KR100641694B1 - Titania manufacturing method for denitrification catalyst extrusion - Google Patents

Abstract

         Selective Catalytic Reduction (SCR) is used to reduce nitrogen oxides in the exhaust gas.The catalyst is a product that is dried and calcined by extrusion molding in the form of honeycomb by mixing a carrier material and a catalyst material. The furnace is mainly Titania. The present invention is a method for producing titania loaded with tungsten oxide excellent in extrusion property and excellent in performance as a catalyst, and a configuration thereof. Method for preparing titania powder loaded with tungsten oxide suitable for denitrification catalyst extrusion which can control the primary and secondary particle size of titania, the specific surface area can be controlled, and the average particle pore size is over 100Å. The composition is disclosed. The powder is obtained by adjusting the hydrolysis process of titanium sulfate produced in the manufacturing process performed by the sulfuric acid method, which is one of the industrial titania manufacturing processes, to be suitable for catalytic performance and extrusion molding, to obtain metatitanic acid, and neutralize the obtained metatitanic acid with a basic solution. In the case where a precursor capable of forming tungsten oxide is dissolved and added, followed by drying and firing to prepare titania powder, tungsten oxide may be loaded in an amount of 0.1 to 15 wt% based on titania. This can be applied as a carrier material for extrusion molding of selective reduction catalyst (SCR) that effectively removes nitrogen oxides (NOx) discharged from thermal power plants, incinerators, various chemical plants, and the like.

        Nitrogen compounds (NOx), SCR (Selective Catalytic Reduction), Titania, Tungsten Oxide, Extrusion                                                                                                                                                                                                                                                                                                

Description

Manufacturing Method of Titania for Extrusion Forming of De-NOx Catalyst

1 is a manufacturing process diagram of a titania supported on tungsten oxide.

2 is an X-ray diffraction analysis (XRD) result diagram of the tungsten oxide-supported titania powder prepared in Example 2. FIG.

Figure 3a is a tungsten dispersion measurement results using the EDS of the tungsten oxide loaded titania powder prepared in Example 2.

3b is a result of measuring tungsten dispersion using EDS of the tungsten oxide-supported titania powder prepared in Example 4. FIG.

Figure 4a is a result showing the nitrogen oxide removal efficiency for Example 2, 3, 4, commercial A when NH ₃ / NOx is 0.8.

Figure 4b is a result showing the nitrogen oxide removal efficiency for Example 2, 3, 4, commercial A when NH ₃ / NOx is 0.8.

The present invention relates to a method for preparing titania powder for flue gas denitrification (De-NOx) catalyst carrier extrusion molding and its composition, and more particularly, to a method for producing particulate titania having a specific surface area and an average pore size in a particle of 100 mm 3 or more. It is about.

In particular, when used as a catalyst by extrusion molding, a suitable titania should be supplied to the extrusion process, since the secondary particle size and pore structure influence the production efficiency by controlling the strength and shrinkage rate of the final catalyst and the topdressing characteristics in the extrusion process. Hydrolysis processes that control the particle size and pore structure of metatitanium are very important. In addition, since the sulfur compound (SO ₃ ) contained in titania is involved in the binding force between the clay in the extrusion process and the catalytic performance, the content control is essential.

Sulfuric acid method In the titania manufacturing process, hydrolysis conditions are controlled and used for various purposes such as pigments, rubbers, ceramic fillings, and medical use. Hydrolysis conditions are controlled by the amount of seed required to grow the particles, hydrolysis concentration, hydrolysis temperature, stirring conditions, reaction time, so that the hydrolysis process control is essential to obtain metatitanic acid suitable for extrusion molding to be.

The SCR process reacts harmful nitrogen oxides (NOx) generated in exhaust gases such as thermal power plants, large-scale incinerators, and various chemical plants with ammonia (NH ₃ ) in the presence of a suitable catalyst to produce harmless nitrogen (N ₂ ) and water (H _2). O) is a method of decomposing into a reaction, characterized in that the reaction of NH ₃ and SO ₂ does not occur in addition to the reaction of NOx and NH ₃ , denitrification catalyst mainly vanadium (V), tungsten (W), molybdenum (Mo), Oxides such as nickel (Ni), iron (Fe), and copper (Cu) are used, and as the catalyst carrier, titania, alumina, silica, zirconia, and the like are mainly used.

