SCR (Selective Catalytic Reduction) modified honeycomb catalyst for synergistically removing mercury and nitrate at low temperature and preparation method thereof
By preparing a low-temperature SCR modified catalyst with a porous honeycomb carrier and an active component impregnation solution, the problem of low mercury removal efficiency of existing catalysts at low temperatures is solved, efficient synergistic removal of mercury and nitrate and sulfur resistance are achieved, and the catalyst life is extended.
Patent Information
- Application Number
- CN202510834405.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-20
- Publication Date
- 2025-09-09
AI Technical Summary
Existing SCR catalysts have difficulty in effectively oxidizing elemental mercury (Hg0) under low temperature conditions and are susceptible to high-temperature sintering and SO2 poisoning, resulting in low mercury removal efficiency and short life, and are unable to achieve the combined removal of multiple pollutants in coal-fired flue gas.
A low-temperature SCR modified honeycomb catalyst was prepared using a porous honeycomb carrier and an active component impregnation solution. The acid sites of the carrier were increased by acidification treatment, and active components such as rubidium nitrate, V2O5, and WO3 were added to promote the oxidation of Hg0. The denitrification activity and sulfur resistance were enhanced by elements such as manganese and cerium.
The mercury oxidation removal rate and the sulfur resistance of the catalyst were significantly improved at low temperatures, the denitrification efficiency and service life were increased, and the combined removal of NOx and Hg in coal-fired flue gas was achieved.
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Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of catalysts, and in particular relates to an SCR modified honeycomb catalyst for synergistic removal of mercury and nitrate at low temperature and a preparation method thereof. Background Art
[0002] Mercury, as a special heavy metal substance, has the characteristics of high volatility and bioaccumulation. It has been listed as one of the most toxic global air pollutants by various countries and regions in the world. Among them, coal-fired power plants are one of the main man-made sources of mercury pollution in the atmosphere. At the same time, nitrogen oxides (NO x Mercury is a major pollutant contributing to environmental problems such as acid rain, ozone layer depletion, and global warming. Comprehensive control of various atmospheric pollutants from coal-fired power plants is urgent. With increasingly stringent requirements for mercury pollution control, the development of mercury removal technologies is imperative.
[0003] There are three main forms of mercury in coal-fired flue gas: elemental mercury (Hg 0 ), divalent mercury (Hg 2+ ) and particulate mercury (Hgp). Hg 0 It is the main form of mercury emissions from coal-fired power plants. Most of the mercury emissions from coal-fired power plants in my country are elemental mercury Hg 0 Hg in flue gas 2+ The compound is easily soluble in water, and the wet flue gas desulfurization device can remove 80% to 95% of Hg in the flue gas. 2+ , but for elemental mercury Hg which is hardly soluble in water 0 The capture effect is not significant. To improve the removal effect of mercury, Hg 0 Converted to Hg 2+ When the mercury in the flue gas is Hg 2+ When mercury is present, the oxidation removal rate of mercury is greatly improved. Since the SCR flue gas denitrification technology of coal-fired power plants has an oxidizing effect on elemental mercury, the SCR device can be used to effectively achieve NO x The key to the combined removal of Hg and Hg lies in the SCR catalyst. However, the existing SCR catalyst is not conducive to the removal of Hg 0 The oxidation of Hg can easily cause the catalyst to sinter and clog at high temperature, become deactivated by SO2 poisoning, and have a short life. In addition, commercial vanadium-based catalysts are mainly operated at 300-400℃. When they are operated at a low temperature of 200-300℃, high concentrations of SO2 and dust will inhibit the oxidation of Hg. 0 oxidation.
[0004] Therefore, the development and research of catalysts with high-efficiency denitrification and synergistic demercuration activity at low temperatures and good sulfur resistance, which can achieve the combined removal of multiple pollutants in coal-fired flue gas, has important scientific significance and environmental value, and its application prospects are very broad. Summary of the Invention
[0005] The present invention provides an SCR modified honeycomb catalyst for the synergistic removal of mercury and nitrate at low temperatures, which has high-efficiency denitration and synergistic mercury removal performance under low temperature conditions.
