Rhenium-containing NH3-SCR catalyst and preparation method and application thereof

Abstract

The invention provides a rhenium-containing NH3-SCR (selective catalytic reduction) catalyst as well as a preparation method and application thereof. The catalyst comprises a carrier TiO2 and an active component loaded on the carrier, the active components are vanadium oxide and ammonium perrhenate. The catalyst guarantees good catalytic activity at the temperature of 250-350 DEG C while reducing the vanadium content, has excellent sulfur resistance and good water resistance, is simple in preparation process, low in cost and free of secondary pollution, can be used for catalytic treatment of fixed source NOx, and has good industrial application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of air pollution control, and in particular to a rhenium-containing NH3-SCR catalyst and a preparation method and application thereof. Background Art

[0002] Currently, nitrogen oxides NO x It is one of the most concerned atmospheric pollutants. It can cause environmental problems such as haze, photochemical smog and acid rain, which endanger the environment and human health. At present, the most effective method to control nitrogen oxide pollution is the selective catalytic reduction technology (NH3-SCR) with NH3 as the reductant. The most widely used NH3-SCR catalyst is the vanadium-based catalyst. However, the temperature window of commercial vanadium-based catalysts is generally high, which limits their application in the low-temperature section. In addition, the vanadium content in common vanadium-based catalysts is high (V2O5 accounts for 5% by mass), and V2O5 has high biological toxicity (LD50 = 10 mg / / kg), which will bring potential harm to public health. Therefore, reducing the vanadium content while ensuring the activity of vanadium-based catalysts in the low-temperature section has attracted the attention of researchers.

[0003] Rhenium in ammonium perrhenate is in a high-valent state, so it is often used as an oxidant. In addition, the rhenium element does not form stable sulfate. Therefore, the catalyst with ammonium perrhenate as the active component should have good oxidation performance and not adsorb sulfur dioxide, and have a good anti-sulfur effect. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention provides a rhenium-containing NH3-SCR catalyst and a preparation method and application thereof. The catalyst is added with ammonium perrhenate, which reduces the vanadium content while ensuring good catalytic activity in the temperature range of 250°C-350°C, and has excellent sulfur resistance and good water resistance. The preparation process is simple, the cost is low, and there is no secondary pollution. It can be used for fixed source NO x Catalytic treatment has good industrial application prospects.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A rhenium-containing NH3-SCR catalyst consists of a carrier and an active component; the carrier is TiO2; the active component is vanadium pentoxide and ammonium perrhenate.

[0007] Furthermore, in the catalyst, the mass of vanadium pentoxide in the active component is 1% of the total mass of the carrier.

[0008] Furthermore, in the catalyst, the mass of ammonium perrhenate in the active component is 0.5% to 5.0% of the total mass of the carrier.

[0009] Furthermore, in the catalyst, the particle size of the carrier TiO2 is 10-100 nm.

[0010] A preparation method of a rhenium-containing NH3-SCR catalyst comprises the following steps: step A, preparing an appropriate amount of TiO2, adding it into ultrapure water and stirring it evenly to obtain a TiO2 suspension; step B, dissolving an appropriate amount of NH4ReO4 in ultrapure water, then adding an appropriate amount of NH4VO3 and H2C2O4, stirring them fully and mixing them evenly; step C, adding the solution obtained in step B into the TiO2 suspension, stirring it to reach stability, heating and stirring it in a water bath until all the water is evaporated to obtain a solid powder; step D, placing the solid powder obtained in step C in an oven for drying, and calcining it in a muffle furnace to obtain a V-Re / TiO2 catalyst.

[0011] Specifically, step A is: take an appropriate amount of TiO2 into a beaker, add ultrapure water and stir evenly with magnetic force.

[0012] Specifically, other vanadium-based precursors, such as vanadium tetrachloride, may also be used in step B.

[0013] Specifically, step C is: adding the solution obtained in step B to the TiO2 suspension, stirring magnetically for 30 minutes to achieve stability, heating to 95° C. in a water bath and stirring magnetically until all water is evaporated to obtain a solid powder.

[0014] Specifically, step D is: placing the solid powder obtained in step C in an oven and drying it at 105°C for 12 hours. Calcining it in a muffle furnace at 450°C for 2 hours at a heating rate of 10°C / min. Grinding the calcined catalyst fully, sieving it after grinding, retaining particles of 40-60 mesh, and obtaining a V-Re / TiO2 catalyst.

[0015] When pure ammonium perrhenate is calcined, it will usually completely decompose into Re2O7 at 400°C. In the preparation process of the catalyst of the present invention, the ratio of ammonium perrhenate to vanadium-based precursor and TiO2 carrier is adjusted to ensure a specific calcination temperature and time to obtain an ammonium perrhenate-supported catalyst.

[0016] The rhenium-containing NH3-SCR catalyst is used in the field of tail gas treatment from fixed sources.

