Method for preparing high-activity denitration catalyst from washed tailings slime

Abstract

The present application relates to a kind of high activity denitration catalysts prepared with washing end slime, which utilizes washing end slime as raw material, through surface modification treatment, auxiliary lifting, copolymerization flocculation and heat treatment conversion four main processes, with surface modification to enhance the coordination between coal slime and metal Ce 4+ , Fe 3+ Ion, adding Fe and other auxiliary to further improve the denitration activity of catalyst, copolymerization flocculation utilizes ethylenediamine and Ce 4+ , Fe 3+ Ion to form complex system, then copolymerization reaction with acrylamide, realize the separation of coal slime mixture and water, achieve flocculation purpose;Finally, through heat treatment to further promote active center formation, enhance the adsorption of material to NO and oxygen molecule, increase low temperature NH3-SCR denitration catalytic activity, prepare denitration catalyst with good catalytic activity and SO2 resistance.

Description

Technical Field

[0001] The invention belongs to the field of adsorption material preparation and catalytic denitration, and particularly relates to a method for preparing a high-activity denitration catalyst by washing terminal coal slime. Background Art

[0002] Currently, my country's annual raw coal processing capacity is approximately 2.4 billion tons, generating approximately 200 million tons of coal slime. Coal slime, a semi-solid product formed from water-containing coal powder during the coal washing process, is difficult to dry due to its fine particle size, low calorific value, high viscosity, and high water retention. It easily reliquefies and flows everywhere, severely impacting the environment and ecology. Consequently, coal slime water has become a major source of pollution in the coal industry.

[0003] From a structural perspective, the coal slime at the end of washing has a high ash content, low calorific value, small particle size, and a high content of fine particles, with fine particles smaller than 200 mesh accounting for approximately 70% to 90%. In terms of composition, excluding the carbon component, the remaining composition is mainly clay minerals and polyionic components such as SiO2 (20-60%), Al2O3 (10-35%), and Fe2O3 (5-35%), which have high thermal stability. Furthermore, the large number of oxygen-containing hydrophilic groups such as hydroxyl and carboxyl groups on the surface of the coal particles in the coal slime at the end of washing, as well as the strong electronegativity of the clay mineral surface, make the coal slime susceptible to electrostatic adsorption with metal cations, which is conducive to the loading and dispersion of metal / metal oxide active components, thus providing favorable conditions for its use as a catalyst carrier.

[0004] Flue gas SCR (SCR) is one of the current technologies for reducing nitrogen oxide emissions. However, due to the toxic effects of impurities such as dust in the flue gas, as well as the presence of certain concentrations of SO₂ in the flue gas, ammonium salts are more likely to deposit on the catalyst surface at low temperatures, reducing catalyst performance and causing catalyst deactivation. Consequently, poor catalytic activity and SO₂ tolerance are the main challenges facing current low-temperature SCR denitrification catalysts. Ce-based catalysts, due to their excellent oxygen carrier properties and SO₂ tolerance, have become a research hotspot for low-temperature denitrification catalysts. Oxygen vacancies on the CeO₂ surface can capture or release O atoms, facilitating the adsorption and oxidation of NO. Under certain conditions, NO in the reaction gas can be oxidized to NO₂. Since NO₂ is more readily reduced to N₂ by NH₃, this facilitates the NH₃-SCR reaction. To further enhance the catalytic activity and SO₂ tolerance of Ce-based catalysts, the introduction of metal or metal oxide promoters and supports with large surface areas are currently the primary approaches used by researchers.

[0005] The present application combines the characteristics that the coal slime is easy to have electrostatic adsorption with metal cations due to the large amount of oxygen-containing hydrophilic groups such as hydroxyl and carboxyl on the surface of the coal particles and the strong electronegativity of the clay mineral surface, and the excellent oxygen carrier characteristics and SO2 resistance of the Ce-based catalyst, increases the carrier effect of the coal slime as the catalyst carrier through surface modification, and further improves the catalyst denitration activity by adding Fe and other additives, while reducing the hydrophilicity of the coal slime, to prepare a composite denitration catalyst through simple heat treatment. SUMMARY

