JP2000126615A - Production of wear-resistant catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the wear resistance of a catalyst by rolling and applying a catalyst paste obtained by adding a specified oxide or salt to titanium oxide and kneading on a reticular substrate, then drying and/or baking the paste to obtain a catalytic body and impregnating the catalytic body with a sol-like liq. contg. colloidal silica. SOLUTION: Molydbenum(Mo) and/or tungsten (W), the oxide or salt of vanadium(V), inorg. fiber and water are added to a titanium oxide (titania) row material having a high specific surface area, kneaded and made into paste. The obtained catalyst paste is applied on a metallic substrate or a ceramic reticular substrate and formed into sheet. The obtained catalyst-coated body is put between rollers or dies, formed into a specified shape, e.g. corrugated, and then baked to obtain a baked catalytic body. The baked catalytic body is impregnated with silica sol and finally dried and/or baked. Consequently, the colloidal silica grain is easily infiltrated, and a high-strength catalyst is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an abrasion-resistant catalyst, and more particularly to a method for producing a catalyst for removing nitrogen oxides (NOx) for catalytic reduction using ammonia (NH ₃ ). The present invention relates to a method for producing an abrasion-resistant catalyst that is less susceptible to abrasion caused by dust contained therein.

[0002]

2. Description of the Related Art NOx in flue gas emitted from power plants, various factories, automobiles, and the like is a substance that causes photochemical smog and acid rain, and ammonia (NH ₃ ) and the like are effectively removed therefrom. Flue gas denitration by selective catalytic reduction as a reducing agent is widely used mainly in thermal power plants.
As such a denitration catalyst, a titanium oxide (TiO ₂ ) catalyst using vanadium (V), molybdenum (Mo) or tungsten (W) as an active component is used. In particular, vanadium is contained as one of the active components. These catalysts have become the mainstream of the current denitration catalysts because of their high activity, small degradation by impurities contained in the exhaust gas, and their use at lower temperatures (Japanese Patent Laid-Open No.
No. 128681). The denitration catalyst is usually formed into a honeycomb shape or a plate shape.

When such a denitration catalyst is applied to an exhaust gas containing a large amount of dust such as a coal-fired boiler, if the abrasion strength is low, the abrasion is caused by the dust, which causes a serious hindrance to the operation of the denitration apparatus. Sometimes.
For this reason, great care has been taken to improve the wear resistance of the denitration catalyst, and various proposals have been made. Typical examples thereof include a method of impregnating a catalyst with a binder such as silica sol (Japanese Patent Application Laid-Open No. 57-174143), a method of adding a large amount of molybdenum oxide to a catalyst, calcining the catalyst at a high temperature, and then adding aluminum sulfate or the like. (Japanese Patent Application Laid-Open No. 1-215345).

FIG. 3 is an explanatory view showing a process for producing a conventional wear-resistant catalyst in which a catalyst body is impregnated with silica sol as a binder. In the figure, this method comprises the steps of adding and kneading a catalytically active component such as W, Mo, V, etc. to a titanium oxide raw material, drying the kneaded catalyst, and firing it at, for example, 500 ° C. for 2 hours, A pulverizing step of pulverizing the catalyst component after the preliminary calcination to a particle size of 50 wt% or less and 50 wt%, and a step of preparing a catalyst paste by adding an inorganic fiber and / or a binder to the pulverized material and kneading to obtain a catalyst paste. When,
Applying the catalyst paste to a catalyst substrate, a coating step, a forming step of forming the obtained catalyst-coated body, a firing step of drying or firing the catalyst formed body, and a silica sol on the obtained fired catalyst body. It comprises a strengthening step of impregnation and a final baking step of drying or baking the catalyst body after impregnation of the silica sol.

