JPH06246176A - Production of plate catalyst and processing solution of metal substrate for the catalyst - Google Patents

Abstract

PURPOSE:To prevent the deterioration of the catalyst resulting from the corrosion of the substrate by previously applying a processing soln. consisting of an org, high polymer to be insolubilized by the heat, colloidal silica and fine- grain titania on the metal substrate, heating and drying the soln. to polycondense and insolubilize the soln., applying a catalytic component thereon, drying and calcining the catalystic component. CONSTITUTION:A processing soln. contg. 0.5-5wt.% of a water-soluble polymer such as PVA and vinyl acetate alcohol, 0.5-5wt.% of colloidal silica and 20-70wt.% of fine-grain titania free of a sulfate radical in a tank is applied onto the surface of a metal substrate, then heated in an insolubilizing furnace 6 and dried to insolubilize the coating layer. A catalytic component 7 contg. at least one among V, Mo and W in addition to Ti is pressed and stuck to the insolubilized coating layer by a coating roller 8, dried and fired. Consequently, the deterioration of the catalyst using the metal substrate, especially a decrease in the SO2 oxidation rate due to the corrosion of the substrate is prevented.

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 a plate catalyst and a treatment liquid for a metal substrate for a catalyst, and more particularly to a metal wire mesh,
Sulfur Dioxide (SO ₂ ) Sulfur Trioxide (SO ₂ ) of Denitration Catalyst for Titanium Oxide-Based Ammonia Catalytic Reduction Using Lath Plate as Base Material
_{The present} invention relates to a method for producing a plate-like catalyst having suppressed oxidation activity to ₃ ) and a treatment liquid for a metal substrate for a catalyst.

[0002]

2. Description of the Related Art NOx in smoke emitted from power plants, various factories, automobiles, etc. is a causative agent of photochemical smog and acid rain, and ammonia (NH ₃ ) is reduced as an effective removal method. The flue gas denitration method by selective catalytic reduction as an agent is widely used mainly in thermal power plants. The catalyst is titanium oxide (Ti) containing vanadium (V), molybdenum (Mo) or tungsten (W) as an active ingredient.
O ₂ ) -based catalysts are used, in particular, those containing vanadium as one of the active components are not only highly active, but are also less deteriorated by impurities contained in the exhaust gas,
Since it can be used at lower temperatures, it has become the mainstream of the present denitration catalyst (Japanese Patent Laid-Open No. 50-128681). These titanium oxide-based denitration catalysts are often used by being formed into a honeycomb shape or a plate shape applied to a metal substrate, and the latter plate-shaped catalyst is particularly resistant to abrasion and accumulation due to soot dust, so Widely used for denitration.

As a method for producing a plate-like catalyst, many methods have been invented and devised, and the methods are roughly classified as follows. (1) A method of directly coating the surface of a metal substrate made of SUS (stainless steel) with a catalyst component. (2) A method of coating the catalyst component paste on a mesh-like or porous metal substrate such as a wire mesh. (3) A method of coating or applying a catalyst component after forming an intermediate layer having a rough surface such as ceramic spraying or metal spraying on the surface of a reticulated or porous metal substrate.

Of the above (3), metal aluminum is sprayed on the surface of a metal lath plate (a slit (cut) is formed in a thin metal plate at a predetermined pitch and a tensile force is applied in a direction perpendicular to the slit to form a wire mesh body). The method of applying a catalyst paste to a substrate roughened by performing (AI thermal spraying) by a roller press (Japanese Patent Laid-Open No. 52-14658) is excellent in mass productivity,
Since it is possible to obtain a catalyst with high mechanical strength, it has become the mainstream of plate catalysts in Japan and overseas.

