KR19980083491A - Coating of catalyst on surface of surface oxidized plate - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of coating a catalyst on a surface of a plate made of iron, aluminum, nickel, copper, zinc, tungsten or an alloy composed mainly of them in a high temperature air atmosphere, after surface oxidation.

Description

Coating of catalyst on surface of surface oxidized plate

FIG. 1 is a SEM photograph of the aluminized steel plate of (A) when not surface oxidized by heat treatment and (B) when surface oxidized at 550 ° C. for 10 hours.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of coating a catalyst on a surface of a plate made of iron, aluminum, nickel, copper, zinc, tungsten or an alloy composed mainly of them in a high temperature air atmosphere, after surface oxidation.

In order to effectively coat the material to be coated on the surface of a substrate, the technique of surface treatment of the substrate in an appropriate manner determines the overall coating performance. Generally, the surface treatment method is distinguished according to the substrates of iron, aluminum, polymer, and plastic systems. [JM Sykes, in Surface Analysis and Pretreatments of Plastics and Metals (D.M. Brewls, Edr.), Applied Science Pub., London, 1982, J.M. Lane and D.J. Hourston, Prog. Org. Coat. 21 (1993) 269].

Mechanical treatment, alkaline cleaning, chemical etching and acid anodizing to ensure that a uniform, new oxide layer is exposed on the surface of the iron or aluminum substrate. Surface treatment methods such as) have been used industrially [S. Paul, in Surface Coatings: Science Technology (S. Paul, Edr., 2 Edn.), John Wiley Sons, Chichester, 1996].

Mechanical treatment mainly uses grit blasting, sanding or scrubbing, and in alkaline cleaning, solid alkali salts are mixed with a humectant. Difficult to achieve For this reason, etching and acidic anodizing have been developed to compensate for the disadvantages of mechanical treatment and alkali cleaning. In the etching method, mainly chromic acid / sulfuric acid or dichromic acid / sulfuric acid are used, and sulfuric acid, chromic acid or phosphoric acid is mainly used in anodizing. In this way, the surface of the surface of the iron or aluminum-based substrate treated with a uniform new ridge shaped oxide layer is formed to maintain excellent adhesion of the coating material.

As described above, in order to obtain excellent adhesion of the coating material, the surface treatment process of the substrate is required, and in order to obtain the most effective coating, since an oxide layer in the form of a projection is formed on the surface of the treated substrate, such as etching or anodizing Surface treatment techniques have been widely used in the industry, and as a method of attaching a catalyst, paint type high temperature adhesives are mainly used. However, since the surface treatment method uses acid in a solution state, problems with facility corrosion and waste solution treatment occur, and catalyst coating by heat-resistant paint causes specific surface area reduction by blocking the pores of the catalyst.

Accordingly, the present invention provides a catalyst coating method that does not use a high temperature adhesive of paint type on a plate obtained by thermal surface oxidation, which is a more economical and environmentally friendly surface treatment technique.

More specifically, the coating method of the catalyst according to the present invention is to oxidize the surface of the plate by heat treatment in the reactor of the air atmosphere to form a uniform new new ridge-like oxide layer on the surface of the plate, consisting of a catalyst and an additive It is characterized in that the slurry is coated on the surface of the surface-treated plate.

Hereinafter, the present invention will be described in detail.

In the present invention, when the surface of the plate is oxidized in a high temperature air atmosphere in order to form a molten bump-like oxide layer that can improve the adhesion of the catalyst on the surface of the plate, the temperature of the heat treatment can be adjusted according to the material and processing time of the plate And it is applicable if it is a temperature which can form a uniform oxide layer on a plate surface, Usually, the range of 300-1200 degreeC is preferable, and the range of 500-900 degreeC is especially preferable. When the heat treatment temperature is 300 ℃ or less, a new oxide layer which hardly maintains a good adhesion of the catalyst is hardly formed or uniform even when the oxide layer is formed, and when the heat treatment temperature is 1,200 ℃ or more, the plate may melt depending on the material of the plate. However, it is not preferable because no further improvement of the surface treatment effect can be expected as the temperature increases.

The treatment time for surface oxidation of the plate can be adjusted in consideration of the material of the plate, preferably in the range of 5 to 15 hours. When it is out of such a range, it is not preferable for the same reason as mentioned above regarding heat processing temperature.

The material of the plate to be surface-treated in the present invention may be iron, aluminum, nickel, copper, zinc, tungsten or an alloy containing them as a main component. In particular, when the catalyst is attached to a surface-oxidized plate and subjected to heterogeneous catalysis, iron, aluminum, stainless steel, or an alloy containing these as a main component is preferable.

When coating using a coating slurry consisting of a catalyst and an additive on a surface oxidized plate by heat treatment, CuHM, V ₂ O ₅ / TiO ₂ V ₂ O ₅ -WO ₃ / TiO ₂ was used as the catalyst in the present invention. However, the catalyst is not particularly limited.