[0005]

However, the method of strengthening by impregnating with silica sol in the above prior art is an excellent method with little influence on the denitration activity, but has the following problems. That is, the impregnation effect of the silica sol differs depending on the type of catalyst and the production method, and it has been difficult to obtain sufficient wear strength. Also, at the time of silica sol impregnation, only water, which is a dispersion medium of the sol, is selectively sucked into the catalyst. Therefore, even if the concentration of the silica sol is increased, the amount of impregnated silica does not increase more than a certain amount, and high wear strength is obtained. I can't get anything. Furthermore, in order to obtain sufficient strength, pretreatment such as pre-firing the catalyst raw material is required, and the production process becomes complicated. The purpose of the present invention is
An object of the present invention is to provide a method for producing an abrasion-resistant catalyst which can solve the above-mentioned problems of the prior art and can significantly improve abrasion resistance by impregnation with silica sol.

[0006]

Means for Solving the Problems In order to achieve the above object, the present inventors first studied the reason why the prior art shown in FIG. 3 could not achieve sufficient improvement in wear resistance due to impregnation with silica sol. In order for the binder containing colloidal silica, such as silica sol, to be impregnated into the catalyst, the catalyst must have pores sufficiently larger than the particle size of the colloidal silica. In the conventional method, and after kneading the titanium oxide raw material and the catalyst component, preliminary firing is performed, so that the moisture is reduced, and shrinkage due to subsequent drying or firing is reduced, and a relatively strong catalyst is obtained. However, since the catalyst becomes dense and dense, the proportion of large pores into which colloidal silica particles can enter is reduced, making it difficult for silica sol to be impregnated. Improved body wear strength by impregnation to obtain a finding that can not be sufficiently achieved.

That is, in the above prior art, the catalyst component before being applied to the catalyst substrate is preliminarily calcined to increase the strength to a certain limit, and then the catalyst component is applied to a substrate to form a catalyst. Although it is intended to further increase the strength by impregnating with silica sol, it is considered that the preliminary baking has rather hindered the strength improvement effect by impregnation with silica sol.

[0008] Based on the above findings, the present inventors
As a result of intensive research on a method for producing a wear-resistant catalyst that can significantly improve wear resistance by impregnation with silica sol, a paste-like material (catalyst paste) obtained by adding a catalyst component to a titania raw material having a high specific surface area and kneading the same is obtained. Immediately applied to the catalyst substrate without preliminary firing, dried or fired, and impregnated with silica sol in the obtained fired catalyst body to ensure a sufficient ratio of large pores into which colloidal silica particles can enter. It has been found that the silica sol can be impregnated with the compound, so that the effect of impregnation with the silica sol is enhanced and the abrasion resistance of the catalyst is improved.

That is, the invention claimed in the present application is as follows. (1) At least molybdenum and / or tungsten oxides or salts, vanadium oxides or salts are added to titanium oxide, and the kneaded catalyst paste is rolled and applied to a net-like substrate, and then dried and / or fired. A method for producing an abrasion-resistant catalyst, characterized by impregnating the catalyst body with a sol-like liquid containing colloidal silica.

(2) The method for producing a wear-resistant catalyst according to the above (1), wherein the titanium oxide having an average specific surface area of 90 to 230 m ² / g is used. (3) The titanium oxide has a specific surface area of 90 to 120 m ² /
g. and a mixture of titanium oxide having a specific surface area of 180 to 230 m ² / g. (4) The method for producing an abrasion-resistant catalyst according to any one of the above (1) to (3), wherein the catalyst paste contains oxalic acid.

(5) The method for producing a wear-resistant catalyst according to any one of the above (1) to (4), wherein the catalyst paste contains colloidal silica. (6) The method for producing an abrasion-resistant catalyst according to any one of the above (1) to (5), wherein the network substrate is a metal substrate or an inorganic fiber substrate. (7) The method for producing an abrasion-resistant catalyst according to any one of the above (1) to (6), wherein the SiO ₂ concentration of the sol-like liquid is 5 to 20% by weight.