The catalyst for reducing flue gas denitrification mainly contains vanadium, molybdenum, nickel, and tungsten oxide, which are catalyst components exhibiting a denitrification effect, such as titania, alumina, silica, zirconia, and the like having a large specific surface area. It is manufactured by heat treatment by mixing and supporting the surface of the carrier (US Pat. No. 5,827,489), and this method is manufactured by a process of preparing, supporting and calcining the catalyst and the carrier, respectively, which has a disadvantage of complicated process and high manufacturing cost. .

Among the raw materials, titania is divided into rutile phase and anatase phase, and the rutile phase is mainly used for white pigment, and when the anatase phase has higher oxidation power than rutile phase As the activity of light is high, as disclosed in Korean Patent Registration No. 0430405, it is widely used as a photocatalyst for decomposing organic matter by receiving light and surface activation. In addition, fine titania having a anatase phase has a chemical stability that does not easily react with sulfur compounds, and is used as a carrier material for the denitration catalyst to remove nitrogen compounds by supporting a metal oxide having a large specific surface area and exhibiting catalytic efficacy.

In the manufacture of SCR carriers for denitrification catalysts, the SOx concentration of the flue gas is high depending on the operating conditions, and when the reaction of NH ₃ and SOx proceeds, the NOx removal efficiency is reduced and the catalyst life is shortened. Therefore, the catalyst carrier does not react with the sulfur compound. It must be suspiciously toxic, have a large specific surface area for uniform loading of catalyst components and sufficient catalytic activity sites, and sufficient acid spots to increase NOx removal efficiency in contact with ammonia, and And the pores in the raw material particles should be large enough so that there is no restriction on the movement of the reactants, and also because the characteristics of the clay are very important in extrusion molding, optimization of wettability, plasticity, particle size distribution, shrinkage rate, etc. Required physical properties are required.

The present invention has been made to solve the above problems, high catalyst extrusion molding productivity, excellent denitrification catalyst ability, large specific surface area and average particle pore size, easy to control the physical properties and uniformly carrying the catalyst component flue denitrification It is to provide a titania powder for catalyst carrier extrusion.

That is, an object of the present invention is to obtain a meta-titanium suitable for denitrification catalyst extrusion through a hydrolysis process, and to dissolve and add the tungsten oxide precursor during the treatment process, the primary particle size of 10 ~ 50nm by the heat treatment process It provides a composition having a specific surface area of 50 m 2 / g or more, a particle average pore size of 100 GPa or more, and uniformly supported and distributed tungsten oxide with a titania of chemically stable anatase crystals as a main raw material. .

In the case of tungsten oxide supported on titania, the ammonia injected into the reaction gas is prevented from reoxidation to NOx in the catalytic reaction, thereby improving the catalyst efficiency and operating conditions for operating the SCR system in a wide temperature range. There is an advantage to providing.

In order to realize the above object, in the present invention

In order to obtain the required metatitanic acid, titanium sulfate has primary particles of 10 nm or less by controlling the hydrolysis conditions, that is, the concentration of anatase seed, the hydrolysis temperature, the stirring speed during the hydrolysis, and the reaction time, It provides a process technology for forming secondary aggregated particles, obtaining a metatitanium slurry in which SO ₃ accounts for 4 to 5% by weight relative to TiO ₂ , and provides a tungsten oxide-supported titania composition comprising 0.1 to 15% by weight of tungsten oxide. do.