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: a method for preparing a high-activity denitration catalyst from coal slime at the end of washing and separation, which uses coal slime at the end of washing and separation as raw material, and realizes the surface modification, additive promotion, copolymerization flocculation and heat treatment conversion through four main processes, so as to enhance the coordination between the coal slime and metal Ce 4+ , Fe 3+ ions through surface modification, to improve the denitration activity of the catalyst by adding cerium, iron and other additives, to realize the separation of the coal slime mixture and water and achieve the flocculation purpose by forming a complex system of ethylenediamine and Ce 4+ , Fe 3+ ions and then copolymerizing with acrylamide in the copolymerization flocculation process, and finally to further promote the formation of active centers, enhance the adsorption of NO and oxygen molecules, increase the low-temperature NH3-SCR denitration catalytic activity, and prepare a denitration catalyst with good catalytic activity and SO2 resistance.

[0007] The present application comprises the following steps:

[0008] Surface modification treatment: under the condition of 30-60℃, a certain proportion of surface modifier is added into the coal slime aqueous solution mixture, mixed uniformly, and continuously stirred for a certain time, the mass of the added surface modifier is 1-2% of the mass of the coal slime in the mixture, and mixture A is obtained;

[0009] Additive promotion: a certain amount of cerium and iron salt is added under stirring, and the mixture is stirred uniformly; the total amount of the added metal salt is 0.3-2% of the mass of mixture A, and mixture B is obtained;

[0010] Copolymerization flocculation: a certain amount of ethylenediamine is added into mixture B, and after continuous stirring for a certain time, a certain amount of acrylamide is added, and the reaction is continued for 1-2h under a certain reaction temperature;

[0011] Heat treatment conversion: after cooling to room temperature, filtration, washing and drying, the obtained sample is calcined at a temperature of 400-600℃ under nitrogen atmosphere for a certain time to obtain a composite material.

[0012] Further, the surface modifier in the step of "surface modification treatment" is sodium citrate and sodium polyacrylate, and the molar mixing ratio is 1-2.5:1.

[0013] Further, the cerium salt in the step of "promoter promotion" is cerium nitrate hexahydrate or cerium chloride, and the iron salt is ferric chloride or ferric nitrate, wherein the molar ratio of cerium salt: iron salt is 2-5:1.

[0014] Further, the amount of ethylenediamine added in the step of "copolymer flocculation" is m1=(40.0-80.0)×[C]×V×10 －3 , wherein: m1 is the mass of ethylenediamine, in g; [C] is the concentration of suspended solids in mixture B, in g·L －1 ; V is the volume of the coal slime water solution mixture, in L.

[0015] Further, the amount of acrylamide added in the step of "copolymer flocculation" is m2=(28.0-66.0)×[C]×V×10 －3 , wherein: m2 is the mass of acrylamide, in g; [C] is the concentration of suspended solids in mixture B, in g·L －1 ; V is the volume of the coal slime water solution mixture, in L.

[0016] Further, the reaction temperature in the step of "copolymer flocculation" is 40-70℃.

[0017] Further, the stirring speed in the step of "copolymer flocculation" is 200-300 rpm.

[0018] Further, the calcination time in the step of "heat treatment conversion" is 1h.

[0019] Advantages of the present application:

[0020] The present application combines the characteristics of the large amount of hydroxyl and carboxyl oxygen-containing hydrophilic groups on the surface of the coal particles of the washed and screened coal slime and the strong electronegativity of the clay mineral surface, the electrostatic adsorption of the coal slime with metal cations, the characteristics of the loading and dispersion of the metal / metal oxide active components, the excellent oxygen carrier properties of the Ce-based catalyst, and the SO2 resistance, increases the carrier effect of the coal slime as a catalyst carrier through surface modification, further promotes the catalyst denitration activity by adding Fe and other promoters, and at the same time reduces the hydrophilicity of the coal slime, and prepares a composite denitration catalyst through simple heat treatment, realizes the transformation of waste into treasure of the washed and screened coal slime, and is also beneficial to reducing environmental pollution, realizing clean utilization and high value-added conversion of coal resources. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 It is a main step in a method for preparing a high-activity denitrification catalyst by washing terminal coal slime. DETAILED DESCRIPTION

[0023] The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more precise definition of the protection scope of the present invention.