According to the present invention, a catalyst component is added to a titanium oxide (hereinafter also referred to as titania) material having a high specific surface area, kneaded, immediately applied to a catalyst substrate, and the obtained catalyst coated body is dried or calcined. This is a method for producing an abrasion-resistant catalyst, in which a calcined catalyst body is prepared, and the calcined catalyst body is impregnated with silica sol.

FIG. 1 is an explanatory view showing one example of a method for producing a wear-resistant catalyst of the present invention. In the figure, this catalyst production method comprises the steps of (a) adding an oxide or salt of molybdenum (Mo) and / or tungsten (W), vanadium (V), inorganic fibers and water to a titania raw material, kneading the mixture, and forming a paste. (B) a step of applying the obtained catalyst paste to a metal substrate or a ceramic net-like substrate to form a plate, and (c) a waveform obtained by sandwiching the catalyst-coated body between rollers or a mold. (D) drying or baking step, (e) impregnation step of impregnating with silica sol, and (f) final drying and / or baking step.

In the drying or baking step, the catalyst component tends to shrink due to thermal decomposition of active ingredient salts and dissolution promoting components or sintering of titanium oxide. In the present invention, however, the catalyst paste is applied to a net-like base material. By baking after application, the highly rigid net-like base material works to suppress shrinkage of the catalyst component. Therefore, in the prior art in which pre-baking is performed before application to the base material, the volume of macropores corresponding to the volume change that shrinks is increased, and the relative proportion of large pores is increased. Particles easily penetrate, and a high-strength catalyst can be obtained.

Usually, when a paste obtained by adding an active ingredient to titania having a high specific surface area and kneading the mixture is formed into a plate without preliminary firing, and dried and / or fired, the volume shrinks by about 20%. In the present invention, since the contraction is suppressed by the catalyst substrate, a large amount of macropores can be generated. FIG. 2 is an explanatory diagram showing the difference in the degree of shrinkage depending on the presence or absence of a catalyst substrate in a plate-like catalyst obtained by forming a catalyst paste into a plate shape without preliminary firing, and drying and / or firing. In the figure, it can be seen that the degree of shrinkage of the catalyst is lower when the catalyst component is applied to the substrate in advance (b) than when the substrate is not used (a).

As described above, in the present invention, since the shrinkage of the catalyst is suppressed and a large amount of macropores having a diameter of, for example, 1000 Å (Å) or more can be generated, the colloidal silica particles easily penetrate. The wear resistance of the catalyst is improved. Further, since the colloidal silica particles easily penetrate into the catalyst, it is difficult to separate the silica particles and water as a dispersion medium, and there is no problem of the prior art that only water is supported in the catalyst. Therefore, a high-strength catalyst with little variation in wear resistance can be obtained efficiently.

In the present invention, titania as a catalyst raw material is preferably not subjected to high-temperature heat treatment. The specific surface area of titania averages 90 to 230 m ² /
g, preferably 120 to 230 m ² / g on average. In particular, when the titania having a relatively high specific surface area (180 to 230 m ² / g) and the titania having a relatively low specific surface area (90 to 120 m ² / g) are combined and the average specific surface area is adjusted within the above range, Good results are easily obtained. In the present invention, the active ingredient, titania, water, inorganic fibers and the like are added,
Oxalic acid and amines are preferably added to the kneaded catalyst paste in order to promote the dissolution of the active ingredient, and a binder such as silica sol (colloidal silica) or aluminum sulfate can be added at the same time.

In the present invention, SUS is used as the reticulated base material.
A metal substrate including a metal lath or an inorganic fiber substrate including a glass fiber woven fabric entangled is used, and the catalyst paste is applied to the substrate using, for example, a rolling roller or the like. It is applied to fill.

In the present invention, it is preferable that the catalyst paste is applied to a net-like base material and then molded by being sandwiched between rollers or a mold. In this forming step, a chevron, a corrugation or the like that functions as a spacer when a large number of plate catalysts are stacked is formed. The catalyst molded body is dried and / or calcined to form a calcined catalyst body, which evaporates water, decomposes salts and the like as active components, and facilitates subsequent impregnation with silica sol. In the present invention, the forming step and the drying or baking step do not need to be performed separately, and the forming and drying or baking can be performed at the same time with the catalyst-coated body interposed between heated molds.