In particular, the titania is preferably in the anatase crystal phase, the titanium sulfate concentrate is 90 ~ 120 ℃ hydrolysis reaction temperature, 0.2 ~ 0.4 wt% seed dose, 4 ~ 8 hours reaction time, 30 ~ 60rpm stirring range Various kinds of metatitanium can be obtained by using the method, and metatitanic acid can be used to remove impurities by washing with water, disperse using a basic solution, neutralize, add precursors, dry, and calcinate to produce anatase crystalline titania. Ammonium Meta Tungstate ((NH ₄ ) ₆ W ₁₂ O ₃₉ · _X H ₂ O), Ammonium Para Tungstate ((NH ₄ ) ₁₀ W ₁₂ O ₄₁ ), Ammonium Tungstate to form tungsten oxide in the process Soluble ammonium salt selected from (H ₈ N ₂ O ₄ W), WX _a (X = Ci, Br, etc., a = 4-6), WO _{a '} X _b' (X = Cl, Br, etc., a '= 1 Tungsten halide or tungsten oxide (WO ₃ ), tungstic acid (H ₂ WO ₄ ), tungsten oxide phosphate hydrate (H ₃ O ₄₀ PW ₁₂ ), tungsten hydroxide silicide ( H ₄ O ₄₀ SiW ₁₂ ), sulfide (H ₈ N ₂ S ₄ W) acid form may be preferably applied. This tungsten oxide is to be added 0.1 to 15% by weight based on the final heat treatment titania. If the tungsten precursor is not dissolved in the solvent in the addition, it is not supported on titania but is simply mixed, so that the tungsten precursor may not perform the catalytic role of tungsten correctly in the catalytic reaction and degrade the catalyst efficiency or catalyst durability. It must be dissolved and aqueous so that it can be uniformly supported on the particles, pores and surfaces of titania.

In addition, it is preferable that the specific surface area of titania is 50-120 m <2> / g. It is not preferable that the specific surface area is smaller than 50 m 2 / g because of insufficient support and reaction site of the catalyst component, and larger than 120 m 2 / g, the pore size is very small and the crystal size is small, so that the crystallinity is poor. It may not exhibit 100% of the function, and may cause problems during drying after extrusion of the carrier, and may not have sufficient strength and durability, and thus may not sufficiently serve as a support. In addition, the average pore size of the particles is preferably 100 kPa or more. If the pore size is too small, the sulfur compound and the material after the reaction may be trapped by capillary force, and thus sulfur poisoning may occur and the catalytic activity site decreases, which is not preferable.

Hereinafter, the present invention will be described in more detail with reference to specific examples.

AMT (Ammonium Meta Tungstate ((NH ₄ ) ₆ W ₁₂ O ₃₉ · _X H), which forms a tungsten oxide after heat treatment in the additive addition step, following the process disclosed in Korean Patent Registration No. 0430405, issued April 23, 2004. ₂ O)) and APT (Ammonium Para Tungstate ((NH ₄ ) ₁₀ W ₁₂ O ₄₁ )) was added.

<Example 1>

1 L of concentrated titanium sulfate solution of 150-250 g / L (based on TiO ₂ ) was added to a stainless reactor equipped with an oil pipe capable of heating circulation, and anatase seed was added 0.25%. The temperature of the reactor solution at this time was used as the reactor temperature 90 ~ 120 ℃ through the oil circulation by the heating device. After adding the anatase seed, the primary water is added to make the concentration 140 ~ 150g / L, followed by agitation at a maximum of 60rpm for up to 4 hours, and the secondary water is added to the TiO ₂ reference concentration of 100-120g / L, and then up to 60rpm. Stir up to 4 hours, cool and end. The finished solution was obtained as a metatitanium slurry through two washes / filtrations. It was obtained by adjusting the metatitanium particles of 2.5㎛ or less while changing the above conditions. The secondary particle size can be adjusted to 1 ~ 2.5㎛ by controlling the stirring speed, temperature, reaction time during the hydrolysis conditions, the conditions are shown in Table 1.

Comparison of Hydrolysis Conditions of Example 1 Reaction temperature (℃) Stirring Speed (rpm) Total reaction time Etc Example 1-1 95 30 4 seed Input same mantissa concentration Example 1-2 95 30 8 Example 1-3 95 60 4 Example 1-4 95 60 8 Example 1-5 110 30 4 Example 1-6 110 30 8 Example 1-7 110 60 4 Example 1-8 110 60 8

<Example 2>

The conditions of metatitanic acid are those prepared with metatitanic acid (TiO (OH) ₂ ) having a primary particle of 10 nm or less, a specific surface area of 300 m ² / g or more, and a secondary average particle diameter of 1 to 1.5 μm. To reduce impurities and sulfuric acid components in 300 g of metatitanic acid (based on TiO ₂ ), 2 liters of water is added to the water to reduce impurities and sulfuric acid, which is then filtered and washed with impurities to remove the filtrate. 1.5 liters of water was added to the metatitanic acid separated from the filtrate, neutralized to pH 7-9 by addition of aqueous ammonia, and filtered again. 1 liter of water was added to the filtered metatitanic acid hydrous cake and stirred. Since tungsten precursor Ammonium Meta Tungstate ((NH ₄ ) ₆ W ₁₂ O ₃₉ · _X H ₂ O) is dissolved in water, it is dissolved in 0.3 liter of water so that it is about 10% by weight with respect to titania, and then in a reactor in which metatitanic acid is stirred. Add tungsten solution and react for 2 hours or more. It was dried at 150 ° C. for at least 20 hours, and then pulverized by heat treatment at 500 to 700 ° C. for 1 to 4 hours to obtain a powder.