[0024] like Figure 1 As shown in the figure, the technical solution of the present invention adds sodium citrate and sodium polyacrylate to the coal slime for surface modification, thereby enhancing the bonding between the coal slime and the metal Ce 4+ 、Fe 3+ The coordination between ions can achieve the purpose of enhancing and stabilizing the active components and additive metal particles. Ethylenediamine and acrylamide are added under continuous stirring, and the ethylenediamine and Ce 4+ 、Fe 3+ The ions form a complex system, which further copolymerizes with acrylamide to achieve flocculation effect and realize the separation of coal slime mixture and water. Finally, the organic components are removed by calcination, the active components are activated, and the reducing property of carbon atoms at high temperature is used to convert some high-valent metal Ce into 4+ 、Fe 3+ Reduced to a lower valence state to form Ce 4+ / Ce 3+ 、Fe 3+ / Fe 2+ The present invention is further described below through specific examples. However, the present invention is not limited to the following examples.

[0025] The terminal coal slime water solution mixture in this embodiment is sourced from a coal washing plant in Anhui Province. The basic properties of the coal slime water are as follows:

[0026] project pH Suspended solids (g / L) Viscosity (Pa / s) <![CDATA[密度(g / m 3 )]]> End coal slime water 6.4 75.3 <![CDATA[3.4×10 -3 ]]> 1.04

[0027] The coal slime ash content is 34.5%, and the main components are as follows;

[0028] Element SiO2 <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO BaO <![CDATA[K2O]]> MgO content% 46.5 18.5 8.04 6.2 4.2 1.64 2.05

[0029] Example 1:

[0030] (1) Take 1000 ml of the above-mentioned coal sludge aqueous solution, add sodium citrate and sodium polyacrylate (molar ratio of 1:1) to the mixture at 30°C, mix evenly, and continue stirring for a certain time. The total mass of the added sodium citrate and sodium polyacrylate is 1.5% of the mass of the suspended matter in the mixture;

[0031] (2) adding cerium nitrate and ferric nitrate (Ce:Fe molar ratio is 2:1) under stirring and stirring evenly; the total amount of metal salt added is 0.3% of the mass of the mixture in step (1);

[0032] (3) Add a certain amount of ethylenediamine under stirring at 200 rpm, amount m1 = 40 × [C] × V × 10 －3 , where: m1 is the mass of ethylenediamine, unit is g; [C] is the concentration of suspended matter in the mixture, unit is g·L －1 ; V is the volume of the coal slime-water mixture, in L. Ethylenediamine was added, m1 = 2.87 g.

[0033] (4) After stirring for 1 hour at 40℃, add a certain amount of acrylamide, the amount added is m2 = 36 × [C] × V × 10 －3 , where: m2 is the mass of acrylamide, unit is g; [C] is the concentration of suspended matter in the mixture, unit is g·L －1 V is the volume of the coal slurry-water mixture in L. Add acrylamide, m2 = 2.7 g. Continue the reaction for 1 h.

[0034] (5) After cooling to room temperature, filtering, washing, and drying, the obtained sample was heated to 500° C. under a nitrogen atmosphere and calcined at this temperature for 1 h to obtain a composite material.

[0035] The composite material prepared in this example is an SCR denitrification catalyst. Under the conditions of 10% O2, 400ppm NO, 400ppm SO2 N2 carrier gas as simulated flue gas, NH3 / NO=0.8, and catalyst dosage of 100mg, at 220-400℃, the NO conversion rate is not less than 85%.

[0036] Example 2:

[0037] (1) Take 1000 ml of the above-mentioned coal slurry aqueous solution, add sodium citrate and sodium polyacrylate (molar ratio of 1.2:1) to the mixture at 50°C, mix well, and continue stirring for a certain time. The total mass of the added sodium citrate and sodium polyacrylate is 2% of the mass of the suspended matter in the mixture;

[0038] (2) adding cerium nitrate and ferric nitrate (Ce:Fe molar ratio is 4:1) under stirring and stirring evenly; the total amount of metal salt added is 1% of the mass of the mixture in step (1);

[0039] (3) Add a certain amount of ethylenediamine under stirring at 240 rpm, amount m1 = 80 × [C] × V × 10 －3 , where: m1 is the mass of ethylenediamine, unit is g; [C] is the concentration of suspended matter in the mixture, unit is g·L －1 ; V is the volume of the coal slime-water mixture, in L. Ethylenediamine was added, m1 = 6.03 g.