[0006] The technical solution of the present invention is: The first aspect discloses an SCR modified honeycomb catalyst for synergistic removal of mercury nitrate at low temperature, comprising a porous honeycomb carrier and an active component impregnation solution; The porous honeycomb substrate comprises the following raw materials in parts by weight: 20-40 parts of amphoteric oxide, 1-5 parts of rubidium nitrate, 2-6 parts of polyethylene glycol, 2-6 parts of sodium carboxymethyl cellulose, 1-5 parts of triethanolamine, 1-3 parts of silicon dioxide, 5-10 parts of aluminum oxide, 1-5 parts of calcium oxide, 0.1-3 parts of quartz fiber, 1-3 parts of soybean oil and 15-20 parts of water; The active component impregnation solution includes the following raw materials in parts by weight: 2-6 parts of ammonium metavanadate, 1-5 parts of ammonium metatungstate, 0.1-3 parts of ammonium molybdate tetrahydrate, 5-10 parts of oxalic acid, 0.1-3 parts of manganese nitrate, 0.1-3 parts of cerium nitrate, 0.2-6 parts of palladium nitrate, 0.2-6 parts of platinum nitrate, 0.5-6 parts of alkylphenol polyoxyethylene ether and 5-10 parts of water.
[0007] Preferably, the amphoteric oxide is titanium dioxide.
[0008] In a second aspect, a method for preparing the SCR modified honeycomb catalyst for synergistic removal of mercury and nitrate at low temperature is disclosed, comprising the following steps: 1) Add titanium dioxide to an acid solution for acidification and filter; 2) The obtained acidified titanium dioxide is mixed with rubidium nitrate, polyethylene glycol, sodium carboxymethyl cellulose, triethanolamine, silicon dioxide, aluminum oxide, calcium oxide, soybean oil, quartz fiber and water to form a slurry, which is then placed in a mixer for mixing; 3) The mixed clay is placed in an extruder and extruded into a wet body with a porous honeycomb structure; 4) Place the wet embryo in a drying oven for heating and drying; 5) The dried embryo is then calcined to obtain the final porous honeycomb substrate; 6) Water, ammonium metavanadate, ammonium metatungstate, ammonium molybdate tetrahydrate and oxalic acid are sequentially added to the reaction vessel to form a mixture, and then the alkylphenol polyoxyethylene ether is added. The mixture is then stirred until the solid is completely dissolved at a temperature of 20-80°C; 7) After stopping heating, add manganese nitrate, cerium nitrate, palladium nitrate, and platinum nitrate and continue stirring until dissolved to obtain an impregnation solution; 8) After standing for 1-3 hours, the porous honeycomb substrate is immersed in the impregnation liquid at a temperature of 20-30°C for 10-20 hours; 9) Place the impregnated sample in a drying oven for drying; 10) The dried sample is then calcined to obtain an SCR modified honeycomb catalyst for synergistic removal of mercury and nitrate at low temperature.
[0009] Preferably, in step 1), a hydrochloric acid solution with a concentration of 1-10 mol / L is used, the acidification temperature is 10-50° C., and the acidification time is 1-10 h.
[0010] Preferably, the mixing in step 2) is carried out in a mixer at a rotation speed of 200-300 r / min for 20-40 min.
[0011] Preferably, in step 4), the drying temperature is 100-120° C., the heating rate is 1-10° C., and the drying time is 10-20 h.
[0012] Preferably, in step 5), the calcination temperature is 300-500° C., and the calcination time is 20-30 h.
[0013] Preferably, in step 9), the drying temperature is 100-120° C., and the drying time is 1-10 h.
[0014] Preferably, in step 10), the calcination temperature is 100-300° C., and the calcination time is 1-10 h.
[0015] Hydrochloric acid acidification can increase the acidic reaction sites of the carrier, which is beneficial to the reaction rate of SCR denitrification; while Cl - As an anion, chlorine (such as Cl·free radical) may promote mercury oxidation, further improving the demercuration efficiency and further extending the service life of the catalyst. After acidification treatment, the specific surface area of the catalyst increases and the concentration of chemically adsorbed oxygen on the surface increases, showing higher activity in the demercuration test.
[0016] The rubidium nitrate modified catalyst neutralizes the acidic sites on the support surface through the strong alkalinity of Rb⁺, inhibiting SO2 adsorption and having better SO2 resistance; Soybean oil increases the lubricity of the carrier during extrusion; sodium carboxymethyl cellulose and triethanolamine act as thickeners and adhesives; silicon dioxide, aluminum oxide, and calcium oxide modify the carrier to enhance its strength and plasticity; the addition of quartz fiber makes the catalyst more stable and corrosion-resistant.
