Preparation method and application of ultra-low temperature denitration catalyst

Abstract

The present invention relates to the technical field of catalyst preparation, and specifically to a preparation method and application of an ultra-low temperature denitration catalyst. The preparation method of the ultra-low temperature denitration catalyst comprises the following steps: (1) adding a molybdenum salt and a complexing agent to pure water, heating and stirring, dissolving the molybdenum salt completely, obtaining a molybdenum complex solution, and then roasting to obtain modified molybdenum oxide; (2) adding a vanadium salt and a complexing agent to pure water, heating and stirring, dissolving the vanadium salt completely, cooling, and obtaining a vanadium complex solution; (3) adding titanium dioxide and modified molybdenum oxide to the vanadium complex solution, stirring evenly, drying, and roasting to obtain an ultra-low temperature denitration catalyst. The present invention improves the denitration performance of the denitration catalyst at ultra-low temperatures, while reducing SO 2 / SO 3 Conversion rate.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, and in particular to a preparation method and application of an ultra-low temperature denitration catalyst. Background Art

[0002] Selective catalytic reduction denitrification technology using ultra-low temperature catalysts in the temperature range of 150~180℃, referred to as SCR technology, has been a research hotspot in the field of air pollution control in recent years. With the increasingly stringent environmental protection, the existing industrial flue gas denitrification technology still has many shortcomings. Traditional SCR technology is usually effective in the temperature range of 180~420℃, but too high or too low temperature conditions will affect the efficiency and stability of SCR technology, and it will not be able to better play the effect of SCR technology.

[0003] At present, my country has formed SCR technology and its catalyst system with good application effects in the range of 180~420℃, but there is still room for breakthrough in the use in the ultra-low temperature range. Ultra-low temperature SCR technology is usually carried out after dust removal and desulfurization processes. The improvement of this technology has the advantages of simple flue gas composition, low energy consumption, and low transformation cost. The research focus is on developing a catalyst system that can still maintain good activity at 150~180℃, which needs to have excellent redox performance.

[0004] The development of ultra-low temperature SCR denitrification technology is of great significance to promoting the progress of industrial flue gas denitrification technology. Ultra-low temperature SCR denitrification catalysts have significant advantages in industrial flue gas denitrification. However, this technology still faces some challenges and shortcomings in practical applications. It is necessary to strengthen research in catalyst composition formula optimization, structure regulation, resistance to water and ammonium salt deposition poisoning, etc. to meet the needs of actual working conditions.

[0005] Chinese patent CN116870922A discloses an ultra-low temperature denitrification catalyst and a preparation method thereof. The catalyst is made of raw materials including nano nickel ferrite powder, nano titanium dioxide-graphene powder, ammonium metavanadate, ammonium niobium oxalate, stannous chloride, zirconium sulfate, zirconium oxychloride, rare earth metal salts, ammonium metatungstate, ammonium heptamolybdate, chopped glass fiber, silane coupling agent alcohol solution, titanate coupling agent, hydroxypropyl methylcellulose (HPMC), acesulfame potassium, polyethylene oxide and magic acid.

[0006] This patent adds a variety of auxiliary reagents to the catalyst to improve the denitrification efficiency, and the operation is more complicated. -1 The denitrification efficiency at the air velocity is above 80%. Operations that reduce the air velocity will increase production costs and result in lower production efficiency. Summary of the invention

[0007] In view of the deficiencies in the prior art, the problem to be solved by the present invention is: to provide a method for preparing an ultra-low temperature denitration catalyst, the preparation process is simple, and the obtained ultra-low temperature denitration catalyst can have a good catalytic effect; the present invention also provides an application of an ultra-low temperature denitration catalyst.

[0008] The technical solution adopted by the present invention to solve its technical problem is:

[0009] The method for preparing the ultra-low temperature denitration catalyst of the present invention comprises the following steps:

[0010] (1) adding a molybdenum salt and a complexing agent into pure water, heating and stirring until the molybdenum salt is completely dissolved to obtain a molybdenum complex solution, and then calcining to obtain a modified molybdenum oxide;

[0011] (2) adding the vanadium salt and the complexing agent into pure water, heating and stirring until the vanadium salt is completely dissolved, thereby obtaining a vanadium complex solution;

[0012] (3) Add titanium dioxide and modified molybdenum oxide to the vanadium complex solution, stir evenly, dry, and calcine to obtain an ultra-low temperature denitrification catalyst.