In the present invention, the impregnation of the silica sol is carried out by immersing the dried or calcined catalyst in a silica sol having a predetermined concentration, or by spraying the silica sol on the catalyst with a spray or the like. invade. The silica sol is not particularly limited,
Easily SiO ₂ content obtained using a high intensity catalyst things 5-20%.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to examples. Example 1 1400 twisted yarns of E glass fiber having a fiber diameter of 9 μm
Book / 40% titania, 20% silica sol, 1% polyvinyl alcohol on a net woven with a roughness of 25.4 mm
Was impregnated with the slurry and dried at 150 ° C. to obtain a rigid catalyst substrate.

On the other hand, a specific surface area of about 230 m
² / g ammonium molybdate titania 1.5kg of _{((NH 4) 6 · Mo} 7 O 24 · 4H 2 O) 0.10
kg, 0.046 kg of ammonium metavanadate, 0.081 kg of oxalic acid, and 5 wt% of 20 wt% silica sol as SiO ₂ were added and kneaded while adding water to form a paste. 0.32 kg of kaolin-based inorganic fiber (trade name: kao wool) was added thereto and further kneaded to obtain a catalyst paste having a water content of 30.5%. The obtained catalyst paste was mixed with the previously prepared catalyst substrate 2 having a width of 500 mm.
The sheet was placed between the sheets and applied to the mesh and the mesh surface of the base material using a pair of rolling rollers, and then cut to a length of 480 mm to obtain a 0.7 mm thick plate-like coated body.

The obtained catalyst-coated body is sandwiched between heating molds.
, 4 waveforms are formed at intervals of 120mm with a waveform of height 6mm,
It was baked at 500 ° C. for 2 hours. The fired catalyst body obtained was
iO _Two20% silica sol (Nissan Chemical, Snowte
X-O) to support colloidal silica,
The catalyst was dried and calcined at 450 ° C. for 2 hours to obtain a catalyst. Example 2 Ten twisted yarns of 1,000 E glass fibers having a fiber diameter of 9 μm were used.
Book / 25.4 mm
Stiffness impregnated with the same slurry as the slurry used in Example 1.
To give a catalyst substrate.

On the other hand, separately from this, the specific surface area is about 90 m ^2.
/ G titania 1.05 kg and specific surface area 230 m ² / g
Titania 0.45kg and the ammonium paratungstate _{((NH 4) 10 H 10} · W 12 O 46 · 6H 2 O) and 0.14 kg, ammonium metavanadate 0.046
and 0.084 kg of oxalic acid, and 5 wt% of 20 wt% silica sol as SiO ₂ , kneaded while adding water to form a paste, and 0.33 kg of kaolin-based inorganic fiber (trade name: kao wool) was added thereto. The mixture was kneaded to obtain a catalyst paste having a water content of 31.5%.

Using the obtained paste and the previously prepared catalyst base material, a catalyst-coated body was formed in the same manner as in Example 1, and the obtained catalyst-coated body was molded under the same conditions as in Example 1 and calcined. Thus, a catalyst fired body was obtained. The obtained catalyst fired body was immersed in the same silica sol as in Example 1 to support colloidal silica, and fired under the same conditions as in Example 1 to obtain a plate-like catalyst.

[0026] The mixing ratio of the titania and a specific surface area of 230 m ² / titania having a specific surface area of 90m ² / g used in Example 3-5 Example 2, respectively 1.5 / 0kg / kg, 0.75 / 0. 75kg / kg
A similar plate-like catalyst was prepared in the same manner as in Example 2 except that the amount was 0.45 / 1.05 kg / kg.

