pores. Metal Ti was vapor-deposited on this molded product in a vacuum, and again fired at 900 ° C. in air to form a titanium oxide layer, then immersed in an aqueous solution of nickel nitrate and fired at 400 ° C. in an air atmosphere. Repeated times, the nickel oxide layer was uniformly supported on the surface of the pores. Finally, a catalyst having an average pore diameter of 8 μ and a titanium oxide and nickel oxide layer on the surface of the pores having an average thickness of 4 μ and being almost uniformly carried was obtained. In the above production example, the catalyst pore size was the particle size of the carbon powder to be mixed, and the amount of the active component supported and the thickness of the supporting layer could be freely adjusted by the concentration of the impregnating solution, the number of impregnations, and the vapor deposition time.

Example 4 The plate-shaped catalyst prepared by the method of Example 2 was impregnated with a hexachloroplatinic acid solution, dried, and then dried in an atmosphere of H ₂ 5% at 30%.
It was reduced at 0 ° C., and the platinum component was supported on the surface.

Example 5 The granular catalyst prepared by the method of Example 1 was impregnated in a copper nitrate solution, dried and then calcined at 400 ° C. in an air atmosphere to carry a copper oxide component on the surface.

Using the gas purification catalyst produced as described above, the following gas purification performance test was conducted. (1) Denitration The granular catalyst produced in Example 1 was used. In the catalyst packed bed,
A gas consisting of NOx 300 ppm, O ₂ 3%, H ₂ O 8% and the balance N ₂ was flowed at SV 5000 h ^-1 . The catalyst packed bed and the gas temperature were kept at 350 ° C. When NH ₃ was supplied upstream of the catalyst-packed bed at a molar ratio twice that of NOx in the gas, the NOx removal rate of 92% was maintained almost stably, and the denitration effect of the catalyst was confirmed. (2) Denitration / Dust removal / regeneration (combustion) The plate catalysts produced in Examples 2 and 4 were used. Diesel exhaust gas containing 300 ppm NOx and 200 mg / Nm ³ of dust was flown through the plate-like packing at a flow rate of 4 cm / s. The catalyst and gas temperatures were kept at 320 ° C. When NH ₃ was supplied upstream of the catalyst-packed bed at a molar ratio twice that of NOx in the gas, the NOx removal rate of 86% was maintained for 6 hours, and the denitration effect of the catalyst was confirmed. After passing gas for 6 hours, the gas supplied to the catalyst was switched to air, and the temperature of the supplied air was gradually raised.
In the catalyst of Example 2, the combustion of the collected dust started when the air temperature reached 490 ° C. On the other hand, Example 4
With the catalyst of No. 3, dust combustion started at 420 ° C., and it was confirmed that the Pt component promoted combustion. (3) Desulfurization / Dust removal / Regeneration (simultaneous combustion) The granular catalyst produced in Example 5 was used. In the catalyst packed bed,
SOx600ppm, shed diesel exhaust gas containing dust 200 mg / Nm ³ in SV5000h ^-1. The catalyst packed bed and the gas temperature were kept at 350 ° C. Comparing the gas composition of the catalyst packed bed inlet / outlet, 72% SOx over 6 hours
After the removal rate was maintained, the catalyst passed through and the desulfurization effect of the catalyst was confirmed. After passing the gas for 6 hours, the gas supplied to the catalyst was switched to air, the temperature of the supplied air was raised to 520 ° C., and the dust was burned for 1 hour. When the same diesel exhaust gas as that at the beginning was flowed again in the catalyst layer after the dust combustion, the desulfurization effect was almost restored to the old one, and it was the same after repeating the exhaust gas supply and the dust combustion five times. From this, it was confirmed that the desulfurization component was regenerated at the same time as the dust combustion.

