Denitration catalyst capable of resisting alkali metal, water and sulfur composite poisoning as well as preparation method and application of denitration catalyst

Abstract

The invention relates to a denitration catalyst capable of resisting alkali metal, water and sulfur composite poisoning and a preparation method and application thereof, and belongs to the field of environment-friendly catalytic materials and air pollution control. An organic solvent is used as a template agent, cerium oxide, manganese oxide and tungsten oxide are used as active components, and a cerium-manganese-tungsten composite oxide active component with a porous structure and strong acidity is prepared by a coprecipitation-soft template method. The catalyst has a wide denitration temperature window, high denitration efficiency and excellent composite poisoning resistance stability. The catalyst component is environment-friendly, low in cost and simple in preparation method, and is particularly suitable for stable and efficient purification of NOx in complex flue gas in the cement industry.

Description

Technical Field

[0001] The invention relates to an SCR denitration catalyst which is resistant to compound poisoning by alkali metals, water and sulfur at medium and low temperatures and a preparation method thereof, and belongs to the field of environmental catalytic materials and air pollution control. Technical Background

[0002] Nitrogen oxides (NO x ) is a major atmospheric pollutant that can cause haze, acid rain, ozone holes and photochemical smog, causing serious harm to the environment and human health. Selective catalytic reduction (SCR) denitrification technology has the advantages of high denitrification efficiency, mature technology and no harmful products. It is the most widely used denitrification technology.

[0003] From 2014 to 2020, China's cement industry nitrogen oxide emissions continued to drop from 1.917 million tons to 722,000 tons, but the proportion of emissions in all industrial sources increased from 13.6% to 17.3%, thus achieving the goal of reducing nitrogen oxides (NO x )Ultra-low emissions become a top priority.

[0004] However, in actual application, the flue gas of kilns in various process sections of the cement industry contains high levels of calcium, potassium, sodium and other adhesive dust and SO2, which can easily cause wear and poisoning and deactivation of denitrification catalysts. Among the related technologies of alkali-poisoning-resistant denitrification catalysts reported at home and abroad, (CN201810573766.7) uses titanium-doped mesoporous molecular sieves as carriers, and vanadium, cerium, zirconium, niobium and manganese as active components. After loading alkali metals, the denitrification efficiency is above 85% in the temperature range of 330℃ to 400℃, but its temperature window is narrow and its medium and low temperature resistance to alkali metals is poor. (CN202110034856.0) Using metal oxides doped with non-metallic elements as active components and materials prepared by calcining metal oxides or metal precursor salts as carriers, its denitrification activity is greater than 80% at 270 to 420℃ after loading alkali metals, but its low-temperature activity is poor. (CN202110901325.7) A manganese-based catalyst is prepared, which has the performance of resistance to alkali metal poisoning and sulfur dioxide poisoning at 150°C, but its resistance to combined poisoning is poor.

[0005] Therefore, in the research on SCR denitrification catalysts for the cement industry, it is necessary not only to improve the catalyst's single resistance to alkali metal, water, and sulfur poisoning, but also to significantly improve its resistance to the combined poisoning of alkali metal, water, and sulfur. Therefore, it is of great significance to develop an efficient denitrification catalyst with excellent resistance to sulfur, water, and alkali metal combined poisoning under the actual working conditions of cement kilns. Summary of the invention

[0006] The purpose of the present invention is to solve the problem of poor stability of denitration catalysts in the cement industry against composite poisoning, and to provide a high-efficiency denitration catalyst that can achieve high resistance to alkali metals, water and sulfur at medium and low temperatures; another purpose of the present invention is to provide a method for preparing the above-mentioned denitration catalyst.

[0007] A denitration catalyst resistant to compound poisoning by alkali metals, water and sulfur. The catalyst uses hexadecyltrimethylammonium bromide as a template agent, and cerium oxide, manganese oxide and tungsten oxide as denitration active components.

[0008] In the technical solution of the present invention, the molar ratio of the three elements Ce, Mn and W is 1:(0.02-0.8):(0.02-0.30).