<Example 3>

In the same process as in Example 2, a tungsten precursor is prepared using Ammonium Para Tungstate ((NH ₄ ) ₁₀ W ₁₂ O ₄₁ , hereinafter APT), which is an inorganic chemical product that is insoluble in general water. Nitric acid was added to 0.3 liters of water to adjust the pH to 1 or less, and APT was added so as to be about 10% by weight with respect to titania. The following steps were the same as in Example 2.

<Example 4>

In the same process as in Example 2, the tungsten precursor was added to tungsten trioxide (WO ₃ , 99% purity), which was added to the reaction tank by mixing 10% by weight of tungsten trioxide to titania in 0.3 liter of water. The following steps were the same as in Example 2.

<Test Example 1-Property Comparison>

The physical properties of the metatitanic acid powder prepared in Example 1 and the commercially available titania powders of commercial A company similar to the titania loaded with tungsten prepared in Examples 2 to 4 were investigated. The metatitanic acid powder of Example 1 was analyzed for specific surface area and secondary particle size, and Examples 2 to 4 and commercial A company powder were analyzed for crystal phase, composition, specific surface area, pore size, and particle size. The composition of the powder was uniformly mixed and ground with a binder and filled into a 40 mm round mold, and press-molded to obtain pellets. The oxide composition was analyzed using an X-ray fluorescence analyzer (Venes200, Philips Co.). For powder phase analysis, powder X-ray diffraction analysis was performed at 4 ° / min using CuKα X-ray. In addition, the specific surface area and pore size were measured by a pore analyzer (ASAP2010, Micromeritics Co.) to investigate the specific surface area and pore distribution. In addition, the second average particle size was measured by a particle size analyzer (Accusizer, PSS Co) that is a laser dispersion method. In order to compare the degree of loading of tungsten, the dispersion of tungsten was evaluated by SEM-EDS tungsten mapping for the powders of Examples 2 and 4.

Physical Properties of Metatitanic Acid Obtained through Example 1 Specific surface area (BET, ㎡ / g) Particle diameter (D50, μm) Example 1-1 358 1.09 Example 1-2 310 1.45 Example 1-3 320 1.21 Example 1-4 320 1.25 Example 1-5 297 1.76 Example 1-6 266 2.35 Example 1-7 300 1.54 Example 1-8 277 1.95

Various metatitanic acids were obtained by adjusting the reaction time, reaction temperature, and stirring speed as conditions for obtaining metatitanic acid through Example 1, and prepared metatitanic acid having excellent physical properties and catalytic performance suitable for extrusion molding. In general, the particle size used in extrusion molding is the particle size obtained under the conditions of Examples 1-3 and 1-4, and the secondary average particle diameter of metatitanium is prepared as the particle size at the time of final titania production, and the primary particle diameter is a condition of heat treatment. It grows and regulates accordingly. By utilizing the above conditions, it is possible to control the size of the appropriate particle size in extrusion molding as needed.

Physical property analysis results for the titanium dioxide composition prepared through the Example Example 2 Example 3 Example 4 Commercial A Crystal phase Anatase Anatase Anatase Anatase Specific surface area (m2 / g) 95 93 92 94 Pore size 121 120 130 122 Average particle size (㎛) 1.21 1.23 1.22 1.31 Main composition (% by weight) WO3 9.87 9.75 9.71 9.88 TiO2 88.51 88.62 88.61 88.71 SO3 0.91 0.87 0.89 1.33

As shown in Table 3, most of the physical properties prepared through the examples were prepared in a similar manner, in particular, the pore size of Example 4 was 130 Å, which was slightly larger than those of Examples 2 and 3. This is indirectly seen from the pore size that the composition is similar but not uniformly supported on the surface because tungsten trioxide was mixed in the form of powder particles rather than uniformly supported on the pores and the surface by dissolving the tungsten precursor. In addition, the EDS tungsten scanning result of FIG. 3 shows that when the tungsten aqueous solution of Example 2 was supported rather than when tungsten trioxide was mixed, the EDS scanning result was well and uniformly supported.

