CN101695656B - Method for preparing powdery selective catalytic reduction denitrification catalyst by sol impregnation method - Google Patents

Abstract

The method for preparing the powdery selective catalytic reduction denitration catalyst by using the sol impregnation method is a method for preparing the powdery SCR denitration catalyst by using sol metatitanic acid as an impregnation carrier. The method comprises the steps of carrying out primary impregnation loading on sol metatitanic acid serving as a carrier and an ammonium tungstate-oxalic acid solution, carrying out secondary impregnation loading on the prepared composite powder and an ammonium metavanadate-oxalic acid solution after a calcination, grinding and screening process, and finally carrying out secondary calcination, grinding and screening treatment to complete the preparation process of the powdery SCR denitration catalyst. Compared with the traditional SCR denitration catalyst preparation process, the method has the advantages of simple process and low economic cost, and is suitable for an integrated production mode of a titanium dioxide preparation process and an SCR denitration catalyst production process. The catalyst prepared by the method has the characteristics of large specific surface area, uniform and reasonable micropore structure, good thermal stability, ideal catalytic conversion efficiency on NOx components in smoke and the like.

Description

Method for preparing powdery selective catalytic reduction denitrification catalyst by sol impregnation method

technical field

The invention relates to a preparation method of a powdery selective catalytic reduction (SCR) denitrification catalyst, belonging to the technical field of environmental pollution prevention and clean coal combustion.

Background technique

Coal is the main primary energy in our country. The NOx emitted by a large number of coal-fired power plants every year has brought great damage to the environment. Nitrogen oxides (NOx) are gases caused by acid rain and photochemical smog pollution. my country's NOx pollution is becoming more and more serious. The concentration of nitrogen oxides in the air of some large cities exceeds the standard. The environmental capacity of nitrogen oxides is basically in a saturated state, and photochemical smog even appears in some places.

China implemented the new "Emission Standards of Air Pollutants for Thermal Power Plants" (GB13223-2003) on January 1, 2004, and further strictly regulated NOx emissions; The same pollution discharge fee as that of SO ₂ will be levied on NOx from January. In the "Tenth Five-Year Plan" of my country's power industry environmental protection, specific goals and requirements are also put forward for the NOx control of power plant flue gas. According to these requirements, the vast majority of coal-fired power plants in my country must take measures to control NOx emissions.

As an effective NOx treatment technology, selective catalytic reduction flue gas denitrification technology has the advantages of high efficiency, strong selectivity, and good reliability. After years of development, it has been widely used in developed countries, but it has just start. The cost of catalyst replacement for SCR denitrification accounts for a large proportion of operating costs. The catalysts currently used are all developed and produced abroad and are expensive. Moreover, the existing raw materials for producing denitrification catalysts such as TiO ₂ in China do not meet the technical requirements, and the production technology of denitrification catalysts is not yet available. These have become the main restrictive factors for the widespread application of SCR method in power plant flue gas denitrification treatment in my country. Therefore, the development of low-cost localized SCR catalysts, the formation of independent intellectual property rights and industrialized production will greatly reduce the investment and operating costs of flue gas denitrification in my country, and play a huge role in the development of flue gas NOx treatment in my country and the improvement of my country's environment. impetus.

In the traditional SCR denitration catalyst preparation process, the method of impregnating and loading the cocatalyst and the catalytic active component on the powder catalyst carrier (such as TiO ₂ ) is usually adopted, that is, the material to be impregnated (such as the cocatalyst WO ₃ , the catalytic main substance V ₂ O ₅ ) Dissolving into the immersion solution, immersing the TiO ₂ powder in it, controlling the temperature to evaporate the water, and then the active ingredients will be precipitated and added on the surface of the TiO ₂ matrix, and the loading process is completed. After grinding and calcining, the SCR denitration catalyst is obtained. The operation process of this method is simple, but it has the following problems after analysis: during the impregnation process, co-catalyst components such as WO ₃ can only be loaded on the surface of TiO ₂ powder, and the matrix and impregnated components cannot be tightly combined in structure, which will cause The catalytic activity and thermal stability of the catalyst are affected.