[0009] A method for preparing the above catalyst, the specific steps are as follows:

[0010] (1) Preparation of cerium manganese tungsten active component precursor solution

[0011] The cerium manganese tungsten oxide precursor is added to distilled water, heated and stirred until completely dissolved to obtain a clear solution A; hexadecyl trimethyl ammonium bromide is added to the distilled water, stirred evenly to obtain a dispersion B;

[0012] (2) Preparation of cerium-manganese-tungsten composite oxide catalyst

[0013] Solution A is added to dispersion B, stirred evenly, and then an alkaline agent is added to make the solution alkaline; the solution is then placed in an oven for aging, and finally washed, filtered, dried and calcined in sequence to obtain a cerium-manganese-tungsten composite oxide catalyst;

[0014] (3) Preparation of alkali metal-supported cerium-manganese-tungsten catalyst

[0015] The alkali metal precursor was added into distilled water and stirred until completely dissolved, and then the cerium manganese tungsten catalyst was added into the above solution and continued to be stirred. The sample was then placed in an oven to dry and then transferred to a muffle furnace for calcination.

[0016] In the above preparation method, the cerium manganese tungsten oxide precursor in step (1) is cerium nitrate, manganese nitrate and ammonium metatungstate.

[0017] In the above preparation method, the mass ratio between the cerium manganese tungsten oxide precursor and hexadecyltrimethylammonium bromide in step (1) is 10-15:3-8.

[0018] In the above preparation method, the alkaline reagent in step (2) is ammonia water, and the alkaline pH is 8-12.

[0019] In the above preparation method, the aging temperature in step (2) is 70-110° C. and the aging time is 2-5 h; the drying temperature is 70-90° C. and the drying time is 24 h; the calcination temperature is 400-700° C. and the calcination time is 1-5 h.

[0020] In the above preparation method, the alkali metal precursor in step (3) is potassium nitrate; and the mass ratio of the catalytically active component to the alkali metal precursor is 100:0.5-3.

[0021] The drying temperature is 70-110°C, and the drying time is 10-24 hours; the calcination temperature is 400-700°C, and the calcination time is 1-5 hours.

[0022] In the technical solution of the present invention, the catalyst is used in denitration.

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

[0024] (1) The catalyst of the present invention has excellent denitration activity and anti-composite poisoning stability under the conditions of 150-350°C, alkali metal, water and sulfur coexistence. The denitration efficiency is >80% under the conditions of 150-350°C, 1wt.%K loading, and >90% under the conditions of 180-350°C, 1wt.%K loading. The activity is maintained at more than 85% for 12 hours under the conditions of 200°C, 1wt.%K, 5%H2O and 300ppmSO2.

[0025] (2) The present invention uses organic solvents as modifiers to introduce pore structures and increase surface active sites. At the same time, tungsten doping increases the amount of acid on the catalyst surface, thereby improving the catalyst's ability to resist alkali metal, water, and sulfur poisoning. Under the condition of 1wt.% K loading, the catalyst has a denitration efficiency of >90% at 200°C, 5vol.% H2O, and 300ppm SO2. After 12 hours, its denitration efficiency is stable at more than 85%.

[0026] (3) The preparation method of the present invention is simple, low-cost, has low requirements for synthesis equipment, and has the advantages of extremely strong resistance to alkali / alkaline earth metal poisoning and water and sulfur poisoning. It is suitable for flue gas denitrification containing alkali / alkaline earth metal fly ash and SO2, such as waste incinerators, cement kilns, biomass fuel boilers and glass kilns, and can greatly extend the service life of the catalyst in flue gas denitrification. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The catalysts prepared in Examples 1 to 5 and Comparative Examples 1 to 2 were used to remove NO by NH3-SCR loaded with alkali metals. x Efficiency diagram.

[0028] Figure 2The present invention is Example 2 of the present invention, which is resistant to alkali metal, water and sulfur compound poisoning at 200°C and removes NO x Efficiency diagram. DETAILED DESCRIPTION

[0029] The present invention is further described below in conjunction with embodiments, but the protection scope of the present invention is not limited thereto.