<Test Example 2-Comparison of Catalyst Performance>

The catalytic performance was compared by further loading 1 wt% of vanadium on the powders of Examples 2 to 4 and titania powder of the commercial A company. Ammonium vanadate was dissolved in sufficient water with a ratio of 1: 2 to oxalic acid and dissolved, followed by calcining at titania powder mixture / drying / 500 ° C. for 1 hour. The mixed powder was loaded into the catalytic measuring device reactor and the NOx removal efficiency was compared. The NOx removal efficiency was evaluated under conditions of NH ₃ / NO ratio 0.8 ~ 0.9, NO concentration 500ppm, O ₂ 15%, temperature 200 ~ 500 ℃, space velocity 10,000hr ^-1 .

Figure 4 is a result of comparing the catalytic performance, it can be said that the tungsten supporting method is very important because the NOx removal efficiency of Examples 2 and 3 is superior to Example 4. It is considered that the catalytic reactor can be operated under a wide range of operating conditions because it shows high nitrogen oxide removal efficiency over a wide temperature range even when the NH ₃ / NO ratio is 0.8 and 0.9. In addition, the NOx removal efficiency is more than 3% higher than that of commercial A company, and the temperature range is evenly shown to show catalytic efficiency. The method of preparing the powders prepared in Examples 2 and 3 is excellent, which has a high specific surface area and It is considered as a comprehensive factor such as pore size, suitable crystallinity and uniform tungsten support.

As described above, according to the present invention, a metatitanic acid suitable for preparing titania for catalytic extrusion molding is obtained by controlling hydrolysis conditions, and a precursor capable of neutralizing it with a basic solution to form tungsten oxide is added, followed by drying and calcining. In the case of producing titania powder, it is possible to produce fine titania powder loaded with inexpensive denitrification catalyst composition according to the simplification of the process. By providing durability and the like can exhibit an economic effect. In addition, the fine particle titania obtained in the present invention can be manufactured to have a structural and morphological advantage that is advantageous for extrusion molding, and also a selective reduction catalyst for effectively removing nitrogen oxides (NOx) emitted from thermal power plants, incinerators, various chemical plants, etc. It can be applied as a carrier material of SCR).

Claims (6)

Adding 0.2-0.4% by weight of an anatase seed to a titanium sulfate concentrate of 150-250 g / L based on TiO ₂ at a temperature of 90-120 ° C .; Hydrolyzing two to three times so that the concentration is 100-120 g / L; Reacting for 4 to 8 hours while stirring at 30 to 60 rpm to grow the particles; And Method of producing metatitanic acid comprising the step of cooling and rinsing with water and filtration twice. The method of claim 1, wherein the metatitanic acid has an anatase type, the primary particle size is 10 nm or less, and the secondary particle size is 1 to 2.5 μm. Adding a basic solution to a slurry containing metatitanic acid (TiO (OH) ₂ ) and water in a weight ratio of 1: 5 to neutralize it in the range of pH 7-9; Filtering the neutralized solution to prepare a metatitanic acid hydrous cake; Mixing and reacting the aqueous solution containing tungsten precursor and the metatitanic acid hydrous cake; And After drying the solution, and calcined for 1 to 4 hours at 500 ~ 700 ℃ to produce a titania in which tungsten oxide is supported by 0.1 to 15% by weight. delete The method of claim 3, wherein the tungsten precursor is ammonium metatungstate ((NH ₄ ) ₆ W ₁₂ O ₃₉ · _X H ₂ O), ammonium paratungstate ((NH ₄ ) ₁₀ W ₁₂ O ₄₁ ), ammonium tungstate Denitrification catalyst extrusion molding comprising one or more compounds selected from (H ₈ N ₂ O ₄ W), ammonium sulfide tungstate (H ₈ N ₂ S ₄ W), and tungsten oxide (WO ₃ ) Method for producing titania. The method of claim 3, wherein the titania has a specific surface area of 50 to 120 m 2 / g, and has a primary particle size of 10 to 50 nm.

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