On the other hand, in recent years, there has been a tendency to purify exhaust gas to a high degree, and there are increasing opportunities for the denitration device to operate at a high denitration rate by increasing the catalyst filling amount. Under such conditions, when the above-mentioned V-containing catalyst is used to denitrate the SO ₂ -containing exhaust gas, SO ₂ is oxidized by the catalytic action of V and SO ₂ is oxidized.
₃ is generated, which causes problems such as corrosion of subsequent equipment and precipitation of acidic ammonium sulfate (NH ₄ HSO ₄ ) due to reaction with unreacted NH ₃ . Further, since SO ₃ is difficult to be removed by the wet desulfurization device, most of it is released into the atmosphere, which causes new pollution. S
It is said that O ₃ is more likely to cause respiratory injury than SO ₂ , and also becomes a mist and floats in the atmosphere, and acts on global warming. For this reason, recently in Western countries, S
The demand for highly active denitration catalysts with low O ₂ oxidation activity has increased, and SO ₂ has been optimized by optimizing the catalyst composition such as V content.
Attempts have been made to reduce the oxidation rate, but as a result of the study by the inventors, it has been found that the method using the above-mentioned metal substrate realizes a low SO ₂ oxidation rate due to the catalytic action of the substrate metal element slightly dissolved at the time of manufacturing. Turned out to be difficult.

[0006]

A titanium oxide slurry or powder raw material obtained by the sulfuric acid method, which is inexpensive and has high catalytic performance, is used for the titanium oxide-based NOx removal catalyst. Titanium oxide produced by the sulfuric acid method generally contains 5 to 10 wt% of sulfate radicals, and most of them remain in the catalyst components even after steps such as addition of catalyst components and calcination. Therefore, in the case of a catalyst using a metal substrate, when the paste or slurry of the catalyst component is coated or applied to the substrate by a wet method, the metal substrate is dissolved by the residual sulfuric acid and the substrate component moves into the catalyst component. Among SUS substrate components, iron (Fe),
Elements such as nickel (Ni), chromium (Cr) (Al element on the substrate sprayed with Al) are adsorbed on titanium oxide, and more than SO _{2 in addition} to vanadium (V) which is a denitration catalyst component.
It is known to accelerate the oxidation of Fe, Cr, Ni, Fe, Cr, Ni, etc.
_{2 This is} a major obstacle to lowering the oxidation rate.

The corrosion prevention of such a metal substrate can be achieved by a method of spraying a large amount of a material which is inert to SO ₂ oxidation, such as ceramic spraying or metal Al, but it causes a significant increase in cost and mass production. There is a problem that sex deteriorates. That is, in the case of a catalyst used in a large amount such as a denitration catalyst, as shown in FIG. 4, the strip-shaped metal substrate 1 is subjected to a metal lath process 2, a thermal spraying process 4, and a catalyst paste 7 by a roller 8.
Coating, forming into a predetermined shape such as a corrugated shape 9, and further cutting 1
0, it is indispensable to incorporate the catalyst frame consistently, and in that case, it is necessary to connect the processes by using the roller type driving devices 13-1 and 13-2 and the tension roller 14-1. For this reason, there is a problem that most of the thick ceramic sprayed layer and the corrosion prevention layer such as a glass-like coating agent are exfoliated due to lack of elasticity and difference in elongation with metal, and the effect is lost.

An object of the present invention is to realize mass production which can prevent deterioration of catalytic performance due to a slight substrate corrosion of a catalyst using a metal substrate, which is a problem of the above-mentioned prior art, and in particular, an increase in SO ₂ oxidation rate at low cost. An object of the present invention is to provide an excellent method for producing a plate-shaped catalyst and a treatment liquid for a metal substrate for a catalyst used in this method.

[0009]

In order to achieve the above object, the first invention of the present application is a method for producing a plate-shaped catalyst in which a catalyst component containing a sulfuric acid component is applied to or coated on a metal substrate. Is coated with a treatment liquid consisting of an organic polymer which is insoluble by heat, colloidal silica and finely divided titania, which is then heated and dried and the organic polymer contained is polymerized / condensed to insolubilize the coating layer. The present invention relates to a method for producing a plate-shaped catalyst, which comprises coating or coating a catalyst component, followed by drying and firing.