[0030] The denitration performance evaluation method of the catalyst of the present invention is as follows: simulate the exhaust gas composition, NO intake concentration is 1000ppm, NH3 intake concentration is 1000ppm, O2 content is 10%, SO2 concentration is 300ppm (added when used), H2O content is 5vol.% (added when used), and N2 is the carrier gas. The catalyst dosage is set to 1.2ml, and the reaction space velocity (GHSV) is set to 30000h -1 The reaction temperature range is set to 50-400℃, and the flue gas analyzer is used to monitor NO online before and after the reaction. x concentration changes.

[0031] Example 1

[0032] (1) Preparation of cerium manganese tungsten active component precursor solution

[0033] According to the molar ratio of Ce, Mn and W being 1:0.4:0.14, 8.6844 g of cerium nitrate, 2.8632 g of manganese nitrate and 0.6942 g of ammonium metatungstate were weighed and dissolved in 100 ml of distilled water and stirred evenly to obtain solution A.

[0034] Weigh 4.5 g of hexadecyltrimethylammonium bromide and disperse it in 150 ml of distilled water. Place the mixture in a water bath and stir at 70° C. for 30 min to obtain dispersion B.

[0035] (2) Preparation of cerium-manganese-tungsten composite oxide catalyst

[0036] Liquid A was slowly dripped into liquid B and stirred evenly, 80 ml of ammonia water was added, the pH was adjusted to 10, and the sample was aged in an oven at 100 °C for 5 h. After that, the sample was washed and filtered until neutral, and the sample was dried in an oven at 80 °C for 24 h. After drying, the sample was calcined in a muffle furnace at 600 °C for 3 h.

[0037] (3) Preparation of alkali metal-supported cerium-manganese-tungsten catalyst

[0038] 0.1 g potassium nitrate was dispersed in 20 ml distilled water, and then 1 g cerium manganese tungsten composite oxide catalyst was added and stirred for 2 hours. The sample was then placed in an oven at 80°C for 24 hours. The dried sample was calcined at 600°C for 3 hours to obtain an alkali metal poisoned catalyst.

[0039] (4) Catalyst denitrification performance test

[0040] Under the condition of 1wt.% K loading, the denitration efficiency is >80% at 150-300℃. The denitration efficiency of the cerium-manganese-tungsten composite oxide catalyst loaded with 1wt.% K is >80% under the conditions of 200℃, 5vol.% H2O, 300ppm SO2, and its denitration efficiency is stable at more than 70% after 12h.

[0041] Example 2

[0042] (1) Preparation of cerium manganese tungsten active component precursor solution

[0043] According to the molar ratio of Ce, Mn and W being 1:0.4:0.18, 8.6844 g of cerium nitrate, 2.8632 g of manganese nitrate and 0.8926 g of ammonium metatungstate were weighed and dissolved in 100 ml of distilled water and stirred evenly to obtain solution A.

[0044] Weigh 4.5 g of hexadecyltrimethylammonium bromide and disperse it in 150 ml of distilled water. Place the mixture in a water bath and stir at 70° C. for 30 min to obtain dispersion B.

[0045] (2) Preparation of cerium-manganese-tungsten composite oxide catalyst

[0046] Liquid A was slowly dripped into liquid B and stirred evenly, 80 ml of ammonia water was added, the pH was adjusted to 10, and the sample was aged in an oven at 100°C for 5 h. After that, it was washed and filtered until neutral, and the sample was dried in an oven at 80°C for 24 h. After drying, it was calcined in a muffle furnace at 600°C for 3 h.

[0047] (3) Preparation of alkali metal-supported cerium-manganese-tungsten catalyst

[0048] 0.1 g potassium nitrate was dispersed in 20 ml distilled water, and then 1 g cerium manganese tungsten composite oxide catalyst was added and stirred for 2 hours. The sample was then placed in an oven at 80°C for 24 hours. The dried sample was calcined at 600°C for 3 hours to obtain an alkali metal poisoned catalyst.