Examples 6 and 7 The silica sol used in Example 2 for impregnation of the calcined catalyst was used.
Except that the O ₂ concentration was changed to 10 wt% and 5 wt%, respectively, plate-like catalysts were prepared in the same manner as in Example 2 above, and Examples 6 and 7 were obtained. Example 8 A plate-like catalyst was prepared in the same manner as in Example 1 except that the catalyst baking step of baking at 500 ° C. for 2 hours was omitted, and the catalyst-coated body after heating was immediately immersed in silica sol.

Comparative Example 1 A plate-like catalyst was obtained in the same manner as in Example 1 except that the catalyst body was not impregnated with silica sol. Comparative Example 2 A plate catalyst was obtained in the same manner as in Example 2 except that the catalyst body was not impregnated with silica sol.

Comparative Example 3 A catalyst paste was prepared in the same manner as in Example 1 except that silica sol and kaolin-based inorganic fiber were not mixed.
After drying and pre-firing at 500 ° C for 2 hours,
The same 20 wt% silica sol as used in Example 1 was added to
5 wt% as O ₂ , 0.32 k of kaolin-based inorganic fiber
g and water were added and kneaded to obtain a paste having a water content of 28.5%. A plate-like catalyst was prepared in the same manner as in Example 1 except that the paste was used as a catalyst paste.

Comparative Example 4 A catalyst paste was prepared in the same manner as in Example 2 except that silica sol and kaolin-based inorganic fiber were not mixed.
After drying and pre-baking at 550 ° C. for 2 hours,
20 wt% silica sol similar to that used in Example 2 was added to 1.66 kg of pulverized to 50% by weight or less
5 wt% as O ₂ , 0.32 k of kaolin-based inorganic fiber
g and water were added and kneaded to obtain a paste having a water content of 29.0%, and a plate-like catalyst was prepared in the same manner as in Example 2 except that the paste was used as a catalyst paste.

Comparative Example 5 A plate catalyst was prepared in the same manner as in Example 3 except that the catalyst was not impregnated with silica sol. Comparative Example 6 A plate catalyst was prepared in the same manner as in Example 4 except that the catalyst body was not impregnated with silica sol.

Each of the catalysts of Examples 1 to 8 and Comparative Examples 1 to 6 was cut into 100 mm squares, and a 70-mesh steel grit having a height of 500 m was placed on the surface inclined at 45 degrees.
The abrasion test was performed by dropping 8 kg from the position of m to evaluate the abrasion strength. Table 1 summarizes the obtained results. In Table 1, it is shown that the smaller the wear amount, the higher the wear strength of the catalyst.

[0033]

[Table 1] In Table 1, the plate-shaped catalysts of Examples 1 and 2 in which the calcined catalyst body was impregnated with silica sol had extremely small abrasion amounts as compared with the plate-shaped catalysts of Comparative Examples 1 and 2 in which silica sol was not impregnated. It can be seen that the impregnation significantly improved the wear resistance.

When Examples 1 and 2 are compared with Comparative Examples 1 and 2, and Comparative Examples 3 and 4 are compared with Comparative Examples 5 and 6, the catalysts of Examples 1 and 2 are impregnated with silica sol. It can be seen that the abrasion resistance of Comparative Examples 3 and 4 is substantially improved compared to Comparative Examples 5 and 6, even after the silica sol impregnation step, while the abrasion resistance is significantly improved as compared with Comparative Examples 2 and 3. . From this, it is understood that the method of the present invention in which the paste-like catalyst component is not pre-fired can greatly improve the abrasion resistance of the catalyst as compared with the prior art in which the catalyst component is pre-fired.

Further, from the comparison of Examples 2 to 5, it can be seen that in the present invention, the greater the average specific surface area of the titania raw material, the greater the effect of improving the wear resistance. Further, from the comparison of Examples 2, 6 and 7, the silica sol impregnated with Si
It can be seen that the higher the O ₂ concentration, the better the results. In addition, comparing Example 1 and Example 8, there is no difference in the amount of wear between them, and baking after heat molding of the catalyst-coated body is not always necessary, as long as it is dried to the extent that silica sol is impregnated. It turns out to be good.