A second invention of the present application is characterized in that, in the first invention, the organic polymer is polyvinyl alcohol, the metal substrate is a metal lath, and a sprayed layer of metal aluminum is provided on the surface thereof. The present invention relates to a method for producing a plate catalyst. A third invention of the present application is a method for producing a plate-shaped catalyst in which a catalyst component containing a sulfuric acid component is applied or coated on a metal substrate, and a water-soluble organic polymer of polyvinyl alcohol or vinyl acetate is added in an amount of 0.5 to 0.5%. 5% by weight, 0.5 to 5% by weight of colloidal silica as SiO ₂ , and ₂ % of finely divided titania containing no sulfate group.
The surface of the substrate is coated with a treatment liquid containing 0 to 70 wt% and then heated and dried to insolubilize the coating layer, and at least one of vanadium, molybdenum, and tungsten is added to titanium. The present invention relates to a method for producing a plate-shaped catalyst, which comprises supporting the catalyst component to be dried, followed by firing.

A fourth invention of the present application is the sponge roller according to the third invention, wherein the metal substrate is a belt-shaped substrate, and the metal substrate is continuously supplied into the treatment liquid tank and brought into contact with the treatment liquid. The present invention relates to a method for producing a plate-shaped catalyst, which is characterized in that it is sandwiched between and drained. A fifth invention of the present application is a treatment liquid for coating and pre-treating the metallic substrate prior to coating or coating the metallic substrate with a catalyst component containing a sulfuric acid component. The present invention relates to a treatment solution for a metal substrate for a catalyst, which comprises silica sol and finely divided titania as constituent components.

[0012]

The properties of the constituent components used in the treatment liquid of the present invention alone are as follows, and the present invention is characterized in that a novel effect can be exhibited by combining them. A heat-treated polymerizable film of polyvinyl alcohol (PVA) or the like has high acid resistance and excellent mechanical strength and flexibility, and therefore the formation of a thick film can prevent the above substrate corrosion. When PVA is used alone, it is necessary to use a high-viscosity solution having a high concentration, which not only has a problem in operability, but also disappears when the catalyst supported on the substrate is calcined, resulting in a gap between the catalyst component and the substrate as shown in FIG. The gap 23 causes a large decrease in the remaining strength. In addition, the denitration catalyst component is also excellent in the oxidizing activity of organic matter, and if several percent or more of the organic matter is contained in the catalyst body, abrupt combustion progresses at the time of calcination, leading to burnout of the catalyst.

On the other hand, colloidal substances such as silica sol also form a dense film, but they are not well compatible with metals and have insufficient mechanical strength. For this reason, peeling occurs while passing through the roller type driving device and the tension roller described above (FIG. 4). Further, the fine-grained titania has a low bonding property between particles, the coating film of the slurry is easily peeled off, and the anti-corrosion effect cannot be expected because it is porous.

As described above, an excellent anticorrosion coating can be obtained by insolubilizing the individual components which are not suitable for the metal catalyst substrate in combination within the composition range of the present invention. According to the method of the present invention, as shown in FIG. 1, the titani particles are bonded with the colloidal silica particles, and the gaps between them are filled with PVA, so that a flexible and dense film having high mechanical strength can be formed. It is considered possible.

As a result, not only can an acid-corrosion-resistant coating having a strength that can withstand a roller type driving device necessary for a mass production process can be obtained, but also the following actions and effects can be obtained. (1) The content of organic substances can be suppressed to an extremely low level, and heat generation during calcination of the catalyst can be avoided. (2) Even if PVA disappears by firing, a relatively dense film composed of silica-titania remains, so that the strength reduction that occurs when the organic film is used alone does not occur. (3) The organic film needs to be provided only in the particle gaps shown in FIG. 1 in order to prevent the sulfate radical from coming into contact with the surface of the metal substrate, and the coating thickness can be made extremely low. (4) Since the fine particles of silica and titania accelerate the polymerization of PVA and the like, the insolubilization treatment is completed on the order of seconds and the mass productivity is excellent. (5) Since it is mainly composed of a slurry of fine-grained oxide and has a low viscosity, it does not fill the mesh of the lath substrate or the wire mesh. (6) By the action of PVA, the wettability to the metal surface is improved, and a uniform and defect-free film can be formed.