Next, an example of an apparatus using the granular gas purification catalyst, plate-shaped gas purification catalyst and hollow cylindrical gas purification catalyst of the present invention will be described. (1) Granular Gas Purification Catalyst As shown in FIGS. 1 and 2, this exhaust gas treatment device is formed of a porous support 20 such as a wire mesh, a perforated plate, or a punching metal, and has a particle gas purification catalyst 21 inside. A disk-shaped container 24 having a filling layer 22, and the disk-shaped container 24
A main body 26 for accommodating a disk-shaped container 2
4, a rotation shaft 28 rotatably supported by the main body 2
A partition plate 34 in the direction of the rotation axis for partitioning the interior of the chamber 6 into two chambers 30 and 32, and an exhaust gas inlet 36 connected to one chamber 30.
And a purified gas outlet 38, and a regeneration gas inlet 40 and a regeneration off-gas outlet 42 connected to the other chamber 32. 44 and 46 are gas seal portions. It should be noted that the flow direction of the exhaust gas and the flow direction of the regenerated gas can be the same. In this device, the rotary disk-shaped container 2
The exhaust gas is allowed to pass through a part of the particle packed layer 22 filled in 4 to collect and remove dust in the gas, and at the same time, remove NOx or NOx and SOx in the gas.
The particle packing layer 22 is continuously or intermittently rotated while flowing a regeneration gas to the remaining part of No. 2 to collect dust, denitrate, or collect dust.
Simultaneous and continuous denitration / desulfurization, incineration / removal of dust collected in the particle packed bed, and regeneration of particles (catalyst). Since the granular gas purification catalyst 21 has foamed pores, some gas passes through these pores, but most of the gas is catalyst 2 because the ventilation resistance is large.
It passes through the gap between 1 and 21.

3 and 4 show another example of use of the particulate gas purification catalyst 21. This exhaust gas treating apparatus is formed of a porous support 20, and has a hollow cylindrical container 50 having a particle packing layer 22 therein, and the hollow cylindrical container 50 is provided between the outer surface of the particle packing layer 22 and the inner surface of the main body 26. A main body 26 which is housed so that a gap 52 is formed, and a rotary shaft 2 which is rotatably supported by the main body 26 so that the hollow cylindrical container 50 can rotate.
8, a partition plate 58 for partitioning the inside of the main body 26 into two chambers 54 and 56, an exhaust gas inlet 36 connected to the gap 52 outside the particle packing layer of one chamber 54, and a particle packing layer of one chamber 54. A purified gas outlet 38 connected to the inner hollow portion 60,
The other chamber 56 is provided with a regeneration gas inlet 40 connected to the hollow portion 60 inside the particle packing layer, and a regeneration off-gas outlet 42 provided in a gap 52 outside the particle packing layer of the other chamber 56. 62 and 64 are gas seal parts, 66, 68 and 7
Partition plates 0, 72, 74 and 76 are provided. The flow direction of the exhaust gas and the flow direction of the regenerated gas may be opposite to each other. In this device, the exhaust gas is passed through a part of the particle packed layer 22 filled in the rotary hollow cylindrical container 50 to collect and remove dust in the gas, and NOx in the gas, or NOx and SOx. The particle-packed layer 22 is continuously or intermittently rotated while flowing a regeneration gas to the rest of the particle-packed layer 22 to collect dust / denitrification, or dust / denitrification / desulfurization, and trap in the particle-packed layer. Incineration / removal of collected dust and regeneration of particles (catalyst) at the same time,
And continuously.

(2) Plate-shaped gas purifying catalyst As shown in FIGS. 5 and 6, a metal support 80 integrally supports several to several tens of plate-shaped gas purifying catalysts 82 to form a breathable cylinder. 84 is formed. This breathable cylinder 84 is installed in the same manner as the particle-filled layer 22 shown in FIGS. 3 and 4. Gas is
The gas flows through the foamed pores of the plate-like gas purification catalyst 82 from the outside to the inside of the breathable cylinder 84 or from the inside to the outside. As the metal support, a porous support such as a wire mesh, a perforated plate, or a punching metal may be used instead of the rod-shaped member.

Further, as shown in FIGS. 7 and 8, two plate-shaped gas purification catalysts 82 are provided in pairs, and the blind plates 8 are provided at the lower end and both sides.
6, 88 may be provided to purify the exhaust gas through the plate-shaped gas purification catalyst 82. Reference numeral 90 is a main body, 92 is an exhaust gas inlet, 94 is a purified gas outlet, 96 is a regeneration gas inlet, and 98 and 100 are partition plates. During the regeneration, the purified gas outlet 94 becomes the regeneration off-gas outlet.

(3) Hollow cylindrical gas purifying catalyst As shown in FIGS. 9 and 10, the hollow cylindrical gas purifying catalyst 102 is installed in the same manner as the plate gas purifying catalyst 82 shown in FIGS. 7 and 8. Other configurations are similar to those shown in FIGS. 7 and 8.