[0017] Beneficial effects of the present invention: It can be seen from the technical scheme provided by the present invention that the rhenium-containing NH3-SCR catalyst provided by the present invention uses TiO2 as a carrier, vanadium pentoxide and ammonium perrhenate as active components, and the mass of vanadium pentoxide in the active components is 1% of the total mass of the carrier, and the mass of ammonium perrhenate is 0.5% to 5.0% of the total mass of the carrier, so that the catalytic activity in the temperature range of 250°C-350°C can be guaranteed while reducing the vanadium content, and has good sulfur resistance and water resistance. The catalyst provided by the present invention has a simple preparation process, low raw material price, low production cost, and no secondary pollution, and has good industrial application prospects in the field of tail gas treatment of fixed sources such as coal-fired power plants, cement plants, and glass furnaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Attached Figure 1 : XRD test results of the V-Re / TiO2 catalysts prepared in Examples 1 to 4 and the comparative example V / TiO2 catalyst.

[0019] Attached Figure 2 : NO of the V-Re / TiO2 catalysts prepared in Examples 1 to 4 and the comparative example V / TiO2 catalysts x Catalytic activity.

[0020] Attached Figure 3 : NO reaction rates of the V-Re / TiO2 catalysts prepared in Examples 1 to 4 and the comparative example V / TiO2 catalyst.

[0021] Attached Figure 4 : Experimental results of water resistance and sulfur resistance of the V1-Re5 / TiO2 catalyst prepared in Example 4. DETAILED DESCRIPTION

[0022] The technical solutions in the present invention are described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the present invention.

[0023] The technical solutions in the present invention are described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the present invention.

[0024] A rhenium-containing NH3-SCR catalyst consists of a carrier and an active component; the carrier is TiO2; the active components are vanadium pentoxide and ammonium perrhenate; in the catalyst, the mass of vanadium pentoxide in the active component is 1% of the total mass of the carrier, the mass of ammonium perrhenate is 0.5% to 5.0% of the total mass of the carrier, and the particle size of the carrier TiO2 is 10-100nm.

[0025] Specifically, the preparation method of the rhenium-containing NH3-SCR catalyst may include the following steps:

[0026] Step A: Take an appropriate amount of TiO2 in a beaker, add ultrapure water and stir evenly with magnetic force to obtain a TiO2 suspension.

[0027] Step B: dissolve an appropriate amount of NH4ReO4 in ultrapure water, then add an appropriate amount of NH4VO3 and H2C2O4, stir thoroughly and mix evenly.

[0028] Step C: Add the solution obtained in step B to the TiO2 suspension, stir magnetically for 30 min until it becomes stable, heat to 95° C. in a water bath and stir magnetically until all the water is evaporated to obtain a solid powder.

[0029] Step D: Place the solid powder obtained in step C in an oven and dry it at 105°C for 12 hours. Calcine in a muffle furnace at 450°C for 2 hours at a heating rate of 10°C / min. Grind the calcined catalyst thoroughly, sieve it after grinding, and retain particles of 40-60 mesh to obtain a V-Re / TiO2 catalyst.

[0030] Furthermore, the rhenium-containing NH3-SCR catalyst provided by the present invention can be used in the field of tail gas treatment from fixed sources, while reducing the vanadium content, ensuring the catalytic activity in the temperature range of 250°C-350°C, and has good sulfur and water resistance, and has good industrial application prospects.

[0031] In order to more clearly demonstrate the technical solution and technical effects provided by the present invention, the rhenium-containing NH3-SCR catalyst and its preparation method and application in the present invention are described in detail with specific embodiments below.

[0032] Example 1

[0033] A rhenium-containing NH3-SCR catalyst, the preparation method of which may include the following steps:

[0034] Step A: Take 5 g of TiO2 with a particle size of 25 nm and put it in a beaker. Add 20 mL of ultrapure water and stir magnetically to obtain a TiO2 suspension.

[0035] Step B: Dissolve 0.025 g NH4ReO4 in 50 ml ultrapure water, then add 0.0643 g NH4VO3 and 0.6430 g H2C2O4 and stir thoroughly for 30 min to mix evenly.

[0036] Step C: Add the solution obtained in step B to the TiO2 suspension, stir magnetically for 30 min until it becomes stable, heat to 95° C. in a water bath and stir magnetically until all the water is evaporated to obtain a solid powder.

[0037] Step D: Place the solid powder obtained in step C in an oven and dry it at 105°C for 12 hours. Calcine in a muffle furnace at 450°C for 2 hours at a heating rate of 10°C / min. Grind the calcined catalyst thoroughly, sieve it after grinding, and retain particles of 40-60 mesh to obtain V1-Re 0.5 / TiO2 catalyst.

[0038] Embodiment 2~4

[0039] The same catalyst preparation method as in Example 1 was used, only the mass of NH4ReO4 in step B was adjusted, and V-Re / TiO2 catalysts with NH4ReO4 / TiO2 mass ratios of 1.5%, 3.0%, and 5.0% were prepared, respectively, and were recorded as V1-Re 1.5 / TiO2, V1-Re3 / TiO2, V1-Re5 / TiO2.

[0040] Comparative Example

[0041] The same catalyst preparation method as in Example 1 was adopted, except that NH4ReO4 was not added in step B, to prepare a V1 / TiO2 catalyst having a V2O5 / TiO2 mass ratio of 1.0%.