[0016]

EXAMPLE FIG. 2 shows a manufacturing flow of a catalyst in which the minimum necessary equipments are arranged to carry out the method of the present invention. Thickness 0.2
~ 0.5mm, width about 500mm SUS430 or SUS
The 304 strip 1 is processed into a metal lath by the lath processing machine 2 and then burned with oil adhering during machining in the degreasing furnace 3, and the aluminum spray is sprayed with metal aluminum by the spraying machine 4 to finish the surface rough. Next, a treatment liquid film is formed on the surface of the substrate by passing through the surface treatment liquid tank 5 containing the treatment liquid of the present invention, and then the insolubilization furnace 6 kept at 120 to 200 ° C.
And the organic polymer contained is polymerized / condensed to insolubilize the coating film. Then, separately prepared TiO ₂ and Mo, W, V
The catalyst paste 7 obtained by adding and kneading water and inorganic fibers to the catalyst component consisting of one or more oxides of (1) is pressure-bonded by using the coating roller 8 so as to fill the laths to obtain a plate-shaped catalyst. . The obtained belt-shaped catalyst is further formed into a corrugated or notched chevron to form a spacer in the hydraulic press 9.
It is cut to a length of 300 to 1000 mm. The catalyst element 11 thus obtained is air-dried and then stacked or assembled in a unit 16 as shown in FIG. 3 and calcined at 400 to 600 ° C.

The catalyst of the present invention is produced by the simple method as described above, but the feature of the present invention is that the composition of the treatment liquid and the insolubilization furnace 6 are used, and other steps may be appropriately changed. It goes without saying that you can do it. The composition of the treatment liquid is 0.5 to 5 wt% of a water-soluble organic polymer such as polyvinyl alcohol (PVA) or vinyl acetate.
0.5 to 5 wt% of colloidal silica as SiO ₂ ,
Fine-grained titania is preferably selected in the range of 20 to 70 wt%. As described above, when the amount of the organic polymer compound such as PVA is too large, not only the operability is deteriorated, but also a gap is formed between the catalyst component and the substrate after firing, which causes a decrease in strength. It is preferable to select 1 to 2% to obtain good results.

The colloidal silica amount enough to fill just the TiO ₂ particles gap well, 10-20 wt% by weight of TiO ₂ particles, the liquid density 0.5~5w
Selected as t%. In addition, it is preferable to use TiO ₂ that does not contain a sulfate group obtained by a chlorine method or the like,
Those having a specific surface area of 10 m ² / g or less and an average particle diameter of 1 μm or less are highly dispersed in the liquid and the stability is enhanced.

The same effect can be obtained by coating the metal substrate with the treatment liquid by spraying or brushing.
When a surface-roughened sprayed layer is used, it is dipped in the treatment liquid as shown in FIG. 2 and then sandwiched between sponge-like rollers 12 to remove the excess liquid to form a uniform coating layer. easy. The coating amount is about 50 to 200 g / m ² per unit area of the metal substrate although the coating amount depends on the surface shape, and a film having strong mechanical strength and hardly peeled off is obtained.

Those formed with these coatings are heated to 100 to 200 ° C. in the insolubilization furnace 6 to dry and insolubilize the organic polymer, but the temperature and time are the same as the time when the metal substrate is in the furnace. It is appropriately selected according to the relationship. If the temperature is low and the residence time is short, the insolubilization does not proceed sufficiently, and the film is dissolved by the water in the applied catalyst paste, and a sufficient anticorrosion effect cannot be obtained. On the other hand, when exposed to a high temperature for a long time, not only the film loses its flexibility and peels easily, but also a part of the organic polymer evaporates and the anticorrosion effect also decreases. In the case of the flow shown in FIG. 2, the substrate is continuously supplied at a speed of about 10 m / min,
In the insolubilizing furnace 6, a sufficient effect is obtained with a residence time of about 140 seconds at 140 ° C.

The present invention will be described in detail below with reference to specific examples. Example 1 Polyvinyl alcohol (trade name: Kuraray Popal PV
A-117) Silica sol (trade name: Snowtex-N, SiO ₂ 20 wt) dissolved in 3 kg of water 65 kg
%) 65 kg was added and mixed, and finely divided titania (CR-50 manufactured by Ishihara Sangyo) was added thereto with stirring to obtain a slurry-like treatment agent.

