JPH02198634A - Production of catalyst for removing nitrogen oxide - Google Patents

Abstract

PURPOSE:To allow the easy and sufficient impregnation of a catalyst compsn. in a ceramics fiber sheet by adjusting the particle size distribution of the cata lyst compsn. powder to 50 to 80% particles sized <=0.5mu, 70 to 85% particles sized <=1mu, 90 to 95% particles sized <=5mu, and 92 to 100% particles sized <=10mu. CONSTITUTION:The catalyst compsn. powder consisting of titanium oxide and the oxide of >=1 kinds of elements among vanadium, molybdenum and tungsten is impregnated in the ceramics fiber sheet to produce the catalyst for removing NOx. The grain size distribution of the catalyst compsn. powder is previously adjusted to the range of 50 to 80% particles sized <=0.5mu, 70 to 85% particles sized <=1mu, 90 to 95% particles sized <=5mu, and 92 to 100% particles sized <=10mu at this time. The catalyst compsn. powder completely fills the inter-fiber spacings of the ceramics fiber sheet in this way and the easy and sufficient impregnation thereof to the ceramics fiber sheet is possible.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a catalyst for removing nitrogen oxides, and in particular, a ceramic fiber sheet containing titanium oxide, vanadium, molybdenum,
The present invention relates to a method for producing a catalyst for removing nitrogen oxides impregnated with a catalyst composition such as tungsten.

[Conventional technology]

Generally, titanium oxide (TiO
and an oxide such as molybdenum (Mo), tungsten (W), vanadium (V), etc., in granular form,
Those molded into plate shapes, honeycomb shapes, etc. are used. In particular, in the case of exhaust gas from boilers that use fuel such as heavy oil or coal, it is necessary to treat the gas containing a large amount of soot and ash with a low pressure drop when passing through the catalyst.
377) and honeycomb-shaped catalysts (Japanese Patent Publication No. 60-3856, etc.) are known and have already been put into practical use.

Among these, in those using a metal substrate, the metal substrate is oxidized. Furthermore, honeycomb-shaped honeycombs have problems in that it is difficult to obtain large honeycombs due to the limitations of the molding technology, and that their mechanical strength is low.

[Problem to be solved by the invention]

The above-mentioned conventional techniques do not give much consideration to making it easy to impregnate a ceramic fiber sheet with a catalyst composition, and there are problems with impregnating properties, making it impossible to obtain a high-strength catalyst.

An object of the present invention is to easily and sufficiently impregnate a ceramic fiber sheet with a catalyst composition.

[Means to solve the problem]

The above purpose was achieved by adding water to a catalyst composition powder consisting of titanium oxide and an oxide of one or more elements of vanadium, molybdenum, and tungsten to form a slurry, impregnating a ceramic fiber sheet with the slurry, and drying it for 300 minutes. In the method for producing a catalyst for removing nitrogen oxides which is calcined at ~600°C, the particle size distribution of the catalyst composition powder is such that 50 to 80% of the particles are 0.5μ or less, 70 to 85% are 1μ or less, and 5μ or less.
90-95% of the following particles, 92-95% of particles of 10 μ or less
This is achieved by a method for producing a catalyst for removing nitrogen oxides, which is characterized in that the nitrogen oxide removal catalyst is prepared within a certain range of 100%.

[Function] When the catalytic component oxide particles completely fill the fiber gaps (several microns to several tens of microns) of the ceramic fiber sheet, the finer the particles, the better, forming an extremely dense catalyst body. This state corresponds to a state in which a dense catalyst component layer is reinforced by intertwined ceramic fibers, and the strength of the resulting catalyst body is that of a ceramic sheet surface coated with a catalyst component,
This is significantly higher than that impregnated with a catalyst component solution.

In addition, if there are too many particles of 0.5μ or less, agglomeration will occur, making it impossible to carry out the impregnation operation, which is not preferable. Add salts such as acid ammonium, heat and knead,
After drying the obtained paste, heat it at 500"C or more, 650"C.
Hereinafter, it is preferably fired at 520 to 600°C. This is pulverized using a pulverizer, etc., so that 92% or less is 10μ or less, and water is added to the resulting powder to produce approximately 50~60w.
Prepare a t% slurry. A ceramic fiber sheet is immersed in this slurry, and the gaps between the fibers are filled with the catalyst component oxide slurry. The sheet impregnated with the catalyst component is air-dried or heated and then fired at 300 to 600° C. for practical use.

A feature of this catalyst is that it maintains high strength by filling the gaps between ceramic fiber sheets with a dense layer of catalyst component oxide.