[0020]

Since the present invention is constructed as described above, it has the following effects. (1) Dust collection and denitration, or dust collection, denitration, and desulfurization can be simultaneously and efficiently performed. (2) When the collected dust is incinerated, the burning speed is high, so that it can be performed at a lower temperature, and the incineration process of the collected dust is smoothly performed. (3) When the collected dust is incinerated, the incineration heat of the collected dust causes regeneration of the used desulfurization component (pyrolysis → SO ₂ desorption) at the same time. (4) By carrying out a gas purification treatment (dedusting, denitration, desulfurization) by moving (rotating) the catalyst continuously or intermittently, or by moving the introduction positions of the exhaust gas and the regenerated gas continuously or intermittently. Regeneration (dust incineration / SO ₂ desorption) can be performed simultaneously.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional explanatory view (cross-sectional view taken along line 1-1 in FIG. 2) showing an example of an exhaust gas treating apparatus using a particulate gas purification catalyst of the present invention.

2 is a sectional view taken along line 2-2 in FIG.

FIG. 3 is a vertical cross-sectional explanatory view (3-3 in FIG. 4) showing another example of the exhaust gas treating apparatus using the particulate gas purification catalyst of the present invention.
It is a line sectional view).

4 is a cross-sectional view taken along line 4-4 of FIG.

FIG. 5 is a perspective view showing an example of use of the plate-like gas purification catalyst of the present invention.

FIG. 6 is an enlarged cross-sectional view around the plate-shaped gas purification catalyst shown in FIG.

FIG. 7 is a cross-sectional view showing another example of use of the plate-shaped gas purification catalyst of the present invention.

8 is a sectional view taken along line 8-8 in FIG.

FIG. 9 is a cross-sectional view showing an example of use of the hollow cylindrical gas purification catalyst of the present invention.

10 is a sectional view taken along line 10-10 in FIG.

[Explanation of symbols]

 20 Porous Support 21 Granular Gas Purification Catalyst 22 Particle Packing Layer 24 Disk Container 26 Main Body 28 Rotating Shaft 36 Exhaust Gas Inlet 38 Exhaust Gas Outlet 40 Regeneration Gas Inlet 42 Regeneration Off Gas Outlet 50 Hollow Cylindrical Container 80 Metal Support 82 Plate Gas Purification catalyst 84 Breathable cylinder 92 Exhaust gas inlet 94 Purification gas outlet 96 Regenerated gas inlet 102 Hollow cylindrical gas purification catalyst

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location B01D 53/36 104 A 9042-4D B01J 23/22 A 8017-4G 23/89 A 8017-4G 35 / 04 331 7821-4G

Claims (7)

[Claims] 1. A granular porous body, a plate-shaped porous body or a hollow cylindrical porous body, which comprises at least one of silica and alumina and has foamed pores having a diameter of 1 to 50 .mu. 0.2 to 30 active ingredients composed of oxides of metals selected from the group consisting of vanadium and titanium.
A gas purification catalyst characterized by being uniformly supported in a thickness of μ. 2. The gas purifying catalyst according to claim 1, wherein platinum is added to the active component for promoting combustion of the collected dust. 3. The gas purification catalyst according to claim 1 or 2, wherein copper oxide as a desulfurizing component is added to the active component. 4. An exhaust gas is passed between granular porous bodies by using the gas purification catalyst according to claim 1, 2 or 3, or a plate-shaped porous body or a hollow cylindrical porous body is passed from one surface to the other surface. Nitrogen oxide and dust in the exhaust gas,
Alternatively, a gas purification method characterized by removing nitrogen oxides, dust and sulfur oxides. 5. The gas according to claim 4, wherein a regeneration gas is caused to flow through the used granular porous material, plate-shaped porous material or hollow cylindrical porous material to burn dust and desorb sulfur dioxide. Purification method. 6. A packed bed or a moving bed is formed using a particulate gas purification catalyst, and when the exhaust gas is passed through the bed for purification, the bed is divided into two, and the layer on the gas inlet side is made to have reactivity. Particles that do not have are filled to remove only dust in the exhaust gas, and the gas purification catalyst according to claim 1, 2 or 3 is filled in the layer on the downstream side to perform denitration of the exhaust gas, or denitration and desulfurization. A gas purification method characterized by: 7. When forming a packed bed or a moving bed with a particulate gas purification catalyst and passing exhaust gas through the bed to purify
The layer is divided into three parts, and the layer on the gas inlet side is filled with non-reactive particles to remove only the dust in the exhaust gas.
The second layer is filled with the gas purification catalyst according to claim 3 or the gas purification catalyst supporting only copper sulfate to mainly perform desulfurization of exhaust gas, and the layer on the gas outlet side is according to claim 1 or 2. A method for purifying gas, comprising filling the gas purifying catalyst according to 1 above to denitrate exhaust gas.