[0013] in:

[0014] In the step (1), the molybdenum salt is one or more of ammonium heptamolybdate or molybdenum tetrasulfide, and the complexing agent is hydrazine.

[0015] In the step (1), the mass ratio of molybdenum salt, complexing agent and pure water is 1:1-2:1.5-3.

[0016] In the step (1), the calcination temperature is 500-600°C and the calcination time is 3-4h.

[0017] In the step (2), the vanadium salt is ammonium metavanadate.

[0018] In the step (2), the complexing agent is one or more of malic acid or tartaric acid.

[0019] In the step (2), the mass ratio of vanadium salt, complexing agent and pure water is 1:1-3:4.

[0020] In the step (3), the calcination temperature is 500-600°C and the calcination time is 3-4h.

[0021] The vanadium salt is calculated as vanadium pentoxide, the titanium dioxide is calculated as titanium dioxide, and the mass ratio of vanadium pentoxide, modified molybdenum oxide and titanium dioxide is 8:5: 86-94.

[0022] The applicable temperature of the ultra-low temperature denitration catalyst prepared by the preparation method of the ultra-low temperature denitration catalyst is 150-170°C.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. In the present invention, vanadium salt reacts with a complexing agent. In the presence of hydroxy dicarboxylic acids such as malic acid or tartaric acid, the hydroxyl group and the ammonium in the vanadium salt form a chemical bond, which increases the complexing effect. The dicarboxylic acid increases the acidity of the complexing system, which is beneficial to improve V 5+ / V 4+ After chelation, drying and calcination, vanadium salt has a higher V 5+ / V 4+ Compared with quartz, it has stronger oxidation performance at 150~170℃.

[0025] 2. The present invention uses molybdenum salt to react with hydrazine, and then undergoes complexation and calcination to obtain modified molybdenum oxide, which has a lower Mo content. 6+ / Mo 4+ , due to Mo 6+ It is acidic, so in the reaction of hydrazine, the two NH bonds of hydrazine are more likely to approach Mo 6+ , prompting Mo 6+ Easier to convert into alkaline Mo 4+ , while V 5+ It is acidic and can absorb SO 2 Ways to promote SO 2 with Mo 4+ Combined, therefore, with the basic Mo 4+ Easier with SO 2 combined, thereby protecting V 5+ , reducing SO 2 / SO 3 Conversion rate.

[0026] The present invention reduces the energy required for the denitration catalyst to exert its catalytic effect by pre-complexing with vanadium salts and molybdenum salts, thereby improving the denitration performance of the denitration catalyst at ultra-low temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a process flow chart of the present invention;

[0028] Figure 2 It is a schematic diagram of the catalytic efficiency of the denitration catalysts of Examples 1-4 and Comparative Examples 1-2 of the present invention at different temperatures;

[0029] Figure 3 The denitration catalyst SO of Examples 1-4 and Comparative Examples 1-2 of the present invention is 2 / SO 3 Schematic diagram of conversion rate. DETAILED DESCRIPTION

[0030] The present invention is further described below with reference to the embodiments.

[0031] Example 1

[0032] like Figure 1 As shown, the preparation method of the ultra-low temperature denitration catalyst of the present invention comprises the following steps:

[0033] (1) Add 200 g of molybdenum tetrasulfide and 200 g of hydrazine into a reaction kettle containing 300 g of pure water, heat and stir until the molybdenum tetrasulfide is completely dissolved to obtain a molybdenum complex solution, and then calcine in a muffle furnace at 500° C. for 4 h to obtain modified molybdenum oxide;

[0034] (2) Add 100 g of ammonium metavanadate and 200 g of tartaric acid into a reactor containing 400 g of pure water, and heat and stir until the ammonium metavanadate is completely dissolved to obtain a vanadium complex solution;

[0035] (3) 1000 g of titanium dioxide and 50 g of modified molybdenum oxide were added to the vanadium complex solution, stirred evenly and dried, and then calcined in a muffle furnace at 500 °C for 4 h to obtain an ultra-low temperature denitrification catalyst.

