JP4246412B2 - Exhaust gas treatment catalyst and exhaust gas purification method using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas treatment catalyst, and more specifically, a catalyst suitable for exhaust gas that can efficiently remove harmful substances such as dioxins and nitrogen oxides contained in the exhaust gas, and further contains a lot of dust in the exhaust gas. The present invention relates to a structure in which a catalyst is supported or coated with high strength and an exhaust gas treatment method using the catalyst.
[0002]
[Prior art]
Exhaust gas generated from incineration facilities that treat industrial and municipal waste contains trace amounts of toxic organic halogen compounds such as dioxins, PCBs, and chlorophenol, nitrogen oxides, and carbon monoxide. Dioxins are extremely toxic, even in trace amounts, and have serious effects on the human body, so there is an urgent need for their removal technology. Moreover, nitrogen oxides and sulfur oxides are also contained in exhaust gas generated from boilers that use coal or heavy oil as fuel, causing air pollution. Removal of harmful substances by catalytic decomposition is one of the most effective technologies, and various shapes of catalysts can be produced by forming a powdered catalyst itself or by loading or coating the catalyst on various structures. . However, when a catalyst is supported on or coated on various structures, problems remain in the adhesive strength, such as being easily peeled off depending on the catalyst composition. In particular, when a catalyst is supported on a ceramic filter and used for exhaust gas treatment, air pulses are blown in a direction opposite to the exhaust gas flow at regular intervals to remove dust accumulated on the filter. Desired.
[0003]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for significantly increasing the adhesive strength of a catalyst layer when an exhaust gas treatment catalyst is supported or coated on various structures.
[0004]
[Means for Solving the Problems]
With respect to the above-described problems, the present invention is specified by the first to third inventions as follows.
(1) is the exhaust gas treatment catalyst for treating an exhaust gas containing dust, vanadium, Mo Ribuden, oxides containing at least one element among titanium emission (hereinafter, referred to as "active oxide") met In addition, a powder having an average particle diameter of the oxide of 0.05 to 5 μm, a powder having an average particle diameter of the oxide of 5 to 100 μm, an average diameter of 0.1 to 50 μm, and an average length An inorganic fiber having a diameter of 2 to 1000 μm is mixed in a weight ratio of the powder to the inorganic fiber in the range of 1: 0.01 to 1: 0.2 to form an aqueous slurry, and a fire-resistant three-dimensional structure Ri Na carried on, an exhaust gas treatment catalyst the refractory three-dimensional structure, wherein the ceramic filter der Rukoto of wall flow type.
(2) A second invention is an exhaust gas purification method characterized by allowing exhaust gas to pass through the catalyst described in the above item 1.
(3) The third invention is characterized in that after passing the exhaust gas through the catalyst according to claim 1, gas is circulated from the exhaust gas discharge side of the catalyst at a pressure of 0.1 to 1 atm (101325 Pa). This is a method for regenerating an exhaust gas treatment catalyst.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
First invention of the present invention, is the exhaust gas treatment catalyst for treating an exhaust gas containing dust, vanadium, Mo Ribuden, oxides containing at least one element among titanium emission (hereinafter, "active oxide A powder having an average particle diameter of the oxide of 0.05 to 5 μm, a powder having an average particle diameter of the oxide of 5 to 100 μm, and an average diameter of 0.1 μm. An inorganic fiber having an average length of 1 to 50 μm and an average length of 2 to 1000 μm is mixed in a weight ratio of the powder to the inorganic fiber of 1: 0.01 to 1: 0.2 to obtain an aqueous slurry. , Ri Na is supported on a refractory three-dimensional structure, the refractory three-dimensional structure is a exhaust gas treatment catalyst, wherein a ceramic filter der Rukoto of wall flow type.
[0006]
The oxide containing at least one element selected from vanadium, tungsten, molybdenum, titanium, and silicon according to the present invention (hereinafter referred to as “active oxide”) is not only a single oxide of each element but also an individual oxide. Complex oxides in which elements are combined, preferably, vanadium-titanium, vanadium-molybdenum-titanium, vanadium-molybdenum-titanium-silicon, vanadium-tungsten-titanium, vanadium-tungsten-titanium-silicon complex oxides It is.
