A multifunctional composite wear-resistant and anti-blocking denitrification catalyst and its preparation method

Abstract

The invention discloses a multifunctional composite wear-resistant and anti-blocking denitration catalyst and a preparation method thereof. The catalyst comprises a TiO2 carrier, an active substance V2O5 loaded on the TiO2 carrier, an auxiliary agent WO3, and BN / manganese borate particles doped in the catalyst; in the catalyst, the content of V2O5 is 0.2-1%, the content of WO3 is 3-8%, and the content of BN / manganese borate particles is 5-12%. The invention improves the wear resistance, anti-blocking performance and use stability of the catalyst by doping BN / manganese borate particles in the catalyst.

Description

Technical Field

[0001] The invention relates to a multifunctional composite wear-resistant and anti-blocking denitration catalyst and a preparation method thereof, belonging to the technical field of flue gas denitration. Background Art

[0002] Nitrogen oxides (NO x ) is one of the main air pollutants, which mainly comes from the flue gas emitted by thermal power plants, motor vehicle exhaust, etc. Cement kilns are the third largest NOx after coal-fired power and transportation industries. x Emission source. NO x After being discharged into the atmosphere, it causes environmental problems such as acid rain, photochemical smog and ozone layer depletion through physical and chemical reactions, which have great harm to the environment, human health and production activities, and have attracted widespread attention from countries around the world. x There are many technologies, but the most successful and mature one in industrial practice is the selective catalytic reduction technology. Its principle is that under the action of the catalyst, the reducing agent (such as NH3) selectively reduces NO in the flue gas to x Reduction to N2 and H2O, the catalyst is the core of this technology. Currently, most commercial catalysts are V2O5-WO3 / TiO2 catalysts, in which V2O5 is the active component, WO3 is the auxiliary agent, and TiO2 is the carrier. However, this denitrification catalyst is not suitable for high dust environment of cement kiln flue gas (particle concentration can reach 80g / Nm 3 ~120g / Nm 3 , even up to 140g / Nm 3 ) has problems such as poor wear resistance and easy clogging, which leads to short catalyst life and low efficiency. Summary of the invention

[0003] The object of the present invention is to provide a multifunctional composite wear-resistant and anti-clogging denitrification catalyst and a preparation method thereof, and to improve the wear resistance, anti-clogging performance and use stability of the catalyst by doping BN / manganese borate particles in the catalyst.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A multifunctional composite wear-resistant and anti-clogging denitration catalyst, comprising a TiO2 carrier, an active substance V2O5 loaded on the TiO2 carrier, an auxiliary agent WO3, and BN / manganese borate particles doped in the catalyst; in the catalyst, the content of V2O5 is 0.2-1%, the content of WO3 is 3-8%, and the content of BN / manganese borate particles is 5-12%.

[0006] The preparation method of the multifunctional composite wear-resistant and anti-blocking denitration catalyst comprises the following steps:

[0007] S1, adding manganese borate to a mixture of CTAB, n-butanol and cyclohexane, then adding BN nanospheres and stirring, filtering and washing after aging, vacuum drying and calcining to obtain BN / manganese borate particles;

[0008] S2. Dissolve ammonium metavanadate in oxalic acid, then add ammonium tungstate, TiO2 powder, BN / manganese borate particles, and silicate, stir and let stand, then dry and calcine, cool and grind and sieve to obtain V2O5-WO3 / TiO2 powder catalyst doped with BN / manganese borate particles.

[0009] Preferably, in the step S1, in the mixed system of CTAB, n-butanol and cyclohexane, the mass ratio of CTAB, n-butanol and cyclohexane is 1:(2-4):(1-3);

[0010] The mass ratio of manganese borate to BN nanospheres is 1:(2-5).

[0011] Preferably, in step S1, the aging time is 10-15 hours.

[0012] Preferably, in step S1, the drying temperature is 60-80°C, and the calcination temperature is 700-800°C.

[0013] Preferably, in step S1, the preparation method of BN nanospheres is: mixing boron oxide and methanol in a molar ratio of 1:(2-5) and then standing, separating the solid and liquid and taking the upper liquid; then using the CVD method, using nitrogen to bring the upper liquid into a 950-1000°C high-temperature tube furnace, passing ammonia, cooling and collecting the powder; and then ammoniation the powder at 1400-1500°C.