[0036] Example 2

[0037] like Figure 1 As shown, the preparation method of the ultra-low temperature denitration catalyst of the present invention comprises the following steps:

[0038] (1) Add 100 g of ammonium heptamolybdate and 200 g of hydrazine into a reaction kettle containing 300 g of pure water, heat and stir until the ammonium heptamolybdate is completely dissolved to obtain a molybdenum complex solution, and then roast it in a muffle furnace at 600° C. for 3 h to obtain modified molybdenum oxide; if the amount is insufficient, it can be prepared multiple times according to the amount used in step (3);

[0039] (2) Add 100 g of ammonium metavanadate and 100 g of tartaric acid into a reactor containing 400 g of pure water, heat and stir until the ammonium metavanadate is completely dissolved to obtain a vanadium complex solution;

[0040] (3) 1000 g of titanium dioxide and 50 g of modified molybdenum oxide were added to the vanadium complex solution, stirred evenly and dried, and then calcined in a muffle furnace at 600 °C for 3 h to obtain an ultra-low temperature denitrification catalyst.

[0041] Example 3

[0042] like Figure 1 As shown, the preparation method of the ultra-low temperature denitration catalyst of the present invention comprises the following steps:

[0043] (1) Add 100 g of ammonium heptamolybdate and 100 g of hydrazine into a reaction kettle containing 300 g of pure water, heat and stir until the ammonium heptamolybdate is completely dissolved to obtain a molybdenum complex solution, and then roast it in a muffle furnace at 500° C. for 4 h to obtain modified molybdenum oxide; if the amount is insufficient, it can be prepared multiple times according to the amount used in step (3);

[0044] (2) Add 100 g of ammonium metavanadate and 200 g of malic acid into a reactor containing 400 g of pure water, and heat and stir until the ammonium metavanadate is completely dissolved to obtain a vanadium complex solution;

[0045] (3) 950 g of titanium dioxide and 50 g of modified molybdenum oxide were added to the vanadium complex solution, stirred evenly and dried, and then calcined in a muffle furnace at 500 °C for 4 h to obtain an ultra-low temperature denitration catalyst.

[0046] Example 4

[0047] like Figure 1 As shown, the preparation method of the ultra-low temperature denitration catalyst of the present invention comprises the following steps:

[0048] (1) Add 100 g of ammonium heptamolybdate and 100 g of hydrazine into a reaction kettle containing 300 g of pure water, heat and stir until the ammonium heptamolybdate is completely dissolved to obtain a molybdenum complex solution, and then roast it in a muffle furnace at 600° C. for 3 h to obtain modified molybdenum oxide; if the amount is insufficient, it can be prepared multiple times according to the amount used in step (3);

[0049] (2) adding 100 g of ammonium metavanadate and 300 g of tartaric acid into a reactor containing 400 g of pure water, heating and stirring until the ammonium metavanadate is completely dissolved to obtain a vanadium complex solution;

[0050] (3) 1045 g of titanium dioxide and 50 g of modified molybdenum oxide were added to the vanadium complex solution, stirred evenly and dried, and then calcined in a muffle furnace at 500 °C for 4 h to obtain an ultra-low temperature denitrification catalyst.

[0051] Comparative Example 1

[0052] (1) Add 200 g of molybdenum tetrasulfide into a reaction kettle containing 300 g of pure water, heat and stir until the molybdenum tetrasulfide is completely dissolved to obtain a molybdenum-containing solution, and then calcine in a muffle furnace at 500° C. for 4 h to obtain a molybdenum-containing powder;

[0053] (2) Add 100 g of ammonium metavanadate into a reactor containing 400 g of pure water, and heat and stir until the ammonium metavanadate is completely dissolved to obtain a vanadium-containing solution;

[0054] (3) 1000 g of titanium dioxide and 50 g of molybdenum-containing powder were added to the vanadium-containing solution, stirred evenly and dried, and then calcined in a muffle furnace at 500 °C for 4 h to obtain a denitrification catalyst.