[0017] V2O5 and WO3 are active components of the catalyst reaction, and MoO2 increases the low-temperature activity of the catalyst and expands the temperature reaction window of the catalyst. 0 It has a promoting effect on the removal of sulfur and can improve its sulfur resistance.
[0018] Manganese nitrate, cerium nitrate: Ce element has outstanding oxygen affinity, which can promote the decomposition of H2O and form Hg 0 Oxidized OH - The addition of manganese and cerium can enhance the denitrification activity and the oxidation capacity of mercury, further improving the efficiency of mercury removal.
[0019] Palladium nitrate, platinum nitrate: Pt, Pd and other precious metals have high reactivity, and their high oxidation activity is used in the removal of Hg by trace modification of catalysts. 0 .
[0020] Compared with the prior art, the present invention has the following beneficial effects: The acidified carrier of the present invention significantly improves the oxidation removal rate of mercury. The transition metal additives MoO2 and rubidium nitrate significantly enhance the catalyst's sulfur resistance. The addition of an active dispersant, alkylphenol polyoxyethylene ether, makes the impregnated active ingredients more evenly distributed, improving the catalyst's low-temperature activity. The addition of manganese and cerium enhances denitrification activity and mercury oxidation, further improving mercury removal efficiency. Palladium nitrate and platinum nitrate also improve the catalyst's mercury removal efficiency and effectiveness. DETAILED DESCRIPTION
[0021] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions will be clearly and completely described below in conjunction with the embodiments of the present invention.
[0022] Unless otherwise specified, the materials in the following examples and comparative examples are in parts by mass.
[0023] Example 1 1) Add 30 parts of titanium dioxide to a 10 mol / L hydrochloric acid solution, acidify at 25°C for 6 hours, and filter; 2) The obtained acidified titanium dioxide was mixed with 5 parts of rubidium nitrate, 3 parts of polyethylene glycol, 5 parts of sodium carboxymethyl cellulose, 5 parts of triethanolamine, 3 parts of silicon dioxide, 5 parts of aluminum oxide, 5 parts of calcium oxide, 3 parts of soybean oil, 0.8 parts of quartz fiber, and 18 parts of water to form a slurry, which was then mixed in a mixer at 300 rpm for 35 minutes. 3) The mixed clay is placed in an extruder and extruded into a wet body with a porous honeycomb structure; 4) Place the wet embryo in a drying oven for drying at 120°C, heating at a rate of 4°C for 12 hours. 5) The dried embryo is then calcined at 500°C for 20 hours to obtain the final porous honeycomb substrate; 6) Add 8 parts of deionized water, 5 parts of ammonium metavanadate, 3 parts of ammonium metatungstate, 2 parts of ammonium molybdate tetrahydrate and 8 parts of oxalic acid to the reaction vessel in sequence to form a mixture, then add 4 parts of alkylphenol polyoxyethylene ether, and then stir the mixture until the solid is completely dissolved, the temperature is 40°C; 7) After stopping heating, add 2 parts of manganese nitrate, 2 parts of cerium nitrate, 3 parts of palladium nitrate, and 5 parts of platinum nitrate and continue stirring until dissolved to obtain an impregnation solution; 8) After standing for 3 hours, the porous honeycomb substrate is immersed in the impregnation solution; 9) Place the impregnated sample in a drying oven for drying at 120°C for 3 hours; 10) The dried catalyst is then calcined at 260° C. for 8 h to obtain an SCR modified honeycomb catalyst capable of synergistically removing mercury and nitrate at low temperature.