[0049] (4) Catalyst denitrification performance test

[0050] Under the condition of 1wt.% K loading, the denitration efficiency is >80% at 150-350°C. The denitration efficiency of the cerium-manganese-tungsten composite oxide catalyst loaded with 1wt.% K is >90% at 200°C, 5vol.% H2O, 300ppm SO2, and its denitration efficiency is stable at more than 85% after 12h.

[0051] Example 3

[0052] (1) Preparation of cerium manganese tungsten active component precursor solution

[0053] According to the molar ratio of Ce, Mn and W being 1:0.4:0.22, 8.6844 g of cerium nitrate, 2.8632 g of manganese nitrate and 1.091 g of ammonium metatungstate were weighed and dissolved in 100 ml of distilled water and stirred evenly to obtain solution A.

[0054] Weigh 4.5 g of hexadecyltrimethylammonium bromide and disperse it in 150 ml of distilled water. Place the mixture in a water bath and stir at 70° C. for 30 min to obtain dispersion B.

[0055] (2) Preparation of cerium-manganese-tungsten composite oxide catalyst

[0056] Liquid A was slowly dripped into liquid B and stirred evenly, 80 ml of ammonia water was added, the pH was adjusted to 10, and the mixture was aged in an oven at 100 °C for 5 h. After that, the mixture was washed and filtered until neutral, and the sample was dried in an oven at 80 °C for 24 h. After drying, the sample was calcined in a muffle furnace at 600 °C for 3 h.

[0057] (3) Preparation of alkali metal-supported cerium-manganese-tungsten catalyst

[0058] 0.1 g potassium nitrate was dispersed in 20 ml distilled water, and then 1 g cerium manganese tungsten composite oxide catalyst was added and stirred for 2 hours. The sample was then placed in an oven at 80°C for 24 hours. The dried sample was calcined at 600°C for 3 hours to obtain an alkali metal poisoned catalyst.

[0059] (4) Catalyst denitrification performance test

[0060] Under the condition of 1wt.% K loading, the denitration efficiency is >80% at 200-350℃. The denitration efficiency of the cerium-manganese-tungsten composite oxide catalyst loaded with 1wt.% K is >80% at 200℃, 5vol.% H2O, 300ppm SO2, and after 12h, its denitration efficiency is stable at more than 75%.

[0061] Example 4

[0062] (1) Preparation of cerium manganese tungsten active component precursor solution

[0063] According to the molar ratio of Ce, Mn and W being 1:0.4:0.18, 8.6844 g of cerium nitrate, 2.8632 g of manganese nitrate and 0.8926 g of ammonium metatungstate were weighed and dissolved in 100 ml of distilled water and stirred evenly to obtain solution A.

[0064] Weigh 4 g of hexadecyltrimethylammonium bromide and disperse it in 150 ml of distilled water. Place the mixture in a water bath and stir at 70° C. for 30 min to obtain dispersion B.

[0065] (2) Preparation of cerium-manganese-tungsten composite oxide catalyst

[0066] Liquid A was slowly dripped into liquid B and stirred evenly, 80 ml of ammonia water was added, the pH was adjusted to 10, and the mixture was aged in an oven at 100 °C for 5 h. After that, the mixture was washed and filtered until neutral, and the sample was dried in an oven at 80 °C for 24 h. After drying, the sample was calcined in a muffle furnace at 600 °C for 3 h.

[0067] (3) Preparation of alkali metal-supported cerium-manganese-tungsten catalyst

[0068] 0.1 g potassium nitrate was dispersed in 20 ml distilled water, and then 1 g cerium manganese tungsten composite oxide catalyst was added and stirred for 2 hours. The sample was then placed in an oven at 80°C for 24 hours. The dried sample was calcined at 600°C for 3 hours to obtain an alkali metal poisoned catalyst.

[0069] (4) Catalyst denitrification performance test

[0070] Under the condition of 1wt.% K loading, the denitration efficiency is >80% at 200-300℃. The denitration efficiency of the cerium-manganese-tungsten composite oxide catalyst loaded with 1wt.% K is >70% under the conditions of 200℃, 5vol.% H2O, 300ppm SO2, and its denitration efficiency is stable at more than 65% after 12h.