The gap between the fiber sheets is from several microns to several tens of microns, and it is necessary to impregnate the catalyst particles with fine particles. As means for pulverizing the catalyst particles, there are methods such as pulverizing them with a hammer mill, ball mill, or shaking mill, or pressurizing them with a roll crusher, but any pulverizing method may be used.

Moreover, if the proportion of particles of 0.5 μm or less exceeds 80%, agglomeration occurs, making it difficult to carry out the impregnation operation, which is not preferable.

Therefore, for wet impregnation, the optimum particle size distribution is preferably in the range of 50-80% of 0.5μ or less, 70-85% of 1μ or less, 90-95% of 5μ or less, and 92-100% of 10μ or less. .

The present invention will be explained below using specific examples.

Example 1 60 kg of metatitanic acid slurry containing 30 wt% titanium oxide (T i O□) produced by the sulfuric acid method,
Ammonium metavanadate (NH, VO:+) 0.6
2 kg, and ammonium molybdate ((NH4)
b MO? 024.4 H20) 4.51 kg was added and kneaded while evaporating water using a kneader heated to 140°C. The resulting paste-like material with a water content of 38% was formed into a 3φ column using an extrusion granulator, and then dried using a fluidized bed dryer. The dried granules were baked at 560°C for 2 hours with air flowing through them, and then pulverized with a fine powder pulverizer.
A fine catalyst powder was obtained.

4 kg of water was added to 5 kg of the above catalyst powder and stirred for 10 minutes using a screw type stirrer to obtain a slurry having a concentration of 55 wt%. In this slurry, SiO□/Aj2. Ceramic paper with a weight ratio of O and J of approximately 1.0 (Paper LS manufactured by Isolite Co., Ltd., thickness 11nI11, fiber weight 120 g/
rrf) cut into 500 square pieces was immersed and impregnated with the catalyst slurry while being pressed down with a rubber roller and degassed.

The surface of the paper impregnated with the catalyst slurry was scraped of excess slurry, and then dried at 180°C. Thereafter, it was fired in air at 550° C. for 2 hours to obtain a catalyst molded body.

Comparative Example 1 A catalyst molded body was obtained in the same manner as in Example 1, except that it was pulverized using the pulverizer of Example 1, but a fine powder with a high proportion of coarse particles was obtained.

Example 2 The same procedure as in Example 1 was carried out except that the catalyst was crushed by applying pressure with a roll crusher instead of the pulverizer used in Comparative Example 1.

Example 3 Oxide composition ratio, ')<T i/W/V=9315/2(
%) catalyst composition powder was prepared in the same manner as in Example 2.

Comparative example 2 The catalyst powder of Comparative Example 1 was ground for a long time in a ball mill.

The particle size distribution of the catalyst powders before impregnation in Examples 1 to 3 and Comparative Examples 1 to 2 was measured using a light transmission method using Micron Fort Kaiser Model 5KN-1000 (Seishin Enterprise Co., Ltd.). The results are shown in FIG. From this result, it can be seen that the particle size distribution of Examples 1 to 3 is finer than that of Comparative Example 1, and the impregnation into the ceramic fiber sheet is improved.

Further, the amount of catalyst supported is shown in Table 1. From this table, it can be seen that Comparative Example 2, in which the particle size is too fine, that is, there are many particles of 0.5 μm or less, has poor impregnating properties.

Further, the catalyst was cut into a width of 15-1 and a length of 50 InI11, and the tensile strength was determined using a precision testing machine, and the values are also shown in Table 1. It can be seen from this that as the amount of catalyst supported increases, the strength also increases. From the above, the particle size distribution to be impregnated into a ceramic fiber sheet is as follows: 50-80% is 0.5μ or less, 70-85% is 1μ or less, 90-95% is 5μ or less, and 92-92% is 10μ or less. It can be seen that the range of 100% is suitable.

Table 1 Figure 1 Comparative Example 2 [Effects of the Invention] According to the present invention, the catalyst component oxide can be densely impregnated into the gaps between the ceramic fiber sheets, so that a catalyst molded body with high strength can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a particle size distribution diagram showing examples of the present invention and comparative examples. Applicant Babcock Hitachi Co., Ltd. Agent Patent Attorney Takeshi Kawakita

Claims (1)

[Claims] (1) Add water to a catalyst composition powder consisting of titanium oxide and an oxide of one or more elements of vanadium, molybdenum, and tungsten to form a slurry, impregnate a ceramic fiber sheet with this, and after drying In a method for producing a catalyst for removing nitrogen oxides, which is performed by firing at 600°C, 50 particles having a particle size distribution of 0.5μ or less of the catalyst composition powder are prepared in advance.
~80%, 70-85% particles less than 1μ, 90-95% particles less than 5μ, 92-100 particles less than 10μ
%.