In the coating process of the catalyst, at least one selected from the group consisting of colloidal alumina, colloidal silica, phosphoric acid, cellulose and starch may be selected as an additive used for controlling the coating performance and the properties of the coating slurry. Of these additives, colloidal alumina is more effective when used with hydrophobic catalysts and colloidal silica with hydrophilic catalysts. Examples of the cellulose include methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose and ethyl hydroxyethyl cellulose, and their reference viscosity is preferably 1,500 to 50,000 cps. If it is 1,500 cps or less, more amount is required to control the desired adhesion and physical properties, which causes a decrease in the activity of the catalytic reaction, the mixing and coating performance of the coating slurry is not good when it is above 50,000 cps.

Coating performance of the catalyst can vary depending on the combination of catalyst and additives, and the ratio of catalyst and additives used. For example, the coating slurry for coating the CuHM catalyst to maintain a stable adhesion to the aluminized steel plate is CuHM and colloidal alumina in a weight ratio of 1: 0.1 to 0.6, or CuHM and colloidal alumina and starch 1: 0.1 When used in a weight ratio of ˜0.6: 0.1 to 0.6, it provides excellent coating performance. Especially, when colloidal alumina and starch are used together, it provides optimum coating performance. The composition of this coating slurry is not limited to the catalyst and is effective for other hydrophobic catalysts. Since CuHM catalysts are hydrophobic, colloidal silica exhibits very heterogeneous mixing and coating properties. In addition, when a small amount of 85% phosphoric acid was added to a slurry of a CuHM catalyst and colloidal alumina, an aluminophosphate (AlPO4) gel was formed by a chemical reaction between colloidal alumina and phosphoric acid [E. Jahn, D. Muller, W. Wieker and J. Richter-Mendau, Zeolites, 9 (1989) 177].

In addition, V ₂ O ₅ / TiO ₂ or V ₂ O ₅ -WO ₃ / TiO ₂ and colloidal silica are used in a weight ratio of 1: 0.02 to 0.5, or V ₂ O ₅ / TiO ₂ or V ₂ O ₅ -WO ₃ / When TiO ₂ and colloidal silica, phosphoric acid, cellulose and starch are used in a weight ratio of 1: 0.02 to 0.5: 0.01 to 0.3: 0.01 to 0.3: 0.01 to 0.3, they provide excellent coating performance, especially V ₂ O ₅ / TiO ₂ catalyst. The use of a coating slurry consisting of colloidal silica, 85% phosphoric acid, methylcellulose and starch together provides optimum coating of the catalyst. The composition of this coating slurry is not limited to the catalyst and is effective for other hydrophilic catalysts. Since the V ₂ O ₅ / TiO ₂ catalyst is hydrophilic, the addition of colloidal alumina does not give an effective coating. Additives such as phosphoric acid, methylcellulose, and starch are required to complement the adhesion of the coating slurry on the aluminized steel plate, to obtain proper coating viscosity, dispersion of the slurry and control of the coating thickness, and uniform coating. The ratio of these to the catalyst must be determined very carefully. The composition of the coating slurry is not limited to aluminized steel plates but also applies to substrates made of stainless steel or iron or aluminum alloys.

Coating of the coating slurry of the catalyst and the additive on the surface-treated plate can be carried out by conventional methods such as roll coating.

Coating the catalyst on the surface-treated plate as described above can be used in the manufacture of low pressure difference reactor for the removal of contaminants such as nitrogen oxides, sulfur oxides, carbon monoxide, unburned hydrocarbons, volatile organic compounds and catalytic combustion reaction. However, the case where the catalyst coated plate can be used by the method provided by the present invention is not limited to the field of the catalyst use.

Hereinafter, the present invention will be described in detail through examples.

Example 1. Catalyst Preparation and Physical Properties

V ₂ O ₅ / TiO ₂ and CuHM catalysts were prepared by supporting and ion exchange methods, respectively. The physicochemical properties of the prepared catalysts are shown in Table 1. First, the V ₂ O ₅ / TiO ₂ catalyst was mixed thoroughly with distilled water and titania and ammonium metavanadate solution completely dissolved in an oxalic acid solution. The mixture was stirred for 30 minutes and then stirred at 300 ° C for 3 hours and at 500 ° C for 2 hours. It was prepared by firing.

Zeolon 900Na mother catalyst of PQ Co. was ion exchanged with ammonium ions in a 1N ammonium nitrate solution at 90 ° C, and then repeatedly exchanged with Cu ²⁺ ions for 8 hours at 90 ° C with 1N copper nitrate solution. The CuHM catalyst was prepared by washing and drying and firing for 10 hours in an air atmosphere at 500 ° C.

Table 1 Physical and Chemical Properties of Catalysts

^★ V ₂ O ₅ weight ratio, ^★★ Cu weight ratio

EXAMPLE 2 Surface Treatment of Aluminized Steel Plate and Adhesion of Catalyst

The surface of the aluminized steel plate was thermally oxidized in an air atmosphere using a EUROTHERM (Model 808P) reactor. Scanning electron microscopy of the surface shape of the plate oxidized at 450 ° C, 500 ° C and 550 ° C, respectively, during the treatment time fixed at 10 hours to determine the optimum processing temperature required for the formation of a uniform, new oxide layer on the surface. Observed. At this time, the temperature increase rate up to the final temperature was kept constant at 5 ° C. per minute regardless of the treatment temperature. The adhesion of the coating slurry of CuHM or V ₂ O ₅ / TiO ₂ catalyst and additives to the aluminized steel plates thus treated was compared at different treatment temperatures.