[0071] Example 5

[0072] (1) Preparation of cerium manganese tungsten active component precursor solution

[0073] According to the molar ratio of Ce, Mn and W being 1:0.4:0.18, 8.6844 g of cerium nitrate, 2.8632 g of manganese nitrate and 0.8926 g of ammonium metatungstate were weighed and dissolved in 100 ml of distilled water and stirred evenly to obtain solution A.

[0074] Weigh 5 g of hexadecyltrimethylammonium bromide and disperse it in 150 ml of distilled water. Place the mixture in a water bath and stir at 70° C. for 30 min to obtain dispersion B.

[0075] (2) Preparation of cerium-manganese-tungsten composite oxide catalyst

[0076] Liquid A was slowly dripped into liquid B and stirred evenly, 80 ml of ammonia water was added, the pH was adjusted to 10, and the mixture was aged in an oven at 100 °C for 5 h. After that, the mixture was washed and filtered until neutral, and the sample was dried in an oven at 80 °C for 24 h. After drying, the sample was calcined in a muffle furnace at 600 °C for 3 h.

[0077] (3) Preparation of alkali metal-supported cerium-manganese-tungsten catalyst

[0078] 0.1 g potassium nitrate was dispersed in 20 ml distilled water, and then 1 g cerium manganese tungsten composite oxide catalyst was added and stirred for 2 hours. The sample was then placed in an oven at 80°C for 24 hours. The dried sample was calcined at 600°C for 3 hours to obtain an alkali metal poisoned catalyst.

[0079] (4) Catalyst denitrification performance test

[0080] Under the condition of 1wt.% K loading, the denitration efficiency is >80% at 250-350℃. The denitration efficiency of the cerium-manganese-tungsten composite oxide catalyst loaded with 1wt.% K is >65% under the conditions of 200℃, 5vol.% H2O, 300ppm SO2, and its denitration efficiency is stable at more than 60% after 12h.

[0081] Comparative Example 1

[0082] (1) Preparation of cerium-manganese active component precursor solution

[0083] According to the molar ratio of Ce to Mn being 1:0.4, 8.6844 g of cerium nitrate and 2.8632 g of manganese nitrate were weighed and dissolved in 100 ml of distilled water and stirred evenly to obtain solution A.

[0084] Weigh 4.5 g of hexadecyltrimethylammonium bromide and disperse it in 150 ml of distilled water. Place the mixture in a water bath and stir at 70° C. for 30 min to obtain dispersion B.

[0085] (2) Preparation of cerium-manganese composite oxide catalyst

[0086] Liquid A was slowly dripped into liquid B and stirred evenly, 80 ml of ammonia water was added, the pH was adjusted to 10, and the sample was aged in an oven at 100 °C for 5 h. After that, the sample was washed and filtered until neutral, and the sample was dried in an oven at 80 °C for 24 h. After drying, the sample was calcined in a muffle furnace at 600 °C for 3 h.

[0087] (3) Preparation of alkali metal-supported cerium-manganese catalyst

[0088] 0.1 g potassium nitrate was dispersed in 20 ml distilled water, and then 1 g cerium manganese composite oxide catalyst was added and stirred for 2 hours. The sample was then placed in an oven at 80°C for 24 hours. The dried sample was calcined at 600°C for 3 hours to obtain an alkali metal poisoned catalyst.

[0089] (4) Catalyst denitrification performance test

[0090] Under the condition of loading 1wt.% K, the denitration efficiency reaches 86.5% at 200°C. The denitration efficiency of the cerium-manganese composite oxide catalyst loaded with 1wt.% K is >65% under the conditions of 200°C, 5vol.% H2O, and 300ppm SO2, and its denitration efficiency stabilizes at more than 50% after 12h.

[0091] Comparative Example 2

[0092] (1) Preparation of cerium manganese tungsten active component precursor solution

[0093] According to the molar ratio of Ce, Mn and W being 1:0.4:0.18, 8.6844 g of cerium nitrate, 2.8632 g of manganese nitrate and 0.8926 g of ammonium metatungstate were weighed and dissolved in 100 ml of distilled water and stirred evenly to obtain solution A.