[0014] Preferably, in step S2, the drying temperature is 70-90°C for 8-12h; the calcination conditions are: heating rate 1-3°C / min, first heating to 250-280°C, keeping warm for 1-2h; then heating to 450-550°C at a heating rate 1-3°C / min, keeping warm for 2-3h.

[0015] Preferably, in step S2, the amount of silicate added is 3-8% of the amount of TiO2 powder added.

[0016] Preferably, in step S2, the obtained V2O5-WO3 / TiO2 powder catalyst doped with BN / manganese borate particles has a V2O5 content of 0.2-1%, a WO3 content of 3-8%, and a BN / manganese borate particle content of 5-12%.

[0017] The beneficial effects of the present invention are:

[0018] 1. CaO contained in fly ash will react with SO2, water and ammonia to generate calcium sulfate, which will then scale on the catalyst surface, preventing the reaction substances from diffusing to the catalyst surface and inside, making the catalyst inactive. BN / manganese borate nanospheres have good acid and alkali corrosion resistance and sulfate corrosion resistance, which can effectively inhibit the reaction of SO2 with water and ammonia, and then reduce the possibility of calcium sulfate generation, thereby reducing the risk of catalyst blockage; secondly, the negative charge on the surface of BN (boron nitride) nanospheres can react with Ca in the process of generating calcium sulfate. 2+ Electrostatic attraction occurs between ions, Ca 2+ Ions are attracted by the negative charges on the BN nanospheres, thus avoiding direct contact with the active sites, reducing the rate of catalyst deactivation, improving catalyst stability, and thus extending the service life of the catalyst;

[0019] 2. BN (boron nitride) is a metal compound with high hardness and thermal stability, while boron nitride is an atomic crystal compound with excellent mechanical properties and chemical stability. Such nanoparticles usually have a large specific surface area and excellent mechanical properties. BN / manganese borate particles can combine the advantages of both materials, thus improving the wear resistance of the catalyst. The covalent bonds on the surface of BN / manganese borate ions make the ions carry partial negative charges, so they can interact with metal ions, thereby changing the surface electrochemical properties of the catalyst and improving the reaction rate and selectivity of the catalyst. DETAILED DESCRIPTION

[0020] The present invention will be specifically described below in conjunction with the embodiments.

[0021] Example 1

[0022] The preparation method of BN nanospheres is: mix boron oxide and methanol in a molar ratio of 1:3, let it stand, separate the solid and liquid and take the upper liquid; then use the CVD method to bring the upper liquid into a 950°C high-temperature tube furnace with nitrogen, introduce ammonia, collect the powder after cooling; and then ammoniate the powder at 1450°C.

[0023] The preparation method of the denitration catalyst comprises the following steps:

[0024] S1. Add 2 g of manganese borate to a mixture of 2 g of CTAB, 6 g of n-butanol, and 3 g of cyclohexane, then add 4 g of BN nanospheres and stir, age for 12 h, filter, wash several times, dry at 70 ° C for 3 h under vacuum conditions, and then calcine at 700 ° C for 7 h to obtain BN / manganese borate particles;

[0025] S2. Dissolve ammonium metavanadate in oxalic acid, then add ammonium tungstate, TiO2 powder, BN / manganese borate particles, and silicate, stir and let stand, dry in an oven at 80°C for 10 hours, and then calcine in a muffle furnace, first heating to 270°C at a heating rate of 2°C / min and keep warm for 1 hour; then heating to 500°C at a heating rate of 2°C / min and keep warm for 3 hours. Take out, cool, grind and sieve to obtain V2O5-WO3 / TiO2 powder catalyst doped with BN / manganese borate particles; wherein the amount of silicate added is 5% of the amount of TiO2 powder added.

[0026] According to the above method, the final contents of each substance in the prepared catalyst are: V2O5-WO3 / TiO2-1 with 0.2% V2O5, 6% WO3, and 6% BN / manganese borate particles; V2O5-WO3 / TiO2-2 with 0.2% V2O5, 6% WO3, and 8% BN / manganese borate particles; V2O5-WO3 / TiO2-3 with 0.2% V2O5, 6% WO3, and 10% BN / manganese borate particles.