When the surface shape of the aluminized steel sheet and the adhesion performance of the catalyst were compared with each surface treatment temperature, when the surface treatment was performed at a processing temperature of 550 ° C, an aluminized steel sheet having a more uniform surface oxide layer could be obtained. The surface shape is shown in FIG. Thus, the aluminized steel plate having a uniform and new villus-shaped oxide layer exhibited a stable and strong catalyst adhesion performance.

On the other hand, a coating slurry of CuHM and V ₂ O ₅ / TiO ₂ catalysts and additives was coated on an aluminized steel plate which was not treated by thermal surface oxidation, and the adhesion of these catalysts was excellent. When calcined for 3 hours in an air atmosphere, the attached catalyst was completely dropped. Therefore, it was confirmed that the surface treatment process is required in order for the catalyst to maintain excellent adhesion on the surface of the plate, and that the surface of the plate subjected to the surface treatment should have an oxide layer in the form of a projection.

Example 3 Coating Slurry Preparation and Coating Performance

In order to provide an optimum coating of CuHM, V ₂ O ₅ / TiO ₂ or V ₂ O ₅ -WO ₃ / TiO ₂ catalyst on the surface of the aluminized steel plate of Example 2 subjected to oxidation treatment at 550 ℃ for 10 hours. Based on the catalyst weight in the coating slurry, the optimum composition ratio of colloidal silica, colloidal alumina, phosphoric acid (85%, Aldrich Chemical Co.), methyl cellulose (4,000 cps, Aldrich Chemical Co.) and starch (Shinyo Pure Chemical Co.) Decided.

In the case of the commercial catalyst V ₂ O ₅ -WO ₃ / TiO _{2 It} was possible to obtain excellent coating performance by coating with a weight ratio of colloidal silica to 0.07 catalyst, CuHM and V ₂ O ₅ / TiO prepared directly in the present invention the mole fraction of the slurry for optimal coating of the _second catalyst are given in Table 2 and Table 3.

Table 2: Optimal Coating Slurry Composition of CuHM Catalyst

Table 3 Optimal Coating Slurry Composition of V ₂ O ₅ / TiO ₂ Catalyst

Claims (14)

A method of coating a catalyst, characterized in that the surface of the plate is oxidized by heat treatment in an air atmosphere to form an oxide layer on the surface of the plate and to coat the catalyst on the surface of the plate on which the oxide layer is formed. The method of claim 1, wherein the heat treatment is characterized in that performed at a temperature range of 300 ~ 1200 ℃. The method according to claim 1, wherein the plate is made of iron, aluminum, nickel, copper, zinc, tungsten or an alloy containing these as main components. 4. The method of claim 3 wherein the plate is an aluminized steel plate. The method of claim 1, wherein the catalyst coating is characterized in that the coating surface of the plate with a coating slurry of at least one additive and a catalyst selected from the group consisting of colloidal silica, colloidal alumina, phosphoric acid, cellulose and starch. 6. The method of claim 5 wherein the cellulose is methyl cellulose, hydroxypropyl methylcellulose, hydroxyethyl cellulose or ethyl hydroxyethyl cellulose. The method of claim 6, wherein the cellulose has a reference viscosity of 1,500 to 50,000 cps. 6. The process of claim 5 wherein the catalyst is CuHM, V ₂ O ₅ / TiO ₂ or V ₂ O ₅ -WO ₃ / TiO ₂ . 9. The process according to claim 8, wherein at least one selected from CuHM as a catalyst and colloidal alumina and starch as an additive is used. 10. The method of claim 9, wherein CuHM and colloidal alumina are used in a weight ratio of 1: 0.1 to 0.6. 10. The method of claim 9, wherein CuHM, colloidal alumina, and starch are used in a weight ratio of 1: 0.1 to 0.6: 0.1 to 0.6. 9. A method according to claim 8, characterized in that at least one selected from colloidal silica, phosphoric acid, methyl cellulose and starch is used as V ₂ O ₅ / TiO ₂ or V ₂ O ₅ -WO ₃ / TiO ₂ as an additive and as an additive. Way. The method according to claim 12, wherein V ₂ O ₅ / TiO ₂ or V ₂ O ₅ -WO ₃ / TiO ₂ and colloidal silica are used in a weight ratio of 1: 0.02 to 0.5. The method according to claim 12, wherein V ₂ O ₅ / TiO ₂ or V ₂ O ₅ -WO ₃ / TiO ₂ and colloidal silica, phosphoric acid, methylcellulose and starch are 1: 0.02 to 0.5: 0.01 to 0.3: 0.01 to 0.3: 0.01 A weight ratio of ˜0.3.