[0040] (4) After stirring for 1 hour at 50℃, add a certain amount of acrylamide, the amount added is m2 = 66 × [C] × V × 10 －3 , where: m2 is the mass of acrylamide, unit is g; [C] is the concentration of suspended matter in the mixture, unit is g·L －1 V is the volume of the coal slurry-water mixture in L. Add acrylamide, m2 = 4.57 g. Continue the reaction for 1 h.

[0041] (5) After cooling to room temperature, filtering, washing, and drying, the obtained sample was heated to 500° C. under a nitrogen atmosphere and calcined at this temperature for 1 h to obtain a composite material.

[0042] The composite material prepared in this example is an SCR denitrification catalyst. Under the conditions of 10% O2, 400ppm NO, 400ppm SO2 N2 carrier gas as simulated flue gas, NH3 / NO=0.8, and catalyst dosage of 100mg, at 220-400℃, the NO conversion rate is not less than 85%.

[0043] Example 3:

[0044] (1) Take 1000 ml of the above-mentioned coal sludge aqueous solution, add sodium citrate and sodium polyacrylate (molar ratio of 1.2:1) to the mixture at 40°C, mix well, and continue stirring for a certain time. The total mass of the added sodium citrate and sodium polyacrylate is 1.5% of the mass of the suspended matter in the mixture;

[0045] (2) adding cerium nitrate and ferric nitrate (Ce:Fe molar ratio of 3:1) under stirring and stirring evenly; the total amount of metal salt added is 1.6% of the mass of the mixture in step (1);

[0046] (3) Add a certain amount of ethylenediamine under stirring at 260 rpm, amount m1 = 60 × [C] × V × 10 －3 , where: m1 is the mass of ethylenediamine, unit is g; [C] is the concentration of suspended matter in the mixture, unit is g·L －1 ; V is the volume of the coal slime-water mixture, in L. Ethylenediamine was added, m1 = 4.23 g.

[0047] (4) After stirring for 1 hour at 65℃, add a certain amount of acrylamide, the amount added is m2 = 28 × [C] × V × 10 －3 , where: m2 is the mass of acrylamide, unit is g; [C] is the concentration of suspended matter in the mixture, unit is g·L －1 V is the volume of the coal slurry-water mixture in L. Add acrylamide, m2 = 1.68 g. Continue the reaction for 1 h.

[0048] (5) After cooling to room temperature, filtering, washing, and drying, the obtained sample was heated to 500° C. under a nitrogen atmosphere and calcined at this temperature for 1 h to obtain a composite material.

[0049] The composite material prepared in this example is an SCR denitrification catalyst. Under the conditions of 10% O2, 400ppm NO, 400ppm SO2 N2 carrier gas as simulated flue gas, NH3 / NO=0.8, and catalyst dosage of 100mg, at 220-400℃, the NO conversion rate is not less than 80%.

[0050] Example 4:

[0051] (1) Take 1000 ml of the above-mentioned coal sludge aqueous solution, add sodium citrate and sodium polyacrylate (molar ratio of 1.2:1) to the mixture at 60°C, mix well, and continue stirring for a certain time. The total mass of the added sodium citrate and sodium polyacrylate is 1.5% of the mass of the suspended matter in the mixture;

[0052] (2) adding cerium nitrate and ferric nitrate (Ce:Fe molar ratio of 5:1) under stirring and stirring evenly; the total amount of metal salt added is 2% of the mass of the mixture in step (1);

[0053] (3) Add a certain amount of ethylenediamine under stirring at 300 rpm, amount added m1 = 80 × [C] × V × 10 －3 , where: m1 is the mass of ethylenediamine, unit is g; [C] is the concentration of suspended matter in the mixture, unit is g·L －1 ; V is the volume of the coal slime-water mixture, in L. Ethylenediamine was added, m1 = 6.03 g.