[0036]

According to the first aspect of the present invention, a catalyst paste obtained by adding at least an oxide or salt of molybdenum and / or tungsten, or an oxide or salt of vanadium to titanium oxide and kneading the mixture is formed into a network. After being rolled and applied to a substrate, dried and / or calcined to obtain a calcined catalyst body, and impregnated with a sol-like liquid containing colloidal silica and carried on the calcined catalyst body to obtain a high abrasion resistant high A strong catalyst is obtained. In addition, since the preliminary calcination is not required and the production process of the catalyst can be simplified, a great effect can be obtained economically.

According to the second aspect of the present invention, the titanium oxide has an average specific surface area of 90 to 230 m ² /
In addition to the effects of the present invention,
Colloidal silica is easily impregnated, and a catalyst having more excellent wear resistance can be obtained. According to the invention described in claim 3 of the present application, the specific surface area is 90 to 120 m ² / g as titanium oxide.
By using a mixture of titanium oxide having a specific surface area of 180 to 230 m ² / g, the effect of improving the abrasion resistance by impregnation with silica sol is further increased in addition to the effect of the present invention.

According to the invention of claim 4 of the present application, since the catalyst paste contains oxalic acid, in addition to the effects of the above-mentioned invention, the dissolution of the catalytically active component is promoted and higher catalytic performance is exhibited. . According to the fifth aspect of the present invention,
When the catalyst paste contains colloidal silica, a catalyst having higher strength can be obtained in addition to the effects of the present invention. According to the invention as set forth in claim 6 of the present application, the reticulated substrate is a metal substrate or an inorganic fiber substrate. A more effective impregnation results in a higher strength catalyst.

According to the invention of claim 7 of the present application, a higher strength catalyst can be obtained by setting the SiO ₂ concentration of the sol-like liquid to 5 to 20% by weight.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a production process of a catalyst of the present invention.

FIG. 2 is a schematic diagram showing features of the present invention.

FIG. 3 is an explanatory view showing a conventional technique.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01J 35/06 B01D 53/36 102C (72) Inventor Eiji Miyamoto 3-36 Takaracho, Kure-shi, Hiroshima Babcock-Hitachi F-term in Kure Research Laboratories Co., Ltd. (Reference) 4D048 AA06 AB02 BA06X BA07X BA23X BA26X BA27X BA41X BB03 4G069 AA01 AA03 AA08 AA09 BA02A BA02B BA04A BA04B BA14B BB06A BB06B BC54A BC54B BC59A BC02 EC02 EC02 CA03B02

Claims (7)

[Claims] Claims 1. At least an oxide or salt of molybdenum and / or tungsten or an oxide or salt of vanadium is added to titanium oxide, and the kneaded catalyst paste is rolled and applied to a net-like substrate, and then dried and / or dried.
Alternatively, a method for producing an abrasion-resistant catalyst, comprising calcining to form a catalyst, and impregnating the catalyst with a sol-like liquid containing colloidal silica. 2. The method according to claim 1, wherein the titanium oxide has an average specific surface area of 90 to 230 m ² / g. 3. The titanium oxide has a specific surface area of 90 to 12
0 m ² / g titanium oxide and specific surface area of 180 to 230 m ²
3. The method for producing an abrasion-resistant catalyst according to claim 2, wherein the mixture is a mixture of titanium oxide / g of titanium oxide. 4. The method for producing an abrasion-resistant catalyst according to claim 1, wherein the catalyst paste contains oxalic acid. 5. The method for producing a wear-resistant catalyst according to claim 1, wherein the catalyst paste contains colloidal silica. 6. The method for producing an abrasion-resistant catalyst according to claim 1, wherein the mesh substrate is a metal substrate or an inorganic fiber substrate. 7. The sol-like liquid having an SiO ₂ concentration of 5 to 5.
The method for producing an anti-wear catalyst according to any one of claims 1 to 6, wherein the amount is 20% by weight.