[0055] Comparative Example 2

[0056] (1) Add 200 g of molybdenum tetrasulfide and 200 g of hydrazine into a reaction kettle containing 300 g of pure water, heat and stir until the molybdenum tetrasulfide is completely dissolved to obtain a molybdenum complex solution, and then calcine in a muffle furnace at 500° C. for 4 h to obtain modified molybdenum oxide;

[0057] (2) Add 100 g of ammonium metavanadate into a reactor containing 400 g of pure water, and heat and stir until the ammonium metavanadate is completely dissolved to obtain a vanadium-containing solution;

[0058] (3) Add 1000 g of titanium dioxide and 50 g of modified molybdenum oxide to the vanadium-containing solution, stir evenly and dry, and then calcine in a muffle furnace at 500 °C for 4 h to obtain a denitrification catalyst.

[0059] Comparative Example 3

[0060] (1) Add 200 g of molybdenum tetrasulfide into a reaction kettle containing 300 g of pure water, heat and stir until the molybdenum tetrasulfide is completely dissolved to obtain a molybdenum-containing solution, and then calcine in a muffle furnace at 500° C. for 4 h to obtain a molybdenum-containing powder;

[0061] (2) Add 100 g of ammonium metavanadate and 200 g of tartaric acid into a reactor containing 400 g of pure water, and heat and stir until the ammonium metavanadate is completely dissolved to obtain a vanadium complex solution;

[0062] (3) 1000 g of titanium dioxide and 50 g of molybdenum-containing powder were added to the vanadium complex solution, stirred evenly and dried, and then calcined in a muffle furnace at 500 °C for 4 h to obtain a denitration catalyst.

[0063] The catalysts prepared in Examples 1-4 and Comparative Examples 1-3 were tested at 150°C and 170°C for denitration, respectively. 3 / NO=1:1, airspeed is 15000h -1 , H 2 O volume concentration is 10%, oxygen volume concentration is 6%, SO 2 The denitration efficiency of each catalyst was tested under the simulated condition of 100 ppm. The results are shown in Table 1. Figure 2 Schematic diagram of the catalytic efficiency of the denitration catalysts of Examples 1-4 and Comparative Examples 1-2 at different temperatures. The mass percentage content of each ion in the catalysts of Example 1 and Comparative Examples 1-3 is shown in Table 2.

[0064]

[0065]

[0066] From Table 1 and Figure 2It can be seen that the ultra-low temperature denitration catalysts prepared in Examples 1-4 have higher denitration efficiencies at 150°C and 170°C than the catalysts prepared in Comparative Examples 1-3. This is because the present invention forms a vanadium complex by reacting a vanadium salt with a complexing agent, and the denitration catalyst prepared by mixing the vanadium complex with modified molybdenum oxide and titanium dioxide can adjust the catalyst surface V 5+ and V 4+ The ratio of the catalyst surface elements changes, so that the prepared catalyst has stronger oxidation performance in the temperature range of 150°C-170°C, thereby improving the catalytic effect of the catalyst. Compared with the traditional denitration catalyst, the denitration catalyst prepared by the present invention has a higher V 5+ / V 4+ Compared with other materials, the oxidation performance is stronger, thereby improving the denitration performance and denitration efficiency of the denitration catalyst under ultra-low temperature conditions.

[0067] The ultra-low temperature denitration catalyst prepared in Example 1-4 was heated to 170°C and the space velocity was 15000 h -1 The denitration efficiency detected under the conditions of 1-3 is above 75%, while the denitration catalyst prepared in Comparative Examples 1-3 has a space velocity of 15000h at 170°C. -1 The highest denitration efficiency under the conditions can only reach 68.7%, which shows that the ultra-low temperature denitration catalyst prepared by the present invention has high denitration efficiency and good selectivity.

[0068] Figure 3 The catalysts of Examples 1-4 and Comparative Examples 1-2 were heated to 170°C in SO 2 / SO 3 Conversion rate diagram, Figure 3 It can be seen that Example 1 - 4 SO of the ultra-low temperature denitrification catalyst prepared 2 / SO 3 The conversion rate is lower than that of the catalyst prepared in Comparative Example 1-2. 2 / SO 3 Conversion rate.