[0024] Example 2 1) Add 20 parts of titanium dioxide to 6 mol / L hydrochloric acid solution, acidify at 30°C for 5 hours, and filter; 2) The obtained acidified titanium dioxide was mixed with 3 parts of rubidium nitrate, 2 parts of polyethylene glycol, 3 parts of sodium carboxymethyl cellulose, 4 parts of triethanolamine, 3 parts of silicon dioxide, 7 parts of aluminum oxide, 3 parts of calcium oxide, 3 parts of soybean oil, 2 parts of quartz fiber, and 15 parts of water to form a slurry, which was then mixed in a mixer at a speed of 200 r / min for 30 minutes; 3) The mixed clay is placed in an extruder and extruded into a wet body with a porous honeycomb structure; 4) Place the wet embryo in a drying oven for drying at 110°C, with a heating rate of 5°C for 15 hours. 5) The dried embryo is then calcined at 400°C for 25 hours to obtain the final porous honeycomb substrate; 6) Add 5 parts of deionized water, 2 parts of ammonium metavanadate, 1 part of ammonium metatungstate, 0.5 parts of ammonium molybdate tetrahydrate and 5 parts of oxalic acid to the reaction vessel in sequence to form a mixture, then add 2 parts of alkylphenol polyoxyethylene ether, and then stir the mixture until the solid is completely dissolved, the temperature is 30°C; 7) After stopping heating, add 1 part manganese nitrate, 1 part cerium nitrate, 3 parts palladium nitrate, and 2 parts platinum nitrate and continue stirring until dissolved to obtain an impregnation solution; 8) After standing for 2 hours, the porous honeycomb substrate is immersed in the impregnation solution; 9) Place the impregnated sample in a drying oven for drying at 110°C for 5 hours; 10) The dried catalyst is then calcined at 300° C. for 3 h to obtain an SCR modified honeycomb catalyst capable of synergistically removing mercury and nitrate at low temperature.
[0025] Comparative Example 1 The difference from Example 1 is that sulfuric acid is used for acidification in step 1) of this comparative example, and the remaining preparation methods and steps are the same as those of Example 1.
[0026] Comparative Example 2 The difference from Example 1 is that rubidium nitrate is not added in step 2) of this comparative example, and the remaining preparation methods and steps are the same as those of Example 1.
[0027] Comparative Example 3 The difference from Example 1 is that ammonium molybdate tetrahydrate is not added in step 6) of this comparative example, and the remaining preparation methods and steps are the same as those of Example 1.
[0028] Comparative Example 4 The difference from Example 1 is that in step 7) of this comparative example, manganese nitrate and cerium nitrate are not added, and the remaining preparation methods and steps are the same as those of Example 1.
[0029] The catalysts prepared in the examples and comparative examples were subjected to performance tests. NO conversion rate = (C in -C out ) / C in ×100%, where C in : EntranceNO x Concentration, C out :Export No x concentration.
[0030] Mercury oxidation efficiency (η Hg 0 →Hg²⁺ ): measure Hg 0 The ratio of Hg²⁺ converted to water-soluble Hg²⁺, ηHg 0 →Hg 2+ (%) =[(Hg 0 入口浓度 -Hg 0 出口浓度 ) / Hg 0 入口浓度 ]×100%.
[0031] Reaction conditions: 280℃, flue gas composition NO (520mg / Nm 3 ), O2 (8%), ammonia nitrogen molar ratio of 1:1, SO2 (360mg / Nm 3 )、Hg(520ng / m 3 ), the carrier gas is N2, and the reaction space velocity is 7000h -1 The denitrification efficiency and elemental Hg oxidation rate were measured in a flue gas environment. The specific results are shown in Table 1.
[0032] Table 1
[0033] The denitrification and mercury removal SCR catalysts prepared by the present invention, Examples 1 and 2, both achieved high denitrification efficiencies and achieved mercury oxidation rates exceeding 91%. Example 2 exhibits different acidification concentrations, resulting in different specific surface areas. Lowering the concentration is detrimental to the SCR denitrification reaction rate and mercury removal efficiency. Comparative Example 1 utilizes sulfuric acid for acidification, and the acidification of anionic chloride ions significantly impacts the mercury removal efficiency. A carrier lacking chloride ions fails to further promote mercury oxidation, reducing the mercury removal efficiency. Comparative Example 2 lacks the addition of rubidium nitrate, making it more susceptible to SO₂ adsorption than Example 1. This inhibits both denitrification and mercury removal, shortening its service life. Comparative Example 3 lacks the addition of molybdenum, resulting in a significant decrease in catalyst performance at low temperatures. In Comparative Example 4, Ce also significantly enhances both denitrification and mercury removal; its omission results in significantly lower denitrification and mercury removal efficiencies than those of the examples.
[0034] The oxidation rates of elemental Hg were measured at 200°C and 300°C for the catalysts obtained in the above examples and comparative examples. The measured results are shown in Table 2 together with the results measured at 280°C in Table 1.
[0035] Table 2
[0036] It can be seen from Table 2 that the catalyst prepared in the present invention still has good catalytic performance under low temperature conditions of 200°C.
[0037] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and substance of the present invention, persons of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and such modifications or substitutions are intended to fall within the scope of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.