[0007]
The oxide has an average particle diameter of 0.05 to 5 μm and an oxide having an average particle diameter of 5 to 100 μm, preferably those having an average particle diameter of 0.5 to 5 μm and 5 to 5 μm. It is preferable that a material having an average particle diameter of 20 μm is mixed. It is not preferred that the average particle diameter is only 0.05 to 5 μm because the catalyst layer becomes dense and the pressure loss increases. It is not preferable that the average particle diameter is only 5 to 100 μm because the adhesive strength of the catalyst layer is lowered. As a method for measuring the average particle size, a usual means such as a method using a particle size meter or a measurement using an electron microscope can be used.
[0008]
The inorganic fiber according to the present invention has an average diameter of 0.1 to 50 μm and an average length of 2 to 1000 μm, preferably an average diameter of 0.5 to 20 and an average length of 10 to 100. . If the average diameter is less than 0.1 μm, the inorganic fibers tend to break, and therefore the catalyst layer has a low adhesive strength, which is not preferable. If the average diameter exceeds 50 μm, the volume of the inorganic fibers is large and the catalyst weight ratio is high. This is because it is not preferable because it is relatively small.
[0009]
When the average length of the inorganic fibers is less than 2 μm, it is not preferable because the catalyst particles that contact one inorganic fiber are few and the adhesive strength of the catalyst layer is weak, and when the average length exceeds 1000 μm, the inorganic fibers easily break. Therefore, it is not preferable because the adhesive strength of the catalyst layer is low.
[0010]
The weight ratio of the powder to the inorganic fibers is 1: 0.01 to 1: 0.2, preferably 1: 0.02 to 1: 0.08. If there are few inorganic fibers, the adhesive strength of a catalyst layer will become low, and if there are many inorganic fibers, a catalyst amount will become relatively small and it will lead to the fall of catalyst performance.
[0011]
The fire-resistant three-dimensional structure is a ceramic foam, a ceramic honeycomb, a wall flow type honeycomb monolith (ceramic filter), a metal honeycomb, a wire mesh, or a metal foam.
[0012]
As a method of preparing the catalyst according to the present invention , coarsely pulverized active oxide powder, coarsely pulverized inorganic fiber, and wet pulverized active oxide powder together with moisture are mixed. In this method, an aqueous slurry is formed and supported on a fire-resistant three-dimensional structure . Furthermore, in order to increase the adhesive strength of the catalyst layer, at least one of titania sol, silica sol, alumina sol zirconia sol, soluble boehmite, soluble organic polymer compound, and sulfuric acid was added to the aqueous slurry of the active oxide powder. Things can also be carried or coated on a refractory three-dimensional structure.
[0013]
The second invention of the present invention is an exhaust gas purification method in which exhaust gas is passed through the catalyst. The exhaust gas is preferably at a space velocity of 500 to 10,000 h-1 with respect to the catalyst. In particular, the exhaust gas is suitably used for the treatment of exhaust gas containing a trace amount of harmful substances such as dioxins and nitrogen oxides.
[0014]
The third invention of the present invention is a method for regenerating a catalyst. In particular, the catalyst can be regenerated and used in the treatment of exhaust gas containing these trace harmful substances and dust discharged from the incinerator. As a regeneration method, an air pulse is periodically blown from the opposite direction of the gas flow in order to wipe off the dust accumulated in the fire-resistant three-dimensional structure, so that the adhesive strength of the catalyst layer that can withstand this impact is required. The exhaust gas treatment catalyst is suitably used under such exhaust gas conditions. Since the catalyst according to the present invention has sufficient strength, it can withstand regeneration treatment. In the regeneration method, regeneration is performed by sending a pulse of gas (usually air) from the exhaust gas outlet side of the catalyst at a pressure of 0.1 to 1 (101325 Pa).