[0042] XRD tests were performed on the V-Re / TiO2 catalysts prepared in Examples 1 to 4 and the V1 / TiO2 catalysts prepared in the comparative example. The results are shown in the attached Figure 1 It can be seen that with the increase of NH4ReO4 loading, the peaks attributed to NH4ReO4 were observed in the XRD spectrum of the catalyst (PDF#85-0347).

[0043] Experiments were conducted on a NO catalytic test device using the V-Re / TiO2 catalysts prepared in Examples 1 to 4 of the present invention and the V1 / TiO2 catalyst prepared in the comparative example.

[0044] 100 mg of catalyst was pressed into tablets and granulated (size was 40-60 mesh), and filled on top of the quartz sand core of the fixed bed reactor. Then a small amount of quartz wool was filled on top of the catalyst particles. xThe concentration was 500 ppm and the total gas flow rate was maintained at 200 mL min −1 , gas hourly space velocity (GHSV) is 120000 mL·g −1 ·h −1 Set the temperature control program, where the heating rate is 10 ℃·min −1 , keep the temperature at each target temperature for 0.5 h, and detect the composition of the outlet exhaust gas in real time. x The conversion rate is calculated as follows:

[0045] Among them, Cinput (ppm) and Coutput (ppm) are the NO in and out of the reactor, respectively. x concentration.

[0046] In order to further study the intrinsic reactivity of the catalyst, the catalytic decomposition of NO per unit mass of catalyst per unit time was calculated. x The number of times (conversion frequency, Reaction frequency, denoted as R no ), the calculation formula is as follows:

[0047] Where N A is Avogadro's constant; C mol Input (mol s -1 )、C mol Output (mol s -1 ) are the NO inlet and outlet of the reactor respectively. x Molar flow rate; W (g) is the mass of the catalyst.

[0048] The activity test results of the V-Re / TiO2 catalysts prepared in Examples 1 to 4 and the V1 / TiO2 catalysts prepared in the comparative example are shown in the attached Figure 2-3 It can be seen that after NH4ReO4 loading, the NO x Both the conversion rate and NO reaction rate are greatly improved, and increase with the increase of NH4ReO4 loading.

[0049] The V1-Re5 / TiO2 catalyst with the best catalytic activity was selected for a 16-hour water and sulfur resistance test: The water resistance test was carried out by introducing N2 into a water bubbling device and then mixing it with the remaining gas components to make the water vapor content in the gas flow about 5%. The sulfur resistance test was carried out by additionally introducing SO2 to control the SO2 content in the gas flow to 200ppm. The other conditions were the same as those of the activity test experiment. The experimental results are attached. Figure 4 .

[0050] It can be seen that the V1-Re5 / TiO2 catalyst has good water resistance and excellent sulfur resistance, and can be used under complex flue gas conditions.

[0051] In summary, after the addition of ammonium perrhenate, due to its good oxidizability, the NH3-SCR catalytic activity of the low-vanadium-content V2O5 / TiO2 catalyst is improved, and due to its poor adsorption of SO2, the sulfur resistance of the catalyst is also guaranteed. The catalyst of the present invention not only has good catalytic activity and stable performance, but also has a simple preparation process, low cost, no secondary pollution, and has good application prospects.

[0052] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A rhenium-containing NH3-SCR catalyst, consisting of a carrier and an active component; the carrier is TiO2; the active component is vanadium pentoxide and ammonium perrhenate.

2. A rhenium-containing NH3-SCR catalyst as claimed in claim 1, further wherein the mass of vanadium pentoxide in the active component is 1% of the total mass of the carrier.

3. A rhenium-containing NH3-SCR catalyst according to claim 1, further, the mass of ammonium perrhenate in the active component is 0.5% to 5.0% of the total mass of the carrier.

4. A rhenium-containing NH3-SCR catalyst according to any one of claims 1 to 3, further, the particle size of the carrier TiO2 is 10-100 nm.

5. A method for preparing the rhenium-containing NH3-SCR catalyst according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step A, prepare an appropriate amount of TiO2, add it into ultrapure water and stir evenly to obtain a TiO2 suspension; Step B, dissolve an appropriate amount of NH4ReO4 in ultrapure water, then add an appropriate amount of NH4VO3 and H2C2O4, stir well and mix evenly; Step C, adding the solution obtained in step B to the TiO2 suspension, stirring until it reaches stability, heating and stirring in a water bath until all the water is evaporated to obtain a solid powder; Step D: Dry the solid powder obtained in step C in an oven and calcine it in a muffle furnace to obtain a V-Re / TiO2 catalyst.

6. A preparation method according to claim 5, characterized in that: In step C, the water bath heating temperature is 95°C.

7. A preparation method according to claim 5, characterized in that: In step D, the drying temperature is 105°C, the time is 12 h, the calcination temperature is 450°C, the time is 2 h, and the heating rate is 10°C / min.

8. Use of the rhenium-containing NH3-SCR catalyst according to any one of claims 1 to 4 for the treatment of tail gas from a fixed source.

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