[0027] Comparative Example 1

[0028] It is basically the same as Example 1, except that in Comparative Example 1, manganese borate is added to the denitration catalyst instead of BN / manganese borate particles; and the final content of each substance in the obtained catalyst is: V2O5 0.2%, WO3 6%, manganese borate particles 10%, and it is named V2O5-WO3 / TiO2-4.

[0029] Comparative Example 2

[0030] It is basically the same as Example 1, except that in Comparative Example 2, BN / manganese borate particles are not added to the denitration catalyst; and the final content of each substance in the catalyst is: V2O5 0.2%, WO3 6%, and it is named V2O5-WO3 / TiO2-5.

[0031] Catalytic performance test

[0032] The catalyst denitrification activity experiment was carried out in a fixed bed reactor. The flue gas conditions were: total gas volume 1.8L / min, containing 0.07% NH3, 0.07% NO, 5% O2, carrier gas was N2, and the air velocity was 15000h -1 The catalysts V2O5-WO3 / TiO2-(1, 2, 3, 4, 5) of the same specifications were fixed in the reaction tube in sequence and the catalysts were subjected to NO x The removal rate was calculated and the results are shown in Table 1.

[0033] Catalyst NO x The removal rate (η, %) is calculated using the following formula:

[0034]

[0035] Where: and The NO detected at the inlet and outlet of the SCR reactor are x Concentration (volume fraction).

[0036] The catalyst anti-clogging experiment was also carried out in a fixed bed reactor. The flue gas conditions were: total gas volume 1.8L / min, containing 0.07% NH3, 0.07% NO, 5% O2, 5% H2O, 0.02% SO2, 0.02% CaO powder, carrier gas was N2, and the space velocity was 15000h -1 The catalysts V2O5-WO3 / TiO2-(1, 2, 3, 4, 5) of the same specifications were fixed in the reaction tube in sequence, and the NO of the catalysts was continuously detected at 300°C for 168 hours. x The removal rate and the results are shown in Table 2.

[0037] Table 1 Catalyst NO x Removal rate

[0038] sample 150℃ 200℃ 250℃ 300℃ 350℃ 400℃ <![CDATA[V2O5-WO3 / TiO2-1]]> 66.3 87.2 92.1 97.2 96.7 87.8 <![CDATA[V2O5-WO3 / TiO2-2]]> 67.2 90.1 93.4 98.5 97.5 89.2 <![CDATA[V2O5-WO3 / TiO2-3]]> 68.5 91.2 95.8 99.3 98.7 91.4 <![CDATA[V2O5-WO3 / TiO2-4]]> 64.2 77.5 82.4 88.9 87.6 77.2 <![CDATA[V2O5-WO3 / TiO2-5]]> 58.4 72.5 77.2 86.7 84.8 72.1

[0039] It can be seen from Table 1 that the catalytic activity of V2O5-WO3 / TiO2-1, 2, 3 is significantly higher than that of V2O5-WO3 / TiO2-4, 5 catalysts; the reason is that the negative charge carried by BN / manganese borate ions can react with metal ions, changing the surface electrochemical properties of the catalyst, thereby improving the reaction rate and selectivity of the catalyst.

[0040] Table 2 Catalyst NO x Removal rate (SO2, CaO powder, at 300℃)

[0041]

[0042]

[0043] It can be seen from Table 2 that the catalytic activity of V2O5-WO3 / TiO2-1, 2, 3 in the presence of SO2, CaO powder and at 300°C is significantly higher than that of V2O5-WO3 / TiO2-4, 5 catalysts; the reason is that BN / manganese borate nanospheres have good acid and alkali corrosion resistance and sulfate corrosion resistance, which can inhibit the reaction of SO2 with water and ammonia, thereby reducing the possibility of calcium sulfate formation and the risk of catalyst clogging; and the negative charge of BN / manganese borate nanospheres can attract Ca 2+ions, avoiding direct contact with the active sites, reducing the rate of catalyst deactivation, thereby improving the stability of the catalyst and extending the service life of the catalyst.

[0044] The catalyst V2O5-WO3 / TiO2-(1, 2, 3, 4, 5) was made into a honeycomb catalyst with a cross-section of 150*150mm, 13 holes*13 holes, and a length of 500mm. It was placed in a simulated flue. The flow rate in the catalyst hole was 5m / s and the dust content was 100g / Nm 3 , simulating real flue gas passing vertically from top to bottom through the catalyst pores, ventilation for 10 hours without soot blowing, measuring the pressure difference between the upper and lower ends of the catalyst to reflect the anti-clogging performance of the catalyst. The test results are shown in Table 3.