However, using sol-like metatitanic acid as a catalyst carrier to impregnate and load effective components step by step can effectively solve the above problems.

Contents of the invention

Technical problem: The object of the present invention is to provide a method for preparing a powdery selective catalytic reduction denitration catalyst by an efficient sol impregnation method.

Technical solution: The present invention proposes a method of using sol-like metatitanic acid as an impregnated carrier to prepare a powdery SCR denitration catalyst. It can be summarized that the sol-like metatitanic acid is used as the carrier, and the ammonium tungstate-oxalic acid solution is impregnated and loaded, and then the titanium dioxide-tungsten trioxide composite powder is obtained after calcining and grinding. Then the composite powder and the ammonium metavanadate-oxalic acid solution are impregnated and loaded for the second time, and finally the finished powder catalyst is made after calcining and grinding.

The specific method is:

Step 1. Add titanium oxysulfate TiOSO ₄ into water, and stir continuously to dissolve it completely; at the same time, add a small amount of concentrated sulfuric acid to adjust the pH value of the solution to 1-1.5;

Step 2. Quickly add ammonia water to the solution prepared in step 1 to raise the pH value to 6.5-7.5, and at the same time stir rapidly under the condition of heating at 70°C-85°C for 1-2 hours, and then obtain white metatitanic acid sol H ₂ TiO ₃ ; the sol was repeatedly filtered and washed to remove the impurity ions therein for later use;

Step 3. Dissolve oxalic acid C ₂ H ₂ O ₄ in water to make oxalic acid solution, then dissolve ammonium tungstate salt (NH ₄ ) ₅ H ₆ [H ₂ (WO ₄ ) ₆ ]·H ₂ O in oxalic acid solution , to make colorless ammonium tungstate-oxalic acid solution;

Step 4. Mix the ammonium tungstate-oxalic acid solution prepared in step 3 with the metatitanic acid sol prepared in step 2, and stir for 3 to 5 hours under heating conditions at 50°C to 65°C to obtain the first mixed solution;

Step 5. Dry the mixed solution prepared in step 4 at 100°C to 105°C, then calcinate at 430°C to 450°C in an air atmosphere for 5 to 6 hours, and grind the obtained solid to a particle size of less than 0.1mm after cooling The solid powder is ready for later use;

Step 6. dissolving oxalic acid in water to make oxalic acid solution, then dissolving ammonium metavanadate salt _NH4VO3 in oxalic acid solution to make yellow ammonium metavanadate-oxalic acid solution _;

Step 7. After the ammonium metavanadate-oxalic acid solution prepared in step 6 was left to stand for 1 to 1.5 hours, the solution gradually turned blue;

Step 8. Add the solid powder obtained in step 5 to the ammonium metavanadate-oxalic acid solution prepared in step 7, and stir for 3 to 5 hours under heating at 50°C to 65°C to obtain the second mixed solution ;

Step 9. Dry the second mixed solution prepared in step 8 at 100°C to 105°C, then calcinate at 430°C to 450°C in an air atmosphere for 5 to 6 hours, cool the obtained solid and grind it to the particle size If it is less than 0.1 mm, the desired catalyst is produced.

In step 1, titanyl sulfate TiOSO ₄ is added to water, and the dosage ratio of titanyl sulfate to water is controlled within the range of 8g-12g:100ml.

In step 3, the consumption ratio of oxalic acid and water is controlled within the scope of 8g～10g:800ml.

In step 3, the dosage ratio of ammonium tungstate to titanyl sulfate is controlled within the range of 5.2 to 8.0 g: 100 g.

In step 6, the consumption ratio of oxalic acid and water is controlled within the scope of 8g～10g:600ml.

In step 6, the dosage ratio of ammonium metavanadate to titanyl sulfate is controlled within the range of 0.4-0.8g:100g.