A metal lath (SUS430, thickness: 0.2 mm, spray amount: 50 g /
m ² ) The surface was coated with the above-mentioned treatment agent and insolubilized at 140 ° C. Separately, ammonium molybdate was added to the titanium oxide slurry obtained by the sulfuric acid method with Ti /
What was added so that the Mo ratio was 95/5 atom% was heated and kneaded, dried, and pre-calcined at 500 ° C., and the obtained granules were pulverized to obtain a catalyst raw material. 70 kg of water to 150 kg of this powder
kg and 30 kg of kaolin-based intangible fiber were added and kneaded to prepare a catalyst paste.

The catalyst paste was applied to a metal substrate coated with the above treating agent using a roller type coating machine 8 as shown in FIG. 2 to obtain a plate-shaped catalyst. The obtained plate-shaped catalyst was cut into a chevron shape, cut, air-dried in the atmosphere for 72 hours, and then dried at 500 ° C. for 2 hours.
It was calcined for an hour to obtain a catalyst. Comparative Example 1 The treatment solution used in Example 1 was replaced with a solution prepared by dissolving 3 kg of PVA in 195 kg of water, and a catalyst was prepared in the same manner. Comparative Example 2 The treatment liquid used in Example 1 was treated with 65 kg of silica sol in 130 parts of water.
A catalyst was prepared in the same manner in place of the one diluted with kg. Comparative Example 3 The treatment liquid used in Example 1 was treated with 65 kg of titania powder in water 13
A catalyst was prepared in the same manner as the catalyst suspended in 0 kg. Comparative Example 4 A catalyst was prepared in the same manner as in Example 1 except that the insolubilization temperature was changed to 40 ° C. Example 2 The catalyst composition of Example 1 was used with Ti / Mo / V atomic ratio of 94.5.
The material of the metal lath is SUS instead of /5/0.5.
A catalyst was prepared in the same manner except that 430 was changed to SUS304. Comparative Example 5 A catalyst was prepared without the surface treatment of the present invention in the method described in Example 2. Experimental Example 1 With respect to the catalysts of Examples 1 and 2 and Comparative Examples 1 to 5, the denitration rate and the SO ₂ oxidation rate were measured under the following conditions.

[0024]

[Table 1] The plate catalyst was cut into a rectangle of 100 to 200 mm, and the amount of catalyst stripped when dropping 10 times from a height of 50 cm was measured to calculate the ratio of the stripped catalyst component.

The results obtained are summarized in Table 2.

[0026]

[Table 2] As is clear from this table, when each component constituting the treatment liquid of the present invention is used alone (Comparative Examples 1 to 3), the peeling rate of the catalyst is high and the bonding strength between the catalyst and the metal substrate is low. It can be seen that the catalyst stripping rate is remarkably reduced by using the treatment liquid in which the respective components are mixed at a predetermined ratio (Examples 1 and 2). In addition, the catalysts of the comparative examples are all SO compared to the examples.
_{2 The} oxidation rate is high, and the higher one shows a value more than 4 times. This also shows that the method for treating a metal substrate of the present invention has a remarkable effect in reducing the SO ₂ oxidation rate of the denitration catalyst.

Further, any NOx removal efficiency of the catalyst of Example showed a high value compared with that of Comparative Example, the present invention is SO ₂
It is shown that not only the increase of the oxidation rate is prevented but also the reduction of the denitration rate due to the dissolution of the sprayed Al layer is prevented. Example 3 The catalyst component of Example 1 was changed to Ti / W = 9/1 (atomic ratio),
A catalyst was prepared by changing the SUS430 substrate to the SUS304 substrate and changing the catalyst firing temperature from 500 ° C to 600 ° C. Comparative Example 6 A catalyst was obtained by using the metal lath which was not subjected to the surface treatment of the present invention in the preparation of the catalyst of Example 3. Experimental Example 2 The catalysts of Example 3 and Comparative Example 6 were held at 600 ° C. for 500 hours to examine changes in denitration performance. In the catalyst of Comparative Example 6, iron moved from the metal substrate into the catalyst component due to thermal diffusion and turned reddish brown, showing a large decrease in activity. On the other hand, the catalyst of Example 3 did not show discoloration and showed almost no activity decrease.