[0094] (2) Preparation of cerium-manganese-tungsten composite oxide catalyst

[0095] Ammonia water was added to solution A to adjust the pH to 10, and the solution was placed in an oven at 100°C for aging for 5 hours. The solution was then washed and filtered until neutral. The sample was placed in an oven for drying at 80°C for 24 hours. After drying, the sample was placed in a muffle furnace for calcination at 600°C for 3 hours.

[0096] (3) Preparation of alkali metal-supported cerium-manganese-tungsten catalyst

[0097] 0.1 g potassium nitrate was dispersed in 20 ml distilled water, and then 1 g cerium manganese tungsten composite oxide catalyst was added and stirred for 2 hours. The sample was then placed in an oven at 80°C for 24 hours. The dried sample was calcined at 600°C for 3 hours to obtain an alkali metal poisoned catalyst.

[0098] (4) Catalyst denitrification performance test

[0099] Under the condition of 1wt.% K loading, the denitration efficiency is >80% at 150-300℃. The denitration efficiency of the cerium-manganese-tungsten composite oxide catalyst loaded with 1wt.% K is >70% under the conditions of 200℃, 5vol.% H2O, 300ppm SO2, and its denitration efficiency is stable at more than 60% after 12h.

[0100] Table 1 shows the denitration activity of the catalyst prepared by the present invention and its stability against alkali metals / water / sulfur

[0101]

Claims

1. A denitration catalyst resistant to composite poisoning of alkali metals, water and sulfur, characterized in that The catalyst uses hexadecyltrimethylammonium bromide as a template agent, and cerium oxide, manganese oxide and tungsten oxide as denitration active components.

2. The alkali metal-supported cerium-manganese-tungsten catalyst according to claim 1, characterized in that: The molar ratio of the three elements Ce, Mn and W is 1:(0.02-0.8):(0.02-0.30).

3. A method for preparing the catalyst according to claim 2, characterized in that: The specific steps are as follows: (1) Preparation of cerium manganese tungsten active component precursor solution The cerium manganese tungsten oxide precursor is added to distilled water, heated and stirred until completely dissolved to obtain a clear solution A; hexadecyl trimethyl ammonium bromide is added to the distilled water, stirred evenly to obtain a dispersion B; (2) Preparation of cerium-manganese-tungsten composite oxide catalyst Add solution A to dispersion B, stir evenly, and then add alkaline reagent until alkaline; Then, the solution is placed in an oven for aging, and finally washed, filtered, dried and calcined in sequence to obtain a cerium-manganese-tungsten composite oxide catalyst; (3) Preparation of alkali metal-supported cerium-manganese-tungsten catalyst The alkali metal precursor was added into distilled water and stirred until completely dissolved, and then the cerium manganese tungsten catalyst was added into the above solution and continued to be stirred. The sample was then placed in an oven to dry and then transferred to a muffle furnace for calcination.

4. The preparation method according to claim 3, characterized in that: In step (1), the cerium manganese tungsten oxide precursor is cerium nitrate, manganese nitrate and ammonium metatungstate.

5. The preparation method according to claim 3, characterized in that: In step (1), the mass ratio between the cerium manganese tungsten oxide precursor and hexadecyltrimethylammonium bromide is 10-15:3-8.

6. The preparation method according to claim 3, characterized in that: In step (2), the alkaline reagent is aqueous ammonia, and the alkaline pH is 8-12.

7. The preparation method according to claim 3, characterized in that: In step (2), the aging temperature is 70-110° C. and the aging time is 2-5 hours; the drying temperature is 70-90° C. and the drying time is 24 hours; the calcination temperature is 400-700° C. and the calcination time is 1-5 hours.

8. The preparation method according to claim 3, characterized in that: In step (3), the alkali metal precursor is potassium nitrate; the mass ratio of the catalytic active component to the alkali metal precursor is 100:0.5-3. The drying temperature is 70-110°C, and the drying time is 10-24 hours; the calcination temperature is 400-700°C, and the calcination time is 1-5 hours.

9. Use of the catalyst according to claim 1 in denitration.

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