Beneficial effects: the prepared catalyst has the following characteristics: in terms of microstructure, the catalyst is granular in appearance, and the internal components of the particles are mainly titanium dioxide (carrier) and tungsten trioxide (promoter), and the two are closely combined. The outer layer of the particles is covered with a vanadium pentoxide component (main catalyst) to form a thin layer. This structure is beneficial for the carrier to give full play to its supporting and dispersing effect on the co-catalyst, and it is also beneficial to exert the co-catalyst to improve the overall thermal stability of the catalyst, improve the electronic interaction between V ₂ O ₅ and TiO ₂ , and improve the activity and selectivity of the catalyst. and stability effects. In addition, the main catalyst forms a thin outer layer, which is beneficial to its full contact with the NOx components in the flue gas, and effectively plays the role of the catalyst in catalytic reduction of NOx. The surface-microscopic characterization analysis of the catalyst shows that the catalyst prepared by this method has a larger reaction specific surface area than the traditional method; and the performance test also shows that the catalyst has an ideal NOx catalytic conversion efficiency.

In addition, in terms of suitability for industrial production, compared with the traditional powder impregnation method for catalyst preparation, the sol impregnation method can omit the drying step of the intermediate product metatitanic acid sol in the preparation process of the titanium dioxide matrix, and directly use the sol to load the active ingredients, reducing the complexity and cost of the catalyst manufacturing process. The invention can effectively promote the connection between the titanium dioxide production industry and the SCR catalyst preparation industry, and the invention has good applicability to the integrated production mode of the two.

Detailed ways

In the preparation method of an efficient powdery SCR denitration catalyst according to the present invention, the catalyst components and content ratio are controlled to be 1% V ₂ O ₅ -10% WO ₃ /TiO ₂ (mass fraction), and the preparation steps as follows:

1) Add a certain amount of titanyl sulfate to an appropriate amount of water (the ratio of titanyl sulfate to water is controlled at 10g: 100ml), stir continuously to make it completely dissolve, and add a small amount of concentrated sulfuric acid at the same time to adjust the pH value of the solution to about 1 (conc. The consumption ratio of sulfuric acid and water is controlled at 0.5ml: 100ml);

2) Quickly add a certain amount of ammonia water to the solution prepared in step 1, so that its pH value rises to about 7 (the ratio of industrial use of 30% concentration ammonia water to water is about 50ml: 300ml), while heating at 80°C Under rapid stirring for 1 hour, a white metatitanic acid sol (H ₂ TiO ₃ ) was obtained. Repeatedly filter and wash the sol to remove the impurity ions therein for later use;

3) Dissolve oxalic acid in water to make oxalic acid solution (the ratio of oxalic acid to water is controlled at 10g: 800ml), and then dissolve quantitative ammonium tungstate salt in the oxalic acid solution (the ratio of ammonium tungstate to titanyl sulfate is 6.6g: 100g), made into colorless ammonium tungstate-oxalic acid solution;

4) Mix the ammonium tungstate-oxalic acid solution prepared in step 3) with the metatitanic acid sol prepared in step 2), and stir for 3 hours under heating at 60°C;

5) Dry the mixed solution prepared in step 4) at 105°C, and then calcinate at 450°C for 5 hours in an air atmosphere. After cooling, the obtained solid is ground to a particle size of less than 0.1mm and then used for later use. The impregnation process is completed ;

6) Dissolve a certain amount of oxalic acid in water to make an oxalic acid solution (the ratio of oxalic acid to water is controlled at 10g: 600ml), and then dissolve a certain amount of ammonium metavanadate salt in the oxalic acid solution (ammonium metavanadate and titanyl sulfate The consumption ratio is 0.8g: 100g), makes yellow ammonium metavanadate-oxalic acid solution;

7) After the ammonium metavanadate-oxalic acid solution prepared in step 6) was left to stand for 1 hour, the solution gradually turned blue;

8) Add the solid powder prepared in step 5) into the ammonium metavanadate-oxalic acid solution prepared in step 7), and stir for 3 hours under heating at 60°C;

9) Dry the mixed solution prepared in step 8) at 105°C, then calcinate at 450°C for 5 hours in an air atmosphere, cool the obtained solid and grind it to a particle size of less than 0.1mm, after completing the second impregnation process, then The required powdery SCR denitration catalyst is prepared.