[0069] Table 2 shows the mass percentage content of each ion in the catalysts of Example 1 and Comparative Examples 1-3. It can be seen from Comparative Example 1 and Example 1 that the present invention uses molybdenum complexes and vanadium complexes to effectively reduce Mo 6+ content, increasing V 5+ The content of V can be increased to a certain extent by using molybdenum complexes. 5+ The content of Mo can be reduced to a certain extent by using vanadium complex. 6+ The content of molybdenum complex and vanadium complex, Mo 6+ The effect of reducing the content and V5+ The effect of increasing the content is better; and the molybdenum complex and V 5+ / V 4+ ratio between vanadium complex and Mo 6+ / Mo 4+ There is a synergistic effect between the two ratios, so using one complex will also have a positive effect on the other substance. When both elements react in the form of complexes, the synergistic effect is best, and the product quality of the prepared denitrification catalyst is better.

[0070] The present invention adds a complexing agent to convert the Mo element into molybdenum oxide as much as possible, thereby reducing the Mo 6+ Mo content increased 4 + content, achieving the V 5+ Protection and reduction of SO 2 / SO 3 Conversion rate; Mo 4+ Alkaline, V 5+ and SO 2 is acidic, but Mo 4+ Easier with SO 2 Combined, protecting the V 5+ , while reducing SO 2 / SO 3 The present invention improves V 5+ / V 4+ ratio, thereby improving the oxidation performance of the catalyst; V 5+ The stronger the electron-accepting ability of the ion, the stronger its non-metallic property, so the stronger its oxidizing property, which increases V 5+ / V 4+ Compared with the above, the overall oxidation performance of the ultra-low temperature denitration catalyst is more excellent; at the same time, further analysis shows that the ultra-low temperature denitration catalyst prepared in Examples 1-4 has a SO 2 / SO 3 The conversion rate is below 0.8%, while the catalyst prepared in Comparative Example 1-2 has a SO conversion rate of less than 0.8% at 170°C. 2 / SO 3 The lowest conversion rate can only reach 1.2%. The catalyst prepared in Comparative Example 3 has a SO conversion rate of 1.2% at 170°C. 2 / SO 3 The conversion rate is 1.4%, so the anti-SO 2 / SO 3 Strong conversion rate.

Claims

1. A method for preparing an ultra-low temperature denitration catalyst, characterized in that: The following steps are involved: (1) adding a molybdenum salt and a complexing agent into pure water, heating and stirring until the molybdenum salt is completely dissolved to obtain a molybdenum complex solution, and then calcining to obtain a modified molybdenum oxide; The molybdenum salt is one or more of ammonium heptamolybdate or molybdenum tetrasulfide, the complexing agent is hydrazine, and the mass ratio of the molybdenum salt, the complexing agent and the pure water is 1:1-2:1.5-3; (2) adding vanadium salt and complexing agent into pure water, heating and stirring until the vanadium salt is completely dissolved, thereby obtaining a vanadium complex solution; the complexing agent is one or more of malic acid or tartaric acid; (3) Add titanium dioxide and modified molybdenum oxide to the vanadium complex solution, stir evenly, dry, and calcine to obtain an ultra-low temperature denitrification catalyst.

2. The method for preparing the ultra-low temperature denitration catalyst according to claim 1, characterized in that: In step (1), the calcination temperature is 500-600°C and the calcination time is 3-4h.

3. The method for preparing the ultra-low temperature denitration catalyst according to claim 1, characterized in that: In step (2), the vanadium salt is ammonium metavanadate.

4. The method for preparing the ultra-low temperature denitration catalyst according to claim 1, characterized in that: In step (2), the mass ratio of vanadium salt, complexing agent and pure water is 1:1-3:

4.

5. The method for preparing the ultra-low temperature denitration catalyst according to claim 1, characterized in that: In step (3), the calcination temperature is 500-600°C and the calcination time is 3-4h.

6. The method for preparing the ultra-low temperature denitration catalyst according to claim 1, characterized in that: The vanadium salt is calculated as vanadium pentoxide, the titanium dioxide is calculated as titanium dioxide, and the mass ratio of vanadium pentoxide, modified molybdenum oxide and titanium dioxide is 8:5: 86-94.

7. An application of an ultra-low temperature denitration catalyst prepared by the method for preparing an ultra-low temperature denitration catalyst according to any one of claims 1 to 6, characterized in that: The applicable temperature of ultra-low temperature denitrification catalyst is 150-170℃.

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