Claims
1. SCR modified honeycomb catalyst for synergistic removal of mercury and nitrate at low temperature, characterized in that: It includes a porous honeycomb carrier and an active component impregnation liquid; The porous honeycomb substrate comprises the following raw materials in parts by weight: 20-40 parts of amphoteric oxide, 1-5 parts of rubidium nitrate, 2-6 parts of polyethylene glycol, 2-6 parts of sodium carboxymethyl cellulose, 1-5 parts of triethanolamine, 1-3 parts of silicon dioxide, 5-10 parts of aluminum oxide, 1-5 parts of calcium oxide, 0.1-3 parts of quartz fiber, 1-3 parts of soybean oil and 15-20 parts of water; The active component impregnation solution includes the following raw materials in parts by weight: 2-6 parts of ammonium metavanadate, 1-5 parts of ammonium metatungstate, 0.1-3 parts of ammonium molybdate tetrahydrate, 5-10 parts of oxalic acid, 0.1-3 parts of manganese nitrate, 0.1-3 parts of cerium nitrate, 0.2-6 parts of palladium nitrate, 0.2-6 parts of platinum nitrate, 0.5-6 parts of alkylphenol polyoxyethylene ether and 5-10 parts of water.
2. The SCR modified honeycomb catalyst for synergistic removal of mercury and nitrate at low temperature according to claim 1, characterized in that: The amphoteric oxide is titanium dioxide.
3. The method for preparing the SCR modified honeycomb catalyst for synergistic removal of mercury and nitrate at low temperature according to claim 2, characterized in that: The following steps are involved: 1) Add titanium dioxide to an acid solution for acidification and filter; 2) The obtained acidified titanium dioxide is mixed with rubidium nitrate, polyethylene glycol, sodium carboxymethyl cellulose, triethanolamine, silicon dioxide, aluminum oxide, calcium oxide, soybean oil, quartz fiber and water to form a slurry, which is then placed in a mixer for mixing; 3) The mixed clay is placed in an extruder and extruded into a wet body with a porous honeycomb structure; 4) Place the wet embryo in a drying oven for heating and drying; 5) The dried embryo is then calcined to obtain the final porous honeycomb substrate; 6) Water, ammonium metavanadate, ammonium metatungstate, ammonium molybdate tetrahydrate and oxalic acid are sequentially added to the reaction vessel to form a mixture, and then the alkylphenol polyoxyethylene ether is added. The mixture is then stirred until the solid is completely dissolved at a temperature of 20-80°C; 7) After stopping heating, add manganese nitrate, cerium nitrate, palladium nitrate, and platinum nitrate and continue stirring until dissolved to obtain an impregnation solution; 8) After standing for 1-3 hours, the porous honeycomb substrate is immersed in the impregnation liquid at a temperature of 20-30°C for 10-20 hours; 9) Place the impregnated sample in a drying oven for drying; 10) The dried sample is then calcined to obtain an SCR modified honeycomb catalyst for synergistic removal of mercury and nitrate at low temperature.
4. The method for preparing the SCR modified honeycomb catalyst for synergistic removal of mercury nitrate at low temperature according to claim 3, characterized in that: In step 1), a hydrochloric acid solution with a concentration of 1-10 mol / L is used, the acidification temperature is 10-50° C., and the acidification time is 1-10 h.
5. The method for preparing the SCR modified honeycomb catalyst for synergistic removal of mercury and nitrate at low temperature according to claim 3, characterized in that: In step 2), the mixing is carried out in a mixer at a speed of 200-300 r / min for 20-40 min.
6. The method for preparing the SCR modified honeycomb catalyst for synergistic removal of mercury nitrate at low temperature according to claim 3, characterized in that: In step 4), the drying temperature is 100-120°C, the heating rate is 1-10°C, and the drying time is 10-20 hours.
7. The method for preparing the SCR modified honeycomb catalyst for synergistic removal of mercury and nitrate at low temperature according to claim 3, characterized in that: In step 5), the calcination temperature is 300-500° C. and the calcination time is 20-30 hours.
8. The method for preparing the SCR modified honeycomb catalyst for synergistic removal of mercury nitrate at low temperature according to claim 3, characterized in that: In step 9), the drying temperature is 100-120° C. and the drying time is 1-10 hours.
9. The method for preparing the SCR modified honeycomb catalyst for synergistic removal of mercury nitrate at low temperature according to claim 3, characterized in that: In step 10), the calcination temperature is 100-300° C. and the calcination time is 1-10 h.