[0045] Table 3 Catalyst anti-clogging performance

[0046]

[0047] It can be seen from Table 3 that the compression resistance, wear resistance and anti-clogging performance of V2O5-WO3 / TiO2-1, 2, 3 are significantly better than those of V2O5-WO3 / TiO2-4, 5 catalysts; the reason is that BN / manganese borate particles can combine excellent thermal stability and mechanical properties, thus improving the wear resistance and compressive strength of the catalyst; and BN / manganese borate nanospheres can effectively inhibit the reaction of SO2 with water and ammonia, thereby reducing the possibility of calcium sulfate generation, thereby reducing the risk of catalyst clogging.

[0048] The above is only a preferred implementation of the patent of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the patent of the present invention. These improvements and modifications should also be regarded as the scope of protection of the patent of the present invention.

Claims

1. A multifunctional composite wear-resistant and anti-blocking denitrification catalyst, characterized in that: The catalyst comprises a TiO2 carrier, an active substance V2O5 loaded on the TiO2 carrier, an auxiliary agent WO3, and BN / manganese borate particles doped in the catalyst; in the catalyst, the content of V2O5 is 0.2-1%, the content of WO3 is 3-8%, and the content of BN / manganese borate particles is 5-12%.

2. The method for preparing the multifunctional composite wear-resistant and anti-blocking denitration catalyst according to claim 1, characterized in that: The steps include: S1, adding manganese borate to a mixture of CTAB, n-butanol and cyclohexane, then adding BN nanospheres and stirring, filtering and washing after aging, vacuum drying and calcining to obtain BN / manganese borate particles; S2. Dissolve ammonium metavanadate in oxalic acid, then add ammonium tungstate, TiO2 powder, BN / manganese borate particles, and silicate, stir and let stand, then dry and calcine, cool and grind and sieve to obtain V2O5-WO3 / TiO2 powder catalyst doped with BN / manganese borate particles.

3. The method for preparing the multifunctional composite wear-resistant and anti-blocking denitration catalyst according to claim 2, characterized in that: In the step S1, in the mixed system of CTAB, n-butanol and cyclohexane, the mass ratio of CTAB, n-butanol and cyclohexane is 1:(2-4):(1-3); The mass ratio of manganese borate to BN nanospheres is 1:(2-5).

4. The method for preparing the multifunctional composite wear-resistant and anti-blocking denitration catalyst according to claim 2, characterized in that: In the step S1, the aging time is 10-15 hours.

5. The method for preparing the multifunctional composite wear-resistant and anti-blocking denitration catalyst according to claim 2, characterized in that: In the step S1, the drying temperature is 60-80°C, and the calcination temperature is 700-800°C.

6. The method for preparing the multifunctional composite wear-resistant and anti-blocking denitration catalyst according to claim 2 or 3, characterized in that: In step S1, the preparation method of BN nanospheres is: mixing boron oxide and methanol in a molar ratio of 1:(2-5), allowing the mixture to stand, and separating the solid from the liquid to obtain the upper layer of liquid; Then, the CVD method is used to bring the upper liquid into a 950-1000°C high-temperature tube furnace with nitrogen, and ammonia is introduced. After cooling, the powder is collected; and then the powder is ammoniated at 1400-1500°C.

7. The method for preparing the multifunctional composite wear-resistant and anti-blocking denitration catalyst according to claim 2, characterized in that: In step S2, the drying temperature is 70-90°C for 8-12h; the calcination conditions are: heating rate 1-3°C / min, first heating to 250-280°C, keeping warm for 1-2h; then heating to 450-550°C at a heating rate 1-3°C / min, keeping warm for 2-3h.

8. The method for preparing the multifunctional composite wear-resistant and anti-blocking denitration catalyst according to claim 2, characterized in that: In the step S2, the amount of silicate added is 3-8% of the amount of TiO2 powder added.

9. The method for preparing the multifunctional composite wear-resistant and anti-blocking denitration catalyst according to claim 2, characterized in that: In the step S2, the obtained V2O5-WO3 / TiO2 powder catalyst doped with BN / manganese borate particles has a V2O5 content of 0.2-1%, a WO3 content of 3-8%, and a BN / manganese borate particle content of 5-12%.

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