[0054] (4) After stirring for 1 hour at 70℃, add a certain amount of acrylamide, the amount added is m2 = 66 × [C] × V × 10 －3 , where: m2 is the mass of acrylamide, unit is g; [C] is the concentration of suspended matter in the mixture, unit is g·L －1 V is the volume of the coal slurry-water mixture in L. Add acrylamide, m2 = 4.57 g. Continue the reaction for 1 h.

[0055] (4) After cooling to room temperature, filtering, washing, and drying, the obtained sample was heated to 500° C. under a nitrogen atmosphere and calcined at this temperature for 1 h to obtain a composite material.

[0056] The composite material prepared in this example is an SCR denitrification catalyst. Under the conditions of 10% O2, 400ppm NO, 400ppm SO2 N2 carrier gas as simulated flue gas, NH3 / NO=0.8, and catalyst dosage of 100mg, at 220-400℃, the NO conversion rate is not less than 80%.

[0057] The above description is merely an embodiment of the present invention. Common knowledge regarding the specific structure and characteristics of the solution is not described in detail herein. It should be noted that those skilled in the art will be able to make various modifications and improvements without departing from the structure of the present invention. These modifications and improvements should also be considered within the scope of protection of the present invention and will not affect the effectiveness and practicality of the present invention.

Claims

1. A method for preparing a high-activity denitration catalyst by washing terminal coal slime, characterized in that: The following steps are involved: Surface modification treatment: adding a surface modifier in a certain proportion to the coal slime aqueous solution mixture at 30-60°C, mixing evenly, and continuously stirring for a certain time. The mass of the added surface modifier is 1-2% of the mass of the coal slime in the mixture to obtain a mixture A. Additive enhancement: add a certain amount of cerium salt and iron salt under stirring, and stir the mixture evenly; the total amount of metal salt added is 0.3-2% of the mass of mixture A to obtain mixture B; Copolymerization flocculation: Add a certain amount of ethylenediamine to mixture B, continue stirring for a period of time, then add a certain amount of acrylamide, and continue the reaction at a certain reaction temperature for 1-2 hours; Heat treatment conversion: After cooling to room temperature, filtering, washing, and drying, the obtained sample is calcined at 400-600°C in a nitrogen atmosphere for a period of time to obtain a composite material; The surface modifiers described in the step "surface modification treatment" are sodium citrate and sodium polyacrylate, with a molar mixing ratio of 1-2.5:

1.

2. The method for preparing a high-activity denitration catalyst by washing terminal coal slime according to claim 1, characterized in that: The cerium salt described in the step "additive enhancement" is cerium nitrate hexahydrate or cerium chloride, and the iron salt is ferric chloride or ferric nitrate, wherein the molar ratio of cerium salt:iron salt is 2-5:

1.

3. The method for preparing a high-activity denitration catalyst by washing terminal coal slime according to claim 1, characterized in that: The amount of ethylenediamine added in the step "co-flocculation" is: m1 = (40.0-80.0) × [C] × V × 10 －3 , where: m1 is the mass of ethylenediamine, unit is g; [C] is the concentration of suspended matter in mixture B, unit is g·L －1 ; V is the volume of the coal slime water solution mixture, in L.

4. The method for preparing a high-activity denitration catalyst by washing terminal coal slime according to claim 3, characterized in that: The amount of acrylamide added in the step "co-flocculation" is: m2 = (28.0~66.0) × [C] × V × 10 －3 , where: m2 is the mass of acrylamide, in g; [C] is the concentration of suspended solids in mixture B, in g·L －1 ; V is the volume of the coal slime water solution mixture, in L.

5. The method for preparing a high-activity denitration catalyst by washing terminal coal slime according to claim 3 or 4, characterized in that: The reaction temperature in the step "co-flocculation" is 40-70°C.

6. The method for preparing a high-activity denitration catalyst by washing terminal coal slime according to claim 3 or 4, characterized in that: The stirring speed in the step "co-flocculation" is 200 to 300 rpm.

7. A method for preparing a high-activity denitration catalyst by washing terminal coal slime according to any one of claims 1, 3 or 4, characterized in that: The calcination time in the step "heat treatment conversion" is 1 hour.

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