As can be seen from these results, the method of the present invention is effective not only for the influence of the substrate components due to the sulfuric acid corrosion during the catalyst production but also for the prevention of the deterioration due to the thermal diffusion of the substrate components.

[0029]

EFFECTS OF THE INVENTION According to the present invention, it is possible to obtain a catalyst having a high denitration rate as well as being able to prevent an increase in the SO ₂ oxidation rate due to substrate corrosion during the catalyst production of the denitration catalyst using a metal substrate. Become. As a result, it is possible to easily obtain a denitration catalyst having a reduced SO ₂ oxidation activity without thickening an expensive surface treatment layer such as thermal spraying, and it is possible to meet the increased demand in recent years.

Further, the surface treatment of the present invention is effective not only in the production of the catalyst but also in the prevention of the catalyst deterioration due to the thermal diffusion of the substrate components which becomes a problem when the catalyst is used at a high temperature.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a metal substrate surface coating layer of a catalyst obtained in the present invention.

FIG. 2 is a flow chart of the catalyst production method of the present invention.

FIG. 3 is a view showing a catalyst unit in which a corrugated plate catalyst according to the present invention is housed in a frame.

FIG. 4 is a flow chart of a conventional catalyst manufacturing method.

FIG. 5 is an explanatory diagram of a problem to be solved by the present invention.

[Explanation of symbols]

1 ... Stainless strip, 2 ... Lath processing machine, 3 ... Degreasing furnace, 4
... Spraying machine, 5 ... Surface treatment liquid tank, 6 ... Insolubilizing furnace, 7 ... Catalyst paste, 8 ... Coating roller, 9 ... Molding machine, 10 ... Cutting machine, 11 ... Catalyst element, 12 ... Sponge roller, 1
3 ... drive roller, 14 ... tension roller, 15 ... outer frame, catalyst unit.

Claims (5)

[Claims] 1. A method for producing a plate-shaped catalyst in which a catalyst component containing a sulfuric acid component is applied to or coated on a metal substrate, which is a treatment comprising an organic polymer which is previously insolubilized by heat on a metal substrate, colloidal silica and fine titania. A plate characterized in that it is coated with a liquid, then heated and dried, and the organic polymer contained therein is polymerized / condensed to insolubilize the coating layer, and the catalyst component is applied or coated on this, followed by drying and firing. Of producing a particulate catalyst. 2. The method for producing a plate-shaped catalyst according to claim 1, wherein the organic polymer is polyvinyl alcohol, the metal substrate is a metal lath, and a sprayed layer of metal aluminum is provided on the surface thereof. 3. A method for producing a plate-shaped catalyst, which comprises coating or coating a metal substrate with a catalyst component containing a sulfuric acid component, wherein the water-soluble organic polymer of polyvinyl alcohol or vinyl acetate is 0.5 to 5 wt%. A treatment liquid containing 0.5 to 5 wt% of colloidal silica as SiO ₂ and 20 to 70 wt% of fine titania containing no sulfate is coated on the surface of the substrate, and then heated and dried to insolubilize the coating layer. A method for producing a plate-shaped catalyst, which comprises supporting a catalyst component containing at least one of vanadium, molybdenum, and tungsten in addition to titanium, drying and calcining. 4. The metal substrate according to claim 3, wherein the metal substrate is a belt-shaped substrate, and the metal substrate is continuously supplied into the treatment liquid tank to be brought into contact with the treatment liquid, and then sandwiched between sponge rollers to drain the liquid. A method for producing a plate-shaped catalyst, which is characterized. 5. A pretreatment liquid for coating the metallic substrate prior to coating or coating with a catalyst component containing a sulfuric acid component, which comprises an organic polymer, silica sol, and finely divided titania. A treatment liquid for a metal substrate for a catalyst, which is a component.