The sol-like metatitanic acid material is directly used in the preparation process. Compared with the traditional catalyst preparation method using powdered titanium dioxide as a carrier, the steps of drying and grinding the intermediate product metatitanic acid sol in the preparation process of the titanium dioxide matrix are omitted, reducing complexity and cost of the catalyst manufacturing process. Using sol-like metatitanic acid as the carrier for one impregnation process is conducive to the uniform loading of co-catalyst components on the surface of the carrier. The prepared catalyst has a large specific surface area and uniform surface micropore structure, and has good thermal stability. sex.

The powder impregnation method is used for the secondary impregnation loading process, which is helpful for the layered loading of the main catalyst components on the surface of the carrier and the cocatalyst. And because the main catalyst component will not be covered and masked by other substances, it is beneficial for its full contact with the flue gas, so the prepared catalyst has good catalytic conversion performance for the NOx component in the flue gas.

Claims (1)

1. A method for preparing an efficient powdery SCR denitration catalyst, characterized in that the catalyst components and mass fraction ratio are controlled to be 1% V ₂ O ₅ -10% WO ₃ /TiO ₂ , and the preparation steps are as follows: 1). Add a certain amount of titanyl sulfate to an appropriate amount of water. The ratio of titanyl sulfate to water is controlled at 10g: 100ml. Stir continuously to dissolve it completely. At the same time, add a small amount of concentrated sulfuric acid to adjust the pH value of the solution to 1. Concentrated sulfuric acid The dosage ratio with water is controlled at 0.5ml: 100ml; 2). Quickly add ammonia water to the solution prepared in step 1) to raise the pH value to 7. At the same time, stir rapidly under the condition of heating at 80°C for 1 hour, and then obtain a white metatitanic acid sol H ₂ TiO ₃ . The sol was filtered and washed repeatedly to remove the impurity ions in it for later use; 3). Dissolve oxalic acid in water to make oxalic acid solution. The dosage ratio of oxalic acid and water is controlled at 10g:800ml, and then quantitative ammonium tungstate is dissolved in the oxalic acid solution. The dosage ratio of ammonium tungstate and titanyl sulfate is 6.6 g: 100g, made into colorless ammonium tungstate-oxalic acid solution; 4). Mix the ammonium tungstate-oxalic acid solution prepared in step 3) with the metatitanic acid sol prepared in step 2), and stir for 3 hours under heating at 60°C; 5). Dry the mixed solution prepared in step 4) at 105°C, then calcinate at 450°C for 5 hours in an air atmosphere, cool the obtained solid and grind it to a particle size of less than 0.1mm for later use, and the first impregnation is completed process; 6). Dissolve a certain amount of oxalic acid in water to make an oxalic acid solution. The ratio of oxalic acid to water is controlled at 10g: 600ml, and then a certain amount of ammonium metavanadate is dissolved in the oxalic acid solution. The dosage ratio is 0.8g: 100g to make a yellow ammonium metavanadate-oxalic acid solution; 7). After the ammonium metavanadate-oxalic acid solution prepared in step 6) was left to stand for 1 hour, the solution gradually turned blue; 8). Add the solid powder prepared in step 5) into the ammonium metavanadate-oxalic acid solution prepared in step 7), and stir for 3 hours under heating at 60°C; 9). Dry the mixed solution prepared in step 8) at 105°C, and then calcinate at 450°C for 5 hours in an air atmosphere. After cooling, the obtained solid is ground to a particle size of less than 0.1 mm. After the second impregnation process is completed, Then the desired powdery SCR denitration catalyst is prepared.