[0015]
【Example】
Example 1
A sample in which a catalyst component and glass fiber are supported on a ceramic filter (material: cordierite, average pore diameter: 15 μm, rib thickness: 0.9 mm, aperture: 5.0 mm, length: 500 mm) manufactured by NGK It was prepared as follows. An aqueous solution of vanadium and molybdenum was added to the titanium oxide powder and glass fiber, kneaded using a kneader, and formed into a pellet. This was dried and calcined to obtain an exhaust gas treatment catalyst. 1 kg of the obtained catalyst was pulverized with a hammer mill to obtain a powder (A). The average particle size of the powder (A) was 14 μm. The average diameter of the glass fibers was 3 μm and the average length was 30 μm. 2 liters of water was added to 0.33 kg of the powder (A) and pulverized with an attritor until the average particle diameter became 1.5 μm. 0.33 g of the powder (A) was added to the slurry thus obtained. This slurry was immersed in a ceramic filter, and excess slurry was removed, followed by drying and firing at 450 ° C. The amount of catalyst supported on the obtained catalyst-supporting ceramic filter (B) was 85 g / L.
[0017]
(Comparative Example 1)
In the same manner as in Example 1, 1.5 liters of water was added to 0.5 kg of the powder (A) and pulverized with an attritor until the average particle size became 1.5 μm, and the resulting slurry was immersed in a ceramic filter. After removing the excess slurry, drying and baking at 450 ° C. were performed. The amount of catalyst supported on the obtained catalyst-supporting ceramic filter (D) was 81 g / L. Although the state of the glass fiber was measured with a scanning electron microscope but could not be detected, it is considered that the length is approximately 5 nm or less.
For these samples (B) and (D), electron micrographs of the catalyst layer surface are shown in the figure. Further, an air pulse with a pressure of 2 kgf / cm2 was blown into each sample for 1 second at 1 minute intervals, and the amount of catalyst layer peeled after 300 hours was measured.
[0018]
Catalyst supported ceramic filter (B) Stripping amount is 1% or less of supported component weight Catalyst supported ceramic filter (C) Stripped amount is 5% of supported component weight
Catalyst supported ceramic filter (D) Peeling amount is 74% of supported component weight
[0019]
【The invention's effect】
The catalyst according to the present invention has inorganic fibers having a specific size on the catalyst surface, so that the peel strength of the catalyst is improved, and in particular, the strength is improved as compared with the catalyst coated with the same inorganic fiber on the catalyst surface. . The catalyst according to the present invention is suitably used for the treatment of exhaust gas containing a trace amount of harmful substances such as dioxins and nitrogen oxides.
[Brief description of the drawings]
FIG. 1 is a scanning electron micrograph of a catalyst surface according to (B) in Example 1. FIG. It can be seen that glass fibers are present on the catalyst surface.
FIG. 2 is a scanning electron micrograph of the catalyst surface according to (D) in Comparative Example 1. It can be seen that no glass fiber is seen on the catalyst surface.

Claims (3)

Is the exhaust gas treatment catalyst for treating an exhaust gas containing dust, vanadium, Mo Ribuden, oxides containing at least one element among titanium emission (hereinafter, referred to as "active oxide") is an in and the A powder having an average particle diameter of oxide of 0.05 to 5 μm, a powder having an average particle diameter of the oxide of 5 to 100 μm, an average diameter of 0.1 to 50 μm, and an average length of 2 An inorganic fiber having a thickness of 1000 μm is mixed in a weight ratio of the powder to the inorganic fiber in the range of 1: 0.01 to 1: 0.2 to form an aqueous slurry, and is supported on the fire-resistant three-dimensional structure. Do Te Ri, exhaust gas treatment catalyst the refractory three-dimensional structure, wherein the ceramic filter der Rukoto of wall flow type. An exhaust gas purification method comprising passing exhaust gas through the catalyst according to claim 1. A method for regenerating an exhaust gas treatment catalyst , wherein after exhaust gas is passed through the catalyst according to claim 1, gas is circulated from the exhaust gas discharge side of the catalyst at a pressure of 0.1 to 1 atm (101325 Pa) .

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